Green High-Performance Concrete with Manufactured Sand 9811963126, 9789811963124

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Green High-Performance Concrete with Manufactured Sand

Zhengwu Jiang

Green High-Performance Concrete with Manufactured Sand

Zhengwu Jiang Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education School of Materials Science and Engineering Tongji University Shanghai, China

ISBN 978-981-19-6312-4 ISBN 978-981-19-6313-1 (eBook) https://doi.org/10.1007/978-981-19-6313-1 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

Concrete is the world’s largest man-made construction material, and it is gradually developing toward high performance and ultra-high performance. With the development of modern engineering structures in the direction of large span, towering, heavy load, and the needs of harsh environmental conditions, high-performance concrete has been widely used in high-rise buildings, municipal engineering, bridges, ports, underground structures, marine structures, and other projects. As one of the most important components of concrete, aggregate is limited by natural resources. Natural sand, mainly river sand, is increasingly unable to meet the demand for concrete consumption that will continue to grow in the future. With the development of concrete technology, the shortage of natural resources, and the needs of environmental protection, the use of manufactured sand to fully replace river sand has become an inevitable trend for the sustainable development of the concrete industry. Comprehensive research on the production process, characteristics, technical indicators of manufactured sand, and technologies of high-performance concrete with manufactured sand not only provides theoretical support and technical guidance for the development of concrete technology, but also has important guiding significance for improving the long-term durability and service life of concrete structural engineering. This book presents comprehensive research achievements by the author’s research group on manufactured sand, high-performance concrete with manufactured sand, and practical applications in engineering projects. This book contains 8 chapters, including the introduction, production of manufactured sand, features of manufactured sand, properties and microstructures of concrete with manufactured sand, mix design of concrete with manufactured sand, self-compacting concrete with manufactured sand, rock-filled concrete with manufactured sand, and special high-performance concrete with manufactured sand. This book organically combines professional theoretical foundation with professional practical knowledge, which is scientific, knowledgeable, advanced, practical, and interesting. The comprehensive information presented in the book will be helpful to students, researchers, and concrete technologists.

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Preface

The content of this book not only is the accumulation of the author’s theoretical research, scientific research, and engineering practice in the field of concrete materials for many years, but also refers to a large number of technical documents worldwide. Due to our limited knowledge on certain aspects, errors in the book are inevitable. Readers are welcomed to point out the errors across the book, and the authors are hereby thankful in advance.

Shanghai, China May 2022

Zhengwu Jiang

Acknowledgements

The author acknowledges the financial supports provided by the following sponsors. • National Natural Science Foundation of China (No. 51878480, 52078369) The author acknowledges the help from professors and graduate students in the author’s group who contributed a great deal to the related research and preparation of the book, including Prof. Qing Chen, Prof. Wenting Li, Dr. Zilong Deng, Dr. Zhengcheng Yuan, Dr. Chen Li, Dr. Hongen Zhang, Mr. Kaifei Yang, Mr. Chao Han, Mr. Xin Xiao, Ms. Manli Tian, Mr. Lei Zhou, Mr. Jun Yin, Mr. Zhilong Tao, Mr. Jun Li, Mr. Chunpu Xu, Mr. Xinping Zhu, Mr. Bei He, Mr. Yi Zhang, Mr. Bin Li, Mr. Bin Zhang, Mr. Mingjun Xie, Mr. Qiaomu Zheng, Mr. Fuzhu Xie., and Mr. Wenbin Gao. The author especially expresses his gratitude to Dr. Qiang Ren from Tongji University and Prof. Shilong Mei from Guizhou University for their help and cooperation on the continuous research. Special thanks to Production Editors, Mr. Bharath Kumar and Ms. Sunny Guo, for their contribution to the compilation of this book.

March 2022

Zhengwu Jiang

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Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.1 Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.2 High-Performance Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.3 Sustainable Development of Concrete . . . . . . . . . . . . . . . . . . . 1.2 Aggregate and Manufactured Sand (MS) . . . . . . . . . . . . . . . . . . . . . . . 1.2.1 Aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.2 Manufactured Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 1 1 2 3 4 4 8 11

2 Production of Manufactured Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Production Process of Manufactured Sand . . . . . . . . . . . . . . . . . . . . . 2.1.1 Dry Production Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.2 Wet Production Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Production Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.1 Vibrating Feeder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2 Crushing Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.3 Fines Removal Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Improvement of Production Technology . . . . . . . . . . . . . . . . . . . . . . . 2.3.1 Production Process Optimization . . . . . . . . . . . . . . . . . . . . . . . 2.3.2 Production Equipment Optimization . . . . . . . . . . . . . . . . . . . . 2.3.3 Slurry Recovery Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.4 Quality Control Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13 13 14 15 17 17 18 22 24 24 27 34 42 45 46

3 Features of Manufactured Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Lithology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Particle Size Distribution and Fines Content . . . . . . . . . . . . . 3.2.1 Fineness Modulus and Grading . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Fines Content and Mud Content . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Clay Content and MB Values . . . . . . . . . . . . . . . . . . . . . . . . . .

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3.3.1 3.3.2 3.4 3.4.1 3.4.2 3.5 3.5.1 3.5.2 3.5.3 3.5.4 References

Characterization of Clay Content of MS . . . . . . . . . . . . . . . . . MB Values of MS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Geometric Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Literature Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Geometric Features of MS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Determination of Specific Surface Area via the Random Section Method . . . . . . . . . . . . . . . . . . . . . . . . Theoretical Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Theory Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Result Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .....................................................

4 Properties and Microstructure of Concrete with Manufactured Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Fresh Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Workability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Rheological Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Mechanical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 Compressive Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2 Elastic Modulus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.3 Relationship Between Compressive Strength and Elastic Modulus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.4 Positive and Negative Effects of MS . . . . . . . . . . . . . . . . . . . . 4.4 Durability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1 Resistance to Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.2 Resistance to Permeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.3 Resistance to Freezing and Thawing . . . . . . . . . . . . . . . . . . . . 4.4.4 Resistance to Sulfate Attack . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.5 Resistance to Acid Attack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.6 Dimensional Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.7 Alkali-Aggregate Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Modeling of Concrete with Manufactured Sand . . . . . . . . . . . . . . . . . 4.5.1 Multi-level Viscosity Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.2 Multi-level Modulus Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.3 Multi-level Diffusion Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Microstructure of Concrete with Manufactured Sand . . . . . . . . . . . . 4.6.1 Hydration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.2 Pore Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

49 53 57 57 60 79 79 83 86 93 97 103 103 105 105 112 145 146 149 153 155 159 160 164 168 169 171 174 174 180 180 191 207 223 223 229 231 231

Contents

5 Mix Design of Concrete with Manufactured Sand . . . . . . . . . . . . . . . . . 5.1 Raw Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.1 Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.2 Mineral Admixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.3 Manufactured Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.4 Coarse Aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.5 Chemical Admixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.6 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Mix Proportioning Methods of High-Performance Concrete . . . . . . 5.2.1 Determination of the Concrete Target Mean Strength . . . . . . 5.2.2 Calculation of Concrete Mix Proportion . . . . . . . . . . . . . . . . . 5.2.3 Trial, Adjustment, and Determination of Mix Proportion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.4 Special Performance Check . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Mix Proportioning Methods of Self-Compacting Concrete . . . . . . . . 5.3.1 Blocking Criteria Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.2 ICAR Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.3 Su’s Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.4 Densified Mixture Design Algorithm (DMDA) . . . . . . . . . . . 5.3.5 Excessive Paste Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.6 Packing Model-Based Method . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.7 Target Grading Method (TG Method) . . . . . . . . . . . . . . . . . . . 5.4 Mix Design of Concrete Based on Surplus Coefficient of Mortar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.1 Technical Route . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.2 Design Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Mix Design Method of Manufactured Sand Concrete Based on Aggregate Shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.1 Mix Design Principle of High-Performance Concrete with Manufactured Sand Based on Aggregate Shape . . . . . . 5.5.2 Design Steps for Mix Proportion of High-Performance Concrete with Green Manufactured Sand Based on Aggregate Shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Optimization of Mix Proportion of Concrete with Manufactured Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.1 Optimization Technology of Fines . . . . . . . . . . . . . . . . . . . . . . 5.6.2 Optimization Technology of Manufactured Sand and Coarse Aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.3 Optimization Technology of Mineral Admixtures . . . . . . . . . 5.6.4 Optimization Technology of Additives . . . . . . . . . . . . . . . . . . 5.7 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Contents

6 Self-Compacting Concrete with Manufactured Sand . . . . . . . . . . . . . . . 6.1 An Overview of Self-Compacting Concrete (SCC) . . . . . . . . . . . . . . 6.2 Pumping Pressure of Concrete with Manufactured Sand . . . . . . . . . . 6.2.1 Theoretical Prediction of the Pressure Loss of Concrete . . . . 6.2.2 Establish of Pumping Pressure of Concrete with Manufactured Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.3 Influence of Manufactured Sand Features on the Pumping Pressure of Concrete . . . . . . . . . . . . . . . . . . . 6.3 Optimization of Mix Proportion of SCC with Manufactured Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.1 Design of Mix Proportion of SCC with Manufactured Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.2 Optimization of Mix Proportion of SCC with Manufactured Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 Engineering Application of SCC with Manufactured Sand . . . . . . . . 6.4.1 Qingshuihe Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.2 Beipanjiang Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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7 Rock-Filled Concrete with Manufactured Sand . . . . . . . . . . . . . . . . . . . 7.1 An Overview of RFC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Performance Requirements for Rock . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Simulation of Rock Accumulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 Algorithm Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.2 Results and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 Mix Design of Superfluid SCC with MS . . . . . . . . . . . . . . . . . . . . . . . 7.4.1 Requirements on the Properties of SFSCC with MS . . . . . . . 7.4.2 Mix Design Procedures of Superfluid SCC with MS . . . . . . . 7.4.3 Optimization of Mix Proportion of Superfluid SCC with MS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 Properties of RFC with MS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.1 Mechanical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.2 Durability Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.3 Drying Shrinkage Behavior of RFC with MS . . . . . . . . . . . . . 7.5.4 Impermeability of RFC with MS . . . . . . . . . . . . . . . . . . . . . . . 7.5.5 Internal Temperature Rise of RFC with MS . . . . . . . . . . . . . . 7.6 Engineering Application of RFC with MS . . . . . . . . . . . . . . . . . . . . . . 7.6.1 An Overview of the Bijie-Weining Express Project . . . . . . . . 7.6.2 On-Site Construction of RFC with MS . . . . . . . . . . . . . . . . . . 7.6.3 Evaluation of Fresh and Hardened Properties of On-Site RFC with MS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.7 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Contents

8 Special High-Performance Concrete with Manufactured Sand . . . . . . 8.1 Anti-Disturbance Concrete with MS . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.1 Raw Materials and Test Methods . . . . . . . . . . . . . . . . . . . . . . . 8.1.2 Results and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.3 Engineering Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Underwater Anti-Washout Concrete with MS . . . . . . . . . . . . . . . . . . . 8.2.1 Raw Materials and Test Methods . . . . . . . . . . . . . . . . . . . . . . . 8.2.2 Results and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.3 Engineering Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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About the Author

Dr. Zhengwu Jiang is a tenured professor at the School of Materials Science and Engineering, Tongji University, China. He is the director of Key Laboratory of Advanced Civil Engineering Materials, Ministry of Education, China. He is also the editor in chief of Journal of Building Materials, the vice chairman of Cement Committee and Solid Waste Committee (the Chinese Ceramic Society), the director of the Fundamental Theory and Application of Concrete Committee (the Architectural Society of China), ACI and RILEM members. Dr. Jiang is engaged in academic research in the field sustainable cement-based materials, properties of cement-based materials under extreme environment, self-healing cement-based materials, and highperformance concrete with manufactured sand. He is the author of more than 200 technical papers and 7 monographs and received more than 80 patents. He is the editor of more than 10 Chinese standards related to high-performance concrete with manufactured sand. Due to his contribution to the sustainable development of high-performance concrete in China, Dr. Jiang has been awarded with more than 10 national, provincial, and ministerial awards, including the 2nd prize of National Technology Invention Award and the 2nd prize of the Ministry of Education Technology Invention Award. His research output has been applied in more than 60 key projects including the world’s highest bridge, Beipanjiang Bridge.

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Chapter 1

Introduction

1.1 Concrete 1.1.1 Concrete Concrete is a composite material that is made of cementitious materials, water, aggregates, and chemical admixtures if required. The history of concrete can be traced back to 3600 B.C. The calcined plaster was mixed with water and river sand to make gypsum mortar that was used in pyramids. The lime, sand, and clay were mixed with water by the ancient Chinese to repair the Great Wall in 220 B.C. The ground volcanic ash was mixed with lime and sand to prepare mortar with high strength and good water resistance by the ancient Greeks and Romans. Concrete has been the most widely used civil engineering materials in the world. In the 1820s, the production process of Portland cement was developed and used as a cementitious material for the preparation of concrete with desired strength and durability. The cost of the production is low due to the widespread raw materials of Portland cement. As a result, the development and application of concrete was greatly accelerated. In 1848, reinforced concrete with greatly improved tensile properties was invented by Frenchman Monier. In 1900, the exhibition of the application of reinforced concrete in many aspects at the World Exposition triggered a revolution of building materials. In 1918, the theory of water-to-binder ratio was put forward and the theoretical foundation of concrete strength calculation was initially laid. After World War II, the prestressed concrete gradually developed in Western European countries. The crack resistance and durability of concrete were greatly improved by the prestressing technique, while the weight of components and the consumption of raw materials were reduced. Moreover, the development of large-span, high-rise, and heavy-duty buildings was promoted by the prestressing technology [1, 2]. Since the 1960s, the performance of concrete has been further improved by the application of concrete admixtures. In addition, fluid concrete and fiber reinforced concrete came out due to the invention of superplasticizers and a variety of fibers. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Z. Jiang, Green High-Performance Concrete with Manufactured Sand, https://doi.org/10.1007/978-981-19-6313-1_1

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1.1.2 High-Performance Concrete The concept of high-performance concrete (HPC) was firstly proposed in the late 1980s and early 1990s based on the durability design of concrete structures [3–5]. Norway experts conducted researches firstly on the HPC in 1986. It was officially named by the National Institute of Standards and Technology (NIST) and the American Concrete Institute (ACI) in 1990. The durability was taken as the primary design index for HPC, which shows characteristics such as high strength, high workability, high impermeability, and high volume stability [6–8]. HPC shows its unique advantages in long service, economic rationality, adaptability to environmental conditions and is of great significance to engineering quality, engineering economy, environment, and labor protection [9]. Therefore, HPC is called “the 21st Century Concrete”. The research, development, and application of HPC have made a major breakthrough in the technical performance of traditional concrete. So far, HPC has been used in a large number of important projects, especially in bridges, high-rise buildings, seaport construction, and so on. Nevertheless, different viewpoints on HPC have been proposed by different scholars according to actual engineering requirements [3, 4]: (1) High-durability concrete The American and Canadian scholars represented by Mehta emphasize that durability should be the most important property for HPC, with high impermeability and high volume stability [5]. (2) High-strength or ultra-high-strength concrete Some Japanese scholars believe that high strength is the most important property for HPC. Modern high-strength concrete with dense hardened cement, refined pore, and improved interface structure is formulated by using mineral superfine powders and superplasticizer, providing concrete with higher strength and durability. (3) High-fluid or self-compacting concrete Some Japanese scholars like Okamura believe that HPC is high-fluidity concrete or self-compacting concrete (SCC). SCC is a kind of concrete that achieves self-compaction and self-leveling only by the gravity of the concrete itself. It is especially suitable for components with complex shapes and steel bars, where it is difficult to vibrate. It greatly accelerates the concrete pouring speed and eliminates the noise caused by vibration. (4) Green HPC In May 1997, the concept of green HPC was proposed by Chinese academician Wu Zhongwei. The “green” refers to saving resources and showing little damage to the environment. In line with the principle of sustainable development, it not only meets the needs of contemporary people, but also does not endanger the survival and development of future generations [10–12]. The reduction of Portland cement clinker consumption and the increased content of mineral admixtures derived from industrial waste residues are the main characteristics of green HPC.

1.1 Concrete

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In addition, Professor Feng Naiqian [4] believes that the high performance refers to excellent performance in different design loads, construction conditions, and service environments. Therefore, HPC is not only concrete with comprehensive properties, but also concrete that can meet various special conditions.

1.1.3 Sustainable Development of Concrete As the largest building material in the world, concrete has been widely used in urban construction, roads, bridges, airports, dams, tunnels, underground engineering, ocean engineering, and other infrastructure construction. However, significant costs are required to maintain the concrete structures with durability problems. Moreover, common concrete is usually abandoned as construction waste after a short service life. In addition, the production of cement with high energy consumption and high carbon emissions has a great impact on the environment. Therefore, the extensive use of concrete brings about resources, energy, and environmental problems. The impact and potential impact of concrete on the environment during its life cycle should be considered for the sustainable development of concrete. The life cycle of concrete includes raw material acquisition and preparation, concrete production and processing, concrete usage and resource recovery, and so on [13]. Generally, sustainable concrete has high performance to meet design requirements, low energy and natural resource consumption, low environmental load, and carbon emissions during its life cycle. The high performance of sustainable concrete refers to high workability, strength, and durability. Among them, high durability can reduce the consumption of concrete by extending the service life of concrete materials, components, and structures. Besides, the cement concrete industry is one of the biggest carbon dioxide emitters, and carbon emissions should be reduced at every stage of the concrete life cycle, especially in cement production. In addition, it is necessary to establish the life cycle assessment of concrete, and indexes such as carbon footprint should be used in the evaluation of sustainable concrete [14]. The sustainable development of the concrete industry is inevitable. Ideally, sustainable concrete should meet the characteristics of green production, high performance, and low carbon emissions during its life cycle. The technical approach to the development of sustainable concrete should be proposed in terms of ideology, technology, industry, and management.

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1 Introduction

1.2 Aggregate and Manufactured Sand (MS) 1.2.1 Aggregate Aggregate occupies 60–80% of concrete in volume. It includes natural pebbles, crushed stone, river sand, MS, sintered ceramsite, and other light aggregate. Aggregate has a significant influence on the performance of concrete. Aggregate acts as the skeleton of the concrete, while the cement paste wraps the surface of the aggregates and fills the gaps between aggregate particles. After hardening of the cement, the aggregate is joined together to form a strong whole. The skeleton formed by aggregate prevents the cracking and abrasion of concrete and mortar. In addition, the properties of the aggregate have a great influence on the strength, workability, and durability of concrete. For instance, the strength, surface characteristics, cleanliness, gradation, particle shape, maximum particle size, and contents of clay and clay lump of aggregate have an impact on the strength of concrete. The gradation, particle shape, water absorption, surface characteristics, and contents of clay and clay lump of aggregate affect the workability of concrete. The gradation, porosity, pore structure, permeability, saturation, contents of clay and clay clump, elastic modulus, thermal expansion coefficient, hardness, contents of deleterious substances of aggregate affect the durability of concrete [15].

1.2.1.1

Category of Aggregate

Aggregate can be classified according to the particle size, density, and source (see Table 1.1). In the construction industry, aggregate can be divided into coarse aggregate and fine aggregate according to their particle size. According to aggregate density, it can be divided into lightweight aggregate, normal-density aggregate, and heavyweight aggregate. Aggregate can be divided into natural aggregate, artificial aggregate, and by-product aggregate according to their sources. Natural aggregate, such as river sand, river pebbles, sea sand, sea rocks, mountain sand, mountain rocks, is formed under the action of natural forces such as washing and weathering, while artificial aggregate, such as expanded shale, ceramsite, and expanded perlite, is produced from natural or waste materials via mechanical processing according to scientific standards. By-product aggregate is the industry by-product, like crushed slag, expanded slag, coal cinder, etc. Recycled aggregate is produced by recycling waste concrete (Fig. 1.1).

1.2.1.2

Development of Aggregate in China

The development of aggregate in China is accompanied by the development of civil engineering. Since the founding of the People’s Republic of China, it can be roughly

1.2 Aggregate and Manufactured Sand (MS)

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Table 1.1 Category of aggregate [4] Properties

Name

Description

Particle size

Fine aggregate

Particle size 4.75 mm

Source

Natural aggregate

River sand, river pebble, mountain sand, mountain pebble, seas and, sea pebble, lava gravel

Artificial aggregate

Expanded shale, ceramsite, expanded perlite

By-product aggregate

Crushed slag, expanded slag, and coal cinder

Recycled aggregate

Recycled concrete, recycled mortar

Lightweight aggregate

Absolute dry density 2900 kg/m3 Barite, iron ore, etc.

Density

divided into three stages: the initial stage, the developing stage, and the transition stage (see Table 1.2) [17]. (1) The initial stage (1949–1978) The development of civil engineering was slow during this period. Moreover, the supply of construction aggregate was sufficient, and almost all the aggregate is natural aggregate. (2) The development stage (1978–2010) Various construction projects sprung up, driving the rapid development of the aggregate industry. Although the demand of aggregate was huge, there were almost no restrictions in the mining process. Thus, the production of aggregate basically met the market demand for construction. The main source of aggregate in this period is still natural aggregate. Manufactured aggregate and by-product aggregate emerged and were gradually used. (3) The transition stage (2011–present) The traditional mining of construction aggregate at the cost of destructiveness has been restricted from various aspects. At this time, a set of strict standards for the variety, quality, and performance of aggregate has been set. The previous mining methods of aggregate were unsustainable. With the contradiction between increasing market demand for aggregates and the restriction of natural aggregates, the aggregate industry began to transform, and artificial aggregate began to dominate during this period. At the current stage, the development of aggregate in China presents the following characteristics. First, natural sand resources are rapidly decreasing. After years of mining, natural sand resources are rapidly decreasing, and natural sand in some areas is nearly exhausted. In order to protect river embankments and dams, and to maintain ecological balance, the exploitation of river sand has been restricted or even

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1 Introduction

(a) Natural aggregate

(b) Artificial aggregate

(c) By-product aggregate Fig. 1.1 Schematic diagram of various aggregates [16]

prohibited by the local governments. Natural sand is becoming scarcer and more expensive. Second, the application of MS in construction is on the rising. The development of HPC has higher requirements on the quantities and qualities of sand and gravel. MS and stone have become the main development direction and main body of the industrial structure transformation and upgrading of the aggregate industry. The

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(d) Recycled aggregate Fig. 1.1 (continued)

Table 1.2 Development stages of aggregate for construction Stage

Period

Features

The initial stage

1949–1978

Low demand, sufficient supply, sufficient natural reserves, slow development, natural aggregate as the main construction aggregate

The developing stage

1978–2010

Large demand, sufficient supply, insufficient natural reserves, rapid development, natural aggregate as the main construction aggregate, emergence of MS, and by-product aggregate

The transformation stage 2011–present Large demand, tight supply, exhaustion of natural reserves, manufactured aggregate as the main construction aggregate

capacity of the current production line ranges from 800 to 1200 tons/h. Third, the management of the aggregate industry has intensified. Driven by national safety and environmental policies, local governments have intensified the management of the aggregate industry. The fourth is upgrading the industry and extending the industrial chain. With the upgrading of the traditional sand and stone mining industry, the industrial chain is being extended and outdated production capacity is being eliminated or closed. The industry is developing appropriately according to the market capacity under the premise of improved technology, intensified product standards, and raised barriers to entry. The fifth is technological progress and harmonious development. The sand and stone industry will accelerate the transformation of its development mode in terms of technological progress, industrial scale, and structure. The acceleration of industry technological progress and technological innovation is regarded as an important supporting point for upgrading and leading the development of the industry. Energy conservation, emission reduction, and the development of circular economy are taken as the main attack points. The simultaneous development of environmental protection and harmonious society is being realized.

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1.2.2 Manufactured Sand 1.2.2.1

Overview of MS

According to the Chinese National Standards implemented in 2002, MS refers to the granular rock material passing the 4.75 mm sieve after clay removal, mechanical crushing, and sieving [18]. Artificial sand is the common name of MS and mixed sand. Mixed sand refers to sand mixture with both MS and natural sand [19]. As the development of economy and infrastructure, MS is becoming increasingly important in developing countries, especially in China. Since the 1960s, in the civil construction projects of Chinese hydropower system, researches have been conducted to produce MS and stone from local materials and apply them in concrete. The MS was firstly applied in construction in Guizhou Province, and the first local standard of MS in China (1978) was also issued by Guizhou Province. Since then, local standards or regulations for the application of MS were gradually issued in Yunnan, Henan, Guangxi, Guangdong, Hunan, Sichuan, Anhui, and other provinces. Hong Kong, China, is also an area where MS was used very early [13, 20, 21]. In order to protect the environment and resources, the national and local governments issued regulations and policies to restrict or prohibit the exploitation of natural sand, which further promotes the use of MS [14]. In 2015, the Ministry of Industry and Information Technology of PRC issued the Action Plan for the Production and Application of Green Building Materials, which accelerated the industrialization, standardization, and greening of MS and stone. On May 18, 2016, the State Council of China issued a proposal to actively use tailings, waste rock, construction waste, and other solid waste to replace natural resources and to develop MS and stone, concrete admixtures, block wall materials, low-carbon cement, etc. Although many provinces in China have introduced regulations to restrict or prohibit the mining of river sand and promote the application of MS, the MS industry still faces outstanding problems such as weak quality assurance capabilities, irrational industrial structure, low level of green development, and imbalance between local supply and demand. To solve these problems, “Several Opinions on Promoting the High Quality of the Machine-made Sand and Stone Industry” was issued by ten departments of China on November 11, 2019. It was pointed out that key technologies and processes, such as particle shaping, grading adjustment, energy saving and consumption reduction, and comprehensive utilization, should be focused on by the MS and stone industry, to lead the high-quality development of MS and stone. Compared with natural aggregate, manufactured aggregate has three advantages. The first is source advantage. Various waste resources can be used to produce manufactured aggregate, conforming to the scientific development concept and adapting to a conservation and circular economy. In recent years, alternatives of river sand in many areas are needed due to the shortage of resources, which promotes the usage of various industrial wastes. Standards for using industrial wastes as the aggregate for construction have been issued. The second is quality advantage. MS and stone have high surface energy and hydrophilicity and complete gradation with stone powder

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finer than 75 µm. Besides, manufactured aggregate can be produced from a variety of mineral components. Moreover, the gradation and particle shape of manufactured aggregate can be adjusted due to the stable and automated production methods. It needs to be mentioned that all these can be achieved only by scientific and strict production according to related standards. The third is management advantage. There is a stable legal entity for the production of manufactured aggregate with the mining license. Besides, the site of production is fixed. In addition, manufactured aggregate has two other characteristics. First, the cost or price of manufactured aggregate varies greatly due to the influence of resources and regional economy. Second, the quality and properties of MS and stone vary due to the variety of origins [14, 16]. In short, the replacement of river sand by MS to prepare concrete has become an inevitable trend. Huge economic and social benefits will be brought by the application of MS in concrete.

1.2.2.2

Scale and Distribution of Aggregate Production Enterprises

According to statistics [17], there were about 107,000 mines in China by 2013, of which nearly 57,000 were sand and stone mines, involving 20 types of minerals like limestone for buildings, clay for bricks and tiles, sand for bricks and tiles, sand for construction, granite for construction, etc. From the statistical results, only 2704 of the 56,888 sand and stone mines were large scale, accounting for only 5% of the total; 625 are medium scale, accounting for 11% of the total; 47,925 were small-scale mines, accounting for 84% of the total share (see Fig. 1.2).

Fig. 1.2 Numbers and percentages of sand and stone enterprises (Drawn according to [17])

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1 Introduction

Fig. 1.3 Regional distribution of the top 100 aggregate production enterprises (Drawn according to [17])

There are some rules of aggregate production enterprises in the geographical distribution due to differences in technology, resources, capital, and other factors of production as well as market preferences. There are already more than 3000 manufacturers of aggregate production equipment in China. The analysis of the geographical distribution of the top 100 of 3000 manufacturers shows that 60% of them are in the eastern region, 35% in the central region, and 5% in the western region (see Fig. 1.3).

1.2.2.3

Problems in the MS Industry

There are some problems in the aggregate industry due to the decentralization of the industry, traditional production methods, and lack of competent authorities [20]: (1) The industry does not receive the attention it deserves and lacks a unified longterm plan. For example, there is no industry plan throughout China, neither the mineral indexes of aggregate in the localities. Aggregates are not treated as industrial products and managed seriously by local governments. In recent years, the central and local governments of China have paid increasing attention to natural resources and environmental protection. Restrictions on the mining of aggregates have been proposed, without solutions for the current situation. (2) The regulation of entering the aggregate industry is lacking. More than 95% of the enterprises that produce MS and stone do not have a laboratory. The MS is not produced in accordance with the “Sand for Construction” (GB/T 14684), “Pebbles and Crushed Stone for Construction” (GB/T 14685), and other standards. In addition, it is difficult to guarantee the quality of engineering due to restrictions of region and the limitation of the construction period. (3) The qualities of manufactured aggregate restrict the development of concrete. From reports of concrete batching plants and results of random inspections on

References

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manufactured aggregate in market, the particle shape of manufactured aggregate is poor and the fineness modulus ranges from 3.4 to 3.7. The gradation of the manufactured aggregate is also failed to meet the requirement in the standard “Design of Concrete Structure Durability” (GB/T 50476). (4) The foundation of the industry and information exchange platform need to be established. A lot of basic works have not been unfinished, like the standard system of MS and stone due to the lack of supervision on the aggregate industry. By now, there are only a few isolated product standards for manufactured aggregate. (5) The environmental protection measures in most enterprises are insufficient. The nonstandard mining has a great impact on the surrounding environment due to the dust, wastewater, and noise.

References 1. G. Du, Application and development of prestressed concrete for buildings in China in the paste 40 years. China Civil Eng. J. 30(1), 3–15 (1997) 2. G. Du, Achievements and prospect of prestressed concrete structures in China. Build. Struct. 10, 30–35 (1999) 3. D. Ding, High performance concrete and its application in engineering (China Machine Press, Beijing, China, 2007) 4. N. Feng, New practical concrete encyclopedia (Science Press, Beijing, China, 2001) 5. P.K. Mehta, Concrete. Structure, properties and materials (Prentice-Hall Incorporated: Englewood Cliffs, NJ United States, 1986) 6. N. Feng, F. Xing, High performance concrete technology (Atomic Energy Press, Beijing, China, 2000) 7. Z. Chen, Development and utilization of high-strength and high-performance concrete. China Civil Eng. J. 3–11 (1997) 8. N. Feng, Development and application of high performance concrete. Constr. Tech. 4, 1–6 (2003) 9. Y. Yao, L. Wang, P. Tian, High performance concrete (Chemical Industry Press, Beijing, China, 2006) 10. Z. Wu, H. Lian, High performance concrete (China Railway Press, 1999) 11. Z. Wu, Development prospects and problems of high performance concrete (HPC) (Architecture Technology, 1998), pp. 8–13 12. Z. Wu, Green high performance concrete and scientific and technological innovation. J. Build. Mater. 1, 3–9 (1998) 13. X. Chen, Application of manufactured sand in commercial concrete. Min. Metall. 11, 74–75 (2004) 14. J. Chen, W. Zhou, Discussion on development and problems of artificial sand in China. Arch. Tech. 38(11), 849–852 (2007) 15. J. Chen, Rethinking the construction aggregates in China. China Concrete 1, 18–21 (2010) 16. Z. Jiang, Q. Ren, J. Wu, C. Zhang, A. Zhong, Study on properties of machine-made sand and relevant issues of applications in concrete. New Build. Mater. 37(11), 1–4 (2010) 17. J. Han, X. Xiao, The current situation and development trend of aggregates in China. China Concrete 9, 36–42 (2013) 18. T/CECS G: K50-30-2018(EN), Technical specifications for high-performance concrete with manufactured sand in highways.

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19. GB/T 14684 Sand for construction (2011) 20. J. Chen, Current situation of machine-made sand and rock industry in China and prospects. China Concrete 2, 62–64 (2011) 21. J. Zhu, X. Lang, X. Jia, Present situation and development of pelletized sand production. Mining Metal. (4), 38–42 (2001)

Chapter 2

Production of Manufactured Sand

2.1 Production Process of Manufactured Sand At present, most enterprises are backward in production, with low efficiency, poor quality, and high cost, which has a negative impact on the quality of construction engineering [1]. Small hammer crusher or impact crusher was usually adopted to produce MS in most small-scale sand and gravel plants. Although the hammer crusher has the characteristics of high yield, easy maintenance, and simple structure, the maintenance cost of the equipment is high. The morphology and grading of sand particles could not be controlled well by this crushing equipment. Moreover, the content of coarse particles and the fineness modulus of MS are high. For some large-scale water conservancy construction projects in China, the production technology of MS mainly includes coarse, medium, and fine crushing and rod mill crushing. The quality of MS can be controlled according to the needs of the project. However, this technology is rarely used by manufacturers due to the high cost. Factors such as technology, equipment, transportation, environmental protection, and type of parent rock should be considered in the production of MS. The production process could be divided into sand/gravel co-production process and separate produced sand process according to the processing methods of MS. In the practical project, it is recommended to give priority to the sand/gravel co-production process, which should be adjusted according to the changes of parent rock and the requirements of concrete for sand or gravel. The production process of MS is mainly divided into the dry production process and wet production process according to the fines removal methods, and the dry production process should be the first choice. When the methylene blue (MB) value and fines content of the MS produced by the dry method could not meet the quality requirements of MS, the wet method should be adopted.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Z. Jiang, Green High-Performance Concrete with Manufactured Sand, https://doi.org/10.1007/978-981-19-6313-1_2

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2.1.1 Dry Production Process 2.1.1.1

Process Introduction

Dry production process of MS refers to that a set of dust devices is used to control the fines content of the MS instead of water washing in the production process of MS. The particle size distribution of MS produced by this method is controllable, with low energy consumption and low environmental load. Moreover, the produced MS can be used without seasonal restrictions. Therefore, the dry production process has become the mainstream of producing MS. The typical dry production process is shown in Fig. 2.1, and the specific production process is as follows: (1) Parent rock: the mined raw materials are transported to the raw material form with rainproof facilities and fed to the vibrating feeder. (2) Soil removal: the soil in raw materials is removed through the vibrating feeder to prevent unclean raw materials from entering the production line. (3) Coarse crushing: raw materials are uniformly transported into a jaw crusher for preliminarily crushing. (4) Medium crushing: the crushed aggregate is transported by belt conveyor to a cone crusher or counterattack crusher for further crushing. (5) Screening: the aggregate after medium crushing and fine crushing is transported to the screening equipment by the belt conveyor and classified according to particle size. The aggregates meeting the particle size requirements are sent to the storage bin by the belt conveyor for producing MS and finally screened. The aggregates that do not meet the particle size requirements are sent back to the cone crusher or counterattack crusher by the belt conveyor for re-crushing, forming a closed circuit and cycles. (6) Producing of sand: some aggregates with a particle size of 5–40 mm and below 5 mm are sent to the vertical impact crusher for producing sand, and the fines content is adjusted by fines removal equipment.

Fig. 2.1 Dry production process of MS

2.1 Production Process of Manufactured Sand

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(7) Spray humidification: the MS is humidified by the spray system to prevent segregation. (8) MS: the productions are transported to the storage bin by a belt conveyor. 2.1.1.2

Advantages

(1) The grading, fineness modulus, and fines content of MS are easy to control, which is beneficial to improve the workability and compactness of concrete. (2) The collected fines can be reused. (3) The operation cost of the production is low. (4) It is not restricted by water source and environment. (5) The production process is short, and the equipment is easy to control. The automatic or unmanned production and operation could be implemented. 2.1.1.3

Disadvantages

(1) The cost of equipment, site construction, and energy consumption are larger than that of the wet production process. (2) The air pollution is greater than that of the wet production process. (3) Fines has not been widely used. (4) The requirement for moisture content of raw materials is high, which is easy to cause the MB value to exceed the standard. (5) The content of fines is relatively high and is not suitable for the high-grade concrete.

2.1.2 Wet Production Process 2.1.2.1

Process Introduction

Compared with the dry production process, the wet production process is the same in crushing, producing, and screening, but different in fines removal. In the wet production process, the sand washer is used to replace the fines concentrator and fines removal equipment in the dry production process. The fines or dust in MS is washed away, and the fines and fine sand are recovered through the recovery machine. Currently, there are mainly two types of sand washers in the market: wheel sand washers and spiral sand washers. The particle grading of MS is reasonable, and the shape is good. The wet production process is the earliest and most mature production process in China, and it is generally used in areas with abundant water resources. The typical wet production process is shown in Fig. 2.2. The aggregate with a particle size of 5–40 mm, accompanied with water, is fed to the pin crusher through the vibrating feeder. After crushing, the material is discharged and then enters the “spiral classifier” for cleaning and grading. The qualified sand is

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Fig. 2.2 Wet production process of MS

transported to the dewatering screen for dehydration and then to the sand pile, while the fines and mud are discharged with water.

2.1.2.2 (1) (2) (3) (4)

Advantages

There is less air pollution in the production process compared to the dry process. The MS is clean with low mud content and fine content. The coarse and fine particles of MS are mixed evenly. The moisture content requirement of raw materials is low.

2.1.2.3

Disadvantages

(1) Water is essential to production, and the mud discharged during production is difficult to deal with. (2) The fines content in MS produced by wet process is low, which leads to the unreasonable grading and the large fineness modulus of MS, resulting in the poor workability of the concrete, especially for the concrete with low strength grade or cement content. (3) The moisture content of the MS is high. (4) The production cost is high due to the investment of infrastructure and equipment. (5) It cannot be operated normally in dry areas or freezing seasons.

2.2 Production Equipment

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2.2 Production Equipment The wet production process of MS is shown in Fig. 2.3.

2.2.1 Vibrating Feeder Vibrating feeder is a kind of equipment that can feed parent rocks from the storage bin to the crushing machine uniformly, regularly, and continuously and can also roughly screen the parent rock and remove the soil. It is widely used in industries such as metallurgy, coal mine, beneficiation, building materials, chemical industry, and abrasive. The vibrating feeder is composed of a feeding tank, a vibrator, spring support, a transmission device, etc. The centrifugal force is generated in the vibrator by the rotation of the eccentric block, so that the movable parts such as the screen chamber and vibrator are going to move around a circle. The materials are transported by the vibration of the feeding tank. The vibrating feeder is widely used due to the simple structure, reliable operation, convenient adjustment and installation,

Fig. 2.3 Wet production flowchart of MS

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Fig. 2.4 Vibrating feeder

lightweight, small volume, and convenient maintenance. Moreover, dust pollution can also be prevented by this equipment. The vibrating feeder is shown in Fig. 2.4.

2.2.2 Crushing Equipment The core production equipment of the sand-producing machine is the crusher, and it can be divided into jaw crusher, hammer crusher, cone crusher, counterattack crusher, double-roll crusher, gyratory crusher, rotary disk crusher, and vertical impact crusher.

2.2.2.1

Jaw Crusher

Jaw crusher is mainly composed of frame, moving jaw, eccentric shaft, jaw plate, elbow plate, and other parts. The materials in the crushing chamber are broken under the action of the moving jaw, which is driven by the eccentric shaft. The moving jaw is a formed steel casting with a movable jaw plate on the front. The upper part of the movable jaw plate is suspended on the frame by an eccentric shaft and roller bearing. The lower part is supported on the elbow plate and has rolling contact with the elbow plate. Flywheel and belt pulley are installed at both ends of the eccentric shaft. The other end of the elbow plate is supported on the adjusting seat and is in rolling contact with the bearing. In addition to supporting the moving jaw, the elbow plate plays an insurance role when the external materials that cannot be broken enter the crushing chamber and the load of the machine suddenly increases, that is, it breaks rapidly and protects other parts from damage. The adjusting seat is installed in the chute on both sides of the frame and is close to the adjusting wedge. The discharge port size could be controlled through the adjusting wedge. Jaw crusher is mainly used for medium-size crushing of ores and bulk materials. The jaw crusher is shown in Fig. 2.5.

2.2 Production Equipment

19

Fig. 2.5 Jaw crusher

2.2.2.2

Hammer Crusher

Hammer crusher is a kind of crusher, and the rotor with a hammer (also known as hammerhead) is the main part of this equipment. The rotor consists of a spindle, disk, pin, and hammer. The material is fed into the machine from the upper feeding port and is crushed by the impact, impact, shearing, and grinding of a high-speed hammer, which is driven by the motor. There is a sieve plate in the lower part of the rotor. The particles smaller than the size of the sieve hole are discharged through the sieve plate. The coarse particles larger than the size of the sieve hole remain on the sieve plate and continue to be hit and ground by the hammer. Finally, they are discharged out of the machine through the sieve plate. The hammer crusher is shown in Fig. 2.6.

2.2.2.3

Cone Crusher

Cone crusher is an advanced hydraulic crusher with high power, large crushing ratio, and high productivity. The structure of the cone crusher is different from that of traditional cone crusher in design, which has the main advantages of all kinds of cone crushers known so far. It is suitable for fine crushing and ultra-fine crushing of hard rocks, ores, slag, refractories, etc. The structure of cone crusher mainly consists of frame, horizontal shaft, moving cone, balance wheel, eccentric sleeve, upper crushing wall (fixed cone), lower crushing wall (moving cone), hydraulic coupling, lubrication system, hydraulic system, control system, etc. The cone crusher is shown in Fig. 2.7.

20 Fig. 2.6 Hammer crusher

Fig. 2.7 Cone crusher

2 Production of Manufactured Sand

2.2 Production Equipment

21

Fig. 2.8 Counterattack crusher

2.2.2.4

Counterattack Crusher

The material is broken by the high-speed impact of the plate hammer that is driven by the rotor, is thrown to the impact elbow plate to be broken again, and then bounces back from the impact surface to the plate hammer action area to be broken again. This process is repeated until the material is broken to the required particle size. When the particle size of the crushed ore is smaller than the gap between the hammer and the impact plate, it is discharged from the lower part of the machine, that is, the crushed product. The self-weight safety device is used on the back upper frame of the impact crusher. When the non-broken materials enter the crushing chamber, the front and rear impact frames will retreat, and the non-broken materials will be discharged from the body. The counterattack crusher is shown in Fig. 2.8.

2.2.2.5

Pin Crusher

The pin crusher is named after the steel rod loaded in the cylinder and is widely used in the first-class grinding of artificial sand, mineral processing plants, chemical plants, and electric power departments. There are two types of pin crushers: the dry type and the wet type. The cylinder is driven by the motor through the reducer and the peripheral big gear or by the low-speed synchronous motor directly through the peripheral big gear. Under the action of centrifugal force and friction, the steel rod is lifted to a certain height and falls in the state of throwing or releasing. The material continuously enters into the cylinder from the feeding port and is crushed by the

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2 Production of Manufactured Sand

Fig. 2.9 Pin crusher

moving steel rod, and the product is discharged out of the machine through overflow and continuous feeding force. The characteristic of a pin crusher is that the grinding medium is in line contact with the material, so there is selective effect on the grinding process. The particle size of the product is relatively uniform, and the over-crushed particles are less. When used in rough grinding, the capacity of the pin crusher is larger than that of the ball mill and vice versa. The pin crusher is shown in Fig. 2.9. In general, the quality of the product produced by cone crusher and vertical impact crusher is better than those produced by counterattack crusher, hammer crusher, and rotary disk crusher. The quality of the product that produced by jaw crusher, the roller crusher, and the gyratory crusher is the worst, but the cone crusher and vertical impact crusher have higher manufacturing costs.

2.2.3 Fines Removal Equipment The content of fines in MS must be controlled effectively. The high content of fines will significantly reduce the performance of MS. The removal method of fines in MS is mainly divided into the dry method and wet method. Dry fines removal technology is widely used in small and medium-sized sand factories in the north, arid, and water shortage areas. The core equipment of the dry production process is a dry fines classifier.

2.2.3.1

Dry Fines Classification

Dry fines classification is the classification of grinding products by using flowing air. The internal structure of the equipment remains stationary during operation. Parts of the coarse fluid can be separated by changing the speed, direction, inertia, and other factors of the airflow containing material separation. The advantages of dry fines removal are that the fines content of MS can be adjusted by this technology, and

2.2 Production Equipment

23

Fig. 2.10 Fines classifier

the MS has good grading, low water content, high production efficiency. Moreover, no water is needed in the production process, and it is not affected by seasons. The disadvantages are high requirements for the quality of sand and gravel materials, poor appearance of MS products, serious dust pollution, and high one-time investment. The fines classifier is shown in Fig. 2.10.

2.2.3.2

Sand Washer

Wet production process has a long history, which is suitable for the water-rich areas in South China. Wet fines removal equipment mainly includes a spiral sand washer (Fig. 2.11a) and wheel sand washer (Fig. 2.11b). The working principle of the spiral sand washer is that the material falls into the high-speed rotating impeller vertically from the upper part of the machine. Under the action of the high-speed centrifugal force, it collides and smashes with another part of the material around the impeller

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2 Production of Manufactured Sand

Fig. 2.11 Different types of sand washer: a spiral sand washer and b wheel sand washer

in the form of umbrella flow. After the material collides with each other, it will form a vortex between the impeller and the frame and smash it by repeated collision and friction. After that, material is discharged through the lower part. Moreover, the required size of products is controlled by the screening equipment. The spiral sand and gravel washing machine has low power consumption and high washing cleanliness. Wheel-type sand washing machine is also known as wheel bucket sand washing machine. The sand and gravel are fed into the washing groove from the feeding groove, roll, and grind under the drive of the impeller to remove the impurities covering the surface of the sand and gravel and to destroy the water vapor layer covering the sand particles, so as to facilitate dehydration. At the same time, water is added in the form of strong flow to take away impurities and foreign matters with a small specific gravity. The clean sand and gravel are taken away by the blades and finally are poured into the discharge chute from the rotating impeller. The advantages of wet fines removal are that the surface of MS is clean, the appearance is good, and the production environment is clean. The disadvantages are very prominent, that is, huge consumption of water, the high water content of MS products, less fine particles, large modulus of fineness, low output, and serious pollution of production sewage.

2.3 Improvement of Production Technology 2.3.1 Production Process Optimization 2.3.1.1

Optimization of Dry Production Process

Good gradation, appropriate fines content, low mud content, and a reasonable grain shape are the characteristics of high-quality MS. The waste tailings stone particles with 3–5 mm size produced in the processing of high-quality stones are used as raw materials for the production of MS. The

2.3 Improvement of Production Technology

25

Fig. 2.12 Flowchart of using tailings waste to produce MS

production process mainly lies in screening and fines removal as it has been coarse crushed and fine crushed. The process is as follows: Firstly, the block stone less than 750 mm is coarsely crushed through the jaw crusher, and the small gravels formed by crushing are transported to the cone crusher for medium crushing. During this period, the gravels larger than 40 mm return to the crusher for further crushing, and the gravels smaller than 40 mm are finely crushed by a vertical impact crusher. Finally, the fine gravels of different specifications are produced after being reshaped and recycled for many times. Meanwhile, 3–5 mm waste tailings stone particles are recovered, which are used as raw materials for producing MS. At present, the grain size of MS products mainly includes 0–3, 3–5 mm, etc. The specific particle size of the products can be adjusted by changing the screen aperture according to the demand. The simplified flowchart of MS production is as follows (Fig. 2.12).

2.3.1.2

Optimization of Wet Production Process

The disadvantage of the wet production process is that the fines content of produced sand is low, which has negative influence on the quality of MS and the performance of concrete mixture, as well as the environment. However, the fines content and the wastewater could be controlled with the development of new technology. For example, the process of recovering fines by the cyclone is canceled, and the pretreatment process of the sand scraper is added in a typical project in China. The first screen wastewater and other workshop wastewater are completely separated for precipitation and concentration. The fines are recovered by the pressure filter, and the traditional concept that the lost fines cannot be completely recovered in the wet production process has been broken.

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2 Production of Manufactured Sand

2.3.1.3

Semidry Production Process

The proposal of the semidry production process has aroused great concern in the industry due to the limitations of wet and dry production processes [2]. The energy-saving, environmental protection, intelligence, and high quality in the whole production process have been considered in the semidry production process. (1) Replace grinding with breaking and more breaking and less grinding Replacing grinding with breaking and more breaking and less grinding are the main principles of the semidry production process. By using this method, some traditional and high energy consumption produced sand equipment can be canceled without changing the quality of MS. From the perspective of the performance of crushing equipment, the quality index of product grain shape and particle size distribution are determined by the crushing way. From the perspective of the grain shape index, the vertical shaft broken by stone is better than that by iron, the vertical impact crusher is better than the impact crusher, and the cone crusher and the rotary crusher are better than the jaw crusher. From the perspective of rock lithology, the crystal structure of the rock is one of the important factors affecting the crushing process and equipment selection. The rock with a granular crystal structure is easy to be crushed into square gravel, while the rock with a layered crystal structure is easy to be processed into flaky gravel. Rock hardness is also an important index of process design and equipment selection. The rock with higher hardness is not easy to break, so the crushing equipment with higher crushing force should be selected. The rock with smaller hardness is easy to break, so the impact crusher can be used. For the rock with strong abrasiveness and high work index, the four-stage or three-stage crushing process is often adopted according to the aggregate size requirements. For rocks with low abrasiveness and moderate work index, the three-stage crushing process is often used. The content of fines in MS is related to the production process and rock lithology. Due to different requirements of concrete for fines in different industries, pneumatic classification technology is adopted as fines collecting measure in the production process. (2) A combination of wet and dry production process For the rock with a mud content of more than 2% in aggregates, the semimanufactured materials shall be fully washed before middle crushing, so there is no mud or other harmful substances in aggregate. Semidry production process shall be adopted in the process of middle crushing and fine crushing. (3) Intelligent energy saving The parameters of process control and production test adjustment are input into the central control system in this method. This can not only keep the optimum operating condition to the crushing equipment, but also integrate the feeding equipment, water supply, and high-frequency screening, so that the equipment in

2.3 Improvement of Production Technology

27

the technological process is always in full load operation. The demand of water is strictly controlled in the production process. The key points of energy saving are water, electricity, wearing parts, full-load operation, and utilization rate of the equipment. Practical experience shows that the efficiency difference of crusher can be 20–30% with or without an automatic control system. The production of high-quality manufactured aggregate can be automatically controlled according to the demands by using the PLC intelligent control technology. (4) Environmental protection The semidry production process can save 35–50% of land resources (flat type is 35%, slope type is 50%) and raw materials compared with the traditional production process. In the process of producing, the waste mud and impurities can be used for rehabilitation and restoration of ecological balance. The water consumption per cycle of traditional method is 2.5–4 m3 /t, while that of the semidry production is only 0.8 m3 /t. The utilization rate of equipment has been greatly improved due to the implementation of automatic program control. The power consumption of conventional production is 9–12 kW·h/t, and that of the semidry production process is 3.5–4.5 kW·h/t. From the beginning of design, the semidry production process follows the principle of "environmental safety", including general layout, engineering cost, plane layout, water supply and drainage, fines removal. Moreover, the noise is less than 80 dB, and dust content in the air is less than 30 mg/m3 . Meanwhile, the production process uses energy-saving and environment-friendly production equipment and process, and the moisture content of MS and gravel is controlled between 3 and 4%. Therefore, the green production process can be realized by this technology.

2.3.2 Production Equipment Optimization 2.3.2.1

Crushing Equipment

In addition to the traditional jaw crusher and cone crusher used in the process of primary and secondary crushing, the vertical impact crusher can be used to obtain the MS with ideal particle morphology, reduce the particle angle, and make the particle shape closer to that of the natural sand. This equipment is shown in Fig. 2.13. The principle of vertical impact crusher: the gravel falls directly into the highspeed rotating turntable from the upper part of the machine. Under the action of high-speed centrifugal force, the gravel and another part of the target gravel which are distributed around the turntable in the form of an umbrella will produce highspeed impact and crushing. After that, the vortex motion of gravels is caused by the rotation of the turntable, resulting in repeated collision, friction, and crushing until the required particle size is obtained. The vertical impact crusher has the following advantages: (a) The fine gravel equipment is the most advanced crushing technology in the world. (b) The structure is

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2 Production of Manufactured Sand

Fig. 2.13 Vertical impact crusher

novel, unique, and stable. (c) Low energy consumption, high yield, and high crushing ratio. (d) The equipment has the advantages of small volume, simple operation, convenient installation, and maintenance. (e) Powerful plastic function, the product has a square shape and large bulk density. (f) In the production process, the gravel can form a protective bottom layer, the crusher frame is not worn and durable. (g) Parts easily worn are made of extra-hard and wear-resistant materials, which are small in volume, light in weight, and accessories are easily replaced.

2.3.2.2

Fines Removal Equipment

In fact, there are a lot of fines for MS in engineering. How to separate the fines and effectively control the fines content has been a long-term problem? At present, there is a new type of ore fines separator, which has solved the technical problems such as high energy consumption and the low separation rate of the existing fines separator. An important improvement of the new type of MS and fines separator is that the flat plate C is provided with an air vent. When the material falls from the flat plate, one part of the updraft drives the fines to return to the vent from the pipe along with the air return port; the other part of the updraft directly returns to the vent from the inside of the shell. When there is no air vent on the plate C, the area of the channel along the upward air flow in the frame will be greatly reduced, which is not conducive to the movement of the air flow and further weakens the separation effect. Another improvement is that a flange is installed on the frame, through which the frame can relate to the air inlet equipment. The frame is also provided with a protective plate, which can prevent materials from splashing when entering from the conveyor belt. Figure 2.14 is the main view of the new MS and fines separator. When the machine works, the material is fed from port 1. At the same time, the blower connected with flange 10 starts to generate the updraft. In this way, the waste gas containing fines can flow into the waste gas collection station through vent 11. In addition, the air velocity can be adjusted by the blower.

2.3 Improvement of Production Technology

29

Fig. 2.14 Structure diagram of a new type MS and fines separator

2.3.2.3

Selection of Main Equipment for MS Production

(1) Technical requirements of vibrating feeder in MS production Generally, the vibrating feeder is located between the feeding bin and the jaw crusher in the production of MS, which can feed the massive and granular materials from the storage bin to the crushing device evenly, regularly, and continuously. The pressure of the material on the tank should be reduced as far as possible in the configuration design considered the performance requirements of the equipment. In general, the size of the outlet in the feeding bin should not be greater than 1/4 of the width of the tank, and the flow speed of the material should be controlled from 6 to 18 m/min. For the materials with a large amount, the ore blocking plate with enough height should be set but not fixed at the discharge place at the bottom of the storage bin. The inclination angle of the back wall of the silo should be set as 55°–65° for the smooth discharge of materials. (2) Selection principle of crusher in MS production In the production process of MS, a three-stage crushing process is generally adopted, namely coarse crushing, medium crushing, and sand producing. The crushers used in different crushing stages are not the same. The jaw crusher is the most commonly used for coarse crushing, the counterattack crusher is generally used for medium crushing, and the vertical impact crusher is generally used for the sand-producing machine. The performances of various crushers are shown in Table 2.1.

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Table 2.1 Performances of common crushers Type

Crushing method

Motion mode

Crushing ratio

Application scope

Material type

Jaw crusher

Crushing

Reciprocating

4–6

Coarse, medium crushing

Hard and medium-hard materials

Cone crusher

Crushing

Gyration

Coarse crushing 4–6; medium and fine crushing 3–17

Coarse, medium, and fine crushing

Hard and medium-hard materials

Roller crusher

Crushing

Slow rotation

3–8

Medium and fine crushing

Hard and soft materials

Hammer crusher

Impact

Fast rotation

Single rotor type 10–15, double rotor type about 30

Medium and fine crushing

Hard, medium-hard, and soft materials

Counterattack crusher

Impact

Fast rotation

Over 10, up to 40

Medium crushing

Medium-hard material

Vertical impact Impact crusher

Fast rotation

/

Fine crushing

Medium-hard material

(3) Selection principle of sand-producing machine The rod mill crusher, counterattack crusher, and vertical impact crusher are generally adopted in the sand producing. Their performances are shown in Table 2.2. From Table 2.2, the MS produced by rod mill crusher has good gradation, the MS produced by counterattack impact crusher has good gradation but poor grain shape, while the MS produced by vertical impact crusher has poor gradation but good grain shape. Some people hold that the rod mill crusher should be used, because the rod mill has a selective effect on the fines and grinds the gravel in a gradual way. Hence, there is a less over-grinding phenomenon. However, the rod mill crusher has some defects, such as low output, high operation cost, high labor intensity. In the actual production, the combination of counterattack crusher and vertical impact crusher is suggested to be used, and the MS with good grain shape, good grading, and high output can be obtained. (4) Influence of vibrating screen on MS production. In the production of MS, the most important factor affecting its gradation is the screening process, in which the shape and size of the screen hole and the inclined angle of the sieve surface are the key parameters affecting the quality of MS. There are many fines in the production of MS, and the grading requirements are strict, so it is not suitable to use a rectangular and circular sieve, and a square

2.3 Improvement of Production Technology

31

Table 2.2 Comparison of rod mill crusher, counterattack crusher, and vertical impact crusher Type

Crushing method

Influence factor

Production method of MS

Characteristics of MS

Rod mill crusher

Crushing

/

The gravel with a certain size is crushed by a rod mill crusher, and the MS is obtained by screening

The fineness modulus and gradation are good, and the fines content is low

Counterattack crusher

Impact

Rotor speed and clearance between plates and hammers of counterattack crusher

The MS obtained by the counterattack crusher is a material whose particle size is less than 5 mm after coarse crushing and medium crushing, which is the by-product of gravel production

The MS has good grading, relatively uniform content at all levels, a smooth gradation curve, but more edges and corners, and a poor grain shape

Vertical impact crusher

Impact

Crusher rotor linearity, material moisture content, feed quantity, feed particle size

The gavel with a certain size is crushed by a vertical impact crusher, and the MS is obtained by screening

The grading of MS is “more at both ends, less in the middle”, and the grain shape with round granular is better

sieve is generally recommended. The screen size shows a direct effect on the quality and production of MS. Generally, the larger the screen size is, the larger the fineness modulus of MS is and the lower the fines content is, and vice versa. Therefore, a screen size of 3.5–4.5 mm is recommended in the general produced sand process. To achieve better screening efficiency and handling capacity of materials, the inclination angle of screen surface is generally about 20° according to the experience of vibrating screen manufacturers. (5) Selection of fines removal equipment for MS. There will be 10–20% fines ( illite > kaolinite. There are many studies on the effects of different types of clay on the properties of cement-based materials: (1) Clay adsorbs mixing water and water-reducing agents and produces volume expansion, which will affect the workability of cement-based materials. Norvell et al. [22] found that the water requirements (w/c) of mortar were 0.60, 0.51, and

3.3 Clay Content and MB Values

51

Fig. 3.1 Structural illustration of montmorillonite, reprinted from ref. [20], copyright 2012, with permission from Elsevier

Fig. 3.2 Structural illustration of illite, reprinted from ref. [21], copyright 2020, with permission from Elsevier

0.90, respectively, when 4% kaolinite, illite, and montmorillonite were mixed with the mortar under the same fluidity. In addition, the adsorption of water reducers by clay would aggravate the loss of fluidity of cement-based materials, and the adsorption of different types of clay on various water reducers

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3 Features of Manufactured Sand

Fig. 3.3 Structural illustration of kaolinite, reprinted from ref. [21], copyright 2020, with permission from Elsevier

was different. The adsorption capacity rank for the naphthalene-based waterreducing agent (NS) was cement > kaolinite > montmorillonite. The adsorption capacity of sodium lignosulfonate (LS) was kaolinite > montmorillonite > cement. However, the influence of montmorillonite on the fluidity and viscosity of the slurry is still the largest under the combined action of adsorbing water and water reducers. (2) Clay affects the workability of cement-based materials by adsorbing water and water reducers, further affecting other properties of cement-based materials. Many scholars have found that the incorporation of clay shows a negative effect on the mechanical properties of concrete. Norvell et al. [22] found that when the clay content was 4%, the compressive strength of the specimen mixed with montmorillonite was significantly deteriorated, compared with the control mix without clay, which was less than 50% of the control mix, while illite and kaolinite had little effect on the strength of concrete. Muñoz et al. [23] found that the 28d compressive strength of concrete decreased by 88% and 75% with the addition of Na-montmorillonite and Ca-montmorillonite, respectively. Illite and kaolinite have little effect on compressive strength. The effect of clay on tensile strength is similar to that of compressive strength. Besides, the existence of clay has adverse effects on drying shrinkage and durability of cement-based materials. Norvell et al. [22] found that when the clay content was 4%, the 28d dry shrinkage of montmorillonite-doped specimens was 2–3 times that of the control mix without clay, while illite and kaolinite had little effect on dry shrinkage. Muñoz et al. [23] found that illite had little effect on dry shrinkage compared with the control mix. The 120d drying shrinkage increased by 15% under the effect of kaolinite. The addition of Na-montmorillonite and Ca-montmorillonite has

3.3 Clay Content and MB Values

53

significantly promoted drying shrinkage of specimens after 120 d, and the effect of Ca-montmorillonite was greater than that of Na-montmorillonite. Muñoz et al. [23] also studied the effect of clay on freezing–thawing resistance. Kaolinite has almost no effect on freezing–thawing resistance. However, after only 16 freeze–thaw cycles, the freezing–thawing resistance of specimens containing Na-montmorillonite decreased by 60%, indicating that clay with high water adsorption can significantly reduce the freezing–thawing resistance of concrete. Gullerud et al. [15] found that the coating of clay on aggregate showed a negative effect on the freezing–thawing resistance of concrete because the coating of clay adsorbed water and weakened the bonding between aggregate and cement paste, so the possibility of aggregate shedding increased.

3.3.2 MB Values of MS 3.3.2.1

Test Mechanism of MB Method

Since clay in MS powder has a significant adverse effect on the performance of fresh mixed and hardened concrete, methylene blue (MB) method is widely used to characterize the content and adsorption capacity of clay in MS in domestic and foreign standards. In the current Chinese National Standard GB/T 14,684–2021, the methylene blue value is defined as an index used to determine the adsorption capacity of MS and mixed sand. Methylene blue is a cationic dye that is easily soluble in water and appears blue in the aqueous solution. The formula of the MB molecule is shown in Fig. 3.4. It can be seen that the MB molecule has a certain amount of positive charge, while the clay surface is usually negatively charged, which means that clay has a strong adsorption capacity for methylene blue molecules. Therefore, MB was used to study the adsorption capacity of clay in MS. During the test, MB solution is gradually added to the suspension prepared with water and particles whose size is below 2.36 mm in MS. And MB molecules are gradually adsorbed by the clay particles. When the clay particles are completely covered by MB molecules, free methylene blue molecules begin to exist in the suspension. At this point, use the glass rod to stain the suspension on the filter paper. While water

Fig. 3.4 The formula of the MB molecular

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3 Features of Manufactured Sand

Fig. 3.5 Methylene blue test: a blue stain surrounded by a colorless wet area (negative outcome of the test); b blue stain surrounded by a light blue halo (positive outcome of the test)

diffuses outward, MB also diffuses outward and is diluted by water, and finally, a light blue halo is formed, as shown in Fig. 3.5. Then, MB value can be calculated according to the amount of MB solution added.

3.3.2.2

Comparison of Methylene Blue Method at Home and Abroad

The MB methods in domestic and foreign standards are also different. The Chinese National Standard GB/T 14,684 is compared with the British Standard BS EN 933–9, the American Association of State Highway and Transportation Officials Standard AASHTO T330, and the American Society of Testing Materials Standard ASTM C1777, and the comparison is listed in Table 3.2. The MB methods of GB/T 14,684, BS EN 933–9, and AASHTO T330 are a kind of titration process, gradually adding the MB solution and artificially determining the endpoint. MB method in ASTM C1777 is a kind of colorimetric method. During the test process, a sufficient amount of methylene blue solution is added to the test tube, and the amount of MB that is not adsorbed is determined by a spectrophotometer, and then, the MB value can be calculated. According to the test mechanism of the titration method, there are excessive unabsorbed MB molecules in the solution at the endpoint, and there is an artificial error in the determination of the endpoint. Therefore, the MB value of the titration method is higher than the actual value. Compared with the titration method, the result of the colorimetric method is more accurate and convenient for field use, but the disadvantage is that the equipment is relatively expensive and the operation requirements are higher. For the three standards using the titration method, the test methods in GB/T 14,684 and BS EN 933–9 are basically the same. The main differences between the test methods in AASHTO T330 and the former two standards are the selection of sample particle size, the amount of methylene blue added in a single time, and the sample screening method. The MB value of samples with a particle size of 0–2.36 mm or 0–2 mm is more comprehensive

3.3 Clay Content and MB Values

55

Table 3.2 Comparison of MB methods between China, Britain, and America GB/T 14,684

BS EN 933–9

AASHTO T330

ASTM C1777

Sample size range (mm)

0–2.36 or 0–0.075

0–2 or 0–0.125

0–0.075

0–4.75

Composition of suspension

200 g sample + (500 ± 5) mL distilled water

200 g or (30 ± 0.1) g sample + (500 ± 5) mL distilled water or deionized water

(10 ± 0.05) g sample + 500 mL distilled water

(20 ± 0.1) g sample + (30 ± 0.1) g methylene blue solution

Methylene blue solution concentration (g/L)

10

10

5

5

Sample screening method

Dry screening

Dry screening

Water screening

Dry screening

Ambient temperature

/

/

15–25 °C

/

Mixing method

Mixer, mixing speed: (400 ± 40) r/min

Mixer, mixing / speed: (600 ± 60) r/min for the first 5 min, and (400 ± 40) r/min to the end of the test

Shake the mixture by hand for (60 ± 1) s, allow to rest for (180 ± 5) s, and shake the mixture again for (60 ± 1) s

Amount of MB solution added each time

5 mL

5 mL

0.5 mL

/

Amount of MB solution added last time

5 mL or 2 mL

5 mL or 2 mL

0.5 mL

/

Endpoint criteria

Color halo diameter: about 1 mm, maintains 5 min

Color halo diameter: about 1 mm, maintains 5 min

Color halo maintains 5 min

/

Calculation formula

MB = 10 V/M

MB = 10 V/M

MB = 5 V/M

MB = 10(C i − C f ) (MMB )/MFM

Remark In the calculation formula, MB = MB value (g/kg), V = total amount of MB solution added (mL), M = sample mass (g), C i = average actual initial concentration of MB test solution in percent (%), C f = final concentration of MB solution in percent (%), M MB = mass of MB test solution (g), and M FM = mass of fine aggregate or mineral filler (g)

than that of samples with a particle size of 0–0.125 mm or 0–0.075 mm, which can reflect the overall adsorption capacity of MS. However, the results are affected by the passing rate of 2.36 mm or 2 mm sieve of MS, which cannot reflect the adsorption capacity of clay in fine powder. The MB value of samples with a particle size of 0– 0.125 mm or 0–0.075 mm can reflect the adsorption of clay in fine powder, but cannot

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3 Features of Manufactured Sand

reflect the influence of fine powder content in MS. In addition, the concentration of MB solution and the amount of solution added per time in GB/T 14,684 and BS EN 933–9 standards are higher than that in the AASHTO T330 standard, so theoretically the accuracy of the former two standards is lower than the latter.

3.3.2.3

Factors Affecting the MB Value

There are many factors affecting the MB value of MS, which can be summarized in the following categories: (1) Stone powder and clay content. The MB value of MS increases with the increase of stone powder and clay content, and the influence of stone powder content is small, while the influence of clay content is significant. Shen et al. [24] found that the MB value increased linearly and slowly with the increase of pure stone powder content. When the stone powder content increased from 10 to 20%, the MB value only increased from 0.40 to about 0.55. However, the MB value increased from 1.4 to 4.0 when the clay content increased from 3 to 10%. Petkovšek et al. [25] used different clay minerals to study the relationship between MB value and clay content in fine powder with particle size < 0.063 mm. The results showed that the MB value increased linearly with the increase of clay content, as shown in Fig. 3.6. Therefore, it can be considered that the MB value increases approximately linearly with the increase of stone powder content and clay content, but the growth rate with clay content is significantly higher than that with stone powder content. (2) Types of clay. Although the MB value of MS increases linearly with the increase of clay content, the growth rate varies significantly with different clay types. Different types of clay minerals have different specific surface areas and cation exchange capacities, so their physical and chemical adsorption capacities for MB molecules are significantly different. Norvell et al. [22] partially replaced the sand with 4% kaolinite, illite, and montmorillonite powder, and the measured MB values were 7.5 mg/L, 5.5 mg/L, and 77.5 mg/L, respectively. (3) The lithology of the MS parent rock. The influence of parent rock on MB value mainly depends on the type and content of clay minerals in the parent rock. There is little difference in MB value between parent rocks without clay minerals. Shen et al. [24] found that the MS itself would adsorb a certain amount of MB molecules. 5% stone powders ground from parent rocks with different lithology were mixed into the MS. It was found that the MB values of the MS varied between 0.15 and 0.35. It was considered that the parent rock of the MS would provide a base value for the MB value, which would have impact on the accuracy of the MB value. Figure 3.7 was summarized by the author’s research team. It showed the relationship between MB value and stone powder content of MS with different lithology produced by different processes under various projects. It could be seen that there was no obvious regular relationship between MB value and stone powder content of MS prepared by the same lithology parent

3.4 Geometric Features

57

Fig. 3.6 MB value changes with clay content in 0–0.063 mm fine powder (L1 –L5 represent different types of clay minerals in limestone powder), reprinted from ref. [25], copyright 2010, with permission from Springer Nature

rock and the same production process, which may be caused by the difference in clay content and properties of MS parent rock used in different projects. 4. Size range of MS. For the same MS, if the particle size range of the sample to be tested is different, the measured MB value is also significantly different. Shen et al. [24] found that with the decrease in particle size of MS, the proportion of fine particles below 0.075 mm increased, and the MB value gradually increased. However, the MB value of MS without fine particles below 0.075 mm changed little with the decrease in particle size, indicating that fine particles were the main contributor to the MB value. Therefore, the smaller the particle size range of the same MS sample, the higher the proportion of fine powder particles below 0.075 mm, the higher the clay content, and the higher the MB value measured.

3.4 Geometric Features 3.4.1 Literature Review The geometric features of fine and coarse aggregate particles affect not only their mutual interactions as well as interactions with cementitious materials, but also the workability, mechanical properties, and durability of concrete. It was suggested by Barrett [26] and has been widely acknowledged that the shape of a granular particle

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3 Features of Manufactured Sand

Fig. 3.7 The relationship between MB value and stone powder content of different lithology MS produced by different processes

can be described at different scales in terms of form (overall shape), angularity (large scale smoothness), and surface texture (fine-scale smoothness), as illustrated in Figs. 3.8 and 3.9. Form evaluates the similarity among the particle’s dimensions, i.e., length, width, and height. Angularity describes the surface features at the scale of one order of magnitude smaller than the particle size. It reflects variations at the corners, that is, variations superimposed on the form. Surface texture or roughness captures more detailed surface features. It is superimposed on the corners and is also a property of particle surfaces between corners. For instance, at the coarse scale, a particle is normally defined as equidimensional, elongated, flat, etc. At the fine scale, the particle may have a smooth or rough surface or a combination of these for the case of a partially crushed particle. At the intermediate scale, the particle may or may not have angular edges. These three scales are geometrically independent, although there may be a natural correlation between them in the process affecting one may promote or inhibit the development of others. The following are some shape parameters frequently used in literature: elongation ratio, flatness ratio, sphericity, roundness, angularity, shape factor, fullness ratio, convexity ratio, etc. It needs to be mentioned that most direct methods are based on image processing techniques.

3.4 Geometric Features

59

Fig. 3.8 A particle with its component elements of the form (red and blue solid lines), angularity (blue dashed circles), and surface texture (green dotted circles)

Fig. 3.9 The hierarchical view of form, roundness, and surface textures, reprinted from [26], copyright 2006, with permission from sedimentology

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3 Features of Manufactured Sand

3.4.2 Geometric Features of MS 3.4.2.1

Parameters of Overall Shape

The overall shape was firstly defined by Folk [27]. It is evaluated based on the relationships between the dimensions of the long, medium, and short axes of a 3dimensional (3D) particle. For a 2-dimensional (2D) structure, the overall shape is expressed as the relationship between the dimensions of two directions. (1) Overall shape parameters based on 3D methods Due to the development of imaging processing techniques, like 3D laser scanners [28–30], X-ray computed tomography [31–34], and stereo photography [35, 36], the 3D structure of a particle can be captured and reconstructed. Consequently, the 3D dimensions of a particle can be measured. a. Elongation Elongation and flatness are common parameters to describe overall particle shape. Figure 3.10 shows the 3D dimensions of a particle. Elongation is the ratio of the longest dimension to the intermediate dimension of the particle, expressed below [37–39].

Elongation =

Fig. 3.10 Diagram of the dimensions of a particle

Llongest Lintermediate

(3.1)

3.4 Geometric Features

61

b. Flatness Flatness is the ratio of the intermediate dimension to the shortest dimension, shown below [37–39]. Flatness =

Lintermediate Lshortest

(3.2)

In addition to the relationship between the intermediate and the shortest dimensions, all the three dimensions were also used to calculate the flatness value, shown below [40]. Flatness =

Llongest + Lintermediate 2Lshortest

(3.3)

c. Flakiness Flakiness is reciprocal to flatness, calculated as the ratio of the shortest dimension to the intermediate dimension [41]. Flakiness =

Lshortest Lintermediate

(3.3)

d. Sphericity According to the dimensions shown in Fig. 3.10, sphericity was proposed and has been widely used to measure the form of particles, calculated as follows [41–44]: √ Sphericity =

3

Lshortest · Lintermediate L2longest

(3.5)

e. Shape factor Similar to sphericity, the shape factor is also used as an index of 3D particle shape [38, 41, 43–45]. Lshortest Shape factor = √ Llongest · Lintermediate

(3.6)

f. Area sphericity The area sphericity was proposed as the ratio between the front area (Afront ) and the top area (Atop ) shown as follows [46]:

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3 Features of Manufactured Sand

Area sphericity =

Afront Atop

(3.7)

All the 3D shape parameters have a value of 1 when the particle is equaldimensional. When the particle is increasingly deviating from the equal-dimensional shape, the shape parameters of elongation, flatness, and area sphericity increase while flakiness, sphericity, and shape factor decrease from 1. (1) Overall shape parameters based on 2D methods Even though 3D image-based methods are more likely to avoid the bias on the dimension of particles, 3D imaging techniques are not commonly used for daily analyses owing to their capital intensiveness and complicated operation requirement. As a result, 2D image-based methods, as easy-to-perform quantification methods, are more welcomed and well developed for the characterization of particle shape. a. Length/width ratio Based on the 2D images (projections, cross-sections, etc.) of particles, the overall shape may be evaluated by the length/width (L/W ) ratio (Eq. (3.8)) of the circumscribed rectangle of the object (Fig. 3.11a) [47–49]. Besides, an equivalent rectangle (Fig. 3.11b) can also be used to evaluate the particle shape while the term equivalent rectangular aspect ratio was used [48].

L/W =

Length Width

(3.8)

b. Aspect ratio Other than a rectangle, an ellipse was also employed to evaluate the overall shape of a particle. Aspect ratio, also known as the axial ratio, is the length ratio between the major axis and minor axis of the circumscribed ellipse (Fig. 3.12a) or the fitted ellipse (Fig. 3.12b) [50]. The calculation of the aspect ratio is shown in Eq. (3.9). It needs to be mentioned that there are several ways to determine the equivalent ellipse.

Fig. 3.11 Length/wide ratio of a particle based on a the circumscribed rectangle and b the equivalent rectangle

3.4 Geometric Features

63

Fig. 3.12 2D image of a particle with a the circumscribed ellipse and b the fitted ellipse

This equivalent ellipse may be specified as the one with the same normalized second central moments as the object region. It can also be an ellipse with the same area, first-degree moment, and second-degree moment as the particle image [51].

Aspect ratio =

Rmajor Rminor

(3.9)

c. Elongation factor The elongation factor is related to the Feret diameter of the particle. The Feret diameter, as shown in Fig. 3.13, is the minimum distance between a pair of parallel lines that can enclose the particle’s projection [52]. The elongation factor is calculated as the ratio between the maximum and minimum Feret diameters, shown as follows:

Enlongation factor =

DF,max DF,min

(3.10)

where DF,max and DF,max are the maximum Feret diameter and the minimum Feret diameter, respectively. Fig. 3.13 Illustration of Feret diameter

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3 Features of Manufactured Sand

Fig. 3.14 Illustration of the maximum Feret diameter and its perpendicular diameter, reprinted from ref. [53], copyright 2016, with permission from Elsevier

In addition to the minimum Feret diameter, the diameter perpendicular to the maximum Feret diameter, shown in Fig. 3.14, was also used to calculate the elongation factor while it was used as the aspect ratio in literature [53, 54]. d. Compactness factor The compactness factor is the ratio of the area of the particle’s projection (A) to that of its circumscribed rectangle (ARectangle ) (see Fig. 3.11a), shown as follows [48]: Compactness factor =

A Arectangle

(3.11)

e. Area ratio Similar to the compactness factor, the area of the circumscribed ellipse (see Fig. 3.12a) was also used to evaluate the overall shape of the particle, known as area ratio and calculated as below [55]. Area ratio =

Acircumscribing ellipse A

(3.12)

f. f -value Westerholm et al. [56] characterized the overall shape of aggregate by using the parameter of f -value, which is defined in Fig. 3.15 based on the image analysis of thin sections obtained by an optical microscope. Particles can be divided into four categories according to their f -values, i.e., very elongated (0 ≤ f -value ≤ 0.25), elongated (0.25 ≤ f -value ≤ 0.50), cubic elongated (0.50 ≤ f -value ≤ 0.75), and circular elongated (0.75 ≤ f -value ≤ 1).

3.4 Geometric Features

65

Fig. 3.15 Definitions of f -value describing the shape of particles, reprinted from ref. [56], copyright 2008, with permission from Elsevier

g. Roundness In addition to the relationship between the 2D dimensions of the particle, roundness is also used as a measurement of form and determined as follows [51, 57]: Roundness =

P2 4π · A

(3.13)

where P and A are the perimeter and area of the 2D projection of the particle, respectively. A circular object has a roundness of 1.0, while other shapes have roundness values higher than 1.0. The reciprocal of roundness is also widely used. Other than roundness, other terms like circularity or sphericity may be used. Roundness was also proposed as the area ratio between the projection and its circumscribing circle, calculated as follows [58]: Roundness =

4A 2 π · Dcir

(3.14)

where Dcir is the diameter of the circumscribing circle. h. Fourier parameter Fourier series can be used for the expression of particle shape. The profile of a particle can be defined by the function R(θ ) shown in Fig. 3.16, which traces out the distance between the boundary and the central point concerning the angle θ (0◦ < θ < 360◦ ). R(θ ) can be analyzed using Fourier series coefficients as follows [51]: R(θ ) = a0 +

∞ n=1

[an cos(nθ ) + bn sin(nθ )]

(3.15)

where n represents frequency while an and bn are the Fourier coefficients, which can be evaluated using the integrals shown below.

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3 Features of Manufactured Sand

Fig. 3.16 Illustration of Fourier series and the increment in the particle radius

 a0 =

2π

R(θ )dθ

(3.16)

0

an =

1 π

1 bn = π



2π

R(θ )cos(nθ )dθ n = 1, 2, 3, . . .

(3.17)

R(θ )sin(nθ )dθ n = 1, 2, 3, . . .

(3.18)

0



2π 0

If R(θ ) is only known numerically at a discrete number of angles, the above integrals (Eqs. (3.16)–(3.18)) can be represented using the following summations. 1 2π −θ R(θ + θ ) + R(θ ) ) ( θ =0 2π 2   1 2π−θ R(θ + θ ) + R(θ ) (sinn(θ + θ ) − sinnθ ) an = θ=0 2π 2   1 2π −θ R(θ + θ ) + R(θ ) (−cos(θ + θ ) − cosnθ ) bn = θ =0 2π 2 a0 =

(3.19) (3.20) (3.21)

where R(θ ) is measured at predefined increments, and θ takes on values from 0 to (2π − θ ) with an increment θ . The higher the value of n used, the better the actual particle profile is reproduced. Based on the Fourier series, Wang et al. [59] proposed a shape parameter, αS , using the an and bn coefficients, which is denoted as follows: αS =

4 j=0

[(

an 2 bn 2 ) +( ) ] a0 a0

(3.22)

The shape parameters (overall shape, angularity, and roughness) can be specified by the same function in Eq. (3.22). However, various frequency magnitudes

3.4 Geometric Features

67

of the harmonics should be used to capture the particle boundary while considering the particle shape at different scales. Specifically, the overall shape is captured using harmonics with a lower frequency than angularity while roughness requires the highest frequency of harmonics. However, it is still an open area of research to define the boundaries of frequencies representing overall shape, angularity, and roughness. i. Form index Similar to the Fourier series, Masad et al. [43] proposed the parameter of form index to describe the overall shape of a particle. As illustrated in Fig. 3.15, the length of a line that connects the center of the particle to the boundary of the particle is termed radius. Form index measures the increment of the particle radius, calculated by the following equation. Form index =

 θ =360−θ  Rθ +θ − Rθ   θ =0 R θ

(3.23)

here θ is the directional angle and R is the radius in different directions. It can be inferred that a perfect circle has a form index of zero, while highly anisotropic shapes have higher form index values. Although the form index is based on 2D measurements, it can easily be extended to analyze the 3D images of aggregates.

3.4.2.2

Parameters of Angularity

Angularity is more complicated than overall shape, it cannot be directly measured from the relationship between the object and regular shape in terms of dimensions or areas. (1) Fourier parameter As introduced in Sect. 1.1.2, Fourier series analysis can be used to measure the angularity of particles. Angularity is captured using harmonics with frequencies that are higher than form but lower than roughness. The angularity was given by Wang et al. [59] according to Fourier series analysis, shown below. αA =

25 j=5

[(

bn 2 an 2 ) +( ) ] a0 a0

(3.24)

where a0 , an , and bn can be determined from Eqs. (3.19)–(3.21). (2) Lost area Masad et al. [43, 60] used the erosion-dilation technique to capture the angularity and roughness of fine aggregate. Erosion is a morphologic operation (Fig. 3.17) in which pixels are removed from a binary image according to the number of neighboring pixels that have a different color. Progressive erosion layer by layer gradually eliminates small objects as well as outward-pointing irregular elements of the surface.

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3 Features of Manufactured Sand

Dilation is the reverse process of erosion, where a layer of pixels is added to the object to form a simplified version of the original object. An angular image would change during the erosion-dilation cycles since surface angularities lost under the erosion process will not be all restored by dilation [61]. The angularity was measured by the area lost during the erosion-dilation process concerning the total area of the original particle, described by the following expressions.

Surface parameter =

A1 − A2 A1

(3.25)

where A1 and A2 are the areas of the object before and after erosion-dilation operations, respectively. Highly angular particles would lose more area than a smooth one. Thus, the surface parameter would be higher. For a low-resolution image, the surface

Fig. 3.17 Illustration of erosion and dilation process, reprinted from ref. [51], copyright 2007, with permission from Elsevier

3.4 Geometric Features

69

parameter measures the angularity of the particle. For a high-resolution image, the erosion-dilation procedure would lead to the disappearance of fine details of the surface. Then, the surface parameter evaluates the surface texture of the particle. The detail of surface texture was proposed to be on the order of 0.015 mm, and the angularity elements were on the order of 0.075 mm. However, the resolution for angularity and roughness is still a matter of debate [60, 62]. (3) Effective width In its simplest form, fractal behavior is defined as the self-similarity exhibited by an irregular boundary when captured at different magnifications. Fractal behavior has many applications in science [63]. As introduced in Sect. 1.2.2, smooth boundaries erode or dilate at a constant rate. However, irregular or fractal boundaries have more pixels touching opposite-color neighbors. Therefore, they do not erode or dilate uniformly. This effect has been used to estimate fractal dimensions and, consequently, the angularity along the object boundary. This procedure is also shown in Fig. 3.17. It contains various erosion-dilation cycles and measures the increment in the effective width of the boundary (total number of pixels divided by boundary length and number of cycles) [64]. Then, the effective width is plotted against the number of erosiondilation cycles on a log–log scale. For a smooth boundary, the effective width remains constant at various cycles while the graph would show a linear variation for an angular boundary with the slope representing the fractal length of the boundary. This method was used by Masad et al. [65] to evaluate the angularity of a wide range of aggregates. (4) Gradient angularity index The gradient vectors of particles are shown in Fig. 3.18. As seen, the direction of the gradient vector of adjacent points on the boundaries of an angular particle changes more rapidly than that of a rounded particle. Thus, the gradient angularity index (GAI) is calculated as follows [44]:

Fig. 3.18 Illustration of the gradient vector for adjacent points of the particle with different shapes, reprinted from ref. [44], copyright 1987, with permission from American Society of Civil Engineers

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3 Features of Manufactured Sand

Fig. 3.19 Illustration of radius angularity index

GAI =

N −3 j=1

|θi − θi+3 |

(3.26)

where θi denotes the orientation angle of the i-th edge point, and N is the total number of points on the edge of the particle. (5) Radius angularity index The radius angularity index traces the difference between the radius of a particle and its equivalent ellipse at each orientation, shown in Fig. 3.19. The radius angularity index is calculated by the following equation [66].

Radius angularity index =

θ =360−θ |Rθ − REEθ | θ =0 Rθ

(3.27)

where Rθ is the radius of the particle at a directional angle θ , and REEθ is the radius of an equivalent ellipse at the same θ. A perfect circle has a radius angularity index of zero, while a highly angular shape has a higher radius angularity index. (6) Angularity index The angularity index method was developed by tracing the slope variation at each vertex of the particle projection outline, which is obtained from each of the top, side, and front images [67]. As shown in Fig. 3.20, the outline is approximated by an n-side polygon. The angle subtended at each vertex of the polygon is then computed. The angularity of each projection is determined from the equation below.

Angularity = A =

θ=170 θ =0

e × P(e)

(3.28)

where e is the starting angle value for each 10° interval, and P(e) is the probability that changes with the angle in the range of e to (e + 10◦ ). Note that A takes zero for a perfect circle and 720 for triangles and rectangles. Then, the angularity of a particle is determined by averaging the angularity of all three views weighted by their areas as given in the following equation.

3.4 Geometric Features

71

Fig. 3.20 Illustration of an n-side polygon approximating the outline of a particle, reprinted from ref. [51], copyright 2007, with permission from Elsevier

Angularity index =

A(font) × Area(font) + A(top) × Area(top) + A(side) × Area(side) Area(front) + Area(top) + Area(side)

(3.29) (7) Convexity area ratio Convex ratio is a measurement of convexity [42, 53, 68]. It is defined as the ratio of the area of the particle to the area of its corresponding convex hull (Aconvex_hull ) as shown in Eq. (3.30), while the convex hull is the smallest convex polygon that can contain the particle projection, as shown in Fig. 3.21.

Convexity area ratio =

Fig. 3.21 Illustration of a particle projection and its convex hull

A Aconvex_hull

(3.30)

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3 Features of Manufactured Sand

Another form of convexity area ratio, named fullness ratio, was also proposed as a measurement of angularity, calculated as follows [38, 68]: √ Fullness ratio =

A Aconvex_hull

(3.31)

Mora and Kwan [68] compared several shape parameters and found the convexity ratio and fullness ratio may show superiority for the measurement of angularity.

3.4.2.3

Parameters of Roughness

(1) Fourier parameter As introduced in Sect. 1.1.2, Fourier series analysis can be used to measure the roughness of particles. The roughness is given by Wang et al. according to Fourier coefficients, shown below. αR =

180 j=26

[(

bn 2 an 2 ) +( ) ] a0 a0

(3.32)

where a0 , an , and bn can be determined from Eqs. (3.19)–(3.21). Roughness is captured using harmonics with frequencies that are higher than both form and angularity. (2) Texture index Wavelet theory offers a mathematical framework for multi-scale image analysis [69], which works by mapping an image onto a low-resolution image and a series of detailed images. Figure 3.22a shows the original image, which can be decomposed into a low-resolution image (Image 1 in Fig. 3.22b) by iteratively blurring. The remaining images contain information on the fine intensity variation (high frequency) that was lost in Image 1. Specifically, Image 2 and Image 3 contain the information that is lost in the y and x directions, respectively, while Image 4 contains the information lost in both x and y directions. Image 1 in Fig. 3.22b can be further decomposed similarly to the first iteration, which gives a multi-resolution decomposition and facilitates the quantification of texture at different scales. An image can be represented in the wavelet domain by these blurred and detailed images. The texture parameter is the average energy on Images 2, 3, and 4 at each level, while the texture index is taken at a given level as the arithmetic means of the squared values of the detail coefficients at that level.

Texture index =

1 3 N (Di,j (x, y))2 i=1 j=1 3N

(3.33)

3.4 Geometric Features

73

Fig. 3.22 Illustration of the wavelet decomposition, reprinted from ref. [44], copyright 1987, with permission from American Society of Civil Engineers

where Di,j (x, y) is the decomposition function, N denotes the level of decomposition, i takes values 1, 2, or 3, for the three detailed images of texture, and j is the wavelet coefficient index. Owing to the multi-resolution nature of the decomposition, the texture index has a physical meaning at each level. At higher levels, it reflects the “coarser” texture of the sample, while it depicts the “finer” texture at lower levels.

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3 Features of Manufactured Sand

(3) Lost area As mentioned above, the erosion-dilation technique can be used to capture the surface texture of fine aggregate. The area change due to the erosion-dilation process is taken as the measurement of roughness. A higher resolution image is required for roughness evaluation than that for angularity. It was proposed that the detail of surface texture was found to be on the order of 0.015 mm. Therefore, it seems that the resolution for roughness analysis should be better than 0.015 mm/pixel. However, this value is supposed to be determined according to the scale of surface texture to be studied. For instance, higher-order length scale may be used for surface texture analysis for coarser particles. (4) Roughness value Shen et al. [47] used a coaxial laser confocal microscope to scan the surface with a laser beam, as shown in Fig. 3.23, and calculated the roughness value (Ra ) based on Eq. (3.34). A particle with a more tortuous surface has a higher roughness result.

Ra =

1 L



L

|y(x)|dx

(3.34)

0

where L is the length in μm, and y(x) is the height between the detecting point and the baseline while the baseline is determined by making the surrounded area above the baseline equal to that below the baseline.

Fig. 3.23 Illustration of the a testing and b calculation of roughness, reprinted from ref. [47], copyright 2016, with permission from Elsevier

Fig. 3.24 Illustration of a line on a plane array of parallel lines, reprinted from ref. [79], copyright 2017, with permission from Springer Nature

3.4 Geometric Features

75

(5) Convexity perimeter ratio Convexity perimeter ratio was proposed to evaluate the surface roughness of particles, which is calculated as the ratio between the perimeter of the convex hull (Pconvex hull ) (shown in Fig. 3.21) and the perimeter of the object region (P) [53, 70, 71], as shown below. Convexity perimeter ratio =

3.4.2.4

P Pconvex hull

(3.35)

Other Parameters

In addition to the direct methods primarily based on image process techniques, indirect tests are also widely used, especially in real engineering practice since it is normally inexpensive and easy to conduct. Numerous methods and parameters, primarily semiquantitative or qualitative, have been proposed to evaluate the geometric characteristic of aggregate. (1) Uncompact void content It is stipulated in ASTM C1252 [72] that the uncompact void content test can be used to evaluate the geometric features of fine aggregate. It covers the determination of the loose, uncompact void content of a sample of fine aggregate, which indicates the particles’ angularity, sphericity, and surface texture compared with other fine aggregates tested in the same grading. The uncompact void content (U ) can be calculated by the following equation. U =

V − F/G × 100% V

(3.36)

where V is the volume of cylindrical measure, F is the net mass of fine aggregate in measurement, and G is the dry specific density of fine aggregate. Aggregate with less spherical particles and a higher amount of anisotropic, angular, and rough particles has a higher uncompact void content, and vice versa. (2) Flow time The flow time test is an indirect measurement of fine aggregate geometric features by measuring the time required for a defined volume of aggregate passing through a standardized funnel. The test funnel has two standard diameters which are 12 mm and 16 mm. The 12-mm-diameter funnel applies to fine aggregate with the particle size range of 0.07–2.36 mm while the 16-mm-diameter funnel for fine aggregate with the particle size range of 0.075–4.75 mm. For the flow time test, a greater value of flow time represents a greater fiction angle, indicating higher non-sphericity and angularity features.

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3 Features of Manufactured Sand

(3) Flakiness index The flakiness index method was proposed in EN 933–3 [73] to evaluate the flakiness of particles by sieving with rectangular (bar sized) sieve openings. The main principle comprises two screening sessions. First, the sample is divided into fractions di /Di by using conventional sieves with square openings. Each fraction di /Di of sample is then screened using a bar sieve with the bar distance of Di /2. The flakiness index for a tested aggregate fraction is calculated as the mass (M1 ) of particles with at least one dimension less than Di /2 (i.e., particles passing the bar sieve), with respect to the total dry mass of the tested particles (M2 ), shown below. Flakiness index =

M1 × 100% M2

(3.37)

(4) Index of aggregate particle shape and texture The index of aggregate particle shape and texture was proposed in ASTM D3398 [74]. This test method takes the particle index of aggregate as an overall evaluation of particle shape and surface texture features. This method is based on the weighted average void content of specified sizes. The sample is separated into nine categories between 19 mm and 75 μm. The bulk-specific gravity of each size range is determined. Meanwhile, the mold is filled in three courses, each rodded ten times, and the net weight of the aggregate is determined. Then, the procedure is repeated with each layer being rodded 50 times. The index can be determined using the following equations. Ia = 1.25V10 − 0.25V50 − 32.0

(3.38)

V10 = (1 − (

M10 )) × 100 s·v

(3.39)

V50 = (1 − (

M50 )) × 100 s·v

(3.40)

where V10 and V50 are the voids (%) in aggregate compacted at 10 and 50 drops per layer, respectively, M10 and M50 are the average mass values of aggregate in the mold compacted at 10 and 50 drops per layer, respectively, s is the bulk-specific gravity, v is the volume of the mold, and 32.0 is an empirical constant representing the porosity of smooth, uniformly sized spheres at zero compaction effect. It was found that a particle index value of 14 seems to divide the natural and MS. (5) Friction angle The friction angle method was developed by Hu et al. [75, 76] to evaluate the shape of the aggregate. For loosely falling aggregate, a cone-shaped aggregate pile can

3.4 Geometric Features

77

gradually be formed because of the internal friction angle of particles. The slope of the aggregate pile can be calculated from the diameter and height of the cone and defined as the friction angle. A higher friction angle, represented by a higher slope, indicates the higher friction between aggregate particles, as a result, the high angularity of particles.

3.4.2.5

Summary of Geometric Parameters of Aggregate

There exist a large number of parameters to evaluate the geometric features (overall shape, angularity, and surface roughness) of aggregate particles, direct or indirect, 2D image-based or 3D image-based. Direct methods, primarily based on image process techniques, show more priority than indirect ones in terms of quantitatively measuring the overall shape, angularity, and roughness, while indirect methods qualitatively evaluate the overall geometric features. The direct methods for the determinations of overall shape, angularity, and roughness are summarized in Table 3.3. Most particle shape parameters in Table 3.3 are based on the difference between the parameters of the studied object and those of the regular shapes like circumscribed or fitted circles, rectangles, and ellipses. Besides, these parameters are obtained from individual particles. The geometric features of the aggregate mixture may be taken either as the arithmetic mean or weighted mean value of the shape parameters of the individual particle. 3D images can be obtained with the aid of a 3D laser scanner, X-ray computed tomography, or stereo photography, while 2D images may be from the projection of the particle from a particular or random direction. 3D image-based methods can provide more detailed information on the particle shape, angularity, and surface texture, while 2D image-based methods are more easy to perform whereas with the possibility of bias in the evaluation of geometric features due to the loss of the features on the third dimension. It needs to be mentioned that the random sections of particles can be used to alleviate the subjectivity and bias in the assessment of 3D objects involved by 2D measurement. Even though there have been many methods for the measurement of particle shape, there are still no commonly accepted methods. The selection of methods depends on the research purpose and the availability of testing apparatuses. For instance, the erosion-dilation method can be used for measurements of angularity and roughness while it is still not clear for the determination of resolutions of images for these properties. It was proposed by Masad and Button [60] that the roughness should be captured at the scale of 15 μm, while Shen et al. [47] proposed 0.4 μm as the resolution for surface texture scanning. From the author’s viewpoint, this should be determined based on the scale to be studied regarding the roughness and angularity.

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3 Features of Manufactured Sand

Table 3.3 A partial list of definitions of various shape parameters Geometric features Overall shape

Parameter Elongation Flatness

Flakiness

Definition

[37–39, 77, 78]

Lintermediate Lintermediate Lshortest Llongest +Lintermediate 2Lshortest Lshortest Lintermediate

√

[37–39] [26, 40] [41]

Llongest ·Lintermediate L2longest

[41–44]

√

Lshortest Llongest ·Lintermediate

[38, 41, 43–45]

Area sphericity

Afront Atop

[46]

Length/width ratio

L W Rmajor Rminor

[47–49]

Sphericity

3

Shape factor

Aspect ratio Elongation factor

Compactness factor Area ratio F-value

Roundness

Fourier parameter Form index Angularity

References

Llongest

Fourier parameter Lost area Effective width Gradient angularity index

[50]

DF,max DF,min

[52]

DF,max DF,per

[53]

A

[48]

ARectangle Acircumscribing ellipse A Dmin Dmax rmin rmax 4π·A P2

[55] [56] [56] [56]

P2 4π·A 4A 2 π·Dcir

[49, 51, 53, 57] [58]

4

2

an 2 j=0 [( a0 )

+ ( ab0n ) ] 

θ =360−θ  Rθ+θ −Rθ  Rθ θ =0

25

an 2 j=5 [( a0 )

2

+ ( ab0n ) ]

A1 −A2 A1

–

N−3 j=1

θ =0

Rθ

θ =360−θ |Rθ −REEθ |

Angularity index

θ =170

Fullness ratio

e × P(e)

Aconvex hull

√

[59]

[65] |θi − θi+3 |

θ =0 A

[43]

[26, 43, 51, 60]

Radius angularity index

Convex ratio

[59]

A Aconvex hull

[44, 60] [60, 66] [67] [42, 53, 68] [38, 68] (continued)

3.5 Determination of Specific Surface Area via the Random Section method

79

Table 3.3 (continued) Geometric features

Parameter

Roughness

Fourier parameter

Definition

180 an 2 bn 2 j=26 [( a0 ) + ( a0 ) ] 1 3 N 2 i=1 j=1 (Di,j (x, y)) 3N

Texture index

A1 −A2 A1 1 L L 0 |y(x)|dx P Pconvex hull

Lost area Roughness value Convexity

References [59] [44, 51] [26, 43, 51, 60] [47] [53, 70, 71]

3.5 Determination of Specific Surface Area via the Random Section method 3.5.1 Theoretical Background The random sectioning method was proposed by Smith and Guttman [79] in 1953 to measure the internal boundaries between various phases in 3D structures. First, under a 2D condition, when a line segment of length l falls at random on a plane array of parallel lines spaced a distance d apart, the probability of the line segment crossing a parallel line is the average length of the segment projected on the normal to the array, divided by the distance between the lines, calculated as follows: l proj d

p=

(3.41)

where l proj is the average of segment projected on the normal to the array, which can be calculated as Eq. (3.42) given that all directions of the line segment have equal a priori probability. l proj

2 = π



π/2

l · cosθ dθ =

0

2l π

(3.42)

Thus, p=

2l πd

(3.43)

If an irregular plane curve is placed at random on the same array, there will in general be N intersections. The curve can be divided into several short segments with lengths l. Each segment can be considered nearly straight. Then, the probability (p1 ) that any one of these segments intersects the array is determined by Eq. (3.44).

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p1 =

2l πd

(3.44)

Thus, the average value N can be obtained as follows: N = p1 ·

2l l = l πd

(3.45)

where l is the total length of the curve. Even though the segments are connected by being parts of the same curve, each segment takes random positions and orientations as the curve as a whole does, hence the additivity of the number of intersections. Figure 3.25 illustrates the isolated area A crossed by a grid of lines with a distance of d. If d is small, or if a coarse grid is applied many times at random, the total length L of the gridline can be determined as follows:

L=

A d

(3.46)

If the total length of the isolating curves in the area is l, then the ratio of the length of curves to the area of the structure can be determined by combining Eqs. (3.5) and (3.6). πN l = A 2 L

Fig. 3.25 Isolated area of a 2D structure traversed by a grid of lines, reprinted from ref. [79], copyright 2017, with permission from Springer Nature

(3.47)

3.5 Determination of Specific Surface Area via the Random Section method

81

It can be seen that the ratio of the length of curves to the area of the structure is independent of d. Thus, it is not necessary to utilize a well-ruled grid of parallel lines. Instead, any array of lines repeatedly randomly applied to the structure is satisfactory as long as a sufficient number of intersections is counted. If the structure itself is random, a single line of sufficient length is adequate and this line is not necessarily straight. There are no limitations whatever as to the validity of Eq. (3.47) except for the critically important requirement of randomness. Then, this relation is extended to three dimensions, concerning the relationship between a random 2D section and a 3D structure. Figure 3.26 describes an irregular solid body with a closed surface that is intersected by a stack of parallel planes with a distance of d. It is assumed for simplicity that the surface does not intersect more than one plane at a time. The position of the surface of the object can be defined by the distance z of a fixed point on the surface of the object to the intersection plane. The orientation of this surface can be described by the angle ω for simplicity. The area (A) of the intersection is thus a function of ω and z. The average area (A) for all possible positions and orientations of the object can be determined based on Eq. (3.48) [79]. A=

dω



dzA(ω, z) dω dz

(3.48)

For each orientation, A(ω, z)dz is the volume element of the object. Thus, as z varies between the limits 0 and d, 

d 0

Fig. 3.26 A solid body intersected by a set of parallel planes, reprinted from ref. [80], copyright 2021, with permission from Elsevier

A(ω, z)dz = V

(3.49)

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Fig. 3.27 A unit surface intersected by a set of parallel planes, reprinted from ref. [80], copyright 2021, with permission from Elsevier

Therefore, Eq. (3.48) can be simplified as Eq. (3.50), which indicates that the average area of intersection for all possible positions and orientations of the object is the volume of the body divided by the distance of the parallel planes. A=

V d

(3.50)

There is no restriction on the shape of the surface or the connectivity of the object enclosed by it. Now, we consider a surface element of the object (red area in Fig. 3.26), which intersects one of the parallel planes. This surface element can be taken as a plane shown in Fig. 3.27. The length of the intersection is l, and its average for all positions and orientations can be expressed as Eq. (3.51) [79]. l=

dω



dzl(ω, z) dω dz

(3.51)

For each orientation, ldz is the surface element of the figure projection on a certain plane which is normal to the stack of planes and includes the intersection. Then, ldz = dS sinθ

(3.52)

where θ is the angle between the normal to the figure and the normal to the parallel planes. Thus, the integration over z presents the total area of the surface projected on the vertical plane. The orientation angle ω can be specified as a function of θ expressed as follows:

3.5 Determination of Specific Surface Area via the Random Section method

dω = sinθ dθ

83

(3.53)

Since the range (0, π/2) of θ covers all possible orientations, Eq. (3.51) can be specified as Eq. (3.54). π/2

sin2 θ d θ πS l = π/20 d = 4d 0 sinθ d θ 0 dz S

(3.54)

This result is not confined to plane figures given that any surface is constituted by a large number of plane elements. Besides, these elements take random positions and orientations when the figure as a whole dosage so. It needs to be mentioned that the contributions to the surface and the length of intersection are additive. As a result, Fig. 3.27 holds for any surface, however complex. Therefore, the average length (l) indicates the average perimeter of all possible sections of the object. By combining Eqs. (3.50) and (3.54), the following equation can be obtained. l A

=

π S 4V

(3.55)

This result does not depend on d , which indicates that the stack of parallel planes is not necessarily required. It is practicable to average the line length and area of the intersections of any solid by a randomly oriented and placed plane. Equation (3.55) can be presented as Eq. (3.56), from which the SSA of a particle can be determined based on the ratio of average perimeter to the average area of sections at random positions and from random orientations. This equation is supposed to be valid for particle mixtures if the number of intersections is large enough. SSA =

S 4 l = V πA

(3.56)

3.5.2 Theory Verification The SSA calculation from Eq. (3.56) by random sectioning is verified by polydispersed spheres for simplicity. A total of 20,000 polydispersed spheres were randomly generated in a box with dimensions of 100 mm × 100 mm × 100 mm, shown in Fig. 3.28. The PSD of the generated spheres is shown in Fig. 3.29. The real SSA of the spheres can be calculated from their PSD, shown below.

SSA =

20,000 2 S i=1 π Di = 20,000 π 3 V D i=1 6 i

where Di is the diameter of the i-th sphere.

(3.57)

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3 Features of Manufactured Sand

Fig. 3.28 Generation of spheres in a box

Fig. 3.29 PSD of the generated spheres in the box

By randomly sectioning the box, sections like Fig. 3.30 can be obtained. The diameter distribution of circles on each section is available, shown in Fig. 3.31. From the diameter distribution of circles, the SSA is calculated based on Eq. (3.56), shown as follows:

n π di 4 SSA = ni=1 π 2 π i=1 4 di

(3.58)

3.5 Determination of Specific Surface Area via the Random Section method

85

Fig. 3.30 Random sections of the spheres in the box

Fig. 3.31 Diameter distribution of circles on the section

where di is the diameter of i-th circle on the section. The measured SSA from the random sectioning and the real SSA are drawn in Fig. 3.32 with the 2% relative error lines superimposed. In general, the measured SSA shows quite similar results to the real SSA. When at least two sections are used for calculation, the measured SSA shows a relative error smaller than 2%. This small error is considered dependent on the randomness of the sections. This means the random sectioning method is theoretically reliable for the determination of SSA of particles.

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Fig. 3.32 Comparison between measured SSA from random sectioning and real SSA

3.5.3 Experiment 3.5.3.1

Sample Preparation

MS was purchased from an industrial company in Ghent, Belgium, and it was produced in Doornik, Belgium. With the lithology of limestone, it has the main mineral composition of calcium carbonate. MS particles with a diameter between 0.5 mm and 1.0 mm (see Fig. 3.33a) were sieved, washed, and dried before being impregnated into epoxy resin (EpoFix Resin, Struers Inc., USA) in a silicon mold. The hardened sample was then polished with silicon paper #180, #320, #1200, and 2000# successively until no visible notch can be observed at each localized area. A smooth surface with abundant exposed particles can be obtained after these procedures, seen in Fig. 3.33b. Finally, the optical microscope (Leica S8 APO, Leica Microsystems, Germany) was used to capture the section image of particles. It needs to be noted that fluorescent dye (EpoDye, Struers Inc., USA) was preferred to intensify the contrast between the objects and the background from the comparison shown in Fig. 3.34.

3.5.3.2

Image Processing

The objective of image processing is to measure the perimeter and surface of particles on the cross-section. A digital image is a 2D discrete function that has been digitized both in spatial coordinates and magnitude of feature value. A digital image is viewed as a 2D matrix whose row and column indices identify a small square area of the image called a pixel. The captured color image (shown in Fig. 3.35a) was transformed into a gray image (Fig. 3.35b) for the convenience of thresholding, which is a segmented method, extracting the object from the background in an image [81, 82].

3.5 Determination of Specific Surface Area via the Random Section method

87

Fig. 3.33 Sand particles (a) and sample for image acquisition (b) under an optical microscope (c) [80]

Fig. 3.34 Comparison of images a without dye, b with white dye, and c with fluorescent dye

The exact value of the threshold is of great significance to determine the boundary position of the object and therefore determine the perimeter and area of the object. Manual and automatic ways exist to determine the threshold value. For the manual method, the operator himself defines the appropriate boundary values based on previous tests. Compared to manual methods, automatic thresholding methods show numerous advantages. For instance, they can automatically adjust the threshold value according to the contrast between objects and the background. In terms of automatic methods, several algorithms have been proposed [82, 83], primarily based on the

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Fig. 3.35 a Original and b gray images of MS particles [80]

gray level histogram of the image. The following are the main automatic thresholding methods and their algorithms used during image processing. (1) K-means clustering algorithm K-means clustering algorithm considers the values in the two regions of the histograms (background and foreground pixels) as two clusters [82, 84]. The objective is to pick a threshold value to meet the requirement that each pixel on each side of this threshold is closer in intensity to the mean of all pixels on that side of the threshold than the mean of all pixels on the other side of the threshold. Specifically, let the pixels of a given image be represented in L gray levels [0, 1, 2 … L − 1]. The number of pixels at level i is denoted by h(i) and the total number of pixels by N. Let μ1 (t) be the mean of all pixels less than the threshold and μ2 (t) be the mean of all pixels greater than the threshold. The aim is to find a gray value that meets the following criteria: ∀i ≥ t : |i − μ1 (t)| > |i − μ2 (t)|

(3.59)

∀i < t : |i − μ1 (t)| < |i − μ2 (t)|

(3.60)

and

For each potential boundary, a partition error (PE), which is a measure of clustering efficiency, is determined. PE(t) =

L−1  [h(i)(i − μ(t))]

(3.61)

i=0

Finally, the t value that holds the lowest PE is regarded as the optimal threshold. (2) Maximization of the inter-class variance The maximization of the inter-class variance method is also known as Ostu’s method [85], which is one of the most popular techniques of optimal thresholding. It is

3.5 Determination of Specific Surface Area via the Random Section method

89

based on discriminant analysis and maximizes the “between-class variance” of the gray level histogram to present the best separation of classes. In this approach, the histogram is divided into a certain number of classes. When the position of the class limit varies, the value of the variance changes and the position, which maximizes that value, is determined. The gray level histogram is normalized and considered as a probability distribution. The probability of occurrence of each gray level p(i) is determined as follows:  h(i) p(i) = 1 , p(i) ≥ 0, N i=0 L−1

p(i) =

(3.62)

The zeroth-(ω(t)) and the first-order cumulative moments of the histogram up to the t-th level (μ(t)) and the total mean level (μT ) of the original picture are calculated. ω(t) =

t 

p(i)

(3.63)

i · p(i)

(3.64)

i · p(i)

(3.65)

i=0

μ(t) =

t  i=0

μT =

L−1  i=0

The optimal threshold t ∗ is based on the following equation. σB2 (t ∗ ) = maxσB2 (t)a t∈GL

(3.66)

where σB2 (t) =

[μT ω(t) − μ(t)]2 ω(t)[1 − ω(t)]

(3.67)

(3) Fuzzy thresholding algorithm Fuzzy set theory was applied to partition an image space by minimizing the measure of fuzziness of the image [86–88]. Given a certain threshold value, the membership function of a pixel is defined by the absolute difference between the gray level and the average gray level of its belonging region (i.e., the object or the background). The larger the absolute difference is, the smaller the membership value becomes. It is expected that the membership value of each pixel in the input image is as large as possible. The optimal threshold can then be effectively determined. Specifically, in the notation of fuzzy set, the image set I = f (x, y) of size M × N can be written as follows.

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3 Features of Manufactured Sand

I = {(f (x, y), μI (f (x, y)))}

(3.68)

The membership function μI (f (x, y)) can be viewed as a characteristic function that represents the fuzziness of a (x, y) pixel in I. 1 1+|f (x,y)−μ0 (t)|/C 1 1+|f (x,y)−μ1 (t)|/C

μI (f (x, y)) =

iff (x, y) ≤ t iff (x, y) > t

(3.69)

where the average gray levels μ0 (t) and μ1 (t) can be regarded as the target values of the background and the object for a given threshold value t, and C is a constant value such that 0.5 ≤ μI (f (x, y)) ≤ 1. μ0 (t) =

t 

i · h(i)/

i=0

μ1 (t) =

L−1 

t 

h(i)

(3.70)

i=0

i · h(i)/

i=t+1

L−1 

h(i)

(3.71)

i=t+1

The measure of fuzziness that was used in this work was the entropy E(I) by using Shannon’s function S(μ(xi )) [87]. The optimal threshold can then be determined by minimizing the measure of fuzziness E(X). S(μI (i)) = −μI (i)ln[μI (i)] − [1 − μI (i)]ln[1 − μI (i)]

(3.72)

1  S(μI (i))h(i) E(I ) = MN ln2 i=0

(3.73)

t ∗ = argminminE(I )

(3.74)

L−1

t∈GL

(4) Entropy maximization This algorithm uses the entropy of the gray level histogram by applying information theory [89]. In this case, the histogram is divided into several classes. This threshold by entropy gives good results when there are few objects [90, 91]. The entropy maximization method consists in determining the gray level t that maximizes the entropy (∅(t)). The entropy function is computed as follows [92]: ∅(t) = −[

 t   pi min

w0



pi · log w0

 +

 max   pi t+1

w1



 pi · log ] w1

(3.75)

where pi is the probability for a given pixel to have an intensity equal to i (pi = Ni /N ), and Ni is the number of pixels that have the i intensity. N is the total number of pixels.

3.5 Determination of Specific Surface Area via the Random Section method

91

w0 and w1 are, respectively, the probability to find a pixel intensity lower or higher than t. w0 = w1 =

t  min max 

pi pi

(3.76)

t+1

(5) Tangent-slope method During the thermogravity curve analysis, it is usual to define the onset of decomposition temperature of a certain constituent by drawing the tangent lines of the two contiguous segments on this curve [93]. This method has been applied to defining the threshold value [94, 95]. When the cumulative frequency is plotted against the gray level, the critical overflow point corresponds to the inflection of the cumulative curve, which can be estimated from the intersection between two tangent linear segments as shown in Fig. 3.36 [94, 96]. The gray value at this intersection can be used as the upper threshold level. This presents a critical point where a large increase in the threshold value will cause a sluggish increase in the thresholded area. (6) Minimum error algorithm The minimum error algorithm views the gray level histogram as a probability density function (PDF) of the gray levels of both the object and background (j = 1, 2) [97].

Fig. 3.36 Illustration of the tangent-slope method to determine the threshold value

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Fig. 3.37 Probability density of gray level histogram

Each of them is considered to follow a normal distribution with a mean value of m(j), a standard deviation of σ (j), and a PDF of P(j). The PDF of the gray level of gray image Fig. 3.35b is shown in Fig. 3.37, where two normally distributed segments are observed, which is exactly the feature of the minimum error algorithm. However, the parameters ofm(j), σ (j), and P(j) are usually unknown. Instead, a criterion function J (j) is employed, expressed as Eq. (3.77) [97, 98]. J (t) = 1 + 2[Pt (t)Lnσ1 (t) + P2 (t)Lnσ2 (t)] − 2[Pt (t)LnP1 (t) + P2 (t)LnP2 (t) (3.77) where P1 (t) =

t 

p(i)

(3.78)

p(i) = 1 − P1 (t)

(3.79)

i=0

P2 (t) =

L−1  i=t+1

1  i · p(i) P1 (t) i=0 t

m1 (t) =

(3.80)

3.5 Determination of Specific Surface Area via the Random Section method

93

L−1 1  i · p(i) P2 (t) i=t+1

(3.81)

1  [i − m1 (t)]2 · p(i) P1 (t) i=0

(3.82)

L−1 1  [i − m2 (t)]2 · p(i) P1 (t) i=t+1

(3.83)

m2 (t) =

t

σ1 (t) =

σ2 (t) =

The optimal threshold t ∗ is determined by minimizing J (t), as described in Eq. (3.84). t ∗ = argminmin J (t) t∈GL

(3.84)

3.5.4 Result Analysis The gray image can be transformed into a binary image with the determined threshold value. Then, numbers of pixels representing particles and their boundaries are available. Therefore, the SSA of the particles can be measured according to Eq. (3.56), calculated as follows: 4 NP S = V π NA L0

(3.85)

where NA and NP are the numbers of pixels corresponding to objects and their boundaries, and L0 is the edge length of each pixel. It needs to be mentioned that the objects crossed by the boundaries of the frame need to be removed to eliminate the influence due to fragmentary objects. During image analysis, several factors may influence SSA results, including the number of particles used for calculation, the threshold value, and the resolution of the pixel. (1) Number of particles The number of particles should be large enough to present intersections at random positions and from random orientations, indicated by a steady SSA result. Figure 3.37 shows the measured SSA results from various numbers of MS particles. It is seen that SSA presents rather fluctuating values within the first few tens of particles and then shows increasingly steady results as the number of particles increases. To be specific, SSA in the range of 12–13 mm2 /mm3 can be noticed if more than 400 particles are used. In addition, the coefficient of variation of SSA from 800 to 1500 particles is 0.4% while the maximum relative error of SSA from more than 800 particles to that

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Fig. 3.38 SSA results versus the number of particles used for calculation, reprinted from ref. [80], copyright 2021, with permission from Elsevier

from 800 particles (i.e., SSA/SSA800 -1, superposed in Fig. 3.38) is 1.0%. This means a rather steady SSA without obvious variation is reached from 800 particles. As a result, we believe that 800 particles are sufficient to approach the steady SSA based on the random sectioning method for the MS used in this study. It needs to be mentioned that the number of particles for a steady SSA result depends on the dispersity of particle shape and particle size. A larger number of MS particles are required when particles have higher dispersity in shape and a wider particle size distribution. (2) Threshold value Thresholding is a vital procedure for image processing. Various threshold values ranging from 20 to 200 were used for image processing, and SSA values were calculated as shown in Fig. 3.39. In general, SSA decreases with the increase of threshold value. SSA shows a dramatic decrease before a critical value, followed by a sluggish decrease after this critical value. This critical value is considered to be the threshold value, which is 40 for the gray image (Fig. 3.39) according to the minimum error algorithm (see above). The binary images after thresholding at 30, 40, and 100 are shown in Fig. 3.39. It is observed that when the threshold is smaller than the critical value (Fig. 3.39a), particles were partially eroded, making boundaries more tortuous. Erosion decreases the area of objects and increases their perimeter at the same time. This influence is supposed to be more significant when the thresholding value further decreases. As a result, SSA sharply increases with decreasing threshold values before the critical point. However, the increase of threshold value after the critical point

3.5 Determination of Specific Surface Area via the Random Section method

95

dilates the particles (Fig. 3.39c), which overestimates the area of objects on the one hand. On the other hand, objects will merge with the adjacent ones, resulting in a loss of perimeter. Thus, the SSA is decreasing with the increase of the threshold value. This influence is gentler, indicated by the sluggishly decreasing trend. In addition to the minimum error algorithm, other commonly used thresholding methods including the tangent-slope method [96], K-means method [82], Otsu’s method [85], fuzzy algorithm [87], and entropy maximization method [90] were also tried and the determined threshold values are also superposed in Fig. 3.39. It can be seen that compared with SSA based on the minimum error algorithm, the tangent-slope method shows 54.2% higher SSA results, while the K-means method, Otsu’s method, fuzzy algorithm, and entropy maximization methods, respectively, present 17.0, 17.1, 17.1, and 27.0% lower SSA results than SSA obtained from the minimum error algorithm.

Fig. 3.39 SSA results with respect to threshold values with marked threshold values from several commonly used thresholding methods, reprinted from ref. [80], copyright 2021, with permission from Elsevier

Fig. 3.40 Binary images after thresholding at a 30, b 40, and c 100, reprinted from ref. [80], copyright 2021, with permission from Elsevier

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3 Features of Manufactured Sand

Fig. 3.41 SSA results from images with various resolutions, reprinted from ref. [80], copyright 2021, with permission from Elsevier

(3) Resolution of pixel A proper resolution is desired for image analysis. Figure 3.41 shows SSA variation with the resolution of the pixel. SSA exhibits an increasing trend with the increase of resolution (decrease of pixel size). Specifically, SSA shows 24.0, 35.8, 54.0, 55.5, and 56.6% higher values when the resolution increases from 128 μm/pixel to 64 μm/pixel, 32 μm/pixel, 16 μm/pixel, 8 μm/pixel, and 4 μm/pixel, respectively. This trend is attributed to the fact that a higher resolution captures more details on the geometrical shape like surface texture. It can be seen in Fig. 3.41 that boundary information is increasingly clear when the resolution is gradually improved. Therefore, the resolution should be as high as possible for SSA determination if the geometrical features at a smaller scale are expected to be considered. However, it is also noted that SSA shows a sluggish increase when the resolution is better than 16 μm/pixel. Specifically, SSA increases by 2.8% when the resolution increases from 16 μm/pixel to 8 μm/pixel. Further improvement of resolution from 8 μm/pixel to 4 μm/pixel provides a 2.0% higher SSA value. Therefore, a resolution better than 16 μm/pixel provides relatively reliable SSA results. A resolution of 4 μm/pixel is further used in this study.

References

97

Fig. 3.42 Binary images with resolutions of a 128 μm/pixel, b 64 μm/pixel, and c 4 μm/pixel, reprinted from ref. [80], copyright 2021, with permission from Elsevier

References 1. H. Hafid, G. Ovarlez, F. Toussaint, P. Jezequel, N. Roussel, Assessment of potential concrete and mortar rheometry artifacts using magnetic resonance imaging. Cem. Concr. Res. 71, 29–35 (2015) 2. S.E. Chidiac, F. Mahmoodzadeh, Constitutive flow models for characterizing the rheology of fresh mortar and concrete. Canadian J. Civil Eng. 40(5), 475–482 (2013) 3. C.F. Ferraris, J.M. Gaidis, Connection between the rheology of concrete and rheology of cement paste. ACI Mater. J. 89(4), 388–393 (1992) 4. D.J. Jeffrey, A. Acrivos, The rheological properties of suspensions of rigid particles. AIChE J. 22(3), 417–432 (1976) 5. D. Sun, H. Shi, K. Wu, S. Miramini, B. Li, L. Zhang, Influence of aggregate surface treatment on corrosion resistance of cement composite under chloride attack. Constr. Build. Mater. 248, 118636 (2020) 6. L. Qin, X. Zhang, W. Genqiu, Y. Li, J. Zhang, Method of source rock testing and artificial sand evaluation before the production line putting into operation. New Build. Mater. 39(1), 24–26 (2012). ((in Chinese)) 7. D. Nian, X. Nian, Comparative analysis and practical application of manufactured sand. Build. Mater. Devel. Orientation 1, 71–72 (2013). ((in Chinese)) 8. B. Li, G. Ke, S. Zhao, J. Wang, G. Qing, Research on pavement performance of manufactured sand concrete. J. Build. Mater. 13(4), 529–534 (2010). ((in Chinese)) 9. J. Yang, The production and application in concrete of manufactured sand. Shanxi Arch 35(34), 166–167 (2009). ((in Chinese)) 10. GB/T 14684 Sand for construction (2011) 11. J. Zhu, J. Zhu, X. Lang, X. Jia, Present situation and development of pelletized sand production. Mining Metal 4, 38–42 (2001). ((in Chinese)) 12. Y. Wang, J. Wang, M. Zhou, B. Li, X. Guan, Effects of manufactured fine aggregate and aggregate micro stone powder on frost-resistance performance of concrete. J Build Mater 11(6), 726–731 (2008). ((in Chinese)) 13. J. Wang, M. Zhou, T. He, G. Ke, G. Cui, Effects of stone dust on resistance to freezing of manufactured sand concrete. J. Chinese Ceramic Soc. 36(4), 482–486 (2008). ((in Chinese)) 14. L. Zhan’Ao, Z. Mingkai, L. Beixing, Research progress on influence of microfines on manufactured sand concrete’s performance. Mater. Reports 28(19), 100–103 (2014). ((in Chinese)) 15. K.J. Gullerud, The effects of aggregate coatings on the performance of Portland cement concrete (University of Wisconsin, Madison 2002) 16. W.A, Tasong, C.J. Lynsdale, J.C. Cripps, Aggregate-cement paste interface. ii: influence of aggregate physical properties. Cement Concrete Res. 28(10), 1453–1465 (1998) 17. ˙IB. Topçu, A. Demir, Relationship between methylene blue values of concrete aggregate fines and some concrete properties. Canadian J. Civil Eng. 35(4), 379–383 (2008)

98

3 Features of Manufactured Sand

18. M.L. Nehdi, Clay in cement-based materials: critical overview of state-of-the-art. Construct. Build. Mater. 51, 372–382 (2014) 19. S. Benyamina, B. Menadi, S.K. Bernard, S. Kenai, Performance of self-compacting concrete with manufactured crushed sand. Adv. Concrete Construct. 7(2), 87–96 (2019) 20. S. Ng, J. Plank, Interaction mechanisms between Na montmorillonite clay and MPEG-based polycarboxylate superplasticizers. Cem. Concr. Res. 42(6), 847–854 (2012) 21. Y. Ma, C. Shi, L. Lei, S. Sha, B. Zhou, Y. Liu, Y. Xiao, Research progress on polycarboxylate based superplasticizers with tolerance to clays—a review. Constr. Build. Mater. 255, 119386 (2020) 22. J.K. Norvell, J.G. Stewart, M.C. Juenger et al., Influence of clays and clay-sized particles on concrete performance. J. Mater. Civil Eng. 19(12), 1053–1059 (2007) 23. J.F. Muñoz, M.I. Tejedor, M.A. Anderson, S.M. Cramer, Detection of aggregate clay coatings and impacts on concrete. ACI Mater. J. 107(4), 387–395 (2010) 24. W. Shen, Z. Yang, X. Zhou et al., Quantitative Study on Influence factors of manufactured sand’s methylene blue value. J. Wuhan Univ. Technol. 35(12), 44–47 (2013). ((in Chinese)) 25. A. Petkovšek, M. Maˇcek, P. Pavšiˇc, F. Bohar, Fines characterization through the methylene blue and sand equivalent test: comparison with other experimental techniques and application of criteria to the aggregate quality assessment. Bulletin Eng. Geol. Environ. 69(4), 561–574 (2010) 26. P.J. Barrett, The shape of rock particles, a critical review. Sedimentology 27(3), 291–303 (1980) 27. T.-S. Vu, G. Ovarlez, X. Chateau, Macroscopic behavior of bidisperse suspensions of noncolloidal particles in yield stress fluids. J. Rheol. 54(4), 815–833 (2010) 28. J. Anochie-Boateng, J. Komba, E. Tutumluer, 3D laser based measurement of mineral aggregate surface area for south African hot-mix asphalt mixtures, in Proceedings of the Transportation Research Board 90th Annual Meeting (Washington DC, United States, 2011) 29. J.K. Anochie-Boateng, J. Komba, E. Tutumluer, Aggregate surface areas quantified through laser measurements for south African asphalt mixtures. J. Transp. Eng. 138(8), 1006–1015 (2012) 30. J. Fonseca, C. O’Sullivan, M.R. Coop, P.D. Lee, Non-invasive characterization of particle morphology of natural sands. Soils Found. 52(4), 712–722 (2012) 31. O. Ersoy, E. Sen, E. Aydar, I. Tatar, H.H. Celik, Surface area and volume measurements of volcanic ash particles using micro-computed tomography (micro-CT): a comparison with scanning electron microscope (SEM) stereoscopic imaging and geometric considerations. J. Volcanol. Geotherm. Res. 196(3–4), 281–286 (2010) 32. D. Su, W.M. Yan, 3D characterization of general-shape sand particles using microfocus Xray computed tomography and spherical harmonic functions, and particle regeneration using multivariate random vector. Powder Technol. 323, 8–23 (2018) 33. S.T. Erdogan, P.N. Quiroga, D.W. Fowler, H.A. Saleh, R.A. Livingston, E.J. Garboczi, P.M. Ketcham, J.G. Hagedorn, S.G. Satterfield, Three-dimensional shape analysis of coarse aggregates: new techniques for and preliminary results on several different coarse aggregates and reference rocks. Cem. Concr. Res. 36(9), 1619–1627 (2006) 34. M.A. Taylor, E.J. Garboczi, S.T. Erdogan, D.W. Fowler, Some properties of irregular 3-D particles. Powder Technol. 162(1), 1–15 (2006) 35. P.R. Mouton, Unbiased stereology: a concise guide (The Johns Hopkins University Press, Maryland, 2011) 36. G.C. Cho, J. Dodds, J.C. Santamarina, Particle shape effects on packing density, stiffness, and strength: natural and crushed sands. J. Geotech. Geoenviron. 132(5), 591–602 (2006) 37. L. Wang, W. Sun, E. Tutumluer, C. Druta, Evaluation of aggregate imaging techniques for quantification of morphological characteristics. Transport. Res. Rec. 2335(1), 39–49 (2013) 38. C.-Y. Kuo, J.D. Frost, J.S. Lai, L.B. Wang, Three-dimensional image analysis of aggregate particles from orthogonal projections. Transport. Res. Rec. 1526(1), 98–103 (1996) 39. ASTM D4791, Standard test method for flat particles, elongated particles, or flat and elongated particles in coarse aggregate (2010)

References

99

40. C.K. Wentworth, A method of measuring and plotting the shapes of pebbles; 730C (1923), pp. 91–102 41. R.D. Barksdale, M.A. Kemp, W.J. Sheffield, J.L. Hubbard, Measurement of aggregate shape, surface area, and roughness. Transport. Res. Rec. 1301, 107–116 (1991) 42. W.C. Krumbein, Measurement and geological significance of shape and roundness of sedimentary particles. J. Sediment. Res. 11(2), 64–72 (1941) 43. E. Masad, D. Olcott, T. White, L. Tashman, Correlation of fine aggregate imaging shape indices with asphalt mixture performance. Transport. Res. Rec. 1757(1), 148–156 (2001) 44. C. Chandan, K. Sivakumar, E. Masad, T. Fletcher, Application of imaging techniques to geometry analysis of aggregate particles. J. Comput. Civ. Eng. 18(1), 75–82 (2004) 45. B.C. Aschenbrenner, A new method of expressing particle sphericity. J. Sediment. Res. 26(1), 15–31 (1956) 46. S. Arasan, A.S. Hasiloglu, S. Akbulut, Shape properties of natural and crushed aggregate using image analysis. Int. J. Cil. Struct. Eng. Mech. 1(2), 221 (2010) 47. W.G. Shen, Z.G. Yang, L.H. Cao, L. Cao, Y. Liu, H. Yang, Z.L. Lu, J. Bai, Characterization of manufactured sand: particle shape, surface texture and behavior in concrete. Constr. Build. Mater. 114, 595–601 (2016) 48. F.L. Liu, H.Y. Fang, S.J. Chen, L. Zhou, J.H. Yang, Experimental study on manufactured sand shape detection by image method. J. Test. Eval. 47(5), 3515–3532 (2019) 49. J.P. Gonçalves, L.M. Tavares, R.D. Toledo Filho, E.M.R. Fairbairn, E.R. Cunha, Comparison of natural and manufactured fine aggregates in cement mortars. Cem. Concr. Res. 37(6), 924–932 (2007) 50. X. Xie, G. Lu, P. Liu, D. Wang, Q. Fan, M. Oeser, Evaluation of morphological characteristics of fine aggregate in asphalt pavement. Constr. Build. Mater. 139, 1–8 (2017) 51. T. Al-Rousan, E. Masad, E. Tutumluer, T. Pan, Evaluation of image analysis techniques for quantifying aggregate shape characteristics. Constr. Build. Mater. 21(5), 978–990 (2007) 52. C. Igathinathane, S. Melin, S. Sokhansanj, X. Bi, C.J. Lim, L.O. Pordesimo, E.P. Columbus, Machine vision based particle size and size distribution determination of airborne dust particles of wood and bark pellets. Powder Technol. 196(2), 202–212 (2009) 53. H. Hafid, G. Ovarlez, F. Toussaint, P.H. Jezequel, N. Roussel, Effect of particle morphological parameters on sand grains packing properties and rheology of model mortars. Cem. Concr. Res. 80, 44–51 (2016) 54. S. Park, Study on the fluidity and strength properties of high performance concrete utilizing crushed sand. Int. J. Concr. Struct. Mater. 6(4), 231–237 (2012) 55. R.S. Bangaru, A. Das, Aggregate shape characterization in frequency domain. Constr. Build. Mater. 34, 554–560 (2012) 56. M. Westerholm, B. Lagerblad, J. Silfwerbrand, E. Forssberg, Influence of fine aggregate characteristics on the rheological properties of mortars. Cem. Concr. Compos. 30(4), 274–282 (2008) 57. T. Kraenkel, D. Lowke, P. Schiebl, Effect of coarse aggregate on properties of self-compacting concrete, in Proceedings of the 2nd International Symposium on Design, Performance, and Use of Self-Compacting Concrete (Beijing, China, 2009), pp. 201–211 58. G.C. Cordeiro, L. de Alvarenga, C.A.A. Rocha, Rheological and mechanical properties of concrete containing crushed granite fine aggregate. Constr. Build. Mater. 111, 766–773 (2016) 59. L. Wang, J. Park, L. Mohammad, Quantification of morphology characteristics of aggregate from profile images, in Proceedings of the 82nd Transportation Research Board Annual Meeting (Washington, D.C., 2003) 60. E. Masad, J.W. Button, Unified imaging approach for measuring aggregate angularity and texture. Comput.-Aided Civ. Inf. 15(4), 273–280 (2000) 61. R. Ehrlich, S.K. Kennedy, S.J. Crabtree, R.L. Cannon, Petrographic image analysis, I. Analysis of reservoir pore complexes. J. Sediment. Res. 54(4), 1365–1378 (1984) 62. T. Tan, Z. Fan, C. Xing, Y. Tan, H. Xu, M. Oeser, Evaluation of geometric characteristics of fine aggregate and its impact on viscoelastic property of asphalt mortar. Appl. Sci. 10(1), 130 (2019)

100

3 Features of Manufactured Sand

63. B. Mandelbrot, The fractal geometry of nature (WH freeman, New York, 1984) 64. C. John, F. Russ, B. Neal, The image processing handbook (CRC Press, Boca Roton, 2017) 65. E. Masad, J.W. Button, T. Papagiannakis, Fine-aggregate angularity: automated image analysis approach. Transport. Res. Rec. 1721(1), 66–72 (2000) 66. C. Chandan, K. Sivakumar, T. Fletcher, E. Masad, Geometry analysis of aggregate particles using imaging techniques. J. Comput. Civ. Eng. (2002) 67. C. Rao, E. Tutumluer, I.T. Kim, Quantification of coarse aggregate angularity based on image analysis. Transport. Res. Rec. 1787(1), 117–124 (2002) 68. C.F. Mora, A.K.H. Kwan, Sphericity, shape factor, and convexity measurement of coarse aggregate for concrete using digital image processing. Cem. Concr. Res. 30(3), 351–358 (2000) 69. S.G. Mallat, A theory for multiresolution signal decomposition: the wavelet representation. IEEE Trans. Pattern Anal. Mach. Intell. 11(7), 674–693 (1989) 70. V. Janoo, Quantification of shape, angularity, and surface texture of base course materials; Cold Regions Research and Engineering Lab Hanover NH (1998) 71. C.-Y. Kuo, R.B. Freeman, Imaging indices for quantification of shape, angularity, and surface texture of aggregates. Transport. Res. Rec. 1721(1), 57–65 (2000) 72. ASTM C1252, Standard test method for uncompacted void content of fine aggregate (as influenced by particle shape, surface texture, and grading) (2017) 73. BS EN 933–3, Tests for geometrical properties of aggregates—part. 3: determination of particle shape—Flakiness Index (2012) 74. ASTM D3398, Standard test method for index of aggregate particle shape and texture (2000) 75. J.O. Hu, K.J. Wang, Effect of coarse aggregate characteristics on concrete rheology. Constr. Build. Mater. 25(3), 1196–1204 (2011) 76. J. Hu, A study of effects of aggregate on concrete rheology (Iowa State University, Iowa, 2005) 77. M. Ozol, Chapter 35—shape, surface texture, surface area, and coatings, in Significance of tests and properties of concrete and concrete-making materials, ed. by C. Best (ASTM International: West Conshohocken, PA, 1978), pp. 584–628 78. W.B. Zheng, X.L. Hu, D.D. Tannant, K. Zhang, C. Xu, Characterization of two- and threedimensional morphological properties of fragmented sand grains. Eng. Geol. 263, 105358 (2019) 79. C.S. Smith, L. Guttman, Measurement of internal boundaries in three-dimensional structures by random sectioning. J. Met. 5(1), 81–87 (1953) 80. Q. Ren, L. Ding, X. Dai, Z. Jiang, G. Ye, G. De Schutter, Determination of specific surface area of irregular aggregate by random sectioning and its comparison with conventional methods. Constr. Build. Mater. 273, 122019 (2021) 81. R. Kohler, A segmentation system based on thresholding. Comput. Graph. Image Process. 15(4), 319–338 (1981) 82. U. Gonzales-Barron, F. Butler, A comparison of seven thresholding techniques with the kmeans clustering algorithm for measurement of bread-crumb features by digital image analysis. J. Food Eng. 74(2), 268–278 (2006) 83. M. Coster, J.-L. Chermant, Image analysis and mathematical morphology for civil engineering materials. Cem. Concr. Compos. 23(2), 133–151 (2001) 84. J.A. Hartigan, Clustering algorithms (Wiley, New York, 1975), p.351 85. N. Otsu, A threshold selection method from gray-level histograms. IEEE T. Syst. Man Cy-S 9(1), 62–66 (1979) 86. H.-J. Zimmermann, Fuzzy set theory—and its applications (Springer Science & Business Media, New York, 2011) 87. L.-K.. Huang, M.-J.J. Wang, Image thresholding by minimizing the measures of fuzziness. Pattern Recogn. 28(1), 41–51 (1995) 88. T. Chaira, A. Ray, Threshold selection using fuzzy set theory. Pattern Recogn. Lett. 25(8), 865–874 (2004) 89. R.M. Gray, Entropy and information theory (Springer Science & Business Media, New York, 2011)

References

101

90. J.N. Kapur, P.K. Sahoo, A.K.C. Wong, A new method for gray-level picture thresholding using the entropy of the histogram. Comput. VIsion Graph. Image Process. 29(3), 273–285 (1985) 91. A. Ammouche, D. Breysse, H. Hornain, O. Didry, J. Marchand, A new image analysis technique for the quantitative assessment of microcracks in cement-based materials. Cem. Concr. Res. 30(1), 25–35 (2000) 92. T. Pun, A new method for grey-level picture thresholding using the entropy of the histogram. Signal Process. 2(3), 223–237 (1980) 93. D. Dollimore, T.A. Evans, Y.F. Lee, G.P. Pee, F.W. Wilburn, The significance of the onset and final temperatures in the kinetic analysis of TG curves. Thermochim. Acta 196(2), 255–265 (1992) 94. H.S. Wong, N.R. Buenfeld, M.K. Head, Estimating transport properties of mortars using image analysis on backscattered electron images. Cem. Concr. Res. 36(8), 1556–1566 (2006) 95. P.R. Da Silva, J. De Brito, Experimental study of the porosity and microstructure of selfcompacting concrete (SCC) with binary and ternary mixes of fly ash and limestone filler. Constr. Build. Mater. 86, 101–112 (2015) 96. H.S. Wong, M.K. Head, N.R. Buenfeld, Pore segmentation of cement-based materials from backscattered electron images. Cem. Concr. Res. 36(6), 1083–1090 (2006) 97. J. Kittler, J. Illingworth, On threshold selection using clustering criteria. IEEE T. Syst. Man Cy-S SMC-15(5), 652–655 (1985) 98. Q.-Z. Ye, P.-E. Danielsson, On minimum error thresholding and its implementations. Pattern Recogn. Lett. 7(4), 201–206 (1988)

Chapter 4

Properties and Microstructure of Concrete with Manufactured Sand

4.1 Introduction Aggregates account for about 60–80% of the volume in hardened concrete. Specifically, fine aggregate generally accounts for about 20–40%. Therefore, the fine aggregate has an important impact on the workability, strength, and durability of the concrete. In Chap. 3, it is pointed out that manufactured sand (MS) is significantly different from natural sand in terms of particle shape, grading, and fines content. Compared with natural sand (NS), MS not only has a poorer grading and a larger fineness modulus, but also present rough surfaces and sharp corners. The variations of properties, especially the fines content, result in performance variation in concrete. For natural sand, particles smaller than 75 μm are called clay powder, which is mostly impurities such as clay, mica, and organic matter. These impurities will significantly increase water consumption, inhibit cement hydration, and degrade the bond between cement stone and aggregate. Therefore, in order to reduce the harm of aggregate impurities to concrete performance, the Chinese standard GB/T 14684-2011 (Sand for Construction) strictly limits the content of particles smaller than 75 μm in natural sand. However, with respect to MS, the fine particle smaller than 75 μm is a by-product during production process, and most of them are stone powder whose physical and chemical properties are the same as those of the parent rock. Therefore, the fines should be treated differently compared with those in natural sand. With respect to MS, the influence of fines content on concrete performance has become one hotspot of scholars’ research. An appropriate content of fines is beneficial to concrete, which reached a consensus for many scholars. Moreover, the content of fines has always been one of the control indicators of MS in the standards of various countries. Table 4.1 shows the upper limits of fines content in standards. The Chinese National Standard GB/T14684-2011 (Sand for Construction) basically stipulates the fines content according to the concrete strength grade. For concrete with a strength grade greater than C60, the fines content should be less than 3%. For concrete with anti-freezing, impermeability, or other requirements, the fines content should be less © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Z. Jiang, Green High-Performance Concrete with Manufactured Sand, https://doi.org/10.1007/978-981-19-6313-1_4

103

104

4 Properties and Microstructure of Concrete with Manufactured Sand

than 5% corresponding to C30–C60 strength grades. Concrete with a strength grade less than C30, the fines content should be less than 7%. However, according to the region and purpose of utilization, fines content can be negotiated and determined by the supplier and the demander, on the basis of experimental verification. In Chap. 3, it has been pointed out that the MS in actual projects generally possesses a fines content exceeding the requirement in GB/T14684-2011. Numerous experiments have proved that when the methylene blue (MB) value of MS meets the requirements of GB/T14684-2011, the higher fines content has no obvious adverse effect on the concrete. Table 4.1 Upper limits of fines content in standards of different countries [1] Country

Standard code

China

GB/T14684-2011 (sand for 75 construction), jt/t 819 (manufactured sand for cement concrete in highway engineering), t/cECS G: K50-30 (technical specification for highway manufactured sand high-performance concrete)

3–7

Japan

JIS A50005: 2009 (crushed 75 stone and manufactured sand for concrete)

9

India

IS 383-2016 (coarse and fine aggregate for concrete specification)

75

15

America

ASTM C33/ C33M-13 (standard specification for concrete aggregates)

75

7

Australia

AS 2758.1-2014 (aggregates and rock for engineering purposes—concrete aggregates)

75

20

Canada

CAS A23.1-14/A23.3-14 (concrete materials and methods of concrete construction/test methods and standard practices for concrete)

75

5

European Union

BS EN 12620: 2013 (aggregates for concrete)

63

–

Judgment basis/ 1−γ −2

(4.106)

1 (4.107) 1

According to the iterative calculation of the above formula, the modulus of MS mortar influenced by the parameter γ can be predicted.

4.5.2.3

Verification and Discussion

It is necessary to verify the model after the model predicting the effect of MS shape on mortar containing fines has been set up. Then, the influence of the MS shape on the modulus of mortar can be further analyzed.

200

4 Properties and Microstructure of Concrete with Manufactured Sand

Verification of modulus of the fines-cement composite system (level 2) Prior to validation of level 2, the shear modulus, bulk modulus, and modulus of elasticity of each component, such as hydration products, unhydrated products, water, voids, and fines, need to be clarified. The values for each component can be determined according to Table 4.33 from the literature. Haecker [138] has obtained the effective modulus (including elastic modulus and shear modulus) of fines-cement composite system with 5.2% fines. In their experiments, the cement used was similar to ASTM I type cement, where D cement contained 5.2% limestone stone fines, the water to cement ratio changed from 0.25 to 0.6, and the effective modulus of the fines-cement sample was tested after 28-day curing. The test data are used to validate the model. The W /C value and the relationship between the model’s modulus of the fines-cement system and the measured modulus are shown in Figs. 4.59 and 4.60. The relative error between the theoretical modulus value calculated by the model and the experimental value is shown in Tables 4.34 and 4.35. It can be seen from the above verification that the calculated results from the model of the fines-cement system are in good agreement with the experimental results. For the shear modulus, the maximum and the minimum relative error between the theoretical and the experimental results are only 7.45% and 0.78%, respectively. Table 4.33 The modulus values for each component in level 2 Components

K/GPa

μ/GPa

E/GPa

v

References

Hydration products

13.89

10.42

25

0.2

[137, 139]

Unhydrated products

75

56.25

135

0.27

[137, 139]

Water

2.2

0

0

0.5

[137, 139]

Void

0

0

0

0

–

LFines

29

19.11

47

0.23

[140, 141]

Fig. 4.59 Verification of shear modulus in fines-cement system

4.5 Modeling of Concrete with Manufactured Sand

201

Fig. 4.60 Verification of elastic modulus in fines-cement system

Table 4.34 The relative error of shear modulus between the theoretical and experimental values W /C

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

Experimental values (GPa)

12.8

11.5

10.2

9.4

8.2

7.5

6.8

6.0

Theoretical values (GPa)

12.7

11.0

9.7

8.7

7.9

7.2

6.6

6.1

4.90

7.45

3.66

4.00

2.94

1.67

Relative error (%)

0.78

4.35

Table 4.35 The relative error of elastic modulus between the theoretical and experimental values W /C

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

Experimental values (GPa)

31.0

29.0

25.8

24.2

21.5

19.0

17.0

15.5

Theoretical values (GPa)

30.7

26.7

23.6

21.2

19.2

17.5

16.1

15.0

12.40

10.70

Relative error (%)

0.97

7.93

8.53

7.89

5.29

3.23

Although the maximum relative error is12.40% for the elastic modulus, most of those is less than 10%. Therefore, the validity of the model predicting the modulus of the fines-cement system based on the microscopic theory has been confirmed. Verification of modulus of manufactured sand mortar In this section, three sets of test data were selected to verify the modulus of MS mortar. Verification 1: In Level 3, the volume fraction and particle parameters of the inhomogeneity are the key parameters of this model independent of the lithology of aggregate. Then, the model to predict the modulus is not only applicable to the MS mortar, but also applicable to other sands, such as silica sand and river sand. Thus, the experimental data from the literature [142] were used to testify the model. In their experiments, the mortar specimens were prepared using ASTM Type I/II Portland cement and silica sand with the W /C of 0.30. The hardened paste’s bulk modulus and shear modulus were 22.51 GPa and 11.8 GPa, respectively, and the bulk modulus

202

4 Properties and Microstructure of Concrete with Manufactured Sand

Table 4.36 The modulus values of mortar under different volume fraction of sand ci

0.15

0.27

0.40

0.52

0.65

K eff,M1 /GPa

24.14

26.81

27.69

29.96

30.12

μeff,M1 /GPa

13.35

14.87

16.91

19.26

20.23

and shear modulus of the sand was 44.0 GPa and 37.0 GPa, respectively. The bulk modulus K eff,M1 and the shear modulus μeff, M1 of the mortar under different volume fraction ci of sand are shown in Table 4.36. Since the shape parameter of the sand is not given in the literature, it is assumed to be the sphere, that is, γ = 1, and then the test values and the theoretical values calculated from the model are compared, as shown in Figs. 4.61 and 4.62. It can be seen from the figures that when the volume fraction of sand is 0.15, 0.27, 0.4, and 0.52, the experimental values agree well with the theoretical values, the maximum relative error for the bulk modulus is just 4.5%, and the maximum relative error of the shear modulus is 6.79%. When the volume fraction of sand is 0.65, the test values of the bulk modulus and the shear modulus are slightly larger than the theoretical values. Therefore, the effectiveness of the model of MS shape on the modulus of mortar is validated. Verification 2: Kuo [126] prepared some mortar specimens with different volume fractions (0, 0.29, 0.38, 0.49) of fine aggregate which is like ellipsoid with γ = 1.13 and water-cement ratio of 0.45. The tested bulk modulus and the shear modulus of the fine aggregate are 19.46 GPa and 18.44GPa, respectively. The cement paste;s bulk modulus and shear modulus with W/C of 0.45 are 6.45 and 5.32 GPa. The bulk modulus K eff,M2 and shear modulus μeff ,M2 of mortar with different volume fractions of fine aggregate are shown in Table 4.37. The verification curves based on literature data are shown in Figs. 4.63 and 4.64. It is not difficult to obtain that the tested effective modulus of mortar agrees with the theoretical value. The maximum relative error of bulk modulus is only 1.78%, Fig. 4.61 Comparison of bulk modulus between experimental values from Wang [142] and the theoretical values

4.5 Modeling of Concrete with Manufactured Sand

203

Fig. 4.62 Comparison of shear modulus between experimental values from Wang [142] and the theoretical values

Table 4.37 The modulus values of mortar with different volume fractions of fine aggregate ci

0.29

0.38

0.49

K eff,M2 /GPa

8.856

9.634

10.831

μeff,M2 /GPa

7.640

8.375

9.487

and the maximum relative error of shear modulus is 4.0%. Therefore, the model’s validity is once again verified by the experimental data. Verification 3: According to the literature published by Tian [143], they used Portland cement without mineral admixture and limestone MS to prepare the mortars with W/C of 0.4, 0.5, 0.6, and 0.7. The tested density of cement was 3200 kg/m3 , and the density of MS was 2650 kg/m3 . The molded mortar specimen was subjected to a uniaxial compressive strength test at 20 °C and relative humidity of 60% for 14 days, and the stress–strain curve was recorded. Regardless of the volume shrinkage of Fig. 4.63 Comparison of bulk modulus

204

4 Properties and Microstructure of Concrete with Manufactured Sand

Fig. 4.64 Comparison of shear modulus

mortar, the volume fractions calculated at the ratio of sand/cement of 1.0, 1.5, and 2.0 were 0.34, 0.44, and 0.51, respectively. The stress–strain curve of the mortar specimen with W/C of 0.4 is selected for model verification. The elastic modulus of the MS mortar with the volume fraction of 0.34, 0.44, and 0.51was 36.8 GPa, 26.1 GPa, and 28.1 GPa from the stress–strain curve of mortar, and Poisson’s ratio of mortar with W/C of 0.4 can be taken as 0.24 from the literature [144]. Therefore, the bulk modulus K eff,M3 and shear modulus μeff,M3 of mortar specimen are exhibited in Table 4.38. Based on the above analysis, the results show that the experimental values are between γ = 1 and γ = 0.3, as shown in Figs. 4.65 and 4.66. By comparing the experimental value with the theoretical value of γ = 1, it is found that the maximum relative error of the bulk modulus is only 1.77%, and the maximum relative error of the shear modulus is 1.42%. Therefore, the model has been verified with reasonable effectiveness. The analysis of the effect of fines on the modulus of manufactured sand mortar The influence of the fines content on the modulus of mortar is explored based on taking the volume fraction of MS as 0.3 and W /C as 0.4. From Figs. 4.67 and 4.68, it can be seen that the bulk modulus and shear modulus of the MS mortar gradually increase with the increase of the fines content. The reason is that not all of the fines can participate in the hydration reaction of the cement and the inert fines as the inclusions will strengthen the modulus of mortar. Moreover, the modulus reaches the minimum value when the shape of the MS is spherical. Table 4.38 The modulus of mortar with different volume fractions of manufactured sand ci

0.34

0.44

0.51

K eff,M3 /GPa

15.256

16.731

17.949

μeff,M3 /GPa

9.578

10.521

11.290

4.5 Modeling of Concrete with Manufactured Sand Fig. 4.65 Comparison of bulk modulus

Fig. 4.66 Comparison of shear modulus

Fig. 4.67 Relationship between the bulk modulus of mortar and fines content

205

206

4 Properties and Microstructure of Concrete with Manufactured Sand

Fig. 4.68 Relationship between the shear modulus of mortar and fines content

The analysis of effect of the shape of manufactured sand on the modulus of manufactured sand mortar In the section, the data were selected for the analysis of the effect of MS shape on the modulus of MS mortar. The influence of the different shape of MS, such as flat or needle, on the modulus of mortar is explored based on taking the volume fraction of MS as 0.3. The relationship between the modulus of the MS and the shape of sand is shown in Figs. 4.69 and 4.70. It can be seen that regardless of the MS shape is flat or needle. The shape is closer to the sphere; the modulus of the mortar present is lower. Meanwhile, the modulus reaches the minimum when the shape is the sphere. The modulus of mortar reduces gradually with the increase of parameter γ when the shape of MS is flat. The decreasing speed gradually becomes slow and reaches the minimum as the sphere shapes. However, the needle-like MS presents converse results. For needle-like MS, the modulus of the mortar increases gradually with the Fig. 4.69 Relationship between the bulk modulus of mortar and shape of manufactured sand

4.5 Modeling of Concrete with Manufactured Sand

207

Fig. 4.70 Relationship between the shear modulus of mortar and shape of manufactured sand

increase of γ . The growth rate gradually becomes slow. Once γ reaches a value, the modulus tends to be steady. What’s more, the effect of the flat MS on the modulus of mortar is higher than that of the needle from the slope of the curve. Conclusion Based on the micromechanics theory, the influence of the MS shape on the modulus of mortar is analyzed. The following conclusions are obtained: (1) Considering the effect of fines, a multi-level model of predicting the modulus of MS mortar with fines is proposed. And the validity of the model is verified by the experimental data. (2) As the replacement rate of fines to cement gradually increases, the modulus of MS mortar shows an increasing trend and is influenced by the shape of MS. (3) Regardless of the shape of MS is a needle or flat, the shape is closer to the sphere, and the modulus of the MS mortar presents lower. Meanwhile, the modulus is the smallest when the shape of MS is spherical. (4) The modulus of mortar reduces gradually with the increase of parameter γ when the shape of MS is flat. The decreasing speed gradually becomes slow and reaches the minimum as the sphere shapes. For needle-like MS, the modulus of the mortar increases gradually with the increase of γ . The growth rate gradually becomes slow. Once γ reaches a value, the modulus tends to be steady. What’s more, the effect of the flat MS on the modulus of mortar is higher than that of the needle from the slope of the curve.

4.5.3 Multi-level Diffusion Model Although the diffusion coefficient of concrete can be experimentally measured, it is difficult to differentiate the effects of various factors, such as particle shape, volume fraction, and so on, on the diffusion coefficient of concrete. Therefore, theoretical

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4 Properties and Microstructure of Concrete with Manufactured Sand

investigations remain essential. Extensive studies have been done by researchers to theoretically investigate the effect of aggregate characteristics on the transport properties of mortar and concrete, mainly based on random walk algorithm [145, 146], finite element method [147–149], self-consistent model [150, 151], effective medium theory [152], Maxwell model [153], and lattice Boltzmann model [154]. However, most of the proposed models are based on circular or spherical aggregates assumption while only limited models considering the complex shapes of aggregates are suitable for coarse aggregate. It was found that the analytical solutions of the diffusion coefficient of concrete can be obtained by taking aggregates as ellipsoids [155]. Based on the 3D random packing method, Liu [156] proposed a numerical model and revealed that the shape effect of oblate coarse aggregates is greater than that of prolate or convex polygonal aggregates. By modeling aggregates as ellipsoidal inclusions in the matrix of the interfacial transition zone, an equivalent aggregate model was constituted, and the lattice model was then applied to the analysis of chloride diffusion in concrete by Zheng [157–159]. Results showed that the chloride ion diffusion coefficient decreases with the increasing aspect ratio of coarse aggregate. Although diverse diffusion models of cement-based materials have been proposed, most of them are based on coarse aggregate. Besides, as a kind of powder materials, fines probably has physical and chemical effects on the transport properties of cement-based materials [160–163]. However, little literature can be found about the transport property prediction of blended paste considering fines effects. Therefore, the proposed models cannot be directly used to predict the transport properties of mortar or concrete with MS due to the inevitable employment of fines in mixtures and the non-spherical shape of MS particles. To predict the diffusion coefficient of MS mortar considering MS particle shape and fines effects, a multi-level micromechanical model is proposed. MS mortar is represented as composite cement, fines-cement paste, and MS mortar at three levels based on its multi-level microstructures. Homogenization procedures are performed at each level. The effects of fines, including chemical and dilution effects, are, respectively, considered at first- and second-level homogenizations. The shape of MS particles, characterized by its aspect ratio with ellipsoid assumption, is incorporated at the third-level homogenization. For verification, available data from experiments and existing models are employed.

4.5.3.1

The Role of Fines in Cement Paste

Rocks with lithology of limestone, basalt, granite, quartzite, marble, diabase, and so on have been used to produce MS in view of their availability. Fines of different lithology has various roles in cement paste. The overwhelmingly widespread fines is targeted. By now, comprehensive and systematic studies have been conducted on the roles of fines in hardening cement paste, which can be summarized as follows. Fines is mainly composed of calcite. Based on calculations and experimental observations, part of calcite is reactive and affects the mineralogy of hydrated cement pastes [164–168]. Calcite reacts with calcium monosulfoaluminate at the presence

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209

of water and portlandite, possibly producing hemicarboaluminate, monocarboaluminate, ettringite, C4 AHx , gypsum, or mixtures thereof. But in practice, only ettringite and monocarboaluminate will be produced based on commonly used Portland cement composition (altered cements are excepted from this presentation). The reactive proportion of calcite mainly depends on sulfate and alumina contents [156, 164]. Table 4.39 shows Al2 O3 and SO3 contents of several Portland cements from literature and calculated reactive calcite ratios in cement-based materials on Ref. [168]. In practice, fines exists with MS particles and is not considered as the binder in the mix proportion. Therefore, the reactive part of calcite to cement ratio is also calculated based on the reactive calcite ratio in cement. It can be found that the reactive calcite to cement ratios are in the range of 3.2–4.3%. The average value of 3.8% is taken to simplify the calculation for the following modeling work. As mentioned, the reactive part of limestone reacts with monosulfoaluminate, etc., liberating sulfate to form ettringite. The additional ettringite formation slightly increases the molar volume of solids, thus reducing the porosity and permeability of paste. Therefore, the reactive portion of limestone is taken as cement. The reactive part of fines, together with cement, acts as binder. Besides chemical influence, fines also provides dilution, nucleation, and filler effects [27]. The dilution effect happens when cement is replaced by inert or partially inert fines, increasing the water to react with cement particles [174, 175]. However, fines exists in MS and is not considered as binder here in mix proportion and the water to cement ratio is not influenced by fines content. Thus, the dilution effect on the water to cement ratio is not considered. The inert part of fines which is impermeable reduces the porous volume fraction of the cement paste in hardened paste, diluting the porous matrix. The nucleation effect of fines possibly promotes the early hydration of cement [176]. However, fines does not significantly impact at a later age for higher hydration degree when cement hydration has proceeded close to its ultimate level, which is the case in this modeling work. Therefore, the nucleation effect can be ignored in this model. The filling effect of fines is prominent when the fines is finer than cement [177]. But normally, the Table 4.39 Al2 O3 and SO3 contents of several Portland cement from references References

Composition in mass (%) Al2 O3

SO3 / Al2 O3

SO3

Reactive calcite ratio in cement (%)

Reactive calcite to cement ratio (%)

[153]

4.64

2.31

0.50

3.8

4.0

[162]

5.07

3.37

0.66

3.6

3.7

[169]

4.94

3.07

0.62

3.6

3.7

[170]

4.60

2.20

0.48

3.8

4.0

[171]

4.52

3.35

0.74

3.1

3.2

[172]

4.99

3.29

0.66

3.5

3.6

[173]

5.34

3.38

0.63

4.1

4.3

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4 Properties and Microstructure of Concrete with Manufactured Sand

produced fines sieved from MS is in the identical order of magnitude with cement in terms of particle size. Thus, the filling effect of fines is ignored. Therefore, two significant roles of fines have been considered, one as a reactive participant in the hydration process and the other as an inert filler providing dilution effect on porous paste.

4.5.3.2

Multi-level Micromechanical Model for MS Mortar

MS mortar is heterogeneous and generally consists of different constituents or phases. Constituents of this material can be treated as homogeneous at a certain length scale, but the constituents themselves may become heterogeneous when observed at a smaller length scale. Usually, MS mortar is composed of hydration products, unhydrated clinker, fines, MS particles, and interfacial transition zone (ITZ) in the hardened paste. It has been reported that adjacent ITZs would interconnect and form a continuous path for ions penetration when the aggregate volume is too high, known as the percolation effect. Some researchers found that the ITZ porosity increases with the increasing aggregate volume and a sudden increase in ion diffusivity was observed when aggregate volume increased to a critical value [178, 179]. On the other hand, some researchers observed a continuous decrease with the increment of aggregate volume and concluded that the percolation of ITZ had limited influence on the overall transport property of cement-based materials, compared to the overall pore structure [145, 169, 173, 180, 181]. In the primary model, the percolation effect is not considered and ITZ is deemed to have negligible influence on the transport performance of mortar compared to factors like water to cement ratio, hydration degree, and aggregate volume fraction. The ITZ influence is expected to be extended in the following work. Besides, it is commonly recognized that ITZ porosity increases with the increasing aggregate volume, accompanied by the decreased porosity in matrix paste due to the constant water to cement ratio. It can be considered that the total porosity of matrix and ITZ paste is not influenced by aggregate volume. It has been demonstrated that equivalent ellipsoids can accurately assess the inherent characteristics of aggregate [119, 156]. The shape of the MS particle is herein assumed to be ellipsoid. It is also assumed that MS particles are evenly distributed in the paste, and there is no direct contact between the particles in MS mortar. Based on the above assumptions and multi-level concept, the structure of MS mortar can be described at three levels according to previous work [134, 182–184]. The main principle concerning the setup of this three-level scheme is to address the roles of MS particle, the inert portion of fines, and the reactive portion of fines in MS mortar. (i)

The fundamental level is assumed to be the scale of pores, defined by level 1. The usual size of this level is in the submicrometer and micrometer range. The material at this level, named composite cement, is a bi-phase material

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211

composed of a reactive portion of fines and cement as the solid phase, and pore structure as the gaseous phase. (ii) At level 2, this material is seen as a biphasic composite with composite cement as the matrix and the inert portion of fines being inclusions. The distance between any two inert fines is considered large enough compared to their size. The characteristic size of this level is in the micrometer range. (iii) Level 3 is assumed to be the scale of MS particles and is characterized in the millimeter range. At this level, MS mortar is taken as a bi-phase material with fines-cement paste and MS particles being matrix and inclusions, respectively. Therefore, the diffusion model considering the particle shape and fines effects can eventually be established if the diffusion coefficients of MS mortar at levels 1, 2, and 3 are subsequently predicted.

4.5.3.3

Micromechanics-Based Multi-level Predictions for the Diffusion Coefficient of MS Mortar

A multi-level homogenization framework is proposed to quantitatively estimate the diffusion coefficient of MS mortar based on the previous works [186–190]. Specifically, the first equivalent matrix made up of cement, a reactive portion of fines and pores, is reached with the first-level homogenization, through which the chemical effect of fines is considered. The inert portion of the fines is considered at secondlevel homogenization. With the third-level homogenization, the effect of MS particle shape is considered. (1) Diffusion coefficient prediction of composite cement Composite cement can be seen as a bi-phase composite material composed of solid paste and pores, as shown in Fig. 4.71. Pores in the matrix can be divided into continuous pores with tortuous effect, continuous pores with ink-bottle, dead-end pores and isolated pores, shown in Fig. 4.72 [191]. The former two types of pores are effective to transport aggressive substances while the latter two are not. Usually, the effective diffusion coefficient of tortuous continuous pores can be characterized by the tortuosity, while that of a continuous pore with ink-bottle can be evaluated by the constrictivity [192]. Composite cement paste can be treated as an effective continuum. The effective diffusion coefficient can be expressed by the relationship with pore structure parameters based on the effective media theory [193, 194], shown as follows. Dp σ =ϕ 2 D0 τ

(4.108)

where Dp is the effective diffusion coefficient of a porous material (m2 /s); ϕ is porosity; σ and τ are constrictivity and tortuosity of the pore networks, respectively; and D0 is the diffusion coefficient of ion transport in bulk water, such as D0 = 2.03 × 10–9 m2 /s for chloride ion at room temperature.

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4 Properties and Microstructure of Concrete with Manufactured Sand

Fig. 4.71 Multi-level structure of MS mortar, reprinted from ref. [185], copyright 2019, with permission from Elsevier

Fig. 4.72 Pore structure of hardened composite cement paste, reprinted from ref. [185], copyright 2019, with permission from Elsevier

Porosity is composed of capillary and gel pores for cementitious materials, as seen in Eq. (4.109). ϕ = ϕcap + ϕgel

(4.109)

where ϕcap and ϕgel are the porosities of capillary and gel pores, respectively, which can be calculated according to the Powers theory, illustrated as the following equations [131].

4.5 Modeling of Concrete with Manufactured Sand

ϕcap = ϕgel =

213

0.19ε + 0.32

(4.110)

W − 0.36ε B W + 0.32 B

(4.111)

W B

where WB represents water to composite cement ratio and ε is hydration degree. Therefore, the total porosity can be obtained by Eqs. (4.110) and (4.111) as follows. ϕ=

W − 0.17ε B W + 0.32 B

(4.112)

There is a relationship between water to composite cement ratio and water to ). cement ratio ( W C W 1 W = B 1+α C

(4.113)

where α is reactive fines ratio to cement. Simplistically, α can be taken as 3.8%. The hydration degree of composite cement can be expressed as follows [136]. εmax = 1 − e(−3.3W/B)

(4.114)

Tortuosity is defined as the ratio of the length of the actual ion transport pathway to the corresponding length on the projected plane. The quantitative relationship between the tortuosity and the total porosity of the material is established as follows [195, 196]. τ = −1.5tanh[8(ϕ − 0.25)] + 2.5

(4.115)

Constrictivity is used to characterize the structural characteristics of the continuous pores with ink-bottle, which is related to the pore size. The relationship between the constrictivity and the peak pore radius in the paste has been derived [195, 197], expressed as:    peak + 6.2] + 0.405 σ = 0.395tanh 8[log rcp peak

(4.116)

where rcp is the peak radius of pores (m), corresponding to the maximum porosity in peak pore size distribution. The relationship between σ and rcp is illustrated in Fig. 4.73. In cementitious paste, pores are widely distributed over the nanometer-tomicrometer scale and pores with varying sizes are randomly connected, while the peak peak radius of capillary pores ranges from 20 to 120 nm [191]. Since rcp is normally

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4 Properties and Microstructure of Concrete with Manufactured Sand

Fig. 4.73 Constrictivity versus peak radius of capillary pores, reprinted from ref. [185], copyright 2019, with permission from Elsevier

peak

no larger than 120 nm, log(rcp /m) is consequently smaller than −6.9. According to Fig. 4.73, constrictivity is about 0.01 for pores in the cementitious paste. Therefore, porosity, constrictivity, and tortuosity of pore structure in the composite can be calculated and the diffusion coefficient of the composite cement can be accordingly predicted by Eq. (4.108). (2) Diffusion coefficient prediction of fines-cement paste Cement hydration takes place surrounding cement particles with denser microstructure around cement particle than that around inert fines, which can be taken as “micro-aggregate” in composite cement paste matrix. The difference between structure around fines and that in composite cement paste matrix is considered negligible in the primary model. The inert portion of fines is taken as isolated spherical inclusions evenly distributed in the composite cement matrix with a perfect connection between the inclusions and matrix. Since the volume of fines is much smaller than that of composite cement paste in fines-cement paste, the distance between any two distributed inert fines in the paste is larger than their particle diameter. To evaluate the performance of composite with spherical inclusions, a sphere selfconsistent model, shown in Fig. 4.74, was proposed, which has been employed to the prediction of elasticity, viscoelasticity, elastoplasticity, [198, 199], thermal and thermoelastic behaviors [200], as well as chloride ion diffusion in mortar and concrete [151, 201]. This model is herein employed to determine the diffusion coefficient of fines-cement paste, shown in Fig. 4.75. In the composite sphere model, phase 1 constitutes the central core. Phase (i) is affected by phase (i − 1) and phase (i + 1). Only when the effective diffusion coefficient of phase (n) equals that of phase (n + 1) can the effective diffusion coefficient of the (n + 1) phase composite be obtained, expressed as follows.

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215

Fig. 4.74 N + 1 phase model of composite spheres, reprinted from ref. [185], copyright 2019, with permission from Elsevier

Fig. 4.75 Bi-phase model of fines-cement paste, reprinted from ref. [185], copyright 2019, with permission from Elsevier

eff D(i) = Di +

Di (R3i−1 /R3i )   eff Di / D(i−1) − Di + (1/3)/[(R3i − R3i−1 )/R3i ]

(4.117)

eff where Di is the effective diffusion coefficient of phase (i) and D(i) is the effective diffusion coefficient of the composite spheres made up of phase 1 to phase i; and Ri and Ri-1 are the radii of phase (i) and phase (i − 1), respectively. The fines-cement paste is treated as a bi-phase material where an inert portion of fines are inclusions embedded into the matrix of composite cement paste. The inert fines constitutes the central core, while composite cement paste is the second phase. Both the inert fines and composite cement can be assumed to be homogeneous eff ) of this bi-phase and isotropic. Therefore, the effective diffusion coefficient (DPCP material is given as:

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4 Properties and Microstructure of Concrete with Manufactured Sand eff DPCP = DB +

DB (R31 /R32 ) DB /(DS − DB ) + (1/3)/[(R32 − R31 )/R32 ]

(4.118)

where R32 − R31 = 1 − fS R32

(4.119)

R31 = fS R32

(4.120)

where DS and DB are the diffusion coefficients of the inert portion of fines and composite cement, respectively, and fS is the volume fraction of the inert portion of fines in cement-fines paste. Therefore, the effective diffusion coefficient of the fines-cement paste is expressed as follows. eff DPCP = DB +

DB × fs DB /(DS − DB ) + (1/3)/[1 − fs ]

(4.121)

Since the inert portion of fines is relatively impermeable, that is, DS = 0, then Eq. (4.121) can be deformed into Eq. (4.122). eff DPCP = DB +

DB × fs −1 + (1/3)/[1 − fs ]

(4.122)

The volume fraction of the inert portion of fines can be calculated as follows with the assumption that there is no chemical shrinkage during the hydration of composite cement. fs =

Vlp,i + Vlp,r

Vlp,i β−α = ρlp C + Vcement + Vwater β + ρcem + W

ρlp ρwat

(4.123)

where ρ and V are the density and volume of a component, respectively; the subscripts “lp”, “lp,i”, and “lp,r” denote fines, inert, and reactive portions of fines, respectively; β represents fines to cement ratio in mass. Therefore, the effective diffusion coefficient of the fines-cement paste can be predicted by Eq. (4.122). In particular, Eq. (4.108) should be used with WB replaced if the paste is not doped with fines. by W C (3) Diffusion coefficient prediction of MS mortar Micromechanics theory has been proven to be a practical approach to reveal the quantitative relationship between the macroscopic properties and microstructure of composite materials. Micromechanics theory is employed to investigate the effect of MS particles on the transport performance of MS mortar at the third-level homogenization. Based on this theory, the explicit formula for the diffusion coefficient of

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217

N-phase composites with randomly distributed ellipsoidal inclusions can be obtained as shown below [40].

D

eff

=D

(1)

(1)

+D [

N  2

(r)

h

−1 (r)

h

−1

1 − ] 3

(4.124)

−1

−1 1 (r) D(1) g (r) D(1) (r) = f [2 + + +1−g ] (4.125) 3 D(r) − D(1) 2 D(r) − D(1)

where D(1) and D(r) are the diffusion coefficients of matrix and phase (r), respectively; f (r) is the volume fraction of the inclusions dispersed in the matrix; and g (r) is the shape parameter function of inclusions. MS mortar can be regarded as a bi-phase material composed of inclusions of the ellipsoidal MS particles and the matrix phase of fines-cement composite. Therefore, eff ) can be expressed as follows. the effective diffusion coefficient of MS mortar (DM −1 1 −1  eff eff eff DM = DPCP + DPCP [ hMS − ] 3

(4.126)

where MS

h

−1

−1 eff eff DPCP DPCP g MS 1 MS MS + + +1−g ] = f [2 eff eff 3 2 DMS − DPCP DMS − DPCP (4.127)

Shape parameter g MS of ellipsoidal particles is shown as follows [152].

g MS

⎧   √ √ 1 ⎪ γ −2 arctan γ −2 − 1 − γ −2 − 1 γ < 1 ⎪ 3 ⎪ ⎪ ⎨ (γ −2 −1) 2 2 γ =1 = 3 √ −2

⎪ √ ⎪ ⎪ 1 −2 1+√1−γ −2 ⎪ 2 1 − γ − γ ln γ >1 ⎩ 3 1− 1−γ −2 2(1−γ −2 ) 2

(4.128)

where γ is the aspect ratio of ellipsoidal MS particles. MS particles are free from ion transporting, that is DMS = 0. Thus, hMS =

−1 −1  g MS 1 MS f [2 −1 + + −g MS ] 3 2

(4.129)

eff According to Eqs. (4.126)–(4.129), the diffusion coefficient of MS mortar (DM ) can be eventually predicted.

218

4.5.3.4

4 Properties and Microstructure of Concrete with Manufactured Sand

Verification and Discussion

(1) Verification for the diffusion coefficient prediction of fines-cement composite Abundant data are available in literature about the chloride diffusivity of pure cement with various water to cement ratios, while only limited literature about that of the blended cement paste with fines can be found. Chloride diffusion coefficient results of pure cement with various water to cement ratios are employed from Sun [191], Caré [201], Ngala [173] and Huang [202]. Cherif [162] measured the chloride diffusion coefficient of fines-cement composite paste which was fabricated with ordinary Portland cement (ASTM I) and 25% fines (in mass). Before comparison, the dosage of fines should be expressed by fines to cement ratio (β). Fines replacing 25% of cement corresponds to β of 33.3%. The predicted eff and experimental ones at different W/C ratios are chloride diffusion coefficient DPCP shown in Fig. 4.76. It can be seen that the diffusion coefficients of both pure cement and blended cement with limestone increase with the increasing W/C ratio for both experimental data and predicted ones. For pure cement paste, all the experimental data are closely around the predicted line, indicating that the simulation leads to a favorable agreement with the experiments. For cement with additional 33.3% limestone powder, the chloride ion diffusion coefficient from Cherif is 5.80 × 10–12 m2 /s, while the value calculated by the prediction model is 6.27 × 10–12 m2 /s, showing a relative error of 8.1% for the predicted result to the experiment. This deviation may be caused by factors like different raw materials, hydration degree, and test methods [134, 135, 186, 203–205]. Besides, the gel pores are considered effective for the diffusion of substances in hardened paste in Eq. (4.5), which leads to overestimation of gel pores effect and contributes to the higher predicted value as well [206]. This influence is Fig. 4.76 Predicted and experimental diffusion coefficients of hardened cement paste and fines-cement paste, reprinted from ref. [185], copyright 2019, with permission from Elsevier

4.5 Modeling of Concrete with Manufactured Sand

219

expected to be addressed in future investigations. However, this relative error can be considered reasonable for cement-based materials and the prediction model for the diffusion coefficient of the fines-cement composite is validated [207]. It has to be noted that the chloride ion diffusion coefficient of the hardened pure cement paste is higher than that of the fines-cement paste with fines under the same water to cement ratio. This can be attributed to the fact that the reactive portion of fines reduces the water to binder ratio, developing a denser microstructure of composite cement paste. Besides, the inert portion of fines which is impermeable provides a dilution effect on the porous composite cement paste. (2) Verification for the diffusion coefficient prediction of MS mortar To verify the effectiveness of the model for the prediction of diffusion coefficient of MS mortar, experimental and theoretical data of Garboczi [208], Wong [181], Zheng [158] and Liu [156] are employed. Garboczi tested the relative diffusion coefficients of chloride ions in concrete with different volume fractions (fi ) of coarse aggregate while Wong conducted the diffusion coefficient of oxygen-based media in cement-based materials in the same manner. The prediction model of the relative diffusion coefficient is obtained from Eq. (4.126), shown as follows. eff DM 1 −1 −1 = 1 + [(hMS ) − ] eff 3 DPCP

(4.130)

The relative diffusion coefficient comparison between prediction and experiment is seen in Fig. 4.77. It is seen that the predicted relative diffusion coefficients show a similar trend with experimental ones. Specifically, both exhibit gradual decrement with the increase of aggregate volume fraction. This is because the aggregate inclusions are impermeable, providing an increasing tortuosity effect on the transporting path of aggressive matters in the composite with the increase of volume fraction. Moreover, it is also worth mentioning that predicted values are slighter lower than experimental ones. This may be attributed to the fact that the proposed prediction model does not consider the permeability characteristic of the interfacial transition zone between the aggregate and the paste. Predictions from Liu [156] are also employed in Fig. 4.77, who conducted a 3D numerical investigation by means of a random packing model with aggregate taken as ellipsoids. It is noticeable that the proposed model agrees well with the existing model, while minor deviation may be attributed to different assumptions and modeling methods. Zheng [159] experimentally and theoretically investigated the effect of coarse aggregate shape on the chloride diffusion coefficient of concrete. Three types of glass spheroids with aspect ratios of 1, 2, and 3 were employed as coarse aggregates. The comparisons of predicted and experimental chloride diffusion coefficients of concrete at different W/C ratios are shown in Fig. 4.78. For both experimental and predicted results, the diffusion coefficient of chloride ion decreases with the increase of aggregate volume fraction and the diffusion coefficient of chloride ion decreases with the increase of shape parameter γ . The maximum relative errors

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4 Properties and Microstructure of Concrete with Manufactured Sand

Fig. 4.77 Predicted and experimental relative diffusion coefficients of cement-based materials with various amounts of aggregates, reprinted from ref. [185], copyright 2019, with permission from Elsevier

between the predicted and experimental values at the W/C ratios of 0.5 and 0.6 are 13.9% and 10.8%, respectively, which are within a reasonable range [152]. Prediction from Zheng is also depicted in Fig. 4.78, derived an analytical approximation for the chloride diffusivity of concrete with ellipsoidal coarse aggregates. It is worth mentioning that our proposed prediction shows a similar trend to that from Zheng. However, in Zheng’s prediction, fine aggregates were modeled as spheres. The result calculated from this assumption is higher than that from ellipsoid assumption, which results in the deviation between prediction and that from Zheng. Therefore, the validity of the multi-level prediction model for the diffusion coefficient of MS mortar is primarily verified by comparing theoretical values calculated from the proposed model with available experimental data and limited relevant models.

Fig. 4.78 Predicted and experimental chloride diffusion coefficients of cement-based materials with various γ values, reprinted from ref. [185], copyright 2019, with permission from Elsevier

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221

(3) Discussion on the relationship between diffusion coefficient of MS mortar and limestone content The proposed model can be applied to predict the diffusion coefficient of MS mortar considering fines effects. Figure 4.79 shows the diffusion coefficient of MS mortar with a constant MS particle volume fraction of 0.3 and various limestone contents. It is clearly observed that the diffusion coefficient of MS mortar gradually decreases with the increasing fines content. This can be explained by the fact the reactive portion of fines reduces the water to binder ratio, developing a denser microstructure of composite cement paste. The inert portion of fines is impermeable, providing a dilution effect on the porous composite cement paste and thus lowering the volume fraction of porous composite paste in the fines-cement paste. As a result, the increased fines content results in the reduced diffusion coefficient of MS mortar. The slope of curves in Fig. 4.79 represents the influence degree of fines content on the diffusion coefficient of MS mortar. It can be known that all curves’ slopes corresponding to different shape parameters are quite similar. This means that the influence degree of fines on the diffusion coefficient of MS mortar is independent on MS particle shape. (4) Discussion on the relationship between diffusion coefficient of MS mortar and MS particle shape The relative diffusion coefficient of Eq. (4.130) is used as the index to evaluate the effect of MS particle shape on the diffusion coefficient of MS mortar, and predictions are shown in Fig. 4.80. It is clearly seen that whether the shape of MS particles is oblate or prolate, a higher diffusion coefficient is observed when the MS particle shape is closer to the sphere. When the MS particle is spherical, the diffusion coefficient reaches the maximum value. Besides, the diffusion coefficient sharply declines with the decreasing parameter γ when the MS particle is oblate. But for the mortar with prolate MS particles, this value slowly decreases with the increase of γ . Therefore, it can be inferred that the effect of MS particle shape on the diffusion coefficient

Fig. 4.79 Diffusion coefficient of MS mortar with various amounts of fines, reprinted from ref. [185], copyright 2019, with permission from Elsevier

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4 Properties and Microstructure of Concrete with Manufactured Sand

Fig. 4.80 Relationship between diffusion coefficient of MS mortar and MS particle shape parameter, reprinted from ref. [185], copyright 2019, with permission from Elsevier

is more prominent when it is oblate than prolate, which is in accordance with the conclusion from Liu [156].

4.5.3.5

Conclusions

This section proposes a multi-level model to describe the structure of MS mortar from submicrometer to millimeter scale. Micromechanical, effective medium and selfconsistent theories, as well as multi-level homogenization procedures, are employed to develop a prediction model for the diffusion coefficient of MS mortar with the particle shape and fines effects considered. The validity of the model is primarily verified by experimental data and existing models. The following concluding remarks can be drawn as follows. (i)

The diffusion coefficient of MS mortar decreases gradually with the increase of the fines content due to the chemical and dilution effects of fines. The influence degree of fines is independent on MS particle shape. (ii) The effect of MS particle shape on the diffusion coefficient of mortar is of great significance. Whether the shape of MS is oblate or prolate, a higher diffusion coefficient can be obtained when the MS particle shape is closer to the sphere. Mortar with spherical MS particles exhibits the maximum diffusion coefficient. (iii) When the shape of MS particles is oblate, the diffusion coefficient of mortar sharply declines with the diminishing of parameter γ. For the mortar with prolate MS particles, the diffusion coefficient reduces slowly as γ increases. The effect of MS particle shape on the diffusion coefficient is more significant when it is oblate than prolate.

4.6 Microstructure of Concrete with Manufactured Sand

223

4.6 Microstructure of Concrete with Manufactured Sand The microstructure determines the macroscopic performance of materials. Most research focuses on the macro-mechanical properties and durability of concrete with MS. However, there are few studies on the microstructure of concrete with MS and its effect on the macroscopic properties. There is not a full understanding of the relationship between the microstructure and performance of concrete with MS.

4.6.1 Hydration The authors investigated the influence of fines (LS) fineness on the hydration of Portland cement paste. Hydration products and processes were analyzed by X-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TGDSC), and isothermal calorimetry tests.

4.6.1.1

Hydration Products

(1) XRD XRD patterns of hardened paste at 24 h are exhibited in Figs. 4.81 and 4.82. It can be seen that peaks representing hydrates, including Portlandite, ettringite, and unhydrated C3 S and C2 S, can be found in hardened pure cement paste. Besides, additional peaks corresponding to Calcite are expectedly observed for blended paste with LS. Overall, there is no obvious difference in the intensity of XRD patterns between the sample with LS and the control except the calcite patterns. However, by comparing the relative intensity of two main peaks between 30° and 35°, which represent superposed C3 S and C2 S, and Portlandite, respectively, it can be noticed that the peak of C3 S and C2 S is higher than that of Portlandite for the control while it shows opposite for hardened paste with LS. This means C3 S and C2 S hydrate to a higher degree for hardened paste with LS than that for the control. Besides, it also can be observed that the difference between the intensity of peak for Portlandite and that for C3 S and C2 S is more obvious for P-LS4 than P-LS1. Therefore, it can be inferred that LS promotes cement hydration at 24 h, which is more significant when LS is finer. It was demonstrated that carboaluminate might be produced for cement with fines [209]. To determine whether chemical reaction between LS and cement hydrates happens before 24 h, as well as mainly produces carboaluminate [164, 165], step canning was further performed on XRD analysis from 6° to 30° during which peaks representing carboaluminate mainly distributes if produced [167, 210]. From patterns in Fig. 4.82, no peaks can be found standing for carboaluminate. Therefore, it is inferred that LS does not participate in the chemical reaction with cement hydrates before 24 h.

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4 Properties and Microstructure of Concrete with Manufactured Sand

Fig. 4.81 Continuous scanned XRD patterns of hardened paste from 5° to 80°, reprinted from ref. [14], copyright 1989, with permission from American Society of Civil Engineers

Fig. 4.82 Step scanned XRD patterns of hardened paste from 6° to 30°, reprinted from ref. [14], copyright 1989, with permission from American Society of Civil Engineers

4.6 Microstructure of Concrete with Manufactured Sand

225

(2) TG-DSC TG-DSC curves of hardened paste at 24 h are shown in Fig. 4.83. Two endothermic peaks are found for pure cement paste according to DSC curves, one around 100 °C for water evaporation and dehydration, and the other around 450 °C due to the dehydroxylation of Portlandite. Besides, endothermic peaks around 760 °C, which represent the decarbonation of CaCO3 for blended paste with LS. The limit temperatures for different reactions during heating are diverse from one author to another, due to different heating rates, sample fineness, and so on [211, 212]. Generally, the composition transformation of cement hydrates can be divided into four phases. The first phase below 105 °C represents the physically adsorbed water evaporation. Mass loss between 105 and 400 °C is due to the dehydration of hydrates. Hydrates decomposition between 400 and 500 °C corresponds to the dehydroxylation of Portlandite, and the last phase from 600 to 800 °C implies the decarbonation of CaCO3 [213]. Therefore, the mass values of samples at the temperature of 500 °C approximately represent the mass of total fines used. Based on the weight reduction from 400 to 500 °C due to water loss, contents of produced Ca(OH)2 (fCH ) from per gram of cement can be approximated as follows.

fCH =

m400 − m500 MCH · m500 · (1 − fLS ) MH2 O

(4.131)

where m400 and m500 are mass values of samples at 400 °C and 500 °C, respectively. MCH and MH2 O are molar masses of Ca(OH)2 and H2 O, taken as 74.10 g/mol and 18.02 g/mol, respectively. fLS is the mass ratio of LS in cementitious fines, which can be calculated from its volume fraction (VLS ), as shown below. fLS =

Fig. 4.83 TG-DTG-DSC curves of hardened paste, reprinted from ref. [14], copyright 1989, with permission from American Society of Civil Engineers

VLS · ρLS VLS · ρLS + (1 − VLS ) · ρcem

(4.132)

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4 Properties and Microstructure of Concrete with Manufactured Sand

Table 4.40 Ca(OH)2 calculated from TG curves Sample

Control

P-LS1

P-LS2

P-LS3

P-LS4

fCH (g/g cement)

5.04

6.51

7.05

7.35

7.51

where ρLS and ρcem are the density of LS and cement, respectively. According to Eqs. (4.131) and (4.132), produced Ca(OH)2 contents from per gram of cement are determined and listed in Table 4.40. It is obviously shown that the incorporation of LS promotes the production of Ca(OH)2 despite its particle size. This promotion is more prominent for finer LS. Specifically, LS4 increases Ca(OH)2 content by 48.9%. It means LS promotes cement hydration, and this promotion is increasingly significant with decreasing LS size.

4.6.1.2

Hydration Process

The isothermal calorimetry results until 24 h are exhibited in Fig. 4.84 with heat normalized per gram of cement. Heat liberation is rather intense in the first few minutes since the contact of cement with water due to cement dissolution as well as hydrations of free lime [214], C3 S [10], C3 A [215], or (and) calcium sulfate hemihydrate [214]. This pre-induction period is too short-lived for heat evolution to be fully collected. Then, the heat flow is significantly slowed down, known as the induction period. The zoomed area around the induction period termination is shown in Fig. 4.84b, and LS is found to shorten the induction period. Specifically, induction period termination of blended paste with LS4 appears 26.2% before the pure cement paste. The end of the induction period means the beginning of C3 S further hydration. Thus, the shortened induction period demonstrates the promotion of LS on C3 S hydration. This influence is more significant as LS particle size decreases.

Fig. 4.84 Isothermal calorimetry results of mixtures a until 24 h and b the zoomed area around the induction period termination, reprinted from ref. [14], copyright 1989, with permission from American Society of Civil Engineers

4.6 Microstructure of Concrete with Manufactured Sand

227

Following the end of the induction period is the acceleration stage during which hydration suddenly accelerates and reaches a maximum in a few hours. It can be noted from Fig. 4.84b that LS increases the slope of the heat flow curve during the acceleration period. A higher slope implies faster dissolution and hydration of C3 S. Thus, LS accelerates C3 S hydration. This improvement is increasingly prominent when LS is finer. Besides, the higher heat flow peaks of mixtures with LS than the control in Fig. 4.84a also provide proof for these accelerating effects. For instance, LS4 endows 53.7% higher heat flow for cement hydration. Due to the combined effects of induction period shortening and accelerating on cement hydration, LS amplifies the cumulative released heat shown in Fig. 4.84.a. Therefore, it can be inferred that LS promotes cement hydration, which is more influential significant with the decreasing size.

4.6.1.3

Hydration Degree

Both cumulative released heat and non-evaporable water content were used to calculate cement hydration degrees with calculations shown below. (1) Calculation from cumulative released heat Heat release results can be used to calculate hydration degrees at a particular time, α(t), based on the following equation [216]. α(t) =

Q(t) Q∞

(4.133)

where Q(t) is the cumulative released heat at time t while Q∞ is defined as the cumulative released heat upon complete hydration (at t = ∞), which can be determined according to Eq. (4.134) [217]. Q∞ = 500fC3 S + 260fC2 S + 866fC3 A + 420fC4 AF + 624fSO3 + 1186ff −CaO + 850fMgO

(4.134)

where fi terms represent the mass fraction of phase i. Mass fractions of C3 S, C2 S, C3 A, and C4 AF can be calculated from Bogue’s equation. (2) Calculation from non-evaporable water content Non-evaporable water content (Wn' ) per gram of cement, which can be obtained from the TG curve, was also used to determine the hydration degree (α) of cement according to the following formula [218]. α=

Wn' × 100% βthe

(4.135)

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4 Properties and Microstructure of Concrete with Manufactured Sand

where βthe is the maximum non-evaporable water content theoretically, which can be determined as follows. βthe = 0.24mC3 S + 0.21mC2 S + 0.40mC3 A + 0.37mC4 AF + 0.33mf −CaO

(4.136)

where mC3 S , mC2 S , mC3 A , mC4 AF , and mf −CaO are mass contents of C3 S, C2 S, C3 A, C4 AF, and free CaO in cement. The non-evaporable water content per gram of cement was measured with the following equation: Wn' =

m105 − m500

(4.137)

Vcem m500 ρcem ρVcem cem +ρLS VLS

where m105 is sample mass at 105 °C. The calculated hydration degrees from the two methods are shown in Table 4.41. Hydration degrees from non-evaporable water contents exhibit higher values than that calculated from hydration heat. This discrepancy arises from the fact that various minerals in cement, hydrating at different rates, have different hydration heat and water consumption capacities. Besides, the limit temperature for evaporable and nonevaporable water loss is indefinable and temperature may overlap for evaporable and non-evaporable water deprivation. Even at 105 °C, there might be a certain amount of evaporable water remaining due to too high-temperature rising rate, leading to overestimating non-evaporable water content. It also has to be mentioned that the released heat of data logging was not considered since the addition of water in cement to the beginning, resulting in underestimated total released heat. These combined effects result in lower hydration degrees from isothermal calorimetry than from TG analyses. However, hydration degrees from both methods show a quite similar trend. LS increases cement hydration degree despite LS size, and this improvement is increasingly prominent with the decrease of LS size. Specifically, hydration degree increases by 40% from TG analysis and 43.8% from the isothermal calorimetry test when LS4 partially replaces cement. The promotion effect can be attributed to the dilution effect (w/c increase) when cement is partially replaced by LS1 [174], and additional improvement is provided by the nucleation effect when LS is finer [219]. Hydration degrees at different specific surface areas are diagramed in Fig. 4.85. It is seen that hydration degrees are enhanced in proportion with specific areas except for pure cement. These deviations prove the dilution effect, while the proportional increase Table 4.41 Hydration degrees (%) at 24 h calculated from both methods Sample

Control

P-LS1

P-LS2

P-LS3

P-LS4

From hydration heat

19.2

21.6

22.8

26.3

28.2

From non-evaporable water content

21.0

25.5

27.7

29.4

30.2

4.6 Microstructure of Concrete with Manufactured Sand

229

Fig. 4.85 Hydration degrees versus specific areas, reprinted from ref. [14], copyright 1989, with permission from American Society of Civil Engineers

indicates the additional nucleation contribution. This contribution provides additional sites on the LS surface for hydrates precipitation, reducing the energy barrier to precipitate from the pore solution [220]. As a result, hydration is accelerated.

4.6.2 Pore Structure As we all know, concrete is a kind of porous material with a complex pore structure and wide distribution scale. The pore structure of concrete significantly impacts mechanical and transmission performances. Many articles have pointed out that concrete’s mechanical properties and durability with MS are different from those with natural sand [127, 221–224]. This can be attributed to the difference in particle shape, grading, fines content, etc., between MS and natural sand and the difference in the pore structure of the concrete due to these differences in properties. Zhao et al. adopted the MIP technique to investigate the effect of water to cement ratio and sand to cement ratio on the pore structure of MS mortar and natural sand mortar [225]. They found that the porosity of MS mortar is higher than that of natural sand at the same mix proportion. On the contrary, the probable pore size and threshold radius of MS mortar are finer. Besides, the probable pore size and threshold radius increased with increasing water to cement ratio and sand to cement ratio. Tian et al. also found that threshold diameter increases with increasing sand to cement and water to cement ratios. The threshold region (Region II) becomes flattened and horizontal, increasing sand concentration in MS mortar. They thought this was mainly because of the reorientation effect of fine aggregates on pore structure. Shen et al. [226] found that the pore diameters of concrete with MS are mainly distributed between 0 and 50 nm, and the percentage of pore diameters (>200 nm) is less than that of RS concrete. The porosity of concrete with MS is lower than that of river sand. The most

230

4 Properties and Microstructure of Concrete with Manufactured Sand

Fig. 4.86 ITZ of concrete with manufactured sand and river sand, reprinted from ref. [226], copyright 2018, with permission from American Society of Civil Engineers

probable pore size of concrete with river sand and MSB is 24.42 nm and 21.34 nm, respectively.

4.6.2.1

Morphology

Current research proves that concrete compactness with MS is higher than concrete with natural sand at the same mix proportion. Mane et al. [227] pointed out that 60% percentage replacement of natural sand by MS improves the microstructure of concrete compared to concrete without any pozzolanic materials. Shen et al. [226] found that the concrete with MS has a narrower interfacial transition zone (ITZ) than natural sand. Additionally, only a small amount of Aft is found in the ITZ of concrete with MS, while a lot of stick Aft, Afm, and portlandite crystal existed in that with natural sand. Similar results were observed by Yang et al. [228]. This is mainly due to the multi-angled and rougher surface of MS. On the one hand, a multiangled shape may cause the interlocking between MS particles. On the other hand, the rough surface and edges of MS are beneficial for the bonding between the paste and aggregate.

References

231

4.7 Concluding Remarks This chapter introduces the workability, mechanical property, durability, and microstructure of concrete with MS. This contributes to understanding the difference between concrete with MS and concrete with natural sand. This also supports the development, design, and application of HPC with MS. (1) The characteristics of MS, including fines content, fines fineness, particle shape, grading, and clay content, significantly influence concrete’s workability and rheological properties. Based on the theory of slurry thickness, a multi-level rheological prediction model considering particle shape is proposed, which can effectively predict the rheological properties of concrete with MS. (2) The characteristics of MS have similar influences on concrete’s compressive strength and modulus. It is found that the static elastic modulus of concrete with MS has a linear relationship with the square root of compressive strength. In addition, it is also found that fines and MS have the same positive and negative effects on HPC with MS. (3) The durability, including crack resistance, impermeability, freeze–thaw resistance, sulfate erosion resistance, acid erosion resistance, dimensional stability, and the alkali-aggregate reaction of concrete with MS are introduced. This will be helpful for reference in related engineering applications. (4) A multi-level viscosity model, a multi-level modulus model, and a multilevel diffusion model considering the particle shape and the effect of fines are proposed to predict the viscosity, modulus, and diffusion properties of mortar with MS. (5) The XRD pattern shows that fines does not react with cement within 24 h, but promotes cement hydration. Isothermal calorimetry and TG-DSC analysis further quantitatively demonstrate the acceleration and amplification effect of fines on cement hydration. Under the same mix ratio, the porosity of concrete with MS is higher than that with natural sand. The interface transition zone of concrete with MS is narrower than that of concrete with natural sand.

References 1. P. Quiroga, The effect of the aggregates characteristics on the performance of Portland cement concrete (2003) 2. G. Tattersall, Workability and Quality Control of Concrete (CRC Press, 1991) 3. V.A. Hackley, C.F. Ferraris, Guide to rheological nomenclature: measurements in ceramic particulate systems (2001) 4. M. Sonebi, Report on measurements of workability and rheology of fresh concrete (2008) 5. B.-X. Li, J.-l. Wang, M.-K. Zhou, C60 high performance concrete prepared from manufactured sand with a high content of microfines. Key Eng. Mater. 405–406, 204 (2009) 6. J. Wang, Research of effects and mechanism of manufactured sand characteristics on Portland cement concrete (Wuhan University of Technology, 2008)

232

4 Properties and Microstructure of Concrete with Manufactured Sand

7. C. Marek, Importance of fine aggregate shape and grading on properties of concrete, in Proceedings of the Proceedings of the Third Annual International Center for Aggregates Research (1995) 8. J. Mewis, N.J. Wagner, Current trends in suspension rheology. J. Non-Newton Fluid 157(3), 147–150 (2009) 9. K. Vance, A. Kumar, G. Sant, N. Neithalath, The rheological properties of ternary binders containing Portland cement, limestone, and metakaolin or fly ash. Cem. Concr. Res. 52, 196–207 (2013) 10. J.W. Bullard, H.M. Jennings, R.A. Livingston, A. Nonat, G.W. Scherer, J.S. Schweitzer, K.L. Scrivener, J.J. Thomas, Mechanisms of cement hydration. Cem. Concr. Res. 41(12), 1208–1223 (2011) 11. N. Roussel, A. Lemaître, R.J. Flatt, P. Coussot, Steady state flow of cement suspensions: a micromechanical state of the art. Cem. Concr. Res. 40(1), 77–84 (2010) 12. K. Vance, A. Arora, G. Sant, N. Neithalath, Rheological evaluations of interground and blended cement–limestone suspensions. Constr. Build. Mater. 79, 65–72 (2015) 13. R.A. Schankoski, R. Pilar, L.R. Prudêncio Jr., R.D. Ferron, Evaluation of fresh cement pastes containing quarry by-product powders. Constr. Build. Mater. 133, 234–242 (2017) 14. Q. Ren, M. Xie, X. Zhu, Y. Zhang, Z. Jiang, Role of limestone powder in early-age cement paste considering fineness effects. J. Mater. Civ. Eng. 32(10), 04020289 (2020) 15. J.J. Chen, A.K.H. Kwan, Superfine cement for improving packing density, rheology and strength of cement paste. Cem. Concr. Compos. 34(1), 1–10 (2012) 16. T. Vuk, V. Tinta, R. Gabrovšek, V. Kauˇciˇc, The effects of limestone addition, clinker type and fineness on properties of Portland cement. Cem. Concr. Res. 31(1), 135–139 (2001) 17. D.P. Bentz, C.F. Ferraris, M.A. Galler, A.S. Hansen, J.M. Guynn, Influence of particle size distributions on yield stress and viscosity of cement-fly ash pastes. Cem. Concr. Res. 42(2), 404–409 (2012) 18. T. Fletcher, C. Chandan, E. Masad, K. Sivakumar, Aggregate imaging system for characterizing the shape of fine and coarse aggregates. Transp. Res. Record J. Transp. Res. Board 1832(1), 67–77 (2003) 19. A.K.H. Kwan, C.F. Mora, H.C. Chan, Particle shape analysis of coarse aggregate using digital image processing. Cem. Concr. Res. 29(9), 1403–1410 (1999) 20. T. Al-Rousan, E. Masad, E. Tutumluer, T.Y. Pan, Evaluation of image analysis techniques for quantifying aggregate shape characteristics. Constr. Build. Mater. 21(5), 978–990 (2007) 21. C.F. Mora, A.K.H. Kwan, Sphericity, shape factor, and convexity measurement of coarse aggregate for concrete using digital image processing. Cem. Concr. Res. 30(3), 351–358 (2000) 22. P.J. Barrett, The shape of rock particles, a critical-review. Sedimentology 27(3), 291–303 (1980) 23. M.A. Taylor, E.J. Garboczi, S.T. Erdogan, D.W. Fowler, Some properties of irregular 3-D particles. Powder Technol. 162(1), 1–15 (2006) 24. L.B. Wang, W.J. Sun, E. Tutumluer, C. Druta, Evaluation of aggregate imaging techniques for quantification of morphological characteristics. Transp. Res. Rec. 2335, 39–49 (2013) 25. E. Masad, J.W. Button, Unified imaging approach for measuring aggregate angularity and texture. Comput-Aided Civ Inf 15(4), 273–280 (2000) 26. R. Cepuritis, S. Jacobsen, B. Pedersen, E. Mortsell, Crushed sand in concrete—effect of particle shape in different fractions and filler properties on rheology. Cem. Concr. Compos. 71, 26–41 (2016) 27. M. Westerholm, B. Lagerblad, J. Silfwerbrand, E. Forssberg, Influence of fine aggregate characteristics on the rheological properties of mortars. Cement Concrete Comp. 30(4), 274– 282 (2008) 28. H. Hafid, G. Ovarlez, F. Toussaint, P.H. Jezequel, N. Roussel, Effect of particle morphological parameters on sand grains packing properties and rheology of model mortars. Cem. Concr. Res. 80, 44–51 (2016)

References

233

29. X. Chateau, G. Ovarlez, K.L. Trung, Homogenization approach to the behavior of suspensions of noncolloidal particles in yield stress fluids. J. Rheol. 52(2), 489–506 (2008) 30. J. Hu, K.J. Wang, Effects of size and uncompacted voids of aggregate on mortar flow ability. J. Adv. Concr. Technol. 5(1), 75–85 (2007) 31. J H. A study of effects of aggregate on concrete rheology (2005) 32. J.O. Hu, K.J. Wang, Effect of coarse aggregate characteristics on concrete rheology. Constr. Build. Mater. 25(3), 1196–1204 (2011) 33. O.A. Cabrera, L.P. Traversa, N.F. Ortega, Effect of crushed sand on mortar and concrete rheology. Mater. Constr. 61(303), 401–416 (2011) 34. H. Barnes, J. Hutton, K. Walters, An Introduction to Rheology (1989) 35. S.T. Erdogan, N.S. Martys, C.F. Ferraris, D.W. Fowler, Influence of the shape and roughness of inclusions on the rheological properties of a cementitious suspension. Cem. Concr. Compos. 30(5), 393–402 (2008) 36. K.D. Kabagire, P. Diederich, A. Yahia, M. Chekired, Experimental assessment of the effect of particle characteristics on rheological properties of model mortar. Constr. Build. Mater. 151, 615–624 (2017) 37. S. Dagois-Bohy, S. Hormozi, E. Guazzelli, O. Pouliquen, Rheology of dense suspensions of non-colloidal spheres in yield-stress fluids. J. Fluid Mech. 776 (2015) 38. J. Galloway, Grading, shape, and surface properties (ASTM special technical publication, 1994) 39. A. Ganaw, A. Ashour, Rheological properties of mortars prepared with different sands. ACI Mater. J. 111(5), 561–568 (2014) 40. T. Kraenkel, D. Lowke, C. Gehlen, Effect of coarse aggregate on properties of self-compacting concrete. Rilem. Proc. 65, 201–211 (2009) 41. R.H. Davis, Y. Zhao, K.P. Galvin, H.J. Wilson, Solid-solid contacts due to surface roughness and their effects on suspension behaviour. Philos. T R. Soc. A 2003(361), 871–894 (1806) 42. C. Servais, R. Jones, I. Roberts, The influence of particle size distribution on the processing of food. J. Food Eng. 51(3), 201–208 (2002) 43. P. Banfill, The influence of fine materials in sand on the rheology of fresh mortar, in Proceedings of the Proceedings of the British Masonry Society (1998) 44. P.F.G. Banfill, Rheological methods for assessing the flow properties of mortar and related materials. Constr. Build. Mater. 8(1), 43–50 (1994) 45. K.K. Daddy, P. Diederich, A. Yahia, M. Chekired, Influence of shape, size, and solid concentration of particles on rheological properties of self-consolidating mortar, in Proceedings of the SCC 2016 8th International RILEM Symposium on Self-Compacting Concrete (2016), p. 429 46. D. Han, J.H. Kim, J.H. Lee, S.T. Kang, Critical grain size of fine aggregates in the view of the rheology of mortar. Int. J. Concr. Struct. Mater. 11(4), 627–635 (2017) 47. B.M. Aissoun, S.D. Hwang, K.H. Khayat, Influence of aggregate characteristics on workability of superworkable concrete. Mater. Struct. 49(1–2), 597–609 (2016) 48. T.S. Vu, G. Ovarlez, X. Chateau, Macroscopic behavior of bidisperse suspensions of noncolloidal particles in yield stress fluids. J. Rheol. 54(4), 815–833 (2010) 49. Q. Ren, L.C. Ding, X.D. Dai, Z.W. Jiang, G. Ye, G. De Schutter (2021) Determination of specific surface area of irregular aggregate by random sectioning and its comparison with conventional methods. Constr. Build. Mater. 273 50. C.Y. Kuo, R.B. Freeman, Imaging indices for quantification of shape, angularity, and surface texture of aggregates. Geomaterials 2000 (1721), 57–65 (2000) 51. V.K. Bui, Y. Akkaya, S.P. Shah, Rheological model for self-consolidating concrete. ACI Mater. J. 99(6), 549–559 (2002) 52. J.W. Peng, D.H. Deng, Q. Yuan, L. Fang, Y. Wang, Effect of fine sand on the rheology of fresh cement asphalt mortar. Adv Mater Res-Switz 1049, 285–293 (2014) 53. A.K.H. Kwan, L.G. Li, Combined effects of water film thickness and paste film thickness on rheology of mortar. Mater. Struct. 45(9), 1359–1374 (2012)

234

4 Properties and Microstructure of Concrete with Manufactured Sand

54. C.F. Ferraris, J.M. Gaidis, Connection between the rheology of concrete and rheology of cement paste. ACI Mater. J. 89(4), 388–393 (1992) 55. J.H. Lee, J.H. Kim, J.Y. Yoon, Prediction of the yield stress of concrete considering the thickness of excess paste layer. Constr. Build. Mater. 173, 411–418 (2018) 56. C.F. Ferraris, N.S. Martys, Relating fresh concrete viscosity measurements from different rheometers. J Res Natl Inst Stan 108(3), 229–234 (2003) 57. K. Day, Concrete mix design, quality control and specification (2006) 58. W.Q. Zuo, J.P. Liu, Q. Tian, W. Xu, W. She, P. Feng, C.W. Miao, Optimum design of lowbinder self-compacting concrete based on particle packing theories. Constr. Build. Mater. 163, 938–948 (2018) 59. Q. Ren, Y. Tao, D. Jiao, Z. Jiang, G. Ye, G. De Schutter, Plastic viscosity of cement mortar with manufactured sand as influenced by geometric features and particle size. Cem. Concr. Compos. 122, 104163 (2021) 60. L. Heymann, S. Peukert, N. Aksel, On the solid-liquid transition of concentrated suspensions in transient shear flow. Rheol. Acta 41(4), 307–315 (2002) 61. K.D. Kabagire, A. Yahia, M. Chekired, Toward the prediction of rheological properties of self-consolidating concrete as diphasic material. Constr. Build. Mater. 195, 600–612 (2019) 62. D. Kabagire, P. Diederich, A. Yahia, New insight into the equivalent concrete mortar approach for self-consolidating concrete. J. Sustain. Cement Mater. 1–10 (2015) 63. S. Nishibayashi, A. Yoshino, S. Inoue, T. Kuroda, Effect of properties of mix constituents on rheological constants of self-compacting concrete, in Production Methods and Workability of Concrete (CRC Press, 1996), p. 8 64. V. Bui, D. Montgomery, Mixture proportioning method for self-compacting high performance concrete with minimum paste volume, in Proceedings of the First International RILEM Symposium on Self-Compacting Concrete (1999), pp. 373–384 65. A.K.H. Kwan, J.J. Chen, Adding fly ash microsphere to improve packing density, flowability and strength of cement paste. Powder Technol. 234, 19–25 (2013) 66. A.K.H. Kwan, Y. Li, Effects of fly ash microsphere on rheology, adhesiveness and strength of mortar. Constr. Build. Mater. 42, 137–145 (2013) 67. A.K.H. Kwan, P.L. Ng, K.Y. Huen, Effects of fines content on packing density of fine aggregate in concrete. Constr. Build. Mater. 61, 270–277 (2014) 68. S.K. Ling, A.K.H. Kwan, Adding ground sand to decrease paste volume, increase cohesiveness and improve passing ability of SCC. Constr. Build. Mater. 84, 46–53 (2015) 69. Y. Ghasemi, M. Emborg, A. Cwirzen, Effect of water film thickness on the flow in conventional mortars and concrete. Mater. Struct. 52(3) (2019) 70. R.X. Zhang, D.K. Panesar, New approach to calculate water film thickness and the correlation to the rheology of mortar and concrete containing reactive MgO. Constr. Build. Mater. 150, 892–902 (2017) 71. A.K.H. Kwan, L.G. Li, Combined effects of water film, paste film and mortar film thicknesses on fresh properties of concrete. Constr. Build. Mater. 50, 598–608 (2014) 72. F. de Larrard, T. Sedran, Optimization of ultra-high-performance concrete by the use of a packing model. Cem. Concr. Res. 24(6), 997–1009 (1994) 73. L.G. Li, A.K.H. Kwan, Concrete mix design based on water film thickness and paste film thickness. Cement Concrete Comp 39, 33–42 (2013) 74. L.G. Li, A.K.H. Kwan, Mortar design based on water film thickness. Constr. Build. Mater. 25(5), 2381–2390 (2011) 75. J.J. Li, Y.H. Chen, C.J. Wan, A mix-design method for lightweight aggregate self-compacting concrete based on packing and mortar film thickness theories. Constr. Build. Mater. 157, 621–634 (2017) 76. A. Schwartzentruber, C. Catherine, Method of the concrete equivalent mortar (CEM)—a new tool to design concrete containing admixture. Mater. Struct. 33(232), 475–482 (2000) 77. T.K. Erdem, K.H. Khayat, A. Yahia, Correlating rheology of self-consolidating concrete to corresponding concrete-equivalent mortar. ACI Mater. J. 106(2), 154–160 (2009)

References

235

78. K. Khayat, S.-D. Hwang, Effect of high-range water-reducing admixture type on performance of self-consolidating concrete. Special Publication 239, 185–200 (2006) 79. F.J. Rubio-Hernández, J.F. Velázquez-Navarro, L.M. Ordóñez-Belloc, Rheology of concrete: a study case based upon the use of the concrete equivalent mortar. Mater. Struct. 46(4), 587–605 (2013) 80. J.J. Assaad, E. Chakar, Relationships between key ASTM test methods determined on concrete and concrete-equivalent-mortar mixtures. J. ASTM Int. 6(3), 1–13 (2009) 81. I.M. Krieger, T.J. Dougherty, A mechanism for non-Newtonian flow in suspensions of rigid spheres. Trans. Soc. Rheol. 3(1), 137–152 (1959) 82. F. Mahaut, S. Mokeddem, X. Chateau, N. Roussel, G. Ovarlez, Effect of coarse particle volume fraction on the yield stress and thixotropy of cementitious materials. Cem. Concr. Res. 38(11), 1276–1285 (2008) 83. Z. Toutou, N. Roussel, Multi scale experimental study of concrete rheology: from water scale to gravel scale. Mater. Struct. 39(2), 189–199 (2006) 84. R. Farris, Prediction of the viscosity of multimodal suspensions from unimodal viscosity data. Trans. Soc. Rheol. 12(2), 281–301 (1968) 85. C. Hu, F. de Larrard, The rheology of fresh high-performance concrete. Cem. Concr. Res. 26(2), 283–294 (1996) 86. D.B. Genovese, J.E. Lozano, M.A. Rao, The rheology of colloidal and noncolloidal food dispersions. J. Food Sci. 72(2), R11–R20 (2007) 87. Tests for mechanical and physical properties of aggregates—part 3: determination of loose bulk density and voids (1998) 88. J.E. Wallevik, Minimizing end-effects in the coaxial cylinders viscometer: viscoplastic flow inside the ConTec BML viscometer 3. J. Non-Newton Fluid 155(3), 116–123 (2008) 89. J.E. Wallevik, Relationship between the Bingham parameters and slump. Cem. Concr. Res. 36(7), 1214–1221 (2006) 90. D. Feys, G. Heirman, G. De Schutter, R. Verhoeven, L. Vandewalle, D. Van Gemert, Comparison of two concrete rheometers for shear thickening behaviour of SCC, in Proceedings of the Proceedings of the 5th International RILEM Symposium on Self-Compacting Concrete (SCC2007) (2007), pp. 365–370 91. J.P. Goncalves, L.M. Tavares, R.D. Toledo, E.M.R. Fairbain, E.R. Cunha, Comparison of natural and manufactured fine aggregates in cement mortars. Cem. Concr. Res. 37(6), 924–932 (2007) 92. A.B. Metzner, Rheology of suspensions in polymeric liquids. J. Rheol. 29(6), 739–775 (1985) 93. T. Chai, R.R. Draxler, Root mean square error (RMSE) or mean absolute error (MAE)?— arguments against avoiding RMSE in the literature. Geosci. Model Dev. 7(3), 1247–1250 (2014) 94. M. Pala, E. Ozbay, A. Oztas, M.I. Yuce, Appraisal of long-term effects of fly ash and silica fume on compressive strength of concrete by neural networks. Constr. Build. Mater. 21(2), 384–394 (2007) 95. Z.A. Liu, M.K. Zhou, B.X. Li, Relationships between modified methylene blue value of microfines in manufactured sand and concrete properties. J. Wuhan Univ. Technol. 31(3), 574–581 (2016) 96. L.I. Jian, Y. Xie, B. Liu, X. Xue, Study on the preparation technology of concrete containing limestone aggregate chips. J. Build. Mater. 4(1), 89–92 (2001) 97. L. Fenglan, Z. Qian, X. Yangyang, Experimental study on high-strength concrete mixed with proto-machine-made sand. Water Resour. Hydropower Eng. 41(7), 76–78 (2010) 98. C. Biao, W. Jiliang, Y. Yuhui, Z. Mingkai, Effects of stone-dust on resistance to chlorine ion permeating and volume stability of C80 manufactured-sand concrete. J. Wuhan Univ. Technol. 29(8), 41–43 (2007) 99. L. Jianping, Prediction of the elastic moduli of cement-based materials (Zhejiang University of Technology, 2008) 100. Y. Qing, A numerical modeling method for predicting the elastic modulus of cement paste (Zhejiang University of Technology, 2013)

236

4 Properties and Microstructure of Concrete with Manufactured Sand

101. L. Jiang, Structural characteristics of ITZ and prediction of elastic modulus of concrete (Zhejiang University of Technology, 2005) 102. P.K. Mehta, P.-C. Aïtcin, Principles underlying production of high-performance concrete. Cement Concrete Aggreg. 12(2), 70–78 (1990) 103. P.K. Mehta, Concrete technology at the crossroads–problems and opportunities. Special Publ. 144, 1–30 (1994) 104. R.W. Burrows, The visible and invisible cracking of concrete (1998) 105. K. Wiegrink, S. Marikunte, S.P. Shah, Shrinkage cracking of high-strength concrete. Mater. J. 93(5), 409–415 (1996) 106. D. McDonald, P. Krauss, E. Rogalla, Early-age transverse deck cracking. Concr. Int. 17(5), 49–51 (1995) 107. R. Bloom, A. Bentur, Free and restrained shrinkage of normal and high-strength concretes. ACI Mater. J. 92(2), 211–217 (1995) 108. J.K. Kim, C.S. Lee, C.K. Park, S.H. Eo, The fracture characteristics of crushed limestone sand concrete. Cem. Concr. Res. 27(11), 1719–1729 (1997) 109. W. Jiliang, Z. Mingkai, H. Tusheng, K. Guoju, C. Gong, Effects of stone dust on resistance to chloride ion permeation and resistance to freezing of manufactured sand concrete. J. Chinese Silicate Soc. 36(4), 482–486 (2008) 110. A.M. Neville, Properties of concrete, vol. 4 (Longman London, 1995) 111. V. Moskvin, F. Ivanov, S. Alekseev, E. Guzeev, Corrosion of concrete and reinforced concrete, methods of their protection (M.: Stroyizdat, 1980) 112. T.E. Stanton, Expansion of concrete through reaction between cement and aggregate (2008) 113. V. Bonavetti, H. Donza, G. Menendez, O. Cabrera, E.F. Irassar, Limestone filler cement in low w/c concrete: a rational use of energy. Cem. Concr. Res. 33(6), 865–871 (2003) 114. R. Talero, C. Pedrajas, M. Gonzalez, C. Aramburo, A. Blazquez, V. Rahhal, Role of the filler on Portland cement hydration at very early ages: rheological behaviour of their fresh cement pastes. Constr. Build. Mater. 151, 939–949 (2017) 115. Z.Q. Xiong, P. Wang, Y.L. Wang, Hydration behaviors of Portland cement with different lithologic stone powders. Int. J. Concr. Struct. M 9(1), 55–60 (2015) 116. J.M. Brader, Nonlinear rheology of colloidal dispersions. J. Phys. Condens. Matter 22(36), 363101 (2010) 117. Z. Zhou, J. Scales, V. Boger, Chemical and physical control of the rheology of concentrated metal oxide suspensions. Chem. Eng. Sci. 56(9), 2901–2920 (2001) 118. K.D. Qin, A.A. Zaman, Viscosity of concentrated colloidal suspensions: comparison of bidisperse models. J. Colloid Interf. Sci. 266(2), 461–467 (2003) 119. L.B. Wang, J.Y. Park, Y.R. Fu, Representation of real particles for DEM simulation using X-ray tomography. Constr. Build. Mater. 21(2), 338–346 (2007) 120. A. Breki, M. Nosonovsky, Einstein’s viscosity equation for nanolubricated friction. Langmuir 34(43), 12968–12973 (2018) 121. A. Einstein Eine neue bestimmung der moleküldimensionen (ETH Zurich, 1905) 122. D. Quemada, C. Berli, Energy of interaction in colloids and its implications in rheological modeling. Adv. Colloid Interf. Sci. 98(1), 51–85 (2002) 123. S. Mueller, E.W. Llewellin, H.M. Mader, The rheology of suspensions of solid particles. P. Roy. Soc. A Math. Phys. 466(2116), 1201–1228 (2010) 124. G.B. Jeffery, The motion of ellipsoidal particles immersed in a viscous fluid, in Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character 102(715), 161–179 (1922) 125. P.K. Senapati, D. Panda, A. Parida, Predicting viscosity of limestone–water slurry. J. Minerals Mater. Character. Eng. 8(03), 203 (2009) 126. T.H. Kuo, H.H. Pan, G.J. Weng, Micromechanics-based predictions on the overall stress-strain relations of cement-matrix composites. J. Eng. Mech. 134(12), 1045–1052 (2008) 127. P.A. Jadhav, D.K. Kulkarni, An experimental investigation on the properties of concrete containing manufactured sand. Int. J. Adv. Eng. Technol. 3(2), 101–104 (2012)

References

237

128. F. Fabro, G.P. Gava, H.B. Grigoli, L.C. Meneghetti, Influence of fine aggregates particle shape in the concrete properties 4, 191–212 (2011) 129. Z.M. Wang, A.K.H. Kwan, H.C. Chan, Mesoscopic study of concrete I: generation of random aggregate structure and finite element mesh. Comput. Struct. 70(5), 533–544 (1999) 130. A.R. Mohamed, W. Hansen, Micromechanical modeling of concrete response under static loading—part 1: model development and validation. ACI Mater. J. 96(2), 196–203 (1999) 131. T.C. Powers, T.L. Brownyard, Studies of the physical properties of hardened Portland cement paste, in Proceedings of the Journal Proceedings (1946), pp. 101–132 132. D.P. Bentz, E.F. Irassar, B. Bucher, W.J. Weiss, Limestone fillers to conserve cement in low w/cm concretes: an analysis based on powers’ model. Concrete Int. 31(11 and 12), 41–46 and 35–39 (2009) 133. D.P. Bentz, E.F. Irassar, B.E. Bucher, W.J. Weiss, Limestone fillers conserve cement; part 1: an analysis based on powers’ model. Concr. Int. 31(11), 41–46 (2009) 134. Q. Chen, H.H. Zhu, J.W. Ju, F. Guo, L.B. Wang, Z.G. Yan, T. Deng, S. Zhou, A stochastic micromechanical model for multiphase composites containing spherical inhomogeneities. Acta Mech. 226(6), 1861–1880 (2015) 135. W.A. Klemm, L.D. Adams, An investigation of the formation of carboaluminates (ASTM International, 1990) 136. D.P. Bentz, Modeling the influence of limestone filler on cement hydration using CEMHYD3D. Cem. Concr. Compos. 28(2), 124–129 (2006) 137. L. Stefan, F. Benboudjema, J.-M. Torrenti, B. Bissonnette, Prediction of elastic properties of cement pastes at early ages. Comput. Mater. Sci. 47(3), 775–784 (2010) 138. C. Haecker, E.J. Garboczi, J.W. Bullard, R.B. Bohn, Z. Sun, S.P. Shah, T. Voigt, Modeling the linear elastic properties of Portland cement paste. Cem. Concr. Res. 35(10), 1948–1960 (2005) 139. J.S. Qian, C.J. Shi, Z. Wang, Activation of blended cements containing fly ash. Cem. Concr. Res. 31(8), 1121–1127 (2001) 140. V. Palchik, Y.H. Hatzor, Crack damage stress as a composite function of porosity and elastic matrix stiffness in dolomites and limestones. Eng. Geol. 63(3–4), 233–245 (2002) 141. J.W. Kim, M.S. Kim, P.G. Kim, S.J. Nor, C. Park, Y.D. Jo, S.G. Park, The mechanical properties of limestones distributed in Jecheon. Tunnel Underground Space 22(5), 354–364 (2012) 142. J.A. Wang, J. Lubliner, P.J.M. Monteiro, Effect of ice formation on the elastic-moduli of cement paste and mortar. Cem. Concr. Res. 18(6), 874–885 (1988) 143. Z.H. Tian, J.W. Bu, Mathematical model relating uniaxial compressive behavior of manufactured sand mortar to MIP-derived pore structure parameters. Sci. World J. (2014) 144. R.N. Swamy, Dynamic Poisson’s ratio of portland cement paste, mortar and concrete. Cem. Concr. Res. 1(5), 559–583 (1971) 145. D.P. Bentz, E.J. Garboczi, E.S. Lagergren, Multi-scale microstructural modeling of concrete diffusivity: identification of significant variables. Cement Concrete Aggreg. 20, 129–139 (1998) 146. J.J. Zheng, C.Y. Zhang, Y.F. Wu, L.Z. Sun, Random-walk algorithm for chloride diffusivity of concrete with aggregate shape effect. J. Mater. Civil Eng. 28(12) (2016) 147. L.Y. Li, J. Xia, S.S. Lin, A multi-phase model for predicting the effective diffusion coefficient of chlorides in concrete. Constr. Build. Mater. 26(1), 295–301 (2012) 148. X.L. Du, L. Jin, G.W. Ma, A meso-scale numerical method for the simulation of chloride diffusivity in concrete. Finite Elem. Anal. Des. 85, 87–100 (2014) 149. B. Savija, M. Lukovic, E. Schlangen, Lattice modeling of rapid chloride migration in concrete. Cem. Concr. Res. 61–62, 49–63 (2014) 150. Y.P. Xi, Z.P. Bazant, Modeling chloride penetration in saturated concrete. J. Mater. Civil Eng. 11(1), 58–65 (1999) 151. S. Care, E. Herve, Application of a n-phase model to the diffusion coefficient of chloride in mortar. Transport Porous Med. 56(2), 119–135 (2004) 152. H.L. Duan, B.L. Karihaloo, J. Wang, X. Yi, Effective conductivities of heterogeneous media containing multiple inclusions with various spatial distributions. Phys. Rev. B 73(17) (2006)

238

4 Properties and Microstructure of Concrete with Manufactured Sand

153. Y.C. Choi, B. Park, G.S. Pang, K.M. Lee, S. Choi, Modelling of chloride diffusivity in concrete considering effect of aggregates. Constr. Build. Mater. 136, 81–87 (2017) 154. R.A. Patel, Lattice Boltzmann method based framework for simulating physico-chemical processes in heterogeneous porous media and its application to cement paste (Ghent University, 2016) 155. J.J.J. Zheng, Z.Q.Q. Guo, X.F.F. Huang, P. Stroeven, L.J. Sluys, ITZ volume fraction in concrete with spheroidal aggregate particles and application: part II. Prediction of the chloride diffusivity of concrete. Mag. Concrete Res. 63(7), 483–491 (2011) 156. L. Liu, D.J. Shen, H.S. Chen, W.X. Xu, Aggregate shape effect on the diffusivity of mortar: a 3D numerical investigation by random packing models of ellipsoidal particles and of convex polyhedral particles. Comput. Struct. 144, 40–51 (2014) 157. J.J. Zheng, X.Z. Zhou, Y.F. Wu, X.Y. Jin, A numerical method for the chloride diffusivity in concrete with aggregate shape effect. Constr. Build. Mater. 31, 151–156 (2012) 158. J.J. Zheng, X.Z. Zhou, Effective medium method for predicting the chloride diffusivity in concrete with ITZ percolation effect. Constr. Build. Mater. 47, 1093–1098 (2013) 159. J.J. Zheng, X.Z. Zhou, X.F. Huang, C.Q. Fu, Experiment and modeling of the effect of aggregate shape on the chloride diffusivity of concrete. J. Mater. Civil Eng. 26(9) (2014) 160. A.A. Hamami, P. Turcry, A. Ait-Mokhtar, Influence of mix proportions on microstructure and gas permeability of cement pastes and mortars. Cem. Concr. Res. 42(2), 490–498 (2012) 161. Q.T. Phung, N. Maes, D. Jacques, E. Bruneel, I. Van Driessche, G. Ye, G. De Schutter, Effect of limestone fillers on microstructure and permeability due to carbonation of cement pastes under controlled CO2 pressure conditions. Constr. Build. Mater. 82, 376–390 (2015) 162. H. Hornain, J. Marchand, V. Dohot, M. Moranvilleregourd, Diffusion of chloride-ions in limestone filler blended cement pastes and mortars. Cem. Concr. Res. 25(8), 1667–1678 (1995) 163. R. Cherif, A.A. Hamami, A. Ait-Mokhtar, J.F. Meusnier, Study of the pore solution and the microstructure of mineral additions blended cement pastes. Energy Proc. 139, 584–589 (2017) 164. B. Lothenbach, G. Le Saout, E. Gallucci, K. Scrivener, Influence of limestone on the hydration of Portland cements. Cem. Concr. Res. 38(6), 848–860 (2008) 165. T. Matschei, B. Lothenbach, F.P. Glasser, The role of calcium carbonate in cement hydration. Cem. Concr. Res. 37(4), 551–558 (2007) 166. M. Zajac, A. Rossberg, G. Le Saout, B. Lothenbach, Influence of limestone and anhydrite on the hydration of Portland cements. Cem. Concr. Compos. 46, 99–108 (2014) 167. A. Scholer, B. Lothenbach, F. Winnefeld, M. Zajac, Hydration of quaternary Portland cement blends containing blast-furnace slag, siliceous fly ash and limestone powder. Cement Concrete Comp. 55, 374–382 (2015) 168. L. Pelletier-Chaignat, F. Winnefeld, B. Lothenbach, C.J. Muller, Beneficial use of limestone filler with calcium sulphoaluminate cement. Constr. Build. Mater. 26(1), 619–627 (2012) 169. K. Wu, H.S. Shi, L.L. Xu, G. Ye, G. De Schutter, Microstructural characterization of ITZ in blended cement concretes and its relation to transport properties. Cem. Concr. Res. 79, 243–256 (2016) 170. H.J. Du, S.D. Pang, Enhancement of barrier properties of cement mortar with graphene nanoplatelet. Cem. Concr. Res. 76, 10–19 (2015) 171. G. Ye, X. Liu, G. De Schutter, A.M. Poppe, L. Taerwe, Influence of limestone powder used as filler in SCC on hydration and microstructure of cement pastes. Cement Concrete Comp. 29(2), 94–102 (2007) 172. A.M. Poppe, G. De Schutter, Cement hydration in the presence of high filler contents. Cem. Concr. Res. 35(12), 2290–2299 (2005) 173. V.T. Ngala, C.L. Page, Effects of carbonation on pore structure and diffusional properties of hydrated cement pastes. Cem. Concr. Res. 27(7), 995–1007 (1997) 174. M. Cyr, P. Lawrence, E. Ringot, Efficiency of mineral admixtures in mortars: quantification of the physical and chemical effects of fine admixtures in relation with compressive strength. Cem. Concr. Res. 36(2), 264–277 (2006)

References

239

175. Q. Ren, Z.W. Jiang, H.X. Li, X.P. Zhu, Q. Chen, Fresh and hardened properties of selfcompacting concrete using silicon carbide waste as a viscosity-modifying agent. Constr. Build. Mater. 200, 324–332 (2019) 176. B. Craeye, G. De Schutter, B. Desmet, J. Vantomme, G. Heirman, L. Vandewalle, O. Cizer, S. Aggoun, E.H. Kadri, Effect of mineral filler type on autogenous shrinkage of self-compacting concrete. Cem. Concr. Res. 40(6), 908–913 (2010) 177. G. De Schutter, Effect of limestone filler as mineral addition in self-compacting concrete, in Proceedings of the 36th Conference on Our World in Concrete & Structures: ‘Recent Advances in the Technology of Fesh Concrete’ (OWIC’S 2011) (2011), pp. 49–54 178. K. Wu, L.L. Xu, G. De Schutter, H.S. Shi, G. Ye, Influence of the interfacial transition zone and interconnection on chloride migration of portland cement mortar. J. Adv. Concr. Technol. 13(3), 169–177 (2015) 179. D.N. Winslow, M.D. Cohen, D.P. Bentz, K.A. Snyder, E.J. Garboczi, Percolation and pore structure in mortars and concrete—reply. Cem. Concr. Res. 24(8), 1569–1581 (1994) 180. A. Delagrave, J.P. Bigas, J.P. Ollivier, J. Marchand, M. Pigeon, Influence of the interfacial zone on the chloride diffusivity of mortars. Adv. Cem. Mater. 5(3–4), 86–92 (1997) 181. H.S. Wong, M. Zobel, N.R. Buenfeld, R.W. Zimmerman, Influence of the interfacial transition zone and microcracking on the diffusivity, permeability and sorptivity of cement-based materials after drying. Mag. Concrete Res. 61(8), 571–589 (2009) 182. Z.G. Yan, Q. Chen, H.H. Zhu, J.W. Ju, S. Zhou, Z.W. Jiang, A multi-phase micromechanical model for unsaturated concrete repaired using the electrochemical deposition method. Int. J. Solids Struct. 50(24), 3875–3885 (2013) 183. Q. Chen, H.H. Zhu, Z.G. Yan, J.W. Ju, Z.W. Jiang, Y.Q. Wang, A multiphase micromechanical model for hybrid fiber reinforced concrete considering the aggregate and ITZ effects. Constr. Build. Mater. 114, 839–850 (2016) 184. X.J. Yang, J.S. Liu, H.X. Li, L.L. Xu, Q. Ren, L. Li, Effect of triethanolamine hydrochloride on the performance of cement paste. Constr. Build. Mater. 200, 218–225 (2019) 185. Q. Ren, G. De Schutter, Z. Jiang, Q. Chen, Multi-level diffusion model for manufactured sand mortar considering particle shape and limestone powder effects. Constr. Build. Mater. 207, 218–227 (2019) 186. H.H. Zhu, Q. Chen, Z.G. Yan, J.W. Ju, S. Zhou, Micromechanical models for saturated concrete repaired by the electrochemical deposition method. Mater. Struct. 47(6), 1067–1082 (2014) 187. H.H. Zhu, Q. Chen, J.W. Ju, Z.G. Yan, F. Guo, Y.Q. Wang, Z.W. Jiang, S. Zhou, B. Wu, Maximum entropy-based stochastic micromechanical model for a two-phase composite considering the inter-particle interaction effect. Acta Mech. 226(9), 3069–3084 (2015) 188. Q. Chen, Z.W. Jiang, Z.H. Yang, H.H. Zhu, J.W. Ju, Z.G. Yan, Y.Q. Wang, Differential-scheme based micromechanical framework for saturated concrete repaired by the electrochemical deposition method. Mater. Struct. 49(12), 5183–5193 (2016) 189. Q. Chen, M.M. Nezhad, Q. Fisher, H.H. Zhu, Multi-scale approach for modeling the transversely isotropic elastic properties of shale considering multi-inclusions and interfacial transition zone. Int. J. Rock Mech. Min. 84, 95–104 (2016) 190. Y.Y. Huang, C. Xu, H.X. Li, Z.W. Jiang, Z.Q. Gong, X.J. Yang, Q. Chen, Utilization of the black tea powder as multifunctional admixture for the hemihydrate gypsum. J. Clean. Prod. 210, 231–237 (2019) 191. G.W. Sun, Y.S. Zhang, W. Sun, Z.Y. Liu, C.H. Wang, Multi-scale prediction of the effective chloride diffusion coefficient of concrete. Constr. Build. Mater. 25(10), 3820–3831 (2011) 192. E. Garboczi, D. Bentz, Computer simulation of the diffusivity of cement-based materials. J. Mater. Sci. 27(8), 2083–2092 (1992) 193. E.J. Garboczi, Permeability, diffusivity, and microstructural parameters—a critical-review. Cem. Concr. Res. 20(4), 591–601 (1990) 194. B.H. Oh, S.Y. Jang, Prediction of diffusivity of concrete based on simple analytic equations. Cem. Concr. Res. 34(3), 463–480 (2004)

240

4 Properties and Microstructure of Concrete with Manufactured Sand

195. K. Nakarai, T. Ishida, K. Maekawa, Multi-scale physicochemical modeling of soilcementitious material interaction. Soils Found. 46(5), 653–663 (2006) 196. J. Van Brakel, P. Heertjes, Analysis of diffusion in macroporous media in terms of a porosity, a tortuosity and a constrictivity factor. Int. J. Heat Mass Transf. 17(9), 1093–1103 (1974) 197. K. Maekawa, T. Ishida, T. Kishi, Multi-scale modeling of concrete performance integrated material and structural mechanics. J. Adv. Concr. Technol. 1(2), 91–126 (2003) 198. E. Herve, A. Zaoui, N-layered inclusion-based micromechanical modelling. Int. J. Eng. Sci. 31(1), 1–10 (1993) 199. E. Hervé, A. Zaoui, Elastic behaviour of multiply coated fibre-reinforced composites. Int. J. Eng. Sci. 33(10), 1419–1433 (1995) 200. E. Hervé, Thermal and thermoelastic behaviour of multiply coated inclusion-reinforced composites. Int. J. Solids Struct. 39(4), 1041–1058 (2002) 201. S. Caré, Influence of aggregates on chloride diffusion coefficient into mortar. Cem. Concr. Res. 33(7), 1021–1028 (2003) 202. X.-F. Huang, J.-J. Zheng, X.-Z. Zhou, Simple analytical solution for the chloride diffusivity of cement paste, vol. 3 (The World of Building Materials, 2010) 203. T. Luping, L.-O. Nilsson, Rapid determination of the chloride diffusivity in concrete by applying an electric field. Mater. J. 89(1), 49–53 (1993) 204. P. Klieger, Carbonate additions to cement (ASTM International, 1990) 205. A. Delagrave, J. Marchand, M. Pigeon, Influence of microstructure on the tritiated water diffusivity of mortars. Adv. Cem. Mater. 7(2), 60–65 (1998) 206. E.P. Nielsen, M.R. Geiker, Chloride diffusion in partially saturated cementitious material. Cem. Concr. Res. 33(1), 133–138 (2003) 207. U. Dilek, M.L. Leming, Deicer salt scaling resistance of concrete containing manufactured sands. J. Test Eval. 35(2), 134–142 (2007) 208. E.J. Garboczi, D.P. Bentz, Multiscale analytical/numerical theory of the diffusivity of concrete. Adv. Cem. Mater. 8(2), 77–88 (1998) 209. E.F. Irassar, D. Violini, V.F. Rahhal, C. Milanesi, M.A. Trezza, V.L. Bonavetti, Influence of limestone content, gypsum content and fineness on early age properties of Portland limestone cement produced by inter-grinding. Cem. Concr. Compos. 33(2), 192–200 (2011) 210. N. Li, L.L. Xu, R. Wang, L. Li, P.M. Wang, Experimental study of calcium sulfoaluminate cement-based self-leveling compound exposed to various temperatures and moisture conditions: hydration mechanism and mortar properties. Cem. Concr. Res. 108, 103–115 (2018) 211. P. Thongsanitgarn, W. Wongkeo, A. Chaipanich, C.S. Poon, Heat of hydration of Portland high-calcium fly ash cement incorporating limestone powder: effect of limestone particle size. Constr. Build. Mater. 66, 410–417 (2014) 212. S. Tsivilis, G. Kakali, E. Chaniotakis, A. Souvaridou, A study on the hydration of portland limestone cement by means of TG. J. Therm. Anal. Calorim. 52(3), 863–870 (1998) 213. Q. Zhang, G. Ye, Quantitative analysis of phase transition of heated Portland cement paste. J. Therm. Anal. Calorim. 112(2), 629–636 (2013) 214. N.Y. Mostafa, P.W. Brown, Heat of hydration of high reactive pozzolans in blended cements: isothermal conduction calorimetry. Thermochim. Acta 435(2), 162–167 (2005) 215. J. Bensted, Some applications of conduction calorimetry to cement hydration. Adv. Cem. Res. 1(1), 35–44 (1987) 216. E.I. Nadelman, K.E. Kurtis, Application of powers’ model to modern Portland and Portland limestone cement pastes. J. Am. Ceram. Soc. 100(9), 4219–4231 (2017) 217. A.K. Schindler, K.J. Folliard, Heat of hydration models for cementitious materials. Aci. Mater. J. 102(1), 24–33 (2005) 218. T.C. Powers, T.L. Brownyard, Studies of the physical properties of hardened Portland cement paste. J. Proc. 43(9), 101–132 (1946) 219. V. Rahhal, V. Bonavetti, L. Trusilewicz, C. Pedrajas, R. Talero, Role of the filler on Portland cement hydration at early ages. Constr. Build. Mater. 27(1), 82–90 (2012)

References

241

220. E. Irassar, Sulfate attack on cementitious materials containing limestone filler—a review. Cem. Concr. Res. 39(3), 241–254 (2009) 221. V. Bhikshma, R. Kishore, C.R. Pathi, Investigations on flexural behavior of high strength manufactured sand concrete, in Challenges, Opportunities and Solutions in Structural Engineering and Construction (CRC Press, 2009), pp. 533–542 222. S.B. Zhao, X.X. Ding, M.S. Zhao, C.Y. Li, S.W. Pei, Experimental study on tensile strength development of concrete with manufactured sand. Constr. Build. Mater. 138, 247–253 (2017) 223. H.J. Li, F.L. Huang, G.Z. Cheng, Y.J. Xie, Y.B. Tan, L.X. Li, Z.L. Yi, Effect of granite dust on mechanical and some durability properties of manufactured sand concrete. Constr. Build. Mater. 109, 41–46 (2016) 224. B.X. Li, J.L. Wang, M.K. Zhou, Effect of limestone fines content in manufactured sand on durability of low- and high-strength concretes. Constr. Build. Mater. 23(8), 2846–2850 (2009) 225. H.T. Zhao, Q. Xiao, D.H. Huang, S.P. Zhang, Influence of pore structure on compressive strength of cement mortar. Sci. World J. (2014) 226. W.G. Shen, Y. Liu, Z.W. Wang, L.H. Cao, D.L. Wu, Y.J. Wang, X.L. Ji, Influence of manufactured sand’s characteristics on its concrete performance. Constr. Build. Mater. 172, 574–583 (2018) 227. K.M. Mane, D.K. Kulkarni, K.B. Prakash, Properties and microstructure of concrete using pozzolanic materials and manufactured sand as partial replacement of fine aggregate. Sn Appl. Sci. 1(9) (2019) 228. R. Yang, R. Yu, Z.H. Shui, C. Guo, S. Wu, X. Gao, S. Peng, The physical and chemical impact of manufactured sand as a partial replacement material in ultra-high performance concrete (UHPC). Cement Concrete Comp. 99, 203–213 (2019)

Chapter 5

Mix Design of Concrete with Manufactured Sand

5.1 Raw Materials 5.1.1 Cement 5.1.1.1

Classifications and Compositions

According to GB 175-2007, ordinary cement includes Portland cement (PI, PII), Portland ordinary cement (PO), Portland pozzolanic cement (PP), Portland fly ash cement (PF), Portland blast-furnace slag cement (PS), and Portland composite cement (PC). The compositions of the common Portland cement are shown in Table 5.1.

5.1.1.2

Strength Grade

In the grinding process, cement with different strengths and characteristics is often added with fly ash, volcanic ash, granulated blast-furnace slag, and even kiln ash in cement kilns, while a large amount of industrial solid waste is disposed at the same time. The strength indexes of cements are listed in Table 5.2.

5.1.1.3

Chemical Indexes

The chemical indexes of cement include insoluble, loss on ignition, sulfur trioxide, magnesium oxide, chloride ion content, etc., which should meet the requirements of Table 5.3.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Z. Jiang, Green High-Performance Concrete with Manufactured Sand, https://doi.org/10.1007/978-981-19-6313-1_5

243

244

5 Mix Design of Concrete with Manufactured Sand

Table 5.1 Compositions of the common Portland cement Codename

Type

PI

Portland cement

PII

Composition Clinker + gypsum

Granulated blast-furnace slag

Pozzolanic material

Fly ash

Limestone

100

–

–

–

–

≥ 95

≤5

–

–

–

≥ 95

–

–

–

≤5

Portland ordinary cement

PO

≥ 80 and < 95

> 5 and ≤

Portland blast-furnace slag cement

PSA

≥ 50 and < 80

> 20 and ≤ 50b

–

–

–

PSB

≥ 30 and < 50

> 50 and ≤ 70b

–

–

–

Portland pozzolanic cement

PP

≥ 60 and < 80

–

> 20 and ≤ – 40c

–

Portland fly ash cement

PF

≥ 60 and < 80

–

–

Portland composite cement

PC

≥ 50 and < 80

> 20 and ≤ 50e

20a

–

> 20 and ≤ – 40d

a

The components are active materials in accordance with GB 175-2007, in which it is allowed to be replaced by inactive mixtures no more than 8% by mass of cement or kiln ash no more than 5% by mass of cement conforming to GB 175-2007 b This is the active material in accordance with GB/T203 or GB/T18046, where substitution of active or inactive material or any material in kiln ash no more than 8% by mass of cement is allowed conforming to GB 175-2007 c This is the active material in accordance with GB/T2847 d This is the active material in accordance with GB/T1596 e This is made up of two or more active materials or/and inactive materials in accordance with GB 175-2007, which is allowed to be replaced by kiln ash in accordance with GB 175-2007 and no more than 8% by the mass of cement

5.1.1.4

Other Indexes

In addition to the strength and chemical composition, there are requirements for alkali content, fineness, setting time, and stability for cement. The content of alkali in cement can be calculated as Na2 O + 0.658K2 O as a selective index. Alkali content in cement should not exceed 0. 60% or be determined by consultation if active aggregate is used. The fineness of cement is also a selective index. The fineness of Portland cement and ordinary Portland cement is assessed by the specific surface area, which should be larger than 300 m2 /kg. The fineness of Portland blast-furnace slag cement, Portland pozzolanic cement, Portland fly ash cement, and composite Portland cement are

5.1 Raw Materials

245

Table 5.2 The strength indexes of various strength grades of cement Type

Strength grade

Portland cement

Ordinary Portland cement

Blast-furnace slag Portland cement Pozzolanic Portland cement Fly ash Portland cement Composite Portland cement

Compressive strength (MPa)

Flexural strength (MPa)

3d

28d

3d

28d

42.5

≥ 17.0

≥ 42.5

≥ 3.5

≥ 6.5

42.5R

≥ 22.0

52.5

≥ 23.0

52.5R

≥ 27.0

62.5

≥ 28.0

62.5R

≥ 32.0

42.5

≥ 17.0

42.5R

≥ 22.0

52.5

≥ 23.0

52.5R

≥ 27.0

32.5

≥ 10.0

32.5R

≥ 15.0

42.5

≥ 15.0

42.5R

≥ 19.0

52.5

≥ 21.0

52.5R

≥ 23.0

≥ 4.0 ≥ 52.5

≥ 4.0

≥ 7.0

≥ 5.0 ≥ 62.5

≥ 5.0

≥ 42.5

≥ 3.5

≥ 8.0

≥ 5.5 ≥ 6.5

≥ 4.0 ≥ 52.5

≥ 4.0

≥ 7.0

≥ 5.0 ≥ 32.5

≥ 2.5

≥ 42.5

≥ 3.5

≥ 5.5

≥ 3.5 ≥ 6.5

≥ 4.0 ≥ 52.5

≥ 4.0

≥ 7.0

≥ 4.5

assessed by the residual percentage. The residue should be less than 10% for the 80 µm square hole sieve or less than 30% for the 45 µm square hole sieve. The open time of concrete is directly affected by the setting time of cement. The initial setting time of Portland cement should be longer than 45 min, and the final setting time should be shorter than 390 min. The initial setting time of ordinary Portland cement, slag Portland cement, volcanic ash Portland cement, fly ash Portland cement, and composite Portland cement should not be less than 45 min, and the final setting time should not be longer than 600 min. The stability of cement is tested by boiling method. The cement with poor stability is forbidden in construction.

5.1.2 Mineral Admixtures 5.1.2.1

Fly Ash

Fly ash is commonly produced by coal ash after combustion in boilers and collected by dust collectors. It is grayish brown, usually acidic, with a specific surface area of 2500–7000 cm2 /g and particle sizes ranging from several hundred microns to several microns. The main components are SiO2 , Al2 O3 , Fe2 O3, CaO, etc.

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5 Mix Design of Concrete with Manufactured Sand

Table 5.3 Chemical indexes of common cement Variety

Codename

Insoluble (wt.)/%

Loss on ignition (wt.)/%

SO3 (wt.)/%

MgO (wt.)/%

Cl− (wt.)/%

Portland cement

PI

≤ 0.75

≤ 3.0

≤ 3.5

≤ 5.0a

≤ 0.06c

PII

≤ 1.50

≤ 3.5

Ordinary Portland cement

PO

–

≤ 5.0

Blast-furnace slag Portland cement

PSA

–

–

≤ 4.0

≤ 6.0b

PSB

–

–

Pozzolanic Portland cement

PP

–

–

Fly ash Portland cement

PF

–

–

Composite Portland cement

PC

–

–

– ≤ 3.5

≤ 6.0b

a

The content (mass fraction) of MgO in cement is allowed to be relaxed to 6.0% if the cement steam test is acceptable b A boiling test should be carried out on the cement to ensure its stability if the MgO content (mass fraction) in the cement is greater than 6.0%

Fly ash is divided into Grades I, II, and III according to its quality. In addition, it can also be divided into type F and type C based on the types of coal. Type F fly ash comes from anthracite or bituminous coal, and type C fly ash comes from lignite or subbituminous coal. The addition of fly ash in concrete reduces the amount of cement and fine aggregate as well as the water consumption for concrete. The workability and pumpability of concrete are also improved. Moreover, the creep, hydration heat, and thermal expansion of concrete are reduced, and the impermeability and modification of concrete are also improved. Table 5.4 shows the technical requirements of fly ash to prepare mortar and concrete.

5.1.2.2

Slag Powder

After being quenched and granulated, molten silicate aluminate produced by blastfurnace ironmaking process turns into a potentially hydraulic material, known as granulated blast-furnace slag, or slag for short. Granulated blast-furnace slag powder is composed of the mixture of granulated blast-furnace slag after grinding together with a small amount of gypsum, referred to as slag powder. Slag powder can be

5.1 Raw Materials

247

Table 5.4 The technical requirements of fly ash for mixing concrete and mortar Technical requirements

Items Fineness (45 µm square hole sieve residue), Type F fly ash not more than/% Type C fly ash Water demand ratio, not more than/%

Type F fly ash

Loss on ignition, not more than/%

Type F fly ash

Grade I

Grade II

Grade III

12.0

25.0

45.0

95

105

115

5.0

8.0

15.0

Type C fly ash Type C fly ash Water content, not more than/%

Type F fly ash

1.0

Type C fly ash SO3 , not more than/%

Type F fly ash

3.0

Free CaO, not more than/%

Type F fly ash

1.0

Type C fly ash

4.0

Type C fly ash

5.0

Type C fly ash

Stability increased distance after boiling Le Chatelier, not more than/mm

divided into three grades: S105, S95, and S75 according to the specific surface area and activity index. The comprehensive properties of concrete and cement can be improved obviously when slag powder has been used as supplementary cementitious materials. As a new admixture of high-performance concrete, slag powder possesses the advantages of improving the performance of concrete as follows: (1) The late strength of cement concrete can be greatly improved, which can reach the strength grade of ultra-high-strength concrete. (2) It can effectively inhibit the alkali-aggregate reaction of concrete and improve the durability of concrete. (3) It is especially suitable for marine engineering due to its positive effect on seawater erosion resistance of concrete. (4) It can significantly reduce the bleeding of concrete and improve the workability of concrete. (5) It can significantly improve the compactness and impermeability of concrete, and it is suitable for mass concrete because the heat of hydration of concrete can be significantly reduced. Table 5.5 lists the technical specifications of slag powder. 5.1.2.3

Silica Fume

Silica fume is the powder material consisting mainly of amorphous, which is collected from the flue port in the process of smelting ferrosilicon alloy or industrial silicon. Silica fume has a density of approximately 2.2 g/cm3 , and it is generally composed of ultra-fine, smooth, glassy spherical particles with a specific surface area between 15,000 and 20,000 m2 /kg. The particle size of most silica fume particles is less than 1 µm, and the average particle size is about 0.1–0.2 µm, about 1/100 of the diameter

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5 Mix Design of Concrete with Manufactured Sand

Table 5.5 Technical indicators of slag powder Grade

Items

S105 Density/gcm–3

≥

S95

S75

2.8

Specific surface area/m3 kg−1 ≥

500

400

300

Active index/% ≥

7d

95

75

55

28d

105

95

105

Fluidity ratio/% ≥

95

Water content (mass fraction)/% ≤

1.0

SO3 (mass fraction)/% ≤

4.0

Cl− (mass fraction)/% ≤

0.06

Ignition loss (mass fraction)/% ≤

3.0

Vitreous content (mass fraction)/% ≥

85

Radioactivity

Qualified

of cement particles. Silica fume particles can be highly dispersed in concrete, filling in the pores and improving the compactness of concrete. Meanwhile, high pozzolanic activity of silica fume leads itself to fast react with calcium hydroxide produced by cement hydration. Therefore, the addition of silica fume can significantly enhance the strength and durability of concrete. Table 5.6 lists the technical requirements for silica fume.

5.1.2.4

Other Mineral Admixtures

(1) Steel slag powder Steel slag is the waste slag produced in the process of steel making. The oxidation products of the elements in the metal charge, the eroded charge and repair materials, the impurities brought by the metal charge, such as mud and sand, and the slag-making materials specially added to adjust the properties of steel slag, such as limestone, dolomite, iron ore, and silica, are the main sources of steel slag. The slag production rate is about 15–20% of the mass of crude steel. According to the process of steelmaking, steel slag can be divided into open hearth slag, converter slag, and electric furnace slag, among which, open hearth slag can be divided into early slag and late slag. Electric furnace slag can also be divided into oxidation slag and reduction slag. About 80% of steel slag in China is converter slag. The workability of concrete can be improved by adding proper amount of steel slag at a low water to binder ratio. However, when the water to binder ratio is high, the excessive addition of steel slag will reduce the segregation resistance of concrete. When steel slag content is less than 20%, the early compressive strength of concrete is lower than that of pure cement concrete, but the compressive strength after 28 days is close to or even slightly higher than that of pure cement concrete.

5.1 Raw Materials Table 5.6 Technical requirements for silica fume

249 Items

Index

Solid content (liquid material)

Production control value ± 2%

Total alkali content (%)

≤ 1.5

SiO2 content (%)

≥ 85.0

Cl content (%)

≤ 0.1

Moisture content (powdery materials) (%)

≤ 3.0

Ignition loss (%)

≤ 4.0

Water demand ratio (%)

≤ 125

Specific surface area (BET method) (m2 /g)

≥ 15

Activity index (7d rapid method) (%)

≥ 105

Radioactivity

I ta ≤ 1.0 and I r ≤ 1.0

Inhibition of alkali-aggregate 14d expansion rate reduction reactivity value ≥ 35% Resistance to chloride ion penetration

28d electric flux ratio ≤ 40%

Note 1 The solid content of silica mortar should be calculated first, and then, the relevant indicators of silica fume should be checked against this table Note 2 Inhibition of alkali-aggregate reactivity and resistance to chloride ion permeability are selective test items, which are determined by agreement between the supplier and the buyer

When the steel slag content exceeds 20%, the compressive strength of concrete decreases with the steel slag content increasing. Moreover, the addition of appropriate steel slag (generally less than 20%) can improve the chloride penetration resistance of concrete, but the effect is not as good as fly ash or slag. (2) Phosphorus slag In the process of preparing yellow phosphorus by electric furnace method, the matter formed by quenching of molten material with calcium silicate as the main component is called granulated electric furnace phosphorus slag, or phosphorus slag for short. The addition of phosphorus slag can prolong the initial and final setting time of concrete slurry, greatly reduce the heat of hydration and shrinkage, and also improve the tensile strength of concrete, ultimate tensile value, durability, and the bond strength between new and old concrete. (3) Kaolin Metakaolin (MK for short) is a kind of volcanic ash material, which is anhydrous aluminum silicate (Al2 O3 ·2SiO2 , AS2 ) formed by dehydration of kaolin

250

5 Mix Design of Concrete with Manufactured Sand

(mainly kaolinite, Al2 O3 ·2SiO2 ·2H2 O, AS2 H2 ) at an appropriate temperature (540– 880 °C). Metakaolin will show cementitious properties under appropriate excitation conditions. Metakaolin is a kind of mineral admixture with high volcanic activity. The active components Al2 O3 and SiO2 in metakaolin can react with Ca(OH)2 produced during cement hydration to form hydration products such as calcium silicate hydrate and calcium aluminate hydrate, thus reducing the alkali content of concrete, reducing or eliminating the alkali-aggregate reaction, and improving the strength of concrete. Metakaolin particles are very fine (less than 10 µm), so it can greatly improve the compactness, carbonization resistance, and acid and alkali resistance of concrete.

5.1.3 Manufactured Sand Aggregate particles produced by mechanical crushing and screening and with a size less than 4.75 mm are called manufactured sand (MS), but soft rock and weathered rock particles are not included. The main characteristics of MS are as follows: At present, it is medium-coarse sand with a rough surface and sharp edges, with fineness modulus between 2.6 and 3.6 and containing a certain amount of fines. The grain size and gradation of MS are very different due to the different sources, equipment, and technology of MS production. For example, some MS has more flake particles, showing a poor grain gradation. However, MS can be used in concrete and mortar as long as it can meet all the technical indicators in the national standard. See Chap. 3 for technical and quality indexes of MS.

5.1.4 Coarse Aggregate The coarse aggregate commonly used for preparing concrete is gravel or pebble with a particle size greater than 5 mm. Gravel is a kind of rock particle formed by natural rock or pebble after crushing and screening. Pebbles are formed under natural conditions.

5.1.4.1

Particle Shape and Surface Characteristics

The fluidity of concrete mixture containing crushed stone is poor due to the rough and angular surface of crushed stone. But the strength of concrete is higher because the bond between gravel and cement is better. On the contrary, pebbles are spherical particles with a smooth surface. The fluidity of concrete containing pebbles is better, but the strength is poorer. There are some needle and flake particles in the coarse aggregate. When the length of rock particles is greater than 2.4 times of average particle size, the aggregate is

5.1 Raw Materials

251

defined as needle-like particles. When the thickness of rock particles is less than 0.4 times the average particle size, the aggregate is defined as flake particles. Average particle size refers to the average of the upper and lower particle sizes. The excess needle and flake particles will reduce the workability and strength of concrete.

5.1.4.2

Maximum Particle Size

The upper limit of nominal grain size in coarse aggregate is called the maximum particle size of the coarse aggregate. As the aggregate particle size increases, its surface area and the amount of cement slurry or mortar required decrease. Therefore, the maximum particle size in coarse aggregate should be as large as possible under engineering conditions. Experimental results show that the optimum maximum particle size depends on the cement content of concrete. Aggregate with large particle size should be used in concrete with low cement content (cement content ≯ 170 kg/m3 ). However, an aggregate size larger than 40 mm is not suitable for ordinary concrete. The maximum aggregate size is also limited by the structure and reinforcement density. According to the Code for Construction of Concrete Structure Engineering (GB 50666-2011), the maximum particle size of concrete coarse aggregate should not exceed 1/4 of the size of the structure section and should not exceed 3/4 of the minimum distance between reinforcing bars. For solid concrete slabs, the maximum particle size of aggregate should not exceed 1/3 of the plate thickness and should not exceed 40 mm.

5.1.4.3

Quality Requirements for Crushed Stones

The quality requirements of stones shall meet the Standard for the Technical Requirements and Test Method of Sand and Crushed Stone (or Gravel) for Ordinary Concrete (JGJ52-2006). (1) Aggregate should be screened using a square hole screen. The gradation of gravel or pebbles must meet the requirements in Table 5.7. Aggregates with single gradation shall be mixed with aggregates of other sizes for continuous grading or mixed with aggregates of continuous gradation. When the pebble particle gradation does not meet the requirements in Table 5.7, improvement measures should be taken to ensure the quality of the project. (2) The content of needle and flake particles in gravel or pebbles should meet the requirements in Table 5.8. (3) The mud content in gravel or pebbles shall meet the requirements of Table 5.9. For concrete with frost resistance, impermeability, or other special requirements, the mud content of the gravel or pebbles used should not exceed 1.0%. When the mud content of gravel or pebbles is non-clay fines, the mud content can be increased from 0.5%, 1.0%, and 2.0% in Table 4.6 to 1.0%, 1.5%, and 3.0%, respectively.

95–100

95–100

95–100

95–100

–

5–16

5–20

5–25

5–31.5

5–40

Monograding

95–100

5–10

Continuous grading

–

–

–

–

–

10–20

16–31.5

20–40

31.5–63

40–80

2.36

–

–

–

95–100

95–100

95–100

90–100

90–100

90–100

85–100

80–100

4.75

–

–

95–100

–

85–100

70–90

70–90

–

40–80

30–60

0–15

9.5

–

95–100

–

85–100

–

–

–

30–70

–

0–10

0

16.0

Square hole screen mesh size/mm

Cumulative sieve residue by mass/%

Nominal size/mm

Grading

Table 5.7 Grading range of gravel or pebbles

95–100

–

80–100

–

0–15

30–65

15–45

–

0–10

0

–

19.0

–

–

–

–

0

–

–

0–5

0

–

–

26.5

–

75–100

–

0–10

–

–

0–5

0

31.5

70–100

45–75

0–10

0

–

0–5

0

–

–

–

–

37.5

–

–

0

–

–

0

–

–

–

–

–

53.0

30–60

0–10

–

–

–

–

–

–

–

–

–

63.0

0–10

0

–

–

–

–

–

–

–

–

–

75.0

0

–

–

–

–

–

–

–

–

–

–

90

252 5 Mix Design of Concrete with Manufactured Sand

5.1 Raw Materials

253

Table 5.8 The content of needle and flake particles in gravel or pebbles Concrete strength grade

≥ C60

C55–C30

≤ C25

The content of needle and flake particles (by mass/%)

≤5

≤ 15

≤ 25

Table 5.9 Mud content in gravel or pebbles

Table 5.10 The clay lump content in gravel or pebbles

Concrete strength grade

≥ C60 C55–C30

≤ C25

The mud content (by mass/%)

≤ 0.5

≤ 2.0

≤ 1.0

Concrete strength grade

≥ C60 C55–C30

≤ C25

Clay lump content (by mass/%)

≤ 0.2

≤ 0.7

≤ 0.5

(4) The clay lump content in gravel or pebbles shall meet the requirements listed in Table 5.10. For concrete with frost resistance, impermeability, and other properties and strength less than C30, the clay lump content of gravel or pebble shall not exceed 0.5%. (5) The strength of crushed stone can be expressed by the compressive strength and crushing value of coarse aggregate. The compressive strength of coarse aggregate should not be less than 1.5 times that of the corresponding concrete. When the concrete strength grade is greater than or equal to C60, the rock compressive strength test shall be performed. Aggregate strength should first be provided by the production unit, and the crushing value index can be used for quality control in engineering. The crushing value of crushed stone should meet the requirements in Table 5.11. The strength of the pebbles is expressed by the crush value index. The crushing value should meet the requirements in Table 5.12. Table 5.11 The crushing value of crushed stone

Rock variety

Concrete strength grade

Crushing value /%

Sedimentary rock

C60–C40 ≤ C35

≤ 10 ≤ 16

Metamorphic rock or C60–C40 deep igneous rock ≤ C35

≤ 12 ≤ 20

Ejected igneous rock

≤ 13 ≤ 30

C60–C40 ≤ C35

Note Sedimentary rocks include limestone, sandstone, etc. Metamorphic rocks include gneiss, quartzite, and so on. Deep-formed igneous rocks include granite, syenite, diorite, and peridotite. The ejected igneous rocks include basalt and diabase

254 Table 5.12 Crushing value of pebbles

5 Mix Design of Concrete with Manufactured Sand Concrete strength grade

C60–C40

≤ C35

Crushing value%

≤ 12

≤ 16

Table 5.13 Solidity index of gravel or pebbles Environmental conditions and performance requirements of concrete

Mass loss after 5 cycles/%

Concrete served under low temperature and wet or dry alternating condition, or concrete with special requirements for fatigue resistance, wear resistance, corrosion resistance, and impact resistance

≤8

Concrete used under other conditions

≤ l2

Table 5.14 The content of deleterious substances in gravel or pebbles Item

Technical requirement

Content of sulfide and sulfate (converted into SO3 , by mass)/%

≤ 1.0

Organic impurity content in pebbles (tested by Color should not be darker than standard color. Otherwise, concrete should be prepared for colorimetry) strength comparison test, and compressive strength ratio should not be less than 0.95

(6) The solidity of gravel and pebbles should be tested by sodium sulfate solution. The mass loss of samples after five cycles of testing should meet the requirements in Table 5.13. (7) The content of sulfide and sulfate in gravel or pebbles, as well as the content of deleterious substances such as organic impurity in pebbles, shall meet the requirements of Table 5.14. (8) The alkali activity of gravel or pebbles in concrete should be tested for concrete exposed to moisture for a long time. When granular sulfate or sulfide impurities exist in gravel or pebbles, the sulfur content should be determined before engineering application to ensure the durability of concrete. The type and quantity of aggregate should be examined first by the lithofacies method when the alkali activity test is carried out. Quick mortar method and mortar length method should be used to test the alkali activity when active silica is detected in aggregate. The rock column method should be used to test the alkali activity when active carbonate is identified in aggregate. The alkali content in concrete should be controlled less than 3 kg/m3 when it is known that the aggregate has a potential hazard caused by the alkali-silicic acid reaction, or other measures that can inhibit the alkali-aggregate reaction should be adopted.

5.1 Raw Materials

255

Aggregate should not be used in concrete when there is a potential alkali-carbonate reaction hazard. If it is unavoidable, durability should be assessed based on concrete tests before application.

5.1.5 Chemical Admixtures Concrete admixtures are defined as materials added before or during concrete mixing, other than cementitious materials, aggregates, water, and fiber components, to improve the properties of fresh and/or hardened concrete without harmful effects on human, biological, and environmental safety. There are many kinds of concrete admixtures, which are of great significance to improve concrete workability, strength, and durability, increase the utilization of industrial solid wastes, and reduce cement consumption, cost, resources, and energy consumption. Large water demand, poor workability, and easy bleeding are typical characteristics of concrete with MS, especially in low-strength concrete with less cement. However, the working performance of high-performance concrete with MS can be improved by adding admixtures to meet the design requirements.

5.1.5.1

Classification

Concrete admixtures are generally divided into five categories according to their main functions: (1) Admixtures to improve the rheological properties of fresh concrete, including water-reducing admixtures, pumping admixtures, air-entraining admixtures, water-retention admixtures, etc. (2) Admixtures to regulate the setting and hardening properties of concrete, including early strength admixtures, retarding admixtures, accelerating admixtures, etc. (3) Admixtures to adjust the gas content of concrete including air-entraining admixture, foaming admixture, defoaming admixture, etc. (4) Admixtures to improve the durability of concrete, including air-entraining admixture, anti-freeze, corrosion-inhibiting admixtures, etc. (5) Admixtures to improve other properties of concrete, including air-entraining admixture, expanding admixture, and waterproofing admixture. According to the actual functional requirements, different types of concrete admixtures have been developed, and the specific classification is shown in Table 5.15.

256

5 Mix Design of Concrete with Manufactured Sand

Table 5.15 Classifications of concrete chemical admixtures [1] Type of admixture

Desired effect

Materials

Accelerators

Accelerate setting and early strength development

Calcium chloride Triethanolamine, sodium thiocyanate, calcium formate, calcium nitrite, calcium nitrate

Air detrainers

Decrease air content

Tributyl phosphate, dibutyl phthalate, octyl alcohol, water insoluble esters of carbonic and boric acid, silicones

Air-entraining admixtures

Improve durability in freeze–thaw, deicer, sulfate, and alkali-reactive environments Improve workability

Salts of wood resins (Vinsol resin), some synthetic detergents, salts of sulfonated lignin, salts of petroleum acids, salts of proteinaceous material, fatty and resinous acids and their salts, alkylbenzene sulfonates, salts of sulfonated hydrocarbon

Alkali-aggregate reactivity inhibitors

Reduce alkali-aggregate reactivity expansion

Barium salts, lithium nitrate, lithium carbonate, lithium hydroxide

Anti-washout admixtures

Cohesive concrete for underwater placements

Cellulose, acrylic polymer

Bonding admixtures

Increase bond strength

Polyvinyl chloride, polyvinyl acetate, acrylics, butadiene-styrene copolymers

Coloring admixtures

Colored concrete

Modified carbon black, iron oxide, phthalocyanine, umber, chromium oxide, titanium oxide, cobalt blue

Corrosion inhibitors

Reduce steel corrosion activity in a chloride-laden environment

Calcium nitrite, sodium nitrite, sodium benzoate, certain phosphates or fluorosilicates, fluoroaluminates, ester amines

Damp proofing admixtures

Retard moisture penetration into dry concrete

Soaps of calcium or ammonium stearate or oleate Butyl stearate Petroleum products

Foaming agents

Produce lightweight, foamed concrete with low density

Cationic and anionic surfactants Hydrolyzed protein

Fungicides, germicides, and insecticides

Inhibit or control bacterial and fungal growth

Polyhalogenated phenols Dieldrin emulsions Copper compounds

Gas formers

Cause expansion before setting

Aluminum powder (continued)

5.1 Raw Materials

257

Table 5.15 (continued) Type of admixture

Desired effect

Materials

Grouting admixtures

Adjust grout properties for specific applications

See air-entraining admixtures, accelerators, retarders, and water reducers

Hydration control admixtures

Suspend and reactivate cement hydration with stabilizer and activator

Carboxylic acids Phosphorus-containing organic acid salts

Permeability reducers

Decrease permeability

Latex Calcium stearate

Pumping aids

Improve pumpability

Organic and synthetic polymers Organic flocculents Organic emulsions of paraffin, coal tar, asphalt, acrylics Bentonite and pyrogenic silicas Hydrated lime (ASTM C 141)

Retarding admixtures

Retard setting time

Lignin Borax Sugars Tartaric acid and salts

Shrinkage reducers

Reduce drying shrinkage

Polyoxyalkylene alkyl ether Propylene glycol

Superplasticizers (type 1)

Increase flowability of concrete Reduce water to binder ratio

Sulfonated melamine formaldehyde condensates Sulfonated naphthalene formaldehyde condensates Lignosulfonates Polycarboxylates

Superplasticizer and retarder (type 2)

Increase flowability with retarded set Reduce water–cement ratio

See superplasticizers and also water reducers

Water reducer

Reduce water content at least 5%

Lignosulfonates Hydroxylated carboxylic acids Carbohydrates (also tend to retard set so accelerator is often added)

Water reducer and accelerator Reduce water content See water reducer, Type A (minimum 5%) and accelerate (accelerator is added) set Water reducer and accelerator Reduce water content See water reducer, Type A (minimum 5%) and accelerate (accelerator is added) set Water reducer and retarder (type D)

Reduce water content (minimum 5%) and retard set

See water reducer, Type A (retarder is added)

Water reducer-high range

Reduce water content (minimum 12%)

See superplasticizers (continued)

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5 Mix Design of Concrete with Manufactured Sand

Table 5.15 (continued) Type of admixture

Desired effect

Water reducer-high range-and Reduce water content (minimum 12%) and retard retarder set Water reducer-mid range

5.1.5.2

Materials See superplasticizers and also water reducers

Reduce water content Lignosulfonates (between 6 and 12%) without Polycarboxylates retarding

Common Chemical Admixtures

Several kinds of admixtures that are commonly used in concrete are introduced as follows according to concrete admixtures (GB 8076-2008). (1) High-performance water reducer High-performance water reducer is a new kind of admixture developed in recent years, and polycarboxylate is the main product at present. It is made up of comblike molecules, which consists of the main chain with free carboxylic anion groups and polyoxyethylene side chains. High-performance water reducers with different properties can be produced by changing the type, proportion, and reaction conditions of monomers. High-performance water reducer with hardening accelerating or retarding effect on concrete can be produced by introducing different functional groups, but also mixed with different components. Its main features are as follows. a. Low dosage (the solid content of high-performance water reducer is generally 0.15–0.25% of the mass of the cementitious material) and high water reduction rate. b. The workability and its retention of concrete can be improved by highperformance water reducer. c. The contents of chloride ion and alkali in the high-performance water reducer are kept as low level. d. Concrete shrinkage can be reduced by high-performance water reducer, while volume stability and durability can be improved at the same time. e. The adaptability of high-performance water reducer to cement is optimal. f. The production and application of high-performance water reducer are harmless to the environment. (2) Superplasticizer Compared with ordinary water-reducing agents, superplasticizers have a higher water-reducing rate and a lower air-entraining capacity, so it has been widely used in China. At present, several superplasticizers used in China are shown below. a. Naphthalene series water-reducing admixture. b. Sulfamate-based series water-reducing admixture. c. Aliphatic (aldehyde-ketone condensate) series water-reducing admixture.

5.1 Raw Materials

259

d. Melamine and modified melamine series water-reducing admixture. e. Anthracene series water-reducing admixture. f. Scrubbing oil series water-reducing admixture. (3) Ordinary water-reducing admixture The main component of ordinary water-reducing admixture is lignosulfonate, which is usually made from the by-product of pulp production by the sulfite method. Calcium lignosulfonate, sodium lignosulfonate, and magnesium lignosulfonate are common. They have the effects of retardation, reducing water, and entraining air. Different types of water-reducing admixtures can be prepared by adding different types of setting regulators to ordinary water-reducing admixtures, such as accelerating-type, standard-type, and retarding-type water-reducing admixtures. (4) Air-entraining water-reducing admixture Air-entraining water-reducing agent is an admixture with both air-entraining and water-reducing functions. It is composed of air-entraining admixture and waterreducing agent, whose performance is different according to engineering requirements. (5) Pumping admixture Pumping admixture is an admixture used to improve the pumping performance of concrete. It is compounded by multiple components such as water-reducing admixture, coagulant regulator, air-entraining admixture, lubricant, and so on. The performance of products is different according to engineering requirements. (6) Accelerating admixtures The accelerating admixture is an admixture that can accelerate the hydration and hardening of cement and promote the growth of the early age strength of concrete. It can shorten the curing age of concrete, speed up the construction progress, and increase the turnover rate of the formwork and site. Accelerating admixtures are mainly inorganic salts, organic substances, and so on, while more and more composite accelerating admixtures are used at present. (7) Retarding admixtures The retarding admixtures is an admixture that can keep the workability of concrete for a long time and delay the setting and hardening duration of concrete. The retarding admixtures can be divided into two categories, namely organic and inorganic as follow. a. Sugars and carbohydrates, such as starch and cellulose derivatives. b. Hydroxy carboxylic acids, such as citric acid, tartaric acid, gluconic acid, and their salts. c. Soluble borate, phosphate, etc.

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5 Mix Design of Concrete with Manufactured Sand

(8) Air-entraining admixture Air-entraining admixture is an admixture that introduces a large number of evenly distributed microbubbles into the mortar or concrete during the mixing process. Moreover, these bubbles remain stable even after the slurry has been hardened. There are many types of air-entraining admixtures, mainly including: a. b. c. d. e. f.

Soluble resinate (rosin acid). Vinxal resin. Saponified tour oil. Sodium dodecyl sulfonate. Sodium dodecylbenzene sulfonate. Soluble salt of sulfonated petroleum hydroxy group, etc.

5.1.5.3

Special Chemical Admixtures

In addition to the above chemical admixtures, special admixtures suitable for special applications have been developed according to the needs of projects, such as underwater anti-dispersants [2–4] and thickeners.

5.1.6 Water Water for mixing and curing of concrete with MS shall conform to the current Standard of Water for Concrete (JGJ63). Its pH value shall exceed 6.0.

5.2 Mix Proportioning Methods of High-Performance Concrete In general, three proportion relations between the dosage of cement, water, and aggregates are mainly controlled for the mix design of high-performance concrete. The relation between water and cement, fine aggregate and coarse aggregate, and cement slurry and aggregate are represented by water to binder ratio, the percentage of fine aggregate in aggregates, and water consumption per unit, respectively. These three parameters strongly affect the performance of concrete, and they are necessary for concrete to meet the design requirements in the mix design. The first step of mix design is to select raw materials and inspect the quality of raw materials. Then, the preliminary calculation should be carried out according to the technical requirement of concrete to get the “trial mix proportion”. The “basic mix proportion” can be obtained after laboratory mixing and adjustment. After strength test (or tests for other required performance), the “laboratory mix proportion” is determined. Finally, the “laboratory mix proportion” is modified according to the

5.2 Mix Proportioning Methods of High-Performance Concrete

261

characteristics of on-site raw materials (such as moisture content of sand and stone) to obtain the “engineering mix proportion”. General steps of high-performance concrete mix design are as follows: (1) determination of the target mean strength; (2) calculation of the mix proportion; (3) trial, adjustment, and determination of mix proportion; and (4) check of specific performance.

5.2.1 Determination of the Concrete Target Mean Strength The target mean strength of concrete shall be determined according to the following provisions: (1) The target average strength should be calculated according to Eq. 4.1 when the design strength grade of concrete is below C60. (2) The target strength shall be calculated on average according to Eq. 4.2 when the design strength grade of concrete is not less than C60. The standard deviation of concrete strength shall be determined by the following provisions: When strength data of more than 30 mixes with the same strength grade formed in the last 1–3 months are known, the standard deviation σ of concrete strength shall be determined according to the following equation: √ Σ σ =

n i=1

2 f cu,i − nm 2fcu

n−1

(5.1)

where σ is the standard deviation of concrete strength; f cu,i is the specimen strength of mix i (MPa); mfcu is the average strength of n mixes (MPa); n is the number of specimen, and the value of n should be not less than 30. For the concrete with strength grade no greater than C30, when the calculated standard deviation of concrete strength is not less than 3.0 MPa, it should be calculated according to Eq. 4.3. Otherwise, 3.0 MPa should be taken as the standard deviation of concrete strength. For the concrete whose strength grade is greater than C30 and less than C60, when the calculated standard deviation of concrete strength is no less than 4.0 MPa, it should be calculated according to Eq. 4.3. Otherwise, 4.0 MPa should be considered as the standard deviation of concrete strength.

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5.2.2 Calculation of Concrete Mix Proportion (1) Water to binder ratio When the strength grade of concrete is less than C60, the water to binder ratio should be calculated as follows: W/B =

· fb f cu,0 + αa · αb· f b a

(5.2)

W /B water to binder ratio of concrete; α a , α b regression coefficient; fb 28d compressive strength of mortar (MPa). The regression coefficients (α a , α b ) should be determined according to the following regulations: (1) The regression coefficients are determined by the relationship between water to binder ratio and concrete strength. (2) When the test statistics are not available, they can be determined according to Table 5.16. When the 28d compressive strength of mortar is not available, it can be calculated as follows: f b = γ f · γs · f ce

(5.3)

where γ f and γ s represent the influence coefficient of fly ash and granulated blastfurnace slag, respectively, which can be determined according to Table 5.17, and f ce is the 28d compressive strength of mortar (MPa). When the 28d compressive strength of mortar is not available, it can be calculated as follows: f ce = γc · f ce,g

(5.4)

where γ c is the surplus coefficient of cement strength grade, which can be determined according to experimental data. It can also be determined according to Table 5.18 when data are not available. f ce,g is the strength grade of cement (MPa). (2) Water consumption and admixture consumption Table 5.16 Regression coefficient (α a , α b ) value table Variety of coarse aggregate

Crushed stone

Pebble

αa

0.53

0.49

αb

0.20

0.13

5.2 Mix Proportioning Methods of High-Performance Concrete

263

Table 5.17 Influence coefficient of fly ash and granulated blast-furnace slag Dosage/%

Influence coefficient of fly ash γ f

Influence coefficient of granulated blast-furnace slag γ s

0

1.00

1.00

10

0.85–0.95

1.00

20

0.75–0.85

0.95–1.00

30

0.65–0.75

0.90–1.00

40

0.55–0.65

0.80–0.90

50

–

0.70–0.85

Note The upper limit value of the corresponding dosage in the table should be taken as the influence coefficient of Grades I and II fly ash The lower and upper limits of the corresponding dosage in the table should be taken as the influence coefficient value of S75 and S95 granulated blast-furnace slag powder, respectively, while the influence coefficient value of S105 granulated blast-furnace slag powder should be the upper limit value in the table plus 0.05 The influence coefficient should be determined by testing when the dosage of fly ash or granulated blast-furnace slag is higher than the dosage listed in Table 5.17

Table 5.18 Surplus coefficient of cement strength grade (γ c ) Cement strength grade

32.5

42.5

52.5

Surplus coefficient

1.12

1.16

1.10

The water consumption (m0 ) per cubic meter of stiff consistency concrete or plastic concrete shall meet the following requirements: (1) The water consumption can be determined according to Tables 5.19 and 5.20 when the water to binder ratio of concrete is in the range of 0.40–0.80. (2) The water consumption could also be determined through experiments when the water to binder ratio of concrete is less than 0.40. In addition, the unit water consumption can also be roughly estimated as follows: W0 =

10 (T + K ) 3

(5.5)

Table 5.19 Water consumption of stiff consistency concrete/kgm–3 Mixture consistency Test item Viber consistency/s

Index

Maximum nominal particle size of pebble/mm

Maximum nominal particle size of crushed stone/mm

10.0

16.0

20.0

40.0

20.0

40.0

16–20

175

160

145

180

170

155

11–15

180

165

150

185

175

160

5–10

185

170

155

190

180

165

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5 Mix Design of Concrete with Manufactured Sand

Table 5.20 Water consumption of plastic concrete/kgm–3 Mixture consistency

Maximum nominal particle size of pebble/mm

Maximum nominal particle size of crushed stone/mm

Test item

Index

10.0

20.0

31.5

40.0

16.0

20.0

31.5

40.0

Slump/mm

10–30

190

170

160

150

200

185

175

165

35–50

200

180

170

160

210

195

185

175

55–70

210

190

180

170

220

205

195

185

75–90

215

195

185

175

230

215

205

195

Note The value of water consumption in this table corresponds to the case of using medium sand to prepare concrete. The water consumption per cubic meter of concrete can be increased by 5–10 kg when fine sand is used, while it can be reduced by 5–10 kg when coarse sand is used The water consumption should be adjusted when mineral admixtures and admixtures are used

Table 5.21 The K value in the calculation equation of unit water consumption Coefficient

Crushed stone

Pebble

Maximum particle size (mm) K

10

20

40

80

10

20

40

80

57.5

53.0

48.5

44.0

54.5

50.0

45.5

41.0

Note The K value needs to be increased by 4.5–6.0 when Portland pozzolanic cement was used. The K value needs to be increased by 3.0 when fine sand was used

where T is the slump of concrete mixture (cm); K represents the coefficient which depends on the type of coarse aggregate and the maximum particle size, which can be obtained from Table 5.21. The water consumption per cubic meter (mw0 ) of concrete with fluidity or high fluidity (with additives) can be calculated as follows: m w0 = m w0' (1 − β)

(5.6)

mw0 the water consumption per cubic meter of concrete (kg); mw0 ' the estimated water consumption per cubic meter of concrete (kg/m3 ) that meets the slump requirement when no admixture is added. Based on the water consumption of concrete with 90 mm slump, the water consumption needs to be increased by 5 kg for every 20 mm increase of slump. When the slump is higher than 180 mm, the increased water consumption can be reduced; β water-reducing rate of admixtures (%), and it should be determined by experiments. The consumption of admixture per cubic meter of concrete (ma0 ) should be calculated as follows: m a0 = m b0 βa

(5.7)

5.2 Mix Proportioning Methods of High-Performance Concrete

265

ma0 consumption of admixture per cubic meter of concrete in calculated mix proportion (kg); mb0 consumption of cementitious material per cubic meter of concrete (kg); β a dosage of admixture (%), which should be determined by concrete experiments. (3) Dosages of cementitious material, mineral admixture, and cement The amount of cementitious material per cubic meter of concrete (mb0 ) should be calculated as follows and adjusted by the trial mixing. The amount of cementitious material should be determined economically and reasonably when the performance of the mixture is satisfied. m b0 =

m w0 W/B

(5.8)

mb0 the amount of cementitious material per cubic meter of concrete (kg/m3 ); mw0 the amount of water per cubic meter of concrete (kg/m3 ); W /B water to binder ratio of concrete. The amount of mineral admixture per cubic meter of concrete (mf 0 ) should be calculated as follows: m f 0 = m b0 β f

(5.9)

mf 0 is the amount of mineral admixture per cubic meter of concrete (kg/m3 ), and β f is the content of mineral admixture (%) in the binder. The amount of cement per cubic meter of concrete (mc0 ) should be calculated as follows: m c0 = m b0 − m f 0

(5.10)

where mc0 is the amount of cement per cubic meter of concrete (kg/m3 ). (4) The percentage of fine aggregate in total aggregate The percentage of fine aggregate in total aggregate should be determined according to technical indicators of aggregate, performance of concrete mixture, construction requirements, and existing data. The determination of the percentage of fine aggregate in total aggregate should meet the following requirements when the data are not available. (1) For concrete with a slump less than 10 mm, the percentage of fine aggregate in total aggregate should be determined by experiments. (2) For concrete with a slump of 10–60 mm, the percentage of fine aggregate in aggregates can be determined according to the type of coarse aggregate and the maximum nominal particle size and the water to binder ratio in Table 5.22.

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5 Mix Design of Concrete with Manufactured Sand

Table 5.22 The percentage of fine aggregate in aggregate of concrete/% Water to binder ratio

Maximum particle size of pebble/mm

Maximum particle size of crushed stone/mm

10.0

16.0

20.0

40.0

20.0

40.0

0.40

26–32

25–31

24–30

30–35

29–34

27–32

0.50

30–35

29–34

28–33

33–38

32–37

30–35

0.60

33–38

32–37

31–36

36–41

35–40

33–38

0.70

36–41

35–40

34–39

39–44

38–43

36–41

Note a. Values in this table are the percentage of fine aggregate in aggregate of medium sand; for finding sand or coarse sand, the values can be reduced or increased accordingly b. The percentage of fine aggregate in total aggregate can be increased appropriately when MS was used for preparing concrete c. The percentage of fine aggregate in aggregate can be increased appropriately when monograding coarse aggregate was used to prepare concrete

(3) For concrete with a slump greater than 60 mm, the percentage of fine aggregate in aggregates could be determined by experiment or be increased by 1% with an increase of 20 mm slump based on the reference values in Table 5.22. (5) Amount of coarse and fine aggregates When the amounts of coarse and fine aggregate are determined by the mass method, the following equations should be used: m f 0 + m c0 + m g0 + m s0 + m w0 = m cp βs = mg0 ms0 βs mcp

m s0 × 100% m g0 + m s0

(5.11) (5.12)

the amount of coarse aggregate per cubic meter of concrete (kg/m3 ); the amount of fine aggregate per cubic meter of concrete (kg/m3 ); the percentage of fine aggregate in aggregate (%); assumed mass of the concrete mixture per cubic meter (kg), which can be 2350–2450 kg.

When the amounts of coarse and fine aggregate are determined by the volume method, the following equations should be used: m f0 m g0 m s0 m w0 m c0 + + + + + 0.01α = 1 ρc ρf ρg ρs ρw βs =

m s0 × 100% m g0 + m s0

(5.13) (5.14)

5.2 Mix Proportioning Methods of High-Performance Concrete

267

where ρ c represents density of cement (kg/m3 ), which can be measured according to Test Method for Determining Cement Density (GB/T 208) or be chosen in the range of 2900–3100 kg/m3 ; ρ f represents density of mineral admixture (kg/m3 ), which can be measured according to Test Method for Determining Cement Density (GB/T 208); ρ g represents apparent density of coarse aggregate (kg/m3 ) and shall be determined in accordance with the Standard for Technical Requirements and Test Method of Sand and Crushed Stone (or Gravel) for Ordinary Concrete (JGJ52); ρ s represents apparent density of fine aggregate (kg/m3 ) and shall be determined in accordance with the standard Standard for Technical Requirements and Test Method of Sand and Crushed Stone (or Gravel) for Ordinary Concrete (JGJ52); ρ w represents density of water (kg/m3 ), which can be 1000 kg/m3 ; α represents the air content (%) in concrete; and α can be taken as 1 when air entrainment admixture was not used.

5.2.3 Trial, Adjustment, and Determination of Mix Proportion (1) Trial mix The concrete mixing test should be carried out by a forced mixer, which should conform to the standard Mixers for Concrete Test (JG224). The mixing method should be the same as that used in construction. The molding conditions of the laboratory should comply with the Standard for Test Method of Performance of Ordinary Fresh Concrete (GB/T 50080). The minimum amount of concrete in a trial mix should meet the requirement of Table 5.23 and should not be less than 1/4 of the nominal capacity of the mixer and should not be larger than the nominal capacity of the mixer. Trial mixing should be carried out on the basis of calculated mix proportion. Parameters, except the water to binder ratio, are adjusted to ensure the performance of concrete mixture to meet the requirements of design and construction. The trial mix proportion shall be determined according to the revised parameters. The concrete strength test should be carried out on the basis of the trial mix proportion and should meet the following requirements: (1) Three different mix proportions should be used, one of which should be the trail mix proportion as determined above. The water to binder ratio of the other two mix proportion should be increased and decreased by 0.05 compared with the trail mix proportion, the water consumption should be the same as that of the Table 5.23 Minimum mixing amount for concrete trial mix

Maximum nominal particle size of coarse aggregate/mm

Mix quantity/L

≤ 31.5

20

40.0

25

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5 Mix Design of Concrete with Manufactured Sand

trial mix proportion, and the percentage of fine aggregate in aggregates could be increased and decreased by 1%, respectively. (2) The performance of the mixture should meet the requirements of design and construction. (3) At least one group of specimens should be made for each mix proportion, and trial compression test should be carried out when the specimen is cured until 28d or the design curing age under standard curing environment. (2) Adjustment and determination The adjustment of mix proportion should meet the following requirements: (1) The cementitious materials-water ratio corresponding to the strength which is slightly larger than the target mean strength is determined by the linear relationship diagram between the strength and the cementitious materials-water or using the interpolation method. (2) The water consumption (mw ) and the chemical admixture consumption (me ) should be adjusted according to the determined water to binder ratio on the basis of the trial mix proportion. (3) The amount of cementitious material (mb ) should be calculated by multiplying the water consumption by the determined cementitious materials-water ratio. (4) The amount of coarse aggregate and fine aggregate (mg and ms ) should be adjusted according to the amount of water and cementitious material. The calculation of apparent density and mix proportion correction coefficient of concrete mixture should meet the following requirements: (1) The apparent density of concrete mixture after adjustment of mix proportion should be calculated as follows: ρcc = m c + m f + m g + m s + m w ρ cc mc mf mg ms mw

(5.15)

calculated value of apparent density of concrete mixture (kg/m3 ); cement consumption per cubic meter of concrete (kg/m3 ); the amount of mineral admixture per cubic meter of concrete (kg/m3 ); the amount of coarse aggregate per cubic meter of concrete (kg/m3 ); the amount of fine aggregate per cubic meter of concrete (kg/m3 ); water consumption per cubic meter of concrete (kg/m3 ).

(2) The correction coefficient of concrete proportion should be calculated as follows: δ=

ρc,t ρc,c

δ correction coefficient of concrete mix proportion; ρ ct measured value of apparent density of concrete mixture (kg/m3 ).

(5.16)

5.3 Mix Proportioning Methods of Self-Compacting Concrete

269

The mix proportion need not be adjusted when the absolute difference value between the measured value and the calculated value of the apparent density of the concrete mixture does not exceed 2% of the calculated value; otherwise, the amount of each component in mix proportion should be multiplied by the correction coefficient (δ). Concrete with durability requirements should be verified by durability tests. In one of the following situations, the mix design should be re-carried out: (1) when there are special requirements for concrete performance or (2) when there is a significant change in the variety and quality of raw materials such as cement, chemical admixtures, or mineral admixtures.

5.2.4 Special Performance Check For concrete with special performance requirements, such as impermeable concrete, frost-resistant concrete, high-strength concrete, pumping concrete, and mass concrete, the mix proportion can be calculated and verified according to the requirements in Specifications for Mix Proportion Design of Ordinary Concrete (JGJ 55).

5.3 Mix Proportioning Methods of Self-Compacting Concrete Self-compacting concrete (SCC) is a kind of widely used building material that can be placed and consolidated under its weight without vibration. SCC is able to flow into every corner of a mold, pass reinforcement, and fill gaps due to its excellent deformability and segregation resistance. Compared to conventional vibrated concrete, SCC has advantages like producing durable and reliable concrete structures, saving labor, and eliminating the consolidation noise. By now, there are many mix proportioning methods of SCC, as shown below.

5.3.1 Blocking Criteria Method Petersson et al. developed a model for the mix design of SCC considering the least amount of paste based on the void content and the blocking criteria [5, 6]. This method, known as CBI method, is based on the interaction between the blocking volume ratio and clear reinforcement spacing to fraction particle diameter ratio. Concrete was considered as the mixture of solid aggregate phase in liquid paste phase formed by powder, water, and admixtures.

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5 Mix Design of Concrete with Manufactured Sand

The minimal paste volume from the mixture is first found between coarse and fine aggregate by measuring the void contents for different combinations of coarse and fine aggregates using the modified ASTM C29/29M. The minimal paste volume should fill all voids between aggregate particles and also cover the surface of aggregate particles. The blocking risk and its criteria of this method are shown by Eq. (5.17). Paste volume should meet the blocking risk criteria as well. The mix design procedure of this method is shown in Fig. 5.1. Blocking risk =

Σ (n si /n sbi ) ≤ 1

(5.17)

where n si is the volume ratio of a single-size group i of aggregate to total volume of concrete and n sbi is the blocking volume ratio of the single-size group i of aggregate to the total volume of concrete. Bui proposed a similar method to determine the maximum allowable aggregate volume (least paste volume) based on the blocking criteria, expressed as Eq. (5.18) [7]. Fig. 5.1 Mixture design process of Petersson’s method

5.3 Mix Proportioning Methods of Self-Compacting Concrete

Vmax

) ( ρg + ρs − ρg ∗ N g =Σ Σ Psy ∗(1−Ng )∗ρg Pgx ∗N g ∗ρs + Vgx Vgy

271

(5.18)

where Vmax is the maximum allowable aggregate volume in SCC. ρg and ρs are apparent densities of coarse and fine aggregates. N g is the mass ratio of coarse to total aggregate. Pgx is volume ratio of the coarse aggregate group x to total coarse aggregate, and Psy is volume ratio of fine aggregate y to total fine aggregate. Vgx and Vgy are the blocking volumes of group x and y in coarse aggregate and fine aggregates, respectively. Besides, Bui and his co-worker also investigated the minimum paste volume from the liquid-phase criteria [8]. They found that the required average spacing between particle surfaces (spherical aggregate assumption) depended on the water to binder ratio and average aggregate diameter. Based on this, the minimum required paste volume (V p,min ) of SCC was calculated by Eq. (5.19). V p,min = Vt − (

Vt − Void )3 Dss,min + 1 Dav

(5.19)

where Vt is the total concrete volume. Void is aggregate void content of the compacted aggregate matrix. Dss,min is the required minimum spacing between aggregate surfaces. Dav is the average diameter of aggregates.

5.3.2 ICAR Method A three-step method, known as the ICAR method, was proposed by Koehler and his co-workers from ICAR, the University of Texas at Austin [9–11]. In this method, the first step is selecting aggregates and determining the compacted voids. In the second step, the minimum volume of paste for filling voids is calculated from the compacted void content and visually rated shape and angularity of aggregate as shown in Eq. (5.20). Then, experiments are performed to determine this minimum paste volume to provide both filling and passing abilities. Vpaste

)( ) ( 100 − Vpaste - spacing 100 − Vvoid,agg = 100 − 4

(5.20)

where Vpaste is the paste volume fraction in concrete and Vvoid,agg is the void volume fraction on bulk aggregate. Vpaste−spacing is the paste volume fraction in concrete for spacing, which can be calculated from the visual shape and angularity rating (Rs−a ), as indicated in Eq. (5.21). Rs−a values can be selected according to Table 5.24. ( Vpaste - spacing = 8 +

) 16 − 8 (Rs−a − 1) 4

(5.21)

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5 Mix Design of Concrete with Manufactured Sand

The third step focuses on the paste composition. Parameters like w/c and w/cm were determined based on hardened property requirements while w/p was determined based on workability. The procedure of this method is shown in Fig. 5.2. This method visually rated the shape and angularity from 1 to 5 and estimated the minimum paste volume based on the compacted void and aggregate features. However, aggregate shape and angularity are considered based on visual estimation and their rating could be selected as different values by different users.

5.3.3 Su’s Method The principal consideration of Su’s method is to fill the paste of binders into voids of the aggregate framework piled loosely. Packing factor (PF) was defined as the mass ratio of aggregate of tightly packed state to that of loosely packed state in SCC. A higher PF value implies a greater amount of aggregate in SCC. The content of fine and coarse aggregates can be calculated by Eqs. (5.22) and (5.23). ( ) S Wg = PF × WgL 1 − a Ws = PF × Ws L

S a

(5.22) (5.23)

where Wg and Ws are contents of coarse and fine aggregates in SCC. WgL and Ws L are unit volume masses of loosely piled saturated surface-dry coarse and fine aggregates in air. s/a is the volume ratio of fine aggregates and total aggregates. The flowchart of this method is shown in Fig. 5.3. Cement is considered as the primary provider of the compressive strength, and its content is determined based on the linear relationship between compressive strength and cement content. The water to binder ratio can be determined according to its relationship with compressive strength, also conforming to the durability requirement from ACI 211.1 [12]. Mineral admixtures like FA and GGBS are used to compensate for the difference between the required paste amount and cement paste for providing enough workability for SCC. Water for FA and GGBS is determined separately to keep the FA paste and GGBS paste with the same fluidity as cement paste. SP dosage is set as the saturation point of the binder. During the trial, workability and compressive strengths are the criteria and adjustments should be made on PF value, w/c, water content, sand ratio, and SP dosage to make the mixture meet the criteria. Based on Su’s ideal, Sebaibi et al. proposed a simplified method: After the determination of cement amount and w/c, additional SF was employed according to NF EN 206-1 [13]. However, this simplified method did not take into consideration the paste requirement based on aggregate packing. In Su’s method, PF value was assumed instead of being determined based on the features of aggregates. To make Su’s method more reliable, Choi et al. proposed a

Modest deviation from equidimensional

Most particles near equidimensional

Well-rounded

Most rive/glacial gravels and sands

Shape

Angularity

Example

Subangular or subrounded

Most particles not equiaxial but also not flat or elongated

3

Partially crushed river/glacial Well-shaped crushed gravels or some very coarse aggregate or MS well-shaped MS with most corners > 90°

Rounded

2

1

Visual shape and angularity rating (Rs−a )

Table 5.24 Guidelines for assigning visual shape and angularity rating [10] 5

Crushed coarse aggregate or MS with some corners ≤ 90°

Angular

Crushed coarse aggregate or MS with many corners ≤ 90° and large convex areas

Highly angular

Some flat and/or elongated Few particles particles equidimensional; abundance of flat and/or elongated particles

4

5.3 Mix Proportioning Methods of Self-Compacting Concrete 273

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5 Mix Design of Concrete with Manufactured Sand

Fig. 5.2 Procedure of ICAR mix method

method to calculate PF value [14]. The procedure of determining the PF value is shown in Fig. 5.4. In this method, PF value is dependent on the packing densities of aggregate at compacted and loosely fill stages, expressed as Eq. (5.24). PF =

) ( M S,com S S MC,com + × 1− × MC,loo a M S,loo a

(5.24)

where MC,com and MC,loo are unit weight values of coarse aggregate at compacted and loosely filled stages while M S,com and M S,loo are unit weight values of fine aggregate at compacted and loosely filled stages, respectively. Su’s method and its modified versions are simple and able to produce SCC with the low amount of binder. However, sand to aggregate ratio was assumed empirically during the mixture design.

5.3 Mix Proportioning Methods of Self-Compacting Concrete

275

Fig. 5.3 Flowchart of Su’s mix design method

5.3.4 Densified Mixture Design Algorithm (DMDA) DMDA was firstly proposed for the mixture design of HPC and then applied in SCC [15–17]. SCC is considered as the mixture of aggregate and paste composed of cement, water, and chemical admixtures. The main principle is to maximize the volume of solid materials and minimize the contents of cement and water. Fly ash is considered as part of aggregate used to fill the void between aggregates shown

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5 Mix Design of Concrete with Manufactured Sand

Fig. 5.4 Procedure of determining the PF value

in Fig. 5.5, providing “the least void” for cement and water to fill. The mix design procedure of this method is shown in Fig. 5.6. The amount of paste was determined by an amplifier for lubricating. The influence of this amplifier on the workability and strength of concrete was studied, and an optimum amplifier could be selected based on the evaluation of properties. This method was also used for the mixture design of self-consolidating lightweight concrete [18–20]. However, the minimizing of the packing void of solid materials needs extensive trials and the amplifier is variable for different raw materials. Fig. 5.5 The procedure of aggregate packing

5.3 Mix Proportioning Methods of Self-Compacting Concrete

277

Fig. 5.6 Mix design procedure of DMDA method

5.3.5 Excessive Paste Theory The actual packing level of aggregate and paste volume is integrated into proportioning the mixture [21]. The flowchart of the mix design method is shown in Fig. 5.7. Based on the particle packing (PP) of aggregate, a correction lubrication factor (CLF) is chosen to obtain the aggregate volume (PPCLF ) for a given concrete volume, as shown in Eq. (5.25). PPCLF = PP × CLF

(5.25)

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5 Mix Design of Concrete with Manufactured Sand

Fig. 5.7 Flowchart of mix design by Kanadasan and Razak

5.3.6 Packing Model-Based Method In order to develop a methodology for optimizing concrete mixes by void minimization, it is crucial to select a suitable particle packing model which can estimate the packing density of concrete particle mix system as accurately as possible. Particle packing models, which are used to estimate the packing density of the solid combinations, can reduce paste and water usage. Several particle packing models have been developed, and the comparison among these models can be found in Ref. [22]. Sedran et al. proposed the solid suspension model (SSM) for the mix design of SCC [23]. The paste volume and composition were fixed, and contents of sand, fine, and coarse gravels were optimized with their total volume fraction kept at 78.7% of the total solid mass and content mass of concrete. The fine gravel was kept be greater than 10% while sand content was 30% for unconfined aggregate and 35% for confined one. Gap-graded concrete must be avoided to prevent segregation. It was also demonstrated that SSM may converge, in some cases, on gap-graded concrete. This may happen if an intermediate fraction of grains has a low packing density due to angular shape. Although such concrete is optimized from the viewpoint of packing density, it will present a trend to segregation. A more continuous skeleton must be preferred, even with slightly higher water demand.

5.3 Mix Proportioning Methods of Self-Compacting Concrete

279

Sedran proposed a method based on the compressible packing model (CPM) [23], which is detailedly described by de Larrard [24]. CPM calculated the virtual packing density of solid particles composed of a set of n monosized granular classes with a mean diameter of di , where d1 ≥ d2 ≥ · · · ≥ dn , according to the packing structure, as indicated by the following equations [25]. γ = inf(γi ) γi =

1−

βi [ ( j=1 yi 1 − βi + bi j βi 1 −

Σi−1

√

1 βi

)]

(5.26)

−

( ) βi 1 − a y i i j j=i+1 βj

Σn

) ( d j 1.02 1− 1− di ) ( di 1.5 bi j = 1 − 1 − dj

ai j =

(5.27)

(5.28)

(5.29)

where γ is the maximum packing density attainable with the material considered with an infinite amount of compaction energy. βi and yi represent the virtual packing density and volume content of class i. ai j describes the loosening effect exerted by the class j on the class i (if i ≤ j), and bi j is the wall effect exerted by the class j on the class i. Then, by employing the compaction index K as Eq. (5.30), the relationship between virtual packing density and actual packing density (ϕ) was established. K =

n Σ i=1

Ki =

( n Σ i=1

)

yi βi 1 ϕ

−

1 γi

(5.30)

In this method, a BTRHEOM rheometer and a RENE-LCPC software were used together for the mix design. The procedure of this method is shown in Fig. 5.8. Radhika and Kumar used the CPM method to determine the aggregate proportion [26]. Then, Su’s method (packing factor) was used to determine the aggregate usage in the mixture.

5.3.7 Target Grading Method (TG Method) With closer packing of aggregate, more paste will be available in the mix to act as a lubricant, which improves the workability of concrete. Besides, with closer packing of all solid constitutes, more water will be available. For a specific workability, less paste (mainly binder and water) is needed for a closer particle packing system,

280

5 Mix Design of Concrete with Manufactured Sand

Fig. 5.8 Mix design procedure of CPM method

which is beneficial to not only the properties like shrinkage but also the cost and environmental influence. On the other hand, most existing design methods for SCC assume that powder particles have to be covered with a water layer of a certain thickness and the coarse aggregates again have to be covered with a layer of mortar. The grading of this mortar is largely secondary. Its workability is controlled by high amounts of fines and the addition of highly effective plasticizers. Based on this separation of coarse and fine aggregates, there are also limitations which should be considered during composing a

5.3 Mix Proportioning Methods of Self-Compacting Concrete

281

mix. For instance, the volumetric content of gravel in the total aggregate volume and the content of sand in the mortar volume are fixed. A specific PSD for the generation of dry concrete mix was applied to make such limitations unnecessary [27]. In the DMDA method, the end dense-graded curve was quite close to Fuller’s curve [expressed as Eq. (5.31)] after the iterative dense packing of particles [28]. Therefore, Hwang et al. proposed a mixture design method via Fuller’s gradation curve as well as minimum coating thickness [16, 29, 30]. The fuller’s gradation curve and error function were applied to find the theoretical blended ratio of all solid materials down to nano-size particles. ( P(D) =

D Dmax

)0.5 (5.31)

where P(D) is a fraction of the total solids smaller than size D in the solid system with the largest size of Dmax . q is the distribution modulus and equals 0.5 for Fuller’s Model. The surface area of aggregate is calculated by assuming spherical aggregate particles to simplify the calculation. Then, paste amount is determined as the summation of void volume of aggregate and lubricating part while the latter is the production of surface area of aggregate and paste layer thickness. The thickness is determined based on the property evaluation of mixtures with various layer thicknesses. However, it is demonstrated that packing density is highly influenced by particle shapes [31]. This spherical assumption is different from reality and gives rise to error which is dependent on the similarity between aggregates and spheres. Besides, the determination of layer thickness is dependent on massive trials. In terms of particle packing, Andreasen and Adersen derived a generalized model than Fuller’s one, shown below [32]. ( P(D) =

D Dmax

)n (5.32)

where P(D) is a fraction of the total solids being smaller than size D in the solid system with the largest size of Dmax . q is the distribution modulus and equals 0.5 for Fuller’s Model. To take into consideration the minimum size of particle (Dmin ), a modified equation shown as Eq. (5.33) was proposed by Funk and Dinger [33], named FD model. It has been demonstrated that particles with FD grading have low packing void. q

P(D) =

D q − Dmin q q Dmax − Dmin

(5.33)

The distribution modulus determines the character of a mixture regarding its fineness. Higher values will lead to coarser mixtures and vice versa. The optimized PSD modulus q varies from one research to another. The best description of sand and

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5 Mix Design of Concrete with Manufactured Sand

coarse aggregate PSD is provided with q of 0.2 according to Mueller [34] and q of 0.25 used by Le et al. [35] A value between 0.21 and 0.25 was proposed by Hunger for entire solid materials [36]. The optimized q should result in “the least void”. With the spherical particle assumption, Brouwers derived an equation to predict the packing void fraction of particles with FD gradation, seen in Eq. (5.34). This equation contains the void fraction of the single-sized particles (ϕ1 ) and a parameter (β), which are both governed by the particle shape and method of packing only. Therefore, for specific particles, the optimized modulus q could be determined by minimizing the packing density ϕ. ( ϕ = ϕ1

Dmin Dmax

) (1−ϕ1 )β (1+q 2 )

(5.34)

According to this ideal particle gradation curve, design methods based on the optimization of the volumetric proportions of solids were proposed and widely used. The target PSD represents the objective or goal of the optimization problem. This value shall either be minimized or maximized. The optimization was determined by minimization of the sum of the squares of the residuals (RSS) between the real PSD and the ideal one, shown in Eq. (5.35). A design method is based on the optimization of the volumetric proportions of sand and coarse aggregate according to an ideal particle gradation curve: ⎞2 ⎛ n m Σ Σ ( i+1 ) ( i+1 ) ⎝ − Ptar Di ⎠ → min RSS = Pi, j Di i=1

(5.35)

j=1

where m represents the number of ingredients ( ) in the packing ( ) system while n represents the grading number of PSD. Pi, j Dii+1 and Ptar Dii+1 are the real and ideal fractions of particles smaller than size of Dii+1 , which is the geometric mean of the upper and lower size the respective fraction obtained by sieving or laser diffraction analysis according to Eq. (5.36). Dii+1 =

√

Di Di+1

(5.36)

Based on this optimization method, the proportions among aggregates were determined [37–39]. The maximum paste volume was set as 10% of the total concrete volume and 135 kg/m3 for concrete made with Portland cement of specific gravity of 315 kg/m3 . The composition of powder was determined by replacing cement with SCMs according to the procedure in Fig. 5.9. Water content was kept at 17–20% of total concrete volume depending on air volume, aggregate properties, etc. The prepared mixtures showed high filling ability, adequate passing ability, and stability with powder contents between 278 and 312 kg/m3 for a compressive strength target range of 25–35 Mpa.

5.3 Mix Proportioning Methods of Self-Compacting Concrete

Fig. 5.9 Procedure to determine the powder composition

283

284

5 Mix Design of Concrete with Manufactured Sand

In this method, the maximum binder content was fixed at 10% of the total concrete volume and water content was also fixed. Therefore, maximum paste volume was fixed while it is highly dependent on the features of aggregates like packing and particle shape, and this maximum value might be insufficient if aggregates have elongated or flaky shapes or gap grading. Besides, hardened properties like strength are not considered in this method. Similar to the above method, Le et al. used the FD model to determine the ratio of aggregate components but fixed the exponent q at 0.25 [35]. However, the paste volume was determined using the ICAR method and depended on the packing void fraction together with aggregate shape and angularity. Then, w/cm ratio was determined based on its relationship with compressive strength, also satisfying the limit values regulated in DIN EN 206-1 and DIN 1045-2 based on the durability consideration. The primary SP dosage was selected as the saturation dosage of the corresponding mortar. The detailed procedure of this method is shown in Fig. 5.10. Both above two methods are based on the fact that the optimization of aggregate packing leads to strong and dense grain skeletons, which no longer requires high amounts of paste and cement for required workability and appropriate strength. On the other hand, it is also well known that the optimization of all solids leads to reduction of water demand because less void volume has to be filled with water. Therefore, lower w/c ratios can be achieved. Therefore, fresh concrete can adequately be defined as a mixture of solids, water, air, and admixtures. All solids form a certain packing and are surrounded by a layer of water to lubricate particles. Based on this, a mix design method was proposed by Brouwers and his co-workers based on the grading of all involved solids [27, 36, 40, 41]. Any number of PSDs of the individual materials can be combined to a total grading, with the requirement of the best fit with a target FD grading. The deviation of the actual from the desired grading was minimized using the least square method. Then, based on the fact that one cubic meter of fresh concrete is composed of m solids (Vsolid ), water (Vw ), and voids (Vair ) as shown in Eq. (5.37), parameters like cement content, water content, and the ratio between binders according to the requirements of properties were employed as constraints to solve the mix proportion. Limitations of these parameters were further specified by Wang et al. [42] who prepared SCC with 20% lower binder content than the rational method. Vsolid =

m Σ

Vsolid,k = Vtotal − Vw − Vair

(5.37)

k=1

A lower quantity of cement means reduced CO2 emission due to the cement production.

5.3 Mix Proportioning Methods of Self-Compacting Concrete

Fig. 5.10 Procedure of mix design by Le et al. [35]

285

286

5 Mix Design of Concrete with Manufactured Sand

Fig. 5.11 Technical route

5.4 Mix Design of Concrete Based on Surplus Coefficient of Mortar Mortar is mainly used to fill the gap of coarse aggregates and cover its surface in concrete. Appropriate mortar content can improve the compactness, workability, and stability of concrete. The mortar surplus coefficient (F f ) refers to the ratio of the volume of surplus mortar after filling the void to the void volume caused by the accumulation of coarse aggregate.

5.4.1 Technical Route See Fig. 5.11.

5.4.2 Design Steps The design steps of mortar surplus coefficient method are as follows: (1) Determine the types and proportions of raw materials, including the water to binder ratio, the percentage of mineral admixtures, and the mass ratio of cementitious materials to MS. (2) Assume the amount of coarse aggregate and mortar surplus factor F f . (3) The volume V m of mortar is calculated by Eq. (5.39). (4) The water consumption, MS mass, and equivalent cement mass are calculated according to the mass ratio of cementitious material and MS, and water to binder ratio by Eq. (5.40). (5) The mass of cement and mineral admixtures are calculated through the proportion of mineral admixtures. The preliminary mix proportion is determined based on the above five steps. (6) Modify it according to the apparent density of the design. ] Mg Mg Mg Mg / − − F f = Vm − ρa ρb ρa ρb [

(5.38)

5.5 Mix Design Method of Manufactured Sand …

287

where F f is the surplus coefficient of mortar, Vm is the volume of mortar (m3 ), Mg is the content of coarse aggregate (kg), ρa denotes the bulk density of coarse aggregate (kg/m3 ), and ρb represents the apparent density of coarse aggregate (kg/m3 ). Vm =

Mc' Ms Mw + + ρc ρs ρw

(5.39)

where Mc' is the equivalent cement content (kg), Ms is the content of sand (kg), Mw represents the content of mixing water (kg), ρc stands for the apparent density of cement (kg/m3 ), ρs is the apparent density of sand (kg/m3 ), and ρw is the apparent density of mixing water (kg/m3 ). Mc' = Mc +

ρc × Mk ρk

(5.40)

where Mc represents the content of cement (kg), Mk is the content of mineral admixtures (kg), ρc means the apparent density of cement (kg/m3 ), and ρk is the apparent density of mineral admixtures (kg/m3 ).

5.5 Mix Design Method of Manufactured Sand Concrete Based on Aggregate Shape The problems of the existing mix proportion design methods are shown as follows: (1) The influence of aggregate shape is not considered. (2) There are fines in MS. The change of the percentage of fine aggregate in total aggregate means the change of fines content in concrete and the properties of slurry, making the mix proportion of MS concrete more complicated. (3) Too little amount of cementitious material will reduce the workability of concrete. On the contrary, an excessive amount of cementitious material can lead to durability problems.

5.5.1 Mix Design Principle of High-Performance Concrete with Manufactured Sand Based on Aggregate Shape From the point of view of workability, the slurry in concrete is divided into two parts, one is used to fill the accumulated voids between aggregates, and the other is used to cover the aggregate surface to form a lubricating layer. In the loose accumulation of aggregates, the contact between aggregates may be considered point-to-point. If the slurry is just enough to fill the gap of aggregate accumulation, the aggregate surface is covered with slurry except for the contact point (points A, B, C, and D in Fig. 5.12). However, it is still difficult to ensure free sliding

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5 Mix Design of Concrete with Manufactured Sand

Fig. 5.12 Schematic diagram of filling aggregate accumulation voids with slurry

and rolling between aggregates even if there is a certain thickness of lubrication layer at the contact point due to the diversity of aggregate shapes. Hence, the concept of the spreading coefficient was proposed. However, the elongation coefficient can only be determined by the experiment, but not by calculation. The minimum spreading degree of aggregate should be just enough to allow the aggregate to rotate freely, so the spreading coefficient should be a function of the aggregate shape characteristics. The more spherical the aggregate shape is, the less the aggregate needs to be spread to achieve free rotation. As shown in Fig. 5.13, the concrete is considered to be composed of coarse aggregate, mortar with MS, and inclusion bubbles. The mortar with MS can be divided into two parts. One part fills the accumulation gap of coarse aggregate, and the other is used to disperse the coarse aggregate, the extent of which is related to the shape of the coarse aggregate. The mortar with MS is composed of MS and cementitious pastes, while MS is composed of MS particles (> 75 µm) and fines (< 75 µm). The fines in the MS is also a part of the slurry; that is, the slurry can be considered to be composed of cement, supplementary cementitious materials (such as fly ash), fines, water, and chemical admixtures. The amount of mortar with MS is determined by the accumulation gap and the particle shape of coarse aggregate, as shown in Eq. (5.41).

Fig. 5.13 Composition of concrete

5.5 Mix Design Method of Manufactured Sand …

289

Vmortar = ϕG + VG f G

(5.41)

where ϕG is the bulk porosity of coarse aggregate, which can be determined by the bulk density of coarse aggregate (ρ B,G ) and an apparent density (ρ A,G ) (Eq. 5.42). VG is the absolute volume of coarse aggregate. ϕG = 1 − VG =

ρ B,G ρ A,G

(5.42)

MG ρ A,G

(5.43)

where MG is the mass of coarse aggregate. f G is a function of aggregate shape. It represents the demand for surplus mortar due to the non-spherical characteristics of aggregate. There are many testing methods for aggregate shape, among which the effective quantitative characterization method is the image method. It is common for aggregate shape to be characterized by roundness (the area ratio of aggregate projection to the smallest circumcircle). However, only the two-dimensional characteristics of aggregate can be reflected based on roundness. The spherical similarity (Q) is proposed to represent the degree to which the aggregate shape is close to the sphere based on the roundness. Its calculation method is as follows. Σ Q=

Qx = N Ry =

Σ( Σ R y ) 23 n

N

4S y π L 2y

(5.44) (5.45)

where Q x is the spherical similarity of the x-th aggregate (x = 1, 2, … N), R y is the projection roundness of the X aggregate in the Y direction (y = 1, 2, 3), and n is the number of projection directions (take 3). S y and L y are the projection area and the minimum circumcircle diameter in the y-th direction, respectively. Based on Eqs. (5.44) and (5.45), the spherical similarity (Q G ) of coarse aggregate can be obtained. Q G is not greater than 1. Only when the coarse aggregate is an absolute sphere, Q G is 1. Then, the shape function f G of coarse aggregate is obtained. fG =

1 −1 QG

(5.46)

Thus, it can be considered that if the aggregate is an absolute sphere, then f G is 0. At this time, the role of mortar is only to fill the gap of coarse aggregate accumulation.

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5 Mix Design of Concrete with Manufactured Sand

MS is composed of particles and slurry, and the slurry volume is determined by the accumulation space among MS and the shape of MS particles. Vmortar = Vpaste + VMS

(5.47)

Vpaste = ϕMS + VMS f MS

(5.48)

where ϕMS is the accumulated porosity of MS particles (excluding fines), which can be determined by the accumulated density (ρ B,MS ) and apparent density (ρ A,MS ) of MS particles (Eq. 5.48). VMS is the absolute volume of MS. ϕMS = 1 − VMS =

ρ B,MS ρ A,MS

MMS · (1 − α) ρ A,MS

(5.49) (5.50)

where MMS is the mass of MS and α is the content of fines in MS. The spherical similarity (Q MS ) of MS is calculated by Eqs. (5.44) and (5.45). Q MS is not greater than 1. Only when the MS particle is an absolute ball, Q MS is taken as 1. Then, the shape function f MS of MS is obtained. f MS =

1 −1 Q MS

(5.51)

Set the amount of fly ash (β) first, then the water-cementitious material ratio is determined according to the Technical Specification for Application of SelfCompacting Concrete (JGJ/T 283-2012). W B

Vmortar = Vpaste + Vpaste =

MMS · (1 − α) ρMS

MFA MMS · α Mw MC + + + ρC ρFA ρSP ρw

MG MMS (1 − α) MC MFA MMS · α Mw + + + + + + Vvoid = 1 ρ A,G ρ A,MS ρC ρFA ρSP ρw The dosage of admixture is adjusted according to the workability.

(5.52) (5.53) (5.54)

5.5 Mix Design Method of Manufactured Sand …

291

5.5.2 Design Steps for Mix Proportion of High-Performance Concrete with Green Manufactured Sand Based on Aggregate Shape Step 1 The performance parameters ρ A,G , ρ B,G , ρ A,MS , ρ B,MS , ρC , ρFA , ρSP , α of raw materials should be determined first. Step 2 Test the spherical similarity Q G , Q MS of aggregate and calculate the shape function f G , f MS of coarse aggregate and MS particles. Step 3 Set the fly ash content as 20%, adjust it according to the test strength, and calculate the water-cementitious material ratio WB according to the design strength. The fluidity of the slurry should be tested under the water-cementitious material ratio. Step 4 Adjust the water consumption of fines to make the fines slurry have the same fluidity as the cementitious material slurry. (Supplementary test: The cement slurry strength with different fines contents under the same fluidity is mixed with the adjusted water consumption). Step 5 If the content of coarse aggregate is x, then Vmortar = 1 −

x ρ B,G + fG ρ A,G ρ A,G

ρ A,G ρ B,MS − ρ A,MS ρ B,G + xρ A,MS f G ρ A,G (1 − α)(1 + f MS ) ) ( MW,SP 1−α α MMS 1 − ρρ B,MS − + f − MS ρW ρ A,MS ρSP A,MS

MMS =

Mc =

1 ρC

+

β (1−β)ρFA

0.42 f ce (1−β+βγ ) (1−β)ρW ( f cu,0 +1.2)

(5.56)

(5.57)

β MC 1−β

(5.58)

0.42 f ce (1 − β + βγ ) ) MC + MW,SP ( (1 − β) f cu,0 + 1.2

(5.59)

MFA = MW =

+

(5.55)

Therefore, the amount of MS, cement, fly ash, and water has a functional relation with the mass x of coarse aggregate. The mass of coarse aggregate and the mass of each component of concrete can be determined by Eq. (5.54). Step 6 Adjust the dosage of admixture according to the workability of concrete. Step 7 Adjust the amount of fly ash according to the strength. If the surplus of concrete strength is large, the fly ash content should be increased. If the strength is insufficient, reduce the fly ash content and repeat Steps 5– 7 (Fig. 5.14).

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5 Mix Design of Concrete with Manufactured Sand

Fig. 5.14 Flowchart for mix design of high-performance concrete with MS based on aggregate shape characteristics

5.6 Optimization of Mix Proportion of Concrete with Manufactured Sand 5.6.1 Optimization Technology of Fines 5.6.1.1

Limits of Fines

Clay minerals are often introduced into the fines of MS due to their parent rock or production process. Clay in fines will lead to concrete strength and durability problems caused by the large demand of concrete admixtures, rapid loss of workability, and increasing defects in hardened concrete. Therefore, the mud content of fines should be judged. Methylene blue adsorption test is used to limit the content of fines in MS according to MB value (Table 5.25).

5.6.1.2

Determination of Fines Content

The fines are often added into the slurry in the way of “external mixing” as the fines exist in the MS.

5.6 Optimization of Mix Proportion of Concrete with Manufactured Sand Table 5.25 Limits of fines content in MS/%

Category of MS

I

293 II

III

MB < 1.4 or qualified

≤7

≤ 10

≤ 12

MB ≥ 1.4 or unqualified

≤4

≤5

≤7

Clay content

0

≤ 0.5

≤ 1.0

The increase of fines content in MS will increase the volume of slurry; thus, the workability of concrete will be improved and the number of cementitious materials can be reduced under the constant workability. However, the increase of MS powder content means the decrease of the water-powder ratio due to the constant watercementitious material ratio. Although the slurry volume increases, the fluidity of the slurry decreases. Therefore, the excessive fines content will bring the deterioration of working performance of concrete caused by the decrease of slurry fluidity. Meanwhile, the mechanical properties and durability of concrete can be increased with the increase of fines content, because the amount of aggregate under the constant workability is improved as the surplus of slurry in concrete increases. However, the high-level content of fines contributes to the decrease of cementitious component content in slurry due to no hydration activity of fines, thus resulting in the decrease of mechanical properties and durability of concrete. Generally, the content of fines in MS should be controlled between 6 and 15%, and the content of fines in engineering should be determined from tests.

5.6.2 Optimization Technology of Manufactured Sand and Coarse Aggregate 5.6.2.1

Optimization Technology of Manufactured Sand

MS has a significant impact on the performance of concrete. Therefore, the performance of concrete can be effectively improved through the optimization of MS. (1) Lithology optimization of MS The parent rock lithology of MS should be uniform. Since MS and gravel are produced at the same time in plants, the compressive strength of parent rock of MS should not be less than 75 MPa in order to ensure the strength of sand and coarse aggregate to meet the requirements of concrete. Moreover, the parent rock should not have alkali activity. (2) Control of fines content Fines in MS have a significant effect on the performance of concrete, especially in the presence of clay minerals. The content of fines in MS shall be controlled according to the requirements of 4.3.1.

294

5 Mix Design of Concrete with Manufactured Sand

(3) Optimization of grading of MS In MS, there are more particles on both sides (> 2.36 and < 0.15 mm), while there are fewer particles in the middle (0.15–2.36 mm), especially 0.3–1.18 mm, showing a typical phenomenon of “more at both ends, less in the middle”. Sometimes, a certain particle size is broken, resulting in poor gradation. But because MS is produced by machine, its gradation is stable and adjustable. Secondly, the grain size of MS is coarse, which size belongs to the typical medium-coarse sand. It can be seen from Sect. 2.1.2 that the gradation of MS has different influence on the workability, mechanical properties, and durability of concrete. In addition, the good gradation makes the accumulation gap of MS smaller and the demand for slurry smaller. With the mix proportion fixed, the workability is improved while the amount of cementitious material is reduced. The decrease of cementitious material not only reduces the production cost of concrete, but also increases of aggregate content in concrete system. As the most stable component in concrete, the increase of aggregate can improve the mechanical properties, volume stability, and long-term durability of concrete. Therefore, the gradation of MS should be optimized by adjusting the production process according to the performance requirements of concrete with MS. (4) Optimization of grain shape of MS The shape of MS has different effects on the workability, mechanical properties, and durability of concrete. The closer to the sphere the shape of MS is, the smaller viscosity of the mortar with MS and the greater mortar fluidity is, which is conducive to the workability of concrete. In addition, the shape and gradation of MS affect the accumulation porosity of MS particles. According to the mix proportion design principle of high-performance concrete with MS, the closer the shape to the sphere of MS is, the smaller of the required amount of slurry, which can improve the slurry surplus. Therefore, the workability of concrete can be improved, or the amount of cementitious material can be reduced under the constant workability of concrete. However, according to the theoretical study on the modulus and diffusion coefficient of MS, with a closer shape to the sphere, both the strength and chloride ion diffusion efficient are higher. Therefore, from the perspective of mechanical properties and durability, the optimal shape of MS may be not spherical. On one hand, the shape of MS can be optimized to reach better workability of concrete in the premise of meeting the requirements of mechanical properties and durability. On the other hand, the amount of slurry can be reduced by optimizing the shape of MS with required workability. What’s more, the amount of coarse aggregate and MS can be increased, with the mechanical properties, volume stability, and durability of concrete improved. Therefore, the mechanical properties and durability of concrete can be improved by adjusting the mix proportion under the constant workability of concrete.

5.6 Optimization of Mix Proportion of Concrete with Manufactured Sand

5.6.2.2

295

Optimization Technology of Coarse Aggregate

From the perspective of workability, coarse aggregate should have a large spheroid similarity, so the mortar demand and slurry demand are reduced, and the workability of concrete can be improved when the mixture proportion is controlled. It can be seen from Table 5.26 that the concrete has a good workability based on a reasonable mix proportion design. The slump is kept above 25 cm, the slump expansion is kept above 65 cm, and the inverted slump time is not more than 5.0 s. The workability of concrete is further optimized when the shaped aggregate is used (Fig. 5.15). Shaping can effectively improve the workability of concrete; hence, it can reduce the amount of mortar and paste. As a stable component of concrete, the increase of coarse aggregate can improve the mechanical properties, volume stability, and durability of concrete. Therefore, the shaping of coarse aggregate can indirectly improve the mechanical properties, volume stability, and long-term durability of concrete. Table 5.26 Influence of coarse aggregate shaping on performance of concrete with MS Coarse Maximum Slump/mm Slump Inverted Cohesiveness Compressive aggregate particle flow/mm slump strength/MPa size/mm time/s 3d 7d 28d Shaping

19

275

710

3.6

Better

60.1

75.7

89.3

Not shaping

19

255

650

4.7

Better

61.3

74.4

89.5

Fig. 5.15 Photos of coarse aggregate

296

5 Mix Design of Concrete with Manufactured Sand

5.6.3 Optimization Technology of Mineral Admixtures 5.6.3.1

Optimization of Mineral Admixtures

There are many kinds of mineral admixtures with various qualities. The compatibility test with cement and admixtures should be carried out before application. As shown in Table 5.27, primary fly ash, L80 phosphorous slag powder, S95 slag, and composite admixtures can significantly improve the initial fluidity of cement paste and reduce the time loss of fluidity. When the content of composite admixture and L70 phosphorus slag powder reaches a certain value, the initial fluidity of the slurry can be improved and the fluidity time loss can be reduced. For silica fume, the slurry has no fluidity when the content of water-reducing admixture is 0.3%, while the slurry has little fluidity when the content of water-reducing admixture is increased to 0.4%. Therefore, silica fume can significantly reduce the initial fluidity and increase the fluidity loss. In order to ensure that the concrete has good initial fluidity and low fluidity loss over time and that the concrete strength has a surplus, the first-grade fly ash mixed with silica fume or composite admixture is selected as the cementitious system of concrete. Compatibility test should be carried out before application due to the diversity and regional characteristics of mineral admixtures.

5.6.3.2

Compound Mixing Technology of Mineral Admixtures

There are different physical and chemical characteristics of mineral admixtures, such as the composition and content of active ingredients and particle size distribution. The optimization of mineral admixtures can be obtained by adjusting the above characteristic parameters. At the same time, the compatibility test of mineral admixtures should be carried out before the application of mineral admixtures. As shown in Table 5.28, the mixed admixtures of phosphorus slag and different minerals have diversified the fluidity and retention, indicating an inconsistent compatibility. The mixture of different mineral admixtures is optimized according to their influence on the mechanical properties and durability of concrete on the premise of meeting the requirements of compatibility. For example, the strength of concrete with different mineral admixtures is shown in Fig. 5.16. It can be seen that the type of mineral admixtures and their dosage on the concrete strength is significant. Therefore, the high-performance concrete with MS can be prepared with a large amount of mineral admixtures on the premise of meeting the compatibility and performance requirements of concrete.

5.6 Optimization of Mix Proportion of Concrete with Manufactured Sand

297

Table 5.27 Influence of single mineral admixture on fluidity of cement paste Sample

Mineral admixtures

Water-reducing admixture/%

Fluidity/mm Initial

1h

2h

4h

JC-Control

0

210

255

240

140

JC-1

10%FA II

240

275

270

255

JC-2

15%FA II

250

285

280

255

JC-3

20%FA II

260

290

295

280

JC-4

5.0%SF

160

195

165

无

JC-5

7.5%SF

135

145

115

无

JC-6

10%SF

120

105

无

无

JC-7

3%CA

185

250

250

115

JC-8

6%CA

195

260

270

215

JC-9

9%CA

200

270

280

245

JC-10

10%L70PS

185

270

270

270

JC-11

20%L70PS

220

295

295

295

JC-12

30%L70PS

250

310

315

305

JC-13

10%L80PS

260

285

280

255

JC-14

20%L80PS

280

300

295

275

JC-15

30%L80PS

285

310

305

290

JC-16

10%S95SL

255

300

280

245

JC-17

20%S95SL

285

300

295

260

JC-18

30%S95SL

285

295

300

285

JC-19

10%FA I

280

295

275

225

JC-20

20%FA I

300

295

300

270

JC-21

30%FA I

315

305

300

290

JC-22

5%(SP)

240

270

255

150

JC-23

7.5%(SP)

275

290

280

230

JC-24

10%(SP)

280

285

280

245

JC-25

3%(HPCA)

240

265

245

200

JC-26

6%(HPCA)

255

275

270

225

JC-27

9%(HPCA)

255

275

270

225

0.3

0.4

0.3

5.6.4 Optimization Technology of Additives Admixture is an important component of high-performance concrete with MS, especially for the workability of self-compacting concrete MS. The addition of waterreducing admixture, tackifier, and other admixtures can lead to appropriate viscosity, good fluidity, cohesiveness, plasticity, and mechanical properties under the low water to binder ratio, so as to meet the performance requirements of high-performance concrete with MS.

298

5 Mix Design of Concrete with Manufactured Sand

Table 5.28 Fluidity of cementitious materials with composite addition Sample JC-17

Cement/%

Composite addition

Fluidity/mm Initial

1h

2h

4h

20

–

220

295

295

295

10

10%FA II

235

300

300

295

JC-20

10%SF

0

0

0

0

JC-21

10%CA

285

300

295

285

JC-37

10%L80PS

280

295

290

270

JC-38

10%S95SL

285

305

295

265

JC-39

10%FA I

290

305

295

275

JC-40

10%SP

280

295

295

270

JC-41

10%HPCA

270

295

290

265

JC-19

80

Phosphorous slag powder/%

Fig. 5.16 Effect of mineral admixtures on concrete strength (SF, FA, and LP in the figure represent silica fume, fly ash, and phosphorus slag, respectively)

5.6.4.1

Water-Reducing Admixtures

The water-reducing admixture should be compatible with the cementitious materials and fines in MS concrete, as shown in Table 5.29. It can be seen that the addition of CS-SP1 superplasticizer makes the slump and extension of concrete with MS better and the loss and inverted slump time smaller. If the compatibility between water-reducing admixture and concrete components is poor, the workability of concrete will be damaged with incidental segregation and bleeding, which further brings negative effects on the strength and durability of concrete. It can be seen from Table 5.29 that the 3/7/28-day strength of MS concrete mixed with CS-SP1 admixture is the highest due to its good workability. It can be considered that the CS-SP1 superplasticizer has the best compatibility with the concrete raw materials considering the mixture performance and mechanical properties of concrete with MS.

23.5 22.0

25.5 23.5

2.0%V500 7.3 21.0

60.0

65.0

63.0

61.0

1.5%V3320

10.1

12.0

23.5 22.0

24.0 23.5

1.6%LX-6

1.4%CS-SP1 56.0

66.0

58.0

56.0

1h

0h

1h

0h

2h

Slump flow/cm

Slump/cm

Dosage and type of water-reducing admixtures

Table 5.29 Performance of MS concrete mixed with different water-reducing admixtures

50.0

64.0

55.0

42.0

2h

21.0

7.3

10.1

12.0

0h

27.6

7.7

13.1

14.1

1h

Inverted slump time/s

31.4

10.0

13.5

18.0

2h

20.5

20.5

21.9

18.9

3d

36.7

28.5

38.5

36.5

7d

54.7

51.6

60.3

55.3

28d

Compressive strength/MPa

5.6 Optimization of Mix Proportion of Concrete with Manufactured Sand 299

300

5.6.4.2

5 Mix Design of Concrete with Manufactured Sand

Tackifier

Tackifier is one of the indispensable admixtures for preparing high-performance concrete with MS, especially for self-compacting concrete with MS. As shown in Table 5.30, although the initial slump of MS concrete mixed with V3320 waterreducing admixture reaches 24.0 cm, the initial slump flow is 48.0 cm, and the inverted slump time in 1 h is more than 30.0 s, resulting in segregation. However, the addition of tackifier obviously increases the slump and extension of concrete and improves the inverted slump time. The workability of MS concrete mixed with CS-SP1 waterreducing admixture and tackifier is obviously improved, and slump and extension are slightly increased. However, the inverted slump time is significantly shortened, which makes the concrete with MS have good cohesion. Therefore, tackifier should be adopted in high-performance concrete with MS, and its dosage should be determined by tests.

5.6.4.3

Other Additives

Other admixtures should be selected according to the specific performance requirements of concrete. For example, anti-washout admixtures should be used in underwater concrete, and pumping admixture should be used in ultra-high pumping concrete. Furthermore, expansive admixture should be used in steel pipe arch concrete.

5.7 Concluding Remarks 1. The properties of cement, mineral admixtures, manufactured sand, coarse aggregate, chemical admixtures, and other raw materials have significant influence on the working performance, mechanical properties, and durability of concrete with MS. The concrete with different properties can be prepared by adjusting the type, composition, particle size, dosage, and other characteristic parameters of raw materials. 2. General steps of high-performance concrete mix design are as follows: determination of the target mean strength; calculation of the mix proportion; trial, adjustment, and determination of mix proportion; and check of specific performance. 3. Due to the wide variety of raw materials for SCC, a lot of mix design methods such as blocking criteria method, ICAR method, packing model-based method, target grading method, and other methods have been proposed. 4. Mortar and aggregate are the main components of concrete, which have dominant influence on the compactness, workability, and stability of concrete. Therefore, the mix proportion design of concrete with MS considering the surplus coefficient of mortar and spherical similarity of aggregate is also proposed.

23.0 23.0

0

0.02

1.2%CS-SP1

1.2%CS-SP1

24.0 24.5

0

0.01

1.5%V3320

22.0

23.5

22.0

24

20.0

11.1

24.8

25.5

48.0

57.0

55.0

65 55.0

50.0

60.0

45.0

1h

0h

2h

0h

1h

Slump flow/cm

Slump/cm

1.5%V3320

Dosage of tackifier/%

Dosage and type of water-reducing admixtures

Table 5.30 Influence of different amount of tackifier on concrete performance

54.0

44.0

58.0

42.0

2h

11.1

24.8

25.5

30.0

0h

12.5

27.6

28.0

33.0

1h

Inverted slump time/s

14.1

31.2

31.1

36.3

2h

18.9

–

20.5

–

3d

36.5

–

36.7

–

7d

Compressive strength/MPa

55.3

–

54.7

–

28d

5.7 Concluding Remarks 301

302

5 Mix Design of Concrete with Manufactured Sand

References 1. S.H. Kosmatka, B. Kerkhoff, W.C. Panarese, Chemical admixtures for concrete, in Design and Control of Concrete Mixtures, eds. by Steven H. Kosmatka, S. Kerkhoff, William C. Panarese, vol. 5420 (Portland Cement Association, Skokie, Illinois, 2002), pp. 105–118 2. C.-S. Jiang, L.-N. Lu, S.-B. Guan, Q.-J. Ding, S.-G. Hu, Preparation of high performance non-dispersible concrete. J. Wuhan Univ. Technol. Mater. Sci. Ed. 19(2), 67–69 (2004) 3. B. Han, L. Zhang, J. Ou, Non-dispersible underwater concrete, in Smart and Multifunctional Concrete Toward Sustainable Infrastructures (Springer, 2017), pp. 369–377 4. Z. Sun, J. Zhengwu, H. Wu, Investigations on properties of underwater anti-washout concrete. J. Build. Materials 03(29–34) (2006) 5. O. Petersson, P. Billberg, B.K. Van, A model for self-compacting concrete, in Proceedings of the International RILEM Conference on Production Methods and Workability of Concrete (Paisley, 1996), pp. 483–492 6. O. Petersson, P. Billberg, Investigation on blocking of self-compacting concrete with different maximum aggregate size and use of viscosity agent instead of filler, in Proceedings of the Proceedings of the 1st international RILEM symposium on SCC, 1999, pp. 333–344 7. V.K. Bui, A Method for the Optimum Proportioning of the Aggregate Phase of Highly Durable Vibration-Free Concrete (Asia Institute of Technology, Bangkok, Thailand, 1994) 8. V. Bui, D. Montgomery, Mixture proportioning method for self-compacting high performance concrete with minimum paste volume, in Proceedings of the 1st International RILEM Symposium on Self-Compacting Concrete (Stockholm, Sweden, 13–14 Sept, 1999), pp. 373–384 9. E. Koehler, D. Fowler, Proportioning SCC based on aggregate characteristics, in Proceedings of the 5th International RILEM Symposium on Self-Compacting Concrete, 2007, pp. 67–72 10. E.P. Koehler, Aggregates in Self-Consolidating Concrete (2007) 11. E.P. Koehler, D.W. Fowler, ICAR Mixture Proportioning Procedure for Self-Consolidating Concrete (2007) 12. 211.1 A, Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete. 211.1, 1996, 1 13. N. Sebaibi, M. Benzerzour, Y. Sebaibi, N.-E. Abriak, Composition of self compacting concrete (SCC) using the compressible packing model, the Chinese method and the European standard. Constr. Build. Mater. 43, 382–388 (2013) 14. Y.W. Choi, Y.J. Kim, H.C. Shin, H.Y. Moon, An experimental research on the fluidity and mechanical properties of high-strength lightweight self-compacting concrete. Cem. Concr. Res. 36(9), 1595–1602 (2006) 15. C.L. Hwang, L.S. Lee, F.Y. Lin, Densified mixture design algorithm and early properties of high performance concrete. J. Chin. Inst. Civ. Hydraulic Eng. 8(2), 217–219 (1996) 16. C.L. Hwang, S.L. Hsieh, Y.Y. Chen, The effect of coating thickness on aggregate on the property of SCC by Fuller’s ideal curve and error function, in Proceedings of the 5th International RILEM Symposium on Self-Compacting Concrete (Ghent, 2007), pp. 83–88 17. P.K. Chang, Y.N. Peng, C.L. Hwang, A design consideration for durability of high-performance concrete. Cem. Concr. Compos. 23(4–5), 375–380 (2001) 18. C.-L. Hwang, M.-F. Hung, Durability design and performance of self-consolidating lightweight concrete. Constr. Build. Mater. 19(8), 619–626 (2005) 19. H.Y. Wang, Study on durability of densified high-performance lightweight aggregate concrete. Comput. Concr. 4(6), 499–510 (2007) 20. T.Y. Tu, Y.Y. Jann, C.L. Hwang, The Application of Recycled Aggregates in SCC, vol. 42 (RILEM Publications, Bagneux, 2005), pp. 145–152 21. J. Kanadasan, H.A. Razak, Mix design for self-compacting palm oil clinker concrete based on particle packing. Mater. Des. (1980–2015) 56, 9–19 (2014) 22. M. Jones, L. Zheng, M.J.M. Newlands, Comparison of particle packing models for proportioning concrete constitutents for minimum voids ratio. Mater. Struct. 35(5), 301–309 (2002)

References

303

23. T. Sedran, F. De Larrand, F. Hourst, C. Contamines, Mix design of self-compacting concrete, in Proceedings of the International RILEM Conference on Production Methods and Workability of Concrete (Paisley, 1996) 24. F. De Larrard, Concrete Mixture Proportioning: A Scientific Approach (E & FN Spon, London, 1999) 25. T. Sedran, F. De Larrard, Optimization of self-compacting concrete thanks to packing model, in Proceedings of the Proceedings 1st SCC Symposium, CBI Sweden, RILEM PRO7, 1999, pp. 321–332 26. K.L. Radhika, P.R. Kumar, Mix proportioning of self compacting concrete based on compressible packing model, in Design, Performance and Use of Self-Consolidating Concrete, vol. 93, eds. by C. Shi, Z. Ou, K.H. Khayat (RILEM Proceedings, RILEM Publications, Bagneux, 2014), pp. 80–90 27. M. Hunger, H.J.H. Brouwers, Development of Self-Compacting Eco-Concrete (2006) 28. C. Hwang, C. Tsai, The Effect of Aggregate Packing Types on Engineering Properties of SelfConsolidating Concrete (2005) 29. Z. Cai, J. Zhang, S. Ye, L. Li, Z. Huang, New approach to design concrete mix proportions by coating thickness of aggregates. J. Build. Mater. 12(2), 152–157 (2009) 30. H. Wang, C. Hwang, S. Yeh, An approach of using ideal grading curve and coating paste thickness to evaluate the performances of concrete-(1) Theory and formulation. Comput. Concr. 2012(10), 19–33 (2012) 31. U. Stark, A. Mueller, Optimization of packing density of aggregates, in Proceedings of the Second International Symposium on Ultra High Performance Concrete, 2008, pp. 121–127 32. A. Andreasen, J. Anderson, The Relation of Grading to Interstitial Voids in Loosely Granular Products (With Some Experiments), 1929 33. D. Dinger, J. Funk, Predictive Process Control of Crowded Particulate Suspensions, Applied to Ceramic Manufacturing, 1994 34. F.V. Mueller, Design Criteria for Low Binder Self-Compacting Concrete, Eco-SCC. Ph.D. thesis. Reykjavik University, Iceland, 2012 35. H.T. Le, M. Müller, K. Siewert, H.-M. Ludwig, The mix design for self-compacting high performance concrete containing various mineral admixtures. Mater. Des. 72, 51–62 (2015) 36. M. Hunger, An Integral Design Concept for Ecological Self-Compacting Concrete (2010) 37. B. Esmaeilkhanian, K.H. Khayat, O.H.J.M. Wallevik, Mix design approach for low-powder self-consolidating concrete: eco-SCC—content optimization and performance. Mater. Struct. 50(2), 124 (2017) 38. B. Esmaeilkhanian, K. Khayat, A. Yahia, O. Wallevik, Mix Design Procedure for Low-Powder Self-Consolidating Concrete: Eco-SCC (2016) 39. B. Esmaeilkhanian, K. Khayat, O. Wallevik, Ecological Self-Consolidating Concrete: Design and Performance (2014) 40. G. Hüsken, H.J.H. Brouwers, A new mix design concept for earth-moist concrete: a theoretical and experimental study. Cem. Concr. Res. 38(10), 1246–1259 (2008) 41. H.J.H. Brouwers, H.J. Radix, Self-compacting concrete: theoretical and experimental study. Cem. Concr. Res. 35(11), 2116–2136 (2005) 42. X.H. Wang, K.J. Wang, P. Taylor, G. Morcous, Assessing particle packing based selfconsolidating concrete mix design method. Constr. Build. Mater. 70, 439–452 (2014)

Chapter 6

Self-Compacting Concrete with Manufactured Sand

6.1 An Overview of Self-Compacting Concrete (SCC) The concept of SCC was first proposed by Japanese Scholar Okamum in 1986. Subsequently, Ozawa et al. from the University of Tokyo carried out research on SCC. In 1988, for the first time, SCC was successfully developed using commercially available raw materials and showed satisfactory properties, including proper hydration heat release, good compactness, and so on. SCC has many advantages. For instance, SCC can ensure the good compactness of concrete. The surface quality of the concrete is improved by using SCC resulting in no surface bubbles, no honeycomb pitted surface, and no surface repair. The adoption of SCC also increases the freedom of structural design. The SCC matrix can be poured into complex shapes, thin walls, and densely reinforced structure. In addition, the use time of template and mixer is prolonged due to the no vibrating abrasion. Moreover, the SCC can also reduce the overall cost of the project. The adoption of SCC improves the production efficiency, shortens the construction period, and greatly reduces the labor intensity of workers. What’s more, the working environment and safety are improved because of no vibrating noise, and workers’ health risks caused by high vibrating noise are eliminated. At present, the research on self-compacting concrete with MS is mainly carried from the optimization of the mix proportion and the combination of structural design, production quality control, on-site construction technology, and engineering application. The optimization of mix proportion mainly focuses on the sensitivity of SCC with MS from raw materials to proportions. On the basis of a large number of experiments, the chemical admixtures, mineral admixtures, aggregate quality, and other factors are analyzed for the performance of self-compacting concrete to establish quantitative relationships. The optimal mix proportion of self-compacting concrete is studied using optimization theory based on the characteristics of regional materials. There are relatively few theoretical studies on the physical and mechanical properties and durability of self-compacting concrete with MS.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Z. Jiang, Green High-Performance Concrete with Manufactured Sand, https://doi.org/10.1007/978-981-19-6313-1_6

305

306

6 Self-Compacting Concrete with Manufactured Sand

6.2 Pumping Pressure of Concrete with Manufactured Sand With the development of the ultra-high-rise building, much progress has been achieved via pumping concrete technology in recent years. Due to the mechanization of pumping concrete, a variety of technical measurements can not only improve the performance of concrete, but they can also reduce the intensity of labor and environment pollution. Moreover, they are a great progress of modern construction technology of concrete, with the application level and scale as one of the important sign to measure the level of economy and technology among counties and regions. As the amount of building construction and the height of pumping continuously increase, as well as pumping time continuously increases, higher requirements have been put forward for the workability loss with time of pumping concrete. At the same time, the building structure of ultra-high pumping construction generally uses high-strength concrete, which has high viscosity and pumping resistance. So the contradiction between the time-loss of workability, viscosity, and workability and the contradiction between mechanical properties and high fluidity of concrete, are the key problem in the mix design and construction of ultra-high pumping concrete, while pumping technology and procedure control are the key factors affecting pumping efficiency. Ultra-high pumping concrete with MS is a type of high-performance concrete, which possesses high fluidity, low viscosity, high cohesiveness, and can meet the construction requirements of ultra-high pumping of building structures higher than 100 m. Based on controlling the quality of raw materials, optimizing mix design and preparation, rationalizing pumping construction and maintenance, as well as other whole-process quality control methods, the construction schedule, and engineering quality of ultra-high-rise building are improved. Therefore, the mechanical performance and durability performance of ultra-high pumping concrete with MS are guaranteed.

6.2.1 Theoretical Prediction of the Pressure Loss of Concrete In the concrete pumping process, the flowing of concrete in conveying pipeline depends on the promotion caused by pumping pressure. During flowing process, concrete is subjected to the action of resistance, such as the friction force of pipeline wall and viscous force of concrete, which causes the loss of pumping pressure. Besides, the diameter and the length of pipeline, as well as the concrete will cause the loss of pumping pressure [1–4].

6.2 Pumping Pressure of Concrete with Manufactured Sand

6.2.1.1

307

The Pressure Loss Principle of Ultra-High Pumping Concrete with Manufactured Sand

Studies indicate that the flowing of concrete in pipeline follows Bingham equation and friction in concrete can be expressed as follows. f = k1 + k2 v

(6.1)

where v is the flowing velocity. k1 is the adhesive stress intensity between concrete and pipeline wall (MPa), and k2 is resistance coefficient related to the flowing velocity of concrete [MPa/(ms−1 )]. In order to facilitate the analysis and calculation, it is assumed that concrete is a kind of continuous medium that cannot be compressed to flow in conveying pipeline at a uniform speed. In the conveying pipeline, the concrete on the dx cylinder is taken as the study object, as shown in Fig. 6.1.   According to the balance mechanism of force, the pressure of concrete πr 2 d p at the place of (x + dx) is the sum ofviscous force in  pipeline [2πr dx(k1 + k2 v)], the component of gravity of concrete πr 2 dxγ sin θ , and the inertia forces of motion   2 πr dxρ dv , that is: dt 2πr (k1 + k2 v)dx + πr 2 γ sin θ dx + πr 2 ρdx

dv = πr 2 d p dt

(6.2)

In the equation, r is the radius of conveying pipeline, ρ is the weight of concrete, γ is the volumetric weight of concrete, θ is the angle between conveying pipeline and horizontal plane. By sorting out the above equation, the pressure loss in the conveying pipeline per unit length is: 2 ∂p dv = (k1 + k2 v) + ρ + γ sin θ ∂x r dt

Fig. 6.1 Schematic diagram of concrete flowing in the pumping pipeline

(6.3)

308

6 Self-Compacting Concrete with Manufactured Sand

According to the above equation, the pumping pressure loss is inversely proportional to the diameter of pipeline r , that is, the pumping pressure loss is at a small value with the large diameter of pipeline. At the same time, the pumping pressure loss is related to the conveying speed v, which reflects on the displacement of the main pump of concrete. If the displacement is enormous, the pumping pressure loss is much larger. Meanwhile, the flowing of concrete has a certain inertia force, and the length of conveying pipeline L can cause considerable pumping pressure loss. When pumping vertically, the volumetric weight has a great influence on the pumping pressure loss, and there is a great pumping pressure loss at the bend of pipeline.

6.2.1.2

Pumping Rate and Pumping Line

The friction is equivalent to the cohesiveness of concrete to the inner wall of pipeline when the concrete starts to move. After the concrete starts to move, the increment of friction resistance is linearly related to the flowing rate of concrete in the pipeline. Friction resistance can be expressed by the friction relationship between the “plunger flow” and inner wall of conveying pipeline: f = k1 + k2 v

(6.4)

It can be seen from the above equation that the pumping pressure will increase with the increase of the flowing rate of concrete in the pipeline. The influence of flowing rate of concrete in pipeline on the loss of pressure is shown in Fig. 6.2 [5]. When the concrete pump works at rated throughput, the flowing rate of concrete in pipeline and the pumping resistance will increase with the reduce of the pipeline diameter. Therefore, selection of pipeline with different diameter will affect the pumping resistance. Figure 6.3 shows the relationship between the flowing rate and diameter of pipeline and throughput. Fig. 6.2 Influence of flowing rate on the loss of pumping pressure [6]

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309

Fig. 6.3 Relationship between pipeline diameter and flowing rate and throughput

In the case of given pipeline diameter, the flowing rate of concrete in the pipeline is proportional to the throughput of concrete. If the throughput of concrete is increased, the flowing rate will increase, thus the pumping resistance will increase. The throughput of concrete is linearly related to the pumping resistance. The increment of pumping resistance is proportional to the placing distance of concrete. Concrete will generate friction in the inner wall of pipeline. The larger the friction surface is (the longer the pipeline is), the higher the flowing resistance of concrete and the pumping pressure; its needs are higher. From the outlet of the concrete pump to the end of pipeline, the pumping pressure reduced from maximum to zero. The pumping resistance that generated by pumping concrete vertically is related to the vertical height and the volumetric weight of concrete. For example, the concrete in a conveying pipeline with a height of 100 m can generate a static pressure about 2.5 MPa. When pumping concrete vertically, the static pressure must overcome additionally. The bending of the conveying pipeline of concrete also will result in the increase of pumping resistance, which depends on the angle and radius of bending pipeline. To calculate the length of all the bending pipeline equivalent to the horizontal pipeline on the entire pipeline of concrete laid completely, we can use the following empirical equations: For the bending pipeline with a diameter of 1 m, equivalent of the horizontal length (m) =

the sum of angle of all bending pipeline 30

For the bending pipeline with a diameter of 0.5 m, equivalent of the horizontal length (m) =

the sum of angle of all bending pipeline 15

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6 Self-Compacting Concrete with Manufactured Sand

6.2.2 Establish of Pumping Pressure of Concrete with Manufactured Sand The performance of fresh concrete in casting is collectively called workability, which including fluidity, cohesion, and water-retaining properties. For pumping concrete, the flow properties and the interaction with the surrounding environment during flow process in the pipeline are the important parts of many factors that affect whether concrete can be successfully pumped, casted, and used efficiently.

6.2.2.1

Rheological Model of Pumping Concrete

Bingham proposed the concept of Bingham Body and proposed that two basic rheological parameters, yield stress and viscosity, which could be used to characterize the properties of fluids. If η = 0, τ0 = 0 and t = ∞, the fluid that described by the above equation is called Bingham fluid [7]. All colloidal solutions and suspensions that can form structures are Bingham fluids, and the rheological equation of Bingham fluid is as follows. τ = τ0 + η

dv dt

(6.5)

where τ is the shear stress at the shear rate of dv/dt. η is the dynamic viscosity. τ0 is yield stress. t is relaxation period. The typical stress–strain rate curve of Bingham fluid is showed in Fig. 6.4. Fresh concrete is the concrete mixture that coarse and fine aggregate solid particles suspended in the cement paste. Numbers of studies show that the flow of concrete mixture in pipeline follows the Bingham equation. Shear stress τ0 and dynamic viscosity η are the main parameters that determine the flow characteristics of fluid. The yield shear stress τ0 is the maximum stress that prevents plastic deformation. When τ0 < τ , the mixture will not flow. Only when τ0 > τ , the flow starts. The yield shear stress of mixture is generated by the adhesion and friction between the material composition. The yield shear stress τ0 and dynamic viscosity η can be measured by experiments. By this way, the study on the pumpability of concrete Fig. 6.4 Typical shear stress–shear strain rate of Bingham fluid

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Fig. 6.5 Bingham fluid flow alone the pipeline

can be transformed into the study on rheological properties of fresh concrete during the pipeline transportation process, that is, to study the pumpability of concrete by measuring τ 0 and η [8–12]. According to the above analysis, it can be considered that pumping concrete is Bingham fluid, which flows alone the pipeline under the action of thrusting force, as shown in Fig. 6.5. From Fig. 6.5, the following equation can be derived. Pπr 2 = 2πlr τ ⇒ τ = P

r 2l

(6.6)

According to Bingham model, the above equation can be expressed as follows.  1 r dv = P − τ0 dr η 2l

(6.7)

Under the boundary conditions of r = R and v = 0, the flow velocity can be calculated as follows.    1 P  2 2 R − r − τ0 (R − r ) v= (6.8) η 4l Theoretically, the distribution of velocity of Bingham fluid flowing alone the pipeline is shown in Fig. 6.6. When r < r0 , the flowing rate is expressed as follows. Q0 =

 Pπ 2  2 r R − r02 4lη

(6.9)

2l P

(6.10)

where r0 = τ

Fig. 6.6 Distribution of velocity of Bingham fluid flowing alone the pipeline

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When r0 < r < R, according to Buckingham–Reiner equation, it is figured out that the flowing rate is available as shown below. 



 1 2τ0 l 4 Pπ 4 4 2τ0 l R 1− + Q0 = 8lη 3 P R 3 P R

(6.11)

According to the above equations, η and τ0 will affect the flowing rate, and the pumping properties of pumping concrete are related to η and τ0 .

6.2.2.2

Rheological Characteristics of Pumping Concrete

Driven by the concrete pump, the Reynolds number of concrete mixture flowing in the pipeline is less than 2000. Therefore, under the current pumping technology, the flow of pumping concrete in conveying pipeline belongs to laminar flow theoretically. However, concrete mixture accords with Bingham fluid, namely it is non-Newtonian fluid. Therefore, the flow of pumping concrete in conveying pipeline, not only follows the flow characteristics of laminar flow, but also has some other unique features. According to the rheological equation of Bingham fluid, the flow will begin when τ > τ0 . Referring to the variation law of shear stress of laminar flow, the shear stress τ0 near the pipeline wall is the largest. Thus pushed by the concrete pump, as long as the shear stress at the wall follows τ > τ0 , the concrete mixture will start to flow in the pipeline. The concrete mixture will not flow if τ > τ0 at any radius. Within the radius, the concrete mixture moves forward at the same speed as a solid (plunger) with no relative motion in the plunger. This is the principle of the plunger flow as pumping concrete through the conveying pipeline [12]. When concrete is pumped, the cement paste (or cement mortar) will be pushed to the periphery under the action of pressure, forming a thin cement (or cement mortar) layer at the internal surface of conveying pipeline, which acts as a lubricant. During pumping, flowing generated if the shear stress produced by the thrust of concrete pump higher than the yield stress of cement paste (or cement mortar). The condition when τ0 is beneficial for pumping, which is the reason why a certain amount cement paste or cement mortar is pressed to lubrate the pipeline wall before pumping concrete formally and construction. In fact, consequently, plunger flow is fully filled with the whole section of conveying pipeline. Due to the existence of lubrication layer or not and the varying composition of lubrication layer, the rheological curve is different, as shown in Fig. 6.7.

6.2.2.3

Ultimate Shear Stress of Pumping Concrete

Ultimate shear stress τ 0 is also called yield stress. It is the minimum applied force that required for flow and deformation of materials, fresh concrete only begins to flow when τ > τ0 . During pumping process, pumping can be carried out when τ > τ0

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Fig. 6.7 Effect of lubrication layer on rheological curve

caused by pumping pressure. For all the compositions of concrete mixture, only water can be pumped, and only water can transfer pressure to other compositions. Therefore, for the concrete mixture which has a certain amount of cement and fixed grading aggregate, the amount of water must reach to a certain value to make solid particles suspended in the cement paste to flow under the action of pumping pressure. That is, with the increase of water to binder ratio, the concrete is transformed from unsaturated concrete to saturated concrete. The ultimate shear stress of fresh concrete is closely related to slump of concrete. The theoretical study shows that, with the increase of τ 0 , the slump of concrete decrease linearly. There is a minimum slump for specific concrete. If the slump is less than this value, the pumping pressure is not enough to overcome its own yield stress, and the pumping cannot be carried out. The cohesiveness of concrete refers to the ability that coarse and fine aggregate always keeps uniform distribution in cement paste under the action of external force. The high cohesiveness means the concrete has high cohesion, good stability, and segregation resistance. Segregation can be divided into two types, one is the shear stress of coarse aggregate caused by gravity higher than the yield stress of concrete and segregate from the cement paste, or due to the different rheological properties of coarse aggregate and mortar. During the pumping process, the pressure gradient of concrete in transport direction makes well-flowing mortar flowing first, with the aggregate residue in the rear. The other is that cement paste is too thin, the volume of cement paste is far less than the accumulate pore of mixed aggregate, and cement paste slips out of the pore, resulting in that pressure cannot be transferred to the coarse aggregate and cannot be push to move forward. This indicates that, in the cement paste with coarse and fine aggregate, there are two conditions to keep the two phases of solid and liquid without relative displacement: one is that there must be enough mortar (more than the accumulate pore of mixed aggregate). The fine particles that accumulate closely provide corresponding yield stress to overcome the gravity subsidence of coarse aggregate. The other is that the pores of mixed aggregate are filled with cement paste, the cement paste cannot flow freely.

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Therefore, the cohesiveness and stability of fresh concrete depend on the smaller slump which related to the certain yield stress and also depend on the level that concrete paste overfills the pore volume of mixed aggregate. Therefore, the yield stress of concrete is not only the premise of concrete flow, but also the condition of prevent concrete segregation. For the start of flowing, the slump of concrete should not be too small. The yield stress of concrete with much lower slump is too large to overcome by the shear stress formed by pumping. Thus, pumping cannot be carried out. In order to prevent concrete segregation, the slump of concrete should not be too high. Higher slump will cause yield stress far smaller, and the aggregate in concrete is easy to segregation.

6.2.2.4

Plastic Viscosity of Pumping Concrete

Plastic viscosity is a physical parameter that reflects viscous force. Viscous force is different from cohesiveness. The former indicates the frictional resistance among different flow layers with different speed when the fluid flows parallels, and the latter indicates the segregation resistance. The solid particles suspended in cement paste will generate internal friction to resist the relative motion when the relative motion is carried out, which generates viscous force. As for microscopic, this performance can be understood as the molecular attraction of various particles (cement, fly ash, and sand that diameter is less than 0.3 mm) in unit distance. The flowing of fresh concrete in the pipeline can be considered as the continuous deformation of mixture under the action of constant shear stress, which is called plasticity in rheology. The pumping concrete requires small viscosity. The content of particles in unit volume of slurry determines the viscous force of slurry, which evaluates the pumpability of concrete in turns. When the content of particles is much little, the pores of mixed aggregate are filled with insufficient amount of slurry, causing segregation and bleeding, thus the concrete cannot be pumped (pump blocking). When the number of particles increases largely, the viscous force of concrete and friction of the pipeline are too high to pump. Therefore, the relationship between content of particles and pumpability of concrete is shown in Fig. 6.8.

Fig. 6.8 Relational graph of content of particle and pumpability of concrete

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315

Water-reducing admixture and air-entraining admixture can reduce the viscous force. The absorption between cement particles or hydration products and waterreducing admixture can interrupt the connection among the internal particles and lead to the particles in the state of dispersion.

6.2.2.5

Particle Setting Model of Pumping Concrete

When pumping concrete flows between steel bars, it can take the model of continuum fluid, and the assumption is unreasonable that all particles in pumping concrete do not connect with each other. The interaction between particles increases the flow resistance of concrete. Therefore, the flow resistance on the shear plane will increase with the increase of normal stress. Besides, the fluidity of pumping concrete will variation with the flow time and the level of stirring, which is the so-called thixotropy phenomenon. Bingham fluid cannot describe the situation that flow resistance variation with normal stress and the thixotropy of pumping concrete, consequently, there are experts putting forward to use particle setting model to describe above rheological behavior [13]. It can be considered that the essence of concrete is the aggregation of water, cement particles, and aggregate particles. All the particles in the aggregation are in contact with adjacent particles. In generally, the contact inclined plane and maximum shearing stress plane (MS) of particles are not parallel, which will vary with the location of particles, as shown in Fig. 6.9. The angle between contact inclined plane and MS is denoted by θi , , which is named as contact angle of particles. The structure of particles aggregation can be describe by the average value (θm ) of θi through the distribution of particles. The number of contact point in unit length MS plane can be denoted by N. The internal friction caused by the contract between particles can use Coulomb friction theory. Therefore, all cement particles and aggregate particles are under the action of frictional resistance, whether the particles are static or moving. Besides Fig. 6.9 Contract angle and contract inclined plane of particles

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Vander Waals force, there are electrostatic repulsion between particles. Any interaction and total potential energy of cement particles can vary with the relative distance between particles. This potential energy between particles becomes the barrier to the movement of cement particles and leads to the movement of cement particles related to time. A static cement particle can be considered in equilibrium state under the action of gravity and repulsion. When the cement particles move, it will be subjected to other types of resistance (called viscous resistance) rather than the balance of gravity, and repulsion has been broken. If particles are desired to move, firstly, the force between particles must have to exceed the resistance between particles which caused by atomic or molecular contract in the contract plane of particles. As for the non-deformation condition, the maximum shear stress τmax supported by the internal friction in particle aggregation can be describe by the follow equation. τmax = σn tan(θm + ϕm ) +

N f wm tan ϕm cos θm (1 − tan θm tan ϕm )

(6.12)

In the equation, σn is the normal stress in MS plane, θm is average contract angle of particles, ϕm is average friction angle, f wm is the average cohesive force acting onto the contract point of particles, which is caused by surface tension and surface suction. It is impossible to measure or estimate the distribution of force between particles at this stage due to that the distribution of force between particles is affected by many factors, such as the location, shape, and size of particles. However, it is reasonable to consider that larger particles are subjected to larger force between particles, since larger particles have larger section. Therefore, regardless of the ability of pore water and the condition of air aggregation under the action of external force owing to viscous resistance, it is assumed that the stress part (τc ) applied to the cement pellets is proportional to the ratio of the volume of cement particles to the volume of all solid particles. When the shear stress is acting on the aggregation of particles, τc can be expressed by the following equation. τc =

Vc τ = Sd τ Vc + Va

(6.13)

In this equation, Vc , Va are the volume of cement particles and volume of aggregation in unit volume concrete, respectively. Sd is stress distribution coefficient. As shown in Fig. 6.10, (a) is imaginary cube in MS plane, (b) is the deformation of vertical particle layer. Considering the aggregation of particles as the unit size cube on the MS plane and shear stress τ0 acting on MS plane, the imaginary cube is consisted by multiple particle layers parallel or vertical to the MS plane. The thickness of any layer is equal to the maximum diameter of particle. Under the action of shear stress, the movement of any particle i will generate inclination i cos θi in vertical particle layer where it is located when n particles move on the vertical particle layer. The shear deformation of imaginary cube, such as the shear strain on MS plane, can be

6.2 Pumping Pressure of Concrete with Manufactured Sand

317

Fig. 6.10 Microscopic view of viscous fluid under the action of external force

expressed by following equation. γ =

n 1 i cos θi = n m cos θm L0 i=1

(6.14)

In the equation, i is the move distance of particle, and m is the average move distance of n particles. If considering an independent removable cement particle as a flow unit, the viscous theory of Eyring can be used to describe the rheological behaviors of cement particles. According to this theory, if the force on a particle is higher than the friction resistance, the particle is called potential active particle. In terms of probability, whatever vertical or parallel, the number of particles (N ca ) in each particle layer is as equal. Therefore, the moving cement can be considered as a kind of special particles, whose kinetic energy is the sum of Brownian motion and the energy gained from external force. It is enough to overcome the energy barrier caused by the viscous resistance and internal friction between particles. Based on the viscous theory of Eyring, the average probability (Pc ) of a PA particle becomes a moving cement particle per unit time that can be expressed by the following equation. Therefore, the number of moving cement n in a particle layer per unit time can be expressed by following equation.

f V m 2kT

Ec kT exp − A= h kT

Pc = 2 A sinh

n = Nca Pc

(6.15) (6.16) (6.17)

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where m is the average moving distance of cement particles. k is Boltzmann constant (1.380662 × 10−23 J/K). T is absolute temperature (K). h is Planck constant (6.6260755 × 10−23 J/s). Ec is the average potential energy of cement particles (J). f V is the average shear stress that used to match the viscous resistance that act on PA particles, which is defined as follows. fV =

(τc − τcf ) Nca

(6.18)

In the equation, τc f is the shear stress that match the friction resistance of cement particles. Therefore, the apparent viscosity coefficient of fresh concrete is as below. ηα =

τ 2 ANca cm cos θcm sinh

(τc −τcf ) cm 2kT Nca



(6.19)

6.2.3 Influence of Manufactured Sand Features on the Pumping Pressure of Concrete 6.2.3.1

The Pumping Performance and Evaluation Index of Ultra-High Pumping Concrete with Manufactured Sand

Due to the high height of pumping and the high design strength, the first problem that needs to be solved in the process of mix design and pumping construction is the unification of viscosity and workability. In general, the viscosity of high-strength concrete is much high with poor workability, while the ultra-high pumping concrete with MS has a higher requirement on workability. It is the key problem of mix design and preparation to ensure concrete with proper viscosity and workability. In addition, the slump loss of concrete becomes obvious due to the ultra-high height of pumping and the long distance of pumping. Therefore, desirable slump loss resistance is the key property to guarantee the quality of construction. Based on the previous discussion, the pumping performance of ultra-high pumping concrete with MS should meet requirements as shown in Table 6.1 [14]. Different engineering projects should be adjusted according to construction conditions in practice.

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Table 6.1 List of evaluation index of pumping performance of ultra-high pumping concrete with MS Must-to-be controlled index

≥ 240 mm

Slump

≥ 600 mm

Divergence Slump loss Divergence loss

1h

≤ 10 mm

2h

≤ 20 mm

1h

≤ 20 mm

2h

≤ 50 mm

Pressure bleeding ratio

≤ 20% when 10 s

Gas content

3 ~ 5%

Fallout time of slump cylinder

≤ 10 s

Adaptation of cement and chemical Good admixture Auxiliary control index Reference control index

6.2.3.2

Time of T50

≤ 15 s

Experiment of V funnel

≤ 25 s

Experiment of U funnel

≥ 320 mm

h2 /h1 of L flow leveling instrument

≥ 0.8

The Performance of Ultra-High Pumping Concrete with Manufactured Sand

The mix proportion and the performance of raw materials of ultra-high pumping concrete with MS have a great influence on performance of pumping, which mainly includes the following aspects [15]. (1) The dosage of cementitious materials The dosage of cementitious materials will affect the pumping resistance of the concrete conveying pipeline directly. Generally, with the lower dosage of cementitious materials, the resistance of pumping rises to high level and the pumping pressure is large. The viscous force of concrete and the pumping resistance will increase if the dosage of cementitious material is too large. (2) The addition of SCMs The addition of SCMs can improve the workability and mechanical properties at later stage effectively. Appropriate SCMs, especially fly ash, can improve the fluidity, stability, and the time-loss of fluidity of concrete effectively. (3) The fine aggregate and mud content of MS MS is composed of gravel by means of ground-breaking mining, mechanical crushing and screening. It is inevitably to produce some fine aggregate powder (fine aggregate) with particle size less than 0.075 mm, which occupies about 10–15% of the total amount of MS. Compared with natural sand, MS has rough particles, more edges

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and corners, poor grading, poor workability of mixture, and easy to segregation in the preparation process. In engineering application, some projects remove the fine aggregate in MS by water washing, which destroys the natural grading of MS. It is harmful to the maximum density of aggregate. The fine aggregate in MS can be considered as inert addition. Appropriate fine aggregate can fully fill the pores between the aggregate, increase the total paste volume of concrete, improve the workability of concrete, and reduce the pumping resistance. In the condition that the pores between aggregate are fully filled, the water demand of concrete will not be increased due to the existence of fine aggregate. However, the compactness, strength, and durability of concrete are enhanced. Otherwise, when the content of fine aggregate is up to the high level, it will obviously increase the viscous force of concrete and pumping pressure [16, 17]. Limited by the production equipment, craft, and raw materials, there will be a certain mud content in MS. When the content of mud is high, the work performance of polycarboxylate superplasticizer, as well as the strength of concrete will be reduced, and the durability of concrete will also be affected. At the same time, the time-loss of slump, divergence and viscosity of concrete mixture, and the pumping pressure of mixture will increase obviously. Therefore, full attention should be paid to the content of fine aggregate and mud in the preparation process for ultra-high pumping concrete with MS. Appropriate content of fine aggregate and much lower content of mud should be adopted. (4) Coarse aggregate The type and particle size distribution of aggregate has a great influence on pumping pressure. The pebble and river sand is the best aggregate of pumping concrete. Whereas in the actual engineering construction, gravel is generally used due to its large surface area and prominent corner angle, leading to the high resistance in conveying pipeline, and thus the loss of pumping pressure also becomes large. Aggregate specially deviated from the standard particles will also increase the loss of pumping pressure and reduce the pumping capacity. Table 6.2 lists the maximum diameter of coarse aggregate that suitable for various conveying pipelines. (5) Chemical admixtures Some chemical admixtures are often added according to the actual situation in the preparation and construction process of ultra-high pumping concrete with MS. When Table 6.2 Maximum diameter of coarse aggregate suitable for different conveying pipeline

Diameter of pipeline (mm)

Maximum diameter of coarse aggregate/mm Pebble

Gravel

100

30

25

125

40

30

150

50

40

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the chemical admixtures and cement have good compatibility, it can improve the fluidity of concrete effectively and reduce the loss of pumping pressure of concrete. The combination of superplasticizer and retarder or retarder superplasticizer can reduce the slump loss of concrete by inhibiting the early hydration reaction of cement. The combination of superplasticizer and air-entraining agent can increase the fluidity and cohesion of concrete mixture, thus reducing the segregation and bleeding of concrete. The pumping pressure of concrete is also reduced by introducing a large number of tiny uniform bubbles.

6.2.3.3

Other Performance Requirements of Ultra-High Pumping Concrete with Manufactured Sand

(1) Mechanical properties Mechanical strength is the main factor that restricts the performance of structure, and it is the main design index in engineering design. If the strength of ultra-high pumping concrete with MS is insufficient, it will have a great impact on the performance of structural components. The poor mechanical properties will reduce the strength and stiffness of components, resulting in affecting the bearing capacity of the structure. What’s more, it will increase the deflection and other deformation of the structure and reduces the crack resistance of structural components. In addition, the insufficient mechanical strength will aggravate the generation and development of cracks. Due to that the internal structure of concrete is not compact enough, it is usually accompanied by the decrease of durability. Therefore, the concrete strength of different parts should meet the relevant specifications and standards as well as the specific design requirements. (2) Durability The ultra-high pumping concrete with MS is usually mass concrete in practice, and thus, the main durability problems are temperature cracks and shrinkage cracks under windy conditions. Therefore, the ultra-high pumping concrete with MS should have much lower hydration heat, higher early strength, and anti-cracking performance. As for concrete with special requirements, special technology can be used to improve the early anti-cracking performance. In addition, other durability problems such as carbonation, freeze–thaw, chloride ion penetration, and sulfate corrosion of concrete in special structural parts should be considered under special regional conditions, in accordance with the current standard.

322

6.2.3.4

6 Self-Compacting Concrete with Manufactured Sand

The Key Problems of Ultra-High Pumping Concrete with Manufactured Sand

High-strength concrete is always used in ultra-high pumping buildings. As we all know, although the slump and expansion of high-strength concrete and ordinary concrete are almost identical, the expansion time is different and the viscosity of highstrength concrete is larger. Therefore, the key problem in the process of ultra-high pumping is as follows [18]. (1) The contradiction between viscosity and workability The plastic viscosity of concrete is a physical parameter reflecting viscosity, which indicates the frictional resistance between different flow layers with different speed when the fluid flows parallelly. The solid particles suspended in the cement paste produce internal friction to resist the relative motion. Due to the increasing amount of cementitious materials and the presence of a certain amount of lime powder in the MS, the adhesion coefficient and velocity coefficient of the ultra-high pumping concrete with MS increase, which leads to the increase of the viscosity coefficient. However, the pumping construction requires that the concrete should possess the lower viscosity. The content of particles in unit volume determines the viscosity of cement paste, which determines the pumpability of concrete from the other side. When the particle content is too less, the pores of the mixed aggregate will be filled by thinner particle paste, which will produce segregation and bleeding, so that the concrete cannot be pumped (blocked). When the particle content is much higher, the viscosity of the concrete and the pipe friction are too large, in that it is also difficult to pump. The balance of viscosity and workability of fresh concrete is the primary problem that restricts the ultra-high pumping concrete with MS. How to make concrete with appropriate viscosity and workability is the key issues of concrete design and preparation. (2) The time-loss of slump, divergence, and viscosity The slump loss of pumping concrete mixture is mainly due to the physical solidification of cement particles to form a three-dimensional network structure. The concrete pumping admixtures adsorb on the surface of cement particles or early hydration products, then the cement particles disperse to release free water. As a result, the consistency of cement paste becomes thinner. However, as the cement hydration continues, the pumping admixtures adsorbed on the cement particles and early hydration products, or surrounded by hydration products, or reacting with hydration products, cannot disperse well, resulting in the cement particles agglomerating, forming a three-dimensional network structure, which makes the consistency of the water slurry thickening.

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As for ultra-high pumping concrete, the time interval between concrete mixing and pouring is pretty long due to the high pumping height and long pumping distance. The time-loss of slump, slump flow, and viscosity in concrete becomes more obvious, which has a greater impact on the pumping performance of concrete and seriously restricts the project quality and construction progress. (3) The relationship between the fine aggregate content of MS and the performance of concrete Compared with natural sand, MS has the undesirable features, i.e., coarse particles, edges and corners, poor gradation, poor workability, and easy segregation in the preparation process. The fine aggregate produced in the production process can be considered as an inert admixture. Appropriate fine aggregate can fully fill the gaps between aggregates and increase the total slurry amount of concrete, thus improving the workability of concrete and reducing the pumping resistance. When the gap between aggregates is fully filled, the existence of fine aggregate will not increase the water demand of concrete. However, when the content of fine aggregate exceeds a certain range, the viscosity of ultra-high pumping concrete with MS will be greatly improved and the pumping resistance will increase significantly. The mixture of ultra-high pumping concrete with MS requires lower viscosity and higher cohesion, and the content of fine aggregate in MS should be properly controlled. In order to ensure good slump flow and viscosity loss with time, the mud content in MS should be strictly controlled. If necessary, the MS should be obtained from washing method of crushed coarse aggregate. (4) Guarantee of mechanical properties of ultra-high fluidity concrete With the increase of pumping height, the fluidity and pumpability of concrete are required to be higher. However, ultra-high pumping concrete often requires high strength at the same time. With the increase of concrete strength, the viscosity and the pumping resistance increase, while the pumpability decreases, and the difficulty of pumping rises sharply. For ultra-high-strength pumping concrete, high fluidity can be pumped and high strength are indispensable. The key problem is to solve the ultra-high pumping concrete engineering with high strength under high fluidity. To settle the above problems, comprehensive measures should be taken, such as optimizing raw material varieties and concrete mix proportion, adjusting admixture components to solve the time-loss issues, improving the surplus coefficient of strength, standardizing on-site sampling, on-site maintenance, etc.

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6.3 Optimization of Mix Proportion of SCC with Manufactured Sand 6.3.1 Design of Mix Proportion of SCC with Manufactured Sand Compared with the ordinary concrete, the self-compactability of SCC with MS mainly refers to three aspects, including fluidity, gap passage, and segregation resistance. The mix proportion of self-compacting concrete with MS should be designed according to the structure and construction conditions, as well as the self-compacting performance of environmental conditions. The experimental mix proportion shall be proposed on the basis of strength, durability, and other necessary performance requirements. Furthermore, the influence of water to binder ratio on the design strength and the influence of water to binder ratio on self-compacting performance should be considered in the mix design of self-compacting concrete with MS. The mix design of self-compacting concrete with MS should adopt the absolute volume method. For the selection of ultra-fine materials, it is better to select the type with the lowest water requirement. It also requires the chemical admixture to increase cohesion while maintaining large fluidity. Besides, increasing the amount of SCMs should be considered. As for the SCC with MS with low-strength grades, a tackifier can be added appropriately after confirmation by tests when the viscosity of the paste cannot be achieved by only increasing the amount of SCMs. In addition, it is necessary to use the superplasticizer, i.e., polycarboxylic acid with a water reduction rate greater than 30% to increase the viscosity of the cement paste with high fluidity maintaining (Fig. 6.11). Researchers in University of Tokyo, Japan, first carried out the study on mix design of SCC [19] and proposed the prototype method of self-compacting concrete. Then, the scholars from Japan, Thailand, the Netherlands, France, Canada, China, and other countries further carried out self-compacting concrete research on the design method

Fig. 6.11 Preparation of SCC with MS

6.3 Optimization of Mix Proportion of SCC with Manufactured Sand

325

of compacted concrete. However, the widely accepted self-compacting concrete design methods are still in vacant. From the relevant data, the performance index of self-compacting concrete should be kept as follows: with the slump as 240–270 mm, the slump flow ought to be greater than 600 mm. In order to achieve these special performance indicators of self-compacting concrete, a large number of research have been conducted. A mix proportion method proposed by Okamura [20] is to carry out cement slurry and mortar tests firstly. The main purpose is to check the performance and compaction ability of superplasticizers, cement, fine aggregates, and pozzolanic materials and carries out the self-compacting concrete test again at last. Beijing Construction Engineering Group in China proposes a design method based on a four-layer system of concrete, mortar, cement paste, and cementitious materials. The design algorithm of compact mixture proposed by scholars in Taiwan of China is derived from the principle of maximum density and supermortar theory. The principle of preparing SCC with MS is to fill the gaps of the aggregate skeleton with cement slurry (cementitious material). The following are the more general design steps for the mix proportion of SCC with MS. Calculation of concrete mix proportion: (1)

(2)

(3)

(4)

(5) (6) (7)

(8)

The main parameters for the design of SCC with MS mix proportion include the loose volume of coarse aggregate in the mixture, the volume of sand in the mortar, the water to binder ratio of the slurry, and the amount of mineral admixture in the cementitious material. The loose volume V g0 (0.5–0.6 m3 ) of the coarse aggregate dosage is set in 1 m3 concrete, and the coarse aggregate dosage mg is calculated in 1 m3 concrete according to the bulk density ρg0 of the coarse aggregate. The compact volume V g of the 1 m3 concrete coarse aggregate is calculated according to the apparent density ρg of the coarse aggregate, and the compact volume Vm of the mortar is calculated from the total volume of the 1 m3 mixture minus the compact volume V g of the coarse aggregate. The volume content of sand in the mortar is set as 0.42–0.44, and the dense volume Vs of sand is calculated according to the dense volume of mortar Vm and the volume content of sand. The sand dosage m s in 1 m3 concrete is calculated based on the compact volume of sand Vs and the apparent density ρs of sand. The compacted volume of slurry V p is obtained by subtracting the compacted volume Vs of sand from the mortar volume Vm . The water to binder ratio is determined according to the design strength grade of the concrete. The volume of the mineral admixture in the cementitious material is set according to the requirements of concrete durability and temperature rise control. The apparent density ρb of the cementitious material is calculated according to the volume ratio of the mineral admixture and the cement and their respective apparent density. The volume ratio of water and cementing material is calculated according to the apparent density and water to binder ratio of the cementitious material, and

326

6 Self-Compacting Concrete with Manufactured Sand

the volume of the cementitious material and water is calculated according to the slurry volume V p , volume ratio and respective apparent density. Then, the total amount of cementitious material mb and unit water consumption mw are calculated. The total amount of cementitious materials should range from 450 to 550 kg/m3 , and the unit water consumption should be less than 200 kg/m3 . (9) According to the volume of cementitious material and the volume of mineral admixture and their respective apparent density, the amount of cement and mineral admixture per 1 m3 of concrete is calculated respectively. (10) The variety and dosage of additives are chosen according to the experiment. Trial mixing, adjustment, and determination: (1) The preliminary mix proportion is calculated. (2) The initial mix proportion is tested and adjusted. (3) During the trial mixing and trial mixing of SCC with MS, the minimum mixing volume of each plate of concrete should not be less than 30 L, the workability of the mixture should be tested to meet the requirements of the corresponding evaluation indicators, and the strength of the concrete should be checked whether the strength of the mix is reached. If necessary, the corresponding durability index should also be tested. (4) It is recommended to choose 3 benchmark mix proportions that meet the requirements for the workability of the mixture to make concrete strength test pieces. At least one set of test pieces should be made for each mix proportion, and the strength is tested when the standard curing reaches 28 days. (5) For projects with special application conditions, if necessary, a full-scale test can be conducted on the determined mix proportion at the concrete mixing plant or construction site to check whether the designed mix proportion meets the engineering application conditions. (6) According to the trial mix, adjustment, concrete strength inspection results, and full-scale test results, the appropriate mix proportion is determined to meet the design requirements.

6.3.2 Optimization of Mix Proportion of SCC with Manufactured Sand The mix design of self-compacting concrete with river sand is listed as below, with a water to binder ratio of 0.35, a sand ratio of 50%. The LX-6 polycarboxylic acid superplasticizer is adopted with the content of 1.2%. The maximum particle size of the coarse aggregate is 25 mm, and the coarse aggregate gradation is 5–10 mm:10–20 mm:20–25 mm = 30%:40%:30%. The mix design of self-compacting concrete follows: cementitious material:sand:gravel:water:superplasticizer = 500:860:860:175:6 (kg/m3 ). The feasibility of MS SCC prepared with the mix proportion of self-compacting concrete with river sand is also analyzed (Table 6.3).

6.3 Optimization of Mix Proportion of SCC with Manufactured Sand

327

Table 6.3 Mix proportion of concrete Test number

Mix proportion of concrete Mineral admixture

SG1

Water reducer

Type

Content/%

Type

Content/%

Type

Content/%

Fly ash

0

Silica fume

0

LX-6 water reducer

1.5

SG2

20

0

1.2

SG3

40

0

1.2

SG4

40

3

1.2

From the test results (Table 6.4), it can be seen that SCC with MS has poor workability with the mix proportion of river sand. As shown in Fig. 6.12, the concrete has poor cohesiveness. Table 6.4 Performance of concrete Test number

Slump/cm

Slump flow/cm

Outflow time from the inverted slump cone/s

0h

1h

2h

0h

1h

2h

0h

1h

2h

SG1

21

16

13.5

55

31

28

38

58.5

Upon 3 min

SG2

21

18

15

49

35

29.5

36.5

72.5

Upon 3 min

SG3

23.5

22

20.5

61

47

39

13.9

14

15.9

SG4

23.5

21.5

19

47

38

34

8.8

9

11

Fig. 6.12 State of self-compacting concrete with MS prepared by river sand self-compacting concrete mixture design

328

6 Self-Compacting Concrete with Manufactured Sand

Judging from the test results and the observed concrete conditions, there are many problems in the MS SCC prepared by the mixing design of river sand SCC. (1) The performance indicators of fresh concrete are far from the performance requirements of self-compacting concrete, and the outflow time of the mixture from the inverted slump cone is too long. (2) Fresh concrete has obvious pile-up phenomenon, with small slump and uneven surface. (3) There is a phenomenon of bleeding, large-size coarse aggregate float on the surface of the slurry, and the coarse aggregate do not flow with the slurry. (4) The early strength is low, the test specimen is not strong enough when the mold is demolished in one day, resulting in excessive damage to the test specimen, etc. The main reason for these phenomena is that raw materials of SCC with MS are quite different from river sand self-compacting concrete. Therefore, the mix proportion of river sand self-compacting concrete cannot be simply adopted. The mix proportion parameters of self-compacting concrete should be adjusted according to the characteristics of the raw materials to prepare the self-compacting concrete required by the design.

6.3.2.1

Water to Binder Ratio

In order to determine the basic parameters of mix proportion for the self-compacting concrete with MS, the maximum particle size of the coarse aggregate is adjusted to 20 mm to analyze the influence of different water to binder ratio on concrete performance. Besides, LX-6 polycarboxylic acid superplasticizer is used and the sand ratio is selected as 50%, with the maximum coarse aggregate particle size as 20 mm and fly ash content as 40% (Table 6.5). It can be seen from Table 6.6 that when the contents of superplasticizer and silica fume are kept as 1.2% and 5%, respectively, and the water to binder ratio is adjusted Table 6.5 Concrete mix proportion under different water to binder ratio Test number

Water to binder ratio

SG5

0.4

SG6-1

0.3

SG6-2

0.32

SG7-1

0.3

SG7-2

0.34

SG7-3

0.35

Mix proportion of concrete Mineral admixture

Superplasticizer

Gradation of coarse aggregate/%

Type

Content/%

Content/%

5–10 cm

10–20 cm

Silica fume

3

1.2

40

60

5 1.5

50

50

6.3 Optimization of Mix Proportion of SCC with Manufactured Sand

329

Table 6.6 Properties of concrete under different water to binder ratio Test number

Water to binder ratio

Slump/cm

Slump flow/cm Outflow time from the inverted slump cone/s

0h

2h

0h

2h

0h

2h

State of slurry

SG5

0.4

23

23.5

65

67

24.5

32.1

Bleeding, segregation

SG6-1

0.3

24

–

59

–

27.6

–

Sticky and thick

SG6-2

0.32

24.5

22.5

65

55

18

26

Sticky

SG7-1

0.3

–

–

–

–

–

–

Cannot mix

SG7-2

0.34

23

–

57

–

11.9

–

Very good

SG7-3

0.35

23.5

22

61

48

12.1

15.1

Good

from 0.3 to 0.32, the performance of fresh concrete has been improved. There is no bleeding or segregation, but the outflow time of the mixture from the inverted slump cone is longer, indicating that the concrete mixture has a higher viscosity. When the performance of the fresh concrete is improved by increasing the content of admixtures or increasing the water to binder ratio, it is found that the slump of the concrete does not increase. However, the phenomenon of central stacking becomes more serious. The bleeding and segregation occur in the concrete mixture when the water to binder ratio increases to 0.4, and the outflow time of inverted slump cylinder flows out. This shows that simply relying on the increasing of the admixture and water to binder ratio can no longer improve the fluidity and cohesiveness of concrete. It is necessary to use other admixture composite technologies, large content of mineral admixtures, and other technical methods to improve the performance of fresh concrete mixture.

6.3.2.2

Type and Ratio of Mineral Admixtures

(1) Mineral admixture and its content Concrete mix proportion parameters are listed as follows: sand ratio of 50%, water to binder ratio of 0.35, content of SP1 water-reducing agent of 1.2%, and the maximum particle size of coarse aggregate of 20 mm. Table 6.7 analyzes the influence of different mineral admixtures and their compounds on concrete performance (Table 6.8). It can be seen from Table 6.7 that when the content of fly ash and silica fume is 20% and 3% respectively, the admixture content has been increased to 1.5%. As a result, with the occurrence of bleeding and segregation, the outflow time of the mixture from the inverted slump cone becomes much longer (Table 6.8). After a certain amount of tackifier added, the viscosity of the concrete mixture has been improved, while the concrete mixture is still segregated slightly. When the amount of

330

6 Self-Compacting Concrete with Manufactured Sand

Table 6.7 Mix proportion of concrete mixed with single or compound different mineral admixtures Test number

Proportion of concrete Mineral admixture

SG6 SG7-1

Gradation of coarse aggregate, mm

Type

Content/%

Type

Content/%

5–10 (%)

10–20 (%)

Fly ash

20

Silica fume

0

40

60

3

SG7-2 SG10-1

40

5

SG10-2 SG12-1

40

5

50

50

SG12-2

Water reducer

Tackifier

Content/%

Content/%

1.5

–

1.5

–

1.5

0.5

1.2

–

1.2

0.6

1.5

–

1.6

0.2

SG13

40

10

1.2

–

SG19-1

40

8

1.2

–

SG19-2

1.4

–

SG19-3

1.5

0.05

Table 6.8 Properties of concrete mixtures mixed with single or compound different mineral admixtures Test number

Slump/cm

Slump flow/cm

0h

0h

2h

Outflow time State of slurry from the inverted slump cone/s 2h

0h

2h 68.5

Bleeding and segregation

–

Bleeding and segregation

SG6

24

24

67

66

37.5

SG7-1

24

–

72

–

22

SG7-2

25.5

22.5

71

72.5

27.8

53.8

SG10-1

22

–

68

–

14.8

–

–

SG10-2

24.5

23

62

53.5

10.6

23.7

–

Good

SG12-1

22

–

51

–

7.5

–

Bleeding and segregation

SG12-2

24.5

23

66

52

6.4

6.1

Good

SG13

21.5

19.5

45

34

12.9

20.5

SG19-2

23

–

64

–

15.6

SG19-3

23

23

62

58

15

–

–

–

32.7

–

6.3 Optimization of Mix Proportion of SCC with Manufactured Sand Table 6.9 Compressive strength of concrete mixed with single or compound different mineral admixtures

331

Test number

Compressive strength/MPa 3d

7d

28d

SG6

23.1

44.1

59.3

SG7-2

28.2

49.4

58.3

SG10-2

14.9

27.5

51.1

SG12-2

18.2

32.2

55.6

SG13

16.4

28.791

59.3

SG19-3

17.1

35.1

53.7

fly ash and silica fume increases with the amount of admixture adjusting at the same time, the concrete mixture achieves promising performance. As the content of silica fume continues increasing, however, the cohesiveness of the concrete mixture can be increased and the stacking problem can be solved. Nonetheless, if the content of silica fume is incorporated too much, the higher water demand due to the larger specific surface area of silica fume will result in the reduction of workability. The increase of water demand leads to the higher water to binder ratio or the larger dosage of waterreducing agent; thus, the dosage of silica fume could not be too large. Compounding a large amount of fly ash and silica fume can effectively improve the workability of self-compacting concrete. Although the early strength of concrete becomes slightly lower, the later increases rapidly. Therefore, the technology of high-volume mineral admixture is an important technology for the preparation of self-compacting concrete with MS (Table 6.9). (2) The amount of different cementitious materials The amount of cementitious material has a significant influence on the performance and mechanical properties of the self-compacting concrete mixture. Mix proportion parameters of SCC are listed below: sand ratio of 50%, water to binder ratio of 0.35, fly ash content of 40%, silica fume content of 5%, SP1 water-reducing agent content of 1.2%, and the maximum coarse aggregate particle size of 20 mm. The coarse aggregate gradation is 5–10 mm:10–20 mm = 1:1 (Table 6.10). The effects of the amount of cementitious material on the performance of selfcompacting concrete are given in Table 6.11. It can be seen that if the amount of cementitious material becomes too tiny, the concrete slump and slump flow will not meet the requirements. With the increase of the amount of cementitious material, the performance of the self-compacting concrete mixture is improved, and the concrete slump and slump flow are also increased. Besides, the outflow time of the mixture from the inverted slump cone is shortened, thus indicating that the performance of self-compacting concrete mixture is better. From the perspective of strength development, the strength of concrete at each age does not increase with the increase of the amount of cementitious material. Therefore, the effect of the amount of cementitious material on its performance should be considered comprehensively to determine the appropriate amount.

25.5 24.5

0.1

SG16-2

25

0.05

0.1

22

SG16-1

550

23.5 22

25.5

SG16

2h

23

24

25.5

–

24.5

20.5

21.5

22

23

–

23

19

20.5

21

–

68

69

64

68

68

62

65

41

67

67.5

–

62

58

58

63

–

1h

0h

–

1h

0h 17

Slump flow/cm

Slump/cm

0

SG15-1

0

SG15

500

0.2 0.3

SG14-1

0

450

SG14

SG14-2

Content of tackifier, ‰

Amount of cementitious material (kg/m3 )

No.

Table 6.10 Effect of the amount of cementitious material on the performance of concrete mixture

2h

62

60

–

53.5

53

46.5

51

–

6.6

5

7

8.8

14.8

15.3

14.3

28

0h

8

5.6

–

10.6

16.4

18

16

–

1h

15

8.5

–

23.7

19.5

35.5

19.1

–

2h

Outflow time from the inverted slump cone/s

332 6 Self-Compacting Concrete with Manufactured Sand

6.3 Optimization of Mix Proportion of SCC with Manufactured Sand

333

Table 6.11 Effect of the amount of cementitious material on the compressive strength of concrete mixture Test number

Amount of cementitious material (kg/m3 )

Compressive strength/MPa 3d

7d

28d

SG14-2

450

15.7

33.9

54.3

SG15-1

500

21.9

37.7

61.3

SG16-2

550

17.1

33.2

55.8

6.3.2.3

Ratio of Fine Aggregate in Aggregates

Mix proportion parameters of SCC is listed below: water to binder ratio of 0.35, fly ash content of 40%, silica fume content of 5%, the maximum coarse aggregate particle size of 20 mm. The coarse aggregate gradation is 5–10 mm:10–20 mm = 40%:60%. The ratio of fine aggregate in aggregates is adjusted in the mix design of SCC with MS, and the performance is also analyzed (Table 6.12). From the data in Table 6.13, it can be seen that when the ratio of fine aggregate in aggregates becomes too small, the phenomena of bleeding and segregation of the concrete mixture may occur, and the value of slump flow and slump cannot meet the requirement. However, the outflow time of the mixture from the inverted slump cone is relatively small. The slump flow and slump of the concrete mixture with a sand ratio of 50% are relatively proper, and the outflow time of the mixture from the inverted slump cone is moderate. When the concrete sand ratio increases to 55%, the performance of the concrete mixture is much better and the concrete fluidity becomes larger, while the outflow time of the mixture from the inverted slump cone is not ideal with the higher viscosity. From the perspective of strength development, as the ratio of fine aggregate in aggregates increases, the strength of each age increases at first and then decreases. Considering the influence on the performance and strength of concrete mixture, it can be considered that the ratio of fine aggregate in aggregates of self-compacting concrete prepared with MS should be selected at about 50%. Table 6.12 Mix proportion of concrete under different ratio of fine aggregate in aggregates Test number

Factor

Superplasticizer

Tackifier

Type

Sand ratio/%

SP-1

Content/%

Content/ten thousandths

1.5

45

4

SG19

1.5

50

5

SG20

1.4

55

–

SG18

Sand ratio

Mix proportion of concrete

334

6 Self-Compacting Concrete with Manufactured Sand

Table 6.13 Properties of concrete under different ratio of fine aggregate in aggregates Test number

Slump/cm

0h

1h

2h

0h

1h

2h

0h

1h

2h

3d

7d

28d

SG18

21.5

20.5

21.5

63

61

58

6.5

7

10

18.0

38.1

58.1

Slump flow/cm

Outflow time from the inverted slump cone/s

Compressive strength/MPa

SG19

26.0

25.5

22.5

72

71

72.5

8.8

10.8

15.8

28.3

49.4

73.1

SG20

23.5

22.5

21.5

64

53

54

26

39

38

25.2

43.2

65.3

6.3.2.4

Gradation of Coarse Aggregate

Mix proportion parameters of SCC is listed below: ratio of fine aggregate in aggregates of 50%, water to binder ratio of 0.35, fly ash content of 40%, silica fume content of 5%, maximum coarse aggregate particle size of 20 mm, and water-reducing agent content of 1.5%. The influence of gradation of coarse aggregate is determined in the mix design of SCC with MS with the performance analyzed (Table 6.14). It can be seen from (Table 6.15) that the gradation of coarse aggregate has a certain effect on the properties of concrete mixture. As the fine aggregate in the coarse aggregate decreases, the fluidity of the concrete increases, and the segregation of concrete mixture trends to be more serious. The incorporation of a certain tackifier is needed. From the perspective of strength development trend, with the decrease of fine aggregate in coarse aggregate, the strength of concrete gradually increases. Considering the impact of the gradation of coarse aggregate on the performance and Table 6.14 Concrete mix proportion of different gradation of coarse aggregate Test number

Concrete mix proportion Superplasticizer

Mineral admixture

Tackifier

Type

Content/%

5–10 mm

10–20 mm

Content/%

SP-1

1.3

60

40

0

SG22

1.5

50

50

0.2

SG23

1.5

40

60

0.5

SG21

Table 6.15 Concrete properties of different gradation of coarse aggregate Test number Slump/cm

0h

1h

2h

Slump flow/cm

Outflow time from inverted slump cone/s

0h

0h

1h

2h

1h

Compressive strength/MPa 2h

3d

7d

28d

SG21

24

23

20.5 66

64

44

10.1 12

12.3 17.2

28.0

52.3

SG22

23.5 22

21.5 63

58

55

10.1 13.1 13.5 21.9

38.5

60.3

SG23

26.0 25.5 22.5 72

71

72.5

8.8 10.8 15.8 28.3

49.4

73.1

6.3 Optimization of Mix Proportion of SCC with Manufactured Sand

335

strength of the concrete mixture, it is believed that the performance of MS SCC prepared with the maximum particle size of the coarse aggregate as 20 mm is better than the coarse aggregate gradation as 5–10 mm:10–20 mm = 1:1.

6.3.2.5

Superplasticizer

Mix proportion parameters of SCC is listed below: sand ratio of 50%, water to binder ratio of 0.35, fly ash content of 40%, silica fume content of 5%, and the maximum coarse aggregate particle size of 20 mm. The coarse aggregate gradation is 5–10 mm:10–20 mm = 1:1. Under the condition of above parameters, four polycarboxylic acid superplasticizer are adopted into SCC to determine their influence on concrete, including LX-6, SP1, V500, and V3320 (Table 6.16). Four superplasticizers are used to keep the initial slump of concrete mixture at about 23 cm. At the same time, different dosages of tackifiers are added to adjust the fluidity and cohesiveness of concrete. It can be seen from Table 6.17 that SP1 and V500 exhibit better slump flow, and the slump loss is small. According to the results of outflow time in the inverted slump cylinder, V500 is the smallest, followed by SP1, while the values of LX-6 and V3320 are both too large. From the perspective of concrete compressive strength, at the age of 3d, 7d, or 28d, the concrete with SP1 shows the highest strength. Therefore, SP1 can be regarded as the optimal waterreducing agent for the preparation of self-compacting concrete with MS from the above discussion. Table 6.16 Influence of different superplasticizers on concrete performance Test Superplasticizer number

Content of Slump/cm tackifier/‰

Slump flow/cm

type

content

0h

1h

SG8

LX-6

1.6

10

24

23.5 20.5 61

2h

SG9

SP1

1.4

2

23.5 22

SG10

V500

2.0

5

SG11

V3320

1.5

20

23.5 22

Outflow time from the inverted slump cone/s

0h 1h 2h 0h

1h

42

12

21.5 63

58

55

10.1 13.1 13.5

25.5 23.5 23.5 65

66

64

7.3

7.7 10

56

50

21

27.6 31.4

20

60

14.1 18

Table 6.17 Compressive strength of concrete under different stage Test number

2h

56

Superplasticizer

Compressive strength/MPa

Type

3d

7d

28d

SG8

LX-6

18.9

36.5

55.3

SG9

SP1

21.9

38.5

60.3

SG10

V500

20.5

28.5

51.6

SG11

V3320

20.5

36.7

54.7

336

6 Self-Compacting Concrete with Manufactured Sand

6.4 Engineering Application of SCC with Manufactured Sand 6.4.1 Qingshuihe Bridge 6.4.1.1

Project Overview

Guiyang-Weng’an Expressway Construction in Guizhou Province is a further improvement and optimization of urban loop network in China, with a total length of 70.722 km. Located in the east of Guizhou Province, Qingshuihe Bridge is the main traffic route from Guiyang to Weng’an. The main bridge is a single -pan simply supported steel truss girder suspension bridge, with a main span of 1130 m and a calculated span of main cable as 258 m + 113 m + 345 m. The approach bridge can be divided into two sections. The cable tower is a reinforced concrete frame structure, with a height of 230 m and 236/220 m at banks of at Kaiyang and Weng’an, respectively. C50 SCC with MS is used in the cable tower, which settles the technical problems to control the high fluidity, high filling, and anti-segregation.

6.4.1.2

Key Technology for Preparation of SCC with Manufactured Sand in Qingshuihe Bridge

The effects of water to binder ratio, the percentage of fine aggregate in aggregates, the dosage of cementitious material, and fly ash on the performance of C50 SCC with MS are studied. Combined with the aggregate optimization, the incorporation of chemical admixtures, and large amount of mineral admixtures, the mix design methods have been proposed to prepare C50 cable tower SCC with high workability to meet the performance requirements. Based on previous tests, the standard mix proportion of C50 SCC with MS has been obtained in Table 6.18. (1) Water to binder ratio The water to binder ratio of the reference mix is 0.31. The influence of the variation of water to binder ratio on the workability and compressive strength of C50 SCC with MS has been analyzed, and the specific test results are shown in Table 6.19. Table 6.18 Standard mix proportion of C50 cable tower SCC with MS (kg/m3 ) Cementitious material

Cement

Fly ash

Sand

Stone

Water to binder ratio

The Water percentage of fine aggregate in aggregates

Water reducer (%)

510

357

153

1007

824

0.31

55

1.0

158

Admixture (%)

1.45

1.1

1.0

Water to binder ratio

0.29

0.31

0.33 275/730

275/700

270/650

T /K (mm/mm)

7

15

15

Td (s)

Table 6.19 Influence of different water to binder ratio on SCC with MS

Fine

Fine

Partial cohesion

Cohesiveness

No

No

No

Segregation

No

No

No

Bleeding

43.04

42.2

57.06

3d

47.2

47.9

47.5

7d

52.0

52.4

53.2

28d

Compressive strength (MPa)

6.4 Engineering Application of SCC with Manufactured Sand 337

338

6 Self-Compacting Concrete with Manufactured Sand

It can be seen that for SCC with C50 MS, the variation of water to binder ratio has a great influence on the state of concrete mixture. The mix with a water to binder ratio of 0.29 has the same slump time as the reference mix, while the content of superplasticizer required is 1.45%, which is much higher than the control. At the same time, much lower water to binder ratio will lead to higher cohesiveness of concrete. In addition, when the water to binder ratio increases, the required amount of superplasticizer becomes smaller, but the fluidity and viscosity problems are improved. With the decrease of water to binder ratio, the compressive strength of concrete at 7d and 28d increases continuously, but the increased range is not obvious. Therefore, on the premise of ensuring the strength of C50 self-compacting concrete with MS, the water to binder ratio should be increased. (2) The percentage of fine aggregate in aggregates The percentage of fine aggregate in the reference mix is 55%. The influence of the change of fine aggregate percentage on the workability and compressive strength of C50 SCC with MS has been studied, and the chemical admixture content is adjusted according to the concrete state. The specific test results are shown in Table 6.20. It can be seen from Table 6.20 that with the increase of the percentage of fine aggregate in aggregates, the problem of high viscosity for concrete mixture has been adjusted to ensure the construction condition, which indicates that the percentage of fine aggregate in aggregates has a great influence on the workability of SCC. With the increase of the percentage of fine aggregate in aggregates, the fluidity of concrete is improved with the water to binder ratio. The total amount of cementitious material and the content of fly ash was kept at constant. In addition, the 3d and 7d strengths of concrete increase gradually, which indicates that the increase of the percentage of fine aggregate in aggregates is beneficial to the early strength. However, the 7d and 28d strengths of concrete increase at first but then decrease, which indicates that the later strength of concrete should be considered by appropriately increasing the percentage of fine aggregate in aggregates. Too large amount of the percentage of fine aggregate in aggregates leads to the reduced strength of concrete. (3) Total amount of cementitious materials The total amount of cementitious materials in reference mix is 510 kg/m3 . The influence of the total amount of cementitious materials on the workability and compressive strength of C50 SCC with MS has been studied, and the chemical admixture content is adjusted according to the concrete state. The test results are shown in Table 6.21. It is found from Table 6.21 that when the amount of cementitious material increases to 535 kg/m3 , the slump time and viscosity of concrete mixture are reduced compared with the reference mix. When the cementitious material reduces to 485 kg/m3 , the admixture content reaches to 1.35%, but the workability is not as good as that of the control, which indicates that the reduction of the total amount of cementitious material is not conducive to the workability of concrete, and the demand for admixtures increases. In addition, with the increase of cementitious materials, the strength of concrete at 3d, 7d, and 28d decreases gradually. Therefore, the

1.1 1.1 1.2

50

55

60 260/590

275/700

250/640 10

15

14 Good

Good

General

No

No

Slightly

No

No

Slightly

42.5

42.2

39.4

3d

46.2

47.9

48.1

7d

The percentage of fine aggregate in aggregates/% Water reducer/% T /K (mm/mm) Td (s) Cohesiveness Segregation Bleeding Compressive strength/MPa

Table 6.20 Influence of different the percentage of fine aggregate in aggregates on concrete performance

50.1

52.4

47.4

28d

6.4 Engineering Application of SCC with Manufactured Sand 339

340

6 Self-Compacting Concrete with Manufactured Sand

Table 6.21 Effect of different amount of cementitious materials on concrete performance Cementitious Water to Water T /K (mm/mm) Td Cohesiveness Compressive material binder reducer (s) strength/MPa (kg/m3 ) ratio (%) 3d 7d 28d 485

0.31

1.35

265/630

11

General

43.0

48.4

54.3

510

0.31

1.1

275/700

15

Good

42.2

47.9

52.4

535

0.31

1.1

265/650

7

Good

42.5

47.8

51.5

workability should be considered comprehensively, and the amount of cementitious materials should be controlled reasonably. (4) Fly ash content The content of fly ash in the reference mix is 30%. The influence of fly ash content on the workability and compressive strength of C50 SCC with MS has been studied, and the content of admixture is adjusted according to the concrete state. The test results are shown in Table 6.22. From the above results, it can be seen that with the increase of fly ash content, the viscosity of slurry is weakened, thus the content of superplasticizer reduces with the mixture in good condition. In addition, fly ash has a great influence on the early strength of concrete. With the increase of fly ash content, the 3d, 7d, and 28d strengths of concrete decreases. When the content of fly ash is more than 30%, however, the 28d strength of concrete cannot meet the requirements of mechanical properties.

6.4.1.3

Construction and Application Effect of SCC with Manufactured Sand in Beipanjiang Bridge

Based on the optimization of raw material and mix design, the optimal mix proportion is listed in Table 6.23. From January to October 2014, the construction of the cable tower has been completed, and the placing pier body has high flatness with almost no cracks, as shown in Figs. 6.13 and 6.14. The workability of C50 cable tower SCC with MS was tested on site with a slump of 255 mm. The concrete samples were cured under natural conditions after casted with a 28d compressive strength of 62.3 MPa, which met the local engineering requirements. Furthermore, the engineering quality was quite excellent after testing by relevant institutions.

55

55

55

20

30

40

The percentage of fine aggregate in aggregates/%

Fly ash/%

0.31

0.31

0.31

Water to binder ratio

Table 6.22 Influence of fly ash content on concrete performance

1.01

1.1

1.15

Water reducer/%

260/685

275/700

260/660

T /K (mm/mm)

14

15

11

Td (s)

Good

Good

Good

Cohesiveness

39.31

42.2

50.23

3d

45.6

47.9

55.4

7d

48.68

52.4

56.75

28d

Compressive strength (MPa)

6.4 Engineering Application of SCC with Manufactured Sand 341

342

6 Self-Compacting Concrete with Manufactured Sand

Table 6.23 Construction mix proportion of C50 cable tower SCC with MS (kg/m3 ) Cement

Fly ash

MS

Crushed stone

Water

Admixture

425

75

857

928

165

5

Fig. 6.13 Recent photograph of cable tower concrete

Fig. 6.14 Perspective of cable tower

6.4 Engineering Application of SCC with Manufactured Sand

343

6.4.2 Beipanjiang Bridge 6.4.2.1

Project Overview

Located at the junction of Guizhou Province (DuGe, Liupanshui) and Yunnan Province (Lalong, Xuanwei), China, Beipanjiang giant bridge belongs to Bijie to DuGe of Hangrui Expressway with a total length of the bridge as 1341.40 m. The shape design is adopted by steel truss girder cable-stayed bridge with a main span of 720 m. The total height of cable tower of Beipanjiang Bridge is adopted as 246.5 m, of which the height of cable tower base is 19.5 m with the H-shaped upper tower. The technical problems of C50 SCC with MS are solved to obtain high fluidity, high filling, and segregation resistance.

6.4.2.2

Key Technology for Preparation of SCC with Manufactured Sand in Beipanjiang Bridge

The previous work has studied the influence of fly ash content, cementitious material content, the percentage of fine aggregate in aggregates, water to binder ratio, and other mix parameters on the performance of concrete, and the mix optimization technology of C50 cable tower SCC with high workability has been put forward. Based on a large number of previous tests, the basic mix proportion of C50 SCC with MS is obtained in Table 6.24. (1) The percentage of fine aggregate in aggregates The percentage of fine aggregate in aggregates of the reference mix is 44%, and the influence of the percentage of fine aggregate in aggregates variation on the workability and compressive strength of C50 cable tower SCC with MS has been studied. The specific test results are shown in Table 6.25. It can be seen from Table 6.25 that the percentage of fine aggregate in aggregates has a great influence on the workability of SCC (Fig. 6.15). With the same indexes of water to binder ratio and the total amount of cementitious material and the amount of fly ash, the fluidity of concrete becomes better with the increase of the percentage of fine aggregate in aggregates. As the percentage of fine aggregate in aggregates Table 6.24 Standard mix proportion of C50 MS concrete (kg/m3 ) Cementitious material

Cement

Fly ash

Sand

Stone

Water to binder ratio

The Water percentage of fine aggregate in aggregates (%)

Water reducer (%)

510

306

208

915

915

0.314

50

1.1

160

344

6 Self-Compacting Concrete with Manufactured Sand

Table 6.25 Effect of different the percentage of fine aggregate in aggregates on concrete performance The percentage of fine aggregate in aggregates/%

Admixture/%

T /K (mm/mm)

Td (s)

44

0.885

240/590

8.0

46

1.0

240/685

50

1.088

55

1.2

Cohesiveness

Compressive strength/MPa 3d

7d

Relatively poor

31.6

40.5

9.7

Relatively poor

31.7

40.6

265/685

10.5

Good

32.1

44.6

260/790

10.2

Relatively cohesive

32.2

41.5

is 50%, the concrete mixture is in good condition. Whereas when the percentage of fine aggregate in aggregates is too large, the mixture becomes more cohesive. In addition, with the increase of the percentage of fine aggregate in aggregates, the 3d compressive strength of C50 cable tower SCC with MS increases, and the 7d compressive strength increases firstly but then decreases. (2) Content of fly ash The content of fly ash in the reference mix is 40%, and the influence of the content of fly ash on the workability and compressive strength of C50 cable tower SCC with MS has been studied. The specific test results are shown in Table 6.26.

Fig. 6.15 State of concrete mixture with 46% the percentage of fine aggregate in aggregates

6.4 Engineering Application of SCC with Manufactured Sand

345

Table 6.26 Influence of fly ash content on concrete performance Fly ash (%)

Admixture/%

T /K (mm/mm)

Td (s)

40

1.1

260/720

9.1

30

1.0

265/710

20

1.04

265/705

Cohesiveness

Compressive strength/MPa 3d

7d

28d

60d

Good

31.1

43.5

54.5

57.8

13.7

Good

36.7

46.2

60.1

73.7

7.5

Good

43.1

53.8

72.4

76.1

It can be seen from Table 6.26 that with the decrease content of fly ash, the paste of mixture becomes sticky and the fluidity of concrete decreases. In addition, with the increase of fly ash content, the compressive strength of C50 cable tower SCC with MS in 3d, 7d, 28d, and 60d is gradually decreasing. (3) Content of the coarse aggregate (an average parameter of 5–10 mm) The content of the coarse aggregate with an average parameter of 5–10 mm is adopted as 45% in the reference mix, and the influence of the content of the coarse aggregate on the workability and compressive strength of has been studied for the C50 cable tower SCC with MS. The chemical admixture content has been adjusted according to the working state of concrete. The specific test results are shown in Table 6.27. It can be seen from Table 6.27 that with the increase of the content of coarse aggregate (5–10 mm), the fluidity and the collapse time of concrete mixture are increased. With the increase of coarse aggregate (5–10 mm) content and the decrease of coarse aggregate (10–20 mm), the 3d and 7d compressive strengths of C50 cable tower SCC with MS increase, while the 28d compressive strength decreases. What’s more, the 60d compressive strength increases firstly but then decreases. (4) Total amount of cementitious materials The total amount of cementitious materials is kept as 510 kg/m3 in the reference mix. The influence of the varying content of cementitious materials is studied on the workability and compressive strength of C50 cable tower SCC with MS. The addition of admixture has been adjusted according to the working state of concrete. The specific test results are shown in Table 6.28. Table 6.28 shows that the increase of the total amount of cementitious materials is conducive to increasing the fluidity and flow speed of concrete and reducing the amount of admixture. In addition, with the increase of the total amount of cementitious materials, the 3d and 7d compressive strengths of C50 cable tower SCC with MS increase at first but then decrease, and the 28d compressive strength increases gradually. In addition, the 60d compressive strength exhibits the same trend as that at 3d and 7d.

0.936

65

70

35

30

0.953

1.1

10–20 mm (%)

55

5–10 mm (%)

Admixture (%)

45

Ratio of coarse aggregate

260/650

260/725

260/720

T /K (mm/mm)

5.8

6.7

9.1

Td (s)

Sticky

Good

Good

Cohesiveness

No

No

No

Segregation

Table 6.27 Influence of the content variation of coarse aggregate (5–10 mm) on concrete performance

No

No

No

Bleeding

28.1

30.5

31.1

3d

36.9

37.3

43.5

7d

59.2

56.8

54.5

28d

60.8

62.3

57.8

60d

Compressive strength (MPa)

346 6 Self-Compacting Concrete with Manufactured Sand

6.4 Engineering Application of SCC with Manufactured Sand

347

Table 6.28 Influence of total amount of cementitious materials on concrete performance Total amount of cementitious materials

Admixture (%)

T /K (mm/mm)

Td (s)

Cohesiveness

Compressive strength/MPa 3d

7d

28d

60d

510

1.1

260/720

9.1

Good

31.1

43.5

54.5

57.8

530

0.854

265/760

8.6

Good

30.8

37.6

51.4

66.3

490

0.861

260/680

14.6

Relatively sticky

26.8

37.7

54.6

64.5

Table 6.29 Construction mix proportion of C50 cable tower SCC with MS (kg/m3 ) Cement

Fly ash

MS

Crushed stone

Water

Admixture

395

99

843

950

163

4.446

Table 6.30 Basic performance indexes of C50 ultra-high pumping SCC with MS Slump (mm)

220

6.4.2.3

1-h slump loss (mm)

Slum flow (mm)

0

520–550

Cohesiveness

good

Water holding capacity

Grasp bottom, segregation, and bleeding

Compressive strength (MPa) 28d

60d

good

no

52.2

61.9

Construction and Application Effect of SCC with Manufactured Sand in Beipanjiang Bridge

Based on the technologies of raw materials optimization and mix design, the advised mix proportion is shown in Tables 6.29 and 6.30. The following methods are adopted on the construction site. (1) The sequence placement of on-site concrete is listed as follows: inspection before placing → concrete casting → concrete leveling → concrete vibration → concrete curing. (2) Concrete feeding mode: the concrete is pumped into the mold by the delivery pump, and the concrete is placed by the multi-point tumbling barrel. (3) Inspection before concrete placing: the support, formwork, reinforcement, and embedded parts are checked and recorded before concrete placing. There must be no sundries and ponding in the formwork, and the reinforcement must be clean. The joints of the formwork shall be tight, and the release agent shall be painted inside. The uniformity and slump of the concrete must be checked before the concrete is put into the formwork. (4) Control of concrete placing direction, sequence, and layer thickness: the concrete must be placed layer by layer according to a certain thickness, sequence,

348

6 Self-Compacting Concrete with Manufactured Sand

Fig. 6.16 Construction of main tower of Beipanjiang Bridge

direction, and the upper concrete shall be placed before the initial setting of the lower concrete or remolding. (5) Manual tamping is strictly adopted during concrete placing. Through the control of on-site construction technology, the SCC with MS is successfully applied in the project. Figure 6.16 shows the site of the main tower construction of Beipanjiang Bridge.

6.5 Concluding Remarks Self-compacting concrete with MS exhibits advantages in performance and mechanical durability of concrete; thus, it is suitable for the construction and can be widely used in different building structures. Through the quality control of raw materials, reasonable mix design, and strict mixing system, the workability, mechanical property, and durability of SCC with MS can be effectively controlled. The use of MS not only can greatly reduce the utilization rate of river sand and protect the ecological environment, but also has desirable social and economic benefits.

References 1. G.M. Liu, W.M. Cheng, L.J. Chen, G. Pan, Z.X. Liu, Rheological properties of fresh concrete and its application on shotcrete. Constr. Build. Mater. 243 (2020) 2. S. Jiang, X. Chen, G. Cao, Y. Tan, X. Xiao, Y. Zhou, S. Liu, Z. Tong, Y. Wu, Optimization of fresh concrete pumping pressure loss with CFD-DEM approach. Constr. Build. Mater. 276 (2021)

References

349

3. K.P. Jang, M.S. Choi, How affect the pipe length of pumping circuit on concrete pumping. Constr. Build. Mater. 208, 758–766 (2019) 4. M. Choi, N. Roussel, Y. Kim, J. Kim, Lubrication layer properties during concrete pumping. Cem. Concr. Res. 45, 69–78 (2013) 5. M. Choi, C.F. Ferraris, N.S. Martys, D. Lootens, V.K. Bui, H.R.T. Hamilton, Metrology needs for predicting concrete pumpability. Adv. Mater. Sci. Eng. 2015 (2015) 6. Q. Yao, Pumping pressure and its determination of concrete. Constr. Machin. 9, 7 (1994). ((in Chinese)) 7. J.W.-S. Bernad Massey, Mechanics of Fluids (Taylor & Francis, USA, New York, 2006) 8. C. Hu, F. de Larrard, The rheology of fresh high-performance concrete. Cem. Concr. Res. 26(2), 283–294 (1996) 9. T. Yen, C.W. Tang, C.S. Chang, K.H. Chen, Flow behaviour of high strength high-performance concrete. Cement Concr. Compos. 21(5–6), 413–424 (1999) 10. S.-c Deng, X.-b Zhang, Y.-h Qin, G.-x Luo, Rheological characteristic of cement clean paste and flowing behavior of fresh mixing concrete with pumping in pipeline. J. Cent. South Univ. Technol. 14, 462–465 (2007) 11. M. Jolin, F. Chapdelaine, F. Gagnon, D. Beaupré, Pumping concrete: a fundamental and practical approach, in Proceedings of the International Conference on Shotcrete for Underground Support, 2006, pp. 334–347 12. Z. Li, State of workability design technology for fresh concrete in Japan. Cem. Concr. Res. 37(9), 1308–1320 (2007) 13. J.E. Wallevik, Relationship between the Bingham parameters and slump. Cem. Concr. Res. 36(7), 1214–1221 (2006) 14. E.P. Koehler, D.W. Fowler, Summary of concrete workability test methods. Trend (2003) 15. D. Feys, K.H. Khayat, R. Khatib, How do concrete rheology, tribology, flow rate and pipe radius influence pumping pressure? Cement Concr. Compos. 66, 38–46 (2016) 16. E. Secrieru, D. Cotardo, V. Mechtcherine, L. Lohaus, C. Schrofl, C. Begemann, Changes in concrete properties during pumping and formation of lubricating material under pressure. Cem. Concr. Res. 108, 129–139 (2018) 17. M.S. Choi, Y.J. Kim, S.H. Kwon, Prediction on pipe flow of pumped concrete based on shearinduced particle migration. Cem. Concr. Res. 52, 216–224 (2013) 18. K. Kovler, N. Roussel, Properties of fresh and hardened concrete. Cem. Concr. Res. 41(7), 775–792 (2011) 19. H. Okamura, M. Ouchi, Self-compacting concrete. J. Adv. Concr. Technol. 1(1) (2003) 20. H. Okamura, K. Ozawa, Self-compacting high performance concrete. Struct. Eng. Int. 6(4) (2010)

Chapter 7

Rock-Filled Concrete with Manufactured Sand

7.1 An Overview of RFC RFC technology is a new type of mass concrete technology. The large-size aggregate (boulder or rubble) is directly put into the construction bin to form a rock block with a certain amount of voids. Then superfluid self-compacting concrete (SFSCC) is adopted to fill the voids. In this way, a dense, low hydration heat concrete structure is formed with SFSCC and large-size aggregates [1], as shown in Fig. 7.1. The technology of RFC presents the following characteristics: good resistance to temperature cracks, good durability, fast construction speed, good construction quality, raw materials available, low cost, and so on. Consequently, it has wide applications in mass concrete engineering fields, like water conservancy, hydroelectric dams, transportation, energy, municipal, and railway [2–8]. At present, some scholars have done some research on the performance of RFC. Jin et al. studied the flow performance and filling capacity of RFC, which randomly placed three specimens in a 500 mm × 500 mm × 2000 mm plexiglass mold by three methods [9–12]. There was no rock in the first 500 mm of No. 1 mold to test the state and performance of SCC, while there was no rock in the last 500 mm of No. 3 mold to test the state and performance of SCC passing through the rock block. Samples are taken from three areas of specimens, including the areas only filled by SCC before and after passing through the rock block and the area of RFC. The strength test is also conducted by rebound test. The results show that the SCC does not only present well-accepted flow and gap filling performance in the rock block, but also forms dense concrete with better mechanical properties. Shi and Zhang focused on the mechanical properties of RFC through the samples directly cut from the large-scale test block of RFC with the size of 1500 mm × 500 mm × 500 mm [13–16]. They found that when the self-flowing distance of SCC is within 1500 mm, the compressive strength of RFC is not lower than that of SCC itself. The axial compressive stress–strain curves of RFC prism are close to a straight line. Additionally, the proportionality limit is similar to the strength limit. There is

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Z. Jiang, Green High-Performance Concrete with Manufactured Sand, https://doi.org/10.1007/978-981-19-6313-1_7

351

352

7 Rock-Filled Concrete with Manufactured Sand

Fig. 7.1 Schematic diagram of RFC

only slight plastic deformation, and the failure is a sudden longitudinal splitting. The interfaces between the block stone and the SCC in the RFC present better adhesion. Huang et al. applied RFC technology in the reinforced structure. He adopted stones, waste concrete blocks, and lightweight materials as large aggregates to cast reinforced concrete beams [17]. The mechanical properties of the beams of RFC with three kinds of aggregates under different failure modes were compared, carrying out the flexural beam and shear beam tests. The experimental results show that the bending and shear capacity of stone or waste concrete block-filled SCC beams are higher than that of SCC beams. The former also has a lower cost. The bending capacity of light-material-filled SCC beams is similar to that of SCC beams, while its shearing capacity decreased. Furthermore, the decrease depends on the accumulation rate of lightweight materials. Wu et al. tested the compressive strength, impermeability, and frost resistance of C20 RFC [18]. They found that the C20 RFC meets the design requirements of strength and durability. In terms of theoretical research, Huang et al. numerically simulated the flow process by using the discrete element method, analyzing the flow condition and predicting the filling compactness [19]. Based on the meso-mechanical model, Tang et al. classified the RFC as a multi-phase medium, which was composed of selfcompacting concrete, block stone, and their interface, and established a numerical simulation model [20–22]. The relationships between strength and constitutive of three components were obtained according to three-phase medium mechanical parameters. A series of four-point bending tests were carried out to prove the reliability of the model results. The results showed that the model can simulate the whole process of RFC flexural test, and the stress–displacement curve as well as failure mode was obtained in good agreement with the test results. Xu et al. simulated and compared the temperature field distribution in mass concrete prepared with ordinary concrete and RFC [23]. The results demonstrated that the internal hydration heat and the temperature of RFC are lower than those of ordinary concrete, which was beneficial to large volume of cracks control. In addition, Shen et al. adopted a vision system in surface quality management of RFC, aiming to solve the shortcomings of manual inspection such as strong subjectivity and low accuracy [24, 25]. They divided the on-site targets into moving targets

7.3 Simulation of Rock Accumulation

353

Table 7.1 Mud content and mud block content index of rock Project

Clay content (%)

Mud content (%)

Index

≤ 0.5

≤ 0.5

and static targets, developing corresponding visual information processing algorithms. The results demonstrated that the system can be used for the construction management of RFC and other similar projects. In summary, the feasibility and unique advantages of RFC technology have been extensively tested and confirmed. However, as a new type of material, there are various problems in promoting its engineering application. Therefore, it is necessary to study its various properties in depth.

7.2 Performance Requirements for Rock According to Chinese Standard JTG E41-2005, rock should meet the requirements specified in JTJ 041-2000. (1) The rock used for RFC with MS should be free of peeling layers and cracks. The particle size of rock grains without weathering is 300–1000 mm. (2) The compressive strength of water-saturated rock should be no less than 30 MPa. (3) The clay content and mud content of rock should meet the index requirements given in Table 7.1.

7.3 Simulation of Rock Accumulation 7.3.1 Algorithm Description In order to theoretically analyze the accumulation process and degree of largediameter aggregates, the degree of rock accumulation and the controlling factors of void ratio are explored based on the actual conditions. According to construction conditions, computer programming is used to simulate the accumulation process of rock block via analyzing key control parameters. The three-dimensional simulation of the aggregate accumulation process is still at the stage of exploration all over the world. It is generally believed that from a macroscopic perspective, the three-dimensional accumulation of aggregates is uniform. Therefore, a two-dimensional model method is used to simplify and simulate the accumulation process. There are several research literatures about the concrete random aggregate model [26–32]. However, the purpose of most research is to simulate the distribution of aggregate in concrete and then conduct research on mechanical properties. Therefore, most research focused on the generation of aggregates, the

354

7 Rock-Filled Concrete with Manufactured Sand

judgment of convexity and concave, ignoring the stacking process of aggregates. The existing stacking algorithms are randomly generated in the designated area, which is not only inefficient, but cannot also truly simulate the stacking process. Therefore, this section focuses on improving the algorithm of the traditional two-dimensional simulation method, which greatly facilitates the operating efficiency of the computer program and makes the aggregate stacking process in accord with the actual situation. The main innovation of this method is to use the angle method to judge the convexity and concavity of the polygon, which is more efficient and stable than the traditional area method and ray method. In addition, with regard to the traditional two-dimensional simulation, the aggregates are random in the specified area resulting in the calculation running inefficiently and cannot simulate the real process of aggregate stacking. This section draws on the game rules of Tetris, which can be fed from bottom to top, from left to right, and can simulate large particle sizes realistically [33].

7.3.1.1

Overall Program Design Ideas

The whole program can be divided into the following modules (Fig. 7.2).

7.3.1.2

Algorithm Description of Each Module

(1) Polygonal aggregate production module adopts polar coordinate method (Fig. 7.3). The main parameters of polygonal aggregates are listed as follows: the number of sides of aggregate n and the particle size of aggregate ranging from amax to amin . Specific generation process: (1) The edge number n of randomly generated aggregates (set in advance, for example, specify that n is within 4–8). (2) Set the origin of the coordinate axis to the center point (0, 0) of the aggregate. (3) Randomly generate n angles, that is, the absolute angle of the polar coordinate corresponding to each side, which is represented by ∅i . The parameter δ ranges from 0 to 1, which on behalf of the range of angle values < ∅i < 2π (1 + δ)/n. The closer δ is to 1, the corresponds to each side to 2π [1−δ] n better the uniformity of the aggregate is, and the closer δ is to 0, the fewer the grain shape of the aggregate with lots of needles and flakes is. The random variable p ranges from 0 to 1, which is assumed to be a normal distribution, and pi (i = 1 – n) can be obtained via running n times continuously ∅i = 2π [1 + (2 pi − 1)δ]/n. Since there are five random pi , five angles can be obtained. But generally, the sum of these five is )not equal to 2π, so the ( angles  following adjustments are needed: ∅i = ∅i × 2π/ nj=1 j . ∅i is the absolute angle of the polar coordinate corresponding to each side.

7.3 Simulation of Rock Accumulation

355

Fig. 7.2 Overall program design for aggregate accumulation

It is assumed that a vertex S1 of the polygon is on the initial axis of polar coordinates, the vertex is changed arranging in a counterclockwise direction, then the angle between S 2 OS 1 is θ1 , and then the angle of S i OS 1 is θi−1 (θ0 = 0 can be set, indicating that the angle of S 1 OS 1 is 0). i  ∅ j ; i = 1, 2, … n – 1; θ0 = 0; Then θi = j=1

(4) The random variable q is set ranging from 0 to 1 and the particle size of the aggregate range from amax to amin , then the polar radius Ri = q × (amax /2 − amin /2) + amin /2. (5) The position of each vertex of the generated polygon S i . 

xi = Ri × cos θi−1 yi = Ri × sin θi−1



(6) When stacking aggregate, the center P0 (x 0 , y0 ) of aggregate stacking can be firstly determined, followed by moving each vertex.

356

7 Rock-Filled Concrete with Manufactured Sand

Fig. 7.3 Schematic diagram of random generation of polygonal aggregate



xi = x0 + Ri × cos θi−1 yi = y0 + Ri × sin θi−1



(2) Whether the aggregate is convex Since the aggregates are generated at the origin, the angle between two adjacent edges can be used to judge the degree of unevenness. As shown in Fig. 7.4, assuming ∠OS 1 S n = α 1 , ∠OS 1 S 2 = β 1 ; And so on: ∠OS i S i – 1 = α i , ∠OS i S i+1 = β i ; Then for any vertex S i , when α i + β i < π, the vertex is a convex point; otherwise, it is a concave point. If all the vertices of the polygon are convex points, the polygon is convex; if one of the vertices of the polygon is concave, the polygon is concave. (3) Aggregate overlap judgment module and area calculation module Use the area invasion rule to judge the overlap of aggregates; the specific steps are as follows: (1) For any convex polygonality, S 1 , S 2 … S n are the serial numbers that have been arranged in a counterclockwise direction, P(x, y) is any point inside, then the area of the|triangle ΔPS|i S i+1 is the area calculated by the following formula: | x y 1 || | 1| Ai = 2 | xi yi 1 ||; | |x i+1 yi+1 1

7.3 Simulation of Rock Accumulation

357

Fig. 7.4 Angle formed by each vertex and center point of the polygonal aggregate

Then: A =

n 

Ai (In order to facilitate program calculation, set the

i=1

coordinate value of S n+1 as S 1 .); A is the total area of the polygonal aggregate; (2) O is the center of polar coordinates (set to coordinates x 0 and y0 ), and then the area of the aggregate can be calculated; (3) Determine whether a certain point P is inside the aggregate, then Ai is greater than 0, this point is inside the aggregate, as shown in Fig. 7.5a; Ai has one equal to zero, and this point is on the aggregate boundary, as shown in Fig. 7.5b;

Fig. 7.5 Determination of point P

358

7 Rock-Filled Concrete with Manufactured Sand

Ai has a value smaller than zero, which is outside the aggregate at this point, as shown in Fig. 7.5c. 7.3.1.3

The Boundary Criterion of Aggregate

After each polygon is generated (assuming that the polygon cannot be rotated, it can only move parallel or vertically during the movement), Si(x i , yi ) can be obtained; Each vertex of the polygon must meet the following boundary: 0 ≤ x i ≤ a, 0 ≤ yi ≤ b (a and b are the length and width of the designated area, respectively).

7.3.2 Results and Analysis 7.3.2.1

The Simulation of Aggregate Accumulation Process

For the purpose of realizing the computer simulation of the aggregate delivery process and calculating the void ratio, therefore, the computer can automatically move the aggregates just like playing a Tetris game and stack them as densely as possible from bottom to top and from right to left. The specific implementation procedure is the aggregates are firstly placed down from the right until obstructed and then searched from right to left where they can fall until the search is completed. The specific accumulation process is as follows (Fig. 7.6).

7.3.2.2

The Influence of Accumulation Parameters on the Accumulation Degree of Large-Size Aggregate

➀ Determination of basic parameters The accumulation parameters are composed of several sides of the two-dimensional polygon corresponding to the large-size aggregate, the range of the aggregate size, the uniformity coefficient of the aggregate, and the area of the stacking area. The more sides of a polygon are beneficial to the automatically generated aggregate shape of approximate circle. According to other references, the gravel aggregate presents generally 4–8 sides. Considering the actual situation of the project, the particle size range of the large particle size aggregate is set at 30–500 mm. The actual construction area and the cross section are supposed as 2 m × 5 m and 2 m × 2 m, respectively, in which the height of each construction is 2 m.

7.3 Simulation of Rock Accumulation

359

Fig. 7.6 Schematic of the aggregate accumulation process

Generally, other parameters remain constant during the study with regard to the influence of a single parameter change on the degree of accumulation. ➁ The influence of aggregate size range variation on accumulation degree of largesize aggregate (1) The influence of the change of the maximum size of aggregate on the degree of accumulation of large-size aggregate The change of natural porosity formed after the accumulation of large-size aggregates is studied when the maximum particle size Dmax is 1000 m, 500 mm, and 250 mm, respectively (The minimum particle size Dmin is kept at 30 mm). The simulation results are given in Table 7.2 (Figs. 7.7, 7.8 and 7.9).

360

7 Rock-Filled Concrete with Manufactured Sand

Table 7.2 Influence of the change of the maximum size of aggregate on the porosity of large aggregate Dmax/mm

1000

500

250

Porosity (%)

31.8

28.6

24.8

Fig. 7.7 Dmax = 1000 mm

Fig. 7.8 Dmax = 500 mm

(2) The influence of the minimum size of aggregate on the degree of accumulation of rock According to the above results, the porosity is higher when the maximum size of the aggregate is 1000 mm, so all Dmax are set to 1000 mm for the following procedures. The influence of the minimum size of aggregate (30, 100, 200 mm) on the degree

7.3 Simulation of Rock Accumulation

361

Fig. 7.9 Dmax = 250 mm

of accumulation of large-size aggregates is studied, which are given in Table 7.3 (Figs. 7.10 and 7.11). (3) The influence of the uniformity coefficient of aggregate on the degree of accumulation of large-size aggregate Table 7.3 Influence of the change of the minimum size of aggregate on the porosity of large aggregate Dmin/mm

30

100

200

Porosity (%)

31.8

35.0

36.9

Fig. 7.10 Dmin = 100 mm

362

7 Rock-Filled Concrete with Manufactured Sand

Fig. 7.11 Dmin = 200 mm

The uniformity coefficient of the aggregate q ranges from 0 to 1. The closer q is to 0, the closer the shape of the aggregate is to a regular polygon. Conversely, the closer q is to 1, the more irregular the aggregate is. The influence of the change of aggregate uniformity coefficient on the degree of rubble filling is studied (Dmax = 1000 mm, Dmin = 200 mm) (Figs. 7.12 and 7.13; Table 7.4). The parameters used are Dmax = 1000 mm, Dmin = 200 mm, and q = 0.5. The simulation results are given in Table 7.5 (Figs. 7.14 and 7.15). Fig. 7.12 q = 0.2

7.3 Simulation of Rock Accumulation

363

Fig. 7.13 q = 0.8 Table 7.4 Influence of aggregate uniformity coefficient on porosity of large-size aggregate q

0.2

0.5

0.8

Porosity (%)

30.6

36.9

37.8

Table 7.5 Influence of accumulation area on the accumulation porosity of large-size aggregate Accumulation area

1m×1m

2m×2m

4m×4m

Porosity (%)

48.6

36.9

30.8

Fig. 7.14 Accumulation area of 1 m × 1 m

364

7 Rock-Filled Concrete with Manufactured Sand

Fig. 7.15 Accumulation area of 4 m × 4 m

7.4 Mix Design of Superfluid SCC with MS 7.4.1 Requirements on the Properties of SFSCC with MS 7.4.1.1

The Principle of Mix Design for SFSCC

The principles of mix design for SFSCC are as follows: (1) The workability of SFSCC should meet the evaluation index requirements, while the strength and durability of SFSCC must meet the requirements of engineering design. In addition, the economic analysis of mix design needs to be reasonable. (2) The mix design and calculation of SFSCC should be carried out according to the properties of raw materials, the size and shape of structure, and the size and filling degree of large-grain aggregates. Additionally, it should be determined after trial and adjustment in the laboratory. (3) Appropriate amounts of cementitious materials, high-volume mineral admixture, and special polycarboxylate acid chemical admixtures are chosen to optimize the fluidity of concrete. (4) Special chemical admixtures are used to make the concrete present good fluidity while maintaining good cohesion without segregation and bleeding. (5) Under the conditions of satisfying the performance of fresh concrete, the watercementitious material ratio should be as small as possible to ensure the strength and durability of the concrete. 7.4.1.2

The Index Requirements of Performance of Fresh Concrete

The index requirements of fresh SFSCC are given in Table 7.6.

7.4 Mix Design of Superfluid SCC with MS

365

Table 7.6 Testing methods and index requirements of performance of fresh concrete Number

Method

Index requirements

Testing performance

1

Slump (SL), mm

250 ≤ SL ≤ 290

Fluidity

2

Slump flow (SF), mm

650 ≤ SF ≤ 800

Filling

3

Flow time of inverted slump cone (Td), s

Td ≤ 6

Fluidity Gap pass ability Filling

4

Slump after 1 h (SL), mm

SL ≤ 250

Fluidity retention

5

Slump flow after 1 h (SF), mm SF ≤ 550

6

Flow time of inverted slump cone after 1 h (Td), s

Td ≤ 7

Gap pass ability retention Fluidity Gap pass ability Filling

In addition to the above requirements, the performance of fresh concrete also needs to meet the following indexes: (1) atmospheric bleeding rate ≤ 1.0%, (2) the initial setting time and the final setting time should be less than 10 h and 24 h, respectively, (3) vapor rate < 4.0%, and (4) T 50 ≤ 10 s. The workability of concrete is tested according to the “Standard for test method of performance on ordinary fresh concrete” (GB/T 50080).

7.4.1.3

The Performance Index Requirements of Hardened Concrete

The performances of hardened concrete include mechanical properties and durability. The mechanical properties and durability of hardened concrete are tested in accordance with the “Standard for test methods of concrete physical and mechanical properties” (GB/T 50081) and the “Standard for test methods of long-term performance and durability of ordinary concrete” (GB/T 50082), respectively. Conformity assessment is performed according to the “Standard for evaluation of concrete compressive strength” (GB/T 50107). The mix design of SFSCC is mainly composed of calculation and determination of mix proportion.

7.4.1.4

Calculation of Mix Proportion

The calculation of mix proportion for SFSCC is generally designed according to the assumed volume method. (1)

The main parameters of mix design for SFSCC include the loose volume of coarse aggregate in the fresh concrete, the volume of sand and watercementitious material ratio in the mortar, and the amount of mineral admixture in the cementitious material.

366

7 Rock-Filled Concrete with Manufactured Sand

The loose volume of the coarse aggregate per 1 m3 of concrete (V g0 ) is set as 0.5–0.7 m3 . The dosage of coarse aggregate per 1 m3 of concrete (mg ) is calculated according to the bulk density of coarse aggregate (ρ g0 ). (3) The compacted volume of coarse aggregate per 1 m3 of concrete (V g ) is calculated according to the apparent density of coarse aggregate (ρ g ). The compacted volume of the mortar (V m ) is calculated by subtracting V g from the total volume of concrete. (4) The volume content of sand in mortar is set as 0.42–0.44. The compacted volume of sand (V s ) is calculated in terms of V m and the volume content of sand. (5) The amount of sand per 1 m3 of concrete (ms ) is calculated based on V s and the apparent density of sand(ρ s ). (6) The compacted volume of mortar V p is obtained by subtracting the compacted volume of sand V s from the volume of mortar. (7) The water-cementitious material ratio is determined according to the designed strength grade of concrete. (8) The volume of mineral addition in the cementitious material is set depending on the requirements of concrete durability and temperature rise control. The apparent density of cementitious material (ρ b ) is calculated based on the volume ratio of the mineral addition to cement and their respective apparent densities. (9) The volume of cementitious material and water, the total amount of cementitious material (mb ), and the unit water consumption (mw ) are calculated depending on the apparent density of the cementitious material, watercementitious material ratio, mortar volume (V p ), and volume ratio, respectively. The total dosage range of cementitious material should be 450– 550 kg/m3 , and unit water consumption should be less than 200 kg/m3 . The mineral addition is calculated using equal mass instead of cement. (10) The amount of cement and mineral addition per 1 m3 of concrete are calculated according to the volume of cementitious material, the volume of mineral addition, and their respective apparent densities. (11) The variety and dosage of chemical admixture are selected according to the experiment. (2)

7.4.1.5

Trial Mix, Adjustment, and Confirm

(1) The initial mix proportion is calculated according to the above steps and range. (2) The initial mix proportion is tested and adjusted according to the performance requirements of SFSCC. (3) During the trial mixing of SFSCC, the minimum mixing volume of each batch of concrete should be more than 30 L, and the workability of fresh concrete should be tested if it meets the corresponding evaluation index requirements given in Table 7.6. The concrete strength should be checked if it meets the requirements

7.4 Mix Design of Superfluid SCC with MS

367

of the target mean strength. If necessary, the corresponding durability index should also be tested. (4) Three basic mix proportions that satisfy the workability requirements of concrete are selected to make concrete strength test pieces. At least one set of test pieces should be made for each mix proportion. The compressive strength test is performed after 28 days of standard curing. (5) If necessary, a full-scale experiment should be performed based on the determined mix proportion at the concrete mixing plant or construction site to check whether the designed mix proportion satisfies the engineering application conditions. (6) The appropriate mix proportion that meets the design requirements is determined according to the trial mix, adjustment, concrete strength test results, and fullscale experiment results.

7.4.2 Mix Design Procedures of Superfluid SCC with MS The basic mix design route of SFSCC includes the following aspects: (1) Performance test detection and analysis on construction site raw materials The workability and mechanical properties of concrete are determined by the quality and performance of raw materials. In order to determine the quality of material, the performance of raw materials needs to be tested and analyzed before the concrete mix design and preparation. (2) The initial mix proportion is determined according to the performance of concrete and the budget, etc. (3) The fresh concrete is adjusted on the basis of the initial mix proportion according to the performance parameters of raw materials so as to obtain the basic mix proportion meeting the requirements of workability. (4) The influence of different parameters of mix proportion on the performance of concrete is studied, mainly including water-cementitious material ratio, percentage of fine aggregate in aggregates, fly ash content, cementitious material content, etc. (5) The basic mix proportion is optimized according to the results of parameter changes and the further development of performance. (6) The mix design of concrete is prepared according to the ambient.

368

7 Rock-Filled Concrete with Manufactured Sand

7.4.3 Optimization of Mix Proportion of Superfluid SCC with MS 7.4.3.1

Adjustment of Initial Mix Proportion

The following mix proportion is selected as the initial mix proportion based on the previous experiments. The basic mix proportion needs to be adjusted depending on the properties of raw materials (including moisture content of aggregate, fines content of MS, solid content of chemical admixture, etc.). The concrete is mixed according to the mix proportion of Mix 1-1, as given in Table 7.7. From the results of the slump test in Fig. 7.16, Table 7.8, the fresh concrete of Mix 1-1 is slightly grouted and exhibits a certain number of bubbles. In addition, there are a lot of stones exposed on the surface. The fresh concrete is slightly bleeding and therefore with poor fluidity. The fresh concrete is adjusted from the following aspects according to the results of Mix 1-1: (1) the percentage of fine aggregate in aggregates, (2) water consumption, (3) the type of chemical admixture, and (4) the concrete bulk density adjusting to 2300 kg/m3 as a constant. The workability and strength of concrete are given in Table 7.8 (Fig. 7.17). Both unwashed sand and small gravel with a particle size of 5–10 mm were used from Mix 1-1 to Mix 1-13. The results showed that when the fly ash content is reduced from 65% to about 55%, both the inverted slump cone flow time and viscosity of fresh concrete increase, and compressive strength after 7 days greatly increases as well. On-site washed sand and small gravel with a particle size of 5–10 mm were used in Mix 1-14. It can be observed that the slump and expansion of Mix 1-14 are increased, the inverted slump cone flow time of fresh concrete is only 4.4 s, which does not segregate and bleeding, and its compressive strength after 7d curing is 28.4 MPa. All in all, Mix 1-14 meets the design requirements, which is set as the initial basic mix proportion (Table 7.9).

7.4.3.2

The Influence of the Change of Mix Proportion Parameters on the Performance of Concrete

The influences of different types of water reducer, fly ash content (55, 60, 65%), cementitious material consumption (475, 500, 525 kg/m3 ), the percentage of fine aggregate in aggregates (50, 55, 60%), water-cementitious material ratio (0.30, 0.33, 0.36), different raw materials, and other mix proportion parameters on the performance of concrete are studied based on the initial basic mix proportion. The main test indexes include the initial slump and the slump flow, the flow time of inverted slump cone, and the cube compressive strength at 3d, 7d, 28d, and 60d.

Cementitious material

500

Number

1-1

250

Cement

Table 7.7 Initial mix proportion (kg/m3 )

50

Fly ash (%) 800

Sand 800

Stone 0.34

W /B 50

The percentage of fine aggregate in aggregates (%)

170

Water

0.837

Water reducer (%)

270/685

T /K

7.4 Mix Design of Superfluid SCC with MS 369

370

7 Rock-Filled Concrete with Manufactured Sand

Fig. 7.16 Workability of fresh concrete with regard to Mix 1-1

For Mix 1-14, slump and slump flow of 2 h, inverted slump cone flow time, bulk density, compressive strength at 90d, and elastic modulus at 28d were measured. (1) The influence of different types of water reducer The water reducers used in the test are the No. 1 polycarboxylate superplasticizer of Xingheng, the No. 2 polycarboxylate superplasticizer of Xingheng, the polycarboxylate superplasticizer and retarder of Xingheng, and the polycarboxylate superplasticizer and retarder of Mingtai (Fig. 7.18; Table 7.10). Comparing four types of chemical admixtures, the concrete mixed with polycarboxylate superplasticizer and retarder of Mingtai has poor adaptability to cement, presenting poor fluidity. Comparing Mix 1-14 with Mix 1-16, it can be found that the two water reducers are beneficial to the workability of concrete. Although the overall condition of the fresh concrete is ideal with the mixture non-sticky, the water reduction rate of polycarboxylate superplasticizer and retarder of Xingheng is higher with less dosage. Meanwhile, comparing Mix 1-14 with Mix 1-15, it can be found that the No. 1 polycarboxylate superplasticizer of Xingheng is more beneficial to the fluidity and flow speed of the fresh concrete than polycarboxylate superplasticizer and retarder of Xingheng. Based on Mix 1-15, the washed sand was replaced with ordinary sand in Mix 1-17. The overall condition of the mixture was good, the inverted slump cone flow time was 9.2 s, and the slurry was slightly sticky (Table 7.11). As shown in the table, comparing Mix 1-4 with Mix 1-14, it can be found that the 7d compressive strength of concrete mixed with polycarboxylate superplasticizer and retarder of Mingtai is lower than that mixed with the No. 1 polycarboxylate superplasticizer of Xingheng. Comparing Mix 1-14 with Mix 1-15, the result showed that the 7d compressive strength of concrete mixed with the No. 1 polycarboxylate superplasticizer of Xingheng is higher than that mixed with the polycarboxylate superplasticizer and retarder of Xingheng.

65

50

500

500

500

500

500

500

500

475

500

1-4

1-6

1-7

1-9

1-10

1-11

1-12

1-13

1-14-A

55

55

55

55

50

65

65

65

500

1-3

Fly ash (%)

Cementitious material (kg/m3 )

Number

Table 7.8 Workability and strength of concrete

60

60

60

60

60

61

61

61

60

58

The percentage of fine aggregate in aggregates (%)

0.33

0.33

0.34

0.33

0.33

0.33

0.346

0.346

0.346

0.32

W /B

PCE (Xingheng1), 0.857%

PCE (Xingheng1), 1.4%

PCE (Xingheng1), 1.2%

PCE (Xingheng1), 1.37%

PCE (Xingheng1), 1.56%

PCE (Xingheng1), 1.5% Air entraining admixture, 0.02%

PCE (Xingheng1), 1.0%

PCE (Xingheng1), 1.2%

Water reducer of Mingtai,1.1%

PCE (Xingheng1), 1.17%

Chemical admixture

275/790

285/845

280/840

285/800

260/720

265/705

275/760

280/825

270/800

270/825

T /K (mm/mm)

4.4

10.4

10.6

8.9

8.4

11.3

4.4

3.8

3.6

–

Td (s)

28.4

31.4

27.0

31.0

33.0

30.8

19.7

20.4

19.2

21.9

Compressive strength at 7d (MPa)

7.4 Mix Design of Superfluid SCC with MS 371

372

7 Rock-Filled Concrete with Manufactured Sand

Fig. 7.17 Slump of fresh concrete with regard to Mix 1-14

(2) The change of fly ash content The influence of fly ash content (55, 60, and 65%) on both the workability performance and compressive strength of C30 SFSCC was studied (Table 7.12). With regard to mixes 1-14-B, 1-18, and 1-19, it can be seen that as the content of fly ash increases, the fluidity of concrete increases as well. Comparing Mix 1-18 with Mix 1-19, the result shows that the fresh concrete has a slight segregation when the content of fly ash increases by 5% and the content of water reducer keeps constant (Table 7.13). It can be seen from the above that fly ash has great influence on the early strength of concrete. At a given age, the compressive strength tends to decrease with the increase of fly ash content. The results show that the addition of fly ash is unfavorable to the early strength of C30 SFSCC. (3) The change of the total amount of cementitious materials The effects of different amounts of cementitious materials (475, 500, and 525 kg/m3 ) on workability and compressive strength of C30 SFSCC were studied (Fig. 7.19; Table 7.14). Comparing the above three mixes, it is interesting to note that the encapsulation of fresh concrete for Mix 1-21 is not the better one, that is to say, some stones are exposed on the surface, and the paste is lightly sticky. The influence of the total amount of cementitious materials is carried out on the workability of concrete, and it can be seen that the increase of the total amount of cementitious materials is beneficial to the fluidity and flow rate of fresh concrete and can reduce the number of chemical admixtures (Table 7.15). The result shows that the impact of the total amount of cementitious material on the compressive strength after 3d and 7d is not obvious with Mix 1-20 and Mix 1-21. When the total amount of cementitious material increases from 475 to 525 kg/m3 ,

Cementitious material

500

Number

1-14

500

Cement 55

Fly ash (%)

Table 7.9 Initial basic mix proportion after adjustment (kg/m3 )

981

Sand 654

Stone 0.33

W /B 60

The percentage of fine aggregate in aggregates (%)

165

Water

0.857

Water reducer (%)

7.4 Mix Design of Superfluid SCC with MS 373

374

7 Rock-Filled Concrete with Manufactured Sand

Fig. 7.18 Fresh concrete of Mix 1-15

the 28d compressive strength of concrete increases at first and then decreases. Meanwhile, when the total amount of cementitious material is 475 kg/m3 , the 28d and 60d compressive strengths are higher than that with 525 kg/m3 . (4) The change of the percentage of fine aggregate in aggregates The influence of different percentage of fine aggregate in aggregates (50, 55, and 60%) on workability and compressive strength of C30 SFSCC was studied (Fig. 7.20; Table 7.16). It can be seen that the percentage of fine aggregate in aggregates has a great influence on the workability of SFSCC. On the premise of keeping the content of water reducer and other parameters constant, when the percentage of fine aggregate in aggregates is 50%, the fresh concrete is lightly sticky, and the slurry and wrapping between the aggregates are insufficient and weak. When the percentage of fine aggregate in aggregates is increased to 60%, the viscosity of concrete decreases obviously, which facilitates the status of concrete. To sum up, the percentage of fine aggregate in aggregates is an important parameter affecting the fluidity and encapsulation of C30 SFSCC (Table 7.17). The result shows that with the decrease of percentage of fine aggregate in aggregates, the 3d and 7d compressive strength of C30 SFSCC firstly increase and then decrease. However, the compressive strength after 28d curing showed a trend, which firstly decrease and then increase, and the 60d compressive strength curing keeps increasing gradually. (5) The change of water-cementitious material ratio The effects of different water-cementitious material ratio (0.30, 0.33, and 0.36) on the workability and compressive strength of C30 SFSCC were studied (Fig. 7.21; Table 7.18). The result shows that when the water-cementitious material ratio is reduced to 0.3, the fresh concrete is very sticky with many bubbles. After standing for a period,

65

65

55

55

500

500

500

500

500

1-4

1-5

1-15

1-16

1-17

55

55

500

1-14-A

Fly ash (%)

Cementitious material (kg/m3 )

Number

60

60

60

61

60

60

The percentage of fine aggregate in aggregates (%)

0.33

0.33

0.33

0.346

0.346

0.33

W /B

275/790

T /K (mm/mm)

PCE (Xingfeng1) and retarder (Xingheng) 0.951%

PCE (Xingheng1), 0.7%

PCE (Xingfeng1) and retarder (Xingheng), 0.857%

280/765

275/770

280/730

PCE (Xingheng1) and 280/850 retarder (Mingtai),1.5%

PCE (Xingheng1) and 270/800 retarder (Mingtai), 1.1%

PCE (Xingheng1), 0.857%

Chemical admixture

Table 7.10 Influence of different types of water reducer on the workability of concrete

9.2

4.7

7.9

–

3.6

4.4

Td (s)

High viscosity

In good order

High viscosity

High viscosity and severe segregation

High viscosity and severe segregation

In good order

State

7.4 Mix Design of Superfluid SCC with MS 375

65

500

500

500

500

1-4

1-15

1-6

1-17

55

55

55

PCE (Xingheng1), 0.857%

60

60

60

60

275/790

0.33

0.33

0.33

275/770

PCE (Xingheng1) and 280/765 retarder (Xingheng), 0.951%

PCE (Xingheng2), 0.7%

PCE (Xingheng1) and 280/730 retarder (Xingheng), 0.857%

9.2

4.7

7.9

3.6

4.4

31.7

26.7

28.6

19.2

28.4

T /K (mm/mm) Td (s) Compressive strength at 7d (MPa)

0.346 PCE (Xingheng1) and 270/800 retarder (Mingtai), 1.1%

0.33

55

500

1-14-A 60

Chemical admixture

Number Cementitious material Fly ash (%) The percentage of fine W /B (kg/m3 ) aggregate in aggregates (%)

Table 7.11 Influence of different types of water reducer on the compressive strength of concrete

376 7 Rock-Filled Concrete with Manufactured Sand

7.4 Mix Design of Superfluid SCC with MS

377

Table 7.12 Influence of different fly ash content on the working performance of concrete Number

Cementitious material (kg/m3 )

Fly ash (%)

The W /B percentage of fine aggregate in aggregates (%)

T /K (mm/mm)

Td (s)

State

1-14-B

500

55

60

0.33

270/705

2.9

In good order

1-18

500

60

60

0.33

275/765

3.1

In good order

1-19

500

65

60

0.33

280/730

3.4

Slight segregation

Table 7.13 Influence of different fly ash content on the compressive strength of concrete Number

Fly ash (%)

T /K (mm/mm)

Td (s)

Compressive strength (MPa) 3d

7d

28d

60d

1-14-B

55

270/705

2.9

22.0

28.4

49.7

48.6

1-18

60

275/765

3.1

15.3

23.4

39.5

39.7

1-19

65

280/730

3.4

13.2

21.3

37.5

43.1

Fig. 7.19 Slump of fresh concrete of Mix 1-21

the fresh concrete hardened immediately and presented floating slurry on the surface. When the water-cementitious material ratio increases to 0.36, the consistency of fresh concrete reduces distinctly and the inverted slump flow time is only 1.8 s, resulting in the weak wrapping for some stones. All in all, the water-cementitious material ratio of C30 SFSCC should be controlled reasonably according to both workability and compressive strength (Table 7.19).

378

7 Rock-Filled Concrete with Manufactured Sand

Table 7.14 Effects of different cementitious materials on the workability performance of concrete Number

Cementitious material (kg/m3 ) (%)

Fly ash (%)

The W /B percentage of fine aggregate in aggregates (%)

T /K (mm/mm)

Td (s)

State

1-14-B

500

55

60

0.33

270/705

2.9

Good

1-20

525

55

60

0.33

275/710

1.7

Good

1-21

475

55

60

0.33

270/725

2.4

Slight segregation

Table 7.15 Influence of different cementitious materials on the compressive strength of concrete Number

Cementitious material (kg/m3 )

T /K (mm/mm)

Td (s)

3d

7d

28d

60d

1-14-B

500

270/705

2.9

22.0

28.4

49.7

48.6

1-20

525

275/710

1.7

16.6

25.7

39.5

42.5

1-21

475

270/725

2.4

16.7

26.7

44.2

44.2

Compressive strength (MPa)

Fig. 7.20 Fresh concrete of Mix 1-23

The results have shown that the influence of water-cementitious material ratio on the strength of concrete was outstanding. When the water-cementitious material ratio is reduced to 0.3, the compressive strength of concrete after 7d curing reaches to 30.1 MPa, which fully meets the design requirements. The 3d and 7d compressive strengths of concrete are reduced by about 3 MPa with water-cementitious material ratio of 0.36 comparing to Mix 1-14, and they are reduced to 41.6 MPa and 42.7 MPa at 28d and 60d, respectively. The results fully meet the design requirements.

7.4 Mix Design of Superfluid SCC with MS

379

Table 7.16 Influence of different percentage of fine aggregate in aggregates on the workability of concrete Number

Cementitious material (kg/m3 )

Fly ash (%)

The W /B percentage of fine aggregate in aggregates (%)

T /K (mm/mm)

Td (s)

State

1-14-B

500

55

60

0.33

270/705

2.9

Good

1-22

500

55

55

0.33

285/790

2.1

Poor cohesiveness

1-23

500

55

50

0.33

280/715

3.0

Sticky and slight segregation

Table 7.17 Influence of different percentage of fine aggregate in aggregates on the compressive strength of concrete Number The percentage of fine aggregate T /K (mm/mm) Td (s) Compressive strength in aggregates (%) (MPa) 3d

7d

28d

60d

1-14-B

60

270/705

2.9

22.0 28.4 49.7 48.6

1-22

55

285/790

2.1

23.3 28.9 46.3 49.3

1-23

50

280/715

3.0

22.6 25.2 47.5 51.7

Fig. 7.21 Slump of fresh concrete for Mix 1-25

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7 Rock-Filled Concrete with Manufactured Sand

Table 7.18 Influence of different water-cementitious material ratio on the workability of concrete Number

Cementitious material (kg/m3 )

Fly ash (%)

The W /B percentage of fine aggregate in aggregates (%)

T /K (mm/mm)

Td (s)

State

1-14-B

500

55

60

0.33

270/705

2.9

In good order

1-24

500

55

60

0.36

270/745

1.8

Low viscosity

1-25

500

55

60

0.30

280/785

3.2

A lot of bubbles and slight segregation

Table 7.19 Influence of different water-cementitious material ratio on the compressive strength of concrete Number Water-cementitious material ratio T /K (mm/mm) Td (s) Compressive strength (MPa) 3d

7d

28d

60d

1-14-B

0.33

270/705

2.9

22.0 28.4 49.7 48.6

1-24

0.36

270/745

1.8

19.0 25.5 41.6 42.7

1-25

0.30

280/785

3.2

24.9 30.1 53.4 55.7

(6) The change of raw material (1) Washed sand and small gravel (5–16 mm) The effects of washed sand and 5–16 mm small gravel on the workability and compressive strength of C30 SFSCC were studied. The test results are given in Tables 7.20 and 7.21. It can be seen that when the particle size of small gravel increases ranging from 5–10 to 5–16 mm, the status of concrete mixture becomes poor, which presents poor cohesion and so on. Table 7.20 Effects of small gravel with different particle size on the workability of concrete Number

Fly ash (%)

The particle size of small gravel (mm)

T /K (mm/mm)

Td (s)

State

1-14-B

55

5–10

270/705

2.9

In good order

1-26

55

5–16

280/775

3.2

Poor cohesiveness

1-27

60

5–16

275/740

2.7

Poor cohesiveness

1-28

65

5–16

280/715

3.7

Poor cohesiveness

7.4 Mix Design of Superfluid SCC with MS

381

Table 7.21 Effects of small gravel with different particle size on the compressive strength of concrete Number The particle size of small gravel T /K (mm/mm) Td (s) Compressive strength (mm) (MPa) 3d

7d

28d

60d

1-14-B

5–10

270/705

2.9

22.0 28.4 49.7 48.6

1-26

5–16

280/775

3.2

18.4 27.4 45.6 50.2

1-27

5–16

275/740

2.7

20.6 27.3 44.3 49.2

1-28

5–16

280/715

3.7 s

15.7 22.6 40.6 50.1

It can be seen that when the particle size of small gravel increases ranging from 5–10 to 5–16 mm, compressive strengths of concrete after 3d, 7d, and 28d curing all decrease with the increase of fly ash content among mixes of 1-26, 1-27, and 1-28. In addition, the 60d compressive strength of concrete firstly decreases and then increases. When the particle size of small gravel increases ranging from 5–10 to 5–16 mm, the workability of concrete decreases, and the 3d, 7d, and 28d compressive strengths also decrease. (2) Unwashed sand and small gravel (5–16 mm) Unwashed sand and 5–16 mm small gravel are used to study the effect of C30 SFSCC on the workability and compressive strength. The results are given in Tables 7.22 and 7.23 (Fig. 7.22). The results show that the overall slump flow time of fresh concrete with unwashed sand increases, the flow rate is slow, and the viscosity is relatively higher. Meanwhile, the workability of concrete is facilitated by increasing the amount of cementitious material. It can be seen from the above table that the compressive strength of concrete with unwashed sand is lower than that of Mix 1-14 at different ages. Meanwhile, when the cementitious material increases by 30 kg/m3 comparing Mix 1-32 and Mix 1-33, the compressive strength of concrete decreases after 3d and 7d curing, but increases after 28d and 60d curing. In order to develop the optimal mix proportion, the compressive strength should be appropriate to ensure good workability. In terms of experimental results, the compressive strength of most concrete after 28d curing is above 40 MPa, and the surplus is relatively large. Therefore, the mix ratio can be adjusted through the following aspects: (1) increase fly ash content, (2) increase water-cementitious material ratio, and (3) reduce the amount of cementitious material (Table 7.24). Compared with Mix 1-14, the fresh concrete presents slightly bleeding for Mix 1-19 increasing to 65% of fly ash content, which should be adjusted via reducing a certain amount of water reducer. The fresh concrete with the water-cementitious material ratio of 0.36 becomes very light, and a small part of the large stones has not

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7 Rock-Filled Concrete with Manufactured Sand

Table 7.22 Influence of different raw materials on the workability of concrete Number

Cementitious material (kg/m3 )

Fly ash (%)

The percentage of fine aggregate in aggregates (%)

W /B

T /K (mm/mm)

Td (s)

State

1-14-B

500

55

60

0.330

270/705

2.9

In good order

1-29

500

60

58

0.330

–

–

High viscosity and slight segregation

1-30

475

60

56

0.337

270/730

5.6

Poor cohesiveness and high viscosity

1-31

470

60

54

0.347

–

–

Poor cohesiveness and high viscosity

1-32

470

60

56

0.351

275/730

5.6

Poor cohesiveness and high viscosity

1-33

500

60

56

0.330

270/765

3.6

Good cohesiveness

been wrapped well, which should be adjusted by increasing the percentage of fine aggregate in aggregates by 2% (Table 7.25). From the above, the 28d and 60d compressive strengths of Mix 1-19 are 37.5 MPa and 43.1 MPa, respectively, when increasing fly ash content to 65%, which meets the requirements of design.

7.5 Properties of RFC with MS 7.5.1 Mechanical Properties The mechanical property of RFC members with MS includes compressive strength and bending strength. (1) Compressive strength of RFC members with MS The 28d compressive strength of C20 RFC members with MS after standard curing and core drilling sampling was tested, respectively, which are shown as follows:

500

1-33

60

60

60

475

470

1-30

1-32

55 55

500

500

1-14-B

Fly ash (%)

1-26

Cementitious material (kg/m3 )

Number

56

56

56

61

60

The percentage of fine aggregate in aggregates (%)

Table 7.23 Influence of different raw materials on the compressive strength of concrete

0.33

0.35

0.34

0.33

0.33

W /B

270/765

275/730

270/730

280/775

270/705

T /K (mm/mm)

3.6

5.6

5.6

3.2

2.9

Td (s)

19.3

20.6

–

18.4

22.0

3d

22.0

24.0

26.2

27.4

28.4

7d

45

39.7

–

45.6

49.7

28d

55.9

44.8

–

50.2

48.6

60d

Compressive strength (MPa)

7.5 Properties of RFC with MS 383

384

7 Rock-Filled Concrete with Manufactured Sand

Fig. 7.22 Slump of fresh concrete for Mix 1-32

Table 7.24 Workability comparison between basic mix proportion and optimized mix proportion Number

Cementitious material (kg/m3 )

Fly ash (%)

The W /B percentage of fine aggregate in aggregates (%)

T /K (mm/mm)

Td (s)

State

1-14-B

500

55

60

0.33

270/705

2.9

In good order

1-19

500

65

60

0.33

280/730

3.4

Slight segregation

1-24

500

55

60

0.36

270/745

1.8

Low viscosity

Table 7.25 Compressive strength comparison between basic mix proportion and optimized mix proportion Number

Fly ash (%)

Water-cementitious material ratio

T /K (mm/mm)

Td (s)

1-14-B

55

0.33

1-19

65

1-24

55

Compressive strength (MPa) 3d

7d

28d

60d

270/705

2.9

22.0

28.4

49.7

48.6

0.33

280/730

3.4

13.2

21.3

37.5

43.1

0.36

270/745

1.8

19.0

25.5

41.6

42.7

a. The compressive strength of RFC members with MS is 27.1 MPa, which fully meets the design requirement. b. The 28d and 90d compressive strengths of concrete specimens are 28.9 MPa and 34.2 MPa, respectively, which exceeds the design requirement.

7.5 Properties of RFC with MS

385

(2) Bending strength of RFC members with MS The bending strength of RFC members with MS was 3.13 MPa, which fully meets the design requirements.

7.5.2 Durability Performance The changes of external environment medium, temperature, and humidity generate the influence on concrete since pouring, setting, and hardening to a certain extent. Although the strength of concrete increases with the continuous hydration of internal unhydrated cement particles, the performance of concrete is able to be weakened due to various environmental factors. Concrete can be eroded by acid, alkali, salt, and other media and damaged by CO2 , SO3 , NOx , and other harmful media in the air during the service process. The concrete is damaged by freeze–thaw attributing to the internal moisture and washed by freshwater for a long time even resulting in dissolution and erosion. Moreover, the internal alkali-aggregate reaction is also able to occur resulting in structural damage and very serious economic losses when the design and raw material selection are not considered carefully. There are many factors causing the deterioration of concrete durability, such as poor impermeability of concrete, freeze–thaw cycle damage of concrete, chemical erosion, carbonation, freshwater erosion, alkali-aggregate reaction, and so on. Therefore, the durability of concrete in the process of design, construction, and curing should be paid attention to.

7.5.3 Drying Shrinkage Behavior of RFC with MS Drying shrinkage is defined as the shrinkage of concrete in the unsaturated air which decreases the internal pores and the adsorption water of gel pores. The influencing factors of drying shrinkage are composed of the cement composition, cement content, water-cementitious material ratio, hydration degree, aggregate variety and dosage, chemical admixture, mineral addition, specimen size, environmental humidity and temperature, etc. With the decrease of water-cementitious material ratio, the porosity of cement paste decreased obviously mitigating the shrinkage of cement mortar in various dry environments. The drying shrinkage of concrete increased with the increase of slag powder content. When the relative humidity of environment decreases, the drying shrinkage of cement mortar also increases with the gradual reduction of growth rate, which is similar to that under certain humidity conditions. The results show that the drying shrinkage of cement mortar generates different effects on the drying shrinkage of concrete depending on various ambient temperatures and types of superplasticizer. This series of experiment results further provides theoretical guidance for the engineering construction of low dry shrinkage concrete

386

7 Rock-Filled Concrete with Manufactured Sand

and mass concrete. In addition, the effect of fly ash on drying shrinkage has also been studied [34–36]. Due to the existence of rock block in RFC with MS, which generates inhibitory effect on concrete, the drying shrinkage deformation of RFC with MS needs to be further studied. At present, domestic researchers have done some research on the drying shrinkage of RFC with MS. In order to explore the relationships between RFC and SCC and the influence of aggregate content on dry shrinkage, Liu Hao and Jin Feng conducted expriments on C25 normal SCC, RFC, and RFC with aggregate content of 25%, 30%, and 35%, respectively. The experimental results show that (1) with regard to the same size of normal SCC and RFC, the dry shrinkage of RFC is less than that of ordinary SCC and gradually decreases with the increase of rock content; (2) the dry shrinkage of ordinary SCC gradually decreases with the increase of aggregate content; (3) with regard to ordinary SCC specimens with different sizes, the dry shrinkage decreases with the increase of size; (4) the formula of εRFC = εSCC (1 − V rock )0.72 could better reflect the dry shrinkage of RFC. According to the volume ratio of rock (εRFC ) and the self-compacting coefficient at any time, the formula of ε = ε (1 − V rock ) could reflect the dry shrinkage of RFC. The dry shrinkage ratio (εSCC ) of dense concrete could be deduced from the dry shrinkage ratio of ordinary RFC with different rock contents (V rock ) at any time.

7.5.4 Impermeability of RFC with MS In recent years, the durability of concrete has attracted the attention of many countries. For a long time, the research and design of concrete durability were based on the evaluation of concrete permeability. For the concrete with poor impermeability, water is able to cause erosion and freezing inside. The permeability of concrete refers to the penetrative, diffused, or migratory ability for gas, liquid, or ion under the action of pressure, chemical potential, or electric field [37–39]. The research methods on the permeability of concrete mainly include the water pressure method, the chloride ion penetration method, the air permeability method, and so on. The water pressure method was widely used due to being more simple and realistic [40]. At present, domestic researchers have done some research on the impermeability of RFC with MS. Liu et al. [36, 41] studied the impermeability of RFC and the relationship between the impermeability of RFC and SCC through three methods, which include concrete impermeability experiment (step-by-step pressure method), permeability coefficient experiment of full graded concrete and water pressure experiment, in order to establish the evaluation system of impermeability of RFC. The results show that (1) according to the impermeability test of concrete (step-by-step compression method), RFC and normal SCC have excellent impermeability under the same conditions, but the impermeability of RFC is lower than that of normal SCC; (2) through the permeability coefficient test of full graded concrete, the permeability coefficient of

7.5 Properties of RFC with MS

387

dense concrete and RFC was normal concrete > RFC > normal SCC, which prove excellent impermeability for normal concrete and ordinary SCC; (3) through indoor water pressure test, the conclusion is similar to that obtained via the permeability coefficient test of full graded concrete. In addition, it is found that there was a good correlation between the permeability coefficient of RFC and SCC, and the reliability of indoor water pressure test is also preliminarily verified. To sum up, the impermeability of normal concrete, ordinary SCC, and RFC is as follows: ordinary SCC > RFC > normal concrete. The reason can be attributed to the low permeability aggregate in concrete cutting off the continuity of capillary channel, while when the aggregate size is too large, the long cementation surface is able to be damaged, resulting in a negative impact on the impermeability.

7.5.5 Internal Temperature Rise of RFC with MS The influence of concrete hydration on cracking sensitivity of concrete structure has attracted a large amount of attention. A number of engineering practices showed that many small concrete structures crack due to internal temperature rise. The American Concrete Society believes that temperature control measures should be taken to prevent temperature cracks in mass concrete engineering [42]. RFC is a new type of mass concrete developed on the basis of SCC technology. The RFC with dense, sufficient strength, impermeability, and durability is obtained, which makes full use of the self-compacting performance of SCC to fill the gaps of rock block and reduce the internal temperature rise of concrete to the benefit of mitigating concrete cracking and so on. At present, domestic researchers have done some research on the internal temperature rise of RFC. Jinfeng and Li Le studied the adiabatic temperature rise performance of RFC by combining the physical test of adiabatic temperature rise of SCC with the numerical test of adiabatic temperature rise process of RFC and put forward a simple calculation method of adiabatic temperature rise of RFC [43]. For general RFC, the temperature non-uniformity caused by rock is ignored when the maximum particle size of rock grains was less than 100 cm. The simulation analysis of temperature and stress of RFC is carried out with homogenized RFC. At present, the RFC used in research and engineering applications mainly adopted the particle size range of 30–100 cm. In the analysis of conventional temperature problems, the non-uniform effect of rock on the temperature field at the early stage is ignored, and RFC is considered as a homogeneous material. The thermal properties of homogenized RFC are obtained by weight average according to the material properties of SCC and rock. According to the existing research results, the adiabatic temperature rise of RFC can be simply calculated through the heat balance equation based on the assumption that rock does not generate heat. Pan, et al. studied the adiabatic temperature rise law of SCC and RFC through the adiabatic temperature rise test and obtained the adiabatic temperature rise parameters of RFC based on the basis [44, 45]. Meanwhile, the temperature data of RFC are obtained via the field temperature monitoring test of

388

7 Rock-Filled Concrete with Manufactured Sand

RFC, which is beneficial to extract the thermal performance parameters of RFC including thermal conductivity, specific heat, adiabatic temperature rise, and surface heat dissipation coefficient. Compared with the results of indoor tests, the actual hydration temperature of RFC in the engineering field was obtained. Finally, the concrete gate dam project of shaping II hydropower station with backfill RFC was simulated in the construction period, overflow period, and operation period, and the results of temperature field and stress field were analyzed. The calculation results showed that RFC had good performance in mass concrete construction. Due to a small amount of cement used per cubic meter, the hydration temperature rise of concrete is effectively reduced, which avoids excessive tensile stress with regard to the concrete structure in the later stage, ensuring the safety of RFC structure. On the basis of Pan DingCai’s research, Liu Hao not only studied the adiabatic temperature rise law of both RFC with 42.3 and 49% stacking ratio and SCC according to the adiabatic temperature rise test of RFC and SCC, but also verified the accuracy of heat balance formula of RFC considering temperature characteristics and obtained the adiabatic temperature rise law of ordinary RFC (rock content of 55%) [36]. Meanwhile, the thermal expansion coefficient of rock, SCC, and RFC was measured through the thermal expansion coefficient test, and the simple formula between the linear expansion coefficient of RFC and the linear expansion coefficient of SCC and rock is obtained with the linear expansion coefficient of 55%. Xu, et al. simulated the pouring of mass concrete with normal concrete and RFC technology based on the same conditions and studied the calculation of hydration heat temperature field of mass concrete combined with a regular hexahedral project. The whole pouring process using ANSYS software was analyzed and calculated. Additionally, the program command flow in APDL language of ANSYS during the whole calculation and analysis process was confirmed [23]. Based on the same conditions, the temperature field results of C20 normal concrete and RFC are compared, and the RFC can more effectively control the hydration heat and reduce the maximum temperature inside the concrete. This research demonstrated the superiority of the new construction technology of RFC with respect to controlling hydration heat and cracks in mass concrete. In conclusion, compared with the normal concrete, the internal hydration heat of RFC is less with the large volume cracks controlled more effectively.

7.6 Engineering Application of RFC with MS 7.6.1 An Overview of the Bijie-Weining Express Project Bijie-Weining Expressway, as a key section of Tongren Xuanwei Expressway, is an important part of “eight vertical and eight horizontal” in Guizhou Expressway network planning. Bijie-Weining Expressway starts from Longtan at the intersection of Hangzhou Rui Expressway and Xiamen Chengdu Expressway in the south

7.6 Engineering Application of RFC with MS

389

of Bijie City, enters Houzhai and Baimaoyuan in Weining County, and ends at Zhoujiayuanzi in the north of Weining City connecting with Liupanshui Weining Expressway. The whole line (about 125.5 km) is constructed with the total investment of 8.644 billion yuan of the project. The technology of RFC with MS in the construction process of highway retaining wall with regard to the eighth contract section of Biwei Expressway is adopted. The design speed of the project is 80 km/h, the width of integral subgrade and separated subgrade is 21.5 m and 2 × 11.25 m, respectively, and the design vehicle load grade of bridge and culvert is based on Grade I. The project route is generally divided from east to west, with the general terrain high in the west and low in the east. The undulating terrain belongs to the complex terrain area, namely, ravines are vertical and horizontal, and the terrain cutting is fierce. The geomorphic units are divided into tectonic denudation and karst mountain geomorphic areas according to their genesis and morphology. The surface water is rich with regard to the project route area with a large number of mountain streams and valleys. Because of the steep terrain, the flow of the stream is obviously controlled by the rain, and the water level is high in the rainy season, which is contrary to the phenomenon in the dry season. There are three types of groundwater including pore water in the loose layer, karst water, and bedrock water, in which precipitation is the main recharge source. The lithology of stone along with the project route is mainly composed of limestone and dolomite with high rock strength and good quality. The main structures of subgrade are basically constructed with RFC, which becomes the difficulty of subgrade construction due to large amounts of engineering applications.

7.6.2 On-Site Construction of RFC with MS Based on the analysis of the construction materials in the project site, the C20 SFSCC with MS, which is suitable for project construction, is prepared combined with the research results of RFC. The specific construction process includes the installation of pouring body mold, the warehousing of rock, the production, and the pouring of C20 SFSCC with MS, followed by curing. The specific construction process is shown in Fig. 7.23. (1) Installation of mold The mold and supporting parts should be selected according to the engineering structure type, load size, foundation soil type, construction procedure, equipment, and material supply. The thickness of masonry walls or precast concrete block used as a template should be determined based on different pouring volumes or geometric section sizes, which generally are not less than 50 cm. The formed mold should be compact in structure without slurry leakage, which does not affect the uniformity and strength development of RFC with MS, and can ensure the correct and regular

390

7 Rock-Filled Concrete with Manufactured Sand

Fig. 7.23 Process flowchart

shape of the structure (molding geometric size). Meanwhile, the mold and associated supports should possess enough bearing capacity, rigidity, and stability to bear the lateral pressure of pouring SFSCC with MS and the load generated during the construction process as shown in Fig. 7.24. In addition, the supporting column of the mold in which the upper and lower mold are aligned should be placed on the solid ground (base) surface and have sufficient rigidity, strength, and stability with appropriate spacing, so as to prevent the support from sinking and causing the deformation of the mold. (2) Cleaning and warehousing of rock The appropriate rock which is directly put into the form by dump truck should be strictly selected to ensure the construction quality. In order to avoid mixing soil brought by the wheels, the washing platform should be set up on the warehousing road to wash the wheel. Even though there is no suitable warehousing road, the rock can also be stored by crane, cable car, manual, and other means as shown in Fig. 7.25. (3) Production and pouring of SFSCC with MS Before the production of SFSCC with MS, the mix proportion must be calculated and confirmed in strict accordance with the requirements. Compared with the production of normal concrete, the mixing time should be appropriately extended (10–20 s).

7.6 Engineering Application of RFC with MS

391

Fig. 7.24 Mold installation of RFC with MS

Fig. 7.25 Warehousing of RFC with MS

The moisture content of aggregate should be measured no less than 2 times during the production process. Based on the significant change in the moisture content, the measurement times should be increased, and the water consumption and aggregate consumption should be adjusted in time. It is interesting to note that the mix proportion should not be optionally changed. The position and size of the molds, support, and embedded parts must be checked before the pouring of the SFSCC with MS, which should be knocked outside the molds in order to prevent uneven pouring and surface bubbles and monitored. The concrete delivered to the site shall not be constructed when the slump flow was lower than the lower limit of the designed expansion. Reliable methods should be adopted to adjust the slump. The construction of RFC with MS should be forbidden in rain days. It is noted that the maximum free-falling height should be less than 2 m. With regard to the free-falling height more than 2 m, tumbling or other auxiliary measures should be taken to prevent too large drop of concrete into the molds. The point of placing that was full of concrete should move from low elevation to high elevation keeping one direction, and the moving distance should not exceed 3 m. Repeated placing at the pouring point should be avoided, as shown in Fig. 7.26. During placing,

392

7 Rock-Filled Concrete with Manufactured Sand

Fig. 7.26 Placing process of RFC with MS

the movement and deformation of molds and positioning devices shall be prevented. When pouring continuous concrete layer by layer, the upper layer of concrete should be poured before the initial setting of the next layer of concrete in order to integrate the upper and lower layers of concrete. In addition to reaching the designed top elevation of the structure, a large number of stone blocks should be placed 100– 300 mm higher than the surface of placing in order to strengthen the combination of layers. Concerning the RFC with MS, water roughing machines with 25–50 MPa high pressure should be used for the construction horizontal joint to meet the requirement of anti-seepage. In addition, surface treatment is also needed for the poured RFC with MS. (4) Curing of RFC with MS Curing is an important measure to prevent cracks in RFC with MS, which should be assigned to special personnel, and the curing scheme should be formulated no less than 14 days. The concrete should be cured in time after casting, and the curing time should be appropriately extended for the parts with special requirements. After placing, the RFC with MS should be covered, sprinkled, sprayed, or moisten with film, spray curing agent (liquid), and other curing measures. When the compressive strength of the concrete reached 2.5 MPa, if necessary the molds could be loosened in which the gap was about 3–5 mm. The sprinkler pipe was set up at the top for spray curing. After the molds were removed, the surface should be covered with sacks or straw curtains to avoid direct sunlight on the surface. The continuous water spraying curing time shall be determined according to the engineering environmental conditions, as shown in Fig. 7.27. During winter construction, the RFC with MS is forbidden to directly on the exposed part for water curing, and the thermal insulation material and plastic film shall be used for heat preservation and moisture conservation, which is determined by thermal calculation for the thickness of insulation material.

7.6 Engineering Application of RFC with MS

393

Fig. 7.27 Curing of RFC with MS

7.6.3 Evaluation of Fresh and Hardened Properties of On-Site RFC with MS To better understand the actual construction quality and performance of RFC with MS, the objective experiment data are selected as the corresponding basis and reference for the application of RFC with MS in Huizhen Expressway construction project.

7.6.3.1

Test on the Performance of SFSCC with MS

The test items of the mechanical properties of the SFSCC with MS are as follows: (1) Slump. (2) Slump flow. (3) Inverted slump cone flow time. Record the workability of each bin (plate) of SFSCC with MS and prepare the record form and testing tools before concrete production. The performance index of self-compacting in and out of the machine must meet the relevant standards.

394

7 Rock-Filled Concrete with Manufactured Sand

Table 7.26 Basic requirements for sampling and forming of SFSCC with MS Number Content

Requirements

1

Timing of concrete sampling The sampling shall be conducted from the opening to the closing of each concrete bin at an even interval. Only one group of concrete can be sampled from each concrete bin, and no less than six mixes of concrete can be sampled from each working shift

2

Molding requirements

Pour the concrete into the mold evenly and do not vibrate

3

Curing of specimens

After molding, the specimen shall be placed in the standard curing environment or shady place immediately, avoiding direct sunlight; after mold removal, the specimen shall be placed in the standard curing room for curing

4

Mold removal

Early damage to concrete should be avoided when the molds were removed, and it is not allowed to knock and break the mold by human

7.6.3.2

Compressive Strength Test of SFSCC with MS

In the production and pouring process of SFSCC with MS, standard cube specimens of 15 cm should be reserved in each bin according to the current “hydraulic concrete test specification” (DL/T5150). The compressive strength of SFSCC with MS at different ages (3d, 7d, 28d, 90d) and the same age as the compressive test of core samples is tested according to the relevant provisions of the standard. According to the compressive strength of 30 mixes of standard samples at 28d and 90d, the statistical analysis was carried out. According to “Standard for evaluation of concrete compressive strength” (GB/T 50107–2010), the standard deviation of strength in actual production was calculated to evaluate the strength grade of 28 and 90 days of SFSCC with MS. Concrete sampling and forming shall meet the requirements in Table 7.26.

7.6.3.3

Compactness Test of RFC with MS

The detection methods for the compactness of RFC with MS include the embedded rubber rod water injection method and the ultrasonic pile testing method. (1) Water injection with the embedded rubber rod Before the rock was put into the form, the rubber pulling rod of 100 mm diameter should be embedded in the pouring body and pulled out before the final setting of the SCC. The embedded depth and the number of embedded rubber rods should not be less than half of each pouring height and not be less than 3, respectively. For the structure with a small pouring size, the drilling spacing should be appropriately reduced, while the number of samples should be no less than 3.

7.7 Concluding Remarks

395

The pullout hole is filled with water, which is observed and recorded for the leakage of water, and the drop height of water level (mm) is recorded in 1 h, 2 h, 4 h, 8 h, and 24 h, respectively. In the process of testing, the borehole should be covered and sealed to prevent the evaporation of water affected by the external environment. When the drop height of water level in 24 h was less than 50 mm, the compactness of RFC with MS is good, which is beneficial to the density of RFC with MS. (2) Ultrasonic pile testing method As the ultrasonic pile testing method was used to test the concrete compactness, PVC pipe with a diameter of 10 mm should be embedded in the retaining wall formwork to form a hole as the acoustic pipe. In the process of rock block stacking and placing, the acoustic pipe should be embedded every 5 m to prevent bending deformation. For the structure with a small pouring size, the drilling spacing should be appropriately reduced. The ultrasonic pile testing method refers to “Technical Specification of Dynamic Pile Tests for Highway Engineering” (JTG/T F81-01).

7.6.3.4

Core Compressive Strength Test of RFC with MS

Once there is a dispute on the construction quality of RFC with MS and further inspection is needed, core drilling sampling can be conducted for compressive strength inspection of RFC with MS. The number of cores should not be less than 6. The compressive strength of core samples at 28d, 60d, or specified age is tested to obtain the average compressive strength, which should meet the design requirements.

7.7 Concluding Remarks In summary, the theoretical research, experimental research, and engineering application research of RFC with MS were systematically carried out to obtain theoretical and engineering research results based on the formulation of reasonable research technical scheme and route. The conclusions are as follows: (1) RFC with MS is a new type of concrete, which can be widely used in mass concrete, retaining walls and other concrete projects to solve the problems of rock accumulation degree and porosity control technology, preparation technology, construction technology, and maintenance technology of SFSCC with MS. (2) The rock should be chosen with dense structure, uniform texture, stable, and no cracks. Furthermore, its compressive strength should be no less than 30 MPa. In frozen and flooded areas, the frost resistance and erosion resistance should be enhanced, and large stones should be used as much as possible. The strength grade of concrete should be no less than C15, and the mortar grade for masonry retaining wall should be selected according to the type, position, and purpose

396

7 Rock-Filled Concrete with Manufactured Sand

of retaining wall. Therefore, the gravity retaining wall can fully meet the design and construction requirements. (3) According to the design requirements of retaining wall, the basic performance requirements of SFSCC with MS are put forward. The initial slump is 270 mm ± 20 mm, and the slump flow is more than 650 mm. The slump and the slump flow after 1 h are not less than 250 mm and 650 mm, respectively. The backflow expansion is not less than 500 mm, and the outflow time of the backflow slump is no more than 6 s. (4) The SFSCC with MS has ultra-low viscosity, high fluidity, and cohesiveness. By selecting raw materials and optimizing the mix proportion reasonably, the C20 and C30 SFSCC with MS meet the performance requirements of retaining wall. (5) The site tests showed that the surface of RFC with MS is smooth and defect free, the internal structure is dense, and the concrete fills the internal pores between rock grains, which is worthy of further promotion and application.

References 1. B. Wang, D. Zhou, Z. You, J. Wu, Z. Jiang, Study on perparation and properties of C20 superfluidity self-compacting concrete with manufactured sand. Ready-Mixed Concr. 4(4), 38–41 (2012) 2. L. Zou, D. Dong, Quality control of mass concrete. Concrete 7, 145–146 (2010) 3. F. Jin, M. Huang, X. An, H. Zhou, Engineering application of rock-fill concrete, in Proceedings of the International Symposium on Dam Technology and Long-Term Performance, 2011, pp. 275–279 4. L. Yin, Application status and development trend of rock-filled concrete. Water Resour. Hydropower Eng. 43(7), 1–4 (2012) 5. J. Mu, T. Hu, W. Zheng, J. Wu, Z. Jiang, Study on the properties and project application of rubble self-compacting concrete with manufacutured sand. China Sci. Technol. Exp. Concr. Technol. 4, 31–34 (2012) 6. J. Gao, Application of rock-filled concrete technology in railway and highway project of xinjiang. Concrete 2, 123–125 (2009) 7. S. Chen, F. Jin, H. Zhou, J. Wang, Feasibility study of underwater rock-filled concrete. J. Hydroelectr. Eng. 31(6), 214–217 (2012) 8. D. Zhang, G. Zhang, Y. Jing, S. Liu, The application of rock-fill concrete in weitan hydropower station. J. Libr. Inf. Sci. 20(33), 211–213 (2010) 9. F. Jin, X. An, J. Shi, C. Zhang, Study on rock-fill concrete dam. J. Hydraul. Eng. 36(11), 78–83 (2005) 10. J. Shi, Z. Zhang, F. Jin, X. An, C. Zhang, X. Yang, Z. Qin, Experiment on self-compacting concrete filling rock-fill. J. Univ. South China (Sci. Technol.) 19(1), 38–41 (2005) 11. X. An, F. Jin, J. Shi, Experimental study of self-compacting concrete filled prepacked rock. Concrete 1, 3–6 (2005) 12. J. Shi, S. Zhou, F. Jin, C. Zhang, Testing the self-compacting rock-fill concrete strength by the rebound method. Nondestruct. Test. 28(6), 285–287+295 (2006) 13. J. Shi, S. Zhou, Z. Zhang, F. Jin, C. Zhang, X. Yang, Z. Qin, Behavior of self-compacting rock-fill concrete beam under normal section stressing. J. Water Resour. Architect. Eng. 3(4), 3 (2005)

References

397

14. Z. Zhang, J. Shi, X. Yang, F. Jin, Experimental research on the tensile performance of the self-compacting rock-filled concrete. Concrete 10, 38–41 (2007) 15. Z. Zhang, Experimental Study of Mechanical Behavior of the Self-Compacting Rock-Fill Concrete and Numerical Simulation. University of South China 16. J. Shi, Z. Zhang, F. Jin, C. Zhang, Experimental research on mechanical behavior of selfcompacting rock-fill concrete. Chin. J. Rock Mechan. Eng. 26(S1), 3231–3236 (2007) 17. M. Huang, X. An, H. Zhou, Experimental study of application of rock-filled-concrete in beam structures. J. Shenyang Jianzhu Univ. (Nat. Sci.) 23(3), 353–357 (2007) 18. Y. Wu, Q. Liu, Application of C20 self-compacting concrete within rock-filled concrete. Concrete 3, 117–120 (2010) 19. H. Miansong, The Application of Discrete Element Method on Filling Performance Simulation of Self-Compacting Concrete in RFC (Tsinghua University, 2010) 20. X. Tang, C. Zhang, Simulation of meso-fracture for concrete based random aggregate model. J. Tsinghua Univ. (Sci. Technol.) 48(3), 5 (2008) 21. X. Tang, C. Zhang, Layering disposition and FE coordinate generation for random aggregate arrangements. J. Tsinghua Univ. (Sci. Technol.) 48(12), 2048–2052 (2008) 22. X. Tang, J. Shi, Z. Zhang, C. Zhang, Meso-scale simulation and experimental study on selfcompacted rock-fill concrete. J. Hydraul. Eng. 7, 844–849 (2009) 23. J.J. Xu, Xiping, Rock-filled concrete in the mass concrete temperature field analysis. Concrete 7, 33–36 (2013) 24. Q. Shen, X. An, Y. Yu, Rock-filled quality evaluation based on visual information. J. Tsinghua Univ. (Sci. Technol.) 1, 48–52 (2013) 25. Q. Shen, Study on the Processing Method and Application of Visual Information in Rock-Filled Concrete Construction Management (Tsinghua University, 2011) 26. A. Wettimuny, A. Penumadu, Application of fourier analysis to digital imaging for particle shape analysis. J. Comput. Civil Eng. 18(1), 2–9 (2004) 27. C. Du, L. Sun, Numerical simulation of aggregate shapes of two-dimensional concrete and its application. J. Aerosp. Eng. 20(3), 172–178 (2007) 28. Z. Gong, Multi-Scale Numerical Simulation Research of Concrete Based on Random Aggregate (Zhejiang University, 2013) 29. J. Zhang, N. Jin, X. Jin, J. Zheng, Numerical simulation method for polygonal aggregate distribution in concrete. J. Zhejiang Univ. (Eng. Sci.) 38(5), 581–585 (2004) 30. Z. Gao, G. Liu, Two-dimensional random aggregate structure for concrete. J. Tsinghua Univ. (Sci. Technol.) 43(5), 710–714 (2003) 31. Q. Gao, Z. Guan, Y. Gu, Y. Yin, Automatic generation of finite element model for concrete aggregate. J. Dalian Univ. Tech. 46(5), 641–646 (2006) 32. L. Sun, C. Du, C. Dai, Numerical simulation of random aggregate model for mass concrete. J. Hohai Univ. (Nat. Sci.) 33(3), 291–295 (2005) 33. D. Zhou, Z. Jiang, Z. Yuan, K. Yang, J. Mu, T. Hu, D. Ren, Study on the stacking process of extra-huge aggregates by two-dimensional computer simulation. J. Build. Mater. 04, 567–571 (2013) 34. Z. Liang, D. Sun, A. Wang, F. Wang, M. Deng, J. Sun, Influence of water/binder ratio on drying shrinkage, compressive strength and pore structure of composite cement paste. J. Anhui Jianzhu Univ. 3(3), 22–24 (2012) 35. H. Wu, Effects of mineral admixtures on drying shrinkage properties of concrete. Sci. Technol. Innov. 25, 328+275+330 (2009) 36. J. Weng, Drying Shrinkage and Autogenous Shrinkage Experimental Research of High Performance Concrete (Fuzhou University, 2006) 37. X. He, Q. Shi, Y. Liu, Influence factors and improvement methods of permeability of concrete. Sci. Technol. Eng. 7(20), 5430–5433 (2007) 38. J. Fan, Evaluation Method of Permeability of Concrete (Harbin Institute of Technology, 2006) 39. F. Cao, B. Ma, Y. Li, G. Rao, X. Zhang, The analysis on the concrete permeability and test methods. Concrete 10, 3 (2002)

398

7 Rock-Filled Concrete with Manufactured Sand

40. Q. Yang, B. Zhu, Testing methods on the permeability and influence factors of permeability of concrete. Low Temperature Archit. Technol 5, 7–10 (2003) 41. M. Huang, H. Zhou, X. An, F. Jin, A pilot study on integrated properties of rock-filled concrete. J. Build. Mater. 11(2), 206–211 (2008) 42. J. Wang, P. Yan, J. Han, Experiment analysis of concrete adiabatic temperature rise. J. Build. Mater. 8(4), 446–451 (2005) 43. F. Jin, L. Li, Z. Hu, X. An, Preliminary study on temperature rise property of thermal insulation of rock-fill concrete 39(5), 59–63 (2008) 44. D. Pan, Rock-fill concrete experiments on thermal properties and studies on thermal stress (2009) 45. G. Zhang, D. Pan, Q. Liu, Testing study on internal temperature of massive rock-filled concrete. Build. Sci. 9, 34–37 (2009)

Chapter 8

Special High-Performance Concrete with Manufactured Sand

8.1 Anti-Disturbance Concrete with MS Ordinary concrete forms lots of microcracks in the early stage of setting and hardening due to external disturbance, such as vehicle-bridge coupling vibration caused by the high speed of heavy vehicles [1, 2]. Anti-disturbing concrete is able to resist the damage caused by vehicle-bridge coupling vibration, thereby ensuring the quality of placing concrete under continuous traffic loads. In the field of civil engineering, vibration is generally considered as sinusoidal harmonic vibration. The characterization method of vibration intensity is very important due to the different influence of traffic-induced load on the performance of newly placing concrete. The maximum particle vibration velocity is used to characterize the vibration intensity by some researchers, which is proportional to the stress generated by the stress wave propagating inside the material. According to Dowding’s study [3], the stress level of the concrete stress field in a vibration environment could be estimated through vibration velocity. The maximum particle vibration velocity could better reflect the structure damage compared with the maximum amplitude, acceleration, and other parameters [4]. The results showed that the vibration caused by traffic load did not cause the segregation, bond strength decrease, slow strength development, and crack formation of newly placing concrete with good mix proportion by means of laboratory research, engineering field experience, and questionnaire survey. Maintaining the smoothness of bridge deck, especially expansion joint, was the most effective measure to reduce vehicle vibration amplitude. Based on the results of Furr and Fouad, Harsh and Darwin [4] selected a sinusoidal vibration with a frequency of 4 Hz and an amplitude of 0.5 mm as the simulated vibration source. In addition, vibration with amplitude of 13 mm and frequency of 0.5 Hz was applied every four minutes to characterize the vibration response of heavy vehicles passing the bridge which corresponds to a maximum acceleration of 35 mm/s2 and a maximum velocity of 36 mm/s continuing to vibrate for 30 h from the completion of concrete placing. They studied the influence of the thickness of concrete overlay, the diameter of steel bar, and the concrete slump on © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Z. Jiang, Green High-Performance Concrete with Manufactured Sand, https://doi.org/10.1007/978-981-19-6313-1_8

399

400

8 Special High-Performance Concrete with Manufactured Sand

the bond strength and compressive strength of reinforced concrete under vibration environment. The results showed that the vibration increased the bond strength and compressive strength of reinforced concrete when the concrete slump is smaller than 114 mm. The bond and compressive strengths decreased by 3.7% and 8% respectively when the slump is larger than 191 mm.The result testified that the influence of vibration on concrete performance might be controlled by the concrete slump. Large slump concrete tended easily to bleed during vibration resulting in the decreasing of surface strength, which was attributed to the increasing of water to binder ratio on the concrete surface. What is more, the strength of the concrete depended on the strength of the weak position. For the concrete with smaller slump, vibration was beneficial to the concrete compaction and the development of strength. The concrete slump should be controlled within 100 mm in order to avoid the influence of traffic load-induced vibration on concrete performance. The maximum vibration velocity of 25.777 mm/s was measured in situ at the joint of arch bridge apex and deck by Muller-Rochholz and Weber [5] when two trucks with the weight of 10 and 3.45 t passed through a rigid-framed arch bridge with a span of 104 m at a speed of 80 km/h. Therefore, the simulated vibration with a frequency of 6–2 Hz and a maximum vibration velocity of 25 mm/s was adopted to study the influence of vibration on newly placing concrete with the water to binder ratio of 0.45. The vibration time was 30 h from the beginning of concrete molding without the concrete slump and other relevant parameters. The results showed that this vibration intensity had no effect on the compressive strength of lightweight aggregate concrete, which was inferred that well-designed lightweight aggregate concrete could resist the vibration with the speed of 50 mm/s and frequency of 12 Hz. Dunham [6] studied the influence of induced vibration on early age concrete performance. Results showed that the compressive strength of concrete subjecting to vibration for 7 and 28 days was slightly higher than those of common concrete under different amplitude and vibration time. However, the splitting tensile strength of 28d was slightly lower compared with normal curing concrete, and the lowest average was only 7% lower than the control group. Dunham pointed out that the vibration compaction did not affect the compressive strength of concrete and had a slight negative effect on the tensile capacity with lower 8%. Wei [7] studied the influence of different vibration conditions (combination of different vibration frequency and amplitude, and different vibration starting time) on the splitting tensile strength of concrete. The simulated vibration conditions were 4 Hz + 3 mm, 1 Hz + 5 mm, 1 Hz + 3 mm, and 4 Hz + 5 mm with different vibration starting time of 1, 2.5, 3.5, 4.5, 6, and 8 h after concrete molding lasting for 30 min. The experimental results showed that vibration was beneficial to improve the splitting tensile strength of concrete. However, the vibration of large amplitude (> 5 mm) caused a certain damage to the concrete performance. It was important to note that vibration damping measures should be taken.

8.1 Anti-Disturbance Concrete with MS

401

Bu [8] studied the influence of long-term low-frequency vibration on the compressive strength and compactness of concrete with the vibration conditions including 1 min vibration every 5 min lasting for 16 h, frequency of 20 Hz, and amplitude of 0.3, 0.5, 1.0, and 2.0 mm, respectively. The results of 28 days showed that longterm vibration which was beneficial to improve the delamination phenomenon in the process of concrete setting could enhance the compressive strength and compactness of concrete as well as the bonding strength of steel bar. Meanwhile, long-term vibration could destroy the film formed by hydration and make cement surface always expose to water, which was beneficial to the hydration of cement. In addition, Ansell and Silfwerbrand [9] presented some research results and investigation examples on the vibration resistance of the early age concrete. Furr and Fouad [10] studied the effect of vibration on newly placing concrete during bridge deck widening, which observed nearly 30 cases of bridge widening engineering without any apparent problems where adjacent lanes remained open to traffic. Cusson and Repette [11] indicated that severe cross-break occurred for several days after the concrete was placed, which might be attributed to temperature gradient stress, shrinkage, and vibration. Two different kinds of vibration, which included the adjacent lane passing through heavy construction tools and vibration during bridge repair keeping adjacent lane open to traffic, caused greater stress to the concrete. After collating a large number of literature and experimental studies, Issa asserted that the bridge deck vibration caused by the adjacent lane opening to traffic did not damage the concrete with well mix proportion and small slump. Another important conclusion was that strict limits on the speed of heavy trucks during construction were beneficial to reduce the damage. Brandl and Gunzler mentioned that the vibration of 4–16 h after placing could cause very serious loss of bonding strength of both concrete and steel bar. The results showed that the concrete of 4–48 h after molding placed in the vibration environment (frequency of 9 Hz and the maximum speed of 20 mm/s) would lead to the loss of 50% bonding strength. In conclusion, some researchers believed that traffic load has little influence on newly placing concrete, while others hold the opposite view. This was attributed to the great difference in the simulated vibration parameters selected and the performance of the concrete used. The main problems include two parts as follows: (1) The influence of vibration caused by traffic load on the newly placing concrete was not consistent due to the differences on the vibration source, vibration starting time, vibration duration, and the concrete performance. This made people doubt whether the bridge deck maintenance and concrete placing could be carried out under open traffic conditions. (2) The influence of vibration caused by traffic load on concrete with different workability (or different types) was lack of systematic research. Most scholars did not pay attention to the workability of concrete in their studies due to the similar type of used concrete with dry rigidity or small slump, which limited the difference of concrete performance.

402

8 Special High-Performance Concrete with Manufactured Sand

Table 8.1 Mix proportion and workability of C50 reference concrete Group

W/B ratio

Sand ratio (%)

Cement (kg/m3 )

water-reducing admixture (%)

Slump (mm)

Slump flow (mm)

Reference concrete

0.35

44

500

0.75

220 ± 20

500 ± 50

8.1.1 Raw Materials and Test Methods 8.1.1.1

Raw Materials

The P. II 52.5 Portland cement was selected. The fine aggregate was river sand with fineness modulus of 2.2 belonging to grading zone III. The coarse aggregate consisted of two particle size ranges including the larger coarse aggregate (60%wt.) with size range of 9.5–19 mm and the smaller coarse aggregate (40%wt.) with size range of 4.75–9.5 mm. The polycarboxylate water-reducing admixture was used to optimize the workability. The C50 concrete was adopted as the reference concrete in the research process due to which it was mostly used in the highway bridge. The mix proportion and workability of C50 reference concrete without bleed or segregate were finally determined as given in Table 8.1.

8.1.1.2

Test Methods

(1) Testing for workability (slump and slump flow) and setting time and mechanical properties (compressive strength and flexural strength) of concrete are in accordance with the current Chinese standard GB/T 50080 and GB/T 50081, respectively. The concrete strength retention rate referred to the ratio of the strength value after simulating the vehicle-bridge coupling vibration environment to the strength value of concrete specimens under normal curing state at the same age. (2) Ultrasonic pulse velocity of concrete reflected the internal compactness, which was measured by CTS-25 non-metallic ultrasonic detector, as shown in Fig. 8.1. The ultrasonic pulse velocity was measured for the upper and lower parts of the concrete specimens due to segregation after vibration in order to obtain the average value, as shown in Fig. 8.2. (3) Mortar segregation cylinder (diameter of 150 mm) was used to measure the early segregation of concrete. After standing or vibrating for a certain time, the proportion of aggregate in the upper (height of 200 mm) and lower (height of 100 mm) of the segregation cylinder was measured to judge the segregation

8.1 Anti-Disturbance Concrete with MS

403

Fig. 8.1 Non-metallic ultrasonic detector

Fig. 8.2 Test method for upper (a) and lower (b) pulse velocity of specimen

degree. The S1 (aggregate segregation coefficient) and S2 (settlement coefficient between layers) were used to evaluate the concrete segregation according to S1 = m 2,s × 2/m 1,s S2 =

m 2,fs /m 2,es m 1,fs /m 1,es

(8.1) (8.2)

where m 1,s is the total mass of upper coarse aggregate, m 2,s is the total mass of lower coarse aggregate, m 1,fs is the mass of upper smaller coarse aggregate, m 2,fs is the mass of lower smaller coarse aggregate, m 1,es is the mass of upper larger coarse aggregate, and m 2,es is the mass of lower larger coarse aggregate.

404

8 Special High-Performance Concrete with Manufactured Sand

For concrete with ordinary aggregate, the S1 value is generally greater than 1. The closer S1 is to 1, the smaller the concrete segregation degree is. S2 is equal to 1 indicating that the upper and lower layers are absolutely uniform. S2 is greater than 1 indicating that the settlement rate of small aggregate is greater than that of large aggregate, which generally does not occur for concrete with ordinary aggregate. S2 is less than 1 indicating that the settlement rate of small aggregate is less than that of large aggregate. The smaller the S2 , the greater the external disturbance, which resulted in serious segregation of concrete. (4) The static elastic modulus was measured to characterize the deformation performance of concrete. Elastic modulus could reflect the relationship between stress and strain of concrete, which was one of the necessary parameters to calculate the deformation, crack, and temperature stress of mass concrete. The specific test method of static compression modulus of elasticity with the non-standard test model of 100 mm × 100 mm × 300 mm was carried out according to the current Chinese standard (GB/T 50081). (5) The durability of anti-disturbance concrete with MS was evaluated by carbonization resistance and chloride ion penetration resistance. The carbonation resistance of concrete was characterized by the carbonation degree of concrete specimen in a certain concentration of CO2 gas, which was measured according to the current Chinese standard (GB/T 50082) test method with the specimen size of 100 mm × 100 mm × 100 mm. The rapid chloride ion migration coefficient method was adopted according to the Chinese standard (GB/T 50082). (6) The stereo microscope of XTZ-03 produced by Hangzhou Quantum Testing Instrument Co., Ltd was selected to characterize the internal microstructure of concrete. X-ray diffractometer produced by Rigaku International Corporation was used to analyze the crystal phase and mineral composition of cement slurry. The pore size distribution and porosity of concrete were measured by mercury porosimeter of Quanta chrome AUTOSCAN-60. The concrete samples for mercury injection test were taken from the concrete interface between coarse aggregate and mortar at specific age. The hydration of samples was stopped by steeping with absolute alcohol for one week, and then samples were dried to constant weight with vacuum drying oven.

8.1.2 Results and Analysis According to the literature review and field research results [12–15], the basic vibration parameters were determined as follows: amplitude of 3.5 mm, frequency of 5 Hz, normal mode (vibration for 15 s, then stop for 45 s), and vibration time period of 18 h from the concrete molding. For a specific parameter research process, the research parameter was only changed; meanwhile, other vibration parameters kept constant.

8.1 Anti-Disturbance Concrete with MS

8.1.2.1

405

Factors Influencing the Anti-Disturbance Performance of Concrete with MS

(1) Vibration with different frequencies (a) Compressive strength The reference concrete for group 1-5 were normally placed after molding, while the other groups subjected to the simulated vehicle-bridge coupling vibration with different frequencies. The 1d, 7d, and 28d compressive strengths of each group were evaluated, as given in Table 8.2. Results from Table 8.2 show that vibration with different frequencies has no significant influence on the compressive strength of concrete due to low vibration frequency and small amplitude. In addition, the concrete for compressive test is prepared with small dimension of 100 × 100 × 100 mm generating a great restriction on concrete, which can mitigate the damage caused by low-frequency vibration. Vibration with different frequencies slightly improves the early strength of concrete due to the appropriate bleeding. Water evaporation reduces the water to binder ratio and the porosity of concrete, which is beneficial to improve the early strength. It can be seen that the compressive strength cannot clearly reflect the influence of simulated vehicle-bridge coupling vibration with different frequencies on concrete performance. (b) Flexural strength Concrete pavement and bridge deck are often directly subjected to repeated vehicle loads and the influence of temperature, humidity, and other environmental factors which lead to the high-quality requirements of concrete. The level of flexural strength as primary evaluation index is directly related to the service life of engineering [16–18]. The size and load of the simulated vibration testing machine are limited. The 7d flexural strength, which is generally used as one of the early control indexes of the pavement in practical engineering, is mainly determined in each group. The influence of vibration with different frequencies on the flexural strength of concrete is obvious, as given in Table 8.3. It can be seen that the flexural strength of concrete decreases obviously after vibration, which is 80–85% of the reference group. Moreover, the retention rate of flexural strength after vibration decreases as the vibration frequency increases. On the one hand, the flexural strength is sensitive to cracks, pores, and other defects of concrete. On the other hand, the mold of flexural strength test is the dimension of 100 mm × 100 mm × 515 mm. The restriction of compressive group with the dimension mold of 100 mm × 100 mm × 100 mm is relatively larger due to the small size of mold. Therefore, the internal and surface of the flexural testing concrete are greatly impacted by vibration, which is reflected by the decrease of flexural strength.

5

8

2-2

2-3

Vibration for 15 s, then stop for 45 s

18

25.6

28.5

28.3

27.4

100

111

110

107

56.8

60.4

58.0

60.6

7d

3.5

0

2

1-5

Retention rate

Compressive strength (MPa) 1d

Amplitude (mm)

Vibration mode Vibration time period (h)

Vibration parameter

Frequency (Hz)

2-1

Group

Table 8.2 Influence of vibration with different frequencies on compressive strength

93.7

99.7

95.7

100

Retention rate (%)

68.2

69.1

65.5

68.6

28d

99.4

101

95.5

100

Retention rate (%)

406 8 Special High-Performance Concrete with Manufactured Sand

8.1 Anti-Disturbance Concrete with MS

407

Table 8.3 Influence of vibration with different frequencies on flexural strength of concrete Group

Vibration parameter Frequency (Hz)

Amplitude (mm)

Vibration mode

Time period (h)

7-d flexural strength (MPa)

7-d retention rate of flexural strength (%)

1-5

0

3.5

8.69

100

2

7.43

85.4

2-2

5

Vibration for 15 s, then stop for 45 s

18

2-1

7.25

83.4

2-3

8

7.16

82.3

(c) Ultrasonic pulse velocity The ultrasonic pulse velocity testing results for the upper and lower parts of the concrete with different ages after simulated vehicle-bridge coupling vibration with different frequencies are given in Table 8.4 and shown in Fig. 8.3, respectively. The ultrasonic pulse velocity of concrete increases significantly as concrete age goes. The greater the pulse velocity, the higher the internal density of concrete is. The pulse velocity of concrete firstly increases and then decreases with the increase of vibration frequency, which indicate that excessive vibration frequency exceeding 2–5 Hz will damage the concrete structure. Table 8.4 Ultrasonic pulse velocity with different ages Group Frequency 1d velocity (m/s) 7d velocity (m/s) 28d velocity (m/s) (Hz) Upper Lower Average Upper Lower Average Upper Lower Average 1-5

0

4032

4010

4021

4608

4709

4659

4983

4902

4943

2-1

2

4255

4255

4255

4695

4739

4688

4985

4954

4970

2-2

5

4210

4292

4251

4444

4405

4571

4901

5102

5002

2-3

8

4008

4175

4092

4335

4620

4451

4773

5000

4887

5000 4800

Wave speed/(m/s)

Fig. 8.3 Influence of different vibration frequencies on the average ultrasonic pulse velocity

4600 0Hz 2Hz 5Hz 8Hz

4400 4200 4000 0

5

10

15

20

Age of the concrete

25

30

408

8 Special High-Performance Concrete with Manufactured Sand

(d) Early segregation For the determination of concrete segregation, the coarse and fine aggregate mass of the segregation cylinder in different parts were measured after 3 h of molding. The mass for the aggregates from different parts of the segregation cylinder was determined through washing with water and then drying. Results from Table 8.5 and Fig. 8.4 show the influence of vibration with different frequencies on the concrete segregation. The aggregate segregation coefficient S1 increases with the increase of vibration frequency indicating the influence of vibration on the early performance of concrete. Vibration intensifies aggregate subsidence and slurry floating, resulting in the intensification of concrete segregation. Meanwhile, the greater the frequency is, the greater the concrete segregation is. The difference of aggregate segregation coefficient is difficult to distinguish to fully reflect the influence of vibration on the concrete segregation due to which the diameter and height of the segregation cylinder are small. In addition, it is found that the setting and hardening speed of the upper concrete is slower than that of the lower concrete, especially in the case of vibration. The water to binder ratio of the lower concrete gets smaller hindering the downward movement of the upper aggregate (like the harsh concrete) and leading to a small difference of absolute value of aggregate segregation coefficient, which is attributed to the aggregate segregation and the free water in the lower part migrating up during the vibration process. The S 2 (settlement coefficient between layers) decreases with the increase of vibration frequency, which indicate that the proportion of fine aggregate in the lower concrete is small. The difference in settlement velocity between fine aggregate and coarse aggregate increases with the increase of vibration frequency. The greater the vibration frequency, the greater the disturbance of coarse aggregate than fine aggregate. Overall, the method for measuring the early segregation of concrete can reflect the influence of simulated vehicle-bridge coupling vibration on concrete performance to some extent. However, this method still needs to be further improved. (2) Vibration with different amplitude Amplitude, which is seen as an important parameter of vehicle-bridge coupling vibration, is affected by many external factors such as traffic load, traffic speed, and bridge deck roughness. Vehicle-bridge coupling vibration with different amplitudes has great influence on the concrete performance. This section focuses on studying the influence of three different amplitudes of 0.5, 3.5, and 7 mm on the performance of reference concrete. (a) Compressive strength The results for the influence of different amplitudes on the compressive strength are given in Table 8.6. It is interesting to note that the early strength of concrete increases with different vibration amplitude. Meanwhile, the early strength retention rate increases with the increase of the vibration amplitude. From the perspective of 28d strength, the influence effects on the compressive strength of concrete are not

Standing 3 h

3.5 mm, 2 Hz

3.5 mm, 5 Hz

3.5 mm, 8 Hz

1-5

2-1

2-2

2-3

Placement conditions and time

Group

588

609

599

630

1309

1330

1436

1219

1897

1939

2035

1849

1172

1187

1074

1084

2067

2198

2338

2288

Coarse aggregate

Upper concrete (200 mm)/g Fine aggregate

Coarse aggregate

Lower concrete (100 mm)/g

Fine aggregate

Total

Table 8.5 Influence of vibration with different frequencies on concrete segregation

3254

3272

3422

3460

Total

1.19

1.24

1.16

1.10

S1

0.80

0.85

0.94

0.88

S2

8.1 Anti-Disturbance Concrete with MS 409

Fig. 8.4 Influence of vibration with different frequencies on aggregate segregation coefficient and settlement coefficient between layers

8 Special High-Performance Concrete with Manufactured Sand 1.3

Aggregate segregation coefficient and settlement coefficient between layers

410

1.2 1.1 S1 S2

1.0 0.9 0.8 0

2

4

6

8

Vibration Frequency/Hz

consistent with regard to different vibration amplitudes. The compressive strength retention rate of concrete after vibration is less than 95% when the amplitude is less than 5 mm. However, the compressive strength retention rate is as high as 114% when the amplitude is 7 mm. The reason is that the total bleeding amount and bleeding rate of concrete accelerate with the increase of amplitude. The water evaporation, which leads to the decrease of actual water to binder ratio, improves the development of early strength. The positive effect of increasing strength due to bleeding is greater than the adverse effect of vibration on concrete. In addition, the concrete is greatly restricted and constrained by the mold during the vibration process, which can avoid the damage of concrete to a certain extent. Therefore, the vibration generates little influence on the compressive strength even though both surface microcracks and poor wear resistance are observed. Although the large amplitude obviously improves the compressive strength of concrete with different ages, it also generates adverse effects on the concrete structure, especially for the construction of large-area bridge deck resulting in large-area plastic cracking, poor surface wear resistance and larger surface roughness without appropriate treatment. (b) Flexural strength The flexural strength of concrete with regard to each group for 7d and individual group for 28d was mainly studied. The specific results are given in Table 8.7. Vehicle-bridge coupling vibration has a great influence on the flexural strength of concrete. The loss rate of flexural strength increases with the increase of amplitude. Especially, when the amplitude is 7 mm, the loss of flexural strength is close to 20% resulting in negative effect on practical engineering. Vibration will cause more concrete surface slurry, higher water to binder ratio, and water evaporation, which lead to settlement shrinkage. Moreover, more surface cracks are caused by slowly hardening, as shown in Fig. 8.5.

12.7 15.9

3.5

7.0

3-2

3-3

11.4

12.4

0.5

18

5

0

1-6

3-1

Vibration for 15 s, stop 45 s

1d

128

102

91.9

100

Retention rate (%)

Compressive strength

Frequency (Hz)

Amplitude (mm)

Vibration mode Time period (h)

Vibration parameters

Group

Table 8.6 Influence of different vibration amplitudes on compressive strength of concrete

46.6

42.7

42.1

42.1

7d (MPa)

110

101

100

100

Retention rate (%)

64.4

53.1

53.4

56.5

28d (MPa)

114.0

93.9

94.6

100

Retention rate (%)

8.1 Anti-Disturbance Concrete with MS 411

412

8 Special High-Performance Concrete with Manufactured Sand

Table 8.7 Influence of vibration with different amplitude on flexural strength Group

Vibration parameters

Flexural strength

Amplitude (mm)

Frequency (Hz)

Vibration Time mode period (h)

7d (MPa)

Retention 28d rate (%) (MPa)

Retention rate (%)

1-6

0

5

7.77

100

7.91

100

3-1

0.5

6.73

86.6

–

–

3-2

3.5

Vibration 18 for15s, stop 45 s

6.74

86.7

–

–

3-3

7.0

6.37

82.0

6.68

84.5

Fig. 8.5 Surface exposure of group 3-3 (5 Hz, 7 mm, 18 h)

(c) Ultrasonic pulse velocity The influence of vibration with different amplitude on the ultrasonic pulse velocity of concrete is givenin Table 8.8. The vibration has little influence on the ultrasonic pulse velocity of concrete when the amplitude is less than 5 mm. The vehicle-bridge coupling vibration with the amplitude of 7 mm has a significant improvement on the ultrasonic pulse velocity of concrete, which also shows a good correlation with the high strength of the testing concrete. This is mainly due to the large amplitude of vibration accelerating the bleeding of concrete, which facilitates the increase of the strength. However, the influence on the internal structure of concrete needs to be further studied through combining with other aspects of comprehensive analysis. (d) Early segregation Results from Fig. 8.6 show that the variation of amplitude has great influence on the segregation performance of concrete. S1 tends to increase as the amplitude increases. The proportion of surface aggregate gradually decreases from the top to the bottom, which intensifies the concrete segregation between layers resulting in inhomogeneity of concrete. As a result, the volume fraction of the upper slurry is higher and the elastic modulus is lower, which is not conducive to resisting load leading to damage.

8.1 Anti-Disturbance Concrete with MS

413

Table 8.8 Influence of vibration with different amplitude on ultrasonic velocity Group Amplitude 1d pulse velocity (m/s) 7d pulse velocity (m/s) 28d pulse velocity (m/s) (mm) Upper Lower Average Upper Lower Average Upper Lower Average 0

3788

3916

3852

4407

4598

4503

4549

4719

4634

3-1

0.5

3-2

3.5

3724

3969

3847

4447

4667

4557

4423

4779

4601

3854

3907

3881

4430

4672

4551

4522

4744

3-3

7

4633

4065

4007

4036

4675

4762

4719

4739

4938

4838

Fig. 8.6 Influence of vibration with different amplitudes on aggregate segregation coefficient and settlement coefficient between layers

1.4

Aggregate segregation coefficient and settlement coefficient between layers

1-6

1.3 1.2 1.1

S1 S2

1.0 0.9 0.8 0.7 0.6 -1

0

1

2

3

4

5

6

7

8

Vibration amplitude/mm

As the amplitude increases, S2 almost decreases linearly, which indicates that the variation of amplitude has a great influence on the settlement between layers. The settling velocity of coarse aggregate is much greater than that of fine aggregate when the amplitude increases. The results show that the concrete is greatly disturbed when the amplitude is large. (3) Vibration with different modes The proposed vibration mode is mainly according to the actual situation. In the case of highway bridges opening to traffic, vehicle-bridge coupling vibration is mainly caused by the heavy vehicles as well as the high-speed ordinary vehicles. This kind of vibration in general will not continue. Therefore, the vibration mode can be simply divided into three kinds according to the traffic flow of highway bridge: (a) normal mode, vibration for 15 s, stop for 45 s; (b) busy mode, vibration for 30 s, stop for 30 s; and (c) extreme mode, always vibrating (vibration for 60 s, no stop). Table 8.9 shows the influence of different vibration modes on the 7d flexural strength and 28d compressive strength of concrete. From the perspective of 7d flexural strength, the vibration mode still has an obvious influence on the flexural strength of concrete. The longer the continuous vibration time per minute, the lower the retention rate of 7d flexural strength is. The influence of vibration mode on the strength of

414

8 Special High-Performance Concrete with Manufactured Sand

Table 8.9 Influence of different vibration modes on the 7d flexural strength and 28d compressive strength of concrete Group Vibration parameters

1-6

7d flexural strength

28d compressive strength

Amplitude Frequency Vibration Time Tested Retention Tested (mm) (Hz) mode period value rate (%) value (h) (MPa) (MPa)

Retention rate (%)

3.5

5

Standing

18

7.77

100

56.5

100

4-1

Normal

6.74

86.7

53.1

93.9

4-2

Busy

6.45

83.0

51.9

91.8

4-3

Extreme

6.14

79.0

50.6

89.6

concrete also is prominent basing on the result of 28d compressive strength. Therefore, the proper controlled traffic flow is beneficial to improve the strength of concrete and ensure the project quality. (4) Vibration with different time period The vibration time period mainly refers to the starting time and duration time of simulated vehicle-bridge coupling vibration applying on concrete. According to the actual situation, this vibration acting on concrete starts from the placing of concrete. However, considering that the effect of vehicle-bridge coupling vibration on the concrete can be ignored when the concrete age develops to a certain stage, the simulation experiment can be simplified. This section focuses on the vibration starting time of 0 h, 3 h, 6 h, 9 h, 12 h, and 15 h after concrete molding, respectively. The influence of different vibration time periods on the 7d flexural strength and 28d compressive strength of concrete with the vibration duration time of 3 h was determined. Furthermore, the time period of concrete, which is most vulnerable to vibration damage, was studied to further analyze both the damage mechanism of concrete under the simulated vehicle-bridge coupling vibration and the preparation of anti-disturbing concrete. It can be seen from Table 8.10 that different vibration time periods have a great influence on the 7d flexural strength of concrete. The vibrations of both 6–9 and 9–12 h have a certain adverse effect on the compressive strength of concrete, while the effect for other time periods is relatively small. Figure 8.7 shows the influence of different vibration time periods on the flexural strength of concrete. In the early stage (0–6 h), vibration leads to the existence of bleeding channels and the formation of water sac under the aggregate due to concrete segregation and bleeding affecting the strength of concrete. However, deformation can offset some of the side effects attributing to the plastic status of concrete at this stage. In addition, water evaporation reducing the actual water to binder ratio also has a positive effect on flexural strength. Therefore, the loss of flexural strength at this stage is relatively small combining the effect. In the middle stage (6–15 h), the initial internal friction and physical adhesion force between particles gradually generate a certain chemical adhesion force with

8.1 Anti-Disturbance Concrete with MS

415

Table 8.10 Influence of different vibration time period on basic mechanical properties of concrete Group Vibration parameters

7d flexural strength

Amplitude Frequency Vibration Time (mm) (Hz) mode period (h) 5

Tested Retention Tested value rate (%) value (MPa) (MPa)

Retention rate (%)

100.0

55.2

100.0

96.9

55.8

101.1

92.5

57.3

103.8

5-3

Vibration Standing 6.60 for 15 s, 0–3 6.39 stop for 3–6 6.10 45 s 6–9 5.88

89.1

53.4

96.7

5-4

9–12

98.9

53.0

96.0

5-0

3.5

28d compressive strength

5-1 5-2

6.53

12–15

5.77

87.4

55.5

100.5

15–18

6.70

101.5

56.7

102.7

Fig. 8.7 Influence of different vibration time periods on the flexural strength retention rate of concrete

Percentage of flexural strength of vibrated samples compare to control sample/%

5-5 5-6

100 80 60 40 20 0

control

0~3

3~6

6~9

9~12

12~15 15~18

Concrete Vibration at certain time period after casting

the increase of cement hydration. However, vibration may cause damage to concrete attributing to the small cohesion of concrete, which result in the decrease of flexural strength of concrete. In the later stage (after 15 h), the effect of vibration on the flexural strength of concrete is limited due to the fact that concrete gradually close to the final setting can resist the external vibration.

8.1.2.2

Long-Term Mechanical Properties of Anti-Disturbance Concrete with MS

Results from Table 8.11 show that the anti-disturbance admixture improves the compressive strength at all ages mainly due to the more compact structure of antidisturbance concrete, which is beneficial to resist the performance damage caused by vehicle-bridge coupling vibration.

416

8 Special High-Performance Concrete with Manufactured Sand

Table 8.11 Long-term compressive strength of ordinary concrete and anti-disturbance concrete Compressive strength (MPa)

Group

3d

7d

28d

60d

90d

Ordinary concrete

30.11

42.66

50.51

53.83

58.15

Anti-disturbance concrete

38.94

47.42

59.73

62.82

66.51

Table 8.12 Static compression elastic modulus of ordinary concrete and anti-disturbance concrete Static compression elastic modulus (MPa)

Group

3d

7d

28d

60d

Ordinary concrete

3.12 × 104

3.67 × 104

4.20 × 104

4.03 × 104

Anti-disturbance concrete

3.75 × 104

3.96 × 104

4.37 × 104

4.55 × 104

The static compression elastic modulus of ordinary concrete and anti-disturbance concrete is given in Table 8.12. The elastic modulus of anti-disturbance concrete gradually increased with the age. In addition, the early elastic modulus of antidisturbance concrete is higher than that of ordinary concrete, which is beneficial to the early tensioning process of bridge deck engineering.

8.1.2.3

Durability of Anti-Disturbance Concrete with MS

The carbonation depth of ordinary concrete and anti-disturbance concrete is given in Table 8.13 and shown in Fig. 8.8. Results show that the carbonation depth of the two types of concrete is zero at all ages, which are probably due to the small water to binder ratio and porosity, good compact structure, and strong carbonation resistance of high-strength concrete. Generally speaking, the anti-disturbance admixtures have no adverse influence on the carbonation performance of concrete. The results from Table 8.14 show that the addition of anti-disturbance admixture makes the concrete more compact, which is beneficial to improve the anti-chloride ion permeability of concrete and the durability of concrete structure. Table 8.13 Carbonation depth of ordinary concrete and anti-disturbance concrete

Group

Carbonation depth (mm) 7d

28d

60d

Ordinary concrete

0

0

0

Anti-disturbance concrete

0

0

0

8.1 Anti-Disturbance Concrete with MS

417

Fig. 8.8 Carbonization pictures of a ordinary concrete and b anti-disturbance concrete at 60d

Table 8.14 Chloride migration coefficient of ordinary concrete and anti-disturbance concrete

8.1.2.4

Group

Chloride migration coefficient (m2 /s)

Ordinary concrete

2.56 × 10–12

Anti-disturbance concrete

2.24 × 10–12

Microscopic Analysis

The results show that the simulated vehicle-bridge coupling vibration has little effect on the cement production of concrete at 7d compared Figs. 8.9 with 8.10, which consists of obvious crystal diffraction peaks of hydration products such as C–S–H gel, Aft, and Ca (OH)2 . In addition, diffraction peaks of unhydrated C3 S and C2 S are also observed, and the position of the peaks is close to each other. The porosity and pore size distribution of cement paste with 7d age tested by MIP are given in Table 8.15. The total porosity of concrete after vehicle-bridge 8000

Fig. 8.9 X-ray diffraction pattern of reference concrete cured normally at 7d

▲ Ca(OH)2

●

■ C-S-H ● AFt

Intensity/counts

6000

★ C3S ☆ C2S

4000 ▲ ▲ ■

2000

●

■ ★ ☆ ● ☆

▲ ★

■ ▲

● ★

0

0

20

40

60

Two-Theta(deg)

80

418

8 Special High-Performance Concrete with Manufactured Sand 8000

Intensity/counts

Fig. 8.10 X-ray diffraction pattern of reference concrete at 7d after vehicle-bridge coupling vibration

6000

▲ Ca(OH)2 ▲ ▲ ■ C-S-H ■ ■ ● AFt

4000

☆ C2S ☆

●

★ C3S ▲ ▲

2000

●

■ ■ ★

▲

☆

☆★ ☆

0

0

20

40

■▲

★ ▲

60

80

Two-Theta(deg)

coupling vibration decreases compared with the standing concrete, which indicates that vehicle-bridge coupling vibration is beneficial to reduce the total porosity of concrete. The average pore size and medium pore diameter reduce greatly indicating that vibration can refine pore size. The proportion of both harmless pore and moreharm pore increases, which may be due to the refinement of a large number of less-harm pore and harmful pore by vibration. However, the effect of vibration on the more-harm pore is limited resulting in increasing the proportion of more-harm pore. The vibration leads to the rise of air bubbles and free water in concrete. Some of them remain permanently in the interface transition zone (between mortar and aggregate) and the interior of the paste due to the blocking effect of coarse aggregate in the rising process, resulting in the damage of concrete performance.

8.1.3 Engineering Application 8.1.3.1

An Overview of Hanjiadian No. 1 Bridge

Hanjiadian No. 1 bridge, built in 2006, is located in the national trunk line of the Lanhai Expressway. The main bridge is a continuous rigid structure of prestressed concrete with a total length of 454 m (122 m + 210 m + 122 m). The overall view picture of the bridge, which includes a one-way vertical slope of 2.6999% and the cross-slope of 2% in both directions, is shown in Fig. 8.11. The bridge has been in operation for four years and have presented some diseases such as the midspan deflection of main span, the top of the box beam, the cracking of the bottom plate, and so on, which promote to strengthen the main bridge after investigation and study.

Total pore specific surface area/m2 g−1

8.130

9.646

Total porosity /ml g−1

0.1332

0.0955

Standing

Vibration

Condition

39.6

65.6

Average pore size/nm

4.9

11.4

Medium pore diameter/nm

Table 8.15 Results of MIP test of ordinary concrete and concrete after vibration

11.84

6.77

Harmless pore/% (< 20 nm) (%) 8.27

10.88

Less-harm pore/% (20–50 nm) (%)

6.70

12.31

Harmful pore/% (50–200 nm) (%)

Classification of pore size (by total porosity/ml g−1 )

73.19

70.04

More-harm pore/% (> 200 nm) (%)

8.1 Anti-Disturbance Concrete with MS 419

420

8 Special High-Performance Concrete with Manufactured Sand

Fig. 8.11 Hanjiadian No. 1 bridge

8.1.3.2

Mix Proportion and Properties of On-Site Anti-Disturbance Concrete with MS

The mix proportion of engineering concrete including self-compacting antidisturbance concrete with MS (SCA) and pumping anti-disturbance concrete with MS (PA) is given in Table 8.16. The performance comparison between two types of anti-disturbance concrete with MS and engineering used ordinary concrete is given in Table 8.17. Results show that when polyacrylonitrile fiber and anti-disturbance admixture are added, the compressive strength at each age is not only improved, but also the difference between initial setting time and final setting time is also shortened and the hydration speed of anti-disturbance concrete is faster, which are helpful to mitigate the adverse influence of traffic vibration on concrete performance. The maintenance and reinforcement work lasting for three months were completed in November 2010. The speed limit measurement was only carried out during the construction without interrupting the traffic. Table 8.16 Mix proportion of C50 engineering anti-disturbance concrete with MS Group

Cement (kg/m3)

Fly ash (kg/m3)

W /B

Sand rate (%)

Water reducer (%)

Anti-disturbance admixture (%)

Fiber (kg/m3 )

SCA

424

106

0.3

55

2.0

5

0.8

PA

450

50

0.3

50

1.8

6

0.8

8.2 Underwater Anti-Washout Concrete with MS

421

Table 8.17 Performance comparison between anti-disturbance concrete with MS and ordinary concrete Group

Polyacrylonitrile Initial Initial fiber (kg/m3 ) slump/slump setting flow (mm) time (min)

Final setting time (min)

1d compressive strength (MPa)

3d compressive strength (MPa)

Ordinary 0 self-compacting concrete

245/565

260

390

21

39

SCA

0.8

230/560

230

300

25

44

Ordinary pumping concrete

0

200/440

240

360

22

43

PA

0.8

200/450

230

300

26

46

8.1.4 Summary (1) The vehicle-bridge vibration leads to water evaporation facilitating the improvement of early strength and further has great influence on the concrete performance. (2) The segregation of concrete is intensified due to vehicle-bridge vibration, resulting in poor uniformity of concrete. (3) The use of anti-disturbance concrete with MS can ensure the maintenance work without interrupting traffic.

8.2 Underwater Anti-Washout Concrete with MS Traditional construction methods of underwater concrete cannot guarantee the homogeneity of materials, the reliability of joints, and the bond strength between steel bars and concrete [19]. These will cause segregation, the loss of cement, the decline of quality, and environmental pollution problems. When the fresh concrete passes through the water layer, the aggregate and cement will separate. In addition, the cement will set and harden during the sinking process, resulting in the loss of binding ability. Therefore, underwater concrete has needed to be casted in the isolated condition away from the ambient water, and the casting process cannot be interrupted to reduce the adverse effects of water. Underwater anti-washout concrete has superior technical performance and is cost effective [20–23]. Based on the construction technical requirements, it enables a direct pouring process due to which the intrinsic performance of underwater antiwashout concrete is improved. In contrast to the poor dispersion resistance and low underwater strength of ordinary concrete, underwater anti-washout concrete exhibits superior properties such as self-leveling, self-compacting, and non-vibration, which is beneficial to simplify the construction process of underwater engineering.

422

8 Special High-Performance Concrete with Manufactured Sand

The underwater anti-washout admixture is the key technology to overcome the separation of fresh concrete with water. This novel chemical admixture can significantly improve the cohesion of concrete mixture, which fundamentally solve the problems of dispersion and segregation in the underwater construction of ordinary concrete [22]. Underwater anti-washout admixtures are generally water-soluble high molecular polymer with long chain structure, which have the effect on connection and bridging between cement particles. The water-soluble polymer of concrete disperses into the mixing water in the form of molecular and combines with the partial mixing water through hydrogen bond. Therefore, the mixing water is restricted in the network structure of water-soluble polymer, so as to avoid the dispersion with the cement particles and underwater anti-washout admixtures wrapped due to the washing of external water molecules [24]. In practice, the addition of underwater anti-washout admixture is the most critical measure in the preparation of underwater anti-washout concrete [25]. From the report of Sonebi and Khayat [26, 27], the main components of the commonly used underwater anti-washout admixtures are Welan resin and cellulose in recent years, which also are supplemented by fly ash, ground slag, retarding admixtures, naphthalene sulfonate and melamine resin, etc. As for China, underwater anti-washout concrete was firstly studied in the 1980s, which has been widely used in water conservancy and hydropower, transportation, petroleum, and civil engineering [28]. The underwater anti-washout admixtures commonly used in engineering are polypropylene and cellulose. In detail, the former mainly belongs to anionic polymer electrolyte, which possesses ideal flocculation effect with a small dosage. The latter also presents good flocculation effect since hydrogen of the hydroxyl group on the ternary ring of cellulose is substituted by the alkyl group (etherified), which not only shows the reducing water function with a small dosage, but also possesses the evident air entrainment and retarding effect with a large dosage [29]. As a result, the main priority of underwater anti-washout concrete is to select the raw materials and prepare appropriate underwater anti-washout admixtures. Underwater anti-washout concrete with MS as fine aggregate is a kind of highperformance concrete with promising underwater anti-washout performance. The present research focuses on the use of MS, the underwater dispersion resistance of concrete, and the practical application of underwater anti-washout concrete. As for the research on underwater, anti-washout performance is mainly about the optimization of underwater anti-washout admixtures and the impact of mineral admixtures based on the successfully application. Yoursri K M developed a novel type of underwater anti-washout admixtures with application value [30], which was confirmed in practical engineering. MS, which is commonly compared with natural sand to verify the practical significance in the early stage, has been mostly applied to explore the effects on performance and mechanism of high-performance concrete recently [31– 33]. Here, the raw materials, mix design, performance, and practical engineering application of underwater anti-washout concrete with MS are introduced as follows.

8.2 Underwater Anti-Washout Concrete with MS

423

8.2.1 Raw Materials and Test Methods 8.2.1.1

Raw Materials

The cement used for the preparation of underwater anti-washout concrete with MS should comply with the corresponding standards, and the cement strength grade should not be lower than P. II42.5. The active MS is strictly forbidden to use in the underwater anti-washout concrete with MS under seawater environment. The used cement was P. II52.5 Portland cement. The MS with fineness modulus of 2.2–2.3 and the continuous grading coarse aggregate with size range of 5–25 mm were selected, respectively. The underwater anti-washout admixture and polycarboxylate water-reducing admixture were used to optimize the concrete performance.

8.2.1.2

Test Methods

Testing for workability (slump and slump flow), mechanical properties, and durability of concrete are conducted in accordance with the current Chinese standard GB/T 50080, GB/T 50081, and GB/T 50082, respectively.

8.2.2 Results and Analysis The performance between underwater anti-washout concrete and ordinary concrete is obviously different in engineering. The underwater anti-washout concrete mixture should possess the properties of anti-washout, fluidity, and water to land strength ratio. The action mechanism of flocculants from charge neutralization, adsorption bridging, and surface adsorption was analyzed to illustrate the effects on cement system and fluidity [34].

8.2.2.1

Workability

Based on previous experiments, two flocculants of PVAD and HPMC were adopted to study the properties of underwater anti-washout concrete. Three optimal mixing proportions MP1, MP2, and MP3 (MP0 as control group) were selected to determine the optimal concrete performance as given in Table 8.18. Table 8.18 Optimal mixing proportions of underwater anti-washout admixture Underwater anti-washout admixtures

MP1

MP2

MP3

PVAD content (wt./%)

0.005

0.020

0.030

HPMC content (wt./%)

0.020

0.005

0.030

424

8 Special High-Performance Concrete with Manufactured Sand

Fig. 8.12 Workability of different concrete mixtures retaining the same slump

In order to ensure the quality of underwater concrete, underwater construction usually uses non-vibration casting method, which demands self-compacting and selfleveling properties for underwater concrete mixture. The concrete mixture, which poured to flow through the gap between steel bars, fills the various parts of the mold by own weight when casting. Furthermore, the higher the viscosity of underwater concrete is, the better the fluidity is, and the slump can ultimately reach 20–27 cm. Therefore, the combination of slump and slump flow, which was carried out under the same condition, is generally used to comprehensively evaluate the fluidity. Especially, the slump of concrete mixture was basically controlled as 22 ± 2 cm. As shown in Fig. 8.12, it can be seen that with regard to the concrete mixtures with MP1, MP2, and MP3, the slump flow is smaller and the flow time of inverted slump is larger compared with MP0, which indicate the larger viscosity. As for MP1, MP2, and MP3, MP1 presents large slump and short flow time of inverted slump indicating good workability compared with MP2 and MP3.

8.2.2.2

Mechanical Properties

According to different environmental conditions, the mechanical properties of underwater anti-washout concrete with MS can be divided into onshore compressive strength and underwater compressive strength, and the index of “water to land strength ratio” can be used to comprehensively characterize the strength loss of underwater anti-washout concrete. A novel type of underwater anti-washout admixtures JS, which is beneficial to the development of the concrete strength and anti-washout performance, has been improved through lots of experiments. The properties of novel underwater antiwashout admixture JS will be studied in the following. It can be seen from Table 8.19 that with respect to the same mix proportion, the concrete with JS presents both higher 28-day onshore absolute strength and water to land strength ratio than the similar type products purchased from China, which can be listed in specific as follows. (1) The 28d compressive strength of concrete with product A was 32.5 MPa, while the water to land strength ratio is only 74.8% (0.5 m) and 62.2% (1 m), respectively. The 28d compressive strength of concrete with product B was 28.1 MPa, while the water to land strength ratio is only 74.7% (0.5 m). It is interesting to note that the 28d compressive strength of concrete with JS can reach 36.2 MPa,

8.2 Underwater Anti-Washout Concrete with MS

425

Table 8.19 Effects of JS underwater anti-washout admixture on concrete strength Group

Admixture W /B type/content (%)

SH-11 JS, 1.5

Slump Slump The (mm) flow depth (mm) of water

0.445 240

424

0.5

28d onshore compressive strength (MPa)

28d underwater compressive strength (MPa)

28d water to land strength ratio (%)

36.2

31.5

87.0

29.4

81.2

49.4

92.6

44.8

84.1

24.3

74.8

20.2

62.2

1.0 SH-12 JS, 1.2

0.340 245

420

0.5

52.3

SH-13 Product A (China), 2.0

0.60

420

SH-14 Product B (China), 2.0

0.560 21.0

36.0

0.5

28.1

21.0

74.7

SH-15 /

0.71

/

/

30.7

/

/

1.0 220

0.5

32.5

1.0

8.0

which is 11.4% and 28.8% higher than the formers, respectively. More importantly, the addition of JS can greatly improve the washout resistance of concrete during underwater casting. With regard to the depth of water of 0.5 m and 1 m, the water to land strength ratio can be up to 87.0%–92.6% and 81.2%–84.1%, respectively. (2) With the addition of JS, the strength grade for the underwater concrete with better underwater anti-washout performance reaches up to C40, which provide a promising guarantee for the underwater structural engineering from the perspective of materials. 8.2.2.3

Durability Performance

(1) Shrinkage The results of shrinkage from Table 8.20 illustrate that the shrinkage variation of underwater anti-washout concrete with MS is consistent with that of ordinary concrete. However, the final shrinkage value of underwater anti-washout concrete with MS is relatively less indicating the reducing for the damage of shrinkage cracking. (2) Permeability resistance The permeability resistance of concrete mainly depends on the compactness of cement paste, pore structure, and aggregate-paste interface zone. Results from Table 8.21 show that underwater anti-washout concrete with MS containing JS presents better permeability resistance performance, which exceed the permeability resistance grade of P30.

426

8 Special High-Performance Concrete with Manufactured Sand

Table 8.20 Results of shrinkage of anti-washout underwater concrete Group

Shrinkage value/× 10–6 1d

3d

7d

14d

28d

60d

90d

180d

SH-11

52

84

147

265

324

386

401

423

SH-12

61

86

162

251

332

380

397

420

SH-15

74

103

245

308

425

464

497

516

Table 8.21 Results of permeability resistance of underwater anti-washout concrete Group

Pressure/MPa

The depth of impermeability/cm

Permeability resistance grade

SH-11

2.0

1.8

> P30

SH-12

2.0

0.6

> P30

SH-15

0.3

15

P2

Table 8.22 Comparison of resistance of concrete to freezing and thawing Group

Freezing-and-thawing cycles

Strength loss rate/%

Weight loss rate/%

SH-11

50

− 12.3

0

SH-12

50

− 9.6

0

SH-15

50

2.2

2.4

(3) Resistance to freezing and thawing The results given in Table 8.22 illustrate that the resistance of underwater antiwashout concrete with MS to freezing and thawing is much higher than that of ordinary concrete. After 50 freezing-and-thawing cycles, the weight of SH-11 and SH-12 is kept constant and the compressive strength increased. However, the compressive strength of SH-15 decreased by 2.2% along with the weight loss of 2.4%. It can be attributed to the fact that with regard to anti-washout underwater concrete with MS, the compactness is greatly improved after adding JS and the air content is higher than that of ordinary concrete facilitating the development of higher resistance performance of concrete to freezing and thawing. Moreover, the existence of polymer enhances the cracking resistance in the anti-washout underwater concrete with MS, which is conducive to the resistance of concrete to freezing and thawing. (4) Resistance to chemical attack The variations of mechanical properties (compressive strength) were measured for three groups of concrete, which were immersed in 2.5% HCl solution, 20% NaOH solution, and 20% MaSO4 solution for three months, as listed in Table 8.23. From Table 8.23, it can be seen that SH-15 has the poor resistance of acid attack, alkali, and sulfate. However, with regard to SH-11 and SH-12, the damage of acid attack was much less than that of SH-15, and the compressive strength decreased

8.2 Underwater Anti-Washout Concrete with MS

427

Table 8.23 Variations of mechanical properties of concrete after chemical attack Group Compressive strength before immersed (MPa)

Acid attack

Alkali erosion

Sulfate attack

Compressive Strength Compressive Strength Compressive Strength strength loss rate strength loss rate strength loss rate immersed in (%) immersed in (%) immersed in (%) 2.5% HCl 20% NaOH 20% MaSO4 for 3 months for 3 months for 3 months (MPa) (MPa) (MPa)

SH-11 36.2

30.5

15.7

40.5

− 11.9

39.2

− 8.3

SH-12 52.3

47.9

10.1

58.4

− 9.6

57.1

− 7.1

SH-15 30.7

22.5

26.7

27.5

10.4

26.4

14.0

instead of increasing after concrete was immersed in alkali and salt solution, which is due to the fact that these two groups of concrete have good impermeability as a result of the addition of active SCMs facilitating the resistance to alkali and sulfate erosion. (5) Carbonation resistance The carbonation depth of three groups was tested after a month of accelerated carbonation in the carbonation box. As shown in Fig. 8.13, it can be seen that the carbonation depth of anti-washout underwater concrete with MS is 0 cm, which is much less than that of ordinary concrete with 1.6 cm. Under the same conditions of CO2 concentration, relative humidity, and ambient temperature, the alkali content and pore structure of cement paste are the main factors affecting carbonation rate. It can be predicted that the alkali content is lower than that of ordinary concrete due to the addition of slag, silica fume, and other SCMs in the anti-washout underwater concrete, which is beneficial to form the high compactness of anti-washout underwater concrete with MS resulting in the lower the carbonation rate. (6) Chloride diffusion rate In seawater, chloride ions diffuse onto the surface of the steel bars embedded in the concrete, which destroys the passive film attached on the surface of the steel bars causing the corrosion and serious reduction in the service life of the concrete. Fig. 8.13 Comparison of carbonation depth of underwater anti-washout concrete and ordinary concrete

428

8 Special High-Performance Concrete with Manufactured Sand

Fig. 8.14 Diffusion depth of Cl− for underwater anti-washout concrete and ordinary concrete

Therefore, the chloride diffusion rate is an important parameter for concrete structures in seawater, seaport, and offshore. The diffusion depth of Cl− in three groups was measured when concretes were immersed in 20% NaCl solution for three months. As shown in Fig. 8.14, it can be seen that the chloride diffusion rate in the underwater anti-washout concrete with MS is much lower, which is attributed to the lower water to cementitious materials ratio and the higher compactness. In addition, the addition of active SCMs not only further improves the compactness of concrete, but also enhances the solidification of Cl− , which significantly reduces the chloride diffusion rate. According to the above comparison for the durability indexes between underwater anti-washout concrete with MS and ordinary concrete, it can be considered that the permeability resistance, the resistance to freezing and thawing, carbonation resistance, and the resistance of chloride diffusion are much better than ordinary concrete due to the addition of underwater anti-washout admixtures and active SCMs. In addition, compared with the ordinary concrete, the resistance of chemical attack is also improved and the shrinkage rate is lower. In conclusion, the results ensure that anti-washout underwater concrete with MS can be perfectly used in seawater and freshwater.

8.2.3 Engineering Application 8.2.3.1

An Overview of Huayudong Bridge

The Huayudong Bridge is located in the Qingzhen area of Guizhou Province, China, which cross the Hongfeng Lake Reservoir. The investigation results show that the karst is developed in the foundation of No. 4 Huayudong Bridge Pier. The borehole reveals that the karst cave is divided into three layers including the top layer, the middle layer, and the bottom layer. The floor for the top layer of the karst cave with 1.5 m height is only 0.4 m away from the foundation bottom, as the upper layer of karst cave is fragile, which has a great impact on the foundation stability, so the top layer needs to be enhanced. The middle layer with a height of 4.2 m is large scale and higher strength, and the bedrock with the minimum thickness of 6.1 m in this roof is continuous and stable, so relative treatment is not required. With regard

8.2 Underwater Anti-Washout Concrete with MS

429

Table 8.24 Mix proportion of underwater anti-washout concrete for engineering (kg/m3 ) Cement

JS

Coarse aggregate

Fine aggregate

Water

550

11

820

777

207

to the bottom layer with the height of 0.8 m, the scale of karst cave development is tiny, so the effect on the foundation can be regardless. In addition, the karst of underlying foundation in the arch foundation of the Guiyang bank in Huayudong Bridge has developed with large scale. The karst cave, which consists of a height of about 13ma lateral development width of 2 to 4 m and the roof bedrock of 2.7 m, is nearly elliptical development. The karst cave is fully filled with water, which is connected to the water of Hongfeng Lake by pipelines indicating a greater impact on the stability of the working foundation. Therefore, the karst cave is indeed to be enhanced.

8.2.3.2

Mix Proportion and Properties of On-Site Anti-Washout Concrete with MS

The mix proportion of engineering concrete is given in Table 8.24. It can be seen from Table 8.25 that the mix proportion fully meets the requirements of the construction for underwater anti-washout concrete. Engineering practice shows that underwater anti-washout concrete with JS has excellent properties including underwater washout resistance, self-leveling, and self-compacting. Compared with the traditional ordinary underwater concrete construction technology, the construction technology of anti-washout underwater concrete can simplify the constructing process, which is beneficial to shorten the period of construction and reduce the cost of project. The quality of karst cave reinforcement project is also ensured without polluting the water of the reservoir (Fig. 8.15).

8.2.4 Summary (1) The addition of underwater anti-washout admixture greatly improves the water to land strength ratio, which guarantees the engineering application. (2) The durability of underwater anti-washout concrete with MS is much better than ordinary concrete due to the addition of underwater anti-washout admixtures and active SCMs.

25.5

34.4

425

220

93.3

Onshore (MPa)

27.4

7d

Onshore (MPa)

Water–land strength ratio (%)

3d

Slump flow

Slump

Underwater (MPa)

Compressive strength

Workability/mm

Table 8.25 Performance of underwater anti-washout concrete

29.7

Underwater (MPa) 86.2

Water–land strength ratio (%)

46.4

Onshore (MPa)

3d

40.0

Underwater (MPa)

86.2

Water–land strength ratio (%)

430 8 Special High-Performance Concrete with Manufactured Sand

References

431

Fig. 8.15 Application of anti-washout concrete in the Huayudong Bridge

8.3 Concluding Remarks (1) The vehicle-bridge vibration basically generates adverse influence on the concrete performance. However, the use of anti-disturbance concrete with MS can ensure the maintenance work without interrupting traffic. (2) The addition of underwater anti-washout admixture and the optimal proportion greatly improves the mechanical properties and durability of underwater antiwashout concrete with MS.

References 1. G. Diana, F. Cheli, Dynamic interaction of railway systems with large bridges. Veh. Syst. Dyn. 18(1–3), 71–106 (1989) 2. Y. Yang, C. Lin, Vehicle–bridge interaction dynamics and potential applications. J. Sound Vib. 284(1–2), 205–226 (2005) 3. C.H. Dowding, Construction vibrations (1996) 4. S. Harsh, D. Darwin, Traffic induced vibrations and bridge deck repairs (1986) 5. J. Muller-Rochhotz, Traffic vibration of a bridge deck and hardening of lightweight concrete. Concr. Int. 8(11), 23–26 (1986) 6. M.R. Dunham, A.S. Rush, J.H. Hanson, Effects of induced vibrations on early age concrete. J. Perform. Constr. Facil. 21(3), 179–184 (2007) 7. J. Wei, J. Xing, Z. Fu, Effect of traffic load induced bridge vibrations on concrete tensile properties. J. Southeast Univ. Nat. Sci. Edn. 40(5), 1057–1060 (2010) 8. L. Bu, The research on Influence of The Post-Casting Section of Continuous Rigid Bridge Suffered Vibration of Train Travelling (Hunan Universitiy: Master Thesis 2001) 9. A. Ansell, J. Silfwerbrand, The vibration resistance of young and early-age concrete. Struct. Concr. 4(3), 125–134 (2003) 10. H.L. Furr, F.H. Fouad, Effect of moving traffic on fresh concrete during bridge-deck widening. Transp. Res. Rec. 860, 28–36 (1982)

432

8 Special High-Performance Concrete with Manufactured Sand

11. D. Cusson, W.L. Repette, Early-age cracking in reconstructed concrete bridge barrier walls. ACI Mater. J.-Am. Concr. Inst. 97(4), 438–446 (2000) 12. R. Jiang, F. Au, Y. Cheung, Identification of vehicles moving on continuous bridges with rough surface. J. Sound Vib. 274(3–5), 1045–1063 (2004) 13. L. Deng, Y. Yu, Q. Zou, C. Cai, State-of-the-art review of dynamic impact factors of highway bridges. J. Bridg. Eng. 20(5), 04014080 (2015) 14. Y.-B. Yang, Y.-S. Wu, A versatile element for analyzing vehicle–bridge interaction response. Eng. Struct. 23(5), 452–469 (2001) 15. X. Yin, Z. Fang, C. Cai, L. Deng, Non-stationary random vibration of bridges under vehicles with variable speed. Eng. Struct. 32(8), 2166–2174 (2010) 16. R. Malm, A. Andersson, Field testing and simulation of dynamic properties of a tied arch railway bridge. Eng. Struct. 28(1), 143–152 (2006) 17. T.-L. Wang, Ramp/bridge interface in railway prestressed concrete bridge. J. Struct. Eng. 116(6), 1648–1659 (1990) 18. M.J. Steenbergen, Dynamic response of expansion joints to traffic loading. Eng. Struct. 26(12), 1677–1690 (2004) 19. S. Grzeszczyk, K. Jurowski, K. Bosowska, M. Grzymek, The role of nanoparticles in decreased washout of underwater concrete. Constr. Build. Mater. 203, 670–678 (2019) 20. B.D. Neely, J. Wickersham, Repair of red rock dam. Concr. Int. 11(10), 36–39 (1989) 21. B. Davies, Laboratory methods of testing concrete for placement underwater. Proc. Marine Concr. 279–286 (1986) 22. K.L. Saucier, B.D. Neely, Antiwashout admixtures in underwater concrete. Concr. Int. 9(5), 42–47 (1987) 23. K.H. Khayat, Effects of antiwashout admixtures on fresh concrete properties. Mater. J. 92(2), 164–171 (1995) 24. M.A. Sikandar, N.R. Wazir, A. Khan, H. Nasir, W. Ahmad, M. Alam, Effect of various antiwashout admixtures on the properties of non-dispersible underwater concrete. Constr. Build. Mater. 245, 118469 (2020) 25. K.H. Khayat, J. Assaad, Relationship between washout resistance and rheological properties of high-performance underwater concrete. Mater. J. 100(3), 185–193 (2003) 26. K.H. Khayat, M. Sonebi, Effect of mixture composition on washout resistance of highly flowable underwater concrete. Mater. J. 98(4), 289–295 (2001) 27. M. Sonebi, K. Khayat, Effect of mixture composition on relative strength of highly flowable underwater concrete. Mater. J. 98(3), 233–239 (2001) 28. MFS, Engineering application of antiwashout underwater concrete in energy infrastructure construction. Adv. Concr. Struct. Durabil. Proc. ICDCS2008 1(2), 1243–1247 (2008) 29. Z. Jiang, Z. Sun, P. Wang, Effects of polymers on properties of underwater, in Proceedings of the PRO 42: 1st International RILEM Symposium on Design, Performance and Use of Self-Consolidating Concrete-SCC’2005, China, 2005, p. 153 30. K. Yousri, Self-flowing underwater concrete mixtures. Mag. Concr. Res. 60(1), 1–10 (2008) 31. R. Yang, R. Yu, Z. Shui, C. Guo, S. Wu, X. Gao, S. Peng, The physical and chemical impact of manufactured sand as a partial replacement material in ultra-high performance concrete (UHPC). Cement Concr. Compos. 99, 203–213 (2019) 32. J. Wang, K. Niu, B. Tian, L. Sun, Effect of methylene blue (MB)-value of manufactured sand on the durability of concretes. J. Wuhan Univ. Technol. Mater. Sci. Edn. 27(6), 1160–1164 (2012) 33. B. Li, G. Ke, M. Zhou, Influence of manufactured sand characteristics on strength and abrasion resistance of pavement cement concrete. Constr. Build. Mater. 25(10), 3849–3853 (2011) 34. V.S. Ramachandran, Concrete Admixtures Handbook: Properties, Science and Technology (William Andrew, 1996)