Use of recycled plastics in eco-efficient concrete 9780081026762, 0081026765

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Use of Recycled Plastics in Eco-efficient Concrete

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Woodhead Publishing Series in Civil and Structural Engineering

Use of Recycled Plastics in Eco-efficient Concrete Edited by

Fernando Pacheco-Torgal Jamal Khatib Francesco Colangelo Rabin Tuladhar

Woodhead Publishing is an imprint of Elsevier The Officers’ Mess Business Centre, Royston Road, Duxford, CB22 4QH, United Kingdom 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States The Boulevard, Langford Lane, Kidlington, OX5 1GB, United Kingdom Copyright © 2019 Elsevier Ltd. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library ISBN: 978-0-08-102676-2 For information on all Woodhead publications visit our website at https://www.elsevier.com/books-and-journals

Publisher: Matthew Deans Acquisition Editor: Gwen Jones Editorial Project Manager: Charlotte Rowley Production Project Manager: Joy Christel Neumarin Honest Thangiah Designer: Mark Rogers Typeset by TNQ Technologies

Contents

List of contributors 1

2

3

4

xi

Introduction to the use of recycled plastics in eco-efficient concrete F. Pacheco-Torgal 1.1 The waste plastic problem 1.2 Outline of the book References

1

Techniques for separation of plastic wastes Silvia Serranti and Giuseppe Bonifazi 2.1 Introduction 2.2 Plastic waste sources and typologies 2.3 The plastic recycling chain 2.4 Plastic waste separation technologies 2.5 Recycled plastics quality control 2.6 Technical challenges in plastic recycling References

9

Hydraulic separation of plastic wastes Monica Moroni, Emanuela Lupo and Floriana La Marca 3.1 Introduction 3.2 Principles of the hydraulic separation process 3.3 Devices for the hydraulic separation within mechanical recycling plants 3.4 The hydraulic separator channel 3.5 Separation efficacy of the hydraulic separator channel 3.6 Conclusions References Production of recycled polypropylene (PP) fibers from industrial plastic waste through melt spinning process Rabin Tuladhar and Shi Yin 4.1 Introduction 4.2 Physical cutting of waste plastic 4.3 Mechanical recycling of plastic wastes 4.4 Production of recycled plastic fibers

1 4 7

9 10 13 15 28 30 33 39 39 40 46 48 54 65 66 69 69 70 71 75

vi

Contents

4.5 4.6 4.7

5

6

7

8

Material characterization Mechanical properties of recycled PP fibers Conclusions Acknowledgments References

Fresh properties of concrete containing plastic aggregate Sheelan M. Hama and Nahla N. Hilal 5.1 Introduction 5.2 Mix proportion and design 5.3 Workability of fresh concrete containing plastic aggregate 5.4 Fresh density of concrete containing plastic aggregate 5.5 Self-compacting plastic aggregate concrete 5.6 Conclusions References Further reading

77 80 82 83 83 85 85 85 94 101 103 113 113 114

Mechanical strength of concrete with PVC aggregates A.A. Mohammed 6.1 Introduction 6.2 Properties of concrete with PVC waste aggregate 6.3 Summary References

115

Characteristics of concrete containing EPS J.M. Khatib, B.A. Herki and A. Elkordi 7.1 Introduction 7.2 Preparation of EPS 7.3 Physical properties of EPS 7.4 Chemical properties of EPS 7.5 Substitution levels of EPS 7.6 Production and applications of EPS concrete 7.7 Density of concrete containing EPS 7.8 Fresh properties of concrete containing EPS 7.9 Mechanical properties 7.10 Thermal conductivity 7.11 Durability-related properties of concrete containing EPS 7.12 Structural performance of reinforced concrete beams 7.13 Conclusions and recommendations References

137

Lightweight concrete with polyolefins as aggregates Francesco Colangelo and Ilenia Farina 8.1 Introduction 8.2 Production of expanded granules 8.3 Use of recycled polyolefins in different sectors

167

115 117 134 134

137 139 140 141 141 146 146 146 148 153 154 156 156 158

167 168 170

Contents

8.4 8.5

9

10

11

12

vii

Use of polyolefins as recycled aggregates in lightweight concrete (case study) Future trends References Further reading

Properties of concrete with plastic polypropylene aggregates Z. Pavlík, M. Pavlíkov a and M. Z alesk a 9.1 Introduction 9.2 Waste polypropylene-based aggregates for concrete 9.3 Structural properties of concrete with PP aggregates 9.4 Mechanical properties of concrete with PP aggregates 9.5 Thermal properties of composites with PP aggregates 9.6 Hygric properties of composites with PP aggregates 9.7 Possible application of PP in concrete production and future trends Acknowledgments References Virgin and waste polymer incorporated concrete mixes for enhanced neutron radiation shielding characteristics Santhosh M. Malkapur and Mattur C. Narasimhan 10.1 Introduction 10.2 Neutron radiation and shielding 10.3 Use of hydrogenous aggregates and polymers in radiation shielding 10.4 Use of virgin HDPE powder as partial replacement to sand 10.5 Properties of PISCC mixes in their fresh states 10.6 Neutron radiation shielding properties of polymer incorporated concrete mixes References

170 183 183 186 189 189 191 197 199 207 210 211 211 211 215 215 216 223 227 231 235 245

Performance of dioctyl terephthalate concrete B. S¸ims¸ek, T. Uyguno glu, H. Korucu and M.M. Kocakerim 11.1 Introduction 11.2 Dioctyl terephthalate concrete 11.3 Comparison of the polyethylene terephthalate and dioctyl terephthalate concrete 11.4 Conclusions and recommendations References

249

Recycling of PET in asphalt concrete I. Aghayan and R. Khafajeh 12.1 Introduction 12.2 Using PET waste as modifier in asphalt mixture 12.3 Conclusion References

269

249 251 257 262 264

269 270 282 283

viii

13

14

15

16

Contents

Recycling of different plastics in asphalt concrete M.A. Dalhat, Khaleel Al-Adham and M.A. Habib 13.1 Introduction 13.2 Polymer modification of asphalt and the need for plastic recycling in asphalt concrete 13.3 Materials and methods 13.4 Results 13.5 Future trends 13.6 Summary and conclusions Acknowledgments Conflict of interest References

287

Replacement of stabilizers by recycling plastic in asphalt concrete Goutham Sarang 14.1 Introduction 14.2 Need for stabilization of asphalt concrete 14.3 Addition of plastic in asphalt concrete 14.4 Performance of asphalt concrete with plastics 14.5 Field investigations 14.6 Conclusion References

307

The use of recycled plastic as partial replacement of bitumen in asphalt concrete Marta Vila-Cortavitarte, Pedro Lastra-Gonz alez,  Miguel Angel Calzada-Pérez and I. Indacoechea-Vega 15.1 Introduction 15.2 Bitumen’s role in asphalt 15.3 Modification of asphalt mixtures with polymers 15.4 Modification of asphalt mixtures with polystyrene 15.5 General Conclusions 15.6 Future lines of study References Concrete reinforced with metalized plastic waste fibers Ankur C. Bhogayata 16.1 Introduction 16.2 Metalized postconsumer plastic wastes: challenges and issues for management 16.3 Feasibility of MPW in concrete: outcomes from pilot studies 16.4 Role of MPW fibers in the workability and strength properties of conventional concrete 16.5 Effect of MPW fibers on the deformation due to the axial compression by modified concrete

287 288 289 293 302 302 303 303 303

307 308 314 315 317 318 318 327 327 328 329 332 344 345 346 349 349 349 350 355 360

Contents

16.6 16.7 16.8 16.9

17

18

19

20

ix

Advantages and limitations of the usage of MPW in concrete Important findings and concluding remarks Future trends Sources of further information and advice References Further reading

364 365 366 366 366 367

Performance of concrete with PVC fibres Senthil Kumar Kaliyavaradhan and Tung-Chai Ling 17.1 Introduction 17.2 Performance of concrete with PVC fibres 17.3 Conclusions 17.4 Future research perspective Acknowledgments References

369

Recycled waste PET for sustainable fiber-reinforced concrete Dora Foti 18.1 Introduction 18.2 Use of PET in concrete 18.3 Tests (summary) and results 18.4 Conclusions Acknowledgments References Further reading

387

Properties of recycled carpet fiber reinforced concrete Hamid Reza Pakravan, Ali Asghar Asgharian Jeddi, Masoud Jamshidi, Farnaz Memarian and Amir Masoud Saghafi 19.1 Introduction 19.2 Carpet types and fiber recycling methods 19.3 Properties of recycled carpet fiber 19.4 Physical properties of concrete containing recycled carpet fiber 19.5 Durability-related properties of concrete containing recycled carpet fiber 19.6 Mechanical properties of concrete containing recycled carpet fiber 19.7 Future trends References

411

Performance of asphalt concrete with plastic fibres Nura Usman and Mohd Idrus Mohd Masirin 20.1 Introduction 20.2 Polyethylene terephthalate 20.3 The use of polyethylene terephthalate in asphalt mixture

427

369 370 383 383 383 384

387 389 398 408 408 408 410

411 412 415 416 418 418 422 423

427 428 428

x

Contents

20.4 20.5 20.6 20.7 21

Recycled polyethylene terephthalate fiber Characteristics of recycled PET fiber Application of recycled PET fiber in asphalt mixture Conclusion References

Sustainability of using recycled plastic fiber in concrete Rabin Tuladhar and Shi Yin 21.1 Introduction 21.2 Sustainability in construction materials 21.3 Comprehensive LCA of recycled plastic fibers used for reinforcing concrete 21.4 Conclusions Acknowledgments References

Index

429 430 431 437 438 441 441 442 448 458 459 459 461

List of contributors

I. Aghayan

Shahrood University of Technology, Shahrood, Iran

Khaleel Al-Adham Civil & Environmental Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia Ali Asghar Asgharian Jeddi Textile Engineering Department, Amirkabir University of Technology, Tehran, Iran Ankur C. Bhogayata Department of Civil Engineering Marwadi Education Foundation’s Group of Institutions, Rajkot, India Giuseppe Bonifazi Department of Chemical Engineering, Materials & Environment, Sapienza University of Rome, Rome, Italy
Miguel Angel Calzada-Pérez GCS Research Group, University of Cantabria, Av. de los Castros 44, Santander, Spain Francesco Colangelo Department of Engineering, University Parthenope of Naples, Materials Science and Engineering Research GroupdMASERG, Centro Direzionale, Is. C4, Naples, Italy M.A. Dalhat Transportation and Traffic Engineering Department, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia A. Elkordi

Faculty of Engineering, Beirut Arab University, Beirut, Lebanon

Ilenia Farina Department of Engineering, University Parthenope of Naples, Materials Science and Engineering Research GroupdMASERG, Centro Direzionale, Is. C4, Naples, Italy Dora Foti Department of Civil Engineering Sciences and Architecture, Polytechnic University of Bari, Bari, Italy M.A. Habib Civil & Environmental Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia Sheelan M. Hama Iraq B.A. Herki

Department of Civil Engineering, University of Anbar, Ramadi,

Faculty of Engineering, Soran University, Erbil, Iraq

Nahla N. Hilal

Department of Civil Engineering, University of Anbar, Ramadi, Iraq

xii

List of contributors

I. Indacoechea-Vega GITECO Research Group, University of Cantabria, Av. de los Castros 44, Santander, Spain Masoud Jamshidi School of Chemical Engineering, Iran University of Science and Technology (IUST), Tehran, Iran Senthil Kumar Kaliyavaradhan Key Laboratory for Green and Advanced Civil Engineering Materials and Application Technology of Hunan Province, College of Civil Engineering, Hunan University, Changsha, China R. Khafajeh Shahrood University of Technology, Shahrood, Iran J.M. Khatib Faculty of Engineering, Beirut Arab University, Beirut, Lebanon; Faculty of Science and Engineering, University of Wolverhampton, Wolverhampton, United Kingdom M.M. Kocakerim Department of Chemical Engineering, C¸ankırı Karatekin University, Uluyazı Campus, C¸ankırı, Turkey H. Korucu Department of Chemical Engineering, C¸ankırı Karatekin University, Uluyazı Campus, C¸ankırı, Turkey Floriana La Marca

DICMA-Sapienza University of Rome, Rome, Italy

Pedro Lastra-Gonz
alez GITECO Research Group, University of Cantabria, Av. de los Castros 44, Santander, Spain Tung-Chai Ling Key Laboratory for Green and Advanced Civil Engineering Materials and Application Technology of Hunan Province, College of Civil Engineering, Hunan University, Changsha, China Emanuela Lupo

DICEA-Sapienza University of Rome, Rome, Italy

Santhosh M. Malkapur Department of Civil Engineering, Faculty of Engineering and Technology, M.S. Ramaiah University of Applied Sciences, Bengaluru, India Mohd Idrus Mohd Masirin Faculty of Civil and Environmental Engineering, Universiti Tun Hussein Onn Malaysia, Rarit Raja Johor, Malaysia Farnaz Memarian Textile Engineering Department, Amirkabir University of Technology, Tehran, Iran A.A. Mohammed Department of Civil Engineering, College of Engineering, University of Sulaimani, Sulaimani, Iraq Monica Moroni DICEA-Sapienza University of Rome, Rome, Italy Mattur C. Narasimhan Department of Civil Engineering, National Institute of Technology Karnataka (NITK) Surathkal, Mangalore, India F. Pacheco-Torgal Portugal

C-TAC Research Centre, University of Minho, Guimar~aes,

List of contributors

xiii

Hamid Reza Pakravan Textile Engineering Department, Amirkabir University of Technology, Tehran, Iran Z. Pavlík Department of Materials Engineering and Chemistry, Faculty of Civil Engineering, Czech Technical University in Prague, Prague, Czech Republic M. Pavlíkov
a Department of Materials Engineering and Chemistry, Faculty of Civil Engineering, Czech Technical University in Prague, Prague, Czech Republic Amir Masoud Saghafi Tehran, Iran

Technical and Production Director, Savin Carpet Company,

Goutham Sarang Assistant Professor (Senior), School of Mechanical and Building Sciences (SMBS), Vellore Institute of Technology - Chennai Campus, Chennai, Tamil Nadu, India Silvia Serranti Department of Chemical Engineering, Materials & Environment, Sapienza University of Rome, Rome, Italy B. S¸ims¸ek Department of Chemical Engineering, C¸ankırı Karatekin University, Uluyazı Campus, C¸ankırı, Turkey Rabin Tuladhar Centre of Tropical Environmental and Sustainability Science, College of Science and Engineering, James Cook University, Townsville, QLD, Australia Nura Usman Faculty of Civil and Environmental Engineering, Universiti Tun Hussein Onn Malaysia, Rarit Raja Johor, Malaysia; Department of Civil Engineering, Hassan Usman Katsina Polytechnic, Katsina, Nigeria T. Uyguno glu Department of Civil Engineering, Afyon Kocatepe University, Ahmet Necdet Sezer Campus, Afyon, Turkey Marta Vila-Cortavitarte GITECO Research Group, University of Cantabria, Av. de los Castros 44, Santander, Spain Shi Yin College of Science and Engineering, James Cook University, Townsville, QLD, Australia M. Z
alesk
a Department of Materials Engineering and Chemistry, Faculty of Civil Engineering, Czech Technical University in Prague, Prague, Czech Republic

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Introduction to the use of recycled plastics in eco-efficient concrete

1

F. Pacheco-Torgal C-TAC Research Centre, University of Minho, Guimar~aes, Portugal

1.1

The waste plastic problem

Deriving from the Greek word ’’plastikos’’ meaning fit for moulding, plastics comprise mainly two broad categories (thermoplastics and thermosetting plastics). The former include plastics (polyethylene, polypropylene, polysterene, polycarbonates, etc.) that can be heated up to form products and if needed can be reheated and melted again for new forms. In contrast, the latter (polyurethane, polyesters, phenolic and acrylic resins, silicone, etc.) can be melted and formed, but unlike thermoplastics cannot be remelted. The global production of fossil-based plastics has grown more than 20-fold since 1964 to 322 million ton in 2015 (Wei and Zimmermann, 2017; PlasticsEurope, 2017). Not only the production of plastics consumes yearly 4%e8% of the global crude oil extraction meaning that if plastics are disposed instead of being recycled, these resources are lost but the worst part is that plastic waste is harmful because pigment contains many trace elements that are highly toxic and need hundreds of years to degrade (Huysman et al., 2017). More worrying is the several millions of tons of plastic waste that are entering the ocean each year, for quite some time, whose damaging action has been addressed by several authors (Eriksen et al., 2014; Jambeck et al., 2015; Sussarellu et al., 2016; Green et al., 2016; MacArthur, 2017; Lamb et al., 2018). Between 8 and 24 tons of plastic waste enter oceans each minute (Haward, 2018). According to ten Brink et al. (2018), the annual cost of marine litter is conservatively estimated at US$ 40 billion. And in July 19, 2017 Science magazine published an article warning that by 2050, we’ll have produced 26 billion tons of plastic waste, half of which will be dumped in landfills and the environment (Guglielmi, 2017). It’s then no surprise that target 14.1 of the 2030 Agenda for Sustainable Development seeks to prevent and significantly reduce marine pollution of all kinds, in particular, from land-based activities, including marine debris, by 2025. Yes, it’s true that on 17th of April 2018 a paper published in the Proceeding of the National Academy of Sciences of the United States of America (Austin et al., 2018) reported the discovery of an enzyme that can digest highly crystalline PET and also polyethylene-2,5furandicarboxylate (PEF). However, as Oliver Jones, analytical chemist at RMIT University in Melbourne, recognized “there is still a way to go before you could recycle large amount of plastic with enzymes” (Gabbatiss, 2018). But a more wise Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00001-3 Copyright © 2019 Elsevier Ltd. All rights reserved.

2

Use of Recycled Plastics in Eco-efficient Concrete

position was made by Adisa Azapagic, at the University of Manchester who mentioned that “A full life-cycle assessment would be needed to ensure the technology does not solve one environmental problemdwastedat the expense of others, including additional greenhouse gas emissions” (Carrington, 2018). And if a lesson can be extracted from this case, it is that scientists should have some lessons on public communication, a problem recognized several years ago (Soapbox Science, 2012; Goldstein, 2012; Grant, 2016). In the meantime a study published on May of 2018 showed that each liter of sea ice on the Arctic contained around 12,000 particles of plastic (La Daana et al., 2018). No wonder then that a previous study (Wilcox et al., 2015) revealed that around 90% of seabirds have plastic waste particles in their gut that they mistakenly took to be fish eggs. Also, Rochman (2018) recently showed that the ocean is not the only place to suffer damaging environmental impacts. Around 26 million tons of plastic waste are generated in Europe every year, which makes Europe the second largest producer of plastic materials, being responsible for 20% of the world production. Packaging applications, the largest application sector, represent 39.6% of the total plastic demand (Huysman et al., 2017). In the past years significant share of European waste plastics leave the EU to be treated in third world countries, where different environmental standards may apply (EUROSTAT, EuropePlastics). However, since January of 2018 China decided to ban the imports of 24 kinds of waste including waste plastic which will aggravate the problem of plastic waste in Europe. And that is why plastic waste is one of the five priority areas in the EU action plan for the circular economydCE (EC, 2015a). The CE concept may have been inspired by Rachel Carson’s Silent Spring and the “limits to growth” thesis of the Club of Rome in the 1970s (Winans et al., 2017) and is being promoted by the EU, but several national governments still argue (Geissdoerfer et al., 2017) that the conceptual relationship between the CE and sustainability is not clear, having detrimental implications for the advancement of sustainability science. Others (Korhonen et al., 2018) mentioned that the CE practice has almost exclusively been developed and led by practitioners, that is, policy-makers, businesses, business consultants, business associations, and business foundations and as a result the research content of the CE concept is superficial and unorganized. Still in the European Union context, looking into the past is worth remembering that the previous Directive 94/62/EC had imposed a recycling target which required 22.5% of waste plastic packaging to be recycled. This target increased toward 55% by 2030 (EC, 2015b) but on March 14 of the 2017 the European Parliament voted for legislation to aim for a recycling rate target of 70% by 2030, with a proposed 80% target for packaging materialsdincluding paper, cardboard, plastics, glass, metal, and wood. This constitutes a high ambition postured by the EU and there is still some controversy regarding job creation in the field of waste recycling. While the report cited by the European Parliament mentioned the possibility of creation of 1e3 million jobs (IP, 2017) the fact is that the European Commission has presented a much lower number of just 170,000 direct jobs (Politico, 2018). Most of these optimistic projections usually tend to forget that as Cooper and Gutowski (2017) recently pointed the fact that reusing a product does not guarantee an environmental benefit because of the need to upgrade old product efficiencies and the fact that more efficient new products can be on the

Introduction to the use of recycled plastics in eco-efficient concrete

3

market. For instance, as contradicting as it may seem, Dunant et al. (2018) showed that reused steel is somewhat more expensive than new steel elements. Fig 1.1 shows plastic post-consumer waste rates of recycling, energy recovery, and landfill per country in 2016 and also the group of 10 countries that have implemented landfill restrictions. The figure illustrates in a very clear way the effort that needs to be taken to close the gap between the state-of-the-art plastic waste recycling and the new recycling targets. Of course energy recovery is nothing more than incineration (Eriksson and Finnveden, 2017). Also the proof that the new and ambitious waste plastic recycling approved by the European Parliament could be hard to achieve is given by Karl-H. Foerster, executive director of industry organization Plastics Europe, who responded to the parliamentary proposals, saying that: “Taking into account today’s recycling technology, we already

Figure 1.1 Plastic waste rates of recycling, energy recovery, and landfill per country (Plastics, 2017).

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Use of Recycled Plastics in Eco-efficient Concrete

consider that the 55% plastics packaging preparing for re-use and recycling target proposed by the Commission is challenging. We would therefore like to call on the Presidency of the Council to carefully assess the impact prior to adopting any substantive amendment to the rules on the calculation initially proposed by the Commission.” That position however must be seen in the light of the interests of the associates of Plastics Europe which are in the business of plastic manufacture and not in the business of waste plastic recycling. Of course, some European countries like the Netherlands, which in 2014 already recycled 50% of (packaging) plastics, aiming for 52% in 2022 (Gradus et al., 2017) will be in a better position to achieve this requirements. Be there as it may, the truth is that even countries with top performance concerning plastic waste recycling like Austria recognized that in order to achieve the proposed increased target major steps will be needed with respect to both collection and sorting of waste plastic (Van Eygen et al., 2018). This also means that even in Europe there’s still much to do in order to aim at a 100% recycling target (zero plastic waste scenario). In January 16 of 2018 the European Strategy for Plastics in a Circular Economy was released (COM, 2018). The document confirmed that more than 85% of plastic was sent to China. The document mentions that internalizing the environmental costs of landfilling and incineration through high or gradually rising fees or taxes could improve the economics of plastic recycling. However, this is just wishful thinking lacking a sound study. More likely it could constitute an incentive for illegal dumping or for exportation of plastic wastes to Africa as was mentioned in a United Nations University study (PiP, 2017) meaning that at this moment it is not possible to forecast how increasing recycling targets and the use of internalizing the environmental costs through rising fees or taxes may lead to an increase of smuggling waste to third world countries. The concept of eco-efficiency was firstly coined in the book Changing Course (Schmidheiny, 1992) in the context of 1992 Earth Summit process. This concept includes "the development of products and services at competitive prices that meet the needs of humankind with quality of life, while progressively reducing their environmental impact and consumption of raw materials throughout their life cycle, to a level compatible with the capacity of the planet.” All of these give an important value to the option of recycling waste plastics through concrete, which is the most consumed material in our planet, about 25 gigatonnes per year around 3.5 ton per capita (Hossain et al., 2018). Not to mention the several billion tons of asphalt concrete used by the pavement industry each year. The use of recycled plastics in eco-efficient concrete can be done mainly by replacing natural aggregates, as binders and also as recycled fibers, allowing for improvements in the ductility of concrete composites. Those are the areas covered by this book.

1.2

Outline of the book

This book thus provides an updated state-of-the-art review on the use of recycled plastics in eco-efficient concrete. Part I encompasses processing of plastic wastes (Chapters 2e4).

Introduction to the use of recycled plastics in eco-efficient concrete

5

Chapter 2 concerns techniques for the separation of plastic waste namely gravity separation, electrostatic separation, magnetic density separation, flotation, and sensor-based sorting. Auxiliary technologies usually found in plastic recycling plants are also described: magnetic and Eddy current separators. The importance of recycled plastic quality control and product certification is strongly pointed out, reporting both traditional and advanced quality measurement techniques. Chapter 3 discusses hydraulic separation of plastic waste. This chapter presents an original device for the hydraulic separation of plastic polymers from mixtures. An extensive experimental campaign was conducted to investigate the effectiveness of the apparatus, using two geometric arrangements, nine hydraulic configurations, and three selections of polymers at three stages of a material’s life cycle. Experimental data were also employed to validate a numerical model developed within the framework of Computation Fluid Dynamics. The separation results were evaluated in terms of grade and recovery of a useful material. Chapter 4 presents the case for the production of recycled plastic fibers. The production process includes melt-spinning and hot-drawing processes, which increase crystallinity of the plastic polymer fibers and improve its mechanical properties. Part II concerns the case of concrete with recycled plastic as aggregate or binder (Chapters 5e15). Chapter 5 reviews the fresh properties of concrete with plastic aggregates. The chapter also reviews the case for fresh properties of self-compacting concrete. Chapter 6 covers mostly the mechanical strength of concrete with polyvinyl chloride (PVC) aggregates including compressive and tensile strength and modulus of elasticity. Chapter 7 provides a comprehensive review of concrete containing Expanded Polystyrene (EPS), covers recent research, including some recent research by the authors, with some details on the compositions of concrete mixes, presentation, and discussion of the results obtained. The review includes the influence of different amounts of EPS as a replacement for natural aggregates on the different mechanical, physical, and durability properties of lightweight aggregate concretes (LWAC). The chapter also includes the methods and techniques for recycling waste EPS to be utilized in concrete. Chapter 8 deals with the use of polyolefin waste aggregates (PWA) obtained from recycled plastics and used as plastic aggregates to replace the natural ones to produce lightweight aggregate concrete (LWAC). The mechanical properties (compressive and tensile strength) and physical properties (porosity, density, and thermal stability) are determined. Furthermore, the postfire residual mechanical performance, ultrasonic testing, and compression force are evaluated. Chapter 9 is concerned with waste polypropylene-based aggregates, in terms of its physical, mechanical, and hygric properties and, in particular, of thermal attributes and optimum energy performance in building construction. Chapter 10 addresses polymers for enhancing neutron radiation shielding of concrete. Past research in the field is reviewed. The feasibility issues and concerns while using virgin and waste pulverized High-density polyethylene (HDPE) polymeric materials as partial replacement to fine aggregates for making concrete mixes with enhanced neutron radiation shielding characteristics are discussed. The fresh and

6

Use of Recycled Plastics in Eco-efficient Concrete

hardened properties of these mixes and their effect on neutron radiation shielding are also discussed. Chapter 11 reviews the reuse of dioctyl terephthalate (DOTP) obtained from waste PET into concrete. Fresh properties as well as mechanical properties of hardened concrete are reviewed, along with thermal conductivity. Performance comparisons between DOTP concrete and PET concrete are also reviewed. Chapter 12 covers studies investigated in the usage of PET wastes in asphalt mixture. The volume and mechanical properties of asphalt mixtures containing PET wastes along with the physical characteristic of the PET-modified binder are examined. Chapter 13 discloses results on a case study of asphalt concrete performance with different plastic wastes. Mechanical properties and durability parameters are covered. Emissions footprint is also covered. Chapter 14 discusses the need of stabilization of asphalt concrete and different stabilizer materials using recycling plastics. Suitable methods for incorporating waste plastics, advantages of each, performance of waste plastic added mixtures are discussed in detail with brief information on some field evaluations. Chapter 15 reviews the use of recycled plastic as partial replacement of bitumen in asphalt concrete. The need for stabilization of asphalt concrete is reviewed. The performance of asphalt concrete with plastics is also addressed. Finally, Part III covers concrete with recycled plastic fibers (Chapters 16e22). Chapter 16 surveys the usage of metalized plastic waste (MPW) as a cement concrete constituent in a macrofibrous form. The chapter focuses on how to obtain the optimum quantity of MPW fibers with a suitable size to be used in concrete and changes in the deformation response due to the axial compression along with the evaluation of preliminary material properties. Chapter 17 addresses concrete with PVC fibers in the fresh and hardened state. It is suggested that the use of PVC fibers, either 0.8% (by weight of cement) or 0.2% (by volume of concrete), could significantly improve the performances of concrete. Limitations and practical issues on the utilization of PVC fibers in concrete mixes are identified. Hence, recommendations and future research needs on the practical implications of the use of PVC fibers are given at the end of the chapter. Chapter 18 addresses the case of polymers added to concrete in the form of binder or as discrete elements (fibers) or continuous (strips) can limit the presence of cracks and especially avoid the corrosion processes in reinforced concrete structural elements. In more detail, the effect of polyethylene terephthalate (PET) on concrete mix is especially considered. Laboratory results of concrete reinforced with PET fibers derived from recycled water bottles and with different shapes are analyzed. Chapter 19 presents an overview of physical and mechanical properties of concrete containing recycled carpet waste fibers, as well as the carpet structure and fiber properties. Chapter 20 gives details of a case study on the performance of asphalt concrete reinforced with recycled PET fibers. Chapter 21 closes Part III with a chapter on the life cycle assessment. The production of 100% recycled polypropylene fibers is compared with the environmental impacts of virgin PP fibers and steel reinforcing mesh.

Introduction to the use of recycled plastics in eco-efficient concrete

7

References Austin, H.P., Allen, M.D., Donohoe, B.S., Rorrer, N.A., Kearns, F.L., Silveira, R.L., et al., 2018. Characterization and engineering of a plastic-degrading aromatic polyesterase. Proceedings of the National Academy of Sciences 201718804. Carrington, D., 2018. Scientists Accidentally Create Mutant Enzyme that Eats Plastic Bottles. https://www.theguardian.com/environment/2018/apr/16/scientists-accidentally-createmutant-enzyme-that-eats-plastic-bottles. COM, 2018. 28 Final. A European Strategy for Plastics in a Circular Economy. Brussels, 16.1.2018. http://ec.europa.eu/environment/circular-economy/pdf/plastics-strategy.pdf. Cooper, D.R., Gutowski, T.G., 2017. The environmental impacts of reuse: a review. Journal of Industrial Ecology 21 (1), 38e56. La Daana, K.K., Gårdfeldt, K., Lyashevska, O., Hassell€ov, M., Thompson, R.C., O’Connor, I., 2018. Microplastics in sub-surface waters of the Arctic Central Basin. Marine Pollution Bulletin 130, 8e18. Dunant, C.F., Drewniok, M.P., Sansom, M., Corbey, S., Cullen, J.M., Allwood, J.M., 2018. Options to make steel reuse profitable: an analysis of cost and risk distribution across the UK construction value chain. Journal of Cleaner Production 183, 102e111. EC, 2015a. Closing the Loop - an EU Action Plan for the Circular Economy. COM (2015) 614. European Commission, Brussels, Belgium. EC, 2015b. Proposal for a Directive of the European Parliament and of the Council Amending Directive 94/62/EC on Packaging and Packaging Waste. COM(2015) 596. European Commission, Brussels, Belgium. Eriksen, M., Lebreton, L.C., Carson, H.S., Thiel, M., Moore, C.J., Borerro, J.C., et al., 2014. Plastic pollution in the world’s oceans: more than 5 trillion plastic pieces weighing over 250,000 tons afloat at sea. PLoS One 9 (12), e111913. Eriksson, O., Finnveden, G., 2017. Energy recovery from waste incinerationdthe importance of technology data and system boundaries on CO2 emissions. Energies 10 (4), 539. Gabbatiss, J., 2018. Plastic-eating Enzyme Accidentally Created by Scientists Could Help Solve Pollution Crisis. https://www.independent.co.uk/news/science/plastic-eatingenzyme-pollution-solution-waste-bottles-bacteria-portsmouth-a8307371.html. Geissdoerfer, M., Savaget, P., Bocken, N.M., Hultink, E.J., 2017. The circular economyea new sustainability paradigm? Journal of Cleaner Production 143, 757e768. Goldstein, M., 2012. Pacific Plastic, Sea Skaters, and the Media: Behind the Scenes of My Recent Paper. http://www.deepseanews.com/2012/05/pacific-plastic-sea-skaters-and-themedia-behind-the-scenes-of-my-recent-paper/. Gradus, R.H., Nillesen, P.H., Dijkgraaf, E., van Koppen, R.J., 2017. A cost-effectiveness analysis for incineration or recycling of Dutch household plastic waste. Ecological Economics 135, 22e28. Grant, R., 2016. Why Scientists Are Losing the Fight to Communicate Science to the Public. https://www.theguardian.com/science/occams-corner/2016/aug/23/scientists-losingscience-communication-skeptic-cox. Green, D.S., Boots, B., O’Connor, N.E., Thompson, R., 2016. Microplastics affect the ecological functioning of an important biogenic habitat. Environmental Science & Technology 51 (1), 68e77. Guglielmi, G., 2017. In the next 30 years, we’ll make four times more plastic waste than we ever have. Science. http://www.sciencemag.org/news/2017/07/next-30-years-we-ll-make-fourtimes-more-plastic-waste-we-ever-have.

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Haward, M., 2018. Plastic pollution of the world’s seas and oceans as a contemporary challenge in ocean governance. Nature Communications 9 (1), 667. Hossain, M.U., Poon, C.S., Dong, Y.H., Xuan, D., 2018. Evaluation of environmental impact distribution methods for supplementary cementitious materials. Renewable and Sustainable Energy Reviews 82, 597e608. Huysman, S., De Schaepmeester, J., Ragaert, K., Dewulf, J., De Meester, S., 2017. Performance indicators for a circular economy: a case study on post-industrial plastic waste. Resources, Conservation and Recycling 120, 46e54. IP, 2017. Towards a Circular Economy-Waste Management in the EU. IP/G/STOA/FWC/2013001/LOT 3/C3. http://www.europarl.europa.eu/RegData/etudes/STUD/2017/581913/EPRS_ STU(2017)581913_EN.pdf. Jambeck, J.R., Geyer, R., Wilcox, C., Siegler, T.R., Perryman, M., Andrady, A., et al., 2015. Plastic waste inputs from land into the ocean. Science 347 (6223), 768e771. Korhonen, J., Honkasalo, A., Sepp€al€a, J., 2018. Circular economy: the concept and its limitations. Ecological Economics 143, 37e46. Lamb, J.B., Willis, B.L., Fiorenza, E.A., Couch, C.S., Howard, R., Rader, D.N., et al., 2018. Plastic waste associated with disease on coral reefs. Science 359 (6374), 460e462. MacArthur, E., 2017. Beyond plastic waste. Science. http://science.sciencemag.org/content/358/ 6365/843. PiP, 2017. Person in the Port Project. United Nations University, Bonn. http://collections.unu. edu/eserv/UNU:6349/PiP_Report.pdf. Plastics, 2017. Plastics - the Facts. PlasticsEurope. Brusselse Association of Plastics Manufacturers, Brussels. https://www.plasticseurope.org/download_file/force/1055/181. Politico, 2018. Hope for Circular Economy Jobs Could Be a Waste. https://www.politico.eu/ article/circular-economy-jobs-waste-garbage-trash-recycling/. Rochman, C.M., 2018. Microplastics researchdfrom sink to source. Science 360 (6384), 28e29. Soapbox Science, 2012. Reaching Out: Science Has a PR Problem. http://blogs.nature.com/ soapboxscience/2012/05/30/reaching-out-science-has-a-pr-problem. Stephan Schmidheiny with BCSD, 1992. Changing Course: A Global Perspective on Development and the Environment. MIT Press, Cambridge, MA. Sussarellu, R., Suquet, M., Thomas, Y., Lambert, C., Fabioux, C., Pernet, M.E.J., et al., 2016. Oyster reproduction is affected by exposure to polystyrene microplastics. Proceedings of the National Academy of Sciences 113 (9), 2430e2435. ten Brink, P., et al., 2018. Circular Economy Measures to Keep Plastics and Their Value in the Economy, Avoid Waste and Reduce Marine Litter. Economics Discussion Papers, No. 2018-3. Kiel Institute for the World Economy (IfW), Kiel. Van Eygen, E., Laner, D., Fellner, J., 2018. Circular economy of plastic packaging: current practice and perspectives in Austria. Waste Management 72, 55e64. Wei, R., Zimmermann, W., 2017. Biocatalysis as a green route for recycling the recalcitrant plastic polyethylene terephthalate. Microbial Biotechnology 10, 1302e1307. Wilcox, C., Van Sebille, E., Hardesty, B.D., 2015. Threat of plastic pollution to seabirds is global, pervasive, and increasing. Proceedings of the National Academy of Sciences 112 (38), 11899e11904. Winans, K., Kendall, A., Deng, H., 2017. The history and current applications of the circular economy concept. Renewable and Sustainable Energy Reviews 68, 825e833.

Techniques for separation of plastic wastes

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Silvia Serranti, Giuseppe Bonifazi Department of Chemical Engineering, Materials & Environment, Sapienza University of Rome, Rome, Italy

2.1

Introduction

Mechanical recycling, which is the processing of waste by physical means, represents the main approach to follow in order to recover plastics. This process typically includes different actions, such as collection, screening, manual and/or automatic sorting, size reduction, washing, extrusion, and granulation that may occur in different sequences and more than one at a time, according to the characteristics of the feed plastic waste, in terms of origin, size, shape, and composition (Hopewell et al., 2009; Ragaert et al., 2017). Foundation of each mechanical process, finalized to separate a specific material inside a flow stream containing other materials also, is to know the different properties of the target material, with respect to the actions to be applied (i.e., comminution, classification, separation). Important material properties useful to select the best separation strategies for segregation of plastic waste include: particle size, class distribution, density, magnetic and electric properties, color, shape, etc. Density usually represents one of the most utilized properties to perform material separation. Unfortunately, some polymers are characterized by very close values of density (Al-Salem et al., 2009); in these cases this property cannot be successfully utilized, especially to obtain high-quality single polymer streams. The need of powerful technologies to perform plastic waste separation, being at the same time cost-effective and able to guarantee high quality of products in terms of purity is more and more stringent in order to produce secondary plastics that are competitive in the market in comparison with the virgin polymers. In fact, the actual economic and environmental constraints dramatically increase the interest of many players (i.e., industries, recyclers, technology developers, engineers, etc.) both in waste-sorting technologies, for the production of high-quality secondary polymers, and in developing automatic sensors for quality assessment of waste-derived secondary polymers. On December 2015 plastic was in fact identified by the European Commission as a key priority in the “EU Action Plan for a circular economy” (COM, 2015) and in January 2018 a “European strategy for plastics in a circular economy” (COM, 2018) was adopted in order to use such a resource in a more sustainable way, including measures for the improvement in plastic sorting and recycling capacity and in quality of recycled plastics.

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00002-5 Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete

A mechanical process aimed to perform plastic waste recycling is based on the utilization of fast, accurate, and reliable tools and equipment specifically addressed to separate and recover single polymer streams, eliminating polluting elements (i.e., other polymers or other materials) present in the feed. As already stated, recycling plant layout has to be developed and managed taking into account the different polymers in the feed as well as the presence of other materials, both aspects in relation to the plastic waste sources (Ignatyev et al., 2014), that is: virgin and used ones. The polymer-based products that belong to the first source class (i.e., virgin waste) never reached the consumer (i.e., runners from injection molding, waste from production, changeovers, fall-out products, cuttings, and trimmings). These start-of-life plastic wastes are usually uncontaminated both from other polymers and/or nonpolymers. Obviously, they represent the higher-quality grades of polymer waste. End-of-life plastic wastes belong to the second source class (i.e., postconsumer waste). These latter can strongly vary both in quantity and in quality according to the collecting source and/or the adopted collecting strategies. Mechanical recycling can be applied to plastic waste sorting following two different approaches, that is, at macro- or microscale. Plastic macrosorting is usually performed when the waste flow stream contains the polymers to be recovered as macroobjects easy to be identified and separated. In this case, any specific mechanical action (i.e., size reduction/screening) has to be preliminary applied and waste plastics, usually bottles and containers, are separated. Specific polymer attributes are first detected by specialized sensing devices and according to their characteristics further separated, usually following air-blowebased strategies. Manual separation strategies are also applied and human knowledge is at the base of the separation, It is a labor-intensive, costly, and inefficient option, even if today plastic containers are labeled according to the constituting polymer and/or blend of polymers. Plastic microsorting is usually applied when waste plastics are recovered as flakes, that is, individuals resulting from milling actions, inside a flow stream of mixed waste characterized by different physical chemical attributes. In this case, handling costs decrease and the quantity of waste strongly increases, but more complex, and often also sophisticated technologies have to be designed, implemented, set up, and applied. These technologies (e.g., size reduction, screening, separation, etc.) are usually sequentially applied. In the latter case, sorting units and related logics, both addressed to separation and/or recovered polymer flow stream quality assessment play a preeminent role.

2.2 2.2.1

Plastic waste sources and typologies Production of plastic waste

Over the last 50 years the role and importance of plastics in our economy have grown steadily. World plastic production has increased twentyfold compared to the 1960s reaching 335 million tonnes in 2016 (Plastics the Facts, 2017), and should double in the next 20 years. In the EU, plastic production reached 60 million tonnes in

Techniques for separation of plastic wastes

11

2016. The largest plastic producers are China (29%), followed by Europe (19%) and NAFTA (18%). Despite the global increase in plastic production, the potential for recycling plastic waste is still largely unexploited. The reuse and recycling of plastic at the end of life are very low, especially compared to other materials such as paper, glass, and metal. The European plastics converter demand by segment in 2016 is reported in Fig. 2.1, showing that the packaging sector accounts for 39.9%, followed by building and construction (19.7%); automotive (10%); electrical and electronic equipment (6.2%); household, leisure, and sports (4.2%), agriculture (3.3%). Other sectors, including appliances, mechanical engineering, furniture, medical, etc., account for the remaining 16.7% (Plastics The Facts, 2017). In Fig. 2.2 the European distribution of plastic waste generation by segment in 2015 is reported. It is evident that the main source of plastic waste is packaging, accounting for 59% of the total plastic waste. It can be noticed that from production to waste, different plastic products are characterized by different life cycles, depending on their use, for example, plastic packaging has a service life of less than 1 year, plastic for industrial equipment can have a service life of 40 years or more. That is the reason why the volume of collected plastic waste in 1 year usually does not match the volume of plastic production. About 27.1 million tonnes of plastic waste were collected in Europe in 2016 (Plastics The Facts, 2017), of which 31.1% was collected for recycling, 41.6% for energy recovery and 27.3% still went to landfill. Even if the percentage of recycled plastics is quite low, a positive aspect is that in the past 10 years (from 2006 to 2016) plastic waste recycling has increased by 79% and landfill has decreased by 43%. Unfortunately, even if the EU situation is improving, in many countries landfill is still the first or second option for plastic waste. Concerning plastic packaging waste treatment, in 2016 recycling was the first option accounting for 40.9%, followed by energy recovery (38.8%) and landfill (20.3%). Plastic demand by different market sectors (%) Packaging 39.90% Building & construction 19.70% Automotive 10.00%

Electrical & electronic 6.20% Household, leisure & sports 4.20% Agriculture 3.30% Others 16.70%

Figure 2.1 Plastic demand by different market sectors in 2016. Plastics The Facts, 2017.

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Use of Recycled Plastics in Eco-efficient Concrete EU plastic waste generation (%) Others 14.00% Agriculture 5.00% Non packaging household 4.00% Electrical & electronic 8.00%

Packaging 59.00% Automotive 5.00%

Building & construction 5.00%

Figure 2.2 EU plastic waste generation in 2015. COM, 2018. A European Strategy for Plastics in a Circular Economy. p. 28.

It was estimated that plastic production and the incineration of plastic waste generate a total of about 400 million tonnes of CO2 per year (Ellen MacArthur Foundation, 2016). Increased use of recycled plastics can reduce dependence on fossil fuel extraction for plastic production and contain CO2 emissions. According to estimates (Rahimi and García, 2017), recycling of plastic waste from around the world could result in annual energy savings of 3.5 billion barrels of oil. Alternative types of raw materials are also being developed (for example, bio-based plastics or plastics produced from carbon dioxide or methane), which offer the same functionalities of traditional plastics with a potentially lower environmental impact, but currently represent a very small slice of the market. Very large quantities of plastic waste, generated both on land and at sea, are dispersed in the environment, causing considerable economic and environmental damage. Worldwide, between 5 and 13 million tonnes of plastics end up in the oceans each year, representing between 1.5% and 4% of the world production of this material (Jambeck et al., 2015). Plastic is estimated to account for over 80% of marine litter. The plastic residues are transported by sea currents, sometimes even for very long distances, and can be deposited on land, break up into microplastics, or form dense areas trapped in oceanic gyres. The phenomenon is accentuated by the increasing amount of plastic waste generated every year, also due to the growing diffusion of “single-use” plastic products, for example, packaging or other consumer products thrown away after only one short use, rarely recycled, and subject to being dispersed in the environment. These products include small packaging, bags, disposable cups, lids, straws, and cutlery, in which the plastic is widely used for its lightness, low costs, and practical features. New sources of plastic dispersion are also increasing, generating further potential risks to the environment and human health. Microplastics, defined as tiny plastic fragments smaller than 5 mm, accumulate in the sea, where, due to their small size, they can be easily ingested by marine fauna, and can also enter the food chain. Recent studies have found the presence of microplastics in the air, in drinking water, and in foods, and their impact on human health is still unknown.

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13

Furthermore, the increase in the market share of plastics with biodegradable properties creates new opportunities but also generates risks. In the absence of a clear labeling for consumers and without proper collection and processing of waste, it could lead to an increase in the dispersion of plastics and create problems for mechanical recycling. On the other hand, biodegradable plastics can certainly be useful for some applications and innovation in this sector is welcomed.

2.2.2

Typologies of polymers, characteristics, and uses

The term “plastic” is derived from the Greek word “plastikos,” meaning fit for moulding. This refers to the material’s malleability or plasticity during manufacture, which allows it to be cast, pressed, or extruded into a variety of shapesdsuch as films, fibers, plates, tubes, bottles, boxes, and much more. There are two categories of plastics: thermoplastics and thermosets. Thermoplastics can be melted when heated and hardened when cooled, the process is reversible. Due to their characteristics, they can be reheated, reshaped, and frozen many times Thermoplastics include polyethylene terephthalate (PET), low-density polyethylene (LDPE), polyvinyl chloride (PVC), high-density polyethylene (HDPE), polypropylene (PP), and polystyrene (PS) among others. On the contrary, thermosets undergo a chemical change when heated, so they cannot be remelted and reshaped. Thermosets are widely used in electronics and automotive products. Thermoset plastics include epoxy, polyester, melamine, phenol formaldehyde, vulcanized rubber, silicone, polyurethane (PUR), etc. Each plastic is identified by a resin code that was introduced to facilitate recycling operations (ASTM, 2014). In Table 2.1 a list of the main plastic types, with their typical applications, is reported. The most diffused polymers, according to plastic converter demand, are (Fig. 2.3): PP, LDPE, HDPE, PVC, PUR, PET, and PS. Such polymers are also the most abundant in plastic waste with some variations according to different lifespan of products. Polyethylene (LDPE and HDPE) is the most abundant polymer in plastic waste, due to their dominance in packaging applications, followed by PP, forming together the polyolefin family, accounting for 56.1% of plastic production demand. Other polymers, accounting for 19.3% of the total, are mainly represented by acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), polytetrafluoroethylene (PTFE), utilized in many different fields, such as medical, electronics, aerospace, etc.

2.3

The plastic recycling chain

The plastic recycling chain can be divided in the following operations: Collection

Manual sorting

Material/ Screening polymer sorting

Size reduction

Washing

Extrusion & granulation

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Use of Recycled Plastics in Eco-efficient Concrete

Table 2.1 Main plastic types and their typical applications Resin code

Polymer name

Applications

Polyethylene Terephthalate

Drink bottles, detergent bottles, clear film for packaging, food trays, carpet fibers

High-Density Polyethylene

Detergent bottles, mobile components, agricultural pipes, pallets, toys

Polyvinyl Chloride

Packaging for food, medical materials, pipes, window frames, cable insulation

Low-Density Polyethylene

Foil and films for dry cleaning, bread, frozen food, fresh produce and household garbage, toys, squeezable bottles

Polypropylene

Containers for food, medicine bottles, bottle caps, bins, automobile applications

Polystyrene

Disposable cutlery, cups and plates, meat trays, protective packaging for furniture, electronic items and toys

Other. Use of this code indicates that a package is made with a resin other than the six listed above, or is made of more than one resin and used in a multilayer combination.

Other packaging

European plastics demand by polymer types 19.3%

19.3%

17.5%

12.3% 10.0% 6.7%

PS

7.4%

7.5%

PET

PUR

PVC

HDPE

LDPE

PP

Figure 2.3 European plastics converter demand by polymer types in 2016. Plastics The Facts, 2017.

Others

Techniques for separation of plastic wastes

15

Each step of the chain affects the others. For example, the selection of the sorting technology will depend on the characteristics of collected plastic waste (types, composition, etc.) and the final destination of the recovered product will depend on its quality. Collection is carried out adopting different systems, depending also on the different sources, such as plastics from household waste and from industrial waste. Collection can be, for example, monomaterial, if plastic is collected as source-separated fraction, or multimaterial, if plastic is collected with other packaging materials (aluminum, glass, etc.). Manual sorting is usually necessary at the beginning of the recycling process for the preliminary removal of films, cardboard, and bulky items and is usually carried out by operators checking the waste stream on the conveyor belt. Screening is applied to remove small objects such as glass and stones. Typical screening equipment are drum or vibrating screens. Usually waste is divided into three fractions: undersize (300 mm). Usually plastic is concentrated in the middle size fraction. Material/Polymer Sorting has the aim to obtain high-quality recycled plastic products, preferably single polymer stream. Sorting technologies are based on different physical-chemical properties of waste materials, such as shape, density, size, color, or chemical composition of objects. Material sorting consists in the removal of the unwanted contaminants such as pieces of metals, glass, paper, etc., from the plastic waste stream. Polymer sorting is applied to separate polymers by type; this step is of paramount importance in order to obtain high-quality single polymer stream. The different plastic waste separation technologies are described in Section 2.4. Size reduction is usually carried out by shredding or cutting techniques; such operations can be present before or after the sorting step, depending on the plant layout and on the typology of plastic waste stream. Plastics are usually shredded in flakes having a size of 5e10 mm. Extrusion and granulation: this step is necessary to produce a granulate which is easier to use for converters than flakes. The polymer flakes are fed into the extruder, are heated, and then forced through a die to form a continuous polymer product (strand) which can then be cooled in a water bath before being pelletized. The granulation process is used to reduce the strands to pellets which can then be used for the manufacture of new products.

2.4

Plastic waste separation technologies

Plastic waste separation has the main aim to remove unwanted contaminants (such as metals, glass, etc.) and to obtain high purity polymers. In the following sections the different separation technologies usually adopted in plastic recycling plants are described. The choice of the technology (or combination of more than one technology) will depend on the feed characteristics and on the quality requirements for the output products, for example, single polymer stream or mixed polymer stream.

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2.4.1 2.4.1.1

Use of Recycled Plastics in Eco-efficient Concrete

Gravity separation Dry

Air classifier Air classifiers use air as the medium to separate lighter materials from heavier ones. The waste stream enters the column with a raising current of air and lighter objects are blown upward whereas heavier ones are dropped down (Fig. 2.4). Air classifiers are usually utilized to remove light contaminants such as dust, small foam particles, paper, glass powders, and polymer foils from the main plastic waste stream. To reach this goal, aspirators, wind sifters of air-cyclonesebased techniques are utilized. The separation occurs based on the different behavior of particles when subjected to a stream of air. Even if the separation principle is quite simple, air-based classification has to take into account different parameters (i.e., particle density, morphological and morphometrical characteristics) that interact with single polymer terminal velocity, thus affecting separation efficiency and corresponding operative setup (Shapiro and Galperin, 2005). Air classifiers can be utilized after a gravity separation step or at the beginning of the process before or after a preliminary comminution stage, to properly handle/separate complex plastic-rich parts from end-of-life durables (e.g., automotive-derived parts, electrical and electronic devices, appliances, etc.).

Ballistic separator Ballistic separation is based on a simple principle, that is, the different movement characteristics of particles of different size, shape, and weight, spatially defined as 2D or 3D structures (Christensen and Fruergaard, 2011). Ballistic separation can be successfully utilized both for mixed waste containing plastics and for plastic waste streams. In the first case, film, paper, cardboard, textiles, and fibrous materials can be assigned to a 2D flat and light class of products; on the contrary, plastic containers, bottles, stone, Light

Feed

Air stream

Heavy

Figure 2.4 Schematic representation of an air classifier.

Techniques for separation of plastic wastes

17

wood, cans, and ferrous materials can be assigned to a 3D class of rolling and heavy products. In the second case, films and flakes belong to 2D individual domains; on the contrary, containers and/or crumpled containers belong to 3D individual domains. In both cases separation occurs thanks to the utilization of a so-called ballistic separator, or ballistic screen. Such a device is usually constituted by a series of screening paddles, or perforated plates, whose number, size, and shape profile can vary according to the feed rate and physical characteristics of the waste materials, affected by an orbital motion and characterized by an inclined position, usually ranging from 10 degrees to 20 degrees. The materials fed to this separator, according to their 2D or 3D structure and physical characteristics (i.e., weight, morphological and morphometrical characteristics) follow different trajectories with respect to the orbital blades movement. The 2D and light materials are conveyed to the upper part of the ballistic separator, whereas 3D, heavier, and “rolling” individuals move toward the lower part of the separator. The continuous shaking of the waste produces also a screening effect: particles characterized by a size smaller than the distance between the different screening paddles pass through, generating a third flow stream.

2.4.1.2

Wet

Sink-float separation Sink-float separation processes are based on the utilization of the different density properties of materials. Separation is based on the fact that when materials are introduced in a tank containing a fluid of a specific density, lighter materials will float and heavier ones will sink (Fig. 2.5). A sink-float separation unit is efficient when materials are characterized by quite different density values (Callister and Rethwisch, 2010). Therefore this method can be used to separate plastics from heavier materials, or polymers characterized by different densities (i.e., PET from PP/PE or ABS from

Floating plastic flakes

Sinking plastic flakes

PP, HDPE, LDPE Float plastics with specific gravity < 1 g/cm3 Sink plastics with specific gravity < 1 g/cm3

Figure 2.5 Sink-float separation.

PVC, PET, ABS Water specific gravity = 1 g/cm3

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Use of Recycled Plastics in Eco-efficient Concrete

PS), whereas it cannot be utilized for separation of polymers characterized by quite close density values, as for example polyolefins (PP, LDPE, HDPE). Presence of contaminants, air bubbles on polymer surface, polymer alteration, fillers, and additives can affect separation efficiency.

Jigging Jigging is one of the oldest methods of gravity concentration (Hori et al., 2009). Jigging can be defined as an “enhanced gravity based separation” method: a water stream is pulsed, or moved by pistons upward and downward, through the material bed. Individuals are separated according to their densities, but also thanks to the systematic and repetitive applied pulsation, whose frequency and amplitude is strictly related to physical, morphological, and morphometrical attributes of materials. With reference to plastic waste, this procedure is quite efficient in many cases, allowing to enhance polymer separation with respect to their relatively low density differences. Thanks to the repetitions of these actions, particles stratify, across the bed height, according to their specific density: the heaviest form the lowest layer and the lightest constitute the highest.

Hydrocycloning Hydrocycloning is a density sorting technology based on the centrifugal/centripetal forces and fluid resistance of different particles having different characteristics (Bradley, 1965). A slurry is usually fed to the cyclone. A selected solid/liquid ratio and operative pressure is adopted. As a result, the fluid pressure transfer produces, inside the device, a rotational fluid motion, thus permitting separation among the different materials (i.e., polymer-contaminant or polymer-polymer characterized by different densities). Lighter fractions will be transported to the upper part of the cyclone, the heavier ones to the bottom (Fig. 2.6). Light plastics stream Plastic waste feed

Heavy plastics stream

Figure 2.6 Plastic hydrocyclone separator.

Techniques for separation of plastic wastes

19

Materials have to be properly milled before hydrocyclone-based sorting. The separation mechanism can be synthetically summarized as follows. The slurry is tangentially fed to the inlet, causing the material to rotate within the vessel and ultimately to form a vortex. Heavier materials are forced outward by centrifugal force and down from the barrel section into the cone section. Materials heavier than fluid (i.e., usually water) flow down the inner wall and exit through the apex; the lighter materials sweep into the center vortex by inward fluid motion and are carried out to the outlet. When hydrocyclones are selected, several factors have to be considered in order to reach an optimal and efficient utilization: the need of relatively complex fluiddynamic circuits (i.e., presence of pumps, storage bins, pipes, valves, etc.) and the need to perform a strict feed characteristics control (i.e., constancy of water/solids ratio, polymers particle morphological and morphometrical characteristics, polymers surface status).

2.4.2

Electrostatic separation

Electrostatic separation is usually applied when dielectric particles are handled. Dielectric particles, when electrostatically charged, can be separated according to their polarity charge (Reinsch et al., 2014). The electrostatic separation architecture is commonly constituted by two electrodes: one positive and the other negative. Particle charging conditions and modality are of paramount importance in this kind of separation. Plastic particles charging is usually carried out utilizing the triboelectric effect. This effect is based on rubbing together plastic waste particles of different characteristics; as a result they transfer their electrical charge and surfaces are thus affected by different electrical charges allowing to perform separation inside an electric field where also charged electrodes are present. For example, charged plastics falling down freely in the area between two electrodes change their trajectory due to the mobilized attractive/repulsive electrostatic forces and as a consequence can be “easily” collected and separated (Fig. 2.7). This separation can be successfully applied with reference to several polymers, according to the triboelectric charging sequence (Dodbiba et al., 2001): ðþ Þ ABS  PP  PC  PET  PS  PE  PVC  PTFE ð Þ When two plastics in this sequence are rubbed against each other, the plastic closer to the positive end is charged positively and the one closer to the negative end is charged negatively. For example, if PVC is rubbed against PET, PVC is charged negatively and PET positively. On the contrary, when PET is rubbed against PP, PET is charged positively and PP negatively. Main disadvantages of this separation are linked to: (1) the operative conditions (i.e., plastics and more in general the waste stream have to be dry), (2) particle size and shape (i.e., particle surface characteristics and particle size affect the “chargeability”), (3) presence of additives/fillers (Albrecht et al., 2011) and, finally, (4) presence of dirtiness on particle surface that can change or inhibit particle surface charging.

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Use of Recycled Plastics in Eco-efficient Concrete

Plastics waste feed

Tribocharger

Negatively charged particles Positively charged particles

Positive electrode (+)

Negative electrode (–)

Output products

Figure 2.7 Schematic representation of a triboelectric separation process.

2.4.3

Magnetic density separation

Magnetic density separation (MDS) is a density-based sorting process realized utilizing a “magnetic fluid” constituted by a liquid (i.e., water) and magnetic particles (i.e., iron oxide particles of about 10e20 nm) suspended in the liquid (Bakker et al., 2009). Through a special magnetic field (Rem et al., 2013) an artificial gravity is produced, as a magnetic force. Such a force varies exponentially in the vertical direction, and the effective density of the liquid also varies accordingly in the same direction. The result is that waste particles (i.e., plastic particles) will float in the liquid at a level where the effective density is equal to their own density. In other words, particles characterized by different densities are suspended at different heights (Hu et al., 2013). Adopting this strategy, it is thus possible to separate plastic particles characterized by very close density values, such as PP and PE (Serranti et al., 2015) (Fig. 2.8) and PVC and rubber from construction and demolition waste (Luciani et al., 2015). Particular care has to be addressed to the correct fulfilling of the following fundamental steps: (1) wetting, to make the polyolefin surface hydrophilic (Hu et al., 2010), (2) feeding, separating, and collecting to avoid turbulence in the flow stream, before, during, and after the separation, negatively affecting particle flow inside the magnetic fluid.

Techniques for separation of plastic wastes

21

Magnet PP

Plastic waste feed

Splitter PE Ferro fluid

PP PE

Mixing zone

Separation zone

Collection zone

Figure 2.8 Schematic representation of a magnetic density separation system for PP and PE.

Such technology is very useful to produce high-quality secondary raw materials, that is, single polymer stream with a very low presence of impurities.

2.4.4

Flotation

Flotation processes are based on the different surface wettability properties of materials (Wang et al., 2015). In principle, flotation works very similarly to a sink and float process, where the density characteristics of the materials, with respect to that of the medium where they are placed are at the base of the separation. Sometimes a centrifugal field is applied to enhance separation. Flotation works in a different way in the sense that in a liquid medium, usually water, a “carrier” is introduced, air bubbles, responsible to float hydrophobic particles that adhere to the bubbles with respect to the hydrophilic ones that sink. According to surface plastic characteristics, this technique can be profitably applied, in principle, to separate waste polymers (Fraunholcz, 2004). To enhance or reduce plastic surface characteristics (i.e., hydrophobic or hydrophilic) appropriate collectors, conditioners (Singh, 1998; Shen et al., 2002), and flotation cell operative conditions (i.e., air flow rate, agitation) can be utilized. Usually plastic flotation is carried out in alkaline conditions (Takoungsakdakun and Pongstabodee, 2007). Once floated, hydrophobic polymers are recovered as well as the sunk ones (i.e., hydrophilic) at the bottom of the cell. This technique, even if it is well-known (Buchan and Yarar, 1995) and in principle quite powerful is not widely used mainly for three reasons: (1) it is a wet technique, this means that water has to be recovered and processed before reutilization, due to the presence of the reagents and contaminants, (2) polymer surface status (i.e., presence of dirtiness/pollutants and/or of physical/chemical alteration) can strongly affect floatability, and (3) large variation of waste plastics feed in terms of composition. Flotation allows to separate PS, PVC, PET, PC, and mixed polyolefins (MPO).

2.4.5

Sensor-based sorting

Plastic sorting, with respect to other materials, and/or different polymers, is usually carried out utilizing specific materials’/polymers’ physical properties allowing separation. Separation often occurs defining handling architectures (i.e., separation

22

Use of Recycled Plastics in Eco-efficient Concrete

equipment) designed and set up in order to enhance how waste particles behave in respect of the selected property to perform separation. This behavior is usually accomplished, as previously stated, through particle trajectory changes at the device output/s and/or through concentration in different section of the separation equipment. The mechanical removal of these different streams generates concentrates, wastes and, in some cases, one or more intermediate compositional product classes, called “middlings.” Material physical property can be thus considered as the “direct” responsible of separation. The adoption of sensors to perform sorting means to follow a different approach, requiring the utilization and the implementation of online analytical logics and robotic units to perform the separation. Materials in fact, have to be first detected, then identified and topologically assessed in the stream; after these steps automated devices realize the sorting. Following this approach, it substantially means to take into account two aspects. The first one is linked to the sensing principle selected to perform materials identification and the second one is related to the required actuators logics/architectures utilized to collect the materials of interest from the investigated waste flow stream. Sensorbased sorting techniques are thus substantially classified according to these principles (i.e., sensing and collection). In all cases there are three main components of the sorting architecture: a conveyor belt for materials feeding, a sensor connected to a computer analyzing data collected from the waste stream on the conveyor belt, and a pneumatic system to mechanically separate materials (Fig. 2.9). Sensors do not require contact with the materials and are nondestructive.

2.4.5.1

Visible spectroscopy

Sorting in the visible range is mainly focused on the utilization of spectroscopic analytical techniques, performed in the wavelength range 400e700 nm, or on the adoption of digital imaging. Both the approaches are not particularly efficient in the case of plastic recycling, being that the detection principle is mainly based on what is detectable according to investigated individuals’ pictorial attributes, that is, visible spectra, when spectroscopy analysis is performed, or digital color components (RGB, HSY, etc.), size, shape, and surface textural attributes when imaging is applied (J€ahne, 1993). Feed waste

Sensor

Air gun

Conveyor belt Material 1 Material 2

Figure 2.9 Schematic representation of a sensor-based sorting system.

Techniques for separation of plastic wastes

23

Both the approaches are not very efficient to perform polymer sorting; for this reason, they are not widely utilized except sometimes at the beginning of the process and when polymers are constituted by large products (i.e., several centimeters) whose color and/ or shape (Zhu and Basir, 2006) can be associated to a known specific polymer-based manufactured product (i.e., container, pipe, frame, etc.). They can be used also at the end of a plastic recycling process to sort by color a monomaterial stream of plastics, as for example, green, blue, and transparent PET.

2.4.5.2

Near infrared spectroscopy

Near infrared spectroscopy (NIR) is probably the most utilized technology in plastic recycling. It is based on the collection of reflected spectra of polymers properly energized by a light source (Beigbeder et al., 2013). The investigated wavelength range is usually 1000e700 nm; in some cases it is extended to the SWIR region (1000e2500 nm). The NIR sensor sorting system includes: a conveyor belt, illumination system and optical sensor, a separation unit with compressed air nozzles. Many different polymers can be separated by near infrared sensors as they are characterized by different spectral signature in such wavelength range (i.e., PP, PE, PVC, PET, PS, etc.). Plastics can be also separated from other materials, as paper, wood, glass, stones, etc. The reasons of the wide use of this technique are mainly related to: (1) NIR does not require any direct contact with the investigated object, (2) it can be applied defining very flexible architectures, thanks to the possibility to largely utilize fiber opticse based architectures both to energize and to collect the spectral response of plastics (i.e., analysis and identification, in respect of previously set up reference spectral libraries of the different polymers’ infrared absorption bands), (3) high detection/identification speed, (4) multiple detection (i.e., multiple check of the same sample), and (5) no color interference. The size of flakes to be sorted as well as flakes disposal on the conveyor belt plays an important role, affecting the sensor detection. Sensing probes, in fact, are characterized by a physical dimension that influences the investigated image field and, as a consequence, the analytical spatial resolution of the single sensing unit (i.e., usually installed as an array). Black or very dark polymers are almost impossible to be identified due to their low surface reflectance.

2.4.5.3

Hyperspectral imaging

Hyperspectral imaging (HSI) is an innovative fast, and nondestructive technique able to collect both spectral and spatial information from an object. The collected information generates a data structure defined “hypercube,” that is a dataset containing both spatial data (i.e., pixel coordinates: x and y axis) and spectral data (i.e., z axis, representing the spectrum associated to each pixel). The investigated spectral range depends on the sensor mounted on the device and can vary from VIS to NIR, SWIR, or MWIR regions, depending on applications. The application of this technique dramatically grew in these last years in many sectors (i.e., chemical, pharmaceutical, agricultural, food industry, etc.) and also in recycling: glass recycling (Bonifazi and Serranti, 2006), compost product quality control (Dall’Ara et al., 2012), recycled aggregates

24

Use of Recycled Plastics in Eco-efficient Concrete

from concrete (Serranti and Bonifazi, 2014; Bonifazi et al., 2015, 2018b) and characterization of different plastic waste (Serranti et al., 2012a,b; Hu et al., 2013; Ulrici et al., 2013). This large use is intimately linked to some intrinsic characteristics of the HSI sensing device (Bonifazi and Serranti, 2014) as: (1) the possibility to perform a continuous monitoring of waste large flow streams as disposed on a conveyor belt thanks to the scan line camera architecture, (2) easy topological definition of the individual to sort, (3) utilization of different time scaleerelated sampling strategies, in case of specific product oriented control/quality actions to develop, (4) implementation of fast and reliable recognition logics, strongly linked to HSI detectors characteristics (e.g., possibility handle spectra, images, or both spectra and images), (5) total absence of environmental impacts and/or safety constraints related to the HSI utilized device, and finally (6) relatively low cost of the device. With reference to polymer recycling, HSI is particularly powerful (Jansen et al., 2012) allowing to implement online sorting and/or quality control strategies, thanks to the possibility to identify the spectral regions, in the NIR/SWIR range (1000e1700 or 1000e2500 nm), where polymer molecules absorb light by overtone or combination vibrations (Workman and Weyer, 2007). This behavior produces spectral signature characteristics of the polymer thus allowing its identification (Bonifazi et al., 2018a). In the last years, high-speed spectral cameras working in the MWIR wavelength range were introduced in the market in order to sort black polymers that are not classified by sensors working in the commonly investigated spectral ranges (400e2500 nm) due to the higher light absorption and the consequent low reflectance (e.g.,: Rozenstein et al., 2017). HSI-based sorting architectures are usually constituted by a conveyor unit (i.e., belt) carrying materials to sort (Serranti et al., 2006). A sensing unit inspects and continuously acquires spectra at a fixed rate. Spectra are then processed by a classification engine previously set up, according to a material spectral reference library, and individual/s recognition is performed. An array of compressed air nozzles mounted at the end of the conveyor belt provides to separate through a shot of air the recognized individuals (Tatzer et al., 2005; Pic on et al., 2010).

2.4.5.4

X-ray fluorescence

Sorting based on X-ray fluorescence (XRF) is based on the detection of the emitted wavelengths, as well as of the released energy, by a sample previously energized by X-ray whose atoms release energy generating an X-ray fluorescence radiation. The elements contained in the sample influence the emission both in terms of wavelengths and energy. Such a technique is quite powerful and it is largely used in the waste sector, mainly in wood recycling (Blassino et al., 2002) to evaluate the presence of potential harmful elements (i.e., arsenic, chromium, copper, etc.). In the waste plastic sector, this technique is primarily utilized to sort PVC from PET (Brunner et al., 2015). The use of this technique is expected to increase in the future, as it can be applied to the separation of brominated plastic from an input stream of shredded plastics. Bromine is in fact largely used as flame-retardant, especially in electronic devices. Other XRF-based approaches have been proposed as the Energy

Techniques for separation of plastic wastes

25

Dispersive X-ray Fluorescence (EDXRF) (Bezati et al., 2011) adding tracers to the polymer matrix. Sorting architectures are similar in both cases (i.e., XRF and EDXRF). Referring to EDXRF, the operative unit is constituted by an X-ray beam energizing the waste flow stream (i.e., particles transported on a conveyor belt) to analyze and sort. X-ray beam is focused and passed through the material until it reaches the detector. The signal collected by the detector is processed, the presence of tracers identified, their amount evaluated, and according to predetermined rules, the corresponding plastic individuals blow out by air. XRF does not require any sample preparation/collection; it can identify black and/ or very dark polymers, as well the presence of contaminants on polymers surface and as individuals. The disadvantages of this technique in plastic sorting is that it is not able to distinguish between polymers. Furthermore, there are some safety constraints related to the utilization of X-ray sources.

2.4.5.5

Laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is an analytical technique based on the utilization of high power laser pulse that performs an ablation of the sample to analyze, thus producing plasma plumes (Cremers and Radziemski, 2006). The radiation produced by the ablated portion of the investigated material is then analyzed by a CCD-based spectrometric device (Gondal et al., 2007). Following this approach (i.e., identification of the atomic emission lines), it is thus possible to analyze the properties of waste in terms of constituent materials (Sattler and Yoshida, 1993) and/or, as in the case of polymers, elements present as carbon and hydrogen and their resulting line intensity ratio (C/H) (Anzano et al., 2008). Recently a compact and reliable architecture was proposed to perform the recognition of polymer particles following a statistical analysis starting from the information collected by the so-called laser-induced plasma spectroscopy (LIPS) and processed performing linear and rank correlations, in the wavelength interval: 200e800 nm (Anzano et al., 2006) or performing, as previously outlined, instant ratio analysis of molecular bands to identify the different energetic materials (Anzano et al., 2011). Following this latter approach PVC, PS, PET, PP, LPDE, and HDPE can be identified. Sorting architecture is constituted by mechanical units that, according to the LIPS based detection, sort polymers into their respective bins.

2.4.6

Auxiliary separation technologies

Auxiliary separation technologies, referred to as plastic waste recycling, are those allowing to clean the plastic waste stream from the presence of other materials with different characteristics and/or nature. They are usually applied at the beginning (i.e., scalping) or at the end (i.e., refining) of the process. Materials usually removed through such techniques are: (1) ferrous metals, as low-grade stainless steel, nickel alloys, etc., (2)nonferrous metals, as aluminum. Magnets (Wills, 2016) and Eddy current (Rem, 1999) based separators, respectively, are commonly utilized.

26

2.4.6.1

Use of Recycled Plastics in Eco-efficient Concrete

Magnetic separation

The magnetic separation is commonly applied utilizing belt magnets, magnetic head pulleys, and drum magnets (Svoboda, 2004). Schematic representations of the different typologies of magnetic separators are reported in Fig. 2.10. In belt magnets, the magnet is usually installed above the plastic waste flow stream (Fig. 2.10a). Belt magnet

Feed waste

(a)

Conveyor belt Magnetic particles Non magnetic particles Feed waste

(b)

Magnetic head pulley

Conveyor belt Magnetic particles Non magnetic particles Feed waste

(c)

Conveyor belt Magnetic particles Non magnetic particles Magnetic drum

Figure 2.10 Different typologies of magnetic separators. (a) Overbelt magnetic separator; (b) Magnetic head pulley separator; (c) Magnetic drum separator.

Techniques for separation of plastic wastes

27

The overhead magnetic field has a belt moving across its surface at approximately a 90 degree angle to the material flow. Ferrous metal particles are thus attracted, removed from plastics, and discharged, as the moving belt of the separator turns away from the magnetic field. Magnetic head pulleys are usually installed at the end of a conveyor belt, beneath the belt (Fig. 2.10b). Ferrous metal particles are thus held to the belt, while plastics can be downloaded. Drum magnets are commonly installed inside feeder chutes, between chutes and conveyors (Fig. 2.10c). Ferrous metals are held by the drum, until a divider provides to its discharge; on the contrary, plastic wastes continue their flow. All the previous mentioned devices are normally positioned at the beginning of the plastics recycling plant having the aim to remove large magnetic polluting individuals. To perform a strong refining/control of the final products, high-intensity permanent magnets are usually utilized (Svoboda and Fujita, 2003.).

2.4.6.2

Eddy current separation

Eddy current separation is based on the use of a high speed magnetic rotor system and is used to remove nonferrous metals (i.e., aluminum and copper) from waste plastic streams. Due to the high speed of the rotor, an electric current, called Eddy current, is induced into conducting metals. The induced electric current produces a magnetic field, opposed by the field created by the rotor, repelling the conducting metals. The remaining materials such as plastics, glass, and other dry recyclables will simply freefall over the rotor, separating them from the repelled metals (Fig. 2.11). Eddy current separators are usually located in the preliminary stages of the process. Such a choice is mainly due to the fact that Eddy current separation process is highly dependent on the size of the feed particles according to its separation principle. The magnitude of the repulsive forces depends on the specific conductivity, mass, morphological and morphometrical characteristics of the particles, and on the intensity and distribution of the magnetic field (Van der Walk et al., 1986).

Feed waste Magnetic high-speed rotor

Conveyor belt

Non metal particles Non ferrous metal particles

Figure 2.11 Schematic representation of an eddy current separator.

28

2.5

Use of Recycled Plastics in Eco-efficient Concrete

Recycled plastics quality control

The quality certification of recycled plastic products is fundamental to increase their economic value and to foster their penetration in the market. Product quality assessment is an important aspect in all industrial manufacturing sectors, but this is particularly true for the recycled materials whose market is still hindered by many barriers. Recycled polymeric materials are expected to have the same high quality and performance characteristics of those of the corresponding virgin polymers; however, the achievement of high quality levels requested by the end users through the mechanical recycling process is not an easy task. Furthermore, many plastic brand owners and manufacturers distrust recycled plastics and fear that they cannot assure their need of high volumes of reliable material with clearly defined constant quality specifications. As a consequence, there is a low demand for recycled plastic, especially in high value products, and its use is often limited to low-value or niche applications (COM, 2018). It is evident that there is a strong need not only to ensure and to improve quality of plastic recycled products through technological innovation in the recycling process, but also to develop and define specific quality standards for recycled plastic products. The quality requirements must be related to the different applications of plastic products such as food contact or durable goods like electronics and automobiles. Recycled plastics can vary from virgin resins in a number of ways, including contamination originated from multiple sources (e.g., impurities, the use-phase, misuse, degradation, improper separation of materials, legacy substances, or crosscontamination during waste collection). Such incidental contaminants can affect the quality and safety of recyclates and therefore fast, cost-effective quality control strategies should be developed and implemented at plastic recyclers’ premises, in order to produce a certified output that meet customer specifications (Vilaplana and Karlsson, 2008).

2.5.1

Recycled plastics quality measurements

The quality assessment of recycled plastic products should be based not only on the same testing equipment commonly utilized for virgin resins, but also on specific characterization measurements related to the possible contamination and degradation of a plastic recycled material. Traditionally the basic measurements to evaluate plastic product quality and performance in different applications are rheological and mechanical properties (e.g., melt flow rate, tensile and impact strength, etc.). For recycled plastics it is important to assess also other important properties that can affect quality, such as the degree of mixing, in terms of presence of polymeric impurities in a single polymer stream, the level of degradation (chemical and structural/textural alteration), and the presence of low-molecular weight compounds such as contaminants, additives, etc. (Karlsson, 2004; Vilaplana et al., 2007). One of the main challenges related to the production of plastic recycled materials lies in the fact that different polymers are incompatible and immiscible at molecular level; even low levels of contaminations will affect the quality of the target stream,

Techniques for separation of plastic wastes

29

for example, the presence of small amounts of PVC in a PET stream will make it brittle and yellowish when recycled (Hahladakis and Iacovidou, 2018). It follows that plastic must be recycled as much as possible in single polymer streams. For a plastic producer, stability in composition of the plastic raw material fed to the plant is very important, since even small variations in melting point or other properties can affect the production, in terms of functionality, strength, or durability of products that is not acceptable for some high-tech applications such as medical devices or automobile components. This means that a constant and stable composition of a recycled plastic stream must be assured. The methods commonly utilized to check the quality of a single polymer recycled stream in terms of presence of other polymers are applied at laboratory scale, which means time-consuming operations, involving the presence of a trained operator, a sample collection, and preparation step. Examples of commonly adopted techniques at laboratory scale are DSC (Differential Scanning Calorimetry) and FT-IR (FourierTransform Infrared Spectroscopy). An alternative solution to check the quality of the recycled plastic products is the use of hyperspectral imaging that can be applied online directly on the conveyor belt without any sample preparation (Serranti et al., 2011; Luciani et al., 2015) (Fig. 2.12). Polymer mixing evaluation can be achieved through the definition of classification models, allowing the identification of different plastics at the same time. HSI in the NIR/SWIR wavelengths ranges (1000e1700/2500 nm) coupled with chemometrics were successfully applied to set up fast and reliable quality control strategies at recycling plant scale (i.e., better and more strict control of sorting and separation process stages) with reference to many different polymers, including PP, HDPE, LDPE, PET, PVC, etc. (Bonifazi et al., 2018a).

Spectral-imaging instrumentation Illuminant

Monitor

Moving belt

Console

PC

Figure 2.12 HSI platform working in the NIR range (1000e1700 nm) developed for quality control of different recycled polymers.

30

Use of Recycled Plastics in Eco-efficient Concrete

The possible presence of harmful substances can also limit the use of recycled plastic as secondary raw materials, especially in applications related to food packaging, due to possible dangerous contamination. X-ray fluorescence can be used to check the presence of hazardous materials and elements, such as brominated flame retardants and chlorine-containing materials, both of which can only be detected at the elemental level through X-ray analysis. Other analytical techniques can be used to determine the presence of additives in plastics, such as inductively coupled plasma optical emission spectrometry (ICP-OES) or LIBS (Vilaplana and Karlsson, 2008).

2.6

Technical challenges in plastic recycling

In the following sections, some of the main current hot research topics on plastic recycling are introduced.

2.6.1

PP-PE separation

Polypropylene and polyethylene, belonging to the family of polyolefins, are the most produced plastics at global level. A mixture of PP-PE is commonly an output of a recycling plant treating plastics, especially when dealing with household waste due to their wide use in packaging. However, in order to produce high-quality secondary polyolefins that means single polymer streams, a purity of at least 97% must be reached (Bakker et al., 2009). MDS, as already mentioned in Section 2.4.3, was proposed as a powerful technology to separate PP and PE (Fig. 2.8). Its innovation is based on the use of a medium characterized by a gradient of density, allowing to separate not only materials with very low differences in density, as PP and PE, but also more than two materials in one single step (Serranti et al., 2015).

2.6.2

LDPE-HDPE separation

LDPE and HDPE are both semicrystalline polymers but the degree of crystallinity is higher for HDPE and lower for LDPE, due to the different number of polymer branches (da Silva and Wiebeck, 2017). Their mechanical separation is not an easy task, due to their very similar physical characteristics, and especially their density (i.e., LDPE: 0.926e0.939 g/cm3 and HDPE: 0.940e0.965 g/cm3). The possibility to correctly identify these two polymers by fast and reliable methods working online is still a challenge and represents an important goal to reach. In a recent study, an innovative strategy based on SWIR-HSI was explored allowing LDPE, HDPE, and other polymers to be recognized in one shot in a plastic waste flow stream (Serranti et al., 2018) (Fig. 2.13). The study was carried out at laboratory-scale, but it is very promising and it could be applied in the near future also at plant-scale, thanks to the fast growing of HSI technologies and corresponding computing power.

Techniques for separation of plastic wastes

31

(a) 0.9 PVC PP PS LDPE HDPE

0.8

Reflectance

0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 1000

1500 2000 Wavelength (nm)

2500

(b) PP LDPE HDPE PS

PVC

Figure 2.13 a) Average reflectance spectra in the SWIR range (1000e2500 nm) of different polymers; (b) source image and corresponding prediction map of the different polymers obtained by the application of classification algorithms on hyperspectral images.

2.6.3

Black or dark color polymers

Recycling of end-of-life black or dark color plastics is hampered by the availability of suitable technology to sort them by polymer type (Turner, 2018). NIR sensorbased sorting, commonly adopted in plastic recycling plants, is unable to identify black or dark color plastics, usually colored with carbon black, due to their very low reflectance in this investigated spectral region. Recent studies explored the potential of MWIR detection (3e12 mm) in black plastic waste sorting (Rozenstein et al., 2017). Black or dark color polymers are in fact characterized by specific absorption features in this spectral range. The first integrated efficient industrial equipment to sort black polymers using MWIR technology have started to be commercialized in the last years.

32

2.6.4

Use of Recycled Plastics in Eco-efficient Concrete

Biopolymers

Biodegradable plastics can be mistaken for and mixed with conventional plastics, contaminating recyclate streams, as they cannot be recycled using conventional mechanical recycling techniques. In recent years, the biopolymer PLA (polylactic acid) has been introduced in the market as an environmentally friendly packaging solution alternative to the very popular PET. PLA is biodegradable and compostable, being entirely made from corn or sugarcane, and it is characterized by a look and feel very similar to that of PET. As a consequence of its diffusion, the recycling industry started to be concerned by the use of this biopolymer, since the potential contamination of PLA in the PET recycling stream can have a negative impact on the physical properties, for example, on molecular weight, of extruded rPET, making the material unfit for use (La Mantia et al., 2012). The use of HSI in the NIR range (1000e1700 nm) was successfully applied to recognize and classify PET and PLA polymer flakes, in order to develop an innovative strategy for quality control and/or sorting action in plastic recycling streams (Ulrici et al., 2013) (Fig. 2.14).

2.6.5

Marine plastics

The quantity of marine plastics dramatically grew accordingly to the increased production of polymer-based goods (C ozar et al., 2014, 2015, 2017) and their improper disposal at their end-of-life (Barnes et al., 2009; Hidalgo-Ruz et al., 2012; Andrady, 2017). Marine plastic litter originates from several sources, both land- and sea-based. It can be found on beaches, seafloor, and water (Pham et al., 2014; Suaria and Aliani, 2014; Munari et al., 2016). Once plastic litter enters the ocean, it undergoes degradation processes due to UV radiation, oxidation, and wave action (Claessens et al., 2013), inducing fragmentation and the generation of abundant small plastic particles (Cozar et al., 2014), the so called microplastics, that is waste polymers individual below 5 mm. These small particles can easily enter the marine food chain, transferring

(a)

(b)

(c)

White tile Transparent PLA flakes Transparent PET flakes Expanded PLA flakes Expanded PET flakes

1 cm

Figure 2.14 (a) Acquisition scheme of different PLA and PET flakes, both transparent and expanded; (b) corresponding RGB image; (c) prediction map obtained by the application of classification algorithms on hyperspectral images.

Techniques for separation of plastic wastes

33

hazardous substances to the biota and causing important environmental impacts (Anderson et al., 2016). Their recovery is thus of primary importance even if their characteristics, due to the previous mentioned alteration effects, can influence both their behavior in the marine environment (i.e., flowing and floating properties) and the further potential collecting/recycling strategies. Polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC) are the main sources of microplastics (Rocha-Santos and Duarte, 2015; Suaria et al., 2016). Their fast, reliable, and robust identification thus represent the first step to better understand generating sources and transport mechanisms in the seas, as well as the setup of correct separation/classification strategies to maximize the recovery in different classes of products. The previously mentioned HSI approach can dramatically contribute to fulfill both the goals, as presented in a recent study (Serranti et al., 2018).

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Bezati, F., Froelich, D., Massardier, V., Maris, E., 2011. Addition of X-ray fluorescent tracers into polymers, new technology for automatic sorting of plastics: proposal for selecting some relevant tracers. Resources Conservation and Recycling 55 (12), 1214e1221. Blassino, M., Solo-Gabriele, H.M., Townsend, T., 2002. Pilot scale evaluation of sorting technologies for CCA treated wood waste. Waste Management and Research 20, 290e301. Bonifazi, G., Capobianco, G., Serranti, S., 2018a. A hierarchical classification approach for recognition of low-density (LDPE) and high-density polyethylene (HDPE) in mixed plastic waste based on short-wave infrared (SWIR) hyperspectral imaging. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 198, 115e122. Bonifazi, G., Palmieri, R., Serranti, S., 2015. Hyperspectral imaging applied to end-of-life (EOL) concrete recycling. Technisches Messen 82 (12), 616e624. Bonifazi, G., Palmieri, R., Serranti, S., 2018b. Evaluation of attached mortar on recycled concrete aggregates by hyperspectral imaging. Construction and Building Materials 169, 835e842. Bonifazi, G., Serranti, S., 3-4 February 2014. Quality control by hyperspectral imaging (HSI) in solid waste recycling: Logics, algorithms and procedures. In: Proceedings of SPIE-IS&T Electronic Imaging - The International Society for Optical Engineering, Image Processing: Machine Vision Applications VII, 9024. Article number 90240T, 2014, DOI: 10.1117/ 12.2038374 San Francisco, CA, United States. Bonifazi, G., Serranti, S., 2006. Imaging spectroscopy based strategies for ceramic glass contaminants removal in glass recycling. Wastes Management 26 (6), 627e639. Bradley, D., 1965. The Hydrocyclone. Pergamon, New York. Brunner, S., Fomin, P., Kargel, C., 2015. Automated sorting of polymer flakes: fluorescence labeling and development of a measurement system prototype. Waste Management 38, 49e60. Buchan, R., Yarar, B., 1995. Recovering plastics for recycling by mineral processing techniques. Journal of the Minerals Metals & Material Soceity 47, 52e55. Callister, W., Rethwisch, D., 2010. Materials Science & Engineering. Wiley & Sons. Christensen, T.H., Fruergaard, T., 2011. Recycling of plastic. In: Christensen, T.H. (Ed.), Solid Waste Technology and Management, vol. 2. Blackwell Publishing Inc. Claessens, M., Van Cauwenberghe, L., Vandegehuchte, M.B., Janssen, C.R., 2013. New techniques for detection of microplastics in sediments and field collected organisms. Marine Pollution Bulletin 70, 227e233. COM, 2015. Action Plan for a Circular Economy, p. 614. COM, 2018. A European Strategy for Plastics in a Circular Economy, p. 28. C ozar, A., et al., 2015. Plastic accumulation in the Mediterranean Sea. PLoS One 10 (4), e0121762. Available at: http://dx.plos.org/10.1371/journal.pone.0121762. C ozar, A., et al., 2017. The Arctic Ocean as a dead end for floating plastics in the North Atlantic branch of the thermohaline circulation. Science Advances 3 (4), e1600582.  C ozar, A., Echevarría, F., Gonzalez-Gordillo, J.I., Irigoien, X., Ubeda, B., Hernandez-Le on, S.,  Palma, A.T., Navarro, S., García-de-Lomas, J., Ruiz, A., Fernandez-de-Puelles, M.L., Duarte, C.M., 2014. Plastic debris in the open ocean. PNAS 111, 10239e10244. Cremers, D.A., Radziemski, L.J., 2006. Handbook of Laser-Induced Breakdown Spectroscopy. Wiley, Chichester. da Silva, D.J., Wiebeck, H., 2017. Using PLS, iPLS and siPLS linear regressions to determine the composition of LDPE/HDPE blends: a comparison between confocal Raman and ATRFTIR spectroscopies. Vibrational Spectroscopy 92 (2017), 256e266.

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Dall’Ara, A., Bonoli, A., Serranti, S., 2012. An innovative procedure to characterize properties from tailored composts. Environmental Engineering and Management Journal 11, 1825e1832. Dodbiba, G., Shibayama, A., Miyazaki, T., Fujita, T., 2001. Electrostatic separation of the shredded plastic mixtures using a tribo-cyclone. Magnetic and Electrical Separation 11 (1e2), 63e92. Ellen MacArthur Foundation, 2016. The New plastics Economy. Fraunholcz, N., 2004. Separation of waste plastics by froth flotation - a review, part I. Minerals Engineering 17, 261e268. Gondal, M.A., Hussain, T., Yamani, Z.H., Baig, M.A., 2007. The role of various binding materials for trace elemental analysis of powder samples using laser-induced breakdown spectroscopy. Talanta 72 (2), 642e649. Hahladakis, J.N., Iacovidou, E., 2018. Closing the loop on plastic packaging materials: what is quality and how does it affect their circularity? The Science of the Total Environment 630, 1394e1400. Hidalgo-Ruz, V., Gutow, L., Thompson, R.C., Thiel, M., 2012. Microplastics in the marine environment: a review of the methods used for identification and quantification. Environmental Science and Technology 46 (6), 3050e3075. Hopewell, J., Dvorak, R., Kosior, E., 2009. Plastics recycling: challenges and opportunities. Philosophical Transactions of the Royal Society of London. Series B, Biological 364, 2115e2126. Hori, K., Tsunekawa, M., Ueda, M., Hiroyoshi, N., Ito, M., Okada, H., 2009. Development of a new gravity separator for plastic - a hybrid-jig. Materials Transactions 50, 2844e2847. Hu, B., Fraunholz, N., Rem, P.C., 2010. Wetting technologies for high-accuracy sink-float separations in water-based media. The Open Waste Management Journal 3, 71e80. Hu, B., Serranti, S., Fraunholcz, N., Di Maio, F., Bonifazi, G., 2013. Recycling-oriented characterization of polyolefin packaging waste. Waste Management 33, 574e584. Ignatyev, I.A., Thielemans, W., Vander Beke, B., 2014. Recycling of polymers: a review. Chemsuschem 7, 1579e1593. J€ahne, B., 1993. Digital Image processing: Concepts, Algorithms, and Scientific Applications, second ed. Springer, Berlin. Jambeck, J.R., Geyer, R., Wilcox, C., Siegler, T.R., Perryman, M., Andrady, A., Narayan, R., Law, K.L., 2015. Plastic waste inputs from land into the ocean. Science 347, 768e771. Jansen, M., Feil, A., Pretz, T., 2012. Recovery of plastics from household waste by mechanical separation. In: Thomé-Kozmiensky, J.K. (Ed.), Waste Management, Recycling and Recovery, vol. 3. TK Verlag, Neuruppin, pp. 169e175. Karlsson, S., 2004. Recycled polyolefins. Material properties and means for quality determination. In: Albertsson, A.C. (Ed.), Long Term Properties of Polyolefins, Advances in Polymer Science, vol. 169. Springer, Berlin, Heidelberg. La Mantia, F.P., Botta, L., Morreale, M., Scaffaro, R., 2012. Effect of small amounts of poly(lactic acid) on the recycling of poly(ethylene terephthalate) bottles. Polymer Degradation and Stability 97, 21e24. Luciani, V., Bonifazi, G., Rem, P., Serranti, S., 2015. Upgrading of PVC rich wastes by magnetic density separation and hyperspectral imaging quality control. Waste Management 45, 118e125. Munari, C., Corbau, C., Simeoni, U., Mistri, M., 2016. Marine litter on Mediterranean shores: analysis of composition, spatial distribution and sources in north-western Adriatic beaches. Waste Management 49, 483e490.

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Pham, C.K., Ramirez-Llodra, E., Alt, C.H.S., Amaro, T., Bergmann, M., Canals, M., et al., 2014. Marine litter distribution and density in European seas, from the shelves to deep basins. PLoS One 9 (4), 1e13. Pic on, A., Ghita, O., Iriondo, P.M., Bereciartua, A., Whelan, P.F., 2010. Automation of waste recycling using hyperspectral image analysis. In: IEEE Conference Emerging Technologies and Factory Automation (ETFA). IEEE, pp. 1e4. Plastics The Facts, 2017. Ragaert, K., Delva, L., Van Geem, K., 2017. Mechanical and chemical recycling of solid plastic waste. Waste Management 69, 24e58. Rahimi, A., García, J.M., 2017. Chemical recycling of waste plastics for new materials production. Nature Reviews Chemistry 1, 0046. Reinsch, E., Frey, A., Albrecht, V., Simon, F., Peuker, U.A., 2014. Continuous electric sorting in the recycling process of plastics. Chemie Ingenieur Technic 86, 784e796. Rem, P.C., 1999. Eddy Current Separation. Delft University of Technology, Eburon, Delft, The Netherlands. Rem, P., Di Maio, F., Hu, B., Houzeaux, G., Baltes, L., Tierean, M., 2013. Magnetic fluid equipment for sorting secondary polyolefins from waste. Environmental Engineering and Management Journal 12, 951e958. Rocha-Santos, T., Duarte, A.C., 2015. A critical overview of the analytical approaches to occurrence, the fate and the behaviour of microplastics in the environment. TrAC-Trends in Analytical Chemistry 65, 47e53. Rozenstein, O., Puckrin, E., Adamowski, J., 2017. Development of a new approach based on midwave infrared spectroscopy for post-consumer black plastic waste sorting in the recycling industry. Waste Management 68, 38e44. Sattler, H., Yoshida, T., 1993. New sorting system for recycling of magnesium and its alloys after use. In: Proceeding of 1st International Conference on Processing Materials for Properties, pp. 861e864. Serranti S., Gargiulo A. and Bonifazi G., 2012b. Classification of polyolefins from building and construction waste using NIR hyperspectral imaging system. Resources Conservation & Recycling 61, 52e58. Serranti, S., Bonifazi, G., February 05e06, 2014. Hyperspectral imaging applied to end-of-life concrete. In: Proceedings SPIE Conference on Image Sensors and Imaging Systems, 9022, 9022T. https://doi.org/10.1117/12.2039242. San Francisco, CA. Serranti, S., Bonifazi, G., Pohl, R., 2006. Spectral cullet classification in the midinfrared field for ceramic glass contaminants detection. Waste Management Research 24 (1), 48e59. Serranti, S., Gargiulo, A., Bonifazi, G., 2011. Characterization of post-consumer polyolefin wastes by hyperspectral imaging for quality control in recycling processes. Waste Management 31, 2217e2229. Serranti, S., Gargiulo, A., Bonifazi, G., 2012a. Hyperspectral imaging for process and quality control in recycling plants of polyolefin flakes. Journal of Near Infrared Spectroscopy 20, 573e581. Serranti, S., Luciani, V., Bonifazi, G., Hu, B., Rem, P.C., 2015. An innovative recycling process to obtain pure polyethylene and polypropylene from household waste. Waste Management 35, 12e20. Serranti, S., Palmieri, R., Bonifazi, G., Cozar, A., 2018. Characterization of microplastic litter from oceans by an innovative approach based on hyperspectral imaging. Waste Management 76, 117e125. Shapiro, M., Galperin, V., 2005. Air classification of solid particles: a review. Chemical Engineering and Processing 44, 279e285.

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Shen, H., Pugh, R.J., Forssberg, E., 2002. Floatability, selectivity and flotation separation of plastics by using a surfactant. Colloids and Surfaces A Physicochemical and Engineering Aspects 196, 63e70. Singh, B.P., 1998. Wetting mechanism in the flotation separation of plastics. Filtrieren und Separieren 35, 525e527. Suaria, G., Aliani, S., 2014. Floating debris in the Mediterranean Sea. Marine Pollution Bulletin 86 (1e2), 494e504. Suaria, G., Avio, C.G., Mineo, A., Lattin, G.L., Magaldi, M.G., Belmonte, G., Moore, C.J., Regoli, F., Aliani, S., 2016. The Mediterranean Plastic Soup: synthetic polymers in Mediterranean surface waters. Scientific Reports 6. https://doi.org/10.1038/srep37551 e37551. Svoboda, J., 2004. Magnetic Techniques for the Treatment of Materials - Reviews of Magnetic Separators. Kluwer Academic Publishers. Svoboda, J., Fujita, T., 2003. Recent developments in magnetic methods of material separation. Minerals Engineering 16, 785e792. Takoungsakdakun, T., Pongstabodee, S., 2007. Separation of mixed post-consumer PET-POMPVC plastic waste using selective flotation. Separation and Purification Technology 54, 248e252. Tatzer, P., Wolf, M., Panner, T., 2005. Industrial application for inline material sorting using hyperspectral imaging in the NIR range. Real-Time Imaging 11 (2), 99e107. Turner, A., 2018. Black plastics: Linear and circular economies, hazardous additives and marine pollution. Environment International 117, 308e318. Ulrici, A., Serranti, S., Ferrari, C., Cesare, D., Foca, G., Bonifazi, G., 2013. Efficient chemometric strategies for PET-PLA discrimination in recycling plants using hyperspectral imaging. Chemometrics and Intelligent Laboratory Systems 122, 31e39. Van der Walk, H.J.L., Braam, B.C., Dalmijn, W.L., 1986. Eddy-current separation by permanent magnets - part I: theory. Resources and Conservation 12, 233e252. Vilaplana, F., Karlsson, S., 2008. Quality concepts for the improved use of recycled polymeric materials: a review. Macromolecular Materials and Engineering 293, 274e297. Vilaplana, F., Ribes-Greus, A., Karlsson, S., 2007. Analytical strategies for the quality assessment of recycled high-impact polystyrene: a combination of thermal analysis, vibrational spectroscopy, and chromatography. Analitica Chimica Acta 604, 18e28. Wang, C.Q., Wang, H., Fu, J.G., Liu, Y.N., 2015. Flotation separation of waste plastics for recycling-a review. Waste Management 41, 28e38. Wills, B.A., 2016. Mineral Processing Technology, eighth ed. Butterworth-Heinemann, Oxford, UK, p. 498. Workman Jr., J., Weyer, L., 2007. Practical Guide to Interpretive Near-infrared Spectroscopy. CRC Press, Boca Raton, FL. ISBN:9781439875254-CAT# K13491. Zhu, H., Basir, O., 2006. A novel fuzzy evidential reasoning paradigm for data fusion with applications in image processing. Soft Computing 10 (12), 1169e1180.

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Hydraulic separation of plastic wastes

3

Monica Moroni 1 , Emanuela Lupo 1 , Floriana La Marca 2 1 DICEA-Sapienza University of Rome, Rome, Italy; 2DICMA-Sapienza University of Rome, Rome, Italy

3.1

Introduction

In the last decades the considerable increase of plastic usage in many sectors has determined an augmentation in polymer production and, thus, in waste generation. Consequently, plastic waste management is becoming a main concern, both for regulatory and environmental issues, involving policy makers and research institutions. In 2016, the global plastic production was 335 million tons, the European production accounting for roughly 18% of the world’s total production (Plastic Europe, 2017). Plastic materials after use are resources that, via adequate processing, can be used as alternatives to virgin materials or traditional fuels. In particular, processing plastic wastes to replace primary raw materials is called recycling, whereas replacing traditional fuel is called energy recovery (Kr€ahling and Sartorius, 2012). Both of these processes reduce the amount, and therefore the impacts, of plastic materials at their end of life and make it possible to decrease plastic waste disposal in landfill. From 2006 to 2016, the volume of collected plastic waste increased by þ11%. Remarkably, recycling increased by þ79%, energy recovery by þ61%, while landfill decreased by 43% (Plastic Europe, 2017). Recycling may be accomplished using chemical or mechanical processes. Chemical recycling is driven by thermal (e.g., pyrolysis) or chemical (selective solvents) processes that essentially break down the original polymer chains and molecules within the original material (Jody and Daniels, 2010). Mechanical recycling of plastic solid waste requires several treatment steps, usually: cutting/shredding, to reduce particle size and to get a suitable shape for further processing; separation in dry conditions to eliminate impurities such as paper, dust, and other nonplastic materials; polymer separation to separate polymer per type; milling to homogenize particle size of single-polymer plastics. Further steps, that is, washing/drying, agglutination, and extrusion are designed to prepare the end-product according to the market standards (Al-Salem et al., 2009). Mechanical recycling is generally considered as the best option in plastic waste management, particularly if it produces high-quality products (pure and homogeneous secondary raw materials). This can favor virgin material substitution, thus reducing

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00003-7 Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete

environmental impact and resource depletion (Shonfield, 2008; Astrup et al., 2009; Hopewell et al., 2009; Lupo et al., 2016). For a complete review of separation processes employed in mechanical recycling plants and promising technologies for plastic mixtures separation under research refer to Section 3.3 of this chapter. This chapter focuses on an innovative wet technology for separation of plastic particles, suitable to be employed in the separation step of mechanical recycling plants, representing a valuable alternative to existing technologies. In fact, it allows overcoming the typical problems of the most used separation methods, such as: the need of additives (that create secondary pollution) for flotation, dense sorting, and cyclones; the influence of moisture, surface status, and feeding speed of particles for electrostatic separation; the complexity and cost of equipment for optical methods (Lupo et al., 2016). The device treats a mixture of plastics and water with the aim of separating the useful fraction. The separation process relies on the differences of density, dimension, and shape among the plastics in the mixture and on the characteristic flow pattern developing inside the device. It is suitable for the separation of polymers with a density higher than 1000 kg/m3. An image analysis technique was used to characterize the velocity flow field within the apparatus and to study its relation with the separation capability. For these purposes, a novel algorithm for particle identification and tracking has been employed, that is, HLPT (Hybrid Lagrangian Particle-Tracking). It is a hybrid technique that simultaneously provides particle centroids and correspondent velocity predictor through the solution of the optical flow equation (Moroni et al., 2017). In addition, complementary tools have been used to characterize the apparatus, exploiting computational fluid dynamic (CFD) methods. CFD was employed to investigate the properties of the fluid flowing within the apparatus in the different operating conditions. The advantage using this approach compared to the experimental investigation is the ability to simulate a large number of different operating conditions quite faster than with other approaches, reducing the total effort required in laboratory. On the other hand, the numerical tool prescribes a set of experimental data for its calibration and validation.

3.2 3.2.1

Principles of the hydraulic separation process Multiphase flow overview

The separation process taking place within the separator involves the interaction among two phases. A phase refers to the solid, liquid, or vapor state of matter (Crowe, 2006). In a multiphase flow, the concept of phase is applied in a broader sense: it can be defined as an identifiable class of material that has a particular inertial response to and interaction with the flow, and it may exert an influence on the field it is immersed into. For example, particles belonging to the same dimensional class but inhomogeneous in composition, and consequently in density, have dissimilar behaviors within the flow field. Then they can be considered as different phases. Multiphase systems

Hydraulic separation of plastic wastes

41

are essentially governed by the same physical laws as the single phase counterparts. In continuum mechanics, the conceptual model for the single phase flow is formulated in terms of field equations describing the conservation laws of mass, momentum balance, energy balance, etc. These field equations are then complemented by appropriate constitutive equations for thermodynamic state, stress, energy transfer, chemical reactions, etc. However, the derivation of such equations for multiphase flows is more complicated. For instance, for multiphase systems, the classification of the flow structure into laminar, transitional, and turbulent developed for single phase flows does not apply. In fact, the complex nature of two- or multiphase flows originates from the existence of multiple deformable and moving interfaces, which determine significant discontinuities of the flow properties and a complicated flow field near the interfaces. In dispersed-dense two-phase flows, that is, in flows characterizing hydraulic separation processes, one phase consists of discrete elements (such as particles in a gas or liquid), and the discrete elements are not connected (Crowe, 2006). We have focused our investigation on dispersed-dense two-phase flows, where solid particles are considered the dispersed (or dense) phase and water is the continuous phase. The particle volume fraction is introduced to distinguish the nature of a mixture. It is defined as the total volume of the dispersed solid phase Vs in a mixture of volume Vm. as ¼

Vs Vm

(3.1)

A dense flow regime is achieved in case of large as. In this case, the interparticle spacing is relatively small and particle motion and transport are governed by collisions and/or contacts. In collision-dominated flow, the collisions between the particles control the features of the flow, such as in a fluidized bed. In a contact-dominated flow, the particle motion is controlled by continuous contacts, such as in a granular flow. On the contrary, in dispersed systems the spacing between carried particles is so large that fluid dynamic forces (i.e., drag and lift) govern particle motion. Furthermore a dilute disperse flow takes place when the average distance between the centers of the particles is larger than two diameters (i.e., if the outer surfaces of the particles, assumed to have a spherical shape, are separated by a distance which is greater than one diameter) (Crowe, 2006). Another qualitative estimate of the disperse or dense nature of a two-phase flow can be made by comparing the ratio of the velocity response time (or relaxation time) of a particle, sp, to the average time between particleeparticle collisions, sc. The response time is the time required by a particle to respond to a change of the local fluid velocity (Crowe, 2006). For Stokes flow (Elghobashi, 1994) it can be expressed as: sp ¼

r_ s ds2 18m

(3.2)

42

Use of Recycled Plastics in Eco-efficient Concrete s

When spc < 1 the flow is dispersed, the particles have sufficient time to respond to s the local fluid dynamic forces before the eventual next collision; when spc > 1 the particle has no time to respond to the fluid dynamic forces before the next collision and the flow is dense (Crowe, 2006).

3.2.2

Phase coupling

To understand the interaction between different phases (carrier or continuous and discrete or dispersed), it is mandatory to study their coupling regimes. The carrier phase can be described in terms of density, temperature, pressure, and velocity field, the discrete phase in terms of concentration, size, temperature, and velocity field. Coupling can take place through mass, momentum, and energy transfer between phases. Mass coupling regards addition or removal of mass (for example, through evaporation of the discrete phase or condensation of the carrier fluid). Momentum coupling is the result of an interactional force, such as a drag force, between the dispersed and continuous phases. Energy coupling occurs through heat transfer between phases (Crowe, 2006). Exchanges of mass and energy do not occur in the application presented here; then, only momentum coupling will be considered. Four coupling regimes can be identified (Fig. 3.1). In one-way coupling regimes, the dispersed phase motion is affected by the continuous phase while there is no reverse effect; if there is a mutual effect between the flows of the phases, then the flow is two-way coupled; if disturbances of the discrete phase on the carrier one affect the motion of the discrete phase, the flow is three-way coupled; finally four-way coupling addresses the situation where, in addition to discrete carrier phase interaction, particleeparticle collisions also affect the multiphase motion (Crowe, 2006). Fig. 3.2 shows the qualitative relationship between particle volume fraction and coupling regimes in case of particlefluid turbulence interaction. The particle Reynolds number, which represents the ratio of convective forces to viscous forces, can be expressed as (Di Giacinto et al., 1982): Rep ¼

_ s  ujds rju m

(3.3)

For low particle volume fractions and particle Reynolds numbers, it is expected that one-way coupling dominates. However, as the particle Reynolds number is increased and the particles begin to generate wakes, fluid phase turbulence will be produced/ enhanced requiring two-way coupled models. Also the increase of the particle volume fraction will lead to two-way coupling. When particle volume fractions exceed 103, four-way coupling occurs in which particleeparticle interactions are significant. This region is associated with dense phase flows (Crowe, 2006).

Dispersed flow

Sparse flow

Dilute

Hydraulic separation of plastic wastes

43

One-way coupling: Continuous-fluid affects particle motion (e.g., particle rotated by vortex) Two-way coupling: Above plus particle motion affects continuous-fluid motion (e.g., particle wake increases dissipation)

Three-way coupling: Above plus particle disturbance of the fluid locally affects another particle’s motion (e.g., drafting of a trailing particle)

Increasing mass or volume fraction

Dense flow

Four-way coupling: Above plus particle collision affects motion of the both particles (e.g., particle reflection)

Collision-dominated flow

High-frequency of collisions (e.g., energetic fluidized beds)

Contact-dominated flow

High-frequency of contact (e.g., nearly settled beds)

Figure 3.1 Dilute, dispersed, and dense flow conditions based on various interphase and intraphase coupling (Crowe, 2006).

3.2.3

Dispersed multiphase flows modeling

Two types of reference frame are used for the formulation of dispersed flows, namely the Lagrangian framework and the Eulerian framework. In the former case, the reference frame moves with the particles, and the instantaneous position of a particle is described as a function of its initial location and the time elapsed. Lagrangian models are sometimes referred to as noncontinuum models because the particle phase is treated in a discrete way, unlike the fluid phase, which is treated as a continuous phase. In the Eulerian models, the spatial reference frame is stationary, and the particles pass through fixed control volumes. In this approach, the characteristics of the particulate phase are obtained by solving partial differential equations in a given coordinate system. These models which treat the particles as a continuum, similarly to the fluid phase, are also known as continuum models or two-fluid models (Shirolkar et al., 1996).

44

Use of Recycled Plastics in Eco-efficient Concrete

Four way particle to particle coupling region

10–3

αs

Two way coupling region

10–6

One way coupling region

10–9 10–2

10–1

100

101 Rep

102

103

104

Figure 3.2 Two-phase coupling regions for particleefluid turbulence interaction (Crowe, 2006).

3.2.4

Conservation equations of diluted dispersed two-phase flows in an Eulerian reference framework

For dilute suspensions, the equations for the fluid phase in the three principal directions (x,y,z) are: •

Mass conservation vu vv vw þ þ ¼0 vx vy vz

•

(3.4)

Momentum     2 vu vuu vuv vuw vp v u v2 u v2 u r þ þ þ þ þ ¼ þm vt vx vy vz vx vx2 vy2 vz2   v vu vv vw þ ðl þ mÞ þ þ  Fx vx vx vy vz

(3.5)

Hydraulic separation of plastic wastes

45

  2   vv vvu vvv vvw vp v v v2 v v2 v þ þ þ ¼ þm r þ þ vt vx vy vz vy vx2 vy2 vz2   v vu vv vw þ ðl þ mÞ þ þ  Fy vy vx vy vz

(3.6)

  2   vw vwu vwv vww vp v w v2 w v2 w þ þ þ ¼ þm þ þ r vt vx vy vz vz vx2 vy2 vz2   v vu vv vw þ ðl þ mÞ þ þ  Fz  rg vz vx vy vz

(3.7)

where u, v, and w are the three velocity components; p is pressure; F is the phase interaction force.

The equations for solid phase in the three principal directions are: •

Mass conservation vas vas us vas vs vas ws þ þ þ ¼0 vt vx vy vz

•

(3.8)

Momentum   vas us vas us us vas us vs vas us ws þ þ þ ¼ þFx r_ s vt vx vy vz

(3.9)

r_ s

  vas vs vas vs us vas vs vs vas vs ws þ þ þ ¼ þFy vt vx vy vz

(3.10)

r_ s

  vas ws vas ws us vas ws vs vas ws ws þ þ þ ¼ þFz  as r_ s g vt vx vy vz

(3.11)

where us, vs, and ws are the three velocity components of the solid particle; as is the volume fraction of the dispersed phase.

Two parameters are used to evaluate the different level of coupling between the previous groups of equations: the Stokes number (St) and the loading ratio (b) (Di Giacinto et al., 1982). The Stokes number indicates whether it is appropriate to consider the particles to be in equilibrium with the fluid flow (Di Giacinto et al., 1982). It estimates the particle rapidity to respond to flow changes. It is defined as the ratio of the particle response time sp, and the characteristic time of the flow field sF. St ¼

sp sF

(3.12)

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Use of Recycled Plastics in Eco-efficient Concrete

If St > 1, then the particle will have essentially no time to respond to the fluid velocity changes, and the particle velocity will be slightly affected by fluid velocity variations (Crowe, 2006). The loading ratio is defined as the ratio of the particle phase bulk density rs and the fluid phase bulk density r. b¼

rs r

(3.13)

The loading ratio b, multiplies the effects of the Stokes number on the momentum equations, increasing the coupling of the fluid and solid phases. For very small values of b, the fluid phase is independent from the solid phase and only a one-way coupling occurs between the two equation systems. For large values of b, a two-way coupling occurs between the two equation systems, and they must be solved simultaneously. The effect of the particles on the fluid flow field cannot be neglected anymore, becoming more relevant at smaller Stokes number (Di Giacinto et al., 1982).

3.3

Devices for the hydraulic separation within mechanical recycling plants

The polymer separation step in mechanical recycling is recognized as crucial to increase the quality of the secondary raw materials. Separation can occur in wet conditions such as with flotation, dense sorting (sink/float), and cyclones (Shent et al., 1999; Gent et al., 2009), or dry conditions such as with electrostatic separation and optical methods (Tilmatine et al., 2009; Yanar and Kwetkus, 1995; Di Maio et al., 2010). Nowadays, several promising technologies for plastic mixtures separation have undergone research, such as electrostatic separation (Park et al., 2007; Wu et al., 2013), influenced by moisture, surface status, and feeding speed of particles; processes based on differential thermal behaviors (Carlini et al., 1995); and optical properties (Scott, 1995; Ahmad, 2004), requiring complex and high-priced equipment, and, above all, separation by density. Separation by density provides the separation of plastic mixtures in two products based on particles settling velocity within a fluid medium, typically water, but also air. It is accomplished in three different ways: pneumatic separation, centrifugal separation (cyclones), and sink/float separation. The pneumatic separation requires the construction of large industrial plants and it has a rather high cost (Nakajima et al., 1999; Eswaraiah et al., 2008). Cyclones are effective tools for separation, but plastic

Hydraulic separation of plastic wastes

47

materials must be finely ground and, to increase the product quality, more than one step is typically required (Gent et al., 2011; Malcolm Richard et al., 2011). The sink/float separation requires a process medium with an intermediate density between that of the polymers to be separated. Plain water can be used as separation medium only for plastic mixtures with densities higher and lower than 1 g/cm3. In the other cases, chemical additives need to be used to create a medium of intermediate density between the polymers to be separated or innovative solutions need to be applied. This is the case of Magnetic Density Separation, MDS (Rem et al., 2013), which utilizes a liquid separation medium which contains magnetic iron oxide particles with a size of about 10e20 nm suspended in water; due to a magnetic force, varying in the vertical direction, the liquid presents a density gradient allowing the separation of plastic particles of different densities. In some applications (Luciani et al., 2015; Serranti et al., 2015), the MDS is coupled with hyperspectral imaging to control the quality of recovered plastics. Usually sink/float separation is quite simple, but it becomes difficult if mixtures are characterized by slight differences in density. Polymer density values range in the interval: PET 1.37e1.45 g/cm3, PVC 1.30e1.60 g/cm3, PC 1.20e1.22 g/cm3, HDPE greater or equal to 0.94 g/cm3, LDPE 0.91e0.94 g/cm3, PP 0.86e0.95 g/ cm3. Therefore, if the separation step is carried out via gravimetric methods, mixtures of PET, PVC, and PC are expected to be found in the fraction heavier than 1 g/cm3. Therefore, after the gravimetric separation has been conducted, a further separation step may be required to purify the recovered polymers to the target standard quality for secondary raw materials (Dodbiba et al., 2002; Pongstabodee et al., 2008). Several research studies have investigated experimental methods suitable to separate mixtures of polymers of density higher than 1.00 g/cm3. Froth flotation is based on the difference in surface properties (hydrophilic vs. hydrophobic), provided by proper conditioning (Marques and Tenorio, 2000). Flotation shows advantages such as cost-effectiveness and high separation efficiency, especially for plastics with similar density (Jody et al., 2003; Takoungsakdakun and Pongstabodee, 2007; Carvalho et al., 2010; Wang et al., 2012); it has been widely applied for PET and PVC separation (Marques and Ten orio, 2000; Burat et al., 2009; Yenial et al., 2013; Saisinchai, 2014). On the other hand, froth flotation for plastic separation is particularly challenging due to the inherent hydrophobicity of most plastics, which require proper conditioning treatments in order to selectively change the surface characteristics of a specific polymer. This can be achieved by chemical reagents addition (Shen et al., 2001; Basarova et al., 2005; Pascoe, 2005; Takoungsakdakun and Pongstabodee, 2007), or by physical methods, such as boiling treatment, where molecular rearrangement of polymers is obtained in response to elevated temperature exposure (Wang et al., 2014). Other interesting methods for separation of polymers of density higher than 1.00 g/ cm3 are the shaking table (Carvalho et al., 2007) and the fluidized bed (Carvalho et al., 2009) separation, both derived from mineral processing, which show satisfactory results; nevertheless, they do require a somewhat complex flow sheet.

48

3.4 3.4.1

Use of Recycled Plastics in Eco-efficient Concrete

The hydraulic separator channel Experimental apparatus

The hydraulic separator comprises a channel with a characteristic shape realized by combining two rigid transparent plastic walls. Each wall consists of eight halfcylinders, which form eight inner chambers. In Fig. 3.3 the chambers are labeled according to their positions along the flow direction (Cn, with n ¼ 1, ., 8). The geometry of the separation channel may be modified to realize different geometric arrangements, making it possible to identify the optimal one in terms of separation efficiency. This may be accomplished by shifting the upper half-cylinder profile respect to the lower one. This makes it possible to setup and study different internal geometries (and consequently different flow patterns within the device), assuring a remarkable flexibility of the apparatus. Two different apparatus configurations have been tested combining two internal geometries, hereinafter named arrangement A and B. In arrangement A the ratio between lengths L1 and L2 is roughly equal to 1.9; in arrangement B the ratio between lengths L1 and L2 is roughly equal to 1 (Fig. 3.4). Water is the working fluid. It is fed using eight input ducts (Ii, with i ¼ 1, ., 8) located along the first chamber, with axes normal to the semicylindrical tubes. The device is also equipped with eight outlet ducts (Ok, with k ¼ 1, ., 8) placed in the last chamber, in a symmetrical position with respect to the input ducts. The outlet ducts are provided with taps, to be possibly disconnected from the flow circulation. Further, the lower part of each chamber presents a collecting duct (Rj, j ¼ 1, ., 8) allowing the extraction of the material settled in each chamber during the separation process (Fig. 3.5(a) and (b)). Also the collecting ducts are provided with taps to be disconnected from the flow circulation during the tests. The reproducibility of the experimental tests has been ensured using a constant flow rate during each test. For this purpose the apparatus is filled via a semiclosed circuit. A

C1

C2

C3

C4

C5

C6

C7

C8

Figure 3.3 Two-dimensional representation of the hydraulic separator channel. (a)

L1 = 0.032 m

(b)

L2 = 0.017 m

L1 = 0.0245 m

L2 = 0.0245 m

Figure 3.4 Separator channel geometric arrangements (a) A and (b) B.

Hydraulic separation of plastic wastes

49

y z

L1 = 0.032 m

x

L3 = 0.052 m

dr = 0.025 m

Ok (k = 1,...,8)

I4

C8

C7

C6

C5

Outlet ducts

C4

C3

C2

C1

Flow direction Inlet ducts

Ii (i = 1,...,8)

(a)

Rj (j = 1,...,8)

(b)

Figure 3.5 a) Three-dimensional schematic representation of the hydraulic separation channel with inner, outlet, and collecting ducts; reference system; (b) picture of the hydraulic separator.

variable height tank is connected to all eight inlet ducts. The water level within the tank is controlled through an overflow exit. The plastic sample is introduced within the separator via another supply tank connected to the inlet duct I4 and set to a sufficient height to guarantee the material is fed within the apparatus (about 25 cm of hydraulic load) (Fig. 3.6). A pump allows transferring water collected from the outlet ducts into the tank. At a given internal geometry, the flow rate within the apparatus will depend on the tank height and on the number of the opened outlet ducts, hereinafter hydraulic configurations. Variable height tank Hydraulic separator

LED based illumination

Supply tank 1 personal computer 2 high-speed cameras

2 high-speed camera link digital video recorders

Figure 3.6 Experimental setup overall view.

50

Use of Recycled Plastics in Eco-efficient Concrete

Table 3.1 Flow rates for the tested geometric arrangements at different hydraulic configurations

Case

Flow rate in arrangement A (10L3 m3/s)

Flowrate in arrangement B (10L3 m3/s)

2 (O3,O6)

#1

0.72

0.72

3 (O2,O4,O6)

#2

0.92

0.91

4 (O2,O4,O6, O8)

#3

1.08

1.11

2 (O3,O6)

#4

0.84

0.84

3(O2,O4,O6)

#5

1.08

1.08

4 (O2,O4,O6, O8)

#6

1.24

1.22

2 (O3,O6)

#7

0.92

0.91

3(O2,O4,O6)

#8

1.22

1.19

4 (O2,O4,O6, O8)

#9

1.36

1.38

Hydraulic load (m)

Number of opened outlet ducts

Q1 ¼ 1.0

Q2 ¼ 1.5

Q3 ¼ 2.0

The two different apparatus geometric arrangements have been tested at nine hydraulic configurations. For each case, the achieved flow rate was measured by evaluating the time required to fill a known water volume output from the outlet ducts. The measurement was repeated several times and the average value was calculated. Table 3.1, which reports the flow rates obtained for the nine cases, suggests the internal geometry does not remarkably influence the flow rate within the apparatus. On the other hand, for each geometric arrangement, the number of opened outlet ducts does.

3.4.2

Equipment and methodology for the fluid mechanics investigation

Water was seeded with a reflecting neutrally buoyant passive tracer and illuminated by a LED-based planar illuminator (COBRA Slim) in a section aligned along the longitudinal direction. The acquisition system comprises the high-speed (400 Hz) and highresolution (1280  1024 pixels) Mikrotron EoSens camera connected to a digital video recorder (IO Industries DVR Express Core). Each experiment was approximately 60 s long to record a consistent amount of data and ensure a robust enough statistical analysis. After seeding the flowing fluid (water) with the tracer, a set of images of the fluid motion in the separator was taken; the images were elaborated to obtain the trajectories and the velocity fields of the tracer particles. Hybrid Lagrangian Particle Tracking (HLPT; Shindler et al., 2010, 2012) was used to reconstruct tracer trajectories, from which velocity and acceleration can be directly obtained. The HLPT algorithm is based on the solution of the optical flow equation and selects areas of each image where strong brilliance gradients exist. Such areas can be

Hydraulic separation of plastic wastes

51

associated to tracer particles and are good features to track from frame to frame. Once the particles are identified, the algorithm calculates their coordinates of the barycenter and reconstructs the trajectory of each particle, calculating their displacement in the subsequent frames. Image processing was achieved in three steps: (1) a preprocessing step aimed at removing the background and improving image contrast; (2) particle detection and temporal tracking via HLPT to isolate particles and track them in consecutive frames; (3) postprocessing to obtain the relevant flow parameters (Moroni and Cenedese, 2005). The adaptive Gaussian arithmetic average method described in Moroni et al. (2014) was employed to map randomly spaced Lagrangian data onto the regular grid.

3.4.3

Tested plastic samples

Polymers employed to test the efficacy of the device are both traditional plastics (PET, PC, and PVC) and bioplastics (PLA and MATER-BI). To guarantee the entrance of the samples within the device, only polymers with density greater than water were tested. For each polymer, samples of material at different stages of a product life cycle were selected, that is, primary raw or virgin (V) materials, waste (W), and secondary raw or regenerated (R) materials. The virgin plastic particles have nearly spherical or cylindrical shape with rather regular and homogenous sizes. Urban plastic waste samples were collected from many sources. Each waste sample was washed, purified from impurities, and then shredded by a knife mill to obtain irregularly shaped flakes or pieces. Lastly, secondary raw (regenerated) plastics were provided by two Italian plants for plastic recovery and recycling (“Rigenera S.r.l.” - Terni; “Montello S.p.a.” - Montello (BG)). The samples tested within the apparatus are identified with the name of the polymer, a sequential number used to distinguish different samples of the same polymer, the letters V, W, or R indicating the phase of the life cycle (virgin, waste, or regenerated materials, respectively), the letters G, F, or P indicating the particle shape (granules, flakes, or pieces, respectively). Four samples of traditional plastics (PC 1VG, PET 2-VG, PVC 1-VG, PVC 2-VG) and two samples of bioplastics (PLA 1VG, MATER-BI 1-VG) were selected as virgin materials; three samples of traditional plastics (PC 2-WF, PET 6-WF, PVC 4-WP) and two samples of bioplastics (PLA 2WF, MATER-BI 2-WF) were selected as waste materials; three samples of traditional plastics (PC 3-RF, PET 4-RF, PVC 6-RF) were selected as regenerated materials. Two size classes were chosen for the particle dimensions (d is the size): • •

size class I: 2.00  103 m < d < 3.36  103 m size class II: 3.36  103 m < d < 4.76  103 m.

These size classes were selected to verify the influence of the particle size on the separation process. The size class II represents an upper limit for plastic particle sizes that can be treated within the hydraulic separator. Traditional plastic and bioplastic samples used in this work are given in Table 3.2, which describes their origin, shape, density, and size class.

52

Use of Recycled Plastics in Eco-efficient Concrete

Table 3.2 Polymer sample characteristics: life cycle stage (virgin, waste, regenerated), shape (granular, flake, piece), density, size, class Name

Life cycle stage

Shape

Density (kg/m3)

Size class

PC 1-VG

Virgin material

Granules

1180

II

PC 2-WF

Waste

Flakes

1210

I, II

PC 3-RF

Regenerated material

Flakes

1200

I, II

PET 2-VG

Virgin material

Granules

1310

I

PET 6-WF

Waste

Flakes

1350

I, II

PET 4-RF

Regenerated material

Flakes

1330

I, II

PVC 1-VG

Virgin material

Granules

1190

I

PVC 2-VG

Virgin material

Granules

1300

II

PVC 4-WP

Waste

Pieces

1610

I, II

PVC 6-RP

Regenerated material

Pieces

1440

I, II

PLA 1-VG

Virgin material

Granules

1240

II

PLA 2-WF

Waste

Flakes

1220

I, II

MATER-BI 1-VG

Virgin material

Granules

1250

II

MATER-BI 2-WF

Waste

Flakes

1230

I, II

3.4.4

Mono- and Multimaterial Separation Tests

Separation tests have been conducted on both mono- and multimaterial samples. Fixed volumes of material (6.21  106 m3 and 12.42  106 m3) were introduced within the separator in order to observe their behavior. According to both sample property (shape, dimension, and density) and operating conditions of the separator (Table 3.1), particles can settle in the chambers or escape from the output ducts. The purpose of monomaterial tests is to provide useful information on the behavior of one type of plastics. For this reason, monomaterial samples are composed by a certain polymer. After each test the amount of material settled in each chamber or expelled from the apparatus was quantified. Monomaterial tests make it possible to understand which materials are the most suitable for multimaterial separation tests. The purpose of multimaterial tests is to evaluate the real separation efficacy of the apparatus, fundamental prerequisite for its application in real plants. For this reason, multimaterial samples are composed of two polymers, hereinafter polymer #1 and polymer #2. Four combinations of polymers were chosen: 85% of polymer #1 and 15% of polymer #2, 60% of polymer #1, and 40% of polymer #2, 40% of polymer #1 and 60% of polymer #2, 15% of polymer #1 and 85% of polymer #2. Either polymer #1 or polymer #2 may be the useful fraction. Samples composed by 85% of one polymer, most likely the useful fraction, and 15% of the other one have been tested to evaluate the possibility of purifying a plastic typology polluted by an extraneous

Hydraulic separation of plastic wastes

53

polymer (secondary separation stage). The other sample compositions allow testing the possibility of using the hydraulic separator for processing mixtures with similar concentrations, for instance, within multistep recycling processes. The result of a separation test consists of two fractions, that is, the first one collected within the apparatus chambers and the other one expelled from the separator. The fraction containing the useful phase is called concentrated fraction. The effectiveness of the separation tests can be measured by means of three indices: •

grade of useful phase in the concentrated fraction, equal to the ratio of the weight of the useful phase to the total weight of the recovered concentrated fraction, expressed as a percentage; it provides an indication of the useful phase and contaminant content in the concentrated fraction; recovery of useful phase, equal to the ratio of the weight of the recovered useful phase to the weight of the useful phase in the original sample, expressed as a percentage; it permits the comparison of the amount of useful phase in the concentrated fraction and in the sample; concentration rate, equal to the ratio of the grade of the useful phase in the concentrated fraction and the grade of the useful phase in the original sample.

• •

The separation process is optimal when grade and recovery of the useful phase are equal to 100% and the concentration rates are 1.18, 1.67, 2.50, 6.67 for percentages of the useful phase in the mixture of 85, 60, 40, 15, respectively. Table 3.3 shows the percentages of each polymer in the two-plastic mixture employed in the multimaterial tests. In both monomaterial and multimaterial tests, volumes of 6.21  106 m3 and 12.42  106 m3 of solid material were introduced within the separator through the secondary tank connected to duct I4. The larger volume was chosen considering the maximum volume available in a single chamber of the apparatus for particles to settle. All tests employ a procedure consisting of the following steps: 1. 2. 3. 4. 5. 6. 7. 8.

weighing and wetting of the sample adjustment of the water tank height connection of the primary tank to all eight inlet ducts complete saturation of the separator opening of the output nozzles connection of the secondary tank to duct I4 and feeding of the sample test execution, recovering of the material expelled from the output ducts end of the water supply

Table 3.3 Multimaterial sample composition Sample #

Polymer #1

Polymer #2

Test purpose

1

85%

15%

2

15%

85%

Purification of a plastic typology polluted by a contaminating polymer

3

60%

40%

4

40%

60%

Separation of mixtures with similar concentrations, possibly by multistep processing

54

Use of Recycled Plastics in Eco-efficient Concrete

9. recovery of material settled in each chamber 10. drying of recovered materials prior to weighing.

Before each test, samples were weighed with a precision scale and wetted to ensure the correct material feeding and test reproducibility. The duration of each experiment was approximately 240 s, 180 s being the time required for the particles to be introduced through the inlet nozzle and the remaining 60 s the time required to test the permanence of the particles in different chambers. To evaluate the amount of plastic particles settled in each chamber and expelled from the apparatus, plastics were recovered separately, properly dried, and weighed.

3.5

Separation efficacy of the hydraulic separator channel

3.5.1 3.5.1.1

Results from the experimental activities Monomaterial separation tests

Monomaterial tests were conducted with samples of 6.21  106 m3 solid volume (Lupo et al., 2016) and 12.42  106 m3 solid volume (Moroni et al., 2018). Figs. 3.7e3.9 present the sedimentation efficacy, h, defined as the ratio between the amount of material settled within the apparatus and the material treated within the separator. Each plot shows h of the plastic sample for both solid volumes, that is, 6.21  106 m3 and 12.42  106 m3. Additionally, h is plotted for increasing fluid flow rate. For a given fluid flow rate, the comparison among h values makes it possible to evaluate the effectiveness of the hydraulic separator as a function of the solid volume fraction treated within the device. Increasing the solid phase volume and keeping unchanged the fluid flow rate, the solid phase volume fraction as increases from 2.6  105 to 5.2  105; as being in the order of 105 and particle Reynolds number to the order of 103, a two-way coupling among the phases takes place. Two-way coupling implies a mutual influence between the two phases, that is, a reciprocal exchange of forces. Those forces, usually referred to as two-way coupling forces, are directly proportional to the solid-phase volume fraction and to the difference between the velocity of the fluid and solid phases and inversely proportional to the squared solid particles’ diameter. Fig. 3.7(a) shows that PC 2-WF, belonging to the size class I, is completely expelled from the apparatus except for case #1 and 12.42  106 m3 of solid particles input to the device, being in this case roughly 5% the amount of material that settles in the separator chambers. PC 2-WF, belonging to the size class II, behaves as the PC 2-WF that belongs to size class I (Fig. 3.8(a)) and is completely expelled from the apparatus in all cases except case #1. For this sample, the amount of polymer settled within the device slightly increases, doubling the volume of the sample. For the same fluid flow rate (case #1) and both solid volume fractions, a higher sedimentation efficacy is observed for the samples with solid particles belonging to the larger size class. Samples of PC 3-

Hydraulic separation of plastic wastes

55 6.21 10–6m3

(a) PC 2-WF I

(%) 100

PC 3-RF I (%)

100

80

0.0

#8

0.0 0.0

#3

0.0

0.0 0.0

0.0

#5

0.0

0.0 0.0

0.0

0.0

#2

#6

#9

#3

#8

#9

#4

#7

93.8 92.1

99.7 99.7

97.6 97.5

#4

#7

#8

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

12.6

#6 #9

0.8 0.0

1.0 0.0

0.0 0.0

0.0 0.0

0.0 0.0

#1

#4

#7

#2

#5

#3

#8

#6

#9

20 0

#8

#6

0.0 0.0

0.0 2.0

#3

2.2 1.7

#5

#9

#1

#4

#7

#2

#5

#3

#8

0.0 0.0

1.0 0.0

40 0.6 1.0

60

40

2.9 1.9

80

60 7.2 12.9

80

#2

MATER-BI 2-WF I

0.0 0.0

(%) 100

#1

0.0 0.0

(h)

0.6 0.0

0

7.6 6.5

20

9.4 12.7

#9

0.5 0.5

6.0 5.3

29.0 14.2

#6

5.5 4.1

#8

40

PLA 2-WF I

(%) 100

#3

60

1.2 3.3

#3

80

16.7 26.1

#5

#5

79.2 85.0

#2

#2

PVC 6-RP I (%) 100

76.3 82.2

80.8 86.2

96.9 99.6

PVC 4-WP I

#7

13.7

32.7

27.0

39.7

47.6

83.6

82.0

#1

1.8

0

(f)

0.0

0.0

0.0

0.0

#6

51.5 47.2

#4

0.0

0.0

0.0

0.0

0.0

1.2

#5

20

70.5 77.9

#2

0.0

11.1

18.7

10.0

28.1

#7

20

0

#7

PET 4-RF I

40

40

20

#4

60

60

#1

#1

0.0

0.0

0.0

57.5

80

99.9 99.8

43.3

#4 100.0 100.0

100.0 100.0

#1

0

(d) 100

80

(g)

#9

(%)

20

0

#6

0.0

#8

0.0

0.0

#3

0.0 0.0

#5

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

#2

90.3

88.0

40

(%) 100

#7

PET 6-WF I

60

(e)

0.0

#4

80

0

0.0

0.0

#1

(c) (%) 100

0.0

20

4.0

40

20

0.0

60

40

11.4 3.4

80

60

0

12.42 10–6m3

(b)

#6

#9

Figure 3.7 Monomaterial separation test results expressed in terms of sedimentation efficacy for waste and regenerated samples belonging to size class I shown for increasing flow rates. Samples of 6.21  106 m3 and 12.42  106 m3 are plotted in the same graph. (a) PC 2-WF; (b) PC 3-RF; (c) PET 6-WF; (d) PET 4-RF; (e) PVC 4-WP; (f) PVC 6-RP; (g) PLA 2-WF; and (h) MATER-BI 2-WF samples.

RF, belonging to both size classes, are completely expelled from the experimental apparatus for all hydraulic configurations but for case #1. For case #1, the test conducted with a solid volume of 6.21  106 m3 of PC 3-RF belonging to the size class I (Fig. 3.7(b)) shows that the polymer settles in a higher percentage (11.4%) than in the other case (3.4%). The analogous behavior was observed for PC 3-RF belonging to the size class II with different percentages, 19% instead of 12.4% (Fig. 3.8(b)). Then, PC 3-RF shows a different behavior respect to PC 2-WF since increasing the concentration of solid material, the percentage of material settling within the apparatus

56

Use of Recycled Plastics in Eco-efficient Concrete 6.21 10–6m3

(a)

12.42 10–6m3

(b)

PC 2-WF II

(%) 100

PC 3-RF II

(%) 100

80

#6

#9

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

#6

0.0

0.0

0.7

0.0

0.0

0.0

0.0

0.0

11.0

11.4

24.1

25.1

40.7

45.0

68.3

92.4

#9

#2

#5

#3

#8

#6

8.5

3.8

19.3

12.1

43.7

76.0

71.6

77.9

80.8

99.5

97.9

99.0

100.0

100.0

99.4

#7

#9

79.6

#1

#4

#7

#2

#5

#3

#8

#6

0.0

0.0

1.3

0.0

0.0

0.9

0.0

0

2.0

20

3.2

0.0

0.0

0.0

#8

0.0

0.2

#3

0.0

0.7

#5

0.0

0.6

#2

0.0

0.0

0.8

#7

#4

40

22.1 3.3

#4

0.6

8.9

#1

#8

57.3

60

45.8

80

60

35.2

80

0

#9

MATER-BI 2-WF II

(%) 100

20

#1

(h)

PLA 2-WF II

(%) 100

40

65.4

83.3

0

#9

2.9

#6

#6

17.4

#8

26.2

#3

#3

20

12.5

(g)

#5

#2

#5

40

25.3

#7

#2

60

20

#4

#8

50.7

49.0

78.3

40

#1

#7

#4

80

60

#3

#5

PVC 6-RP II

(%) 100 67.6

95.4

98.9

97.8

96.2

99.8

98.8

99.9

100.0

100.0

100.0

100.0

100.0

100.0

80

0

#1

(f)

PVC 4-WP II 100.0

0

#9

98.1

0.0

0.0

#6

11.3

#8

0.4

0.0

0.0

0.4

0.0

0.0

#3

96.3

(e)

4.0

1.8

#5

#2

20

95.8

#7

#2

PET 4-RF II

40 11.9

10.5

#4

(%) 100 60

25.7

77.9

20

#7

#4

#1

(d) 80

40

#1

0

#9

0.0

20

0.0

0.0

#6

0.0

0.0

0.0

0.0

0.0

0.0

0.0

#8

62.4

80.8

95.3

94.6

60

(%) 100

#3

#5

PET 6-WF II

80

0

0.0

#2

(c) (%) 100

0.0

0.0

#7

#4

#1

0.0

0.0

0.0

0.0

10.6

0.0

0

12.4

40

20

11.6

60

40

19.0

80

60

#9

Figure 3.8 Monomaterial separation test results expressed in terms of sedimentation efficacy for waste and regenerated samples belonging to size class II shown for increasing flow rates. Samples of 6.21  106 m3 and 12.42  106 m3 are plotted in the same graph. (a) PC 2-WF; (b) PC 3-RF; (c) PET 6-WF; (d) PET 4-RF; (e) PVC 4-WP; (f) PVC 6-RP; (g) PLA 2-WF; and (h) MATER-BI 2-WF samples.

decreases. The different behavior of PC samples is related to the shape of the particles, which influences the sedimentation efficacy. PC 2-WF particles have a flat surface and a very jagged perimeter while PC 3-RF particles have a flat, more regular surface. PC 1-V is completely expelled from the separator for all cases except for cases #1 and #4 (Fig. 3.9(a)). In both of these cases, by increasing the volume of solid particles, sedimentation is disadvantaged. Therefore, due to their regular shape, the behavior of PC 1-VG granules is more similar to PC 3-RF than to PC 2-WF.

Hydraulic separation of plastic wastes

57

#3

#8

#6

(%) 100 72.1

#8

0.0 0.0

0.0 0.0

0.0 0.0

#3

#6

#9

PVC 2-VG

#1

#4

#7

#7

#2

#5

#3

#8

#6

#9

#3

#8

0.0 0.0

0.0 2.2

39.2 34.0

33.7

0.0 6.0

#1

#4

20

1.2 2.7

2.1 0.0

3.6 1.3

9.4

#4

40 2.2 2.8

29.1

60 11.4 22.0

80

60

0

#5

#6

#9

0 #7

#2

#5

#3

#8

1.5 0.0

96.4 94.1

99.4 99.5

80

20

#2

MATER-BI 1-V

(%) 100

40

31.5

(f)

PLA 1-VG 100.0 100.0

0

#9

1.8 1.1

#6

0.5 0.0

#8

0.0 0.0

0.0 0.9

0.0 0.0

#3

61.9

#5

38.8

(e)

0.0 0.0

#2

97.1 97.0

#4

0.0 1.2

1.2 6.9

#7

0

100.0 100.0

#5

1.6 4.1

50.5

48.6

20

6.7

40

#1

#2

60

20

(%) 100

#7

80

40

#1

#4

(d)

98.8 98.3

60

0.4 0.0

#1

PVC 1-VG

80

92.5 95.6

0

#9

91.5 88.4

(c) (%) 100

#2 #5

100.0 99.8

#7

99.0 96.3

#4

82.1 85.4

#1

20

100.0 100.0

0

32.7 23.6

40 13.5 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

60

40

79.6 79.2

80

60 20

PET 2-VG

98.9 100.0

80

(%) 100

82.8 76.2

(%) 100

(b)

PC 1-VG

99.2 100.0

(a)

12.42 10–6m3

1.1 0.0

6.21 10–6m3

#6

#9

Figure 3.9 Monomaterial separation test results expressed in terms of sedimentation efficacy for virgin material samples shown for increasing flow rates. Samples of 6.21  106 m3 and 12.42  106 m3 are plotted in the same graph. (a) PC 1-VG; (b) PET 2-VG; (c) PVC 1-VG; (d) PVC 2-VG; (e) PLA 1-VG; and (f) MATER-BI 1-VG samples.

PET 6-WF belonging to the size class I (Fig. 3.7(c)) is completely expelled from the apparatus for flow rates larger than 1.08 L/s (case #3). For case #1 and 6.21  106 m3 of solid volume treated within the device, 88% of the polymer settles within the separator chambers, whereas 90.3% of the solid volume settles after doubling the sample. A similar behavior was observed for case #4, when 43.3% and 57.5% of material settles within the apparatus when 6.21  106 m3 and 12.42  106 m3 of solid volume are treated within the device respectively. For case #7, the opposite behavior is observed. In fact, the percentage of material settling within the apparatus decreases (from 28.1% to 18.7%) as the amount of material treated within the apparatus is doubled. For case #2, the percentage of material settling within the apparatus is almost the same regardless of the volume treated within the apparatus. Insignificant or null quantities of polymer settle within the apparatus for case #5 and both solid volumes. For case #1, roughly 95% of PET 6-WF belonging to size class II settles within the hydraulic channel regardless of the volume treated within the apparatus (Fig. 3.8(c)). For case #4, the

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Use of Recycled Plastics in Eco-efficient Concrete

test carried out with 6.21  106 m3 of solid phase volume shows a larger percentage of polymer settling within the apparatus (80.8%) than the other test. Analogously, by increasing the flow rate (case #7), the percentage of material settling within the apparatus is larger (62.4% instead of 10.5%) for a smaller amount of solid volume treated within the apparatus. Also, for case #2, when 6.21  106 m3 of solid volume is treated within the device, the percentage of material settling within the apparatus is larger than in the other case, that is, 25.7% instead of 11.9%. Further increasing the flow rate, an opposite behavior is observed, that is, a larger percentage of material settles when a larger amount of material is treated within the apparatus. For the two solid volumes treated within the apparatus and for the hydraulic configuration denoted case #1, roughly the same percentage of PET 4-RF belonging to the size class I settles (82% and 83.6%; Fig. 3.7(d)). For case #4, a smaller percentage of the sample settles within the apparatus when smaller quantities of polymer are treated within the device (39.7% rather than 47.6%). The opposite behavior is observed for case #7. In this case, a smaller percentage of samples was collected in the separator chambers when 6.21  106 m3 of solid volume was treated within the device (32.7% rather than 27%). For case #2, roughly the same percentage of material settles for both solid volumes investigated. The behavior of PET 4-RF belonging to the size class II is analogous to the one described for the material belonging to the lower size class (Fig. 3.8(d)). The PET sample of virgin material (PET 2-VG) behaves similarly to waste or regenerated PET samples (Fig. 3.9(b)). For case #1 and both solid volumes treated within the apparatus, the polymer completely settles. For case #4, for tests employing 6.21  106 m3 of solid volume, 92% of the sample settles whereas, doubling the solid volume treated within the device, 95% of plastic material remains within the apparatus. For case #7, a similar percentage of material settles for both the solid volumes. For case #2, the amount of material settling within the device seems to depend on the solid volume treated. In this case, 32.7% and 23.6% of polymer can be collected within the device for 6.21  106 m3 and 12.42  106 m3 solid volume samples respectively. The polymer is completely expelled from the apparatus for cases #5, #3, #8, #6, and #9 and both solid volumes. All PET samples show that for a low fluid phase velocity, the increase of the solid volume fraction determines the increase of the sedimentation efficacy. In fact, increasing the volume of solid particles treated within the device, the fluid phase slows down and the sedimentation processes is favored. For large flow rates, the fluid phase velocity increases as well as drag effects on the particles. Then those particles reach the outlet ducts in larger amounts determining a reduction of the sedimentation efficacy. PVC 4-WP belonging to the size class I (Fig. 3.7(e)) completely settles within the device for low values of the fluid flow rate (cases #1, #4, #7). For case #2, more than 43% of polymer settles for both solid volumes. For cases #5 and #3, tests conducted treating 6.21  106 m3 of solid particles show a lower percentage of material settling within the device with respect to tests with 12.42  106 m3 of solid particles (Fig. 3.7(e)). Instead, for cases #8, #6, and #9, a larger percentage of solid particles settle within the device for the 6.21  106 m3 volume tests than for the 12.42  106 m3 volume ones. For cases #1, #4, #7, and #2, PVC 4-WP belonging to the size class II (Fig. 3.8(e)) completely settles within the device. For cases #3

Hydraulic separation of plastic wastes

59

and #8, the percentage of material settling within the device is higher than 95% and slightly larger when a lower amount of polymer is treated within the device. For case #6, 78% of the sample settles within the device when 6.21  106 m3 of solid particles are treated while 67% of the polymer can be collected in the separator chambers when the solid volume is doubled. For case #9, the larger is the amount of polymer treated within the device, the higher is the percentage of material settling within the device (49% instead of 25%). For cases #1, #4, and #7, the same percentage of PVC 6-RP belonging to the size class I (Fig. 3.7(f)) settles in the separator chambers for both solid volumes treated within the device. For cases #2 and #5, a higher percentage of polymer settles within the device for the test with the larger amount of solid volume (77.9% instead of 70.5% and 12.7% instead of 9.4%). For cases #3 and #8, the opposite occurs. For case #9, the polymer is completely expelled from the device. For cases #1, #4, #7 and #2, PVC 6-RP belonging to the size class II (Fig. 3.8(f)) almost completely settles in the device. For cases #5, #3 and #8, the percentage of material settling within the device is higher for the tests conducted with samples of smaller volume. The opposite behavior was observed for cases #6 and #9. For case #1, PVC 1-VG almost completely settles in the separator chambers for both volumes treated within the device (Fig. 3.9(c)). For cases #4 and #7, a remarkable difference between the percentages of material that settles within the chambers as a function of the amount of material treated within the device was observed. In fact, the tests conducted inserting 6.21  106 m3 of solid particles show a significantly higher percentage of settled material with respect to the tests where the amount of treated material was doubled. For cases #2 and #5, an opposite behavior was observed. In fact, as the fluid flow rate increases, a higher percentage of material settles within the separator chambers when 12.42  106 m3 rather than 6.21  106 m3 of solid particles are treated within the device. For low flow rates, PVC 2-VG completely settles in the separator chambers for both volumes treated within the device (Fig. 3.9(d)). For cases #7 and #2, a slightly larger percentage of solid particles settles within the chambers in the tests with 6.21  106 m3 of polymer treated within the device. The opposite occurs for cases #5, #8, and #6. Therefore, for low values of the flow rate (lower than 1 L/s), no remarkable differences in the percentage of PVC sample settling within the device were observed for both solid volumes investigated. For slightly larger values of the flow rate, between 1 L/s and 1.13 L/s, the increase in the amount of solid material introduced into the separator results in a reduction of the sedimentation efficacy, since the interaction between the solid and the fluid phases is more effective and the fluid phase tends to drag the solid particles toward the outlet ducts. For values of the flow rate larger than 1.13 L/s, increasing the amount of material treated within the device, a higher percentage of solid particles tend to settle within the apparatus. For case #1, a small percentage of PLA 2-WF belonging to the size class I (Fig. 3.7(g)) settles in the separator chambers in the test with 6.21  106 m3 of polymer treated within the device. The increase of the solid volume determines the increase of the sedimentation efficacy. The bioplastics are almost completely expelled from the apparatus for flow rates larger than 0.84 L/s. For cases #1 and #4, a remarkable percentage of PLA 2-WF belonging to the size class II settles in the separator chambers when a lower amount of polymer is treated within the device (45.8% instead of 35.2%

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Use of Recycled Plastics in Eco-efficient Concrete

and 8.9% instead of 3.3%, respectively). An opposite behavior was observed for case #7, being the percentage of settled material equal to 22.1% when 12.42  106 m3 of bioplastics are treated within the device and almost equal to 0% for half volume. For cases #1, #4, and #7, PLA 1-VG (Fig. 3.9(e)) completely settles within the separator chambers. For case #2, the percentage of PLA 1-VG settling in the separator is remarkable for both volumes (roughly 96%). For cases #5, #3, and #8, a smaller percentage of biopolymer settles for the smaller solid volume case (6.21  106 m3). The sample is completely expelled from the apparatus for flow rates larger than 1.24 L/s. For case #1, the larger is the amount of MATER-BI 2-WF belonging to the size class I treated within the device, the larger is the percentage of settled material (85% instead of 79.2%; Fig. 3.7(h)). A similar behavior was observed for cases #4 and #7 (26.1% instead of 16.7% and 3.3% instead of 1.2%, respectively). Instead, the opposite behavior was observed for case #2. For case #1, MATER-BI 2-WF belonging to the size class II settles in analogous percentages for both volumes of material treated within the device (Fig. 3.8(h)). Increasing the flow rate (cases #4, #7 and #2), larger percentages of MATER-BI 2-WF belonging to the size class II settle in the separator chambers when 12.42  106 m3 of solid volume are treated within the device rather than 6.21  106 m3. For cases #1 and #4, a considerable percentage of MATER-BI 1-VG (Fig. 3.9(f)) settles in the separator chambers for both solid volumes treated within the device. For cases #7 and #2, the sedimentation efficacy is remarkable (higher than 17%) and larger when larger amounts of biopolymer are treated. The sedimentation efficacy is lower than 4% for flow rates larger than 1.08 L/s.

3.5.1.2

Multimaterial separation tests

Multimaterial tests were conducted with mixtures of traditional plastics, that is, PETPVC, PET-PC, and PVC-PC, and mixtures of traditional and bioplastics, that is, PETPLA. Both grade and recovery were computed because the separation process may be considered effective if both quantities are remarkable, that is, the useful phase is not contaminated by the other material and a considerable amount of useful fraction is recovered from the initial sample. As a general criterion, multimaterial samples of polymers #1 and #2 (where polymer #1 is expected to settle and polymer #2 to be expelled) were tested at the hydraulic configurations and sample sizes assuring percentages of polymer #1 expelled from the apparatus or polymer #2 settled within the apparatus lower than 5% (hereinafter multimaterial test consistency criterion). This information was obtained from the monomaterial tests. We will present the results of multimaterial tests conducted with PET-PVC and PET-PLA mixtures. The results of multimaterial separation tests conducted with mixtures of traditional plastics of volume equal to 12.42  106 m3 are similar to the ones obtained with a volume equal to 6.21  106 m3. Also increasing the volume of the sample, the content of the useful phase has always been improved no matter its initial concentration in the mixture and the polymer separation is generally enhanced for particles of larger size and it is not influenced by the shape of the particles. PET-PVC samples containing PET 6-WF (hereinafter PET_WF) and PVC 4-WP (hereinafter PVC_WP) were tested. Due to the polymer densities, PET was collected

Hydraulic separation of plastic wastes

61

98.1 77.1 88.6 99.2

93.6 78.6 97.0 99.2

98.9 87.3 86.3 98.8

71.6

97.5

99.4 91.8

Sample #3

98.3 99.7 83.3

87.7 93.1 96.0 92.6

Sample #2

Case #5, size class II

Sample #3

Sample #4

46.1

82.5 96.9 95.0 74.4

91.0 84.9

96.7 98.2

Case #5, size class I

Sample #1 Sample #2

Sample #4

Sample #1

Grade PET_WF

Recovery PET_WF

Sample #2

Grade PVC_WP

Sample #3

98.5 95.9

97.9 100.00 100.0

Sample #3

76.0 90.1

92.5 82.2 97.4 99.0

Sample #2

90.0 98.1 98.9 93.9

96.1 91.0 95.3 98.1

Sample #1

89.7

100.0 91.1 90.1 100.0

Case #8, size class II

100.0 93.6 77.0 100.0

Case #3, size class II

91.6 90.5 99.0

Sample #4

99.1

Sample #1

Sample #4

Recovery PVC_WP

Figure 3.10 Results of multimaterial tests of PET_WF/PVC_WP mixtures with particles belonging to size classes I and II.

in the concentrated fraction expelled from the apparatus. For PET_WF/PVC_WP samples, the multimaterial tests were conducted for particles belonging to the size class II and cases #5, #3, and #8. To test the influence of the particle size on the separation effectiveness, multimaterial separation tests were carried out also for particles of PET_WF and PVC_WP that belong to the size class I and the hydraulic configuration denoted as case #5. For particles that belong to the size class I, the grades of PET and PVC increase according to the polymer concentration within the initial mixtures except for mixture with 40% PET_WF and 60% PVC_WP (Fig. 3.10). For all the cases investigated, the concentration of PET within the concentrated fractions was significantly larger than its concentration in the initial mixtures. The recovery of PET is remarkably consistent no matter its initial concentration (96.6% on average). For instance, for samples composed of 85% of PET and 15% of PVC, the separation process was significantly effective with a grade of PET of 96.7%, recovery of 98.2% (Fig. 3.10), and concentration rate 1.14. At the same hydraulic configuration, increasing the particle size (size class II), the grade of PET increases for all the studied cases ranging within the interval 93.6%e99.4% for its concentration in the initial mixture increasing from 15% to 85% (Fig. 3.10). The recovery is in general lower than for particles of size class I. This is due to the larger size of the particles which favors their sedimentation within the apparatus at a larger extent than smaller size particles. The test results for cases #3 and #5 are remarkable. Though the flow rate is the same (1.1  103 m3/s), the hydraulic configuration is different (four opened outlet ducts and 1.0 m of hydraulic head for case #3 instead of three opened outlet ducts and 1.5 m of hydraulic head for case

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Use of Recycled Plastics in Eco-efficient Concrete

#5) and the separation process is more effective for case #3 with higher grades and recoveries respect to case #5 (Fig. 3.10). This is due to local effects occurring within the recirculation areas which appear more vigorous, increasing the number of opened outlet ducts. Then, eventual PET particles trapped within the PVC accumulations may be captured by the vortices within the recirculation zones and, after interacting with the main current flow, they can be expelled from the apparatus. This phenomenon has an effect on both the recovery and grade of PET and on the grade of PVC. Noticeably the recovery of PVC is significantly large for all the cases investigated, ranging from 98.1% to 100.0%. Increasing the flow rate, the grade of PET slightly decreases while the opposite behavior is observed during the recovery. On the other hand, the grade of PVC increases while the recovery decreases. This depends on the higher velocities established or occurring within the apparatus with the larger flow rate, which prevents lighter particles from settling and increases the amount of PET expelled from the apparatus. Similarly, the flow may drag a small amount of PVC particles up to their discharge from the apparatus. As a consequence, the grade of PVC will improve while the grade of PET will worsen. Multimaterial tests conducted on mixtures of PET and PLA will be described next. The motivation for these tests was the attempt to understand if the hydraulic separator is suitable to separate bioplastics that may enter a mechanical recycling process and act as pollutant of the traditional polymers to be recovered. Mixtures of PET 6-WF and PLA 2-WF belonging to size class I were employed. Tests with PET 4-RF were not conducted because its characteristics are very similar to PET 6-WF. Monomaterial separation tests showed that for case #1 PET mostly settles within the separator chambers, while PLA is mainly expelled. Multimaterial tests were conducted using mixtures of 85% PET and 15% PLA and 60% PET and 40% PLA because the percentage of

Recovery PLA

Grade PLA

Grade PET

Recovery PET

%

40 30

79.1

37.1

50

50.4

60

64.4

70

70.2

83.1

80

86.1

90

91.4

100

20 10 0 PET 6-WF 60%/PLA 2-WF 40% PET 6-WF 85%/PLA 2-WF 15%

Figure 3.11 Grade and recovery of polyethylene terephthalate (PET) and polylactic acid (PLA) for multimaterial tests of PET 6-WF/PLA 3-WF, hydraulic configuration case #1.

Hydraulic separation of plastic wastes

63

PLA expected in the plastic waste stream is lower than the percentage of PET. Fig. 3.11 shows the remarkable grade of PET (91.4%) obtained for case #1 and mixture with 85% PET and 15% PLA. PET grade slightly decreases (79%) when the percentage of PET in the sample decreases. The recovery of PET is remarkably consistent no matter its initial concentration (86.0% and 83.0%).

3.5.2

Results from the numerical simulations

Computational Fluid Dynamics (CFD) is a science that produces quantitative predictions of fluid-flow phenomena based on the conservation laws governing the fluid motion (Kundu et al., 2012). The CFD software ANSYS FLUENT (ANSYS, 2011a,b) was used for the investigation of the velocity field within the separation channel of both water and mixtures of plastic particles and water. The first step for the numerical simulations is the creation of the system geometry, which involves the reconstruction of the system containing the flow under investigation through a model as similar as possible to reality. This step can be done with a separate CAD package. The following step is the domain discretization by using the grid generation tool. In ANSYS FLUENT, three kinds of grid may be chosen: structured, unstructured, hybrid. The choice has to take into account the fluid-flow characteristics. For instance, for viscous calculation a boundary layer mesh has to be constructed. For turbulent flow calculations, the distance from the wall of the first cell in the boundary layer mesh has to take into account in the near-wall treatment of the turbulence model (Vierendeels and Degrotoe, 2014). Fig. 3.12 presents two examples of discretization implemented with ANSYS FLUENT, i.e., the unstructured and hybrid grids.

(a)

(b)

0.015

0 0.0075

0.03 (m) 0.022

Figure 3.12 (a) Unstructured and (b) hybrid grids.

0.03 (m)

0.015

0 0.0075

0.022

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Use of Recycled Plastics in Eco-efficient Concrete

(a) 0.5 0.4 0.3 0.2 0.1

23.86 23.855 23.85 23.845 23.84 23.835 23.83 23.825 23.82 23.815 23.81

0 –0.1 –0.2 –0.3 –0.4 –0.5 10.25

10.3

10.35

10.4

10.45

10.5

10.55

10.6

10.65

0.5 0.4 0.3 0.2 0.1 0

23.86 23.855 23.85 23.845 23.84 23.835 23.83 23.825 23.82 23.815 2.81

(b)

–0.1 –0.2 –0.3 –0.4 –0.5 10.25

10.3

10.35

10.4

10.45

10.5

10.55

10.6

10.65 0.5 0.4 0.3 0.2 0.1 0 –0.1 –0.2 –0.3 –0.4

23.86 23.855 23.85 23.845 23.84 23.835 23.83 23.825 23.82 23.815 23.81 10.25

10.3

10.35

10.4

10.45

10.5

10.55

10.6

10.65

–0.5

0.5 0.4 0.3 0.2 0.1 0 –0.1 –0.2 –0.3 –0.4

23.86 23.855 23.85 23.845 23.84 23.835 23.83 23.825 23.82 23.815 23.81 10.25

10.3

10.35

10.4

10.45

10.5

10.55

10.6

10.65

–0.5

Figure 3.13 Streamlines overlapped onto colormaps for case #9 obtained with the (a) laminar and (b) realizable k-ε model. Each figure shows horizontal velocity magnitude on top and vertical velocity magnitude at the bottom for the grid dimension 3  103 m.

The choice of the numerical model was related to the knowledge of the velocity field within the apparatus derived from the experimental tests. From the measurements, Reynolds numbers ranging in the interval 1500e2800 were obtained. Hence, a laminar model was initially implemented in ANSYS Fluent. Then turbulence models were used to make comparisons with the laminar model. Adequate boundary conditions were set at the inlet, outlet, and wall boundaries, in order to properly compute the flow field in the area of interest. Fig. 3.13 shows the streamlines overlapped to the colormaps of the horizontal and vertical velocity components, for laminar and RANS turbulence models and for the hydraulic configuration denoted case #9. The horizontal velocity is positive along

Hydraulic separation of plastic wastes

65

the principal transport current and, due to the motion of the vortices, it is negative in the left side of the lower recirculation zone and in the right side of the upper one. Instead the vertical velocity component presents positive values and tends to increase in the zone between the lower cusps and the right side of the upper vortex; vice versa it has negative values and tends to decrease in the zone between the upper cusps and the left side of the lower vortex. Colormaps obtained by different models show almost the same results and are validated by the experimental ones.

3.6

Conclusions

In this contribution, the effectiveness of the hydraulic separator has been evaluated according to the type of polymer used and the hydraulic configuration. Separation tests are useful to evaluate the effectiveness of the hydraulic separator for the separation of plastic particles. The monomaterial separation tests allow the identification of polymers of given density, size, and shape, which can either settle inside the hydraulic separator or be expelled from the apparatus in a certain hydraulic configuration. The results of these tests, conducted with the two different geometric arrangements, demonstrate that geometric arrangement A is more effective than geometric arrangement B for a larger number of combinations of the plastic materials. For this reason, arrangement A has been employed in multimaterial tests. Under proper hydraulic configurations, the separation of one type of polymer from a mixture of two different polymers is feasible. In particular good results have been achieved using PET-PVC, PET-PC, PVC-PC, and PET-PLA mixtures. The monomaterial tests carried out with solid material samples of 6.21  106 m3 and 12.42  106 m3 demonstrate that there are no significant differences in the percentage of settled material within the experimental apparatus. This implies the possibility to treat with the hydraulic separator a greater quantity of solid material in the same amount of time. It is worth noting that with respect to the tests conducted with 6.21  106 m3 of solid material, as long as the particle sedimentation velocity is comparable to the fluid phase velocity, the solid particles tend to settle to a lesser extent. Conversely, when the fluid phase velocity is greater than the sedimentation velocity of the particles, an opposite behavior is observed. In fact, a greater percentage of material settles in the 12.42  106 m3 volume tests. The different behavior is related to the increased turbulence that develops within the apparatus as the fluid flow increases, which results in an enhanced solidefluid interaction. Multimaterial tests carried out with a solid volume of 12.42  106 m3 confirm the possibility of separating one polymer from a mixture consisting of two polymers with different physical characteristics. The comparison of multimaterial separation tests conducted with solid samples of 6.12  106 m3 and 12.42  106 m3 shows no significant variations of the separation efficiency. Thus, even by increasing the treated solid volume for unit time, the hydraulic separator is suitable to recover high-quality products.

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Use of Recycled Plastics in Eco-efficient Concrete

Monomaterial tests conducted on PLA and MATER-BI samples showed that the hydraulic separator can be effectively employed to separate bioplastics. A numerical model is presented and validated as well. This step is carried out comparing different turbulent models with the experimental results. To further characterize the tool, few improvements are certainly to be considered. First of all, separation tests with a further increased plastic particle concentration within the fluid phase can be useful to study the eventual change of the coupling regime within the investigated two-phase system. In addition, other geometric arrangements may be experimentally tested to evaluate their influence on the apparatus effectiveness.

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Eswaraiah, C., Kavitha, T., Vidyasagar, S., Narayanan, S.S., 2008. Classification of metals and plastics from printed circuit boards (PCB) using air classifier. Chemical Engineering and Processing 47 (4), 565e576. Gent, M.R., Menendez, M., Tora~no, J., Diego, I., 2009. Recycling of plastic waste by density separation: prospects for optimization. Waste Management and Research 27 (2), 175e187. Gent, M.R., Menéndez, M., Tora~no, J., Torno, S., 2011. Optimization of the recovery of plastics for recycling by density media separation cyclones. Resources, Conservation and Recycling 55, 472e482. Hopewell, J., Dvorak, R., Kosior, E., 2009. Plastics recycling: challenges and opportunities. Philosophical Transaction of Royal Society B 364, 2115e2126. Jody, B.J., Daniels, E.J., 2010. End-of-life Vehicle Recycling: The State of the Art of Resource Recovery from Shredder Residue. National Technical Information Service, US Department of Commerce, Springfield, USA. Jody, B., Pomykala, J., Daniels, E., 2003. Cost effective recovery of thermoplastics from mixed scrap from mixed-scrap plastics. Materials Technology 18e24. Kr€ahling, H., Sartorius, I., 2012. Plastics after use: sustainable management of material and energy resources. Polymer Science: A Comprehensive Reference 10, 581e595. Kundu, K.P., Cohen, I.M., Dowling, D.R., 2012. Fluid Mechanics. Elsevier. Luciani, V., Bonifazi, G., Rem, P., Serranti, S., 2015. Upgrading of PVC rich wastes by magnetic density separation and hyperspectral imaging quality control. Waste Management 45, 118e125. Lupo, E., Moroni, M., La Marca, F., Fulco, S., Pinzi, V., 2016. Investigation on an innovative technology for wet separation of plastic wastes. Waste Management 51, 3e12. Malcolm Richard, G., Mario, M., Javier, T., Susana, T., 2011. Optimization of the recovery of plastics for recycling by density media separation cyclones. Resources, Conservation and Recycling 55, 472e482. Marques, G.A., Tenorio, J.A.S., 2000. Use of froth flotation to separate PVC/PET mixtures. Waste Management 20, 265e269. Moroni, M., Cenedese, A., 2005. Comparison among feature tracking and more consolidated velocimetry image analysis techniques in a fully developed turbulent channel flow. Measurement Science and Technology 16 (11), 2307e2322. Moroni, M., Cicci, A., Bravi, M., 2014. Experimental investigation of a local recirculation photobioreactor for mass cultures of photosynthetic microorganisms. Water Research 52, 29e39. Moroni, M., Lupo, E., La Marca, F., 2017. Investigation on an innovative technology for wet separation of plastic wastes. Waste Management 66, 13e22. Moroni, M., Lupo, E., Della Pelle, V., Pomponi, A., La Marca, F., 2018. Experimental investigation of the productivity of a wet separation process of traditional and bio-plastics. Separations 5 (2), 26. Nakajima, J., Nakazawa, H., Sato, H., Kudo, Y., 1999. Removal of PVC from PET by air separation. In: The 5th International Symposium on East Asian Recycling Technology, Japan, pp. 269e272. Park, C.H., Jeon, H.S., Park, J.K., 2007. PVC removal from mixed plastics by triboelectrostatic separation. Journal of Hazardous Materials 144 (1e2), 470e476. Pascoe, R.D., 2005. The use of selective depressants for the separation of ABS and HIPS by froth flotation. Minerals Engineering 18, 233e237. Plastics Europe, 2017. Plastics e The Facts 2016. An Analysis of European Latest Plastics Production, Demand and Waste Data.

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Pongstabodee, S., Kunachitpimol, N., Damronglerd, S., 2008. Combination of threestage sinkefloat method and selective flotation technique for separation of mixed post-consumer plastic waste. Waste Management 28, 475e483. Rem, P., Di Maio, F., Hu, B., Houzeaux, G., Baltes, L., Tierean, M., 2013. Magnetic fluid equipment for sorting of secondary polyolefins from waste. Environmental Engineering and Management Journal 12 (5), 951e958. Saisinchai, S., 2014. Separation of PVC from PET/PVC mixtures using flotation by calcium lignosulfonate depressant. Engineering Journal 18 (1), 45e53. Scott, D., 1995. A two-colour near-infrared sensor for sorting recycled plastic waste. Measurement Science and Technology 6 (2), 159. Serranti, S., Luciani, V., Bonifazi, G., Hu, B., Rem, P.C., 2015. An innovative recycling process to obtain pure polyethylene and polypropylene from household waste. Waste Management 35, 12e20. Shen, H., Forssberg, E., Pugh, R.J., 2001. Selective flotation separation of plastics by particle control. Resources, Conservation and Recycling 33, 37e50. Shent, H., Pugh, R.J., Forssberg, E., 1999. A review of plastics waste recycling and the flotation of plastics. Resources, Conservation and Recycling 25 (2), 85e109. Shindler, L., Moroni, M., Cenedese, A., 2010. Spatialetemporal improvements of a two-frame particle-tracking algorithm. Meas. Sci. Technol. 21, 115401. https://doi.org/10.1088/09570233/21/11/115401. Shindler, L., Moroni, M., Cenedese, A., 2012. Using optical flow equation for particle detection and velocity prediction in particle tracking. Applied Mathematics and Computation 218 (17), 8684e8694. Shirolkar, J.S., Coimbra, C.F.M., Queiroz McQuay, M., 1996. Fundamental aspects of modeling turbulent particle dispersion in dilute flows. Progress in Energy and Combustion Science 22, 363e399. Shonfield, P., 2008. LCA of Management Options for Mixed Waste Plastic. Waste Resource Action Programme, WRAP Final Report, London. Takoungsakdakun, T., Pongstabodee, S., 2007. Separation of mixed post-consumer PETe POMePVC plastic waste using selective flotation. Separation and Purification Technology 54 (2), 248e252. Tilmatine, A., Medles, K., Bendimerad, S.E., Boukholda, F., Dascalescu, L., 2009. Electrostatic separators of particles: application to plastic/metal, metal/metal and plastic/plastic mixtures. Waste Management 29 (1), 228e232. Vierendeels, J., Degrotoe, J., 2014. Introduction to Computational Fluid Dynamics. Annual Lecture Series Von Karman Institute. Wang, H., Chen, X.-L., Bai, Y., Guo, C., Zhang, L., 2012. Application of dissolved air flotation on separation of waste plastics ABS and PS. Waste Management 32, 1297e1305. Wang, C.-Q., Wang, H., Liu, Q., Fu, J., Liu, Y., 2014. Separation of polycarbonate and acrylonitrileebutadieneestyrene waste plastics by froth flotation combined with ammonia pretreatment. Waste Management 34, 2656e2661. Wu, G., Li, J., Xu, Z., 2013. Triboelectrostatic separation for granular plastic waste recycling: a review. Waste Management 33, 585e597. Yanar, D.K., Kwetkus, B.A., 1995. Electrostatic separation of polymer powders. Journal of Electrostatics 35 (2e3), 257e266. € Burat, F., Y€uce, A.E., G€uney, A., Kangal, M.O., 2013. Separation of PET and PVC Yenial, U., by flotation technique without using alkaline treatment. Mineral Processing and Extractive Metallurgy Review: International Journal 34 (6), 412e421.

Production of recycled polypropylene (PP) fibers from industrial plastic waste through melt spinning process

4

Rabin Tuladhar 1 , Shi Yin 2 1 Centre of Tropical Environmental and Sustainability Science, College of Science and Engineering, James Cook University, Townsville, QLD, Australia; 2College of Science and Engineering, James Cook University, Townsville, QLD, Australia

4.1

Introduction

Traditionally, steel mesh is used in concrete footpaths to control shrinkage cracks and enhance its robustness. As an alternative to steel mesh, various fibers such as steel and natural and synthetic fibers are also used in concrete to improve its postcracking performance. The most commonly used synthetic fibers in concrete are virgin macro plastic fibers. Macro plastic fibers are normally 30e60 mm long with cross-sectional area of 0.6e1 mm2 (Yin et al., 2015a). Micro plastic fibers can be mixed with concrete directly in concrete trucks and poured at site, eliminating the need of cutting and placing steel mesh. Macroplastic fibers also provide excellent postcracking performance by bridging cracks in concrete and preventing crack propagation. Plastic fibers, therefore, have increasingly become popular for construction of concrete footpaths, precast elements, and shotcrete tunnel linings. Polypropylene (PP) macro plastic fibers are the most commonly used plastic fibers in construction industry due to their ease of production, high alkaline resistance, high tensile strength, and high Young’s modulus (Yin et al., 2015a). Recently, researchers have focused on the potential of using recycled plastic fibers in concrete. Global plastic production every year is more than 335 million tons, out of which only 9% is currently being recycled leading to burgeoning plastic pollution (Plastics Europe, 2017; Velis, 2014). Being able to recycle a part of this plastic waste into fibers that can be used in concrete gives a whole new opportunity of recycling plastic waste and reducing global plastic pollution. Furthermore, use of recycled plastic fibers in concrete contributes toward sustainable development by reducing the consumption of steel and virgin plastic raw materials. Plastics can broadly be classified into two typesethermosets and thermoplastics. Thermosets undergo a chemical change when heated. These plastics cannot be remelted and reformed (Plastics Europe, 2017). Examples of thermosets are polyurethane (PUR), epoxy resins, acrylic resins, vinyl ester, silicone, etc. Thermoplastics, on

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00004-9 Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete

the other hand, melt when heated and harden when cooled. This process is reversible for thermoplastics, making it easier to reheat, recycle, and reshape into different products. Some commonly used thermoplastics are polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polyethylene (PE), polyvinylchloride (PVC), high-density polyethylene (HDPE), and low-density polyethylene (LDPE). Thermoplastic wastes can be recycled into plastic fibers. Most of the research so far is focused on recycling PET plastics and is limited to laboratory-scale tests with extremely low production rates (Foti , 2011; Fraternali et al., 2011; Kim et al. 2010; Oliveira and Castro-Gomes, 2011). Furthermore, PET plastics are found to degrade when embedded in highly alkaline cement matrix in concrete making its use impractical (Yin et al., 2016). Literature on production and use of recycled PP fibers is very limited. Our research is focused on the industrial-scale production of recycled PP fibers with high mechanical properties. This paper illustrates our research on the mechanical recycling of PP fibers from industrial PP wastes. Our production process includes melt spinning and hotdrawing processes where recycled PP plastic waste is first melted into granules and then extruded and hot drawn. Unlike other methods available in the literature, this process is suitable for large-scale commercial production. Melt spinning and hot-drawing processes highly orient the PP molecular chains, significantly improving their crystallinity, and hence, improving the tensile strength and Young’s modulus of the fibers. Material characterization were conducted using Fourier transform infrared (FTIR) and differential scanning calorimeter (DSC) tests to determine the crystallinity and structure of virgin and recycled PP raw materials and fibers. Tensile tests were also carried out on virgin and recycled PP fibers to determine the suitability of the production process. Fibercon QLD, our industrial partner, provided us an access to the fiber manufacturing plant in Ballarat, Australia. Most of the experimental studies were carried out at James Cook University Townsville, Australia. Material characterization test (DSC) was done at material laboratory at Royal Melbourne Institute of Technology (RMIT), Melbourne, Australia.

4.2

Physical cutting of waste plastic

Some researchers have tried producing recycled plastic fibers by physically cutting plastic wastes. Oliveira and Castro-Gomes (2011) produced straight recycled plastic fibers by cutting lateral sides of PET bottles using semiautomatic cutting machines. Fibers produced were 2 mm wide, 0.5 mm thick, and 35 mm long with an aspect ratio of 31. Foti (2011) produced circular PET fibers by transversely cutting PET bottles into circular plastic rings. It was observed that the circular recycled fibers performed better than the straight-cut fibers due to better concrete-fiber bonding. These techniques of recycling plastic bottles into plastic fibers do not require any complex recycling and manufacturing processes. However, the technique is laborintensive and is only feasible for small-scale production of recycled plastic fibers. Furthermore, variability in the type and quality of plastic bottles used in the process results in poorer and unreliable mechanical properties of the fibers. Fibers

Production of recycled polypropylene (PP) fibers

71

recycled through these techniques only could achieve tensile strength of around 160 MPa and Young’s modulus of about 3 GPa (Foti, 2011). These techniques are not suitable for industrial-scale production and commercial use of recycling plastic fibers in concrete.

4.3

Mechanical recycling of plastic wastes

Mechanical recycling of plastic wastes includes mechanical processing of plastic wastes to produce secondary products. This process is also called as secondary recycling. Mechanical recycling is the most commonly used method to recycle thermoplastic wastes, as it is relatively easy and economic. Mechanical recycling of plastic wastes is also the most suitable method to produce recycled plastic fibers. Researchers have used mechanical recycling of different types of plastic wastes such as PP, PET, and HDPE to produce recycled plastic fibers for reinforcing concrete. Fraternali et al. (2011), Ochi et al. (2007), and Kim et al. (2010) produced recycled PET fibers by mechanical recycling of plastic wastes. PET granules are easily crystallized and can stick on the inner wall of the extruder making it difficult and costly to reprocess PET. Furthermore, PET plastics are found to degrade when embedded in highly alkaline cement matrix in concrete (Yin et al., 2016). This research is focused on production of recycled PP fibers because of its ease in recycling, good mechanical properties, and high alkali resistance.

4.3.1

Steps in mechanical recycling of plastic wastes

Mechanical recycling of plastic wastes normally involves a series of treatment and processing stages such as collection, sorting, milling, washing and drying, and reprocessing.

4.3.1.1

Collection and sorting plastic wastes

Postconsumer and postindustrial plastic wastes require different sorting and processing techniques. Postconsumer plastic wastes collected from municipal waste recovery facilities are usually commingled with other domestic waste products such as organic wastes, metal, wood, glass, etc. Postindustrial plastic wastes are produced through industrial processes and include off-specification materials, production scrap, packaging, and offcuts. Industrial plastic waste is usually more homogenous and requires less sorting and washing efforts compared to postconsumer plastic wastes. Plastic wastes are sorted manually and using automated techniques to separate them from other waste components such as metals, glass, wood, and organic matter. It is also important to separate different types of plastics based on their resin categories such as PET, PP, HDPE, and PS for efficient recycling and to increase the value of the recycled products. Mixing different types of plastic resins can significantly degrade physical and mechanical properties of recycled plastics. Presence of dyes, additives, and contaminants also degrade the quality of recycled products.

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Use of Recycled Plastics in Eco-efficient Concrete

Manual sorting of different types of plastic wastes is done by visual identification based on appearance, texture, color, shape, and labeling. Manual sorting can be done for large-size waste products; however, it is a very labor-intensive and inefficient process. Near infrared (NIR) spectroscopy is an automated technique which is widely used in sorting plastic wastes. In NIR sorting technique, plastic wastes are subjected to nearinfrared light waves (Ragaert et al., 2017). Different types of plastic wastes are separated based on their different reflectance of near-infrared light waves. This technique, however, cannot be used for black or dark-colored plastics. Plastic wastes can also be exposed to X-rays to detect and separate PVC plastic wastes. Due to chlorine content in PVC, they are easily detectable by exposing them to X-rays.

4.3.1.2

Shredding, cleaning, and sorting plastic resin types

After sorting plastics into different streams based on their resin types and quality, they are shredded or ground into small flakes as smaller size plastic flakes are easier to be transported and processed. Air shifters and ballistic separators are used to remove contaminants such as dirt and paper labels. They are also used to separate light-weight plastics from the heavier plastics. Electrostatic sorting technique separates different plastic resins by passing plastic flakes through an electric field. This technique is effective in removing dust and separating plastics with similar densities such as PP and PE (Ruj et al., 2015). Plastic flakes are washed and dried, if required. Further sorting of plastic resin types is done using float-sink technique. Float-sink sorting (or flotation) system is commonly used for sorting shredded plastic flakes taking advantages of different densities of plastic resins. In the float-sink sorting method, shredded plastic flakes are placed in liquid (usually water) where lighter plastics such as PP, PE, HDPE, and LDPE float whereas heavier plastics such as PS, PET, PVC sink in the water bath (Ragaert et al., 2017).

4.3.1.3

Reprocessing of plastic

Plastic flakes after sorting are melted and extruded to form plastic pellets or granules. These recycled plastic pellets/granules are transported to plastic manufacturers for reuse. Recycled plastics are produced from plastic pellets/granules using either wetspinning, dry-spinning, or melt spinning techniques (Adomaviciute et al., 2018). Among these techniques, melt spinning technique is the most commonly used method for production of plastic fibers. During reprocessing, plastic properties degrade as it undergoes high temperature and mechanical shearing. Due to the degradation of plastic while reprocessing, recycled plastic pellets are generally not used to produce the same material as its original form. Recycled plastics are mostly used to produce products of lower grade than their original forms. Various reprocessing techniques are often used by recycling industries during the mechanical recycling of plastic waste to improve the properties of recycled plastic.

Production of recycled polypropylene (PP) fibers

4.3.2

73

Degradation of plastic during reprocessing

During service life of plastic products, properties of plastics degrade due to long exposure to sunlight, air, water, heat, weathering, and chemical reactions. Degradation also occurs during the mechanical recycling of plastic wastes due to thermomechanical degradation (Mbarek et al., 2006). Thermal degradation occurs due to high temperature and presence of oxygen during reprocessing. Large shear force applied during reprocessing of plastic causes mechanical degradation due to breaking of molecular chain segments. Thermomechanical degradation results in chain scission, branching, and cross-linking of polymers. During the recycling process, plastics are often subjected to double heating and reprocessingdonce at the reprocessing plants where plastic wastes are processed into plastic granules, and again at the manufacturing plants where recycled plastic granules are processed to produce end products. This double heating and reprocessing further cause deterioration of recycled plastic properties. Deterioration of properties of plastic also occurs due to mixing of contaminants (such as paper scraps additives) and heterogenous resin types and grades. Different polymers have unique and incompatible degrees of polymerization and chemical structures. Mixing of various types of polymers along with the presence of contaminants further complicates the recycling process (Brems et al., 2012). Extent of degradation of plastic during mechanical recycling process greatly varies for different polymer resin types (Fig. 4.1, Yin et al., 2015c). Oblak et al. (2015)

HDPE

Linear

Chain branching

Linear

Crosslinking

Linear

Chain scission

Crosslinking

LDPE

PP

Liquid-like material

Increasing reprocessing cycles

Figure 4.1 Thermomechanical degradation of plastic due to chain branching, cross-linking, and chain scission of HDPE, LDPE, and PP with increase of reprocessing cycles (Yin et al., 2015c).

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Use of Recycled Plastics in Eco-efficient Concrete

observed chain scission and chain branching with repeated extrusion cycles in HDPE which reduced longterm mechanical stability and performance. Degradation of PP due to high temperature zone and repeated processing cycles were studied by Costa et al. (2005). The authors reported that at low temperature (270
C) and higher extrusion cycles (>19) resulted in chain scission and reduction in molar mass. This significantly reduced tensile strength and breaking strain. It, however, had little effects on yield stress and Young’s modulus. Degradation of plastic during its service life and recycling process compromises its physical and mechanical properties and poses processability issues. HDPE and LDPE have low thermal stability. Melt flow index (MFI) in HDPE and LDPE shows 70% decrease after six reprocessing cycles. Decrease in MFI makes recycled HDPE and LDPE plastic difficult to extrude making production process more energy-intensive (Martin-Alfonso et al., 2012). MFI in PP is stable up to six reprocessing cycles indicating that PP has good thermal stability and less processability issues compared to HDPE and LDPE (Aurrekoetxea et al., 2001). To produce recycled plastic fibers, various reprocessing techniques can be implemented to overcome the deterioration of properties and processability issues. Crystallization and melt-bending recycled plastics with various types of resins can improve mechanical properties of recycled plastic fibers.

4.3.2.1

Crystallization

Researchers have observed that reprocessing PP waste up to six cycles increased Young’s modulus from 1700 to 2000 MPa, and yield stress from 34.8 to 36.4 MPa (Aurrekoetxea et al., 2001). Increase in Young’s modulus and yield stress of recycled PP at low number of reprocessing cycles is attributed to increase in crystallization due to the rearrangement of molecular chains broken during recycling. However, for HDPE and LDPE, no significant changes in crystallinity and stiffness were observed up to 10 cycles of reprocessing. Increase in reprocessing cycle (>30) resulted in decrease in crystallinity in HDPE and LDPE (Oblak et al., 2015; Jin et al., 2012).

4.3.2.2

Melt blending

Recycled plastics are often blended with virgin plastics or other polymer resins during recycling process to improve their mechanical properties. This process is termed as melt blending. Mixing of recycled plastic (HDPE, LDPE, and PP) with virgin polymer of same type improves their tensile strength comparable to the properties of 100% virgin plastic (Meran et al., 2008; Yin et al., 2015b). Fig. 4.2 shows improvement in tensile strength of HDPE, LDPE, and PP plastic fibers produced by blending recycled polymers with the virgin polymer of the same type (Meran et al., 2008). Blending recycled plastic with various other recycled plastic polymers also shows improvement in mechanical properties. Hasanah et al. (2014) and Strapasson et al. (2005) observed that blending of recycled PP with HDPE and LDPE improved its tensile properties and

Production of recycled polypropylene (PP) fibers

Tensile strength (MPa)

80

75

HDPE LDPE PP

70

60

50

40

100% Recycled 80%

60%

40%

20%

Virgin

Figure 4.2 Tensile strength of HDPE, LDPE, and PP recycled plastic fibers blended with the same type of virgin polymers (Meran et al., 2008).

Young’s modulus. When reprocessing mixed polymer types and commingled plastic wastes, chemical compatibilizers can be used to improve adherence between different polymer phases (Siddique et al., 2008).

4.4

Production of recycled plastic fibers

This research focused on the industrial-scale production of recycled plastic fiber through mechanical recycling of industrial thermoplastic wastes. Using industrial plastic wastes ensures constant source of recycled plastic with reliable quality control. Plastic waste used for recycling in this study is 100% recycled PP produced by diaper industries as offcuts and off-specification items during diaper manufacturing process. PP offcuts were mechanically reprocessed into recycled PP granules as described in Section 4.3.1 (also in Fig. 4.3). Recycled PP granules were further processed to produce 100% recycled PP fibers. The production process used in the research is melt spinning and hot-drawing technique (Fig. 4.4). In this process, recycled plastic granules or pellets are melted in an extruder. Temperature in the extruder range from 218 to 235
C. Molten filaments Industrial plastic waste collection

Sorting: manual, NIR, X-ray techniques

Recycled PP granules

Shredding

Plastic flakes

Extrusion

Ballistic seperator and electrostatic sorting

Float-sink sorting of different resin types

Figure 4.3 Mechanical recycling of industrial plastic wastes to produce recycled PP granules.

76

Use of Recycled Plastics in Eco-efficient Concrete

Recycled PP granules

Spinning pack Extruder Fiber cutting Oven

Indent roller

Water bath

Figure 4.4 Melt spinning setup for producing recycled plastic fiber.

are then extruded through a spinning pack and are cooled and solidified by passing them through a water bath. Extruded fibers are then hot-drawn into smaller crosssectional area (around 0.9 mm2) through an oven at 120e150
C. Monofilament fibers pass through the second roller system and the surface of the fibers are indented using an indent roller. Indents on surface of fibers improve their bonding strength in concrete matrix. After indentation, fibers are cut into approximate length of 50 mm. Characteristics of raw material used to produce fibers used in this study are given in Table 4.1. As shown in Table 4.1, raw recycled PP granules have higher melt flow index (MFI) than the raw virgin PP granules. This shows that the raw recycled PP has lower molar mass and shorter molecular chains resulting from chain scissions that occurred during recycling process and service life of plastics. 100% recycled plastic fibers were produced extruding raw recycled PP granules through melt spinning process. Similarly, 100% virgin PP fibers were produced from raw, virgin PP granules. Apart from these fibers, 50:50 virgin-recycled PP fibers (melt blend of 50% virgin and 50% recycled PP); 5:95 virgin HDPE-virgin PP (melt blend of 5% virgin HDPE and 95% virgin PP); and 5:95 virgin HDPE-recycled PP fibers (melt blend of 5% virgin HDPE and 95% recycled PP) were also produced. Table 4.1 Characteristics of raw material used for manufacturing plastic fibers Raw material

Virgin PP granule

Recycled PP granule

HDPE granule

Density (g/cm3)

0.90

0.90e0.92

0.957

230
C)

230
C)

0.4 (at 190
C)

Melt flow indexdMFI (2.16 kg, dg/min)

3.5 (at

Tensile stress at yield (MPa)

31

35

31.4

Flexural modulus (GPa)

1.25

1.48

0.8

13 (at

Production of recycled polypropylene (PP) fibers

77

Figure 4.5 (a) 100% recycled PP fibers (b) 100% virgin PP fibers (c) 50:50 virgin-recycled fibers (d) 5:95 HDPEdPP fibers.

Different fiber types are shown in Fig. 4.5. All the fibers produced had same dimensions (1.5 mm width, 0.7 mm thickness, and 47 mm length).

4.5

Material characterization

Molecular orientation and crystallinity have significant effects on the mechanical properties of plastic fibers. Material characterization of recycled and virgin polypropylene fibers was conducted using Fourier transform infrared (FTIR) and differential scanning calorimeter (DSC). The results were compared with that of raw virgin and recycled polypropylene granules used to produce the fibers to study the effects of hotdrawing and melt spinning processes on the molecular orientation and crystallinity of recycled plastic.

4.5.1

Molecular orientation in recycled PP fiber

PerkineElmer spectrum 100 FTIR spectrometer was used for FTIR measurements. Molecular orientation in the extruded fiber and raw recycled granules were studied by measuring the amount of light absorbed by the materials at different wavelengths using FTIR spectrometer. Crystal and amorphous contents were measured in terms of intensity of absorption bands at 998 and 1153 cm1, respectively (Yin et al., 2015b). The molecular orientation (R) was quantified by dividing the intensity of absorption bands in parallel direction (Aparallel) by the intensity in perpendicular direction (Aperpendicular). The degrees of orientations (f) of crystal and amorphous were calculated using Eq. (4.1) (Li et al., 2014). Polymer with absolute value of f close to zero shows no molecular orientation. f ¼ ðR  1Þ=ðR þ 2Þ

(4.1)

Fig. 4.6(a) shows FTIR spectra for raw recycled granules before melt spinning process. Intensity of absorption at 998 and 1153 cm1 bands are very similar in both parallel and perpendicular directions, giving small f values (f998 ¼ 0.09 and f1153 ¼ 0.05). This shows that raw recycled plastic pellets do not exhibit molecular

78

Use of Recycled Plastics in Eco-efficient Concrete

(a)

(b) 998

1153

950

1000

1050 1100 Wavenumber /cm–1

1150

Parallel Perpendicular

Absorbance

Absorbance

998

Parallel Perpendicular

1200

1153

1000

1050 1100 Wavenumber /cm–1

1150

1200

Figure 4.6 FTIR spectra measurements in perpendicular and parallel directions for (a) recycled PP raw pellet and (b) recycled PP fiber produced by melt spinning process.

orientations. Fig. 4.6(b) shows the FTIR spectra for recycled plastic fibers after melt spinning and hot-drawing process. For recycled plastic fibers, f998 was calculated as 0.5 which shows that crystal phase of recycled PP fibers exhibits considerable molecular orientations compared to recycled PP granules. Improvement of molecular orientation in recycled plastic fiber after melt spinning and hot-drawing has significant positive effects on the tensile strength of the fibers as later shown in Section 4.5.

4.5.2

Crystallinity in recycled PP fibers

PerkineElmer Pyris-1 differential scanning calorimeter (DSC) was used to study the crystal structure and melting behavior of the raw recycled granules and recycled PP fibers produced from melt spinning and hot-drawing process. DSC measurements were also compared with that of raw virgin PP granules and virgin PP fibers. For DSC measurements, 3 mg of PP granules were weighed and heated from 30 to 220
C at the rate of 10 K/min to study the melting behavior of the plastics. The samples were kept at 220
C for 5 min to erase their thermal history. The samples were then cooled to 30
C at the rate of 10 K/min to monitor their crystallization behavior and were reheated to 220
C to study their melting behavior at different temperatures. Peak temperatures were measured for crystallization (Tc) and melting (Tm). Crystallinity of the plastics was calculated using Eq. (4.2).  Crystallinity ¼ DHf DH
 100 f

(4.2)


Here, DHf is the heat of fusion of the plastic and DHf is the heat of fusion of a totallyD crystalline plastic taken as 207 J/g. DSC heating curves for different plastics granules and fibers are shown in Fig. 4.7. Fig. 4.7 shows that raw recycled PP granules have a broader melting endotherm than that of raw virgin PP granules. This shows that the raw virgin PP granules have mixed crystal sizes; whereas, raw recycled PP granules has more uniform crystal sizes. Table 4.2 presents the heat of fusion (DHf) and crystallinity obtained through the

Production of recycled polypropylene (PP) fibers

79

12 Raw recycled PP granules Raw virgin PP granules Heat flow endo up (mW)

10

8

6

4

2

0 100

140

120

160

180

200

Temperature (°C)

Figure 4.7 DSC heating curves for raw virgin and recycled granules.

Table 4.2 Heat of fusion and crystallinity of virgin and recycled PP PP compositions

Heat of fusion DHf (J/g)

Crystallinity (%)

Raw virgin PP granules

76.2

36.8

100% virgin PP fiber

106.7

51.5

Raw recycled PP granules

85.9

41.5

100% recycled PP fiber

105.4

50.9

DSC tests. Crystallinity of virgin PP fiber increased to 51.5% compared to that of raw virgin PP granules (36.8%), which show increase in crystallinity of PP fiber after the melt spinning and hot-drawing process. Similarly, for the recycled PP, the process improved crystallinity of recycled PP fiber to 50.9% from 41.5% for recycled PP granules. Due to higher crystallinity, both virgin and recycled PP fibers exhibit better mechanical properties compared to their raw granules as later shown in Section 4.5. After the melt spinning and hot-drawing process, virgin and recycled PP fibers exhibit a double melting endotherm at around 154 and 168
C (Fig. 4.8). The peaks located at 154
C is attributed to the b-form crystals and the peak at 168
C is attributed to the a-form crystals. As seen in Fig. 4.8 recycled PP fiber has much higher heat of fusion for b-form crystals than the virgin PP fiber. b-Form crystals are much less stable than the a-form crystals (Hirose et al., 2000). Due to large presence of stable a-form crystal in virgin PP fibers, virgin PP fibers shows higher tensile strength compared to the recycled PP fiber as shown in Fig. 4.10.

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Use of Recycled Plastics in Eco-efficient Concrete

Heat flow endo up (mW)

16

Recycled PP fibre Virgin PP fibre

14

α-form

12 β-form

10 8 6 4 2 0 100

120

160 140 Temperature (°C)

180

200

Figure 4.8 DSC heating curves for virgin and recycled fibers produced through melt spinning and hot-drawing process.

4.6

Mechanical properties of recycled PP fibers

Mechanical properties (tensile strength and Young’s modulus) of plastic fibers have significant influences on the postcracking performance of the plastic fiber reinforced concrete (Yin et al., 2015d, 2016). In this research, tensile tests on plastic fibers were conducted according to ASTM D3822-07 (ASTM D3822, 2007). United STM Test System (STM-50
kN) fitted with 2
kN load cell was used for all the tensile tests (Fig. 4.9). Gauge length of 25.4 mm and extension speed of 15.24 mm/min (60% of the gauge length/min) were used for the tests. Tensile tests were carried out for five different fiber types (1) 100% virgin PP fiber; (2) 100% recycled PP fiber; (3) 50:50 virgin-recycled fiber (4) 5:95 virgin HDPE-virgin PP fiber, and (5) 5:95 virgin HDPE-recycled PP fiber. 30 specimens were tested for each kind of fiber.

Figure 4.9 United STM Test system used for fiber tensile tests.

Production of recycled polypropylene (PP) fibers

81

Typical stress-strain curves for five different types of fibers are shown in Fig. 4.10. Average values of tensile strength, Young’s modulus, and elongation at break from 30 samples are presented in Table 4.3. Mechanical properties of both virgin and recycled PP fibers (Table 4.3) are superior compared to the properties of raw virgin and recycled PP granules presented in Table 4.1. Improved crystallization and crystal orientation in PP due to melt spinning and hot-drawing process are responsible for the increase in mechanical properties of the fibers compared to their raw material counterparts. Amongst the five different fibers tested, 100% virgin fiber had the best performance with 457.1 MPa tensile strength and 7526 MPa Young’s modulus. Tensile strength and Young’s modulus of 100% recycled PP fiber were 341.6 and 7115 MPa. The thermomechanical process of recycling and presence of impurities in recycled plastic cause cross-linking and chain scission. The damage in molecular chain of recycled PP and natural aging of plastic during its service life results in the lowering of tensile 500

Tensile strength (Mpa)

(a)

(b)

(e)

400

(c)

(d)

300

200 (a) (b) (c) (d) (e)

100

0 0

2

4

100% virgin PP fibre 5:95 HDPE-virgin PP fibre 100% recycled PP fibre 5:95 HDPE-recycled PP fibre 50:50 virgin-recycled PP fibre

6 8 10 12 Tensile elongation (%)

14

16

18

Figure 4.10 Typical stress-strain curves for different blends of PP fibers. Table 4.3 Tensile properties of recycled PP fiber compared with fiber produced by melt blending with different resins PP compositions

Tensile strength (MPa)

Young’s modulus (MPa)

100% recycled PP fiber

341.6

7115

100% virgin PP fiber 50:50 virgin-recycled PP fiber

457.1 435.5

7526 9016

5:90 virgin HDPE-recycled PP fiber

341.9

6467

5:95 virgin HDPE-virgin PP fiber

436.0

6837

82

Use of Recycled Plastics in Eco-efficient Concrete

strength and Young’s modulus of recycled PP fibers as seen in Table 4.3. Nevertheless, the mechanical properties achieved in 100% recycled PP fibers were shown adequate for the required postcracking performance in concrete as presented by the authors in their other publications (Yin et al., 2015d, 2016). Melt blending 50% recycled PP with 50% virgin PP significantly improved tensile strength and Young’s modulus compared to the 100% recycled PP. However, blending 5% virgin HDPE with virgin or recycled PP showed no improvement in the mechanical properties of the fibers (Table 4.3).

4.7

Conclusions

Virgin plastic fibers are commonly used in concrete footpaths, driveways, carparks, and concrete precast elements such as drainage pits, culverts, and sleepers. It is already well established that plastic macro fibers control shrinkage cracks in concrete and improve postcracking performance of concrete. Recently many researches have focused on developing recycled plastic fiber to reinforce concrete elements. Use of recycled plastic fibers in concrete gives a new platform to use recycled plastics; and moreover, it reduces the amount of steel and virgin plastic being used in concrete industry. Researchers have tested performance of various types of recycled plastic fibers such as PP, PET, and PVC in concrete. However, most of the research so far has been focused on lab-scale production and testing of recycled plastic fibers. Given the amount of fibers required for the commercial applications, it is not feasible to produce recycled fibers at industrial scale by these methods. This research is focused on industrial-scale production of recycled PP fibers by mechanical recycling. Melt spinning and hot-drawing processes were successfully used to produce recycled PP fibers from industrial wastes. Effects of melt spinning and hotdrawing processes on the crystallinity and mechanical properties of fibers were examined using FTIR and DSC measurements. Performance of 100% recycled PP fibers was compared with 100% virgin PP and blended plastics. The study showed that recycled PP granules produced by mechanical recycling exhibited degradation of mechanical properties due to breaking of molecular chains caused by chain scission and branching. However, when these recycled granules are extruded through melt spinning and hot-drawing processes, there is significant improvement in crystallinity. This resulted in increase in tensile strength and Young’s modulus. In this research, recycled PP fibers with tensile strength of 340 MPa and Young’s modulus of 7100 MPa were successfully produced. Fibers produced by melt blending 50% recycled PP with 50% virgin PP achieved superior mechanical properties (435 MPa tensile strength and 9000 MPa Young’s modulus) which were comparable to that of virgin PP (450 MPa tensile strength and 7500 MPa Young’s modulus). However, 5% HDPE blended with 95% virgin or recycled PP did not produce any significant improvement in the properties of the fibers. The 100% recycled PP fibers produced through this research is now commercially available in the market as “Emesh”dhttp://www.emesh.com.au/. Twelve tons of Emesh have since been successfully used to reinforce concrete in footpaths, carparks,

Production of recycled polypropylene (PP) fibers

83

and precast elements, replacing traditionally used steel mesh in large projects such as The Science Place Building (JCU, Townsville); Burdekin Shire Council footpaths; Gold Coast light rail intersections; Morely’s Funerals Carpark; Parkinson Road footpath JCU; and Townsville boat ramp traffic island infills.

Acknowledgements The authors acknowledge Fibercon QLD for funding support and for giving us access to fiber manufacturing facilities for the research. The authors also thank Prof. Robert A. Shanks, Royal Melbourne Institute of Technology (RMIT), Melbourne, for letting us use his laboratory for DSC tests.

References Adomaviciute, E., Baltusnikaite-Guzaitiene, J., Juskaite, V., Zilius, M., Briedis, V., Stanys, S., 2018. Formation and characterization of melt-spun polyproplene fibers with propolis for medical applications. Journal of the Textile Institute 109 (2), 278e284. ASTM D3822, 2007. Standard Test Method for Tensile Properties of Single Textile Fibers. Book of ASTM Standards, Philadelphia, The U.S. Aurrekoetxea, J., Sarrionandia, M.A., Urrutibeascoa, I., Maspoch, M.L., 2001. Effects of recycling on the microstructure and the mechanical properties of isotactic polypropylene. Journal of Materials Science 36 (11), 2607e2613. Brems, A., Baeyens, J., Dewil, R., 2012. Recycling and recovery of post-consumer plastic solid waste in a European context. Thermal Science 16, 669e685. Costa, H.M.D., Ramos, V.D., Rocha, M.C.G., 2005. Rheological properties of polypropylene during multiple extrusion. Polymer Testing 24 (1), 86e93. Foti, D., 2011. Preliminary analysis of concrete reinforced with waste bottles PET fibers. Construction and Building Materials 25, 1906e1915. Fraternali, F., Ciancia, V., Chechile, R., Rizzano, G., Feo, L., Incarnato, L., 2011. Experimental study of the thermos-mechanical properties of recycled PET fiber-reinforced concrete. Composite Structures 93, 2368e2374. Hasanah, T.I.T.N., Wijeyesekera, D.C., Lim, A.J.M.S., Ismail, B., 2014. Recycled PP/HDPE blends: a thermal degradation and mechanical properties study. In: 4th Mechanical and Manufacturing Engineering. 1 and 2, pp. 465e466. Hirose, M., Yamamoto, T., Naiki, M., 2000. Crystal structures of the alpha and beta forms of isotactic polypropylene: a Monte Carlo simulation. Computational and Theoretical Polymer Science 10 (3e4), 345e353. Jin, H., Gonzalez-Gutierrez, J., Oblak, P., Zupancic, B., Emri, I., 2012. The effect of extensive mechanical recycling on the properties of low density polyethylene. Polymer Degradation and Stability 97, 2262e2272. Kim, S.B., Yi, N.H., Kim, H.Y., Kim, J.J., Song, Y., 2010. Material and structural performance evaluation of recycled PET fiber reinforced concrete. Cement and Concrete Composites 32, 232e240. Li, J., Li, H.L., Meng, L.P., Li, X.Y., Chen, L., Chen, W., et al., 2014. In-situ MR imaging on the plastic deformation of iPP thin films. Polymer 55 (5), 1103e1107.

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Martin-Alfonso, J.E., Valencia, C., Sanchez, M.C., Franco, J.M., Gallegos, C., 2012. The effect of recycled polymer addition on the thermorheological behavior of modified lubricating greases. Polymer Engineering & Science 53 (4), 818e826. Meran, C., Ozturk, O., Yuksel, M., 2008. Examination of the possibility of recycling and utilizing recycled polyethylene and polypropylene. Materials & Design 29, 701e705. Mbarek, S., Jaziri, M., Carrot, C., 2006. Recycling polyethylene terephthalate wastes: properties of polyethylene terephthalate/polycarbonate blends and the effect of transesterification catalyst. Polymer Engineering & Science 46, 1378e1386. Oblak, P., Gonzalez-Gutierrez, J., Zupancic, B., Aulova, A., Emri, I., 2015. Processability and mechanical properties of extensively recycled high density polyethylene. Polymer Degradation and Stability 114, 113e145. Ochi, T., Okubo, S., Fukui, K., 2007. Development of recycled PET fiber and its application as concrete-reinforcing fiber. Cement and Concrete Composites 29, 448e455. Oliveira, L.A.P.D., Castro-Gomes, J.P., 2011. Physical and mechanical behavior of recycled PET fiber reinforced mortar. Construction and Building Materials 25, 1712e1717. Plastics Europe, 2017. Plastics e The Facts 2017. An Analysis of European Plastics Production, Demand and Waste Data. www.plasticseurope.org. Ragaert, K., Delva, L., Geem, K.V., 2017. Mechanical and chemical recycling of solid plastic waste. Waste Management 69, 24e58. Ruj, B., Pandey, V., Jash, P., Srivastava, V.K., 2015. Sorting of plastic waste for effective recycling. International Journal of Applied Sciences and Engineering Research 4 (4), 564e571. Siddique, R., Khatib, J., Kaur, I., 2008. Use of recycled plastic in concrete: a review. Waste Management 28, 1835e1852. Strapasson, R., Amico, S.C., Pereira, M.F.R., Syclenstricker, T.H.D., 2005. Tensile and impact behavior of polypropyelene/low density polyethylene blends. Polymer Testing 24, 468e473. Velis, C., September 2014. Global Recycling Markets e Plastic Waste: A Story for One Player e China. International Solid Waste Association e Globalization and Waste Management Task Force, Vienna. Yin, S., Tuladhar, R., Shi, F., Combe, M., Collister, T., Sivakugan, N., 2015a. Use of macro plastic fibers in concrete: a review. Construction and Building Materials 93, 180e188. Yin, S., Tuladhar, R., Shanks, R.A., Collister, T., Combe, M., Jacob, M., et al., 2015b. Fiber preparation and mechanical properties of recycled polypropylene for reinforcing concrete. Journal of Applied Polymer Science 132 (16). Yin, S., Tuladhar, R., Shi, F., Shanks, R.A., Combe, M., Collister, T., 2015c. Mechanical reprocessing of polyolefin waste: a review. Polymer Engineering & Science 55 (12), 2899e2909. Yin, S., Tuladhar, R., Collister, T., Combe, M., Sivakugan, N., Deng, Z., 2015d. Post-cracking performance of recycled polypropylene fiber in concrete. Construction and Building Materials 101, 1069e1077. Yin, S., Tuladhar, R., Riella, J., Chung, D., Collister, T., Combe, M., 2016. Comparative evaluation of virgin and recycled polypropylene fiber reinforced concrete. Construction and Building Materials 114, 134e141.

Fresh properties of concrete containing plastic aggregate

5

Sheelan M. Hama, Nahla N. Hilal Department of Civil Engineering, University of Anbar, Ramadi, Iraq

5.1

Introduction

Fresh concrete is characterized as a completely mixed concrete in a rheological state before it begins to set. In this stage (almost initial 48 h) the concrete is in its plastic stage beginning from mixing operations to concrete surface finished process. This stage determines the quality and durability of concrete, and also the strength and efficiency of the concrete structure later; it also has impact on construction speed. Fresh concrete is simply a transient stage, but it is important to see that quality, durability, and strength of concrete is truly influenced by the level of its compaction. The consistency of fresh concrete indicates that the mix can be transported, placed, compacted, and finished effectively and easily without segregation of its ingredients. This chapter is devoted to the properties of fresh concrete incorporating plastic waste as aggregate. The fresh properties of concrete with plastic waste as aggregate from experimental work data will be presented and compared with similar existing literature, if found. These properties will be discussed in three main sections: mix proportion and design, workability of fresh concrete, and early age properties represented by its unit weight (fresh density).

5.2 5.2.1

Mix proportion and design Concrete requirements

The fundamental reason for the mix design is to get a product that will be performing according to foreordained requirements. These requirements can be listed as follows: (a) Quality: usually strength of concrete gives an indication about concrete quality because it is directly related to hydrated cement structure. Another important characteristic which influences the quality of concrete is durability which is controlled essentially by its porosity. Permeability of hydrated cement paste is commonly related to the capillary porosity that is controlled by w/c proportion and level of hydration. There is a relationship between strength and durability. Therefore, routine mix design is mainly focused on strength and workability only, except for concrete exposes to hard environmental conditions. In this case, additional arrangements should be made to keep up durability of concrete (e.g., reduce w/c ratio without workability losses by using SP, increasing concrete cover of steel reinforcement). Generally, the strength at 28 days is utilized as design index for structural purposes.

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00005-0 Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete

(b) Economy and environmental issues: is the most important factor that should be considered in civil engineering. Reducing the cost is the goal of any designer. A strong connection between economy and environmental issues starts to appear through using waste materials in concrete. For example, the cost of one cubic meter of concrete can be reduced by partially replacing cement with less expensive materials (like fly ash, glass powder, eggshell powder, or ground blast-furnace slag); also by partially or totally replacing natural aggregate by waste aggregate (like plastic, building wreck, etc.). Some waste materials can be used as fibers (e.g., plastic fibers, steel fibers extracted from old tyres, natural sources fibers, etc.). Some of these wastes not only achieve economic and environmental goals but also could improve concrete properties like strength, durability, and ductility. (c) Workability: this requirement is necessary to ensure easy handling of the concrete mix and its controlled concrete strength and durability. Workability is a wide and subjective term for fresh concrete depicting how effectively freshly mixed concrete can be mixed, transported, placed, compacted, and finished as homogenous mix without segregation. There are several tests to evaluate the workability of fresh mix: slump test, compacted factor test, flow table test, VeBe test, and Kelly ball test which is practical for field test. Slump test represents the most common and easy test to give good indication about concrete workability.

5.2.2

Aggregate preparation and mix proportion for concrete incorporating plastic waste as aggregate

The mix design for concrete incorporating waste plastic as aggregate is not different so much on that for the usual concrete. The objective of this test program is to compare fresh properties of concrete with and without plastics which were utilized as fine or coarse aggregates. The waste plastic aggregate is incorporated as partial replacement of either the coarse aggregate (gravel or crushed stone) or the fine aggregate (sand). For all mixes Portland cement (type I), the chemical composition and physical properties of which are listed in Tables 5.1 and 5.2, respectively, was used. The cement complies to the Iraqi standard specification No.5/1984. Table 5.1 Chemical composition of portland cement Chemical analysis

Test results % by weight

Limits of Iraqi specification No. 5/1984

CaO

61.20

e

Al2O3

5.10

SiO2

21.40

MgO

1.84

5% (maximum)

SO3

1.14

2.8 (maximum)

Fe2O3

3.40

e

e

Fresh properties of concrete containing plastic aggregate

87

Table 5.2 Physical properties of cement Physical properties

Test results

Limits of Iraqi specification No. 5/1984

Fineness by Blain method cm2/gm

3500

2300 (minimum)

Initial setting (min.)

138

45 (minimum)

Final setting (min.)

242

600 (maximum)

Setting time (vicat apparatus)

Compressive strength for cementemortar cube at: 3 days (MPa)

22.8

15 (minimum)

7 days (MPa)

30.2

23 (minimum)

5.2.2.1

Waste plastic as fine aggregate

There are several important points that should be considered before starting any mix design: shape and size of plastic particle, specific gravity, and gradation of utilizing plastic. All experiment works are started by determining the specific gravity and the gradation of the natural and plastic aggregate. Due to the difference in the specific gravity of natural aggregate (sand) and plastic aggregate, the volumetric design method is adopted. Sand is partially substituted by plastic as percentage by its volume. Following are the mix proportions for the control mix and mixes with fusing different types of plastic as fine aggregates with varying substitution levels.

Fine PET plastic aggregate Soft drink plastic bottles can be classified as polyethylene terephthalate (PET). It can be obtained from waste bottles which are available widely and can be easily collected from the households, landfills, and from a disposal area in Ramadi. It is a clear tough kind of plastic with good mechanical properties and good chemical resistance properties. Soft drink bottles were collected, and then cut using modified shredder machine to small fraction. The size of shredded PET granules ranged between 1.0 and 3.5 mm. The resulting plastic aggregates were small rectangular shapes as shown in Fig. 5.1.

(a)

(b)

(c)

Figure 5.1 (a) Soft drink plastic bottle (b) PET plastic fine aggregate (c) PET particles.

88

Use of Recycled Plastics in Eco-efficient Concrete

The specific gravity, sulfate content%, and absorption% of fine and coarse aggregate were determined and summarized in Table 5.3. The absorption of plastic was neglected. River sand and crushed stone were used as fine and coarse aggregate, respectively. The gradation of aggregate was performed by sieve analysis, in accordance with Iraqi slandered specifications No. 45 (see Table 5.4). The natural fine and coarse aggregates were soaked in water for 24 h, and then spread to dry in air in order to achieve saturated dry surface aggregate. Examination was done on two groups of concrete. The first group was made without superplasticizer and second was made with adding Sika ViscoCrete-5930 (High-performance superplasticizer), the properties of which are listed in Table 5.5, with different dosages. For the first group, mix proportion of 1:1.5:3 (cement: sand: crushed stone) was designed with a 0.38 w/c ratio and seven PET aggregates level of substitutions: 10%, 15%, 20%, 25%, 30%, 35%, and 40%. The mix design was made to get reasonable concrete strength and to reduce the strength degradation by increasing the amount of plastic. The second group with mix proportion of 1:1.5:3 (cement: sand: crushed stone) was designed with a 0.38 w/c ratio and 15.0% PET. High-performance superplasticizer type F was used as percentage of cement weight at following dosages: 0.50%, 0.6%, 0.7%, and 0.8% in order to improve concrete workability without increasing w/c ratio to ensure producing concrete with good quality. Table 5.3 Physical properties of aggregates Ingredients Property

Gravel

Sand

Plastic

Specific gravity

2.65

2.60

1.38

Sulfate content (SO3)%

0.09

0.43%

-

Absorption %

0.52%

0.72%

Neglected

Table 5.4 Sieve analysis of fine and coarse aggregate % Passing Sieve no.

Gravel

Sand

Plastic

14

100

100

100

10

85

100

100

4.75

6.8

92

91

2.36

0.8

78

13

1.18

0

64

5

0.6

0

51

0

0.3

0

13

0

0.15

0

5

0

Fresh properties of concrete containing plastic aggregate

89

Table 5.5 Properties of superplasticizer Properties

Description

Main action

ViscoCrete-5930 is third generation superplasticizer for concrete and mortar. It meets requirement for superplasticizer according to ASTM C 494 Type F and G

Dosage

0.2%e0.8% by weight of cement for soft plastic concrete 0.8%e2% by weight of cement for self-compact concrete

Basis

Aqueous solution of modified polycarboxylate

Appearance

Turbid liquid

Density

1.095 kg/L

The plastic replaced the sand by volume. Both the plastic aggregate and the saturated sand were considered to be in a state of 0% absorption. Therefore, as the volume of sand was reduced and plastic was added, the water content in the mixes did not need to be adjusted.

High-density polyethylene fine plastic aggregate Waste of polyethylene packages from fruit and vegetables crates were collected from local grocers. Using special cutting machine these crates were cut to get fine uniform rounded-shapes particles as shown in Fig. 5.2. This type of plastic aggregate can be classified as high-density polyethylene (HDPE). The produced plastic aggregate passed through sieve No.4.75 and retained on sieve No. 2.36. Sieve analysis of natural fine and coarse aggregate is clarified in Fig. 5.3. Mix proportion of 1:1.5:3 (cement:sand: crushed stone) was adopted with a 0.35 w/c ratio, 1% superplasticizer (ViscoCrete5930, see Table 5.5) and %plastic: 0%, 10%, 20%, and 30%. Moreover, silica fume was likewise utilized as the substitution of cement at substitution proportion of 10% for strength requirement considerations and cost saving. The chemical composition of silica fume is given in Table 5.6.

Figure 5.2 High-density polyethylene fine plastic aggregate.

90

Use of Recycled Plastics in Eco-efficient Concrete

% Passing

Sand

Gravel

100 90 80 70 60 50 40 30 20 10 0 0.1

1

Sieve size, mm

10

100

Figure 5.3 Sieve analysis of sand and crushed stone. Table 5.6 Chemical Composition of Silica Fume Oxides

By weight%

SiO2

92.80

Al2O3

0.02

Fe2O3

0.01

CaO

0.25

MgO

0.01

K2O

0.06

Specific gravity was 2.45, 0.96, and 2.67 for sand (fine aggregate), HDP, and crushed stone (coarse aggregate). Fig. 5.4 shows dry initial mixing of fine and coarse aggregate.

Fine aggregate from waste compact disks Compact disk base layer are made of polycarbonate plastic which is a very durable material with high impact-resistance and low scratch-resistance. Waste compact disks were collected from a number of departments of College of Engineering. After collection of the compact disks, they were soaked in water and washed to remove residue paper sticking on it. Then they were cut to slices using CD-shredder machines and then crushed down to be used as fine aggregate and passed through sieves; the results of sieve analysis are listed in Table 5.7. Fig. 5.5 clarifies the preparation procedure of fine aggregate from waste compact disks. The specific gravity of crushed waste compact disk granules was 1.21. The natural fine and coarse aggregate were the same as used for PET mix the physical properties of which are listed in Table 5.3. The natural fine and coarse aggregate sieve analysis are the same as mentioned in Table 5.4. Mix proportion of 1:1.5:3 (cement:sand:crushed stone) was adopted with a

Fresh properties of concrete containing plastic aggregate

91

Figure 5.4 Dry mixing of fine and coarse aggregate. Table 5.7 Sieve Analysis of Fine Plastic Aggregate From Compact Disks Sieve no.

% Passing

10.00

100

4.75

95

2.36

24

1.18

8

0.60

0

0.38 w/c ratio, 0.75% high-performance superplasticizer (ViscoCrete-5930), the properties of which are mentioned before in Table 5.5 and % plastic: 0.0%, 5.0%, 7.5%,10.0%, 12.5%, and 15.0%.

5.2.2.2

Waste plastic as coarse aggregate

The concrete mixes were prepared in a similar manner as mentioned in previous section, which requires aggregate’s sieve analysis and defined w/c ratio of coarse and fine aggregate quantities. The contrasts among the different mixes are reduced solely to the nature coarse aggregates and replaced by plastic.

Plate cover of water drink bottle as coarse aggregate The cover of drinkdwater bottles were collected and reused as coarse aggregate; it can be classified as high-density polyethylene. After collecting process, the cover plates were soaked in water to clean the glue and dirt sticking to it and was then left to dry. The plastic covers were cut and passed through sieves. Sieve analysis details for all used aggregate are listed in Table 5.8. Specific gravity, sulfate content%, and absorption% of using aggregates are summarized in Table 5.9. Mix proportion of 1: 1.25:2.75 (cement:sand:crushed stone) was adopted with a 0.42 w/c ratio. The coarse

92

Use of Recycled Plastics in Eco-efficient Concrete

Figure 5.5 Steps of fine aggregate preparation from compact disks. Table 5.8 Sieve analysis of fine and coarse aggregate % Passing Sieve no.

Gravel

Sand

Plastic

20

100

100

100

14

100

100

85

10

89

100

79

4.75

14

91

9.4

2.36

0.5

75

0

1.18

0

24

0

0.6

0

53

0

0.3

0

10

0

0.15

0

5

0

Fresh properties of concrete containing plastic aggregate

93

Table 5.9 Physical properties of aggregates Ingredients Property

Gravel

Sand

Plastic

Specific gravity

2.68

2.64

0.94

Sulfate content (SO3)%

0.05

0.42%

e

Absorption %

0.50%

0.68%

Neglected

aggregate was replaced by plastic at this level 5.0%, 10.0%, 15.0%, and 20.0% by volume. Fig. 5.6 shows the process for preparing plastic coarse aggregate.

Coarse aggregate from waste compact disk wastes Waste compact disks were also used as coarse aggregate (see Fig. 5.7). Details of sieve analysis are listed in Table 5.10. Same natural aggregate that was used above was used here (see Tables 5.8 and 5.9). The crushed coarse plastic aggregate was used with five replacement levels: 0.0%, 5.0%, 10.0%, 15.0%, 20.0%, and 25% by volume of coarse aggregate. Mix proportion of 1:1.25:2.75 (cement:sand: crushed stone) was adopted with a 0.45 w/c ratio.

Figure 5.6 Steps of coarse aggregate preparation from plate cover of drink water bottles.

94

Use of Recycled Plastics in Eco-efficient Concrete

Figure 5.7 Coarse aggregate preparation from compact disks.

Table 5.10 Sieve Analysis of Compact Disk Coarse Aggregate

5.3

Sieve no.

% Passing

16

100

14

92

10

24

4.75

8

2.36

0

Workability of fresh concrete containing plastic aggregate

Concrete workability is an imperative issue to guarantee that the produced concrete can uniformly flow through batches with keeping its fluidity during the transportation timeframe to ensure it is completely filling the structure and easy to finish appropriately.

5.3.1

Definition of workability

Workability of concrete has many definitions but can be summarized as the required exertion to control a freshly mixed quantity of concrete so to be easily transported, placing, compacting and finishing with the least loss of homogeneity and without segregation among its ingredients.

5.3.2

Measurement of workability

There are several workability test techniques for fresh concrete ranging from simple tests that can be done in short time (few minutes) to complex tests which require expensive equipment and experienced operators.

Fresh properties of concrete containing plastic aggregate

(a)

95

(b)

Figure 5.8 Workability measurement (a) slump cone test (b) compacting factor test.

Briefly, the most common utilizing laboratory tests to estimate workability of fresh mix, arranged by significance, are as follows 1. Slump test: is the most broadly utilized test, which mainly characterizes the consistency of concrete. 2. Vebe test: is more appropriate for mixtures with low consistency. 3. Compacting factor test: evaluates the compactibility characteristic, and it is good for dry mix because of its sensitivity to low workable mix. 4. Ball penetration test: this test is related to mechanical work.

There are many other tests for determining workability, and many test procedures have been developed for lab and field utilization. Indeed, even with numerous techniques to measure workability and the expansion in information of concrete rheology, the common slump test is the most suitable test to evaluate concrete workability. Slump test and compacting factor test are adopted in this work to evaluate the workability of concrete due to replacement of natural aggregate by plastic as shown in Fig. 5.8.

5.3.2.1

Workability of concrete incorporating waste plastic as fine aggregate

Fine PET plastic aggregate The results of the slump cone test of waste PET fine plastic aggregate concrete mixtures are shown in Fig. 5.9. The mixes with plastic substitution levels beyond 10% demonstrated significant loss in workability. Particularly for the 35% and 40% substitution levels, the mixes demonstrated lost union and cohesion and displayed unworkable conditions and approximately zero slump at 40% PET as shown in Fig. 5.10. The percentages of slump decreasing were: 20.5%, 38.5%, 56.4%, 64.1%, 76.9%, 89.7%, and 97.4% for 10%, 15%, 20%, 25%, 30%, 35%, and 40%, respectively.

Use of Recycled Plastics in Eco-efficient Concrete

Slump (mm)

96 90 80 70 60 50 40 30 20 10 0 0

5

10

15

20

25

30

35

40

45

PET plastic fine aggregate content (%)

Figure 5.9 Slump of PET plastic fine aggregate concrete without SP.

Figure 5.10 Slump for 40% PET fine aggregate.

This reduction in slump is due to angular sharper edges of plastic particles which resulted in more rough contact surfaces and increased the friction among mixture’s contents. From the result above one can see that PETFA%
15% gave slump less than 50 mm (low workability). The workability of these mixes also has been evaluated by compact factor test. The calculating compact factors (ratio of the weight of partially compacted concrete to the weight of fully compacted concrete) are listed in Table 5.11. The mix with 40% PETFA has almost 2 mm slump while it has a compact factor of about 0.85 (hard concrete). The compact factor test is more sensitive to mix with low slump value, that is, low workability. Other researchers were also investigated about effect of PET fine aggregate on slump of concrete. Rahmani et al. (2013) and Islam et al. (2015) also found that at constant w/c ratio, the slump decreased with increasing of the PET fine aggregate content. To improve mixtures’ workability without increasing amount of water, which negatively affects the strength and durability, SP was used with different percentages to improve fluidity of the mixtures.

Fresh properties of concrete containing plastic aggregate

97

Table 5.11 Compact factor for concrete containing PETFA % PETFA

Compact factor

0

0.9260

10

0.9158

15

0.9104

20

0.8982

25

0.8880

30

0.8754

35

0.8662

40

0.8495

80 70 Slump (mm)

60 50 40 30 20 10 0 0

0.25

0.5

0.75

1

SP content (%)

Figure 5.11 Slump of 15% PET plastic fine aggregate concrete with %SP.

The percentage of slump increased was: 17.6%, 38.5%, 52.9%, 100.0%, and 117.6% for 0.5%, 0.6%, 0.7%, and 0.8% SP, respectively, as shown in Fig. 5.11.

High-density polyethylene fine plastic aggregate The results of the slump cone test of waste HDPFA concrete mixtures are shown in Fig. 5.12. The mixes with HDPFA for all substitution levels showed an improvement in workability, particularly for the 30% substitution levels. The percentages of slump increasing were: 9.3%, 13.5%, and 25.0% for 10%, 20%, and 30%, respectively. This increase in slump is due to uniform rounded shapes of plastic particles and smooth surface texture contents besides the plastic have zero absorption, which results in saving mixing water. The compact value for reference mix and mixes with plastic are close and it ranges from 0.92 to 0.91. This means that using this plastic aggregate can be used to produce concrete with good workability (Table 5.12).

98

Use of Recycled Plastics in Eco-efficient Concrete

100

Slump (mm)

90 80 70 60 50 0

5

10

15 20 HDPFA content (%)

25

30

35

Figure 5.12 Slump of high-density plastic fine aggregate concrete. Table 5.12 Compact factor for concrete containing HDPFA % HDPFA

Compact factor

0

0.9165

10

0.9184

20

0.9200

30

0.9250

Fine aggregate from waste compact disks The results of the slump cone test of waste compact disk fine plastic aggregate (CDFPA) concrete mixtures are shown in Fig. 5.13. These outcomes demonstrate that concrete slump tends to decrease sharply with increasing the waste plastic ratio. The percentage decreases of slump were: 27.9%, 32.6%, 48.8%, 55.8%, and 62.7% for 5.0%, 7.5%, 10.0%, 12.5%, and 15.0% CDFPA, respectively. This reduction in slump is due to nonregular angular edge of plastic particles which results in declination in mixture fluidity as mentioned before. Ismail and Jaeel (2016) also found that slump values of waste compact disk concrete mixes decreased with comparison to the slump of the reference concrete mix. From compact factor test results (see Table 5.13), the consistency of compact disk fine plastic concrete range from plastic hard to plastic (0.91e0.85).

5.3.2.2

Workability of concrete incorporating waste plastic as coarse aggregate

Drink water plastic bottle’s cover as coarse aggregate Outcomes of slump test of waste cover plastic aggregate (CPA) concrete mixtures are shown in Fig. 5.14. The results show that CPA mix slump reduces slightly from

Slump (mm)

Fresh properties of concrete containing plastic aggregate

99

100 90 80 70 60 50 40 30 20 10 0 0

2

4

6

8

10

12

14

16

CDFPA content (%)

Figure 5.13 Slump of compact disk plastic fine aggregate concrete.

Table 5.13 Compact factor for concrete containing CDFPA % CDFPA

Compact factor

0.0

0.9394

5.0

0.9140

7.5

0.9068

10.0

0.8856

12.5

0.8699

15.0

0.8540

100

Slump (mm)

80 60 40 20 0 0

5

10 15 CPA content (%)

Figure 5.14 Slump of cover plastic coarse aggregate concrete.

20

25

100

Use of Recycled Plastics in Eco-efficient Concrete

Table 5.14 Compact factor for concrete containing CPA % CAP

Compact factor

0

0.9492

5

0.9186

10

0.9085

15

0.8955

20

0.8902

reference mix slump. The percentage decreases of slump were: 29.5%, 40.8%, 50.0%, and 64.3% for 5%, 10%, 15% and 20%, respectively. As shown from these results, the slump of CPA mixes is lower than for reference mix. As shown from these results, the slump of CAP mixes and reference mix are nearly close. This may be due to similarity between shape of CPA and naturally crushed coarse aggregate. Both aggregate have sharp angular ends. According to compact factor values (see Table 5.14), the consistency of producing concrete range between plastic to plastic hard. That means the concrete produced has good workability.

Coarse aggregate from waste compact disks Results of slump test of waste compact disk plastic coarse aggregate concrete (CDPCA) mixtures are shown in Fig. 5.15. The results show that CDPCA mixes slump reduce sharply when compared to reference mix slump. The percentage decreases of slump were: 31.7%, 43.5%, 64.7%, 74.1%, and 82.3% for 5.0%, 10%, 15%, 20%, and 25%, respectively. The consistency of the produced coarse plastic concrete ranges between plastic hard to hard, while the consistency of the reference mix can be classified as plastic (Table 5.15). 90 80 Slump (mm)

70 60 50 40 30 20 10 0 0

5

10

15 20 CDPCA content (%)

Figure 5.15 Slump of compact disk plastic coarse aggregate concrete.

25

30

Fresh properties of concrete containing plastic aggregate

101

Table 5.15 Compact factor for concrete containing CDPCA

5.4

% CDPCA

Compact factor

0

0.9392

5

0.8995

10

0.8960

15

0.8805

20

0.8648

25

0.8550

Fresh density of concrete containing plastic aggregate

Effect of different types of plastic on fresh density of concrete was investigated. As it is clear from Fig. 5.16 to 5.20, all types of plastic aggregate either used as fine or coarse aggregate reduced the fresh density. This is due to low specific gravity of plastic compared to specific gravity of natural fine or coarse aggregate. Following the percentage decreases in fresh density for different types of plastic aggregate which were used in this work as partial replacement of either fine or coarse with comparing to reference mix without plastic aggregate: 1. Fine PET plastic aggregate: The percentage decreases of fresh density were: 3.0%, 4.8%, 6.9%, 8.0%, 9.6%, 10.5%, and 15.0% for 10%, 15%, 20%, 25%, 30%, 35%, and 40%, respectively (see Fig. 5.16). 2. High-density polyethylene fine plastic aggregate: The percentages of fresh density decreasing were: 3.6%, 7.7%, and 11.4% for 10%, 20%, and 30%, respectively (see Fig. 5.17).

2500 2400

2373

Density, kg/m3

2302 2300

2258 2210

2200

2184

2145

2124

2100 2008 2000 1900 1800 0

10

15 20 25 30 35 % PET fine plastic aggeregate

Figure 5.16 Density of PET plastic fine aggregate concrete without SP.

40

102

Use of Recycled Plastics in Eco-efficient Concrete

2450 2386

2400

Density, kg/m3

2350

2300.8

2300 2250

2202

2200 2150

2115

2100 2050 2000 1950 0

10

20

30

% HDPFA

Figure 5.17 Density of high-density plastic fine aggregate concrete. 2400

2382

2362

2358

Density, kg/m3

2350 2300.4 2300

2284 2245

2250

2200

2150 0

5

7.5

10

12.5

15

% CDPFA

Figure 5.18 Density of compact disk plastic fine aggregate concrete. 3. Fine aggregate from waste compact disks: The percentage decreases of fresh density were: 0.8%, 1.0%, 3.4%, 4.1%, and 5.8% for 5.0%, 7.5%, 10.0%, 12.5%, and 15.0%, respectively (see Fig. 5.18). 4. Drink water plastic bottle’s cover as coarse aggregate: The percentage decreases of fresh density were: 1.0%, 3.5%, 7.1%, and 8.2% for 5.0%, 7.5%, 10.0%, 12.5%, and 15.0%, respectively (see Fig. 5.19). 5. Coarse aggregate from waste compact disks: The percentage decreases of fresh density were: 1.7%, 4.6%, 6.8%, 7.7%, and 10.9% for 5.0%, 10%, 15%, 20%, and 25%, respectively (see Fig. 5.20).

In general, the other types of plastic other than that utilized in this work caused a reduction in fresh density of concrete as proved by other researchers (Akça€ozoglu et al., 2010 Rai et al., 2012).

Fresh properties of concrete containing plastic aggregate

2400

2368 2344

2350 Density, kg/m3

103

2284

2300 2250

2200 2200

2175

2150 2100 2050 0

5

10 % CPA

15

20

Figure 5.19 Density of CP plastic coarse aggregate concrete. 2400

2366 2326

2350 Density, kg/m3

2300

2258

2250

2204

2200

2184

2150

2108

2100 2050 2000 1950 0

5

10

15 % CDPCA

20

25

Figure 5.20 Density of compact disk plastic coarse aggregate concrete.

There are a large number of researches going on about using of plastic as aggregate, but just a few which consider the fresh properties. So this chapter provides a good reference and data to fill the gap in this field.

5.5

Self-compacting plastic aggregate concrete

Self-compacting concrete (SCC) is not different from the conventional vibrated concrete. With regard to ingredients, it comprises of the same ingredients as conventional concrete, which are cement, aggregates, and water, in addition of chemical and fine mineral admixtures with various dosages. Usually, the utilization of chemical admixtures are necessary like high-range water reducers (superplasticizers) in order to obtain the self-compactability of the concrete and to enhance the rheological properties of

104

Use of Recycled Plastics in Eco-efficient Concrete

self-compacted concrete. In present work, the cement content was partially replaced with fly ash and also ViscoCrete-5930da high-performance superplasticizer, to enhance the flowing and strength of the concrete; plastic aggregate are used to partially replace either the fine or coarse aggregate.

5.5.1

Definition of self-compacting concrete

Self-compacting concrete (SCC) or self-consolidating concrete is that type of concrete which has the ability to flow and consolidate under self-weight through flowing in the formwork without needing inner or outer vibration for the compaction. It is sufficiently cohesive to fill the spaces of different size and shape without segregation among its ingredients or bleeding. This makes SCC especially helpful wherever placing is difficult: intense-reinforced concrete members and in unusual shape members. It has an exceptionally smooth surface level after placing. There are requirements that should be achieved to ensure the self-compactibility of fresh concrete; these requirements are: 1. Filling capacity: represents ability of SCC to flow and occupy all spaces inside the formwork under its self-weight. 2. Passing capacity: represents ability of SCC to pass under its self-weight through tight spacing, for example, spaces among steel reinforcing bars. 3. The segregations resistance: SCC composition should remain uniform and homogeneous through transporting and placing.

Several tests can be utilized successfully to achieve the above requirements as follows (see Fig. 5.21): 1. Slump flow test: this test is giving an indication with regards to the consistency, filling capacity, and workability of SCC. Same slump cone is utilized as for the classic slump test. For SCC the diameter of the spread mixing will be measured, also T50 which represents the time for 500 mm flow diameter. 2. L-Box test: this test measures passing and filling ability of concrete mix using L-shape apparatus. The concrete is permitted to flow from the vertical section passing through reinforcing bars placed at the intersection of the two areas of the apparatus. H2/H1, T20, and T40 will be measured. H2/H1 represent the ratio of the height of the concrete at the horizontal and vertical ends of theapparatus, while T20 and T40 represent the time that SCC takes to flow a distance of 200 and 400 mm, respectively. 3. V-funnel test: this test gives an indication about SCCs viscosity by utilizing V-funnel apparatus. The time of SCC flowing through the funnel orifice will be measured.

Limitations are specified by EFNARC (2005) to classify the concrete as SCC and to provide ease of flow through reinforcement and formwork without segregation and without needed for compaction or vibration.

5.5.2

Fresh properties of Self-compacting concrete incorporating waste plastic aggregate

Self-compacting concrete mixtures were designed having a constant w/b ratio of 0.32 with 1% SP (Sika ViscoCrete-5930: High-performance superplasticizer concrete

Fresh properties of concrete containing plastic aggregate

105

V-funnel test

Slump flow diameter test L-box test

Figure 5.21 SCC fresh properties tests.

admixture type G and F, and it meets the ASTM C 494 requirement) and total binder content of 550 kg/m3. The class F fly ash was used as a 25% of total binder content in all mixtures. Chemical composition of fly ash is listed in Table 5.16. River gravel was used as coarse aggregate with a maximum size of 12.5 mm with specific gravity 2.67. Khayat et al. (2000) proposed a mixing method. This method was adopted in this work to get the same uniformity and homogeneity in all mixes. Workability and passing ability of the fresh mixtures were tested by means of slump diameter flow (measured as average of two diameters), T50 (the time), V-funnel time, and L-box ratio.

5.5.2.1

Fine plastic aggregate SCC

The provided research on the effect of waste plastic as fine aggregate on fresh properties of SCC are limited and most of them presented and discussed effect of PET on

106

Use of Recycled Plastics in Eco-efficient Concrete

Table 5.16 Chemical composition of using fly ash Chemical analysis

% By weight

CaO

5.14

SiO2

58.6

Al2O3

22.10

MgO

1.52

SO3

0.44

Fe2O3

6.54

these properties (Sadrmomtazi et al., 2016, Hama and Hilal 2017 and Mermerdas¸ et al., 2017). In this work HDPE plastic is used as fine aggregate in SCC. HDPE plastic was used as fine aggregate and partially replaced natural fine aggregate (sand) in order to produce self-compacting concrete (SCCHDPFA). The slump flow diameter values in the vicinity of 768 and 792 mm were produced in this investigation. The slump flow diameter was measured as average of two perpendicular horizontal diameters. Slump flow diameter of reference self-compacting concrete was 768 mm. While the flow diameter of SCCHDPFA was 772, 778, 782, 789, and 792 mm for 5.0%, 7.5%, 10%, 12.5%, and 15% as introduced in Fig. 5.22. Test outcomes showed that the SCCHDPA produced according to EFNARC (2005) can be classified as SF3 as well as a reference one. T50 slump flow and V-funnel flow times are given in Fig. 5.23. The slump flow time of 0%, 5.0%, 7.5%, 10%, 12.5%, and 15% HDPFA were 1.45, 1.36, 1.32, 1.25, 1.20, and 1.03 s, respectively. While V-funnel flow times of 0.0%, 5.0%, 7.5%, 10%, 12.5%, and 15% HDPA were 6.78, 6.74, 6.65, 6.58, 6.50, and 6.2 s, respectively. The produced SCC can be categorized as VS1/VF1 (viscosity class). HDPFA slightly improved fluidity of SCC when compared to reference mix without plastic aggregate.

Slump flow diameter, mm

795 790 785 780 775 770 765 0

2

4

6

8

10

12

14

16

% HDPFA

Figure 5.22 Slump diameter of high-density plastic fine aggregate self-compacting concrete.

Fresh properties of concrete containing plastic aggregate

107

8 6.78

7

6.74

6.65

6.58

6.5

6.2

Time, sec

6 5 T50 4 V-funnel time 3 2

1.45

1.36

0

5

1.32

1.25

1.18

1.03

1 0 7.5 10 % HDPFA

12.5

15

Figure 5.23 Slump flow and V-funnel times with %HDPFA. 1 0.99 0.978

0.98

H2/H1

0.97

0.96

0.96 0.948

0.95 0.94

0.95 T50

0.942 0.935

0.93 0.92 0.91 0.9 0

5

7.5

10 % plastic

12.5

15

Figure 5.24 H2/H1 ratio with %HDPFA.

The results of L-box ratio (H2/H1) are presented in Fig. 5.24. The H2/H1 for reference mix was 0.935, while for SCCHDPFA it was 0.942, 0.948, 0.95, 0.96, and 0.978 for 5.0%, 7.5%, 10.0%, 12.5%, and 15.0% HDPFA, respectively. According to these results and EFNARC limitations the passing ability can be classified as PA2 (High passing ability). T20 and T40 L-box times give an indication about the easy flow of SCC concrete mix. The T20 and T40 results are shown in Fig. 5.25. The T20 and T40 times for reference mix were 2.5 and 6.68, respectively. T20 for SCCHDPFA mixes were 2.36, 2.30, 2.24, 2.02, and 1.92 for 5.0%, 7.5%, 10.0%, 12.5%, and 15.0% HDPFA, respectively. The T40 for SCCHDPFA mixes were 6.44, 6.15, 5.68, 5.04, and 4.32 for 5.0%, 7.5%,

108

Use of Recycled Plastics in Eco-efficient Concrete

8 7

6.68

6.44

6.15 5.68

Time, sec

6

5.54

5.2

5 T20

4 3

2.5

2.36

T40 2.3

2.24

2.02

2

1.92

1 0 0

5

7.5

10 % plastic

12.5

15

Figure 5.25 T20 and T40 L-box flow times with %HDPFA.

10.0%, 12.5%, and 15.0% HDPFA respectively. The results also ensure that using of HDPFA as fine aggregate enhance flowability of SCC.

5.5.2.2

Coarse plastic aggregate

Two type of waste plastic were used as coarse aggregates: waste compact disk coarse aggregate (CDCA) and cover plate coarse aggregate (CPCA) waste plastic as shown in Fig. 5.26.

Compacted disk plastic as coarse aggregate Slump diameter of reference self-compacting concrete was 768 mm. while diameter of slump flow for SCCCDCA was 646, 605, 554, and 425 mm for 5%, 10%, 15%, and 20% as introduced in Fig. 5.27. Test outcomes showed that the produced SCCHDPA according to EFNARC (2005) can be classified as SF1 for 5%, 10%, and 15% CDCA, while 20% is out of limit (see Fig. 5.28) and to improve its workability using higher SP dosage is recommended. T50 slump flow and V-funnel flow times are presented in Fig. 5.29. The slump flow time of 0%, 5%, 10%, and 15% CDCA were 1.45, 3.34, 3.92, 5.35, and 1.18s, respectively. While V-funnel flow times of 0%, 5%, 10%, and 15% CDCA were 6.78, 11.65, 16.28, and 20.08 s, respectively. The producing SCC with CDCA can be categorized as VS2/VF2 (viscosity class). Only 15% of 20% CDCA mix pass through the orifice; the rest of the mix is stuck in the apparatus. The results of L-box ratio (H2/H1) are presented in Fig. 5.30. The H2/H1 for reference mix was 0.935, while for SCCCDCA it was 0.86, 0.76, 0.64, and 0.28 for 5%, 10%, 15%, and 20% CDCA, respectively. The coarse compact disk aggregate reduced sharply the passing ability of SCC, especially at 20% substitution level. The T20 and T40 results are shown in Fig. 5.31. The T20 and T40 times for reference mix were 2.5 and 6.68, respectively. T20 for SCCCDCA mixes were 13.44,

Fresh properties of concrete containing plastic aggregate

109

(a) Compact disk

Resulting coarse aggregate

(b) Cover plate of drinking water bottle

Resulting coarse aggregate

Figure 5.26 Utilized coarse aggregate in SCC mixes.

Slump diameter, mm

850 800

SF3

750 700

SF2

650 600

SF1

550 500 450 400 0

5

10

15

20

25

% CDCA

Figure 5.27 Slump diameter of compact disk plastic coarse aggregate self-compacting concrete.

14.65, 16.98, and 22.84 for 5%, 10%, 15%, and 20% CDCA, respectively. While T40 for SCCCDCA mixes were 13.44, 14.65, 16.98, and 22.84 for 5%, 10%, 15%, and 20% CDCA, respectively. The results show that using CDCA as coarse aggregate reduced sharply the fluidity of SCC.

110

Use of Recycled Plastics in Eco-efficient Concrete

Figure 5.28 diameters of slump flow for 20% CDCA. 25 20.08 20 Time, sec

16.28 15

T50

11.65

V-funnel time

10 6.78 5

3.34

5.35

3.92

1.45

0 0

0 0

5

10

15

20

% CDCA

Figure 5.29 Slump flow T50 and V-funnel times with %CDCA. 1

0.935 0.86

0.9

0.76

0.8

0.64

Time, sec

0.7 0.6 0.5 0.4

0.28

0.3 0.2 0.1 0 0

5

10 % CDCA

Figure 5.30 H2/H1 ratio with %CDCA.

15

20

Fresh properties of concrete containing plastic aggregate

111

25

22.84

20 Time, sec

16.98 15

14.65

13.44

10

8.02

6.68 5

2.5

T20 T40

6.42 3.82

4.63

0 0

5

10

15

20

% CDCA

Figure 5.31 T20 and T40 L-box flow times with %CDCA.

Water drink plastic bottle cover as coarse aggregate Slump diameter flow for SCC CPCA was 768, 696, 650, and 554 mm for 0%, 5%, 10%, and 15% CPCA as introduced in Fig. 5.32 Test outcomes showed that the produced SCC according to EFNARC (2005) can be classified as class SF2 for 5%. The 10% and 15% CPCA can be classified as SF1, while the reference mix can be classified as SF3 as mentioned earlier. T50 slump flow and V-funnel flow times in Fig. 5.33. The slump flow time of 0%, 5%, 10%, and 15% CPCA were 1.45, 2.28, 3.36, and 4.05 s, respectively. While Vfunnel flow times of 0%, 5%, 10%, and 15% PET were 6.78, 10.4, 14.55, and 18.28 s, respectively. The produced SCCCPCA can be categorized as VS2/VF2 (viscosity class). CPCA reduced fluidity and increased viscosity of SCC compared to the reference mix without plastic aggregate.

Slump diameter, mm

850 800

SF3

750 700

SF2

650 600

SF1

550 500 0

5

10

15

20

25

% CPA

Figure 5.32 Slump flow diameter of CP plastic coarse aggregate self-compacting concrete.

112

Use of Recycled Plastics in Eco-efficient Concrete

20

18.28

18

Time, sec

16

14.55

14 12

10.4

T50

10 8

V-funnel time

6.78

6 4 2

1.45

4.05

3.36

2.28

0 0

5

10

15

% plastic

Figure 5.33 Slump flow T50 and V-funnel times with %CPCA. 0.96 0.94

0.935

Time, sec

0.92 0.9

0.885

0.88

0.862

0.86

T50 0.84

0.84 0.82 0.8 0.78 0

5

10

15

% plastic

Figure 5.34 H2/H1 ratio with %CPCA.

The results of L-box ratio (H2/H1) are shown in Fig. 5.34. The H2/H1 for reference mix was 0.935, while for CPCA was 0.885, 0.862, and 0.840 for 5%, 10%, and 15% CPCA, respectively. According to these results the passing ability decreased with increasing of plastic substitution. The T20 and T40 results are shown in Fig. 5.35. The T20 and T40 for reference mix was 2.5 and 6.68, respectively. T20 for SCCCPCA mixes were 3.16, 4.68, and 5.62 for 5%, 10%, and 15% CPCA, respectively. While T40 for SCCCPCA mixes were 8.14, 10.25, and 13.68 for 5%, 10%, and 15% CPCA, respectively. The results show that using of CPCA as coarse aggregate reduced the flowability of SCC.

Fresh properties of concrete containing plastic aggregate

113

16 13.68

14

Time, sec

12

10.25

10

8.14

8

6.68 5.62

6 4

T20 T40

4.68 3.16

2.5

2 0 0

5

10

15

% plastic

Figure 5.35 T20 and T40 L-box flow times with %CPCA.

5.6

Conclusions

1. The mix design of concrete (either normal or self-compacting) incorporating waste plastic do not differ from mix design of conventional concrete except for the replacement of a fraction of the natural aggregate (fine or coarse) with a plastic aggregate as a proportion of the volume of natural aggregates. 2. Due to the difference in the specific gravity of natural aggregate and plastic aggregate, the volumetric design method should be adopted. 3. The shape and content of plastic concrete had affected the concrete workability. The increasing of angular shape plastic aggregate content (PETFA, CDFA, CDCA, and CPCA) led to decrease in the slump of concrete. While HDPFA with rounded particle shape increases workability, this may be due to less friction between concrete content. 4. In general, all types of plastic aggregate (either fine or coarse) decreased the density of concrete due to low specific gravity of plastic aggregate compared to specific gravity of natural aggregate. 5. The SCC with HDPFA can be classified as SF3 and VS1/VF1. 6. The SCC with CPCA, CDCA range from SF2 to SF1 and VS2/VF2 depending on plastic content. As plastic content increases, the workability decreases. 7. L-box tests results show that HDPFA increases passing ability of SCC, while CPCA and CDCA reduced passing ability, especially CDCA.

References Akça€ozoglu, S., Atis¸, C.D., Akça€ozoglu, K., 2010. An investigation on the use of shredded waste PET bottles as aggregate in lightweight concrete. Waste Management 30 (2), 285e290. https://doi.org/10.1016/j.wasman.2009.09.033. Hama Sheelan, M., Hilal Nahla, N., 2017. Fresh properties of self-compacting concrete with plastic waste as partial replacement of sand. International Journal of Sustainable Built Environment 6, 299e308. https://doi.org/10.1016/j.ijsbe.2017.01.001.

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Use of Recycled Plastics in Eco-efficient Concrete

Iraqi specification No.5, 1984. Portland Cement. Central Agency for standardization and Quality Control, Planning Council, Baghdad, Iraq. Islam, M.J., Islam, A.K.M.R., Meherier, M.S., 2015. An investigation on fresh and hardened properties of concrete while using polyethylene terephthalate (PET) as aggregate. International Journal of Civil & Environmental Engineering 9 (No:5), 558e561 scholar. waset.org/1307-6892/10001238. Ismail Zainab, Z., Jaeel Ali, J., 2016. Environmental friendly concrete using waste compact discs as fine aggregate replacement. In: Fourth International Conference on Sustainable Construction Material and Technologies. In: http://www.claisse.info/Proceedings.htm. Khayat, K.H., Bickley, J., Lessard, M., 2000. Performance of self-consolidating concrete for casting basement and foundation walls. ACI Materials Journal 97 (3), 374e380. https:// www.concrete.org/publications/internationalconcreteabstractsportal.aspx? m¼details&ID¼4630. Mermerdas¸, K., Nassani, D.N., Sakin, M., 2017. Fresh, mechanical and absorption characteristics of self-consolidating concretes including low volume waste PET granules. Civil Engineering Journal 3 (10), 809e820. https://doi.org/10.28991/cej-030916. Rahmani, E., Dehestani, M., Beygi, M.H.A., Allahyari, H., Nikbin, I.M., 2013. On the mechanical properties of concrete containing waste PET particles. Construction and Building Materials 47, 1302e1308. https://doi.org/10.1016/j.conbuildmat.2013.06.041. Rai, B., Tabin, R.S., Bhavesh, K., Duggal, S.K., 2012. Study of waste plastic mix concrete with plasticizer. International Scholarly Research Network, ISRN Civil Engineering 5. https:// doi.org/10.5402/2012/469272. Article ID 469272. Sadrmomtazi, A., Milehsara, S.D., Omran, O.L., Nik, A.S., 2016. The combined effects of waste Polyethylene Terephthalate (PET) particles and pozzolanic materials on the properties of self-compacting concrete. Journal of Cleaner Production 112, 2363e2373. https://doi.org/ 10.1016/j.jclepro.2015.09.107.

Further reading ASTM, 2005. Chemical Admixtures for Concrete, C494. American Society of Testing and Material International. Iraqi specification No.45, 1984. Aggregate from Natural Sources for Concrete. Central Agency for Standardization and Quality Control, Planning Council, Baghdad, Iraq.

Mechanical strength of concrete with PVC aggregates

6

A.A. Mohammed Department of Civil Engineering, College of Engineering, University of Sulaimani, Sulaimani, Iraq

6.1

Introduction

Polyvinyl chloride (PVC) is one type of thermoplastic polymer that is currently penetrating many aspects of life through its wide use, and has become a universal polymer. This material is produced by polymerization of the vinyl chloride monomer and can be processed into a hard and soft product. It can be made softer and more flexible by the addition of plasticizers. This polymer is processed into either shortlife products, such as for packaging food and medical devices, or long-life products such as plumbing pipes, doors, windows, and roofing sheets. At global level, demand for PVC exceeds 35 million tonnes per year, and it is rated second after polyethylene plastics. In Europe, PVC is the most widely used plastic after polypropylene (PP) and different types of polyethylene (PE) (PE-LD, PE-LLD, PE-HD, PE-MD). Records (PlasticsEurope, 2013) show that 10.3% of total plastics used in Europe is PVC. It is mainly used for the purposes of building and construction, packaging, electrical and electronics, and automotive. The global widely use of PVC usually results in a large amount of waste as the material approaches the end of its useful economic life. These wastes are increasing day by day, and are disposed in landfills (PlasticsEurope, 2013; Sadat-Shojai and Bakhshandeh, 2011), but this process nowadays is not acceptable in many countries because of decrease in available landfilling areas and potential environmental hazards. Recycling following a legal route seems to the solution for PVC wastes. The process of recycling and its acknowledgment have increased during recent years (Nakamura et al., 2009; Arnold and Maund, 1999; Janajreh et al., 2015). According to Vinylplus (Vinylplus) reports, more than 568 tonnes of PVC have been recycled in 2016, and a steady increase of recycling can be observed during the last 2 years. Most of the PVC recycled was window profile and related products followed by flexible PVC applications. With respect to the methods of recycling, both mechanical and/or chemical recycling may be a solution to diminish the problem of environmental pollution instead of landfilling or incineration of such municipal solid wastes. In spite of the benefits related to recycling process, unfortunately in many developing countries the rigorous methods of recycling is not followed and the waste is usually transferred to landfills (Sadat-Shojai and Bakhshandeh, 2011). Landfilling is still the first option in many EU countries. Almost 8 million tons of plastics wastes were landfilled in Europe in

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00006-2 Copyright © 2019 Elsevier Ltd. All rights reserved.

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2014 (PlasticsEurope, 2013). It should be noted that there is a problem related to recycling of mixed plastics. Separation of plastic material before it contaminates collected waste can reduce the properties of byproduct. Both primary and secondary recycling techniques are majorly used in Asian countries, but there is a degradation of various properties of plastic solid waste being obtained as byproduct and consumes a very high amount of energy (Singh et al., 2016). In fact, the recycling of a virgin plastic material can be done 2 to 3 times only, because, after every recycling, the strength of plastic material is reduced due to thermal degradation (Vicente et al., 2009). Efforts have been made by various researchers to obtain byproducts of similar properties as of virgin material by various other tertiary techniques which include chemical treatment of plastic solid waste as it includes the recovery of energy from polymer (Singh et al., 2016). With regard to the PVC plastic, since there are many varieties of PVC in use, the amount of related waste is high and becomes a serious attack for land and water pollution. The risk of this type of polymer is higher than others such as polyethylene terephthalate (PET) because of the existence of chlorine in its chemical structure, which is about 57%. Therefore there is a serious need for cleaning the environment from the PVC products waste and close the way for any further pollution. Beside the mentioned methods of recycling, there is another solution to diminish the attack of wastes against environment via following a special method of recycling, which is the reuse of the plastic waste in concrete production. Ochi et al. (Ochi et al., 2007) reported a number of applications of R-PET fiber reinforced concrete in Japan, including production of shotcrete concrete for mine construction, narrow section pavements, slope spraying, tunnel support, bridge piers. Using this type of plastic fiber was found effective for crack control in concrete. Consuming plastic wastes in construction may be the best one for the developed countries, having poor recycling systems. Indeed, the plastic waste added to concrete is not active like cement or pozzolans and unable to develop a binding medium. This waste is usually added in the form of powder and shredded particles, which are considered as filler materials, or used as fibers. Also, there is a chance to produce relatively large aggregate particles from melting plastic waste and cutting to desired sizes. Different properties of concrete containing different plastic wastes such as PET, HDPE, PP, and PE have now been understood as a result of many experimental tests. Although there are relatively large amount of works on the behavior of concrete containing plastic wastes, a few number of research works investigating the properties of concrete containing PVC aggregate is available in the literature. Postconsumed wastes of this plastic employed for producing concrete aggregate are restricted to long-life PVC products, and any short-life product seems to be not suitable for this purpose. PVC wastes are mainly those plastics obtained from demolished building for the rehabilitating purpose, in which plastic doors, windows, plumbing pipes, electrical wire covers, and sheets used for secondary roofing and covering walls all remained waste. Other waste are some extra parts that remained after cutting true PVC members during processing for completing the job in question. For instance, a

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117

part of the new PVC sheets used for making secondary roofing in a building, cut for the erection purpose and the extra sheets will be a waste. For each story in a residential house there is about 10 kg of the waste if the sheet is used in both secondary roof and covering walls. There is an increase in these wastes because of the citizens’ demand to renew their buildings. Therefore, recycling of PVC sheets besides other plastics is quite important, and there is a need for the waste stream management. As stated before, one method of recycling it is the use of the waste in concrete production, and there is a chance to use PVC in concrete to consume the waste. This process seems to be a viable solution to the problem of recycling costs and high disposal costs. Unfortunately, researches on the different properties of concrete containing shredded PVC is limited as compared with those carried out on concrete containing other plastics such as PET waste.

6.2

Properties of concrete with PVC waste aggregate

To investigate the performance of concrete containing PVC material the fundamental properties were investigated experimentally by some researchers. Published works by Kou et al. (Kou et al., 2009), Senhadji et al. (Senhadji et al., 2015), Haghighatnejad et al. (Haghighatnejad et al., 2016), Gesoglu et al. (Gesoglu et al., 2017), and Gull et al. (Gull et al., 2014) deal with this important subject technology. Table 6.1 summarizes test variables attempted by these researchers. The main experimental results obtained by each investigator are presented in the sections to follow.

6.2.1

Behavior of PVC aggregate

Here, properties of PVC materials added to concrete is presented. Researchers tried to study some fundamental properties of concrete containing PVC powder or aggregate. Kou et al. (2009) used PVC plastic granules (see Fig. 6.1) with fineness modules (FM) of 4.42 as a fine aggregate in concrete mixes. The PVC plastic granules produced by grinding scraped uPVC pipes to small granules, with about 95% passing the 5 mm sieve. The density of this plastic aggregate was found to be 1400 kg/m3. These granules were used to replace a fraction of river sand used in the concrete mixtures (by volume). Senhadji et al. (2015) used PVC lightweight aggregate produced by grinding scrapped PVC pipes into small granules, which were classified as fine aggregate (Fig. 6.2) or medium aggregate (Fig. 6.3) having particle size ranges of 0e3 mm and 3e8 mm, respectively. Densities of the fine and coarse PVC materials were 1.4 gm/cm3 and 1.44 gm/cm3, respectively. Bulk density of the two aggregates was found to be 575 kg/m3 and 750 kg/m3, respectively. Fineness modulus of fine PVC aggregate was 3.46 and the particle’s shape was angular. Plastic material obtained from scrapping PVC pipes was used by Haghighatnejad et al. (2016), to study the effect of curing conditions on concrete properties. Scraped PVC pipes were ground into

118

Table 6.1 Description of concrete properties with PVC waste studied by the past investigators Type of PVC

Description of waste

Kou et al. (2009)

Scrapped PVC pipes

Senhadji et al. (2015)

PVC content

Property studied

95% passing 5 mm sieve

5, 15, 30, 45%a

Slump, density, compressive strength, splitting tensile strength, elastic modulus, Poisson’s ratio, drying shrinkage, chloride ion penetration.

Scrapped PVC pipes

Graded 0e3 mm and 3e8 mm

30, 50, 70%a

Workability, density, compressive strength, ultrasonic wave velocity, resistance to chloride ion penetration.

Haghighatnejad et al. (2016)

Scrapped PVC pipes

5 mm max. size

20, 30, 40, 50%a

Slump, absorption, compressive strength, splitting tensile strength, elastic modulus.

Gesoglu et al. (2017)

Pulverized PVC

150 microns average size

5, 10, 15, 20, 25%b

Compressive strength, splitting tensile strength, flexural tensile strength, elastic modulus, fracture mechanics.

Gull et al. (2014)

E-waste (chapped wire)

3 cm, 4 cm, and 5 cm fibers

0.4, 0.6, 0.8, 1%c

Compressive strength, splitting tensile strength.

as sand replacement. by cement weight. by concrete volume.

b c

Use of Recycled Plastics in Eco-efficient Concrete

a

Reference

Mechanical strength of concrete with PVC aggregates

119

Figure 6.1 PVC aggregate used by Kou et al. (2009).

Natural sand

PVC sand

Figure 6.2 Fine PVC aggregate used by Senhadji et al. (2015).

small pieces with particle size of less than 5 mm (see Fig. 6.4). Sieve analysis indicates that the aggregate passed by 94.8% on 4.75 mm sieve. Plastic powder used by Gesoglu et al. (2017) in their tests on self-compacting concrete had a specific gravity and a mean diameter of 1.53 and 153 microns, respectively. Sieve analysis indicates that this finely graded aggregate passed by 100% on 400 microns sieve. It had a negligible water absorption capacity after 24 h submersion. Gull et al. (2014) used a different kind of PVC product in their concrete mixes. E
waste used was electrical copper wire insulation which is one type of soft PVC product, which has been used in the form of macrofibers, to investigate the residual compressive and tensile strengths.

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Natural aggregate (3/8)

PVC aggregate (3/8)

Figure 6.3 Medium PVC aggregate used by Senhadji et al. (2015).

Figure 6.4 PVC aggregate used by Haghighatnejad et al. (2016).

Figure 6.5 PVC copper wire insulation used by Gull et al. (2014).

The wire used was of 4 mm diameter, 0.8 mm thickness (see Fig. 6.5), and cut to different lengths of 3, 4, and 5 cm and then used in concrete. In this way, this addition seems to be a macrofiber rather than an aggregate. The tensile strength of this plastic was found to be 2.6 N/mm2 and density equal to 1.38 gm/cm3.

Mechanical strength of concrete with PVC aggregates

6.2.2

121

Properties of fresh concrete

It is important to know the relation between PVC particles added to concrete and fresh concrete properties. These properties are mainly the fresh concrete density and workability. Both properties of concrete containing some forms of PVC particles were measured in the laboratory. However, the knowledge about this topic is limited and there is a need for other studies in this context. Workability of fresh concrete determined by slump test was measured in the laboratory by Kou et al. (2009), Senhadji et al. (2015), and Haghighatnejad et al. (2016) because they believed that the existence of PVC particles may affect this property of concrete. Slump values of concrete tested by Kou et al. (2009) were between 170 and 175 mm. In the mixes, dosages of superplasticizer were adjusted in order to obtain slump values within 160e180 mm. This slump range is necessary for the production of a highly workable lightweight aggregate concrete. To maintain good workability of concrete mix with PVC content of 5%, 15%, and 45%, the superplasticizer dosages in concrete mixtures were added by 2.4%, 12.2%, and 31.7%, respectively. Increasing the superplasticizer dosage was found necessary because of the reduction of concrete workability containing PVC aggregate. This slump loss was attributed to the angular shape and larger sizes of the PVC granules. Increasing PVC aggregate in the mix was found to reduce the consistency of the fresh concrete. When the river sand was replaced with 45% PVC aggregate (by volume), harsh concrete mix with bleeding was obtained. Test results by other researches are in contrast with those mentioned. According to the experiments by Senhadji et al. (2015), there is an improvement ratio of workability by 82%, 114%, and 128% for concrete mix with 30%, 50%, and 70% PVC aggregate, respectively. Therefore, there is a difference in the fresh concrete behavior of lightweight and normal weight concretes. This enhancement was attributed to the nonabsorptive nature of the PVC aggregate in which concrete mixes containing PVC aggregates had more free water. This will lead to the slump increase. It is worthy to note that no bleeding or segregation was observed even though the concrete mixes were made without the addition of bonding additives. Test results by Haghighatnejad et al. (2016) showed that normal concrete with a slump of 10 cm decreased to 7.5, 6.8, 5.5, and 5.2 cm by the incorporation of 20%, 30%, 40%, and 50% PVC aggregate, respectively. Accordingly, there is a systematic reduction in slump value with the increase in PVC aggregate content. This reduction in slump was attributed to the sharp edges of PVC aggregate used. These results are in agreement with those by Kou et al. (2009) and in contrast with those by Senhadji et al. (2015). Further researches on workability of concrete with PVC aggregate may be required to highlight the true variation slump. Other tests of workability such as flow test can be done to illustrate more the fresh concrete behavior with the existence of PVC aggregate. Gull et al. (2014) found that slump and compacting factor of concrete containing e-waste macrofiber were 17 mm and 0.9 mm, respectively. The incorporation of the e-waste plastic seems to have no effect on fresh concrete properties.

122

6.2.3

Use of Recycled Plastics in Eco-efficient Concrete

Physical properties

Physical Properties of concrete with PVC aggregate mentioned here are density and different absorptions. These important properties of the recycled concrete were measured by those who worked on this subject of concrete technology. Different types of concrete densities namely fresh wet density, hardened density, air-dried and oven-dried densities were measured by Kou et al. (2009). Results show that these densities are significantly reduced when the fine aggregate is partially replaced with PVC aggregate. Wet density of concrete was varied between 3.1% and 14.8%, hardened density between 3.5% and 14.1%, and oven dry density between 7.1% and 13.6%. Reduction of the density of air-dried concrete was lower and found to be in the range of 1.1%e12%. According to these measurements, there is a small effect of curing regime on the residual density especially for concrete with low PVC aggregate content. Experimental tests by Senhadji et al. (2015) show that there is a decrease in the fresh and dry densities, as the PVC aggregate content increases. Replacement of sand with 30%, 50%, and 70% of PVC aggregates led to reductions in dry density of up to 12%, 18%, and 27%, respectively. For fresh concrete the density reductions were 5.5%, 11%, and 22.5%. One can observe that there is some effect of concrete curing on the residual density, especially at low PVC aggregate content. The reduction in density was mainly attributed to the lower specific weight of the PVC aggregate used as sand replacement in concrete. The authors noted that the densities are lower than 2000 kg/m3 which is the maximum dry density for structural lightweight concrete according to the RILEM LC2 classification (RILEM LC2, 1978). Fig. 6.6 shows variation of concrete density with PVC aggregate variation, based on the data of the two mentioned studies. It is observed that the existence of PVC aggregate has a smaller role on reducing the density of 2600 2400

Density (kg/m3)

2200 2000 1800 1600 Kou et al. (2009)

1400

Fresh density

Senhadji et al. (2015)

Hardened density Air dried density

1200

Oven dried density

Fresh density Air dried density

1000 0

10

20

50 30 40 PVC content (%)

Figure 6.6 Variation of concrete density with PVC aggregate.

60

70

80

Mechanical strength of concrete with PVC aggregates

123

the lightweight concrete. With regard the other physical property of concrete with PVC aggregate which is the absorption, Haghighatnejad et al. (2016) observed that the initial 30 min absorption of mixtures was in the range of 0.21%e1.02%. They reported that according to CEB-FIP (CEB-FIB model code, 1990) the concrete having this absorption capacity is categorized as “good” concrete. It was also observed that final water absorption is between 0.39% and 2.04%, which is relatively low. According to the obtained results, increasing PVC aggregate in the mix will lead to the reduction in both initial and final absorptions. For concrete subjected to continuous water curing, the incorporation of 20%, 30%, 40%, and 50% RPVC decreased the initial absorption of normal concrete by 40.5%, 39.6%, 45.8% and 62.8%, respectively. These values for final absorption were determined to be 54.6%, 47.4%, 34.7%, and 69.5%. Changing curing condition was found to have an influence on concrete absorption. Concrete subjected to continuous water curing showed the lowest absorption value and the highest absorption value was obtained for the specimens cured under continuous room curing. For concrete with initial water curing for several days followed by room curing condition, the absorption characteristics of concrete with PVC aggregate is decreased by increasing initial water curing period. Concrete with 20% PVC aggregate initially cured in water for 3 days has absorption of 0.93%, whereas the initial water curing of concrete with the same PVC content for seven and 14 days leads to the absorption of 0.64% and 0.6%, respectively. The effect of curing regime on both initial and final absorptions of concrete with PVC aggregate is more than that on compressive strength.

6.2.4

Mechanical properties

Mechanical properties of concrete with PVC aggregate studied by the past researchers are compressive strength, splitting tensile strength, flexural tensile strength, modulus of elasticity, and fracture mechanics. Each property in some detail is presented in the sections to follow. Table 6.2 shows percentage of change of important concrete properties containing PVC aggregate, powder, or e-waste chapped wire, continuously cured in water.

6.2.4.1

Compressive strength

Test results obtained by Kou et al. (2009) show that the compressive strength of lightweight concrete is reduced with the increase in PVC granules content. The compressive strengths were 9.1%, 18.6%, 21.8%, and 47.3% lower than that of control mix, for 5%, 15%, 30%, and 45% PVC aggregate, respectively. They found that there is a very good correlation between hardened concrete density and compressive strength. For lightweight concrete with PVC aggregate compressive strength and density are correlated in the following relationship: f c 0 ¼ 0:0716 gc
89:96

(6.1)

where f c 0 is compressive strength measured in MPa and gc is concrete density measured in kg/m3. R2 for the above equation was found to be 0.9576.

Table 6.2 Percentage change of concrete properties as a result of using PVC aggregate Physical properties

Mechanical properties (MPa)

Other properties

Unit weight (kg/m3) PVC content (%)

Fresh

(Air dried)

Abs. (%)

Scrapped pipe ( Pb

if Pb > Pt

(10.16) (10.17)

where, Pt ¼ weight of polymers in the top section of the column, Pb ¼ weight of polymers in the bottom section of the column, S ¼ static segregation, percent

10.5

Properties of PISCC mixes in their fresh states

In general, the previous works on concrete mixes with different polymeric materials have indicated both reduced as well as enhanced workability characteristics. Workability changes are mainly dependent on type of polymer, form, and amount of volume replacement (Al-Manaseer and Dalal, 1997; Ismail and Al-Hashmi, 2008; Kou et al., 2009; Albano et al., 2009; Choi et al., 2009, Pacheco-Torgal et al., 2012). Malkapur et al. (2017a,b) in their work, replaced the fine aggregate component of the control concrete (CC mix) by virgin HDPE polymeric material in three different proportions, that is, at 77.2, 103.0, and 128.7 L per cubic meter of concrete. These three volumes corresponded to a 30%, 40%, and 50% volume of fine aggregates in all the PISCC mixes. It is noted that the PISCC mixes in general had the tendencies of reduced workability characteristics with increasing polymer contents. However, when higher binder contents and higher dosages of superplasticizers were used, it was observed that, from the point of rheology, the mixes recorded good workability (Fig. 10.10). The slump flow values were found to be greater than 550 mm for polymeric replacements up to 40%, whereas these values were found to be in the range of 550e565 mm at about 50% replacement levels (Table 10.2). Higher V-funnel times greater than 7 s and relatively lower blocking ratios in the L-box test, ranging from 0.86 to 0.93 were observed for all the PISCC mixes. The authors opined that the relatively lower slump flow values, higher V-funnel times, and lower blocking ratios in L-box tests were indicative of higher viscosity in PISCC mixes. The higher viscosities were due to the higher fine contents in the PISCC mixes, facilitated to counter the segregation characteristics and provide stability for these mixes. At lower W/B ratios and lower polymer replacements, the PISCC mixes satisfied all the three desired rheological properties completely. At higher W/B ratios and higher polymer replacement levels, the PISCC mixes are just about passing the SCC requirements as per ACI 237R (2007). The spread mass of the PISCC mixes were found to be homogeneous and stable, showing a visual segregation index (VSI) value of zero in seven of the PISCC mixes. A numerical value of VSI ¼ 1 was observed for two mixes indicating slight bleeding observed as a water sheen on the surface.

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Figure 10.10 Slump flow characteristics of PISCC mixes (Mix VP7) (Malkapur et al., 2017b). Table 10.2 Properties of PISCC mixes in fresh states (Malkapur et al., 2017b) Mix

Polymer content l/m3

Slump flow (mm)

V-funnel flow time (sec)

L-box test

VSI

CC

0.0

620

8

0.96

0

VP1

77.2

595

7

0.93

0

VP2

103.0

580

8

0.90

0

VP3

128.7

555

12

0.89

1

VP4

103.0

585

11

0.90

0

VP5

128.7

550

11.5

0.86

1

VP6

77.2

600

10

0.90

0

VP7

128.7

565

11

0.86

0

VP8

77.2

590

7

0.91

0

VP9

103.0

585

10

0.90

0

The desired levels of the filling ability, passing ability, and stability of an SCC mix are dictated by the application for which it is used. For example, passing ability is very important for reinforced concrete applications, that too in sections with congested reinforcement that restricts the flow of concrete into place (ACI 237R, 2007). Malkapur et al. (2017a,b) concluded that the PISCC mixes tested had lower slump flow values and were not suitable for higher or medium levels of reinforced concrete applications as per ACI 237R (2007). Hence, in view of the range of fresh properties observed for these mixes, they could be used for concrete elements with lower levels of reinforcement or plain concrete applications such as shielding walls of nuclear installations.

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233

10.5.1 Static segregation characteristics of PISCC mixes A specific threshold for segregation of coarse aggregates in an SCC mix has not yet been established. Different codes suggest different segregation values. EFNARC (2002) suggests that the static segregation should be less than 15%, whereas ACI 237R (2007) suggests the value to be less than 10%. Table 10.3 presents the static segregation values obtained for the coarse aggregates and polymeric materials (both virgin and waste). The mixes with virgin HDPE are referred as VP mixes and mixes with waste HDPE are referred as WP mixes. The PISCC mixes with both virgin and waste HDPE polymeric materials showed acceptable static segregation values for coarse aggregates. For mixes with virgin HDPE, polymer segregation was found to be acceptable in all the cases except VP3, showing a relatively higher segregation value of 10.4%. For mixes with waste HDPE, slightly higher values of segregation were observed for WP6 and WP7; however, these values have not crossed the limiting value of 15% (EFNARC, 2002). Such acceptable static segregation values may be interpreted as indicative of a fairly uniform distribution of the polymeric particles in all the PISCC mixes. In general, the relatively lower values of static segregation for both the polymeric particles and the coarse aggregates indicated that the matrices in all the tested mixes are dense and stable enough to hold the particles in place. The better segregation resistance of polymeric particles is attributed to the higher surface area and the protruding tail-like shapes formed due to high heat liberated during the pulverizing process of polymeric material in a roto-molding machine (Fig. 10.11). In the fresh state of concrete, the paste deposits on the crevices and corners of the irregularly shaped polymeric particles, making it relatively heavier and difficult to escape from the matrix. That is why the use of higher fines content is very important in proportioning PISCC mixes. Additionally, the protruding tail-like shapes act like anchorages, holding back the polymeric particles

Table 10.3 Segregation characteristics of PISCC mixes (Malkapur et al., 2017b) Mix

Segregation of virgin HDPE polymer, Svp, (%)

Mix

Segregation of waste HDPE polymer, Swp, (%)

VP1

4.5

WP1

5.2

VP2

5.7

WP2

10.0

VP3

10.4

WP3

7.6

VP4

5.9

WP4

4.0

VP5

7.5

WP5

9.3

VP6

6.2

WP6

11.5

VP7

2.8

WP7

13.7

VP8

3.7

WP8

7.2

VP9

4.1

WP9

8.0

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Figure 10.11 Polymeric particles with protruding tail-like shapes (Malkapur et al., 2017b).

within the matrix. These characteristics result in a better segregation resistance of polymers in PISCC mixes.

10.5.2

Strength characteristics

Various research works have been carried out for evaluating the performance of concrete mixes with plastic aggregates as coarse or fine aggregates. Most of the works conducted included replacement levels up to 50% by volume of aggregates or 20% by weight (both represent approximately similar quantities). Irrespective of the type and replacement level, the incorporation of plastics is found to decrease the various strength properties of resulting mortar and concrete specimens (Choi et al., 2009; Panyakapo and Panyakapo, 2008; Ismail and Al-Hashmi, 2008; Siddique et al., 2008; Frigione, 2010; Malkapur et al., 2014; Gesoglu et al., 2017). Malkapur et al. (2016) reported 28-day compressive strength range of 20e32 MPa for both virgin and waste HDPE polymeric materials as compared to a reference concrete mix (0% polymer), compressive strength of 36.8 MPa. Among these mixes, mixes with 30% polymer content achieved a maximum of about 30 MPa and mixes with 50% replacement achieved a minimum strength of about 20 MPa corresponding to 15.2%e44.8% losses in their strengths, respectively. The reduction in compressive strength of concrete specimens varied from 5% to 72% for a change in replacement level of 10%e50% (by vol.). Similarly, the reductions reported in flexural strengths and split tensile strengths varied between 0%e45% and 0%e60% for a replacement level of 0%e50%, respectively. The reduction in split tensile strength and flexural strength are reported to be relatively less prominent than the reduction in compressive strength of these concrete mixes. Modulus of elasticity was found to decrease up to 60% of the value of control concrete. In other works, improvement in toughness behavior leading to absorption of higher amounts of energy and more ductile nature which enables better arrest of cracks generated during the failure were also reported (Saikia and Brito, 2012). The reductions in various strength characteristics are mainly attributed to the very low binding strength between the surface of the plastic particles and the cement paste. Other reasons such as formation of weak transition zone near the aggregates due to

Virgin and waste polymer incorporated concrete mixes for enhanced neutron radiation

235

higher w/c ratio which is because of the accumulation of free water (Kou et al., 2009; Frigione, 2010) have also been cited. The changes in the strength performance of different polymeric materials at similar replacement levels are attributed to the differences in the plastic types used, their size and shape. Nevertheless, most of these concrete mixes with partial replacement of plastic aggregates meet the several strength criteria for normal structural as well as lightweight concrete. In general, decrease in the strength characteristics of polymer incorporated concrete mixes are attributed to: 1. Smooth surface of the polymers; hence the polymeric particles tend to bond loosely with the cement paste (Frigione, 2010; Thorneycroft et al., 2018). Due to this poor bond characteristic, failure takes place through the cement pasteepolymer interface at much lower stress levels. 2. It is possible that there is an accumulation of water or paste in the corners and crevices of the polymeric particles. This leads to higher W/B ratio near the surface of polymers and in turn weak transitions near the surface. With increase in polymer content, number of such pasteepolymer interfaces will increase resulting in reduced compressive strengths (Malkapur et al., 2017b).

10.6

Neutron radiation shielding properties of polymer incorporated concrete mixes

10.6.1 General Malkapur et al. (2017a,b) conducted experiments in the first phase, to study the neutron radiation shielding properties of concrete mixes with virgin HDPE polymeric material, used as partial replacement to sand. They included flux transmission and dose transmission measurements for all the mixes. The total neutron cross-section and halfvalue layer (HVL) thickness were calculated for all the mixes from these measurements.

10.6.2 Hydrogen loading in different PISCC mixes As discussed earlier, hydrogen content is very important for neutron radiation shielding and as a possible step in enhancing neutron radiation shielding characteristics. Malkapur et al. (2017a,b) used additional hydrogen content in the form of polymeric powder material as a partial replacement to sand in different proportions. Since it is the amount of hydrogen present in the mix which affects the neutron radiation shielding characteristics of a mix, the relative amounts of hydrogen present in different mixes, as compared to that of control mix CC (100%), are computed. The total amount of hydrogen in any mix is calculated by adding the amounts of hydrogen present in it 1. as fixed water in fine and coarse aggregates, 2. as hydrogen in polymers, and 3. as hydrates in hydrated paste.

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Loss on Ignition (LOI) tests were carried out as per the guidelines of ASTM: C-637(2009), for the determination of amounts of fixed water in the aggregates. A standard CHNS (Carbon, Hydrogen, Nitrogen, and Sulfur) test was conducted to evaluate the amount of hydrogen in polymers. A hydrogen content of 14.5% (by mass) has been obtained for virgin HDPE polymeric material. Thermogravimetric Analysis (TGA) was used to estimate the hydrates of the paste (cement and fly ash). The weight loss between 100 and 950 C is taken as the weight of total combined water in cement hydrates (Vedalakshmi et al., 2003; Mohamed and Mohamed, 2012). The hydrogen contributions from different sources and the relative hydrogen contents in different PISCC mixes with virgin HDPE polymeric material are given in Table 10.4. The largest contribution of hydrogen is from the polymers incorporated, followed by the hydrates of paste, and small contributions have been observed from the fixed water content of fine and coarse aggregates. It is observed that the relative hydrogen loading in various PISCC mixes with virgin HDPE polymeric material were in the range of 152%e217% as referred to that of the control mix, CC. On the other hand, relative hydrogen loading (indicated in last column of Fig. 10.3) in various PISCC mixes with waste HDPE polymeric material was in a range of 148.8%e210.5%. It is seen that differences in relative hydrogen loading values of virgin and waste HDPE polymeric material are not significant. When polymers are added as a partial replacement to sand, the corresponding proportion of sand will fall. This means, as the hydrogen is loaded in the form of polymers, a small amount of hydrogen in the form of fixed water that is contained

Table 10.4 Relative hydrogen loading for PISCC mixes with incorporated concrete mixes (contributions from aggregates, polymers and cement hydrates) Relative hydrogen loading (%)

Hydrogen contribution, kg/m3 Mix

Fixed water of aggregates

Fixed water of hydrates

Total weight

Virgin HDPE

Waste HDPE

CC

0.027

0.000

14.764

14.792

100

100

MP1

0.022

10.295

12.270

22.587

152.7

148.8

MP2

0.019

13.732

12.034

25.784

174.3

169.1

MP3

0.016

17.168

12.441

29.625

200.3

193.7

MP4

0.018

13.732

13.218

26.968

182.3

177.1

MP5

0.015

17.168

14.921

32.104

217.0

210.5

MP6

0.019

10.295

12.699

23.014

155.6

151.6

MP7

0.014

17.168

14.709

31.891

215.6

209.0

MP8

0.019

10.295

14.764

25.078

169.5

165.6

MP9

0.016

13.732

14.311

28.058

189.7

184.4

Polymers

Virgin and waste polymer incorporated concrete mixes for enhanced neutron radiation

237

in sand is removed. Nonetheless, hydrogen loading in the first case is quite large compared to the latter. The net hydrogen content is considered in estimating the hydrogen loading for all the mixes.

10.6.3 Shielding characteristics of PISCC mixes Malkapur et al. (2017a,b) observed significant improvements in the neutron radiation shielding properties for all the PISCC mixes with virgin HDPE polymeric material. Tables 10.5 and 10.6 summarize the different shielding properties of PISCC mixes with virgin HDPE and waste HDPE polymeric material. It was found that significant reductions in flux transmission values for all the PISCC mixes (both virgin and waste) were observed at a reference thickness of 150 mm. The range of this decrease in flux transmission varied between 5% and 8.5%. The mix VP7 had the least transmission compared to all the other mixes with a reduction of 8.5%, and mix VP9 had the largest transmission value among the PISCC mixes with a percentage reduction of 5% vis-
a-vis control concrete mix, CC. Similarly, for PISCC mixes with waste HDPE polymeric material, flux transmission decreased in the range of 5%e8.2%. The mix WP7 had the least transmission compared to all the other mixes with a reduction of 8.2%, and mix WP8 had the largest transmission value among the PISCC mixes with a percentage reduction of 5% vis-
a-vis control concrete mix, CC. In general, a decreasing trend of flux transmission values with increasing polymer contents has been observed for all the PISCC mixes. Also, similar test setup and test conditions were maintained as in transmission studies and the equivalent dose rates were measured by changing the PLC detector to REM (Roentgen Equivalent Man) counter. The equivalent dose rates were found to be reduced to a large extent for all the PISCC mixes indicating considerable decrease in the incident energy of the neutrons. The percentage reductions in dose rates were in the range of 9.8%e16.1% for the PISCC mixes with virgin HDPE polymeric material. The mix VP7 had the highest reduction in the dose rate of about 16.1%. Similarly, for PISCC mixes with waste HDPE polymeric material, the reductions in dose rates were in the range of 9.4%e13.2%. In general, it was observed that the reductions in dose rates were relatively more pronounced as compared to reductions of fluxes at the same reference thickness of 150 mm used herein. The results of total neutron cross-section for all the PISCC mixes indicated definite increase in the total neutron cross-section values of all the PISCC mixes. These improvements varied from 3.3% to 5.7% of the control mix for mixes with both virgin and waste HDPE polymeric material. Similarly, noticeable reductions in the computed HVL thicknesses of the PISCC mixes are observed. A maximum reduction of HVL thickness by 5.4% was observed for the mix VP7 and the minimum reduction of 3.2% was observed for the mixes VP8 and VP9. Similarly, a variation of 3.2%e5.2% was observed for PISCC mixes with waste HDPE polymeric material. In general, it is observed that the PISCC mixes produced with waste HDPE powder as a partial replacement to sand are as good in shielding characteristics as the ones produced by using the virgin HDPE polymeric material.

238

Table 10.5 Measured flux and dose transmission values, total neutron cross-sections and HVL thicknesses for different PISCC mixes with virgin HDPE for ref. thickness 150 mm (Malkapur et al., 2017a) P L1 ) B% Dose transmission C% HVL (cm) D% Mix Flux transmission A% t (cm 0.2091  0.0083

0.0

0.1043  0.0042

0.0

0.1751  0.0087

0.0

6.64

0.0

VP1

0.1974  0.0078

5.6

0.1082  0.0043

3.7

0.1550  0.0101

11.5

6.41

3.5

VP2

0.1930  0.0075

7.7

0.1097  0.0043

5.1

0.1543  0.0133

11.9

6.32

4.9

VP3

0.1954  0.0076

6.5

0.1088  0.0042

4.3

0.1533  0.0145

12.5

6.37

4.1

VP4

0.1963  0.0124

6.1

0.1085  0.0069

4.0

0.1518  0.0130

13.3

6.39

3.9

VP5

0.1971  0.0078

5.8

0.1083  0.0043

3.8

0.1536  0.0093

12.3

6.40

3.6

VP6

0.1971  0.0078

5.7

0.1083  0.0043

3.8

0.1580  0.0108

9.8

6.40

3.6

VP7

0.1913  0.0079

8.5

0.1103  0.0045

5.7

0.1470  0.0086

16.1

6.28

5.4

VP8

0.1984  0.0076

5.1

0.1078  0.0041

3.4

0.1518  0.0113

13.3

6.43

3.2

VP9

0.1987  0.0075

5.0

0.1077  0.0041

3.3

0.1572  0.0125

10.3

6.43

3.2

*AdPercentage reduction in flux transmission w.r.t. CC, *BdPercentage improvement in HVL thickness w.r.t. CC.

P t

w.r.t. CC, *CdPercentage reduction in dose transmission w.r.t. CC, *DdPercentage reduction in

Use of Recycled Plastics in Eco-efficient Concrete

CC

CC

0.2091  0.0083

0.0

0.1043  0.0042

0.0

0.1751  0.0103

0

6.64

0

WP1

0.1979  0.0095

5.4

0.1079  0.0046

5.1

0.1541  0.0111

12

6.42

3.4

WP2

0.1937  0.0093

7.9

0.1097  0.0046

5.1

0.1587  0.0943

9.4

6.32

5

WP3

0.1939  0.0076

7.3

0.1093  0.0039

4.3

0.1526  0.0102

12.9

6.34

4.6

WP4

0.1959  0.0940

6.4

0.1086  0.0048

4.0

0.1541  0.0123

12

6.38

4

WP5

0.1929  0.0081

7.8

0.1097  0.0044

3.8

0.1521  0.0930

13.2

6.32

5

WP6

0.1970  0.0087

5.8

0.1083  0.0047

3.8

0.1559  0.0103

11

6.40

3.7

WP7

0.1920  0.0091

8.2

0.1100  0.0045

5.7

0.1532  0.087

12.6

6.30

5.2

WP8

0.1987  0.0067

5

0.1077  0.0041

3.4

0.1575  0.099

10.1

6.43

3.2

WP9

0.1985  0.0059

5.1

0.1077  0.0041

3.3

0.1542  0.0115

12

6.43

3.3

*AdPercentage reduction in flux transmission w.r.t. CC, *BdPercentage improvement in HVL thickness w.r.t. CC.

P t

w.r.t. CC, *CdPercentage reduction in dose transmission w.r.t. CC, *DdPercentage reduction in

Virgin and waste polymer incorporated concrete mixes for enhanced neutron radiation

Table 10.6 Measured flux and dose transmission values, total neutron cross-sections and HVL thickness characteristics of PISCC mixes with waste HDPE for ref. thickness 150 mm P L1 Mix Flux transmission A% ) B% Dose transmission C% HVL (cm) D% t (cm

239

240

10.6.4

Use of Recycled Plastics in Eco-efficient Concrete

Statistical analysis of shielding properties

Malkapur et al. (2017a,b) statistically analyzed the obtained shielding properties of PISCC mixes with virgin HDPE polymeric material, in order to understand the importance of different mix parameters. Based on similar works in the past, Taguchi’s DOE technique was selected for the statistical analysis (Chitawadagi et al., 2010; Sahin et al., 2011). It was aimed to find the effect of input parameters on the output characteristics. In this case, mix parameters were taken as input parameters and the resulting neutron shielding coefficients were taken as output parameters. From Taguchi’s mean of means it was found that the most important factor which decides the shielding efficiency is the polymer content in the PISCC mixes. The other factors like binder content and water-to-binder ratio did not seem to have significant effects. Similar observations have been made in few of the previous studies (Kharita et al., 2010; Malkapur et al., 2015). Hence, polymer content against the mean of means of different shielding parameters such as flux and dose transmission measurements, total neutron cross-section values and HVL (in cm) were plotted in Fig.10.12, indicating the variation of these shielding parameters vis-
a-vis varying polymer content. It is clearly seen that all the shielding properties have got enhanced with increasing polymer content. The reductions in the flux transmission values were found to be 5.5%, 6.3% and 6.9% for 77.3, 103 and 128.7 L/m3 of polymer incorporation. The decreases in the dose rates recorded were 11.5%, 11.8% and 13.6%, respectively, for 77.3, 103, and 128.7 L/m3 of polymer incorporation. The authors opined that the further enhanced reduction percentages in the dose rates compared to reductions in flux transmission values indicate the moderation effects of hydrogen contained in the polymer. It is a well-known fact that hydrogen has a higher scattering cross-section but poor absorption cross-section; the energy of the incident neutrons reduces to a larger extent during the elastic collision process, but these neutrons are not fully captured as a whole. That is why the reduction in dose rates are larger compared to reduction in flux transmission values. Hence, it was concluded that the PISCC mixes are more prominent in reducing the dose rates. The reductions in the HVL thickness were found to be 3.4%, 3.9%, and 4.4% for 77.3, 103, and 128.7 L/m3 of polymer incorporation respectively. The increase in the total neutron cross-section values compared to CC mix are found to be 3.6%, 4.1%, and 4.6% for 77.3, 103, and 128.7 L/m3 of polymer incorporation. All these results indicate the efficiency of PISCC mixes in shielding the neutron radiation.

10.6.5

Effect of hydrogen loading on shielding characteristics of PISCC mixes

It is observed that irrespective of the type of polymer, whether virgin or waste HDPE polymeric material, it is the hydrogen content which decides the shielding characteristics. Malkapur et al. (2017a,b) studied the effect of hydrogen loading on the neutron radiation shielding properties of concrete mixes with virgin HDPE polymeric material. A plot of the relative hydrogen loading (%) versus flux transmission values (Fig. 10.13)

HVL thickness cm

Total neutron cross section (Σt) cm-1

Dose transmission

Flux transmission

Virgin and waste polymer incorporated concrete mixes for enhanced neutron radiation

0.198 0.197 0.196 0.195 77.2

103.0

128.7

77.2

103.0

128.7

77.2

103.0

128.7

77.2

103.0

128.7

0.156

0.154

0.152

0.10900 0.10875 0.10850 0.10825 0.10800 6.430 6.405 6.390 6.375 6.360

Polymer content, L/m3

Figure 10.12 Effect of polymer content on the shielding properties of concrete mixes (Malkapur et al., 2017b).

241

242

Use of Recycled Plastics in Eco-efficient Concrete

Measured values at a reference thickness of 150 mm 0.215

Flux transmission

0.210 0.205 0.200 0.195 0.190 0.185 0.180 100

120

140

160

180

200

220

Relative hydrogen loading (%)

Figure 10.13 Flux transmission values versus relative hydrogen loading for PISCC and control mixes (Malkapur et al., 2017a).

showed in general that there is a decreasing trend of flux transmission values. As the hydrogen loading increases, the transmission values decrease. A maximum of about 8.5% decrease in the transmission value has been observed for a hydrogen loading of about 215.6% for VP7 mix in comparison with control concrete (CC). The total cross-section values plotted in Fig. 10.14 showed in general that there is an increasing trend of cross-section values with increase in hydrogen loading. The maximum and minimum improvements of 5.7% and 3.3% in the total neutron crosssection values were observed for the mixes VP7 and VP9, respectively. The improved shielding properties were attributed to the additional hydrogen loading in the mixes, facilitated by addition of increasing amounts of polymers as a source of hydrogen. Also, the effect of hydrogen loading on the equivalent dose rates were studied and significant reductions in the equivalent dose rates were observed for all the PISCC mixes, indicating considerable decrease in the incident energy of the neutrons (Fig. 10.15). The reductions in dose rates were found to be more pronounced compared to reductions of fluxes at the reference thickness of 150 mm used herein. The mix VP7 had the highest reduction in the dose rate of about 16.1%, at hydrogen loading of about 215.6%. The average decreases in the dose rates were 11.5%, 11.8%, and 13.6% for 77.3, 103, and 128.7 L/m3 (approx. 30%, 40%, and 50% of sand replacement) polymer incorporation, respectively. Also, it was found that cross-section values calculated from the dose transmission measurements were higher than those calculated using the flux transmission measurements,

Virgin and waste polymer incorporated concrete mixes for enhanced neutron radiation

243

Measured values at a reference thickness of 150 mm

0.116

Total neutron cross section (cm-1)

0.114 0.112 0.110 0.108 0.106 0.104 0.102 0.100 100

120

140 160 180 Relative hydrogen loading (%)

200

220

Figure 10.14 Total neutron cross-section versus relative hydrogen loading of PISCC and control mixes (Malkapur et al., 2017a). 0.190

Dose transmission values measured at a thickness of 150 mm

0.185 0.180

Dose transmission

0.175 0.170

R2=0.85

0.165 0.160 0.155 0.150 0.145 0.140 0.135

100

120 140 160 180 Relative hydrogen loading (%)

200

220

Figure 10.15 Relative hydrogen loading versus dose transmission values for PISCC and control mixes (Malkapur et al., 2017a).

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Use of Recycled Plastics in Eco-efficient Concrete

indicating the better efficiency of the mixes in reducing the dose rates rather than the flux. It is evident that hydrogen has a higher scattering cross-section and poor absorption cross-section; this leads to the energy of the incident neutrons being reduced to a larger extent, but these neutrons are not fully captured as a whole. Hence, it can be concluded that the PISCC mixes are more useful in reducing the dose rates. Use of waste HDPE polymeric material for making concretes with enhanced neutron radiation shielding characteristics. It is observed that waste HDPE polymeric powder had the similar fresh and hardened properties and even the neutron radiation shielding characteristics. The only difference between them is in terms of hydrogen content. However, this difference in hydrogen content could not yield much difference in the neutron radiation shielding properties of the mixes. Hence, it can be said that the waste HDPE can be comfortably used in producing concrete mixes with enhanced neutron radiation shielding. In view of the tremendous volume of plastic waste generated and the disposal problems it creates, the waste HDPE polymeric material in the form of powder is a potential material that can be used for enhancing neutron radiation shielding characteristics. Hence, it can be concluded that out of many innumerable reuses that are being tried all over the world, it can also be a good option to use waste HDPE plastic for hydrogen loading of shielding concrete mixes.

10.6.6

Future trends

There is a scope for further improvement in these mixes (i.e., to reduce the flux transmission values), by incorporating additional ingredients. It is learnt from the several past studies that, it is required to have all the three major interactions namely elastic, inelastic scattering, and absorption phenomenon to most effectively attenuate the neutrons. The observed improvements are only due to the elastic scattering phenomenon effected by hydrogen loading, and any further improvement can be facilitated only by triggering the other two phenomena, that is, inelastic scattering and absorption phenomenon. This can be achieved by using high density ingredients and materials with high neutron absorption cross-sections in the concrete. As it is well-known that the neutron radiation will be in the form of a spectrum, which includes neutrons with a wide energy range of energy, reactor spectrum source can be used to identify the range of energy at which these polymer incorporated concrete mixes are most effective, and these mixes could be recommended at such places. Decommissioning of nuclear installations after their service life and their dismantling are connected with the necessity of the dismounting and handling of large amount of radioactive equipment and structures. In order to successfully plan the dismantling of the concrete shield, activation of the structure should be known in advance. Experiments and calculations need to be carried out for the determination of the induced activity of concrete used in construction. Neutron activation studies can be carried out on the polymer incorporated concrete mixes to study the activity of such concrete mixes, which will facilitate in decision making in employing such concrete mixes in nuclear installations.

Virgin and waste polymer incorporated concrete mixes for enhanced neutron radiation

245

These mixes can be used in medical cyclotrons, linear accelerators, and other such nuclear installations. They are not recommended at places where high working temperatures are present like inner walls of reactor as these mixes do not possess the fire-resistance characteristics, due to presence of polymeric material which has a melting point of about 130 C. Further studies are required to be carried out to assess the damage due to high temperatures.

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Mortazavi, S.M.J., Mosleh-Shirazi, M.A., Roshan-Shomal, P., Raadpey, N., BaradaranGhahfarokhi, M., 2010. High-performance heavy concrete as a multi-purpose shield. Radiation Protection Dosimetry 142 (2e4), 120e124. Okuno, K., 2005. Neutron shielding material based on colemanite and epoxy resin. Radiation Protection Dosimetry 115 (1e4), 258e261. Pacheco-Torgal, F., Ding, Y., Jalali, S., 2012. Properties and durability of concrete containing polymeric wastes (Tyre rubber and polyethylene terephthalate bottles): an overview. Construction and Building Materials 30, 714e724. Panyakapo, P., Panyakapo, M., 2008. Reuse of thermosetting plastic waste for lightweight concrete. Waste Management 28, 1581e1588. Piotrowski, T., Tefelskib, D.B., Sokołowskaa, J.J., Jaworskaa, B., 2015. NGS Concrete-New Generation Shielding Concrete against ionizing radiation - the potential evaluation and preliminary investigation. Acta Physica Polonica A 128, 9e13. Ragheb, M., 2011. Lecture Notes on Neutron Cross Sections, FSL-33, Department of Nuclear, Plasma and Radiological Engineering. University of Illinois. Available at: https://netfiles. uiuc.edu/mragheb%20Sections.pdf. Rinard, P., 2009. Neutron Interactions with Matter, Los Alamos Technical Report. Available at: http://www.fas.org/sgp/othergov/doe/lanl/lib-www/la-pubs/00326407.pdf. Sadrmomtazi, A., Dolati-Milehsara, S., Lotfi-Omran, O., Sadeghi-Nik, A., 2016. .The combined effects of waste Polyethylene Terephthalate (PET) particles and pozzolanic materials on the properties of self compacting concrete. Journal of Cleaner Production 112, 2363e2373. Sahin, R., Polat, R., Icelli, O., Celik, C., 2011. Determination of transmission factors of concretes with different water/cement ratio, curing condition, and dosage of cement and air entraining agent. Annals of Nuclear Energy 38, 1505e1511. Saikia, N., Brito, J.D., 2012. Use of plastic waste as aggregate in cement mortar and concrete preparation: a review. Construction and Building Materials 34, 385e401. Siddique, R., Khatib, J., Kaur, I., 2008. Use of recycled plastic in concrete: a review. Waste Management 28, 1835e1852. Stoces, B., Burian, J., Otopal, P., Rataj, J., 1968. Comparison of Shielding Effect of Two Types of Concrete, Report UJV 2099-R. Institute of Nuclear Research, Czechoslovak Academy of Sciences. Thorneycroft, J., Orr, J., Savoikar, P., Ball, R.J., 2018. Performance of structural concrete with recycled plastic waste as a partial replacement for sand. Construction and Building Materials 161, 63e69. Vedalakshmi, R., Sundara Raj, A., Srinivasan, S., Ganesh Babu, K., 2003. Quantification of hydrated cement products of blended cements in low and medium strength concrete using TG and DTA technique. Thermochimica Acta 407, 49e60. Yarar, Y., Bayulken, A., 1994. Investigation of neutron shielding efficiency and radioactivity of concrete shields containing colemanite. Journal of Nuclear Materials 1720e1723. Yılmaz, E., Baltas, H., Kiris, E., Ustabas, I., Cevik, U., El-Khayatt, A.M., 2011. Gamma-ray and neutron shielding properties of some concrete materials. Annals of Nuclear Energy 38, 2204e2212.

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Performance of dioctyl terephthalate concrete

11


lu 2 , H. Korucu 1 , M.M. Kocakerim 1 B. S¸ims¸ek 1 , T. Uygunog 1 Department of Chemical Engineering, C¸ankırı Karatekin University, Uluyazı Campus, C¸ankırı, Turkey; 2Department of Civil Engineering, Afyon Kocatepe University, Ahmet Necdet Sezer Campus, Afyon, Turkey

11.1

Introduction

In recent years, PET manufacturing has increased significantly due to its high mechanical strength, good chemical resistance, durability, and low cost (Foti, 2013; Langer et al., 2015; Mohammed, 2017a). With all these characteristics, PET is one of the plastic materials commonly used in the textile and beverage industry (Saikia and de Brito, 2014). Polymeric wastes, particularly PET, have become an environmental problem because they are widely used (Nikbin et al., 2016; S¸ims¸ek and Uyguno
glu, 2016). Researchers are making great efforts on the elimination of PET, which is very robust to degradation in the natural environment (Aldahdooh et al., 2018; Mohammed, 2017b). One of the most preferred methods for PET disposal is to replace the fine aggregate in the concrete production. There are a lot of studies on the PET disposal in building materials and the effects of waste PET on concrete mortar properties are also investigated in terms of mechanical, workability, and thermal resistance. Islam et al. (2016) used PET aggregate instead of 20% by weight natural aggregate at 0.42 water/cement ratio (Islam et al., 2016). As a result of this study, only a 9% compressive strength loss was obtained, while there was a small change in the slump flow value. Similarly, Rahmani et al. (2013) also used 15% PET by weight aggregate instead of normal aggregate. They found a 15.9% loss in splitting tensile strength, a 20% loss in elastic modulus, a 13.6% loss in flexural strength, and about 7% loss in ultrasonic pulse velocity (Rahmani et al., 2013). Akça€ozo
glu et al. (2013) used waste PET in 60% by weight ratio instead of fine aggregate and achieved a 58% improvement in thermal conductivity despite a drop of 78% in compressive strength (Akça€ ozo
glu et al., 2013). Janfeshan Araghi et al. (2015) carried out a chemical resistance study with 5% H2SO4 solution by using 15 wt% waste PET instead of fine aggregate. While the control concrete had a weight loss of 13.47% and a compressive strength loss of 32.56%, there was a weight loss of 6.57% and a compressive strength loss of 20.7% in the concrete containing 15 wt% waste PET aggregate (Janfeshan Araghi et al., 2015; Sharma and Bansal, 2016). S¸ims¸ek et al. (2018), on the other hand, used 10 wt% waste PET instead of fine aggregate in their study and achieved an improvement of 23.5% in electrical resistance. Considering these studies, it is

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00011-6 Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete

seen that PET causes mechanical strength loss, but it provides the concrete with thermal insulation and chemical resistance (S¸ims¸ek et al., 2018). However, there are many disadvantages of mixing PET directly into concrete. One of these is that PET does not disperse homogeneously in concrete, directly affecting the concrete performance. It is known that PET improves the thermal resistance of concrete and reduces its mechanical strength. However, due to the problems in the homogenous concrete production, PET-reinforced concrete cannot exhibit these properties clearly. There are quite different results between the properties of one surface of the produced concrete and that of the other surface. Another disadvantage is that the PET added to the concrete appears on the concrete surface and forms a compact structure. The appearance of PET in concrete causes aesthetic problems for consumers. However, there is a third method involving the recovery of PET, which involves obtaining of financially and environmentally valuable chemicals with the chemical degradation of PET (S¸ims¸ek et al., 2018). Teraphthalic acid (Al-Sabagh et al., 2016) or dimethyl terephthalate (Luo and Li, 2014) and ethylene glycol emerge during the chemical degradation of PET by hydrolysis; dioctyl terephthalate (DOTP) was derived by alcoholysis of isooctyl alcohol and bis (hydroxyethyl) terephthalate (S¸ims¸ek et al., 2018) or glycolysis with ethylene glycol (Cakic et al., 2017). Of these products, DOTP is a general-purpose plasticizer alternative for conventional orthophthalate, since it is not carcinogenic. S¸ims¸ek et al. (2018) used 10 wt% waste DOTP instead of fine aggregate and achieved an 836% improvement in electrical resistance. In their work, while they achieved a thermal insulation of 4% compared to the control concrete when they used 10 wt% PET instead of fine aggregate, they achieved 33.1% thermal insulation compared to the control concrete when they used 10 wt% DOTP (S¸ims¸ek et al., 2018). DOTP whose commercial production is increasing recently (BASF starts up DOTP plasticizer and 2-EH feedstock plants at Pasadena site; reports 12% sales growth, 2017; BASF to produce DOTP plasticizer in North America, 2016; Theophile and Jeong, 2017) can be used in concrete as an alternative to PET. Thus, more compact concrete mortar can be obtained compared to waste PET-aggregate concrete. It is known that PET is a condensation polymer and can easily be decomposed into low molecular weight products by the appropriate solvent which forms ester bonds (Chen et al., 2014). They can be purified and reused as raw materials for the production of high-quality chemical products. Therefore, the chemical recycling of PET to high-value chemical products by depolymerization provides both environmental and economic benefits and is gaining more and more attention (Chen et al., 2014; Ding et al., 2014; Liu et al., 2013). In general, the alcoholysis of PET in the presence of zinc acetate as a catalyst is preferred for DOTP production (Chen et al., 2014). DOTP is a terephthalate plasticizer and has a very different structure from the orthophthalate esters such as dioctyl phthalate, diisodecyl phthalate, diisononyl phthalate, as can be seen in their structural formulas (Fig. 11.1). This branched chain structure of the DOTP provides many excellent properties that are not found in other plasticizers. Some of these properties include that it is less volatile (thus has permanent properties), has lower viscosity (higher fluidity), is not carcinogenic (does not contain orthophthalate), and has high electrical resistance.

Performance of dioctyl terephthalate concrete

251

O C4H9CHCH2O C C 2H 5

O C OCH2CHC4H9 C2H 5

Figure 11.1 Dioctyl terephthalate structural chemical formula (Liu et al., 2013). Table 11.1 The Properties of PET and DOTP (S¸ims¸ek et al., 2018) Properties

Values for PET (S¸ims¸ek and Uyguno
glu, 2016)

Values for DOTP (S¸ims¸ek et al., 2018)

Molecular weight

N/A

390.57

Formula

(C10H8O4)n

C24H38O4

Ester content, %

N/A

99.8

N/A

0.03

1.38

0.98

N/A

60

1.57

1.49

50

46

350

405

235

N/A

Phthalic acid, wt% Specific gravity, g/cm

3

Viscosity, cP Refractive index Freezing point, Boiling point,

C

C

Melting temperature,

C

14

Volume resistivity, ohm*m

10

1013

Tensile strength, kg/cm2

80

N/A

Form

Solid

Liquid

Due to its structure, it has low ductility. And this reduces the brittleness of the plastic at low temperatures. All these characteristics make DOTP an alternative to PET in concrete. The properties of PET and DOTP have been summarized in Table 11.1. In this study, the workability and mechanical, thermal, and electrical properties, most of which were mentioned above, which symbolize the performance of DOTPreinforced concrete, will be comparatively examined with the performance of PETreinforced concrete.

11.2

Dioctyl terephthalate concrete

11.2.1 Workability performance Fresh concrete is deformed when it is mixed, pumped, or placed by effect of selfweight or vibration (Brostow and Uyguno
glu, 2014). Protection of desired properties of concrete against these effects depends on its uniformity and rheological property (Topccedil and Uyguno
glu, 2010). The Slump test has been widely used extensively

252

Use of Recycled Plastics in Eco-efficient Concrete

20 y = –0.055x + 18.40 R2 = 0.614

Slump flow (cm)

19 18 17 16 15 14 13 0

10

20

30 40 50 The amount of DOTP(kg)

60

70

Figure 11.2 The change of the slump flow value of dioctyl terephthalate concrete.

in civil engineering to estimate the “workability” of fresh concrete for two decades (Topccedil and Uyguno
glu, 2010). The slump flow value of dioctyl terephthalate concrete (DIMIC) which is the most important workability criterion decreased with the increasing of the DOTP amount according to S¸ims¸ek et al. (2018) study (Fig. 11.2). DOTP used up to 10% of the cement and caused a slump loss of about 22%. DOTP has a high viscosity, and oil-like structures reduce the fluidity of concrete. DOTP, which forms a mechanical barrier around the cement granules, prevents hydration of the cement with water. In their studies, they used super-plasticizer with high DOTP dosage to remove this disadvantage and to improve the workability performance of the concrete. The amount of DOTP is identified for 1 m3 concrete (S¸ims¸ek et al., 2018).

11.2.2

Compressive strength

The mechanical properties of concrete are a key factor for estimating the stiffness and strength of the buildings and members (Davraz et al., 2018). The determination of the compressive strength of concrete is very important for structures that require strict control of the deformability (Davraz et al., 2018). As expected, 7-days and 28-days compressive strengths of concrete decrease as the amount of DOTP in the concrete increases. This result is expected for all plasticizers. It can be thought that the oily and liquid DOTP plasticizer partially prevents the hydration of the cement paste, and therefore the hydration reaction does not take place completely. The sudden decrease in mechanical strength of DOTP-reinforced concrete, determined by S¸ims¸ek et al. (2018), limits the use of DOTP for normal weight concrete. However, DOTP additive can be used for cement and concrete mortar where compressive strength is not that important (Fig. 11.3) (S¸ims¸ek et al., 2018).

Performance of dioctyl terephthalate concrete

253

Mechanical strength (MPa)

70

7 days compressive strength

60

28 days compressive strength

50 y = –0.54x + 51.02 R2 = 0.772

40 30 20

y = –0.48x + 43.87 R2 = 0.785

10 0

0

10

20

30 40 50 The amount of DOTP (kg/m3)

60

70

80

Figure 11.3 The change of the mechanical strength value of dioctyl terephthalate concrete.

11.2.3 Ultrasonic pulse velocity The ultrasonic pulse velocity (UPV) measurement can be utilized for the determination of concrete uniformity, cracks or voids’ presence, changes in properties with time. As the amount of DOTP in the concrete increases, the ultrasonic pulse velocity of the concrete decreases. It can be said that this is due to the porous structure of DOTPreinforced concrete (S¸ims¸ek et al., 2018). The dramatic drop in ultrasonic pulse velocity and the porous structure of DOTP-reinforced concrete is another indication that DOTP-reinforced concrete has good quality (Fig. 11.4) (S¸ims¸ek et al., 2018). When

Ultrasonic pulse velocity (Km/s)

5

y = –0.010x + 4.738 R2 = 0.951

4.9 4.8 4.7 4.6 4.5 4.4 4.3 4.2 4.1 4 0

10

20

30

40

50

60

70

The amount of DOTP(kg/m3)

Figure 11.4 The change of the ultrasonic pulse velocity value of dioctyl terephthalate concrete.

254

Use of Recycled Plastics in Eco-efficient Concrete

UPV of concrete is higher than 4.5 km/s, the concretes are classified as good and highquality concrete grade, the concrete are in a good concrete grade with UPV of 3.5e4.5 km/s (Erdo
gan, 2007).

11.2.4

The percentage of water absorption

Water absorption of the components influence the properties of the concrete (Topçu and Uyguno
glu, 2010). The low absorption is also an indication of good compaction achieved by the concrete self-weight (Khatib, 2008). The durability of concrete is largely determined by the rate at which harmful agents can penetrate into the concrete. Water absorption is measured by measuring the increase in mass as a percentage of dry mass (Abdullah et al., 2018; Herki and Khatib, 2013). Although the percentage of water absorption increases partially as the amount of DOTP increases, a considerable decrease in the percentage of water absorption is observed compared to the reference concrete in which no DOTP is used. The fact that DOTP lowers the water absorption percentage can be interpreted as that it increases the resistance of the concrete against water (Fig. 11.5) (S¸ims¸ek et al., 2018).

11.2.5

The splitting tensile strength

The strength properties of concrete are affected with increasing density of components. The reduction in splitting strength is related to the weakness of aggregates and other particles such as DOTP. As expected, as the amount of DOTP in the concrete increases, the splitting tensile strength of concrete decreases. This result is again expected for all plasticizers (Fig. 11.6) (S¸ims¸ek et al., 2018).

2.2 y = –0.006x + 1.426 R2 = 0.100

Water absorption (%)

2 1.8 1.6 1.4 1.2 1 0.8 0.6 0

10

20

30

40

50

60

70

The amount of DOTP(kg/m3 )

Figure 11.5 The change of the percentage of water absorption value of dioctyl terephthalate concrete.

Performance of dioctyl terephthalate concrete

255

Splitting tensile strength (MPa)

3.8 y = –0.024x + 3.421 R2 = 0.820

3.3

2.8

2.3

1.8 0

10

20 30 40 50 The amount of DOTP (kg/m3)

60

70

Figure 11.6 The change of the splitting tensile strength value of dioctyl terephthalate concrete.

11.2.6 Thermal conductivity One of the most important thermal properties of concrete is the thermal conductivity value. Thermal conductivity coefficient is the quantity of heat that is transported through a unit cube of two surfaces of perpendicular distance to each other in a given unit of time when the difference in temperature of the two surfaces is 1 C and its unit is W/m*K (Uyguno
glu et al., 2016). Thermal conductivity depends upon the pore structure and density of concrete (Topçu and Uyguno
glu, 2010) and the cement paste matrix (Lu and Dong, 2015). In other words, the thermal conductivity increases (Topçu and Uyguno
glu, 2010) with increase of concrete density or compactness (Uyguno
glu et al., 2016). The lower value of this is important for the production of insulating concretes while the high value is very important for the conductive concrete production (Sun et al., 2017). The fact that DOTP provides the concrete with thermal insulation property was revealed by the net decrease in the thermal conductivity value compared to the control concrete (Fig. 11.7). This is due to the reason that DOTP has very low thermal conductivity when compared to concrete composites. Building’s thermal efficiency and comfort have been provided with low thermally conductive concrete. Therefore, DOTP blended concrete combines improved thermal efficiency and comfort characteristics with the structural and durability performance of conventional concretes, requiring no changes to conventional construction methods. The significant thermal characteristics of DOTP concrete, in combination with its strength and lightweight, warrant that it is a feasible choice for building industry (S¸ims¸ek et al., 2018).

11.2.7 The electrical resistance The physical and chemical characteristics of concrete affect the electrical resistivity as a property. It allows the assessment of the greater or lesser difficulty with which

256

Use of Recycled Plastics in Eco-efficient Concrete

Thermal conductivity (W/m*K)

1.6 y = –0.007x + 1.458 R2 = 0.912

1.5 1.4 1.3 1.2 1.1 1 0

10

20 30 40 50 The amount of DOTP(g/m3)

60

70

Figure 11.7 The change of the thermal conductivity value of dioctyl terephthalate concrete.

aggressive chemical substances such as acid and chlorine penetrate the concrete’s core before the dissolution of the passive film process and the consequent reinforcement’s corrosion begins (Silva and de Brito, 2013). The onsite monitoring of materials and elements represents an important issue since it is compulsory in order to warrant a complete structural and mechanical assessment of the construction. In this case, the critical aspect is to evaluate information about the materials by means of a nondestructive (NDT) analysis (Faifer et al., 2011). Electrical resistivity measurement among the NDT techniques is becoming popular among researchers for the sustainable quality control, improvement, and durability evaluation of concrete (Layssi et al., 2015). Electrical behavior of cementitious systems can be utilized to discover the evolving microstructure, and thus to provide indications of the mechanical and durability performance of such systems (Neithalath et al., 2010; Pacheco et al., 2014). Overall, the concrete’s electrical resistivity can be defined as the ability of concrete to withstand the transfer of ions subjected to an electrical field (Thomas, 2018). Measured values are usually between 101 and 105 U, which are related to concrete composition, cement type, age, and environmental conditions (Bertolini et al., 2013; Polder, 2001). A change in the degree of saturation will affect the concrete’s resistivity as it would vary the amount of fluid in pore network. It is advisable to use a consistent curing method, provided that the test specimens are in saturated surface dry condition at the time of testing to make reliable and repeatable electrical resistivity measurements for sustainable quality control and improvement applications (Layssi et al., 2015; Madhavi and Annamalai, 2006). Electrical insulated concrete is more preferred to prevent the concrete’s possible aggressive environmental conditions causing the corrosion. When the concrete has electrical resistivity of 100 U*m, it is evaluated as under high corrosion risk. However, concrete is evaluated as under negligible corrosion risk when it has higher electrical resistivity values than 1000 U*m. In general, polymeric materials have very high electrical resistance values. Therefore, concrete can be made

Performance of dioctyl terephthalate concrete

257

4500 y = 58.23x + 367.0 R2 = 0.951

Electrical resistivity (ohm*m)

4000 3500 3000 2500 2000 1500 1000 500 0 0

10

20

30

40

50

60

70

The amount of DOTP(kg/m3)

Figure 11.8 Electrical resistivity of DIMIC depending on DOTP content.

an electrically insulated material by addition of polymer-based addition material (Morris et al., 2002; Uyguno
glu et al., 2018). One of them is dioctyl terephthalate (DOTP) which is obtained by alcoholysis (S¸ims¸ek et al., 2018). Two-dimensional plots, which are drawn by second order model functions, are presented in Fig. 11.8 to analyze the relationship between the electrical resistivity and DOTP content (S¸ims¸ek et al., 2018). The electrical resistivity of concrete increased with increasing amount of dioctyl terephthalate. Optimum dioctyl terephthalate mixed concrete has about 30-times higher electric resistance than the plain concrete (S¸ims¸ek et al., 2018). These results also show that DOTP should be preferred as addition material to produce corrosion resistance concrete (S¸ims¸ek et al., 2018).

11.3

Comparison of the polyethylene terephthalate and dioctyl terephthalate concrete

There are many studies on the disposal of PET in building materials and on the performance of PET-reinforced concrete. Rahmani et al. (2013) used 5%, 10%, and 15% (by weight) cubically and cylindrically shaped waste PET as a replacement for fine aggregate and indicated that the UPV decreased due to the porous structure of the PET-reinforced concrete. In addition, it has been determined that the density and workability properties which are fresh concrete properties of PET-reinforced concrete are lower than those of control concrete. They determined that the slump flow value of PET-reinforced concrete, for water/cement ratio of 0.42, fell from 7 to 4 cm compared

258

Use of Recycled Plastics in Eco-efficient Concrete

to that of the control concrete. Similarly, they determined that PET-reinforced concrete causes a lower modulus of elastic and splitting tensile strength than conventional concrete does. As expected, the compressive strength decreased from 52.20 to 46.59 MPa with 15% PET addition (S¸ims¸ek et al., 2018) and the flexural strength values decreased from 6.25 to 5.4 MPa (Rahmani et al., 2013). Akça€ ozo
glu et al. (2013) also used 30%, 40%, 50%, and 60% (by weight) waste PET in light concrete, as a replacement for fine aggregate. In their study, they found that the addition of PET in 60% ratio, as a replacement for the fine aggregate, decreases the 28-day compressive strength of conventional control concrete from 43.2 to 9.5 MPa, the thermal conductivity value from 0.9353 W/m*K to 0.3924 W/m*K, and the UPV from 4.36 km/s to 2.44 km/s. They obtained from their study that the unit weight of the concrete decreased with PET addition (S¸ims¸ek et al., 2018). With the addition of 60% PET aggregate, the slump flow value of concrete decreased from 16 to 12 cm (Akça€ ozo
glu et al., 2013). Saikia and de Brito (2014) investigated the mechanical properties and abrasion behavior of concrete containing 0%, 5%, 10%, and 15% waste PET particles instead of fine aggregate. They determined that the slump flow value of the aggregate PET-reinforced concrete increased a little whereas the slump flow value of the flake PET-reinforced concrete decreased. It was determined that the compressive strength, the splitting tensile strength, and the elastic modulus decreased as the amount of PET aggregate increased. The abrasion behavior, however, tended to improve for aggregate and PET-reinforced concrete. While control concrete had a 28-day compressive strength of about 44 MPa, this value was 15 MPa for 15% powder PET-reinforced concrete, 28 MPa for fine aggregate PET-reinforced concrete, and about 36 MPa for coarse aggregate PET-reinforced concrete (Saikia and de Brito, 2014). Sadrmomtazi et al. (2016) used waste PET with pozzolanic materials, as the replacement for fine aggregate, in 5%, 10%, and 15% by weight. The slump flow value of control concrete was 678 mm while the slump flow value of 15% PET-reinforced normal weight concrete was determined to be 620 mm. While the air content value of control concrete was 4.2%, the air content of 15% PET-reinforced normal weight concrete decreased to 5.8%. They also observed partial segregation in 15% PET reinforced concrete. The 28-day compressive strength value of control concrete decreased from 36.19 to 18.70 MPa with 15% PET addition, whereas the 28-day compressive strength value of control concrete decreased from 9.73 to 4.86 MPa with 15% PET addition (S¸ims¸ek et al., 2018). In a study by S¸ims¸ek et al., the splitting tensile strength of the concrete decreased from 3.20 to 1.5 MPa with the addition of 15% PET by weight while the water absorption percentage of the concrete increased to 8.8% from 5.1%. The ultrasonic pulse velocity value of control concrete decreased from 4.7 km/s to 3.8 km/s (Sadrmomtazi et al., 2016). Islam et al. (2016) used waste PET in 20%, 40%, and 60% ratios, instead of coarse aggregate, at different water/cement ratios, and also focused on mechanical and fluidity properties. The 28-day compressive strength value of control concrete

Performance of dioctyl terephthalate concrete

259

decreased from 34 to 30 MPa for 0.42 water/cement ratio, the 28-day compressive strength value of control concrete decreased from 32 to 20 MPa in 0.48 water/ cement ratio, the 28-day compressive strength value of control concrete decreased from 30 to 17 MPa in 0.56 water/cement ratio. The slump flow value increased from 1 cm into 3 cm in 0.42 water/cement ratio, from 2 cm to about 4 cm in 0.48 water/cement ratio, from 10 cm into 8 cm in 0.56 water/cement ratio (Islam et al., 2016). Mohammed (2017a) used waste PET to replace fine aggregate as 5%, 10%, and 15% by weight, respectively, and determined the 28-day flexural strength. The flexural strength of the control concrete at 31.36 MPa reached 23.66 MPa with 15% waste PET addition. Concrete density, however, decreased from 2350 kg/m3 to 2314 kg/m3 with 15% PET usage (Mohammed, 2017a). Thorneycroft et al. (2018) also used 10% waste PET of various sizes instead of fine aggregate. While 1.2% increase was observed in the 28-day compressive strength for the PET material that was the same size as the fine aggregate compared to the control concrete, there was 3.7% decrease for waste PET aggregate size of 0.5e2 mm, 4.1% decrease for waste PET aggregate size of 2e4 mm, 78.1.% decrease for waste PET aggregate, size of 2e4 mm, treated with sodium hydroxide and sodium hypochloride, 1.9.% decrease for waste PET aggregate, size of 2e4 mm, treated with sodium hydroxide and sodium hypochloride and washed with water. While 25% increase in the 28-day splitting tensile strength for the PET material which is the same size as the fine aggregate was noted, 13.7% increase for waste PET aggregate size of 0.5e2 mm and 1.5% increase for waste PET aggregate size of 2e4 mm were obtained, there were 52.4.% decrease for waste PET aggregate, size of 2e4 mm, treated with sodium hydroxide and sodium hypochloride, 11.5% decrease for waste PET aggregate, size of 2e4 mm, treated with sodium hydroxide and sodium hypochloride and washed with water (Thorneycroft et al., 2018). S¸ims¸ek et al. (2018) compared the performance of waste PET-reinforced and DOTP-reinforced concrete. For this purpose, they obtained 504 U*m and 3819 U*m as the electrical resistance of concrete with 10% waste PET and DOTP addition, as the replacement for fine aggregate, respectively, and 1.01 W/m*K and 1.45 W/m*K as thermal conductivity. The values of 4.14 km/s and 4.42 km/s were obtained as the UPV for waste PET-reinforced and DOTP-reinforced concrete, respectively. The 7-day compressive strength was determined to be 13.20 MPa for PET-reinforced concrete and 47.74 MPa for DOTP-reinforced concrete; the 28-day compressive strength values, however, were 17.90 and 50.64 MPa for PET-reinforced and DOTP-reinforced concrete, respectively (S¸ims¸ek et al., 2018). When the studies in the literature are examined, in the form of flake or powder, the following comments can be made with the help of the following graph for 10% wt waste PET used as a replacement for fine aggregate. When the slump flow values of 10% PET-reinforced concrete are examined, compared to control concrete, the highest decrease is 37.50% (Rahmani et al., 2013) and the highest increase is 5.88% (S¸ims¸ek et al., 2018). When the slump flow values of 10% DOTP-reinforced concrete were

260

Use of Recycled Plastics in Eco-efficient Concrete

800

Reference concrete

700

10%PET or DOTP concrete

678

620 Slump flow (mm)

600 500 400 300 170 180

200 127 122

100 0

170

140

80

50 PET

PET

PET

Rahmani et al. Saikia and de Sadrmomtazi Brito (2014) et al. (2016) (2013)

PET Şimşek et al. (2018)

DOTP Şimşek et al. (2018)

Figure 11.9 The change of the PET and DOTP concrete slump flow.

examined, a decrease of 17.65%, compared to the control concrete, occurred (S¸ims¸ek et al., 2018). The reason is that DOTP is a viscous product although it forms a more compact structure with concrete (Fig. 11.9). When the 28-day compressive strength values of 10% PET-reinforced and DOTPreinforced concrete are examined in the literature, the highest decrease, compared to control concrete, is 70.09% (S¸ims¸ek et al., 2018) and the lowest decrease is 4.09% (S¸ims¸ek et al., 2018). When the 28-day compressive strength values of 10% PETreinforced concrete were examined, the highest decrease was 48.33% compared to the control concrete (Sadrmomtazi et al., 2016). The reason may be DOTP’s being liquid, whereas PET’s being solid causes less compressive strength loss in PETreinforced concrete (Fig. 11.10). When the UPV values of 10% PET-reinforced and DOTP-reinforced concrete are examined in the literature, the biggest decrease compared to the control concrete was DOPT-reinforced concrete with 13.39% (S¸ims¸ek et al., 2018). However, a 12.77% loss has also been reported for 10% PET-reinforced concrete compared to the control concrete (Sadrmomtazi et al., 2016). However, it can be said that DOTP produces a more porous structure compared to PET and DOTP leads to less UPV value (S¸ims¸ek et al., 2018) (Fig. 11.11). When the literature is examined, even if only 10% polymer is used in either PETreinforced concrete or DOTP-reinforced concrete, a serious splitting tensile strength loss has been observed. S¸ims¸ek et al. (2018) determined 50.14% loss compared to the control concrete, in the splitting tensile strength with 10% DOTP use, and Sadrmomtazi et al. (2016) determined 51.61% loss with flake PET use. PET’s being in either flake or granule form changes strength loss. S¸ims¸ek et al. (2018) achieved a decrease of 4.63% compared to the control concrete, using 10% granule PET (Fig. 11.12).

Performance of dioctyl terephthalate concrete

261

80

Reference concrete 10%PET or DOTP concrete Reduction rate (%)

70

59.85

59.85

60 Compressive strength (MPa)

70.09

53.8

52.2 50

51.6

50.61

48.33

46.59

44

40

36.19 32 27.27

30

18.7

20

15.44

17.9

10.75 10 PET

PET

0 Rahmani et al. (2013)

PET

Saikia and de Sadrmomtazi Brito (2014) et al. (2016)

PET

4.09

PET

DOTP

Şimşek et al. Thomeycroft Şimşek et al. (2018) et al. (2018) (2018)

Figure 11.10 The change of the PET and DOTP concrete 28-days compressive strength.

16 Ultrasonic pulse velocity (Km/s)

14

Reference concrete 10%PET or DOTP concrete Reduction rate (%) 12.77

13.39

12 10 7.53

8 6

5.35 5.25

4

4.78 4.1

4.42

4.784.14

1.87

2 PET 0

4.7

Rahmani et al. (2013)

PET Sadrmomtazi et al. (2016)

PET

DOTP

Şimşek et al. (2018)

Şimşek et al. (2018)

Figure 11.11 The change of the PET and DOTP concrete ultrasonic pulse velocity.

When the thermal conductivity values of PET and DOTP are compared, the decrease of 33.11% with 10% DOTP addition, compared to the control concrete, is only 3.97% for 10% PET addition (S¸ims¸ek et al., 2018). However, DOTP has a serious success in achieving high electrical resistance. Corrosion resistance criterion is one of the most important criteria for constructions built in contact with aggressive natural conditions such as underground waters, sewer lines, and seawater. While

262

Use of Recycled Plastics in Eco-efficient Concrete 60

Splitting tensile strength (MPa)

50

Reference concrete 10%PET or DOTP concrete Reduction rate (%)

51.61

50.14

40 30

PET 20

PET DOTP

17.14

PET 10

7.50 4 3.7

PET 3.5 2.9

3.1

1.5

0 –10

PET 3.67 3.5 4.63

3.26 3.31

3.67 1.83

–1.53

Rahmani et al. Saikia and de Sadrmomtazi Thomeycroft Şimşek et al. Şimşek et al. Brito (2014) et al. (2016) et al. (2018) (2013) (2018) (2018)

Figure 11.12 The change of the PET and DOTP concrete splitting tensile strength. 35

Thermal conductivity (W/m*K)

30

33.11

Reference concrete 10% PET or DOTP concrete Reduction rate (%)

25 20 15 10

DOTP

PET 3.97

5 1.51

1.45

1.51

1.01

0 Şimşek et al. (2018)

Şimşek et al. (2018)

Figure 11.13 The change of the PET and DOTP concrete thermal conductivity values have been determined in the literature.

S¸ims¸ek et al. (2018) achieved an improvement of 23.53% compared to the control concrete with 10% PET, they obtained 836% improvement with 10% DOTP compared to the control concrete (Figs. 11.13 and 11.14).

11.4

Conclusions and recommendations

The most remarkable finding in the study of S¸ims¸ek et al. (2018) is the high electrical resistance of DOTP concrete. With this finding, they have determined that DOTP

Performance of dioctyl terephthalate concrete 4500

Electrical resistance (ohm*m)

4000

263

Reference concrete 10% PET or DOTP concrete Reduction rate (%)

3819

3500 3000 2500 2000 1500

500

DOTP

PET

1000 408

836.03

504

408 23.53

0

Şimşek et al. (2018)

Şimşek et al. (2018)

Figure 11.14 The change of the PET and DOTP concrete electrical resistivity values have been determined in the literature.

concrete has high corrosion resistance. Aggressive environmental conditions adversely affect the sustainable strength of concrete structures. Especially buildings and ports close to the seaside are exposed to sea water. Rain and sewage water also cause mechanical strength loss in the buildings. For this reason, underground concrete, harbors, structures in contact with seawater, urban sewage, and infrastructure concrete must be designed to be resistant to corrosion. The mechanical strength of normal weighted DOTP concrete makes it difficult to use this material as load bearing concrete. However, it can be used as anticorrosive material on the bearing concrete surface as liquid or mortar. Another remarkable finding in the study of S¸ims¸ek et al. (2018) is that DOTP concrete has low thermal conductivity. This feature of DOTP concrete demonstrates that the product can be used in building materials for the purpose of heat insulation and energy saving. Polymeric wastes contribute to energy saving by reducing heat transfer in buildings. DOTP concrete can also contribute to energy efficiency and user comfort in buildings with its low thermal conductivity value. Due to its low mechanical strength and UPV, it can be used not for the purpose of bearing but as a plaster or mortar on the exterior surface. Direct mixing of PET into concrete is the most preferred disposal method in the building industry. This method alleviates the building load and provides thermal insulation to the structure. Moreover, the high electrical resistance of PET makes it a useful material for the design of concrete having corrosion resistance. However, the fact that DOTP obtained by chemical degradation of PET, forms a more compact, homogeneous structure with concrete makes it a more attractive product for corrosion resistant concrete design (Fig. 11.15).

264

Use of Recycled Plastics in Eco-efficient Concrete

(a)

(b)

Figure 11.15 (a) DOTP and (b) DOTP concrete.

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Sun, Y., Gao, P., Geng, F., Li, H., Zhang, L., Liu, H., 2017. Thermal conductivity and mechanical properties of porous concrete materials. Materials Letters 209, 349e352. https://doi.org/10.1016/j.matlet.2017.08.046. Theophile, N., Jeong, H.K., 2017. Electrochemical properties of poly(vinyl alcohol) and graphene oxide composite for supercapacitor applications. Chemical Physics Letters 669, 125e129. https://doi.org/10.1016/j.cplett.2016.12.029. Thomas, B.S., 2018. Green concrete partially comprised of rice husk ash as a supplementary cementitious material e a comprehensive review. Renewable and Sustainable Energy Reviews 82, 3913e3923. https://doi.org/10.1016/j.rser.2017.10.081. Thorneycroft, J., Orr, J., Savoikar, P., Ball, R.J., 2018. Performance of structural concrete with recycled plastic waste as a partial replacement for sand. Construction and Building Materials 161, 63e69. https://doi.org/10.1016/j.conbuildmat.2017.11.127. Topccedil, I.B., Uyguno
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Recycling of PET in asphalt concrete

12

I. Aghayan, R. Khafajeh Shahrood University of Technology, Shahrood, Iran

12.1

Introduction

PET is one of the most prominent types of plastics in the world, which can mostly be found in municipal wastes (Taherkhani and Arshadi, 2017; Navarro et al., 2008). It should be mentioned that PET, a semicrystalline thermoplastic polymer with low friction level, belongs to the polyester material family (Ameri and Nasr, 2016; Shukla and Harad, 2006). PET is normally a semicrystalline resin, the glass transition temperature of which is about 70
C. At higher temperatures, PET’s properties can gradually change into a relatively crystalline polymer (Silva et al., 2015). PET is mostly used in food and drinking water bottles’ packaging industries due to having various features such as decay, odor, and UV resistance; lower costs; transparency; high chemical resistance; stiffness; durability; good mechanical properties; and dimensional stability in high temperatures (Navarro et al., 2008; Ameri and Nasr, 2016; Rahman and Wahab, 2013). PET is produced by polymerization of ethylene-glycol, a colorless liquid obtained via ethylene and terephthalic acid, a crystalline solid obtained via xylene (ethylene-glycol, a colorless liquid obtained via ethylene, and terephthalic acid, a crystalline solid obtained via xylene are polymerized to produce PET). PET is produced in the form of a viscous mass when ethylene-glycol and terephthalic acid are heated in the presence of a chemical catalyst (Rahman and Wahab, 2013; Modarres and Hamedi, 2014b). PET known as thermoplastic polyester relatively accounts for 18% of total polymer manufactured in the world. Considering the global demand, more than 60% of synthetic fibers and 30% of plastic bottles are produced using PET (Padhan et al., 2013). The soft drink bottle industries began to use PET in bottle productions in 1980s; more than 700 million pounds of PET were used for producing drink bottles in 1987 (Shukla and Harad, 2006). Today, huge amount of PET wastes are produced worldwide. For instance, 2675 pounds of PET wastes were produced in USA in 2010. However, only 29.1% of PET wastes were recycled (Container Recycling Institute, 2015). The mass production of PET along with lack of biological degradation can cause serious threats to environment (Siddiqui, 2009). So considering the economical perspective, special attention is given to the polymer material’s wastes, especially PET wastes, to protect the environment. PET wastes are mostly burned in the landfills or buried elsewhere, both of which have adverse impacts on the environment. Burning and burying the wastes cause air and soil pollution, respectively, endangering public health and the environment (Prusty, 2012). Recycling is considered as a proper Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00012-8 Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete

solution to deal with issues regarding PET wastes. Both chemical and physical recycling can be performed on PET wastes. Chemical recycling is not cost-effective because of occurring in high temperature and pressure, in the presence of the chemical catalysts. In the process of physical recycling, PET is polluted as it involves various materials such as the acid derived from poly (vinyl acetate), rosin acid (produced by adhesives), hydrochloride acid (produced by PVC), water, and coloring materials, thereby reducing the chemical and physical properties of PET and decreasing the quality of the product (Padhan et al., 2013; Moghaddam et al., 2014b). Therefore, the main limiting factors in PET recycling are pollution, recycling costs, and materials’ quality. It should be mentioned that high-quality recycled products are needed for various applications. However, applying high-quality PET in some applications like asphalt mixture is not required (Hassani et al., 2005). Recently, waste materials are used in road construction to protect the environment and reduce pollution and energy consumption. This chapter focuses on reviewing the effects of PET wastes on the mechanical properties of asphalt mix (Marshall stability, rutting, resilient modulus, moisture sensitivity, and indirect tensile strength), the volume properties of asphalt (the percentage of air voids in the asphalt mixture and rock materials, flow, Marshall quotient [MQ] and specific gravity) and physical properties of binder (penetration, softening point, viscosity, and dynamic shear rheometer [DSR] test).

12.2

Using PET waste as modifier in asphalt mixture

Three methods are used for adding modified PET particles to asphalt mixture. During the wet process, PET is added to binder and then, the aggregates and the binder containing PET are mixed called the method of wet process. In the dry method, PET and aggregates are initially mixed and later, the binder is added to the aggregates containing PET. The third method is to add PET while the aggregates and binder are mixing (Taherkhani and Arshadi, 2017). The preparation process of PET wastes gathered from plastic bottles for being added to asphalt mixture is shown in Fig. 12.1. In this section, to examine the effects of the modified PET binder, the effects of PET wastes on the mechanical and volume properties of modified asphalt mixture and the physical properties of modified binder are investigated.

12.2.1

The Marshall stability

The pavement’s potential and strength against rutting is shown by Marshall stability. In studies focused on investigating the effects of PET wastes on the Marshall stability of asphalt mixture, similar results were obtained when PET was added to asphalt mixture. First, the stability increased as a certain amount of PET was added to asphalt mixture. Later, the stability was decreased as the PET was added to the mixture (Taherkhani and Arshadi, 2017; G€ ur€ u et al., 2014; Ameri and Nasr, 2016; Ahmadinia et al., 2011; Widojoko and Purnamasari, 2012). According to Ameri and Nasr (2016), it was indicated that first, the Marshall stability reached the maximum value by adding PET to 10% weight of binder, then the

Recycling of PET in asphalt concrete

(a)

271

(b)

Plastic bottle

(c)

Plastic bottle after cutting

(d)

Crushing machine

Crushed plastic particles

Figure 12.1 Preparation of PET particles (Moghaddam et al., 2015c).

Marshall stability was reduced. In another study conducted by Taherkhani and Arshadi (2017), two different ranges of PET particle sizes (1.8e2.36 mm and 0.297e0.595 mm) were added to mixture as the modifier. In this study, PET wastes were added to mixture while the aggregates and binder were mixing. The results indicated that both stability sizes increased as PET was added up to 4% weight of the binder. Then, the process was reversed decreasing the stability. It was mentioned that the size of PET particles had significant effect on Marshall stability in a way that the mixture containing fine PET particles showed higher stability compared to mixture with coarse PET particles. This stability can be attributed to regular shape of PET particles; fine particles have more uniform rigid shape enduring lower deformation under loading. The coarse particles have more irregular forms some of which are curly creating more air voids in the mixture and showing more deformation under loading. Moreover, fine particles with more proper destruction in the mixture fill the air voids thereby increasing the stiffness. In another study, Ahmadinia et al. (2011) concluded that using dry method to add 6% PET (by the weight of aggregate) to stone mastic asphalt (SMA), the mixture reached it maximum level of stability, and then as PET was added to mixture, the stability decreased. The stability’s increase in the modified PET mixture in lower percentages can be attributed to several factors such as the semicrystallized nature of PET (Taherkhani and Arshadi, 2017), the increase of binder viscosity in the presence of the polymer (Ameri and Nasr, 2016), more proper adhesion

272

Use of Recycled Plastics in Eco-efficient Concrete

between the mixture’s materials (Ahmadinia et al., 2011; Widojoko and Purnamasari, 2012) and the angularity of PET particles (Widojoko and Purnamasari, 2012). As higher percentages of PET were added to mixture, the stability was decreased due to lower friction level and stiffness of PET particles (compared to natural aggregates). The binder was also decreased due to using some of its parts for coating PET particles (Taherkhani and Arshadi, 2017). Moreover, as the viscosity of mixtures with higher percentages of PET increased, the compaction resistance was improved, thereby increasing the air voids and decreasing the Marshall stability (Ameri and Nasr, 2016).

12.2.2

Investigating the effects of PET waste on the volumetric properties of asphalt mixture

The volumetric properties of asphalt mixture have significant effects on the mechanical properties and durability of asphalt mixture. This section focuses on examining the effects of modified PET binder on flow, void in mineral aggregate (VMA), air void, MQ, maximum specific gravity, and the density of asphalt mixture. Flow is the ability of the asphalt mixture to adjust to gradual settlements and also movements with no cracking. As the flow value increases, the applicability of the mixture increases while the deformation resistance decreases. However, as the flow value is decreased, the stiffness of the mixture is increased. Some studies indicated that the percentages of PET and binder had similar effects on the flow of SMA mixture in such a way that the increase in the PET and binder led to the increase in the flow (Yildirim, 2007). Other studies concluded that the flow was increased by adding PET to the asphalt mixture (Widojoko and Purnamasari, 2012; Badejo et al., 2017). Ahmadinia et al. (2011) indicated that adding 4% PET to SMA mixture slightly decreased the flow while the process was reversed when higher percentages of the PET were added to the mixture. It was in agreement with Taherkhani and Arshadi’s (2017) results indicating that adding 4% PET (4% weight of the binder) to mixture decreased the flow while adding higher percentages of PET resulted in increasing the flow as well. They also concluded that the mixtures with fine particles had lower levels of flow than the mixtures containing coarse particles. The higher percentages of PET increased the flow which can be attributed to the low internal friction of PET particles in the modified mixture (Moghaddam et al., 2015b). MQ is the mixture deformation resistance index, the value of which is calculated to evaluate the deformation resistance of samples. As the MQ increases, the stiffness increases as well thereby enhancing the deformation resistance under heavy loading (Ahmadinia et al., 2011). In a study conducted by Moghaddam et al. (2014b), it was indicated that adding PET to modified mixture decreased the MQ value. Therefore, PET particles decreased the stiffness of modified mixture compared to control samples which can be attributed to low internal friction of samples containing PET wastes. In another study, two different ranges of PET particle sizes (1.8e2.36 mm and 0.297e0.595 mm) were added to asphalt mixture as the modifier. The results indicated that MQ of both sizes increased as PET was added up to 4% by weight of the binder. It was also mentioned that the value of MQ decreased in higher percentages

Recycling of PET in asphalt concrete

273

of PET. Moreover, mixture containing fine PET particles had higher MQ compared to mixtures with coarse PET particles (Taherkhani and Arshadi, 2017). Ahmadinia et al. (2011) indicated that SMA mixture modified using dry method included some percentages of PET (2%, 4%, and 6%) having higher MQ compared to control samples. As the PET percentage increased, aggregates were replaced by PET decreasing MQ value because PET particles had less stiffness than aggregates. Moreover, the binder film thickness was decreased when higher PET percentages were involved, thereby reducing MQ value (Taherkhani and Arshadi, 2017). The studies focused on bulk specific gravity (BSG) indicated that using PET in asphalt mixture as modifier decreased the BSG value (Ahmadinia et al., 2011; Earnest, 2015). Moghaddam et al. (2014b), indicating that BSG varied in different PET percentages so that in lower and higher percentages of PET, the BSG values increased and decreased, respectively. In another study, it was revealed that the modified SMA mixture containing 8% PET (by weight of aggregate particles) had the lowest BSG value. Moreover, the highest BSG value belonged to the SMA mixture containing 2%e6% PET with high binder percentage (Moghaddam et al., 2015b). Considering the obtained results, it can be seen that lower percentages of PET increased BSG values while the higher PET percentages resulted in a decrease in BSG values because PET had high melting temperature more than sample fabrication temperature. It should be mentioned that as low amount of PET content is added to mixture, air voids among aggregates are filled with solid PET particles (Moghaddam et al., 2014b, 2015b; Earnest, 2015) thereby increasing BSG value. When higher percentages of PET are used in mixture, the solid particles are placed among aggregates increasing the volume of the sample and decreasing the BSG value (Moghaddam et al., 2014b). It can also be said that PET particles start to move among aggregates when higher percentages of PET are involved (Earnest, 2015). The results showed that the modified mixture containing PET had lower density than the control mixture. The modified mixture containing 2%e4% PET (by weight of binder) had the same density as the control sample. As higher PET percentages (higher than 6% PET) were added to the mixture, the density of the modified mixture significantly decreased which can be attributed to the low density of PET particles compared to the aggregates’ density (Widojoko and Purnamasari, 2012). The air void is considered as one of the most important parameters in designing pavements. The air void in the asphalt mixture occurring as the result of insufficient binder coating create cracking in the pavement. However, rutting and asphalt bleeding are created due to having mixtures with low air voids. The previous studies have concluded that as the PET percentage increased, the air voids of the modified mixture increased too (Taherkhani and Arshadi, 2017; Ahmadinia et al., 2011; Badejo et al., 2017; Moghaddam et al., 2015b). The PET particles are rarely crystallized in modified mixture increasing the specific surface. As the surface area increases, more PET particles are mixed with the binder, thereby increasing the air voids of modified mixture. Moreover, adding PET to mixture decreases the density increasing the air voids of the modified mixture (Ahmadinia et al., 2011). Another reason for increasing the air voids of the modified mixture may be the elastic deformation of PET particles under loading (Taherkhani and Arshadi, 2017; Moghaddam et al., 2015b).

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According to Moghaddam et al. (2015b), it was revealed that adding PET to the mixture decreased the air voids. It was also indicated that the modified SMA mixture containing 4% to 6% PET (the weight of aggregates) had the lowest air voids. However, the air voids increased as higher percentages of PET were involved. VMA serving as the air voids among the aggregates is considered as an important parameter used in designing the asphalt mixture. VMA is used to ensure that the binder film thickness is sufficient enough to protect the mixture from the abrasive action of tires and water (Moghaddam et al., 2015b). The results confirmed higher VMA values for all PET percentages used in modified mixture compared to VMA values in control samples (Taherkhani and Arshadi, 2017; Ahmadinia et al., 2011). In another study, considering lower PET percentages, as the PET percentages increased, the VMA value decreased; when the PET percentages higher than 0.6% were involved, the VMA value increased (Moghaddam et al., 2015b). Based on the study conducted by Widojoko and Purnamasari (2012), it was revealed that the air voids among aggregates in both modified mixture and control sample were the same when 2% and 4% PET were involved. However, as the PET percentage increased, the air voids among aggregates in modified mixture significantly increased too. The increase in the VMA value can be attributed to the decrease in the binder causing the air voids to be filled (Taherkhani and Arshadi, 2017).

12.2.3

Indirect tensile strength (ITS) test

ITS test is used to determine the tensile properties of asphalt mixture, the results of which can be used to investigate the cracking and rutting properties of asphalt mixture (Taherkhani and Arshadi, 2017; Moghaddam et al., 2014b). The mixture having higher ITS shows higher cracking and rutting resistances (Taherkhani and Arshadi, 2017). Several studies have focused on investigating the effects of PET wastes on the ITS of asphalt mixture. Taherkhani and Arshadi (2017) conducted ITS test on the mixture containing 6.5% and 7% air voids in dry conditions at 25
C. It should be mentioned that two different PET sizes (i.e., fine particles ¼ 0.297e0.595 mm, coarse particles ¼ 1.8e2.36 mm) were used in this study. The results indicated that both modified mixtures containing 2% PET (by weight of binder) had the highest ITS value. As the PET percentage increased, the ITS decreased. Moreover, the ITS of mixtures with fine PET particles was higher than the ITS of mixtures with coarse PET particles. The highest ITS value was considered for all percentages of fine PET particles in the mixture, while in modified mixture, only those coarse particles containing 2% PET had the highest ITS value. So, it can be concluded that using fine PET particles significantly enhanced the ITS value showing the cracking resistance. The results regarding ITS values in saturated mixture were similar to the results of dry samples. Considering the saturated mixture, the highest ITS value belonged to samples containing 2% PET. However, as the PET percentage increased, the ITS value decreased. This result is in agreement with the research conducted by Modarres and Hamedi (2014a,b) highlighting the fact that if 2% PET was added to a mixture at 5
C and 20
C using dry method, the ITS value of modified mixture would increase but when higher percentages of PET were involved (up to 4% PET), ITS was continuously decreased (Fig. 12.2). The results can be attributed to the accumulation of binder on the surface

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3500 20°C

5°C

Indirect tensile strength (kPa)

3000

2500

2000

1500

1000

500

0 0

2

4

6

8

10

PET(%)

Figure 12.2 Results of ITS test at 5
C and 20
C (Modarres and Hamedi, 2014b).

of PET particles reducing the bitumen film thickness around aggregates. So, the aggregate-bitumen adhesion is decreased thereby reducing the ITS of the modified mixture (Modarres and Hamedi, 2014b; Taherkhani and Arshadi, 2017). According to Moghaddam et al. (2014b), it was shown that the modified mixture in which the PET particles were added using dry method had lower tensile strength under static loading. The tensile strength of saturated mixture containing 1% PET decreased about 200 kPa compared to tensile strength of the control sample. So, it can be concluded that the mixture containing PET particles has more cracking sensitivity in lower temperatures. In another study, both wet and dry methods were used to add PET (5%, 10%, and 15% of binder weight) to asphalt mixture. The results indicated that the control sample had higher ITS compared to the modified dry sample. Moreover, considering wet method, the saturated sample had higher ITS value compared to control sample and dry method (Earnest, 2015).

12.2.4 Moisture sensitivity Stripping, defined as the cracking between aggregates and binder, is considered as one type of pavement distress. Stripping occurs when the moisture is penetrated into aggregates related to the binder-aggregates adhesion. ITS test was used to calculate the tensile strength ratio (TSR) index in both dry and saturated samples to examine the moisture resistance of the mixture. The results showed that TSR increased as 2% PET was added to the mixture, and then the process was reversed. The mixtures with fine PET particles (0.297e0.595 mm) had lower TSR

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than the mixtures with coarse PET particles (1.8e2.36 mm). TSR value of saturated mixture was higher than TSR value of control sample when higher PET percentages were involved (2%e4%). TSR of all mixtures containing 2%e4% PET was higher than the allowable limit. Therefore, PET can be considered as an antistripping material. The increase of moisture resistance can be attributed to the stiffening effect of PET on the binder when lower PET percentages are involved. However, the moisture sensitivity increased in higher PET percentages (up to 4% PET) when the bitumen film thickness was decreased. These results are in agreement with Ameri and Nasr’s (2016) study indicating that the moisture sensitivity improved as PET was added to the modified mixture. However, as higher PET percentages were added to the mixture, the moisture sensitivity was decreased. In another study, viscous polyol PET (VPP) and thin liquid polyol PET (TLPP) derived from PET wastes were used to modify the asphalt mixture. The results indicated that as VPP and TLPP were used in the mixture, the stripping resistance was significantly increased (G€ur€u et al., 2014). Ahmadinia et al. (2012) concluded that as PET was added to SMA mixture using dry method, the TSR index was decreased. Considering the required standard, the standard TSR value varies from 70% to 80%. Considering the TSR results, TSR value was higher than 70% in all samples creating the possibility of having sufficient moisture resistance. It should be mentioned that adding PET to the mixture did not improve the moisture sensitivity of SMA mixture which can be attributed to the crystallized form of PET after being added to mixture. The crystallized PET reduces the bitumen film thickness around aggregates, thereby decreasing the moisture sensitivity resistance. Another study used both wet and dry methods to add PET to asphalt mixture while applying stripping slopedobtained from APA Hamburg testd to investigate the moisture sensitivity. Higher stripping slopes showed that more moisture damages occurred with each wheel pass. Moreover, lower stripping inflection point caused thermal damage to occur sooner than expected. The mixture created using wet method showed the highest stripping slope and lowest stripping inflection point while the mixture created using dry method showed lowest stripping slope and highest stripping inflection point. So, it can be concluded that the mixture created by dry method has good moisture sensitivity resistance (Earnest, 2015).

12.2.5

Fatigue

Generally, fatigue is defined as the cracking occurring as the stress is iterated. The fatigue life of asphalt mixture depends on factors like the type and amount of binder and related air voids. Moghaddam et al. (2012) investigated the fatigue properties of SMA mixture modified using PET by dry method. Various PET percentages, the maximum size of which was 2.36 mm were added to the mixture. Fatigue tests were performed in 3 stress levels (250, 350, and 450 kPa) at 20
C. The results showed that adding PET to the mixture significantly increased the fatigue life compared to control sample. Moreover, adding higher PET percentages highly increased fatigue life. For example, the fatigue life of SMA mixture containing 1% PET (of aggregate’s weight) increased 124.8% considering the stress level of 250 kPa. It is observed that as the stress level increased, the fatigue life decreased. High fatigue life can be ascribed to

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1000000

Fatigue life definition: N1 Temperature:20°C Fatigue life definition: N1 Temperature: 5°C Fatigue life definition: N2 Temperature: 20°C

100000 Fatigue life

Fatigue life definition: N2 Temperature: 5°C

10000

1000 0

2

4 6 PET (%)

8

10

Figure 12.3 Results of fatigue tests at 20
C (at 20% of ITS) and 5
C (at 15% of ITS) (Modarres and Hamedi, 2014b).

factors like enhancing elastic properties of SMA mixture containing PET and the stress distraction of the mixture created by PET particles. Modarres and Hamedi (2014b) examined the effects that addition of PETdusing dry methoddmay have on the fatigue life of the asphalt mixture considering two temperature levels (5
C and 20
C). As can be seen in Fig. 12.3, the results indicated that adding PET had positive effects on the fatigue behavior. Adding PET (up to 10%) to the mixture had profitable effects on the fatigue behavior of the mixture. Considering the fatigue curves of three samples, 0%, 8%, and 10% PET were added to modified mixture at 20
C; the deformation curve of modified mixture had smaller slope than control mixture. So, it can be concluded that the mixture containing PET showed higher fatigue resistance and flexibility compared to control sample. In another study, fatigue test was conducted considering three stress levels at 5
C and 10
C, the results of which indicated that the fatigue life of modified mixture containing PET eusing dry method was higher at both 5
C and 10
C compared to control mixture. Considering the increase in stiffness of binder, the slope of fatigue curve was significantly reduced. Based on the obtained fatigue modulus, addition of 2%e10% PET (by the weight of binder) to the mixture induced positive effects on the mixture’s properties (Al-Hadidy and Yi-qiu, 2009).

12.2.6 Rutting Rutting, one of the most common distresses in asphalt pavement, is defined as the permanent deformation of pavement occurring as the result of applying loads on

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Use of Recycled Plastics in Eco-efficient Concrete

the roads. Rutting significantly reduces the performance of pavement. This section focuses on investigating the effects of PET wastes on rutting resistance of asphalt mixture. Several studies concluded that adding PET wastes to mixture increased the rutting resistance of modified mixture (Ameri and Nasr, 2016; Ziari et al., 2016). Moghaddam et al. (2014b) examined the permanent deformation of modified asphalt containing PET wastesdusing dry methoddunder static and dynamic loading. The results showed that the PET mixture exhibited different behaviors under static and dynamic loading. Although, the permanent deformation increased as PET was added and the maximum deformation happened when 1% PET (by weight of aggregates) was added to the mixture. However, considering static loading, the least permanent deformation was shown for the mixture containing 0.1% PET (by weight of aggregate). Considering dynamic loading, as PET was increased in the mixture, the permanent deformation was decreased. The modified mixture containing 1% PET had the highest resistance against permanent deformation. Therefore, it can be concluded that the PET modified mixture shows a proper performance against rutting under dynamic loading due to the flexibility of PET mixture. Ahmadinia et al. (2012) concluded that the SMA mixture modified by PETdusing dry methoddshowed better deformation resistance than control sample. As seen in Fig. 12.4, the lowest rutting depth belonged to the mixture containing 4% PET (of binder weight) showing a 29% decrease compared to rutting depth of the control sample. The results can be used to create a stiffer (more rigid) SMA mixture, thereby improving the rutting resistance. Moghaddam et al. (2014a) examined the permanent deformation characteristics of PET modified mixture dby dry methoddusing dynamic creep test. They also evaluated the performance of modified mixture against rutting considering stress levels of 300 and 400 kPa, at 10
C, 25
C, and 40
C. The results showed that rutting resistance significantly improved as PET was added to the modified mixture. Considering all stress levels and in all temperatures, the total permanent strain of all samples decreased when higher PET percentages were included. Improving the permanent deformation characteristics of PET modified mixture can be attributed to the PET properties known as a semicrystalline material. It is assumed that adding PET to mixture can improve the performance

Rut depth (mm)

3.00 2.70 2.40

0% PET 2% PET

2.10 1.80

4% PET

1.50 1.20 0.90 0.60 0.30

6% PET 8% PET 10% PET

0.00 0

5

10

15

20 25 30 Time (min)

35

40

45

Figure 12.4 The results of wheel track test (Ahmadinia et al., 2012).

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279

of asphalt mixture in two ways. First, the melting parts of PET wastes reinforce the aggregate-binder adhesion. Then, the solid parts of PET wastes absorb or distract some energies used by loading cycles. Taherkhani and Arshadi (2017) used dynamic creep test to investigate the rutting resistance in stress level of 300 kPa, at 40
C and in the frequency of 1 HZ. For this purpose, two different PET sizes (fine particles: 0.297e0.595 mm, coarse particles: 1.8e2.36 mm) were used to evaluate the rutting process. It was revealed that as the PET increased, the accumulated strain of both sizes of PET particles increased as well. So, it can be said that as the PET percentage increased in the mixture, the permanent deformation resistance decreased. It is in agreement with Earnest (2015) who used wheel track test to add PET to the mixture applying dry method. He concluded that the permanent deformation resistance decreased when higher percentages of PET percentages were included in the mixture. Moreover, the fine PET particles showed more acceptable performance than coarse PET particles concluding that mixtures containing both PET sizes had higher permanent deformation resistance compared to the control sample (Taherkhani and Arshadi, 2017). Moghaddam et al. (2015c) used soft computing technique to estimate the rutting performance of PET modified mixture in which dry method was used to add PET to the mixture. The simulation process regarding the deformation of the mixture was conducted using adaptive neurofuzzy inference system (ANFIS). The input data included percentages of PET wastes, stress level, and temperature. The experimental and ANFIS results were compared by root-mean-square error (RMSE). It was concluded that PET values and environmental conditions had significant impacts of rutting performance of asphalt mixture. As PET was added to the mixture, the total accumulative strain was decreased. Considering the results, it can be said that ANFIS is a precise method to be used in predicting the rutting performance of asphalt mixture.

12.2.7 Stiffness and resilience modulus The stiffness is an essential parameter in designing the asphalt mixture. The resilience modulus (MR) is used in stress-strain measurement to evaluate the elastic properties of asphalt mixture. Many studies have been focused on investigating the effects of PET wastes on stiffness of asphalt mixture. Modarres and Hamedi (2014b) indicated that considering a constant stress level, the maximum stiffness was obtained for 2% PET (by the weight of binder) in modified mixture. Similar results were obtained by Moghaddam et al. (2012) who concluded that as the stress level increased, the resilient module decreased. They also concluded that considering a constant stress level, as PET was added to the mixture, first the SMA mixture stiffness increased and later decreased. The highest level of stiffness belonged to the mixture containing 0.2% PET (by weight of aggregate). In another study also conducted on asphalt mixture by Moghaddam et al. (2014b), similar results were obtained. As can be seen in Fig. 12.5, adding lower percentages of PET to the mixture increased the stiffness of modified mixture and when higher PET percentages were included, the stiffness decreased. It should be mentioned that the highest stiffness was observed in 0.1% PET (by weight of aggregate), which can possibly be attributed to the mechanical properties of PET mixture. Since PET is crystallized after being heated due to high

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Use of Recycled Plastics in Eco-efficient Concrete 4700

Stiffness (Mpa)

4500 4300 4100 3900 3700 3500 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

PET (%)

Figure 12.5 Effect of adding different percentages of PET on stiffness of compacted mixture (Moghaddam et al., 2014b).

melting point, the rigid PET creates a more flexible mixture undergoing more deformation under heavy loading (Moghaddam et al., 2012). Moreover, at higher PET percentages, highly rigid aggregates were replaced by PET particles having low stiffness, decreasing the binder film thickness around the aggregates which can be considered as another reason regarding low stiffness of high percentages of PET in modified mixture (Modarres and Hamedi, 2014b). In another study conducted on SMA-modified mixture containing PET using dry method, lower PET percentages were involved (6% PET). It was observed that the MR increased as PET was added to the mixture. Then, the process was reversed in such a way that adding higher PET percentages decreased the MR. The highest amount of MR was observed for the SMA mixture containing 6% PET (by the weight of binder) in which the MR of modified mixture increased 16% compared to MR of control mixture (Ahmadinia et al., 2012). It was in conformity with Modarres and Hamedi (2014a,b) results indicating that the highest MR belonged to 2% PET. However, when higher PET percentages were included (up to 2% PET), the MR was decreased. In another study, Moghaddam et al. (2015a) investigated the effects of loading and temperature on the stiffness of unmodified and PET-modified mixture for which dry method was used. They also used response surface methodology (RSM) method to examine the effects of stress and temperature on the stiffness modulus of modified and unmodified mixture. The results indicated that PET percentages and stress value had similar effects on stiffness modulus. Moreover, PET wastes had more significant impacts on the mixture stiffness at lower temperatures. Changes in PET percentages had more significant impacts on mixture stiffness than stress level. It should be mentioned that the optimal PET percentage for reaching the highest stiffness value was 0.41% PET (by weight of aggregate).

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12.2.8 Penetration, softening point, flexibility Various studies have focused on investigating the effects of PET on the binder’s physical properties so far. G€ ur€ u et al. (2014) indicated that adding PET to the mixture using dry method increased the softening point and decreased the penetration. It was in agreement with Mahrez and Karim’s (2010) results highlighting that adding 2%, 4%, 6%, and 8% PET (by the weight of binder) to the mixture decreased the penetration of the modified mixture 14%, 21%, 30%, and 35%, respectively, compared to the control mixture. Moreover, the softening point increased as PET was added to the mixture. It should be mentioned that as 2%e8% PET (by the weight of binder) were added to the mixture, the softening point increased from 5% to 13%. Increasing the softening point caused the binder resistance to be increased under heating. So, when PET was added to binder, the temperature sensitivity of the binder was decreased (Mahrez and Karim, 2010), improving resistance to permanent deformation in binder content. When the penetration decreased, the shear strength increased at higher temperatures (Silva et al., 2015). Basically, the increase in softening point and decrease in penetration caused an increase in the adhesion of asphalt mixture (Silva et al., 2015) while enhancing the rutting resistance (Mahrez and Karim, 2010). However, G€ ur€ u et al. (2014) obtained opposite results. They used TLPP and VPP derived from PET wastes to modify the asphalt mixture concluding that addition of PET to the mixture increased the penetration and decreased the softening point of all PET percentages except for 1% VPP. Therefore, softer asphalt was created and cracking sensitivity was also decreased at lower temperatures. Other studies also showed that the addition of PET decreased the flexibility and improved the elastic recovery of the mixture (Silva et al., 2015).

12.2.9 Viscosity Viscosity, one of the main characteristics of asphalt, is defined as the flow resistance at a specific temperature. G€ ur€ u et al. (2014) indicated that as TLPP increased, the viscosity decreased at all test temperatures. The viscosity decrease was 32.5% at 160
C for 10% PET (by the weight of binder) in modified mixture confirming that using TLPP decreased the asphalt’s working temperature. Similar results were obtained for VPP except in 1% PET indicating the increase in viscosity which can be attributed to the increase in asphalt’s adhesion property. Moreover, the working temperature of asphalt mixture containing VPP and TLPP decreased. Other studies also mentioned that adding PET to the mixture increased the viscosity (Ameri and Nasr, 2016; Silva et al., 2015; Mahrez and Karim, 2010). Rutting process, happening in hot places having heavy traffic system, significantly decreases the pavement performance. So, high viscosity binder should be used in asphalt mixtures of hot places. Therefore, adding PET wastes to binder reduced the rutting problems (Silva et al., 2015). Viscosity aging index (VAI), an important factor in examining the aging characteristics of the binder, was used to evaluate the viscosity changes on the aged binder. High degree of aging in binder was shown by high VAI value. The results indicated that the VAI value of modified binder was lower that the VAI of unmodified binder at 135
C concluding that adding

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PET to the mixture increases the binder’s aging resistance (Silva et al., 2015). In another study, rotational viscosity (RV) test was performed on aged mixtures with 5%, 10%, and 15% PET. Factors such as the effects of PET percentages, mixing time, and speed on viscosity were also examined. It was observed that in all mixtures, as the PET percentages increased and the mixing time lasted for 2 h, the RV increased as well (Earnest, 2015).

12.2.10 Dynamic shear rheometer and bending beam rheometer tests Dynamic shear rheometer (DSR) is considered as the stress used in determining the viscoelastic behaviors of binder at moderate to high temperatures. DSR is used to measure complex shear modulus (G) and phase angle (d). The asphalt is softer when the low complex shear modulus is used. If binder containing high G value is added to the mixture, rutting issues may be decreased (Mahrez and Karim, 2010). More elastic mixtures are created as the result of lower values of phase angle enhancing the rutting and aging resistance of the mixture. Shear modulus (G) and phase angle (d) are generally used in evaluating the rutting performance of asphalt mixture (G€ ur€ u et al., 2014). Mahrez and Karim (2010) concluded that PET-modified mixture had higher G compared to control mixture increasing the resistance of binder which can be attributed to the increase in rutting resistance. However, the phase angle value was lower in modified mixture compared to control sample. In another study, DSR and bending beam rheometer (BBR) tests were used to investigate the effects of TLPP and VPP on asphalt performance at low, moderate, and high temperatures. BBR test is used to measure creep stiffness (S) and creep rate (m). Considering the results, it was concluded that when both VPP and TLPP were added to the mixture, the creep stiffness reduced while the creep rate increased. So, cracking resistance of the mixture was improved at low temperatures. DSR test was performed on control mixtures, RTFOT-aged and PAV-aged. The phase angles of RTFOT-aged and control sample were decreased by VPP and TLPP. It is worth mentioning that G was also decreased except for 1% VPP reducing the rutting resistance of the mixture. G*SIN, a parameter used in examining the fatigue resistance of the mixture, was significantly decreased by VPP and TLPP, thereby improving the fatigue resistance of modified mixture (G€ ur€ u et al., 2014).

12.3

Conclusion

Considering the high melting point of PET (about 250 C
), if PET is initially mixed with binder using wet method, PET will not be homogenous in asphalt mixture. Therefore, most studies used dry method to add PET to asphalt mixture. Studies focused on replacing aggregates with PET particles concluded that although the asphalt mixtures containing PET particles improve the permanent deformation of the mixture, they also have negative impacts on Marshall stability and MR. It was also concluded that various PET percentages used as modifier have positive effects

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on properties of modified mixture. So, it can be said that adding some PET percentages to asphalt mixture can increase or decrease the stability. In most studies, it was revealed that using lower PET percentages (2%e4% PET) increase the mechanical properties of modified asphalt mixture (Marshall stability, ITS, rutting, moisture sensitivity, stiffness, and MR). However, when higher PET percentages are included, the mechanical properties of modified asphalt mixture decrease. It was also showed that adding PET to the modified mixture increases the fatigue resistance. Generally, if optimal PET percentages are used in modified asphalt mixture, the mixture properties can be increased. According to the obtained results, using PET waste in asphalt mixture is highly effective because it increases the pavement performance. More studies should be conducted on investigating the usage of PET waste as a replacement of aggregate in asphalt mixtures. It was also observed that previous studies mostly used coarse PET particles (passing sieve No. 8). So, the effect of fine PET particles passing sieve No. 200 on the asphalt mixture properties should be examined.

References Ahmadinia, E., Zargar, M., Karim, M.R., Abdelaziz, M., Shafigh, F., 2011. Using waste plastic bottles as additive for stone mastic asphalt. Materials & Design 32 (10), 4844e4849. Ahmadinia, E., Zargar, M., Karim, M.R., Abdelaziz, M., Ahmadinia, E., 2012. Performance evaluation of utilization of waste Polyethylene Terephthalate (PET) in stone mastic asphalt. Construction and Building Materials 36, 984e989. Al-Hadidy, A.I., Yi-qiu, T., 2009. Mechanistic approach for polypropylene-modified flexible pavements. Material & Design 30 (4), 1133e1140. Ameri, M., Nasr, D., 2016. Performance properties of devulcanized waste PET modified asphalt mixtures. Petroleum Science and Technology 35 (1), 99e104. Badejo, A.A., Adekunle, A.A., Adekoya, O.O., Ndambuki, J.M., Kupolati, K.W., Bada, B.S., Omole, D.O., 2017. Plastic waste as strength modifiers in asphalt for a sustainable environment. African Journal of Science, Technology. Innovation and Development 9 (2), 173e177. Container Recycling Institute, 2015. PET bottle sales and wasting in the US. Retrieved from. http://www.container-recycling.org/index.php/pet-bottle-sales-and-wasting-in-the-us. Earnest, M.D., 2015. Performance Characteristics of Polyethylene Terephthalate (PET) Modified Asphalt. Georgia Southern University, USA (Master’s thesis). G€ ur€u, M., C¸ubuk, M.K., Arslan, D., Farzanian, S.A., Bilici, I., 2014. An approach to the usage of polyethylene terephthalate (PET) waste as roadway pavement material. Journal of Hazardous Material 279, 302e310. Hassani, A., Ganjidoust, H., Maghanaki, A.A., 2005. Use of plastic waste (poly-ethylene terephthalate) in asphalt concrete mixture as aggregate replacement. Waste Management & Recourse 23 (4), 3322e3327. Mahrez, A., Karim, M.R., May 23e25, 2010. Rheological evaluation of bituminous binder modified with waste plastic material. In: 5th International Symposium on Hydrocarbons & Chemistry (ISHC5), Sidi Fredj, Algiers. Modarres, A., Hamedi, H., 2014a. Developing laboratory fatigue and resilient modulus models for modified asphalt mixes with waste plastic bottles (PET). Construction and Building Materials 68, 259e267.

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Modarres, A., Hamedi, H., 2014b. Effect of waste plastic bottles on the stiffness and fatigue properties of modified asphalt mixes. Materials and Design 61, 8e15. Moghaddam, T.B., Karim, M.R., Syammaun, T., 2012. Dynamic properties of stone mastic asphalt mixtures containing waste plastic bottles. Construction and Building Materials 34, 236e242. Moghaddam, T.B., Soltani, M., Karim, M.R., 2014a. Evaluation of permanent deformation characteristics of unmodified and Polyethylene Terephthalate modified asphalt mixtures using dynamic creep test. Materials & Design 53, 317e324. Moghaddam, T.B., Soltani, M., Karim, M.R., 2014b. Experimental characterization of rutting performance of polyethylene terephthalate modified asphalt mixtures under static and dynamic loads. Construction and Building Material 65, 487e494. Moghaddam, T.B., Soltani, M., Karim, M.R., 2015a. Stiffness modulus of Polyethylene Terephthalate modified asphalt mixture: a statistical analysis of the laboratory testing results. Materials & Design 68, 88e96. Moghaddam, T.B., Soltani, M., Karim, M.R., Baaj, H., 2015b. Optimization of asphalt and modifier contents for polyethylene terephthalate modified asphalt mixtures using response surface methodology. Measurement 74, 159e169. Moghaddam, T.B., Soltani, M., Karim, M.R., Shamshirband, S., Petkovic, D., Baaj, H., 2015c. Estimation of the rutting performance of polyethylene terephthalate modified asphalt mixtures by adaptive neuro-fuzzy methodology. Construction and Building material 96, 550e555. Navarro, R., Ferrandiz, S., Lopez, J., Seguí, V.J., 2008. The influence of polyethylene in the mechanical recycling of polyethylene terephtalate. Journal of Material Processing Technology 195, 110e116. Prusty, B., 2012. Use of Waste Polyethylene in Bituminous Concrete Mixes. A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Bachelor of Technology in Civil Engineering. Department of Civil Engineering, NIT Rourkela, National Institute of Technology, Rourkela-769008 (ODISHA). Padhan, R.K., Gupta, A.A., Badoni, R.P., Bhatnagar, A.K., 2013. Poly (ethylene terephthalate) waste derived chemicals as an antistripping additive for bitumen-an environment friendly approach for disposal of environmentally hazardous material. Polymer Degradation and Stability 98, 2592e2601. Rahman, W.M.N.W.A., Wahab, A.F.A., 2013. Green pavement using recycled Polyethylene Terephthalate (PET) as partial fine aggregate replacement in modified asphalt. Procedia Engineering 53, 124e128. Siddiqui, M.N., 2009. Conversion of hazardous plastic wastes into useful chemical products. Journal of Hazardous Material 167 (2009), 728e735. Shukla, S.R., Harad, A.M., 2006. Aminolysis of polyethylene terephthalate waste. Polymer Degradation and Stability 91 (8), 1850e1854. Silva, J.A.A., Lucena, L.C.F.L., Rodrigues, J.K.G., Carvalho, M.W., Costa, D.B., 2015. Use of micronized polyethylene terephthalate (Pet) waste in asphalt binder. Petroleum Science and Technology 33, 1508e1515. Taherkhani, H., Arshadi, M.R., 2017. Investigating the mechanical properties of asphalt concrete containing waste polyethylene terephthalate. Road Material and Pavement Design. https://doi.org/10.1080/14680629.2017.1395354. Widojoko, L., Purnamasari, P.E., August 1e3, 2012. Study the use of cement and plastic bottle waste as ingredient added to the asphaltic concrete wearing course. In: 8th International Conference on Traffic and Transportation Studies Changsha, China.

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Yildirim, Y., 2007. Polymer modified asphalt binders. Construction and Building Materials 21, 66e72. Ziari, H., Kaliji, A.G., Babagoli, R., 2016. Laboratory evaluation of the effect of waste plastic bottle (PET) on rutting performance of hot mix asphalt mixtures. Petroleum Science and Technology 34 (9), 819e823.

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Recycling of different plastics in asphalt concrete

13

M.A. Dalhat 1 , Khaleel Al-Adham 2 , M.A. Habib 2 1 Transportation and Traffic Engineering Department, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia; 2Civil & Environmental Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia

13.1

Introduction

Plastic waste (PW) was long identified among the direct and indirect primary sources of environmental pollution (Thompson et al., 2009). Indirectly, in the sense that producing any plastic material from its virgin source is accompanied by huge carbon and nonmethyl volatile organic compounds emission (IFC, 1998; Kuenen et al., 2013). The direct negative environmental impact of PW is due to their nonbiodegradable nature. PW lingers for as long as 500 years without fully decomposing, polluting water bodies, harming aquatic lives, and damaging cities’ aesthetics during this period (Teuten et al., 2009). Currently, 300 million tons of PW was generated annually, with an increasing rate of 4% (Gourmelon, 2016). Kingdom of Saudi Arabia (KSA) generates around 1.4 million tons a year (Dalhat and Al-Abdul Wahhab, 2017). Recycling was identified as the best PW management strategy, given the fact that recycling decreases virgin plastic demand which prevents the PW from polluting the environment. PWs constitute more than 10% of the municipal solid waste (Huang et al., 2007). Some proposed a waste-toenergy disposal as alternative to landfill disposal (Ouda et al., 2017). But this option could not solve the raw material demand issue related to plastic production, not to mention the additional carbon emission concern that accompanies this option (Scott, 2000; Katami et al., 2002). More robust and all-encompassing recycling alternatives need to be identified and pursued. Most common PWs are hydrophobic and inert material (Scott, 2000). They have bad effects on the surrounding environment by polluting water sources and lands (Thompson et al., 2009). It has been reported that microplastic debris transmits toxic substances to the global drinking water and food chain (Teuten et al., 2009). Moreover, PW materials have negative impact on the landscape and city views (Moore, 2008). Some studies were conducted on the use of recycled plastic waste (RPW) to modify asphalt binder for better asphalt concrete (AC) performance (Fu et al., 2007; Yildirim, 2007; Casey et al., 2008; Dalhat and Al-Abdul Wahhab, 2017; Al-Abdul Wahhab et al., 2016). Recycling of low- and high-density polyethylene (RHDPE and RLDPE) plastics in addition to recycled polypropylene (rPP) in order to improve

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00013-X Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete

the storage stability and performance of local asphalt binders in KSA was reported (Dalhat and Al-Abdul Wahhab, 2017; Al-Abdul Wahhab et al., 2016). Several RPW potential in improving the performance of stone mastic asphalt concrete (SMA) was investigated (Casey et al., 2008). This paper targeted the binder part of the AC, with little focus on the AC mix. Other studies have discussed the substitution of some proportion of mineral aggregate in AC mixes with recycled plastics (Zoorob and Suparma, 2000; Baghaee Moghaddam et al., 2012). RLDPE was used as aggregate replacement in a continuous graded AC (Zoorob and Suparma, 2000). However, emphasis was given to decrease in density and Marshall Stability instead of actual performance. In another study, the asphalt binder and some portion of the fine aggregate were completely replaced with thermoplastic RPW (Dalhat and Al-Abdul Wahhab, 2016). However, only the fundamental mechanical properties and thermal sensitivity of plastic concrete were established. The benefits and environmental implications of utilizing various RPWs in place of virgin polymer in AC are examined in this study. Modified asphalt binders were formulated from recycled low-density and high-density polyethylene (rLDPE and rHDPE), recycled polypropylene (rPP) and in combination with either elastomeric styrene-butadiene-styrene (SBS) or plastomeric polybilt (PB). The PW-modified binders were subjected to series of tests to establish their upper temperature performance limits. AC mixtures of selective PW-modified asphalt binders were formulated and analyzed. Emission estimates related to some selective potential blends were also compared to conventional and virgin polymer equivalent of each blends.

13.2

Polymer modification of asphalt and the need for plastic recycling in asphalt concrete

Asphalt was being used since ancient time for waterproofing and then later as a binding material in pavements (Polacco et al., 2006). As time progressed, it was realized that better asphalt performance could be achieved through modification. In 1950, a wellknown plastomeric polymer called neoprene was used as a modifier of bitumen in USA for roofing purposes (Yildirim, 2007). Commercial production of plastomers begun in early 1960s, and that of elastomers later on in 1965 (Utracki, 1995). In 1972, US government carried out its first investigation of utilizing polymer for the modification of asphalt through the Federal Highway Administration. Improvement in rupture resistance of the polymer modified asphalt (PMA) was reported (Rostler et al., 1972). German and French government separately investigated the utilization of polymer in 1976. They found that PMA possessed superior resistance to permanent deformation in addition to lower temperature sensitivity (Kameua and Duron, 1976; Zenke, 1976). In 1990s, researchers from different countries (Germany Australia, Belgium Austria, Japan, Spain, Poland, Nordic countries, and Gulf countries) had started investigation about PMA with focus on mechanical properties, temperature susceptibility, and morphology (Isacsson and Lu, 1995). Positive improvements in cracking resistance, elastic recovery, fatigue, and rutting resistance were their major

Recycling of different plastics in asphalt concrete

289

findings. However, some problems in storage stability and high cost of commercial polymer were reported. Current environmental challenges related to the demand, disposal techniques, and associated cost of the use of virgin polymers have begun to change the old trend in asphalt polymer modification. A gradual but widespread shift toward the use of recycled plastics as either supplements or substitute to the virgin polymer in asphalt modification is globally observed (Huang et al., 2007; Sulyman et al., 2014; Zhu et al., 2014). Toner cartridge plastic waste was earlier utilized to modify asphalt binder (Yildirim et al., 2004). The amount of toner content that yields a given performance grade was reported. However, problem with storage stability was observed. The effect of recycled ethylene vinyl acetate in comparison to inert and reactive virgin polymers on the viscoelastic properties of asphalt binder was reported (Navarro et al., 2009). The effect of recycled polyethylene on the basic and conventional properties of asphalt binder was examined (Punith and Veeraragavan, 2011). However, no specifics were given on possible achievable performances. The aging mechanism and physical behavior of recycled polyethylene modified asphalt binder were investigated (Fang et al., 2013; Singh et al., 2013). Improvement in aging resistance and physical properties was noticed. However, these studies did not focus sufficiently on key asphalt pavement performance indicators. A withdrawn static standard test due to its inability to reflect field condition was utilized in some cases where storage stability of the modified binders was checked.

13.3

Materials and methods

13.3.1 Material The raw asphalt was collected from Riyadh refinery; its properties are summarized in Table 13.1. The PW was obtained from the municipality recycling bins in Dammam. They were sorted and cleaned. Differential Scanning Calorimetry was conducted using DSC Q1000 on the various samples of PW categories (recycling label 1e6). Only three among them (rLDPE, rHDPE, rPP) possess a melting point low enough to warrant an asphalt-polymer hot blending with minimal oxidation. The RPW (rLDPE, rHDPE, and rPP) were then shredded to easily feed them into the polymer grinding machine, as shown in Fig. 13.1 (a1, b1, and c1, respectively). The PW flakes were further pulverized as shown in Fig. 13.2 (a2, b2, c2), to ensure faster and homogenous

Table 13.1 Basic properties of asphalt binders Property

PG grade

Softening point (oC)

Ductility (cm)

Viscosity (cP)

Penetration (dmm)

Flash Point (8C)

Value

64e22

51

>150

500

69.5

342

290

Use of Recycled Plastics in Eco-efficient Concrete

(a1)

(b1)

(c1)

(a2)

(b2)

(c2)

Figure 13.1 Recycled plastic sample. 100

100

90

90

90

80

Percent passing

70

1/2" Min. 1/2" Max

60

58

No. 8 Min. No. 200 Min

50

No. 200 Max

G1

40

3/8" Max 30

No. 8 Max

28

G2 20

10 10 2

0 0.01

0.1

1

10

100

Aggregate size (mm)

Figure 13.2 Aggregate gradation of asphalt concretes.

mixing with asphalt. Two commercial polymers (elastomer and plastomer), SBS and PB were also used. Table 13.2 shows some basic properties of recycled and commercial polymers used in this research. Fig. 13.2 presents the grading curves of aggregates for the asphalt concrete mixtures. The control points are according to AASHTO standard for dense graded asphalt concrete volumetric mix design (AASHTO:M323 2015).

Recycling of different plastics in asphalt concrete

291

Table 13.2 Physical properties of polymers Polymer

Code

Source/ Nature

Melting point (8C)

Density (g/ cm3)

Blending time (min.)

rHDPE

H

PW

150

0.950

60

rLDPE

L

PW

130

0.940

30

rPP

P

PW

160

0.946

50

SBS

S

Commercial

180

1.060

60

Polybilt

B

Commercial

140

0.943

30

Nomenclature examples: H4 ¼ 4%rHDPE; L2S1 ¼ 2%rLDPEþ1%SBS; P2 ¼ 2%rPP.

13.3.2 Methods and experiment 13.3.2.1 Optimization of blending duration The optimum blending duration of the PWs (rLDPE, rHDPE and rPP) was obtained by measuring the viscoelastic properties (viscosity and complex modulus) of samples extracted at every 10 min interval. The optimum time was selected as the time when no significant difference in these parameters was observed. The blending time of the PWs is presented in Table 13.2.

13.3.2.2 Sample preparation 500 g of hot melted asphalt binder was mixed with appropriate amount (2%, 4%, or 6%) of the PW powder, in combination with 0.0%, 1.0%, 1.5%, or 2.0% SBS or PB in a 1000 mL metal can. The mixture was presoaked for at least an hour at 160
C inside an oven. The blend containing a single modifier was sheared with high shear mixer for the duration and at the blending temperature suitable to that modifier (Table 13.2). Additive with higher blending duration and temperature control the mixing parameter, in case of two additives.

13.3.2.3 Performance testing Rotational viscometer was utilized to measure the viscosities of the PW-modified binders (ASTM D4402/D4402M, 2013) Modified asphalt samples were subjected to a short-term aging using rolling thin film test (ASTM D2872, 2012) Aged and unaged asphalt samples were tested for performance grading (PG) using Dynamic Shear Rheometer test (AASHTO T 315, 2012; ASTMD6373-15, 2015).

13.3.2.4 Asphalt concrete testing Superpave mix design was used to prepare modified and unmodified AC mixtures by optimizing their volumetric properties; this includes optimum asphalt content (OAC) and air voids (Av) and then measure the corresponding design properties that are used

292

Use of Recycled Plastics in Eco-efficient Concrete

to predict their performance in the field. AC performance indicators are voids in mineral aggregate (VMA) and voids filled with asphalt (VFA). All asphalt concrete mixtures were tested for indirect tensile strength ITS at dry and wet conditions according to ASTM D-6931 procedure in order to evaluate the moisture susceptibility of the modified AC mixes. In addition, Resilient Modulus (Mr) of each asphalt mix was measured according to standard procedure ASTM D-4123.

13.3.2.5 Emission estimation Carbon and nonmethane volatile organic compound (NMVOCs) emission levels associated with the manufacturing process of various types of virgin polymers were obtained. Polymers include the HDPE, LDPE, PB (EPA, 2010; Kuenen et al., 2013), SBS, and PP (styrene, butadiene, and propylene) (Saygın et al., 2009). Factors related to CO2 and NMVOC emissions of the recycled PW were obtained based on the required energy for sorting, washing, shredding, granulating, and finally grinding for easier asphalt blending. Table 13.3 shows the emission factors for the various PW and polymers. Table 13.4 summarizes the power and capacity of typical equipment used to process the plastic wastes selected. The amount of CO2 and NMVOCs for the various PW-polymer combinations was estimated relative to the total annual polymer modified asphalt demand in KSA. Table 13.3 Summary of Emission Factors Polymer Type

NMVOCs (kg/ton)

CO2 (MTCO2e/ton)

HDPE

2.30

1.95

LDPE

2.40

2.34

PP

0.19

0.67

SBS

0.27

2.55

PB

2.40

2.42

rLDPE

e

2.1  107

rHDPE

e

2.1  107

rPP

e

2.1  107

Table 13.4 PW processing equipment specification summary Equipment

Capacity (kg/h)

Power (kW)

Shredder/Crusher

50e5000

7.5e250

Granulator

250e500

90e160

Grinder

100e200

4.0

Recycling of different plastics in asphalt concrete

13.4

293

Results

13.4.1 Rotational viscosity Viscosity is the measure of ease with which the asphalt mix could be handled. This includes pumping from storage tank to the mixing chamber, proper coating of aggregate during mixing, and compaction of the asphalt concrete to the required air void. AASHTO specified a limit of 3000 cP at 135
C and 25 rpm, as the maximum for asphalt binder. Fig. 13.3 shows the viscosities of PW-SBS-modified asphalt binders. Most of the PW-SBS-modified binders have met the AASHTO viscosity limit of 3000 cP. Those blends containing 6% rHDPE or 6% rLDPE in combination with SBS could not meet the set limit. However, failing the viscosity limit should not be taken as a conclusive disqualification. It also means that higher mixing and compaction temperatures are needed for such asphalt binders. Both SBS and the PWs result in increased viscosity. This can be observed from the first grouped bars (0% PW) and the first bars of each group in Fig. 13.3. Combining the SBS with rLDPE, rHDPE, or rPP yields a further increase in viscosity, in most cases. Introducing the sufficiently stiff SBS into the existing rLDPE, rHDPE, or rPP microstructure helps establish some comparably strong SBSeSBS and SBSePW linkages, in addition to the rLDPE-rLDPE, rHDPE-rHDPE, or rPP-rPP present within the asphalt binder phase. This leads to an increase in interlayer friction, and thus higher viscosities for the PW-SBS-modified asphalt binders. The viscosity results of the asphalt binder with PW-PB combinations are presented in Fig. 13.4. Overall, most of the PW-PB-modified asphalt binders are within the standard recommended viscosity limits. The viscosity increases with both increase in PW and PB in the case of rPP and rLDPE. The increase in viscosity due to PB is however

Viscosity (cP), 25ºC, 20 rpm

9,000 8,000 7,000 6,000 5,000 4,000 3,000 2,000 1,000

0% SBS

1% SBS

1.5% SBS

Figure 13.3 Viscosities of PW-modified asphalt in combination with SBS.

rP 6%

rP 4%

2% SBS

P

P

P rP 2%

PE 6%

4%

rH

rH

D

D

PE

PE D 2%

rH

D rL 6%

4%

rL

D

PE

PE

PE D rL 2%

0%

PW

0

Use of Recycled Plastics in Eco-efficient Concrete

Viscosity (cP) at 135oC, 20 rpm.

294 8000 7000 6000 5000 4000 3000 2000 1000

0% PB

1% PB

P

P % 6

%

rP

rP

P 4

% 2

rH 6

%

rH % 4 1.5% PB

rP

PE D

PE D

D 2

%

rH

rL 6

%

rL % 4

PE

PE D

PE D

D rL % 2

0%

PW

PE

0

2% PB

Figure 13.4 Viscosities of PW-modified asphalt in combination with PB.

slight and sometimes inconsistent due to difference in contents level as well as the PW and PB properties. The PB assumes two different viscosity changing roles depending on the PW type and content level. The presence of PB can positively influence the viscosity of the PW-modified asphalt binder as in the case of rPP and rLDPE asphalts, and vice versa, as with the case of rHDPE asphalt binder. The observed decrease in viscosity due to PB in rHDPE asphalt can be easily understood by comparing the viscosity of the PB-only asphalt with that of the rHDPE-only binder. The PB asphalt is less viscous while the rHDPE modified binders are highly viscous, especially at high content. The introduction of the PB to the rHDPE microstructural network creates weaker points. The more the PB, the higher the potential weak PBasphalt or PB-rHDPE interfaces. Hence the interlayer shear resistance offered by the PB-rHDPE asphalts, which results in an unstiffening effect by the PB. This phenomena can be seen to manifest in both RLDPE and rHDPE modified asphalt with viscosity above 1500 cP. The observed phenomena can be utilized to solve one of the challenges of PW binders, which is the high viscosity associated with the PW content.

13.4.2

Rutting resistance parameter and phase angle of the PWmodified binder

Rutting is the major asphalt pavement distress in hot climates and specifically KSA (Balghunaim et al., 1988). This is due to high traffic load and elevated pavement temperature from the adverse climate. The standardized binder rutting potential indicator is jG*j/Sin(d) according to Strategic Highway Research program (SHRP) asphalt binder specification (Superpave). Fig. 13.5 shows the jG*j/Sin(d) result of rLDPEmodified asphalt binders in combination with SBS, at various temperatures.

Recycling of different plastics in asphalt concrete

295

30

Control binder L2S0

25

L4S0

20

L2S1

G*/Sinδ (Kpa)

L6S0 L4S1 L6S1

15

L2S1.5 L4S1.5

10

L6S1.5 L2S2

5

L4S2 L6S2

0 64

67

70

73 76 Temperature (°C)

79

82

Figure 13.5 Rutting parameter (G*/Sin d) of rLDPE-SBS-modified asphalt binders.

It can be observed that 2%, 4%, and 6% of recycled rLDPE with different dosages of commercial SBS have resulted in an improved rutting resistance with respect to the control binder. For example, 2% rLDPE and 1% SBS improved the rutting resistance by more than 3-fold at 70
C. Similarly, blend containing 6% rLDPE and 1% SBS possesses almost 7-fold rutting parameter when compared to the control binder. This is as a result of improvement in the viscoelastic moduli (storage and loss modulus) of modified binders, due the presence of rLDPE and SBS molecule within the asphalt microstructure. The hot asphalt blending of the asphalt and the polymer enabled the swelling and melting of the rLDPE and SBS within the asphalt. This creates a mixed-up rLDPEasphalt, SBS-asphalt, or rLDPE-SBS-asphalt composite. rLDPE and SBS being much thermally stable materials influence the base binder viscoelastic characteristic toward the higher side. This will go a long way in improving the high temperature performance of the modified binder. The phase angle tangent of the rLDPE-SBS asphalt is shown in Fig. 13.6. The improvement in the storage modulus or elastic response of the asphalt could generally be observed with more presence of rLDPE and furthered by the SBS. Even though blends containing up to 6% rLDPE showed significantly improved elastic response, their thermal sensitivity tend to wither drastically above 76
C. The plastomeric rLDPE mostly boosts the asphalt elastic response indirectly by stiffening the modified binder, and thus making it less strain sensitive. This expands the linear elastic range of the rLDPE-modified binder, and allows it to recover most of the little sustained strain when stressed. However, the SBS improves the binder elasticity directly due to its elastomeric nature. Four percent of rLDPE with 1% SBS blend showed the best elastic response with increasing temperature. It contained the optimum proportion of the elastomer and plastomer for the current content range and test used. Similar trends were observed in the case of rHDPE, rPP, and in combination with SBS or PB. But for the sake of report brevity, Figs. 13.5 and 13.6 are the only illustrations presented to explain the reason behind the improvement in high temperature performance of PW-modified asphalt binders.

296

Use of Recycled Plastics in Eco-efficient Concrete 16

L2S0 L4S0

14

L6S0 12

L2S1 L4S1

tanδ

10

L6S1 L2S1.5

8

L4S1.5 6

L6S1.5 L2S2

4

L4S2

2

L6S2 Control binder

0 64

67

70

73 76 Temperature (°C)

79

82

Figure 13.6 Tangent of phase angle of rLDPE-SBS-modified asphalt binders.

13.4.3

High performance temperature of PW-modified asphalt binders

The high performance temperature (HPT) of an asphalt binder is that service temperature above which the binder could not perform satisfactorily, in terms of resistance to rutting, bleeding etc. This parameter is of utmost significance, especially for hot KSA climate where the predominant pavement distress is rutting. The high performance temperature of rLDPE-modified asphalt binders are presented in Fig. 13.7. When comparison is made with the control binder, a considerable improvement in the HPT could be observed as a result of the modification. This should be anticipated, as the enhancement in the viscoelastic properties of the PW-modified

High performance temperature (oC)

No C. Poly

1% SBS

1.5% SBS 2% SBS 1% PB

1.5% PB

2% PB

90 80

Line of PG 82°C Line of PG 76 oC

70

Line of PG 70oC Line of PG

60

64oC

50 40 No recycled polymer

2% rLDPE

4% rLDPE

6% rLDPE

Recycled polymer content

Figure 13.7 High performance temperature of rLDPE-modified asphalt binders.

Recycling of different plastics in asphalt concrete

297

High performance temperature (°C)

binder observed from Fig. 13.5 will be reflected in the HPT. The introduction of plastomeric PB and elastomeric SBS to the moderately stiff dispersed RLDPE microstructural system results in a slightly reinforced stiffer rLDPE-PB matrix and highly reinforced rLDPE composite. This is in addition to the increased proportion of less thermal sensitive material than the asphalt itself. Hence this leads to a more temperature-resistant blend with higher HPT. Almost all the rLDPE-SBS and rLDPE-PB modified asphalts could withstand an upper service temperature of 70
C. Apart from 2% rLDPEþ1% PB, all the rLDPE-SBS and rLDPE-PB asphalt binders could also endure a much greater high service temperature of 76
C. A significant increase in the HPT of the asphalt binder due to rHDPE with SBS or PB could be observed from Fig. 13.8. About 2% rHDPE alone is enough to satisfy environments with 70
C high temperature performance requirement. Much adverse climates as that with 76
C seven-day maximum pavement temperature will require at least 3.5% rHDPE-modified asphalt binder to satisfy its HTP specification. Both SBS and PB inclusion to the rHDPE-asphalt microstructural network have positively yielded a better modified asphalt binder. This could be attributed to the fact that the presence of SBS and PB molecules in the modified binder increases the polymer linkages and proportion, thus influencing the thermal resistance of the modified binder toward the high temperature side. As in the case of rLDPE/rHDPE, similar improvement in high temperature performance of rPP-modified asphalt binders could be observed from Fig. 13.9. The presence of SBS and PB in the rPP-modified asphalt has not resulted in substantial improvement in the HPT. PB actually results in declined HPT in the rPP-PB composites. This could be understood by observing the two polymers’ impact on the base asphalt individually. Both rPP and PB yielded higher HPT than the base binder, but for the same quantities, rPP could produce a modified binder with up to 8
C HPT more than the PB. This could be seen when asphalt blends containing only 2% of either rPP or PB were compared, unlike the case of 2% SBS-modified binder. So adding PB to a relatively much thermal-resistant rPP microstructure ended up creating weaker intermediate PB-PB,

No C. Poly

1% SBS

1.5% SBS

2% SBS

1% PB

1.5% PB

2% PB

90 80

Line of PG 82°C Line of PG 76°C

70

Line of PG 70°C Line of PG 64°C

60 50 40 No recycled polymer

2% HDPE

4% rHDPE

Recycled polymer content

Figure 13.8 High performance temperature of rHDPE-modified binders.

6% rHDPE

Use of Recycled Plastics in Eco-efficient Concrete High performance temperature (°C)

298 No C. Poly

1% SBS

1.5% SBS

2% SBS

1% PB

1.5% PB

2% PB

90 80

Line of PG 82°C Line of PG 76°C

70 60

Line of PG 70°C Line of PG 64°C

50 40 No recycled polymer

2% rPP

4% rPP

6% rPP

Recycled polymer content

Figure 13.9 High performance temperature of rPP-modified binders.

PB-asphalt, or PB-rPP linkages than the rPP-rPP or rPP-asphalt physical connections. Hence this results in asphalt composite with lower HTP. Two percent of rPP could yield asphalt binder that can endure environments with 76
C high temperature asphalt binder requirement.

13.4.4

Recycled Plastic asphalt concretes compared

Some of the PW-modified asphalt binders were selected to prepare asphalt concrete mix design. The selection was based on equal upper service temperature performance but according to AASHTO Superpave plus standard (AASHTO-M-332 2014). The Superpave plus includes multiple stress creep and recovery (MSCR) in addition to the conventional temperature sweep test. The MSCR results provide further classification for the asphalt binder in terms of traffic levels. The asphalt binder selected are Table 13.5 Superpave volumetric Parameters of AC mixtures AC mix

OAC (%)

Gradation

VMA (%)

VFA (%)

Fresh

4.80

G1

14.8

72.97

7.5% CR

5.40

G1

15.04

73.41

S4

4.90

G1

14.21

71.85

PB4

4.80

G1

14.47

72.35

L6

5.16

G1

17.60

75.33

L4S1.5

5.28

G1

16.99

76.70

L6B1

5.20

G1

16.96

74.98

H4

5.70

G2

18.55

75.23

H2B1.5

5.00

G2

16.02

74.13

H4S1

5.60

G2

16.46

74.71

P2S1.5

5.16

G1

17.78

73.36

Recycling of different plastics in asphalt concrete

299

those with 76
C upper temperature performance suitable for very heavy traffic (76 (V)), as shown in Table 13.5. Asphalt concrete samples were prepared and compacted using Superpave mix design procedures (AASHTO:M323 2015). Volumetric properties of designed samples were measured. Table 13.5 summarizes the volumetric properties of the asphalt concrete mixtures. The optimum asphalt content (OAC) of each mix was obtained at Av of 4% as per Superpave procedure. This involves the calculation of bulk specific gravity of aggregate blends and the bulk and maximum specific gravity of the mix. The resulted voids in mineral aggregates (VMA) and voids filled with asphalt (VFA) were estimated. It can be observed that higher optimum asphalt contents were required for stiffer polymers like rHDPE and crumb rubber (CR). The moisture sensitivity test results for the designed mixtures are shown in Fig. 13.10. The indirect tensile strengths (ITSs) of the dry samples along with the retained strength index (RSI) are presented. The RSI is defined as the ratio of ITS of the moisture conditioned AC mix samples to the dry AC mix samples. It is a major moisture resistance that any AC must meet according the AASHTO AC mix design standard. The various PW modified AC mixtures have all met the minimum requirement of 80% RSI, but with different margins. Most of the PW-modified AC mixtures showed RSI above 90%, a value higher than those for the conventional AC and the regular polymers of AC such as PB and SBS. The results seen here showed that the PW-modified AC mixtures can be not only as good as the regular polymer modified ACs, but even better in terms of resistance to moisture damage. The same can be said about the ITS of the PW-modified AC mixtures. The first five top ranking AC mixtures with highest ITSs are all PW-modified asphalt bases. This is a further proof of how competitive the PW ACs are relative to conventional ACs or polymer-modified ACs. It can be seen that the ACs with the highest ITSs contains purely PW-modified asphalt.

ITS (kPa)

RSI (%) 100 90 80

1500

70 60 50

1000

40 30 500

20

Retained strength index 'SRI' (%)

Indirect tensile strength 'ITS' (kPa)

2000

10 0

Fresh 7.5%CR 1366

S4

PB4

L6

L4S1.5

L6B1

H4

1529

1402

2030

1693

1753

1209

1587

1399

1879

81.2

90.1

87.2

99.8

82.8

90.4

94.7

97.8

92.7

84.1

ITS (kPa) 1059

RSI (%)

84.0

H2B1.5 H4S1

P2S1

0

Figure 13.10 Indirect tensile strength and moisture sensitivity of the various PWs concretes.

300

Use of Recycled Plastics in Eco-efficient Concrete Mr @ 20 deg

Mr @ 44 deg

Resilient modulus 'Mr' (MPa)

16000 14000 12000 10000 8000 6000 4000 2000 0

L6

L4S1.5

L6B1

H4

H2B1.5

H4S1

P2S1

Fresh

Mr @ 20 deg

15203

13089

14092

8669

12031

9242

13568

8557

Mr @ 44 deg

8587

8531

8758

3198

7227

4077

7414

Figure 13.11 Resilient modulus of the plastic waste asphalt concretes.

Results of Mr for the PW-modified ACs at two temperatures (20 and 44
C) are shown in Fig. 13.11. The idea is to further rank these selected AC mixtures in terms of thermal sensitivity and elastic resilience. The Mr is a measure of the AC elastic recovery performance. The hierarchy of performance of the PW ACs in terms of Mr is similar to that observed for ITS. However, the various PW ACs showed distinct thermal sensitivity as shown in Fig. 13.12. The observed trend is not sufficient to give a reason for the variation of the thermal sensitivity in terms of the PW-polymer combination. But the fact that combining different type of polymers and PW yield diverse thermal performance is a positive thing, because the practice of combining different plastics in asphalt modification is not currently popular. Now, possibility of combining different polymers to get a better hybrid is clearly known. 500

Loss in Mr (MPa/ o C)

450

400 350 300 250 200 150 100 50 0

L6

L4S1.5

L6B1

H4

H2B1.5

H4S1

P2S1

Figure 13.12 Thermal sensitivity of the plastic wastee modified asphalt concretes.

Recycling of different plastics in asphalt concrete

301

13.4.5 An estimate of the environmental benefit of plastic recycling in AC: KSA perspective

NMVOCs

223026

CO2

189088

NMVOCs

152334

CO2

201756

NMVOCs

300288

L2S0.6 L2PB1.5

NMVOCs

P1.5

NMVOCs

PB4.7

CO2

NMVOCs

S3.34

L4

H2S1

H3

Global demand of asphalt binder as either construction material, or otherwise, was estimated to be around 120 million metric tons with annual appreciation forecast of approximately 4% in 2015 (Freedonia, 2014). The total asphalt demand per year in KSA was pegged at 4.6 million metric tons (United-Nation, 2013). It was established that road construction generates about 85% of the asphalt demand, while applications such as waterproofing, roofing, and others creates the remaining 15% demand (Freedonia, 2014; Zhu et al., 2014). Due to the adverse climate in KSA, road construction in most of the regions require asphalt polymer modification (Dalhat and Al-Abdul Wahhab, 2017). Conservatively (Zhu et al., 2014), the amount of polymer demand due to road construction is around 6% of the 85% of the asphalt demand. This implies that around 187,680 tons of polymer is consumed by road construction sector in KSA annually. On the other hand, more than 7-fold of the polymer demand is generated in plastic waste in KSA. The process of manufacturing polymer from virgin source results in several environmental implications in the form of emissions (see Table 13.2). Carbon and NMVOC emissions are few but critical among the substances emitted during polymer manufacturing processes. The related CO2 and NMVOC estimates for the convention polymer modified asphalt (PMA) such as SBS-asphalt and PB-asphalt were compared to the PWmodified asphalt. In addition, the PW content in the PW-asphalt was hypothetically replaced with its virgin equivalent to estimate the case of purely virgin polymermodified asphalt as further comparison. The emission estimates results for asphalt binders with 76
C and 82
C upper PG are shown in Figs. 13.13 and 13.14, respectively. It can be observed that the pure PW-modified asphalt binders, such as L4

NMVOCs

292781 262752

CO2

259937

NMVOCs

155211

CO2

194249 8915

CO2

31436 352838 355779

CO2 28208 266412

CO2 0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

NMVOCs (kg/Yr), CO2 (MTCO2e/Yr) Conventional PMA Purely virgin polymer With PW

Figure 13.13 Emission analogy for PW-asphalt combination meeting 76
C HPT

400,000

H4.4

NMVOCs

L4S1.5 L2PB2 L6PB1.1 H4S1.1

NMVOCs

L6S1

NMVOCs

PB6.9

Use of Recycled Plastics in Eco-efficient Concrete

NMVOCs

S5.1

302

NMVOCs

CO2

CO2

NMVOCs CO2 NMVOCs CO2

NMVOCs CO2

CO2

CO2

CO2

0

100,000

200,000

300,000

400,000

500,000

600,000

NMVOCs (kg/Yr), CO2 (MTCO2e/yr)

Conventional PMA

Purely virgin polymer

With PW

Figure 13.14 Emission analogy for PW-asphalt combination meeting 82
C HPT

(4% rLDPE) and H3 (3% rHDPE), etc., resulted in negligible CO2 and NMVOC emissions. The combination of the PW with the conventional polymers also showed significantly lower CO2 and NMVOC emissions than when virgin polymers were employed. Adopting the PW-modified asphalt in KSA alone has the potential of eliminating as high as 500,000 million metric tons of carbon emission along with 500 tons of NMVOCs from atmosphere annually. On average, 27 million metric tons of CO2 could be cut, for every ton of virgin polymer replaced with PW.

13.5

Future trends

The recent trend is the replacement of the virgin polymer in the asphalt binder as well as some portion of the mineral aggregate with PW (Dalhat, 2017). The asphalt binder and some component of the mineral aggregate were recently substituted by PW completely to form a plastic bounded concrete (Dalhat and Al-Abdul Wahhab, 2016; Dalhat and Wahhab, 2017). The combination of polymer and fiber in asphalt modification, specifically for dense grade asphalt concretes, is also another new evolving trend.

13.6

Summary and conclusions

The benefits and environmental implications of utilizing various recycled PWs in asphalt concrete is examined. The PW-modified binders are subjected to series of tests to establish their upper temperature performance limit. Asphalt concrete mixtures of

Recycling of different plastics in asphalt concrete

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selective PW-modified asphalt binders are formulated and analyzed. Emission estimates related to some selective potential blends are estimated and compared to conventional and virgin polymer asphalt. Significant improvement in viscoelastic behavior of the asphalt binder modified with the PW and in combination of virgin polymers is observed. This results in an increase in the upper performance grade temperature of PW-modified asphalt binders. Most of the PW-modified AC mixtures show Mr, ITS, and RSI values higher than those for the conventional AC and the regular polymers AC such as PB and SBS, indicating that PW asphalt concretes can not only be as good as the conventional ACs, but even better in terms of crack resistance and moisture sensitivity. The various PW asphalts showed distinct thermal susceptibility, which confirms the feasibility of combining different PWs for much better thermal properties. The pure PW-modified asphalt binders result in negligible CO2 and NMVOC emissions. Combination of the PW with the conventional polymers also showed significantly lower CO2 and NMVOC emissions than when the virgin polymers were employed. Adopting the PW-modified asphalt in KSA alone has the potential of eliminating as high as 500,000 million metric tons of carbon emission along with 500 tons of NMVOCs from atmosphere annually.

Acknowledgments The authors acknowledge the support provided by Imam Abdulrahman bin Faisal University and King Fahd University of Petroleum and Minerals (KFUPM), KSA, in carrying out this research.

Conflict of Interest The authors wish to declare that they have no conflict of interest.

References AASHTO:M323, 2015. Standard Specification for Superpave Volumetric Mix Design. WASHINTON DC, 2001, AASHTO. AASHTO-M-332, 2014. Standard Specification for Performance-graded Asphalt Binder Using Multiple Stress Creep Recovery (MSCR) Test. American Association of State and Highway Transportation Officials. AASHTO T 315, 2012. Standard Method of Test for Determining the Rheological Properties of Asphalt Binder Using a Dynamic Shear Rheometer (DSR). American Association of State and Highway Transportation Officials, Washington, DC, 20001. ASTM D4402/D4402M, 2013. Standard Test Method for Viscosity Determination of Asphalt at Elevated Temperatures Using a Rotational Viscometer. ASTM International, West Conshohocken, PA, https://doi.org/10.1520/D4402_D4402M. ASTM D2872, 2012. Standard Test Method for Effect of Heat and Air on a Moving Film of Asphalt (Rolling Thin-film Oven Test). ASTM International, West Conshohocken, PA, https://doi.org/10.1520/D2872-12E01.

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ASTM D6373e15, 2015. Standard Specification for Performance Graded Asphalt Binder. ASTM International, West Conshohocken, PA, https://doi.org/10.1520/D6373-15. Al-Abdul Wahhab, H.I., Dalhat, M.A., et al., 2016. Storage stability and high-temperature performance of asphalt binder modified with recycled plastic. Road Materials and Pavement Design 1e18. Baghaee Moghaddam, T., Karim, M.R., et al., 2012. Dynamic properties of stone mastic asphalt mixtures containing waste plastic bottles. Construction and Building Materials 34 (0), 236e242. Balghunaim, F., Al-Dhubaib, I., et al., 1988. Pavement rutting in the Kingdom of Saudi Arabia: a diagnostic approach to the problem. In: Proceedings of the 3rd IRF Regional Conference, Riyadh, vol. 6, pp. 209e232. Casey, D., McNally, C., et al., 2008. Development of a recycled polymer modified binder for use in stone mastic asphalt. Resources, Conservation and Recycling 52 (10), 1167e1174. Dalhat, M.A., 2017. Fatigue and Rutting Performance of Hybrid Recycled Plastic Asphalt Concrete. Civil and Environmental Department, Dammam (King Fahd University of Petroleum and Minerals. PhD.). Dalhat, M.A., Al-Abdul Wahhab, H.I., 2017. Performance of recycled plastic waste modified asphalt binder in Saudi Arabia. International Journal of Pavement Engineering 18 (4), 349e357. https://doi.org/10.1080/10298436.2015.1088150. Dalhat, M.A., Al-Abdul Wahhab, H.I., 2016. Cement-less and asphalt-less concrete bounded by recycled plastic. Construction and Building Materials 119, 206e214. Dalhat, M.A., Wahhab, H.I.A.-A., 2017. Properties of recycled polystyrene and polypropylene bounded concretes compared to conventional concretes. Journal of Materials in Civil Engineering 29 (9), 04017120. EPA, 2010. Plastics. OCSPP. U.S, Environmental Protection Agency. http://www3.epa.gov/ climatechange/wycd/waste/downloads/plastics-chapter10-28-10.pdf. Fang, C., Wu, C., et al., 2013. Aging properties and mechanism of the modified asphalt by packaging waste polyethylene and waste rubber powder. Polymers for Advanced Technologies 24 (1), 51e55. Freedonia, 2014. World Asphalt - Demand and Sales Forecasts, Market Share, Market Size, Market Leaders. Retrieved Study #: 3129, from. http://www.freedoniagroup.com/WorldAsphalt.html. Fu, H., Xie, L., et al., 2007. Storage stability and compatibility of asphalt binder modified by SBS graft copolymer. Construction and Building Materials 21 (7), 1528e1533. Gourmelon, G., 2016. Global Plastic Production Rises, Recycling Lags. World Watch Institute, Washington, D.C. http://www.worldwatch.org/global-plastic-production-rises-recyclinglags-0. Huang, Y., Bird, R.N., et al., 2007. A review of the use of recycled solid waste materials in asphalt pavements. Resources, Conservation and Recycling 52 (1), 58e73. IFC, 1998. Pollution Prevention and Abatement Handbook: Petrochemicals Manufacturing. World Bank Group, International Finance Coorperation World Bank Group, p. 5. Isacsson, U., Lu, X., 1995. Testing and appraisal of polymer modified road bitumensdstate of the art. Materials and Structures 28 (3), 139e159. Kameau, G., Duron, M., 1976. Influence of static and sequenced elastothermoplastic copolymers on the mechanical properties of bituminous mixtures. Bulletin de Liaison des Laboratoires des Ponts et Chaussees 18, 135e139 ([In French].). Katami, T., Yasuhara, A., et al., 2002. Formation of PCDDs, PCDFs, and coplanar PCBs from polyvinyl chloride during combustion in an incinerator. Environmental Science & Technology 36 (6), 1320e1324.

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Kuenen, J., Appelman, W., et al., 2013. EMEP/EEA Emission Inventory Guidebook. 2.B Chemical industry. E. E. Agency, Copenhagen K (EEA.). Moore, C.J., 2008. Synthetic polymers in the marine environment: a rapidly increasing, longterm threat. Environmental Research 108 (2), 131e139. Navarro, F.J., Partal, P., et al., 2009. Bitumen modification with reactive and non-reactive (virgin and recycled) polymers: a comparative analysis. Journal of Industrial and Engineering Chemistry 15 (4), 458e464. Ouda, O.K.M., Raza, S.A., et al., 2017. Waste-to-energy potential in the Western Province of Saudi Arabia. Journal of King Saud University - Engineering Sciences 29 (3), 212e220. https://doi.org/10.1016/j.jksues.2015.02.002. Polacco, G., Stastna, J., et al., 2006. Relation between polymer architecture and nonlinear viscoelastic behavior of modified asphalts. Current Opinion in Colloid & Interface Science 11 (4), 230e245. Punith, V., Veeraragavan, A., 2011. Behavior of reclaimed polyethylene modified asphalt cement for paving purposes. Journal of Materials in Civil Engineering 23 (6), 833e845. Rostler, F.S., White, R.M., Cass, P.J., March 1972. Modification of Asphalt Cements for Improvement of Wear Resistance of Pavement Surfaces. Report No.: FHWA-RD-72-24 Final Rpt. Federal Highway Administration, Washington, D.C. Saygın, D., Patel, M.K., et al., 2009. Chemical and Petrochemical Sector. Potential of Best Practice Technology and Other Measures for Improving Energy Efficiency. International Energy Agency, p. 60. Scott, G., 2000. ‘Green’ polymers. Polymer Degradation and Stability 68 (1), 1e7. Singh, B., Kumar, L., et al., 2013. Polymer-modified bitumen of recycled LDPE and maleated bitumen. Journal of Applied Polymer Science 127 (1), 67e78. Sulyman, M., Sienkiewicz, M., et al., 2014. Asphalt pavement material improvement: a review. International Journal of Environmental Science and Development 5 (5), 11. Teuten, E.L., Saquing, J.M., et al., 2009. Transport and release of chemicals from plastics to the environment and to wildlife. Philosophical Transactions of the Royal Society of London B Biological Sciences 364 (1526), 2027e2045. Thompson, R.C., Moore, C.J., et al., 2009. Plastics, the environment and human health: current consensus and future trends. Philosophical Transactions of the Royal Society of London B Biological Sciences 364 (1526), 2153e2166. United-Nation, 2013. Energy and Renewables: UN Statistics Division Energy Statistics Database for Saudi Arabia., KNOEMA. http://knoema.com/atlas/sources/UNSD. Utracki, L.A., 1995. History of commercial polymer alloys and blends (from a perspective of the patent literature). Polymer Engineering & Science 35 (1), 2e17. Yildirim, Y., 2007. Polymer modified asphalt binders. Construction and Building Materials 21 (1), 66e72. Yildirim, Y., Hazlett, D., et al., 2004. Toner-modified asphalt demonstration projects. Resources, Conservation and Recycling 42 (3), 295e308. Zenke, G., 1976. On the use of polymer-modified bitumen in asphalt mixes. Stationaere Mischwerk 10 (6), 255e264 [In German]. Zhu, J., Birgisson, B., et al., 2014. Polymer modification of bitumen: advances and challenges. European Polymer Journal 54, 18e38. Zoorob, S.E., Suparma, L.B., 2000. Laboratory design and investigation of the properties of continuously graded Asphaltic concrete containing recycled plastics aggregate replacement (Plastiphalt). Cement and Concrete Composites 22 (4), 233e242.

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Replacement of stabilizers by recycling plastic in asphalt concrete

14

Goutham Sarang Assistant Professor (Senior), School of Mechanical and Building Sciences (SMBS), Vellore Institute of Technology - Chennai Campus, Chennai, Tamil Nadu, India

14.1

Introduction

Road transportation is generally the most effective and preferred mode of transport, for both freight and passenger movement, due to its easy accessibility and adaptability to individual needs. Generally, roads can be laid with asphalt surfacing, known as flexible pavements, or with cement concrete, called rigid pavements. Most of the roads are flexible types with sub base, base, and surface course over the compacted subgrade layer. Asphalt concrete is conventionally used in the surface layer of flexible pavements. Asphalt concrete is the mixture of asphalt binder, crushed aggregates, and mineral filler in the suitable proportion. The mineral filler used in the mixture together with the binder fill the voids created due to the arrangement of different sizes of aggregates. Depending on the availability and the requirement of pavement, the type of aggregate is chosen, whereas, the expected pavement temperature is the major deciding factor in selecting the asphalt binder. The correct size and proportion of the aggregates and the quantity of binder are arrived through various mixture design procedures, including Marshall mix design, Superpave mix design, etc. The proportion of different sizes of aggregates (technically described as aggregate gradation) is more critical in asphalt concrete, when compared to cement concrete, since it has a significant effect on the performance. The aggregates in conventional asphalt mixture are dense or well graded to provide the maximum possible density, with the orientation of aggregates. Maximum density is achieved by packing the finer-sized aggregates and mineral filler in the voids between coarser sized aggregates. Gap-graded or open-graded mixtures are also used in the asphalt pavement surfaces for specific purposes. Gap-graded mixtures have higher proportion of coarser sized aggregates and mineral filler, and no or small amount of finer aggregates. When the amount of voids is almost the same in the mixtures using dense and gap-graded structures, it is very high in open-graded mixtures, since they generally do not have any mineral filler. This structure is used in porous pavements, where water can be removed easily from the pavement surface and may be used for storm water management. Typical gradation curves for dense, gap-, and open-graded mixtures are shown in Fig. 14.1.

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00014-1 Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete Dense graded

Gap graded

Open graded

100

80

% finer

60

40

20

0 0.01

0.1

1 Sieve size (mm)

10

100

Figure 14.1 Typical gradation curves for dense, gap- and open-graded mixtures.

The asphalt concrete mixtures are prepared by heating the constituent materials and mixing them properly at a temperature range of 150 Ce180 C, and these are known as hot mix asphalt (HMA) mixtures, generally used in the pavement surface course. The stipulated temperatures are maintained while laying the mixture in the field and while compacting it. Most of the flexible pavements constructed all around the world use this technology. High energy requirement to achieve the increased temperature, adverse effects on the environment, etc., lead to the development of mixtures which can be prepared at relatively lower temperature, called warm mix asphalt (WMA), and mixtures which do not require heating, known as cold mix asphalt.

14.2

Need for stabilization of asphalt concrete

Asphalt mixtures are intended to render a resilient, relatively waterproof, loaddistributing medium with considerable stability and durability. Being a viscoelastic material, asphalt behaves as an elastic solid at low temperatures and as a viscous liquid at high temperatures. Asphalt is generally susceptible to low temperature cracking, as well as excessive deformation at higher temperature, and hence, both should be addressed simultaneously. In order to use the asphalt binder in the pavement, it should be soft enough to control thermal cracking at low temperatures and stiff enough to control rutting (Jew et al., 1986; Prowell, 2000). Properties of asphalt and asphalt mixes can be improved by incorporating certain additives or a blend of additives. Asphalt treated with these additives or modifiers is known as “Modified asphalt” and is expected to provide mixtures with improved

Replacement of stabilizers by recycling plastic in asphalt concrete

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life, depending upon the degree of modifications and type of additives used. Tia et al. (1994) reported that Haas et al. (1983) defines these modifiers as: “An asphalt cement additive is a material which would normally be added to and/or mixed with the asphalt before mix production, or during mix production, to improve the properties and performance of the resulting binder and the mix, or where an aged binder is involved, as in recycling, to improve or restore the original properties of the aged binder.” Roberts et al. (1996) listed the advantages of using suitable additives in HMAs. It can provide the mixture with stiffness at high service temperatures as well as softness at low service temperatures. Additives can improve the asphalt-aggregate bonding and resistance to aging, fatigue, and abrasion of the mixture. They help in obtaining thicker asphalt film on aggregates improving the durability of the mixture. Reduction in the thickness of pavement layers and life cycle costs with an overall performance improvement can be achieved by using additives in asphalt concrete. The asphalt modifiers are generally classified into filler, extender, rubber, plastic, fiber, oxidant and antioxidant, hydrocarbon, antistripping agent, combination of plastic and rubber, other waste materials, etc. When crusher dust, cement, fly ash, lime, etc., are used as filler material in asphalt concrete to fill the voids, Sulfur and lignin can be used as extenders (Deme, 1978; FHWA, 2012; Terrel et al., 1980). Oxidation catalysts like manganese salts can be used to increase the stiffness of asphalt concrete mixtures. Sometimes asphalt binder undergoes oxidative hardening while placement, and this can be controlled by using antioxidants with suitable lead compounds. If the asphalt binder lacks the required properties, they can be achieved by incorporating harder or softer hydrocarbons. Stripping of asphalt and aggregates is a common issue with asphalt mixtures all around the world, and this can be controlled to a certain extent with hydrated lime and other antistripping agents (TRB, 2003). The most commonly used modifiers are polymers (both plastic and rubber) and fibers.

14.2.1 Dense graded asphalt concrete A modifier is generally not essential in dense graded asphalt concrete mixtures, but to achieve some specific purpose or to overcome certain deficiencies, a suitable stabilizer can be used. Alexander (1968) reported the usage of different types of modifiers by many researchers and practitioners since 1940s to improve the performance of asphalt binders (Clinebell and Stranka, 1951). In the early stages, asphalt modification using natural and synthetic polymers was more common in Europe than in the United States. When the high initial cost led the US agencies to be reluctant to adopt this technology, its improved life cycle cost made it popular among the contractors in Europe. Later with the development of new polymers and technologies, asphalt mixture modification became common in United States, as well as other countries (Roberts et al., 1996, Brule, 1996, Yildrim, 2007). Punith and Veeraragavan (2007) modified a paving grade asphalt binder using different proportions of reclaimed polythene from Low Density Poly-Ethylene (LDPE) carry bags shredded into size 22 mm. Asphalt concrete was prepared with the modified binder showed improved rutting resistance and temperature susceptibility compared to conventional mixtures and the authors suggested approximately 5%

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Use of Recycled Plastics in Eco-efficient Concrete

(by weight of asphalt binder) polythene content in asphalt concrete mixtures. Along with Styrene Butadiene Styrene (SBS), two other elastomeric polymers (a cohesive product designated as OL and a reactive elastomeric terpolymer designated as EL) € were also used by Ozen et al. (2008) for asphalt binder modification. The possible advantages of binders and pavements with commonly used polymers include increase in softening point, viscosity, ductility, fracture toughness, elastic modulus, flexural strength, creep resistance, reduction in embrittlement by aging, rut susceptibility and low temperature cracking, enhanced Marshall stability, resilient modulus, tensile strength and traction, and overall improvement in performance both in the laboratory and field (Alexander, 1968; Shim-Ton et al., 1980; Denning and Carswell, 1981; Kortschot and Woodhams, 1984; Jew et al., 1986; Carpenter and VanDam, 1987; Lee and Demirel, 1987, Shuler et al. 1987, Nahas et al., 1990; Choquet and Ista, 1992; Dhalaan et al., 1992; Tia et al., 1994; Zaman et al., 1995; Hossain et al., 1999; Palit et al., 2004; Hamzah et al., 2006). Along with different types of polymers, various natural and synthetic fibers also perform as a good modifier in asphalt concrete. Asphalt mixture being weak in tension, McDaniel (2015) indicated that the incorporation of suitable fibers having good tensile properties results in the increase of the tensile strength of the mixture. This is accomplished by the transfer of stresses to the strong fibers, reducing the stresses on the relatively weak asphalt mix. Fibers were used in pavements as a reinforcement and crack retarding material from the beginning of 19th century. Researchers reported the treatment of fiber in the early years in the United States including the usage of asbestos fiber in the 1920s and cotton fibers during 1930s (Maurer and Malasheskie, 1989; Serfass and Samanos, 1996; Al-Qadi et al., 2008; McDaniel, 2015). Based on the availability and suitability, different types of fibers including asbestos, metallic wire, etc., were used in asphalt mixtures (Kietzman, 1960, Tons and Krokosky, 1960). Maurer and Malasheskie (1989) used different fabrics and polyester fiber in pavements and observed that the fiber-reinforced asphalt concrete performed well and the method of random inclusion of fibers was cost-effective, easy to apply, and not causing any delay in construction compared to the other methods adopted in that study. Polyester and polypropylene fibers were observed to increase the fracture energy by 50%e100% when incorporated in asphalt mixtures (Jenq et al., 1993) and similar improvement was observed with nylon fibers also by Lee et al. (2005). Huang and White (1996) concluded that asphalt overlays modified with polypropylene fibers were stiffer and had increased fatigue life compared to conventional overlays. Polypropylene and aramid fibers improved the performance of asphalt mixture by controlling major pavement distresses like permanent deformation, fatigue cracking, and thermal cracking (Kaloush et al., 2010). Glass fibers were also used successfully in asphalt concrete in combination with polypropylene fibers (Abtahi et al., 2013). Jahromi and Khodaii (2008) obtained improvement in mechanical properties like fatigue characteristics, deformation, etc., with the usage of carbon fibers in asphalt mixture. Tapkin (2008) observed that polypropylene fibers stabilized asphalt mixtures possessed increased Marshall and fatigue properties. Xu et al. (2010) studied the reinforcing effects and mechanisms of polyester, polyacrylonitrile, lignin, and asbestos fibers in asphalt concrete mixtures under temperature and water effects, and observed that fibers resulted in

Replacement of stabilizers by recycling plastic in asphalt concrete

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significant improvement in the rutting resistance, fatigue life, and toughness of mixture.

14.2.2 Gap- and open-graded asphalt concrete While stabilizers are incorporated in dense-graded mixtures for additional benefits, the aggregate structure of gap-graded and open-graded mixtures (as mentioned in the section 14.1 Introduction), and higher asphalt content necessitates the use of a stabilizing additive in these mixtures. Drain down, defined as the portion of the mixture (fines and asphalt) that separates itself from the mixture and flows downward during the elevated temperatures of production, transportation, and placement is a common issue in these two types of mixtures. The presence of increased fine content in gap-graded mixtures like stone matrix asphalt (SMA) and high air void content in open-graded mixtures elevate the drain down. In order to control drain down within limits, stabilizing additives, normally fiber stabilizers, are recommended in these mixtures (Brown and Manglorkar, 1993; Brown et al., 1997; Mallick et al., 2000; Root, 2009). Stabilizer materials may also improve the mixture performance even though generally they are incorporated in order to control the mastic drain down. Suitable fibers are commonly used for this purpose, and AASHTO (1990) reported the wide use of cellulose and rock wool mineral fibers, and less often certain polymers, to control drain down of SMA mixtures in Europe. Mallick et al. (2000) recommend the use of stiffer asphalt binders with polymers for asphalt mixtures with more than 20% voids, especially under medium to high volume traffic conditions. From laboratory observations, Shadman and Ziari (2017) found that to keep the formidability of asphalt in porous mixtures, suitable additives should be used. Most commonly cellulose and mineral fibers are recommended as a drainage inhibitor in asphalt mixtures (Lin et al., 2004, Chiu and Lu, 2007, Ramzanpour and Mokhtari, 2011). Researchers have reported the usage of different cellulose and mineral fibers and polymers (0.2%e0.5%) in various trials conducted in the United States (Brown, 1992; Brown and Manglorkar, 1993; Rademaker, 1996; Brown et al., 1997). Other than conventional ones, researchers have also tried some other types of fibers, including those based on polymers, in SMA mixtures. West (1995) conducted drain down test with different stabilizers including, 0.3% (by weight of total mixture) of cellulose, nylon, polyester, polypropylene fibers, 0.4% slag wool fiber, 12% (by weight of binder) ground tyre rubber, 5% (by weight of binder) Novophalt, and 7% (by weight of binder) Vestoplast. Brown and Cooley (1999) used different stabilizing additives, namely, cellulose fibers, mineral fibers (slag wool and rock wool), and polymers (SBS and polyolefin), and observed that the stabilizer type has significant effect in the low, intermediate, and high temperature performance of SMA fine mortar. Along with cellulose and mineral fiber stabilizers, Schmiedlin and Bischoff (2002) used thermoplastic and elastomeric polymer stabilizers at low and high contents in SMA test sections. The authors reported that the mix temperature should be properly maintained, especially in the case of mixtures with polymers. Putman and Amirkhanian (2004) found that waste fibers, produced from manufacturing processes such as scrap tyre processing and automotive carpet manufacturing, are successful in SMA, by comparing their performance

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with conventional cellulose and other polyester fibers, which are specifically produced for use in HMA. SMA mixtures containing waste fibers showed similar resistance to permanent deformation and moisture susceptibility as that of conventional mixtures, and improved toughness. Xue et al. (2009) used polyester fiber extracted from recycled raw materials with 6.35 mm length, whereas Mahrez and Karim (2010) tried glass fiber in SMA with 80/100 penetration grade asphalt. Out of three natural fibers (coconut, oil palm fibers, and jute fibers), two waste fibers [fibers extracted from refrigerator door panels (FERP), and fibers extracted from old machinery belts [FEMB]), and an artificial fiber (glass fiber) used in SMA, Raghuram and Chowdary (2013) observed better drain down and performance characteristics for the jute fiber and FERP. Verhaeghe et al. (1994) reported that cellulose fibers provide greater stability and higher fatigue cracking resistance to open-graded mixtures. Punith et al. (2004), Punith et al. (2012), and Hassani et al. (2005) used cellulose fiber in open-graded mixtures and observed better results. Presence of fibers also resulted in the increased asphalt binder content, due to the absorption of binder by fiber particles, leading to improved mixture durability. Asphalt binders subjected to suitable modification can also prevent drain down in gap- and open-graded mixtures without any stabilizer, in addition to enhancing the mixture performance. Polymer-modified asphalts (PMA) are considered to provide additional resistance to bleeding, taking out some of the risk associated with high binder contents (Stuart et al., 2001; Shukla and Jain, 1989), and this prompted researchers to use different types of PMA in these mixtures. The most commonly used PMA type in SMA is with an elastomeric polymer SBS (Allen, 2006; Pasetto and Baldo, 2012; Cao and Liu, 2013). Brown and Cooley (1999) and Allen (2006) reported that SMA incorporating SBS PMA produced mixes that were more rut resistant with higher fatigue lives than SMA with unmodified binder. Researchers used SBS and other polymer-based PG binders including PG 70-28, 76-28, and 76-22 in SMA mixtures (Xie et al., 2005; Celaya and Haddock, 2006; Croteau et al., 2006, Vargas-Nordcbeck, 2007; Ishai et al., 2011) and in most of the cases, no other stabilizing additives were required to control drain down. Lin et al. (2004) used four types of commercially available PMA in SMA. The base binder was AC 20 and it was modified with two types of SBS polymers (linear and radial) in two proportions (3% and 6%). The authors used an approach of modified toughness for the evaluation and observed that PMA provided improved modified toughness, which indicates higher stiffness of SMA mixtures. Tayfur et al. (2007) observed least permanent deformation for SMA mix with SBS polymer, compared to mixtures with other polymer and fiber additives. Ghasemi and Marandi (2011) added different combinations of SBS polymer and recycled glass powder with penetration grade 60/70 asphalt and evaluated their advantages in SMA mixtures through Marshall stability, indirect tensile strength, and resilient modulus tests. The additives improved the performance and also provided better mechanical and physical characteristics of both binder and mixture. Hao et al. (2011) observed that the addition of SBS and Trinidad Lake Asphalt in SMA mixture satisfied the requirement, but a combination of both additives showed better performance. In an investigation, Al-Hadidy and Tan (2009) and Al-Hadidy and Yi-qiu (2010) compared SMA mixtures having SBS PMA and starch with control mixture.

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The SBS modified binder resulted in mixes having lesser drain down and increase in stability, Marshall Quotient, rut resistance, and resilient modulus, in comparison with the other mixtures. Mokhtari and Nejad (2013) also made similar observations for SMA with SBS PMA, compared to control mix and mix with FischereTropsch wax added asphalt. Ramzanpour and Mokhtari (2011) observed that the effect of Rheofalt (added in three dosages 5%, 10%, and 15%) in SMA with ACd60/70 asphalt was more than that of SBS (5% by weight of binder) in terms of moisture resistance, whereas SBS was more capable of improving the Marshall and rutting properties. An evaluation of control and SBS SMA mixtures through Marshall Quotient approach, repeated creep test, indirect tensile strength test, and Wheel tracking tests showed the higher performance for polymer added mixtures (Sengul et al., 2013). SBS content of 6.5% was used in PMA by Khodaii et al. (2013) and Haghshenas et al. (2015). Researchers have also tried to use rubber-modified asphalt binders in SMA with an aim to avoid stabilizing fibers and to improve the mix properties (Jain et al., 2004). Generally, the required rubber is collected from used tyres, and they were observed to be performing better than conventional SMAs (Sharma and Goyal, 2006). The natural rubber improves the rutting resistance and ductility, whereas the processed tyre rubber reduces reflective cracking and rutting in SMA mixtures (Ahmadinia et al., 2012). Tyre processing includes punching, splitting, chopping, grinding, and cutting tyres into shredded or “crumb” rubber, as well as chemically altering tyres. Mechanical sizing, including chopping and grinding, is generally used to prepare crumb rubber (CR) by reducing the size of the tyres. Additional grinding and screening operations are carried out to obtain the desirable size range. The rubber modified binder prepared by wet process (by adding crumb rubber in the asphalt as binder modifier) is commonly named as “Asphalt Rubber” (AR) (Epps, 1994, Hossain et al., 1995, Chesner et al., 1998). Better drain down and resistance to deformation were obtained by Kumar et al. (2007) for SMA mixtures with crumb rubberemodified asphalt (CRMA) compared to mixes with natural and patented fibers. Chiu and Lu (2007) modified conventional asphalt binder using coarse and fine-ground tyre rubber after grinding, in different proportions for preparing SMA mixture. It was observed that, only fine rubber could produce a suitable mixture satisfying all volumetric requirements, and it showed better moisture and rutting resistance than the conventional SMA with mineral fiber as stabilizing additive. Dong and Tan (2011) reported excellent performance of SMA pavement with AR, compared to the other two SMAs frequently used in China. Punith et al. (2012) also observed that PG 64-22 asphalt modified with CR helps the SMA mixtures to meet the drain down requirements. Oda et al. (2012) observed improved fatigue behavior for SMA mixtures with AR compared to fiber-added mixes. Peralta et al. (2012) tried to characterize the interactions between asphalt and rubber in the production of AR and a good correlation between the rheological properties of the materials and the physical changes during the process was observed. Sarang et al. (2014a, 2015) successfully used polymer-modified and CRMA binders to prepare SMA mixtures, without any stabilizing additives. Polymer-added asphalt binders produced better results in open-graded mixtures than the ones using fiber stabilizers (Punith et al. 2004, 2012; Suresha et al., 2009;

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Hassani et al., 2005). Sainton (1990) reported constant draining properties, better fatigue and rutting performance under heavy truck traffic and improved resistance to shear stress and weathering for porous asphalt concrete with modified binders. The mixes with modified asphalt possessed higher bulk specific gravity and reduced their air voids and permeability, and improved stone-to-stone contact, compared to the mixes with neat binder. The mixture with CRMA showed better resistance to aged abrasion losses, whereas PMA added mixtures showed higher tensile strength values. For preparing porous asphalt mixtures, along with neat binder PG 64-22, Lyons and Putman (2013) used a SBS modified binder with 3% SBS and two CR modified binder with 5% and 12% CR contents added to neat binder, and emphasized the necessity of stabilizer in those mixtures.

14.3

Addition of plastic in asphalt concrete

Even though polymer addition in asphalt mixtures is considered as a good option to improve pavement performance and life, the cost involved is a serious issue to be considered. Compared to the plain asphalt binder, polymer-modified asphalt binders are costlier and along with the increased energy requirement to prepare the HMAs. As a cost-cutting measure, waste or recycling plastic can be used for the same purpose, instead of virgin polymer. This has wide acceptance, not only due to the cost reduction, also due to its environmental friendliness. The plastic to be added is properly cleaned, and then shredded into sizes generally between 2.36 mm to 600 microns, as shown in Fig. 14.2. However, the method to add these plastics is an issue to be addressed.

Figure 14.2 Shredded waste plastic

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Incorporation of waste plastic in asphalt concrete is a hot topic of discussion even among the researchers. Normally plastics can be added in two methods, namely wet process and dry process.

14.3.1 Wet process In wet process, shredded plastics are directly added to the hot asphalt binder, and they are heated and mixed thoroughly to obtain a uniform mixture. Polymer-modified asphalt binders are prepared in this manner, generally with the help of a sophisticated equipment. High power stirring may be necessary to obtain a uniform blend with proper bonding between the constituent materials. If proper blending is not ensured, plastic materials may get separated from the binder and settle. In the preparation of large quantity of asphalt binder, this method can be adopted because in such cases required equipment can be used. But for small road projects, using sophisticated machineries to carry out proper blending may not be economical. Another issue associated with this process is regarding the shelf-life of the prepared asphalt binder. In many cases, storage stability will be less and the prepared binder may have to be used in a short span of time.

14.3.2 Dry process In the dry process, aggregates are heated as in the case of normal HMAs, and then the recycling plastic (preferably in shredded form) of required quantity is added and mixed properly until uniform mixing is ensured. In this case, the aggregates are coated with plastic, and then the asphalt binder is added to this blend, by maintaining the required temperatures. Indian Roads Congress (IRC) has issued a guideline for using waste plastic in hot asphalt mixes and suggested dry process, listing the following advantages (IRC SP 98, 2013). Plastic coating over stones is easy and the process improves the surface property and binding of aggregates. The temperature required is the same as the road laying temperature and no additional equipment is needed. The flexible films of all types of plastics can be used for this purpose. Still some researchers doubt the binding of asphalt with aggregates, since they are already coated with plastics.

14.4

Performance of asphalt concrete with plastics

Researchers modified asphalt concrete by adding recycling plastics in both wet and dry process methods. As reported by Little (1993), Felsinger Group from Austria conducted a study in 1989 and concluded that recycled low-density polyethylene (LDPE) can be added as a modifier to prepare asphalt binder with equal performance of binder produced by virgin polymer. Liang et al. (1993) observed that recycled polythene did not show much reduction in the quality of modified asphalt, but significant material cost saving was possible, when compared to the addition of virgin polymer. Addition of recycled or waste LDPE, high-density polyethylene (HDPE), plastics, and polyvinyl

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chloride (PVC) with asphalt improves the stability, tensile strength, stiffness, void characteristics, Marshall quotient, and moisture resistance of asphalt mixtures (Panda and Mazumdar, 2002; Hınıslıo glu and A gar, 2004; Bose et al., 2005; Rahman et al., 2013). Polacco et al. (2005) and Garcı’a-Morales et al. (2006) studied the rheology of asphalt binder modified with different recycled polymers and explained the compatibility of each polymer. Asphalt binder modified with shredded waste polythene caused increase in storage stability and resistance to aging, viscosity, degradation, and temperature susceptibility, compared to the unmodified binder, and this modified binder was observed to be improving the performance of asphalt mixture based on the results from dynamic creep test, indirect tensile test, resilient modulus test, and Hamburg wheel track test (Punith and Veeraragavan, 2007, 2010a, 2010b). Even though many research works have been carried out using wet process, comparatively limited studies are reported with the method of dry process for incorporation of waste polymer in asphalt mixtures. Zoorob and Suparma (2000) used recycled plastic pellets with 5.00e2.36 mm size in dense graded asphalt mixture as a replacement to the same sized aggregates. The mixture named as “plastiphalt,” was observed to have increased strength and improved deformation capacity. Hassani et al. (2005) replaced different percentages of 4.75e2.36 mm aggregates with polyethylene terephthalate (PET) granules in asphalt concrete and determined the volumetric and Marshall properties. Some researchers have observed that coating of shredded plastic over the hot aggregate (by dry process) provides the mixture better strength and performance than blending it with asphalt (wet process), and also it helps in the usage of higher quantity of polymers (Vasudevan et al., 2006, 2010, 2012; Ravi Shankar et al., 2013; Shankar et al., 2014). Awwad and Shbeeb (2007) have observed that the polymer coating over aggregates provides a rougher surface structure and better adhesion between aggregates and asphalt, and this improves the engineering properties of the mixture. Addition of waste plastics and waste polymeric packaging material using dry process was reported to be improving the impact value, abrasion value, and water absorption of aggregates (Sabina et al., 2009), along with increasing the stability, tensile strength, moisture susceptibility, and rut resistance thereby improving the pavement performance (Jain et al., 2011). A study conducted by Aslam and Rahman (2009) showed that most of the commonly used polymers do not cause any evolution of gas around 130e140 C and at this temperature, plastic will be in the molten form having well-binding property. IRC also suggests the usage of waste plastics shredded into size between 2.36 mm and 600 mm, by the dry process method (IRC SP 98, 2013). Little (1993) conducted experiments on two types of SMA mixtures with recycled LDPE additives, and they were observed to be performing better than mixes without polymer. Casey et al. (2008) modified asphalt binder by adding some commonly available recycled polymers in different proportions, to use in SMA mixes, and the binder and mixture performances were assessed. Punith et al. (2010) incorporated reclaimed polyethylene obtained from carry bags in SMA by blending with penetration grade 60/70 asphalt (5% by weight of asphalt) and also by shredding and mixing

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with aggregates (0.3% by weight of mixture). Both methods controlled the mixture drain down and performed better than conventional SMA with cellulose fiber additive. Incorporation of waste plastic bottles (PET) at various percentages (2%, 4%, 6%, 8% and 10% by weight of asphalt) in aggregates-asphalt blend was effective in retarding the drain down and improved mixture’s Marshall characteristics, stiffness, and resistance against permanent deformation (Ahmadinia et al., 2011, 2012). Similar observation was made by Moghaddam and Karim (2012) and Moghaddam et al. (2014) with the addition of waste PET flakes (at dosages 0.2%, 0.4%, 0.6%, 0.8%, and 1% by weight of aggregates), obtained from PET bottles, in SMA using dry process method. Sarang et al. (2014b, 2016) prepared SMA mixtures by adding 4%, 8%, 12%, and 16% (by weight of asphalt) of shredded waste plastics in dry process method to plain asphalt binder. Mixture with 8% plastic content performed well, and the results were comparable with the SMA mixture with polymer-modified binder.

14.5

Field investigations

Positive results obtained from the laboratory investigations, in terms of better strength and durability, by using recycling plastics in asphalt concrete, have given confidence to the contractors and agencies to use the technology in field. In Hong Kong, Wang et al. (2017) conducted studies on laboratory prepared asphalt binder samples, and SMA pavements constructed using neat asphalt and different combinations of PMA (30, 85 and 100 %) with neat asphalt, mainly to establish test methods to forensically check the type and quality of PMA. A study conducted in Switzerland on porous asphalt concrete using laboratory specimens and core samples collected from eight pavement sections showed that the mix type not made with PMA was the most water sensitive and the same had poor fatigue behaviour also (Poulikakos and Partl 2009, 2012). In India, different states had constructed roads with waste plastic added asphalt concrete mixtures, even before the release of the IRC guidelines, and after that many states started trying the same. A stretch in the city of Bengaluru, some stretches in the Tamil Nadu state, etc., laid in 2002, are some of the first plastic roads in India (Sapna, 2012; Sribala, 2016). For some stretches with plastic added asphalt concrete, laid during 2002, evaluation was done during 2007e08 period, and compared with a road without plastic (Central Pollution Control Board, 2008). The following parameters were examined for each road: the roughness of the pavement surface, the resistance offered by the pavement surface against skidding of vehicles, the pavement macrotexture for the geometrical deposition, the field density, the structural evaluation for the strength of the pavement, the gradation of the materials in the laid road, different tests on recovered bitumen, the condition of the road (cracks, raveling, potholes, rutting, corrugation edge break, etc.). From the study it was concluded that there was no pothole formation, rutting, or raveling for those roads after 5e6 years of construction. Another interesting development is “100% plastic road” idea by a company, and the same is planned in Rotterdam by the city council (Volkerwessels, 2015; Sims, 2015).

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14.6

Conclusion

Based on the study conducted, the following conclusions can be drawn: • • • • • • • •

Neat asphalt binders may not be sufficient to withstand the increasing traffic load; they have to be improvised using suitable stabilizer/modifier. Among different methods of stabilizing asphalt concrete mixtures, usage of different types of polymers (both rubbers and plastics) and natural and synthetic fibers is very common and effective. Stabilizers are generally a part of the mix design in gap-graded and open-graded mixtures in order to control drain down. Stabilizing additive may not be required if the asphalt binder used in gap- or open-graded mixture is polymer-modified one, or other suitable modifier is included. Most of the researchers observed that, recycling or waste plastic shows similar performance of virgin polymer in stabilizing the asphalt concrete and controlling drain down. Even though many researchers and some design standards consider dry process as the preferable method to incorporate waste plastic in asphalt concrete, the bonding between asphalt binder and aggregates is an issue to be addressed. A few field evaluations reportedly showed better performance of “plastic roads” compared to roads without plastics. Waste or recycling plastics can be recommended as an efficient stabilizer and modifier in asphalt concrete to enhance the mixture stability performance, since they are easily available, economic, and moreover have environmental benefits.

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The use of recycled plastic as partial replacement of bitumen in asphalt concrete

15

Marta Vila-Cortavitarte 1 , Pedro Lastra-Gonz
alez 1 , 2
Miguel Angel Calzada-Pérez , I. Indacoechea-Vega 1 1 GITECO Research Group, University of Cantabria, Av. de los Castros 44, Santander, Spain; 2 GCS Research Group, University of Cantabria, Av. de los Castros 44, Santander, Spain

15.1

Introduction

With more than 34 million kilometers around the globe (NCHRP, 2012), roads are the primary means of transportation worldwide and therefore play a crucial role in economy and social development. However, a significant amount of resources, including materials, energy, and manpower, is required not only for the construction of new pavements, but also for the preservation and renovation of the existing ones. In this sense, and according to the European Asphalt Pavement Association (EAPA), nearly 92% of the European road network is surfaced with asphalt, which is a pavement material composed of mineral aggregates bound with bitumen. Although the consumption of mineral aggregate in the asphalt mixture is considerable, about 950 kg/ton, it is the production of bitumen, a hydrocarbon material obtained from the refining of crude oil, which usually causes the higher environmental, energy, and economic repercussions. It should be noted that while it normally accounts for only 5% of the total asphalt mixture, it could represent more than 60% the material cost in the asphalt mixture. Hence, it is obvious that an ambitious approach to the efficient use of this material is required. On the other hand, the unique properties of plastic material, its versatility, and low cost are leading to a constant growing of its demand. Since a considerable amount of the produced plastic have a short life and are quickly discarded, the need to manage the generated waste increases in proportion to its consumption. According to PlasticsEurope (PlasticsEurope, 2017), at European level, from the almost 50 million tons of the plastic demand in 2016, around 27 million tons were collected, of which 30% were recycled, while the other 70% were burned to recover energy or sent to landfill. In order to improve these numbers, most European policies and directives encourage the “waste hierarchy,” which sets a priority order in the management of waste: reuse, recycling, recovery, and when no other option is possible, disposal. In this context, this chapter addresses the potential reduction of bitumen content by the addition of recycled plastic, namely polystyrene, to the asphalt mixture. Polystyrene (PS) is a thermoplastic material easily mouldable above its glass transition

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00015-3 Copyright © 2019 Elsevier Ltd. All rights reserved.

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temperature (w100
C), which is well below the common production temperature at the asphalt plant and high enough for the usual temperatures when the road infrastructure is in service (Desai and Vora, 2013). Thus, after a brief description of the role of bitumen in asphalt, a review of the different methods and research studies about the incorporation of polymers to bitumen and/or asphalt mixtures is presented. At the end of the chapter and leaning on these two precepts, namely reducing the amount of bitumen and recycling polystyrene, the idea of substituting part of the bitumen by waste polystyrene, emerged with the aim of mitigating the environmental and economic impacts related to the production of the former and the landfilling of the latter. The experimental approach, which has been applied to dense (AC) and porous (PA) mixtures, is described in detail including a full description of the asphalt mixtures’ mechanical performance and characteristics.

15.2

Bitumen’s role in asphalt

As mentioned before, the asphalt mixture is a composite material made of mineral aggregate, with different particle size distribution, and an element capable of binding all the aggregate fractions together. This binder role is played by bitumen. Thus, bitumen is a sticky, black, highly viscous substance with a semisolid appearance at room temperature. Bitumen can be found in natural deposits (natural bitumen) or can be obtained as a byproduct of the distillation of crude oil. The distillation process consists of separating the lighter, low-boiling point fraction of the crude oil from other high molecular weight and low volatile components such as bitumen. The quality and physicochemical properties of the bitumen will depend on the source and properties of the crude oil or blends of crude oil; so depending on the required specifications, the bitumen can be further processed by blending it with other refined products. Actually, several manufacturing methods are available to produce bitumen depending on the crude source and the processing capability of the refinery. Usually a combination of different processes is selected (Rahimi and Gentzis, 2007). From a chemical point of view, bitumen consists of aliphatic compounds, cyclic alkanes, aromatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), and heterocyclic compounds containing nitrogen, oxygen, sulfur atoms, and metals such as iron, nickel, or vanadium. Elementary analyses show that proportions of those compounds usually are: 79%e88% of carbon, 7%e13% of hydrogen, traces to 8% of sulfur, 2%e8% oxygen, 3% nitrogen, and parts per million of other compounds. The exact composition of bitumen depends both on the original crude composition complexity and on the production process used (International Agency for Research on Cancer, 2013). However, the role of the bitumen in the asphalt mixture is not limited to its binding function. Although its cohesion and adhesion properties confer it with the capacity to hold all the mixture components together, other intrinsic properties need to be considered. In this sense, bitumen is a thermoplastic material classified as viscoelastic due to the dependence of its mechanical properties to temperature, load level, and loading rate (Hofko et al., 2017; Costanzi and Cebon, 2015). Thus, the thermoplastic nature of the bitumen makes it fluid and workable at high temperatures to facilitate the coating

The use of recycled plastic as partial replacement of bitumen in asphalt concrete

329

of the aggregates during the production, but highly viscous at ambient conditions, when the traffic is active. In addition, during the passing of traffic, its semisolid character provides elasticity to the road, resulting in a more comfortable riding and less wearing on tyres than other monolithic materials. On the other hand, the fluid character at high temperatures, during the production and compaction, allows the adaptability of the material to the different road layouts, curves, and cambers. The interest in reducing the amount of bitumen is supported by two main issues associated with it. On the one hand, the high cost of this material and the high sensitivity to the volatility of the crude oil price. As can be seen in Table 15.1, bitumen can represent more than 60% of the overall asphalt mixture material cost even with contents in the range of 5% of the total composition. On the other hand, as explained before, bitumen can be obtained from the distillation of crude oil or found in natural deposits; therefore, it is a finite good whose reserves decrease with those of crude oil. Consequently, experts are pointing out to the necessity of reducing the use of these nonrenewable sources by other more environmental and cost-efficient alternatives. As in the case of costs, when analyzing the relative importance of bitumen in terms of GHG emissions and fossil fuel depletion, the production of bitumen produces two to three times more impact than aggregate production (Fig. 15.1). Due to the previously explained economic and environmental reasons, the substitution of bitumen by new materials while maintaining or improving the mechanical performance of the asphalt mixture is being investigated. Following this research line, this chapter deals with the possibility of replacing bitumen with polymeric waste, specifically recycled polystyrene.

15.3

Modification of asphalt mixtures with polymers

The inherent versatility of plastics has stimulated their massive use in different products and applications. However, this proliferation and the short life of these products are causing a pollution issue difficult to treat by the industry, government, and society. Table 15.1 Asphalt Mixtures Typical Costs AC-16 S

PA-16

Ophite

1155.56 V

32%

Limestone (including filler)

254.73 V

7%

Bitumen 50/70 PEN

2195.63 V

61%

Total

3605.92 V

100%

Ophite

1257.67

33%

Limestone

136.10

4%

Polymer-modified bitumen (PMB)

2381.96

63%

Total

3775.3

100%

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Use of Recycled Plastics in Eco-efficient Concrete

9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00

Climate change (Kg CO2 eq) Bitumen

Fossil depletion (Kg oil eq.)

Aggregate

Figure 15.1 GHG emissions and fossil depletion of 1 ton asphalt mixture only considering the production of the raw material (5% bitumen and 95% aggregates). Based on data from Eurobitume, 2012. The Bitumen Industry in Europe. URL http://www. eurobitume.eu/bitumen/industry/ (accessed 12.30.17) and Stripple, H., 2001. Life Cycle Assessment of Road. A Pilot Study for Inventory Analysis.

Thus, in Europe an average of 7.4 million tons (27.3%) of the collected plastics were sent to landfill, although there were member states whose landfill share exceeded 50% of the available treatments. Based on these numbers, it is clear that new solutions for plastic recycling are needed. In this sense, the investigation concerning the use of polymers in asphalt mixes grows with the need to reuse and recycle the plastic material, also supported by the fact that no toxic gas emissions are released at the production temperatures found in the asphalt plant (Desai and Vora, 2013). Concerning the approach to replace bitumen with polymers, it should be noted that the incorporation of different type of additives to the asphalt mixtures is a common practice when looking for improving the mechanical or environmental characteristics of the mixture or production process. The addition of these components is usually done by two different methods: dry or wet process (PG-3, 2017) (EAPA, 2015).

15.3.1

Polymer modification by wet way

“Wet way” or “wet method” refers to the modification of the bitumen by dispersing the additive into it. In this method, special blending equipment and the preprocessing of the additive, which needs to be finely ground to facilitate the interaction with the bitumen, are required. This process consumes time and energy and is limited to specific plants designed for this purpose. In these plants, a better control of the final product characteristics and consequently a more homogeneous mixture is achieved. The modification with polymers is a common practice within the bitumen industry (i.e., SBS, EVA, and CR). On the other hand, in this field, numerous studies have been developed to assess the potential use of recycled polymers to replace virgin

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materials. In this sense, the University College of Dublin (Casey et al., 2008) studied the modification of bitumen with recycled materials coming from the most consumed plastics in Ireland: high density polyethylene (HDPE), low density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), polyethylene terephthalate (PET), and acrylonitrile butadiene styrene (ABS). From these results, it was deduced that, among all the studied plastic waste, both types of polyethylene were the most suitable, since they improved the performance of conventional unmodified bitumen. However, they did not reach the performance level of bitumen modified by virgin polymers. In addition, several articles were found in which bitumen is modified by PE from household waste, specifically plastic bags, and where improvements concerning bitumen aging and static charges were observed (Attaelmanan et al., 2011; Punith and Veeraragavan, 2007). In the same line, other authors found increases in the resilient modulus, the water sensitivity index, and the fatigue resistance when tested over Marshall Specimens (Panda and Mazumdar, 2002). On the other hand, the use of polystyrene to modify bitumen by wet way has been much less developed due to detected problems in the storage stability and the compatibility with the bitumen (Jin et al., 2002). In spite of the numerous and positive research results, the use of waste polymers as bitumen modifiers is not widespread. This is probably due to the difficulties in the mixing process that become larger when it comes to the real-scale application (Ahmadinia et al., 2011). Furthermore, in some qualitative and generic studies, the polymer concentration in bitumen has been limited to 15% (w/w) in order to ensure that a correct dispersion is achieved (Desai and Vora, 2013). For example, in 2007, a bituminous mixture made of rubber from end-of-life tyres (ELT), another with polyethylene from plastic bags (PE) as a bitumen modifier, and one with rubber and PE modified were tested. The conclusion was that the lowest plastic deformation and the highest dynamic modulus were obtained by the mixture whose bitumen was modified only by PE and that the addition of rubber got worse plastic behavior in comparison with the reference mixture (Reyes Lizcano et al., 2007).

15.3.2 Addition by dry way “Dry way” or “dry method” is the process in which the additive is incorporated directly into the mixer as an aggregate, or depending on the asphalt plant, to the dryer to be mixed and heated with the aggregate. The aim of this method is to improve the performance of the asphalt mixture without using the more expensive polymer-modified bitumen. Unlike the wet method, no additional equipment or modification in the asphalt plant is needed and the production process remains the same. Therefore, the dry method results are simple, cheap, and accessible to any asphalt plant. Furthermore, with this process, polymer concentrations over 15% are possible which, if positive in terms of the asphalt mixture performance, would increase the economic and environmental efficiency. Despite the known benefits, the level of development of the dry process is lower comparing to the bitumen modification. However, the research is increasing in

332

Use of Recycled Plastics in Eco-efficient Concrete

recent years. Thus, in India, from 2002 to 2007, more than 1200 km of roads have been paved with asphalt mixtures modified with recycled polymers, namely PE, PP, and PS. In addition, the Indian Ministry of the Environmental and Forest carried out a thorough study on polymer modification of asphalt mixtures (Mauskar, 2008). In this project, polymers ground to 1 e4 mm were mixed with the hot aggregates at 150
Ce170
C before incorporating the bitumen. In 2013, a new study was performed with polymer waste concentrations between 0% and 18% w/w of the amount of bitumen. The dry way was followed by adding the polymer directly to the aggregates and an optimum concentration of 6% was found to increase the Marshall stability and the resistance to fatigue and plastic deformation (Shankar et al., 2013). Although the experience in India was promising, the evaluation of the technology in other climates and different regulatory conditions was needed. In this sense, the research carried out at University of Cantabria (Lastra-Gonz
alez et al., 2016) studied the influence in asphalt concrete of different polymer wastes, namely PS, PE, PP, and ELT-CR. The polymers that substituted part of the filler fraction were added via the dry process. Satisfactory results were obtained for all the evaluated polymers since all the mixtures incorporating polymer waste presented better resistance to plastic deformation and higher stiffness while maintaining the fatigue resilience. In addition, all of them met the technical requirements set out in the Spanish normative for their use in road construction both as wearing and base course.

15.4

Modification of asphalt mixtures with polystyrene

In this section, a research study in which waste polystyrene is used to replace bitumen via dry process is described in detail. Thus, the methodology followed, the results obtained, and its main conclusions are presented. This research emerges from the conclusions obtained in a previous work done by Lastra-Gonz
alez et al. (2016). In this study, the results suggested the possibility that part of the PS added to the asphalt mixture blended with the bitumen increasing the total bitumen content. Based on this idea, the new investigation focused on the design and characterization of dense and porous mixtures with different polystyrene and bitumen contents. In order to do so, firstly, the selection of the PS waste from the different types available was carried out. Polystyrene is a thermoplastic polymer obtained from the polymerization of styrene, which becomes viscous liquid above its glass transition temperature (w100
C). There are four different types of polystyrene: generalpurpose polystyrene (GPPS), high impact polystyrene (HIPS), expandable polystyrene (EPS), and extruded polystyrene (XPS). The GPPS, also known as crystal polystyrene, is transparent, rigid, and brittle. Unlike GPPS, HIPS is opaque and more resistant to impacts. Both of them are low cost and become viscous fluid at temperatures over 100
C. On the other hand, EPS and XPS are very low-density thermoplastic foam materials. Based on those characteristics, HIPS and GPPS were the selected PS to carry on the research.

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Once the additives were selected, the dosage of two different mixtures without adding the polymer was done (a dense AC-16S and a porous PA-16). These mixtures were used as references and were fully characterized according to the following European Standards: bituminous mixtures, material specification, asphalt concrete (EN-13108-1) (AENOR, 2008b), bulk density and air voids content (EN-12698-8), water sensitivity test (EN 12697-12) (AENOR, 2009), wheel tracking test (EN 12697-22) (AENOR, 2008a), compactibility test (EN 12697-10) (AENOR, 2007a), stiffness test (EN 12697-26) (AENOR, 2012a), and resistance to fatigue test (EN 12697-24) (AENOR, 2013). Afterwards, several experimental mixes were designed by keeping the same particle size distribution than the reference mixtures but replacing 1% of bitumen in the asphalt by the polystyrene. This amount corresponded to nearly 25% of the total amount of bitumen used by the reference mixes. The same methodology was followed for the three type of polystyrene selected. In addition, a new reference mixture was designed by reducing 1% of bitumen but without adding polystyrene, in order to evaluate the impact of this reduction. The characterization tests carried out on the reference mixes were repeated on the experimental asphalt mixtures. Based on the results obtained, the PS that provided the best mechanical performance to the asphalt mixtures was selected and the rest of the research was addressed to this material. Then, the process was repeated increasing the percentage of bitumen replaced to 2% w/w in mixture, meaning more than 48% percent of the total bitumen content. Again, mixtures in which 2% of bitumen was removed without adding PS were produced. At this step and as a consequence of disintegration problems found in some specimens, the particle loss of the samples was carried out according to the standard EN1269717 (AENOR, 2007b), in order to ensure that this level of bitumen replacement was possible without compromising the mixture integrity. It is important to mention that this test was carried not only for porous asphalt but for asphalt concrete mixtures as well although it is not a common test in these mixtures. Finally, the dynamic characterization of the most promising mixtures was carried out. Thus, the influence of replacing bitumen with polystyrene was evaluated in terms of asphalt mixture stiffness, fatigue resistance, and workability.

15.4.1 Methodology How this approach was pursued and the results achieved so far are contained in this section which is divided into the following subsections: materials, specimen preparation, laboratory tests and results, and discussion.

15.4.1.1 Materials and sample preparation The asphalt mixtures were obtained by mixing a continuous-dense (AC-16S) and a discontinuous-porous (PA-16) gradation of ophitic aggregates, limestone and filler with a 50/70 pen grade or polymer modified (PMB) bitumen for the dense and porous mixtures, respectively. In the case of the experimental mixtures, polystyrene has been added to replace a certain amount of bitumen.

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Ophite is an igneous rock formed by crystallization under the Earth surface under conditions of low pressure and moderate temperature. This material is typically produced by mining where it is crushed to the desired size. Due to its high resistance to fracture and polish, its use in wearing courses is quite extended. Here, ophitic aggregate with a particle size distribution between 2 and 16 mm (AENOR, 2012b) and density of 2.725 g/cm3 (EN 1097-6) was used in the coarse fraction. The material presented values of Los Angeles (EN 1097-2) and Flakiness Index (EN 933-3) of 15 and 8, respectively, as well as Polished Stone Value (EN 1097-8) of 56. Limestone, with a sand equivalent value of 78 and a density of 2.725 g/cm3, was used in the fine and filler fraction. The properties of the bitumen used are shown in Table 15.2. In this study, three different types of polystyrene, provided by the Technological Institute of Plastics (AIMPLAS, 2017), ISO 14040 (2006), have been initially tested (Fig. 15.2): impact polystyrene recycled from two different sources (HPS and HIPS) and general purpose polystyrene (GPPS). The three samples have been characterized in terms of their particle size distribution (EN ISO 1183-1:2004) and density (EN 933-2) and the results can be found in Tables 15.3 and 15.4 respectively.

Table 15.2 Bitumen Characteristics Test

Bitumen 50/70 PEN

Modified Bitumen PMB 45/80-65

Needle Penetration (25
C;100 g, 5 s) EN-1426 (mm/10)

57

45e80

Softening Point EN-1427

51.6

65

Fraass Breaking Point EN-12593 Elastic Recovery of Modified Bitumen (25
C) UNE-EN 13398

13

15

e

>70%

Figure 15.2 Polystyrene samples used. a, PS recycled from hangers (HPS); b, recycled polystyrene crystal (GPPS); c, recycled high impact polystyrene (HIPS).

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Table 15.3 Particle Size Distribution of PS Samples, 933-2 (% Pass) Sample/Sieve

8

5.6

4

HPS

100.0

92.1

42.5

GPPS

100.0

100.0

HIPS

100.0

100.0

2

1

0.5

0.063

3.2

0.7

0.2

0.0

99.9

0.1

0.1

0.1

0.0

100.0

40.3

0.2

0.2

0.1

Table 15.4 EN ISO 1183-1:2004 results

3

Density (g/cm )

HPS

GPPS

HIPS

0.890  0.16

1.048  0.083

1.024  0.076

For the manufacturing of the asphalt mixes at the laboratory, the following procedure was followed. Firstly, all the aggregate fractions dried and heated to 170
C are dumped into the mixer and blended for 1 min with the bitumen, previously heated to 155
C. Later, the filler is added into the drum (heated at 155
C) and all the components are mixed for 4 min. In the case of the experimental mixtures, the PS was added cold just after the coarse aggregate and was manually blended to achieve a homogenous distribution (see Fig. 15.3). After this prestep, the procedure remains the same. Once obtained, the asphalt mixture, specimens with different geometry were prepared. Thus, depending on the laboratory test to be performed, the following samples were produced: cylindrical Marshall specimens (101.6 mm diameter and 65 mm height), rotary compactor samples (150 mm diameter and 100 mm height), rectangular slabs (410 mm length, 260 mm wide, and 50 mm thick), and prismatic specimens (410 mm length, 60 mm wide and 60 mm thick).

Figure 15.3 Addition of PS by dry way.

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15.4.1.2 Characterization tests In order to evaluate the influence of the use of PS to reduce the bitumen content, the asphalt mixtures were assessed in terms of their density, air void, water sensitivity, permanent deformation, particle loss, easy of compaction, stiffness, and fatigue resistance. The laboratory tests were carried out according to European Standards. Bulk density and air void content (EN 12698-8) were done on four specimens of each manufactured mixture. This test helps the dosage of the reference mixture, which, according to European standards, should have a voids percentage between 4% and 6% in case of an AC-16. The experimental mixtures with polystyrene do not need to accomplish those standards but their resemblance is advisable. Water sensitivity test (EN 12697-12): the retained indirect tensile strength (ITS) is determined by comparing the dry and wet ITS. This test indicates the effect of water on the asphalt mixture performance. ITS was calculated using a conventional mechanic machine that registers the load that the specimens endure before break at 50 mm/min velocity. Table 15.5 shows the minimum value the mixture has to keep to accomplish this standard, meanwhile Fig. 15.4 shows the test development. Wheel tracking test (EN 12697-22). The resistance to plastic deformation of the asphalt mixture is determined by the wheel tracking test (Fig. 15.5). In this test, the track of the wheel after 2000 cycles at 60
C is recorded. Particle loss test (EN 12697-17). This test is carried out in the Los Angeles abrasion machine (Fig. 15.6) and is used to evaluate the integrity of the material in terms of particle loss. Although this test is addressed to porous asphalt, dense mixes were also tested. The objective was to analyze the potential aggregate-bitumen cohesion loss when PS replaced part of the bitumen. Table 15.5 Water sensitivity Standards Test

Mixture

ITSwet/ITSdry

Water Sensitivity (%)

AC

85

PA

85

Figure 15.4 Water sensitivity test.

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Figure 15.5 Wheel tracking test.

Figure 15.6 Particle loss test.

Compactibility test (EN 12697-10) (Fig. 15.7): this test is carried out on the gyratory compactor and aims to determine the influence of PS in the compaction process. Del Rio equation (Eq. (15.1)) was used to quantify test results. N N W X Wi 2paA X ¼ ¼ hi $Si m m m 1 1

(15.1)

where W (kJ) is the compaction energy, m (kg) is the mass, N is the number of cycles, a (rad) is the inclination angle of the cylindrical sample, A (m2) is the transverse specimen area, hi (m) is the specimen height in each cycle i and Si (kN/m2) is the shear stress measured in each cycle i. Stiffness test (EN 12697-26): the stiffness and phase angle were determined in a Zwick Z1000 universal machine at a controlled temperature of 20
C (Fig. 15.8). Frequencies ranges from 0.1 to 30 Hz were combined with a 50 microstrains constant deformation.

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Use of Recycled Plastics in Eco-efficient Concrete

Figure 15.7 Compactibility test.

Figure 15.8 Machine both for stiffness and fatigue tests.

Fatigue test (EN 12697-24): the four point bending test was carried out at 30 Hz and 20
C to determine the fatigue law of the asphalt mixtures. εðm=mÞ ¼ a$103 Nfb

(15.2)

where Nf is the number of loading cycles to fatigue, ε is the strain, and a and b are fatigue constants.

15.4.1.3 Life cycle assessment A life cycle assessment (LCA) has been performed to ensure the environmental soundness of the use of PS to reduce the amount of bitumen. Thus, the inputs and outputs related to 1 km road lane were quantified through a 20 years life cycle analysis. The

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PS is assumed limited to the wearing course. A cradle-to-grave study type and the stages of material production, road construction, maintenance, and end-of-life were selected for the analysis. For the material production, no environmental burdens were assigned to the PS except for those related to each pretreatment, namely sorting, crushing, and sieving. In addition, an impact/credit equal to the impact/credit associated to other potential recycling routes of PS was also included. To do so, the statistics from PlasticsEurope (2017) regarding the rate in Europe of plastic that is sent to landfill/recycled/energy recovered were used. The LCA has been performed following the overall framework provided by the international standard ISO 14044 (2006) including the goal and scope definition, the life cycle inventory analysis, and the life cycle impact assessment. For the latter, the ReCiPe 1.08 hierarchical characterization method, developed by the University of Leiden, was used to transform the resources consumed and the emissions detected during the inventory phase into end-point impacts (Fig. 15.9).

15.4.2 Results and discussions Taking into account both the different types of mixtures and laboratory tests considered, every result showed in this paper was divided in two subsections. Besides, it is important to mention that not only mixtures with substitution of bitumen by PS were dosed, but also some mixtures in which a percentage of bitumen was removed. These mixtures with bitumen deficiency were referred to as w/o 1% and w/o 2% when 1% and 2% of bitumen were removed, respectively, and were fabricated to evaluate how PS contributes to modify the mixture consistency.

15.4.2.1 Asphalt concrete The table below (Table 15.6) gathers the different dosages studied so far for asphalt concrete, AC-16. Raw materials Production

Net burden/credit of secondary materials

Use 29,7%

Primary raw materials (bitumen,aggregate)

Secondary material production (PS)

Evoided PS granulate (credit)

Road construction Use

Recycling

Maintenance

End of life RAP reuse

Figure 15.9 Life cycle assessment methodology test.

39,5% Energy recovery

Electricity (credit)

Thermal energy (credit)

30,8% Landfill

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Table 15.6 AC-16 Dosages Dosage of asphalt concrete Mixtures AC-16 (%) Materials

Reference

Ophite 16#8

33.9

Ophite 8#4

24.6

Ophite 4#2

8.0

Limestone 2#0

w/o 1% Bitumen

1% Polystyrene

2% Polystyrene

32.7

Limestone Filler

0.8

Bitumen/ Mixture

4.3

3.3

3.3

2.3

PS/Mixture

e

e

1.0

2.0

The substitution of 1% of bitumen in mixture by PS means the reduction of the 24% of the total amount of bitumen used in the mixture. At the beginning, this substitution was done using the three different PS samples (GPPS, HPS, and HIPS) and the three were compared with the reference mixture and a mixture in which bitumen reduction was done without adding polystyrene; the last mixture was manufactured in order to see if the addition of polystyrene makes any difference in the mixture performance. According to data presented in the research (Vila-Cortavitarte et al., 2018) there are not significant differences between the three mixtures in which bitumen was substituted (pvalue < .05); nevertheless, all of them registered when comparing them with the reference mixture. Experimental mixture presents less density and consequently a larger voids content, specifically 2.7% more voids than the reference mixture that has 5.1% of voids. According to water sensitivity test there were not differences between reference mixture and experimental mixtures presenting all of them above 100% of conserved resistance. Bigger differences appeared during the rutting test where, as represented in Fig 15.10, the rut slope was reduced between 40% and

% Slope in respect the reference mixture value

160 140 SIN 1%

120 100 80

REF

60 1% GPPS 40 20

1% HIPS 1% HPS

0

Figure 15.10 Slope percentage in respect of the reference mixture value.

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341

60% in comparison with the reference mixture, so the mixture became more rigid by the addition of a fraction of polystyrene instead of part of the bitumen in spite of the higher percentage of voids. Notice, also in Fig. 15.10, that the larger slope reduction was achieved in HPS mixture, so this specific PS sample was the selected to keep on the study of the following experimental mixtures. Then, the substitution of bitumen by PS was done in 2% of mixture what is about 48% of the total amount of bitumen in mixtures. In those specimens, the voids percentage was 6% more than in the regular mixtures. In water sensitivity test, the traction resistance was lower for both the wet specimen (36% lower than the reference mixture resistance) and the dry specimen (45% lower) and in this case the conserved resistance reached 84%. In the rutting test, the 2% substitution mixture had an excellent behavior against plastic deformations (see Fig. 15.10) similar to the results obtained for 1% PS substitution mixtures supporting the increase of the resistance against plastic deformation. However, a lack of cohesion was detected in some of the specimens, especially on the slabs corners which could be almost disaggregated by hand. In order to quantify particle loss percentage the Cantabro Test (EN 12697-17) is carried on. A not admissible particle percentage loss (about 45% of the specimen mass) was registered in 2% specimens so the dynamic characterization of such a percentage substitution was omitted. Nevertheless, this test was also performed to mixtures with 1% of PS to check their suitability; the mass loss was lower than 15% so it was considered acceptable, because this value is allowed by the standards established for porous asphalt mixtures, although this property should be studied more. The dynamic characterization of the mixtures was also included in the study of the HPS mixtures, firstly, by the compactibility test of the mixtures by rotating machine, as it can be seen in Fig. 15.11.

AC16 S ref

AC16 S 1%PS

7

Energy (KJ/kg)

6 5 4 3 2 1 0 2.00

2.10

2.20

Figure 15.11 Compactibility test results.

2.30 Density

2.40

2.50

2.60

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From this test it is concluded that to reach the same density, the energy required is directly proportional to the amount of polystyrene added; that is, the higher the percentage of polystyrene, the greater the energy needed to reach the same density. However, in order to obtain a sufficient resistance against traffic loads, it is not necessary to achieve densities comparable to the reference mixture in the PS-modified mixtures, so that the energy with which they are compacted may not have to be increased. This test, moreover, is consistent with the voids increase that the mixtures have experienced when incorporating polystyrene. Secondly, the dynamic module test was carried out. According to the data presented in Vila-Cortavitarte et al. (2018), it can be seen that the stiffness values are very similar, and that the phase angle of the PS mixture is slightly lower, which would denote a more elastic behavior of the mixture, although it obtained a value of P > .05 and, therefore, the differences were not significant from the statistical point of view. It can be concluded, as a result, that despite the voids difference and the incorporation of PS, the experimental mix does not vary its rigidity. Finally, using the Zwick Z100 hydraulic machine (see Fig. 15.8), the fatigue test was carried out, the results of which are shown below (Table 15.7). Where S0 is the initial tension and corresponds to the value of the tension after 100 cycles under the imposed deformation. The breaking criteria adopted supposes that the mixture is broken once a value of the tension equal to S0/2 is reached; that is to say, when the rigidity of the material is diminished by half. The cycle (N) in which this value is reached will be the break cycle. On the other hand, the value ε6 has been considered as representative of the resistance to fatigue of the material, being the deformation that presents for 106 cycles. The values of the S0 module are very similar, and match those obtained in the dynamic module test for the test frequency (30 Hz). Although the characteristic deformation of the mixture with PS is somewhat lower than the reference, from the statistical point of view there were not significant differences; so, the conclusion is that the mixture does not worsen its behavior to fatigue despite having replaced part of its dosage in bitumen for PS.

Table 15.7 Fatigue test results Results Test

Parameter

REF

1% HPS

EN 1269724. Part D

S0 (MPa)

6905

6540

Characteristic def.(ε6) (mm/m)

154.2

136.8

Fatigue line (ε) (m/m)

1.075∙103 N0.1405

2.138∙103 N0.1990

R2

0.9877

0.8107

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15.4.2.2 Porous asphalt Following the same methodology as in asphalt concrete mixture, a porous asphalt mixture was dosed as a reference and one experimental mixture, one with 1% less bitumen in mixture and another one in which this lack of bitumen was replaced by PS (see Table 15.8). In this case, the substitution of 2% of PS by polystyrene was discarded due to particle loss in previous results and the bitumen used was PMB 85-60/20, a polymer modified bitumen commonly used in porous asphalt mixtures. In spite of the high voids percentage of PA mixtures the addition of polystyrene causes, as in AC mixtures, a significant decrease of the mixture density and, consequently, a higher voids percentage. According to water sensitivity test, it seems the dry specimens are more susceptible to PS addition (15% less of traction resistance), meanwhile the wet specimens behave almost the same than the reference mixture. In PA-16, the study showed significant differences between the mixture without 1% of bitumen and the mixture with 1% of PS. It seems that the polymer, in this case, is providing a resistant factor, but that it does not cover the lack of resistance caused by the reduction of bitumen. Finally, in the Cantabro test of particle loss, we can see how the replacement of bitumen by PS does not reduce the cohesion of the mixture (Table 15.9).

15.4.2.3 Life cycle assessment As it can be seen in Fig. 15.12, results show that reducing the amount of bitumen by adding PS to the asphalt mixture did not significantly improve or worsen the Table 15.8 PA-16 mixture dosages Dosage of Porous Asphalt Mixtures, PA-16 (%) Materials

Reference

Ophite 16#8

49.1

Ophite 8#4

30.0

Ophite 4#2

5.4

Limestone 2#0

w/o 1% Bitumen

1% Polystyrene

12.6

Limestone Filler

2.9

Bitumen/Mixture

4.3

3.3

3.3

PS/Mixture

e

e

1.0

Table 15.9 Particle test results

Particle Test (%)

REF

w/o 1% Bitumen

1% HPS

19.4

22.4

28.8

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%

344

100 50

0 Damage to ecosystems diversity (species.yr) NO PS

Damage to resource availability ($) 10% PS

Damage to human health (daily)

24% PS

Figure 15.12 Life cycle assessment results.

environmental performance of the road life cycle in terms of damage to ecosystems, resource availability, or human health category impacts. Thus, asphalt mixes with better mechanical properties can be achieved without increasing the damage to the environment. On the other hand, if the notable improvement in the plastic deformation observed at laboratory level is assumed to influence the life expectancy of the road pavement, a simulation can be done to quantify the potential benefits for the environment. Fig. 15.12 depicts the simulation of the potential environmental impact reduction in terms of the damage to ecosystems, resource availability, and human health as the lifetime expectancy increases. If confirmed, environmental damage reductions up to 20% could be achieved with service life extensions of 25% (Fig. 15.13).

15.5

General Conclusions

The interest in reducing the bitumen content to reduce costs and environmental impacts has led to the search for new materials able to provide the characteristics and functions offered by the bitumen. Several laboratory and field research have

120

No PS - 0% life extension 10% PS - 5% life extension 10% PS - 15% life extension 10% PS - 25% life extension

10% PS - 0% life extension 10% PS - 10% life extension 10% PS - 20% life extension

% Damage

100 80 60 40 20 0 Damage to ecosystems diversity (species.yr)

Damage to resource availability ($)

Figure 15.13 Simulation of the environmental impacts reduction.

Damage to human health (daily)

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been carried out both by wet way and dry way concerning the polymer modification of bitumen and asphalt mixtures, respectively, the latter having achieved a great research interest in recent years. From the different plastic material evaluated in previous studies, some results suggested the possibility to use polystyrene to replace certain amount of bitumen. Based on these results, dense and porous asphalt mixtures have been designed which incorporate PS by dry way (1 or 2% w/w of the total asphalt mixture), reducing the bitumen content accordingly. Satisfactory results have been obtained when the bitumen was replaced by 1% of PS, achieving good mechanical performance and even increasing the resistance to the plastic deformation comparing to the reference mixtures. Now, field tests are needed to confirm these promising results. However, an unacceptable particle loss occurred when the bitumen was replaced by 2% of PS, so the optimum percentage of PS still needs to be found that ensures a proper cohesion in the mixture. In terms of costs, the current preprocessing of the PS results as expensive as the purchase of bitumen, although, unlike bitumen, the cost of recycled plastics does not depend on the ups and downs of crude oil price. In addition, when more technologies related with the use of plastics appear into the market, the increase in the demand will likely foster the optimization of the pretreatment processes (i.e., grinding and pelletizing) reducing their cost. Finally, it should also be noted that for the production of these mixtures, no initial investment is needed, since the procedure at the asphalt plant remains practically unchanged. This means concerning the environmental soundness of this approach, when using PS to modify the asphalt mixture and reduce the bitumen content, no significant differences on the evaluated category impacts have been found when compared with reference mixtures. Accordingly, asphalt mixtures with enhanced properties can be designed by adding PS without increasing the impact to the environment or increasing their initial cost.

15.6

Future lines of study

Based on the existing research and the results obtained, several gaps have been detected that need to be addressed in order to further develop the technology. • • • • •

Optimization of percentage of PS: to determine the percentage of PS that maximizes the mechanical performance of the asphalt mixture. The possibility to reduce the bitumen content in a lower rate than rate of PS added. Long-term performance: to evaluate the long-time performance of the PS modified mixture including ageing. Quantification of the service-life: to quantify the effect of the higher resistance to plastic deformation provided by the PS in the service life of the asphalt mixture and the road pavement. Different particle sizes: To evaluate the influence of the PS particle size in the interaction with the bitumen and aggregate and therefore in the mechanical performance of the asphalt mixtures. Plastic mix waste fraction: To analyze the potential of using plastic waste fractions with low recycling rate that are currently sent to landfill.

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References AENOR, 2013. Bituminous Mixtures. Test Methods for Hot Mix Asphalt. Part 24: Resistance to Fatigue. UNE-EN 12697-24. AENOR, 2012a. Bituminous Mixtures. Test Methods for Hot Mix Asphalt. Part 26: Stiffness. UNE-EN 12697-26. AENOR, 2012b. Tests for Geometrical Properties of Aggregates - Part 1: Determination of Particle Size Distribution - Sieving Method. UNE-EN 933-1. AENOR, 2012c. Tests for Mechanical and Physical Properties of Aggregates - Part 2: Methods for the Determination of Resistance to Fragmentation. UNE-EN 1097-2. AENOR, 2009. Bituminous Mixtures. Test Methods for Hot Mix Asphalt. Part 12. Determination of the Water Sensitivity of Bituminous Specimens. UNE-EN 12697-12. AENOR, 2008a. Bituminous Mixtures. Test Methods for Hot Mix Asphalt. Part 22. Wheel Tracking. UNE-EN 12697-22:2008þA1. AENOR, 2008b. Mezclas bituminosas. Especificaciones de materiales. Parte 1: Hormig
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altico. UNE-EN-13108-1. AENOR, 2007a. Bituminous Mixtures. Test Methods for Hot Mix Asphalt. Part 10: Compactibility. UNE-EN 12697-10:2003/AC. AENOR, 2007b. Bituminous Mixtures. Test Methods for Hot Mix Asphalt. Part 17: Particle Loss of Porous Asphalt Specimens. UNE-EN 12697-17:2006þA1. AIMPLAS, 2017. Technological Institute of Plastics. http://www.aimplas.es/.09/06. Ahmadinia, E., Zargar, M., Karim, M.R., Abdelaziz, M., Shafigh, P., 2011. Using waste plastic bottles as additive for stone mastic asphalt. Materials and Design 10, 4844e4849. Attaelmanan, M., Feng, C.P., AI, A., 2011. Laboratory evaluation of HMA with high density polyethylene as a modifier. Construction and Building Materials 5, 2764e2770. Casey, D., McNally, C., Gibney, A., Gilchrist, M.D., 2008. Development of a recycled polymer modified binder for use in stone mastic asphalt. Resources, Conservation and Recycling 10, 1167e1174. Costanzi, M., Cebon, D., 2015. Generalized phenomenological model for the viscoelasticity of bitumen. Journal of Engineering Mechanics 5. Desai, R.N., Vora, N.A., 2013. Use of plastic in bituminous concrete mixes. PARIPEX - Indian Journal of Research 2, 176e180. Direcci
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Lastra-Gonz
alez, P., Calzada-Pérez, M.A., Castro-Fresno, D., Vega-Zamanillo, A., Indacoechea-Vega, I., 2016. Comparative analysis of the performance of asphalt concretes modified by dry way with polymeric waste. Construction and Building Materials 112, 1133e1140. Mauskar, J.M., 2008. Performance evaluation of polymer coates bitumen built roads. Programme Objective Series 122, 1e40. National Cooperative Highway Research Program, NCHRP 430. Cost-effective and sustainable road slope stabilization and erosion control, 2012. Panda, M., Mazumdar, M., 2002. Utilization of Reclaimed Polyethylene in Bituminous Paving Mixes. American Society of Civil Engineers. PlasticsEurope, 2017. Association of Plastics Manufacturers. https://www.plasticseurope.org/ download_file/force/1055/181. Punith, V.S., Veeraragavan, A., 2007. Behavior of asphalt concrete mixtures with reclaimed polyethylene as additive. Journal of Materials in Civil Engineering 6, 500e507. Rahimi, P.M., Gentzis, T., 2007. The chemistry of bitumen and heavy oil processing. In: Hsu, C.S., Robinson, P.R. (Eds.), Practical Advances in Petroleum Processing. Springer, p. 149. Reyes Lizcano, F., Madrid Ahumada, M., Salas Callejas, S., 2007. Infraestructura Vial, vol. 17. Shankar, A.U.R., Koushik, K., Sarang, G., 2013. Performance studies on bituminous concrete mixes using waste plastics. Highway Research Journal 6, 1e11. Stripple, H., 2001. Life Cycle Assessment of Road, 2nd revised edition. In: A Pilot Study for Inventory Analysis, IVL Report B1210E. Swedish Environmental Research Institute, Gothenburg.
Indacoechea-Vega, I., 2018. Vila-Cortavitarte, M., Lastra-G
onzalez, P., Calzada-Pérez, M.A., Analysis of the influence of using recycled polystyrene as a substitute for bitumen in the behaviour of asphalt concrete mixtures. Journal of Cleaner Production 170, 1279e1287.

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Concrete reinforced with metalized plastic waste fibers

16

Ankur C. Bhogayata Department of Civil Engineering Marwadi Education Foundation’s Group of Institutions, Rajkot, India

16.1

Introduction

Plastic is one of the most durable modern materials utilized for numerous applications including construction activities (Plastics-the Facts, 2015). Increased usage of plastic in food packaging is also one of the modern sources of plastic usage. Food packaging is governed by metalized plastic sheets to store the food in hygienic condition for extended storage. The usage of metalized plastic has reduced the modern food packaging challenges on one hand and increased the hazardous environmental impacts on the other hand. In spite of the global awareness regarding recycling, reusing, and reducing of the usage of plastic wastes, the metalized plastic waste (MPW) is largely being a challenge to most of the countries (Plastic Waste in the Environment, 2011). The MPW are largely unfit for effective recycling or reuse and therefore are not treated by waste treatment plants and being dumped in the landfills. The utilization of the MPW in construction activities may be a novel and effective way of safe disposal of waste plastics.

16.2

Metalized postconsumer plastic wastes: challenges and issues for management

Thrown-away wrappers, sachets, pouches, packs, and flexible containers used in packaging solid, liquid, or suspensions of food are the direct and primary sources of MPW. It is reported that about 50% of total plastic used in packaging are used in food packaging (Plastics-the facts, 2015) and result in immediate waste on a single usage. Food wastes from houses, institutions, and public places contain about 10% of MPW of solid waste. MPW are present in municipal solid waste (MSW) in about 60% of plastic waste proportion (Hopewell et al., 2009). Nevertheless, overall quantum of MPW is not huge but the hazardous impacts of MPW on environment make them important and objectionable stuff for environmental safety. Compared to other waste plastics belonging to the PVC, PET, and PE resin types, MPWs have more severe and long-lasting impacts on surroundings. The reason for this is MPWs are unfit for recycling and largely dumped in landfill as a part of MSW (Understanding Plastic Films, 1997). Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00016-5 Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete

16.2.1

Reasons for rapid growth in generation of MPW

Metalized plastic extends following advantages to packaging activities over normal packaging plastics • • • •

Better moisture protection to the packaged food. Durable and extended packaged food life. Increases the shelf life for food packs. Good quality control and intact hygiene of stored food.

Above are some of the major reasons for extensive usage of metalized plastic in food packaging. Due to rapid growth in the consumption of packaged food by consumers, the waste generation is also rapidly increasing (Narayan, 2001).

16.2.2

Environmental concerns of MPWs

Following facts of MPWs make them hazardous to the environment • • • • •

Improved durability by metallization causes difficulty in natural degradation of the waste articles. Lighter weight makes MPW to float on water surfaces which eventually results in clogging of natural water drainage. MPWs are highly nonreactive to chemical reactions. This increases prolonged presence of particles of MPWs in land and water and air mediums. MPWs gets accumulated and spread over the landscapes adversely affecting the fertility of soils. As MPWs are not recyclable effectively (Understanding plastic films, 1997), the repeated usage of base material is not possible. Therefore, constant usage of new raw material is required to produce metalized plastics. This adds into the emission of greenhouse gases and more usage of raw material.

16.3

Feasibility of MPW in concrete: outcomes from pilot studies

The feasibility of usage of MPW in concrete was decided based on experimental investigations. The parameters namely size, shape, form, and quantity of MPW were in center of explorations. The obvious form was the fibers rendered from the MPW as the waste was in form of flat thin sheets as shown in Fig. 16.1. Along with the MPW parameters, the concrete constituents were also included in the variables with respect to the water-to-cement ratio. Therefore the mixes are prepared by 0.45, 0.55, and 0.65 water-to-cement ratio. The fibers are shredded into short, medium, and long length at a constant thickness and constant average width. The quantity of MPW fibers were taken as 0%e2% at an increment of 0.5% by volume of concrete mix. Table 16.1 shows the concrete mix proportions and Table 16.2 shows the general properties of MPW.

Concrete reinforced with metalized plastic waste fibers

(a)

351

(b)

Raw form of MPW

(c)

Shredding of MPW

(d)

Type A MPW–5 mm

(e)

Type B MPW–10 mm

Type C MPW–20 mm

Figure 16.1 MPW fibers: process of preparation of fibers from the sheets.

16.3.1 Materials and test specimens Ordinary Portland Cement (OPC grade 53) manufactured by the Ultratech cement company from Gujarat, having a specific gravity of 3.15 g/cm3, was used. Locally available 20 and 10-mm sized aggregates from around the Rajkot city area were used as coarse aggregates. Sand from the banks of Aaji River near Rajkot was used as fine aggregate. The specific gravity of coarse and fine aggregates was 2.71 and 2.63 with 0.5% and 0.78% water absorption, respectively. The fineness modulus of coarse aggregates was 4.76, and for fine aggregates it was 2.99.

16.3.2 Metalized plastic waste fibers Metalized plastic used by food packaging industries was obtained from a plastic packaging industrial unit at Rajkot city. Plastic films made by polypropylene (PP) consisting metallization treatment were shredded into fibers. As shown in Fig. 16.1, mechanical shredding of metalized films was carried out to produce fibers of varying lengths: 5, 10, and 20 mm at a constant 1 mm width and designated as type A, type B, Table 16.1 Concrete mix proportions for 1 m3 volume Sr. no.

Mix

W/C ratio

Cement kg

Aggregates 20 mm kg

Aggregates 10 mm kg

Sand kg

Water kg

1

M1

0.45

438

669

446

638

197

2

M2

0.55

358

673

448

698

202

3

M3

0.65

303

667

445

753

206

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Use of Recycled Plastics in Eco-efficient Concrete

Table 16.2 General properties of MPW Sr. no.

Property/description

Unit

1

Resin type

Polypropylene

2

Name

Metalized polypropylene

3

Recycling code

5 (Polypropylene plastics)

4

Density

0.925 kg/cm3

5

Measured tensile strength

953.57 N/mm2

6

Elongation

10%e12%

7

Elastic modulus

450 N/mm2

8

Thickness

0.08 mm

and type C fibers, respectively. General and test properties of MPW are listed in Table 16.2. The fibers were mixed in varying fractions from 0% to 2% by volume of concrete mix. Concrete containing 0% of MPW was considered as reference concrete.

16.3.2.1 Tests on metalized plastic film The metalized plastic film was tested for obtaining tensile strength and relevant properties. As shown in Fig. 16.2, the film was rendered into a strip of 35 mm width and 300 mm length. The thickness measured was recorded as 0.08 mm. The breaking load was recorded as 2070 N. The relevant quantities are tabulated in Table 16.2. Table 16.1 shows proportions for the mixes prepared with varying water-to-cement ratio and the quantity of the conventional constituents. The MPW fibers were added in all mixes and totally 45 batches were prepared. Table 16.3 shows the details of the quantity and batch details. The primary aim of adding such fibers into the conventional concrete was to take dual advantage of plastic waste management and to study the changes of the fresh and strength properties of the composite. Tests were conducted to assess the role of fibers in crack resistance and tensile strength. The test specimens were prepared according to the specifications of IS: 1199-1959. Cubes and cylinders were the primary specimens utilized to evaluate the hardened concrete properties, namely compressive and splitting tensile strength, respectively. Moreover, the cylinders were utilized to obtain the response to the axial compression by establishing the stressestrain relationship and deformation characteristics. The details of specimens are listed in Table 16.4 and in Fig. 16.3. In the light of the present test results, the flexure tests on confined and unconfined concrete specimens to obtain the effect of MPW fibers on the flexure behavior of the members shall be carried out.

16.3.3

Tests on concrete specimens containing MPW fibers

Fresh behavior of concrete was assessed by conducting slump test. The cube specimens were tested to obtain compressive strength and cylinder specimens were

Concrete reinforced with metalized plastic waste fibers

(a)

Metalized film testing

353

(b)

Measurement of metalized film thickness

Figure 16.2 Tests on metalized plastic films.

evaluated for obtaining splitting tensile strength, as well as to establish the stresse strain relationship of concrete. Each batch and mix was evaluated to obtain the workability by slump test as shown in Fig. 16.4. The slump values were recorded and interpreted for obtaining response of varying concrete to the workability and consistency of the mix. The impact of addition of MPW on workability is discussed in the Section 17.4.1 of Chapter 17. The resistance to the axial compression and splitting action was recorded by conducting tests of compressive strength and splitting tensile strength on specimens as shown in Fig. 16.5. The maximum load value and failure pattern were recorded for each specimen. For each variation of MPW and water-to-cement ratio, the average of three test results were taken and considered as the response of the material. The tests were conducted in accordance with the IS: 516-1959 and IS: 5816-1999 for compressive and splitting tensile strength of specimens, respectively. All the specimens were water-cured for 28 days at an ambient temperature before the testing. The cylinders were subjected to the axial compression to obtain the stresse strain relationship conforming to the provisions of IS: 516-1959 as shown in Fig. 16.6. The stressestrain response by the concrete under axial compression was evaluated by studying the response of the specimens from the initial cracking up to the final failure of the specimen. The stress and corresponding strain values were recorded and presented in the form of a curve. The relationship exhibited the response of concrete due to addition of MPW to deformation before and after the final failure.

354

Table 16.3 Batch and MPW details Batch designation

MPW details Size

MPW type

Mix-1 w/c: 0.45

Mix-2 w/c: 0.55

Mix-3 w/c: 0.65

Volume fraction (%)

Weight in kg

Width in mm

1

Type-A

B1

B16

B31

0

e

e

B2

B17

B32

0.5

4.5

1

B3

B18

B33

1

9.2

B4

B19

B34

1.5

14

B5

B20

B35

2%

18.5

B6

B21

B36

0

e

e

B7

B22

B37

0.5

4.5

1 to 5

B8

B23

B38

1

9.2

B9

B24

B39

1.5

14

B10

B25

B40

2

18.5

B11

B26

B41

0

e

e

B12

B27

B42

0.5

4.5

1

B13

B28

B43

1

9.2

B14

B29

B44

1.5

14

B15

B30

B45

2

18.5

2

3

Type-B

Type-C

Length in mm

Thickness in mm e

5

0.08

e 10

0.08

e 20

0.08

Use of Recycled Plastics in Eco-efficient Concrete

Sr. No.

Concrete reinforced with metalized plastic waste fibers

355

Table 16.4 Specimen details for the tests on hardened concrete Dimensions in mm

Sr. no.

Test

Specimen

L

B

H or D

Total specimens

1

Compressive strength

Cube

150

150

150

135

2

Splitting tensile strength

Cylinder

e

150

300

135

3

Stressestrain relationship

Cylinder

e

150

300

45

Total

315

16.4

Role of MPW fibers in the workability and strength properties of conventional concrete

16.4.1 Effect of MPW fibers on concrete workability Workability of concrete was affected by both the test parameters namely the fraction and type of MPW. Concrete containing type A fibers showed slump reduction by 5%, 8%, 12%, and 16% for varying fractions from 0.5% to 2%. Concrete containing type B and type C reduced the slump relatively more than the former type in the range between 8%, 12%, and 15% up to 18% and 10%, 14%, 18%, and up to 25%, respectively. Fig. 16.7 shows the slump test results prepared with 0.45, water-to-cement ratio. The inclusion of macrofibers affects the viscosity of the mix. Fibers interrupt the consistency of the mix. In addition to conventional constituents of concrete, fibers occupy a large proportion of cement paste due to more surface area. The presence of macrofibers obstructs the flow as they form a mesh-like structure adhering to the fine and coarse particles of the mix and increase viscosity of the fresh mix. The author

Figure 16.3 Cube and cylinder molds before casting of concrete.

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Use of Recycled Plastics in Eco-efficient Concrete

(a)

(b)

Slump test – type-A fibers

Slump test – type-C fibers

Figure 16.4 Slump of concrete containing varying types of MPW fibers.

has observed similar results during one of the experimental investigations performed earlier (Bhogayata and Arora, 2017). From the test results, it was evident that the long-length fibers reduced the slump more than the short-length fibers at a given fraction. Increased fraction of long-

(a)

(b)

Compressive strength test

Figure 16.5 Strength tests on the specimens.

Splitting tensile strength test

Concrete reinforced with metalized plastic waste fibers

(a)

357

(b)

Test specimen

Specimen subjected to axial compression

Figure 16.6 Test setup to obtain the Stressestrain relationship of concrete.

length fibers contributed to the formation of localized entrapment of constituents, while the short-length fibers did not affect the slump alteration significantly at lower dosage namely up to 1% by volume of mix. Short-length fibers get mixed thoroughly with the other constituents and therefore a mesh-like structure was not formed as in the case of long-length fibers (Bhogayata et al., 2013). However, the slump reduced at a higher fraction of short-length fibers also.

Type A

Slump values in mm

125

Type B 100

Type C

75 50 25 0 0

0.5 1 1.5 MPW fraction in % by volume

2

Figure 16.7 Workability response of concrete with varying MPW fiber content (W/C 0.45).

358

16.4.2

Use of Recycled Plastics in Eco-efficient Concrete

Effect of MPW fibers on strength properties of hardened concrete

16.4.2.1 Compressive strength Compressive strength test results are shown in Fig. 16.8. Increased MPW fractions reduced compressive strength. However, it is to be noted that the reduction of strength was negligible up to fiber dosage of 1% by volume of the mix irrespective of the type of MPW. The results revealed that addition of MPW with small fractional value does not alter the compressive strength of mix significantly. Type A fibers showed 5% reduction in strength while type B and type C fibers reduced the strength by up to 9% and 11%, respectively, at 1% volume fraction of fibers. However, beyond 1% dosage of fibers, the rate of strength reduction was increased and varied with the type of MPW. Other researchers have noticed nearly a similar response for the inclusion of waste plastic fibers in concrete. However, it is noticed that the addition of macrofibers contributes to the ductile failure of concrete in compression (Bhogayata and Arora, 2017; Bhogayata et al., 2012; Bhogayata et al., 2013). Fig. 16.9 shows tested specimens with failure crack patterns exhibiting the involvement of the MPW fibers in holding the lumps of concrete.

16.4.2.2 Splitting tensile strength Splitting tensile strength was improved due to the addition of MPW. The resistance to the indirect tension was significantly affected by both the parameters, namely types and fraction of MPW. Type C fibers having longer length compared to other two types exhibited excellent crack resistance by reducing the propagation of microcracks. Gripping of long-length fibers with the constituents contributed to restricting crack development. Fig. 16.10 shows test results of splitting tensile strength. It can be observed that with increased dosage of MPW the resistance against splitting of specimens increases. The strength improved in the range of 2%e8%, 4%e9%, and 8%e14% for fiber types A, B, and C for varying dosage of 0.5%e1%, respectively. A noticeable increase of 21% and 33% in strength was observed in the case of type C fibers up to 1% dosage. Consecutively, type A and type B fibers showed improved strength at a reduced rate of increment at increased dosage beyond 1% volume fraction. Though the rate of strength improvement was reduced, the addition of MPW at a final dosage of 2% demonstrated more splitting strength compared to the reference concrete for all test conditions. Fig.16.11 shows crack that resulted under the effect of indirect tension applied on the specimen. Initial cracks were observed near to the top load platens and progressively propagated as wider cracks to the base. Failure patterns of specimens were studied carefully during the tests. The failure patterns can be one of the indications of the effects of fibers on the development of crack-resisting mechanism and changed nature of the material from brittle to ductile. Failure patterns observed on the specimens during the experiments reflected the contribution of macro MPW. For a given type of MPW, the initial fracture in

(a)

Compressive strength in N/mm2

Concrete reinforced with metalized plastic waste fibers

359

40 35 30 25

0% MPW

20

0.5% MPW

15

1% MPW

10

1.5% MPW 2% MPW

5 0 Type A

Type B

Type C

(b)

Compressive strength in N/mm2

MPW fiber type Compressive strength variation with MPW fibers (W/C 0.45) 40 35 30 25

0% MPW

20

0.5% MPW

15

1% MPW

10

1.5% MPW 2% MPW

5 0 Type A

Type B

Type C

MPW fiber type Compressive strength variation with MPW fibers (W/C 0.55)

Compressive strength in N/mm2

(c)

35 30 25 0% MPW

20

0.5% MPW 15

1% MPW

10

1.5% MPW 2% MPW

5 0 Type A

Type B

Type C

MPW fiber type Compressive strength variation with MPW fibers (W/C 0.65)

Figure 16.8 Effect of addition of MPW fibers on compressive strength of concrete.

360

Use of Recycled Plastics in Eco-efficient Concrete

(a)

(b)

Cube testing

Failure patterns (C fibers)

Figure 16.9 Cracking patterns of concrete specimens for axial compressive loading.

specimens was largely uniform and exhibited by linear microsurface cracks near load platens. Larger cracks developed in the direction parallel to load application at higher loads. An addition of MPW fibers in concrete exhibited improved ductility of the concrete compared to the reference concrete. The cracks developed at the final failure of a specimen containing MPW were less wide opened and accompanied by several micro and medium cracks as shown in Fig.16.11, exhibiting the ductile failure of the concrete compared to reference concrete.

16.5 16.5.1

Effect of MPW fibers on the deformation due to the axial compression by modified concrete Deformation due to axial compression

Cylinder specimens containing varying fractions of MPW fibers and varying water-tocement ratios were evaluated for stressestrain relationship at, before, and after the peak load values. The stressestrain values were recorded at every stage of loading and notable failure. The test results were represented as the graphical format for stress and corresponding strain values according to the guidelines of IS: 516-1959. The primary concern of the test was to study the deformation of the concrete containing MPW fibers with varying types and fractions due to the axial compressive loads. The response of concrete to the axial deformation was studied in two parts namely up to peak load application and post peak load application. Based on the pilot study and response of the concrete to the fresh and strength properties, it was concluded to carry out tests on the cylinder prepared with 0.45 water-to-cement ratio. The response of modified concrete with MPW fibers is shown in Fig. 16.12 in graphical representation for stresses to the corresponding strain values.

(a)

Splitting tensile strength N/mm2

Concrete reinforced with metalized plastic waste fibers

361

4 3.5 3 2.5

0% MPW 0.5% MPW

2

1% MPW

1.5

1.5% MPW

1

2% MPW

0.5 0 Type-A

Type-B

Type-C

(b)

Splitting tensile strength in N/mm2

MPW fiber type Splitting tensile strength of specimens with varying MPW fiber types (W/C 0.45) 4 3.5 3 2.5

0% MPW 0.5% MPW

2

1% MPW

1.5

1.5% MPW

1

2% MPW

0.5 0 Type-A

Type-B

Type-C

MPW fiber type

(c)

Splitting tensile strength in N/mm2

Splitting tensile strength of specimens with varying MPW fiber types (W/C 0.55)

4 3.5 3 2.5

0% MPW 0.5% MPW

2

1% MPW

1.5

1.5% MPW

1

2% MPW

0.5 0 Type-A

Type-B

Type-C

MPW fiber type Splitting tensile strength of specimens with varying MPW fiber types (W/C 0.65)

Figure 16.10 Relationship between splitting tensile strength and MPW fiber types.

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Use of Recycled Plastics in Eco-efficient Concrete

(a)

(b)

Test apparatus

Failure pattern of specimen

(c)

Tested specimen (A fibers)

Figure 16.11 Specimens subjected to splitting action by axial compression.

The test method explained in the code primarily dealing with the investigation of modulus of elasticity of concrete by extensometer was used to determine the strain values corresponding to the applied stress. The rate of loading was maintained at 140 kg/cm2 min. During the tests, the failure patterns, strain at different stages and values of final stress at failure strain, and peak stress values were obtained and recorded. Peak stress and deformation response at corresponding strain required uniform slow loading rate. Effects of addition of MPW on stressestrain relationship were assessed by observing the crack patterns and failure of the specimens. While performing the tests, it was observed that the reference concrete containing 0% MPW showed abrupt loss of strength and brittle failure beyond the peak stress values. Concrete containing MPW fibers showed controlled cracking at peak stress values and beyond the peak stress; the specimens exhibited comparatively less brittle response. Stress and corresponding strain values were recorded for each specimen and converted to normalized values and represented in the graphical format to obtain the stressestrain curve. It is to be noted that the term normalized value represents the numerical value obtained by dividing all the stress values by peak stress value and similarly dividing all the strain values by strain at peak stress value. This was necessary and found comfortable for representing the stressestrain relationship of concrete specimens subjected to axial compression. The graphical presentation of such normalized values is shown in Fig.16.13.

16.5.1.1 Observations Stressestrain curves provide information about the deformation characteristics of concrete containing varying MPW flakes fractions. Addition of MPW reduced the strength of concrete mix; however, it increased the splitting force resistance of the concrete with increased fraction up to 1%.

Concrete reinforced with metalized plastic waste fibers

(a)

363

35

Stress in N/mm2

30 25 0% MPW

20

0.5% MPW 15

1% MPW

10

1.5% MPW

5

2% MPW

0 0

0.002

0.004

0.006

Strain Axial stress-strain relationship of concrete containing MPW fibers-A type

(b)

35

Stress in N/mm2

30 25 0% MPW

20

0.5% MPW 15

1% MPW

10

1.5% MPW

5

2% MPW

0 0

0.002

0.004

0.006

0.008

Strain Axial stress-strain relationship of concrete containing MPW fibers-B type

(c)

35

Stress in N/mm2

30 25 0% MPW

20

0.5% MPW 15

1% MPW

10

1.5% MPW

5

2% MPW

0 0

0.002

0.004

0.006

0.008

Strain Axial stress-strain relationship of concrete containing MPW fibers-C type

Figure 16.12 Stressestrain values for the concrete containing MPW fibers.

364

Use of Recycled Plastics in Eco-efficient Concrete

Normalized stress values

1.2 1 0.8 0.6 0.4 0.2 0 0

0.5

1

1.5

2

Normalized strain values

Figure 16.13 Stressestrain curve for reference concrete with normalized values. • • • • •

Failure of specimens was changed due to the addition of MPW, specifically beyond the peak stress values. The strain values corresponding to the peak stresses increased with increase in the MPW flakes. However, the trend was observed till 1% of dosage. Beyond 1% of dosage, significant reduction in the stress was observed. The graphical presentation of stressestrain values showed that the curves with sharp peaks failed as brittle material while the curves with smooth peaks showed more controlled and less brittle failure of the material beyond the peak stressestrain values. It was observed while performing the experiments, that reference concrete failed catastrophically, after peak stress values. The failure response of modified concrete with MPW showed more control and failed less catastrophically.

Concrete prepared with 0.55 water-to-cement ratio exhibited reduced strength and reduced peak load values before failure of the specimens. It is observed as a general response of concrete to axial compression at higher water-to-cement ratio, concrete failure is more brittle. The patterns of cracks on the surfaces are wider and more inclined toward the upper portion of cylinders. Inclusion of MPW further extended this collapse mechanism and increased fraction of MPW resulted in more of brittle nature of the mixture. Concrete subjected to axial compression prepared with high water-to-cement ratio showed continuously reducing strength of concrete. Increased water content promotes free or excess water in the mix. This increases the voids in the concrete and reduces strength. Addition of MPW up to an extent occupied the air and water voids; however, they do not participate in the strength gaining mechanism and therefore do not improve the strength.

16.6

Advantages and limitations of the usage of MPW in concrete

The MPW can be found as an integral part of any MSW around the globe nowadays. The packaged food wrapped with MPW is in high demand, resulting in huge amount of

Concrete reinforced with metalized plastic waste fibers

365

plastic waste. Such wastes are largely dumped in the landfills and therefore require attention for management and safe disposal. From the experimental studies carried out on concrete containing varying types of MPW as fibers, following are the advantages and limitations that can be listed: • •

•

•

The MPW may be utilized as one of the concrete constituents in fibrous form. The dosage of MPW fibers namely 1% by volume of the concrete can be produced from around 2500 standard sized food packs used for packaging of snacks available in the food stores. Therefore the usage of MPW fibers with even lower dosage in concrete may be one of the ways of waste management of food packaging articles. Along with the advantages of usage of MPW in concrete, one of the primary challenges is the effective collection and separation of such specific wastes from general municipal or postconsumer wastes and keeping them clean from the dirt and other unwanted impurities. However, the challenges may be managed by employing some modern technologies capable of separating the metalized plastics from the mixed wastes. The utilization of MPW fibers in concrete was assessed based on some of the preliminary laboratory investigations in the present study. The author and his group would like to inspire the readers to take up the full-length investigations on the material properties and structural response of the members containing MPW fibers mixed into the conventional concrete.

16.7

Important findings and concluding remarks

Plastics irrespective of types and forms are difficult to completely dispose in nature. Recycling and reuse of plastic waste have not attained an acceptable rate of disposal. Therefore, innovative use of plastic wastes has become highly desirable. The present study dealt with the concept of producing green concrete by utilizing postconsumer MPW as one of the constituents for availing the dual benefit of reducing the energy needs for concrete manufacturing and alternative for waste plastic disposal. Plastics manufactured with varying resins exhibit different characteristics, properties, and responses when used in concrete. Use of MPW was required to be thoroughly examined for its impacts on concrete response and behavior for such reasons. It was a primary objective to investigate quantity of MPW to be added in conventional concrete with appropriate type. Following are the conclusions derived based on the experimental results: • •

•

Addition of MPW of type A and C with 1% by volume of the concrete mix dosage showed effective development in fresh and hardened properties of concrete for all test conditions. This can be an optimum dosage and type of MPW for usage in concrete. Inclusion of MPW improved the splitting resistance, compressive strength to an extent, and ductility beyond the peak stress at larger failure strain compared to the conventional concrete. Potential towards use of MPW was ensured from the experimental investigations for the nonstructural elements like plain cement concrete for leveling purpose and precast concrete members. Experimental investigations showed potential toward preparing green concrete with utilization of MPW in concrete, and the work may contribute to the database available on the specific area of utilization of waste plastics in concrete, nevertheless as a pilot study.

366

16.8

Use of Recycled Plastics in Eco-efficient Concrete

Future trends

The utilization of MPW in the conventional concrete showed a great potential from the sustainability perspective of the construction materials. The work presented here and other similar works by the same author have been accepted by many reputed international technical journals and publishing houses, a sign of the global acceptance of such works. The futuristic trends of utilization of MPW in concrete are seen as more promising with the construction materials and construction-oriented applications other than concrete. For example the author has also published the work on how to utilize MPW for the improvement of the stability of cohesionless soils. The study showed that the shear strength of the cohesionless soil can be improved to an extent at the given proportion of MPW and with specific length of fibers. Currently the author and his team are working on the extended area of study on the structural applications of concrete containing MPW fibers with full-scale test specimens. It would be interesting to note that the reinforced concrete members with rebars are being tested to obtain the structural response of beams, columns, and slabs containing MPW in varying fractions subjected to the primary structural actions. The author and his team are also exploring the use of MPW with alkali-activated concrete composites as a separate vertical of the research laboratory and about to publish the work in near future. It is of great importance to contribute to the global need of 3R strategy namely Recycle, Reuse and Reduce of the hazardous plastic wastes. The present and relevant studies have shown that reuse of discarded MPW can be safely and effectively utilized in concrete and similar materials. Cementitious mortars are the next immediate construction material under the focus of the author and his team, where the advantages of MPW fibers can be feasibly utilized.

16.9

Sources of further information and advice

The readers are advised to refer the research article (Bhogayata and Arora, 2017) published in the international journals for availing more information and database for their futuristic studies in the area of utilizing MPW in construction materials and applications.

References Bhogayata, A.C., Arora, N.K., August 15, 2017. Fresh and strength properties of concrete reinforced with metalized plastic waste fibers. Construction and Building Materials 146, 455e463. Bhogayata, A., Shah, K.D., Vyas, B.A., Arora, N.K., 2012. Feasibility of waste metalized polythene used as concrete constituent. International Journal of Engineering and Advanced Technology 1 (5), 205e207.

Concrete reinforced with metalized plastic waste fibers

367

Bhogayata, A., Shah, K.D., Arora, N.K., March 28, 2013. Strength properties of concrete containing post-consumer metalized plastic wastes. In: International Journal of Engineering Research and Technology, vol. 2. ESRSA Publications. No. 3 (March-2013)). Hopewell, J., Dvorak, R., Kosior, E., 2009. Plastics recycling: challenges and opportunities. Physiological Transactions of the Royal Society B 364, 2115e2126. Narayan, P., September 2001. Analyzing Plastic Waste Management in India Case Study of Polybags and Pet Bottles. Thesis, Master of Science in Environmental Management and Policy Lund, Sweden. A report of European Commission DG ENV by Bio intelligence service and AEA Energy and Environment Plastic Waste in the Environment, April 2011. https://ec.europa.eu/energy. “Plastics-the facts 2015: an analysis of European plastics production, demand and waste data”, A report by plastics Europe. Association of plastic manufacturers. www.plasticseurope.org. Understanding Plastic Films: It’s Uses, Benefits and Waste Management Options, 1997. A report prepared by Headly Pratt Consulting for American Plastic Council.

Further reading Bhogayata, A.C., Arora, N.K., Feb 10, 2018. Impact strength, permeability and chemical resistance of concrete reinforced with metalized plastic waste fibers. Construction and Building Materials 161, 254e266.

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Performance of concrete with PVC fibres

17

Senthil Kumar Kaliyavaradhan, Tung-Chai Ling Key Laboratory for Green and Advanced Civil Engineering Materials and Application Technology of Hunan Province, College of Civil Engineering, Hunan University, Changsha, China

17.1

Introduction

Fibres are introduced to enhance the tensile, flexural, and ductility characteristics of construction materials, mainly concrete. The use of fibre in concrete has seen momentous development in the past 50 years. The conventional concrete is generally weak in tension, has low tensile strain capacity, and is brittle in fracture, whereas, fibresreinforced concrete (FRC) containing fibrous materials enrich the tensile and bending performance of concrete. Also, the inclusion of fibres substantially increases the structural integrity and delays the crack propagation in the hardened concrete (postcracking effect) (Afroughsabet et al., 2016). The fibres are available in different materials (metallic, polymeric, or natural), various shapes and sizes, and are widely used for applications in both precasts and in-situ concrete construction (Afroughsabet et al., 2016). Furthermore, these fibres are readily available in the market for use in concrete applications. The characteristics and performances of FRC change with respect to binder content, fibres matrix interaction, fibres type, aspect ratio, density, concentration, orientation, and distribution in concrete (Zollo, 1997; Afroughsabet et al., 2016). Numerous research works have been conducted to study the characteristics and behavior of various fibres such as steel fibres, glass fibres, carbon fibres, synthetic fibres, natural fibres, and hybrid fibres in concrete (Torgal and Jalali, 2011; Afroughsabet et al., 2016; Sim~ oes et al., 2017; Safiuddin et al., 2018). It has been reported that the incorporation of these fibres in concrete could enhance significantly the fracture toughness, ductility, tensile strength, flexural strength, and resistance to impact and fatigue. Moreover, it reduces shrinkage cracks, controls the micro/macrocrack propagation due to internal and external stress, and improves the durability properties (Afroughsabet et al., 2016). In recent years, researchers have focused their interest toward the use of innovative fibres materials from recycling waste products for sustainable development. According to statistical data, the global generation of plastic waste from the year 1950e2017 was 8.3 billion metric tons and only 9% of this plastic waste was successfully recycled (Statitica, 2018). Extensive research works have been carried out on the utilization of plastic wastes in concrete applications, since it is available in abundance. The municipal plastic wastes such as polyethylene terephthalate (PET) from bottles, low-density polyethylene waste (LDPE), high-density polyethylene waste (HDPE)

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00017-7 Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete

from plastic bags used as aggregate or fibres, and polyvinyl chloride (PVC) from plastic pipes were used as aggregates in the production of mortar and concrete (Siddique et al., 2008; Saikia and Brito, 2012; Gu and Ozbakkaloglu, 2016; Sharma and Bansal, 2016). Recently, few researchers initiated the utilization of hazardous electronic plastic waste (e-waste) as aggregate or fibres in concrete applications (Wang and Meyer, 2012; Wang et al., 2012; Kumar and Baskar, 2014a,b, 2015a,b,c, 2018; Kumar et al., 2016, 2017, 2018). PVC cables/wires are widely used in electric wiring distribution systems in buildings, as well as electrical and electronic equipment. PVC cables are made from the polymerization of vinyl chloride with flame retardants and are broadly used for wire insulation and cable jackets because of their high resistance to fire and water. Usually, the waste PVC cables/wires are recycled for copper and aluminium in an informal manner; however, the outer sheathing of the cables made up of PVC is discarded as e-waste after recycling. Mostly, the discarded outer sheathing of PVC cable is burnt, which produces harmful gases during incineration. Hence, researchers are trying to find a solution to recycle PVC plastics from cables and wires into new products in order to reduce the hazardous burden on the environment. Recently, PVC cable from e-waste has been suggested to be recycled and used as fibres in concrete. Up to date, only few experimental investigations have been carried out to assess the feasibility of using this type of fibres in concrete (FRC) (Kurup and Kumar, 2017a,b; Nidhish and Arunima, 2017; Gull and Balasubramanian, 2014; Jose and Sangeetha, 2017; Basheer and Antony, 2017). Table 17.1 shows the various studies conducted by the researchers incorporating PVC fibres in concrete. In this chapter, the performance of concrete with PVC fibres will be presented. The effect of PVC fibres on the fresh and hardened properties of concrete, as well as its limitations and practical issues, will be discussed.

17.2

Performance of concrete with PVC fibres

The manufacturing process of PVC fibres from e-waste is shown in Fig. 17.1. First, the discarded electrical PVC cables are recycled for metals. After metal recovery, the outer sheaths of cables collected from recycling plants are cut to the desired shape and length by hands (Fig. 17.1). The hand-cut PVC fibres used in concrete by the researchers are shown in Fig. 17.2. The properties of PVC fibres reported in the literature are presented in Table 17.2. The PVC fibres were added to the mixture at 0.4%, 0.6%, 0.8%, 1.0% with respect to the weight of cement or at 0.05%, 0.10%, 0.15%, 0.20%, 0.25% with respect to the volume of concrete (Gull and Balasubramanian, 2014; Kurup and Kumar, 2017a,b; Nidhish and Arunima, 2017).

17.2.1

Effect of PVC fibres on fresh properties of concrete

17.2.1.1 Slump In general, the concrete containing PVC fibres have shown decreasing trend in slump value with the increase of fibres content (Fig. 17.3). However, this reduction was not significant. Kurup and Kumar (2017a) observed that the addition of 1% of PVC fibres

References

Slump

Gull and Balasubramanian (2014)

O

Kurup and Kumar (2017a)

O

Nidhish and Arunima (2017)

O

Fresh

O

Dry

Modulus of elasticity

UPV

O

O

O

O

O

Compaction factor

Compressive strength

Flexural strength

Split tensile strength

O

O

O

O

O

O

O

O

Density

O O

Shear strength

Performance of concrete with PVC fibres

Table 17.1 Fresh and hardened properties of concrete reported in the literature

O

Kurup and Kumar (2017b) Jose and Sangeetha (2017)

O

Basheer and Antony (2017)

O

O

371

372

Use of Recycled Plastics in Eco-efficient Concrete

Figure 17.1 Manufacturing process of PVC fibres from e-waste. (a) Discarded electrical PVC cables. (b) PVC fibres. (C) Outer sheath of PVC cables after metal recovery. (d) PVC outer sheath cut into small lengths.

(by weight of cement) to concrete decreases the slump value by approximately 6.67% (Fig. 17.3). Similarly, Nidhish and Arunima (2017) reported that the inclusion of 0.25% of PVC fibres to the volume of concrete decreases the slump value by about 8.5% (Fig. 17.3). In another study, Kurup and Kumar (2017a) examined the effects of silica powder (10% volume of cement) on PVC fibres concrete and found that the slump value decreased approximately by 10% at 1% of PVC fibre (Fig. 17.3). The authors attributed this slump loss to the random placement of fibres in concrete, as well as to the surface texture, size, and shape of PVC fibres (aspect ratio). Despite this reduction, the slump values of PVC fibresereinforced concrete are still within the required limit between 50 and 75 mm which is considered to be medium workability (Kurup and Kumar, 2017a; Nidhish and Arunima, 2017).

17.2.1.2 Compaction factor Compaction factor is a ratio of the weight of partially compacted concrete to the weight of fully compacted concrete, which is directly correlated with workability. Similar to slump, the compaction factor also decreased with the increase of PVC fibres content.

Performance of concrete with PVC fibres

373

Figure 17.2 PVC fibres from e-waste used in concrete by the researchers ((a) Gull and Balasubramanian, 2014; (b) Kurup and Kumar, 2017a; (c) Kurup and Kumar, 2017b; (d) Nidhish and Arunima, 2017).

Nidhish and Arunima (2017) observed a decrease of the compaction factor by about 6.67% at 0.25% fibre content (Fig. 17.4). The surface texture, volume percentage, and aspect ratio of fibres were influenced by the compaction factor value. The compaction factor value of a mixture up to 0.7 is considered as very low workability; however, the mixtures with PVC fibres have compaction factor above 0.8 which is equal to medium workability.

17.2.1.3 Fresh density/dry density Adding a small amount of PVC fibres in the concrete does not cause significant reduction in the fresh and dry density of PVC FRC as compared to the density of control concrete (Kurup and Kumar, 2017a) (Fig. 17.5). A contradictory finding was also reported in the work of Kurup and Kumar (2017a). The authors noticed that the addition of silica powder in PVC FRC resulted in a slight reduction in fresh and dry density due to its low unit weight (Fig. 17.5). Though the dry density of PVC FRC with silica powder is lower than normal concrete, it is still above the minimum dry density of 2000 kg/m3.

17.2.2 Effect of PVC fibres on hardened properties of concrete 17.2.2.1 Compressive strength Kurup and Kumar (2017a) found that the inclusion of PVC fibres in concrete could increase the compressive strength of concrete. They investigated the effect of PVC fibres on the compressive strength of concrete at different fibre contents (0.6%,

374

Table 17.2 Properties of PVC fiber reported in literature Thickness of insulation (mm)

Tensile strength (MPa)

Density (g/cm3)

Specific gravity

Length of PVC wire fiber (mm)

Width of PVC wire fiber (mm)

Aspect ratio

Gull and Balasubramanian, 2014

4

0.8

2.60

1.38

e

30, 40, 50

e

e

Kurup and Kumar, 2017a

4

0.8

17

e

1.40

35

1

35

Nidhish and Arunima, 2017

4

0.8

17

e

1.40

30

1

30

Kurup and Kumar, 2017b

4

0.8

17

e

1.40

35

1

35

Jose and Sangeetha, 2017

4

e

e

e

1.11

35

1

35

Basheer and Antony, 2017

4

e

e

e

e

30

e

e

References

Use of Recycled Plastics in Eco-efficient Concrete

Diameter of wire (mm)

Performance of concrete with PVC fibres

375

Kurup and Kumar, 2017a

70

Kurup and Kumar, 2017a (silica powder)

68

Nidhish and Arunima, 2017

66 Volume fraction Slump (mm)

64 62 Weight fraction 60 58 56 54 0.0

0.2

0.4

0.6

0.8

1.0

PVC fibre content (%)

Figure 17.3 Effect of PVC fibres on the slump of concrete.

0.8%, and 1.0%). It was reported that compressive strength of concrete increased drastically with the increase of PVC fibres content up to 0.8%. Compared to the control concrete, the maximum compressive strength of concrete with 0.8% PVC fibres increased by about 30.8%. A decrease in compressive strength was observed for fibre content above 0.8% (Fig. 17.6). In another study, Kurup and Kumar (2017a) observed similar trends with the incorporation of 10% silica powder as a substitution of cement in PVC FRC. At 0.8% PVC fibres, the maximum strength of PVC FRC with silica powder at the age of 28 days increased by 38.49% compared to the conventional concrete (Kurup and Kumar (2017a) (Fig. 17.6). Nidhish and Arunima (2017) reported 0.92 Nidhish and Arunima, 2017

0.913 0.91

Compaction factor

0.90

0.897

0.89 0.885 0.88 0.873 0.87 0.866 0.86 0.852

0.85 0.00

0.05

0.10

0.15

0.20

0.25

PVC fibre content (%)

Figure 17.4 Effect of PVC fibres on compaction factor of concrete.

0.30

376

Use of Recycled Plastics in Eco-efficient Concrete

2660 2640

Density (kg/m3)

2620 2600 Dry density Dry density (silica powder) Fresh density Fresh density (silica powder)

2580 2560 2540 2520 2500 2480 0.0

0.2

0.4

0.6

0.8

1.0

PVC fibre content (%)

Figure 17.5 Effect of PVC fibres on the density of concrete. Data sourced from Kurup, A.R., Kumar, K.S., 2017a. Novel fibrous concrete mixture made from recycled PVC fibres from electronic waste. Journal of Hazardous, Toxic, and Radioactive Waste 21 (2), 04016020. https://doi.org/10.1061/(ASCE)HZ.2153-5515.0000338.

that the compressive strength of concrete with 0.2% PVC fibres (by volume) increased by about 21.67% compared to control concrete (Fig. 17.6). Jose and Sangeetha (2017) investigated the effect of adding electronic plastic (e-plastic) as coarse aggregate along with PVC fibres in concrete. The compressive strength of concrete decreased (up to 55

Gull and Balasubramanian, 2014 Kurup and Kumar, 2017a Kurup and Kumar, 2017a (silica powder)

50 Compressive strength (MPa)

Nidhish and Arunima, 2017 Basheer and Antony, 2017

45

40

35

30 0.0

0.2

0.4 0.6 PVC fibre content (%)

0.8

1.0

Figure 17.6 Effect of PVC fibres on the compressive strength of concrete at the age of 28 days.

Performance of concrete with PVC fibres

377

16.46%) with addition of e-plastic as coarse aggregates, whereas, 15% of e-plastic with 0.8% of PVC fibres increased the strength by 8.8% (Jose and Sangeetha, 2017). Conflicting results were reported by Basheer and Antony (2017) that 0.8% PVC fibres in concrete showed a very low increment in compressive strength of about 1.34% compared to control concrete (Fig. 17.6). In general, the improvement of the compressive strength with the use of PVC fibres may be due to the texture, stiffness of fibres, as well as the excellent bond between the fibres and cement mortar (Kurup and Kumar, 2017a; Nidhish and Arunima, 2017). Another reason for the increment of the strength of concrete can be attributed to the active control of cracks growth and confining effect provided by the PVC fibres. Furthermore, the addition of silica powder increases the stiffness of the matrix which made the concrete withstand more loads when compared to conventional concrete (without fibres). On the other hand, Kurup and Kumar (2017a) reported that unlike conventional concrete, concrete with PVC fibres did not show the brittle failure and the conical shape pattern after the compressive strength test. The strength of concrete also depends on the length of fibres, aspect ratio, and volume of fibres used in the matrix. The length of fibres plays a predominant role in determining the performance of concrete. The strength of concrete using a different length of PVC fibres was analyzed by Gull and Balasubramanian (2014). The effect of different lengths of the PVC fibres on the strength of concrete is shown in Fig. 17.7. At 0.8% of PVC fibres content with a fibres length of 4 and 3 cm, the compressive strength was increased up to 5.98% and 6.98%, respectively. However, the 5 cm fibres length has shown a reduction in strength of about 0.29% compared to conventional concrete. It was observed that the PVC fibres with shorter length (3 cm) increased the compressive strength by up to 10.6% at 1% PVC fibres content (Fig. 17.7).

17.2.2.2 Flexural strength Kurup and Kumar (2017a), Nidhish and Arunima (2017), and Gull and Balasubramanian (2014) reported that the incorporation of PVC fibres in concrete increased the flexural strength of concrete (Fig. 17.8). Kurup and Kumar (2017a) reported that higher flexural strength values occur not only when concrete contains fibres but also when using silica powder. It can be seen in Fig. 17.8 that the flexural strength of concrete with 0.8% PVC fibres increased by about 9.11% as compared with control concrete. Similarly, the addition of silica powder in PVC FRC increased the flexural strength by about 16% compared to control concrete. The reason for this increase can be attributed to the fact that PVC fibres continue to carry the load after the cracking of the matrix which causes an increase in load carrying capacity of flexural specimens. Additionally, PVC fibres bridged the cracks and controlled the propagation of cracks which prevented brittle failure during testing (Kurup and Kumar, 2017a). Nidhish and Arunima (2017) observed that the increase of fibres content from 0% to 0.2% (by volume) increases the flexural strength gradually from 4.2 to 4.8 MPa. Beyond 0.2%, a decrease in the flexural strength is observed. The maximum percentage of the flexural strength increases up to 15.71% when using 0.2% PVC fibres in the mix (Fig. 17.8). Gull and

378

Use of Recycled Plastics in Eco-efficient Concrete 34

5 cm

33

Compressive strength (MPa)

4 cm 32

3 cm

31

Strength (MPa)

30 3.60

Split tensile strength (MPa)

3.55 3.50 3.45 3.40 7.0

Flexural strength (MPa)

6.5 6.0 5.5 5.0 4.5 0.0

0.2

0.4

0.6

0.8

1.0

PVC fibre content (%)

Figure 17.7 Effect of PVC fiber length on the various strengths of concrete at the age of 28 days. Data sourced from Gull, I., Balasubramanian, M., 2014. A new paradigm on experimental investigation of concrete for e-plastic waste management. International Journal of Engineering Trends and Technology 10 (4), 180e186.

Balasubramanian (2014) found that 3 cm can be considered as the optimum length of fibres that increases the flexural strength of about 55.5% with respect to conventional concrete. No significant change in the flexural strength values was observed for fibres with 4e5 cm in length (Fig. 17.7).

17.2.2.3 Split tensile strength Similar to compressive strength and flexural strength, the incorporation of PVC fibres increases the split tensile strength of concrete (Kurup and Kumar, 2017a; Nidhish and Arunima, 2017). Kurup and Kumar (2017a) reported that the split tensile strength of concrete containing 0.8% PVC fibres with and without silica powder increases up to 19.6% and 7.11%, respectively (Fig. 17.9). They also found that the tensile cylinder specimens did not split into two parts, because the PVC fibres bridge the cracks and exhibit the postcracking effect of FRC. Similarly, Nidhish and Arunima (2017) reported that the split tensile strength was enhanced by PVC fibres. The split tensile strength of the normal concrete was 3.51 MPa and increased to 3.93 MPa when the concrete mix contained up to 0.2% of fibres (by volume). However, a slight decrease was observed with a further increase in PVC fibres (Fig. 17.9). Jose and Sangeetha (2017) observed that the specimen with 15% e-plastic as coarse aggregates and

Performance of concrete with PVC fibres

8.0 7.5

379

Gull and Balasubramanian, 2014 Kurup and Kumar, 2017a Kurup and Kumar, 2017a (silica powder) Nidhish and Arunima, 2017

Flexural strength (MPa)

7.0 6.5 6.0 5.5 5.0 4.5 4.0 0.0

0.2

0.4

0.6

0.8

1.0

PVC fibre content (%)

Figure 17.8 Effect of PVC fibres on the flexural strength of concrete at the age of 28 days.

0.8% PVC fibres content (by weight) increased the tensile strength by 2.26% when compared with control concrete. Gull and Balasubramanian (2014) investigated the tensile strength of the specimen with a different length of the PVC fibres (Fig. 17.7), and the tensile strength with a length of 5 and 4 cm fibres (1% by weight) was found to be increased by 2.3% and 4.6%, respectively. However, for 3 cm fibres’s Gull and Balasubramanian, 2014

5.5

Kurup and Kumar, 2017a Kurup and Kumar, 2017a (silica powder)

Split tensile strength (MPa)

Nidhish and Arunima, 2017

5.0

4.5

4.0

3.5

0.0

0.2

0.4 0.6 PVC fibre content (%)

0.8

1.0

Figure 17.9 Effect of PVC fiber on the split tensile strength of concrete at the age of 28 days.

380

Use of Recycled Plastics in Eco-efficient Concrete

length, the tensile strength started increasing by 4.6% and began to decrease when the fibres content is increased from 0.6% to 1%. The decreasing trend of tensile strength is not significant; however, the reason for the decrease in strength is not clear and needs to be studied in the future.

17.2.2.4 Shear strength Kurup and Kumar (2017b) used L-shaped specimen suggested by Bairagi and Modhera (2001) to find the shear strength of concrete (Fig. 17.10). Some researchers have referred to this method to study the shear behavior of concrete (Sivaraja and Kandasamy, 2011; Kumar and Baskar, 2015c). Kurup and Kumar (2017b) found that the shear strength of concrete containing PVC fibres decreases with increase in the fibres content (Fig. 17.11). It was noticed that there was no significant reduction in shear strength when 0.6% of PVC fibres (by weight) is incorporated in concrete. Beyond 0.6% of PVC fibres, a decrease in the shear strength was observed. Since the shearing area of the L-shaped specimen is small; the quantity of fibres available might not be uniform. This caused the reduction in shear strength compared to other strengths. However, the shear strength values are within the acceptable range from 6 to 14 MPa (Kumar and Baskar, 2015c). It was observed that the presence of PVC fibres in shear specimens reduces the brittle failure and enhances the ductility than conventional concrete. Since the author used only one aspect ratio of PVC fibres for the shear study, the use of different sizes of PVC fibres is highly recommended to be explored in depth.

17.2.2.5 Modulus of elasticity The effect of the addition of PVC fibres on the modulus of elasticity of concrete is illustrated in Fig. 17.12. Kurup and Kumar (2017a) found that 0.8% PVC fibres content Applied load 150 110 ×10 mild steel plate 12 Φ mild steel bar

60

22 Φ mild steel bar

150

150 × 85 × 10 mild steel plate

90

L-shaped concrete specimen

90

60

All dimensions are in mm

Figure 17.10 Typical layout of shear strength test setup. Reprinted from Kumar, K.S., Baskar, K., 2015c. Shear strength of concrete with e-waste plastic, Proceedings of the Institution of Civil Engineers - Construction Materials 168 (2), 53e56, with permission from ICE Publishing.

Performance of concrete with PVC fibres

381

10.0

Shear strength (MPa)

9.5 9.0 8.5 8.0

7 day (Kurup and Kumar, 2017b) 28 day (Kurup and Kumar, 2017b)

7.5

7 day silica powder (Kurup and Kumar, 2017b) 28 day silica powder (Kurup and Kumar, 2017b)

7.0 6.5 0.0

0.2

0.4 0.6 PVC fibre content (%)

0.8

1.0

Figure 17.11 Effect of PVC fibres on the shear strength of concrete.

increases the maximum modulus of elasticity by about 40%. In the case of adding silica powder, 10% replacement for cement in PVC fibres concrete could increase the modulus of elasticity by about 49.7%. This is likely due to the improvement of the bond between the PVC fibres and the matrix. Beyond 0.8% of fibres content, the modulus of elasticity followed the decreasing trend (Fig. 17.12). Similarly, Nidhish and Arunima (2017) found that the modulus of elasticity values increased as PVC fibres content increased. The

Kurup and Kumar, 2017a

44

Kurup and Kumar, 2017a (silica powder)

Modulus of elasticity (GPa)

42

Nidhish and Arunima, 2017

40 38 36 34 32 30 28 0.0

0.2

0.4

0.6

0.8

1.0

PVC fibre content (%)

Figure 17.12 Effect of PVC fiber on the modulus of elasticity of concrete at the age of 28 days.

382

Use of Recycled Plastics in Eco-efficient Concrete

4.65

PVC fibre PVC fibre + silica powder

4.60

UPV (km/s)

4.55 4.50 4.45 4.40 4.35 0.0

0.2

0.4 0.6 PVC fibre content (%)

0.8

1.0

Figure 17.13 UPV versus PVC fiber content at the age of 28 days. Data sourced from Kurup, A.R., Kumar, K.S., 2017a. Novel fibrous concrete mixture made from recycled PVC fibres from electronic waste. Journal of Hazardous, Toxic, and Radioactive Waste 21 (2), 04016020. https://doi.org/10.1061/(ASCE)HZ.2153-5515.0000338.

mixes containing 0.2% (by volume) PVC fibres are the most effective, resulting in 16.91% increase in the modulus of elasticity than conventional concrete.

17.2.2.6 Ultrasonic pulse velocity test Ultrasonic pulse velocity (UPV) test is a nondestructive popular test used to examine the homogeneity, quality, cracks, cavities, and defects in concrete. Kurup and Kumar (2017a) evaluated the quality of concrete made with PVC fibres using UPV tester. It was reported that UPV of specimens decreased with the increase of PVC fibres content (Fig. 17.13). This decrease is not regarded as occurring because of the porosity or inside defects of concrete. In fact, the plastic has the capacity to absorb the pulse waves which can be the main reason for the decrease in UPV values of concrete (Kumar and Baskar, 2015a). According to BIS 13311-1:1992 (BIS, 1992), when the UPV values range between 3.5 and 4.5 km/s, the concrete is referred to as good concrete and when the values are above 4.5 km/s, the concrete is considered as that of superior quality. From Fig. 17.13, it is clearly shown that the addition of PVC fibres with or without silica powder in concrete did not affect the quality of concrete. The maximum and minimum UPV values of PVC fibres concrete is found to be in the range of 4.35e4.64 km/s.

Performance of concrete with PVC fibres

17.3

383

Conclusions

The recent advancements on concrete with PVC fibres are presented in this chapter. The fresh and hardened properties of concrete with PVC fibres were discussed in detail. The workability of concrete tends to decrease with the increase of PVC fibre content. The incorporation of PVC fibres also reduces the fresh and dry density, but this reduction is negligible. The compressive strength, flexural strength, split tensile strength, modulus of elasticity of concrete were increased with the addition of PVC fibres. There was a decrease in shear strength and UPV with the addition of PVC fibres. However, the reduction is not so prominent. The variations in fresh and hardened properties of PVC FRC is due mainly to the shape, size, quantity of fibres, distribution of fibres, test setup, and additional materials used along with PVC fibres. In several investigations, it was reported that the percentages of PVC fibres, either 0.8% (by weight of cement) or 0.2% (by volume of concrete), could improve the performance of concrete without any significant loss. Moreover, the PVC fibres bridged the crack and prevented brittle failure relative to normal concrete during testing. Overall, the information and discussion provided in this chapter will help to recycle the PVC waste efficiently and to find the suitable applications of PVC FRC in construction and to achieve the goal of sustainable development.

17.4

Future research perspective

The incorporation of PVC fibres in concrete without compromising the workability and strength criteria needs widespread research. Future research should focus on establishing a new method for mixing PVC fibre in concrete, defining a standard shape and size of PVC fibres, as well as an appropriate aspect ratio of PVC so that the properties of concrete could be optimized and controlled in the presence of PVC fibres. No literature is available on the other properties of concrete in the presence of PVC fibres like the durability, bonding properties, leaching characteristics, thermal properties, freezing and thaw resistance, microstructure, and fire behavior. Hence, further research in these areas could benefit the development of PVC fibres in concrete. In FRC production with recycled products, life cycle assessment (LCA) analysis is an important key aspect to be evaluated. The LCA research could be strengthened to develop a realworld application with PVC fibres, to optimize engineering performance, and to maximize the use of sustainable materials.

Acknowledgments The research funding from Hunan Provincial Key Research and Development Plan (2017WK2090) and the NSFC International (Regional) Cooperation and Exchange Program (51750110506) are gratefully acknowledged.

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References Afroughsabet, V., Biolzi, L., Ozbakkaloglu, T., 2016. High-performance fibres-reinforced concrete: a review. Journal of Materials Science 51 (14), 6517e6551. BIS (Bureau of Indian Standards), 1992. Indian Standard Non-Destructive Testing of ConcretedMethods of Test. Part 1 Ultrasonic Pulse Velocity. BIS 13311 (Part 1)-1992, New Delhi, India. Bairagi, N.K., Modhera, C.D., 2001. Shear strength reinforced concrete. Indian Concrete Institute Journal 1 (4), 47e52. Basheer, S., Antony, M., 2017. Experimental investigation of hybrid fibres reinforced concrete short columns using micro steel fibres and e-waste fibres. International Research Journal of Engineering and Technology 4 (4), 2073e2078. Gu, L., Ozbakkaloglu, T., 2016. Use of recycled plastics in concrete: a critical review. Waste Management 51, 19e42. Gull, I., Balasubramanian, M., 2014. A new paradigm on experimental investigation of concrete for e-plastic waste management. International Journal of Engineering Trends and Technology 10 (4), 180e186. Jose, A., Sangeetha, S., 2017. Effect of e- fibres addition on e-plastic incorporated concrete. International Journal of Advanced Research Innovations Ideas and Education 2 (4), 17e23. Kumar, K.S., Baskar, K., 2014a. Preliminary study on concrete with mixed electronic plastic waste. The international Reviewer 1 (1), 1e4. Kumar, K.S., Baskar, K., 2014b. Response surfaces for fresh and hardened properties of concrete with e-waste (HIPS). Journal of Waste Management 2014, 1e14. Kumar, K.S., Baskar, K., 2015a. Development of eco-friendly concrete incorporating recycled high-impact polystyrene from hazardous electronic waste. Journal of Hazardous, Toxic, and Radioactive Waste 04014042. https://doi.org/10.1061/(ASCE)HZ.2153e5515.0000265. Kumar, K.S., Baskar, K., 2015b. Recycling of e-plastic waste as a construction material in developing countries. Journal of Material Cycles and Waste Management 17 (4), 718e724. Kumar, K.S., Baskar, K., 2015c. Shear strength of concrete with e-waste plastic. Proceedings of the Institution of Civil Engineers - Construction Materials 168 (2), 53e56. Kumar, K.S., Gandhimathi, R., Baskar, K., 2016. Assessment of heavy metals in leachate of concrete made with E-waste plastic. Advances in civil engineering materials 5 (1), 256e262. Kurup, A.R., Kumar, K.S., 2017a. Novel fibrous concrete mixture made from recycled PVC fibres from electronic waste. Journal of Hazardous, Toxic, and Radioactive Waste 21 (2), 04016020. https://doi.org/10.1061/(ASCE)HZ.2153-5515.0000338. Kurup, A.R., Kumar, K.S., 2017b. Effect of recycled PVC fibres from electronic waste and silica powder on shear strength of concrete. Journal of Hazardous, Toxic, and Radioactive Waste 21 (3), 06017001e1-4. https://doi.org/10.1061/(ASCE) HZ.2153-5515.0000354. Kumar, K.S., Premalatha, P.V., Baskar, K., 2017. Evaluation of transport properties of concrete made with E-waste plastic. Journal of Testing and Evaluation 45 (5), 1849e1853. Kumar, K.S., Premalatha, P.V., Baskar, K., Pillai, G.S., Hameed, P.S., 2018. Assessment of radioactivity in concrete made with e-waste plastic. Journal of Testing and Evaluation 46 (2), 574e579. Kumar, K.S., Baskar, K., 2018. Effect of temperature and thermal shock on concrete containing hazardous electronic waste. Journal of Hazardous, Toxic, and Radioactive Waste 22 (2), 10, 1061/(ASCE)HZ.2153-5515.0000387.

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Nidhish, Arunima, S., 2017. Parametric study on fibrous concrete mixture made from e-waste PVC fibres. International Journal of Advanced Engineering Research and Development 4 (4), 149e158. Safiuddin., M., Yakhlaf, M., Soudki, K.A., 2018. Key mechanical properties and microstructure of carbon fibres reinforced self-consolidating concrete. Construction and Building Materials 164, 477e488. Saikia, N., Brito, J.D., 2012. Use of plastic waste as aggregate in cement mortar and concrete preparation: a review. Construction and Building Materials 34, 385e401. Sharma, R., Bansal, P.P., 2016. Use of different forms of waste plastic in concrete: a review. Journal of Cleaner Production 112 (1), 473e482. Siddique, R., Khatib, J., Kaur, I., 2008. Use of recycled plastic in concrete: a review. Waste Management 28 (10), 1835e1852. Sim~oes, T., Costa, H., Dias-da-Costa, D., Julio, E., 2017. Influence of fibres on the mechanical behaviour of fibres reinforced concrete matrixes. Construction and Building Materials 137, 548e556. Sivaraja, M., Kandasamy, S., 2011. Potential reuse of waste rice husk as fibres composites in concrete. Asian Journal of Civil Engineering 12 (2), 205e217. Statitica, 2018. Global Data on Plastic Production and Waste 1950-2017. Key Information of Plastic Production and Waste Globally between 1950 and 2017. https://www.statista.com/ statistics/728466/plastic-production-and-waste-worldwide-2017/. Torgal, F.P., Jalali, S., 2011. Natural Fiber Reinforced Concrete. Fibrous and Composite Materials for Civil Engineering Applications (A Volume in Woodhead Publishing Series in Textiles), pp. 154e167. Wang, R., Meyer, C., 2012. Performance of cement mortar made with recycled high impact polystyrene. Cement and Concrete Composites 34 (9), 975e981. Wang, R., Zhang, T., Wang, P., 2012. Waste printed circuit boards nonmetallic powder as admixture in cement mortar. Materials and Structures 45 (10), 1439e1445. Zollo, R.F., 1997. Fiber-reinforced concrete: an overview after 30 years of development. Cement and Concrete Composites 19 (2), 107e122.

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Recycled waste PET for sustainable fiber-reinforced concrete

18

Dora Foti Department of Civil Engineering Sciences and Architecture, Polytechnic University of Bari, Bari, Italy

18.1

Introduction

Concrete is a building material generally made with a mixture of water, cement, and aggregates. It can be considered an artificial conglomerate stone that possesses characteristics similar to those of a rock, including good compression strength and a poor strength to tensile stresses. The main defect of concrete is, in fact, its very low tensile strength, so low that it is often completely neglected in the calculus models. If concrete is today by far the most widely used building material in the world, it is thanks to reinforcements that make up for the poor tensile strength and brittle behavior of the concrete. Among these, steel reinforcement is often utilized, though fibers of different materials are also added to the cement matrix. Typically, they are metal fibers, in polymer, carbon, glass, or natural material. Such a concrete is called fiber-reinforced concrete (FRC). The properties of the composite concrete depend on the characteristics of the two matrices (cement and fibers), on their dosages, and in particular, on the geometry; the volumetric/weight percentage; and the mechanical characteristics of the fiber, the adherence between the fiber and the matrix of concrete; the mechanical characteristics of the matrices. The fibers may help to reduce the phenomenon of cracking and/ or significantly increase the energy absorbed in the process of fracture (toughness). The latter depends on several factors, including, for example, the aspect ratio (i.e., the ratio length/equivalent diameter of the fibers), the amount of fibers, their orientation and their spread within the cement matrix, the physical-mechanical characteristics of the latter. At a constant composition and dosage, the fibers with a greater aspect ratio are more effective. They are characterized, in fact, by a greater surface area that allows the strengthening of the bond with the concrete, reducing the risk of slipping. At the same time, however, the use of slender fibers, which are those with a higher aspect ratio, has also negative effects: it relates especially to the dispersion of fibers within the cement matrix, for which it is not possible to obtain a good dispersion (that instead would be desirable), and the workability of the fresh mix. These side effects generally lead to a limitation of the dose of slender fibers.

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00018-9 Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete

A further important aspect is the shape of the surface: if uneven or wavy it ensures a better adherence to the cement matrix and thus a greater strength to the pull out of the fibers subject to tensile stresses. In recent decades the research is focusing, in particular, on the reuse of waste plastics, thus trying to combine the advantages in terms of a better behavior of the concrete mixture with those derived from the recycling of large quantities of waste that would otherwise be destined to solve problems such as landfill, incineration. In many recent studies efforts have been made to analyze the possible utilizations for postconsumer and recycled plastic in the production of concrete to gain both economic and environmental benefits (Batayneh et al., 2007; Siddique et al., 2008). Among the plastic waste, polyethylene represents the largest fraction, followed by polyethylene terephthalate, most known as PET. It is obtained in large quantity from plastic bottles utilized as containers of beverages and mineral water. As result of the drastic increase in beverage consumption, the production of polyethylene terephthalate (PET) bottles has increased exponentially, also due to the favorable properties of this plastic, including low density, high resistance, weight ratio, high durability, ease of conception/fabrication, and low cost. Particular interest is growing, at present, in the reuse of fibers obtained from waste PET bottles. With the aim to reduce the waste and take profit from this material, some preliminary studies can be found in Silva et al. (2004). The good results in terms of mechanical characteristics push the research toward the utilization of this kind of fibers and the consequent performance of the new concrete mixture. The present study, in fact, mainly concerns the reuse of PET intended for many different applications and, especially, to make up the common bottles of water. Its good characteristics of adhesion with concrete make it more suitable to be used in the mix design of concrete compared to other polymers. In this chapter the state-of-the-art on the use of PET fibers for the reinforcement of concrete is presented. In previous studies such material has been used in different ways with or without manufacturing, the latter employing PET directly cut from waste bottles (Batayneh et al., 2007; Siddique et al., 2008; Soroushian et al., 2003; Silva et al., 2004). PET has been utilized as a binder, in the form of a resin, or as discrete fibers immersed in the mixture, and as continuous long strips arranged as grids to reinforce a concrete element. Discrete fibers have been considered with different shapes (strips or circular fibers) and different length (short and long strips) (Pereora de Oliveira et al., 2011; Foti, 2011, 2013b; Fraternali et al., 2013). In all the cases the goal is to describe how the use of PET fibers, added to concrete, can prevent, or at least limit, the presence of cracks. In particular, the adhesion between concrete and fibrous reinforcement and the global behavior of this fiber-reinforced concrete are observed in order to evaluate the possibility of investigation to deepen in the future. The last part of the present chapter describes the laboratory tests carried out on specimens of concrete reinforced with fibers obtained from waste water bottles made of PET, simply by cutting the bottles without any chemical process or manufacturing. The tests are part of extensive research on the use of PET as a reinforcing material in concrete structures and/or masonry (Foti, 2011, 2013b; Fraternali et al., 2013; Foti et al., 2012, 2013). The tests provide interesting results concerning the strength

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to static and dynamic loads (even impacting) of concrete reinforced with PET fibers, suggesting a possible use of this material especially for those applications frequently subject to shocks and impact forces, such as new jersey parapets, road and airport pavements, wharfs. The reinforcement with PET has the advantage of being less corrosive and less expensive than the reinforcement with metallic nets and grids of carbon steel or glass.

18.2

Use of PET in concrete

In the context of composite materials and in particular of those that make use of polymeric materials, in recent years the research on the use of PET has had a remarkable development. At the base of this choice there are various factors: the wide availability of this material at low cost, considering the large use made thereof, especially in the food industry; the physical and mechanical characteristics, which allow its use in place of the common steel, carbon, or glass fibers; the clear advantages in terms of durability resulting therefrom. To give a major impulse to the development of this solution there was also the problem of the disposal of waste products. PET, in fact, is one of the major components of the waste stream, thinking also of the countless uses that it has, not only in industry but also in our daily lives. For all these reasons, in the last 20 years there have been numerous studies on this topic, with the aim of highlighting the advantages and problems associated with the use of PET, and they provided the basis for further future research.

18.2.1 Mechanical properties of PET PET is a thermoplastic resin composed of phthalates forming part of the family of polyesters. It has a good tensile strength: the tensile stress at break is lower if compared to common steels bars for reinforced concrete but clearly higher than the very low tensile strength of concrete. For example, for a C25/30 concrete the characteristic tensile strength is 2.56 MPa, while for PET it can assume values around 85 MPa. Table 18.1 compares the mechanical characteristics of C25/30 and PET. The elongation at break is very high, like, in general, for many plastics; PET can in fact reach deformations up to 50%. The tensile modulus of elasticity of PET assumes values between 2800 and 3100 MPa lower than concrete. Table 18.1 Mechanical characteristics of C25/30 concrete and PET Tensile Strength

Elongation at Break

C25/ 30

2.56 MPa

e

PET

85 MPa

50%

Tensile Modulus of Elasticity Et

2800e3100 MPa

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Use of Recycled Plastics in Eco-efficient Concrete

PET could be utilized for many applications: it is used for the production of films, tubes, labels, and it is also widely exploited by the food industry for the production of bottles and containers, thanks to the compatibility for contact with food sanctioned by Directive 2000/72/EC of the European Commission. The numbers regarding the production of PET give an idea of how much it has spread, not only in industry but also in our daily lives; in 2006, the estimated annual production amounted to about 12.3 million tons. At the base of this enormous diffusion there is the wide range of uses for which this material is suitable and relatively cheap compared to other materials, even when compared with other plastics (Gu and Ozbakkaloglu, 2016). The same polyethylene (PE), which, for example, is used to make the caps of common bottles for water, has a higher cost than PET (which is used instead for the body of the bottle). This is the reason why there is a high quantity of waste PET for disposal that it would be better to find solutions for its recycling.

18.2.2

PET fibers

In recent years, numerous authors have focused on the use of PET fibers mostly dispersed within the concrete mix, giving rise to a wide range of studies concerning types of fibers that considerably vary in shape, size, surface roughness, and other characteristics. It has been found that in all the cases the percent volume of fiber added to the concrete has a direct influence on both the compressive and tensile strength of ecological concrete and that the fiber length has a direct influence on the tensile strength of ecological concrete (Lopes Pereira et al., 2017). As for the shape and the dimensions, most of these studies involve little fibers, generally with a width of a few millimeters and a length of some centimeters, uniformly distributed into the concrete matrix. The advantages in using discrete PET fibers reinforcement can be summarized as follows: they enable a restraint of the shrinkage microcracks, a delay of the propagation of these cracks within concrete, and a control of the crack widths. However, the main function carried out by the reinforcing fibers in PET resides in the so-called “sewing effect” that the fibers play against numerous microcracks, which naturally tend to form in the concrete also in the early stages of life of the structure. It is a result of the hygrometric shrinkage that tends to propagate and expand under the effect of the tensile stresses. The fibers thus reduce the amplitude of the cracks bridging the two edges, and this produces significant benefits: in particular, the strength and durability of the structure are improved. The structure, in fact, can take advantage of an additional contribution in the postcracking phase due to the increased ductility of FRC compared to an ordinary concrete; durability is improved because most of the phenomena that involve the degradation of concrete are favored and accentuated by the presence of cracks of a certain amplitude, and vice versa the cracks are noticeably less intense and wide when this amplitude is kept under control by the fibers. As anticipated, fibers may vary in many ways; an important element of variability is the slenderness, which directly influences both the adhesion between the fiber and the

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concrete and the workability of the mixture. Adhesion, in particular, is one of the fundamental problems of FRC with synthetic fibers, especially if it is compared with the good adherence that is normally afforded by common steel reinforcement. To increase this adhesion, it is a common practice to act on the roughness of the surface of the fibers: with this aim it is advantageous to use long strips of PET obtained from the common bottles for food use, the surface of which is often characterized by ripples that promote adhesion to the concrete matrix. As mentioned, however, also the conformation of the fibers, through their slenderness, can affect such adhesion. Slenderness is an important characteristic, since it affects the PET-concrete adherence and the fresh mixture workability. Highly slender fibers have high surface areas, which means that fibers adhere to concrete very well, with the effect of great pullout strength. This goes, however, to the detriment of workability, which is instead favored by the use of fibers with low slenderness that could be incorporated into the concrete mix more easily. In Chang et al. (2013), the PET fiber surface was modified by ambient-temperature plasma activation in order to increase the hydrophilicity of PET fibers. This treatment was followed by acrylic acid monomer grafting. The aim was to modify the surface of PET fibers in order to absorb heavy metals in wastewater. The material has been treated by changing some parameters of discharge, such as the power and the time of the treatment to optimize the properties of the surface. After this use in wastewaters, such material could be utilized in constructions. Another possible use of plasma could be to modify the surface of PET to improve the adherence of this material to concrete. One series of tests utilized 2.6% by volume of waste polypropylene fibers that had undergone a plasma treatment process. The composite exhibited lower flexural strength and toughness in comparison with the composite containing untreated fibers. This was possibly due to a reduction of a frictional bond when the fiber surfaces were cleaned by the plasma treatment. This finding was different from that on polyethylene fibers in which plasma treatment was found to enhance the bonding properties (Wu and Li, 1997). To maximize the economic benefits that accompany the use of a material destined for disposal in replacement of expensive steel bars, in most of the studies carried out on this subject the fibers used have been obtained with the material receiving no further treatment. In particular, a favorable solution is the use of the bottles commonly used commercially for mineral water. By cutting these bottles simply by hand it is possible to obtain fibers or strips of various shapes and sizes, exploiting also the surface roughness of such bottles, as previously said, to improve their adherence. In Pereora de Oliveira et al. (2011), Foti (2011, 2013b), and Fraternali et al. (2013) PET fibers to add to concrete have been obtained directly by cutting waste bottles; an increase of toughness of concrete was noticed, while the compressive strength did not change significantly. The workability of the concrete mix is still good if the fiber content is less than 1.5% in volume. The use of such fibers, directly derived from waste material, does not involve particular differences from the mechanical point of view compared to the fibers subjected to treatments of various types. PET fibers to add to concrete, in fact, could be used after a long and expensive extruding process from waste bottles, obtaining PET monofilaments that were cut in short fibers (Ochi et al., 2007). A series of tests

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Use of Recycled Plastics in Eco-efficient Concrete

were performed on these fibers to get the characteristics of mixibility, toughness, and adherence with the concrete mix, showing good results despite the high costs of manufacturing. In Kim et al. (2010), another kind of manufacturing is proposed, coating the surfaces of PET fibers with maleic anhydride grafted polypropylene. Also, an oxygen plasma treatment on the surface of PET fibers is also proposed in order to act as a microreinforcement of the cementitious mix. The result is a concrete mix with a stronger interfacial bonding due to the improvement in adhesion of the fibers’ surface (Trejbal et al., 2016). This improvement ends in a reduced crack opening with an increase in the durability of concrete too. Polypropylene and polyethylene fibers have also been added to concrete after a manufacturing process with the aim to get regular fibers of different length to evaluate the effects of their geometry and shape on the mechanical characteristics of the reinforced concrete (Silva et al., 2013). The influence of shape and dimension of PET fibers on the mechanical properties of concrete has been also investigated in Marthong and Sarma (2016) (Fig. 18.1). In any case an increase in the tensile strength is obtained. With regard to the chemical behavior, in a recent study (Fraternali et al., 2013) the alkali resistance of such PET fibers was evaluated, and the results obtained showed that this resistance only slightly differs from that of polypropylene fibers formed for extrusion from recycled PET. Later prismatic specimens of mortar (40  40  160 mm) were made. They were reinforced with fibers of 2 mm width and with a length that varies in the different specimens (11.3, 22.6, 35 mm). The analysis of the flexural behavior highlighted some interesting aspects. Firstly, the fiber-reinforced specimens were characterized by a reduction of the effort at the first crack with respect to the nonreinforced specimens (this effect reduced, however, becoming almost negligible for

(c)

(d)

1.20

1.50 °

45

°

1.13

3.36

Figure 18.1 Different shapes of PET fibers (Marthong and Sarma, 2016).

1.17

60

2.70 1.

0.70

1.13

8.00

1.00 1.30

50

1.50

1.20

0.

1.00

5.10

8.00

0.8

0

°

39

1.13

34

1.30

0.80 1.131.17

1.50

1.00

(b) 1.20

(a) 0.90

Recycled waste PET for sustainable fiber-reinforced concrete

3.5

UNR

R-PET 3.50

393

R-PET 1.13

R-PET 2.26

3 Load (kN)

2.5 2 1.5 1 0.5 0 0

1

2 Deflection (mm)

3

4

Figure 18.2 Load-deflection curves of tested mortars at 28 days (Fraternali et al., 2013).

fibers with greater length); but the most relevant result was the increase, in specimens with reinforcement in PET, of the ductility and, at the same time, the toughness, measured by the area under the load-deflection diagram (Fig. 18.2). Toughness is an important mechanical characteristic, as it is linked to the ability of a structure to absorb energy. In most researches on the reuse of the waste PET, fibers have been utilized as fiber reinforcement for concrete. Different kinds of fibers have been considered in these studies; different in shape, dimension, and slenderness (Fig. 18.3). The effect of their shape on concrete has been explored for short strips in Pereora de Oliveira et al. (2011) and in Silva et al. (2013); particularly in Silva et al. (2013), the fibers prevented the complete failure of the composite by holding the cement matrix together and transmitting the load previously supported with a slow crack process; instead during a bending test a sudden failure happened with a complete breaking of the specimen.

Figure 18.3 (a) Sample of short lamellar fibers (Foti, 2011); (b) Hand cutting of R-PET strips from postconsumer bottles. Top: exemplary of the examined bottles; center: macrostrips obtained through longitudinal cutting of the bottle; bottom final “R-PET 1.13” (left), “R-PET 2.26” (center), and “R-PET 3.50” (right) strips (Fraternali et al., 2011, 2013).

394

Use of Recycled Plastics in Eco-efficient Concrete

This study demonstrated an improvement of mechanical strength, or anyway a nonsignificant change associated with a strong mechanical interlocking between the fibers/cement matrix interfaces promoted by the section area, roughness, and fibrillation ability of fibers and the crack and microcrack distribution system provided by the uniform distribution and orientation of fibers in the direction opposite to the load stresses (Fig. 18.4). In this way the transfer and spread of the load stresses along fibers prevent cracks diffusion and lead to more resistant and ductile composites. So, that volume fraction of fibers, fiber orientation, and fiber length are critical factors that affect the performance of composites and their ductility. Greater fiber length and volume fractions promote better crack resistance in composites but decrease the workability. In particular, in Pereora de Oliveira et al. (2011) the PET fibers were obtained by mechanical cutting of the lateral sides of waste bottles; the fibers so obtained had dimensions approximately of 2 mm in width, 0.5 mm of thickness, and 35 mm of length. The fibers were added to the concrete mix with a volume percentage equal to 0%, 0.5%, 1.0%, and 1.5%; the best performance of concrete was reached with the last percentage especially regarding the toughness. Instead in Silva et al. (2013), the fiber volume fraction was equal to 2.9% higher than the previous case and the fibers were equal to 12, 24, and 30 mm in length. A different shape of strips, the circular ones, generates an increase of toughness higher than the short lamellar ones and the advantage of an increasing ductility of the composite by a higher dosage of fibers (Foti, 2011, 2013b) (Fig. 18.5). The closed form of the fiber, in fact, produces a better bonding inside the concrete of the two sides of the crack, and it determines a higher adherence if compared to short lamellar strips. In Fraternali et al. (2013) the effects of the presence of longer filaments were compared for cement-based mortar and cement-lime mortars. In the case of cementbased mortars, slight decreases of the first-crack strength due to the R-PET reinforcement was observed; on the contrary, in cement-lime mortar it increased, but the flexural toughness indexes and the residual strength were more effective than the

Figure 18.4 Orientation of fibers in cement matrix: 1dfibers perpendicular to load direction (bridging effect); 2dfibers in the same direction as the applied load (Silva et al., 2013).

Recycled waste PET for sustainable fiber-reinforced concrete

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Figure 18.5 Circular PET fibers (Foti, 2013b).

Figure 18.6 Cracking for bending at the centerline of the beam and detail of a roller support (Foti, 2013b).

cement-lime mortar. In (Foti, 2013b) longer strips composed of four overlapping layers of PET were considered. The results showed that the stresses are predominantly absorbed by concrete before the cracking; only in the postpeak phase the strips of PET absorbed the tensile stress, showing a ductile behavior (Fig. 18.6). In the same research 40-cm length specimens have been reinforced with half PET bottles having a ‘‘C’’ section directly cut, dividing by two parts along the length. It was noted that the specimen did not break completely thanks to the presence of PET half bottle and after a first vertical crack in the middle, the cracks propagated inclined of about 45 degrees, with a similar behavior of a beam subjected to bending test (Fig. 18.7) (Foti, 2013b). This kind of research, which utilizes long strips of PET from waste bottles was carried out also on structural element as plates (Foti and Paparella, 2014). The concrete

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Use of Recycled Plastics in Eco-efficient Concrete

Figure 18.7 Loading test on specimens with half-bottle fibers (Foti, 2013b).

Figure 18.8 Grid of PET bottle strips.

specimens were reinforced with a sort of grid of PET (Fig. 18.8). The test setup for the impact tests was inspired by those of Beckmann et al. (2012): the plate was positioned on a metallic frame and a load was dropped from a constant height. The results showed that the specimens reinforced with PET grids did not totally brake, as can been seen from the superficial cracks produced by the impact (Fig. 18.9). These grids, in fact, increased significantly the ductility of the plates. Another interesting aspect is the thermal conductivity of concrete reinforced with PET fibers. It was noticed that there is an increment in the thermal insulation of the concrete both adding pieces of different shapes of waste rubber of tires and/or plastic

Recycled waste PET for sustainable fiber-reinforced concrete

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Figure 18.9 Upper side of reinforced plate n. 1 after the impact (Foti and Paparella, 2014).

fibers (strip, square, and irregular) (Fraternali et al., 2011; Yesilata et al., 2009). The insulation performance increases by the 18.52% with the addition of square rubber or by a range of 10.27%e18.16% with PET (Rahmani et al., 2013). The latter data coincide more or less with those shown in Fraternali et al. (2011) where the decrease of thermal conductivity (k) is equal to 18%. Possible models for materials with no tensile strengthdlike concretedreinforced with PET fibers have been proposed in Foti (2013a) or derived from Schmidt et al. (2009) and Fraternali et al. (2010). The behavior of PET-reinforced concrete qualitatively reflects what was in general observed for most of fiber-reinforced concretes and consists essentially on an improvement of the postpeak behavior and impact strength. The impact strength was investigated as an influence on concrete of polypropylene fibers (Bayasi and Zeng, 1997), where it was demonstrated that these fibers have a small favorable effect on compressive strength of concrete when 13-mm long fibers were used. In case of recycled plastics, Soroushian et al. (2003) got a higher impact strength of concrete; in particular, the milled mixed plastic particles and the melt-processed plastic fibers, when used at properly selected dosages, yielded important gains in strength of concrete to impact and restrain shrinkage cracking. There are some studies that compare the virgin and recycling materials. The effectiveness of the reinforcement with recycled fibers, in fact, is not equal to those from the virgin material, but calibrating the right dosage rate (generally higher for recycled materials) it is possible to obtain a similar performance for both types of material (Rebeiz, 1995). For this reason, fibers for concrete reinforcement generally need to be durable in the cementitious environment, to be easily dispersed in the concrete mix, to have good mechanical properties, and to be of appropriate geometric configuration in order to be effective.

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Use of Recycled Plastics in Eco-efficient Concrete

Figure 18.10 Specimen of a beam-column joint to be cast with a PET fiberereinforced concrete (Marthong and Marthong, 2016).

Finally, in Marthong and Marthong (2016) the use of concrete reinforced with PET fibers was applied to the reinforcement of a beam-column connection (Fig. 18.10). Then the specimens have been subjected to reverse cycling loading and compared with the behavior of specimens without any waste PET fibers.

18.3

Tests (summary) and results

Since the mid-90s a series of tests on concrete specimens reinforced with PET fibers were carried out at the Testing Laboratory of the Department of Civil Engineering and Architecture at the Polytechnic University of Bari. The numerous studies were focused on concrete elements different from each other; these specimens included fibers in PET with different shapes and sizes: 1. 2. 3. 4. 5. 6. 7. 8. 9.

Cubic specimens (100 mm  100 mm  100 mm) reinforced with circular or “O” fibers. Cubic specimens (100 mm  100 mm  100 mm) reinforced with short lamellar fibers. Prismatic specimens (100 mm  100 mm  400 mm) without reinforcements (1S, 2S). Prismatic specimens (100 mm  100 mm  400 mm) reinforced with short lamellar fibers (1FC, 2FC). Prismatic specimens (100 mm  100 mm  400 mm) reinforced with circular or “O” fibers (1C, 2C), for 0.50% and 0.75% by weight of concrete. Prismatic specimens (100 mm  100 mm  400 mm) reinforced with circular or “O” fibers for 1% by weight of concrete, with superplasticizers. Prismatic specimens (100 mm  100 mm  400 mm) reinforced with half-bottles of PET. Beam-specimens (100 mm  200 mm  1100 mm) with a bigger dimension and reinforced with PET strips Square-shaped slab specimens (800 mm  800 mm  58 mm) reinforced with a grid of PET strips.

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399

For comparison purposes the following tests were also carried out: 10. Beam-specimens (100 mm  200 mm  1100 mm) without reinforcements. 11. Square-shaped slab specimens (800 mm  800 mm  58 mm) without reinforcements.

The first comparison, drawn between ordinary concrete specimens and specimens 1 and 2, had the aim to checking the behavior of these kinds of fiber-reinforced concretes. The prescriptions followed for compression tests are those of the European code (UNI EN 12390:2009), so the loads were applied with a uniaxial testing on both sides of specimens through two plates (Fig. 18.11). In specimens with fibers a reduction of resistance occurred but probably these results are partly distorted by the difficulties encountered during the tests. Also tests on short lamellar fibers of PET were carried out to characterize them. In addition, tensile tests on fibers were performed furnishing an average value of the tensile strength equal to 150 N/mm2. In Fig. 18.12 the test set-up on a short lamellar fiber is shown. Then a comparison was done between specimens 4, 5, and 6 (Fig. 18.13), also with different dosages of PET Fibers (0.50% and 0.75% in weight). To reduce the costs and simplify the FRCs production, the fibers utilized were obtained from ordinary “plastic” bottles through cuts perpendicular to their longitudinal axes. Two types of fibers were utilized, the lamellar ones with a section of 2 mm  0.1 mm and a length of 32 mm and the circular fibers with a width variable around 5 mm and a diameter of 30e50 mm. The concrete mixture utilized was Composite Portland concrete of Type II/A-LL (SN EN 197-1:2000).

Figure 18.11 Typical compressive failure of a specimen reinforced with PET fibers (Marthong and Sarma, 2016).

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Use of Recycled Plastics in Eco-efficient Concrete

Figure 18.12 Direct tensile test on a PET fiber (Foti, 2011).

Figure 18.13 Specimens for the first series of preliminary tests (Foti, 2011).

Recycled waste PET for sustainable fiber-reinforced concrete

401

The prismatic specimens were subjected to bending tests; an Instron electromechanical testing equipment of 50 KN maximum loads performed tests using the Wave maker software Instron Ltd. To verify their behavior, bending tests involved a concentrated load at the centerline to read at each instant the values of load and displacement. The positive influence that the fibers have on the post-peak behavior on concrete elements was confirmed. Both lamellar and “O”-fibers greatly improve the ductility and toughness of the specimens. The increase in toughness is more evident for the “O”-fibers because their special shape helps to bind the concrete on each side of a cracked section, increasing the adherence. The crack pattern in case of bending tests is extremely interesting: a clear single vertical cracking concentrated in the middle, sewn by the fibers (see for e.g., Fig. 18.14 (Fraternali et al., 2011)). It is important to note the deviation of the crack, which did not show the typical V-shape of ordinary concrete failure. Table 18.2 shows the values of the tensile strength obtained during the bending tests. As a consequence of the better behavior of the specimens with circular fibers, it was decided to determine the best dosage of “O”-fibers by weight of the concrete, through the comparison of specimens of test 5 and test 6. An industrial readymade mix concrete was utilized for specimens of test 6 differently from specimens of test 5. For this reason, it was only possible to make comparisons regarding the recovery of the load (Fig. 18.15) and not the peak values.

Figure 18.14 (a) Sewing effect of PET fibers after cracking and (b) detail (Fraternali et al., 2011). Table 18.2 Strength values from the bending tests Specimen

1S

2S

1C (0.75%)

2C (0.75%)

1C (0.50%)

2C (0.50%)

1FC

2FC

fct (N/ mm2)

4.7

4.2

4.8

4.3

3.7

3.6

3.7

3.7

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Use of Recycled Plastics in Eco-efficient Concrete

Specimens reinforced with circular fibers 10 PET 1% - test 1 PET 1% - test 2 PET 0.75% - test 1 PET 0.75% - test 2 PET 0.5% - test 1 PET 0.5% - test 2

Applied load (kN)

8

6

4

2

0 0

2 4 6 8 10 12 14 Maximum deflection at the centerline (mm)

16

18

20

Figure 18.15 Load-deformation plots on specimens with circular fibers (1%, 0.75%, and 0.5%) (Foti, 2013b).

It can be noticed that the recovery of the load, in percentage respect to the peak, is faster for the mix with 1% of PET. The drop of the load is about 70% with respect to the cracking load for PET 0.50%, while 55% for PET 0.75%, and about 35% for PET 1%. Clearly in the case of PET 1% of the fibers are more present in the concrete, so it is easier for the loads to be transferred to the fibers that are able to sew the fracture and to deform in the plastic range. It can be concluded that it is important to increase the percentage of fibers to get an improvement in the concrete behavior but the percentage cannot be high because even after adding superplasticizers the concrete can become less workable. After having analyzed and tested the specimens with a uniform PET fiber reinforcement distributed in the concrete mix, the mechanical characteristics and the behavior of FRC with reinforcement concentrated in the position where high levels of tensile stresses are expected were checked. It does not pursue the prescriptions and the parameters of CNR-DT 204/2006 on the use of fibers. This is true for specimens of test 7, which use strips with C-shaped section obtained from half bottles with a base equal to about 8 cm and two side elevations of about 4 cm and assembled, after an appropriate overlap, with staples (Fig. 18.16). They were placed in the lower part of the specimens, subjected to traction during the bending tests. To verify the behavior of this kind of FRC, it is important to evaluate the adhesion between PET and concrete and the attitude of the strips of PET as a concentrate reinforcement. Therefore, on the specimens a standard test up to a maximum deflection of 20 mm was performed. The crack pattern is extremely interesting: the specimen did not break completely after a first vertical crack concentrated in the mid-section, while inclined shear cracks appeared (Fig. 18.17). Even if the detachment of the bottom area occurred, the concrete and the strips kept a good bond between them.

Recycled waste PET for sustainable fiber-reinforced concrete

403

Figure 18.16 Half bottle reinforcement (Foti, 2013b).

Figure 18.17 Loading tests on specimens with half-bottle fibers (Foti, 2013b). (a) Testing setup; (b) detail of the cracked section.

Fig. 18.18 shows the load-deflection plot; in particular, the crack in correspondence of the peak and a hardening trend with a subsequent recovery of the load and increment of the deformation are noticed. Given the encouraging results, it was decided to test the behavior of larger elements. So, similar analyses on the behavior between PET and concrete were performed on little beams with localized fiber reinforcement. The reinforcing strips in the specimens had dimensions 45 mm  0.2 mm  300 mm, and were superimposed, assembled, and placed along the entire length of the 1m-specimens, as shown in Fig. 18.19. The results of the bending tests showed that only after the cracking of the concrete, which occurred suddenly, the PET strips started to absorb the tensile stress through a ductile behavior and in particular a large deformation before the total failure of the specimen.

404

Use of Recycled Plastics in Eco-efficient Concrete

Load-deflection. specimen n°2

Applied load (kN)

4

3

2

1

0 0

3

6 9 12 15 18 Maximum deflection at the centerline (mm)

21

Figure 18.18 Load-deflection plot for the second specimen (Foti, 2013b).

Figure 18.19 (a) PET strips utilized and (b) their position in the cracking section (Foti, 2013b).

Fig. 18.20 shows the load-deflection plots and highlights the ductile behavior in the postcracking phase of the beams reinforced with PET. Regrettably, the value of the recovery of resistance after cracking is low. This is probably due to the reduced resisting area of PET fibers only equal to 36 mm2. Another important positive result to highlight is that the failure occurred for all the fibers without any sliding from the concrete beam. To complete the research, it was decided to test the behavior of another concrete structural element, a slab. The reinforcement consisted in a sort of grid of long discrete 5 cm wide fiber strips with a 0.2 mm thickness and obtained from PET bottles simply cut along the longitudinal axis and positioned in place of steel (Fig. 18.21). Each strip is assembled to obtain a total length equal to 77 cm and left 1.5 cm from each side of the slab. Ten strips per side were assembled to create a grid that guaranteed the bidirectionality of the reinforcement; two grids were placed in each reinforced slab, not directly in contact

Recycled waste PET for sustainable fiber-reinforced concrete

405

Beam specimens reinforced with PET sheets 12 Beam specimen without fibers Beam specimen 1 Beam specimen 2 Beam specimen 3 Beam specimen 4

Applied load (kN)

10

8 6 4 2

0 0

2 4 6 8 Maximum deflection at the centerline (mm)

10

12

Figure 18.20 Load-deflection plot for little beams reinforced with PET strips (Foti, 2013b).

Figure 18.21 Grid of PET bottle (Foti and Paparella, 2014).

but spaced by a layer of concrete to avoid empty spaces between them due to the ripples of the strips themselves. There are no codified prescriptions for impact tests on concrete, so, in this case the impact load tests (Fig. 18.22) consisted in dropping a steel cylinder, with a weight of 290 N, from a height of 1.0 m and to assess the kind of failure and the crack patterns on the slabs (Figs. 18.22e18.24). As Figs. 18.22e18.24 show, after the tests the non-reinforced plate was completely broken, while the reinforced plate was only subject to superficial cracks that did not lead to a complete failure. So, the presence of the two grids of PET reinforcement ensured the correct response to shocks and impact forces thanks to the more ductile behavior of the concrete plates, thus confirming the improvement of the impact

406

Use of Recycled Plastics in Eco-efficient Concrete

Figure 18.22 (a) Impact instant for the nonreinforced plate n. 1; (b) Impact instant for the reinforced plate n. 1 (Foti and Paparella, 2014).

Figure 18.23 Upper side of nonreinforced plate n. 1 after the impact (Foti and Paparella, 2014).

strength and the ability to withstand very high bidirectional deformations without reaching the failure. Fig. 18.25 shows the average trend of deformation in the tested slabs. The nonreinforced slabs are characterized by attainment of peak in correspondence of the impact and a subsequent sudden fall in correspondence of the break; in the reinforced plates, instead, it is possible to notice a peak at the instant of impact quantitatively not much different from that of nonreinforced plates. After the impact, for the nonreinforced slabs a stable value of deformation occurred, even if the section had no more strength capacity; for the reinforced slabs, instead, after the peak there is a strong decrease of the deformation followed by an increase with a fluctuating trend around a value much higher than zero; this indicates that the slab continues to resist and maintains its structural integrity except for generated fractures which remain superficial. This behavior confirms what was expected due to the higher ductility of the reinforcement provided by the grids, meaning that the plate still has the possibility to transmit a deformation.

Recycled waste PET for sustainable fiber-reinforced concrete

407

Figure 18.24 Detail of the bottom side of the reinforced plate after the impact (Foti and Paparella, 2014). Deformation (%) Non-reinforced slab 1

0,14

Reinforced slab 1

0,12

Reinforced slab 2 Non-reinforced slab 2

0,10 0,08 0,06 0,04 0,02

10,017

10,013

10,009

10,005

9,996

9,992

9,988

9,984

9,980

–0,02

10,000

Time (s)

0,00

Figure 18.25 Time-history of the average deformations for slabs.

In addition, the results showed a good adhesion between concrete and strips, cooperating to absorb the tensile stresses even after the onset of cracks due to bending and shear stresses. In fact, there were no sliding phenomena of any kind and the collapse affected all the strips at the same time. As expected, an interesting postpeak behavior was also found, with a lift of the load, albeit modest, due to the reduced resistant area of the PET strips.

408

18.4

Use of Recycled Plastics in Eco-efficient Concrete

Conclusions

The results obtained confirm, in general, two of the major effects of the use of PET fibers: the greater ductility and the reduction of the workability for dosages of fibers greater than 1% by weight of concrete. This is especially true both for lamellar and “O”-shaped fibers that greatly improve the toughness of the specimens. The enhancement of the toughness is especially evident for the circular fibers; their special shape, in fact, helps to bind the concrete on each side of a cracked section. But the most interesting result concerns the reinforcements made with strips, which represent the most innovative aspect of this research. The tests confirmed the possibility of using strips of PET as reinforcement localized in areas that are expected to be the most stressed in traction. The strips can also be arranged in a grid for concrete plates, so as to give them a very ductile behavior and to avoid the complete failure, thus confirming the improvement of the impact strength. For all these reasons the use of PET strips can be proposed as concentrate reinforcement, in substitution of steel, for structures or secondary structural elements, even if more detailed studies and test campaigns are needed. Different possible uses for this reinforced concrete are proposed, such as, for example, in the production of industrial floors, docks, new jersey barriers, and wharfs in concrete, without forgetting some material properties that include the high efficiency and the resistance to attack by chemicals. Of course, some aspects should be improved in the production of grids and in their characteristics. Finally, it is important to emphasize that it is possible to combine all these benefits with the reuse and the recycle of plastic waste but also with the reduction of the production costs. Future studies will aim at improving the behavior and manufacturing of this reinforcement also improving the adherence of PET with concrete by mean, for example, of coating the surface of the fibers with plasma.

Acknowledgment Francesco Paparella is gratefully acknowledged for his help during the tests at the Laboratory of Testing and Materials “M. Salvati” of the Polytechnic University of Bari, Italy.

References Batayneh, M., Marie, I., Asi, I., 2007. Use of selected waste materials in concrete mixes. Waste Management 27 (12), 1870e1876. Bayasi, Z., Zeng, J., 1997. Properties of polypropylene fiber reinforced concrete. ACI Materials Journal 90 (6), 605e610. Beckmann, B., Hummeltenberg, A., Weber, T., Curbach, M., 2012. Concrete slabs under impact load: drop tower experiments. In: Sudies and Researches, Graduate School in Concrete Structures, Fratelli Pesenti, Politecnico di Milano, Italy, vol. 31, pp. 135e153.

Recycled waste PET for sustainable fiber-reinforced concrete

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Chang, J.-E., Chang, Y.-K., Leu, M.-H., Chen, Y.-L., Huang, J.-H., 2013. Heavy metal removal by ambient-temperature argon plasma modified polyethylene terephthalate (PET) fibers with surface acrylic acid grafting. International Journal of Physical Sciences 8 (6), 244e253. Foti, D., Paparella, F., 2014. Impact behavior of structural elements in concrete reinforced with PET fibers. Mechanics Research Communications 57, 57e66. https://doi.org/10.1016/ j.mechrescom.2014.02.007. ISSN: 0093-6413. Foti, D., Paparella, V., Paparella, F., 2012. Sull’impiego del PET riciclato come materiale di rinforzo del calcestruzzo. L’Edilizia, Structural 174, 54e63. ISSN: 1593-3970. (In Italian). Foti, D., Paparella, V., Paparella, F., 2013. Calcestruzzi fibrorinforzati con fibre di PET. Studio della resistenza all’impatto. L’Edilizia, Structural 176, 1e14. ISSN: 1593-3970. (In Italian). Foti, D., 2011. Preliminary analysis of concrete reinforced with waste bottles PET fibers. Construction and Building Materials 25 (4), 1906e1915. https://doi.org/10.1016/ j.conbuildmat.2010.11.066. Foti, D., 2013a. On the numerical and experimental strengthening assessment of tufa masonry with FRP. Mechanics of Advanced Materials and Structures 20 (02), 163e175. Foti, D., 2013b. Use of recycled waste pet bottles fibers for the reinforcement of concrete. Composite Structures 96, 396e404. Fraternali, F., Negri, M., Ortiz, M., 2010. On the Convergence of 3D free discontinuity models in variational Fracture. International Journal of Fracture 166 (1e2), 3e11. Fraternali, F., Ciancia, V., Chechile, R., Rizzano, G., Feo, L., Incarnato, L., 2011. Experimental study of the thermo-mechanical properties of recycled PET fiber-reinforced concrete. Composite Structures 93, 2368e2374. Fraternali, F., Farina, I., Polzone, C., Pagliuca, E., Feo, L., 2013. On the use of R-PET strips for the reinforcement of cement mortars. Journal of Composites Part B: Engineering 46, 207e210. Gu, L., Ozbakkaloglu, T., 2016. Use of recycled plastics in concrete: a critical review. Waste Management 51, 19e42. Kim, S.B., Yi, N.H., Kim, H.Y., Kim, J.H.J., Song, Y.-C., 2010. Material and structural performance evaluation of recycled PET fiber reinforced concrete. Cement and Concrete Composites 32, 232e240. Lopes Pereira, E., Luis de Oliveira Jr., A., Gomes Fineza, A., 2017. Optimization of mechanical properties in concrete reinforced with fibers from solid urban wastes (PET bottles) for the production of ecological concrete. Construction and Building Materials 149, 837e848. Marthong, C., Marthong, S., 2016. An experimental study on the effect of PET fibers on the behavior of the exterior RC beam-column connection subjected to reversed cyclic loading. Structure 5, 175e185. Marthong, C., Sarma, D.K., 2016. Influence of PET fiber geometry on the mechanical properties of concrete: an experimental investigation. European Journal of Environmental and Civil Engineering 20 (7), 771e784. Ochi, T., Okubo, S., Fukui, K., 2007. Development of recycled PET fiber and its application as concrete-reinforcing fiber. Cement and Concrete Composites 29, 448e455. Pereora de Oliveira, L.P., Castro-Gomez, J.P., 2011. Physical and Mechanical Behaviour of recycled PET fibre reinforced mortar. Construction and Building Materials 25, 1712e1717. Rahmani, E., Dehestani, M., Beygi, M.H.A., Allahyari, H., Nikbin, I.M., 2013. On the mechanical properties of concrete containing waste PET particles. Construction and Building Materials 47, 1302e1308.

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Use of Recycled Plastics in Eco-efficient Concrete

Rebeiz, K.S., 1995. Timeetemperature properties of polymer concrete using recycled PET. Cement and Concrete Composites 17, 119e124. Schmidt, B., Fraternali, F., Ortiz, M., 2009. Eigen fracture: an eigen deformation approach to variational fracture. Multiscale Model Simulation 7 (3), 1237e1266. Siddique, R., Khatib, J., Kaur, I., 2008. Use of recycled plastic in concrete: a review. Waste Management 28, 1835e1852. Silva, D.A., Betioli, A.M., Gleize, P.J.P., Roman, H.R., Gomez, L.A., Ribeiro, J.L.D., 2004. Degradation of recycled PET fibers in Portland cement-based materials. Cement and Concrete Research 35, 1741e1746. Silva, E.R., Coelho, J.F.J., Bordado, J.C., 2013. Strength improvement of mortar composites reinforced with newly hybrid-blended fibers: influence of fibers geometry and morphology. Construction and Building Materials 40, 473e480. Soroushian, P., Plasencia, J., Ravanbakhsh, S., 2003. Assessment of reinforcing effects of recycled plastic and paper in concrete. ACI Materials Journal 100 (3), 203e207. Trejbal, J., Kopeckỳ, L., Tesarek, P., Fladr, J., Antos, J., Somr, M., Nezerka, V., 2016. Impact of surface plasma treatment on the performance of PET fiber reinforcement in cementitious composites. Cement and Concrete Research 89, 276e287. Wu, H.C., Li, V.C., 1997. Basic interfacial characteristic of polyethylene fiber/cement composites and its modification by plasma. In: Brandt, A.M., Li, V.C., Marshall, I.H. (Eds.), Brittle Matrix Composites 5. Woodhead Publishing, Cambridge, UK, pp. 14e23. Yesilata, B., Isiker, Y., Turgut, P., 2009. Thermal insulation enhacement in concretes by adding waste PET and rubber pieces. Construction and Building Materials 23, 1878e1882.

Further reading Donatone, G., Foti, D., Paparella, F., 2010. Soluzioni innovative nel campo dei calcestruzzi fibrorinforzati: analisi preliminare su un calcestruzzo rinforzato con fibre di PET. In Concreto. 95, lug/ago 36e44 (In Italian). Plastics Europe, E., 2013. Plastics-the Facts 2013. An Analysis of European Latest Plastics Production, Demand and Waste Data.

Properties of recycled carpet fiber reinforced concrete

19

Hamid Reza Pakravan 1 , Ali Asghar Asgharian Jeddi 1 , Masoud Jamshidi 2 , Farnaz Memarian 1 , Amir Masoud Saghafi 3 1 Textile Engineering Department, Amirkabir University of Technology, Tehran, Iran; 2School of Chemical Engineering, Iran University of Science and Technology (IUST), Tehran, Iran; 3 Technical and Production Director, Savin Carpet Company, Tehran, Iran

19.1

Introduction

Carpets are a very popular choice of textile floor covering (TFC) materials in homes and commercial centers around the world. This type of product uses over 72% of virgin fibers as opposed to reclaimed or recycled fibers. It is estimated that the usage of new fibers in carpet industry exceeds one million tons globally, and this is expected to rise by around 16% over the next 10 years. Annually a large volume of postconsumer carpets are replaced by new products and dumped into the landfills (McNeil et al., 2007). Approximately 2%e3.5% of all waste disposed in landfills is carpet discard (Miraftab, 2018). It may not appear to be a cause for concern but given the high volume-to-weight ratio and steady rise in consumption it could represent a huge problem for landfill disposing (Miraftab et al., 1999). The rate of carpet disposal is about 4e6 million tons per year worldwide (Wang, 2010). Additionally, carpet wastes are also produced during the manufacturing process such as trimming the edges of carpet (Fig. 19.1) and producing sheared face yarns (Wang et al., 2003). Although there is already an increased attention toward recycling technologies for carpet waste and their use as postproduct applications, most carpet wastes continue to be disposed in landfills (Lemieux et al., 2004). Therefore, innovative alternatives for utilization of the postconsumer carpets have become an emerging need (Mirzababaei et al., 2012). The disposal of fibrous wastes is a major problem for environment due to nondegradable characteristic of this kind of materials in landfills for a very long period of time. This is not only a cause for environmental concern, but also represents a waste of advantageous resources (Putman and Amirkhanian, 2004). In this respect, about million dollars are lost per annum as a result of carpet waste landfilling (Mirzababaei et al., 2013). With a broad spectrum of applications, textiles and fibrous materials contribute to an ever increasing volume in the solid waste stream. Also due to the scarcity of space for landfilling and the high cost of developing and managing landfills, waste utilization has become an attractive alternative to disposal (Siddique et al., 2008). Furthermore, burning of fibrous material wastes releases highly toxic fumes into the surrounding air which puts human health in danger (Reis, 2009).

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00019-0 Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete

Trimmed edge

Waste container

Figure 19.1 Trimmed edge of a woven carpet during carpet manufacturing (Savin Carpet Co.).

Carpets are an enriched sources of fibers attached on the surface of carpet. After an appropriate treatment, the carpet wastes can be used for manufacturing of beneficial products such as a potential fuel substitute in cement kilns, mass production as filler, sound insulating mats, flower pots, or fencing posts (Wang, 2010; Schmidt and Cieslak, 2008). Using mechanical methods, the face yarns of postconsumer carpets can be recycled into short fibers for applications such as reinforcing materials and filler (Wang et al., 2003). Researchers have reported that polymeric fiber waste have a great potential to be used as filler in the different construction materials such as concrete, asphalt, soil, etc. (Wang, 2008). The recycled fibers are generally of lower cost than virgin fibers and using these materials eliminates the need for waste disposal in landfills (Choi, 2017). An important approach to carpet recycling is the development of noncarpet products containing carpet waste in the form of cuttings or fibers (Sotayo et al., 2015). Each year, million tons of carpet wastes are dumped in landfills. Recycling and looking for better alternatives for the use of these waste materials have been steadily increasing worldwide, according to studies. However, to date, only a few studies have been focused on the use of carpet waste in concrete materials. It is worth mentioning that according to Carpet recycling UK (2010), it was estimated that each ton of recycled carpet can save 4.2 tons of CO2 emission.

19.2

Carpet types and fiber recycling methods

Carpet wastes arise from two different sources including disposal of the used carpets (postconsumer carpet) and wastes which are also produced during the manufacturing process, such as trimmed edges of a carpet and sheared face yarns (Wang et al., 2004).

Properties of recycled carpet fiber reinforced concrete

413

The postconsumer carpets are responsible for the largest quantity of disposal waste in comparison to preconsumer waste. In general, there are four type of carpet in the market depending on their structure and the manufacturing methods (Fig. 19.2) as following: 1. 2. 3. 4.

Tufted carpets; with the approximation of 76% of total carpets Woven carpets; with the approximation of 12% of total carpets Needle-punched carpets; with the approximation of 9% of total carpets Others including handmade carpets; with the approximation of 3% of total carpets

Woven carpets or machine carpets are manufactured on looms in a way that simultaneously interlacing face yarns and backing yarns are woven into a final product without need for a secondary backing. Both pile and backing yarns are woven together for fulfilling strength and stability. Usually a small amount of latex coating is applied for extra fixation of tufts. Generally, the face fiber makes 35%e50% of the weight of carpet. The other components such as primary and backing layer, adhesive, and filler are responsible for 10%, 6%e10%, and 30%e40% of a carpet weight (Ucar and Wang, 2011). A tufted carpet is a complex structure that typically consists of two layers of backing and face fibers (piles) tufted into the primary backing, as schematically shown in Fig. 19.1. Several hundred needles push yarn through a primary backing fabric and stitch the pile yarn into backing fabric. A secondary backing is attached by adhesives to the primary backing to keep piles in place. Commonly, a CaCO3-filled styrenebutadiene rubber (SBR) latex is used for joining two backing layers. Generally, the pile fibers in tufted carpets account for 40% of the carpet weight and the remaining 60% include all the other components (Miraftab, 2018). Needle-punched carpet produced from synthetic fibers using barbed and forked needles is an extremely durable carpet, normally used for installation in high traffic areas. PP fibers, due to their lower cost, waterproofness, and stain-resistance properties are the main raw materials used for this type of TFC. The needle-punched carpet, due

(a)

(b) Latex adhesive

Face yarns (piles)

Primary backing

Secondary backing

(C) Weave layer

Latex adhesive

Figure 19.2 Structure of carpets, (a) close-pile tufting, (b) open-pile tufting, (c) woven carpet (machine carpet).

414

Use of Recycled Plastics in Eco-efficient Concrete

to the mineral-filled latex backing and tight fiber fixation, cannot be recycled or directly reused in textile processing. Carpets wastes, due to the complex composition and durable fixation of the fibrous piles with CaCO3-filled SBR and secondary backing layer, are not suitable for the direct reuse in the textile processing (Cieslak and Schmidt, 2002). The latex adhesive is a cross-linked thermoset binder, which cannot be remelted or reshaped. A lot of efforts have been made to reduce the landfill of TFC waste and its impact on the environment. Some technologies that can convert the waste into desirable products are developed, but they are only limited to certain types of waste such as nylon 6 face yarn of TFC (Ucar and Wang, 2011). The nylon 6 fibers could be depolymerized to their monomer units and repolymerized to achieve virgin quality polymers as reported by Shaw Industries (McCoy, 2006). However, it was stated that the carpet face fiber recycling through depolymerization and using for new carpet production is a costly process than a typical carpet manufacturing process (Miraftab et al., 1999). Moreover, the surface fibers can be removed from carpets by relatively simple shearing techniques. To distinguish between different types of fibers, recyclers use a near-infrared spectroscopic analyzer (aka laser gun). As is stated by Bird (2014), fiber reprocessing of carpet waste accounts for 2% of the total carpet waste processing option, and the majority of carpet waste diverted from landfill is used for energy recovery. Nycon Corp. (Corp, n.d) has commercialized reclaimed blended polymer fibers from postconsumer carpets with Nycon-G name for concrete material. The Nycon-G is the combination of nylon and/or propylene fibers with linear density of 12 denier (mass of 9 km fiber). It was claimed that the Nycon-G with 100% recycled nylon fiber has been used in 500 architectural panels for the Heldrich Hotel and the Conference Center in New Brunswick, New Jersey (Corp, n.d). According to the Carpet America’s recovery annual report (CARE, 2016), the rate of recycled carpet was 5% (about 167 million pounds), in which the face fiber accounted for 3% of total recycled waste. The majority of recycled fibers from postconsumer carpets is nylon 6 and nylon 6,6, approximately 72%. The nylon 6 and nylon 6,6 are of the easiest materials for recycling process. These fibers can be recycled in a variety of ways, such as downcycling, reextruding, and depolymerization (McNeil et al., 2007). In Europe region, approximately 700 million square meters of carpets are sold annually and a small quantity, less than 3%, of the total sold was collected for recycling. Each year about 1.6 million tons of postconsumer carpets are disposed in Europe (Zero Waste France, 2017). Recently, new kinds of machinery are developed for pile and tufted carpets which deliver the reclaimed fiber and backing separately (Weib et al., 2003). This process can widen the recycled waste utilization in the other industries (Wang, 2010). Despite the increase in the already considerable effort to develop recycling technologies for carpet wastes and the use of them in the engineering applications, most carpet wastes continue to be disposed in landfills (Lemieux et al., 2004). This is due to fact that all recycling methods require considerable energy and investment in plant.

Properties of recycled carpet fiber reinforced concrete

19.3

415

Properties of recycled carpet fiber

Both natural and synthetic fibers are used in manufacturing carpet yarns. Conventionally, yarns based on natural fibers are used as backing woven fabric for tufted carpets. The general properties of used fibers are summarized in Table 19.1. The synthetic fibers are commonly used in carpet piles. In addition to synthetic fibers, wool fibers are dominant fibers which can be used as piles of carpet. Approximately, synthetic fibers in carpet industry account for 65% of the total market. The fibers in most carpet waste are nylon face fibers and polypropylene yarns, both proven durable and effective in FRC. Other most notably polyester and acrylic fibers are also used for manufacturing carpet. Nylon fiber is the major surface fiber used in carpet industry in approximately 50% of the carpet sold worldwide due to its durability and resiliency behavior. Due to the high value of the nylon fiber, recyclers pay more attention for its recycling methods and processes.

Table 19.1 Physical/mechanical properties of fibers used in carpet manufacturing Specific gravity (kg/m3)

Modulus of elasticity (GPa)

Tensile strength (MPa)

Elongation at break (%)

Acid/ Alkali resistance

Polypropylene (PP) (Pakravan et al., 2016)

910

1.5e4

240e350

15e80

High

Nylon (PA) (Pakravan et al., 2017; Moody and Needles, 2004)

1140

2e5.15

402e905

15e30

High

Polyester (PES) (Moody and Needles, 2004; Goswami, n.d)

1390

3e4

365e1096

15e50

Low

Acrylic (PAN) (Pakravan et al., 2012; Moody and Needles, 2004)

1180

2e3

208e416

20e45

High

Jute (Pakravan et al., 2017)

1300

10e30

390e800

1.5e1.8

High

Steel (ST) for comparison

7840

200

500e2000

0.5e3.5

Low to higha

Fiber type

a

Dependent on the presence/absence of surface coating.

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Use of Recycled Plastics in Eco-efficient Concrete

Polypropylene fiber is a fast growing material for carpet industry because of its easy production and lower price. It is important to note that fibers for carpet manufacturing are industrially produced into cross-sections of various sizes and geometric shapes such as circular, trilobal, kidney, square with four independent hollow tubes, etc., depending on the type of fiber and spinneret shape. Therefore, it should be characterized before its application in concrete materials to discuss the properties of resultant composite. During the past decades many relevant experts have studied the effect of polypropylene, nylon, and acrylic fibers on the performance of concrete materials and have drawn conclusions that incorporation of polypropylene fiber into concrete can enhance both physical and mechanical properties (Song et al., 2005; Ozger et al., 2013; Lee et al., 2012; Pakravan et al., 2012; Sun and Xu, 2009). Jute fiber as a natural fiber is mainly used in carpet backing. This fiber is relatively inexpensive and is most popular choice for the weft yarn of machine-woven carpets. During the carpet manufacturing the edge of carpet is trimmed which produces waste jute yarn as can be seen in Fig. 19.1. Since using simple shredding technique for recycling of fibers from carpet waste generates fibers with variety of length from near zero to 15 mm or above, the length of fibers can be determined by a sieving procedure. Since polyester fibers are susceptible to degradation in alkaline environment of Portland Cement, sorting postconsumer carpet according to the type of face fiber is needed for concrete reinforcement (Wang and Wang, 2006). The interfacial properties between recycled carpet waste fiber and cementitious materials are another factor which determines the overall performance of FRC. Very little has been published on the effect of pullout behavior of recycled carpet fiber from cementitious matrix. Wang et al. (1994) investigated the pullout behavior of carpet face yarn and backing yarn from mortar matrix. Schmidt and Cieslak (2008) determined the reversible work of adhesion between recyclate components of carpet such as nylon and polypropylene pile fiber, coating particles with concrete. They found strong adhesion between pile fibers and concrete, which is even higher than between sand and concrete. Impurities such as dirt, dust particles, or CaCo3 attached to the fibers may decrease the efficiency of recycled carpet fiber in concrete (Vilkner et al., 2004). These impurities can affect interface between fiber and cementitious matrix and also the rheology of mixture.

19.4 19.4.1

Physical properties of concrete containing recycled carpet fiber Slump

Incorporation of carpet waste into concrete mixture exhibited a significant decrease in the slump (Wang, 2010). Decrease in slump of concrete mixture is a characteristic of FRC materials. A decrease in slump of concrete by 42% was reported when the

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recycled carpet waste content in concrete was 1.0% (Kotwal et al., 2012). Mohammadhosseini (2017) investigated workability of concrete mixture containing different volume fractions of carpet fiber waste. They found that slump value of mixture containing carper fiber at volume fractions of 0.25%, 0.5%, 0.75%, 1.0%, and 1.25% was decreased to 130, 70, 55, 45, and 25 mm, respectively.

19.4.2 Unit weight density Waste carpet fibers and cuttings due to their lower weight demonstrate an advantage of density reduction when used in concrete. Pakravan and Memarian 2016 have used needle-felt carpet waste in the form of fibrous waste cuttings in the polymer-based concrete. They used different percentage of waste ranging from 0.5% to 2.5%. The results exhibited that introducing carpet fibrous waste into concrete significantly reduced the density of concrete. The dry density of composite containing 2.5% of carpet cuttings was 23% lower than control sample (Fig. 19.3). Carpet-based fibrous cuttings present bulky properties with a density lower than 500 kg/m3. It is also reported that using recycled carpet waste fiber in concrete at volume fraction of 2.0% can reduce the fresh density of Portland concrete by about 10% (Abdul Awal et al., 2015). The effectiveness of carpet waste on the density reduction of concrete is mainly attributed to the shape of fibers and the geometry. Incorporation of carpet waste in bundle form into concrete mixture has more pronounced effect on concrete density than discrete short fibers (Pakravan and Memarian, 2016).

19.4.3 Shrinkage Fibers play an important effect in reduction of shrinkage, particularly in the early curing stage. The recycled waste fibers also exhibited their impact on drying shrinkage 2000 1800 1600 Density (Kg/m3)

1400 1200 1000 800 600 400 200 0 0

0.5

0.7

1

2

2.2

2.5

Waste content (%)

Figure 19.3 Effect of weight fraction (%) of carpet waste cuttings on dried density of polymer concrete samples Pakravan and Memarian 2016.

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Use of Recycled Plastics in Eco-efficient Concrete

reduction of concrete (Ozger et al., 2013). A reduction of drying shrinkage due to fiber reinforcement was reported by Wang et al. (1994). The amount of reduction has been found in the range of 15%e30% after 500 h of drying.

19.5 19.5.1

Durability-related properties of concrete containing recycled carpet fiber Water absorption and permeability

The water absorption and permeability of concrete containing waste carpet is significantly dependenton the size and geometry of waste particles. In case of carpet waste cuttings, the water absorption of resultant concrete increases by increment in waste content (Pakravan and Memarian, 2016). Using recycled carpet waste in the form of bundle fiber also increases the permeability. If the recycled fibers are used in appropriate volume fraction with short length, the water absorption of concrete can decrease because of effective role of short fiber in controlling drying shrinkage of concrete (Mohammadhosseini et al., 2017). Excessive optimum volume fraction value and length of fiber in concrete give rise to the balling phenomenon, as well as problems with the concrete workability and consequently increases the voids in concrete bulk.

19.6 19.6.1

Mechanical properties of concrete containing recycled carpet fiber Compressive strength

Wang et al. (1994) have used two types of carpet waste fibers including surface yarns and backing fibers in concrete and compared their efficiency with virgin polypropylene fiber. The waste fibers obtained through mechanical disassembling from surface and backing has a length a typical length range of 12e25 mm and 3e25 mm. They found that the compressive strength of concrete containing 1% and 2% of waste fibers is lower than the plain concrete. Also, the effect of carpet waste fibers is similar to virgin fiber. However, the brittleness of concrete samples has decreased by incorporation of carpet waste fibers. Ghosni et al. (2012) also reported a slightly reduction in compressive strength of concrete containing propylene type carpet waste fiber with volume fraction of 1.0%. Recycled nylon fibers from postconsumer carpets also did not show significant effect on the compressive strength of concrete (Ozger et al., 2013). Abdul Awal et al. (2015) has investigated the effect of polypropylene-based recycled carpet fiber on the compressive strength of concrete. The polypropylene fiber had a length of 30 mm and diameter of 0.45 mm. The compressive strength of concrete without fiber was 46.7 MPa. They reported that compressive strength of concrete considerably was decreased by increment in fiber content from 0.5% to 2.0% volume

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fraction. The decrease for concrete containing 0.5%, 1.0%, 1.5%, and 2.0% was 8.5%, 31.6%, 37.5%, and 45.9%, respectively. Although introducing of carpet waste fiber into mixture decreases the compressive strength of concrete, it contributes in ductile behavior during fracture. This behavior can increase the postfailure performance of the concrete containing carpet waste fiber by improving toughness and ductility (Mohammadhosseini, 2017). However, the effectiveness of carpet waste fiber is mainly attributed to the type and physical properties of fibers such as length, diameter, cross-sectional shape, and texture. Pakravan et al. (2016) have reported that carpet wastes in the form of waste cuttings significantly decreased the compressive strength of concrete. This is due to the lower strength of waste cuttings in comparison to the aggregates under compression load. The study by Kotwal et al. (2012) has revealed that recycled carpet fibers can be effective on compressive strength of recycled concrete aggregate (RCA). They used Nycon-G fibers with volume fraction of 0.5% and 1.0% in RCA. The incorporation of recycled carpet waste increased the compressive strength over 40% in comparison to concrete sample without fiber. It is important to note that carpet waste fiber in bundle or cutting shape significantly reduces the compressive strength of resultant concrete. The length of recycled fiber is another factor which may influence the strength of concrete. Higher fiber length leads to entanglement during mixing, which decreases efficiency of fiber and also increases the weak points. In a study by Xuan et al. (2018) the recycled carpet fiber with 20e30 mm length was used in mortar and compared with 12-mm virgin propylene fiber at volume fraction of 0.1%. The results indicated that reduction in compressive strength of mortar with longer fiber is more pronounced than shorter fiber.

19.6.2 Tensile behavior Ozger et al. (2013) have tested the tensile properties of concrete with recovered nylon fiber from postconsumer carpets. The results showed that incorporation of nylon fiber with volume fraction of 0.5% has decreased the tensile strength, but the sample exhibited more ductile properties than control concrete. However, the dosage of carpet fiber was very low. In another research, Ghosni et al. (2012) have investigated the effect of propylene carpet fiber with volume fraction of 1.0% and found an improvement in indirect tensile strength of concrete by 20%. In a study by Mohammadhosseini (2017), polypropylene based recycled bulk-continuous yarn (BCF) from a pile carpet with equivalent diameter of 0.45 mm and length of 20 mm was used with different volume fractions in concrete. The results of splitting tensile strength test exhibited that strength of concrete has remarkably increased by increment in the carpet waste yarn content from 0% to 0.5% of volume fraction. However, when the carpet yarn waste content increased from 0.5% to 1.25%, a sharp decline in tensile strength of concrete has been observed (Fig. 19.4). An increase in tensile strength of mortar containing cement, water-to-cement ratio of 0.5, and sand containing recycled face fiber with length of 20e30 mm at volume fraction of 0.1% were reported by Xuan et al. (2018).

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5

Splitting tensile strength (MPa)

OPC

7-day

28-day

91-day

4.5

4

3.5

3

2.5

2 0

0.25 0.5 0.75 Fiber volume fraction (%)

1

1.25

Figure 19.4 Effect of recycled carpet waste BCF yarn content on the splitting tensile strength of concrete. With permission from Mohammadhosseini H., 2017. Evaluation of the effective mechanical properties of concrete composites using industrial waste carpet fiber. INAE Letters 2, 1e12. https://doi.org/10.1007/s41403-017-0016-x.

It is well understood that low modulus fibers have ability to increase the loadbearing capacity of concrete to some extent (Yap et al., 2013; Mazaheripour et al., 2011). In the fracture process, when a crack starts to develop in an FRC material, the fibers existing across the crack can provide resistance to crack propagation and crack opening prior to pull-out or rupture by bridging mechanism.

19.6.3

Flexural behavior

Flexural strength of concrete materials can be improved by addition of carpet fiber when an appropriate type and content of fibers are used. An improvement by 7% in flexural strength was reported by incorporation of carpet waste with volume fraction of 1.0% (Ghosni et al., 2012). An appropriate dispersion of recycled fibers in concrete bulk has crucial effect on the performance of resultant composite. Wang et al. (1994) evaluated the use of recycled fibers from carpet waste in concrete at volume fractions of 1% and 2%. They found that the important effect of carpet waste fiber in flexural performance of concrete is to convert brittle nature of concrete into pseudoductile behavior where fibers bridging the beam crack. This leads to an increase in the energy absorption of concrete. In a study by Pakravan and Memarian (2016), application of carpet waste fibers in rectangular cuttings form remarkably reduce the flexural strength of concrete, while the load-bearing capacity in postpeak zone is significantly increased (Fig. 19.5). The

Properties of recycled carpet fiber reinforced concrete

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7 15 Flexural toughness index

6

110

5 4 3 2 1 0 0

0.5

1 1.5 2 Carpet waste content (%)

2.5

3

Figure 19.5 Effect of carpet waste fiber content on the flexural toughness indices (I5 and I10 on the basis of ASTM: 1018) (Pakravan and Memarian, 2016).

results show that toughness and energy absorption of concrete under flexural load can be improved by inclusion of carpet waste fiber. It is worth mentioning that recycled carpet fiber in the form of cuttings can be used in higher amount as compared with short-length fibers in concrete. An increase in flexural strength of concrete with incorporation of carpet waste fiber has been reported by Wang (2008). However the effect of increasing fiber dosage in toughness indices is more pronounced than flexural strength improvement. Mohammadhosseini (2017) have reported that the incorporation of carpet waste yarn into concrete has significantly increased the flexural strength in comparison to the concrete without fiber. Improvement in the flexural strength of 28-day cured concrete containing 0.5% of carpet waste yarn is achieved by 23%. An investigation by Wang et al. (1994) revealed that incorporation of recycled polypropylene carpet waste fiber into concrete exhibited comparable results on flexural strength when compared to the virgin fiber. Using simple shredding equipment for disassembling face fiber from postconsumer carpet could reduce the operational cost, which results in low-cost reinforcement fibers for concrete materials.

19.6.4 Impact behavior Some literatures have reported the carpet waste fiber impact behavior of FRC. Ucar and Wang (2011) reported that the impact energy of FRC is not sensitive to the carpet waste fiber content in their study. The fibers were a combination of nylon and polypropylene with length of 50e70 mm and the volume fraction was 0.1%e1.1%. Xuan et al. (2018) also investigated the effect of recycled polypropylene carpet fiber on the impact resistance of mortar. They found that the used fiber (length ¼ 20e30 mm)

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Use of Recycled Plastics in Eco-efficient Concrete

140

At first crack

At failur

No. of blowas

120 100 80 60 40 20 0 0%

0.25%

0.50%

0.75%

1.00%

Recycled carpet yarn volume fraction

Figure 19.6 Effect of carpet waste yarn content on the impact behavior of concrete. Reproduced with permission from Mohammadhosseini H., 2017. Evaluation of the effective mechanical properties of concrete composites using industrial waste carpet fiber. INAE Letters 2, 1e12. https://doi.org/doi:10.1007/s41403-017-0016-x.

is not significant for improving the impact behavior at room temperature. However, the investigation at elevated temperature or high strain rate exhibited a significant positive effect on the impact resistance. Mohammadhosseini (2017) reported that the impact performance of concrete containing waste carpet yarn in terms of number of blows at first crack and at failure has been significantly improved in comparison to concrete without fiber (Fig. 19.6). Despite the flexural and compressive strength which was exhibited and optimum for fiber content equal to 0.5%, the impact behavior steadily increased by increment in fiber content even at 1.25% volume. It should be also considered that the used fiber has triangular cross-section which can provide more frictional bonding with concrete and enhance energy absorption capacity (Pakravan et al., 2016).

19.7

Future trends

Although there are many attempts to recover postcostumer carpet from landfills and to convert them into useful products, still a huge amount of them are disposed each year. Concrete as a mass productive material is the best candidate for recycled carpet waste fiber and cuttings due to its need for manufacturing lighter and durable materials. In recent years, the research has shifted to the use of recycled fibers and particles from steel and plastic sector in concrete, but there is limited works on the application of recycled carpet waste fibers. Application of recycled carpet waste fiber in concrete

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materials poses advantages over virgin fibers due to saving water, energy, and emissions while preventing valuable materials from getting into landfills. Studies have shown that reinforcements of concrete with discrete fibers are proven technology to enhance the performance of this construction material. Used fibers in carpet manufacturing have lower strength and modulus elasticity than conventional fiber for FRC applications, however the recent researches indicate that even with low modulus recycled fiber, considerable improvements in the load-bearing capacity, strain capacity, impact resistance, and crack control of FRC could be achieved. It has been also found that the use of low-cost waste fiber for concrete reinforcement could lead to eco-efficient infrastructure with better durability and reliability.

References Abdul Awal, A.S.M., Mohammadhosseini, H., Hossain, M.Z., 2015. Strength, modulus of elasticity and shrinkage behaviour of concrete containing waste carpet fiber. International Journal of Geomate 1441e1446. https://doi.org/10.21660/2015.17.4345. Annual Report Carpet America Recovery Effort, 2016. https://carpetrecovery.org. Bird, L., 2014. In: Carpet Recycling UK Conference. http://www.carpetrecyclinguk.com/ downloads/27_percent_landfil_diversion_how_the_UK_exceeded_its_targets_two_years_ early_Laurance_Bird_and_Jane_Gardner_Carpet_Recycling_UK.pdf. Carpet recycling UK, 2010. Carpet Recycl Gov Policy. http://www.carpetrecyclinguk.com/ downloads/Carpet_Recycling_and_Government_Policy_. Choi, T., 2017. Environmental impact of voluntary extended producer responsibility: the case of carpet recycling. Resources, Conservation and Recycling 127, 76e84. https://doi.org/ 10.1016/j.resconrec.2017.08.020. Cieslak, M., Schmidt, H., 2002. Possibilities of utilizing textile floor covering wastes. Fibres and Textiles in Eastern Europe 10, 69e73. Ghosni, N., Samali, B., Vessalas, K., 2012. Evaluation of Mechanical Properties of Carpet Fibre Reinforced Concrete. From Mater. to Struct. Adv. through Innov. CRC Press, pp. 275e279. https://doi.org/10.1201/b15320-48. Goswami K.K., n.d. Advances in Carpet Manufacture. . Kotwal, A.R., Kim, Y.J., Hu, J., 2012. Recycled carpet fiber reinforced concrete with recycled concrete aggregate. In: Int. Concr. Sustain. Conf., Seattle, USA. Lee, G., Han, D., Han, M.C., Han, C.G., Son, H.J., 2012. Combining polypropylene and nylon fibers to optimize fiber addition for spalling protection of high-strength concrete. Construction and Building Materials 34, 313e320. https://doi.org/10.1016/ j.conbuildmat.2012.02.015. Lemieux, P., Stewart, E., Realff, M., Mulholland, J.A., 2004. Emissions study of co-firing waste carpet in a rotary kiln. Journal of Environmental Management 70, 27e33. https://doi.org/ 10.1016/j.jenvman.2003.10.002. Mazaheripour, H., Ghanbarpour, S., Mirmoradi, S.H., Hosseinpour, I., 2011. The effect of polypropylene fibers on the properties of fresh and hardened lightweight self-compacting concrete. Construction and Building Materials 25, 351e358. https://doi.org/10.1016/ j.conbuildmat.2010.06.018. McCoy, M., 2006. Finding New Life for Old Carpets. Find New Life Old Carpets, pp. 33e38.

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McNeil, S.J., Sunderland, M.R., Zaitseva, L.I., 2007. Closed-loop wool carpet recycling. Resources, Conservation and Recycling 51, 220e224. https://doi.org/10.1016/ j.resconrec.2006.09.006. Miraftab, M., Horrocks, R., Woods, C., 1999. Carpet waste, an expensive luxury we must do without! Autex Research Journal 1, 1e7. Miraftab, M., 2018. Recycling Carpet Materials, second ed. Adv. Carpet Manuf, pp. 65e76. Mirzababaei, M., Miraftab, M., Mohamed, M., McMahon, P., 2012. Unconfined compression strength of reinforced clays with carpet waste fibers. Journal of Geotechnical and Geoenvironmental Engineering. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000792, 120801060815001. Mirzababaei, M., Miraftab, M., Mohamed, M., McMahon, P., 2013. Impact of carpet waste fibre addition on swelling properties of compacted clays. Geotechnical and Geological Engineering 31, 173e182. https://doi.org/10.1007/s10706-012-9578-2. Mohammadhosseini, H., Yatim, J.M., Sam, A.R.M., Awal, A.S.M.A., 2017. Durability performance of green concrete composites containing waste carpet fibers and palm oil fuel ash. Journal of Cleaner Production 144, 448e458. https://doi.org/10.1016/ j.jclepro.2016.12.151. Mohammadhosseini, H., 2017. Evaluation of the effective mechanical properties of concrete composites using industrial waste carpet fiber. INAE Letters 2, 1e12. https://doi.org/ 10.1007/s41403-017-0016-x. Moody, V., Needles, H.L., 2004. Tufted Carpet : Textile Fibers, Dyes, Finishes, and Processes. William Andrew Pub. Nycon Corp., n.d. http://nycon.com/nycon-g/. Nycon Corp., n.d. http://nycon.com/case-studies/nycon-g-the-heldrich-hotel/. Ozger, O.B., Girardi, F., Giannuzzi, G.M., Salomoni, V.A., Majorana, C.E., Fambri, L., et al., 2013. Effect of nylon fibres on mechanical and thermal properties of hardened concrete for energy storage systems. Materials and Design 51, 989e997. https://doi.org/10.1016/ j.matdes.2013.04.085. Pakravan, H.R., Memarian, F., 2016. Needlefelt carpet waste as lightweight aggregate for polymer concrete composite. Journal of Industrial Textiles 46, 833e851. https://doi.org/ 10.1177/1528083715598657. Pakravan, H.R., Jamshidi, M., Latif, M., Pacheco-Torgal, F., 2012. Influence of acrylic fibers geometry on the mechanical performance of fiber-cement composites. Journal of Applied Polymer Science 125. https://doi.org/10.1002/app.36410. Pakravan, H.R., Jamshidi, M., Latifi, M., 2016. The effect of hybridization and geometry of polypropylene fibers on engineered cementitious composites reinforced by polyvinyl alcohol fibers. Journal of Composite Materials 50, 1007e1020. https://doi.org/10.1177/ 0021998315586078. Pakravan, H.R., Latifi, M., Jamshidi, M., 2017. Hybrid short fiber reinforcement system in concrete: a review. Construction and Building Materials 142. https://doi.org/10.1016/ j.conbuildmat.2017.03.059. Putman, B.J., Amirkhanian, S.N., 2004. Utilization of waste fibers in stone matrix asphalt mixtures. Resources, Conservation and Recycling 42, 265e274. https://doi.org/10.1016/ j.resconrec.2004.04.005. Reis, J.M.L., 2009. Dos. Effect of textile waste on the mechanical properties of polymer concrete. Materials Research 12, 63e67. Schmidt, H., Cieslak, M., 2008. Concrete with carpet recyclates : suitability assessment by surface energy evaluation. Waste Management 28, 1182e1187. https://doi.org/10.1016/ j.wasman.2007.05.005.

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Siddique R., Khatib J., Kaur I., 2008. Use of recycled plastic in concrete: A review 28, 1835e1852. https://doi.org/10.1016/j.wasman.2007.09.011. Song, P.S., Hwang, S., Sheu, B.C., 2005. Strength properties of nylon- and polypropylene-fiberreinforced concretes. Cement and Concrete Research 35, 1546e1550. https://doi.org/ 10.1016/j.cemconres.2004.06.033. Sotayo, A., Green, S., Turvey, G., 2015. Carpet recycling: a review of recycled carpets for structural composites. Environmental Technology and Innovation 3, 97e107. Sun, Z., Xu, Q., 2009. Microscopic, physical and mechanical analysis of polypropylene fiber reinforced concrete. Materials Science and Engineering: A 527, 198e204. https://doi.org/ 10.1016/j.msea.2009.07.056. Ucar, M., Wang, Y., 2011. Utilization of recycled post consumer carpet waste fibers as reinforcement in lightweight cementitious composites. International Journal of Clothing Science and Technology 23, 242e248. https://doi.org/10.1108/09556221111136502. Vilkner, G., Meyer, C., Shimanovich, S., 2004. Properties of glass concrete containing recycled carpet fibers. In: di Prisco, M., Felicetti, R., Plizzari, G.A. (Eds.), 6th Int. RILEM Symp. Fiber Reinf. Concr, Varenna, Italy, pp. 1431e1440. Wang, Y., Wang, Y., 2006. Utilization of Recycled Carpet Waste Fibers for Reinforcement of Concrete and Soil. Recycl. Text. Elsevier, pp. 213e224. https://doi.org/10.1533/ 9781845691424.4.213. Wang, Y., Zureick, A.-H., Cho, B.-S., Scottt, D.E., 1994. Properties of fibre reinforced concrete using recycled fibres from carpet industrial waste. Journal of Materials Science 29, 4191e4199. Wang, Y., Zhang, Y., Polk, M., Kumar, S.M.J., 2003. Recycling of carpet and textile fibers. In: Andrady, A. (Ed.), Plast. Environ. A Handb. John Wiley & Sons, New York, pp. 697e725. Wang, Y., Zhang, Y., Polk, M.B., Kumar, S., Muzzy, J.D., 2004. Recycling of Carpet and Textile Fibers. Plast. Environ. John Wiley & Sons, Inc, Hoboken, NJ, USA, pp. 697e725. https://doi.org/10.1002/0471721557.ch16. Wang, Y., 2008. Utilization of recycled carpet waste fibers for reinforcement of concrete and soil. Polymer-Plastics Technology and Engineering 38, 533e546. https://doi.org/10.1080/ 03602559909351598. Wang, Y., 2010. Fiber and textile waste utilization. Waste and Biomass Valorization 1, 135e143. https://doi.org/10.1007/s12649-009-9005-y. Weib, M., Wustenberg, D., Momber, A.W., 2003. Hydro-erosive separation of plastic fibers from textile compounds. Journal of Material Cycles and Waste Management 5, 84e88. https://doi.org/10.1007/s10163-003-0085-7. Xuan, W., Chen, X., Yang, G., Dai, F., Chen, Y., 2018. Impact behavior and microstructure of cement mortar incorporating waste carpet fi bers after exposure to high temperatures. Journal of Cleaner Production 187, 222e236. https://doi.org/10.1016/ j.jclepro.2018.03.183. Yap, S.P., Alengaram, U.J., Jumaat, M.Z., 2013. Enhancement of mechanical properties in polypropylene- and nylon-fibre reinforced oil palm shell concrete. Materials and Design 49, 1034e1041. https://doi.org/10.1016/j.matdes.2013.02.070. Zero Waste France, 2017. Dtsch Umwelthilfe Chang Mark Rep. https://www.zerowastefrance. org.

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Performance of asphalt concrete with plastic fibres

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Nura Usman 1,2 , Mohd Idrus Mohd Masirin 1 1 Faculty of Civil and Environmental Engineering, Universiti Tun Hussein Onn Malaysia, Rarit Raja Johor, Malaysia; 2Department of Civil Engineering, Hassan Usman Katsina Polytechnic, Katsina, Nigeria

20.1

Introduction

Despite billions of dollars being spent on construction, rehabilitation, and maintenance of asphaltic pavements globally, many distresses such as rutting, fatigue, polish, and bleeding tend to undermine the pavement strength (Johnson, 2013). This is caused by increased vehicular traffic and axle loads, increased pressure to cut construction and rehabilitation cost due to global economic recession, as well as low maintenance culture in developing countries (Baghaee Moghaddam et al., 2014b). Although researchers and engineers work day and night to overcome such problems, still such distresses do appear on our flexible pavements even after maintenance. The conventional method for production of asphalt mixture used in road maintenance is by mixing aggregates and bitumen base on design, but due to material components, climate, loading, and pavement strength, this mixture tends to fail before the designed life (Arangi and Jain, 2015: Sol-Sanchez et al., 2015). To combat such problems, there is a need to modify or strengthen the bearing capacity of the asphalt pavement (Baghaee Moghaddam et al., 2014a). In this regard, modification of bitumen using some classes of recycled plastic such as polypropylene (PP) powder, polypropylene (PP) mulch, low density polyethylene (LDPE), and high density polyethylene (HDPE) proved to be effective (Ahmadinia et al., 2011). On the other hand, some waste polymers such as PET and polyvinyl chloride (PVC) are not readily suitable for bitumen modification due to their high melting point; also medium density polyethylene (MDPE) and acrylonitrile butadiene styrene (ABS) are not readily suitable for bitumen modification (Casey et al., 2008). Furthermore, reinforcement of asphalt mixture using synthetic polymer fibers shows a remarkable result but expensive which could not be adoptive in many developing countries. The use of conventional asphalt concrete mixtures do result in postmaintenance failures which need to be addressed; on the other hand, PET which is the dominant plastic waste (Rahman and Wahab, 2013) and nonbiodegradable is increasingly being produced (Abass, 2014). Therefore, this research introduces new recycled fiber using PET to reinforce asphalt concrete.

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00020-7 Copyright © 2019 Elsevier Ltd. All rights reserved.

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20.2

Use of Recycled Plastics in Eco-efficient Concrete

Polyethylene terephthalate

PET is in the group of thermoplastic polymers and is polyester synthesized from terephthalic acid and a diol, commonly ethylene glycol (Farah et al., 2015). PET is a ubiquitous thermoplastic polymer used for daily household objects to sophisticated engineering applications. Due to its significant water and moisture resistance, it is widely used in making plastic bottles for soft drinks. PET is also known by other trade names such as Mylar, Decron, Terylene, Recron, and Lavsan. It has a high melting temperature of 260 C (Farah et al., 2015). PET possesses significant mechanical strength, toughness, and thermal resistance up to 150e175 C. Its chemical, hydrolytic, and solvent resistance constitutes some of the qualities due to the stiffness of the polymer chains of the PET. Due to its outstanding crease resistance and good abrasion resistance, this polymer can be treated with cross-linking resins to impart permanent wash-and-wear properties (Venkatachalam et al., 2012). The main applications of PET are soft drink container, apparel, curtains, upholstery, threads, tyre cord filaments, industrial fibers, and fabric for industrial filtration (Saleh et al., 2012).

20.3

The use of polyethylene terephthalate in asphalt mixture

PET constitutes about 60% of plastic waste (Rahman and Wahab, 2013) which is a major component of plastic waste; it has and is being utilized to modify and reinforce asphalt and asphaltic mixtures, as well as for treatment of aggregates against moisture and strength improvement. Introduction of PET in asphalt mixtures would in addition to improvement of flexible pavements also help to reduce the global environmental pollution (Tapase and Kadam, 2014). Kalantar et al. (2012) used plastic waste to modify asphalt. The produced asphalt mixture was of good performance with increased rutting resistance, high stiffness at high temperatures, and improved susceptibility to temperature variation. Waste packaging polyethylene and organic montmorillonite were used by Fang et al. (2013) to modify asphalt binder. The resultant binder exhibited decrease in penetration due to polyethylene and decrease in viscosity, as well as increase in crack resistance due to organic montmorillonite. Similarly, Sengoz et al. (2009) studied the use of SBS (StyreneButadiene-Styrene), EVA (Ethylene-vinyl acetate), and EBA (ethylene butyl acrylate) in asphalt binder modification. Their findings indicated that though the modified asphalt exhibited improved penetration and softening and moisture susceptibility, the fundamental properties and morphology of the modified asphalt depends on the amount and nature of the modifying polymer. In another development, Ajim et al. (2015) examined the use of waste LDPE in bituminous road construction. LDPE was used for coating of aggregates and also in bitumen modification. Their result revealed an improvement in mechanical properties of aggregates when coated with 2.5%e12.5%. Modification of bitumen by 7.5% LDPE has yielded a remarkable improvement in Marshall Stability, strength, and fatigue life of the bituminous mix. Shedame and Pitale (2014) studied the use of waste

Performance of asphalt concrete with plastic fibres

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plastic, mainly LDPE, in hot mix asphalt (HMA); it was shredded and coated on the aggregates. Using fly ash as a filler and LDPE as coating additive on the aggregates, the findings of their research indicated a higher Marshall Stability at a maximum plastic coat of 0.76% by total weight of mixture. In their review, Zhu et al. (2014) identified the polymer modification of asphalt as advantageous and listed problems associated with polymer modification of asphalt as high cost, low-aging resistance, poor storage stability, and poor elasticity, which can be remedied by saturation, sulfur vulcanization, antioxidants, hydrophobic clay minerals, and reactive polymers. Also, modification of bitumen requires mechanical blending machines (Lo Presti, 2013) or compatibility agents that would disperse the plastic waste in the bitumen for homogeneity (Fang et al., 2014). The need for blending equipment and compatibility agents tend to increase the cost of bitumen modification and when successfully blended, the storage stability is poor (Zhu et al., 2014). The research conducted on PET coated aggregates shows an increase in mechanical strength and moisture damage resistance, but it requires high energy to coat the plastic on the aggregate’s surface. Therefore the additional energy needed would increase the construction cost. Thus, in this research PET was used to produce fiber that was used for the reinforcement of asphalt mixture. It is an economical and effective way to improve asphalt mixture performance and reduce plastic waste.

20.4

Recycled polyethylene terephthalate fiber

Fiber is a natural or synthetic substance that is significantly longer than its width; fibers are often used in the manufacture of other materials (Kadolph and Marcketti, 2016). Nowadays, fiber is also used in asphalt concrete industry. Many test approaches have been proposed so as to emulate the intricate mechanical behavior of reinforced asphalt pavements to guide engineers in selection of appropriate reinforcing product (Canestrari et al., 2013). PET bottles from packed drinking water and other soft drinks were collected, washed, and dried. The bottles were then processed using shredding and fiber of size 0.78 mm  10 mm is produced, as shown in Fig. 20.1.

Figure 20.1 Recycled PET fiber.

430

20.5

Use of Recycled Plastics in Eco-efficient Concrete

Characteristics of recycled PET fiber

Physical and mechanical tests were conducted on the recycled PET fiber; this is to check the potentiality of the fiber for the effective reinforcement of asphalt mixture. Water absorption test was conducted on the PET according to ASTM D570 and the result was 0.18% as shown in Table 20.1. This very low water absorption makes PET to be a good fiber for asphalt mixture. Tensile strength test was also conducted on the fiber to determine its mechanical strength according to ASTM C1557. Other strength parameters such as elongation were also determined from this test. The test was conducted at room temperature; fiber was gripped in the machine’s jaws and tested until the fiber failed. Fig. 20.2 shows fiber under tension on LR 30K universal testing machine. Table 20.1 Properties of recycled PET fiber Property

Method

Value

Water Absorption (%)

ASTM D570

0.18

Specific Gravity

ASTM D792

1.356

Load (N)

ASTM C1557

32.3

Displacement (mm)

ASTM C1557

5.17

Strain (%)

ASTM C1557

51.7

Tensile Strength (MPa)

ASTM C1557

218

Figure 20.2 Recycled PET fiber under tensile strength test.

Performance of asphalt concrete with plastic fibres

431

From Table 20.1, the tensile strength of recycled PET fiber is 218 MPa, which is considerably capable of improving the mixture performance when used in asphalt mixture. This strength would also allow the fiber to resist mixing and compaction processes without breakage, segregation, or balling. The fiber can also resist a load of 32N which is promising in traffic load resistance.

20.6

Application of recycled PET fiber in asphalt mixture

20.6.1 Mixture design and sample preparations The aggregates’ gradation was performed based on Superpave mix design using nominal maximum aggregate size (NMAS) of 12.5 mm. The aggregates were 24 h oven dried prior to sieving, after which it was sieved based on selected gradation arrangement. The optimum bitumen contents (OBC) were determined using AASHTO-T312-11 procedure, while the mixture test samples were compacted using Superpave gyratory compactor. The mixture design is medium to high category of traffic load, that is, between 3 to less than 30 million Equivalent Single Axle Load (ESALs) in which the mixtures’ design density was achieved at Ndesign of 100 gyrations. All the test samples were prepared based on respective standard specifications and methods. For the recycled fiberereinforced mixes, the optimum bitumen contents were determined at every percentage added, that is, 0.3%, 0.5%, 0.7%, and 1.0%. The selected aggregates’ gradation is within the envelope of upper and lower Superpave gradation limits. Fig. 20.3 shows the aggregate gradation used. Blending of fibers in asphalt concrete mixture was performed by dry process. In dry process, fiber is blended into aggregates at 165  C prior to the addition of bitumen as suggested by Vadood et al. (2015), Yoo and Kim (2015), and Chavan (2013).

120

Design passing

Superpave limits

Percentage passing (%)

100 80 60 40 20 0

0

5

10

15

20

Sieve size (mm)

Figure 20.3 Nominal maximum aggregate size 12.5 mm aggregates gradation.

432

Use of Recycled Plastics in Eco-efficient Concrete

Four different asphalt mixtures at 0.5% increment were selected starting from 4%, 4.5%, 5%, and 5.5%. For each asphalt mixture, three samples were prepared for maximum specific gravity (Gmm) determination using corelok machine and another three samples for bulk specific gravity (Gmb) of compacted mixture. The volumetric properties of these mixtures which are air voids (AV), dust proportion (DP), voids filled with asphalt (VFA). and voids in mineral aggregates (VMA) were then calculated. Graphs of asphalt content versus AV, VFA, and VMA were plotted for both control and reinforced samples, accordingly. From the graphs, OBC was determined as the asphalt content at which 4% air voids were obtained and have satisfied all the Superpave design requirements stated in Table 20.2. The mixing and compaction temperatures are 165 and 155 C, respectively, which was determined from bitumen rotational viscosity test. The test samples were produced based on OBC of the respective recycled PET fiber content shown in Table 20.3. Samples for resilient modulus and static creep tests were prepared at 4% air voids using their respective optimum bitumen contents.

20.6.2

Mixture performance

Performance of asphalt concrete mixture depends on material characteristics, traffic loading, and environmental conditions. The characterization of pavement is the measurement and analysis of the mixture’s response to load, deformation, and environment at various rates of loading and temperatures. The pavement response is complex and involves elastic, viscoelastic, and plastic characteristics of the materials. In this study, Table 20.2 Properties of designed mixture Mix property

Result

Criteria

Air Void (%)

4.0

4.0

VMA (%)

14.0

Min 14

VFA (%)

70.1

65e75

Dust Proportion (%)

1.2

0.6e1.2

Table 20.3 Optimum bitumen contents of designed mixes Mixture

OBC

0% PET fiber (Control)

4.7

0.3% PET fiber

4.7

0.5% PET fiber

4.9

0.7% PET fiber

4.9

1.0% PET fiber

5.2

Performance of asphalt concrete with plastic fibres

433

fundamental (resilient modulus) and simulative (rutting) tests were conducted on designed mixtures.

20.6.2.1 Resilient modulus Resilient modulus (MR) is a ratio of the applied stress and recoverable strain at a particular temperature and load. In this research, specimen preparation and testing procedures for the indirect tensile resilient modulus test was performed according to ASTM-D4123-82, 1995, Standard Test Method for Indirect Tension Test for Resilient Modulus of Bituminous Mixtures using IPC UTM-5P Universal Testing Machine. This machine has close loop system located in an environmental chamber for conditioning and testing of specimens at required test temperature. The test is nondestructive; it is also very essential for determining mechanical properties of asphalt mixtures (Xue et al., 2009). The resilient modulus test involved a range of temperatures, loads, rest periods, and axis of loading. In this study, prior to testing the samples were conditioned at required test temperature for 4 h. The resilient modulus test was conducted at two different temperatures, 25 and 40 C. The specimens were subjected to a cyclic load in the sinusoidal wave shape and test sequence consists of five count of conditioning pulses followed by five loading pulses where data acquisition takes place. The load was applied for a period of 0.1 s and has a rest period of 0.9 s; 1000 ms has been chosen for high volume traffic and 3000 ms simulates the low volume traffic (Tayfur et al., 2007). The deformations and responses were measured by linear variable differential transducers (LVDT). Fig. 20.4 shows a sample under the resilient modulus test. The test is used intensively to characterize the elastic behavior of asphalt concrete and to evaluate its quality under cyclic axial loading (Khodaii et al., 2014). Table 20.4

Figure 20.4 Sample under resilient modulus test.

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Use of Recycled Plastics in Eco-efficient Concrete

Table 20.4 Resilient modulus test result at 25 and 40 C 1000 ms

2000 ms

3000 ms

258C

408C

258C

408C

258C

408C

Mixture

(MPa)

(MPa)

(MPa)

(MPa)

(MPa)

(MPa)

0% PET fiber

3479

1505

2361

1219

1938

924

0.3% PET fiber

5350

1690

4251

1438

3092

1149

0.5% PET fiber

7371

1773

6183

1515

5390

1207

0.7% PET fiber

4349

1144

3747

1099

1961

707

1.00% PET fiber

3054

867

2143

692

1679

479

shows the mean summary of resilient modulus test result for neat and reinforced asphalt mixtures. The test samples were tested in 1000, 2000, and 3000 ms resting periods at 25 and 40 C. Figs. 20.5e20.7 show the resilient modulus of neat and reinforced mixtures axially loaded at 1000, 2000, and 3000 ms rest periods, respectively. From the figures, the resilient modulus values for 0.3% and 0.5% recycled PET fiberereinforced mixtures were adequately increased at both temperatures compared to neat mixture. This is due to the increased stiffness of the reinforced mixtures as a result of high tensile strength of recycled PET fiber at the test temperatures. This is similar to result obtained by Amuchi et al. (2015) in reinforcement of asphalt concrete using polypropylene fiber. Nevertheless, at 0.7% reinforcement, the resilient modulus at 25 C was higher than that of the neat mixture but lower than that of the neat mixture at 40 C. This is attributed by the higher tensile stress resistance of recycled PET fiber at 25 C. At 40 C which corresponds to bitumen’s softening point, the elastic deformation of the mixture is exceeded despite the presence of excess recycled fiber of 0.7%. Moreover, at 1.0% reinforcement the fiber content was high which caused loss of internal friction in the asphalt concrete due to lower friction surface of PET (Moghaddam et al., 2015).

Resilient modulus (Mpa)

Resilient modulus @ 1000ms 8000 7000 6000 5000 4000 3000 2000 1000 0

25°C 40°C

0%

0.30% 0.50% 0.70% Percentage of PET

1.00%

Figure 20.5 Resilient modulus at 1000 ms of neat and recycled fiberereinforced asphalt mixes.

Performance of asphalt concrete with plastic fibres

435

Resilient modulus @ 2000ms Resilient modulus (Mpa)

7000 6000 5000 4000 3000

25°C

2000

40°C

1000 0 0%

0.30%

0.50%

0.70%

1.00%

Percentage of PET

Figure 20.6 Resilient modulus at 2000 ms of neat and recycled fiberereinforced asphalt mixes. Resilient modulus @ 3000ms Resilient modulus (Mpa)

6000 5000 4000 3000

25°C

2000

40°C

1000 0 0%

0.30%

0.50%

0.70%

1.00%

Percentage of PET

Figure 20.7 Resilient modulus at 3000 ms of neat and recycled fiberereinforced asphalt mixes.

20.6.2.2 Static creep Static creep test was used to assess the resistance of neat and recycled PET reinforced asphalt concrete mixtures under stationary loading. BS 598: Part 111: 1995 method was used for the running of the test using IPC UTM-5 Universal Testing Machine. Unlike in dynamic creep test where the stress application is repeatedly applied, in static creep test the stress was applied continuously and steadily on the sample throughout the test period. Static load was applied on the cylindrical samples of mixtures to study the permanent deformation. The test was performed at 40 C, preloaded for 600 s under l0 kPa stress and then loaded with 100 kPa for 1 h. The samples were cured in the IPC UTM-5 machine chamber at the test temperature 4 h prior to the testing; the test was terminated after 3600 cycles. Fig. 20.8 shows asphalt concrete sample under static creep test. Static creep test has been used by researchers to determine rutting characteristics of asphalt mixtures (Rongali et al., 2013). The test was conducted to obtain a creep

436

Use of Recycled Plastics in Eco-efficient Concrete

Figure 20.8 Asphalt concrete sample under static creep test.

deformation of neat and reinforced cylindrical samples under a uniaxial static load; the deformation was measured as a function of time using linear variable differential transducers (LVDT) attached to load cell in IPC UTM-5 universal testing machine. Table 20.5 shows a summary of static creep test result. Figs. 20.9 and 20.10 are plots for permanent deformation and accumulated strain for neat and recycled PET fibere reinforced mixtures, respectively. In Fig. 20.9, the rutting resistance of recycled PET fiber is significantly improved compared to neat mixture. At 0.3% reinforcement the permanent deformation has been reduced by 24%, reduced by 42% at 0.5% reinforcement, but the mixture deformed by 8% compared to neat mixture at 1% reinforcement. The rutting damage was unaffected at 0.7% reinforcement compared to neat mixture. In Fig. 20.10, accumulated strain of mixtures reinforced at 0.3% and 0.5% decreased by 32% and 42%, respectively, compared to neat mixture. Similar to permanent deformation, the accumulated strain of mixtures containing 0.7% recycled fiber was insignificantly affected compared to neat mixture. The strain was increased by 8.6% at 1.0% reinforcement compared to neat mixture.

Table 20.5 Permanent deformation and accumulated strain at 3600 load cycles Sample ID

Permanent

Accumulated

0% PET fiber

0.3330

4886.0

0.3% PET fiber

0.2502

3287.0

0.5% P ET fiber

0.1917

2844.00

0.7% PET fiber

0.3342

4941

1.0% PET fiber

0.3605

5347

Permanent deformation (mm)

Performance of asphalt concrete with plastic fibres

437

0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0

0% PET 0.30% 0.5% PET 0.7% PET 1.0% PET 0

1000

2000 3000 Load cycle (s)

4000

Figure 20.9 Permanent deformation plot for neat and fiber-reinforced asphalt mixtures. 7000

Avial strain (µ )

6000 5000 0%

4000

0.30% 3000

0.50%

2000

0.70%

1000

1.00%

0 0

1000

2000 3000 Load cycle (s)

4000

Figure 20.10 Accumulated strain plot for neat and fiber-reinforced asphalt mixtures.

Generally, rutting performance of asphalt mixtures is influenced by its viscoelastic properties at an ambient temperature (Baghaee Moghaddam et al., 2014a). Therefore, the ability of neat mixture to recover elastic deformation at service temperature has been improved due to the presence of recycled PET fiber. The tensile strength of recycled PET fiber at 40 C restrained the mixture against rutting distress. Another reason for the improvement is that PET is a crystalline polymer material, it is bound strongly with bitumen and bonded firmly to aggregates during compaction; it absorbs some loads applied by traffic loadings at service temperatures.

20.7

Conclusion

This chapter highlighted the advantages of recycled PET fiber in performance improvement of asphalt mixture. Based on experimental studies conducted, the following conclusions were drawn. Water absorption of PET was found to be 0.18%, which is very low. Tensile strength of recycled PET fiber was 218 MPa, which

438

Use of Recycled Plastics in Eco-efficient Concrete

is enough to improve the performance of asphalt mixture. Resilient modulus of fiberreinforced mixtures at 25 and 40 C were improved at 0.3% and 0.5% reinforcement compared to neat mixture. This improvement indicates increase in fatigue resistance (MR @ 25 C) and rutting resistance (MR @ 40 C). The improvement of resilient modulus in PET-reinforced asphalt mixture is more significant at lower temperatures than higher temperatures. Permanent deformation and accumulated strain of recycled PET fiber were decreased at 0.3% and 0.5% reinforcement compared to neat mixture. This indicates improvement of rutting resistance. Generally, mixtures containing 0.5% recycled PET fibers have shown higher rutting and fatigue resistance. Therefore, the optimum recycled PET fiber content is 0.5%.

References AASHTO-T312-11, 2011. Standard Method of Test for Preparing and Determining the Density of Hot-Mix Asphalt (HMA) Specimens by Means of the Superpave Gyratory Compactor. American Association of State and Highway Transportation Officials, Washington. Abass, R.U., 2014. The use of techniques in the management of watse plastic by reuse it in the asphalt mix. Engineering and Technology Journal 32 (10), 1e14. Ahmadinia, E., Zargar, M., Karim, M.R., Abdelaziz, M., Shafigh, P., 2011. Using waste plastic bottles as additive for stone mastic asphalt. Materials and Design 32 (10), 4844e4849. https://doi.org/10.1016/j.matdes.2011.06.016. Ajim, S., sutar, sanket, D., Awasare, A.A.K., 2015. Experimental investigation on use of low density polyethylene (Ldpe) in bituminous road construction. Journal of Information, Knowledge and Research in Civil Engineering 3 (2), 183e190. Amuchi, M., Abtahi, S.M., Koosha, B., Hejazi, M., Sheikhzeinoddin, H., 2015. Reinforcement of steel-slag asphalt concrete using polypropylene fibers. Journal of Industrial Textiles 44 (4), 526e541. https://doi.org/10.1177/1528083713502998. Arangi, S.R., Jain, R.K., 2015. Review paper on pavement temperature prediction model for Indian climatic condition. International Journal of Innovative Research in Advanced Engineering (IJIRAE) 2 (8), 1e9. ASTM-D4123-82, 1995. Standard Test Method for Indirect Tension Test for Resilient Modulus of Bituminous Mixtures in Standard Test Method for Indirect Tension Test for Resilient Modulus of Bituminous Mixtures. American Society for Testing and Materials, ASTM, Washington, pp. D4123eD4182, 1995. Baghaee Moghaddam, T., Soltani, M., Karim, M.R., 2014a. Evaluation of permanent deformation characteristics of unmodified and Polyethylene Terephthalate modified asphalt mixtures using dynamic creep test. Materials and Design 53, 317e324. https://doi.org/ 10.1016/j.matdes.2013.07.015. Baghaee Moghaddam, T., Soltani, M., Karim, M.R., 2014b. Experimental characterization of rutting performance of Polyethylene Terephthalate modified asphalt mixtures under static and dynamic loads. Construction and Building Materials 65, 487e494. https://doi.org/ 10.1016/j.conbuildmat.2014.05.006. Canestrari, F., Belogi, L., Ferrotti, G., Graziani, A., 2013. Shear and flexural characterization of grid-reinforced asphalt pavements and relation with field distress evolution. Materials and Structures 1e17. https://doi.org/10.1617/s11527-013-0207-1.

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Sustainability of using recycled plastic fiber in concrete

21

Rabin Tuladhar 1 , Shi Yin 2 1 Centre of Tropical Environmental and Sustainability Science, College of Science and Engineering, James Cook University, Townsville, QLD, Australia; 2College of Science and Engineering, James Cook University, Townsville, QLD, Australia

21.1

Introduction

Plastics are synthetic organic polymers derived mainly from fossil fuels such as crude oil, natural gas, or coal. Because of their light weight, low cost, durability, and versatility, they are widely used in almost every sector in the modern economy. Due to these inherent benefits, rate of production and use of plastics has skyrocketed, since mass production of synthetic plastics began in 1950s. Worldwide annual plastic production increased from 2 Mt in 1950 to 335 Mt in 2017 (PlasticsEurope, 2017). Polypropylene (PP), which is used to produce packaging for consumer products, diapers, automotive components, textiles, medical devices, etc., accounts for more than 23% of total global plastic usage (PlasticsEurope, 2017). Globally, over 90% of the plastics that we use are produced from fossil feedstock derived from crude oil, natural gas, and coal (Ellen MacArthur Foundation, 2016). Hopewell et al. (2009) estimate that around 4% of world oil and gas production is consumed as feedstock for plastic production. Another 3%e4% of fossil fuel is used as energy in the production process of plastics. Plastics production and incineration of plastic waste are responsible for approximately 400 Mt of CO2 emission per year (PlasticsEurope, 2017). Most of the plastics produced worldwide, especially plastic packaging, are singleuse products and are discarded after short first-uses. Geyer et al. (2017) reported that only 9% of the total plastics produced around the world to date have been recycled so far. The recycling rate of plastics is far below the global recycling rate of paper (58%) and steel (70%e90%) (Ellen MacArthur Foundation, 2016). Majority of the discarded plastic wastes end up in landfills and in the nature causing serious environmental impacts. It is estimated that 5 to 13 Mt of nonbiodegradable plastic waste is discarded every year into the oceans (PlasticsEurope, 2017) causing serious adverse effects on marine environments. Current “linear material flow model” (extract-produce-usedump) in plastic consumption is unsustainable. The more sustainable and desirable alternative for plastic industry is a “circular economy” approach where emphasis is given to repairing/reusing products and extracting maximum value out of them during their service life. In circular economy, materials are recycled and recovered at the end of each service life. Recycling of plastic wastes reduces the use of fossil fuels required for virgin plastic production and consequently reduces CO2 emissions. In this paper,

Use of Recycled Plastics in Eco-efficient Concrete. https://doi.org/10.1016/B978-0-08-102676-2.00021-9 Copyright © 2019 Elsevier Ltd. All rights reserved.

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Use of Recycled Plastics in Eco-efficient Concrete

we present a comprehensive environmental impact assessment of recycling industrial polypropylene (PP) wastes into macroplastic fibers that can be used to reinforce concrete elements. Recycling of plastic wastes into plastic fibers for reinforcing concrete creates a whole new avenue for recycling plastic wastes and contributes toward reducing global plastic pollution. Steel reinforcing mesh (SRM) is traditionally used to reinforce concrete footpaths to prevent drying shrinkage cracks. In recent years, macroplastic fibers are increasingly used in concrete in lieu of steel reinforcement to enhance crack resistance and robustness of concrete. The most commonly used synthetic fibers in concrete are virgin polypropylene (PP) fibers. With an aim to encourage recycling of plastic wastes, our research has produced 100% recycled PP fibers for reinforcing concrete. Recycled fibers considered in this study are produced by mechanical recycling of industrial plastic wastes such as off-cuts and off-specification items from diaper industries. Our production process includes melt-spinning and hot-drawing processes, where recycled PP plastic granules are extruded and hot-drawn into plastic fibers. Detailed production process of recycled PP fibers is covered in Chapter 4 and their performance in concrete is presented in other publications by the authors Yin et al. (2015a) and Yin et al. (2016a). This chapter focuses on the life cycle environmental benefits of production of recycled PP fibers compared to using SRM or virgin PP fibers to achieve equivalent reinforcement in concrete footpaths. Life cycle assessment (LCA) based on ISO14040 and ISO14044 frameworks (ISO14040, 2006; ISO14044, 2006) was used to quantify resource consumption and environmental impacts of producing recycled and virgin PP fibers and SRM. This paper presents a case study for Australian context, where all the input and output data are relevant to the Australian conditions. Nevertheless, the methodology used in the study is replicable around the world with relevant input data. The scope of this study is limited to cradle to gate, that is, up to the production stage of PP fibers and steel mesh.

21.2

Sustainability in construction materials

Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs. Brundtland (1987)

Sustainability performance of a project or a product is evaluated based on their economic, social, and environmental merits (Fig. 21.1). These three pillars of sustainable Figure 21.1 Triple bottom-line framework for sustainable development.

Sustainable development

Society

Environment

Economy

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development are often referred to as the “triple bottom line.” Economic sustainability of a project has always been an integral part of any businesses or industries. Any project or product needs to be economically feasible. The economic performance of a project or a product is measured in terms of its whole life cost, economic output, and productivity. Social sustainability indicators, on the other hand, measure the impact of projects on quality of life; comfort, health, and safety of workers and users; and living standards of an individual or a society at large. Social sustainability also ensures business practices that are fair to the community and the workers. Environmental sustainability includes reduction of harmful impacts on our environment and preservation of natural resources such as air, water, land, and ecosystem. Negative environmental impacts include emission of greenhouse gasses, acidification, eutrophication, and depletion of ozone layer. Reduction in consumption of nonrenewable natural resources (such as fossil fuels) increase use of renewable energy and promote reuse and recycling of materials and products, and managing and reducing wastes contribute toward environmental sustainability. Construction and building industries play a critical role in creating a sustainable society. Stakeholders of construction and building industries should make conscious and informed decisions regarding materials selection, construction techniques, and design methods and practices with a focus on using natural resources responsibly and reducing negative environmental impacts (Sivakugan et al., 2016). Sustainability hierarchy (Fig. 21.2) gives topmost priority to reduce consumption of new (virgin) materials whenever possible. Careful selection of materials and design methods help create cost-effective, safe, and healthy living environments. Use of innovative design practices and materials can reduce the total consumption of virgin materials. The second preference in the sustainability hierarchy is to reuse the products. For instance, plastic products used in packaging and transportation can be reused for different purposes without the need of much processing. Plastic products can also be remanufactured into high-value consumer goods. At the end of life, materials can be recycled to produce new materials (usually of lower grade), which can be used for manufacturing other products. Recycling of materials reduces the amount of virgin materials and contributes toward conservation of energy and materials. Moreover, it reduces the amount of wastes going into landfills. For instance, plastic wastes can be recycled using mechanical recycling, chemical Figure 21.2 Sustainability hierarchy: reduce, reuse, and recycle. Reduce

Reuse

Recycle

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Use of Recycled Plastics in Eco-efficient Concrete

recycling, and energy recovery processes. In mechanical recycling, plastic wastes are reprocessed and extruded into recycled granules which are used to produce products requiring lower grade properties. Chemical recycling of plastic wastes depolymerize plastics into monomers, which are used as feedstock to produce plastics and other materials (Hopewell et al., 2009). Energy recovery from plastic wastes can also be achieved through combustion of plastic wastes as fuel under controlled conditions. Environmental sustainability of a project should be assessed over its entire life (Sivakugan et al., 2016). In construction industry, consumption of energy during the entire life of an infrastructure can be categorized into embodied energy and operational energy. Energy and resources required during the construction phase (including extraction of raw materials, manufacturing of construction materials, transportation, construction, demolition, and waste management at end of life) is called as embodied energy. One of the most important considerations toward achieving sustainable development is to ensure the use of construction materials with low carbon footprint. Carbon footprint measures the potential contribution of human activities on climate change as expressed in terms of weight of CO2 equivalent. On the other hand, energy consumed during operation of the infrastructure (such as heating and cooling systems and maintenance) is termed as operational energy. For a holistic environmental assessment, both embodied and operational energy should be considered. LCA offers a comprehensive and rigorous method to quantify total environmental impact associated with products or services.

21.2.1

Embodied energy

Embodied energy is the energy associated with the manufacturing of a product or services. This includes energy used for extracting and processing of raw materials, manufacturing of construction materials, transportation and distribution, and assembly and construction. Cradle-to-grave approach in calculating embodied energy also includes energy required for refurbishing and maintaining infrastructures during their service life and for demolition and waste management at end of life. Embodied energies (expressed as MJ/kg) for commonly used construction materials are shown in Fig. 21.3. Embodied energy concept can be used to evaluate sustainability of various construction materials by comparing the energy required to produce them. Embodied energy of a structure is significantly influenced by the type of construction materials used, manufacturing efficiency, transportation distance, durability of the materials, and construction methods implemented. Durable materials last longer and reduce the overall embodied energy used over the lifetime of the product. Recycled materials also have significantly lower embodied energy compared to its virgin counterparts as it eliminates the energy required for extraction and processing of raw materials. For instance, production of PP fibers from virgin plastics requires extraction of crude oil, coal, or natural gas; transportation and processing in refineries; polymerization and production of plastic pellets and granules. However, using recycled plastic feedstock to produce PP granules eliminates extraction and processing of fossil fuel and remarkably reduces embodied energy of recycled plastic products. As seen in Fig. 21.3, recycled PP with 70% recycled component is around 25 MJ/kg less than

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Concrete (precast) Concrete (high strength) Concrete (normal strength) Cement Bricks Timber (plywood) Timber (general) Timber (sawn hardwood) Timber (sawn softwood) Glass Commercial steel (20% recycled) Stainless steel Polypropylene (PP) (70% recycled) Polypropylene (PP) Polyethylene terephthalate (PET) Commercial aluminium (30% recycled) Primary aluminium 0

50

150 100 Embodied energy (MJ/kg)

200

250

Figure 21.3 Embodied energy for different construction materials (Tectonica, 2018; Hammond and Jones, 2008).

one-third of the embodied energy of virgin PP. It is important to note that collection, transportation, and processing of recycled materials also consumes energy. Nevertheless, energy required to produce recycled PP is much lower compared to the energy required for extraction and processing of fossil feedstock.

21.2.2 Operational energy Operational energy is the energy required during the entire service life of a structure such as lighting, heating, cooling, and ventilating systems; and operating building appliances. Operational energy is associated with relatively longer proportion of infrastructure’s service life and can constitute 80%e90% of the total energy associated with the structure (Fig. 21.4). However, with the advent of energy efficient building systems and appliances, operational energy of buildings has seen remarkable reduction. For example, plastic is widely used in production of automobiles and aeroplanes due to its light weight and malleability. Use of plastics instead of heavier materials like steel or timber reduces weight and overall consumption of fuel during the operation of automobiles and aeroplanes, thus significantly reducing the operational energy. In construction industries, use of advance polymers such as high-performance insulation Embodied energy (10%–20%)

Operational energy (80%–90%)

Figure 21.4 Operation energy versus embodied energy.

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Use of Recycled Plastics in Eco-efficient Concrete

materials save heating and cooling energy for buildings, reducing overall operational energy.

21.2.3

Life cycle assessment

A typical life cycle of plastic products is schematically illustrated in Fig. 21.5. Majority of commonly used plastics are produced from fossil hydrocarbons derived from crude oil, natural gas, and coal. Fossil feedstocks are processed to manufacture different plastic polymers (Geyer et al., 2017). Plastic raw materials are then transported to manufacturing plants where they are molded or extruded into plastic products. In each of these stages, energy is consumed for processing and transportation. Furthermore, wastes and emissions are produced in each stage. Some plastic products at the end of their service life may be repaired and reused. Remaining postuse plastics are collected as plastic waste. Part of the plastic wastes may undergo chemical recycling where they are converted into monomers and are used as feedstock for manufacturing plastics or other materials. Mechanical recycling is a commonly used method to reprocess plastic wastes into recycled plastic granules, which are further molded and extruded to form other plastic products. Mechanical recycling of plastic waste to produce recycled plastic waste is covered in detail in Chapter 4. Some plastic wastes may be used as fuel to recover energy. However, major portion of the plastic wastes goes unrecycled and is discarded in landfills and in the

waste Fossil feedstock Plastic production

Landfill

End of life plastic waste

Energy

Service life of plastic products

waste

Figure 21.5 Life cycle stages of plastic.

Product manufacturing

waste

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nature as litter. Geyer et al. (2017) estimate that 8300 Mt of virgin plastic has been produced from 1950s to 2015. Approximately 6300 Mt of plastic waste has been generated in this period. Only 9% of the total plastic waste produced has been recycled so far. Staggering amount of plastic waste (around 79% of total plastic waste produced as of 2015) has ended up in landfills or in the environment. Unfortunately, these plastic wastes are nonbiodegradable and remain in the environment for decades causing serious environmental consequences. LCA can be used as a holistic tool to quantify environmental impacts and consumption of raw materials, energy, and water during the entire life cycle of a product. LCA provides a systematic approach to compare environmental impacts among different materials and processes. It helps decision makers to benchmark products based on their sustainability indicators. A complete LCA should account for energy and emissions associated with a product throughout its entire life cycle from raw material extraction to production, use, transportation, operation, recycling, and final disposal. LCA accounts for energy and material flows and environmental impacts at each stage of product life cycle. This comprehensive approach of doing LCA for the whole life of a product is termed as “cradle-to-grave.” Sometimes LCA only limits its scope to certain stages of a product life, for example, from extraction of a material to manufacturing of a product. This approach is called as “cradle-to-grave” and only accounts for the environmental impacts of specific stages of the product life. ISO14040 (ISO14040, 2006) and ISO14044 (ISO14044, 2006) provide a framework for LCA. According to ISO standards, LCA comprises of four distinct phases: Goal and scope definition, life cycle inventory (LCI), life cycle impact assessment (LCIA), and Interpretation of results (Fig. 21.6). Each of these steps is described in the context of recycled plastic fiber production in Section 21.3.

Figure 21.6 Life cycle assessment framework (ISO14040, 2006).

Life-cycle inventory analysis

Life-cycle impact assessment

Results and interpretation

Goal and scope definition

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Use of Recycled Plastics in Eco-efficient Concrete

21.3

Comprehensive LCA of recycled plastic fibers used for reinforcing concrete

This paper presents a detailed LCA of commercial production of recycled PP fibers from industrial plastic wastes for Australian context. Simapro 8.0 was used as LCA tool for this study. LCA results for 100% recycled PP fibers were compared with the results for the production of virgin PP fibers and SRM required to achieve equivalent reinforcing effects in concrete. Fig. 21.7(a) shows a trial footpath constructed at James Cook University (Townsville, Australia) with 100% recycled plastic fiber (Fig. 21.7(b)). Macroplastic fibers can directly be mixed with concrete in concrete trucks and poured straight into formworks at the site. As can be seen in Fig. 21.7(a), use of macroplastic fibers eliminates the need of using SRM in concrete footpath, saving labor time and cost of cutting and placing steel mesh. Fig. 21.7(b) and (c) show 100% recycled PP fiber and virgin PP fiber, respectively. Both of the fibers have same dimensions (1.5 mm width, 0.7 mm thickness, and 47 mm length). Mechanical properties of these fibers are already presented in Chapter 4 (Yin et al., 2015b). Fig. 21.8 shows traditionally used SRM for reinforcing concrete footpaths.

21.3.1

Goal and scope definition

The first step of LCA is to explicitly define the context and scope of the assessment and identify the system boundaries and environmental effects to be considered in the assessment. In this study, “cradle-to-gate” LCA is done which includes material extraction, transportation, and production of the materials. The scope of this study does not include environmental impact at maintenance and post-use disposal stages of concrete footpath. Our study has shown that both plastic fibers and SRMreinforced concrete have similar performance, maintenance requirements, and life spans (Yin et al., 2015a; Yin et al., 2016a). Furthermore, it is assumed that the

(a)

(b)

(c)

Figure 21.7 (a) Concrete footpath constructed with 100% recycled plastic fiber at James Cook University, Townsville, Australia (b) 100% recycled PP fiber (c) virgin plastic fiber.

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Figure 21.8 Traditionally used SL82 steel reinforcement mesh (SRM) in concrete footpaths.

end-of-life disposal procedures of concrete footpath for all the scenarios considered are similar.

21.3.1.1 Functional units The functional unit of this study is reinforcement of concrete footpath of area 100 m  100 m with thickness of 100 mm. According to AS3600 (AS3600, 2009), seven sheets of SL82 SRM are required to reinforce 100 m2 of concrete footpath. One sheet of SL82 SRM is 6 m  2.4 m in size and weighs 52 kg (Fig. 21.8). It consists of 7.6 mm steel bars at 200 mm spacing in both directions. Total steel required to reinforce 100 m2 of concrete footpath using SL82 SRM is 384 kg, whereas to achieve equivalent reinforcement effects in concrete footpath, 0.45% of PP fibers by volume (equivalent to 4 kg PP fiber per cubic meter of concrete) is required (Cengiz and Turanli, 2004). Based on this, total amount of virgin or recycled PP fibers required to reinforce 100 m2 of concrete footpath (100 mm thick) is 40 kg.

21.3.2 Life cycle inventory analysis Life cycle inventory (LCI) identifies different stages of a product life cycle and compiles a database on resource inputs (such as energy, water, land, etc.) and waste outputs (such as atmospheric emissions, waterborne emissions, solid wastes, etc.) associated with each stage. Inventory data for resource flow and emissions during the production of virgin PP fibers, 100% recycled PP fibers, and SRM are presented in Table 21.1. Details of process flowchart, resource consumption, and emission at various stages associated with the three scenarios considered in this study are presented below.

21.3.2.1 Scenario A: production of 364 kg of SL82 SRM using electric arc furnaces and basic oxygen furnaces Input, outputs, and system boundaries for the production of SL82 SRM for the Australian context are presented in Fig. 21.9. Electric arc furnaces (EAF) are predominantly

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Use of Recycled Plastics in Eco-efficient Concrete

Table 21.1 Summary of life cycle inventory data and corresponding sources Data

Sources

Industrial PP reprocessing

• Communication with a manager of Martogg Group (2013) • Simapro 8.0 database, AusLCI unit process library, Low voltage electricity (Simapro, 2010)

Virgin PP granulates production

• Simapro 8.0 database, Australasian Unit Process LCI library, Polypropylene Production Australian Average (Simapro, 2010)

PP granulates transportation

• Scientific publications: Shen et al. (2010) • Communication with the manager of Martogg Group to get actual transportation distances and vehicle types (2013) • Simapro 8.0 database, Australasian Unit Process LCI library, Rigid Truck Transport in Australia (Simapro, 2010), Articulated Truck Transport (Simapro, 2010)

PP fibre production

• On-site investigation, checking real electricity bills to get electricity consumption, and communication with a manager in Danbar Plastic • Simapro 8.0 database, AusLCI unit process library, Low voltage electricity (Simapro, 2010)

Plastic waste landfilling

• Scientific publications: Perugini et al. (2005) and Arena et al. (2003) • Simapro 8.0 database, Australasian Unit Process LCI library, LCI of 1000 kg Plastic in Landfill (Simapro, 2010)

Steel production

• Communication with an executive director of Steel Reinforcement Institution of Australia (SRIA) • Scientific publications: Strezov and Herbertson (2006) • Building Products Life Cycle Inventory (LCI) from Australian Building Products Innovation Council, Steel reinforcing mesh (Building products life cy, 2010) • LCA databases Simapro 8.0 database, Franklin USA 98 library, Steel from Basic Oxygen Furnace (Simapro, 2010), Cold-rolled steel sheet from Electric Arc Furnace (Simapro, 2010)

Concast and rolling mill

• Communication with an executive director of SRIA • Building Products Life Cycle Inventory from Australian Building Products Innovation Council, Steel reinforcing mesh (Building products life cy, 2010) • Simapro 8.0 database, Ecoinvent unit processes library, Milling steel (Simapro, 2010)

Mill steel transportation

• Communication with an executive director of SRIA • Scientific publications: Strezov and Herbertson (2014) • Building Products Life Cycle Inventory from Australian Building Products Innovation Council, Steel reinforcing mesh (Building products life cy, 2010)

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Table 21.1 Summary of life cycle inventory data and corresponding sourcesdcont’d Data

Sources • LCA databases Simapro 8.0 database, Australasian Unit Process LCI library, Domestic Shipping in Australia; AusLCI unit process library, lorry >32t (Simapro, 2010)

Steel mesh production

• Communication with an executive director of SRIA • Building Products Life Cycle Inventory from Australian Building Products Innovation Council, Steel reinforcing mesh (Building products life cy, 2010)

used in Australia for the production of SRM; the remaining SRM is produced through blast furnace (BF) and basic oxygen furnaces (BOF) process (Strezov and Herbertson, 2006). BF and BOF primarily use raw iron ore and coal for producing new steel, whereas, EAF essentially uses scrap metal and electricity to produce steel. Molten iron obtained from EAF and BOF is continuously cast, milled, and cold-rolled into steel bars. The milled steel bars are then cut and resistance welded into SRM sheets. Resource used and environmental impacts of the SRM manufacturing process are obtained from Simapro 8.0 database (Simapro, 2010) and BPIC (Building products life cy, 2010).

21.3.2.2 Scenario B: production of 40 kg virgin PP fiber Virgin PP is produced from petrochemical feedstock such as crude oil, coal, or natural gas. The three key manufacturers of virgin PP in Australia are Kemcor Resins, Montell Geelong, and Montell Clyde plants with total production share of 19%, 37%, and 44%, respectively. Manufactured virgin PP granules are then transported to fiber manufacturing plant, where they are extruded (at temperature range 218 Ce235 C) and hot-drawn in oven (at temperature range 120 Ce150 C). The surface of the fiber is indented and cut into 50 mm long virgin PP fibers. Considering 95% efficiency of plastic fiber production process, 42 kg of virgin raw PP granules are required to produce 40 kg of virgin PP fibers. The remaining 2 kg (approximately 5%) of plastic waste produced during the fiber manufacturing process is discarded into landfill. Data provided by the PP fiber manufacturing plantdDanbar Plastics (Australia) showed that 1445 kWh electricity is consumed to produce one tonne of PP fibers. Fig. 21.10 presents the material flow and emissions during the manufacturing of virgin PP fibers.

21.3.2.3 Scenario C: mechanical recycling of 40 kg recycled PP fiber Recycled plastic fiber considered in this study is produced from mechanical recycling of industrial plastic wastes collected from off-cuts and off-specification items from diaper industries. Our research was focused on producing recycled fiber from

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Use of Recycled Plastics in Eco-efficient Concrete

Metalurgical coal

Iron ore

Limestone

Scrap steel

Electricity

Blast furnace

Wastes-solid, liquid

as

er g

PM10

Electric arc furnace method (EAF)

duc

Basic oxygen furnace (BOF)

Pro

CO2 NOx SO2

Concast and rolling mill

8% slag 1

60% mill steel

3% other byproducts

Mill steel

Water

9% slag 2

20% future scrap value

Electricity

CO2

Gas

Cutting Wastessolid, liquid

NOx SO2 PM10

Liquefied petroleum gas (LPG)

Bending

Welding

Reinforcing steel mesh

Figure 21.9 Flowchart and system boundary for the production of 364 kg of SRM (Yin et al., 2016a,b).

industrial plastic waste instead of domestic plastic waste because of the consistent quality and quantity of industrial PP waste. Fig. 21.11 schematically presents the production process of 100% recycled PP fiber from industrial plastic wastes. Industrial PP waste is first collected and transported (average distance of 75 km) to mechanical reprocessing plants where it is shredded, sorted, and reprocessed into recycled PP granules. Data obtained from the reprocessing plants (Martogg Group, Australia) states 95% efficiency in shredding and recompounding processes. Considering 95% efficiency of fiber production plants, it is estimated that 46.5 kg of industrial plastic waste

Sustainability of using recycled plastic fiber in concrete

Propylene from gasoil Gasoline from gasoil

453

19% PP from kemcor resins

Fuels (methane, diesel) Propylene, catalytic cracking from naphtha Water Hydrogen, from natural gas

Ancillary materials

Air emissions 44% PP from montell clyde

42 Kg virgin PP granules

Water emissions

Polymerisation catalyst Vechicle emissions

Electricity

Transportation

Propylene, catalytic cracking from naphtha Propylene from gasoil Hydrogen, from natural gas Polymerisation catalyst

Fibre production (η = 95%)

37% PP from montell geelong

Process wastes

Inter-unit transportation

Landfill

40 Kg virgin PP fibre

Figure 21.10 Flowchart and system boundary for the production of 40 kg of virgin PP fibers (Yin et al., 2016a,b).

is required to produce 40 kg of recycled PP fibers. Remaining 6.5 kg of processing waste is discarded to landfill. Some of the processing data relating to mechanical recycling of PP waste were obtained from Australian Indicator Set V3.00 method (Simapro, 2010). Recycled PP granules are then transported to fiber manufacturing plants (average distance of 150 km), where they are extruded into recycled plastic fibers. The process of extruding recycled PP fiber from recycled plastic granules is exactly the same as that used for virgin PP fiber.

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Use of Recycled Plastics in Eco-efficient Concrete

46.5 kg industrial PP scraps

Compaction Fuels (methane, diesel) Transportation

Water

Process wastes

Process wastes

Ancillary materials

Shredding (η = 95%)

Recompound (η = 95%)

Vehicle emissions

Air emission

Air and water emissions

42 kg recycled PP granules Transportation

Vechicle emissions

Electricity Process wastes

Fibre production (η = 95%)

Air emissions

Air and water emissions

Landfill

Inter-unit transportation

Vechicle emissions

40 kg industrial recycled PP fibre

Figure 21.11 Flowchart and system boundary for the production of 40 kg of recycled PP fibers (Yin et al., 2016a,b).

21.3.3

Life cycle impact assessment

Life cycle impact assessment (LCIA) quantifies the overall impact of resource consumption and environmental emissions at different stages of a product life cycle (Sivakugan et al., 2016). In this study, Simapro 8.0 was used to conduct LCAs for all the three scenarios presented above. Impact categories considered for this study are: global warming potential (GWP), eutrophication, water use, and fossil fuel consumptions.

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Consumption of fossil fuels (such as coal and oil) and electricity during the production and processing stages of steel mesh and plastic fibers leads to CO2 emissions and associated GWP. CO2 equivalent (in kg) is a standard unit used for measuring GWP. Emissions released to water have potential to cause water-based pollution. Eutrophication, contamination of water bodies with nutrients, can be expressed in terms of PO4 equivalent (in kg). Furthermore, total water and fossil fuel consumption (in kg) are used to quantify the depletion of limited natural resources. Uncertainty in the assessment of environmental impacts due to the variation in LCI input data was considered through uncertainty analysis using Monte-Carlo simulation. Uncertainty distribution for each impact category is derived from 10,000 calculation runs using random LCI data generated within 95% confidence interval for each raw materials input.

21.3.4 Results and interpretations Environmental impacts are evaluated and results are compared among multiple processes in the interpretation step of LCA. Figs. 21.12 and 21.13 present the overall environmental impacts and resource consumptions for SRM, virgin PP fiber, and recycled PP fiber. As mentioned earlier, 40 kg of virgin and recycled PP fiber is required for 100 m  100 m (100 mm thick) concrete footpath to achieve reinforcement equivalent to 364 kg of SRM. Environmental impacts and resource consumptions are presented in terms of CO2 and PO4 equivalent, and water and fossil fuel consumptions, respectively. Industrial recycled PP fibre Virgin PP fibre

161

0.095

97.2

81.7

0.033

0.28 0.2

Global warming (kg CO2 -eq)

Eutrophication (kg PO4 -eq)

Water use (m3)

21.3

Fossil fuels (kg oil-eq)

Figure 21.12 Life cycle impacts for producing 40 kg of virgin PP fiber and recycled PP fiber.

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Industrial recycled PP fibre Steel reinforcing mesh

1250

81.7

Global warming (kg CO2 -eq)

1.09

0.033

Eutrophication (kg PO4 -eq

245

20.9

21.3 0.2

Water use (m3)

Fossil fuels (kg oil-eq)

Figure 21.13 Life cycle impacts for producing 364 kg of SRM and 40 kg of recycled PP fiber.

As shown in Fig. 21.12, CO2 equivalent associated with 40 kg of recycled PP fiber produced from industrial plastic wastes is approximately 50% less than that produced from 40 kg of virgin PP fiber. Recycled PP fiber also has significantly lower eutrophication impact (0.033 kg PO4 equivalent) compared to 0.085 kg PO4 equivalent for virgin PP fiber. There is a noteworthy reduction of nearly 80% fossil fuel consumption for the production of recycled PP fiber compared to the virgin PP fiber. However, no significant difference in water consumption was found between recycled and virgin PP fiber. More staggering reduction across all categories of environmental impacts was observed for production of recycled PP fiber compared to 364 kg of SRM (Fig. 21.13). Compared to SRM, global warming potential and eutrophication for recycled PP fibers were 15 times and 33 times less, respectively. Similarly, reduction in water consumption and fossil fuel consumption was significant at 99% and 91%, respectively. Detailed contributions from different substages of production of virgin and recycled PP fibers are presented in Fig. 21.14. Fiber extrusion process from PP granules is essentially the same for both virgin and recycled PP fibers. Contribution from transportation is also not significantly different for the two fibers. However, virgin PP fiber is produced from fossil fuel feedstock; hence, consumption of fossil fuel and consequently global warming potential for virgin PP fiber are remarkably higher than that for recycled PP fiber, which are produced from 100% industrial plastic waste. Production of virgin PP granules also has notably high eutrophication (PO4 equivalent). Fig. 21.15 presents contributions of major substages of production of 40 kg of recycled PP fiber compared to the production of 364 kg of SRM. Primary steel is

Sustainability of using recycled plastic fiber in concrete 1.2

PP fibre production Transportation for PP granulates Industrial PP waste collecting and reprocessing MRF collection and sorting Virgin PP granulate production

140 Global warming (Kg CO2-eq)

457

120

1.0 0.8

3

Water use (m )

100

PP fibre production Transportation for PP granulates Industrial PP waste collecting and reprocessing MRF collection and sorting Virgin PP granulate production

80 60

0.6 0.4

40 0.2

20

0.0

0

Eutrophication (kg PO4-eq)

0.10

0.08

Industrial recycled PP fibre

Virgin PP fibre

PP fibre production Transportation for PP granulates Industrial PP waste collecting and reprocessing MRF collection and sorting Virgin PP granulate production

0.06

0.04

100

80

Fossil fuels (kg oil-eq)

Industrial recycled PP fibre

Virgin PP fibre

PP fibre production Transportation for PP granulates Industrial PP waste collecting and reprocessing MRF collection and sorting Virgin PP granulate production

60

40

0.02

20

0

0.00 Industrial recycled PP fibre

Industrial recycled PP fibre

Virgin PP fibre

Virgin PP fibre

Figure 21.14 Contributions of substages of production of virgin and recycled PP fiber.

(a)

(b)

1000

1.0

800 600 400 200

Industrial recycled PP fibre

0.8 0.6 0.4 0.2

Industrial recycled PP fibre

SRM

(c)

SRM

(d) Industrial recycled PP fibre (total) Transportation for SRM Continuous cast and rolling mill EAF BOF

250

Fossil fuels (kg oil-eq)

20

3

Industrial recycled PP fibre (total) Transportation for SRM Continuous cast and rolling mill EAF BOF

0.0

0

Water use (m )

1.2

Eutrophication (kg PO4-eq)

Global warming (kg CO2-eq)

1200

Industrial recycled PP fibre (total) Transportation for SRM Continuous cast and rolling mill EAF BOF

15

10

5

200

Industrial recycled PP fibre (total) Transportation for SRM Continuous cast and rolling mill EAF BOF

150

100 50

0

0 Industrial recycled PP fibre

SRM

Industrial recycled PP fibre

SRM

Figure 21.15 Contributions of substages of production of 40 kg of recycled PP fiber and 364 kg of SRM (a) Global warming, (b) Eutrophication, (c) Water, (d) Fossil Fuels.

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produced from iron ore in blast furnace and BOF. It is an energy-intensive process and requires high temperature and water. It is also responsible for significant CO2 production. Electric arc furnaces are more resource and energy efficient and uses 100% scrap steel. EAF technique is mostly used for the production of SRM in Australia. However, compared to the production of recycled PP fiber, production of SRM consumes significantly higher fossil fuel and produces large amount of CO2 equivalent and PO4 emissions. Continuous cast and rolling of steel bars is also responsible for significant water use and CO2 and PO4 emissions. Results of the comparative LCA presented here of PP fibers and SRM clearly shows that there is a substantial environmental benefit of using 100% recycled PP fiber in concrete.

21.4

Conclusions

Plastic production and use have remarkably increased in the last six decades since mass production of plastic began in 1950s. Due to its low cost, light weight, malleability, and durability, plastic is widely used in every sector around the world. Out of 335 Mt of plastic produced globally every year, less than 9% is recycled. Rest of the plastic waste is either incinerated or is discarded in landfills or in nature as plastic litter. To address this burgeoning plastic pollution problems, it is important to encourage “reduce, reuse, and recycle” of plastic products. Mechanical recycling of industrial plastic wastes into recycled plastic fibers for reinforcing concrete gives a whole new opportunity to recycle and use plastic waste. This chapter is focused on the LCA of recycled PP fibers to quantify and compare its environmental benefits to virgin PP fiber and SRM. Concrete footpath of 100 m  100 m area and 100 mm thickness was used as the functional unit for this study. According to AS3600 (AS3600, 2009), 364 kg of SL82 SRM is required to reinforce concrete footpath of 100 m  100 m and 100 mm thickness. Similarly, 40 kg of virgin and recycled plastic fibers is required to achieve equivalent reinforcement. LCA was conducted based on ISO14040 and ISO14044 (ISO14040, 2006); (ISO14044, 2006) framework using Simapro 8.0 software. Scope of the study was limited to cradle-to-gate study which included raw material extraction, processing, transportation, and manufacturing of the fibers and steel for Australian context. The study excluded maintenance and end-of-life impacts from dismantling and disposal of the materials after concrete footpath’s end of life. The LCA results show that 100% recycled PP fibers produced by mechanical recycling of industrial plastic waste have substantially lower resource consumption and emissions compared to both virgin PP fibers and SRM. Recycled plastic fiber consumed 28% and 78% less water and fossil fuel, respectively, compared to virgin PP fiber. Production of recycled fiber also produced 50% less CO2 equivalent and 65% less PO4 equivalent emissions compared to virgin PP fiber. The saving of resources and emission for recycled PP fiber is even more significant compared to SRM. Production of recycled PP fiber can save up to 99% water and 91% fossil fuel consumption compared to SRM. On the other hand, recycled fiber also produces

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93% less CO2 equivalent and 97% less PO4 equivalent compared to the use of SRM. This study clearly shows that the use of recycled PP fiber to reinforce concrete footpath is a superior alternative to both virgin PP fiber and SRM in all the four environmental indicators.

Acknowledgments The authors acknowledge Fibercon QLD for funding support and for giving us access to fiber manufacturing facilities for the research. The authors also thank Danbar Plastics, Ballarat Australia, Martogg group, Steel Reinforcement Institute of Australia (SRIA) for providing us life cycle inventory data for mechanical recycling of plastics, plastic production, and steel reinforcing mesh production.

References AS3600, 2009. AS3600e2009 Concrete Structures. Standard Australia. Arena, U., Mastellone, M.L., Perugini, F., 2003. Life cycle assessment of a plastic packaging recycling system. Int. J. Life Cycle Ass. 8, 92e98. Building Products Life Cycle Inventory, 2010. www.bpic.asn.au/LCI. Brundtland, G. (Ed.), 1987. Our Common Future: The World Commission on Environment and Development. Oxford University Press, Oxford, UK. Cengiz, O., Turanli, L., 2004. Comparative evaluation of steel mesh, steel fibre and highperformance polypropylene fibre reinforced shotcrete in panel test. Cement and Concrete Research 34, 1357e1364. Ellen MacArthur Foundation, 2016. The New Plastics Economy: Rethinking the Future of Plastics and Catalyzing Action. Ellen MacArthur Foundations. www.newplasticseconomy. org. Geyer, R., Jambeck, R.R., Law, K.L., 2017. Production use and fate of all plastics ever made. Science Advances 3 (7). Hammond, G.P., Jones, C.I., 2008. Embodied energy and carbon in construction materials. Proceedings of the Institution of Civil Engineers Energy 161 (2), 87e98. Hopewell, J., Dvorak, R., Kosior, E., 2009. Plastics recycling: challenges and opportunities. Philosophical Transactions of The Royal Society 364, 2115e2126. ISO14040, 2006. Environmental Management e Life Cycle Assessment e Principles and Framework. British Standards Institution, London UK. ISO14044, 2006. Environmental Management e Life Cycle Assessment e Requirements and Guidelines. British Standards Institution, London UK. Martogg, 2013. www.martogg.com.au/www/home (accessed on 13/06/2018). Perugini, F., Mastellone, M.L., Arena, U., 2005. Life cycle assessment of mechanical and feedstock recycling options for management of plastic packaging wastes. Environ. Prog. 24, 137e154. PlasticsEurope, 2017. Plastics e The Facts 2017 an Analysis of European Plastics Production, Demand and Waste Data. PlasticsEurope, Association of Plastics Manufacturers. www. plsaticseurope.org.

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Simapro, 2010. Australian Indicator Set V3.00 Australasian Unit Process LCI. Simapro 8.0 database, Methods library. Sivakugan, N., Gnanendran, C.T., Tuladhar, R., Kannan, B., 2016. Civil Engineering Materials. Cengage Learning, Boston, USA, p. 428. Shen, L., Worrell, E., Patel, M.K., 2010. Open-loop recycling: A LCA case study of PET bottleto-fibre recycling. Resour. Conserv. Recy. 55, 34e52. Strezov, L., Herbertson, J., 2006. A Life Cycle Perspective on Steel Building Materials. Crucible Group Pty Ltd. Tectonica, 2018. www.tectonica-online.com. Yin, S., Tuladhar, R., Collister, T., Combe, M., Sivakugan, N., Deng, Z., 2015a. Post-cracking performance of recycled polypropylene fiber in concrete. Construction and Building Materials 101, 1069e1077. Yin, S., Tuladhar, R., Shanks, R.A., Collister, T., Combe, M., Jacob, M., Tian, M., Sivakugan, N., 2015b. Fiber preparation and mechanical properties of recycled polypropylene for reinforcing concrete. Journal of Applied Polymer Science 132 (16). Yin, S., Tuladhar, R., Riella, J., Chung, D., Collister, T., Combe, M., 2016a. Comparative evaluation of virgin and recycled polypropylene fiber reinforced concrete. Construction and Building Materials 114, 134e141. Yin, S., Tuladhar, R., Sheehan, M., Combe, M., Collister, T., 2016b. A life cycle assessment of recycled polypropylene fibre in concrete. Journal of Cleaner Production 112, 2231e2242.

Index ‘Note: Page numbers followed by “f ” indicate figures and “t” indicate tables.’ A Acrylic acid monomer grafting, 391 Acrylic superplasticizer, 173 Acrylonitrile butadiene styrene (ABS), 427 Adaptive Gaussian arithmetic average method, 51 Agglutination, 39 Air classifiers, 16, 16f Alcoholysis, 250 Alkaline cement matrix, 71 Asphalt concrete (AC) AASHTO Superpave plus standard, 298e299 acrylonitrile butadiene styrene (ABS), 427 aggregate gradation, 289e290, 290f air voids (Av), 291e292 bending beam rheometer (BBR) tests, 282 biological degradation, 269e270 bitumen replacement. See Bitumen blending duration, 291 chemical catalyst, 269 chemical recycling, 269e270 differential scanning calorimetry (DSC), 289e290 direct and indirect primary sources, 287 dry process, 315, 331e332 dynamic shear rheometer (DSR), 282 emission estimation, 292, 292t European Asphalt Pavement Association (EAPA), 327 factors, 269e270 fatigue, 276e277, 277f flexibility, 281 Hamburg wheel track test, 316 high performance temperature (HPT) rHDPE-modified asphalt binders, 297, 297f rLDPE-modified asphalt binders, 296e297, 296f

rPP-modified asphalt binders, 297e298, 298f hydrocarbon material, 327 hydrophobic and inert material, 287 indirect tensile strength (ITS) test, 274e275, 275f, 292 Kingdom of Saudi Arabia (KSA) perspective, 301e302, 301fe302f low-density polyethylene (LDPE), 315e316 Marshall stability, 270e272 mechanical and volume properties, 270 medium density polyethylene (MDPE), 427 modified asphalt binder, 316e317 moisture sensitivity test, 275e276, 299, 299f multiple stress creep and recovery (MSCR), 298e299 municipal wastes, 269 optimum asphalt content (OAC), 291e292, 299 pavement strength, 427 penetration, 281 performance testing, 291 phase angle tangent, 295, 296f physical properties, 289e290, 291t physical recycling, 269e270 plastomeric polybilt (PB), 288 pollution issue, 329e330 polyethylene terephthalate (PET) aggregate gradation, 431, 431f applications, 428 characteristics, 430e431, 430f, 430t corelok machine, 432 cross-linking resins, 428 designed mixture properties, 432, 432t environmental pollution reduction, 428 Equivalent Single Axle Load (ESALs), 431

462

Asphalt concrete (AC) (Continued) Marshall Stability, 428e429 nominal maximum aggregate size (NMAS), 431 optimum bitumen contents (OBC), 431e432, 432t organic montmorillonite, 428 polymer modification, 429 recycled fiber, 429, 429f resilient modulus (MR). See Resilient modulus (MR) static creep test, 435e437, 436f, 436t, 437f waste packaging, 428 polymer addition, 314e315 polymer modification, 288e289 wet method, 330e331 preparation process, 270, 271f production temperatures, 330 recycled plastic sample, 289e290, 290f recycled plastic waste (RPW), 287e288 benefits and environmental implication, 288 recycled polypropylene (rPP), 287e288 recycling of high-density polyethylene (RHDPE), 287e288 recycling of low-density polyethylene (RLDPE), 287e288 response surface methodology (RSM) method, 279e280 Riyadh refinery, 289e290, 289t rotational viscosity, 293e294, 293fe294f rutting parameter, 277e279, 278f, 294, 295f sample preparation, 291 shredded waste plastic, 314e315, 314f softening point, 281 stabilization dense graded asphalt concrete, 309e311 gap- and open-graded asphalt concrete. See Gap- and open-graded asphalt concrete modified asphalt, 308e309 oxidation catalysts, 309 viscoelastic material, 308 stabilizers replacement cold mix asphalt, 308 gap-graded/open-graded mixtures, 307 gradation curves, 307, 308f

Index

hot mix asphalt (HMA) mixtures, 308 maximum density, 307 mineral filler, 307 mixture design procedures, 307 rigid pavements, 307 warm mix asphalt (WMA), 308 stiffness, 279e280, 280f Strategic Highway Research program (SHRP), 294 strength and durability, 317 styrene-butadiene-styrene (SBS), 288 superpave mix design, 291e292 superpave volumetric parameters, 298e299, 298t terephthalic acid, 269 thermal sensitivity, 300, 300f thermoplastic polyester, 269e270 viscoelastic moduli, 295 viscosity, 281e282 voids filled with asphalt (VFA), 291e292 voids in mineral aggregate (VMA), 291e292 volumetric properties, 272e274 waste polymers, 427 wet process, 315 Attenuation coefficient, 219 B Ballistic separation method, 16e17 BeereLambert’s law, 220, 222 Bending beam rheometer (BBR) tests, 282 Biodegradable plastics, 32 Biopolymers, 32, 32f Bitumen cohesion and adhesion properties, 328e329 composition, 328 distillation process, 328 elementary analysis, 328 GHG emissions and fossil fuel depletion, 329, 330f manufacturing methods, 328 material cost, 329, 329t nonrenewable sources, 329 polystyrene (PS), 327e328 AC-16 dosages, 339, 340t addition, dry method, 335, 335f bulk density and air void content, 336 Cantabro Test, 341 characteristics, 332, 334, 334t

Index

compactibility test, 337, 338f compactibility test results, 341, 341f dynamic module test, 342 EN ISO 1183-1:2004 results, 334, 335t fatigue test, 338, 338f fatigue test results, 342, 342t homogenous homogenous, 335 laboratory test, 335 life cycle assessment (LCA), 338e339, 339f, 343e344, 344f mechanical performance, 333 ophite, 334 particle loss test, 336, 337f particle size distribution, 333e334, 335t plastic deformations, 341 polymer modified (PMB) bitumen, 333 porous asphalt, 343, 343t samples, 334, 334f selection of, 332 slope percentage, reference mixture value, 340e341, 340f stiffness test, 337, 338f Technological Institute of Plastics, 334 types, 332 water sensitivity standards, 336, 336t water sensitivity test, 336, 336f wheel tracking test, 336, 337f Zwick Z100 hydraulic machine, 342 Black/dark color polymers, 31 Bulk specific gravity (BSG), 273 C Carpet fiber reinforced concrete disposal rate, 411 durability-related properties, 418 fibrous material wastes, 412 impurities, 416 interfacial properties, 416 manufacturing process, 411, 412f mechanical properties compressive strength, 418e419 flexural behavior, 420e421, 421f impact behavior, 421e422, 422f tensile behavior, 419e420, 420f natural and synthetic fibers, 415 near-infrared spectroscopic analyzer, 414 needle-punched carpet, 413e414 nondegradable characteristics, 411 Nycon-G, 414

463

nylon 6 fibers, 414 physical/mechanical properties, 415, 415t polyester fiber, 416 polypropylene fiber, 416 postconsumer carpets, 411 shrinkage, 417e418 slump, 416e417 sources, 412e413 structure of, 413, 413f textile floor covering (TFC) materials, 411 tufted carpet, 413 types, 413 unit weight density, 417, 417f wastes, 414 woven carpets, 413 Ccapillary water absorption (CWA), 154e155 Chloride ion penetration, 133 Circular economy approach, 441e442 Compressive strength carpet fiber reinforced concrete, 418e419 dioctyl terephthalate (DOTP) concrete, 252, 253f expanded polystyrene (EPS), 148 metalized plastic waste (MPW) fibers, 358, 359fe360f polyolefins, 175 polyvinyl chloride (PVC) fibers, 373e377, 376f, 378f with concrete density, 125, 125f degradation of, 126 e-waste wire, 126e127 failure mode, 127 granules content, 123 granules variation, 127, 127f reduction in, 125 self-compacting concrete, 125e126 strength loss, 125e126 Computational fluid dynamics (CFD), 40, 63 Construction materials carbon footprint, 444 chemical recycling, 443e444 embodied energy, 444e445, 445f energy consumption, 444 environmental sustainability, 442e443 life cycle assessment (LCA) concrete footpath, 448, 448f “cradle-to-gate”, 448e449 cradle-to-grave approach, 447

464

Construction materials (Continued) energy and emissions, 447 environmental impacts, 455e458, 455fe457f framework of, 447, 447f functional units, 449 life cycle impact assessment (LCIA), 454e455 life cycle inventory (LCI) analysis, 449e453, 450te451t, 452fe454f macroplastic fibers, 448 mechanical recycling, 446e447 plastic products, 446, 446f SL82 steel reinforcement mesh (SRM), 448, 449f operational energy, 445e446, 445f social sustainability indicators, 442e443 stakeholders, 443 sustainability development, 442e443, 442f sustainability hierarchy, 443, 443f Continuum mechanics, 40e41 Continuum models, 43 Crude oil extraction, 1 Cutting/shredding process, 39 D Dielectric particles, 19 Differential scanning calorimeter (DSC), 70, 77, 289e290 crystallinity, 78e79, 79f, 79t Dioctyl terephthalate (DOTP) concrete alcoholysis, 250 chemical degradation, 250 chemical recycling, 250 chemical resistance, 249e250 compressive strength, 252, 253f disadvantages, 250 electrical resistance, 250e251, 251f, 255e257, 257f polymeric wastes, 249 properties, 250e251, 251t splitting tensile strength, 254, 255f thermal conductivity, 249e250, 255, 256f thermal insulation, 249e250 ultrasonic pulse velocity (UPV), 249e250, 253e254, 253f water absorption, 254, 254f workability performance, 251e252, 252f Dispersed-dense two-phase flows, 41

Index

Dry technique air classifiers, 16, 16f ballistic separator, 16e17 Dynamic shear rheometer (DSR), 282 E Eddy current separation method, 27, 27f Elastic modulus, 129e131, 130fe131f expanded polystyrene (EPS), 149 polyolefins, 175 Electrical insulated concrete, 255e257 Electrostatic separation, 19, 20f, 40 Electrostatic sorting technique, 78e79 Energy Dispersive X-ray Fluorescence (EDXRF), 24e25 Environmental costs, 3e4 Environmental impacts, 1e2 Equivalent Single Axle Load (ESALs), 431 Eulerian reference framework, diluted dispersed two-phase flows, 43 loading ratio, 45e46 mass conservation, 44e45 momentum, 44e45 Stokes number, 45 European Asphalt Pavement Association (EAPA), 327 European waste plastics, 1e2 Expanded polystyrene (EPS) chemical agents and mechanical techniques, 137e138 chemical properties, 141 civil engineering applications, 137e138 concrete barriers, 146 concrete density, 146 durability properties capillary water absorption (CWA), 154e155 chemical attack, 155 fire resistance, 156 freezeethaw resistance, 155 heat resistance, 156 permeability, 155 water absorption, 154 fresh concrete properties flow table, 147 reinforcement in, 146e147 slump value, 147 workability of, 146e147 industrial byproducts, 137

Index

lightweight concrete (LWC), 137e138 briquetting machines, 169 crushing, 168e169 crystal polystyrene granule, 169 economic assessment, 168 extrusion of, 169 hammer mills and knife mills, 169 magnetic separator, 170 physical treatment, 168e169 polyolefins, 170. See also Polyolefins postconsumption waste, 169 virgin expandable material, 170 wood/paper residues, 170 load-bearing and non-load-bearing members, 137e138 long-span concrete structures, 146 mechanical properties compressive strength, 148 elastic modulus, 149 failure mode, 149e150, 150f flexural strength, 150e151 length/volume change, 152 splitting tensile strength, 149 stabilized polystyrene (SPS), 152e153 stressestrain relationship, 149 ultrasonic pulse velocity, 151e152 normal weight concrete (NWC) production, 137 physical properties, 140e141, 142te143t polystyrene production, 138e139 preparation, 139e140 reinforced concrete beams, 156 structural applications, 146 thermal conductivity, 153e154 types and quantities, 141, 144te145t Extrusion, 39 F Fiber-reinforced concrete (FRC) adhesion characteristics, 388 artificial conglomerate stone, 387 aspect ratio, 387 cement matrix, 388 composition and dosage, 387 discrete fibers, 388 economic and environmental benefits, 388 laboratory tests, 388e389 mechanical characteristics, 387 properties, 387

465

side effects, 387 steel reinforcement, 387 Fineness modulus (FM), 117e120 Float-sink sorting system, 72 Flotation processes, 21 Fossil-based plastics, 1 Fossil fuel extraction, 12 Fourier transform infrared (FTIR), 70, 77 molecular orientation, 77e78, 78f Fracture mechanics, 132 Fresh concrete density compact disk plastic coarse aggregate concrete, 102, 103f compact disk plastic fine aggregate concrete, 102, 102f CP plastic coarse aggregate concrete, 102, 103f high-density plastic fine aggregate concrete, 101, 102f PET plastic fine aggregate concrete, 101, 101f mix proportion and design chemical composition, 86, 86t economy and environmental issues, 86 high-density polyethylene (HDPE), 89e90, 89fe90f, 90t, 91f natural and plastic aggregate, 87 physical properties, 86, 87t polyethylene terephthalate (PET). See Polyethylene terephthalate (PET) quality, 85 requirements, 85e86 waste compact disk, coarse aggregate, 93, 94f, 94t waste compact disk, fine aggregate, 90e91, 91t, 92f water drink bottle cover, coarse aggregate, 90e91, 92t, 93f, 93t workability, 86 properties, 85 quality and durability, 85 self-compacting concrete (SCC). See Self-compacting concrete (SCC) workability ball penetration test, 95 compact disk fine plastic aggregate (CDFPA), 98, 99f, 99t, 100, 100f, 101t compacting factor test, 95, 95f

466

Fresh concrete (Continued) definition, 94 high-density polyethylene fine plastic aggregate (HDPFA), 97, 98f, 98t polyethylene terephthalate (PET), 95e97, 96fe97f, 97t slump test, 95, 95f test techniques, 94 Vebe test, 95 waste cover plastic aggregate (CPA), 98e100, 99f, 100t Froth flotation, 47 G Gap- and open-graded asphalt concrete “Asphalt Rubber” (AR), 313 crumb rubber (CR), 313 drain down, 311 draining properties, 313e314 FischereTropsch wax, 312e313 indirect tensile strength, 312e313 manufacturing processes, 311e312 Marshall stability, 312e313 natural fibers, 311e312 polymer-modified asphalts (PMA), 312e313 resilient modulus tests, 312e313 rubber-modified asphalt binders, 313 stabilizer materials, 311e312 stone matrix asphalt (SMA), 311 Gravity separation method dry air classifiers, 16, 16f ballistic separator, 16e17 wet, 16, 17fe18f hydrocycloning, 18e19, 18f jigging, 18 sink-float separation, 17e18, 17f Greenhouse gas emissions, 1e2 H Hazardous electronic plastic waste (ewaste), 369e370, 373f Heat of fusion, 78e79, 79t High performance temperature (HPT) rHDPE-modified asphalt binders, 297, 297f rLDPE-modified asphalt binders, 296e297, 296f

Index

rPP-modified asphalt binders, 297e298, 298f Hybrid Lagrangian Particle Tracking (HLPT), 40, 50e51 Hydraulic separation agglutination, 39 ANSYS FLUENT software, 63, 63f chemical/mechanical process, 39 computational fluid dynamics (CFD), 40, 63 concentration rates, 53 cutting/shredding process, 39 dispersed multiphase flows modeling, 43 in dry conditions, 39 electrostatic separation, 40 energy recovery, 39 Eulerian reference framework, diluted dispersed two-phase flows loading ratio, 45e46 mass conservation, 44e45 momentum, 44e45 Stokes number, 45 experiment duration, 52 extrusion, 39 high-quality products, 39e40 Hybrid Lagrangian Particle-Tracking (HLPT), 40 image analysis technique, 40 laminar and realizable k-e model, 64e65, 64f mechanical recycling plants, 46e47 monomaterial separation tests, 52 bioplastics, 59e60 flow rate, 57e58 MATER-BI 2-WF, 60 PET 6-WF, 57e58 PVC 4-WP, 58e59 sedimentation efficacy, 54 solid-phase volume fraction, 54 two-way coupling, 54 virgin material samples, 54e56, 57f waste and regenerated samples, 54e56, 55fe56f multimaterial sample composition, 53, 53t multimaterial separation tests, 52 configurations and sample sizes, 60 grade and recovery, 62e63, 62f mechanical recycling process, 62e63 PET-PVC and PET-PLA mixtures, 60

Index

polymer densities, 60e61 recirculation zones, 62 multiphase flow collision-dominated flow, 41 continuum mechanics, 40e41 dispersed-dense two-phase flows, 41 fluid dynamic forces, 42 interparticle spacing, 41 multiphase systems, 40e41 particleeparticle collisions, 41 particle volume fraction, 41 Stokes flow, 41 two-phase flow, 41 velocity response time, 41 multistep recycling process, 52e53 phase coupling carrier phase, 42 mass coupling, 42 momentum coupling, 42 one-way coupling regimes, 42, 43f particleefluid turbulence interaction, 42, 44f particle Reynolds number, 42 policy makers and research institutions, 39 polymer production, 39 polymer sample characteristics, 51, 52t polymer separation, 39 product life cycle, 51 recycling, 39 separation tests effectiveness, 53 separator channel constant flow rate, 48e49 experimental setup, 48e49, 49f flow rates, 50, 50t geometric arrangements, 48, 48f semicylindrical tubes, 48 three-dimensional representation, 48e49, 49f two-dimensional representation, 48, 48f fluid mechanics investigation, 50e51 turbulence models, 64 urban plastic waste samples, 51 virgin plastic particles, 51 washing/drying, 39 wet technology, 40 Hydrocycloning technology, 18e19, 18f Hydrogenous aggregates colemanite aggregates, 223e224 limonite-steel aggregates, 223e224

467

liquid polymer, 224 polymeric materials, 225 Portland cement concrete, 223 selection, 225, 226f statistical evaluation, 223 Styrene Butadiene Rubber (SBR) latex, 224 thermal neutron absorption, 224 thermal neutron dose rates, 223e224 total aggregate content, 223e224 water-cement ratio, 223 Hyperspectral imaging (HSI) technique, 23e24 application, 23e24 architectures, 24 characteristics, 24 spatial and spectral data, 23e24 I Indirect tensile strength (ITS), 274e275, 275f, 292 J Jigging method, 18 K Kingdom of Saudi Arabia (KSA) perspective, 301e302, 301fe302f L Lagrangian framework, 43 Laser-induced breakdown spectroscopy (LIBS), 25 L-Box test, 104 LED-based planar illuminator, 50 Life cycle assessment (LCA), 442 concrete footpath, 448, 448f “cradle-to-gate”, 448e449 cradle-to-grave approach, 447 energy and emissions, 447 environmental impacts, 455e458, 455fe457f framework of, 447, 447f functional units, 449 life cycle impact assessment (LCIA), 454e455 life cycle inventory (LCI) analysis, 449e453, 450te451t, 452fe454f macroplastic fibers, 448 mechanical recycling, 446e447

468

Life cycle assessment (LCA) (Continued) plastic products, 446, 446f polystyrene (PS), 338e339, 339f SL82 steel reinforcement mesh (SRM), 448, 449f Life cycle impact assessment (LCIA), 454e455 Life cycle inventory (LCI) analysis, 449e453, 450te451t, 452fe454f Lightweight aggregate for concrete (LWAC). See Expanded polystyrene (EPS) Lightweight aggregates (LWA), 167 Lightweight concrete (LWC), 137e138 environmental risks, 167 expanded polystyrene (EPS) briquetting machines, 169 crushing, 168e169 crystal polystyrene granule, 169 economic assessment, 168 extrusion of, 169 hammer mills and knife mills, 169 magnetic separator, 170 physical treatment, 168e169 polyolefins, 170. See also Polyolefins postconsumption waste, 169 virgin expandable material, 170 wood/paper residues, 170 lightweight aggregates (LWA), 167 municipal solid waste (MSW), 168 natural resources, 167 thermal insulation, 167 D-Limonene, 139 Loss on ignition (LOI) tests, 236 Low-density polyethylene (LDPE), 190 M Macrosorting method, 10 Magnetic density separation (MDS), 20e21, 21f, 46e47 Magnetic drum separator, 26, 26f Magnetic head pulley separator, 26e27, 26f Magnetic separation method, 26e27, 26f Manual sorting, 72 Marine plastics, 32e33 Marshall stability, 270e272, 428e429 Medium density polyethylene (MDPE), 427 Melt flow index (MFI), 74 Metalized plastic waste (MPW) fibers

Index

advantages and limitations, 364e365 axial compression, deformation characteristics, 362e364 peak stress and deformation response, 362 strain values, 362 stressestrain curve, 362, 364f stressestrain values, 360, 363f test results, 360 compressive strength, 358, 359fe360f concrete mix proportions, 350, 351t concrete specimens slump of, 352e353, 356f strength tests, 353, 356f stressestrain relationship, 353, 357f concrete workability long-length fibers, 356e357 macrofibers, 355e356 response of, 355, 357f short-length fibers, 356e357 type A fibers, 355 crack resistance, 352 cube and cylinder molds, 352, 355f deformation characteristics, 352 food packaging, 349 hazardous environmental impacts, 349 materials and test specimens, 351 parameters, 350 polypropylene (PP), 351e352 postconsumer plastic wastes advantages, packaging activities, 350 direct and primary sources, 349 environmental safety, 349 hazardous environment, 350 municipal solid waste (MSW), 349 preparation process, 350, 351f properties, 350, 352t quantity and batch information, 352, 354t specimen information, 352, 355t splitting tensile strength, 358e360, 361fe362f tensile strength, 352 tests on, 352, 353f water-to-cement ratio, 352 Micromeritics Apparatus (Autopore III), 175 Microplastics, 12 Microsorting method, 10 Modified expanded polystyrene (MEPS), 153e155

Index

Moisture sensitivity test, 299, 299f Multiple stress creep and recovery (MSCR), 298e299 Municipal solid waste (MSW), 168, 349 N Near infrared spectroscopy (NIR), 23, 72, 414 Needle-punched carpets, 413e414 Neutron (n) radiation absorbed dose, 221 absorption reactions, 217e218 atomic density, 220 attenuation coefficient, 219 BeereLambert’s law, 220 cross-section, 219 dose rate, 221 dose transmission measurements, 222e223 flux transmission, 220 flux transmission measurements, 222 half value layer (HVL), 220e221, 235 interactions, 216 kinetic energy, 216 macroscopic cross-section, 220 microscopic cross-section, 219 radiation shield, 218 scattering reactions, 216e217, 217f, 218t shielding efficiency, 221 spontaneous neutron emission, 216 tenth value layer (TVL) thickness, 221 test methodology, 221e222, 222f thermal neutrons, 216 Nominal maximum aggregate size (NMAS), 431 Nonbiodegradable plastic waste, 441e442 Nondestructive (NDT) analysis, 255e257 Nondestructive testing techniques, 151 Nycon-G, 414 Nylon 6 fibers, 414 O Ophite, 334 Optimum asphalt content (OAC), 291e292, 299 Optimum bitumen contents (OBC), 431e432, 432t Overbelt magnetic separator, 26, 26f

469

P Packaging applications, 1e2 Particle Reynolds number, 42 Particle volume fraction, 41 PISCC mixes hydrogen loading, 235e237, 236t L-box tests, 231 properties, 231, 232t reinforced concrete applications, 232 rheological properties, 231 shielding characteristics, 237, 238te239t, 240e244, 242fe243f slump flow characteristics, 231, 232f static segregation characteristics, 233e235, 233t, 234f statistical analysis, 240, 241f strength characteristics, 234e235 visual segregation index (VSI), 231 workability characteristics, 231 Plastic wastes separation auxiliary separation technologies characteristics, 25 Eddy current separation, 27, 27f ferrous metals, 25 magnetic separation, 26e27, 26f nonferrous metals, 25 average reflectance spectra, 30, 31f biopolymers, 32, 32f black/dark color polymers, 31 electrostatic separation, 19, 20f end-of-life plastic wastes, 10 feed characteristics, 15 flotation processes, 21 gravity separation dry, 16e17, 16f wet, 16, 17fe18f high-density polyethylene (HDPE), 30 low-density polyethylene (LDPE), 30 macrosorting method, 10 magnetic density separation (MDS), 20e21, 21f marine plastics, 32e33 material properties, 9 mechanical process, 9 microsorting method, 10 polymer-based products, 10 polypropylene-polyethylene (PP-PE) separation, 30 quality assessment, 9

470

Plastic wastes separation (Continued) quality control contaminations levels, 28e29 hyperspectral imaging (HSI) platform, 29, 29f performance characteristics, 28 polymeric impurities, 28 polymer mixing evaluation, 29 quality certification, 28 rheological and mechanical properties, 28 X-ray fluorescence, 30 quality requirements, 15 recycling chain collection, 15 extrusion and granulation, 15 manual sorting, 15 material/polymer sorting, 15 operations, 13, 13f screening, 15 size reduction, 15 sorting technology, 15 secondary plastics, 9 sensor-based sorting system. See Sensorbased sorting system sources, 10 biodegradable properties, 13 economic and environmental damage, 12 European plastics converter demand, 11, 11f, 13, 14f fossil fuel extraction, 12 microplastics, 12 packaging waste treatment, 11 plastic residues, 12 production, 10e11 raw materials types, 12 “single-use” plastic products, 12 thermoplastics, 13 thermosets, 13 types and applications, 13, 14t waste generation, 11, 12f start-of-life plastic wastes, 10 waste-sorting technologies, 9 Plastomeric polybilt (PB), 288 Poisson’s ratio, 133 POLIMAR, 173 Polyester fiber, 416 Polyethylene plastics, 115 Polyethylene terephthalate (PET)

Index

acrylic acid monomer grafting, 391 adhesion, 390e391 advantages, 390 ambient-temperature plasma activation, 391 asphalt concrete (AC) aggregate gradation, 431, 431f applications, 428 characteristics, 430e431, 430f, 430t corelok machine, 432 cross-linking resins, 428 designed mixture properties, 432, 432t environmental pollution reduction, 428 Equivalent Single Axle Load (ESALs), 431 Marshall Stability, 428e429 nominal maximum aggregate size (NMAS), 431 optimum bitumen contents (OBC), 431e432, 432t organic montmorillonite, 428 polymer modification, 429 recycled fiber, 429, 429f resilient modulus (MR). See Resilient modulus (MR) static creep test, 435e437, 436f, 436t, 437f waste packaging, 428 behavior of, 397 bending tests, 403 cement-based mortar, 394e395 cement-lime mortars, 394e395 cement matrix, 393 chemical behavior, 392e393 circular PET fibers, 394, 395f components, 389 compressive failure, 399, 399f concrete reinforcement, 398, 398f crack and microcrack distribution system, 394 crack resistance, 394e395, 395f vs. dioctyl terephthalate (DOTP) concrete, 263, 264f. See also Dioctyl terephthalate (DOTP) concrete abrasion behavior, 258 building materials, 257e258 compressive strength, 260, 261f concrete density, 259 elastic modulus, 257e258 flexural strength, 259

Index

mechanical properties, 258 pozzolanic materials, 258 slump flow, 257e260, 260f splitting tensile strength, 257e258, 260, 262f thermal conductivity values, 261e262, 262fe263f ultrasonic pulse velocity, 260, 261f water/cement ratio, 258e259 direct tensile test, 399, 400f ecological concrete, 390 European code, 399 fibers, types, 393, 393f food industry, 389 fresh concrete aggregate gradation, 88 chemical resistance, 87 mechanical properties, 87 physical properties, 87e88, 88t saturated sand, 89 sieve analysis, 88, 88t soft drink plastic bottles, 87e88, 87f superplasticizer properties, 88, 89t geometry and shape, 392, 392f grid of, 395e396, 396f, 404e405, 405f half bottle reinforcement, 402, 403f load-deflection curves, 392e393, 393f load-deformation plots, 401, 402f, 403e404, 404fe405f loading test, 395, 396f load stresses, 394, 394f maleic anhydride grafted polypropylene, 391e392 mechanical properties, 389, 389t nonreinforced plate, 405, 406f oxygen plasma treatment, 392 PET strips, 403, 404f physical and mechanical characteristics, 389 plasma treatment process, 391 polyethylene (PE), 390 postcracking phase, 390 post-peak behavior, 401 preliminary tests, 399, 400f reinforced plate, 405, 407f sewing effect, 390, 401, 401f shear cracks, 402, 403f structural integrity, 406 superficial cracks, 395e396, 397f

471

sustainable fiber-reinforced concrete. See Fiber-reinforced concrete (FRC) tensile modulus of elasticity, 389 tensile strength, 401 Testing Laboratory of the Department of Civil Engineering and Architecture, 398e399 thermal conductivity, 396e397 time-history, 406, 407f workability, 391e392 Polylactic acid (PLA), 32, 32f Polymer-based products, 10 Polymer density, 47 Polyolefins acoustic performance, 172 acrylic superplasticizer, 173 casting and curing, 175 cement water ratio, 171 chemical composition and physical properties, 173, 173t compressive strength, 175 conduction and radiation, 172 designation and mix proportion, 174, 175t elastic modulus, 175 exceptional performance, 172 flexural tests, 175 mechanical properties, 181, 182t compression strength tests, 180, 180f hydration mechanism, 180e181 hydrophobic behavior, 180 tensile strength, 181, 181f mechanical resistance, 171 Micromeritics Apparatus (Autopore III), 175 natural hydraulic lime, 174 nonstructural applications, 171 physical properties acrylic superfluidifier, 178 apparent density, 176, 176f concrete specimens, 176, 177t heterogenous morphology, 178, 180f mortar samples, 176, 177t pore size distribution, 177, 178f scanning electron microscopy (SEM), 178, 179f plastic aggregate, 173, 174f plasticization and densification, 173 POLIMAR, 173 polystyrene spheres, 171

472

Polyolefins (Continued) porosity, 175 Portland Cement type II, 173 pozzolanic Portland 325, 171 quality and quantity, 170e171 structural applications, 172 surfactants, 171 technical requirements, 173, 174t thermal exposure, 176 thermal insulation, 172 thermal stability apparent density, 181, 182t compressive strength, 182e183, 182f linear elastic modulus, 181, 182t Polypropylene (PP) aggregates, 441e442 chemical agents, 189 densities and particle size, 191, 193t hygric properties water absorption coefficient, 210, 210t water vapor transport parameters, 210e211, 210t low-density polyethylene (LDPE), 190 mechanical properties, 191, 195t cement hydration reaction, 199e200 compressive strength, 200, 201f, 201te202t flexural strength, 200e203, 202f, 202te203t modulus of elasticity, 203e205, 204f, 204te205t thermal stability, 205e207, 206f natural aggregates (NAs) replacement, 190 physical and chemical properties, 189 postconsumer plastic, 190 preparation, 193e196, 196t, 197f properties, 189, 190t storage and reprocessing conditions, 191 structural properties Archimede’s weight, 197 bulk density, 197 elemental map, 198, 199f lightweight concrete, 197, 198t microstructure and morphology, 198 porosity, 197 scanning electron microscopy (SEM), 198, 198f thermal properties heat transport and storage properties, 207 of lightweight concrete, 207, 208t, 209f

Index

thermodilatometry, 209, 209f thermophysical properties, 191, 195t types, 189e191, 192t waste PP-based aggregates, 191, 194f Polypropylene (PP) fibers, melt spinning process circular recycled fibers, 70 crystallinity crystal structure and melting behavior, 78 a-form crystals, 79 b-form crystals, 79 heating curves, 78e79, 79f heat of fusion, 78e79, 79t hot-drawing process, 79 peak temperatures, 78 tensile strength, 79, 81f virgin and recycled fibers, 79, 80f crystallization, 74 differential scanning calorimeter (DSC), 70, 77 Fourier transform infrared (FTIR), 70, 77 global plastic production, 69 heterogenous resin types and grades, 73 hot-drawing process, 70 industrial-scale production, 75, 75f mechanical properties aging, 81e82 postcracking performance, 80 stress-strain curves, 81 tensile properties, 81, 81t tensile tests, 80 United STM Test system, 80, 80f mechanical recycling alkaline cement matrix, 71 cleaning, 72 electrostatic sorting technique, 78e79 float-sink sorting system, 72 manual sorting, 72 near infrared (NIR) spectroscopy, 72 pellets/granules, 72 plastic flakes, 72 postconsumer and postindustrial plastic wastes, 71 reprocessing techniques, 72 shredding, 72 types, 71 waste components, 71 melt blending, 74e75, 75f melt flow index (MFI), 74

Index

melt spinning setup, 75e76, 76f micro plastic fibers, 69 molecular chain segments, 73 molecular orientation, 77e78, 78f monofilament fibers, 75e76 production rates, 70 raw material, characteristics, 76, 76t synthetic fibers, 69 temperature zone, 73e74 tensile strength, 70e71 thermomechanical degradation, 73, 73f thermoplastics, 69e70 thermosets, 69e70 types, 76e77, 77f Young’s modulus, 70e71 Polypropylene-polyethylene (PP-PE) separation, 30 Polystyrene (PS) bitumen replacement, 327e328 AC-16 dosages, 339, 340t addition, dry method, 335, 335f bulk density and air void content, 336 Cantabro Test, 341 characteristics, 332, 334, 334t compactibility test, 337, 338f compactibility test results, 341, 341f dynamic module test, 342 EN ISO 1183-1:2004 results, 334, 335t fatigue test, 338, 338f fatigue test results, 342, 342t homogenous homogenous, 335 laboratory test, 335 life cycle assessment (LCA), 338e339, 339f, 343e344, 344f mechanical performance, 333 ophite, 334 particle loss test, 336, 337f particle size distribution, 333e334, 335t plastic deformations, 341 polymer modified (PMB) bitumen, 333 porous asphalt, 343, 343t samples, 334, 334f selection of, 332 slope percentage, reference mixture value, 340e341, 340f stiffness test, 337, 338f Technological Institute of Plastics, 334 types, 332 water sensitivity Standards, 336, 336t

473

water sensitivity test, 336, 336f wheel tracking test, 336, 337f Zwick Z100 hydraulic machine, 342 Polyvinyl chloride (PVC) aggregates concrete properties, 117, 118t change of, 123, 124t chloride ion penetration, 133 compressive strength, 123e127, 125f copper wire insulation, 117e120 density, 117e120 elastic modulus, 129e131, 130fe131f eewaste, 117e120 fine aggregate, 117e120, 119f fineness modulus (FM), 117e120 fracture mechanics, 132 fresh concrete density and workability, 121 interfacial transition zone, 133e134 medium aggregate, 117e120, 120f non-destructive behavior, 132e133 physical properties, 122e123, 122f plastic granules, 117e120, 119f Poisson’s ratio, 133 reinforcement corrosion, 133 scraped PVC pipes, 117e120, 120f sieve analysis, 117e120 superplasticizer dosages, 121 tensile strength, 117e120, 127e129, 129fe130f plastic material separation, 115e116 polyethylene plastics, 115 postconsumed wastes, 116e117 primary and secondary recycling techniques, 115e116 R-PET fiber reinforced concrete, 116 thermal degradation, 115e116 vinyl chloride monomer, 115 Vinylplus reports, 115e116 waste stream management, 116e117 Polyvinyl chloride (PVC) fibers characteristics, 369 compaction factor, 372e373, 375f compressive strength, 373e377, 376f, 378f concrete properties, 369e370, 371t flexural strength, 377e378, 379f fresh/dry density, 373, 376f hazardous electronic plastic waste (e-waste), 369e370, 373f in-situ concrete construction, 369

474

Polyvinyl chloride (PVC) fibers (Continued) manufacturing process, 370, 372f modulus of elasticity, 380e382, 381f municipal plastic wastes, 369e370 properties, 370, 374t shear strength, 380, 380fe381f slump, 370e372, 375f split tensile strength, 378e380, 379f statistical data, 369e370 ultrasonic pulse velocity (UPV) test, 382, 382f Portland Cement type II, 173 Postconsumer plastic wastes advantages, packaging activities, 350 direct and primary sources, 349 environmental safety, 349 hazardous environment, 350 municipal solid waste (MSW), 349 Post-consumer waste rates, 2e3, 3f Product life cycle, 51 R Recycled polypropylene (rPP), 287e288 Recycling chain collection, 15 extrusion and granulation, 15 manual sorting, 15 material/polymer sorting, 15 operations, 13, 13f screening, 15 size reduction, 15 sorting technology, 15 Recycling of high-density polyethylene (RHDPE), 287e288, 293e294 Recycling of low-density polyethylene (RLDPE), 287e288, 293e294 Resilient modulus (MR), 279e280, 300, 300f data acquisition, 433 definition, 433 elastic behavior, 433e434 samples, 434, 434fe435f test, 433, 433f, 434t Response surface methodology (RSM) method, 279e280 Riyadh refinery, 289e290, 289t Roentgen Equivalent Man (REM), 222e223 R-PET fiber reinforced concrete, 116

Index

S Secondary plastics, 9 Self-compacting concrete (SCC) chemical admixtures, 103e104 coarse plastic aggregate compact disk plastic, 108e109, 109fe111f waste plastic type, 108, 109f water drink plastic bottle cover, 111e112, 111fe113f definition, 104 fine plastic aggregate, 105e108, 106fe108f fly ash, chemical composition, 104e105, 106t L-Box test, 104 properties tests, 104, 105f requirements, 104 rheological properties, 103e104 slump flow test, 104 V-funnel test, 104 ViscoCrete-5930, 103e104 Sensor-based sorting system components, 22, 22f hyperspectral imaging (HSI), 23e24 laser-induced breakdown spectroscopy (LIBS), 25 logics and robotic units, 22 near infrared spectroscopy (NIR), 23 physical properties, 21e22 visible spectroscopy, 22e23 X-ray fluorescence (XRF), 24e25 Sieve analysis, 117e120 Silica fume (SF), 139 Sink/float separation, 47 Sink-float separation process, 17e18, 17f Stabilized polystyrene (SPS), 140 Steel reinforcing mesh (SRM), 442 Stokes flow, 41 Stone matrix asphalt (SMA), 311e313 Strategic Highway Research program (SHRP), 294 Styrene Butadiene Rubber (SBR) latex, 224 Styrene-butadiene-styrene (SBS), 288 Sustainable Development, 1e2 T Technological Institute of Plastics, 334 Tensile strength

Index

metalized plastic waste (MPW) fibers, 352 polyvinyl chloride (PVC) CEB-FIP code, 128 compressive strength, 128 correlation coefficient, 129 e-waste, 129 regression analysis, 128 self-compacting concrete, 128 splitting tensile strength, 128e129, 129f strength reduction, 127e128 variation of, 129, 130f Terephthalic acid, 269 Testing Laboratory of the Department of Civil Engineering and Architecture, 398e399 Textile floor covering (TFC) materials, 411 Thermal degradation, 115e116 Thermogravimetric analysis (TGA), 236 Thermomechanical degradation, 73, 73f Thermoplastics, 13, 69e70, 269e270 Thermosets, 13, 69e70 Triboelectric separation process, 19, 20f Tufted carpets, 413 Two-fluid models, 43 U Ultrasonic pulse velocity (UPV), 151e152 dioctyl terephthalate (DOTP) concrete, 249e250, 253e254, 253f polyvinyl chloride (PVC) fibers, 382, 382f United STM Test system, 80, 80f V V-funnel test, 104 Vinyl chloride monomer, 115 Virgin and waste polymer absorption phenomenon, 244 hazardous radiation, 215 HDPE powder coarse aggregate segregation, 230 mix design, 229 self-compacting concrete, 229e230 self-compacting concrete technology, 228e229 separation of, 230, 230f

475

static segregation measurement, 229e231, 229f water adsorption characteristics, 228 workability and strength characteristics, 227e228, 227fe228f hydrogenous aggregates colemanite aggregates, 223e224 limonite-steel aggregates, 223e224 liquid polymer, 224 polymeric materials, 225 Portland cement concrete, 223 selection, 225, 226f statistical evaluation, 223 Styrene Butadiene Rubber (SBR) latex, 224 thermal neutron absorption, 224 thermal neutron dose rates, 223e224 total aggregate content, 223e224 water-cement ratio, 223 inelastic scattering, 244 neutron (n) radiation. See Neutron (n) radiation nuclear reactors, 215 particle accelerators, 215 PISCC mixes hydrogen loading, 235e237, 236t L-box tests, 231 properties, 231, 232t reinforced concrete applications, 232 rheological properties, 231 shielding characteristics, 237, 238te239t, 240e244, 242fe243f slump flow characteristics, 231, 232f static segregation characteristics, 233e235, 233t, 234f statistical analysis, 240, 241f strength characteristics, 234e235 visual segregation index (VSI), 231 workability characteristics, 231 relative penetrations, 215, 216f ViscoCrete-5930, 103e104 Visible spectroscopy, 22e23 Visual segregation index (VSI), 231 W Waste-sorting technologies, 9 Waste stream management, 116e117

476

Water-to-cement ratio, 352 Wet technique, 16, 17fe18f, 21, 40 hydrocycloning, 18e19, 18f jigging, 18 sink-float separation, 17e18, 17f Woven carpets, 413 X X-ray fluorescence (XRF), 24e25, 30 Y Young’s modulus, 70e71, 80e81

Index