Bamboo and Sustainable Construction 9819902312, 9789819902316

Citation preview

Environmental Footprints and Eco-design of Products and Processes

Felipe Luis Palombini Fernanda Mayara Nogueira   Editors

Bamboo and Sustainable Construction

Environmental Footprints and Eco-design of Products and Processes Series Editor Subramanian Senthilkannan Muthu, Head of Sustainability - SgT Group and API, Hong Kong, Kowloon, Hong Kong

Indexed by Scopus This series aims to broadly cover all the aspects related to environmental assessment of products, development of environmental and ecological indicators and eco-design of various products and processes. Below are the areas fall under the aims and scope of this series, but not limited to: Environmental Life Cycle Assessment; Social Life Cycle Assessment; Organizational and Product Carbon Footprints; Ecological, Energy and Water Footprints; Life cycle costing; Environmental and sustainable indicators; Environmental impact assessment methods and tools; Eco-design (sustainable design) aspects and tools; Biodegradation studies; Recycling; Solid waste management; Environmental and social audits; Green Purchasing and tools; Product environmental footprints; Environmental management standards and regulations; Eco-labels; Green Claims and green washing; Assessment of sustainability aspects.

Felipe Luis Palombini · Fernanda Mayara Nogueira Editors

Bamboo and Sustainable Construction

Editors Felipe Luis Palombini Department of Industrial Design (DDI) Federal University of Santa Maria (UFSM) Santa Maria, Brazil

Fernanda Mayara Nogueira Faculty of Philosophy, Sciences and Letters at Ribeirao Preto (FFCLRP) University of São Paulo (USP) Ribeirão Preto, Brazil

ISSN 2345-7651 ISSN 2345-766X (electronic) Environmental Footprints and Eco-design of Products and Processes ISBN 978-981-99-0231-6 ISBN 978-981-99-0232-3 (eBook) https://doi.org/10.1007/978-981-99-0232-3 © 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

Contents

Bamboo as a Sustainable Building Material . . . . . . . . . . . . . . . . . . . . . . . . . . Lucas Henrique Pereira Silva, Fábio Friol Guedes de Paiva, Jacqueline Roberta Tamashiro, Maryane Pipino Beraldo de Almeida, Vitor Peixoto Klienchen de Maria, Vivian Monise Alves de Oliveira, and Angela Kinoshita Bamboo Construction: Main Building Techniques and Their Resources, Sustainability, History, Uses, and Classification . . . . . . . . . . . . Victor Almeida De Araujo, Letícia Rubio Colauto, Leticia Gabriele Crespilho Abel, Fábio Silva do Rosário, Juliano Souza Vasconcelos, Elen Aparecida Martines Morales, Juliana Cortez Barbosa, Maristela Gava, and André Luis Christoforo Bamboo Structural Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gilberto Carbonari and Luana Toralles Carbonari Projective Experiments and Local Productive Chains of Constructive Systems with Bamboo Culms . . . . . . . . . . . . . . . . . . . . . . . . Tomás Queiroz Ferreira Barata, Silvia Sasaoka, Gabriel Fernandes dos Santos, and Ariel Ferrari

1

25

61

99

Advancing the Use of Bamboo as a Building Material in Low-Income Housing Projects in Kenya . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 Shahryar Habibi, Esther Obonyo, and Ali M. Memari Lightly Modifying Thick-Walled Timber Bamboo: An Overview . . . . . . . 157 Jonas Hauptman, Ramtin Haghnazar, Greg Marggraf, and Yasaman Ashjazadeh Bamboo Flattening Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 Zhichao Lou, Yanjun Li, and Yihan Zhao

v

vi

Contents

A Century-Old Tradition and Sustainable Technique to Protect Natural Bamboo Through Smoke Treatment—Advantages and Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 Raviduth Ramful A Critical Review on Finite Element Models Towards Physico-Mechanical Properties of Bamboo Fibre/Filler-Reinforced Composite Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 Ranjan Kumar, Sujeet Kumar Mishra, and Kaushik Kumar Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 Raviduth Ramful Performance Assessment Methods and Effects of Bamboo-Based Envelopes in Buildings Under Hot and Humid Conditions . . . . . . . . . . . . . 291 Miguel Chen Austin, Thasnee Solano, Cristina Carpino, Carmen Castaño, and Dafni Mora New Bamboo-Based Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323 Yihua Ren and Yingwu Yin

Bamboo as a Sustainable Building Material Lucas Henrique Pereira Silva, Fábio Friol Guedes de Paiva, Jacqueline Roberta Tamashiro, Maryane Pipino Beraldo de Almeida, Vitor Peixoto Klienchen de Maria, Vivian Monise Alves de Oliveira, and Angela Kinoshita

Abstract Bamboo is an excellent renewable resource, and it can be used as a sustainable building material due to its features, such as fast growth, high resistance, and durability. It is a versatile material and can be used in different applications in civil construction. Bamboo can be applied for structural purposes, such as beams and pillars, and as a component of armature concrete in replacement or reinforcement of steel structures, such as slab panels and beams. Moreover, bamboo has the potential as a biomass resource for renewable energy generation, and bamboo ash can be used as a cement substitute in cementitious matrices. In this chapter, three types of novel engineered bamboo applications are presented, namely as a structural compound, as bamboo fiber reinforced composites, and as the use of bamboo ash as a substitute for cement in cementitious composites. In all applications, results and data are compared to traditional materials. We also present iconic buildings with bamboo applications, such as the International Airport of Madrid-Barajas, the Sports Hall of Panyaden International School, the Modern Education Training Institute—METI Handmade, and the German-Chinese House. Keywords Bamboo · Civil construction · Green building materials · Environmental impacts · Mechanical properties · Bamboo fiber reinforced composites · Supplementary cementitious materials · Green building design

L. H. P. Silva · F. F. G. de Paiva · J. R. Tamashiro · M. P. B. de Almeida · V. P. K. de Maria · V. M. A. de Oliveira · A. Kinoshita (B) University of Western São Paulo—UNOESTE, PGMADRE, Rodovia Raposo Tavares Km 572, Presidente Prudente, São Paulo 19067-175, Brazil e-mail: [email protected] L. H. P. Silva e-mail: [email protected] L. H. P. Silva Federal Institute of Education, Science and Technology, José Ramos Junior St. 27-50 Jd. Tropical, Presidente Epitácio, São Paulo 19470-000, Brazil © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 F. L. Palombini and F. M. Nogueira (eds.), Bamboo and Sustainable Construction, Environmental Footprints and Eco-design of Products and Processes, https://doi.org/10.1007/978-981-99-0232-3_1

1

2

L. H. P. Silva et al.

1 Presentation Bamboo appeared on Earth during the Cretaceous period, which began 100 million years ago and ended over 65 million years ago. Bamboo is originally from Asia and currently occurs naturally in Sri Lanka, Bangladesh, Thailand, and China. Portuguese settlers introduced bamboo to Indonesia, Malaysia, and the Philippines, while Chinese immigrants introduced it to the USA. Later, Chinese settlers brought bamboo to Brazil [1, 2]. According to the Food and Agriculture Organization (FAO) [3], 31 million hectares of forestland worldwide is covered by bamboo, with more than 60% of these areas located in Brazil, India, and China, and it is also abundant in other continents, namely Africa, Latin America, and Asia. Additionally, bamboo covers 1% of the world’s forested areas. In general, Latin America has 10% of bamboo forests, while Asia has 80% and Africa has 10%. Bamboo grows more effectively in warm temperate and tropical climates. It is extremely fast growing, reaching up to 0.08 m per day in these conditions; nevertheless, bamboo can also be cropped in adverse conditions, such as desert or mountain climates when the suitable species is chosen [4]. Ideally, bamboo should be planted during the spring, but it has been planted in late winter in tropical climates. However, there have been successful harvests in cold climates as well, as long as the bamboo trees are planted near trees, walls, and fences to protect from strong winds [5]. Bamboo trees require about eight hours of sunlight daily, although some species need shade during the hottest part of the day. Planting bamboo in a cooler region confers tolerance to less water, while cropping it in a warmer area requires planting it in an area with partial shade to prevent the plant from dehydration during the winter period. Bamboo should be grown in deep, rich, and well-drained soils. If necessary, organic fertilizers could be used to improve soil quality [6]. Bamboo can be propagated using its rhizomes and culms, called vegetative propagation, which chooses a rhizome that is at least one-year-old. Then, pachymorph and leptomorph rhizomes are transplanted based on their morphological aspects and other features [7]. Transplanting pachymorphic rhizomes requires cutting the part where the old rhizome connects to the new rhizome, cutting the culm above the first node, and planting it with the stem above ground and the rhizome below ground. To transplant leptomorphs requires cutting off any buds and, if there is a culm above its first node, placing it between 0.30 and 0.50 m below ground. It is necessary to plant a bamboo culm buried at 0.30 m below ground and keep it moist when transplanting [8, 9]. Planted in strips 1.0–1.5 m apart, bamboo can grow successfully as a dense planting. Irrigation should be done frequently, especially when the plants are young and the weather is dry. In this case, the recommendation is to water it daily. Older bamboo trees could be watered between twice and four times weekly when windy conditions exist. Bamboo does not tolerate soggy soils; thus, watering should leave the soil moist [10].

Bamboo as a Sustainable Building Material

3

Bamboo is harvested between the third and the fifth years of growth. Trees should be cut above the first knot, 0.20 m from the ground. Bamboo trees should be harvested in dry months to avoid frost or drought damage [11]. In bamboo crops, trees are harvested using specialized equipment, and culms with lower moisture content should be harvested in colder and drier weather conditions. This can be achieved by using lighter culms, which facilitate both cutting and transport while protecting the culms from cracking during transportation [12]. When green, bamboo trees lose much water when they are removed from the clump, which can lead the trees to wither and prevent their structural use. Lichens and fungi on the culm surface are signs that it is ready to be cut. Furthermore, less sap circulating through the culms makes them less susceptible to insect and fungal attacks. Saws, chainsaws, and other tools can easily be used to harvest central bamboos, which are probably the oldest trees and, thus, most resistant to pests and decay. However, saws should be used only after removing as much of each branch as possible to avoid chipping or damaging the tree. Treatment and storage operations begin after cutting the bamboo stalks into lengths needed for sale or personal use [13]. Bamboo is often used in some industrial sectors because of its durability, which can last from one to three years without treatment in contact with the ground and from four to six years without treatment and without contact with the ground. However, proper management of culms can ensure greater or better durability for bamboo trees [14].

1.1 Market Despite all possible uses, bamboo does not have a huge trade, due to the misconception about the material, among other reasons, mainly because of ignorance about the benefits and applications of bamboo. In 2020, the consumption of bamboo reached 90 million tons worldwide [15]. In 2019, bamboo exports totaled US$3.054 billion. The main markets of bamboo exports are Asia (81%), Europe (10% or US$297 million), and North America (US$265 million accounting for 9%). China alone represents 67% of all world exports. The same regions are the main import: Europe (33%), North America (32%), and Asia (31%) [16]. The high trade levels of bamboo products in Europe and North America are due to the advanced technologies for bamboo processing in these blocs, despite low or without local production [16].

1.2 Applications In general, bamboo plants can be used from the base to the top. The roots and shoots could be used as a food source and as sculpture crafts, while the bottom,

4

L. H. P. Silva et al.

middle, and top of bamboo trees could be used in crafts, flooring, veneer, mats, plywood, charcoal, and others. Applications of the leaves range from medicinal products to pigmentation and fertilizers, and more recently, leaf ash has been used as supplementary material in cement. Finally, the stick and the leader parts are applied as chopsticks, fiber composites, covering, crafts, and decoration [17]. Figure 1 shows some uses of bamboo plant parts.

Fig. 1 Uses of the bamboo plant parts

Bamboo as a Sustainable Building Material

5

As a renewable energy resource, the value of energy produced from the combustion of Tong bamboo stems is 17,585 kJ/kg, very close to that of palm shells (18,466 kJ/kg); therefore, the biomass of bamboo trees is highly suitable to produce electrical energy with great potential as an alternative to fossil fuels [18]. Furthermore, another study concluded that bamboo has a calorific value comparable to that of wood [19]. As a food resource, bamboo sprouts contain 27% of their edible portion [20]. Bamboo shoots are a source of vitamin B complex, carbohydrates, and proteins, with low fat and calorie content, and their easy availability has aroused the interest of the scientific community [21–23]. In 2017, the international trade of bamboo shoots comprised 19% of total bamboo product exports, including woven, furniture, and industrialized products, among others [16]. Bamboo has been extensively investigated and used in pharmacology and medicine. Recent studies have found that bamboo leaves contain numerous active substances that could be used to treat infections, immune-related maladies, obesityrelated metabolic maladies, and others [24]. For instance, in South Korea, a traditional recipe that combines salt and bamboo (purple bamboo salt) is popularly used in the prevention and treatment of various diseases. Another study has shown the important contribution of purple bamboo salt in the treatment of inflammatory diseases [25]. Another investigation reported the inhibitory activity of bamboo leaf extract solution against the influenza virus (H1N1) and HIV [26]. Furthermore, researchers have investigated the capacity of bamboo leaves ash in the adsorption of textile dyes (methylene blue). The results show that the adsorption of methylene blue reaches 87.79% with a contact time of 20 min [27]. As a building material, bamboo is already well known, and the next topics of this chapter will present an in-depth approach to its possible uses.

2 Applications of Bamboo in Building Materials The construction sector is very important for economies worldwide; however, the sector demands the extraction of large amounts of non-renewable natural resources for the production of construction materials. Bamboo represents an alternative to some of these materials with characteristics similar to traditional ones; besides, bamboo-based materials are biodegradable. This section approaches some applications of bamboo in the civil construction sector. To understand the potential of bamboo as a building material is necessary to comprehend the structure of the bamboo culm. The culm is the above-ground part of the plant composed of nodes and internodes, whose number and spacing vary among species. The nodes are the transverse interconnections of the stem wall with cells oriented radially, while the internodes, which are hollow tubes, are longitudinally oriented [28]. According to Liese [28], a greater fiber concentration occurs on the stem wall’s external face. From a structural viewpoint, the fibers embedded

6

L. H. P. Silva et al.

in the outer wall of the stem provide flexural rigidity, with a purpose analogous to reinforcing steel in concrete. One of the main concerns in the use of natural materials in the construction sector is their durability. In the case of bamboo, the shelf life of untreated and in contact with the ground ranges from one to three years, from four to five years when the materials are not exposed to bad weather, and over 15 years under favorable conditions (internal framing). To increase durability, chemicals such as boron, borax, and boric acid are used to preserve bamboo in large-scale construction projects. Generally, treatments can be carried out in an open tank for cold immersion, modified Boucherie, and pressure treatment against biological attack [17]. In an open tank, the culm is immersed in a preservative solution in water for several days to allow for slow penetration into the bamboo. In the modified Boucherie method, a pressure system connected to one end of the tube is used, axially forcing the preservatives into the stem vessels, leaving the other end, and reducing the treatment time to a few hours. Besides, the solution is recycled. Finally, the pressure method is the most effective; nevertheless, one of the most expensive, requiring specialized equipment (autoclave), and the use of creosote and waterborne preservatives is common. Additional information on preservation methods can be found in the studies of Jayanetti and Follet [29], Janssen [30]. Examples of building applications are shown in Fig. 2 Bamboo allows numerous applications, such as building houses (a) (b), decorative elements and lining (c), mud walls in poorer regions (d), and bamboo flooring (e). Bamboo treated with chemicals or preservatives showed effective durability for up to 40 years [31]. Therefore, bamboo can be an efficient alternative to replace conventional wood and other elements in buildings mainly due to its accelerated growth.

2.1 Bamboo as a Structural Building Material Bamboo is a versatile material with many advantages of its use as a structural material, such as lightweight, sturdy, sustainable, low cost, self-renewing resource, fastgrowing plant, earthquake-resistant, and others [31]. Figure 3 shows some bamboo applications in the structure of schools in rural areas (a) (b) (c) and bridges (d) (e). According to Wanderley et al. [37], there are more than 1200 species of bamboo; however, less than 100 bamboo species have properties for structural application. The most used species are Moso bamboo, Guadua, and Dendrocalamus asper. From a technical perspective, bamboo can reach the maximum structural strength in three years [38]. Some studies have shown that the tensile strength of bamboo can reach 400 MPa, while bamboo fiber has a strength of up to 1000 MPa [39–41]. In general, different types of carbon steel reach between 400 and 1100 MPa of tensile strength. If correctly used, bamboo fibers have a mechanical potential superior to wood and similar to steel, in addition to being a lighter material [42]. Nevertheless, the application of bamboo for structural foundations is restricted due to the accelerated decomposition when in contact with damp soil. This problem

Bamboo as a Sustainable Building Material

7

Fig. 2 Building applications of bamboo: a Wall—Adapted from [32], License CC BY. b Wall and roof structural—Adapted from [33], Public Domain. c Roof lining and light fixture—Adapted from [34], License CC BY. d Wall—Adapted from [35], License CC BY. e Floor—Adapted from [36], License CC BY

Fig. 3 Structural applications of bamboo: a Structure and lining coating—Adapted from [43], License CC BY. b Structure and furniture—Adapted from [44], License CC BY. c Construction structure—Adapted from [45], License CC BY. d Bridge structure—Adapted from [46], License CC BY. e Bridge structure—Adapted from [47], License CC BY

8

L. H. P. Silva et al.

can be partially solved through chemical treatments or with effective preservatives. Some applications have used preformed concrete, concrete columns, or bamboo piles [31]. A widespread application of bamboo that has been replacing wood is its use in trusses/roof structures. The bamboo trusses can be used by bamboo rafters and purlins, providing sturdiness for the structure, besides being lighter and easier to install [31]. There are still few reports on the replacement of steel with bamboo in structural elements. It is known that Portland cement concrete is highly alkali (> 12 pH), which is a suitable characteristic to preserve steel, mitigating the potential effects of its corrosion [48]. In contrast, the high pH of cement affects the cellular structure of lignocellulosic materials, such as wood, bamboo and hemp. [49]. Thus, the use of bamboo in the same way as steel in these situations becomes unfeasible. The studies on durability reported a loss of 50% of the tensile strength of bamboo after one year conditioned in an alkaline medium, and after three years, the loss reached 70% [50]. The hydration of cement results in thermal variation, as lignin is soluble in hot alkaline environments [51]. Alkalinity can be reduced through the use of ternary cement [52] or through carbonation [53], partially mitigating biomass degradation. Therefore, more studies should be carried out on bamboo application as structural reinforcement in concrete.

2.1.1

Mechanical Properties of Bamboo

The physical and mechanical properties of bamboo are influenced by age at harvest, where the optimal age varies among species. The general assumption is after three years. In addition, harvesting at very long ages can result in bamboo with low mechanical strength for application [54]. One factor that must be considered is the moisture content of bamboo, which affects long-term properties. Ahmad and Kamke [55] evaluated the Calcutta bamboo species in terms of the following physical–mechanical parameters: specific gravity of 0.64, bending strength of 137 MPa, modulus of elasticity of 9797 MPa, and tension strength of 156 MPa. The tests showed that the species is lighter and strong, however, with lower mechanical strength compared to steel [55]. CIMOC [56] observed similar characteristics in the Guadua bamboo species, with greater variation in the modulus of elasticity of 21,530 MPa. Studies have compared the mechanical properties between engineered wood and bamboo through glued-laminated wood (glulam) and glued-laminated bamboo (glubam) [57–59]. Glued-laminated wood showed a compressive strength of 26.1 MPa, tensile of 53.0 MPa, and flexural of 42.93 MPa [57], while glued-laminated bamboo demonstrated higher compressive strength results with 51.0 MPa, tension of 82.0 MPa, and flexural of 99.0 MPa [58, 59].

Bamboo as a Sustainable Building Material

9

2.2 Bamboo Fiber Reinforced Composites 2.2.1

Bamboo Scrimber Composites (BSC)

Bamboo scrimber composites (BSC) emerged in the early 1980s to be used as a structural material [60]. BSC can replace traditional wood panels as an alternative to the extraction of hardwoods. As a wooden scrimber, BSC are formed from resinsaturated bamboo fibers, which are compressed, forming a dense and massive block. The literature points to the viability of producing BSC with bamboo species, such as Bambusa chungii [61], Dendrocalamus spp. [62], Phyllostachys heterocycla [63], Neosinocalamus affinis [64], and Bambusa rigida [65]. In the manufacturing process, some natural defects of the raw material, such as joints, anisotropy, irregular thickness, and hollow interior, are removed or distributed equally, showing greater advantages in relation to wood [31, 61, 65]. Due to its mechanical strength, durability, dimensional stability, and coloration similar to hardwood, BSC can be used as a structural element in beams and pillars, external floors, wall fillings with thermal insulation, shear wall panels, and building panels [61, 66]. The rate of swelling of bamboo thickness changes when in contact with water. However, the water absorption resistance of BSC materials increases proportionally to the resin content applied. The flexural strength and modulus of BSC elasticity reach approximately 200 MPa and 22 GPa, respectively [61]. BSC can be used on external floors and buildings due to their low water absorption and mechanical resistance properties with the selection of appropriate processing methods and maximum resin application rates. Studies [15] have investigated the green biocomposite from bamboo and rice straw. Bamboo particles and rice straw were mixed homogeneously at different proportions. Subsequently, the particles were sprayed with modified diphenylmethane diisocyanate (MDI) and lignin-based adhesives. The mixed particles were placed in molds (50 cm2 ) with pressure between 5 and 16 MPa under high temperatures. The internal bond strength reached 0.57 MPa, and after 24 h, it reached a 7% thickness swelling rate. Therefore, the bamboo biocomposite met the requirements of the ISO P-FN MR1 standard for panels in wet conditions [15].

2.2.2

Laminated Bamboo Composites

In 2020, the consumption of bamboo reached 90 million tons worldwide. For each ton of bamboo-based product manufactured, roughly one ton of bamboo residue waste is generated [15]. The use of industrial waste from bamboo processing is only 40%, resulting in 60% of wasted resources with potential use [64]. Laminated bamboo composites consist of bamboo waste mixed with adhesives submitted to hot pressing, resulting in materials for laminates and bamboo fiber panels [64, 67].

10

L. H. P. Silva et al.

Each bamboo species has different characteristics of culm length [68]. The literature reports the fabrication of laminated bamboo composites using bamboo species of Neosinocalamus affinis, Phyllostachys pubescens [69], and Phyllostachys bissetii [70]. Bamboo species with shorter internode lengths are preferred when the culms are used as structural applications [68]. Laminated bamboo behaves as a fiber reinforced composite, presenting a uniform elastic modulus [71]. The improvement of physical and mechanical characteristics can be achieved through the surface abrasion process [70]. Superficial abrasion cleans residues from surfaces, removing suberized and siliceous cells, as well as waxes and silicones deposited on bamboo. Consequently, the increase of roughness favors the impregnation of resins on the surface, increasing the average modulus of rupture, elasticity modulus, and compressive strength of laminated bamboo composites.

2.2.3

Geopolymer-Bamboo Composite

Geopolymers are inorganic, polymeric materials that harden in an alkaline solution due to the polymerization process. They are obtained from the polycondensation of aluminosilicate solids, activated by an alkaline aqueous solution [72]. These reactions produce polysilicoaluminates or polysialates, resulting in geopolymers or inorganic polymers [73]. They are used as additives in cementitious composites, in fire-resistant plastics, coatings, and adhesives, and in high-temperature ceramics. The metakaolin-based geopolymers used as a structural material have advantages compared to ordinary Portland cement. They have higher compressive and flexural strength, accelerated setting time, and rapid development of strength at early ages [74], as well as lower carbon dioxide (CO2 ) emissions in manufacturing and temperature resistance, compared to conventional composites [75, 76]. Geopolymers in traditional composition are fragile and have low fracture toughness and tensile strength [72]. Thus, as in common Portland cement, additives are used to form a composite material with better fracture toughness and tensile strength properties [72]. An alternative to optimize these properties was proposed by Sá Ribeiro et al. [72] using mixed potassium-sodium polysialate geopolymer reinforced with fibers and bamboo strips. The geopolymer was synthesized at 700 °C using highly reactive metakaolin produced from kaolinite. Mechanical strength tests were performed on geopolymer composites reinforced with bamboo fibers, reaching values from 23 to 38 MPa for compression and from 21 to 30 MPa for flexural strength. Therefore, the addition of bamboo fibers provides tenacity properties, in addition to constituting a sustainable alternative to applying bamboo fibers.

2.2.4

Bamboo Fiber (BF) as a Reinforcing Agent in Cement

The search for more sustainable building materials relates to the search for composites that use fibers of organic origin in their composition [77]. In recent years, bamboo fiber (BF) has been used as a reinforcing material due to its greater fracture toughness,

Bamboo as a Sustainable Building Material

11

greater flexural strength, reduced material mass due to its high strength/weight ratio, low cost, and brief regenerative growth cycle [31, 78]. Bamboo fibers usually have a porous structure of parenchymal cells with vascular bundles coming from the plant. The hollow structure confirms the literary values for the apparent density and high water absorption potential of bamboo fibers [79]. Currently, software, such as the Aggregate Image Equipment Measurement System (AIMS), provides the measurement of different parameters of bamboo fibers, such as sphericity, surface texture, the flatness/elongation ratio, 2D shape, and angularity index data [79]. Li et al. studied bamboo fibers of 149 µm treated with a solution of sodium hydroxide (NaOH) for application as reinforcement in prefabricated cementitious composites [78]. The treatment of 10% alkaline increased BF surface area and thermal stability, which is explained by removing lignin and hemicellulose from the fibers. Compared to the composite without addition, the composite with the addition of 0.5% alkali-treated BF presented increased toughness and reduced elasticity modulus. The addition of 0.7% of alkali-treated BF provided an increase in flexural strength, but reduced compressive strength in composites. The improvement of cement composites containing alkali-treated BF may be related to the physical characteristics of the treated fiber, better dispersion of finer particles, better interfacial adhesion, and denser microstructure (less porosity) [78]. Some factors can directly influence the physical and mechanical properties of cement matrix composites with bamboo fibers. Examples of these factors are fiber characteristics, adhesion with the matrix, and detachment caused by the dilation process of fibers by H2 O [77, 80], progressive alkaline hydrolysis by degrading amorphous zones of fibers (hemicellulose and lignin) [77], fiber mineralization by the deposition of cement hydration products (calcium hydroxide), admixture, homogenization, molding, and curing. One of the challenges is to obtain compatibility between fibers and cement matrix, requiring a mechanical interlock or anchorage between the fiber surface and cement hydration products [78]. Among the physical–chemical pretreatments used in the fibers, the literature reports that the alkaline treatment presents greater economy in the process, as it only removes impurities from the fiber surface, making it rougher and improving its adhesion to the matrix [78].

2.3 Bamboo Leaf Ash as Supplementary Cementitious Material The use of ash as supplementary cementitious material was described for the first time by the architect and engineer Marcus Vitruvius Pollio in the first century BC [81]. Pozzolan is the generic name for ash. The term originates from the ash of the Vesuvius volcano eruption in Pozzuoli, an Italian municipality [82]. In that period,

12

L. H. P. Silva et al.

lime-based binders were used, and the inclusion of ash provided better properties that led Vitruvius to recommend ash use in constructions that were in contact with seawater [82]. Pozzolans are substances of siliceous or silico-aluminous composition or a combination of both; therefore, when finely ground and in the presence of water, pozzolans react at normal ambient temperature with dissolved calcium hydroxide (Ca(OH)2 ) to form strength compounds [83]. Ca(OH)2 is obtained as one of the hydration products formed during the hydration of Portland cement, and the reaction with pozzolanic materials containing amorphous silica gives additional amounts of calcium silicate hydrate (C–S–H). Currently, the use of composite cement with different types of pozzolans is a common practice worldwide, and pozzolan use has been standardized in some regions. In Europe, the regulation BS EN 197–1 guides the addition of up to 55% of pozzolanic materials in cement type CEM IV/B [83]. In Brazil, this value is 50% for type III types of cement [84]. The use of pozzolanic ash today is driven by environmental advantages in addition to technical advances, as described previously. For the environment, the use of pozzolans saves natural resources and energy, besides cost reductions and the production of low-CO2 binders. Blast furnace slag is the most common material used to replace cement; however, even if all blast furnace slags were used for the production of sustainable cement, the available volume would be insufficient to meet world demand. Thus, it is necessary to investigate other products with the potential to replace cement. Some agro-industrial residues have been used in the search for supplementary cementitious materials that can partially replace cement, including fly ash [85], rice husk ash [86], sugarcane bagasse ash [87], and more recently bamboo leaf ash (BLA) [88]. Studies investigating BLA as a pozzolanic material began in 2006 [89]. At that time, the authors calcined the bamboo leaves at 600 °C for 2 h and investigated the material chemical composition. For the chemical composition of pozzolanic materials, the amount of SiO2 + Al2 O3 + Fe2 O3 should be greater than 70% [90, 91], and BLA investigated showed an amount of 81.25% wt. The chemical constituent (wt%) of different waste materials reported in studies published in the last 5 years was analyzed by Paiva et al., and BLA presented an amount of SiO2 higher than 70% in all studies [92]. Roselló et al. investigated the structure of plants that influences their chemical composition by performing a microscopy characterization of phytoliths (cells responsible for silica reserves in plants) and observed different types of those cells [93]. Later, many other studies were carried out to investigate the potential of BLA use. Calcination temperature is an important parameter in producing more reactive materials. The proper temperature produces materials with an amorphous structure, characterized by the presence of a halo in the X-ray diffraction pattern. The structure of cells calcined between 350 °C and 850 °C was investigated, and it was observed that the form is maintained within this temperature range [93]. Cociña et al. investigated ashes calcined under controlled conditions (500, 600, 700 °C and 2 h retention time)

Bamboo as a Sustainable Building Material

13

and observed that, at 500 °C, ashes are produced with a reactivity slightly higher than that of the ash calcined at 600 °C [94]. Some authors compared BLA with other wastes. Rodier et al. [95] performed comparative tests between BLA and sugarcane bagasse ash (SCBA). The pozzolanic activity was investigated using electrical conductivity measurements, and the greater the change in the electrical conductivity, the higher the pozzolanic activity of the material. In the ten initial hours, fixation of calcium hydroxide (Ca(OH)2 ) is higher for BLA, and the author concluded that the degree of amorficity of the material and the amount of reactive SiO2 is a determinant factor in pozzolanicity. Villar-Cociña et al. [96] used the same method and materials and observed high BLA reactivity from the qualitative viewpoint, which is comparable to silica fume. Another study compared the pozzolanic activity in BLA and silica fume (SF) (the most effective siliceous product among the pozzolanic materials) [97]. The authors observed a greater reactivity qualitatively for BLA; however, quantitatively, it was evident that SF consumes more calcium hydroxide (CH) than BLA. Other studies investigated the use of ash as a soil stabilizer. The tests were performed in soils by adding varying amounts of BLA. The addition of 2, 4, 5, 6, and 8% of BLA showed that the optimum combination was observed at 6–7% of BLA [98]. For the same purpose, other authors tested soil by adding 0, 5, and 10% of BLA, and the best results were obtained with the mix of 5% of BLA [99]. The bamboo used as a partial cement substitute is the main application for bamboo ash and shows favorable results in composites, such as concretes and mortars. Some authors applied large amounts of cement replacement (up to 30% wt.) in composites and obtained good mechanical strength results [88, 100]. Silva et al. reported that the compressive strength of mortars reduced by less than 5% in comparison with the control, even with 30% cement replacement at 28 curing days [88]. At 90 curing days, Silva et al. and Moares et al. described compressive strength higher than the control highlighting the use of bamboo ash as a good alternative to cement replacement [88, 100]. Bamboo leaves are a good option as biomass for energy production, and leaf calcination produces ash, representing a good alternative to save energy and carbon dioxide emission when used in cement replacement. Moreover, using ashes as partial cement replacement can reduce cement costs in the construction industry [95].

3 Remarkable Buildings with Bamboo 3.1 International Airport of Madrid-Barajas Terminal T4 at Madrid-Barajas Airport (Fig. 4), designed by Estudio Lamela, Rogers Stirk Harbour & Partners, is a well-known example of the use of bamboo for ceiling and shed roofs. The site saves energy with bioclimatic strategies, which include an extensive 200,000 m2 bamboo ceiling on the external and internal facades. Along

14

L. H. P. Silva et al.

Fig. 4 Madrid-Barajas Airport: a Adapted from [103], License CC BY, and b Adapted from [104], License CC BY

the entire passenger area coverage, overlapping bamboo slats of different sizes were used, all treated against fire, forming the famous undulating roof [101]. In addition to the esthetic beauty that this material promotes, the application of bamboo finishing at the airport is interesting because it reminds the traveler of simplicity, generating an impression of a cozy and calm environment [102].

3.2 Sports Hall of Panyaden International School Another example is the Sports Hall of Panyaden International School, designed by Chiangmai Life Construction (Fig. 5) in the city of Chiang Mai in Northern Thailand. A zero-carbon sports building, built using only bamboo in line with the Panyaden mission for “Green School” [105]. The hall has an organic design structure composed of ten bamboo trusses spanning more than 17 m, without steel reinforcements or connections. Covering an area of 782 m2 , with a capacity for 300 people and comprising futsal, basketball, volleyball, and badminton courts, as well as a stage for concerts [106].

Fig. 5 Panyaden International School: a Adapted from [107], License CC BY, and b Adapted from [108], License CC BY

Bamboo as a Sustainable Building Material

15

The building is designed to safely support local high-speed winds, earthquakes, and all other natural forces. In addition, the bamboo structure is left exposed throughout the interior, creating arched openings around the edge of the hall, with a sustainable design strategically made to promote a cool and pleasant climate all year through natural ventilation and isolation [106]. Furthermore, the bamboo was selected and treated with borax (sodium borate), and no toxic chemicals were involved in the treatment process. Moreover, as the bamboo used in the construction absorbed a greater amount of carbon than the carbon emitted during treatment, transport, and construction, the life expectancy of this bamboo hall is at least 50 years, considered a zero-carbon building [106].

3.3 Modern Education and Training Institute—METI Handmade School Located in a village called Rudrapur, in the Dinajpur District, Northern Bangladesh, the Modern Education and Training Institute (METI, Fig. 6) was hand built in four months by local artisans, students, and teachers using natural resources available in the region. It has a built area of 325 m2 and was designed by the Austrian architect Anna Heringer and the German architect Eike Roswag-Klinge, earning them the Aga Khan Award for Architecture in 2007 [111]. Bangladesh is a small country, with only approximately 15 million hectares of land, however, with a population of close to 150 million people [109]. Consequently, feeding and providing education to all these citizens while protecting the environment become a delicate task. Therefore, this is precisely the fundamental objective of METI: to improve the quality of life of residents using principles of sustainability, offering reception and assistance for insertion into the job market. Regarding the building structure, its foundation is made of masonry bricks, and it is divided into two floors. The ground floor walls were made using an adapted technique called “Wellerbau”, which consists of rammed straw-reinforced mud walls

Fig. 6 METI Handmade School: a Adapted from [109], License CC BY, and b Adapted from [110], License CC BY

16

L. H. P. Silva et al.

finished with battered mud. The ceiling consists of a triple layer of bamboo sticks connected with supporting beams using steel pins fixed with nylon lashings. The roof of the second floor uses slatted bamboo for the walls, windows, and doors. Finally, its ceiling is finished with sheets of corrugated galvanized iron [112].

3.4 German-Chinese House The German-Chinese House (Fig. 7) is a structure conceived by the German designer Markus Heinsdorff with the support of German structural engineer Schlaich Bergermann and partners. The construction was representative of the “Goethe-Institute” at the EXPO 2010 in Shanghai [114]. Aa a meeting point between two cultures, the German-Chinese House brings in its project architectural references and constructive technologies from both countries that it bears in its name. The ceiling adopted, made with a PVC membrane capable of blocking direct sunlight but also ensuring adequate lighting, is a tribute to the Asian art of paper-folding Origami [115]. The idea of the project was to use a simple and ancient material, bamboo, in a modern and effective way, bringing a concept of contemporary sustainability. The “giant bamboo” type was adopted. For the connections between bamboo sticks, it was used threaded bolts and stainless steel flange fittings cemented into the ends with up to 4.3 m long. The building has two floors. The upper floor is 4 m high and can be accessed by a steel staircase [115].

Fig. 7 Exterior view of the pavilion “German-Chinese House” from [113], License CC BY

Bamboo as a Sustainable Building Material

17

4 Conclusion In this chapter, a brief review of the global distribution of bamboo, we present bamboo applications and markets and an in-depth analysis of its uses in building materials. The following conclusions can be stated: • As a structural building material, bamboo presents characteristics similar to wood in applications in trusses/roof structures. Furthermore, the good mechanical properties, such as flexural rigidity, enable bamboo use similar to steel in concrete reinforcement. • Products using bamboo fiber reinforced composites have shown excellent results, such as scrimber, laminated, and geopolymer composites. The results with bamboo scrimber show that it can be applied to structural elements, floors, shear walls, etc. • Bamboo leaf ash (BLA) used as a partial cement substitute has shown good mechanical results in replacements up to 30%. Another BLA use is as a soil stabilizer, enhancing the strength and bearing capacity of soil. • Some remarkable bamboo constructions demonstrate the viability of using bamboo in constructions with sustainable materials, resulting in beautiful and functional places. Acknowledgements The authors are grateful to Coordination for the Improvement of Higher Education Personnel (CAPES), Brazil, Finance Code 00 and National Council for Scientific and Technological Development (CNPq grant 309186/2020–0).

References 1. Kleinhenz V, Midmore DJ (2001) Aspects of bamboo agronomy, pp 99–153 2. Tewari DN (1993) A monograph on bamboo. International Book Distributors Dehra Dun India, India 3. Food and Agriculture Organization of the United Nations (2010) Global forest resource assessment 2010. Italy, Rome 4. Medeiros H, Castro W, Salimon CI et al (2013) Tree mortality, recruitment and growth in a bamboo dominated forest fragment in southwestern Amazonia, Brazil. Biota Neotrop 13:29– 34. https://doi.org/10.1590/S1676-06032013000200002 5. Shirin F, Mishra JP, Bhadrawale D et al (2021) Seasonal and hormonal variation during adventitious rhizogenesis in five commercially important bamboo species for production of quality planting material. J For Res 26:377–385. https://doi.org/10.1080/13416979.2021.193 5548 6. Dembitsky VM, Poovarodom S, Leontowicz H et al (2011) The multiple nutrition properties of some exotic fruits: biological activity and active metabolites. Food Res Int 44:1671–1701. https://doi.org/10.1016/j.foodres.2011.03.003 7. Gulabrao YA, Kaushal R, Tewari SK et al (2012) Seasonal effect on rooting behaviour of important bamboo species by culm cuttings. J For Res 23:441–445. https://doi.org/10.1007/ s11676-012-0282-0

18

L. H. P. Silva et al.

8. Zhou G-M, Xu J-M, Jiang P-K (2006) Effect of management practices on seasonal dynamics of organic carbon in soils under bamboo plantations. Pedosphere 16:525–531. https://doi.org/ 10.1016/S1002-0160(06)60084-2 9. Ben-zhi Z, Mao-yi F, Jin-zhong X et al (2005) Ecological functions of bamboo forest: research and application. J For Res 16:143–147. https://doi.org/10.1007/BF02857909 10. Isagi Y, Shimada K, Kushima H et al (2004) Clonal structure and flowering traits of a bamboo [Phyllostachys pubescens (Mazel) Ohwi] stand grown from a simultaneous flowering as revealed by AFLP analysis. Mol Ecol 13:2017–2021. https://doi.org/10.1111/j.1365-294X. 2004.02197.x 11. Zhang D, Zhang A, Xue L (2015) A review of preparation of binderless fiberboards and its self-bonding mechanism. Wood Sci Technol 49:661–679. https://doi.org/10.1007/s00226015-0728-6 12. Pandey AK, Ojha V (2013) Standardization of harvesting age of bamboo shoots with respect to nutritional and anti-nutritional components. J For Res 24:83–90. https://doi.org/10.1007/ s11676-012-0317-6 13. Hong M, Wei W, Yang Z et al (2016) Effects of timber harvesting on Arundinaria spanostachya bamboo and feeding-site selection by giant pandas in Liziping Nature Reserve, China. For Ecol Manage 373:74–80. https://doi.org/10.1016/j.foreco.2016.04.039 14. Lima HC, Willrich FL, Barbosa NP et al (2008) Durability analysis of bamboo as concrete reinforcement. Mater Struct 41:981–989. https://doi.org/10.1617/s11527-007-9299-9 15. Pang B, Zhou T, Cao XF et al (2022) Performance and environmental implication assessments of green bio-composite from rice straw and bamboo. J Clean Prod 375:134037. https://doi. org/10.1016/j.jclepro.2022.134037 16. INBAR (2019) Trade overview 2019: bamboo and rattan commodities in the international market. Beijing 17. Correal FF (2020) Bamboo design and construction. In: Kent A, Harries BS (ed) Nonconventional and vernacular construction materials (second edition). Woodhead Publishing Series in Civil and Structural Engineering, pp 521–559 18. Wahono J, Sumarwan U, Arifin B, Purnomo H (2021) Renewable energy development of sustainable bamboo forest based on community empowerment. J Apl Bisnis dan Manaj. https://doi.org/10.17358/jabm.7.1.188 19. Purbasari A, Samadhi TW, Bindar Y (2016) Thermal and ash characterization of Indonesian bamboo and its potential for solid fuel and waste valorization. Int J Renew Energy Dev 5:95–100. https://doi.org/10.14710/ijred.5.2.95-100 20. Satya S, Bal LM, Singhal P, Naik SN (2010) Bamboo shoot processing: food quality and safety aspect (a review). Trends Food Sci Technol 21:181–189. https://doi.org/10.1016/j.tifs. 2009.11.002 21. Bal LM, Singhal P, Satya S et al (2012) Bamboo shoot preservation for enhancing its business potential and local economy: a review. Crit Rev Food Sci Nutr 52:804–814. https://doi.org/ 10.1080/10408398.2010.511321 22. Tripathi YC (1998) Food and nutrition potential of bamboos. MFP News 8:10–11 23. Rusch F, Araujo VA de, Morales EAM et al (2022) Potential of young bamboos for food industry: production of ingredients from the use of their culms and shoots. Res Soc Dev 11:e55011627967. https://doi.org/10.33448/rsd-v11i6.27967 24. Kimura I, Kagawa S, Tsuneki H et al (2022) Multitasking bamboo leaf-derived compounds in prevention of infectious, inflammatory, atherosclerotic, metabolic, and neuropsychiatric diseases. Pharmacol Ther 235:108159. https://doi.org/10.1016/j.pharmthera.2022.108159 25. Shin H, Lee E, Kim C et al (2003) Anti-inflammatory activity of korean folk medicine purple bamboo salt. Immunopharmacol Immunotoxicol 25:377–384. https://doi.org/10.1081/IPH120024505 26. Ito A, Tsuneki A, Yoshida Y et al (2016) In vitro inhibition of cytopathic effect of influenza virus and human immunodeficiency virus by bamboo leaf extract solution and sodium copper chlorophyllin. Yonago Acta Med 59:61–65

Bamboo as a Sustainable Building Material

19

27. Kuntari K, Fajarwati FI (2018) Utilization of bamboo leaves wastes for methylene blue dye adsorption, p 020062 28. Liese W (1985) Bamboo—biology, silvics, properties, utilization. deustche gesellschaft fur technische zusammenarbeit. German Agency for Technical Cooperation 29. Jayanetti DL, Follet PR (1998) Bamboo in construction: an introduction, INBAR Tech 30. Janssen JJA (2000) Designing and building with bamboo. INBAR Technical Report No. 20 International Network for Bamboo and Rattan 31. Yadav M, Mathur A (2021) Bamboo as a sustainable material in the construction industry: an overview. Mater Today Proc 43:2872–2876. https://doi.org/10.1016/j.matpr.2021.01.125 32. Inhabitat (2010) Sunshine in/bamboo house. Tongji University Shanghai. https://www.flickr. com/photos/inhabitat/4722493883. Accessed 1 Oct 2022 33. Samaniego A (2018) Bamboo cabin. https://pxhere.com/en/photo/1458465. Accessed 1 Oct 2022 34. Verch M (2020) Bamboo baskets with light bulbs as ceiling lamps and decoration in a restaurant in Ho Chi Minh City, Vietnam. https://www.flickr.com/photos/30478819@N08/505974 32632. Accessed 1 Oct 2022 35. Tennen-Gas (2008) Japanese traditional style bamboo reinforced mud wall. https:// commons.wikimedia.org/wiki/File:Japanese_Bamboo_reinforced_mud_wall.JPG. Accessed 1 Oct 2022 36. Pbroks13 (2007) Bamboo flooring. https://commons.wikimedia.org/wiki/File:Bamboo_Flo oring.jpg. Accessed 1 Oct 2022 37. Wanderley M das GL, Sheperd GJ, Giulietti AM (2001) Flora fanerogâmica do estado de São Paulo. Editora Hucitec, São Paulo 38. Escamilla EZ, Habert G (2015) Regionalizing the environmental impact of bamboo-based buildings by integrating life cycle assessment with geographic information systems: a comparative case-study in Colombia. 10th World Bamboo Congr Korea 2015, pp 17–22 39. Akwada DR, Akinlabi ET (2015) Bamboo use in construction industry: How sustainable is it? 40. Osorio L, Trujillo E, Van Vuure AW, Verpoest I (2011) Morphological aspects and mechanical properties of single bamboo fibers and flexural characterization of bamboo/epoxy composites. J Reinf Plast Compos 30:396–408. https://doi.org/10.1177/0731684410397683 41. Wang F, Shao J, Keer LM et al (2015) The effect of elementary fibre variability on bamboo fibre strength. Mater Des 75:136–142. https://doi.org/10.1016/j.matdes.2015.03.019 42. Mofidi A, Abila J, Ng JTM (2020) Novel advanced composite bamboo structural members with bio-based and synthetic matrices for sustainable construction. Sustainability 12:2485. https://doi.org/10.3390/su12062485 43. Cosi AS (2017) Panyaden’s eco-friendly assembly hall and indoor sports hall. https://www.pan yaden.ac.th/2017/07/10/panyaden-eco-friendly-assembly-hall-indoor-sports-hall/. Accessed 1 Oct 2022 44. Forgemind ArchiMedia (2010) Bambu—Ibuku Green School 08. https://www.flickr.com/pho tos/eager/15946400596/. Accessed 1 Oct 2022 45. Forgemind ArchiMedia (2008) Bambu—Ibuku Green School 06. https://www.flickr.com/pho tos/eager/15784872838/in/photostream/. Accessed 1 Oct 2022 46. Forgemind ArchiMedia (2007) Bambu—Ibuku Green School 05. https://www.flickr.com/pho tos/eager/15786539457/in/photostream/. Accessed 1 Oct 2022 47. Wu L (2010) The bamboo bridge in Crosswaters Ecolodge & SPA. https://www.flickr.com/ photos/13523064@N03/5371912960. Accessed 1 Oct 2022 48. Behnood A, Van Tittelboom K, De Belie N (2016) Methods for measuring pH in concrete: a review. Constr Build Mater 105:176–188. https://doi.org/10.1016/j.conbuildmat.2015.12.032 49. Pickering KL, Efendy MGA, Le TM (2016) A review of recent developments in natural fibre composites and their mechanical performance. Compos Part A Appl Sci Manuf 83:98–112. https://doi.org/10.1016/j.compositesa.2015.08.038 50. Hosoda K (1942) Bamboo reinforced concrete. Syukyosya Syoin, Japan 51. Gram H (1983) Durability of natural fibres in concrete. Stockolm

20

L. H. P. Silva et al.

52. John VM, Cincotto MA, Sjöström C et al (2005) Durability of slag mortar reinforced with coconut fibre. Cem Concr Compos 27:565–574. https://doi.org/10.1016/j.cemconcomp.2004. 09.007 53. Tonoli GHD, Santos SF, Joaquim AP, Savastano H (2010) Effect of accelerated carbonation on cementitious roofing tiles reinforced with lignocellulosic fibre. Constr Build Mater 24:193– 201. https://doi.org/10.1016/j.conbuildmat.2007.11.018 54. Correal JF, Echeverry JS, Arbeláez J (2010) Evaluación del comportamiento sísmico de estructuras de Guadua rolliza. In: XXXVI Jornadas Sudamericanas de Ingeniería Estructural. Montevideo, Uruguay, pp 19–21 55. Ahmad M, Kamke FA (2005) Analysis of Calcutta bamboo for structural composite materials: physical and mechanical properties. Wood Sci Technol 39:448–459. https://doi.org/10.1007/ s00226-005-0016-y 56. CIMOC (2011) Validación Tecnológica del Comportamiento de Estructuras de Guadua Rolliza Seca e Inmunizada. Bogotá, Colombia 57. Yang H, Liu W, Lu W et al (2016) Flexural behavior of FRP and steel reinforced glulam beams: experimental and theoretical evaluation. Constr Build Mater 106:550–563. https:// doi.org/10.1016/j.conbuildmat.2015.12.135 58. Xiao Y, Yang RZ, Shan B (2013) Production, environmental impact and mechanical properties of glubam. Constr Build Mater 44:765–773. https://doi.org/10.1016/j.conbuildmat.2013. 03.087 59. Wang R, Xiao Y, Li Z (2017) Lateral loading performance of lightweight glubam shear walls. J Struct Eng 143. https://doi.org/10.1061/(ASCE)ST.1943-541X.0001751 60. Sun X, He M, Li Z (2020) Novel engineered wood and bamboo composites for structural applications: state-of-art of manufacturing technology and mechanical performance evaluation. Constr Build Mater 249:118751. https://doi.org/10.1016/j.conbuildmat.2020.118751 61. Rao F, Zhu X, Zhang Y et al (2022) Water resistance and mechanical properties of bamboo scrimber composite made from different units of Bambusa chungii as a function of resin content. Constr Build Mater 335:127250. https://doi.org/10.1016/j.conbuildmat.2022.127250 62. Gauss C, Kadivar M, Savastano H (2019) Effect of disodium octaborate tetrahydrate on the mechanical properties of Dendrocalamus asper bamboo treated by vacuum/pressure method. J Wood Sci 65. https://doi.org/10.1186/s10086-019-1804-6 63. Qi J, Xie J, Yu W, Chen S (2015) Effects of characteristic inhomogeneity of bamboo culm nodes on mechanical properties of bamboo fiber reinforced composite. J For Res 26:1057– 1060. https://doi.org/10.1007/s11676-015-0106-0 64. Zheng L, Wu Y, Li P et al (2021) Construction of crystallization nucleation and network crosslinking structure in bamboo scrap/magnesium oxychloride composites via nano-SiO2. J Mater Res Technol 15:5496–5506. https://doi.org/10.1016/j.jmrt.2021.11.041 65. Huang X, Xie J, Qi J et al (2018) Differences in physical–mechanical properties of bamboo scrimbers with response to bamboo maturing process. Eur J Wood Wood Prod 76:1137–1143. https://doi.org/10.1007/s00107-018-1293-0 66. Huang Y, Ji Y, Yu W (2019) Development of bamboo scrimber: a literature review. J Wood Sci 65. https://doi.org/10.1186/s10086-019-1806-4 67. Tang G, Zhang Z, Sun P, Jiang T (2020) Experimental research on basical mechanical properties of bamboo plywood. J Phys Conf Ser 1637. https://doi.org/10.1088/1742-6596/1637/ 1/012043 68. Chaowana K, Wisadsatorn S, Chaowana P (2021) Bamboo as a sustainable building material— culm characteristics and properties. Sustain 13. https://doi.org/10.3390/su13137376 69. Chow A, Ramage MH, Shah DU (2019) Optimising ply orientation in structural laminated bamboo. Constr Build Mater 212:541–548. https://doi.org/10.1016/j.conbuildmat.2019. 04.025 70. Tang K, Jiang Y, Chen L et al (2022) Fabrication of laminated bamboo composites from small diameter bamboo (Neosinocalamus affinis) by sand blasting surface modification. Ind Crops Prod 187:115377. https://doi.org/10.1016/j.indcrop.2022.115377

Bamboo as a Sustainable Building Material

21

71. Penellum M, Sharma B, Shah DU et al (2018) Relationship of structure and stiffness in laminated bamboo composites. Constr Build Mater 165:241–246. https://doi.org/10.1016/j. conbuildmat.2017.12.166 72. Sá Ribeiro RA, Sá Ribeiro MG, Sankar K, Kriven WM (2016) Geopolymer-bamboo composite—a novel sustainable construction material. Constr Build Mater 123:501–507. https://doi.org/10.1016/j.conbuildmat.2016.07.037 73. Davidovits J (1991) Geopolymers: inorganic polymeric new materials. J Therm Anal Calorim 37:1633–1656 74. Kriven WM (2010) Inorganic polysialates or “geopolymers”. Am Ceram Soc Bull 89:31–31 75. Ishak S et al (2019) Performance of fly ash geopolymer concrete incorporating bamboo ash at elevated temperature. Materials (Basel) 12:3404. https://doi.org/10.3390/ma12203404 76. Wang Y, Shao Y, Matovic MD, Whalen JK (2016) Recycling combustion ash for sustainable cement production: a critical review with data-mining and time-series predictive models. Constr Build Mater 123:673–689. https://doi.org/10.1016/j.conbuildmat.2016.07.031 77. Camargo M, Adefrs Taye E, Roether J et al (2020) A Review on natural fiber-reinforced geopolymer and cement-based composites. Materials (Basel) 13:4603. https://doi.org/10. 3390/ma13204603 78. Li M, Zhou S, Guo X (2017) Effects of alkali-treated bamboo fibers on the morphology and mechanical properties of oil well cement. Constr Build Mater 150:619–625. https://doi.org/ 10.1016/j.conbuildmat.2017.05.215 79. de Paiva RLM, Caldas LR, de Martins APS et al (2021) Thermal-Energy analysis and life cycle GHG emissions assessments of innovative earth-based bamboo plastering mortars. Sustainability 13:10429. https://doi.org/10.3390/su131810429 80. Tian F, Zhong Z, Pan Y (2018) Modeling of natural fiber reinforced composites under hygrothermal ageing. Compos Struct 200:144–152. https://doi.org/10.1016/j.compstruct. 2018.05.083 81. Maciel (transl) MJ (2009) Vitruvius, De Architectura, 3rd ed. IST Press 82. Siddall R (2000) The use of volcaniclastic material in Roman hydraulic concretes: a brief review. Geol Soc London, Spec Publ 171:339–344. https://doi.org/10.1144/GSL.SP.2000. 171.01.24 83. European Committee for Standardization (2011) BS EN 197-1: cement. Part 1: composition, specifications and conformity criteria for common cements. BSI 84. ABNT (2018) NBR 16697: cimento Portland—Requisítos. Associação Brasileira de Normas Técnicas, Rio de Janeiro 85. Tam VWY, Le KN, Evangelista ACJ et al (2019) Effect of fly ash and slag on concrete: properties and emission analyses. Front Eng Manag 6:395–405. https://doi.org/10.1007/s42 524-019-0019-2 86. Thomas BS (2018) Green concrete partially comprised of rice husk ash as a supplementary cementitious material—a comprehensive review. Renew Sustain Energy Rev 82:3913–3923. https://doi.org/10.1016/j.rser.2017.10.081 87. Singh NB, Singh VD, Rai S (2000) Hydration of bagasse ash-blended portland cement. Cem Concr Res 30:1485–1488. https://doi.org/10.1016/S0008-8846(00)00324-0 88. Silva LHP, Tamashiro JR, Guedes de Paiva FF et al (2021) Bamboo leaf ash for use as mineral addition with Portland cement. J Build Eng 42:102769. https://doi.org/10.1016/j.jobe.2021. 102769 89. Dwivedi VN, Singh NP, Das SS, Singh NB (2006) A new pozzolanic material for cement industry: bamboo leaf ash. Int J Phys Sci 1:106–111 90. ABNT (2015) NBR 12653: pozzolanic material—requirements. Associação Brasileira de Normas Técnicas, Rio de Janeiro 91. ASTM (2019) ASTM C618-19, Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete. ASTM International, West Conshohocken, PA 92. Paiva F, Tamashiro JR, Silva LHP, Kinoshita A (2021) Utilization of inorganic solid wastes in cementitious materials—a systematic literature review. Constr Build Mater 285:1–14. https:// doi.org/10.1016/j.conbuildmat.2021.122833

22

L. H. P. Silva et al.

93. Roselló J, Soriano L, Santamarina MP et al (2015) Microscopy characterization of silica-rich agrowastes to be used in cement binders: bamboo and sugarcane leaves. Microsc Microanal 21:1314–1326. https://doi.org/10.1017/S1431927615015019 94. Villar Cociña E, Savastano H, Rodier L et al (2016) Pozzolanic characterization of cuban bamboo leaf ash: calcining temperature and kinetic parameters. Waste Biomass Valorization 9:691–699. https://doi.org/10.1007/s12649-016-9741-8 95. Rodier L, Villar-Cociña E, Ballesteros JM, Junior HS (2019) Potential use of sugarcane bagasse and bamboo leaf ashes for elaboration of green cementitious materials. J Clean Prod 231:54–63. https://doi.org/10.1016/j.jclepro.2019.05.208 96. Villar-Cociña E, Frías M, Savastano H et al (2021) Quantitative comparison of binary mix of agro-industrial pozzolanic additions for elaborating ternary cements: kinetic parameters. Materials (Basel) 14:2944. https://doi.org/10.3390/ma14112944 97. Villar-Cociña E, Rodier L, Savastano H et al (2019) A comparative study on the pozzolanic activity between bamboo leaves ash and silica fume: kinetic parameters. Waste Biomass Valorization 0:0. https://doi.org/10.1007/s12649-018-00556-y 98. Inim IJ, Affiah UE, Eminue OO (2018) Assessment of bamboo leaf ash/lime-stabilized lateritic soils as construction materials. Innov Infrastruct Solut 3:32. https://doi.org/10.1007/s41062018-0134-7 99. Rahman ASA, Jais IBM, Sidek N et al (2018) Bamboo leaf ash as the stabilizer for soft soil treatment. IOP Conf Ser Earth Environ Sci 140:012068. https://doi.org/10.1088/1755-1315/ 140/1/012068 100. Moraes MJBJB, Moraes JCBCB, Tashima MMM et al (2019) Production of bamboo leaf ash by auto-combustion for pozzolanic and sustainable use in cementitious matrices. Constr Build Mater 208:369–380. https://doi.org/10.1016/j.conbuildmat.2019.03.007 101. Kaur N, Saxena S, Gaur H, Goyal P (2017) A review on bamboo fiber composites and its applications. In: 2017 international conference on infocom technologies and unmanned systems (trends and future directions) (ICTUS). IEEE, pp 843–849 102. Tatematsu BK (2016) Architectural similarities between the structure of adolfo suárez madrid– barajas airport and actin filaments with binding proteins. Wheat J Cell Biol Res 1–10 103. Roletschek R (2017) Flughafen madrid-barajas, eingangsbereich, links die sicherheitskontrolle. https://commons.wikimedia.org/wiki/File:17-12-14-Flughafen-Madrid-BarajasRalfR-DSCF1008.jpg. Accessed 1 Oct 2022 104. Delso D (2013) Terminal 4 del aeropuerto de Madrid-Barajas, España. https://commons.wik imedia.org/wiki/File:Terminal_4_del_aeropuerto_de_Madrid-Barajas,_España,_2013-0109,_DD_05.jpg. Accessed 1 Oct 2022 105. Xiao Y, Li Z, Liu KW (2019) Modern engineered bamboo structures. CRC Press 106. Orhon AV, Altin M (2020) Utilization of alternative building materials for sustainable construction, pp 727–750 107. Takeaway (2011) Panyaden school Chiang Mai 04. https://commons.wikimedia.org/wiki/File: Panyaden_school_Chiang_Mai_04.JPG. Accessed 28 Nov 2022 108. Takeaway (2011) Panyaden school Chiang Mai 03. https://commons.wikimedia.org/wiki/File: Panyaden_school_Chiang_Mai_03.JPG. Accessed 28 Nov 2022 109. Tschaperkotter (2018) Meti School Exterior. https://commons.wikimedia.org/wiki/File: Meti_School_Exterior.jpg. Accessed 10 Oct 2022 110. Hossain N (2008) Heringer meti school. https://commons.wikimedia.org/wiki/File:Heringer_ meti_school.jpg. Accessed 10 Oct 2022 111. Ashraf KK (2007) This is not a building! handmaking a school in a Bangladeshi Village. Archit Des 77:114–117. https://doi.org/10.1002/ad.575 112. Lim JCS (2007) Hand-Made school. Rudrapur, Bangladesh

Bamboo as a Sustainable Building Material

23

113. Deutschland—Land der Ideen (2010) German-Chinese House. https://commons.wikimedia. org/wiki/File:011_DuC_Haus_Nacht_8826~8828_Kingkay_Branded.jpg. Accessed 10 Oct 2022 114. Schittich C (2014) Details around the corner. Archit Des 84:36–43. https://doi.org/10.1002/ ad.1779 115. Sieder M, Rein A, Seise N (2013) Vom Halm zum Tragwerk. Bautechnik 90:816–821. https:// doi.org/10.1002/bate.201300082

Bamboo Construction: Main Building Techniques and Their Resources, Sustainability, History, Uses, and Classification Victor Almeida De Araujo, Letícia Rubio Colauto, Leticia Gabriele Crespilho Abel, Fábio Silva do Rosário, Juliano Souza Vasconcelos, Elen Aparecida Martines Morales, Juliana Cortez Barbosa, Maristela Gava, and André Luis Christoforo Abstract Like wood, bamboo is utilized in different products for civil construction, either in natural or in engineered form. The easy proliferation in small-sized planted forests, rapid harvest cycles, and low environmental impacts in the planting and processing stages gave significant credentials to this renewable bio-based resource in the last years. In addition, different bamboo species are likely to be applied to structural applications. These facts value this biomaterial as a convenient input to V. A. De Araujo (B) · A. L. Christoforo (B) Civil Engineering Postgraduate Program, Federal University of São Carlos, 235 Washington Luis, São Carlos, Brazil e-mail: [email protected]; [email protected] A. L. Christoforo e-mail: [email protected] L. R. Colauto · L. G. C. Abel · F. S. do Rosário · E. A. M. Morales · J. C. Barbosa · M. Gava (B) Forest Science Postgraduate Program, São Paulo State University, 3780 Universitaria, Botucatu, Brazil e-mail: [email protected] L. R. Colauto e-mail: [email protected] L. G. C. Abel e-mail: [email protected] F. S. do Rosário e-mail: [email protected] E. A. M. Morales e-mail: [email protected] J. C. Barbosa e-mail: [email protected] J. S. Vasconcelos Agronomy Postgraduate Program, São Paulo State University, 3780 Universitaria, Botucatu, Brazil e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 F. L. Palombini and F. M. Nogueira (eds.), Bamboo and Sustainable Construction, Environmental Footprints and Eco-design of Products and Processes, https://doi.org/10.1007/978-981-99-0232-3_2

25

26

V. A. De Araujo et al.

supply the civil construction sector, above all, in more sustainable housing and infrastructure. Formerly, bamboo culms and esterillas were used in popular buildings using rudimentary solutions based on vernacular techniques. From the advancement of bioresource technology and industrialization, structural bamboo products and bamboo-based composites are being developed for modern buildings manufactured from prefabrication techniques. As a structural material in its multiple forms, bamboo can be used alone or together with other materials, which contributes to the diffusion of this commodity worldwide. Thereat, bamboo buildings may overcome their usual applications in Asia, Africa, and part of Latin America to be valued as a sustainable alternative for construction by engineering and architecture professionals from Europe, Oceania, and South and North Americas. Keywords Bioproducts · Bio-construction · Green architecture · Sustainable housing · Bamboo construction · Construction technique · Sustainable bioresources · Bamboo

1 Introduction Bamboos are not trees, but they are woody giant herbages belonging to the Gramineae (Poaceae), subfamily Bambusoideae, with similar anatomical features of leaves, although they present diverse plant heights, culm diameters, root formations, and colors [1]. The Bambusoideae family includes 119 genera, organized into three tribes: Bambuseae, with more than 810 tropical woody species, Arundinarieae with around 545 temperate woody species, and Olyreae, with more than 120 herbaceous species [2, 3]. In this perspective, bamboos are featured by woody and herbaceous plants [4]. Bamboos are also important for human nutrition since they are angiosperm plants like corn, wheat, and barley. While herbaceous bamboos are used as ornamental plants due to lower sizes, woody bamboos are tall plants morphologically similar to trees due to the presence of roots, culms, branches, and leaves. According to Araujo [5], the lower part is formed by rhizome and roots, and the upper part has a stem, also called culm, which is a hollow woody cane separated, internally, by transverse septa and, externally, by nodes. Bamboo is a native plant of different territories, which include America, Asia, Africa, and Oceania, although different species were introduced in Europe during the last centuries as well as species were inserted as exotic plants in other continents from different migration processes [6]. Many species became adapted to diversified habitats due to the initiative of immigrants and descendants in the process to insert their cultures into other territories. China, Brazil, Japan, India, Vietnam, Venezuela, and Madagascar are among the nations with significant volumes of natural species [7]. This natural occurrence in Asia, Latin America, and Africa justifies the secular tradition of bamboo culture in their territories.

Bamboo Construction: Main Building Techniques and Their Resources, …

27

The history of bamboo utilization goes back to the beginning of the Asian civilization since this plant emerged in the tertiary era [8]. For many societies, bamboo was used in diversified products. As subsistence elements, they were associated with regional habits and folkloric customs, which became this plant in a material, utilitarian, edible, and religious bioresource. Bamboos were industrially utilized in the first decades of the twentieth century, although the Chinese government prioritized bamboo research toward genetic improvement, processing, and composite products in the 1970s [9]. The “know-how” on bamboo technology is in charge of Colombia, as Latin America was favored with different natural species and the successful insertion of exotic species. The use of bamboo in Mexico has a pre-Hispanic background [10]. Bamboo is present in Brazilian’s daily lives since this plant is utilized in rural appliances, toys, objects, and household items [11]. In the last decades, modern technology revitalized the former uses of bamboo to the point of providing new applications for Engineering, Architecture, Chemistry, Aeronautics, Nutrition, Medicine, Pharmacy, and diverse industrial fields [12]. Bamboo has a clear versatility due to multipurpose applications. For example, plants may be utilized in plantations to recover environments of damaged landscapes and contaminated areas. Leaves and their fragments are applicable to medicine drugs and food tea and flavor. According to Rusch et al. [13], young plants and shoots are successfully applied to food production in fiber, flour, and starch-based products such as biscuits, cakes, nuggets, cookies, and numerous pasta varieties. The goods manufactured from bamboo culms include furniture, construction, charcoal, paper, panels, kites, flutes, toothbrushes, tools, fences, cages, traps, pipes, bicycles, curtains, ladders, light fixtures, cutting boards, foods, and others. Bamboo requires precaution and protection for severe uses, especially in civil construction. Bamboos have the advantage of being an alternative source to supply the global deficit in wood production, which contributes to promoting sustainable development through the mitigation of the intense consumption of natural wood [14]. Due to this favorable prospect, bamboo culture may become a very representative and, why not, a leading supplier for the bioproduct industry in parallel to silviculture. Thereat, there is real potential for the use of bamboo products in construction, since this bioresource is capable of offering structural and environmental benefits.

2 Bamboo as a Sustainable Material for Construction Bamboo is the material of the twenty-first century, which could replace wood, especially because of the global mistreatment and deforestation of natural forests [10]. This replacement is reinforced by the capacity to grow in different climates under shorter harvest cycles than other woody plants (3–5 years), which makes bamboo a versatile bioresource [7]. In terms of dry material, bamboo provides a production yield of 3.3 times that of wood [15]. This performance results in longer and faster woody culms, even than the fast-growing forestry woods such as eucalypt and pine.

28

V. A. De Araujo et al.

Therefore, bamboo management and cultivation share visible benefits due to the easy and quick development of this plant [16]. This high renewability is justified by Kigomo [17] since bamboo does not require a replanting process due to its great capacity for regeneration and propagation. The maximum maturity of bamboo culms is reached up to 6 years, being that immature bamboos are collected in a year or less and, possibly, culms harvested after 5 years may be dead at the time of this longer cycle [8]. The maturation stage is reached when culms are 3 or 4 years old in the culture, suitable for permanent or temporary buildings and the production of composite products. The right cut region is over the first culm node above ground [1]. Thus, bamboo has the condition to be more advantageous than wood because of its shorter cutting cycles, especially by the use of simpler management and lower fertilization of cultures. But it requires attention to pest attacks and harvest periods. According to Liese [18] and Hidalgo-Lopez [1], the highest probability of attack by borers occurs in the driest seasons before the rainy and sprouting periods, since drier phases intensify the starch accumulation in the culms. Additionally, culms are treated to reach greater durability, whose chemical preservatives include creosote, copper sulfate, zinc chloride, sodium pentaclorophenate, chromated zinc chloride, chromated copper arsenate, chromated copper borate, boric acid, and borax [1]. Also, an interesting suggestion about bamboo for construction was given by Jaramillo Benavides et al. [19] toward a lower environmental impact, which can include a process with natural conditions of the plant development, manual stages in the bamboo processing, culm preservation with borax solution, and waste reuse. Bamboo may become a socially and economically interesting alternative crop, as this plant requires simpler processes and precautions in cultivation and management, the reason why this culture needs intensive unskilled labor. This condition results in greater valorization and inclusion of populations from the needy regions. The wide availability in different regions has positioned bamboo as a strong resource for work and income generation for rural communities where this plant is found easily, which contributes to regional development [2]. In practice, bamboo is a cheap or free material source for rural people that they would otherwise spend money to procure from far away or replace with slow-growing trees [20]. Through the use of bamboo in the creation of built environments, the builder diffuses countless possibilities of the art and technique utilized by its ancestors [8]. Thus, the creation of jobs both at the village and industrial levels may be ensured by bamboo, as these plants have indigenous features [21]. Bamboo houses have been popular in regions with bamboo forests, where the craftsmanship is a valuable source of income for rural communities [22]. As a very positive outcome, bamboo production might therefore contribute to reducing poverty and boosting economic growth through plant conversion into products, protecting the natural forests, and mitigating climate change through the intensification of bamboo plantations to supply activities [23]. Bamboos have been found in tropical and temperate areas [1, 7]. Given this regionality, bamboo became a popular resource converted into structural parts used in construction, both in natura forms using culms and engineered alternatives using

Bamboo Construction: Main Building Techniques and Their Resources, …

29

composite panels (Table 1). In addition, bamboo may be used as carbon storage (Table 2), due to vegetative development [18]. Wood and bamboo materials are environmentally friendly, and their products are classified as low-carbon and climate negative levels (Table 3). According to van der Lugt et al. [29], some bamboo products (flattened bamboo board, strand woven bamboo, and plybamboo) are more “carbon-efficient” than steel and concrete. Therefore, there is a real space for the industrialization of bamboo products for construction, since they can offer sustainable benefits due to low-carbon features (Table 3). The sustainability, quality, and structural behavior of bamboo structures may be controlled by digitalization and management in an innovative workflow related to its design and building, as cited by Mimendi et al. [30]. Table 1 Main bamboo species used in civil construction and characteristics Bamboo species

Culm height (m)

Culm diameter (cm)

Occurrence (region)

Way of use

Bambusa balcooa Up to 25

Up to 15

Asia and Oceania

Culms

Bambusa blumeana

15–25

Up to 20

Asia and Oceania

Culms

Bambusa polymorpha

16–25

Up to 15

Asia

Culms

Bambusa tulda

Up to 30

5–10

Asia

Culms

Dendrocalamus asper

20–30

8–20

Asia and Oceania

Culms

Dendrocalamus giganteus

25–60

10–20

Asia and Africa

Culms and panels

Dendrocalamus lactiferous

14–25

8–20

Asia

Culms

Dendrocalamus strictus

8–20

2.5–8

Asia

Culms and panels

Gigantochloa apus

8–30

4–13

Asia

Culms

Gigantochloa levis

Up to 30

5–16

Asia and Oceania

Culms

Guadua angustifolia

Up to 30

Up to 20

America and Asia

Culms and panels

Melocanna baccifera

10–25

5–9

Asia and Oceania

Culms

Phyllostachys edulis

10–20

18–20

America and Asia

Culms and panels

Thyrsostachys siamensis

8–16

2–6

Asia

Culms

Sources Adapted from [7, 24]

30

V. A. De Araujo et al.

Table 2 Material features as bamboo culm Bamboo species

Culm density (culm/ha)

Above-ground biomass (ton/ha)

Carbon storage (ton/ha)

Reference study

Bambusa balcooa 1860

105

52

Pathak et al. [25]

Bambusa tulda

14,132

100

50

Devi and Singh [26]

Dendrocalamus strictus

1364

13

7

Guadua angustifolia

4500

200

100

Melocanna baccifera

39,075

118

58

Pathak et al. [25] Quiroga et al. [27] Singnar et al. [28]

Sources Adapted from studies cited in the table

Table 3 Net global warming potentials of the main biomaterials for construction Index

Material classification

Material type

Climate positive

High carbon

Wood-aluminum window frame

8.43

Wood window frame

4.18

Solid wood (softwood)

1.05

Bamboo cladding and flooring

0.75

Solid wood for finishing (hardwood)

0.41

Cross-laminated timber

0.31

Glued-laminated timber

0.31

Low carbon

Oriented strand board Climate negative

Climate negative

Source Adapted from [31]

Potential value (kgCO2eq /kg)

0.29

Solid wood for structure (hardwood)

−0.14

Glued-laminated bamboo

−0.15

Cross-laminated bamboo

−0.16

Hemp fiber

−0.44

Reed mats

−0.46

Straw

−0.60

Bamboo Construction: Main Building Techniques and Their Resources, …

31

3 Structural Application of Bamboo Products in Construction Bamboo is an ancient material for construction, formerly used in boats, huts, and household items [4]. A Chinese paper from the 1920s evinced the potential of bamboo for construction [32]. Its structural use is also reinforced by the superior tensile and compression strengths of any tree [1]. Over the decades, the use of bamboo evolved due to the better knowledge and improvement of techniques and properties of this material through the insertion of modern technologies to obtain new solutions [4]. This evolution brought to the construction a new use in structural pillars, trusses, and bridges [2]. Bamboo is a lightweight material with good elastic and bending performances, which makes its products very efficient in earthquake-prone areas [33]. Due to its suitable properties compared to other raw materials (Table 4), the main uses of bamboo in construction comprise buildings, silos, dwellings, towers, bridges, and scaffoldings. Bamboobased construction utilizes “woody” culms, both naturally as hollow cylinders and/or industrially as engineered massive blocks and boards. About bamboo culms, different positive features are found such as efficient raw material utilization in tube structures, extreme flexibility associated with high strength, high axial permeability for efficient preservative impregnation, and low radial permeability in the protective layer [35]. Some features are reached by a lignified sclerenchyma tissue [36]. Culms might suffer from limitations on geometry Table 4 Properties of the main construction materials Material

Density (g/cm3 )

Compression strength (MPa)

Tensile modulus (MPa)

Steel

7.9

800

203,000

5

Cast iron

7.8

120

207,000

138

Concrete

2.5

69

48,000

4

Glass

2.5

50

69,000

50

Epoxy

1.8

400

45,000

1100

Polyvinyl chloride 1.5 (PVC)

55

2,400

59

Tensile strength (MPa)

Bamboo scrimber

1.0

135

23,000

295

Glued-laminated bamboo

1.0

62

32,000

118

Laminated bamboo lumber

0.7

77

12,000

90

Bamboo culm

0.7

79

20,000

206

Solid wood (conifer species)

0.5

7

10,000

104

Sources Adapted from [1, 34]

32

V. A. De Araujo et al.

Table 5 Properties of bamboo culms in some different species Bamboo culm

Modulus of elasticity (MPa)

Modulus of rupture (MPa)

Compression strength (MPa)

Tensile strength (MPa)

Dendrocalamus giganteous

14,000

178

61.40

187.00

Dendrocalamus asper

12,875

160

59.30

208.60

Gigantochloa robusta

9650

132

51.10

187.70

Bambusa vulgaris var. striata

7475

112

44.60

130.60

Source Adapted from [1]

and durability, although standardization and processing are possible for structural elements and connections [37]. Despite the different species and properties, bamboo culms can satisfy structural uses (Table 5). There are different glued-bamboo panels and beams, which involve flattened culm plywood, laminated veneer lumber, milled strip laminated lumber, and heavily compressed, crushed culm scrimber-type decking and flooring products [34, 38]. These products contribute to low-carbon activities and efficient structural properties (Tables 3, 4, 5 and 6), offering better environmental and mechanical performances than traditional materials [31]. Using different parameters (resin, species, density, etc.) offers singular properties (Table 6). Moreover, there are other composites based on wood-bamboo blending, as suggested by De Almeida et al. [39], Barreto et al. [40], Chen et al. [41], and others. Bamboo-based panels are fixed with screws and other high-performance metal elements. In addition, Raj and Agarwal [33] stated that culms and strips can be fixed to each other as well as split mats can be woven or fastened to the culm-based posts. Proper jointing and treatment of bamboo need to be ensured [42], insofar as weather conditions interfere with its durability, since this material may decay and deteriorate unless treated with preservation [37]. Table 6 Property range in bamboo composites made using different parameters Composite

Bamboo species

Resin element

Density (g/cm3 )

Modulus of elasticity (MPa)

Modulus of rupture (MPa)

Oriented strand lumber

Dendrocalamus asper

Melamine

0.70–0.80

7750–11,100

40.0–61.0

Phenol

0.69–0.71

4850–6650

35.0–59.0

Isocyanate

0.71–0.76

6900–10,300

45.0–65.0

Laminated bamboo lumber

Phyllostachys pubescens

Resorcinol

0.60–0.70

4800–6600

26.0–74.0

0.80–0.90

6600–7825

57.5–110.0

Sources Adapted from [43, 44]

Bamboo Construction: Main Building Techniques and Their Resources, …

33

4 Bamboo Construction Bamboo construction may be defined as any building essentially formed by bamboobased parts in its structural system, whether in the frames and/or walls. This versatility has been confirmed in different techniques, territories, and times.

4.1 Previous History of Bamboo Construction Bamboo plants cohabit with former American men since their origins [45]. Beyond the Americas, bamboos are also present in tropical and warm temperate ecosystems and cold temperate regions [23]. Indigenous groups conserved the use of this bioresource in construction due to its environmental quality [10]. Therefore, the use of bamboo has been regionally subject to its occurrence and easy availability (Table 1), reasons why bamboo buildings were formerly proliferated in Asian, African, and Latin American countries. The utilization of bamboo in construction is dated to around 9500 years ago since vestiges of a small prehistoric building possibly utilized as a funeral chamber were found near Guayaquil on the coast of Ecuador [1]. This finding was also confirmed by Stothert [46], due to the assumption of structural elements in bamboo found in excavations. In the sixteenth century, bamboo forests were used by indigenous people to build their towns in Colombia [1]. At the time of the Inca civilization, this plant was also used as the main biomaterial in the artisanal production of bridges with complex designs [47]. Still, bamboo was hated by the Spanish colonists, and therefore, bamboo buildings became marked by an oppressive label of misery and death of native Colombians, and the resurgence of bamboo culture flourished from the eighteenth century onward [1]. Therefore, bamboo architecture dates back millennia in America due to its abundance and diversified applications for construction, as this biomaterial can provide efficient thermal conditions in warm humid climates, as in Latin America, being a preference against wood [10]. In parallel, modern architecture and many structural elements were designed and built in Asian countries, above all, China, India, Japan, and Indonesia [12]. Bamboo was the main resource of houses purely produced using this material in Southeast Asia, although the giant bamboo species, marked by lower durability, were used in interior walls and reinforcements for adobe buildings [1]. Combinations of timber framing in structures with bamboo matting for walls were visibly present in China in housing production [48]. While the large domes were developed by Bengalis in India, China presents a relevant participation in the development of porticos with double beams for buildings and large suspension bridges, and Indonesians and Colombians created cable-stayed bridges [12]. According to Hidalgo-Lopez [49], Latin American and Asian countries have dedicated themselves to developing different construction solutions. In the early

34

V. A. De Araujo et al.

1980s, the prefabrication process was formerly utilized in low-cost buildings from Guadua angustifolia bamboo culms in Ecuador, whose proposal was led by HidalgoLopez [1] to supply the housing deficit of an impoverished community in Guayaquil. In addition, some successful attempts were replicated in Costa Rica and Colombia. Thus, a global resurrection of bamboo construction has been perceived due to the higher performance and socio-economic-environmental benefits of this material.

4.2 Current Moment of Bamboo Construction The current importance of bamboo for Asian and Latin American regions has been evinced by the publication of national standard documents to regulate and guide structural uses of bamboo in Colombia, Ecuador, Peru, Bangladesh, and India [50]. Recently, Brazil joined this select group by establishing two codes for bamboo buildings, specifically about the design of structures and the determination of properties for structural uses [51, 52]. Ethiopia, Nepal, and Uganda also instituted similar standards, as verified by Kewei et al. [24]. The relevance of this bioresource has been globally confirmed over the years, the reason why different nations without the occurrence of natural bamboo species are already considering this alternative biomaterial in the design of sustainable buildings. In the last decades, Janssen [21] confirmed that some bamboo-based buildings and frames were built in Europe, possibly encouraged by the consumption of other bamboo products made in developing countries. Designed by Simón Vélez, itinerant bamboo pavilions were built in Germany and France [53]. Inspired by these singular works, other buildings for particular uses were made using bamboo in Germany, Italy, and Spain [54]. In a movement to promote the bamboo processing industry in African countries, two proposals suggest the market development of industrialized construction parts in the eastern region [55], and the greater uses of bamboo materials for sustainable buildings in Nigeria [56]. National strategies were planned to regulate and promote the development of bamboo sectors in Peru, Colombia, Ecuador, China, the Philippines, India, Uganda, Madagascar, Ethiopia, and Rwanda [24]. Today, bamboo initiatives are in the spotlight for construction professionals inspired and interested in more sustainable buildings, including those regions where bamboos are exotics as North America and Europe since these bioresources provide multiple esthetics, high structural performance, and small ecological footprint [54].

5 Bamboo Construction Techniques The difficulties in the theme of bamboo buildings regard unclear approaches and specifications of all construction techniques. This complexity is connected to the

Bamboo Construction: Main Building Techniques and Their Resources, …

35

diversification of available examples, which include former and present concepts as well as simpler and finer styles. Therefore, a more complete collection of techniques is required, the reason why each technique will be specified in the next paragraphs. At the time of Homo erectus, there were consistencies in the occurrence of bamboo forests and much evidence of Asian bamboo-based artifacts and buildings [57]. Millennia later, bamboo was globally used as material by indigenous people in the production of their dwellings and, posteriorly, by Latin Indians in the formation of their villages [1]. For ages, bamboo has been used for different buildings such as houses, shelters, halls [35]. These facts are favored by the good combination of bamboo and wood, both in structures and envelopes of bio-based buildings, as highlighted by Bredenoord [58]. In fact, bamboo and wood prevailed in different eras due to their global occurrences in the natural forests, as bioresources were also used in the Stone, Iron, and Bronze ages. Thereby, indigenous people were possibly the primary societies engaged in the use of wood and bamboo for dwellings, naturally using inchoate technologies. Given the visible number of bamboo species suitable for structural uses (Tables 1 and 6), different construction techniques with bamboo were developed over the progress of societies. Hence, Table 7 specifies each technique with the respective terms for Spanish, French, and Portuguese languages. Next, each technique was addressed to contextualize technological evolution about origins, materials, and technical aspects.

5.1 Hut A hut is a primitive shelter with rustic frames of bamboo culms or wood logs, which includes a structure covered by bamboo culms and branches, bushes, thatch, and straw or a combination of surrounding bioresources [59, 60]. This concept of a rudimentary hut was often revisited in the eighteenth and nineteenth centuries [61]. Bamboo huts were identified in different regions and moments experienced in the Latin American region [1]. Besides the Americas, huts are found in Africa and Asia as dwellings for indigenous, nomadic, and forest-dependent people [62]. Hospitality purpose valorizes this construction technique, especially for rest in rural areas, as indicated in Fig. 1 for different huts.

5.2 Stilt House Using ancient technologies similar to huts, the stilt house is a primitive building made with rustic frames in wood logs and bamboo culms, whose structure is built on piles over any coastal soil or water body [60]. This archaic condition was evinced by the presence of remains of prehistoric settlements formed by stilt houses dated from 5000 to around 500 BC in and around the edges of lakes, rivers, or marshy lands of the

36

V. A. De Araujo et al.

Table 7 Technique nomenclatures of bamboo construction Construction technique nomenclature English

Spanish

French

Portuguese

Hut

Cabaña

Hutte

Mocambo

Stilt house

Palafito

Palafitte

Palafita

Wattle-and-daub

Zarzo y barro

Torchis plaqué

Taipa de mão

Bahareque

Bajareque

Torchis bahareque

Bahareque

Quincha

Quincha

Torchis quincha

Quinxa

Reinforced rammed earth

Tapia

Mur en pisé

Taipa de pilão

Reinforced concrete by culms

Hormigón armado con bambu

Béton armé en chaume Concreto armado em colmos

Reinforced concrete by panel

Hormigón armado con panel

Béton armé en panneau Concreto armado em painel

Japanese wall

Pared japonesa

Mur japonais

Parede japonesa

Pagoda

Pagoda

Pagode

Pagoda

Culm cabin

Cabaña de culmos

Cabane en chaume

Cabana de colmos

Post-and-beam

Entramado pesado

Poteaux-poutres

Pilar-viga

Conical kiosk

Quiosco cónico

Kiosque conique

Quiosque cônico

Geodesic dome

Cúpula geodésica

Dôme géodésique

Cúpula geodésica

A-frame

Estructura en ‘A’

Maison en ‘A’

Estrutura em ‘A’

Woven panel

Panel de esterilla tejida

Panneau tissé

Painel trançado

Prefabricated social housing

Vivienda social prefabricada

Logement sociaux préfabriqué

Habitação social pré-fabricada

Modular bamboo housing

Vivienda modular en bambú

Logement modulaire en bambou

Habitação modular em bambu

Source Self-elaboration

Fig. 1 Huts in: a bamboo structure and thatched roof, b wood and bamboo structure and roof of straws and branches. Author: a Maristela Gava (2019), the Philippines; b Maristela Gava (2019), the Philippines

Bamboo Construction: Main Building Techniques and Their Resources, …

37

Fig. 2 Stilt house in a lake. Author: Maristela Gava (2019), the Philippines

European Alps, more specifically in Switzerland, Germany, France, Austria, Italy, and Slovenia [63]. Very suitable for coastal and flooded zones, the stilt house offers a construction raised on pilings anchored in the subsoil, being deeply embedded in eroded areas by waves and storms [64]. A vernacular derivation was found in the lowlands of the Philippines as well (Fig. 2), whereas pile dwellings (bahay kubo in the Philippine language) are built using different materials such as bamboo, palm leaves, and grasses [65].

5.3 Wattle-And-Daub The wattle-and-daub is a dwelling made from wood and bamboo structural frames with all walls manually filled with mud, manure, straw, and sand [60]. Woven lattices of bamboo strips are internally fixed in these structural frames. According to Lopes [66], indigenous people utilized bamboo and round sticks collected from the nearest hinterlands in Northern Brazil. This construction technique was identified in archeological excavations present in African sites, revealing the prolonged use of this architecture, specifically from the 15th to twentieth centuries, by the Swahili society [67]. Typical Bengali style designed in the fifteenth century is clearly inspired by this technique, whose construction structure of bamboo culms is made by four corner posts tied to diagonals and wall surfaces with alternate recesses and off-set projections as a woody wattle-and-daub [1].

38

V. A. De Araujo et al.

Fig. 3 Wattle-and-daub in a contemporary style. Author: Maristela Gava (2019), Brazil

There are numerous types and forms to construct a wattle-and-daub across the world since they have similarities [68]. But wattle-and-daub has been imprecisely related to bahareque in Latin America as verified by Moore [69] because there are perceptible variations in raw materials and construction processes. In the wattle-and-daub technique, the internal structure can be made using a traditional form, with a cylindrical frame of wood or bamboo grilled by strips or thin canes, or even a contemporary style, with bamboo poles wired and nailed to a frame of lumber [68]. Still, another modern configuration can utilize a culm structure formed by squared frames with parallel-oriented in diagonals as identified in Fig. 3.

5.4 Bahareque Still, on these techniques produced from mud and bamboo frames, bahareque represents a strong manifestation of a low-cost dwelling expressed from materials collected in the regional surroundings. Moore [69] and Muñoz Robledo [70] also defined bahareque as a popular architectural representation of the Andean culture. In general, the structural frames of bahareque variations are similar, since they have been assembled with 10-cm poles spaced at 30 cm fixed at the bottom and top plates [49]. The architectural plurality of bahareques has been contrasted in their wall compositions, insofar as Muñoz Robledo [70] identified different raw materials used, such as mud, bamboo-based panels, wood poles, metals, cement, masonry, reinforced concrete, or even, different mixtures of these singular resources. There are four main

Bamboo Construction: Main Building Techniques and Their Resources, …

39

configurations, according to Robledo Castillo [71], which can be identified by the use of mud, panel, metal, and cement. Mud-based configuration (inlaid clay, and bahareque macizo, bahareque de tierra, or barro embutido in Spanish) is formed by timber poles and/or bamboo culms in the structural frames, which are horizontally crossed by bamboo canes or laths to hold the mud, forming solid walls [72]. Using the same structural frames, the panelized model (bahareque de tabla or bahareque hueco) differs from the use of horizontal covering of bamboo esterillas in hollow walls without inlaid mud, being plastered on both outer surfaces [72]. With contemporary materials, the metal option (bahareque metálico) is covered by sheet metal screwed into the bamboo frame covered with plaster [70]. Using the reinforced masonry concept to resist earthquakes, the cement-based model (bahareque encementado) uses a bamboo frame fortified by galvanized steel meshes and bamboo matrices (canes, laths, or mats) and wall finished by mortar [73], although there is a variety with wood and bamboo [74].

5.5 Quincha A manifest variant of mud and bamboo technique is given by quincha (kincha in Kichwa dialect), whose origins are related to Quechua villages along the Andes. Hidalgo-Lopez [1, 49] denoted that quinchas are low-cost dwellings with thin and strong walls formed by bamboo frames and panelized matrices. A matrix is built by interwoven panels with vertical orientation fixed in the lateral poles or horizontal configuration fixed in the top and bottom plates [75]. Earthquakeresistant lightweight walls of quinchas are covered with mud and straw, or daub, and finished with lime plaster to create a building envelope [76].

5.6 Reinforced Rammed Earth Rammed earth is a vernacular construction technique for dwellings formed by the compaction of subsoil materials into molds, with or without, an internal frame in bamboo or wood [59, 60]. The rammed earth technique requires clay, sand, straw, water, and organic fibers from plants, grasses, and trees [77]. These materials are mixed and distributed into the lumbered molds in layers up to 3 inches tall [78]. Earthquake-resistant version receives an internal structure with wood logs or bamboo culms to improve its seismic absorption [70]. Reinforced rammed earth buildings are present in different Asian and Latin American countries [70, 79, 80].

40

V. A. De Araujo et al.

5.7 Reinforced Concrete By Culms Reinforced concrete with bamboo is an evolutionary construction solution, which alternatively proposes the replacement of steel parts with bioresource ones. According to Hidalgo-Lopez [12], bamboo is positively a bio-alternative input, where culm cables and woven panels with strips are adequate to preserve the structural integrity of reinforced concrete construction. Bamboo was initially utilized as expedient reinforcement for temporary or secondary concrete structures, above all, as a regional alternative to replacing steel bars in underdeveloped regions marked by unavailability, scarcity, or cost unfeasibility of metals [81]. Bamboo-reinforced concrete beams, permanent shutter concrete slabs, and columns are applicable reinforcements, although there is a need to establish a rigorous analysis of the design of bamboo construction [82]. Despite the use of cement and sand, cement mortar composites and concrete elements reinforced with bamboo were realized by Ghavami [83] as non-conventional technologies for ecoconstruction, since they offer lower impacts on the environment. As a way to reduce the water absorption of bamboo in reinforced concrete, the use of waterproofing agents, such as “tack coat”, could minimize the water absorption and increase the bonding strength to protect structural parts for low-cost housing [84]. Therefore, proper treatment of culms may substitute steel as concrete reinforcement [85].

5.8 Reinforced Concrete By Panels The reinforcement strategy of concrete led to the greater use of bio-based resources replacing minerals, where steel bars are replaced by bamboo culms in the prefabrication of concrete elements. The reinforced concrete with bamboo is a bio-alternative of the traditional reinforced concrete solution since Hidalgo-Lopez [12] still completed that recent alternatives are being developed in the prefabrication of reinforced concrete walls, where woven panels with strips, produced under simpler prefabrication, are inserted to form a box and, sequentially, are fully covered with mortar. The robustness of this construction technique has allowed multi-level structures [86].

5.9 Japanese Wall Still in the context of bamboo buildings with mortar, the Japanese wall is a form to obtain a reinforced lightweight construction. This reinforced model is contrasted by the use of lumber frames interlocked by bamboo grades. According to Izumida [87], this traditional construction technique practically disappeared in the 1970s, as a panelized technique on light-woodframe was introduced in Japan. Studs are joined

Bamboo Construction: Main Building Techniques and Their Resources, …

41

by lathes to form a structural frame of sawn wood, whose voids surrounded by lumber elements internally receive bamboo grades composed of sticks (main bracing) and lathes (secondary). This technique requires clay applied to bamboo lathes, especially in the frame spaces, to form solid walls [87]. This structure is wrapped by fabrics, and wall surfaces receive layers of mortar [49].

5.10 Pagoda There is still another construction technique popular in Asia, formed by tower buildings with multiple eaves, designed as pagodas, which are made through regional resources such as sawn wood and bamboo parts. According to Hanazato et al. [88], pagodas are important cultural heritages, since they have long histories featured by secular origins and survival against earthquakes. Formerly, pagodas were made from wood and boards interspersed with simple thatched bamboo roofs [89]. For reasons of flexibility against earthquakes, parts are joined without the use of nails [90]. These towers are constructed either of marble, stone, glazed and unglazed bricks, wood, bamboo, iron, or bronze [91]. A five-storied pagoda in Japan is the main historical temple since it was built with wood parts at the end of the seventh century [88]. In China, a bamboo-shoot pagoda is a central construction in the shape of a lotus flower, which is surrounded by smaller buildings to form a bamboo thicket [91]. Alternatively, pagodas are adapted for housing purposes, utilizing different raw materials (Fig. 4).

5.11 Culm Cabin Log cabins make up a traditional way of living, as these buildings valorize the local resources. This technique requires round- or rough-hewn wood, whose elements are interlocked, as suggested by De Araujo et al. [59]. A wall is formed by stacking trunks one on top of another and overlapping them at the corners [92]. Due to the low material processing, all gaps in walls are filled with mud and chips [93]. There is another configuration where culms are vertically oriented, as identified by Fig. 5, which example requires an internal culm frame to support all vertical elements. Inspired by the use of round elements of wood, bamboo culms may be used in a similar model of log cabins. The “culm cabins” are handcrafted by artisans as a way to value the natural shape of culms under simplistic processing. Both thick and thin culms are utilized, which are stacked and receive mud or cement in the gaps.

42

V. A. De Araujo et al.

Fig. 4 Modern pagoda house inspired by Asian temples. Author: Maristela Gava (2019), Indonesia

5.12 Post-And-Beam Post-and-beam is a very popular construction system based on wood elements, which include logs, lumber, timber, and engineered wood products. Post-and-beam technique refers to a heavy frame formed by large joined posts and beams covered by a slim sealing as identified by De Araujo [60]. But, bamboo may be utilized in this construction system. Porticos are built using posts and beams, including diagonal and braces to stiffen columns [49]. Bamboo railings may be applied to create a robust frame since bamboo culms act like lumber studs of any light-woodframe building. The lower part of frames can receive lumber clapboards with fire-stopping ends, being also a mixed technique [49]. Modern versions may use engineered bamboo products as beams of parallel bamboo strand lumber and laminated bamboo lumber

Bamboo Construction: Main Building Techniques and Their Resources, …

43

Fig. 5 Culm cabin. Author: Maristela Gava (2019), the Philippines

[94]. Strip panels can also be used as wall coverage. Regarding pillars, they can have one, two, or more culms in each post. About multiple culms per individual post, they are reproduced using branched or parallel elements (Fig. 6).

5.13 Conical Kiosk Using some structural concepts from porticos, the conical kiosk is a technique composed of the conical structure of roofing supported by a polygonal frame, which is built using bamboo and, sporadically, lumber—which are used in the beams. In the bamboo-based option, culms are angularly interconnected to form a polygonal wall structure, which supports a cone-shaped roof that starts at a single centralized point and terminates in the polygonal base. Alternatively, a wave-shaped roof may be reproduced to emphasize a contemporary curved style. For example, Fig. 7

44

V. A. De Araujo et al.

Fig. 6 Post-and-beam types: a “branched” and b parallel elements. Author: a Maristela Gava (2019); Indonesia, b Maristela Gava (2016), Colombia

illustrates a modern kiosk with a curved structure produced using bamboo canes, which are covered by textile fabrics. Conical kiosks have a robust pole to centralize and hold the conical structure, usually covered with straw or thatch, whose roofing set is supported by the polygonal structure using screwed connections [49]. Centuries ago, bamboo kiosks were used for rural housing in Colombia, using a six-meter diameter conical roofing made with culms and walls covered by esterillas [95].

Fig. 7 Conical kiosk with curved roofing: a daytime and b at night. Author: Maristela Gava (2019), Indonesia

Bamboo Construction: Main Building Techniques and Their Resources, …

45

Fig. 8 Domes of bamboo strips and canes for: a internal and b external uses. Author: a Maristela Gava (2019), Indonesia; b Maristela Gava (2019), Thailand

5.14 Geodesic Dome Another complex structure is given by geodesic domes in bamboo, which are a polyhedron-shaped lattice-shell construction technique. Heavy loads are supported by these hemispherical structures since they use interconnected structural thin parts of culms or engineered bamboo. Bamboo domes were formerly built in India, although this technique was also applied to the roofing construction of the Taj Mahal in the seventeenth century [12]. From the arrow-and-bow principle, culms are bent and lashed together [96]. Domes are used as confinement solutions and weather protection, both in external coverage or internal closed spaces (Fig. 8). Craftsman moorings or steel connectors are usually applied to interconnect culms, although polyester ropes can be utilized to connect culms and form frames [97]. Using modern resources, domes can be successfully made in engineered parts of laminated bamboo [98]. Animal skins or mortar are used to cover spaces, although textile canvas is also used [96, 97].

5.15 A-Frame With wood and/or bamboo, A-frame cottages are dwellings built with spaced beams spanned by parts using large and angular A-shaped roofs [60]. In Latin America, this construction technique is applied to rural uses, which include peasant life and coffee

46

V. A. De Araujo et al.

Fig. 9 A-frame chalets made with: a culms and esterillas and b culms. Authors: a Maristela Gava (2019), the Philippines; b Juliana Cortez-Barbosa (2019), Indonesia

processing [49]. A-frames can be erected directly from the ground, or even, with a basal frame as illustrated by Fig. 9. Derived from a primitive construction technique, A-frames have easy production and low cost due to the utilization of regional resources, among which bamboo culms are utilized in Latin America [12]. In the ground, culms are arranged to establish a rectangular bottom structure, which receives a sequence of parallel culms fixed in this base and joined at the top in a single ridge beam to form a rafter frame [49]. Currently, engineered bamboo may be used in A-frame chalets due to efficient prefabrication techniques and rigid element connections. Roofs receive a base of esterillas and external finishing of straw, palm leaves, aluminum sheets, zinc sheets, or fiber-cement boards [49].

5.16 Woven Panel In Latin America, another contemporary construction example recreates the prefabrication concept due to the intense use of bamboo, both in culms and woven panels (Fig. 10), to form lightweight buildings. Hidalgo-Lopez [49] analyzed that this technique requires a thin frame of bamboo culms, whose spaces are covered by woven panels of flexible esterillas and strips (5–20 cm wide). There are mixed varieties with other materials, including the main model with lumber frame and woven panels and another type with the application of mortar in the external wall surfaces to fill any orifices and slots [99]. The inside of the wall panel shall be plastered with mud-cement, although woven panels shall be tied properly to

Bamboo Construction: Main Building Techniques and Their Resources, …

47

Fig. 10 Woven panel buildings: a perforated panels and b closed panels. Authors: a Maristela Gava (2019), the Philippines; b Juliana Cortez-Barbosa (2019), Indonesia

the posts of bamboo culms [100]. Still, thin elements can be woven in closed models or perforated configurations (Fig. 10).

5.17 Prefabricated Social Housing A concrete porch system sealed by prefabricated wood-bamboo is a frequent example of panels and standardized parts [101]. Another mixed concept was designed using prefabricated walls formed by a frame of culms and timber-oriented strand boards for social housing [102]. Frames can use processed strips, whose material allows curved styles (Fig. 11). Low-cost options have also been developed involving social housing from prefabricated bamboo panels. Then, Gutierrez [72] described that Ecuador has been a

Fig. 11 Prefabricated housing with: a bamboo and b bamboo and wood parts. Author: a Maristela Gava (2019), Indonesia; b Maristela Gava (2019), Brazil

48

V. A. De Araujo et al.

potential leader in house prefabrication, using panels manufactured in a single plant with lathes and esterillas. This project offers daily prefabrication of 36 tworoom houses, while Jaramillo Benavides [103] proposed a contemporary five-room building concept to be additionally produced for Ecuadorians.

5.18 Modular Bamboo Housing The most up-to-date evolutionary stage of bamboo construction is marked by the intense industrialization of modularized buildings manufactured from bamboo-glued panels and/or wood-bamboo composites. According to Sharma et al. [104], engineered bamboo products have the ability to provide standard sections and more stable properties for members and connections. Typical forms of engineered bamboo include beams of parallel bamboo strand lumber (PBSL) and laminated bamboo lumber (LBL) and panels of glued-laminated bamboo (GluBam) [94]. These modern solutions utilize modularization systems and prefabricated panels to reach optimum performance in the structural, production, and environmental issues [105]. Bamboo-based panels, veneers, and laminated boards are the main resources in use by prefabricated housing [106]. In practice, engineered bamboo products may be successfully interconnected to compose structural modules by means of bolted joints [94]. Due to the need for a specific industrial plant for the production of panels, and especially for the module prefabrication, the modular housing in engineered bamboo combines factors that insert it among the novel alternatives for industrialized construction.

5.19 Main Contrasts of Bamboo Construction Techniques Artisanal technologies and resources are being replaced by manufactured products and standard procedures due to the introduction of industrial processes, although there is an appreciation of eco-techniques and sustainable architecture from mud and, above all, biomaterials [107]. In this way, bamboo and wood have emerged as “raw” and “engineered” solutions for modern sustainable buildings. At least 18 bamboo-based construction techniques were clearly identified in the previous sections through a thorough analysis of the available literature. These techniques included former and reinforced traditional examples, regional solutions, and novel alternatives developed through contemporary resources. Inspired by the approach carried out by De Araujo [60] in his research about the different techniques of construction in wood, Table 7 was designed to describe these bamboo-based building techniques according to their respective materials and origins.

Bamboo Construction: Main Building Techniques and Their Resources, …

49

Around the globe, different styles of traditional construction techniques are confirmed as ancestors of modern structural systems [77]. In practice, De Araujo et al. [59] already defined that traditional techniques are those former methods created and edified before industrialization. Anyway, the primary construction techniques are basically affected by the local resources (wood, bamboo, stone, adobe, mud, brick, and mortar) and constant and predetermined conditions (material properties, soils, geographical positions, natural exposures, and climate risks) [77]. From the industrial period and access to new technologies, novel construction techniques are being designed with parts manufactured through sawing, standardized processing, and prefabrication processes of engineered materials, which are featured by contemporary techniques [108]. Given the approach to the plurality of bamboo construction techniques, summarized in Table 8, bamboo, like wood, may provide diversified concepts and applications.

6 Classification of Bamboo Construction Techniques for Housing The architecture is unique due to the way of expression typified by the culture of communities by means of their traditions and beliefs [77]. Different examples are found in construction—even if the observation prioritizes a specific raw material, as the previous section did about bamboo resources. Due to the awareness of today’s society, bioresources are being considered priorities for a more sustainable future. Thereby, bamboo has been experiencing a resurgence of construction uses in novel architectural structures, engineered composite materials, and low-cost housing projects [109]. Moreover, the Human Settlements Program of the United Nations considers that bamboo construction has a lot of potential in the affordable housing sector [42]. In a generic view, there are five types of bamboo structures, which include: traditional construction, social housing, luxury housing, long-span buildings, and footbridges. However, no construction technique was specified in each category [110]. Another type of bamboo construction was identified by Hidalgo-Lopez [12, 49] as roof structures (Fig. 12), which can include: simple trusses, cabled-stayed trusses, three-dimensional roofing, A-frame roofing, and conical roofing. Posteriorly, newer styles were designed using curved styles (Fig. 13), either with culms and/or engineered bamboo beams, to reproduce shell and wave shapes. However, both cited contributions of Hidalgo-Lopez only described types of bamboo construction identified (and available) until the 1980s. After that period, new techniques were not included as well as no classification of techniques was proposed. Thus, this section proposes a classification of bamboo-based construction techniques.

50

V. A. De Araujo et al.

Table 8 Bamboo construction summary: techniques, origins, and raw materials Origin

Technique nomenclature

Required construction material

Tt

Hut (nomadic/indigenous)

Bamboo, wood, branch, bush, thatch, and straw

Tt

Stilt house

Bamboo, wood, palm leaf, and grass

Tt

Wattle-and-daub

Bamboo, wood, mud, manure, straw, and sand

Tt, Ct

Bahareque

Bamboo, wood, mud, cement, masonry, and metal

Tt, Ct

Quincha

Bamboo, woven panels, mud, straw, and plaster

Tt

Reinforced rammed earth

Bamboo, wood, clay, sand, straw, and organic fiber

Ct

Reinforced concrete by culms

Bamboo, sand, stone, cement, and water

Ct

Reinforced concrete by panels

Bamboo woven panel, sand, stone, cement, and water

Tt, Ct

Japanese wall

Bamboo, sawn wood, clay, paddy straw, and water

Tt

Pagoda

Bamboo and sawn wood

Tt, Ct

Culm cabin

Bamboo, clay, and cement

Tt, Ct

Post-and-beam

Bamboo and sawn wood

Tt, Ct

Conical kiosk

Bamboo and sawn wood

Tt, Ct

Geodesic dome

Bamboo and sawn wood

Tt, Ct

A-frame

Bamboo and engineered bamboo

Tt, Ct

Woven panel

Bamboo, woven panel, and sawn wood

Ct

Prefabricated social housing

Bamboo, wood, engineered bamboo, and engineered wood

Ct

Modular in engineered bamboo

Engineered bamboo and engineered wood-bamboo

Tt traditional technique; Ct contemporary technique Source Self-elaboration designed from information collected in previous subsections

This proposal is presented in Fig. 14 using a similar inspiration led by De Araujo et al. [59], as these authors listed and organized all available construction techniques for housing based on wood products. From all 18 techniques of bamboo construction specified in Table 8, this proposed classification selected each example according to bamboo resources used as structural materials (natural to engineered products) and organized the same by means of possible types of production (artisanal and industrial processes). From those 18 techniques raised in the prospection presented in the previous section (Table 8), the classification of bamboo-based buildings is organized into 8 uniquely artisanal techniques and 2 purely industrial techniques (Fig. 14), which are made with natural and processed bamboo (culms, branches, sticks, esterillas,

Bamboo Construction: Main Building Techniques and Their Resources, …

51

Fig. 12 Examples of roofing structures: a simple truss and b conical roof. Author: a Maristela Gava (2019), Indonesia; b Maristela Gava (2019), Indonesia

Fig. 13 Examples of curved roofing structures: a shell and b waves. Author: a Maristela Gava (2019), Indonesia; b Maristela Gava (2019), Indonesia

strips, and woven panels) and engineered bamboo (woven panel, laminated bamboo lumber, parallel bamboo strand lumber, glued-laminated bamboo, and wood-bamboo panels), respectively. The other 8 models are built using both production processes. The activation of traditional bamboo construction is a way to preserve rural memory during rapid urbanization, as Ding et al. [111] idealized that traditional bamboo construction techniques provide a positive architecture under the background of sustainable urbanization. Today, even commercial uses are observed as identified in Fig. 15. Some contemporary raw materials may be utilized in bahareque (cement and metal) and quincha (interwoven panels), but these techniques of bamboo construction still depend on the artisanal processes to be completed. For example, both techniques require the application of mud, straw, cement, daub, and/or plaster. This technology

52

V. A. De Araujo et al. Material

Technique

Production Process

Hut Branch Stilt house Wattle-and-daub Stick

Culm (cane)

Quincha Reinforced rammed earth

Artisanal

Bahareque

Strip (lath) Reinforced concrete by culms

Esterilla

Reinforced concrete by panels Japanese wall

Woven panel

Pagoda Culm cabin

Laminated bamboo lumber

Parallel bamboo strand lumber

Conical kiosk Geodesic dome

Glued-laminated bamboo panel

A-frame Woven panel

Wood-bamboo panel Prefabricated social housing Modular in engineered bamboo

Author: self-elaboration. Fig. 14 Classification of bamboo construction techniques

Industrial

Post-and-beam

Bamboo Construction: Main Building Techniques and Their Resources, …

53

Fig. 15 Bamboo-based commercial post-and-beam buildings: a hotel complex for rest and food and b two-story bungalow. Author: a Maristela Gava (2019), Indonesia; b Maristela Gava (2019), Indonesia

is essentially dependent on the cultural behavior of ancient societies in the use of raw materials and very artisanal construction processes. From a social sustainability perspective, bahareque buildings are flexible solutions accessible to more families, as rural and urban people may build their low-cost homes [112]. Moreover, bamboo can act as an efficient solution for the reinforcement and structural improvement of construction parts. For example, Dewi and Nuralinah [113] verified that the use of lightweight biomaterials is advantageous for concrete precast structures and earthquake-resistant structures. The use of light parts (culms, strips, sticks, and engineered bamboo beams) has allowed an architectural multiplicity, which may blend materials, technologies, and construction techniques. Figure 16 exemplifies a bamboo building designed using a blend of different construction techniques.

Fig. 16 Multistory scholar building: mixed construction technique of conical kiosk with postand-beam: a main façade and b bottom view of construction. Author: a Maristela Gava (2019), Indonesia; b Maristela Gava (2019), Indonesia

54

V. A. De Araujo et al.

7 Sustainability of Bamboo Construction Techniques The advances in the development of bamboo products have enabled a light, esthetic, and durable construction for a variety of uses with proper treatment of bioresources in use [106]. This argument is strengthened by Salcido et al. [98], as bamboo can reach a negative global warming potential since this bioresource outperforms similar structures made with wooden laminated veneer lumber. Traditional materials can be replaced by bioresources such as bamboo and wood to reach an environmentally positive activity and mitigate the impacts of climate change [114]. This decision is effectively supported by positive environmental results from many studies, as identified by Table 9, which was inspired by Gan et al. [115]. Given the results of Table 9, Gan et al. [115] stated that most bamboo products positively contribute to mitigating climate change impacts compared to benchmark products. From this perspective, bamboo was better than mineral-based solutions. Table 9 Selection by global warming potential: bamboo against other buildings Technique

Bamboo material

Benchmark material

Best choice

Source

Dome (Kiewitt style)

Laminated bamboo

Aluminum

Bamboo

Salcido et al. [98]

Laminated bamboo

Laminated lumber Bamboo

Salcido et al. [98]

Laminated bamboo

Steel

Bamboo

Salcido et al. [98]

Bamboo culm

Brick

Bamboo

Escamilla et al. [116]

Bamboo culm

Concrete

Bamboo

Escamilla et al. [116]

Multistory

Bamboo culm

Brick and concrete

Bamboo

Escamilla et al. [116]

Single-story house

Cement-bamboo

Concrete hollow block

Bamboo

Salzer et al. [117]

Cement-bamboo

Soil–cement block

Bamboo

Salzer et al. [117]

Cement-bamboo

Coconut panel

Coconut

Salzer et al. [117]

Cement-bamboo

Concrete brick

Bamboo

Eleftheriou et al. [118]

Bamboo culm

Concrete

Bamboo

Acevedo Pardo [119]

Bamboo culm

Concrete

Bamboo

Carcassi et al. [31]

Bamboo culm

Wood

Bamboo

Carcassi et al. [31]

Bamboo culm

Concrete

Bamboo

Carcassi et al. [31]

Bamboo culm

Wood

Bamboo

Carcassi et al. [31]

Single-story house

Single-story house

Multistory

Source Adapted from studies cited in the table

Bamboo Construction: Main Building Techniques and Their Resources, …

55

The search for a more sustainable, renewable, and regionally accessible raw material plays a global role in reducing the carbon footprint in construction, since quick urbanizations may be satisfied by the use of bioresources [120]. But, Churkina et al. [121] still suggest that bamboo cultivation can curb the deforestation of woody forests, as this promising culture could provide steady income to small-scale landowners and low-income rural communities. Despite the existence of environmental awareness and bioeconomy-oriented strategies, few nations have yet to work effectively for a greener reality [122]. Given this maturation moment worldwide, there is an opportune space to insert bamboo culture alongside silviculture, especially from intensive plantations. This suggestion is inspired by Churkina et al. [121] remarks, which propose that bamboo cultivation can curb the deforestation of natural forests since this alternative can provide steady income to small-scale landowners and low-income rural communities. The end of this friendly cycle therefore shall match the future demand-oriented to a more sustainable architecture with greener buildings built with bamboo and timber produced from positive forestry practices.

8 Conclusions Bamboo culms and esterillas have been utilized in rudimentary solutions for lowcost and popular buildings through vernacular construction techniques. From the advancement of bioresource technology and construction industrialization, structural bamboo products and bamboo-based composites are being developed to be utilized in modern buildings through sustainable techniques based on rationalized processes of prefabrication and modularization. Due to the multiple forms and resources, either by traditional or by contemporary architectural styles and construction techniques, bamboo can be utilized alone or together with other structural materials, either by “raw” or “engineered” sources, which potentially shall contribute to the diffusion of this bio-commodity worldwide.

References 1. Hidalgo-López O (2003) Bamboo: the gift of the Gods. Oscar Hidalgo-Lopez, Colombia 2. Clark LG, Lodoño X, Ruiz-Sanchez E (2015) Bamboo taxonomy and habitat. In: Liese W, Köhl M (eds) Bamboo: the plant and its uses. Tropical Forestry 10. Springer International, Switzerland, pp1–30 3. Greco TM, Cromberg M (2011). Bambu: cultivo e manejo. Insular, Florianópolis, Brazil 4. Silva RMC (2005) O bambu no Brasil e no Mundo. IEU, Rio de Janeiro, Brazil 5. Araujo CLP (2017) Caracterização e germinação de Dendrocalamus asper (Schultes f.) Backer ex Heyne (Poaceae: Bambusoideae). Dissertation, Federal University of Goias 6. Beraldo AL, Azzini A, Ghavami K, Pereira MAR (2003) Bambu: características e aplicações. In: Freire WJ, Beraldo AL (eds) Tecnologias e materiais alternativos de construção. UNICAMP, Campinas, Brazil, pp 253–299

56

V. A. De Araujo et al.

7. Ahmad Z, Upadhyay A, Ding Y, Emamverdian A, Shahzad A (2021) Bamboo: origin, habitat, distributions and global prospective. In: Ahmad Z, Ding Y, Shahzad A (eds) Biotechnological advances in bamboo. Springer Nature Singapore, Singapore 8. Hidalgo-López O (1974) Bambu—su cultivo e aplicaciones en: fabricacion de papel, construcion, arquitectura, ingeniería y artesania. Estudios Tecnicos, Cali, Colombia 9. Pereira MAR (2012) Projeto Bambu: introdução de espécies, manejo, caracterização e aplicações. Teaching Dissertation, São Paulo State University 10. Cedeño Valdiviezo A, Irigoyen Castillo J (2011) El bambú en México. Arq.urb 6:223–243 11. Teixeira AA (2006) Painéis de bamboo para habitações econômicas: avaliação do desempenho de painéis revestidos com argamassa. Dissertation, University of Brasilia 12. Hidalgo-López O (1978) Nuevas técnicas de construcción con bambú. Estudios Técnicos, Bogotá, Colombia 13. Rusch F, De Araujo V, Morales EAM, Gava M, Domene SMA, Cortez-Barbosa J (2022) Potential of young bamboos for food industry: production of ingredients from the use of their culms and shoots. Res Soc Dev 11:1–8 14. Berndsen RS, Klitzke RJ, Batista DC, Nascimento EM, Ostapiv F (2010) Propriedades físicas do bambu-mossô (Phyllostachys pubescens Mazel ex H. de Lehaie) em diferentes idades e posições do colmo. Floresta 40:183–192 15. Beraldo AL, Aleixo LRP (2019) Bambu: características e aplicações na construção civil e em arquitetura, 1st edn. Canal6, Bauru, Brazil 16. Ueda K (1987) Culture of bamboo as raw material. AOTS, Kyoto, Japan 17. Kigomo B (2007) Guidelines for growing bamboo. Guideline, Series: n.4. KEFRI, Nairobi, Kenya 18. Liese W (1985) Anatomy and properties of bamboo. Recent research on bamboos. In: Rao AN, Dhanarajan G, Sastry CB (eds), Proceedings of the international bamboo workshop, Hangzhou, China 19. Jaramillo Benavides AS, Ilha Librelotto L, Larco Benítez M (2015) Inventario del ciclo de vida del proceso de producción de bambú rollizo tratado de la especie Dendrocalamus asper en el noroccidente de Pichincha. Revista Eidos 8:17–24 20. Boissière M, Atmadja S, Benmakhlouf S, Beyessa M, Kassa H, Hunde T, Assefa F (2020) Developing small-scale bamboo enterprises for livelihoods and environmental restoration in Benishangul-Gumuz Regional State, Ethiopia. Int For Rev 22:306–322 21. Janssen JJ (2000) Designing and building with bamboo. INBAR, Beijing, China 22. Salzer C, Wallbaum H, Lopez LF, Kouyoumji JL (2016) Sustainability of social housing in Asia: a holistic multi-perspective development process for bamboo-based construction in the Philippines. Sustainability 8:1–26 23. Zhao H, Zhao S, INBAR, Fei B, Liu H, Yang H, Dai H, Wang D, Jin W, Tang F, Gao Q, Xun H, Wang Y, Qi L, Yue X, Lin S, Gu L, Li L, Zhu T, Wei Q, Su Z, Wan TBWA, Ofori DA, Muthike GM, Mengesha YM, Castro e Silva RM, Beraldo AL, Gao Z, Liu X, Jiang Z (2017) Announcing the genome atlas of bamboo and rattan (GABR) project: promoting research in evolution and in economically and ecologically beneficial plants. GigaScience 6:1–7 24. Kewei L, Jayaraman D, Estrella PJ, Yongjiu S, Jun Y, Junqi W, Lopez LF, Escardó BDLP, Moreno F (2022) Create an enabling environment for bamboo construction sector in Africa, Asia and Latin America. In: International conference on non-conventional materials and technologies, virtual conference 25. Pathak PK, Kumar H, Kumari G, Bilyaminu H (2016) Biomass production potential in different species of hemicelluloses from bamboo in central Utter Pradesh. The Ecoscan 10:41–43 26. Devi AS, Singh KS (2021) Carbon storage and sequestration potential in aboveground biomass of bamboos in North East India. Sci Rep 11:837–845 27. Quiroga RAR, Li T, Lora G, Anderson LE (2013) A measurement of the carbon sequestration potential of Guadua angustifolia in the Carrasco National Park Bolivia. In: Development research working paper series 04/2013. Institute for Advanced Development Studies, Bolivia

Bamboo Construction: Main Building Techniques and Their Resources, …

57

28. Singnar P, Das MC, Sileshi GW, Brahma B, Nath AJ (2017) Allometric scalling, biomass accumulation and carbon stocks in different aged stands of thin-walled bamboos Schiostachyum dullooa, Pseudostachyum polymorphum and Melocanna baccifera. For Ecol Manage 395:81– 91 29. van der Lugt P, Vogtländer J, van der Vegte JH, Brezet H (2015) Environmental assessment of industrial bamboo products: life cycle assessment and carbon sequestration. In: Proceedings of the 10th world bamboo congress. World Bamboo Organization, Korea, pp 1–16 30. Mimendi L, Lorenzo R, Li H (2022) An innovative digital workflow to design, build and manage bamboo structures. Sustain Struct 2:1–17 31. Carcassi OB, Habert G, Malighetti L, Pittau F (2022) Material diets for climate-neutral construction. Environ Sci Technol 56:5213–5223 32. Meyer HF, Ekelund B (1923) Tests on the mechanical properties of bamboo. Proc Eng Soc China 22:141–169 33. Raj AD, Agarwal AB (2014) Bamboo as a building material. J Civil Eng Environ Technol 1:56–61 34. Huang Y, Ji Y, Yu W (2019) Development of bamboo scrimber: a literature review. J Wood Sci 65:1–10 35. Liese W, Welling J, Tang TKH (2015) Utilization of bamboo. In: Liese W, Köhl M (eds) Bamboo: the plant and its uses. Tropical Forestry 10. Springer International, Switzerland, pp 299–346 36. Palombini FL, Kindlein W, de Oliveira BF, de Araujo Mariath JE (2016) Bionics and design: 3D microstructural characterization and numerical analysis of bamboo based on X-ray microtomography. Mater Charact 120:357–368 37. Sharma P, Dhanwantri K, Mehta S (2014) Bamboo as a building material. Int J Civil Eng Res 5:249–254 38. Nkeuwa WN, Zhang J, Semple KE, Chen M, Xia Y, Dai C (2022) Bamboo-based composites: a review on fundamentals and processes of bamboo bonding. Compos B 235:1–20 39. De Almeida A, De Araujo VA, Morales EAM, Gava M, Munis RA, Garcia JN, Cortez-Barbosa J (2017) Wood-bamboo particleboard: mechanical properties. BioResources 12:7784–7792 40. Barreto MIM, De Araujo V, Cortez-Barbosa J, Christoforo AL, Moura JDM (2019) Structural performance analysis of cross-laminated timber-bamboo (CLTB). BioResources 14:5045– 5058 41. Chen G, Yin M, Wu X, Wang Z, Jiang H (2021) Structural performance of laminated-bamboo lumber nailed connection. Wood Mater Sci Eng 1–13 42. UN-Habitat (2012) Going green: a handbook of sustainable housing practices. UN-Habitat, Nairobi, Kenya. Retrieved from https://unhabitat.org/sites/default/files/download-managerfiles/Going%20Green.pdf 43. Malanit P, Barbu MC, Frühwald A (2011) Physical and mechanical properties of oriented strand lumber made from an Asian bamboo (Dendrocalamus asper Backer). Eur J Wood Wood Prod 69:27–36 44. Nugroho N, Ando N (2000) Development of structural composite products made from bamboo I: fundamental properties of bamboo zephyr board. J Wood Sci 46:68–74 45. Morán-Ubídia J (2001) Usos tradicionales y actuales del bambú en América Latina con énfasis en Colombia y Ecuador. Escuela Politécnica Nacional, Quito, Ecuador 46. Stothert KE (1988) La prehistoria temprana de la península de Santa Elena. Cultura Las Vegas—Museo Banco Central del Ecuador, Guayaquil, Ecuador 47. Carmiol Umaña V (2010) Bambú guadua, en puentes peatonales. Tecnología en Marcha 23:29–38 48. Viollet-Le-Duc E (1876) The habitations of man in all ages. Sampson Low, Marston, Searle, & Rivington, London, United Kindgom 49. Hidalgo-López O (1981) Manual de construcción con bambú. Estudios Técnicos, Bogotá, Colombia. 50. Gatóo A, Sharma B, Bock M, Mulligan H, Ramage M (2014) Sustainable structures: bamboo standards and building codes. Proc Inst Civil Eng Eng Sustain 167:189–196

58

V. A. De Araujo et al.

51. Brazilian Association of Technical Standards (2020) Bamboo structures. Part 1: project (ABNT/NBR-16828-1). ABNT, Rio de Janeiro, Brazil 52. Brazilian Association of Technical Standards (2020) Bamboo structures. Part 2: determination of physical and mechanical properties of bamboo (ABNT/NBR-16828-2). ABNT, Rio de Janeiro, Brazil 53. Lapina AP, Zakieva NI (2021) Bamboo in modern construction and architecture. IOP Conf Ser: Mater Sci Eng 1083:1–6 54. Minke G (2016) Building with bamboo: design and technology of a sustainable architecture, 2nd edn. Birkhäuser, Berlin, pp 27–28 55. Schmidt G (2020) Industrialized bamboo in East Africa: resource, production process and market entrance of a novel scrimber composite. Dissertation, University of Hamburg 56. Auwalu FK, Dickson PD (2019) Bamboo as a sustainable material for building construction in Nigeria. Civil Environ Res 11:30–36 57. Pope G (1988) Recent advances in far eastern paleoanthropology. Annu Rev Anthropol 17:43– 77 58. Bredenoord J (2017) Sustainable building materials for low-cost housing and the challenges facing their technological developments: examples and lessons regarding bamboo, earthblock technologies, building blocks of recycled materials, and improved concrete panels. J Architectural Eng Technol 6:1–11 59. De Araujo VA, Cortez-Barbosa J, Gava M, Garcia JN, Souza AJ, Savi AF, Morales EAM, Molina JC, Vasconcelos JS, Christoforo AL, Lahr FA (2016a) Classification of wooden housing building systems. BioResources 11:7889–7901 60. De Araujo V (2021) Timber construction as a multiple valuable sustainable alternative: main characteristics, challenge remarks and affirmative actions. Int J Constr Manag 2021:1–10 61. Platt SL (2018) Bamboo as a resource for modern vernacular architecture. In: 9th international conference on sustainable built environment, Kandy, Sri Lanka 62. Kahn L (1973) Shelter. Shelter Publications, Bolinas, USA 63. UNESCO (2019) Prehistoric pile dwellings around the Alps. UNESCO, Paris, France. Retrieved from https://whc.unesco.org/document/192715 64. Bush DM, Neal WJ, Longo NJ, Lindeman KC, Pilkey DF, Esteves L, Congleton JD, Pilkey OH (2004) Living with Florida’s Atlantic beaches: coastal hazards from Amelia Island to Key West. Duke University Press, London, UK 65. Cabalfin EG (2020) Bahay Kubo as iconography: representing the vernacular and the nation in Philippine post-war architectures. Fabrications 30:44–67 66. Lopes WGR (1998) Taipa de mão no Brasil: levantamento e análise de construções. Dissertation, University of São Paulo 67. Fleisher J, LaViolette A (1999) Elusive wattle-and-daub: finding the hidden majority in the archaeology of the Swahili. Azania Archaeol Res Africa 34:87–108 68. Carazas Aedo W, Rivero Olmos A (2003) Wattle and daub: anti-seismic construction handbook. Editions CRATerre, Villefontaine, France 69. Moore JD (2021) Bahareque. In: Moore JD. Ancient Andean houses: making, inhabiting, studying. University Press of Florida, Gainesville, US, pp 19–36 70. Muñoz Robledo JF (2010) Tipificación de los sistemas constructivos patrimoniales de “bahareque” en el paisaje cultural cafetero de Colombia. Blanecolor, Manizales, Colombia 71. Robledo Castillo JE (1993) Un siglo de bahareque en el antiguo Caldas. Ancora editores. Bogotá, Colombia 72. Gutierrez JA (2000) Structural adequacy of traditional bamboo housing in Latin America. INBAR, Beijing, China 73. Kaminski S, Lawrence A, Trujillo DJA (2016) Design guide for engineered bahareque housing. INBAR, Beijing, China 74. Vengala J, Rao RS (2020) Sustainable bamboo housing for the earthquake prone areas. IOP Conf Ser: Mater Sci Eng 955:1–6 75. Ordónez Candelaria VR, Mejía Saulés MT, Bárcenas Pazos GM (2002) Manual para la construcción sustentable con bambú. Conafor, Jalisco, Mexico

Bamboo Construction: Main Building Techniques and Their Resources, …

59

76. Rael R (2009) Earth architecture. Princeton Architectural Press, New York, US 77. Vatan M (2017) Evolution of construction systems: cultural effects on traditional structures and their reflection on modern building construction. In: Koç G, Claes MT, Christiansen B. Cultural influences on architecture. IGI Global, Hershey, US 78. Viñuales GM (2007) Tecnología y construcción con tierra. Apuntes 20:220–231 79. Minke G (1984) Earthquake-resistant low-cost houses utilizing indigenous building materials and intermediate technology. In: Proceedings of the International Symposium on Earthquake Relief in Less Industrialized Areas. Zurich, Switzerland 80. De Vries SK (2002) Bamboo construction technology for housing in Bangladesh opportunities and constraints of applying Latin American bamboo construction technologies for housing in selected rural villages of the Chittagong hill tracts, Bangladesh. Dissertation, Eindhoven University of Technology 81. Geymayer HG, Cox FB (1970) Bamboo reinforced concrete. Corps of Engineers, Vicksburg, US 82. Ghavami K (2005) Bamboo as reinforcement in structural concrete elements. Cement Concr Compos 27:637–649 83. Ghavami K (2003) Eco-construction and infrastructure. RIO 3—World Climate & Energy Event, Rio de Janeiro, Brazil 84. Rahim NL, Ibrahim NM, Salehuddin S, Mohammed SA, Othman MZ (2020) Investigation of bamboo as concrete reinforcement in the construction for low-cost housing industry. IOP Conf Ser: Earth Environ Sci 476:1–11 85. Agarwal A, Nanda B, Maity D (2014) Experimental investigation on chemically treated bamboo reinforced concrete beams and columns. Constr Build Mater 71:610–617 86. Korde C, West R (2018) Analysis of an innovative multi-level bamboo structure. In: Singh SB, Bhunia D, Muthukumar G (eds) 2nd International conference on advances in concrete, structural & geotechnical engineering. Bloomsbury Publishing, Rajasthan, India, pp 618–622 87. Izumida H (2003) Japanese clay-walled house; materials, artisans and techniques. In: 9th International conference on study and conservation of earthen architecture, Yazd, Iran 88. Hanazato T, Minowa C, Niitsu Y, Nitto K, Kawai N, Maekawa H, Morii M (2010) Seismic and wind performance of five-storied pagoda of timber heritage structure. Adv Mater Res 133–134:79–95 89. Kaunang IRB (2020) City in Dragon Circle: study of the history of pagoda and its deployment in Manado, 1819–2018. Jurnal Sejarah Citra Lekha 5:3–13 90. Britannica (2022) Pagoda. Retrieved from https://www.britannica.com/technology/pagoda 91. Tang Z, Zhang Y (2002) The generate method of multi-storey Chinese pagodas. In: 2002 generative art international conference, Italy 92. Weslager CA (1969) The log cabin in America: from pioneer days to the present. Rutgers University Press, New Brunswick, US 93. Pollio V (1914) The ten books on architecture. Oxford University Press, London, UK 94. Hong C, Li H, Xiong Z, Lorenzo R, Corbi I, Corbi O, Wei D, Yuan C, Yang D, Zhang H (2020) Review of connections for engineered bamboo structures. J Build Eng 30:101324 95. Farrelly D (1984) The book of bamboo. Sierra Club Books, San Francisco, US 96. Ugarte J, Habusta M (2011) Bamboo the vegetal miracle/Bambú el milagro vegetal. Germany/Costa Rica, Instituto de Arquitectura Tropical 97. Seixas MA, Ripper JLM, Ghavami K (2015) Construction of mobile bamboo dome covered with textile canvas. In: 16th international conference on non-conventional materials and technologies, Winnipeg, Canada 98. Salcido JC, Raheen AA, Ravi S (2016) Comparison of embodied energy and environmental impact of alternative materials used in reticulated dome construction. Build Environ 96:22–34 99. Pereira MA, Beraldo AL (2007) Bambu de corpo e alma. Canal6, Bauru, Brazil 100. Vaghela K, Acharya M, Jethwa P, Kakadiya H, Tanna D, Charan D, Shah Z (2013) Bamboo construction source book. Hunnarshala Foundation, Gujarat, India 101. Mogollón Seba J (1993) Vivienda: soporte modular y participación. Inf Constr 44:62–89

60

V. A. De Araujo et al.

102. Azambuja MA, Kawakami CAF (2015) Painéis em bambu para habitação social. Revista Nacional de Gerenciamento de Cidades 3:153–168 103. Jaramillo Benavides AS (2012) Proposta de sistema construtivo para habitação de interesse social com bambu guadua: um estudo de caso no Equador. Dissertation, Federal University of Santa Catarina 104. Sharma B, Gatoo A, Bock M, Mulligan H, Ramage M (2015) Engineered bamboo: state of the art. Proc Inst Civ Eng Constr Mater 168:57–67 105. Habibi S (2019) Design concepts for the integration of bamboo in contemporary vernacular architecture. Architectural Eng Design Manage 15:475–489 106. DA (2014) Bamboo: green construction material. Retrieved from https://www.devalt.org/ima ges/L2_ProjectPdfs/Resource_Efficiency_Publications_Catalogue_DA.pdf 107. Lopes WGR, Carvalho TMP, Matos KC, De Alexandria SSS (2013) A taipa de mão em Teresina, Piauí, Brasil: a improvisação e o uso de procedimentos construtivos. Digitar 1:70–78 108. De Araujo VA, Vasconcelos JS, Cortez-Barbosa J, Morales EAM, Gava M, Savi AF, Garcia JN (2016b) Wooden residential buildings—a sustainable approach. Bull Transilvania University of Bra¸sov—Series II: Forestry Wood Ind Agri Food Eng 9, 53–62 109. Vogtländer J, van der Lugt P, Brezet H (2010) The sustainability of bamboo products for local and Western European applications. LCAs and land-use. J Clean Prod 18:1260–1269 110. Trujillo DJA, Ramage M, Change W (2013) Lightly modified bamboo for structural applications. Proc Inst Civil Eng Constr Materials 166:238–247 111. Ding D, Xu Q, Liu C, and Zhang D (2020) Activation of traditional construction techniques used in Linpan based on the concept of sustainability: case study of bamboo materials. In: Chan FKS, Chan HK, Zhang T, Xu M (eds) Proceedings of the 2020 international conference on resource sustainability: sustainable urbanisation in the BRI Era (icRS Urbanisation 2020). Springer Nature, Singapore, pp 169–180 112. Palacios A, Angumba P (2021) Bahareque as a sustainable construction system: analysis of unit prices. IOP Conf Ser Mater Sci Eng 1203:1–7 113. Dewi SM, Nuralinah D (2017) The recent research on bamboo reinforced concrete. MATEC Web Conf 103:1–6 114. Borowski PF, Patuk I, Bandala ER (2022) Innovative industrial use of bamboo as key “green” material. Sustainability 14:1955–1968 115. Gan J, Chen M, Semple K, Liu X, Dai C, Tu Q (2022) Life cycle assessment of bamboo products: review and harmonization. Sci Total Environ 849:1–11 116. Escamilla EZ, Habert G, Correal Daza J, Archilla H, Echeverry Fernández J, Trujillo D (2018) Industrial or traditional bamboo construction? Comparative life cycle assessment (LCA) of bamboo-based buildings. Sustainability 10:3096–3110 117. Salzer C, Wallbaum H, Ostermeyer Y, Kono J (2017) Environmental performance of social housing in emerging economies: life cycle assessment of conventional and alternative construction methods in the Philippines. Int J Life Cycle Assess 22:1785–1801 118. Eleftheriou E, Lopez Muñoz LF, Habert G, Zea Escamilla E (2022) Parametric approach to simplified life cycle assessment of social housing projects. Sustainability 14(12):7409–7414 119. Acevedo Pardo C (2014) A comparative life cycle assessment of a social interest housing building: bamboo vs. concrete. Dissertation, Cornell University 120. Crolla K (2017) Building indeterminacy modelling—the ‘ZCB Bamboo Pavilion’ as a case study on nonstandard construction from natural materials. Visual Eng 5:1–12 121. Churkina G, Organschi A, Reyer CPO, Ruff A, Vinke K, Liu Z, Reck BK, Graedel TE, Schellnhuber HJ (2020) Buildings as a global carbon sink. Nat Sustain 3:269–276 122. De Araujo V, Vasconcelos J, Lahr F, Christoforo A (2022) Timber forest products: a way to intensify global bioeconomy from bio-materials. Acta Facultatis Xylologiae Zvolen 64:99– 111

Bamboo Structural Systems Gilberto Carbonari and Luana Toralles Carbonari

Abstract Bamboo is an advantageous material in several aspects, such as mechanical resistance, lightness, and rapid growth. Thus, it is an excellent sustainable alternative, with high strength, low specific weight, and renewable. This chapter will discuss two structural systems with bamboo. The first innovative system refers to bamboo–concrete composite slabs without the use of steel reinforcement, which consists of half-cut bamboo “joists” of the species Dendrocalamus giganteus, combined with EPS plates that function as filling elements. The system is solidified through concreting carried out on site, like the conventional slab capping. From tests performed on six slabs, satisfactory performances were obtained, both in the ultimate limit state (ULS) and service limit state (SLS), showing a system with great potential for structural application. The second innovative system refers to bamboo Howe trusses for building roofing, using the species Dendrocalamus giganteus, reinforced with grout and metal clamps. The results obtained after executing six elements and analyzing their performance when subjected to stresses proved that the reinforcements, besides the use of threaded bars in the joints between elements of the Howe trusses, contribute to a significant increase of mechanical resistance to the structure. Furthermore, the results of the loads and displacements obtained in the tests allow concluding that Howe trusses can be safely used on the buildings’ roofs because meets the criteria of the ultimate limit state and service limit state.

G. Carbonari Centro de Tecnologia E Urbanismo (CTU), Departamento de Estruturas, Universidade Estadual de Londrina (UEL), Rodovia Celso Garcia Cid, PR 445 Km 380. CEP 86.057-970, Caixa Postal 10.011, Londrina, PR, Brazil e-mail: [email protected] L. T. Carbonari (B) Centro de Tecnologia e Urbanismo - Departamento de Arquitetura e Urbanismo, Universidade Estadual de Londrina (UEL), Campus Universitário - Rod. Celso Garcial Cid (PR-445), km 380, CEP: 86051-990, Londrina, PR, Brazil e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 F. L. Palombini and F. M. Nogueira (eds.), Bamboo and Sustainable Construction, Environmental Footprints and Eco-design of Products and Processes, https://doi.org/10.1007/978-981-99-0232-3_3

61

62

G. Carbonari and L. T. Carbonari

Keywords Civil engineering · Structural efficiency · Structural application · Theoretical and experimental analysis · Composite slab · Bamboo–concrete · No steel · Howe trusses

1 Introduction With the accelerated population increase that humanity has been experiencing, reaching more than 7.5 billion people inhabiting the planet, associated with the accumulation of population in urban areas, demands are created that compress the world’s production system and, consequently, its environment. With cities becoming more and more populated, better planning is needed in the construction of infrastructure and housing because as urbanization increases, the impact of civil construction tends to get higher. Considering the social, economic, and environmental impact of the civil construction sectors, the area plays a leading role in the success of an ideal model for life in society. According to information from Global Footprint Network [1], an international research organization partnering with WWF (Worldwide Fund for Nature), an international NGO working in the areas of environmental conservation, research, and restoration, the rate at which natural resources are consumed is 74% greater than the planet’s capacity to regenerate. This clearly exposes the scarcity of the planet’s natural resources and causes the concern with sustainability to be placed in evidence. In this context, the substitution of materials that require high energy consumption for their manufacture, such as steel, for sustainable materials that are easy to find and grow quickly, such as bamboo, is increasingly valued. In addition, bamboo stores about 45% carbon in its biomass, making it a very efficient carbon sink. This percentage is similar to other fast-growing species also considered carbon sequestrators, such as pine and eucalyptus. However, when these data are analyzed together with the annual growth rates, one can see the enormous advantage that bamboo has over other plants in terms of carbon storage [2]. Because it has the characteristic of accelerated growth, bamboo stands out as a fast sequester of carbon, being a natural and forest resource that takes less time to be renewed. This makes it highly attractive compared to other tree species [3]. Thus, considering all the mechanical and socio-ecological qualities of bamboo, it is important to implement bamboo in civil construction, serving as an incentive to obtain new research and construction methods, both nationally and internationally. Going deeper into the economic and environmental impacts, civil construction has become even more interested in creating new construction methods by replacing materials present in its current construction processes. In this context, bamboo presents itself as a solution with great potential.

Bamboo Structural Systems

63

Bamboo, as a renewable and energy-saving material in its production chain, captivates interest in its use in civil construction since it is easily adaptable to different soils and climates, grows relatively fast, and has a low planting cost [4, 5]. Because it reaches full growth in just a few months and reaches its maximum mechanical strength in just a few years, it is abundantly present in tropical and subtropical regions of the planet [6]. Bamboo is an attractive replacement alternative for steel in tensile strength applications, as its tensile strength to specific weight ratio is higher than steel [7, 8]. One of the main difficulties for the implementation of different natural materials as structural composites is the lack of sufficient information on such materials regarding their durability, bamboo also brings its odd geometric shape, which makes it difficult to directly use the standards used in wood tests. Due to its relatively conical geometric shape, together with the existing distance between the nodes, it makes it impossible to acquire homogeneous specimens conceived from the same thatch. All the cited characteristics would not be fully sufficient if the mechanical properties of bamboo were not taken into consideration. Such properties supported by the relations of mechanical strength, specific mass, and stiffness exceed traditional materials in construction [9, 10], such as wood and concrete, and some species of bamboo, can even be compared to steel [11]. This chapter is organized into two parts, addressing different structural systems with bamboo. The first part refers to an innovative system of bamboo–concrete composite slabs without the use of steel reinforcement, which consists of half-cut bamboo “joists” of the species Dendrocalamus giganteus, combined with EPS plates that function as filling elements. The second part refers to an innovative system of bamboo Howe trusses for building roofing, using the species Dendrocalamus giganteus, reinforced with grout and metal clamps.

2 Part 1—Composite Slabs of Bamboo–Concrete, No Steel Brazil has two specific technical standards for bamboo, [12] and [13]. However, bamboo–concrete composite slabs are not included in these standardization proposals. There are a few works on this subject, where we highlight the research developed by Ghawami [14], who tested bamboo–concrete composite slabs. Later, our research group reproduced the same tests [15]. Both works concluded that the adopted cross section did not provide sufficient stiffness and mechanical strength for building use. Thus, it was necessary to change the cross section and incorporate a connection system between the bamboo half-canes with the concrete, detailed in this part of the chapter. This new slab design began to be used in research in 2017 by the research group “Bamboo-UEL” [16, 17], which is in a patent process by the Brazilian National Institute of Industrial Property—INPI (BR 10 2018 015,711 6). Using bamboo as a structural material in buildings is necessary to ensure its long-term durability, especially in the face of insect attack. For this, our Bamboo-UEL research group

64

G. Carbonari and L. T. Carbonari

has achieved success using an efficient natural treatment, which does not harm the environment, with tannin [18]. Since 2013, the stalks treated with the said natural material, extracted from the bark of the black acacia tree, do not present any attack of the insects on the bamboo fibers.

2.1 Materials and Methods The slabs under study are mixed with unidirectional joists using bamboo of the species Dendrocalamus giganteus, concrete, EPS boards, and bamboo connectors. A total of six slabs were tested, all 310 cm long, 75 cm wide, and 20 cm high, as seen in Fig. 1. It is worth mentioning that the measurements referring to the diameters of the half-canes are placed generically because, since it is a vegetable, bamboo stalks suffer natural growth changes in their measurements from one stalk to another. In total, six slabs were tested, three of them with bamboo connectors 4 cm long and spaced every 5 cm, and the other three slabs with connectors also 4 cm long but spaced every 10 cm.

Fig. 1 Cross section (a) and top view (b) of the slabs. Source Carbonari et al. [19]

Bamboo Structural Systems

65

Fig. 2 Extraction and cutting of the bamboo stalks. Source Carbonari et al. [19]

2.1.1

Extraction, Selection, and Measurement of Bamboo Stalks

The stalks chosen for cutting were marked with a control code for identification against the other stalks. As seen in Fig. 2a, the stalks were cut close to one of their nodes, and a V-shaped depression was made to facilitate water drainage, preserving the bush against possible rotting in that region and allowing the development of new bamboo shoots. After removing the bamboo stump (Fig. 2a), the stalks were cut into segments of 330 cm in length and transported to the Structures Laboratory of the UEL. Next, the process of preparing the half-canes began, making a longitudinal cut of these thatch segments with the help of a table saw, as seen in Fig. 2b. With this, the cut of the semicircular sector (half-canes) was standardized with a fixed height of 6 cm, independent of the diameter of the canes, thus avoiding the difference in height between the half-canes, as observed in previous works. Approximately 3 days after cutting, the insecticide JimoCupim® was applied. After the application of this product, the half-canes were spread and kept in the laboratory for two days, with the environment closed. This procedure was repeated 15 days after the first application.

2.1.2

Preparation of the Bamboo Half-Canes and Meshes

The sixteen half-canes selected in the previous step were identified in trios, marked, and drilled according to the points where the connectors would be fixed. The diameter and height of the connectors were set at 5 mm and 4 cm, respectively, as well as the

66

G. Carbonari and L. T. Carbonari

Fig. 3 Bamboo fillet mesh, tied with sisal string. Source Carbonari et al. [19]

depth at which they entered the inner wall of the bamboo, was set at 7 mm. It is important to emphasize that at the ends of the half-canes, the distance between the end of the half-cane and the first connector should be equal to half the normal spacing of that respective half-cane to maintain uniform mechanical properties between connectors and concrete. The two types of connectors spacing were 5 cm and 10 cm. The bamboo mesh from the Dendrocalamus giganteus species was composed of fillets removed on the same day of the cutting and regularization of the radius of the half-canes, these fillets being the excess part of the half-canes, always aiming to get a better use of all the bamboo stalk that was used in the process of this work, as shown in Fig. 3. The meshes were also regularized to have a standard maximum thickness of 1 cm, varying in the transverse and longitudinal directions according to the natural shape of each thatch used. These meshes were separated and treated with the same insecticide used in the half-canes; the fillets were tied with sisal string, a sustainable natural compound. The distance between the fillets was set at 15 cm, forming a mesh of 15 × 15 cm.

2.2 Assembly and Concreting Starting by assembling the forms, to limit the slab measurements and to aid in correct leveling, the forms were positioned and nailed so that the smallest side internal space was 75 cm wide, the maximum width of the laboratory test frame. And the largest internal side with 310 cm in the longitudinal direction of the half-canes.

Bamboo Structural Systems

67

Fig. 4 Assembling the slabs before concreting. Source Carbonari et al. [19]

In a constructive sequence, four beams were positioned approximately similarly spaced from each other; the molds were placed on top of them, and the wedges and the half-canes were positioned on top of the wedges. Then the EPS boards were positioned in the spans of the half-canes; each EPS board has the dimensions of 60 cm long, 20 cm wide, and 10 cm high. With the main items of the slab positioned, the lateral and superior blocking was done with longitudinal and transversal beams, respectively. Figure 4a, b show the details of the slabs’ assembly before concreting. With the assembly ready, the slabs were then concreted. The characteristics of the concrete were: machined concrete with fck = 30 MPa, slump test with a minimum of 120 mm. The slabs were all concreted on the same day, showing that the logistics adopted in the position of the slabs were effective, aiming at speed and ease. It was observed the efficiency of the sealing between formwork and half-cane through the kraft-type adhesive tape, with satisfactory tightness. Figure 5a, b illustrate the concrete slabs. Nine specimens were molded, with 10 cm in diameter and 20 cm in height, for compressive strength testing, following NBR 5738 [20]. Three were broken at 7 days, another three were broken at 14 days, and the last three at 28 days, the day before the flexion test. The specimens, 24 h after molding, were immersed in a curing tank, according to NBR 5738 [20]. Thus, the cross sections of the slabs present the cross section with all its components, shown in Fig. 6.

68

G. Carbonari and L. T. Carbonari

Fig. 5 Recently concreted slabs. Source Carbonari et al. [19]

Fig. 6 Cross section with all components. Source Carbonari et al. [19]

2.3 Test Procedure The bending test consists of the application of an increasing load on the slabs, by means of a load cell, where the values of the applied load and displacements are recorded, until failure. The four-point test method in this work consists of two concentrated loads applied at equal distances from the supports of 1 m, as illustrated in Fig. 7. Three displacement transducers (LVDTs) were used to measure the displacements during load application. Besides these, two comparator clocks (RC) were positioned for a video comparison of the synchrony of displacements in the slab. The three LVDTs were from the brand “KYOWA”, two of them from the model “DT-50A” characterized by having a maximum measurement amplitude equal to 50 mm. These RCs were positioned one at each end of the slab. The third LVDT, model “DT-100A” characterized by having a maximum measurement capacity equal to 100 mm, was positioned at the center of the slab, because it is the point of the structure where

Bamboo Structural Systems

69

Fig. 7 Four-point bending test model. Source Carbonari et al. [19]

the greatest vertical displacement would occur, ensuring the measurement of the displacement exceeds the value of 5 cm. Figure 8a (photo) and c (top view) show the positions of the LVDTs and comparator clocks and the overview of the test system (photo Fig. 8b)

2.4 Results Analysis and Discussion The curves obtained for each slab can be interpreted and analyzed in three stages. The graph in Fig. 9 shows the three stages of the typical measured load × displacement graph of the slabs tested. In the first part of the curve, there is the so-called Phase 1, according to Hooke’s Law. The second part is called Phase 2, which is also linear and begins after the bamboo connectors move within the structure. These connectors move but continue to maintain their function. The third part of the curve, called Phase 3, occurs after the rupture of the structure, and it can be observed that the connectors no longer have contact with the concrete part of the structure, completely losing their function. Figure 10 shows the behavior of the bamboo connectors in each of the abovementioned phases, and the variation in the position of the connectors is evident. All slabs had similar ruptures, following a pattern of the same mechanisms, that is, failure in the connectors that make connections between the bamboo stalks and the concrete, relative displacement between the bamboo wall and the concrete, and the appearance of vertical cracks in the area near the load application points. As the pathologies were similar in all slabs, Fig. 11 shows the locations (Fig. 11a) and illustrations of the cracks (Fig. 11b, c) presented by one of the slabs tested, in this case, slab 5. In Fig. 12, you can see the relative displacement between the bamboo half-cane and the concrete part. The load × displacement curves presented in the graph in Fig. 13 show the values measured on the six slabs tested. In contrast, in a more detailed analysis, it can be observed the behavior of the curves going through phases 1, 2, and 3 already be mentioned.

70

G. Carbonari and L. T. Carbonari

Fig. 8 Location of LVDT’s and comparator clocks (a) and (b); and overview (c). Source Carbonari et al. [19]

Bamboo Structural Systems

71

Fig. 9 Phases of the typical load × displacement curve for slabs. Source Carbonari et al. [19]

Fig. 10 Positioning of the connectors on the phases. Source Carbonari et al. [19]

When the test curves of all the slabs are analyzed, it can be seen that the three phases of mechanical behavior are clearly distinct. To illustrate this mechanism, for one of these phases, Fig. 14 illustrates with real photos of the test the behavior of the connectors during the phases. The objective of giving adherence to the bamboo and concrete composite using bamboo connectors obtained positive results. However, the slabs with a spacing of 5 cm between connectors showed better mechanical behavior than the slabs with a spacing of 10 cm between connectors, all six composite slabs of concrete and bamboo without the presence of steel had a resistance to breaking load considered high, where the smallest was 2390 kgf. However, a larger number of tests and experiments are still needed to prove their structural application.

72

G. Carbonari and L. T. Carbonari

Fig. 11 Positioning and images of the cracks in the slab 05. Source Carbonari et al. [19]

Fig. 12 Image of the displacement of slab 05. Source Carbonari et al. [19]

Bamboo Structural Systems

Fig. 13 Load × displacement curves of all slabs until failure. Source Carbonari et al. [19]

Fig. 14 Image and photos from phases 1, 2 and 3. Source Carbonari et al. [19]

73

74

G. Carbonari and L. T. Carbonari

Table 1 Maximum load in Phase 1 and failure load of the tested slabs

Connector spacing (cm)

Maximum load Phase 1 (Kgf)

Maximum rupture load (Kgf)

Slab 1

10

500

2.700

Slab 2

10

460

2.390

Slab 3

10

320

2.500

Slab 4

5

570

3.300

Slab 5

5

295

3.000

Slab 6

5

720

2.620

Source Carbonari et al. [19]

Table 1 shows the maximum loads supported by the slabs in Phase 1, as well as the breaking loads for each of them. Although there is a certain dispersion between the results, the average of the load values for slabs with 5 cm spacing between connectors presents slightly higher values than those with 10 cm. This is true both for the maximum loads in Phase 1 and for the failure loads. But, observing the load × displacement curves of the 6 slabs in Fig. 13, except for slab 4, the other slabs have stiffnesses very similar to each other. For Phase 2, it can be concluded that the spacing between the 5 cm and 10 cm connectors did not significantly influence the values of both the limit loads and stiffnesses. It is worth noting that all slabs showed similar behavior to the images illustrated in Fig. 14. Note that in the central part of the slab, there is no displacement between the bamboo–concrete interface because, in this region, the internal shear between the two load points is null, and there are no shear stresses in the slab cross sections. In theory, with the purpose of the project in the laboratory, the placement of connectors in that region would not be necessary. Still, it is known that in practice the use of slabs with this system will also suffer distributed loads, so it is necessary to place the connectors uniformly throughout all the half-canes. When the failure processes of all slabs are analyzed, some characteristics can be noticeably observed, such as the noise coming from the rupture of the bamboo. This characteristic can be perceived through the graphs between load and displacement, where there are negative oscillations in the curves revealing the displacement of the connectors within the structure, which even after these displacements manage to maintain their function. This highlights the high ductility of the structure. Even with the differences between their capacities of maximum loads until rupture, all slabs suffered a behavior considered ductile until the end of the loading, not suffering any abrupt rupture, i.e., showing adequate for structural application. Considering the ultimate limit state (ULS) of the slabs, as seen in the load × displacement curves in Fig. 13, all slabs had a ductile behavior, i.e., suitable for structural application. In the serviceability limit state (SLS), it is possible to analyze the mechanical behavior of the slabs for both the standard loads and the displacement limits.

Bamboo Structural Systems

75

Fig. 15 Load × displacement curves (theoretical and practical) of Slab 05. Source Carbonari et al. [19]

Considering a total load (accidental + self-weight) of 350 kgf/m2 (self-weight and overload) on the 3 m long and 0.75 m wide slab, this equals a resultant equivalent load of: Peq = 350 × 0.75 × 3 = 788 kgf This equivalent load is well below the lowest recorded rupture load of the slabs, as seen in Table 1, where the minimum value of the rupture load was approximately 2400 kgf. To verify the SLS, Slab 5, shown in Fig. 15, will be used as an illustrative example. To facilitate the analysis, only a portion of the load × displacement curve was taken, up to a load of ~ 1300 kgf, and a displacement of 8 mm. As can be seen in Fig. 15, Phase 1 goes up to a load of ~ 295 kgf (see Table 1). Furthermore, the difference between the stiffness of Phase 1 (theoretical) and Phase 2 (from testing) is quite evident. Nevertheless, for an equivalent service load of 788 kgf, the displacement equals ~ 4 mm, considered comfortable since the deflection limit value by the standard is L/250, which would give a limit value of up to 12 mm. For this, a free span between slab supports of 3000 mm (3 m) was adopted.

2.5 Concluding Remarks from Part 1 By the proximity of the load × displacement curves of the six slabs tested, it is possible to conclude that the methodology and materials adopted in this work were adequate. The ultimate loads and stiffnesses measured in the tests allow us to consider that the slabs can be used as structural elements in buildings. It is essential to have very close results between the slabs that the height of the half-canes is fixed at a single value, regardless of their outer diameters.

76

G. Carbonari and L. T. Carbonari

Furthermore, it is observed from the long stretch of Phase 2 load × displacement curves that the bamboo connectors can meet the connection between the bamboo half-canes and the concrete, regardless of the spacing adopted (5 cm and 10 cm). The slabs with 5 cm spacing between connectors showed better mechanical behavior than the slabs with 10 cm spacing, as expected. However, a larger number of tests and experiments are still needed to prove its structural application, to meet the SLS and ULS conditions, including in the face of long-term deformations (shrinkage and creep). Next, the second part of this chapter is presented.

3 Part 2—Double-Pitched Truss in Bamboo: Theoretical–Experimental Analysis The objective of the study is to determine the method for the execution of the trusses with the highest possible structural efficiency, comparing two reinforcement techniques in the supports of the trusses: The six bamboo trusses executed have their supports filled with grout, three of them confined by perforated metal strips, and the other three with steel ties. In addition, it aims to analyze whether bamboo trusses are structurally feasible for execution on building roofs, comparing with the experimental results obtained in the tests. Only the species Dendrocalamus giganteus was analyzed due to its large dimensions in outer diameter and thickness, which confer greater mechanical strength compared to other species.

3.1 Physical and Mechanical Properties of Bamboo The physical and mechanical properties of bamboo are directly linked to its anatomical structure. The main physical properties of bamboo are: (a) Thatch age: this is an important factor in determining the resistance of the bamboo. The ideal for monitoring the age of the bamboo is to label it right when it sprouts from the soil, but if this is not possible, you can estimate the age by observing the presence of fungus and surface coloration. (b) Density: varies from 700 to 800 kg/m3 . Janssen [21] compared the factors of strength and stiffness in relation to the density of conventional materials in construction with bamboo, and bamboo would only “lose” to steel in regard to strength. (c) Moisture content: varies with age, cutting season, and species. The younger the bamboo, the higher its moisture content, and until it is three years old, when it is considered green, the moisture content is very high, affecting the strength of the thatch. After the cut, bamboo tends to lose moisture, increasing

Bamboo Structural Systems

77

its structural performance, and the drying process can take from one to four months, depending on the storage conditions of the stalks. Concerning its mechanical properties, the set of factors in bamboo makes it resistant and flexible, and it is called “vegetable steel”. Bamboo is an anisotropic material, as it has different mechanical characteristics in three directions: longitudinal, tangential, and radial. For the species Dendrocalamus giganteus, the average values, according to Carbonari et al. [22], are: (a) Compression parallel to the fibers: 48.27 and 46.32 MPa for specimens with and without knots, respectively. (b) Tensile strength parallel to the fibers: 52 MPa (with knots) and 133 MPa (without knots) for tests with internal fibers and 186 MPa (with knots) and 203 MPa (without knots) for tests with external fibers. (c) Bending: 58.5 MPa. (d) Longitudinal modulus of elasticity: 21.90 GPa for knotted canes and 21.80 GPa for knotless canes. The most fragile mechanical property of bamboo is shear. Ghavami and Marinho [9] obtained average values of 3.56 MPa and 3.37 MPa for specimens with and without knots, respectively.

3.2 Connections of the Bamboo Parts The connections between the parts that make up a structure are fundamental to its integrity, requiring perfect suitability of the materials that will be used in it. Because of bamboo’s not perfectly circular, conical, hollow shape, with several dimensions in its length, diameter, and wall thickness, the connections are one of the biggest difficulties in construction with bamboo [23]. Regarding the cuts in the bamboo for making the fittings, there are the following ways to carve the ends, shown in Fig. 16. One of the precautions that must be taken in the execution of the connections, according to López [24], is for the end of a bamboo stick to have a diaphragm, otherwise, it will be susceptible to flattening under the action of a vertical load. In relation to the joining of the bamboo pieces, this can be done in several ways. Figure 17 shows one of these ways. Regarding reinforcement in bamboo connections, Barbosa and Carbonari [25] proposed concreting the supports of a truss, and the concrete was inserted through the bamboo cavity and sealed with tape and plastic bags. Padovan [23] also cites a connection reinforced with mortar. Another type of reinforcement is metal ties, which are used to tighten the bamboo and prevent cracks from opening in the thatch or to reinforce open cracks. Barbosa and Carbonari [25] also used metal clamps in the supports of a shear.

78

G. Carbonari and L. T. Carbonari

Fig. 16 Ends of bamboo culms. Source López [24], p. 24

Fig. 17 Union through a metal hook. Source López [24], p. 25

3.3 Materials and Methods The procedures for assembling and setting up the trusses, the experimental test, and the verification of a practical application of the trusses are described below. Six bamboo trusses were tested to enable statistically representative findings using the technique of connecting the pieces by threaded bars. The bamboo bars were cut in the bamboo grove of the State University of Londrina. The criterion of choice was to collect bars with ages between 3 and 6 years, to confer greater mechanical resistance. In addition, the bars that were free of pathological agents were selected. The cut was made using chainsaws at the bottom of the bar, with subsequent traction effort at a point about 20 cm above the cut. This was done with a tractor, which pulled a rope tied to it. Subsequently, the bars were cut to the desired size, also with a chainsaw, but with a clearance of 20 cm on each side, due to the future sculptures at the ends necessary to make the connections between the pieces. In addition, an extra bar of each size was cut to serve as a reserve. Figure 18 compares three of the main conditions of the bamboo bars, where the letter A represents a bar appropriate for structural use since it appears to be between

Bamboo Structural Systems

79

Fig. 18 Bamboo grove where the bars were cut (UEL). Source Gonçalves et al. [26]

3 and 6 years old, without presenting pathological agents. The bar with the letter B corresponds to a very young bamboo, less than 3 years old, still growing, so it cannot be used for structural purposes. The bar with the letter C appears much older than 6 years due to the amount of fungus on its surface. After the bamboo bars were cut, they were transported to the laboratory, where they were laid out horizontally, as far away from each other as possible, following the space limitations of the environment, to speed up the moisture loss procedure. It was necessary to wait three months for proper drying (Fig. 19a, b). In these figures, the marked decrease in the greenish coloration indicates that the bars in Fig. 19b were already ready for the beginning of the execution of the trusses. Based on the limitations of the Structures Laboratory of the Londrina State University, previous works, and knowledge about the mechanical properties of bamboo, it was decided to build the trusses with the dimensions shown in Fig. 20. The supports a and b were reinforced with grout and with two types of metal clamps: The “drilled tape”, as shown in Fig. 21a, on trusses 1, 2, and 3, and the “standard tape”, illustrated in Fig. 21b, on trusses 4, 5 and 6. The connections between the bars of the trusses were made with threaded bars, as shown in Fig. 22. The grout was chosen as filler material for the truss supports due to its high fluidity and high characteristic compressive strength of 50 MPa. These two characteristics are essential because this material can easily fill the bamboo stalks, as well as contribute considerably to the mechanical strength of the truss supports. To fill the region of the supports with grout, the trusses were placed in an inverted position on a temporary wooden structure, as illustrated in Fig. 23. The concreting was done by inserting grout in 4 cm diameter holes at the bottom of the supports’ connection. These holes are highlighted and numbered 1–12. The sealing, which

80

G. Carbonari and L. T. Carbonari

Fig. 19 Drying the bamboo bars. Source Gonçalves et al. [26]

Fig. 20 Configuration of the trusses performed. Source Gonçalves et al. [26]

Bamboo Structural Systems

Fig. 21 Configuration of the trusses supports. Source Gonçalves et al. [26]

Fig. 22 Connections made with steel threaded bars. Source Gonçalves et al. [26]

81

82

G. Carbonari and L. T. Carbonari

proved to be efficient in most cases, was done by using bubble wrap and adhesive tape. The trusses were connected with a 1st gen support (Fig. 24a), and a 2nd gen support (Fig. 24b), ensuring that the structure behaved structurally as isostatic. The advantage of this configuration is that the support absorbs the horizontal displacements of the trusses. After assembly and application of the reinforcement in the supports, the trusses were positioned on the frame, where the concentrated loads were applied to the top node of the trusses, as shown in the picture in Fig. 25. The displacements were measured using linear voltage differential transformer (LVDT) displacement transducers. The operation of this device consists of pushing

Fig. 23 Concreting the truss supports. Source Gonçalves et al. [26]

Fig. 24 Trusses supports. Source Gonçalves et al. [26]

Bamboo Structural Systems

83

Fig. 25 Trusses positioned on the portico to perform the test. Source Gonçalves et al. [26]

the rod toward the device itself because it is with the subsequent relief of force that the measurements are made. Three of these sensors were installed in each truss, two at the bottom, and one at the top, as shown in the pictures in Fig. 26. The values of the applied load and the displacements of the three sensors, measured from the beginning of the test until the rupture of each truss, were stored simultaneously in files. To verify if the tested trusses could be used in building roofs, the loads were determined, i.e., the self-weight of its elements, the overload, and the wind actions. For this, two types of roofs were studied, for two usual extremes of the distance between trusses, as described below. (a) Ceramic tiles, wooden laths, rafters and purlins, and bamboo trusses (i) 2.5 m distance between trusses (ii) 5.0 m distance between trusses (b) Thermoacoustic tiles, wooden purlins, and bamboo trusses (i) 2.5 m distance between trusses (ii) 5.0 m distance between trusses. To allow a comparison of the loads acting on a practical application roof with the loads used in the experimental tests of the six bamboo trusses, it is necessary to transform the surface loading (combination of actions of permanent and accidental

84

G. Carbonari and L. T. Carbonari

Fig. 26 Arrangement of the displacement sensors on the trusses. Source Gonçalves et al. [26]

loads) into a point load applied at the upper center point of the truss. A scheme illustrating this procedure can be seen in Fig. 27. After obtaining the equivalent point loads, as described above, for the two types of roofing mentioned above, the safety of the tested bamboo trusses is analyzed for the ultimate limit state (ULS) and serviceability limit state (SLS).

3.4 Results and Discussion After the experimental tests, the ultimate load and displacement data were obtained. Table 2 presents the maximum results for the six shears. It can be seen from the results above that the most efficient technique of reinforcement in the supports was the one where clamps of the “standard tape” type were used, because trusses 4, 5, and 6, which used this technique, presented better results than the other three trusses, which had the use of “drilled strips”. This is due to the greater resistance of the “standard tape” compared to the “pierced tapes”. All six trusses ruptured due to a truss at one of their supports, with the rupture occurring at the supports with the smallest truss area of each truss. Figure 28 shows the load × displacement diagrams, measured on trusses 1, 2, and 3, respectively. The mechanical behavior of the trusses is very close to Hooke’s Law, up to a certain loading level. When the truss’s resistant mechanisms start to fail, accommodation of the trusses and consequent irregularities in the curves occur.

Bamboo Structural Systems

85

Fig. 27 Surface load transformed into a point load (ref. to the test). Source Gonçalves et al. [26] Table 2 Experimental data of the trusses

Trusses

Experimental ultimate load (tf)

Maximum displacement (mm)

1

4.76

45.56

2

4.26

34.6

3

3.72

36.7

4

6.57

37.4

5

5.16

56.2

6

4.90

54.9

Source Gonçalves et al. [26]

86

G. Carbonari and L. T. Carbonari

Fig. 28 Load × displacement diagram for trusses 1, 2, and 3. Source Gonçalves et al. [26]

Bamboo Structural Systems

87

Trusses 1 and 2 had normal behavior at rupture, unlike truss 3, which had a problem in the test, where the piston of the force application machine reached its displacement limit before the truss reached rupture. It is noticed in the graphs of Figs. 28 and 29 that the curves referring to the upper displacement meter, despite having a similar behavior, have a discrepancy in relation to the two lower displacement meters. This discrepancy is because the upper point of the truss force application thatch suffers a crushing. Trusses 4, 5, and 6 were executed with the “standard tape”-type clamp. The respective load × displacement diagrams for these trusses are shown in Fig. 29. Unlike the behavior observed in the other trusses, the load × displacement curves of trusses 5 and 6 showed a plateau. This phenomenon is associated with the fact that the grout did not fill all the internal space of the bamboo during the execution of the trusses, occurring a crushing of the thatch of the truss support during the experimental test. In item “3.4.1” below, the main construction techniques to obtain a bamboo truss with maximum structural efficiency are presented, while in item “3.4.2” it is verified if the bamboo trusses tested in the laboratory can be used in usual roofing, proposing two types of roofing.

3.4.1

Proposal for a Bamboo Truss with Maximum Structural Efficiency

The pictures in Figs. 30a–c illustrate three different situations found during the tests: in Fig. 30a, the support that suffered a rupture of truss 1, is on the verge of collapse; in Fig. 30b, the support that suffered a rupture of truss 6, on the verge of collapse; and in Fig. 30c the support that suffered a rupture of truss 4, on the verge of collapse. Note in Fig. 30a (truss 1) that the upper flange transfers the load both to the bamboo (truss) and to the grout (diametral compression). The problem with this situation is that the bamboo (bottom chord) is directly subjected to a truss, decreasing the strength of the truss. Moreover, with the movement of the upper flange, the threaded bar of this support is requested to bending. These stresses induce the grout to break early. The grout filling of this support was well executed, as there was no crushing between the flanges in this region. In Fig. 30b (truss 6), the upper flange only affects the grout of the lower flange because the bamboo is not being subjected to shear. This tends to occur when the outer diameter of the upper chord is at least 0.01 m smaller than the lower chord. The grout filling in this support, however, was poorly executed due to the intense crushing between the flanges. Although the shear verified in truss 1 did not occur, another problem occurred: due to poor execution, the grout cross section in the region of the support was greatly reduced, thus losing the mechanical strength of this support. Truss 4, illustrated in Fig. 30c, had a breaking load considerably higher than the other trusses because, besides the grout of its supports being well executed, the upper bar directly impacted the grout of the lower bar. Thus, the mechanical

88

G. Carbonari and L. T. Carbonari

Fig. 29 Load × displacement diagram for trusses 4, 5, and 6. Source Gonçalves et al. [26]

Bamboo Structural Systems

89

Fig. 30 Three distinct situations captured on the verge of rupture. Source Gonçalves et al. [26]

strength of the grout was fully used. This can be proven by the absence of shear and crushing in the support region until the imminence of rupture. This is, therefore, the main construction technique that should be applied to obtain a bamboo truss with maximum structural efficiency. The diaphragm, when kept intact in the support region, provides great resistance to crushing and shear and helps in grout confinement. This important constructive technique, analogously to what was seen before, also belongs to truss 4. That is, the grout-threaded rod set, confined by the bamboo and the clamps, is the methodological procedure that most contributes to the gain of mechanical strength of the truss supports. The correct alignment of the upper flanges with the 1st and 2nd gen supports favors a direct compression in the grout confined in the lower flange. This is also a characteristic presented by truss 4, as shown by the straight line in orange in Fig. 31. Trusses 5 and 6 presented a significant crushing between the flanges in the region of the truss support due to a poorly executed grout filling inside the bamboo. This situation would probably be alleviated by inserting a clamp before the meeting between the two flanges, as seen in the photos in Figs. 32a, b. With the construction techniques analyzed, it is possible to determine the specifications of a bamboo truss of maximum structural efficiency. This design is illustrated in Fig. 33. The dimensions shown are those of truss 4 because it was the truss that came closest to this design. These measurements make it possible for the upper flanges to strike the grout of the supports directly. The three bamboo diaphragms that must be kept intact, in the bottom flange are highlighted in green. The clamps are highlighted in blue, four per support and two in the central region of the bottom bar. It also

90

G. Carbonari and L. T. Carbonari

Fig. 31 Alignment of the upper flange with the support. Source Gonçalves et al. [26]

Fig. 32 Proposal for inserting the fourth clamp in the support region. Source Gonçalves et al. [26]

Fig. 33 Design of a bamboo truss with maximum structural efficiency. Source Gonçalves et al. [26]

Bamboo Structural Systems Table 3 Dimensions of the wooden elements

91 Element

Dimensions for span = 2.5 m (cm2 )

Dimensions for span = 5 m (cm2 )

Lath

2.0 × 2.5 cm

2.0 × 2.5 cm

Rafter

4.5 × 5.0 cm

4.5 × 5.0 cm

Purlin

8.0 × 12.0 cm

13.0 × 20.0 cm

Source Gonçalves et al. [26]

highlighted the alignment of the upper chords with the supports of 1st and 2nd gender by the straight lines in orange.

3.4.2

Checking the Practical Application of Bamboo Trusses

To verify whether the bamboo trusses tested in the laboratory can be used in usual roofing, a simulation is performed below for two situations of use in buildings, where in both cases, the same span of the tested trusses is used (3 m), and two extreme distances between trusses, 2.5 m and 5.0 m. (a) Roof with ceramic tiles, purlins, rafters, and wooden laths The wooden roof elements (lath, rafter, and purlin) were checked for ULE and SLE, using the commercial dimensions shown in Table 3. The average dimensions of the outer diameter and thickness of the bars of the bamboo trusses of the species Dendrocalamus giganteus are shown in Table 4. Considering the specific weights of the materials used, the wood 950 kgf/m3 , the bamboo 800 kgf/m3 , and the grout 2200 kgf/m3 , the distributed loads for each structural element are indicated in Table 5. Using the normative parameters, for the region of Londrina-PR, a load of 4.82 kgf/m2 was obtained for the overpressure wind, and 61.76 kgf/m2 for the suction wind. Table 6 shows the concentrated loads equivalent to the distributed load acting on the roof surface, considering the distances between 2.5 m and 5 m trusses for a 3 m shear span. Thus, we have the following combinations of actions for the ultimate limit state for the roof with spans between trusses of 2.5 m: Table 4 Trusses bar dimensions

Bar

External diameter (cm)

Thickness (cm)

1

15.5

1.5

2e3

14.0

1.3

4, 5 e 6

12.0

1.0

Source Gonçalves et al. [26]

92

G. Carbonari and L. T. Carbonari

Table 5 Loads acting on the bamboo trusses

Loads (own weights)

Load for span = 2.5 m (kgf/m2 )

Load for span = 5 m (kgf/m2 )

Ceramic tile

43.20

43.20

Wooden lath

1.19

1.19

Wooden rafter

4.37

4.37

Wooden purlin

12.16

32.93

Bamboo trusses

9.96

4.98

Total permanent loads

70.87

86.67

Overload

25.00

25.00

4.82

4.82

61.76

61.76

Overpressure wind Suction wind

Source Gonçalves et al. [26]

Table 6 Point loads equivalent to the roof surface load

Point loads equivalent (kgf)

Span = 2.5 m

Permanent loads

531.56

Overload

187.50

Overpressure wind Suction wind

Span = 5 m 1.300,00 375.00

36.19

72.37

463.17

926.34

Source Gonçalves et al. [26]

Q d1 = 1.3 · (531.56) + 1.4 · (187.50) = 953.52 kgf Q d2 = 1.3 · (531.56) + 1.4 · (187.50) + 1.4 · 0.5 · (36.19) = 978.85 kgf Q d3 = 1.3 · (531.56) + 1.4 · 0.75 · (36.19) + 1.4 · 0.4 · (187.50) = 834.02 kgf Q d4 = 1.3 · (531.56) + 1.4 · 0.75 · (−463.17) = 204.69 kgf And the following combinations of actions for the ultimate limit state, for the roof with a 5 m span between trusses: Q d1 = 1.3 · (1300) + 1.4 · (375.00) = 2215.00 kgf Q d2 = 1.3 · (1300) + 1.4 · (375.00) + 1.4 · 0.5 · (72.37) = 2265.66 kgf Q d3 = 1.3 · (1300) + 1.4 · 0.75 · (72.37) + 1.4 · 0.4 · (375.00) = 1975.99 kgf Q d4 = 1.3 · (1300) + 1.4 · 0.75 · (−926.34) = 717.34 kgf Thus, the value of the critical point load equivalent to the distributed loads acting on the roof, applied at the upper point of the trusses, is 978.85 kgf ∼ = 0.98 tf when the distance between trusses is 2.5 m, and 2265.66 kgf ∼ = 2.27 tf when the distance between spans is 5 m.

Bamboo Structural Systems

93

Therefore, the shear loads measured on the trusses tested are at least 435% greater than the theoretical point load obtained for the 2.5 m spans, and at least 188% greater for the 5 m span. (b) Roof with thermoacoustic tiles (sandwich) and wooden purlins Performing the verification of the purlin with respect to the ULE and concerning the SLE, one obtains dimensions of 6 cm in base and 8 cm in height when the distance between trusses is 2.5 m and 10 cm by 16 cm when the distance between trusses is 5 m. The bamboo trusses have the same dimensions shown in Table 4. The loads acting on this type of covering are shown in Table 7. The bamboo truss’s self-weight, wind, and overload are considered the same way as the previous item. Table 8 shows the concentrated loads equivalent to the distributed load acting on the roof surface, considering the distances between 2.5 m and 5 m trusses for a 3 m shear span. With this, we have the following combinations of actions for the ultimate limit state for the roof with spans between trusses of 2.5 m: Q ∗d1 = 1.3 · (165.01) + 1.4 · (187.50) = 477.02 kgf Q ∗d2 = 1.3 · (165.01) + 1.4 · (187.50) + 1.4 · 0.5 · (36.19) = 502.35 kgf Q ∗d3 = 1.3 · (165.01) + 1.4 · 0.75 · (36.19) + 1.4 · 0.4 · (187.50) = 357.51 kgf Table 7 Loads acting on the truss with thermoacoustic roof tiles

Loads (own weights)

Load for span = 2.5 m (kgf/m2 )

Load for span = 5 m (kgf/m2 )

Thermoacoustic tile

5.96

5.96

Wooden purlin

6.08

20.27

Bamboo trusses

9.96

4.98

Total permanent loads

22.00

31.21

Overload

25.00

25.00

4.82

4.82

61.82

61.82

Overpressure wind Suction wind

Source Gonçalves et al. [26]

Table 8 Point loads equivalent to the surface load

Point loads equivalent (kgf)

Span = 2.5 m

Span = 5 m

Permanent loads

165.01

468.11

Overload

187.50

375.00

Overpressure wind Suction wind Source Gonçalves et al. [26]

36.19

72.37

463.17

926.34

94

G. Carbonari and L. T. Carbonari

Q ∗d4 = 1.3 · (165.01) + 1.4 · 0.75 · (−463.17) = −238.81 kgf And the following combinations of actions for the ultimate limit state, for the roof with 5 m span between trusses: 

Q ∗d1 = 1.3 · (468.11) + 1.4 · (375.00) = 1133.55 kgf 

Q ∗d2 = 1.3 · (468.11) + 1.4 · (375.00) + 1.4 · 0.5 · (72.37) = 1184.21 kgf 

Q ∗d3 = 1.3 · (468.11) + 1.4 · 0.75 · (72.37) + 1.4 · 0.4 · (375.00) = 894.53 kgf 

Q ∗d4 = 1.3 · (468.11) + 1.4 · 0.75 · (−926.34) = −270.49 kgf The combination of the suction wind, in this case, where the cover is lighter, causes a negative (upward) point load on the truss. There is no data about the rupture of the truss for negative point loads, but it is easy to see that the truss will not be sheared at its supports, which are the weakest points of the structure. Furthermore, loads of 238.81 kgf and 270.49 kgf are small in relation to the critical loads calculated for the structure. Then we have that the critical point load, equivalent to the distributed loads acting on real roofs, applied on the upper point of a real truss is approximately 502.35 kgf ∼ = 0.50 tf for the distance between trusses of 2.5 m and 1184.21 kgf ∼ = 1.18 tf for the distance between spans of 5 m. The ultimate loads of the trusses tested are 848% to 1308% greater than the point load found for the 2.5 m span and 360–555% greater than the point load found for the 5 m span (without considering the load of truss 3, due to the problem in the test). Concerning truss displacement, NBR 7190–1997 considers in item 9.2.1 (limit deflections for current constructions) that for current constructions (with usual loads), the limit deflection f lim is 1/200 of the span. Thus, considering a span of 3 m, the limit displacement of the truss is 15 mm. f lim =

3000 l = = 15mm 200 200

Figure 34 shows two graphs, one for each type of coverage. In each graph are shown the load × displacement diagrams of the six trusses tested, besides the average curve (in black line) and two horizontal lines, referring to the two equivalent loads calculated when the distance between the trusses is 2.5 m and 5 m. Figure 34 shows that for the ceramic roof tile, the displacement limit of 15 mm is exceeded in trusses 3 and 5 for a load of 2.27 tf; however, the average curve of the trusses is below this limit. On the roof with thermoacoustic tiles, for both the spans between trusses of 2.5 m and 5 m, the displacement of the experimental curves is less than 15 mm, satisfying the serviceability limit state (SLS).

Bamboo Structural Systems

Fig. 34 Load (tf) × displacement (mm) diagram. Source Gonçalves et al. [26]

95

96

G. Carbonari and L. T. Carbonari

3.5 Concluding Remarks from Part 2 As far as the truss assembly is concerned, it was found that the grout-threaded bar set, confined by the bamboo and the metallic ties or ribbons, was the main element of mechanical resistance of the supports of the bamboo trusses, improving the weak point of this type of structure considerably. It is also interesting to point out the most efficient configurations of accomplishment and functionality of the trusses: (a) with the ideal fitting between the upper and lower flanges of the trusses, having the thatch of the diagonal bar entering into the thatch of the horizontal bar; (b) with knots (diaphragms) in the thatches susceptible to shearing, for a thatch with knot has a higher resistance than a thatch without knot; (c) with the standard tape, for it is more efficient both in its resistance and in its handling, about the pierced tape. As for the loads, for both types of roof tiles and a distance between 2.5 m to 5.0 m, it was found that the reinforced bamboo trusses resist the internal forces caused by the normative loads acting on the roof. In the case of the truss displacements subjected to the actual loads, with the limit deflection being equal to 15 mm for the verification of the serviceability limit state, for the point loads equivalent to the surface loading of the roof, the displacement did not exceed the limit (compared to the experimental displacements). Thus, we conclude that bamboo properly treated against fungi and woodworm, having its durability guaranteed, is viable for structural use in trusses, being safe both for the ultimate limit state and for the service limit state when properly dimensioned. Bamboo trusses can be used in the roofing of buildings, especially as a substitute for wooden sheaths. After all, bamboo is a highly renewable material, light, and has great mechanical properties, besides contributing to more sustainable development. Thanks to To the technicians of the CTU Laboratories for their collaboration and to the Specialization Course in Structural Engineering-CTU-UEL for the financial support.

References 1. Global Footprint Network (GFN) (2022) No Title. www.footprintnetwork.org. Accessed 18 Oct 2022 2. Lanna SLB, Delgado PS, Ayres E, Lago RM (2012) Eco-design: a eficiência de produtos feitos de Bambu para o sequestro de carbono. In: Anais do P&D Design. Maranhão, p 10 3. Liese W (1985) Bamboos—biology, silvics, properties, utilization. Deutsches Gesellschaft fur Technische Zusammenarbeit—GTZ, Eschborn, Germany 4. Pereira MA (2006) Projeto bambu: manejo e produção do bambu gigante (Dendrocalamus giganteus) cultivado na Unesp-Bauru e determinação de suas características físicas e de resistência mecânica. Relatório Fapesp (2003/14323-7), Bauru 5. Beraldo AL, Pereira MAR (2008) Bambu de corpo e alma. Canal6, Bauru 6. Ghavami K (1994) Desenvolvimento Alternativo para Construção da Habitação de Baixo Custo: Bambu. Rev Debates Sociais-Pobreza Desenvolv 27:119–132

Bamboo Structural Systems

97

7. Ghavami K, Hombeeck R. (1981) Application of bamboo as a construction material: Part I— mechanical properties and waterrepellent treatment of bamboo, Part II—bamboo reinforced concrete beams. In: Latin American Symposium on Rational Organization of Building Applied to low Cost Housing. CIB/IPT, São Paulo, pp 49–66 8. Ghavami K (1995) Ultimate load behaviour of bamboo-reinforced lightweight concrete beams. Int J Cem Concr Compos 17:281–288. https://doi.org/10.1016/0958-9465(95)00018-8 9. Ghavami K, Marinho AB (2001) Determinação das propriedades dos bambus das espécies: Mossô, Matake, Guadua angustifolia, Guadua tagoara e Dendrocalamus giganteus para utilização na engenharia, 53 10. Beraldo AL, Carbonari G (2019) Propriedades anatômicas, físicas, químicas e mecânicas do bambu e ensaios para sua determinação. In: Ostapiv F, Librelotto LI (eds) Bambu: Caminhos para o Desenvolvimento Sustentável no Brasil, 1st ed. UFSC, Florianópolis 11. Carbonari G, Silva Junior N, Pedrosa NH et al (2017) Bamboo—the vegetal steel. Mix Sustentável 3:17–25. https://doi.org/10.29183/2447-3073.mix2017.v3.n1.17-25 12. Associação Brasileira De Normas Técnicas (ABNT) (2020) NBR 16828-1: Estruturas de bambu—Parte 1: Projeto. Rio de Janeiro 13. Associação Brasileira De Normas Técnicas (ABNT) (2020) NBR 16828-2: Estruturas de bambu—Parte 2: Determinação das propriedades físicas e mecânicas do bambu. Rio de Janeiro 14. Ghavami K (2005) Bamboo as reinforcement in structural concrete elements. Cem Concr Compos 27:637–649. https://doi.org/10.1016/j.cemconcomp.2004.06.002 15. Acosta C, Carbonari G (2017) Laje mista de bambu-concreto leve: Estudo teórico e experimental. In: V Encontro de Sustentabilidade em Projeto. Florianópolis: UFSC 16. Carbonari G, Lopes LAM, Rossi GB et al (2019) Lajes mistas de bambu-concreto pré-fabricadas com zero aço: são viáveis tecnicamente? In: VII Encontro de Sustentabilidade em Projeto. Florianópolis: UFSC 17. Rossi GB (2019) Procedimento de ensaio de lajes pré-moldadas mistas de bambu-concreto, com conectores e placas de EPS. Trabalho de Conclusão de Curso (Especialização em Engenharia de Estruturas), UEL 18. Carbonari G, Librelotto LI (2019) Tratamento e preservação dos colmos. In: Ostapiv F, Librelotto LI (eds) Bambu: Caminhos para o Desenvolvimento Sustentável no Brasil. UFSC, Florianópolis 19. Carbonari G, Lopes LAM, Teodoro Neto B, Corbacho FAF (2020) Composite slabs of bambooconcrete, no steel. Mix Sustentável 6:19–28 20. Associação Brasileira De Normas Técnicas (ABNT) (2016) NBR 5738: Concreto—Moldagem e Cura de Corpos de Prova. Rio de Janeiro 21. Janssen JJA (2000) Designing and building with bamboo. INBAR 22. Carbonari G, Da Silva Jr NM, Pedrosa NH et al (2016) Propriedades Mecânicas de Várias Espécies de Bambu. In: XV EBRAMEM—Encontro Brasileiro em Madeiras e em Estruturas de Madeira. Curitiba 23. Padovan RB (2010) O bambu na arquitetura: design de conexões estruturais. Monografia (Especialização em Design),—Universidade Estadual Paulista “Júlio de Mesquita Filho” 24. López OH (1981) Manual de construcción com bambú: construcción rural. Estudios Técnicos Colombianos Ltda, Bogotá 25. Barbosa DR, Carbonari G (2017) Estudo experimental de tesouras de bambu. In: V Encontro de Sustentabilidade em Projeto. UFSC, Florianópolis 26. Gonçalves VM, Carbonari G, Proni G (2019) Bamboo structural application—double pitched truss: theoretical-experimental analysis. Mix Sustentável 5:19–33. https://doi.org/10.29183/ 2447-3073.MIX2019.v5.n1.19-33

Projective Experiments and Local Productive Chains of Constructive Systems with Bamboo Culms Tomás Queiroz Ferreira Barata, Silvia Sasaoka, Gabriel Fernandes dos Santos, and Ariel Ferrari

Abstract In recent decades, a growing appreciation of the use of renewable source materials in design and architecture arose, challenging the competence of designers in selecting inputs for the creation of artifacts and building systems with an emphasis on social and environmental sustainability. Bamboo, both as a plant and as a material, is an excellent element for nature-based technical solutions, stimulating and orienting learning toward more sustainable development. Aiming to meet local demands, this chapter’s objective is to present alternative construction techniques involving the culture and productive chain of bamboo in projects for building contemporary systems and components. Its methodology is organized according to the following procedures: (a) establishment of a theoretical framework on the use of bamboo culms in civil construction and architecture, with emphasis on the handling process, prefabrication, production, and assembly of components and constructive systems; (b) survey of documentation and graphic pieces of projects and products; (c) data survey through technical visits to construction sites; (d) data analysis and systematization of project typologies and the different steps in the production chain of constructive systems, taking into account the present context in the interior of São Paulo, Brazil.

T. Q. F. Barata (B) · A. Ferrari School of Architecture and Urbanism, University of São Paulo, FAUUSP, 876 Lago Street, P.O Box 05508-080, São Paulo, SP, Brazil e-mail: [email protected] A. Ferrari e-mail: [email protected] S. Sasaoka School of Art, Architecture, Communications and Design, São Paulo State University Julio de Mesquita, Eng. Luís E.C.Coube Avenue, 14-01, 17033-360, São Paulo, SP, Brazil e-mail: [email protected] G. F. dos Santos Engineering School at the Fluminense Federal University (Rio de Janeiro State), 156 Passo da Pátria Street, P.O Box 24210-240, Niterói, RJ, Brazil e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 F. L. Palombini and F. M. Nogueira (eds.), Bamboo and Sustainable Construction, Environmental Footprints and Eco-design of Products and Processes, https://doi.org/10.1007/978-981-99-0232-3_4

99

100

T. Q. F. Barata et al.

Results point to the improvement in the quality of constructive components in production processes made with bamboo culms and the optimization and qualification of the productive chain of this material on a local scale. Keywords Bamboo culms · Production chain · Building systems · Sustainable construction · Trusses · Modular panels · Reciprocal frame · Bamboo in natura

1 Introduction Civil construction is one of the sectors that most boosts the economy of any country; however, it triggers several environmental impacts due to excessive consumption of natural resources. The extraction of raw materials for continuous extraction in the manufacture of inputs in the execution of works, such as steel and concrete, exponentially increased the energy expenditure in the production of built spaces, resulting in environmental degradation [1]. Sustainable development in construction and the use of materials such as reforested wood and bamboo in their natural form are considered unconventional but environmentally friendly materials. Although rarely applied in our country and the international community in general, they are alternatives based on low-carbon construction systems [2]. The use of local natural materials involves scientific knowledge based on economic, social, and environmental sustainability criteria, primarily inserted in contexts of local production chains. The use of bamboo in architecture and construction can be considered an efficient response to the challenges of climate change. This requires the development of research that contributes to the development of new construction technologies and materials. A strategic project to strengthen the culture of bamboo construction in our country lies in careful planning and structuring of the bamboo production chain. At first, this systematization would consist of the organization of productive systems of management and controlled production of culms of various species with the improvement of low-impact preservative treatment technologies. This allows for the development of projects made with more complex bamboo structures by architects, engineers, and designers, according to specific technical standards.1 This chapter presents the description and analysis of three prefabricated architectural projects built in the state of São Paulo, Brazil. All three of them involve the production chain of bamboo with an emphasis on the development and production of contemporary building components and systems aiming to meet diverse local demands. The first study refers to an experimental construction carried out in the agricultural area of the School of Mechanical Engineering at the “Júlio de Mesquita Filho” State University, UNESP, in the city of Bauru—a research project funded by a research funding agency.2 The experimentation consisted of the development 1

The Brazilian Association of Technical Standards has recently approved the NBR 16828-2 of January 2021. 2 Project funded by the São Paulo State Research Support Foundation, FAPESP, in 2017.

Projective Experiments and Local Productive Chains of Constructive …

101

of prototypes of different constructive components using bamboo as its main material, as well as earth and local residues. The second study is a residential space located at Demétria, a district in Botucatu, SP. In this project, structural components for roofing were combined using bamboo, metal ties and connections, and reforested wood, which were supported in structural masonry of compressed earth block (CEB). The third study addresses the construction of an agroecological warehouse located in a neighborhood called Chácara Maria Trindade, in the extreme northwest of the municipality of São Paulo. It is a shed with a reciprocal porticoed structure and the use of roof lanterns. The chapter is based on a set of methodological procedures organized on a theoretical framework concerning the production chain of bamboo culms applied in architectural works. The content of the study analyzes local production chains and considers the process of handling, processing, prefabrication, assembly of components, and on-site construction systems. Documentation and graphic pieces of projects and products were used for that, and technical visits were made to the site. The gathering of data systematized the project typologies and different stages of the available building systems’ productive chain, taking into consideration São Paulo’s countryside. The importance of this study is directly related to the promotion of adequate use of bamboo in construction and the improvement of the production processes for building components with bamboo culms, in order to optimize and qualify the productive chain of this material on a local scale.

2 Theoretical Basis The theoretical foundation of the project addresses bamboo as an unconventional but sustainable material applied to civil construction and architecture. It also deals with the different characteristics of its local production chain, such as harvesting the thatch, it’s processing, the necessary preservative treatments, and drying. Finally, the main typologies of building systems using bamboo culms are presented.

2.1 Bamboo as an Unconventional and Sustainable Material In the construction industry, degradation caused by the systematic exploitation of natural resources is still a problem with no definite solution in sight. Compared to other economic activities, this sector has the highest level of consumption of raw materials, up to about 50% mass, making it clearly unsustainable [3]. Regarding the world consumption of wood, construction holds second place, second only to paper manufacturing [4]. Together with Portland cement used as a binder for concrete, which is one of the main materials used in construction, this sector is currently responsible for about 6–7% of the total CO2 released on the planet [3]. However, even with all the existent consumption of these materials, they are not able to meet the

102

T. Q. F. Barata et al.

total demand for housing. Investigating data made available by the UN, Saleme et al. [5] pointed out that there is presently a housing shortage affecting approximately 100 million people in the world, increasing to 1 billion, taking into account the existing buildings in deterioration or in precarious conditions. Data from the João Pinheiro Foundation [6] point out that, in 2015 and in Brazil alone, the housing deficit was over 6 million. Using natural resources with ecological characteristics, such as bamboo and earth, seems to be a viable alternative to the style of production currently promoted by the construction industry. The development and application of new materials spending less energy for their extraction, transport, and processing, bringing about a reduced cost and low environmental impact, has become an indispensable need in our modern world. Bamboo is a renewable raw material, with an annual production of culms, fast growth, and a high yield per area, making it easy to cultivate and exploit, and considering it is an excellent CO2 sequestrator [7]. It is also one of the oldest and most versatile materials used in construction [8], becoming an alternative capable of replacing wood and other materials in various applications arising from design, architecture, and engineering. Earth, as a construction material, is the most important and abundant element in most regions of the world [2]. Its use in construction has advantages over conventional materials such as cement and steel because its production chain is characterized by low energy consumption and carbon emissions [9]. The association of earth with bamboo aiming at being applied in construction is possible through the construction method called mixed technique [10–12].

2.2 Characteristics of Local Production Chains Quantifying areas with the incidence of bamboo throughout the world is a difficult task, since this plant extends over small areas, usually in the middle of forests and, if not, in isolated locations [13]. Another scenario contributes to this difficulty, shown in a survey done in 2010 by the Food and Agriculture Organization [13]. Not all countries with bamboo in their lands reported updated data on the amount of bamboo in these areas, and new countries were also included in the survey. Even with this challenge, the study points out that there are about 31.5 million hectares of land worldwide containing bamboo plantations. Of this total, about 13.4 million hectares are located in South America and 9.3 million in Brazil alone, registered as the country with the largest amount of land with bamboo growth [13]. The amount of species in Brazilian soil is also representative if only the species known in the Americas are considered; 65% of all bamboo species in the South American continent take place in Brazil [7]. Expert knowledge is applied for the identification of species in the selection of bamboo culms, cultivation management, dating the age of the culms, harvesting the bamboos, making seedlings, and planting them. The criterion for choosing the bamboo to be harvested is done according to its final application. Thus, depending on the demand to be met, young bamboo, less than 3 years old, is used [7]. And when

Projective Experiments and Local Productive Chains of Constructive …

103

the bamboo needs to be subjected to physical and mechanical stress, adult bamboo is used, aged between 3 and 7 years [7]. During the different steps of the bamboo production chain after harvesting a bamboo stalk, the processing of the material begins, which consists of cleaning the piece and applying the correct procedures to treat and dry it correctly. The first step consists of cleaning it, made easier with the use of a pressure washer, and, if still necessary, the remaining dirt can be removed with heavy-duty cleaning pads. The bamboo is then treated and dried in order to increase its durability. The treatment and drying of the bamboo, not necessarily in that order, is extremely important to increase its durability, enabling its application in several productions, even in projects which leave it exposed to the weather [14]. Because it is a biological raw material, bamboo can suffer the attack of fungi and insects, which will deteriorate it in about 1–3 years, but if properly treated, this period can be extended considerably, up to 15 years or more [14]. According to researcher [14], its treatment can be divided into two groups, one classified as a physical or natural treatment, more commonly known as curing, and the other classified as a chemical treatment. This researcher defined physical treatments as low-cost procedures traditionally used by rural and village populations in Asian countries. However, the same researcher highlighted the lack of proof of the efficiency of the procedures applied for curing bamboo thatch. Regarding the group of chemical treatments, Hidalgo-Lopez [14] divided them into two categories, one containing the techniques for the temporary treatment of bamboo and the other containing treatments that aim to prolong the life of the material, extending it by many years. The researcher also specifies the preservatives used in these treatments, dividing such chemical inputs into two groups, one through types of oils and the other through water-soluble salts. Hidalgo-López [14] indicated the application of oil-based chemical treatments for bamboo which will be used in outdoor and unfinished productions because it makes the material resistant to direct contact with water, though at the expense of a strong odor and a viscous texture to the touch. In terms of water-soluble salts, among the studies mentioned by the same researcher, he concluded that it is possible to obtain a final material that is resistant to internal and external uses and capable of receiving coats of paint as a final finishing. Regarding the use of chemical preservatives, Pereira and Beraldo [7] made important observations regarding toxicity, efficiency, and cost x benefit ratio. These researchers pointed out that these chemical inputs must be toxic, specifically to the insects and fungi known to deteriorate bamboo, not to the human being and the environment. Their observations on the efficiency of these chemicals had to do with their performance in penetrating deeply into the bamboo piece, without subsequent evaporation and leaching. The same researchers stated the low cost, easy accessibility, and good performance of the material as being the right choice when adopting one or another compound for a certain bamboo species. In chemical treatments using water-soluble salts, two procedures stand out, one using an open tank and one employing pressure-modified Boucherie, both intended to preserve the bamboo for the long term. According to Hidalgo-López [14], the open tank treatment occurs by immersing the bamboo in a solution held in the

104

T. Q. F. Barata et al.

container, which will gradually permeate the material’s interior through diffusion. This researcher evaluated this procedure as one of the best there is because with it, it is possible to treat bamboo in its natural format, recently harvested or air-dried, as well as those which are cracked or processed, such as in the form of talisca. The same researcher added the low-cost factor to this type of treatment. Regarding the pressuremodified Boucherie, Hidalgo-López [14] characterized it as a system capable of treating several culms of recently harvested bamboo simultaneously, requiring a short period of time, as well as being easily adapted for mobility, allowing it to be used close to the harvesting site. The pressure-modified Boucherie is an apparatus composed of a tank, ducts, registers, a manometer, and the instrument that will provide the pressure. A solution is stored in the tank, to be applied in the treatment of the bamboo. The ducts are responsible for transporting the solution contained in the tank to the bamboo culms. Next to these ducts, registers are fixed to control the distribution of this solution from the tank to the bamboo. Nozzles with clamps are used to connect the ducts to the bamboo culms. The apparatus is completed with a manometer housed on the outside of the tank, used to measure the pressure inside the tank. This pressure can be supplied by an air compressor or a manual air pump. Somewhat simpler, the open tank treatment consists of an impermeable container filled with the chemical solution in which the bamboo will be submerged. This tank can be made directly on the ground, in which a trench must be dug and its walls covered with tarpaulin, serving to store the solution. The treatment of bamboo culms using the pressure-modified Boucherie requires less time than that required for treatment by immersing them in an open tank containing the solution at room temperature; while the former takes about 3 h, the latter can take days or even weeks [14]. A detail worth mentioning about the treatment by immersion in an open tank is that, when bamboo culms are used in their natural form, holes are drilled on the inside of the culms’ diaphragm, which allows them to sink more easily, and also improves the diffusion of the solution throughout the stalk [14]. The same author emphasized that these holes must be small, avoiding any damage to the physical–mechanical performance of the thatch, and should not exceed 5/8 inches. Drilling can be done with an iron bar long enough to go through the culms longitudinally and should be smooth and with a sharp point at one of its ends. Another important aspect of the immersion treatment is that, when a more superficial treatment of the bamboo is sought, the material can remain immersed in the solution for a shorter amount of time, from minutes to a few hours. The drying procedure completes the processing of the harvested bamboo. With the loss of humidity inside the bamboo its mass reduces considerably, leading to improvements in the mechanical properties of the material [14]. In order to ensure drying without the influence of weather, bamboo must be stored in covered and ventilated places. In these conditions, the bamboo pieces lose moisture gradually, reducing the appearance of cracks and deformations, as well as reducing the chances of fungus proliferation. Whenever possible, the storage of bamboo culms should be done in the vertical position and spaced apart, which allows for air circulation. Positioning the culms vertically also positively influences the amount of time required

Projective Experiments and Local Productive Chains of Constructive …

105

for them to dry. Hidalgo-Lopez [14] stated that air-drying culms in a vertical position instead of horizontally reduce the drying time by half.

2.3 Potential of Bamboo Usage in Building Systems The adoption of concepts pertaining to sustainability in architecture and civil construction is defining new paradigms in the selection of materials to be used in more environmentally friendly building systems. The primary use of materials from renewable and local sources is gaining prominence among building systems having a low environmental impact [15]. Currently, incentives for the application of materials consuming less energy in their extraction, transport, and processing, including a reduced cost of production, have become an indispensable need in the construction industry, especially in the Latin American context. In order to enable the large-scale use of bamboo as a common building material, assuming, therefore, its economic viability, the need to apply specific scientific knowledge in the different stages of the bamboo production chain [1] needs to be emphasized. The investment in research and the implementation of appropriate technologies for the processes of agricultural development (planting, cultivation, and harvesting) curing of the culms, preservation processes, drying and storage of classified bamboo pieces are all fundamental conditions for proper insertion of the material in the market, favoring the industrialization of this sector. The use of bamboo in natura as a building material can be considered a viable alternative to the abusive use of steel and concrete, helping to reduce the pressure for the use of wood from native and planted forests. In relation to its structural properties, when considering its strength/specific mass and stiffness/specific mass, the values are equal to wood and concrete and may be compared to the cost of steel [16]. Although the supply of this material is not yet standardized in Brazil, it can be considered an ecological and environmentally friendly material, since bamboo in natura meets certain fundamental requirements for more sustainable construction practices. Some of its positive aspects are: minimization of energy consumption in the production of construction components; an incentive to the conservation of natural resources and consequent reduction of local pollution; low consumption of inputs in the material’s production chain; and strengthening of production cycles based on renewable sources of raw material. Bamboo is a construction material with a high exploration potential since it plays an important role in carbon sequestration, contributing to avoiding new greenhouse gas emissions and the consequent rise in global warming. It is characterized by fast growth, taking less time to reach maturity if compared to wood from planted forests. Bamboo’s physical characteristics, as well as its peculiar geometric shape, its low cost, and the ease with which it can be obtained make it widely used as a building material in several countries, especially in tropical and subtropical areas of Asia, and in some Latin American countries.

106

T. Q. F. Barata et al.

In the Brazilian culture, constructions with bamboo have been carried out in an empirical way, remaining a field with limited literature and field research, while in other countries like Colombia, China, and India, the use of bamboo in construction is already in a well-developed phase, and the acceptance of this type of material is already established. Bamboo has impressive vitality, great versatility, lightness, and resistance and can be easily handled with simple hand tools. These qualities have given it the longest and most varied role in the evolution of human culture when compared to any other types of plants [17].

3 Materials and Methods Exploratory research was the methodology adopted for this work, based on surveys and case studies. For Clemente Jr [18], the case study method “enables researchers to deal with a wide variety of evidence brought about from the analysis of documents, field visits, interviews, and participatory observation. In this sense, its main purpose is to present an analytical reflection of the studied context; this type of investigation has much to contribute in the field of evaluative research.” Research based on case studies can favor the use of human intellectual capacities to generate best practices intermittently and continuously. The best approach is to observe successful cases, enter into dialog with them and develop a vision of what could be done differently and more efficiently. Processes that aim to increment improvements or promote increased quality in projects and products, based on case studies, can adopt the following steps: (a) detail the context in which the phenomena occur, (b) monitor and describe the results achieved, (c) evaluate those results, (d) define guidelines to be implemented to improve processes and products. This research is organized in the following methodological procedures: (a) establishment of a theoretical framework on the use of bamboo culms in civil construction and architecture, with emphasis on the handling process, prefabrication, production, and assembly of components and building systems, (b) survey of documentation and graphic pieces from three projects focused on the definition of the constructive and structural conception of the subsystems and respective prefabricated components; for this purpose, 2D and 3D images generated perspectives by means of the software Adobe Illustrator 2020, Rhinoceros 6. 3, AutoCad 2021, Revit Autodesk 2021; (c) data survey through technical visits to construction sites, considering the flow of the production chain, which included preservative treatment, drying of culms, transport and storage of parts, making of templates for production of components and the assembly process on site; (d) data analysis and systematization of project typologies and the steps of the production chain of building systems, taking into account the context of the countryside of São Paulo, Brazil.

Projective Experiments and Local Productive Chains of Constructive …

107

4 Results Results are organized in three case studies, namely: (a) experimental project with modular panels made of bamboo and earth; (b) project made of bamboo flat trusses for residential roofing, and; (c) project of a shed with reciprocal frames.

4.1 Experimental Project with Modular Panels Made of Bamboo and Earth The project consists of a raised floor and a one-fall roof, respectively supporting and housing a module intended for different purposes. In this study, the focus is on a module consisting of modular panels made of bamboo and earth located in the city of Bauru, SP, Brazil. Two pieces of research enabled the creation of the modular panels and their application as a module. The first research was conducted at a master’s level3 and was developed from 2014 to 2016 under the guidance of Prof. Dr. Marco A. R. Pereira. The second research took place from mid-2015 to mid-2017 and was funded by the FAPESP4 funding agency, having as responsible researcher Prof. Dr. Pereira, Fig. 1.

Fig. 1 Structural schema of the modular panels made of bamboo and earth. Source Ariel Ferrari

3

“Participatory Design for Sustainability: development of modular panels for closings, using bamboo associated with soil and waste” is the title of the master’s research authored by Gabriel Fernandes dos Santos, under the guidance of Prof. Dr. Pereira, developed in the Graduate Program in Design at the Faculty of Architecture, Arts, Communication and Design (FAAC) of UNESP, Bauru-SP campus, Brazil. 4 FAPESP research n° 2015/00782-4, carried out from August 2015 to July 2017.

108

4.1.1

T. Q. F. Barata et al.

Use of the Mixed Technique in the Development of Modular Panels

The association of bamboo with soil for the production of constructive components becomes viable through a construction technique known as mixed technique, which presents a production chain characterized by a sustainable, adaptable, and accessible system. This construction technique enables a fast execution, and when applied with the support of innovations resulting from technological development, it may be offered at a low cost (2012). The structural system obtained by the use of the mixed technique is composed of the main or load-bearing structure, the auxiliary structure or infill, the infill or filling of the infill, and the infill coatings. The main structure is composed of two types of elements: the main elements, those supporting most of the load, fundamental to the structure and the secondary elements, which, when associated with the main ones, improve its physical characteristics and locking of the structural outline. The auxiliary structure also favors thermal and acoustic insulation, as well as the definition of the final aesthetics of the construction’s finish. The filling is an optional element in the mixed technique. However, if used, it brings about the need for the application of coatings. A coating element may be used independently, even when the filling has not been carried out, its application being done directly on the elements that make up the auxiliary structure, such as, for example, on slabs obtained from vegetable fibers.

4.1.2

The Bamboo Production Chain for the Production of Modular Panels

In the Bauru region, the bamboo production chain has been developed and consolidated through what was called the “Bamboo Project”, coordinated by Prof. Dr. Marco Pereira. In this project, research and experiments were carried out, from the cultivation of the plant and its processing and application to the dissemination of the results achieved. Thus, a module made of modular panels was conceived based on knowledge generated by the Bamboo Project, as shown in the diagram of Fig. 2. The bamboo species used during the development process of the modular panels, which aimed at building sustainable modules for use in human activities, were:

Fig. 2 Diagram of the production chain of modular panels and assembly of the module for human habitation. Source Elaborated by the authors

Projective Experiments and Local Productive Chains of Constructive …

109

Guadua angustifolia, Guadua chacoensis, Bambusa tuldoides, Bambusa oldhamii, Bambusa sp, Bambusa tulda, Dendrocalamus asper, Dendrocalamus latiflorus, Gigantochloa apus, and Phyllostachys aurea. In this study, the bamboos of the genera Guadua, Dendrocalamus, and Gigantochloa were considered large-sized, the Bambusa genus medium-sized, and the Phyllostachys genus small-sized. During the harvesting stage, we selected culms that were between 3 and 7 years old, which were used for making the structural pieces in their natural form, and those that were less than 3 years old were chosen to be processed and used as complementary elements of the master structures of the panels. The bamboo culms under 3 years old were submitted to 3 types of processing: the production of strips for making wooden frames, using small- and medium-sized bamboos; the flattening of the thatch into mats, using the medium- and large-sized bamboos; and strips to assemble the wooden boards and mats, made from largesized bamboos. These types of processing, which consist of an intervention in the bamboo’s natural form, make use of the natural high humidity existing in the bamboo after harvesting, facilitating the handling of the bamboo and taking advantage of the material’s inherent flexibility, causing a decrease in resistance, which simplifies its perforation for the obtainment of several joints, as for example, in the pneumatic stapling for framing of the plates. This way, the drying of the bamboo pieces destined for the processing happened only after it was done, thus achieving greater homogeneity in the curing process, besides the reduction in the formation of cracks during this phase. The natural and processed culms received chemical or natural preventive treatments against the attack of xylophagous insects and the proliferation of fungus in order to increase the durability of each piece after being harvested. Two types of chemical methods were applied in the treatment of the pieces: immersion and the pressure-modified Boucherie system. In both cases, a solution of water with 8% sodium octaborate was used. The immersion method consisted of immersing the freshly cut and processed bamboos in a water solution for a minimum of 30 min so that it could act by diffusion and the parenchymatous cells could be easily accessed. The Boucherie system advocates that the solution be injected internally into the walls of the culms replacing the bamboo’s natural sap. In this process, the freshly cut and unprocessed culms were treated for about 3 h. Figure 3 shows the bamboo immersed in these two chemical treatment processes. Water vapor and smoking were the natural treatments applied, both carried out by means of a single physical system consisting of two ovens interconnected by means of iron pipes to a set of drums where the bamboo to be treated was housed. A large oven is used to produce the smoke used for smoking, and a small one is used to generate water vapor. This configuration, shown in Fig. 4, allows for greater uniformity in the distribution of both the smoke and the steam generated in the ovens. The process begins with the distribution of the steam generated in the small oven to the drums where the bamboo culms are placed. Once the water vaporization began, the bamboo remained isolated inside the system for a minimum period of 4 h, turning

110

T. Q. F. Barata et al.

a)

b)

Fig. 3 a Container with the solution for immersion; b pressure-modified Boucherie. Source Gabriel F. Santos

Fig. 4 Natural treatment system. Source Gabriel F. Santos

the existing starch in the bamboo sap less attractive to insect attacks. The bamboo was placed before the production of steam or smoke. The smoking process followed the steam treatment. It began with the effects of fire and the closing of the large oven, allowing the smoking process to take place for about two days without any external intervention as an autonomous operation. In this method, the smoke pervades the culms with compounds unpleasant to insects that might attack them. This natural treatment system was developed to meet the local needs of the bamboo production chain and as a low-cost option for the treatment of bamboo culms. Because the water vapor process and the smoking process do not

Projective Experiments and Local Productive Chains of Constructive …

(a)

(b)

111

(c)

Fig. 5 Drying and checking bamboo culms for moisture: a culms housed under cover, b culms housed in a wind tunnel, c using a moisture meter on bamboo culms. Source Gabriel F. Santos

allow the temperature inside the drums to reach values above 100 °C, only small-sized bamboo culms were treated. After finishing the steps related to treatments, the unprocessed bamboo was separated into two lots: the first one was stored vertically in a place protected from the weather, and the second one was stored horizontally in a wind tunnel. The bamboo was not used until it reached a humidity below 20% when it is commonly considered dry and suitable for structural use. Its moisture content was checked with a four-pin wood gauge. These procedures for drying and measuring the moisture content of the bamboo culms can be seen in Fig. 5. The type of treatment applied to the bamboo culms was done according to their state, natural or processed, and the size of each species, as shown in Table 1. The treatment of the processed culms occurred before the intervention made in the bamboo culms still in their natural form. A set of actions was taken into account during the design production in order to guide and articulate the constructive components’ project development: 1—recognizing the investigated demand in order to suggest contextualized solutions; 2—the study of similar demands in order to check already existing panels; 3—deepening of theoretical knowledge in order to substantiate the development of new constructive components; 4—selection of suitable materials for the work at hand; and 5—production of sketches, virtual modeling, and confection of scale models, exploring with creativity through the generation and selection of alternatives, as well as concretizing the attained propositions. Table 1 Groups according to the treatments applied to the culms

Bamboo condition Species

Treatments

In natural form

Large and medium size

Boucherie

Small size

Water steam and/or smoking

Processed

Large, medium, and Soaking small size

Source Elaborated by the authors

112

T. Q. F. Barata et al.

Production of the projected constructive components was based on two guidelines: the use of local resources, reducing costs and environmental impacts; and choosing to make use of a simple interface in order to turn the builders’ activities more efficient throughout the production process so as to be more easily assimilated and used by its users. Once the purchase of the conventional materials to be used and the processing of the bamboo and soil was made, which is considered to be steps 1 and 2, stage 3 was initiated—producing the elements that compose the master and auxiliary structures; stage 4—assembling of the modular panels and stage 5—finishing the modular panels.

4.1.3

The Modular Coordination of the Bamboo and Earth Panels

The process of generating the different construction components adopted the modern construction method called modular coordination. This method enables an increase in productivity during the processing of raw materials and of the production of new components, by systematizing and rationalizing the use of materials and the operations required. This was done considering the decisions to be made for the design and during the different manufacturing actions [19]. Consequently, an optimization in the consumption of energy, raw materials, and design decisions takes place, converting them into sustainable gains and generating a reduction in cost [19]. The construction of the module for housing started with virtual modeling for better visualization and detailing of the panels, during the design stage of the construction elements. This step aimed at defining the dimensions of each element in order to achieve the modularity required regarding the flexibility intended for the housing modules. Thus, panel measurements were defined at 2.80 m for the height, based on the standard values of a one-story building. Its final thickness after the application of coatings was 0.2 m, in keeping with the existence of standardized structural blocks on the market, which are multiples of 0.05 m. The height and width were considered in multiples of 0.7 m for being submultiples of the height of the ceiling previously established for the house. Five types of modular panel models were designed: (a) one unit was 0.7 m width (connector), three units were 1.4 m (flat, door and window I), and one unit was 2.1 m (window II). The three models with 1.4 m width were a reference for generating the other two panels with widths of 0.7 m and 2.1 m, having the same design basis as the “smooth” and “window I” models, respectively. Figure 6 shows the panel models designed with a width of 1.4 m. The five-panel models enabled a wide range of project configurations for room construction due to the width variation existing among them. They can also be associated with conventional elements such as ceramic and concrete blocks, which enables the designer to configure a construction with hydraulic pipes in the rooms. The panels are designed to be easily removed, allowing access to their internal parts, thus enabling the maintenance of the elements of the master structures. Electrical

Projective Experiments and Local Productive Chains of Constructive …

(a)

(b)

113

(c)

Fig. 6 Models designed in the project development: a smooth, b door, c window. Source Gabriel F. Santos

installations can be placed both inside and outside the panel simply by fixing the appropriate channels and conduits.

4.1.4

Prefabrication of the Modular Panels and Module Assembly

Being modular, the elements configuring the panels are quite similar. A template to typify and facilitate the assembly process of the modular panels was created based on the 1:2 scale models. Besides simplifying the constructive logic, the template served as a mobile workstation, allowing its displacement around the construction site. Its structure is composed of two workbenches, each one with three trestles and a top and on them two boards stylized with shapes and colors. The trestles work as support for the benches and as a place to store parts and tools. Figure 7 shows the template, in use during the assembly of the physical prototype of the smooth modular panel. Evaluation of the theoretical and practical aspects of the modular panel models in terms of their usefulness and relevance was done by assembling a module for human habitation. For this, eleven physical modular panel prototypes were made, including all five models previously mentioned: seven units of the “flat panel” model, a “connector” model, a “door panel”, a “window panel I”, and a “window II”. The construction of physical prototypes made it possible to estimate the value of each of the five modular panel models, considering the variables of cost of labor needed to assemble the panels and the materials used, among them natural bamboo, wooden boards, and threaded bars with nuts and washers. Thus, taking into account the fact that two workers are enough to assemble three panels a day regardless of the model, and considering the workers’ daily wage at R$ 80.00, which corresponds to about US$ 23.00 in August 2017, each panel will cost R$ 53.50 or US$ 15.30. Considering the same date, the values of materials used in the modular panels are presented in Table 2 for each of the five models generated.

114

T. Q. F. Barata et al.

a)

b)

Fig. 7 a Template in use during the assembly of the physical prototype of the flat modular panel, b the finished prototype. Source Gabriel F. Santos

Table 2 Unit price of each of the modular panels generated Models

Flat

Costs Bamboo in natural form

Threaded rods, nuts, and washers

Wooden board

Manpower for manufacturing

Estimate of unit price

$ 15.70

$ 18.30

$ 11.50

$ 15.30

$ 60.80

Connector

$ 7.85

$ 18.30

$ 5.75

$ 47.20

Door

$ 12.85

$ 24.65

$ 11.50

$ 64.30

Window I

$ 13.60

$ 22.50

$ 11.50

$ 62.90

Window II

$ 21.45

$ 23.50

$ 17.20

$ 77.45

Source Elaborated by the authors

Figure 8 shows some of the phases of the room assembly; Fig. 9, the finished room; and Fig. 10 its interior. In this construction, the lining was chosen regardless of the roof. The final value of the room was approximately R$ 14,750.00, or US$ 4,214.00.

Fig. 8 Recording of three moments during the assembly of the room. Source Gabriel F. Santos

Projective Experiments and Local Productive Chains of Constructive …

115

Fig. 9 Room with independent lining produced from 11 modular panels. Source Gabriel F. Santos

Fig. 10 Interior view of the room produced. Source Gabriel F. Santos

4.2 Project of Plane Trusses Used for Residential Roofs The bamboo flat trusses project was developed for the roofing of a residence—Casa Yellownaveva, located in an ecological village in the Demetria neighborhood, municipality of Botucatu, São Paulo. The research and construction of this project took place in 2021 and 2022. The project was conceived by architect Celso Pazzanese and was technically based on an executive architecture project: floor plans, sections, and elevations, including descriptive memorial of materials and construction techniques. In this section, the structural components of the roof will be highlighted in more detail, in this case, flat trusses produced with rolled bamboo, metallic components, and steel cables for protension. Non-conventional materials were used in the building’s construction system, such as bamboo (species Dendrocalamus asper, Phyllostachys pubescens and Phyllostachys nigra var. henonis), round reforested wood (Eucalyptus citriodora—Corymbia citriodora), and soil–cement bricks. To avoid the transmission of transverse loads to the walls made of soil–cement bricks—not very

116

T. Q. F. Barata et al.

suitable for this type of stress requirement—the use of citriodora wood beams was adopted as a transmission element.

4.2.1

The Bamboo Structure Roofing Project

The structural calculation for the roofing project with flat bamboo trusses was based on different materials: bamboo, wood, and steel (stringers and connections). Next, a structural analysis of the roof as a whole was made, considering any permanent and accidental loads as well as possible wind loads, using SAP2000 software to identify the structure’s critical loads. The bamboo and wood components were dimensioned according to the current norms of measurement, based on the loads and displacements gathered from the project’s structural analysis. Figure 11 shows the complete bamboo roof structural design system over soil–cement masonry walls. The roof houses the dwelling’s three domains with a pitched roof over each of them; the central abutments receive the rainwater by means of galvanized sheet metal gutters fitted to metal supports. These are composed, beginning from the top to the lower level, of (a) trapezoidal metallic galvalume sheets painted white, with lower thermal-acoustic insulation of expanded polystyrene with a thickness of 50 mm; (b) an insulating layer of non-woven geotextile blanket of 130 g/m2 ; (c) naval plywood lining with 10 mm thickness and 2.50 × 1.60 m, in boards alternately placed over the purlins; (d) main structure made up of bamboo purlins of the specie nigra var. henonis, with an average diameter of 6 cm. and plump of the specie Corymbia citriodora complements with the same diameter, over the bamboo scissors type asper with an average diameter of 14 cm, coupled by metal plate sets 5 mm thick and supported on the eucalyptus beams by the metallic supports described above; (e) support structure and load distribution roof-wall-ground, with treated eucalyptus beams, 17–15 cm diameter, supported on soil–cement masonry walls 15 cm thick,

Fig. 11 Bamboo roof structural design. Source Eduardo Miguel

Projective Experiments and Local Productive Chains of Constructive …

117

Fig. 12 Views of the bamboo roof structure. Source Gabriel F. Santos

and reinforced concrete columns with a 20 cm diameter. Figure 12 shows the flat bamboo trusses supported on the eucalyptus beams embedded in the upper faces of the soil–cement walls.

4.2.2

The Bamboo Production Chain for Flat Trusses

Upon analysis of the bamboo production chain, any problems with the supply of standardized culms, the qualification of labor, treatment techniques, and the processing technologies of culms were identified; this analysis aimed at the improvement of

118

T. Q. F. Barata et al.

processes and the qualification of the raw material. In the region of Botucatu city, local production chains are still carried out at a handcrafted product level. Therefore, there is a lack in the market for the supply of treated culms of specific species for the construction of building components, as shown in the diagram in Fig. 13. For the construction of the roof structures, 222 bamboo culms were used with a variation in length from 0.80 m to 3.25 m and diameters from 0.06 to 0.14 m. The bamboos were purchased in December 2021 from a company located 260 km from Botucatu, in the southern part of the Capital of São Paulo, in the Parelheiros District. Table 3 indicates the amount of culms and dimensions per species for each type of structure. The culms were harvested and treated by the supplying company. The preservative treatment used for this project was based on immersion in water-soluble salts against xylophagous organisms and fungi. The step prior to immersion in the liquid substance requires special attention in relation to the perforation of the nodes along the entire length of the thatch to be filled with the water-soluble solution. The canes purchased for this job were shipped with excessive internal openings in the diaphragm between

Fig. 13 Diagram of the production chain of flat trusses and assembly of the housing module. Source Prepared by the authors

Table 3 Quantity of canes for each structure Quantity Larger structure Smaller structure

Roof eaves Soffits

Length (meters)

Species

Diameter (meters)

asper

0.14

26

3.25

26

1.4

16

2.9

16

1.75

16

2.1

pubescens

0.10

14

1.25

asper

0.14

14

0.8 nigra var. henonis

0.06

72

3.5

10

2.65

10

1.55

2

1.75

Source Eduardo Miguel, 2021

Projective Experiments and Local Productive Chains of Constructive …

119

Fig. 14 Treated bamboo culms. Source Silvia Sasaoka

nodes (average 0.05 m in diameter), jeopardizing the mechanical strength of the canes. Figure 14 refers to the storage and drying of bamboos for use in the work.

4.2.3

Prefabrication of Flat Trusses

The flat trusses prefabrication scheme was developed by designer Gabriel Fernandes dos Santos, architect Celso Pazzanese, and engineer Eduardo Miguel. The project team was entrusted with the planning and definition of the different stages of the production process: modeling in 1:10 scale; projects of templates for prefabrication, and planning the assembly of the different components. Figures 15, 16, 17, and 18 represent four stages of the project development: (a) roof structure modulation sketch; (b) central plane truss illustration; (c) reduced scale physical model; and (d) executive project. For the production of the constructive components on site, an executive project was printed on polyvinyl canvas in 1:1 scale and then positioned on the prefabrication benches. This procedure facilitated specifically the positioning of the struts, drilling, and assembling of the structural components with threaded bars. Figure 19 shows the prefabrication bench and the assembled trusses.

120

T. Q. F. Barata et al.

Fig. 15 Bamboo trusses design development by an architect. Source Celso Pazzanese

Fig. 16 Bamboo truss project by designer. Source Gabriel F. Santos

Fig. 17 Physical model in reduced scale 1:10: Silvia Sasaoka

Projective Experiments and Local Productive Chains of Constructive …

121

Fig. 18 Bamboo truss structure. Source Eduardo Miguel

a)

b)

Fig. 19 a Prefabrication bench and b assembled trusses. Source Gabriel F. Santos

Due to a dimensional disparity between the canes delivered by the supplier, a careful selection was made seeking to combine the different diameters into uniform sets. After being arranged in templates on the benches, the culms were precisely cut, and the central trusses were assembled. Then, they were fitted to the metal supports already fixed to the wooden beams on the walls. The two halves of the central trusses were supported on metallic scaffolding while the central fixing pieces and the tension rods with their turnbuckles were positioned. At this stage, the bamboo– metal joints were grouted with cement filler next to the wooden beam; the scaffolds were removed only after the grout was adequately cured. Parallel to this step, the architect coordinated the different assembly steps of the metal connections which received the flat trusses. During their production, the correct positioning for the support pieces was established so that each truss manufactured could test the system as a whole.

4.2.4

Metal Connections for Flat Trusses

For the steel connections, Fig. 20, possible critical reactions regarding support were considered. These subsidized the conception for the project’s design as well as the

122

T. Q. F. Barata et al.

Fig. 20 3D drawing of the steel connections. Source Eduardo Miguel

choice of metal profiles to be welded so as to check all the cases of possible metal failure indicated in the current standards for steel structures. The development of the steel parts’ prefabrication process components was made based on the different efforts the structure had to undergo as a whole, which was identified and calculated by the site engineer, Fig. 21. Along with the project’s architect, the format of the metallic parts was designed to transfer the load to the eucalyptus beam. For the manufacture of the parts, a survey of service providers with technical capacity was conducted in the city of Botucatu and region. The architect searched for local manufacturers qualified in metallurgy and not only in common metalwork to meet the specific demands of the structural project.

4.3 Shed Project with Reciprocal Frames The construction of the shed with reciprocal frames was carried out in the year 2022 in a peripheral area set in the extreme northwest of the municipality of São Paulo, Brazil. The project, having 64 m2 and a covered area of 100 m2 , has the objective of being an agroecological warehouse and was executed based on an initiative of the Landless Rural Workers Movement (MST-SP), with the financial support of a call for proposals from the Architecture and Urbanism Council of the state of São Paulo (CAU-SP).5 The agricultural warehouse will be used as a warehouse for the 5

A course was held with the support of CAU-SP’s Call for Proposals #003/2021, administrative process #037/2021. It incorporated as much content as possible related to the various uses of bamboo,

Projective Experiments and Local Productive Chains of Constructive …

123

Fig. 21 Bamboo structure details. Source Silvia Sasaoka

distribution of agricultural products produced in various similar settlements in this region. In addition, it will also serve as a space for fairs and various activities occurring in the rural settlement. The construction process had an important educational objective: to train people to work in the various stages of the production chain of construction with bamboo in natura, for which a course was held where a horizontal pedagogical method was adopted. The activities held on the training course were coordinated by architect Francisco de Toledo Barros Diederichsen and included, along with the construction process of the shed, the stages of harvesting, treatment, drying, classification, and storage of the bamboo culms. The specificity of the productive chain of this project presented a great challenge for the project’s execution, from low standards of qualification of the students and lack of financial resources to difficulties in the acquisition of tools and materials for the construction. Undertaking this project under unfavorable conditions required effort and the team’s focused engagement in order to overcome the various difficulties imposed by the construction context. Figure 22 presents the inauguration party of the shed with reciprocal frames.

4.3.1

Construction System Design and Construction Details

The building system’s design consists of a system with four frames associated reciprocally; in it the different components support each other, optimizing the distribution from its cultivation to the many possibilities it offers for the generation of income. It covered a wide range of aspects on the uses and characteristics of this plant, focusing on the development of a group of professionals capable of working with bamboo productive chains. The context of the camp established there takes into account a peripheral reality, and is inserted in an area with rural characteristics, in the municipality of São Paulo.

124

T. Q. F. Barata et al.

Fig. 22 Inauguration party of the shed with reciprocal frames. Source Daniella Caetano Alves da Motta

of loads. The two halves of the frame are connected to each other by means of longitudinal pieces, which simultaneously support and are supported by the frame components. Figure 23 presents the structural scheme of the shed with reciprocal frames.

Fig. 23 Structural schema of the shed with reciprocating frames. Source Ariel Ferrari

Projective Experiments and Local Productive Chains of Constructive …

125

In order to assist the bracing of the structure, a roof overhang was designed to rest on the through beams of the frames, creating a two-level roof. This solution adds important gains to the project, such as air circulation and natural lighting, Fig. 24. For the definition of the roof lantern’s structural arrangement, an association of inclined plane trusses was chosen, positioned on the frames, and supported on each other, as shown in Fig. 25. This way the prefabrication of the roof components was made possible, seeking to simplify the interfaces of the connecting elements and facilitating the assembly process of the roof structure as a whole.

Fig. 24 Constructive detail of the roof lantern. Source Ariel Ferrari

Fig. 25 Trusses of the roof lantern structure. Source Ariel Ferrari

126

4.3.2

T. Q. F. Barata et al.

Bamboo Production Chain for the Production of Porticos

The construction process began with the acquisition of bamboo culms. Two species were used in the construction, one was collected and treated locally and the other was purchased by an external supplier. Due to its availability on the property, bamboo of the species Dendrocalamus asper was chosen as the main material used in the portico structure. A second species, Phyllostachys pubescens, purchased from local thirdparty suppliers, was used in the prefabrication of the flat roof trusses employed in the project. Figure 26 presents the productive chain of the porticos and the assembly of the agroecological warehouse. The collection of the bamboo culms of the genus Dendrocalamus was carried out on a property close to the rural settlement by participants of the course in construction. After defining the clumps of bamboo which would be managed on the property, the work of harvesting the bamboo began. The clumps of Dendrocalamus asper bamboo, besides never having been managed, were also located on sloping ground, which made it difficult to transport due to the size and weight of the culms. A chainsaw and a system of pulleys driven by a vehicle were used in the harvesting process. Thirteen culms were harvested and treated, fractionated into 16 pieces, totaling 154 linear meters of bamboo. Three days of work were used from the beginning of the harvest to the first cuts of bamboo, and more than 16 people were involved in the process. The modified Boucherie method was chosen for the treatment of the sticks. The choice for this type of preservative treatment was due to the need to reduce the time for treatment, in addition to the drying time. The team of technicians responsible for the project elaborated its own equipment to perform the treatment through the modified Boucherie method. In order to do this, it had the support of researchers from the Mechanical Engineering Laboratory at the Universidade Estadual Paulista (São Paulo State University) “Júlio de Mesquita Filho”, UNESP, Bauru campus, SP. The equipment used was developed using a natural gas cylinder, pneumatic hoses, a hitch made with PVC tubing, and a rubber hose. This equipment was used successfully in the treatment of the sticks; the products used for the treatment solution were sodium octaborate 6% and copper sulfate 0.5%. Figure 27 shows the sticks’ treatment process near the harvesting site.

Fig. 26 Diagram of the production chain of the porticos and assembly of the agroecological warehouse. Source Prepared by the authors

Projective Experiments and Local Productive Chains of Constructive …

127

Fig. 27 Modified Boucherie treatment on site. Source Ariel Ferrari

4.3.3

Prefabrication and Assembly of the Structural Components

Once the harvesting and treatment process was completed, the sticks were coded and transported to the structure prefabrication site. Considering the structure design, the frame was divided into two halves in order to reduce the weight of the components, facilitating its transportation and assembly process at the construction site. The template used for this was a simple marking with wooden stakes fixed in the ground, allowing for the support of the parts and the checking of measurements and angles. The volume of waste material from the prefabrication process was very small, due to the careful specification of the appropriate length and selection of the rods. Figure 28 demonstrates the prefabrication stage of the structure’s frames. As the prefabrication works advanced, the project’s components were stored for later transportation to the construction site, Fig. 29. During this stage, many bamboo

Fig. 28 Prefabrication step of the porticos with the use of templates. Source Ariel Ferrari

128

T. Q. F. Barata et al.

Fig. 29 Storage location for sticks of the species Phyllostachys pubescens. Source Ariel Ferrari

Fig. 30 Assembly of prefabricated components. Source Ariel Ferrari

sticks of the Phyllostachys pubescens species were acquired and treated by immersion with an 8% sodium octaborate solution; these sticks were used for the roof construction. Due to the specific characteristics of the reciprocal structure used in the project, all of the porticos had to be shored up until the structure was completed. Tensioned steel cables were used for bracing, which allowed an efficient assembly of the whole system. A tripod and pulley were used to assemble the structure, to lift the frames and make the connections needed between the different structural components, Fig. 30.

5 Final Considerations The three studies on the use of bamboo in building systems presented in this chapter reveal the need for technological increment in the various stages of the production chain. Considering the supply of bamboo in the state of São Paulo, there are

Projective Experiments and Local Productive Chains of Constructive …

129

few qualified suppliers in the market; the few suppliers available are currently challenged in many ways with supplying treated, classified, and adequately sized bamboo culms for application in architectural projects. In this sense, it is clearly necessary to encourage local production and to invest in training producers in order to meet any demands demanding large quantities of bamboo and to comply with the deadlines commonly practiced in civil construction. Another factor that hinders the flow of the construction process with bamboo is the tools currently used, which are still inadequate and not specific for working with this type of material. This factor demands adaptations in the equipment available for lumber processing. A restricted knowledge about bamboo as a construction material among professional designers and technicians was also observed, among them carpenters, joiners, architects, and engineers. Specific considerations regarding the three building systems analyzed in this study are presented below. (a) Considerations about the design made with modular panels of bamboo with soil Research on the use of bamboo culms associated with soil in modular panels has proven to be a viable solution, especially if applied to housing units. The production process of the sealing components, because of its uniqueness and market innovation, had its patent registration requested at the National Institute of Industrial Property (INPI)6 in 2016. In terms of its construction process, reliability between the elaborated project and the prototyping of modular panels was ensured through the efficient operation of the prefabrication of templates. By facilitating a standardized production process, the use of templates improved the effectiveness of the assembly of panels, resulting in increased productivity and a more dimensional regularity of the components. Five years after the end of the project, considering the weather conditions it went through, especially the presence of high humidity and extreme heat in the region, the vertical fence panels were found not to undergo significant changes or pathologies in their behavior. No cracks, deformations, or warping were found on the surfaces or the structure of the panels after a field analysis. This analysis allows us to conclude that construction techniques using bamboo associated with earth is feasible and can be an alternative to the use of conventional materials for housing, especially considering its low cost and the sustainable characteristics of this sealing subsystem. (b) Considerations about the production of bamboo flat roof trusses The technical team that elaborated the bamboo flat roof trusses project sought to develop virtual and physical models of the roof structure, produced models of all the prefabricated components, and, for the construction stages, associated traditional knowledge with technologies applied to constructions that make use of lumber and light materials. It is noteworthy that, for the execution of this work, spending time 6

In September 2022 INPI (National Institute of Industrial Property) granted the letter of invention patent under No. BR 102016021258-8, for the modular panels to Gabriel F. Santos and Marco A. R. Pereira, granting them, throughout the Brazilian territory, the ownership of the invention and guaranteeing them the rights resulting from it, as provided for in the legislation in force.

130

T. Q. F. Barata et al.

with constructive practices aimed at training the workforce was needed, as well as time engaged in specific activities for developing templates and prefabricated stalls. (c) Considerations about the shed with reciprocating frames For the construction of the shed project with reciprocating frames, techniques and procedures capable of adapting to the difficulties imposed by the local reality had to be developed, since a consolidated and developed production chain does not exist in the region. Difficulties were perceived mainly regarding the detailing stages of the executive project, the supply of quality material, the prefabrication of components, and the assembly undertaken at the construction site. The execution of this work had an important educational role, contributing to the training of farmers and settlers in the use of bamboo as a construction material. Finally, it was observed that incentives for research are fundamental to enhance the use of bamboo in construction systems and to qualify the supply and distribution chain. Therefore, overcoming the current bias regarding this material is required, as well as the dissemination of positive results arising from its use in construction systems and to encourage the development of technical standards in Brazil. Taking into account its positive characteristics and ecological and functional aspects, as a building material, bamboo is able to meet the current market demands in civil construction in Brazil. For this reason, it is of great importance to overcome the obstacles hindering its use, whether it be the lack of knowledge regarding its qualities, the incipience of its presence in the construction market, or the necessary training of specialized labor. Thus, it is considered that successful isolated initiatives are not enough to display the full use of bamboo in architecture and civil construction in Brazil. Above all, a structured and standardized market needs to be established, to encourage the cultivation of bamboo on a large scale, to invest in processing and refining technologies for the use of this material, to implement treatment and drying units closer to consumer centers, and to encourage the training of qualified professionals.

References 1. Ghavami K (2014) Materiais e Tecnologias não Convencionais para o Século XXI. PUC Rio 2. Minke G (2005) Manual de construcción en Tierra—La tierra como material de construcción y su aplicación en la arquitectura actual. Editorial Fin de Siglo, Montevideo 3. Pacheco-Torgal F, Labrincha JA (2013) The future of construction materials research and the seventh UN Millennium Development Goal: a few insights, Construction And Building Materials, [S.L.], v. 40, pp 729–737 Elsevier BV. https://doi.org/10.1016/j.conbuildmat.2012. 11.007. Available at: https://doi.org/10.1016/j.conbuildmat.2012.11.007. Accessed 8 Oct 2022 4. Rubio Luna G (2007) Arte y Mañas de la Guadua—Una guia sobre el uso productivo de un bambú gigante, Editorial Info Art 5. Saleme H et al (2003) El bambu: arquitectura, ambiente y desarrollo sustentable, Proyecto, PICT15172, Universidad Nacional de Tucuman 6. FUNDAÇÃO JOÃO PINHEIRO (FJP) (2017) Déficit Habitacional no Brasil 2015: resultados preliminares. Available at: . Accessed 12 Oct 2022

Projective Experiments and Local Productive Chains of Constructive …

131

7. Pereira MAR, Beraldo AL (2008) Bambu de Corpo e Alma. Canal 6 Editora, Bauru 8. Jayanetti DL, Follett PR (1998) Bambu in construction: an introduction. RADA Technology, Buckinghamshire 9. Neves C (2011) Introdução. In: Neves C, Faria OB (Org) Técnicas de Construção com Terra. FEB/UNESP/PROTERRA, pp 9–11 10. Borges O (eds) (2011) Técnicas de construção com terra. Feb-unesp, Bauru 11. Garzón LE (2012) Técnicas Mistas. In: NEVES, Célia 12. Programa Iberoamericano de Ciencia y Tecnología para el Desarrollo (2003) Técnicas Mixtas de Construcción con Tierra. Proyecto XIV.6 PROTERRA, HABYTED, Subprograma XIV— Vivienda de Interés Social 13. Food and agriculture organization—FAO (2010) Global Forest Resources Assessment 2010. Roma: FAO. Available at: http://www.fao.org/forestry/fra/fra2010/en/. Accessed 20 Oct 2022 14. Hidalgo-López O (2003) Bamboo: the gift of the gods. D’Vinni Ltda, Bogotá 15. Scheifer SK (2011) Casas Eco-sustentáveis. Ilus Books, Barcelona 16. Janssen JA (2000) Design and building with bamboo. Technical University of Eindhoven, Eindhoven 17. Farrelly D (1984) The book of bamboo. Sierra Club Books, São Francisco 18. Faria Clemente Jr, SS (2012) Estudo de Caso x Casos para Estudo: esclarecimentos acerca de suas características. In: César, PAB (eds) Formação acadêmica e atuação profissional do turismólogo. 7th Seminário de Pesquisa em Turismo do Mercosul, Caxias do Sul, 2012 19. Greven HA, Baldauf ASF (2007) Introdução à coordenação modular da construção no Brasil: uma abordagem atualizada. ANTAC, Porto Alegre

Advancing the Use of Bamboo as a Building Material in Low-Income Housing Projects in Kenya Shahryar Habibi, Esther Obonyo, and Ali M. Memari

Abstract Although bamboo has been used as a structural material in buildings, the uptake in Kenya has been minimal. The authors’ main objective is to exemplify an approach for using bamboo as a structural material in low-income housing through strategies that respond to context-specific design constraints and socio-cultural needs. Given the need for low-cost housing worldwide and the appropriateness of bamboo for this purpose, a sector of farmers in countries such as Kenya is being encouraged to plant bamboo for the purpose of use as a construction material. The main objective of this paper is to suggest a low-cost residential building design concept based on the use of bamboo as the structural material. This paper initially presents a review of examples of vernacular architecture, the use of locally resourced materials in building elements in Kenya, and the uses of bamboo as a construction material and system, and then develops a typical design of a bamboo-structure residential house based on context-responsive bioclimatic design strategies. The paper also discusses the feasibility of introducing bamboo as a sustainable material for minimizing the financial and environmental impacts attributed to climate change and carbon emissions, from the initial planning to the final construction. It shows that the use of a bamboo-based material should be considered a technological improvement, especially in sustainable architecture design using indigenous materials. Although currently bamboo is not S. Habibi (B) Department of Architecture, University of Ferrara, Via Della Ghiara 36, 44121 Ferrara, Italy e-mail: [email protected]; [email protected] Department of Architecture, Faculty of Architecture and Design, Maltepe University, Istanbul, Turkey E. Obonyo Department of Architectural, The Pennsylvania State University, 219 Sackett, University Park, PA 16802, USA e-mail: [email protected] A. M. Memari Department of Architectural Engineering and Department of Civil and Environmental Engineering, The Pennsylvania State University, 219 Sackett, University Park, PA 16802, USA e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 F. L. Palombini and F. M. Nogueira (eds.), Bamboo and Sustainable Construction, Environmental Footprints and Eco-design of Products and Processes, https://doi.org/10.1007/978-981-99-0232-3_5

133

134

S. Habibi et al.

widely used in the formal construction sector in countries such as Kenya, it may be considered a “green steel” because of its low weight and easy harvesting attributes. Keywords Bamboo · Vernacular architecture · Building elements · Sustainable architecture · Residential house · Low-income housing · Kenya · Carbon emissions

1 Introduction Because of the rapid rate of urbanization, the unmet demand for low-income housing is a critical issue [1, 2]. A lack of affordable locally resourced building materials has further escalated the problem [3]. The housing sector is greatly strained with a disproportionately large number of Kenyans living in urban and peri-urban areas (Fig. 1). The formal sector in large cities such as Nairobi continues to rely partially on important materials, which conflicts with the objectives of lowering the carbon footprint of buildings. Kenya is situated to the east of the African continent with a coastline to the Indian Ocean. It covers 569,140 km2 of land and shares borders with five countries such as Somalia, Ethiopia, and Sudan to the North, Uganda to the West, and Tanzania to the southern border. Kenya lies across the Equator between latitude 5.6°N–5°S and longitudes 33–42°E. In densely populated areas, the average temperatures decrease from about 29 °C in the north to just over 16 °C around Lakes Nakuru and Naivasha in the south. In the Lake Victoria basin, daily maximum temperatures range from 27 °C in July to 32 °C in October and February.

Fig. 1 Population density and settlement points of Kenya. Reprint with permission from [4]

Advancing the Use of Bamboo as a Building Material in Low-Income …

135

This paper discusses the feasibility and viability of developing affordable, sustainable homes, especially using bamboo-based materials in Kenya. It focuses on a conceptual design of a typical housing unit for an average size family with consideration of low-cost construction as an objective. The sustainability conscientiousness in Kenya’s cosmopolitan context can be used as a lever for encouraging the use of locally sustainable materials like bamboo in the micro and macro urban areas [5]. Bamboo is a biodegradable and more eco-friendly construction material [6]. The development of value and supply chains for the production and use of bamboo can help the country to realize its desired economic growth rates in the agriculture and construction sectors in a way that is aligned with the targets for sustainable development [7]. Kenya Vision 2030 [8] sets out a development path aimed at transforming Kenya into a newly industrializing, “middle-income country providing a high-quality life to all its citizens by the year 2030.” This pathway emphasizes an environmental approach to include sustainable development, adaptation, and mitigation strategies. The government of Kenya has focused on implementing Kenya Vision 2030 and its medium-term plan, the Big Four Agenda, to improve the living standards of Kenyans, grow the economy, and leave a lasting legacy. The Big Four Agenda items are as follows: food security, affordable housing, manufacturing, and affordable universal health care.

1.1 Sustainable Development The increasing global attention to the need to reduce the extraction of limited resources has led to attempts to focus on the potential impact of sustainable development goals in the construction industry [9]. The selection of building materials that have minimal environmental impacts represents a key strategy for achieving sustainable building objectives. Bamboo is a renewable, low-cost, and environmentenhancing resource with great potential to improve sustainable development goals [10]. The environmental properties of bamboo make it a suitable material for use in applications that meet a wide range of sustainable development objectives [11]. Bamboo is one of the fastest-growing and most versatile plants on earth [12]. Furthermore, it is relatively lightweight and can also be easily harvested and transported. It is important to mention that the incorporation of the 3Rs principles (reducing, reusing, and recycling) can have a major impact on achieving sustainable development [13]. In addition to resource efficiency/environmental stewardship, sustainable development also has social justice and economic components. The authors’ vision for a bamboo-based building material value chain is inspired by a desire to contribute to the realization of these outcomes. The use of some building materials [14, 15] has also been linked to the release of volatile organic compounds (VOCs) in the indoor environment. The use of natural building materials such as bamboo can therefore result in health benefits for the

136

S. Habibi et al.

occupants through minimizing the amount of VOCs released into the indoor environment. A study by Yu et al. [16] showed that over the life cycle, a bamboo-structure residential building requires less energy and emits less carbon dioxide to meet envelope insulation and structure-supporting requirements in comparison with a typical brick-concrete building. Environmental challenges such as deforestation, soil degradation, and desertification in Kenya have led to demands for more environmentally sustainable building design strategies [17]. The deployment of renewable materials during the construction process is one of the main strategies for improvements in environmental sustainability. Bamboo is a natural and sustainable resource in the tropics and subtropics [18] and has great potential as a supplement for timber in housing applications [19]. A study by Zhao et al. [20] produced a contemporary bamboo cover map of Kenya (Fig. 2), which can be used for the planning of reasonable harvesting and management and habitat modeling for the wildlife living in bamboo forests. The initiatives directed at increasing bamboo forests in Kenya are relatively new. Creating demand for bamboo in housing will give farmers financial and economic incentives to grow it at scale. Extracting actionable insights from geospatial data can help advance sustainable development goals and the environmental performance indicators for supply chains of building materials in the Kenya Rangelands. The authors reviewed the spatial distribution of bamboo to analyze ecology, biodiversity conservation, and ecosystem service management in an area. According to the information in Fig. 2 [20], the estimated total coverage of bamboo in Kenya is 1300 km2 . Highland bamboo species are widely distributed in Mount Elgon, Mount Kenya, Cherangany Hills, the Mau Forest, and the Aberdare Range. Investigation of regional conditions and determination of sustainability indicators of materials are considered the theoretical framework that can optimize the decisionmaking process for sustainable product development. For example, the production and processing of bamboo according to local conditions and sustainability performance indicators can reduce environmental and economic impacts [21]. Therefore, it is necessary to develop concepts and methods for simplifying the use of bamboo as a renewable and sustainable material compared to modern building materials [22].

1.2 The Environmental Sustainability of Bamboo All the lifecycle phases of bamboo, such as harvesting in sustainably managed plantations, transport to processing, storage, and usage, need to be considered. The use of life cycle assessment (LCA) enables a more holistic assessment of the environmental sustainability performance of bamboo across all phases. For example, LCA can be used as a methodological framework to calculate CO2 emissions from the production and incorporation of bamboo from agriculture to the end of its life cycle (Fig. 3). Lugt et al. [23] performed a cradle-to-grave LCA for bamboo in the Netherlands. They also compared its performance in different structural applications to that of

Advancing the Use of Bamboo as a Building Material in Low-Income …

137

Fig. 2 The bamboo cover map of Kenya and 5 zoomed-in areas with abundant bamboos. Reprint with permission from Zhao et al. [20]

Fig. 3 Assessing CO2 balance of bamboo products

138

S. Habibi et al.

Fig. 4 Bamboo-based construction materials: a bamboo poles, b flattened bamboo, c woven bamboo mat, d glue laminated bamboo, e woven bamboo mat panels. Reprint with permission from Escamilla and Habert [26]

steel, timber, and concrete. They rated bamboo culm as 20 times more favorable. A study by Huang et al. [24] analyzed the adaptability of applying natural bamboo fiber and bamboo charcoal as construction infills in building envelopes with local climate and building conditions. The results showed that the application of these materials is beneficial for both bamboo resource utilization and building physical performance improvements. Vogtländer et al. [25] analyzed the environmental impact and sustainability of bamboo materials for local and Western European applications. The yield of bamboo is higher than other wood species. In another study, Escamilla and Habert [26] studied the life cycle assessment of five bamboo-based construction materials such as a bamboo pole, flattened bamboo, woven bamboo mat, glue-laminated bamboo, and woven bamboo mat panels (Fig. 4). The authors contend that inputs related to the harvesting and transport of bamboo have a very limited contribution to the environmental impact, but the nature and amount of energy used in the production process are important parameters. The authors’ proposed methodology can provide accurate data for LCAs of bamboo-based construction materials. In summary, the use of bamboo products in housing can promote economic growth and development in a way that also protects both humans and the environment. It is therefore a key enable of sustainable development (environmental, economic, and social).

1.3 Opportunities and Constraints to Bamboo Housing in Kenya Bamboo has the potential as a building material for affordable housing [27]. It has received increased attention in housing sector efforts seeking to downscale sustainable development goals in the resource-constrained context in developing countries like Kenya. Bamboo is a self-regenerating natural resource and can be

Advancing the Use of Bamboo as a Building Material in Low-Income …

139

used as an alternative material to timber, especially in tropical and subtropical regions. Using bamboo-based products can create vital local economic development and services and provide accomplishment of sustainable development goals. For example, bamboo can be effortlessly prefabricated, assembled, dismantled, and replaced. These specifications might include indicators considering all dimensions of economic, environmental, and social development. An integrated value chain can be developed to ensure the economically sustainable production of bamboo housing and to address the challenges and limitations of using bamboo as the main material in the construction process [28]. The International Network for Bamboo and Rattan (INBAR), a founding member of the UN-Habitatcoordinated Global Network for Sustainable Housing, together with the Ministry of the Environment, the Kenya Forestry Research Institute (KEFRI), and the Kenya Forestry Service (KFS), organized a workshop [29] directed at kick-starting the development of an integrated national bamboo sector policy for Kenya in 2015. Several recommendations were formulated to supply chains for bamboo-based housing applications according to key national goals, such as Kenya’s “Vision 2030.” Bamboosector development is a high-priority focus area for the KEFRI, which is the only government institution that trains researchers on the use of bamboo using low-cost technology. In spite of some initial successes following the formal launch of the bamboo initiative in Kenya, several constraints to the development of scalable and sustainable bamboo-value and supply chains in Kenya. For example, currently, there is a lack of understanding of the industrial potential of bamboo among smallholder producers and local farmers. Even though bamboo-based enterprises require lower capital, it is difficult to establish their role as a substitute for timber in the formal construction sector. In order to increase the uptake of bamboo in the housing sector, it is necessary to increase awareness among architects, developers, and building owners on its value as a low-cost and eco-friendly building material. Information concerning unique properties such as being devoid of VOCs and its high resistance to rapture should be widely disseminated. The bamboo planting program that is embodied in Kenya Vision 2030 project under the greening Kenya initiative was designed to enable Kenyans to contribute extensively to environmental activities by developing small bamboo forests in the pursuit of achieving strategic goals (10% forest cover by 2030). Economic and financial constraints limit many smallholder farmers from investing in bamboo growing because of the number of years it takes for a tree to mature [30]. Financial incentives from the government can be used to address this barrier.

1.4 Sustainable Bamboo Processing and Treatment It is important to develop a bamboo-processing industry based on sustainable and ecofriendly approaches to add value to bamboo and use it as a building material. Bamboo

140

S. Habibi et al.

comes in various shapes and sizes with different mechanical characteristics [30]. Therefore, it is important to investigate strategies to standardize bamboo processing and treatment. For example, drying bamboo is a step in the manufacturing process that increases its structural properties (Fig. 5). It is necessary before its use since dry bamboo is stronger and less susceptible to biological degradation than moist bamboo [12]. The use of bamboo in construction ranges from its deployment in temporary structures, such as structural material in scaffolding and structural building systems, to its uses as a structural element in large structural engineering [31]. Its deployment in such applications is driven by the strength properties. The structural performance of different bamboo species is driven by the cell structure. To incorporate local tradition and design into the bamboo manufacturing process for construction purposes, it is also important to know the physical, chemical, and mechanical properties of the relevant bamboo species. Most of the bamboo resources in Kenya comprise one indigenous bamboo species, Yushania alpina (formerly Arundinaria alpina) [30]. This species is commonly known as alpine bamboo and can be found on the mountain slopes in the high potential areas in Mt Kenya, Aberdare Ranges, Mau Escarpment, Cherangany hills, and Mt Elgon. Yushania alpina is a highland bamboo with a height of 5–19.5 m (average 12 m). On the other hand, a successful bamboo manufacturing sector can be established by creating sustainable planting and harvesting program. Muchiri and Muga [32] developed a yield model to estimate the total bamboo culms biomass in a given area and the proportion that can be harvested on a sustainable basis and for various purposes (Fig. 6). It is important to note that Yushania alpine has potential use in carbon sequestration. Burger et al. [33] identified the steps needed before bamboo can be used for manufacturing. Treating bamboo through preservative and drying methods ensures

Fig. 5 Bamboo processing and treatment process

Advancing the Use of Bamboo as a Building Material in Low-Income …

141

Fig. 6 Yushania alpina at Kieni Forest (left) and measurement of green weight of bamboo culms (right). Reprint with permission from Muchiri and Muga [32]

that it has high quality and durability performance. Treating and preserving bamboo protects it from insects, worms, and fungal pathogens. Sustainable and environmentally friendly approaches should be used to achieve this goal. Traditional techniques like applying heat and pressure can be used in each of the steps shown in Fig. 7. Bamboo can be preserved through leaching bamboo, chemical bamboo preservation, and drying bamboo poles that are dependent on initial moisture content, bamboo wall thickness, environmental humidity, the quantity of solar radiation, the absence or presence of rain, and the speed of the surrounding air (Fig. 8). One should also clean both the internal voids and the outer skin of the bamboo, as well as cutting and perforating bamboo poles. There are many other methods for treating bamboo such as the Boucherie method, vertical immersion, copper chrome arsenic (CCA), copper chrome boron (CCB), zinc chrome, and creosotes [35]. One study [36] investigated different treatment methods for bamboo considering different oils, different temperatures, different treatment durations, and different cooling methods. The results showed that the treatment duration influenced the properties of treated bamboos. Wahab et al. [37] studied tropical bamboo treated in palm

Fig. 7 The stages before the bamboo can be used for manufacturing and the accompanying standardization strategies. Reprint with permission from Burger et al. [33]

142

S. Habibi et al.

Fig. 8 Common methods of preserving bamboo; leaching bamboo (left), chemical bamboo preservation (middle), and drying bamboo poles (right). Reprint with permission from [34]

oil at the following temperatures: 140, 180, and 220 °C, and durations: 30, 60, and 90 min. Results showed that high-temperature treatment decreased the mechanical properties. Furthermore, according to Lee et al. [38], during heat treatment of bamboo, the treatment temperature and duration have a significant bearing on the surface color and contact angle of the bamboo.

2 Physical and Mechanical Properties of Bamboo In order to choose the correct species of bamboo for construction, it is essential to study both the physical and mechanical properties of every species. Bamboo has an anisotropy biological origin, and several factors such as direction, moisture content, diameter, wall thickness, distance to node, height, and age affect its performance. The physical properties of bamboo differ significantly from species to species [39]. Kamruzzaman et al. [40] analyzed some physical and mechanical properties (at different heights and three ages) of four bamboo species (Bambusa balcooa, Bambusa tulda, Bambusa salarkhanii, and Melocanna baccifera) and showed that Bambusa balcooa has the highest moisture content in green condition. As previously stated, most of the bamboo resources in Kenya are of the Yushania alpine species (Arundinaria alpina). This species is known as highland bamboo [41]. The physical properties of bamboo are often referred to the environmental indicators, measures, or factors such as moisture content, mass per volume or density, specific gravity, shrinkage, and fiber saturation point. The fiber saturation point (FSP) determines the bamboo processing and utilization. In fact, the evaluation of the basic concept of FSP is necessary to clarify the physical, mechanical, and rheological properties of wood. According to the wood handbook [42], the fiber saturation point of wood averages about 30% moisture content. Individual species may deviate from the average. Mateo et al. [43] determined that the fiber saturation point of bamboo (Guadua angustifolia Kunth) is in the range of 34% ± 3%. The authors’ literature review [44] established that bamboo can successfully compete with wood in various applications. The critical mechanical properties of bamboo are compression, bending, and stiffness. The values for these properties have a significant application in a subjected structure. International ISO 22157 provides guidelines that can be used to determine the mechanical properties of bamboo such

Advancing the Use of Bamboo as a Building Material in Low-Income …

143

as compression and tensile strength and elasticity modulus. Various research studies have focused on optimizing the mechanical properties of bamboo [45–47]. In order to demonstrate an understanding of bamboo as a potential material for use in structural applications, it is necessary to compare its properties with other construction materials such as timber, masonry, concrete, and steel. Bamboo has been called “green steel” and in some mechanical characteristics, like its surface tensile strength, it is reported to be stronger than steel (582 MPa vs. ~ 350 MPa) [48]. The properties of interest are compressive strength, tensile strength, shear strength, modulus of elasticity, and Poisson’s ratio. A study by Xu et al. [49] was undertaken to investigate the compressive and tensile properties of a bamboo scrimber at elevated temperatures. The results showed that tensile stress–strain relationships of a bamboo scrimber perpendicular to grain direction were linear from the beginning of loading to failure. In a study related to the investigation of the mechanical properties of treated bamboo, the species Bambusa vulgaris, Dendrocalamus asper, and Gigantochloa scortechinii had excellent mechanical properties in compression and tensile strength, especially for construction applications [50]. The literature shows that bamboo has strong mechanical properties comparable with other construction materials; however, the use of bamboo for construction purposes should be standardized.

2.1 Bamboo in Construction Industry On other hand, bamboo has been one of the most important building materials for the construction of low-cost housing [51]. The assessment of bamboo structural components (bamboo axial and flexural members) should be an integral part of the design process and relates directly to construction needs and aims. In the case of critical structural systems, bamboo must have the potential to be used as a substitute for wood-based and timber structures, adobe, and masonry buildings [52]. The use of bamboo in various building components such as floors, roofs, beams, wall panels, and columns is gaining immense importance today. The structural integrity assessment of bamboo is one of the most important factors in determining whether it can meet the construction performance objectives. Awoyera and Adesina [53] highlighted that bamboo has excellent mechanical properties for construction purposes. A study by Asamoah et al. [54] investigated the flexural performance of bambooreinforced concrete beams with the application of self-compacted concrete (SCC) in the construction industry. The result of the study showed that bamboo could be used as transverse reinforcement and as ties for seismic action in concrete construction, which indicates that it can offer an environmentally friendly and sustainable solution to the structural need in developing countries. Clearly, bamboo can be used as a sustainable building material in the selection of wall and roofing materials, appropriate structural systems, and different building applications designed to optimize acoustic insulation and energy efficiency. In order to enhance the efficient use of bamboo as a building material, strategies to replace some of the conventional building materials with bamboo can be developed

144

S. Habibi et al.

Fig. 9 Examples of bamboo as a building material used

with regard to structural, economic, and aesthetic considerations. For example, the use of bamboo in the construction industry may lead to a profound decrease in the demand for brick production, which subsequently results in a significant reduction of CO2 emissions. Furthermore, bamboo usage in building construction is not only economical but also aesthetically pleasing [55]. Implementing bamboo has opened new vistas that can indirectly enhance the minimalist beauty and aesthetics of an architecture project. Bamboo is widely used in the construction of walls and composite members (beams and columns) [56]. Major elements such as posts and beams constitute the structural framework for walls. As a construction material, bamboo can be used for scaffolding, bridges, and roofing material due to its properties such as strength, durability, and lightweight (Fig. 9). Furthermore, the benefits of bamboo as a building material are diverse and can lead to improvements in structural performance, especially in the contexts of fire resistance, safety, and elasticity.

2.2 Bamboo Building Systems Bamboo is used as one of the sustainable construction materials due to its low manufacturing costs and lightweight properties [57]. It is capable of being used for a building system with limited processing or prefabrication. Furthermore, it is one of the most environmentally friendly construction materials to form a structure and build a structural support system with minimal environmental impact. The use of bamboo as a structural material should be compatible with recognized engineering principles. Sassu et al. [58] developed and conducted experimental tests and assessments for a simple bamboo framed structure with innovative low-cost and low-technology joints. In this study, the structural system involved only natural biodegradable materials such as bamboo canes, plywood plates, wooden pins, and canapé ropes, and three different types of bamboo joints were proposed. It is shown that bamboo is a constructional material with efficient mechanical properties related to compression and bending behavior [59]. The framing of structural members and construction details of bamboo are able to meet specific load

Advancing the Use of Bamboo as a Building Material in Low-Income …

145

Fig. 10 Examples of the most common cuts used in bamboo. Reprint with permission from [61]

requirements (dead, imposed, and environmental), which are essential considerations in the design of building systems. Joint systems are the most significant aspects and have a direct impact on construction performances in bamboo structural design. Therefore, bamboo structural and joint systems should be properly investigated prior to any construction. The traditional bamboo joint is considered to have a superior aesthetic appearance for buildings and can promote developments in the emerging field of social housing and bamboo engineering [60]. For example, the lashing-based bamboo joint with multi-knots can be used to create safe structures that are not only sustainable but have the potential for use in particular building typologies, emergency response, and quick-build scenarios (Fig. 10).

3 Engineered Bamboo Products Bamboo can be engineered to form products that may be comparable with wood products in performance through processing [62]. It is important to note that a lack of effective management interventions in growing bamboo poles and harvesting methods can result in a reduction in the quality and quantity of engineered bamboo products [63]. For example, improving engineered bamboo technologies requires a focus on the unique characteristics of bamboo. Knowledge from traditional bamboo construction, such as the diversity of bamboobased knowledge and processing techniques for different species, can inform the development of engineered bamboo products. The development of bamboo products such as composite boards, reconstituted panels, and laminated flattened culm products from bamboo has risen significantly. Unique thermal processing techniques can be refined to form and bend laminated bamboo into the desired shape. Ramage et al. [64] demonstrated how their selected manufacturing process helped them to achieve new forms by modifying the shape of laminated bamboo. They investigated the thermal modification of laminated bamboo in both shape forming and design.

146

S. Habibi et al.

A study by Mahdavi et al. [65] reviewed different methods used to manufacture different types of bamboo products: scrimber, laminated, and rolled bamboo. Xiao et al. [66] outlined the process for creating glued laminated bamboo (glubam), which is composed of thick bamboo veneer sheets or plybamboos. Many of the processes used to convert bamboo into engineered composite products are borrowed from wood composite products [67]. Common processing techniques such as splitting open, sawing open, milling strips, slicing of slivers, stranding, crushing, brooming, veneering, defibrating, element pre-treatment, thermal treatment (caramelizing), and bleaching are being used to produce engineered bamboo products. Pros and cons are associated with the use of traditional use of bamboo as a building material to set the stage for engineered bamboo. One of the most common usages for bamboo today is flooring. Traditional bamboo flooring has pros such as being environmentally friendly, pest resistant, durability, easy maintenance, and climatic adaptation. It also has a variety of cons such as the softness of bamboo floors, unreliable grading system, and scratch-prone, like many hardwood species [68]. Traditional bamboo construction in Kenya can play an important role in providing an economic alternative in combination with engineered bamboo products for creating a durable, healthy, and safe house depending on the climatic condition and the species found in the particular state. The use of bamboo either in its natural form as an entire culm or in engineered form should be considered in the construction process. Although there are concerns about the usage of bamboo as an engineered material, there is a great potential to develop structural elements (i.e., beams, trusses, joists) and optimize structural systems with engineered bamboo methods. However, the development of structural bamboo composites (SBC) is still a work in progress, especially in African countries. For example, there is a huge engineered bamboo sector in Ghana [69] and even in Kenya, but bamboo construction is still not part of the mainstream construction. Studies done in Kenya [70] have shown that due to the incremental benefits, bamboo farming is financially and economically beneficial to other available agricultural crops (e.g., tobacco). The challenge is more on the design guidelines for adhering to the building codes side because the species being favored for bamboo as a building material are not native to the context.

3.1 Plybamboo Engineered bamboo is a product manufactured from bamboo and has the potential as a replacement for wood [71]. It is clear that with the progress of engineered processes, the utilization of bamboo is diversified. Engineered bamboo products can be mainly categorized into three types: laminated bamboo, reconstituted densified bamboo, and bamboo boards. Plybamboo is one type of engineered bamboo product and is mostly applied in flooring (Fig. 11). Plybamboo panels can be used as sheathings for lightweight timber structures, as well as included in existing timber design codes [73].

Advancing the Use of Bamboo as a Building Material in Low-Income …

147

Fig. 11 The main components of Plybamboo. Reprinted [adapted] from study [72], by Z. Huang, Y. Sun, and F. Musso

Fig. 12 The main components of bamboo laminated lumber. Reprinted [adapted] from the study [72], by Z. Huang, Y. Sun, and F. Musso

3.2 Bamboo Laminated Lumber The laminated form of bamboo lumber is known for assembly wall laminates (Fig. 12). Laminated bamboo lumber can be used as support beams due to its low cost and is easily available. It is usually produced as a rectangular cross-section board fabricated by flattening bamboo culms and gluing them in masses to form a bonded composite [74]. From a structural point of view, several studies found [75–78] that the bending properties of bamboo laminated lumber beams may be beneficial in structural applications.

3.3 Bamboo Scrimber Engineered bamboo scrimber (bonded fibers) is processed from the raw bamboo culm into a compressed or laminated product with thermosetting resin in the density range of 800–1200 kg/m3 [79]. Bamboo scrimber refers to solid sections of compressed, adhesive-coated fiber bundles that are heat-cured [80], and/or numerous wood splinters bonded together (Fig. 13). Bamboo scrimber is one of the most important structural materials, which has an extremely high tensile strength and compressive strength compared with wood and other bamboo-based composite materials [81].

148

S. Habibi et al.

Fig. 13 The main components of bamboo scrimber. Reprinted [adapted] from study [72], by Z. Huang, Y. Sun, and F. Musso

Fig. 14 The main components of flattened bamboo panel. Reprinted [adapted] from study [72], by Z. Huang, Y. Sun, and F. Musso

3.4 Flattened Bamboo Flattened bamboo is formed by splitting green bamboo culms, removing diaphragms and other knots from it, and then rolling and flattening it followed by nailing to keep it flat (Fig. 14). Flattened bamboo or locally known as estrella is cheaper to transport than round poles, which makes it an attractive resource for various applications mainly in the construction and furniture industry. It is commonly plastered with mud or cement mortar.

3.5 Bamboo OSB Bamboo-oriented strand board (OSB) products are being used in paneling and sheathing applications (Fig. 15). They have great potential for industrial production, especially in terms of consistent quality and efficiency of mass production. The study [82] evaluated the effect of mechanical and durability properties of OSB made from bamboo and showed that the mechanical parameters of such OSB panels were higher than the minimum property requirement according to standards.

Advancing the Use of Bamboo as a Building Material in Low-Income …

149

Fig. 15 The main components of bamboo OSB. Reprinted [adapted] from study [72], by Z. Huang, Y. Sun, and F. Musso

4 Bamboo Home Design and Building In order to show how bamboo is actually used in building construction, a bamboobased house has been designed in this study. A detailed review of contemporary vernacular architecture and the coverage of sustainability aspects have contributed to the development of the design process [83, 84]. Furthermore, examples of the actual use of bamboo in structural application with a focus on bamboo home design and construction show that various structural and non-structural concepts can be developed for constructing bamboo-based houses. Needless to say, the use of bamboo as a structural material should be compatible with recognized engineering principles. Adherence to context-specific design codes and manuals can result in the framing of structural members and details of the construction of bamboo homes in a way that meets the load-bearing requirements (dead, imposed, and environmental loads). Joints and connections are of great concern as they have a direct bearing on the systemic performance of building systems. Therefore, bamboo structural and joint systems should be properly investigated prior to any construction. The use of joint lashing (Fig. 16) rather than complicated and heavily worked joints is preferred. The natural nodes in the bamboo are points of weakness and can therefore affect the building elements’ durability and strength. The aesthetical goals of the design process play a critical role in driving the adoption of bamboo-based building materials. The 85-m2 (915 sq ft) house shown in Fig. 17 was envisaged as a conceptual residence for low-income families (including single persons) and adapted to local soil and climatic conditions. In order to take advantage of scenic views and available wind resources, the proposed site for the house is shown on the slope of a hill. The outer terraces provide a physical connection to the outside and allow the occupants to enjoy a relaxing and cooler environment during warmer days. The kitchen and the bathroom are positioned toward the east and west sides to promote an open floor plan. The ground floor consists of a living room with a closed-concept kitchen, two bedrooms, one bathroom with a toilet, and three terraces allowing panoramic views of the adjacent hills. The premise here is that the entire building envelope is made from bamboo-based materials. Round bamboo poles are considered a primary construction material in structural components such as roofs and walls. The roofing system consists of a set of timber trusses, which are made up of bamboo, and arranged into triangular shapes

150

Fig. 16 Examples of a traditional joint of bamboo houses

Fig. 17 Architectural illustration of a bamboo-based design in Kenya (Maseno)

S. Habibi et al.

Advancing the Use of Bamboo as a Building Material in Low-Income …

151

Fig. 18 Illustration of indoor space and south elevation

(on a slope of 21 degrees). This house is conceptually designed as a simple and traditional low-income home for the Kenyan climate and culture that uses thatch as an outer covering to provide insulation (Fig. 18).

5 Summary and Conclusions There is a need for the development of bamboo-based initiatives and houses in Kenya, especially in low-income areas. It is necessary to create awareness at the regional and local levels on the potential of bamboo in enhancing sustainable development and the social sustainability of urban renewal projects. In order to achieve these objectives, the country should employ initiatives for scaling up the production of local bamboo building materials and developing efficient technologies to take advantage of natural resources in a sustainable manner. The development of bamboo in construction and structural applications in Kenya is still a challenging issue, especially as a construction material in urban settlements for low-income earners. The country is having a growing demand for housing that can be addressed if bamboo is grown as a crop for construction applications. Although bamboo is included in most—but not all—of Kenya’s urban areas, it is poorly used with regard to sustainable design strategies. Furthermore, bamboo is often a feature of agroforestry systems. The current study represents an architectural design initiative to incorporate bamboo into Kenya Vision 2030, which attempts to systematically report the available information on bamboo resources, utilization, and management in Kenya. The paper has also presented a conceptual bamboo-based house for improving sustainable development goals and has suggested its approach to low-income housing. The study seeks to provide an opportunity to include bamboo as a replacement for wood in sustainable construction and national forest inventories. One of the main results of the current study is that bamboo information is based on different assumptions and definitions in different countries. This work highlights that in partnership with the private sector, the support of established institutions can help develop interventions for processing bamboo into construction material and increasing affordable housing options.

152

S. Habibi et al.

Furthermore, discussion of the engineered bamboo products can encourage opening a novel gateway for better using bamboo as a locally sourced material for construction and provide new job opportunities for farmers and local home builders. In addition to the contribution to climate change mitigation and adaptation, such widespread and targeted use of bamboo can play a key role in avoiding landscape degradation.

References 1. Gooding T (2016) Low-income housing provision in Mauritius: improving social justice and place quality. Habitat Int 53:502–516 2. Wells J, Wall D (2003) The expansion of employment opportunities in the building construction sector in the context of structural adjustment: some evidence from Kenya and Tanzania. Habitat Int 27(3):325–337 3. Cabeza LF, Boquera L, Chàfer M, Vérez D (2021) Embodied energy and embodied carbon of structural building materials: worldwide progress and barriers through literature map analysis. Energy Buildings 231:110612 4. Global Rural-Urban Mapping Project (GRUMP), v1. Maps » Population Density Grid, v1: | SEDAC. [Online]. Available: http://sedac.ciesin.columbia.edu/data/collection/grump-v1/ maps/gallery/search/3?facets=region:africa. Accessed on 18 Jul 2018 5. Awadh AH (2010) An assessment of the viability and potential of bamboo micro enterprises in environmental conservation and poverty alleviation in Nairobi city, Kenya. Master’s thesis, Maseno University, Maseno, Kenya 6. Banik N, Dey V, Sastry G (2017) An overview of lignin and hemicellulose effect upon biodegradable bamboo fiber composites due to moisture. Mater Today: Proc 4(2):3222–3232 7. Maureen OB (2014) Factors influencing the development of bamboo value chain in Kenya: a case study of Nairobi county. Master’s Thesis, University of Nairobi, Nairobi 8. Kenya Vision 2030, [Online]. Available: http://vision2030.go.ke/. Accessed on 19 Jul 2018 9. Clark G (2007) Evolution of the global sustainable consumption and production policy and the United Nations Environment Programmes (UNEP) supporting activities. J Clean Prod 15(6):492–498 10. Adhikari R, Wood D, Sudak L (2015) Low-cost bamboo lattice towers for small wind turbines. Energy Sustain Dev 28:21–28 11. ICRAF. [Online]. Available: http://www.worldagroforestry.org/. Accessed on 19 Jul 2018 12. Liese W, Köhl M (2015) Bamboo: the plant and its uses. Springer Verlag, Cham, Switzerland 13. Samiha B (2013) The importance of the 3R principle of municipal solid waste management for achieving sustainable development. Mediterr J Soc Sci 14. Missia DA, Demetriou E, Michael N, Tolis E, Bartzis J (2010) Indoor exposure from building materials: a field study. Atmos Environ 44(35):4388–4395 15. Shrubsole C, Dimitroulopoulou S, Foxall K, Gadeberg B, Doutsi A (2019) IAQ guidelines for selected volatile organic compounds (VOCs) in the UK. Build Environ 165:106382 16. Yu D, Tan H, Ruan Y (2011) A future bamboo-structure residential building prototype in China: life cycle assessment of energy use and carbon emission. Energy Buildings 43(10):2638–2646 17. Mulinge W, Gicheru P, Murithi F, Maingi P, Kihiu E, Kirui OK, Mirzabaev A (2015) Economics of land degradation and improvement in Kenya. Econ Land Degrad Improv Global Assess Sustain Dev 471–498 18. Fang C-H, Jiang Z-H, Sun Z-J, Liu H-R, Zhang X-B, Zhang R, Fei B-H (2018) An overview on bamboo culm flattening. Constr Build Mater 171:65–74 19. Parkkeeree T, Matan N, Kyokong B (2014) Flattening of half tubular bamboo culms and fixation of bamboo boards. J Trop For Sci 26:101–114

Advancing the Use of Bamboo as a Building Material in Low-Income …

153

20. Zhao Y, Feng D, Jayaraman D, Belay D, Sebrala H, Ngugi J, Maina E, Akombo R, Otuoma J, Mutyaba J, Kissa S, Qi S, Assefa F, Oduor NM, Ndawula AK, Li Y, Gong P (2018) Bamboo mapping of Ethiopia, Kenya and Uganda for the year 2016 using multi-temporal Landsat imagery. Int J Appl Earth Obs Geoinf 66:116–125 21. Atanda J (2015) Environmental impacts of bamboo as a substitute constructional material in Nigeria. Case Stud Constr Mater 3:33–39 22. Sharma B, Gatoo A, Bock M, Mulligan H, Ramage M (2015) Engineered bamboo: state of the art. Proc Instit Civil Eng Constr Mater 168(2):57–67 23. Lugt PVD, Dobbelsteen AVD, Janssen J (2006) An environmental, economic and practical assessment of bamboo as a building material for supporting structures. Constr Build Mater 20(9):648–656 24. Huang Z, Sun Y, Musso F (2018) Hygrothermal performance of natural bamboo fiber and bamboo charcoal as local construction infills in building envelope. Constr Build Mater 177:342– 357 25. Vogtländer J, Lugt PVD, Brezet H (2010) The sustainability of bamboo products for local and Western European applications. LCAs and land-use. J Clean Prod 18(13):1260–1269 26. Escamilla EZ, Habert G (2014) Environmental impacts of bamboo-based construction materials representing global production diversity. J Clean Prod 69:117–127 27. Nurdiah EA (2016) The potential of bamboo as building material in organic shaped buildings. Procedia Soc Behav Sci 216:30–38 28. Mekonnen Z, Worku A, Yohannes T, Alebachew M, Teketay D, Kassa H (2014) Bamboo resources in Ethiopia: their value chain and contribution to livelihoods. Ethnobotany Res Appl 12:511 29. Bamboo—a versatile building material for Kenya? UN-Habitat. [Online]. Available: https:// unhabitat.org/bamboo-a-versatile-building-material-for-kenya/. Accessed on 22 Jul 2018 30. Kigomo BN (20017) Guidelines for growing bamboo. KEFRI Guideline Series: No. 4. Kenya Forestry Research Institute; Nairobi, Kenya 31. Li W-T, Long Y-L, Huang J, Lin Y (2017) Axial load behavior of structural bamboo filled with concrete and cement mortar. Constr Build Mater 148:273–287 32. Muchiri MN, Muga MO (2013) A preliminary yield model for natural Yushania Alpina Bamboo in Kenya. J Nat Sci Res 3(10):77–84 33. Burger M, Oosthuizen G, Oberholzer J, Wet PD, Ras C (2017) Strategies to standardise bamboo for manufacturing process chains. Procedia Manufact 8:330–337 34. Leaching Bamboo, Guadua Bamboo. Available: https://www.guaduabamboo.com/blog/lea ching-bamboo . Accessed on 31 Jan 2022 35. Lahiry AK (2012) Propagation and preservation of bamboo. LAP LAMBERT Academic Publishing 36. Bui Q-B, Grillet A-C, Tran H-D (2017) A bamboo treatment procedure: effects on the durability and mechanical performance. Sustainability 9(9):1444 37. Wahab R, Samsi HW, Sudin M, Moktar J (2004) Strength and durability of bamboo treated through an oil-curing process. J Biol Sci 4(5):658–663 38. Lee C-H, Yang T-H, Cheng Y-W, Lee C-J (2018) Effects of thermal modification on the surface and chemical properties of moso bamboo. Constr Build Mater 178:59–71 39. Li X (2004) Physical, chemical, and mechanical properties of bamboo and its utilization potential for fiberboard manufacturing. Master’s Thesis, Louisiana State University 40. Kamruzzaman M, Saha SK, Bose AK, Islam MN (2008) Effects of age and height on physical and mechanical properties of bamboo. J Trop For Sci 20(3):211–217 41. Amenu BT (2020) Assessment of socio-economic role of Yushania alpina in Dawuro Zone, Essera District, SNNPR, Ethiopia. J Biodivers Endangered Species 8 42. Wood handbook: wood as an engineering material. U.S. Department of Agriculture, Washington D.C. 43. Mateo GG, Isabel BSJ, Fernanda CAM, Guillermo QAJ (2015) Determination of fiber saturation point of bamboo Guadua Angustifolia Kunth. In: Proceedings of the non-conventional materials and technologies conference (NOCMAT),10–13 August, Winnipeg, Canada

154

S. Habibi et al.

44. Okokpujie IP, Akinlabi ET, Fayomi OO (2020) Assessing the policy issues relating to the use of bamboo in the construction industry in Nigeria. Heliyon 6 45. Tan T, Rahbar N, Allameh S, Kwofie S, Dissmore D, Ghavami K, Soboyejo W (2011) Mechanical properties of functionally graded hierarchical bamboo structures. Acta Biomater 7(10):3796–3803 46. Lo T (2004) The effect of fiber density on strength capacity of bamboo. Mater Lett 47. Hojo T, Xu Z, Yang Y, Hamada H (2014) Tensile properties of bamboo, jute and kenaf matreinforced composite. Energy Procedia 56:72–79 48. Shao ZP, Zhou L, Liu YM, Wu ZM, Arnaund C (2010) Difference in structure and strength between internode and node sections of moso bamboo. J Trop For Sci 22(2):133–138 49. Xu M, Cui Z, Chen Z, Xiang J (2017) Experimental study on compressive and tensile properties of a bamboo scrimber at elevated temperatures. Constr Build Mater 151:732–741 50. Awalluddin D, Ariffin MAM, Osman MH, Hussin MW, Ismail MA, Lee H-S, Lim NHAS (2017) Mechanical properties of different bamboo species. MATEC Web Conf 138:01024 51. Puri V, Chakrabortty P, Anand S, Majumdar S (2017) Bamboo reinforced prefabricated wall panels for low cost housing. J Build Eng 9:52–59 52. Chaowana P (2013) Bamboo: an alternative raw material for wood and wood-based composites. J Mater Sci Res 2(2) 53. Awoyera PO, Adesina A (2017) Structural integrity assessment of bamboo for construction purposes. Ref Module Mater Sci Mater Eng 54. Adom-Asamoah M, Banahene JO, Obeng J, Boasiako EA (2017) Bamboo-reinforced self-compacting concrete beams for sustainable construction in rural areas. Struct Concr 18(6):1000–1010 55. Opoku D, Ayarkwa J, Agyekum K (2016) Factors Inhibiting the use of bamboo in building construction in ghana: perceptions of construction professionals. Mater Sci Appl 07(02):83–88 56. Shen HY, Li YS, Zhang ZW, Jiang TY, Liu JZ (2010) Application and prospect of bamboo/steel composite material in civil engineering structure. Adv Mater Res 113–116:989–993 57. Salzer C, Wallbaum H, Lopez L, Kouyoumji J (2016) Sustainability of social housing in Asia: a holistic multi-perspective development process for bamboo-based construction in the Philippines. Sustainability 8(2):151 58. Sassu M, Falco AD, Giresini L, Puppio M (2016) Structural solutions for low-cost bamboo frames: experimental tests and constructive assessments. Materials 9(5):346 59. Xu Q, Harries K, Li X, Liu Q, Gottron J (2014) Mechanical properties of structural bamboo following immersion in water. Eng Struct 81:230–239 60. Widyowijatnoko A, Harries KA (2020) 20—Joints in bamboo construction. In: Harries KA, Sharma B (eds) In Woodhead publishing series in civil and structural engineering, nonconventional and vernacular construction materials (2nd edn), Woodhead Publishing, pp 561–596 61. Building trust solving a world of issues through design. Building trust international. [Online]. Available: https://www.buildingtrustinternational.org/. Accessed on 24 Jul 2018 62. Xiao Y (2016) Engineered bamboo. Nonconventional Vernacular Constr Mater 433–452 63. Sawarkar AD, Shrimankar DD, Kumar A, Kumar A, Singh E, Singh L, Kumar S, Kumar R (2020) Commercial clustering of sustainable bamboo species in India. Ind Crops Prod 154:112693 64. Ramage MH, Sharma B, Shah DU, Reynolds TP (2017) Thermal relaxation of laminated bamboo for folded shells. Mater Des 132:582–589 65. Mahdavi M, Clouston PL, Arwade SR (2012) Discussion of ‘development of laminated bamboo lumber: review of processing, performance, and economical considerations. J Mater Civ Eng 24(11):1429–1430 66. Xiao Y, Yang R, Shan B (2013) Production, environmental impact and mechanical properties of glubam. Constr Build Mater 44:765–773 67. Chaowana P, Barbu MC (2017) 13—Bamboo: potential material for biocomposites. In: Jawaid M,Tahir PM, Saba N (eds) In Woodhead publishing series in composites science and engineering, lignocellulosic fibre and biomass-based composite materials. Woodhead Publishing, pp 259–289

Advancing the Use of Bamboo as a Building Material in Low-Income …

155

68. Huang Z, Sun Y, Musso F (2017) Experimental study on bamboo hygrothermal properties and the impact of bamboo-based panel process. Constr Build Mater 155:1112–1125 69. Agyekum K, Kissi E, Danku JC (2020) Professionals’ views of vernacular building materials and techniques for green building delivery in Ghana. Sci Afr 8 70. Magati PO, Kibwage JK, Omondi SG, Ruigu G, Omwansa W (2012) A cost-benefit analysis of substituting bamboo for tobacco: a case study of smallholder tobacco farmers in South Nyanza, Kenya. Sci J Agri Res Manage 2012 71. Hong C, Li H, Xiong Z, Lorenzo R, Corbi I, Corbi O, Wei D, Yuan C, Yang D, Zhang H (2020) Review of connections for engineered bamboo structures. J Build Eng 30:101324 72. Huang Z, Sun Y, Musso F (2017) Assessment of bamboo application in building envelope by comparison with reference timber. Constr Build Mater 156:844–860 73. Li Z, Xiao Y, Wang R, Monti G (2015) Studies of nail connectors used in wood frame shear walls with ply-bamboo sheathing panels. J Mater Civ Eng 27(7):04014216 74. Nugroho N, Ando N (2001) Development of structural composite products made from bamboo II: fundamental properties of laminated bamboo lumber. J Wood Sci 47(3):237–242 75. Lee AWC, Bai X, Bangi AP (1998) Selected properties of laboratory-made laminated-bamboo lumber. Holzforschung 52(2):207–210 76. Sharma B, Gatóo A, Ramage MH (2015) Effect of processing methods on the mechanical properties of engineered bamboo. Constr Build Mater 83:95–101 77. Wei Y, Jiang SX, Lv QF, Zhang QS, Wang LB, Lv ZT (2010) Flexural performance of glued laminated bamboo beams. Adv Mater Res 168–170:1700–1703 78. Li HT, Deeks AJ, Zhang Q, Wu G (2015) Flexural performance of laminated bamboo lumber beams. BioResources 11(1) 79. Kumar A, Vlach T, Laiblova L, Hrouda M, Kasal B, Tywoniak J, Hajek P (2016) Engineered bamboo scrimber: influence of density on the mechanical and water absorption properties. Constr Build Mater 127:815–827 80. Liu X, Smith GD, Jiang Z, Bock MCD, Boeck F, Frith O, Gatóo A, Liu K, Mulligan H, Semple KE, Sharma B, Ramage M (2015) Nomenclature for engineered bamboo. BioResources 11(1) 81. Gong Y, Zhang C, Zhao R, Xing X, Ren H (2016) Experimental study on tensile and compressive strength of bamboo scrimber. BioResources 11(3) 82. Febrianto F, Jang JH, Lee SH, Santosa IA, Hidayat W, Kwon JH, Kim NH (2015) Effect of bamboo species and resin content on properties of oriented strand board prepared from steam-treated bamboo strands. BioResources 10(2) 83. Habibi S, Obonyo E, Memari AM (2019) A bamboo design concept for low income housing in Kenya. In: Proceedings of the 18th international conference on non-conventional materials and technologies “construction materials & technologies for sustainability” (18th NOCMAT 2019), July 24–26, 2019, Nairobi, Kenya, p 14 84. Habibi S, Obonyo E, Memari AM (2020) A new concept for the integration of bamboo in contemporary vernacular architecture. In: Proceedings of the 43rd IAHS World Housing Congress—housing in the third millennium between tradition and innovation. International Association for Housing Science, March 16–17, 2020, Cochabamba, Bolivia, p 9

Lightly Modifying Thick-Walled Timber Bamboo: An Overview Jonas Hauptman, Ramtin Haghnazar, Greg Marggraf, and Yasaman Ashjazadeh

Abstract The pressing demand to decarbonize construction has ushered in a renaissance for biogenetic building material systems. From hemp blocks to mass timber construction in North America and Europe, the road map is clear for how we might construct a sustainable built environment. However, in tropical and arid regions where current ecosystem preservation is essential to planetary health and where there are far fewer softwood trees, a different approach to climate change mitigation for building construction is needed. Bamboo is already a part of this renaissance worldwide, but further innovations are needed for it to profoundly impact the built environment in these regions. New approaches are required to generate carbon-sensitive solutions for contemporary housing needed for billions of people by mid-century. Currently, bamboo is mainly utilized as round culm (bamboo engineering) or morphologically downcycled into a mere source of fiber for various composites (engineered bamboo). In either case, drawbacks exist, and unless we refine bamboo its impact may remain limited. This chapter will explore two strategies to create basic building blocks and fabrication strategies for lightly modified culm with an emphasis on thick-walled bamboo species. Despite the modification, bamboo can maintain culm integrity and, at the same time, afford slight stock refinement to a more regularized and useful state for construction. This chapter describes a process for species selection, cut culm sorting, orienting, and facing. J. Hauptman (B) School of Design, College of Architecture, Arts, and Design, Virginia Tech, Blacksburg, Virginia, USA e-mail: [email protected] R. Haghnazar · G. Marggraf · Y. Ashjazadeh School of Architecture, College of Architecture, Arts, and Design, Virginia Tech, Blacksburg, Virginia, USA e-mail: [email protected] G. Marggraf e-mail: [email protected] Y. Ashjazadeh e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 F. L. Palombini and F. M. Nogueira (eds.), Bamboo and Sustainable Construction, Environmental Footprints and Eco-design of Products and Processes, https://doi.org/10.1007/978-981-99-0232-3_6

157

158

J. Hauptman et al.

Keywords Engineered bamboo · Bamboo engineering · Lightly modified bamboo · Bamboo digital fabrication · Planning bamboo · Biomaterial fabrication · Mass bamboo · Standardless material

1 Rationale Bamboo holds great promise for low-carbon construction in the global south as a structural building material. It can be used as beams and columns, or to make wall and floor elements (Fig. 1 demonstrates potential application of the Mass Bamboo [1] panel as a floor element). However, for bamboo to be most useful in larger constructions more innovation is needed. Bamboo could benefit from becoming more regular in shape and size, and this can be done through slight modifications that decrease the eccentricities of its form. This chapter intends to inform and inspire basic production of lightly modified (culm) bamboo for prototyping and academic research. The processes and considerations are developed to enable and enhance the structural use of culm bamboo for building and furniture product design, engineering, and analysis. However, these methods are mainly intended for fabrication or prototyping scale production and thus they are not suggested as methods to be applied at an industrial scale. Consideration of accessible technology has informed this research for both philosophical and practical reasons. Bamboo research and development is challenging to fund; for that reason, an attempt has been made to use common fabrication tools for woodworking as a main approach. These tools are inexpensive, readily available in most global markets, and if tooled correctly, appropriate for the job. This may

Fig. 1 A mass bamboo panel using lightly modified bamboo

Lightly Modifying Thick-Walled Timber Bamboo: An Overview

159

benefit readers if they are inspired to work with bamboo in a lightly modified form because these interventions may be performed at low costs and made with tools and equipment that are widely available. They may already be in your woodworking laboratories and workshops. In a book about bamboo, perhaps “why bamboo” is obvious. However, this chapter intended to emphasize that as a biomaterial, the natural morphological structures and form of the culm are truly remarkable as an element of the structure consisting of a semi-round, semi-straight, telescoping, tapering, and node-braced pole-like shape. Although there is a great deal of natural variation among culms from one rhizome, let alone clumps from different geographies or species [2], all timber bamboos resemble a pole. Perhaps this is why humans have been using bamboo to build for over 8000 years [3]. Maybe our use of bamboo is akin to the way birds use other grasses to build with. It may be that humans and bamboo have the potential for both a prolific and symbiotic future. However, in its current trajectory, the human-bamboo relationship needs improvement. At the risk of being too philosophical, culm structures lack the potential for the robust scale that humans require, whether used in a full culm (bamboo engineering) or a desegregated and glued (engineered bamboo) state [4]. To this conundrum, we offer a refinement of the basic bamboo stock into a normalized unit of construction, avoiding the pitfalls of overly natural use as well as those of the overprocessing associated with engineered bamboo. With this approach toward lightly modified bamboo, we aim to preserve three characteristics: biomass, mechanical properties, and morphology.

1.1 Clarification of Light Modification The phrase lightly modified bamboo [5] was used to describe a range of approaches to constructing contemporary vernacular bamboo structures in Colombia. This term initially had a broader meaning, focused on many processes and assemblies that only partially disaggregated bamboo and were performed by traditional bamboo carpenters in the field. Under this broader definition for lightly modified bamboo, one might refine culms through a variety of methods that include cross-cutting, end joining (i.e., fish mouths), bundling, splitting, and/or unrolling bamboo (crushed bamboo mats known in Spanish as Esterilla). These processes are mainly strategies used to create elements that differ from natural bamboo culms with methods that could be deployed manually with fundamental technologies and/or on the construction site. These approaches have been developed and continuously improved incrementally over the past 200 years [6]. However, we believe this term can inspire a refined set of elements and processes with which to create them. Although these processes do not offer a fully industrial approach, they are the basic procedures to transition culm bamboo use from one of the only crafts (skilled field carpentry) to one of shop-based and repeatable fabrication.

160

J. Hauptman et al.

Fig. 2 Top element digitally modified, bottom element analog modified

1.2 General Discussion of Approaches (Analog and Digital) Here, we will describe two approaches (Fig. 2) to modifying bamboo: one with analog machinery and the other with digital tools. These approaches have been advanced from two different research trajectories developed hands-on in the laboratory, one to composite bamboo culms with an approach termed Mass Bamboo [1] and the other for Standardless Material [7] fabrication. Through both projects, an exploration has been made of methods with which bamboo can be delicately altered to keep most of its benefits but offer broader choices for design and construction.

1.3 Species and Solidity To maintain as much biomass as possible, only certain types of bamboo are relevant to lightly modified bamboo. We have focused on woody tropical species (Fig. 3) that have moderate to thick walls, the most exceptional of these species can be characterized as having high solidity. Along with high solidity, it is also important to cut the bamboo down to workable lengths. This is species dependent and may be impacted by culm stiffness and outer morphology such as diameter, straightness, roundness, and taper. Additionally, because bamboo is mostly but not completely solid, equal consideration is placed on the inside diameter. Therefore, wall thickness is the fundamental key determinant for viable species and sizes of parts.

Fig. 3 Left to right Dendrocalamus strictus, Bambusa stenostachya, and Guadua angustifolia

Lightly Modifying Thick-Walled Timber Bamboo: An Overview

161

Table 1 Contextualizing bamboos and various solidities Species

Rhizome type

Solidity (%)

Max processing length (m)

Approximate diameter (cm)

Dendrocalamus strictus

Clumping

95

2

4

Oxytenanthera abyssinica

Clumping

100

Unknown

5–10

Guadua amplexifolia

Clumping

100

Unknown

6–10

Guadua angustifolia

Running Clumper

48

3

14

Bambusa stenostachya

Clumping

73

2

10

Dendrocalamus asper

Clumping

50–70

Unknown

8–20

Although this chapter is not intended to be highly technical regarding bamboo mechanical properties, the authors’ early qualitative research with Tre Gai Bamboo in Mass Bamboo panels [6] and with lightly modified bamboo culm 3-point bend testing [8] suggest that much of culm bamboo stiffness can be retained even if a culm is cut flat on one or two sides as long as there is significant preservation of the initial cross-sectional area. Finally, our method aims to retain the basic morphological structure of bamboo. We posit that bamboo should be maintained as a transversally semi-closed shape with mostly intact nodal structure. Similarly, the major structure of the culm should be kept intact for lightly modified bamboo to be safely performed and rendered useful. Table 1 describes the species we have been exploring. This is not meant to be a comprehensive list of useful bamboos, but instead to share how the procedure may work with different species that have been observed, researched, and/or manipulated by the authors.

2 Analog Facing (AF) Initially developed for the advancement of cross-laminating bamboo, a method for analyzing and facing bamboo may offer others great utility in regularizing some geometric features useful for aggregation. This section provides key concepts and methods to safely create the basic elements of lightly modified bamboo with analog tools and jigs.

162

J. Hauptman et al.

Fig. 4 Graphic representation of the average cross-section correlated to solidity percentiles and terminology to name these ranges

Fig. 5 Graphic representation and terminology of the geometries that result in bamboo irregularity

2.1 Limitations and Considerations Multiple factors make a species productive for analog-faced lightly modified bamboo. The obvious one is that the diameter and stiffness should meet the design, mechanical, and geometric requirements. The next most important factor relates to the bamboo’s average cross-section solidity. High solidity is ideal to be a variable species for lightly modified bamboo, and this translates to a minimum range of 45–65% solid. This includes species that range from the highest end of thin-walled to solid (Fig. 4), as classified in plant science [9]. Of equal importance are the characteristics of (1) centricity, (2) linearity, (3) taper, and (4) roundness of the bamboo (Fig. 5). These aspects, in aggregate, determine what size, lengths, and the number of faces can be achieved when reducing natural bamboo into analog, lightly modified bamboo and will be further discussed in the following section.

2.2 Size Sorting and Grading Commonly, bamboo as a building material is grouped and sold by approximate outer diameters. We refer to this as grade or grading. There is not a universally accepted method to define grades. Different approaches may be used depending on profession and locality. A single grade size with some species and suppliers may vary by 1–4 cm from piece to piece within a graded size. This is for two reasons: natural variation and lack of a global standard. For example, Dendrocalamus strictus only yields usable material for the construction of up to about 3–5 cm in diameter and is sometimes sold as one grade. However, Guadua angustifolia grows much taller and wider and thus

Lightly Modifying Thick-Walled Timber Bamboo: An Overview Table 2 Example of how bamboo seller grades bamboo [10]

Available diameters (cm)

Standard length (m)

6–8

6

163 Avg. weight (kg) 9

8–10

6

12

10–12

6

16

12–14

6

21

has more grades. See Table 2 based on one Colombian seller’s “available diameters,” in which graded sizes vary by 2 cm and four grades are listed. Finally, bamboo may be graded and sold in different lengths from 2 to 6 m, and with the larger lengths in this range, there can be significant variation in diameter from one end to the other of a length.

2.3 Cutting to Length (Cross-Cutting) Due to the variability of grades, more sorting, cutting, and categorizing are necessary to organize bamboos into an outer diameter that can be faced to be parallel. The first consideration is that the bamboo outer diameter at the smallest ends should be sorted into groups with a maximum variation of only 1.5 cm before any other processing occurs. Next, the stock should be divided into consistent length units. It is important to bear in mind that the max lengths of elements will depend on linearity (Fig. 6) and solidity.

2.3.1

Further Sorting (Binning)

In order to bin, crosscuts are made to finished lengths and allow a visual opportunity to look at the wall thickness of the bamboo. At this stage, a second categorization step is performed in which both outer and inner diameters are observed with a jig that confirms acceptable diameter and wall thickness, shown in Fig. 7, and bamboo is binned in intervals of 1 cm. These binned elements are now ready for ripping, and typically, each bin can be ripped to a specific width.

Fig. 6 Three different bamboo species demonstrating out of straightness (the lack of linearity)

164

J. Hauptman et al.

Fig. 7 Demonstrates a jig used to help bin bamboos with similar and acceptable sizes for different thickness face elements

It is also helpful that at least one cut on each final length element is not made at a node to prevent an inaccurate presentation of wall thickness; this normally happens when cutting to repeated and fixed lengths because of the natural variation of bamboo morphological structure. In final fabrications, however, this should be balanced with the possibility of terminating at a node, which has several benefits, including structural and aesthetic integrity and waste reduction. If all cuts are at nodes, then the density of the bamboo is generally a reasonable indicator of wall thickness and weighing the bamboo may be a helpful alternative method to estimate acceptable minimum wall thickness. Cross-cutting has unique challenges because bamboo eccentricities make it unusual to support on across-cutting saw of any type. When bamboo sections are crosscut at each end, the desired result is perpendicular cuts along a theoretical centerline in the longitudinal directions. This center should be established in two dimensions, as seen on the lower left side of Fig. 8, representing the horizontal axis set at 90 degrees. Due to bamboo eccentricities of shape, there may be no benefit to also cutting at 90 degrees in the second/vertical orientation for the analog facing of bamboo, shown in the upper right part of the same Fig. 8. Due to bamboo’s irregular shape, cross-cutting can be dangerous without the correct jigs. When cut with power tools, it can exert uneven tension against the blade and kick back. However, a crosscut jig makes accurate perpendicular cutting easy, fast, and safe. Figure 9 illustrates three different jig permutation. Crosscuts with this method are possible at nodes or internodes, and for a goodquality cut, it is important to avoid tearing out and burning (Fig. 10). These are

Fig. 8 Illustrating parallel cuts on bamboo perpendicular to a theoretical centerline in 2D or 3D

Lightly Modifying Thick-Walled Timber Bamboo: An Overview

165

Fig. 9 Schematic illustrations of three cross-cutting work-holding methods (left) semi-fixed-2D, (middle) length adjustable-2D, and (right) double self-centering 3D

impacted if the blade is not sharp enough or the tooth geometry of the blade is not meant for cross-cutting. In the following figures, a variety of experimental setups have been shared as possible crosscut methods such as manual, push saw, metal cutting hacksaw, and pull saw. It is also possible and productive to use electric power saws ranging from a cross-cutting band saw to several saws with circular blades. For cross-cutting, the blade type is not of particular concern as long as the cutting parameters do not damage the saw blade or produce poor results. What is important is the way the work is supported. Several jigs have been explored to support and align the workpiece for cross-cutting with the objective to produce two quality cuts one at each end of a length, while the element is fixed to a jig. Furthermore, these cuts can be used to establish the theoretical centerline of the element. Several experimental jigs and hacked tools are shown in Figs. 11, 12, and 13, and the final process developed uses a shop-made V-block to support the bamboo and cut it on an electrical crosscut capable saw. The jig for cross-cutting analog-faced bamboo normally is used to make many parts at the same length and thus is a semifixed jig for cutting lengths intended to make many elements at the same length. It

Fig. 10 Left and middle cuts are low-quality, and right is a high-quality cut

166

J. Hauptman et al.

Fig. 11 Analog 3D self-centering jig

is important to recognize if you want the cuts to accurately establish the theoretical centerline and be coplanar, then each element needs fresh cuts from the initial stock on each end.

2.4 Longitudinal Facing 2.4.1

Evaluating Straightness

Once bamboo elements have two coplanar cuts and are sorted where all units are very similar in diameter, wall thickness, and weight per bin, one other aspect must still be considered. This is evaluating rotation position along the longitudinal to determine which axis or orientation is the element’s flattest one. Most bamboo kinks undulate or grow with a slight spiral-like twist. This is especially true of high-solidity species and can be distilled down to the consideration for which orientation has the most significant curvature. When parallel to this direction, the elements are reasonably flat. This step requires visual sighting down the length to observe linear versus arcing geometries. If culms are very straight and have high centricity and linearity, they can be cut with infinite numbers of faces or in any orientation. This, however, is rarely

Lightly Modifying Thick-Walled Timber Bamboo: An Overview

167

Fig. 12 Chop saw 2D squaring with a sled

Fig. 13 Self-centering jig made from the circular saw and self-centering doweling vices

the case, especially with high-solidity clumping bamboo species, and therefore, one should consider which direction the bamboo should be faced in. A slightly arching culm can be very flat when cut parallels to the natural arc and, therefore, can receive two faces. In Fig. 14, a single element is illustrated in three drawings from different views, notice how in the far right view, the element appears straightest. In this case, it would be the orientation to receive parallel ripped faces.

168

J. Hauptman et al.

Fig. 14 Illustrates how the bamboo element can be flat in one orientation but not in others

2.4.2

Sawing Methods

In order to face bamboo, holding the work securely in place is critical. Multiple approaches have been explored, and a best practice has been established. This best practice may be defined as one that adequately achieves a series of priorities at the fabrication or research scale: (1) to be safe to the machinery operators by reducing or eliminating the risk of bodily injury, (2) to eliminate the cause of excessive noise and eliminate open air disbursement of fine particulate bamboo sawdust which is harmful to eyes and the human respiratory system, (3) to produce accurate results, (4) to be achievable with low skill, (5) to be fast and repeatable to achieve, and (6) to leverage inexpensive and available technologies found in a common carpentry or woodworking shop. Next, a chart has been developed (Table 3) to share a qualitative overview and evaluation of the best tools for facing bamboo. Bamboo has traditionally been split as a means to longitudinally disaggregate or flatten; however, its grain does not run straight through nodes, so this process was not strongly considered for the facing application explored within. On the contrary, Table 3 Tools evaluation facing bamboo Machine size

Cabinet table saw

Thickness planer

Resawing bandsaw

Radial arm saw

Cutter type

Circular blade

Knives

25 mm wide

Circular blade

Capacity

Poor

High

Excellent

Excellent

Safety

Moderate

High

Moderate

Moderate

Health

Poor

High

Poor

Excellent

Accuracy

Excellent

Poor

Poor

Excellent

Speed

Good

Poor

Poor

Excellent

Double cut

Poor

Moderate

Moderate

High

Setup cost

High

High

High

Low

Lightly Modifying Thick-Walled Timber Bamboo: An Overview

169

Fig. 15 Upright band saw with the band saw ripping jig

subtractive processes are able to make cuts in any orientation irrespective of grain orientations and thus have been explored. Three general cutting approaches have been tested: (1) bandsaw cutting, (2) thickness planning, and (3) circular sawing. In each case, a jig was necessary, and the goal was to produce a finished face in one pass per side, and ideally not remove elements from the jig. The band saw (Fig. 15) was initially explored and rejected as a viable process for the following reasons: (1) extremely poor dust collection, (2) low accuracy caused by blade kerf and drift, and (3) the requirement of a second process to produce finished surfaces. A thickness planer (Fig. 16) was also evaluated as a sole process and rejected due to the need for complex jigs, many repeated operations, difficulty achieving repeatability, and difficulty attaining flatness because of material deflection. The table saw tested carried a 254 mm (10'' ) diameter blade, and the saw published maximum depth of cut was 80 mm (3–1/8'' ). However, because of the nature of the required cuts illustrated in Fig. 17, the actual stock that can be ripped was larger and it is possible to rip bamboo with a cut depth of up to nearly 8 cm, allowing bamboo with a diameter of approximately 10 cm to be faced on a table saw with a blade of 254 mm. However, the jig that can produce such a part relies on the fence and requires repositioning the bamboo and the fence for each cut. This makes accuracy a challenge and is a slow process per part. Furthermore, with the bamboo not in contact with the table at the edge of the cut, neither the standard in the table nor above table dust collection can be used. Ultimately, a circular blade-ripping method was chosen because a finished face could be established in one operation (Fig. 18). When considering appropriate saw types, the first one tested was a table saw which was effective for smaller outer diameter species at very short lengths (under 75 cm); however, as lengths and diameters

170

J. Hauptman et al.

Fig. 16 Shows bamboo planning jig, photo credit: Will Warasila

Fig. 17 Fence riding table saw ripping jig with a 4-sided faced Bambusa stenostachya element clamped

Lightly Modifying Thick-Walled Timber Bamboo: An Overview

171

Fig. 18 A comparison between table saw and radial arm saw (RAS) note saws represented in blue is carried in the same diameter blade

increase, a common carpenter’s table saw was ineffective due to lack of available blade depth of cut of under 8 cm.

2.4.3

Radial Arm Saw

When considering alternative ripping saws, a radial arm saw of comparable size was explored and offered a significantly more cutting capacity of approximately 15 cm. Furthermore, a radial arm saw also affords a more stable structure for jigs and easily accommodates a dust enclosure. A jig for quickly and accurately holding and aligning the bamboo culm allows an operator to pass the bamboo through the saw blade and make the facing cut (Figs. 19 and 20). If bamboo is straight and solid enough, it can be ripped in lengths up to 2.43 m. It should be noted that radial arm saw can cause ejections if not used properly. Particular care for work holding, blade alignment parallel to the fence, and blade sharpness must be maintained and follow manufacturing instructions for safe saw operation [11]. Although no tool is without any risk or danger if used incorrectly, the radial arm saw in rip mode, equipped with thoughtful jigs and enclosures, is the fastest and safest way to face bamboo accurately in the laboratory or workshop environment. Saw Type and Blade Specification Several models and sizes of radial arm saws have been tested, with multiple blade sizes, but most production has been done on vintage 220 V Dewalt, and Delta radial arm saws, that is capable of taking a 305-mm diameter, 4-mm kerf, 20-tooth carbide tipped ripping blade. It is important to have enough power and a quality saw in good working order. Many of the newer saws and those from other brands do not have the stability or power to rip bamboo. Our preferred saw has been a Dewalt model 7790.

172

J. Hauptman et al.

Fig. 19 A Dewalt 7790 RAS with the front of the dust box removed for photographic purposes. Note the ripping sled with end support and a cambering stilt in the middle of the ripped bamboo element

Fig. 20 Illustration of a vintage Dewalt radial arm saw equipped with the necessary fixating to rip bamboo

Lightly Modifying Thick-Walled Timber Bamboo: An Overview

173

Dust Box/Blade Guard The rationale for building a box around the saw is to keep hands far away from the blade and dust away from the operator, the dust box inlet and outlet should be big enough to not create any risk of waste bamboo pinching when it falls off because that could cause a dangerous ejection, but small enough to allow a high meter cube per hour dust extraction system to create sufficient suction (Fig. 21). Although not shown, soft flaps are used at the opening to reduce the loss of suction at the opening while still allowing unencumbered movement of the sled-mounted bamboo to move through the track and saw blade with ease. Sled Specification and Features The sled is made from 18-mm melamine-coated particle board and 30-mm plywood. It fits a track in the saw with approximately a 0.5-mm gap. The table and track are also made from the same melamine which creates the side walls, and a layer of 6 mm plywood is used to create the capture. They are assembled with pocket-hole screws. Throughout the development of this process, many sled types have been built and tested to hold the bamboo securely for ripping. The final method established has a few key features: (1) It is light, flat, and stiff, accomplished by using the vertical feature to brace the base of the sled, (2) fast and easy bamboo securement method, accomplished with 6 mm steel bolts and barrel nuts used to clamp the stock to the jig at each ends,

Fig. 21 Illustration of the side view of the sled entering the saw and dust box via the track with top capture

174

J. Hauptman et al.

Fig. 22 Radial arm saw bamboo sled

(3) the bamboo is elevated, allowing fall-off to drop well below the depth of the blade, reducing the risk of debris pinching and ejecting, and (4) a middle fulcrum slightly cambers the bamboo, reducing unsupported span and resultant vibration (Fig. 22). Ripping Before ripping with a radial arm saw, it is imperative to understand the two distinct ways to do so: in-rip and out-rip. These refer to the orientation of the open face of the saw blade, meaning the blade is facing toward the saw column during in-rip and facing away from the column in out-rip. The key distinction between these two ripping methods is that the blade rotates in a different direction for each, and therefore, you must feed material into the saw from opposite ends. Figure 22 shows an in-rip setup where the blade is rotating counter-clockwise. In this orientation, the stock should be fed right to the left (looking from the front of the saw) so that the blade is spinning up into the material. In woodworking terminology, this is considered conventional cutting [12]. If the material was fed left to right in this scenario (power cutting), the cut would not be as clean, and there is a higher risk of the material being pulled with the blade and ejected. For an out-rip, the opposite feed direction applies. Using this proper RAS setup, dust enclosure, and work-holding jig described in Sect. 2.4.3 and its subsections, the process of ripping the bamboo is rather straightforward. Once a pole is securely fastened to the jig, insert it into the sled track but do not turn the saw on. Use the bamboo pole as a reference for setting the blade to the desired depth of rip. Be sure to lock the saw in this position on the arm. Once this is complete, back the jig away from the blade and turn the saw on; you’re ready to rip! Ripping is most efficiently completed with two operators: a feeder and a receiver. The feeder will push the jig into the saw until the front clamp is through the dust enclosure. At this point, the receiver takes over and pulls the jig the rest of the way through. It is important that once the receiver begins to pull, the feeder stops pushing. This way, there is no added tension on the jig, and the receiver will not be pulled toward the saw if the receiver has a strong pull. Even more important are the standing positions of the two operators. Always stand on the side of the jig opposite

Lightly Modifying Thick-Walled Timber Bamboo: An Overview

175

of where the bamboo is being faced. In the case of an ejection, you do not want to be standing directly in line with the fall-off. Once the receiver takes over responsibility of moving the stock through the blade, the feeder should stand off to the side of the saw. Ejections will almost always shoot toward the feeder since the blade is spinning in that direction. Lastly, as the receiver pulls the jig through, they should pin the bamboo fall-off to the pole, preventing it from twisting or getting caught up with any system element and being propelled by the blade. Once the first pass is completed, the receiver should hand the jig back to the feeder, the jig rotated 180 degrees, and fed back through for the second face. After both faces are ripped, remove the pole by loosening the bolts, load a new pole, and repeat. Using these methods, ripping bamboo with a radial arm saw can be safe, fast, and efficient. Alternatively, if 3–4 laborers were involved in the process (2 saw operators and 1– 2 loading/unloading jigs), this method is more than twice as efficient. If poles are consistently being fed through the saw with minimal delay between each one, the processing rate is two meters per minute. That would yield enough faced bamboo in an hour to construct almost any prototype-scale structure/product.

3 Digital Surfacing Digital surfacing is an approach where one can use irregular bamboo to execute a freeform design structure in which the irregular quality of natural bamboo does not impact reliable and repeatable assembly. Figure 23 documents small assembly experiment.

Fig. 23 Example of digital surfacing usage as a bolted lap joint in all intersections

176

J. Hauptman et al.

3.1 Rationale Although a lot can be accomplished by manually modifying bamboo, it also requires tradeoffs. For instance, the speed of the analog facing operations is quite high but so is the loss of biomass by comparison to only making local modifications such as pockets, slots, or holes in the stock. Biomass loss or fall-off can reach 15% if the bamboo is very irregular, and in some cases, the stock may be so irregular that facing is not a practical option at all. Furthermore, there are situations in which the quantity or complexity of specific geometry is too small or complex, respectively, to be applied via a manual operation. In some cases, it may be worth considering a more localized approach for modification. This is possible via Computer Numerical Controlled (CNC) milling. A variety of types of CNC machines have been explored. These types of machines are commonly used to make customized parts from flat engineered wood panels but when outfitted with the proper work holding, indexing, or additional axis of movement, they can also be used for linear materials, including round stock and boards made from soft materials such as wood and plastic. It is also possible to CNC mill natural culm bamboo, but this requires custom work-holding jigs to help manage the material’s eccentricities of form and solidity. This section focuses on the methods to milling high-solidity, low linearity bamboo on a CNC milling machine, which can be used to make localized flatness for jointing and other geometries along an otherwise irregular length. Although there are many other opportunities for digital fabrication with bamboo, the discussion here is limited to selectively milling regions for connections.

3.2 Qualifying and Assigning For bamboo to be digitally surfaced, it is important to confirm that there is material where it is needed to achieve the final part. The bamboo must contain usable geometry of the proper size and solidity. In order to determine this, sizing fixtures (Fig. 24) and/or templates have been used. It is important to confirm that there is sufficient outer diameter, centricity, and linearity so that intended to be milled faces may fall within the solid portions of the natural shape of the bamboo element intended for the part. These general confirmations may also include diameter, node distribution, and weight but they lack the detail of the actual bamboo morphological shape. Another approach would be to take a 3D scan which would yield a precise digital twin of the actual bamboo element. However, the recently established methods for scanning bamboo [13] are time-consuming, data-intensive, and expensive, and so presently, the methods described here do not include 3D scanning. Once a section of a bamboo culm is matched by general confirmation, it can be marked for cutting and labeled with a unique identifier so that a machining file can

Lightly Modifying Thick-Walled Timber Bamboo: An Overview

177

Fig. 24 3 Views of one fixture used to qualify that a bamboo element is thick and straight enough for a designed element

be associated with the intended stock. Once this is performed, the stock is ready for cross-cutting and indexing.

3.3 Indexing Now, the selected bamboo can be cut with parallel crosscut ends, in the same general methods as with analog facing, which establishes a 2D theoretical centerline, the cut stock is now ready to receive the final permanent position attribute by adding a pair of registration pucks, shown below in Fig. 25 that are placed by eye on the center of each end cut and affixed by hand. Once these are added, the bamboo is physically configured for machining, and the theoretical centerline for rotary CNC milling is made. Because these indexes need to be firm but also quickly, accurately, and durably affixed, they are made from hardwood plywood and affixed by way of a two-step process of gluing and then adding 3 or 4, 23-gauge headless pin nails to each end of the bamboo-part.

3.4 Geometries Many features can be milled into a high-solidity bamboo pole, such as through holes, slots, profiles and contours, and pockets. In most cases, this can be accomplished with a typical X, Y, and Z 3-axis CNC with an added jig for 4th-axis positioning. Furthermore, twists and rotational surface features can be milled if the machine is equipped with a 4th A-axis (Fig. 26). The most important limiting factor for geometry that can be CNC milled in bamboo is how to create stock stability when and where it is unsupported.

3.4.1

Positioning Strategies

Although establishing a theoretical centerline by adding the work-holding pucks accommodates some machining, there are limitations to how far the bamboo can

178

J. Hauptman et al.

Fig. 25 Documents the process tools and materials used to temporarily affix index pucks to bamboo for 4-axis millings

Fig. 26 Illustrates a range of features that can be milled in bamboo

Lightly Modifying Thick-Walled Timber Bamboo: An Overview

179

Fig. 27 3-Axis milling machine with 4th-axis positioning jig

span unsupported. Also, bamboo’s organic shape makes practical limitations for how to hold it mid-span. On a 4-axis rotary machine, the lengths of Dendrocalamus strictus that can be machined are limited to approximately 1.5 m because there is no easy way to support the middle of the organically shaped bamboo culm. However, on a 3-axis machining with a jig for 4th-axis positioning (Fig. 27), the opportunity to add interstitial supports makes it possible to machine longer lengths of up to 3 m. In either case, it is best to limit the length of unsupported material as much as possible, and in general terms, the best results are obtained at under one meter of unsupported spans.

3.4.2

4th-Axis Positioning Jigs

The fourth-axis position jig is made up of several assemblies, and these include the following (a) base (b) clamping headstock (c) clamping bridge, and (d) clamping tail stock. Although the names are similar to those used on a lathe, it is important to

180

J. Hauptman et al.

recognize that there is no powered rotational control but instead a manual method to set an A-axis position. The A-axis position is set by manually spinning the clamping headstock in its saddle while indexing with a digital angle-finding device, once an angle is set the angle is fixed in two or three places by adjusting the depth and tightening the clamping mechanisms. When a culm is long enough to need a bridge, it is set in a different way because the center and shape of the bamboo are unknown in the middle of the length. In these locations, a set of fixable wedges are adjusted to lightly touch the lower surface of the bamboo, then they are locked, and finally, an additional toggle clamp is adjusted in depth to add downward pressure locking the culm into place. It is important to avoid placing these supports in areas that will be milled.

3.5 4-Axis Milling Machine Fourth-axis milling is very effective at limited lengths because it reduces the need for hand rotation and additional affixing via bridges. This makes for a faster and more reliable workflow. Fourth-axis CNC mills are less common than 3-axis ones. Another option the author has explored is to purpose-built a rotary 4-axis CNC especially made for bamboo. Featured in Fig. 28 is a dedicated machine prototype built for this purpose. The other option is to purchase a machine that offers an A-axis, such as the machine in Fig. 29.

Fig. 28 Virginia Tech BCNC 4-axis DIY prototype

Lightly Modifying Thick-Walled Timber Bamboo: An Overview

181

Fig. 29 Shows the process of 4-axis milling with 12.7 mm cutter, the left is drilling a counterbore, and the right is profiling a lap joint face

3.5.1

Cutters

Multiple cutters have been explored, and for best results, it is helpful to use large shank diameter tools wherever possible because they can handle the vibration caused by milling bamboo, a non-stable workpiece. The following parameters have been used successfully. A step down of 6 mm per pass, with a plunge rate of 400 mm per minute, and a horizontal movement of 1200 mm per minute. All carbide milling tools for wood can be used for bamboo. However, tool life is shorter with bamboo than with other woody materials due to the hard outer layer and its lack of stiffness. For most operations other than drilling, two cutters have been used as shown in Fig. 30. For drilling, no specific challenges exist, so they are not described within, and any diameter over 3 mm can generally be packed into a bamboo element.

3.5.2

Tool Path Strategy

Bamboo has a high probability of tearing out with some cutting geometries, and therefore, sometimes tool path direction is extremely important and should be run in the direction as diagrammed below. In Fig. 31, the authors represent two toolpath strategies for milling bamboo using the two cutters presented in Fig. 30. Although milling parameters are shared here, they do not replace trial and error, are specific to the condition of the bamboo, geometry cut, machine rigidity, and available cutters, and very much may vary if these conditions change.

4 Conclusions and Limitations Opportunities for tooling bamboo for design may be easily understood from an incremental innovation perspective as being situated between wood and steel design and

182

J. Hauptman et al.

Fig. 30 Cutter that effectively mill bamboo (left) carbide tipped straight 2 flute (right) solid carbide 2 flute up cut

Fig. 31 Representations of tool path cutting movement including direction and side of cut, top representing cut with 12.7 mm 2 flute upcut tool, and bottom representing cutting with a 50 mm, 2 flute straight cut tool

fabrications. However, they also suggest new architectural forms within some of the current vernacular architectural styles already emerging with bamboo. In these areas, the consistency of faces that could be joined with repeatable composite assembly is promising. Also, in areas of freeform structures, there is huge potential if we can both express bamboo’s wildness and tame it to be reliable, more knowable, and modestly accurate like many other building systems. Furthermore, the real potential for a Mass Bamboo system for the global south would be possible if these methods continue to be developed and refined. There is a lot more to do if bamboo is to reach its potential although these methods may be useful in the laboratory, workshop, or small-scale distributed manufacturing scenarios, they still lack high efficiency. Furthermore, for lightly modified bamboo to

Lightly Modifying Thick-Walled Timber Bamboo: An Overview

183

be meaningful, there needs to be a stronger understanding of how these modifications impact stiffness, durability, safety, and many other aspects of building. Furthermore, one will need to develop composite or assembly methods in an equally reliable manner. More work needs to be done in the areas of connection design and methodology. Until now, most bamboo innovation is incremental innovation where we mostly barrow processes and strategies from other materials and processes such as from mass or framed timber and steel pipe fabrication. Bamboo is its own category of materials, and it needs global attention, recourses, and novel approaches. Without a doubt, as scanning becomes more viable and material informatics gets tuned to bamboo, these technologies for seeing or sensing bamboo and its ideocracies become more of an opportunity than a risk. This will hold a great impact on the future global south construction landscape of building with bamboo.

References 1. Hauptman J, Hindman D, Hack K, Marggraf G (2022) Smart bamboo systems: combining material intelligence with modern manufacturing systems. NOCMAT 2022 2. Hidalgo-Lopez O (2003) Bamboo: the gift of the gods. O. Hidalgo-Lopez 3. Lucas S (2013) Bamboo (botanical). Reaktion Books 4. Archila HF, Trujillo DJA (2016) Engineered bamboo and bamboo engineering. Exova BM TRADA 5. Chang WS, Trujillo DJA, Ramage M (2013) Lightly modified bamboo for structural applications. Constr Mater 166:238–247 6. International Bamboo and Rattan Organization (INBAR) (2022) Bamboo Housing design accessible for the middle class in the Philippines. https://www.inbar.int. Accessed 16 Nov 2022 7. Schumann K, Hauptman J, MacDonald K (2019) Addressing barriers for bamboo: techniques for altering cultural perception. Architectural Research Centers Consortium (ARCC)—The Future of Praxis 8. Hauptman J, MacDonald K, Schumann K (2019) Structural performance of faced Calcutta bamboo (Dendrocalomus Strictus) for use in joined structural assemblies. In: 4th International sustainable buildings symposium (ISBS), vol 21, pp 257–264 9. Clark DL (2005) Culms, bamboo biodiversity. https://www.eeob.iastate.edu. Accessed 16 Nov 2022 10. Guadua Bamboo. https://www.guaduabamboo.com/bamboo-poles. Accessed 10 Nov 2022. 11. Dewalt 7790 type 6 use and care manual. Dewalt, Division of Black and Decker (U.S.) Inc. Lancaster, PA 12. Kunkel W (1997) How to master the radial arm saw! 13. Lorenzo R, Mimendi L (2020) Digitisation of bamboo culms for structural applications. J Build Eng 29C:101193

Bamboo Flattening Technique Zhichao Lou, Yanjun Li, and Yihan Zhao

Abstract With the rapid growth of China’s economy and people’s high-level pursuit of life, eco-friendly materials are gradually being used in home decoration, furniture, and construction industries. Bamboo is stronger, is tougher, and has a greater abrasion resistance compared to wood and can thus be applied as a material in engineering or home decor. However, bamboo also has several limitations, for example, a small diameter, a longitudinal difference in diameter, thin and hollow walls, and a disposition to corrosion and cracking. Therefore, bamboo was initially used in applications of low technological content and low added value. “Bamboo flattening” is a high-efficiency utilization technology adopted to construct flattened bamboo boards from bamboo tubes or arc-shaped bamboo sheets. For the bamboo tubes, penetrating grooves are requested to be created, which are supposed to be widened during the saturated steam heat treatment and are conducive for the tubes to enter into the flattening machine. And tapered, rectangular, or “V”-shaped protrusions nails with uniform dispersions, or diamond-shaped line grooves with a width, depth, and spacing of 1.5–2.0 mm, 2.0–4.0 mm, and 5.0–8.0 mm are always created to release the generated internal stress during the flattening processes. Compared with traditional bamboo laminated timber, this technology can increase the utilization rate of bamboo resources from the original 30–55%, reducing the adhesive amount by 30%. Herein, the achievements in bamboo flattening technology and corresponding physicochemical mechanisms based on published papers and patents are described. Finally, the future development of bamboo flattening technology is presented. Keywords Bamboo · Flattening · Softening · Drying · Internal stress · Crack-free · Nick-free · Technique

Z. Lou (B) · Y. Li · Y. Zhao College of Materials Science and Engineering, Nanjing Forestry University, Nanjing 210037, China e-mail: [email protected] Y. Zhao e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 F. L. Palombini and F. M. Nogueira (eds.), Bamboo and Sustainable Construction, Environmental Footprints and Eco-design of Products and Processes, https://doi.org/10.1007/978-981-99-0232-3_7

185

186

Z. Lou et al.

1 Introduction With China’s rapid economic growth and people’s pursuit of a higher level of life in recent years, biomass such as wood and bamboo is increasingly being used in decoration, furniture, and construction. However, China’s timber resources are relatively rare [1, 2]. In addition, people are facing a coming worldwide shortage of timber resources with decreased quality. Especially natural, mature, or over-mature forests with large sizes are disappearing. At the same time, due to the worldwide more and more attention to environmental protection, the importation of wood is limited. Commercial logging in natural forests has been completely stopped, and China’s contradiction between supply and demand of timber is widening. It seriously restricts the development and application of high-value wood-based composite materials. Although artificial fast-growing young forest timber is introduced to replace some of the natural wood, the application of such fast-growing timber is relatively narrow due to the corresponding low mechanical properties [3–5]. Compared with wood, bamboo possesses the characteristics of high strength, high toughness, abrasion resistance, and so on. Thus, bamboo has a broad application prospect as structural engineering material or home decoration material [6–8]. China possesses the largest bamboo resources, which is a quarter of the world’s bamboo forest area. Meanwhile, there are about 10,000 kinds of bamboo products in China, with a total industrial output value of 200 billion yuan per year. The bamboo industry in China has played an important role in the development of a green low-carbon economy, the combat of global climate change, precision poverty alleviation, and the promotion of employment, and income of peasants, making an important demonstration and promotion role for the “Replacing wood with bamboo” [9–12]. However, bamboo has its own defects, such as its smaller diameter, the longitudinal difference in diameter, and thin and hollow structural characteristics of walls, and is prone to corrosion and cracking [13, 14]. Therefore, in the early stages of application, bamboo was mainly used for weaving agricultural implements, furniture, and bamboo crafts which are of low technological content and low added value [15]. With the development of bamboo processing technology, a series of high-value products, including bamboo plywood [16, 17], bamboo cement templates [18–20], bamboo scrimber lumber [21–24], sliced bamboo veneer [25–27], bamboo laminate [7, 28, 29], and bamboo winding composite pressure tube [30, 31] are developed in decades. The corresponding application field is broadened into automobiles, trains, construction, pipeline construction, and containers [32]. However, the manufacturing procedure of these bamboo-based panels normally includes cutting, planing, gluing, and pressing, which is complex and less mechanized. This method has a large amount of glue and causes serious dust and gas pollution. And the corresponding utilization rate is as low as 35–50%, restricting the development of the bamboo processing industry. Considering this, the bamboo industry urgently needs to develop a novel bamboo processing technology that can be used to prepare bamboo slices with better performance without changing the original bonding form of bamboo thickness and

Bamboo Flattening Technique

187

width. To simplify the production process, reduce the cost, improve the utilization rate, and add value [33–35]. “Bamboo flattening” is a technology to make a flattened bamboo board from bamboo tubes or arc-shaped bamboo sheets which are pre-softened [36]. Academician Zhang’s group first proposed the technology in the 1980s. The flattened boards are normally used to produce bamboo plywood, which is proven to have high strength and good rigidity [16, 35, 37]. With the development of science and technology and the gradually deepened people’s understanding of bamboo modification, bamboo flattening technology has developed to include crack-free spreading of bamboo tubes and arc-shaped bamboo sheets with large curvature. This paper introduces the detailed achievements in bamboo flattening technology based on published papers and patents. And in terms of physicochemical mechanisms to explore two key processes are bamboo softening and flattening. On this basis, some views on the future development of bamboo flattening technology are put forward.

2 Pre-treatment of Bamboo Before Flattening As we know that 3–5 years of bamboo have the best material performance and processing properties. Bamboo, at this stage, is conducive to being softened and flattened due to its high hemicellulose and stable lignin content [38–41]. Therefore, 3- to 5-year-old moso bamboo is normally chosen as raw material for industrial flattening. Additionally, two requests should be met: (1) The diameter for the tip section should reach 10 cm; and (2) the initial moisture content should be larger than 15%. To be mentioned, the bamboo sections which are 1 m upwards from the roots are not suitable for being flattened due to their greater curvature. However, such sections can be processed into bamboo strips which can be used as raw materials for integrated timber or restructured bamboo. The sections of bamboo are cut into 0.5–2 m long bamboo tubes according to the requested size of the flattening bamboo board products. Among them, the part of bamboo with an inner diameter lower/larger than 12 cm can be truncated into bamboo tubes with lengths smaller/larger than 1 m, respectively, considering their different taperingness. According to different flattening approaches and the following applications, bamboo tubes should be removed from their inner knots and grooved in subsequent treatments [42]. It could also be longitudinally sectioned using a bamboo cutting machine to obtain 2–3 arc-shaped bamboo slices for further use [43]. Figure 1a shows the cross-section micrography of bamboo. Figure 1a shows that bamboo is divided into three parts according to the longitudinal vascular bundle distribution density and the corresponding chemical components: the outer layer, the flesh, and the inner layer. Among them, the outer layer is a part that is close to the outer side of the bamboo culm wall, the vascular bundles of which are small and dense. The vascular bundles gradually become larger from the outer layer to the flesh, and further to the inner layer, while the corresponding amount decreases and their distribution is in a random sparsity. As a result, the mechanical strength

188

Z. Lou et al.

Fig. 1 a The SEM image of the cross-section of bamboo. b The schematic diagram of the bamboo flattening technique

of bamboo decreases gradually from the outside to the inside. The outer layer of bamboo is hard to compress due to its high density and hardness, while the inner layer is susceptible to stretching and cracking due to its softness. Figure 1b shows the schematic diagram of the bamboo flattening technique. We can see that during the flattening process, the outer layer is subjected to extrusion stress, while tensile stress is applied to the inner layer. According to the stress formula, the tensile and compressive stresses inside the inner and outer layers are 200 times higher than the bearable force in the transverse direction. The results show that if the bamboo is not pre-treated, cracks on the inner surface are unavoidable during the flattening process [35]. Therefore, according to the stress formula: σ =

E·S 2r

where σ is the compressive or tensile stress (Pa) on the outer or inner surface of the bamboo during expansion, E is the transverse elastic modulus of bamboo (Pa), S and r are wall thickness (mm) and radius of curvature (mm) of bamboo, respectively, the resulted tensile stress (σ ) of the inner surface can be reduced by reducing the elastic modulus (E) of the bamboo timber, and thus, the cracks can be reduced in width and depth, or even avoided. The methods of softening treatment before flattening mainly include chemical softening treatment and physics assistant softening treatment.

Bamboo Flattening Technique

189

2.1 Chemical Softening Treatment 2.1.1

Softening with Chemical Agents

In the mid-twentieth century, Stamm and Tarkow [44] first proposed using ammonia to soften biomass materials. Ammonia is a good lignin plasticizer. The lignin molecules can be distorted without being dissolved or completely separated. As a result, the chemical linkage between lignin and polysaccharides (cellulose and hemicellulose) becomes weak, leading to the softening of wood [45, 46]. At the same time, ammonia can react with the cellulose in the crystalline area to produce ammoniated cellulose, resulting in a certain degree of cellulose swelling. In addition, the hemicellulose molecules in the cell wall reorient with the presence of ammonia [47–49]. Besides, ammonia, urea, hydrazine, and other alkaline solutions have a similar softening effect on biomass materials [50–52]. Qian et al. [53] studied the effect of the mixed solution of ammonia and urea with different concentrations on the softening of bamboo. The results show that the treated samples’ relative crystallinity increases with urea concentration. And a significant enhancement of the hydroxyl absorption peak of FTIR was observed, indicating the facilitation of water to enter into bamboo during the softening process, and thus, a more efficient softening process is achieved. Fu et al. [54] use bamboo as raw materials, such as Phyllostachys pubescens, mottled bamboo, fish scale bamboo, Phyllostachys bissetii, and bitter bamboo, to compare the softening effect of 15% NaOH, 15% KOH, 40% urea, and 25% ammonia solution, respectively. It was observed that weak alkaline solutions such as urea and ammonia are not as effective as strong alkaline solutions (NaOH and KOH) in softening. However, these chemical agents are expensive, and not conducive to cost control. More importantly, unlike wood, bamboo has a thin and hollow wall. The outer layer is covered by a waxy and hard film, which is not for chemicals to impregnate the bamboo’s interior. In addition, softening with chemical reagents is accompanied by a drastic change in the chemical composition of the bamboo, which affects the quality of the treated material and is harsh to the environment.

2.1.2

Thermochemical Softening Treatment

As we know, plasticity can be improved by increasing the moisture content and temperature of biomass. Thus, the transverse elastic modulus of bamboo can be reduced, and thus, the softening can be realized [55, 56]. As a non-homogeneous polymer, bamboo is a bio-polymer composite consisting of cellulose, hemicellulose, and lignin. Its glass transition temperature (T g ) plays a key role in softening. The stress–strain of bamboo varies with the softening treatment time, resulting in viscoelastic deformation. When the temperature reaches T g , amorphous polymers, such as cellulose, in the amorphous region, and hemicellulose, undergo thermal softening, changing from a glassy state to a viscoelastic and highly elastic state. The elastic modulus, which is treated as a rigid characteristic index, decreases rapidly.

190

Z. Lou et al.

And conversely, the corresponding plasticity strengthens [57–59]. Hemicellulose and lignin have a certain plasticity at 80 °C and 100 °C, respectively, while cellulose exhibits plasticity at 130–150 °C [60–63]. Because cellulose content in bamboo is higher than in wood, the former should be treated at a higher temperature than wood to improve the corresponding plasticity. The methods of thermochemical softening mainly include water-boiling softening, high-temperature softening, and saturated steam softening.

Water-Boiling Softening Takamura [64] report that during the water-boiling heat treatment, water molecules enter the amorphous region of cellulose, hemicellulose, and lignin inside the wood, causing the swelling of the three substances. At the same time, with the increase in temperature, the corresponding molecular thermal motion intensifies, and part of the hydrogen bonds among the three substances are broken. As a result, the cell walls soften followed by wood softening and the corresponding static bending strength decrease. Hillis, Placet and Shrestha et al. [65–67] report that the reduction in the elastic modulus of wood after softening is mainly due to the debonding failure of the lignin intercellular layer under the action of water molecules. Some Chinese scholars have conducted a series of research on bamboo water-boiling softening in combination with these previously published results. Jiang et al. [68] impregnated bamboo in 70–80 °C hot water for 2–3 h. They found that with the increased temperature and moisture content of the treated bamboo samples, their plasticity is improved effectively. Meanwhile, part of the extracts and proteins can be separated during the impregnating process, to enhance the mildew-proof and insectresistant ability of bamboo. Fu et al. [54, 69] studied the effects of water-boiling softening treatment on moisture content, pressure-resistant capacity, and resulted mass of treated bamboo samples. Qian et al. [70] investigated the changes in grain tensile strength, grain compressive strength, static bending strength, and flexural elastic modulus of the treated bamboo samples with different ages (1.5, 3.5, and 5.5) and different relative positions after water boiling. The results showed that waterboiling softening could effectively reduce the modulus of elasticity and enhance the plasticity of moso bamboo. Also, the softening time increased with the increase of bamboo age. Nonetheless, the water-boiling softening process is complicated, and it is difficult to reach the glass transition temperature of cellulose, so it needs to be compensated by extending the treatment time. In addition, bamboo absorbs a large amount of water during the treatment process, which is not conducive to subsequent processing and utilization, increasing the production cost and inducing difficult waste disposal. Therefore, although there are small-scale industrial applications of waterboiling softening treatment at home and abroad, it is difficult to achieve large-scale promotion.

Bamboo Flattening Technique

191

High-Temperature Softening Compared to water-boiling softening, the temperature of high-temperature softening treatment is higher, reaching as high as the requested glass transition temperature of cellulose, thus improving the softening efficiency [71]. However, Starke et al. [72] showed that when the temperature was higher than 200 °C, the mass loss increased while the mechanical strength of bamboo timber decreased significantly. Besides, the effect of treatment time on the resulting bamboo samples was not as large as that of treatment temperature. Jiang and Li et al. [73, 74] heated the bamboo tube through overheated air and found that softening effect was better, which was conducive to flattening treatment. During high-temperature treatment, the hemicellulose in bamboo is degraded to a large extent. The resulting acetic acid further catalyzed dehydration and polycondensation of hydroxyl groups of cellulose molecules, which significantly reduced the number of free hydroxyl groups. At the same time, lignin has higher stability at high temperatures, so the dimensional stability of treated material is improved and hygroscopicity is reduced [23]. High-temperature softening has some advantages, such as a fast softening rate and a good softening effect, and it can be industrialized on a large scale. However, as we know, the elastic modulus of the treated material can be effectively reduced with the joint action of moisture content and temperature. Therefore, it is necessary to equalize the moisture content of the bamboo before high-temperature treatment. Cheng and Zhang [75] first impregnated moso bamboo tubes into the water for 8 h and then heated them at 120 °C in a sealed container to soften bamboo tubes for 30 min. It was found that the elastic modulus of the softened bamboo decreased to 6.42 GPa, the vitrification transition temperature decreased to 88 °C, and the hardness decreased by 42.0% and 54.7% for the bamboo flash nearby the outer layer and inner layer, respectively. However, the distribution ratio of the three substances is uneven transversely and longitudinally, which leads to the obvious difference in moisture content distribution. As a result, the high-temperature softening effect on single bamboo varies. Furthermore, with the evaporation of water, bamboo gradually dries out during the softening process at high temperatures, resulting in a poor softening effect and even cracks.

Saturated Steam Softening Li et al. [41–43, 76, 77] carried out research on the crack-free softening and flattening production technology of bamboo, based on their previous research and aiming at the above problems. Based on the saturated steam heat treatment technology of bamboo bundles in the preparation process of restructured bamboo, the “softening and flattening under high temperature and high humidity” technology was put forward. As we know that compared with water-boiling softening, saturated steam heat treatment can not only realize the thermal modification of bamboo but also effectively improve the physical and mechanical properties with lower pollution [24, 78, 79]. More importantly, treated samples can keep a certain humidity in the saturated steam heat treatment processes. The presence of water not only enhances the heat transfer

192

Z. Lou et al.

(a)

(b)

Fig. 2 Pictures of the bamboo tube (a) and arc-shaped bamboo sheets (b) treated with saturated steam in factory practices

efficiency but also affects the changing rules of the biomass components during the heat treatment process. For example, water can intensify the pyrolysis reaction of cellulose and hemicellulose [80]. Figure 2a, b show photographs of bamboo tube and arc-shaped bamboo slices treated with saturated steam in factory practice. From the photographs, we may see that a multi-layer (2–4 layers) arrangement can be considered when pressure tanks of large size are used to heat, bamboo tubes or sheets, for space full-use. To be mentioned, a certain space should be reserved between each layer so that the hot steam can reach each material smoothly and reduce the difference in softening effect among treated materials. Especially for arc-shaped bamboo slices, in order to avoid the color differences in the treated material caused by the condensate steam water accumulating in the grooves. Therefore, the outer layer should be kept upward while the inner layer should be downward.

2.2 Physical Softening Treatment 2.2.1

Microwave Softening

Norimotom et al. [81–83] first proposed softening wood. Their research indicated that microwave could heat wood rapidly and uniformly, avoiding the water content gradient normally happening during traditional heat treatment methods and improving the quality of softened products effectively. Intensified Brownian movement of water caused by microwaves can effectively increase the temperature of the treated biomass. Then, the glass transition temperatures of three substrates of biomass can be achieved. As a result, the corresponding plasticity increases, and softening is realized [84, 85]. Therefore, the efficiency of microwave softening is

Bamboo Flattening Technique

193

closely related to the initial water content of biomass materials. And increasing the initial water content can accelerate the microwave softening rate. Under the same microwave power and treatment time, with the increase of initial moisture content, the elastic modulus and brittleness of the treated material are proved to be reduced [86– 88]. Corresponding research has been raised to investigate the effect of microwaves on bamboo softening. The results show that the microwave power, the treatment time, and the initial water content incrementally influence the softening efficiency of bamboo [89, 90]. However, microwave treatment has a certain promoting effect on bamboo drying [91, 92].

2.2.2

Softening Treatment Process Assisted by the Change of Bamboo Surface State

There is a gradient in moisture content and chemical composition from the outer layer to the center and further to the inner layer of the bamboo wall. As a result, the content of vascular bundles in bamboo flesh layer decreases gradually from outside to inside. The bamboo culm wall near the outer layer has a high density of vascular bundles and contains more lignin and waxy, which is harder than wood. On the contrary, the inner layer of bamboo with brittle and soft texture mainly consists of thin-walled cells. Therefore, the presence of the outer and inner layers can affect the softening effect. Also, because the two parts are hard and crisp, their transverse elastic modulus is larger than that of the flesh part, which also affects the flattening effect. In order to solve this problem, many attempts have been made by scholars. As early as 1982, it was proposed in the Japanese patent that the inner layer of curved bamboo should be nicked before flattening. In addition, if the hard outer layer is retained and the inner layer is removed, the resulting bamboo exhibits a hard outside and a soft inside. The cracking propagation concentrates on the soft inner side, causing cracks on the inner side. If the inner layer is retained and the outer layer is removed, then a soft outside with a hard inside is achieved. As a result, no crack happens during flattening, although the outer layer is subject to a certain degree of compression. Therefore, Xie et al. removed the inner knot and the outer layer of the semicircular bamboo tube. Then, bamboo blocks with a certain thickness and outer surface circumference can be flattened into a flat shape by heating and pressurizing [93]. In the process of softening and flattening, the drying shrinkage rate of the outer layer is 1.34 times that of the inner layer, so the inner layer is more prone to cracking [94]. In order to interrupt the development of cracks in the bamboo shoots during flattening, Chen and Ding et al. made oblique shallow grooving on the surface of the inner layer of the bamboo shoots to reduce stress concentration and improve the flattening quality [95, 96]. By doing this, the outer layer of bamboo layer is intact, basically retaining the outer layer and inner layer and retaining the effective material quantity to the maximum extent. Meanwhile, it was also found that a higher utilization rate can be obtained when the bamboo tube slice arc length is smaller and the radian is greater. Currently, there are two common surface pretreatment techniques for bamboo in industry. The first method is to break bamboo tube partitions and remove the inner

194

Z. Lou et al.

knots using floating milling technology on a continuous integrated machine. Another method is to use floating milling technology to remove the outer layer and the inner knots. Figure 3a, b, respectively, show the schematic of the machine for removing the bamboo tube’s inner knots and the machine for removing the outer layer. The machine for removing the inner knots of bamboo tubes is composed of the mandrel, pounding head, multi-tooth milling cutter, and limit ring [97–99]. The combined milling cutter is inserted into the bamboo tube, and the punch breaks through the partition. Next, the bamboo tube is supported and rotated by four rubber friction wheels in an opposite direction to the milling cutter. This apparatus is shown in Fig. 3a. Because of the unavoidable asymmetrical pressurization of the cylinders in two directions, the inner wall of the bamboo tube is closer to the outer circumference of the limit ring, while the inner wall of the bamboo tube is used as the basis for milling. This approach overcomes the challenges presented by unavoidable growth defects in some bamboo tubes. With the rotation of the combined milling cutter, the residual inner knots of the bamboo tube are milled to make it level with the inner culm wall, so as to achieve the purpose of efficient and automatic removal of the residual inner knots of the bamboo tube. As shown in Fig. 3b, when the machine for removing the outer layer works, the bamboo tube is fastened from both ends by a tapered clamp head and driven to rotate. The milling head moves from one end to another along the bamboo tube axis. The radial pressure of the milling cutter acting on the bamboo tube is adjusted on the machine, and the limit ring is close to the outer wall of the milled bamboo tube so that the milling head floats up and down with changes to the surface features of each bamboo tube. This allows for the equipment to change the sharpness, out of roundness, and curvature of the bamboo tube [100–103].

(a)

(b)

Fig. 3 Schematic of the machines employed to remove a the inner knots and b the outer layer of the bamboo, respectively

Bamboo Flattening Technique

195

3 Bamboo Flattening Process and Technology The flattening effect of the softened bamboo tube mainly depends on the bamboo’s curvature and outside diameter. Huang et al. [104] studied the change law of the static transverse modulus of elasticity in the flattening process of the bamboo slices with different radians through a three-point bending method. The results showed that the average static transverse modulus of elasticity first increased and then decreased with the decrease of the flattening radian of bamboo slices. Qian et al. [105] treated the bamboo samples with a certain moisture content at 170 °C for 90–100 s. Then, the bamboo samples can be flattened gradually by an external force. It was found that the larger the outer diameter, the easier it was to flatten the bamboo under the same circumferential radius. The results indicate that this was mainly due to the relative deformation of the bamboo spreading flat per unit circumferential length decreasing and stress decreasing after increasing the outer diameter. At present, flattening methods are mainly divided into three types: one-step pressure flattening, pressurized pressure flattening, and continuous flattening [106].

3.1 One-Step Pressure Flattening The softened semicircular bamboo tube is placed on a flat plate hot press by means of chain transport, and bamboo material is flattened under one-time pressure by the temperature and pressure of the upper and lower platens (Fig. 4a) [107]. In order to increase production efficiency, multi-layer flatbed hot presses can be used instead of single-layer presses. This method is simple in equipment and technology, but it is easy to produce penetrating and continuous cracks during the flattening process due to the great stress. Huang et al. [108] proposed a flattening method for original bamboo arc-shaped bamboo sheets. In this method, several curved bamboo sheets with an outer and inner layer and the same width are arranged in a hot press with an adjustable side

Fig. 4 Schematics of a one-step pressure, b pressurized pressure, and c continuous flattening approaches, respectively

196

Z. Lou et al.

pressure mechanism. The direction of the side pressure mechanism is parallel to the direction of the bamboo fiber. Afterward, the hot press was maintained at 180–220 °C for 3–5 min and the pressure was gradually increased until the bamboo sheets were flattened. Meanwhile, the side pressure mechanism maintains a constant transverse pressure (0–0.2 MPa). The surface cracks of obtained flattened bamboo sheets by this method are few or no. This method is suitable for small-scale and low-cost bamboo production, while it is difficult to realize continuous production. In order to overcome this deficiency, Wu [109] and Li [42] designed another bamboo flattening treatment method and the corresponding devices. In this method, after the outer and inner layers are removed, as mentioned above, the treated bamboo tubes are further grooved by a circular saw blade (Fig. 5a). Figure 5b displays the grooved bamboo tubes. Then, the tubes are softened in a pressure tank (Fig. 2a). Due to the gradient distribution of density, hygroscopicity, and cellulose content of bamboo tubes from the inner layer to the flesh and then to the outer layer, the groove will be widened by the saturated steam heat treatment (Fig. 5c). After complete softening, the bamboo tubes are flatted on the flattening equipment in Fig. 5d. As can be seen from Fig. 5d (1), the widened groove is convenient for the tubes to enter the flattening machine. The flattening apparatus is equipped with a couple of axially parallel rollers. As shown in Fig. 5d (2), the surface of the upper roller is smooth, which is convenient for the softened bamboo tube to enter the flattener.

Fig. 5 a Physical picture of the grooving process. b Physical picture of the grooved bamboo tubes. c Physical picture of the grooved bamboo tubes after being treated by saturated steam heat treatment. d (1) Side and (2) front review of the flattening apparatus. e Physical picture of an unfolded board with a nail hole matrix

Bamboo Flattening Technique

197

Conversely, there are tapered, rectangular, or “V”-shaped protrusions nails with uniform dispersions on the surface of the lower roller. During the flattening of the bamboo tubes by the pressure from the upper and lower rollers, the nails on the roller surface generate cracks on the inner layer of the bamboo tubes to release the generated internal stress. By doing this, continuous surface creaking of bamboo can be avoided. It is noted that in order to ensure the yield of this method, the grooved bamboo tubes need to be softened in the saturated steam environment of 160–180 °C for at least 4–20 min and should be put into the pressure tank immediately after being softened. Partial hemicellulose can be degraded rapidly by saturated steam heat treatment, and cellulose and lignin molecules inside the treated bamboo tubes can reach their glass transition temperature, respectively. As a result, the efficient softening of bamboo tubes is realized. The corresponding heat temperature and time depend on the culm-wall thickness, age, and relative position from the ground of the bamboo segments. Figure 5e displays the obtained bamboo board after being flattened by this method. A nail hole matrix can be clearly observed on the inner layer. Such rough surfaces of these flattened bamboo boards should be sanded before use in order to obtain a smooth surface. As a result, the utilization rate of raw materials should be reduced. Another disadvantage of this method is that the length of the bamboo tube should be controlled below 80 cm due to the limitation of bamboo taper, bending, and other factors, which leads to the small size of the obtained flattened bamboo board. This kind of product is mainly used for making bamboo chopping boards. This kind of bamboo chopping board uses flattened bamboo boards on both sides so that the gluing surface does not come in direct contact with food, which is clean and environmentally friendly and is popular with consumers.

3.2 Sectional Pressure Flattening In view of the problems such as the generation of large stress and the formation of deep cracks during the one-step flattening process of the curved bamboo slices with a large radius, scientists have designed another flattening method named sectional press flattening. In this method, the semicircular bamboo tube is fed in sections in the platen of the flattening machine and then pressed and flattened successively (Fig. 4b). In other words, only part of the arc is fed at a time. Based on this method, a stepby-step pressing expansion method is developed. A group of arc pressing equipment which is equipped with positive pressure surfaces with different radii is assembled to press the curved bamboo slices step by step. With the gradual reduction of the positive pressure surface radian of the equipment, the bamboo slices are gradually flattened. The results indicate that the quality of the obtained flattened bamboo board is good. However, the corresponding production efficiency is low, and more equipment and space are requested, which costs a lot of human and financial resources. To sum up, the sectional press flattening methods are difficult to meet the needs of actual production.

198

Z. Lou et al.

3.3 Continuous Flattening Based on the above sectional press flattening method, the continuous flattening method is developed as shown in Fig. 4c. Continuous flattening refers to that in the continuous pressure flattening machine, the bamboo tube is pressed and flattened while feeding along the arc tangent direction. This method can meet the requirements of continuous production and thus can improve production efficiency. According to whether there are nicks on the inner surface of the flattened bamboo board, the continuous flattening method can be divided into two methods, one is the notched flattening method, and the other is the nick-free flattening method.

3.3.1

Notched Flattening Method

Lin et al. designed a flattening method that requires removing the outer layer of bamboo in advance but retaining the inner layer. The corresponding schematic diagram of the equipment and the physical photos of the related parts as shown in Fig. 6 [110, 111]. The equipment is mainly divided into three parts, including the unfold rolling part (Area 1), the flattening part (Area 2), and the reverse roller part (Area 3) (Fig. 6a). The unfolding roller part is equipped with a set of unfolding rollers whose circumferential surface is obliquely arranged with parallel scribers. As shown in Fig. 6b, the axial direction of the scribers and the roller is at an angle of 25–40°. And the direction of the scribers on the adjacent unfolding rollers is set crosswise. In addition, the difference in axial thickness between two adjacent unfolding rollers is 2–4 cm. The bamboo tube, which has been successively treated by removing the outer layer, removing inner knots, slotting, and softening by saturated steam heat treatment at 180 °C, enters into the unfolding roller part of the guide roller. With the gradual increase of the unfolding radian of the bamboo tube, the two sides of the circumference surface of the unfolding rollers in this part are still equipped with parallel scribers while the corresponding middle surface becomes smooth (Fig. 6c). In this way, the bamboo tube is gradually unfolded. And diamond-shaped line grooves with a width of 1.5–2.0 mm, a depth of 2.0–4.0 mm, and a spacing of 8.0–15.0 mm are formed on the corresponding inner layer surface (Fig. 6d). The existence of these grooves is conducive to releasing internal stresses during unfolding. Afterward, the bamboo tube enters the flattening part, which is composed of a series of flat upper and lower rollers. The bamboo board is pressed and compacted through the mutual extrusion of the upper and lower rollers, ensuring the smoothness and firmness of the obtained board. Then, the flattened bamboo board enters the reverse roller part. The rollers equipped in this part are completely different from those of the first two parts. As shown in Fig. 6e, a series of concave upper rollers and convex lower rollers with a smooth surface are equipped. This design mainly makes the flattened bamboo board bend slightly toward the outer layer, resulting in further flattening and shape. The maximum length of the obtained bamboo flattened board can be as long as 140 cm, and the board can be used for bamboo flooring, bamboo-based structural materials,

Bamboo Flattening Technique

199

Fig. 6 a Schematic diagram of the notched flattening equipment. b Physical picture of a set of unfolding rollers whose circumferential surface is obliquely arranged with parallel scribers. c Physical picture of unfolding rollers equipped with parallel scribers at both sides but with a smooth middle surface. d Physical picture of the obtained flattened bamboo board. e Physical picture of a roller of reverse roller component

and so on. However, due to the obvious grooves on the inner surface of the obtained board, a certain thickness of planning should be carried out according to product requirements before actual use so that the utilization rate of bamboo is relatively low.

3.3.2

Non-notched Flattening Method

The flattening methods mentioned above need to make nail holes or notches on the inner layer surface, sacrificing the utilization rate of raw materials and the mechanical properties of products. According to the requirements of the raw material unit for bamboo-based products, Li et al. [43, 112] put forward the production technology of arc-shaped bamboo sheets softened at high temperature and high humidity and flattened without nails or notches, providing a new direction for the efficient utilization of bamboo. Different from other flattening methods, the bamboo tube needs to be pre-treated to remove the outer layer, the flattening treatment processes of the arc-shaped bamboo sheet only include the preparation of arc-shaped bamboo sheets, the softening treatment of bamboo sheets under high temperature and humidity, and the integrated treatment of bamboo sheets planing and flattening. The removal of the

200

Z. Lou et al.

outer and inner layers, as well as the removal of inner knots, is carried out simultaneously with the unfolding treatment of bamboo sheets in a non-notched flattening machine (Fig. 7). Before flattening, the bamboo is first cut into segments according to the taper, bending degree, and application requirements. Then, at least two long grooves are made to axially interpenetrate the bamboo tubes along the fiber direction, and arc-shaped bamboo slices are obtained. The number of bamboo slices is determined by the circumference of the small end of the bamboo segment and the required width of the flattened bamboo board products. The arc-shaped bamboo slices, after slicing, need to be softened by saturated steam heat treatment. The softening temperature and time are mainly determined by the height and thickness of the selected bamboo segment. The softened arc-shaped bamboo slices need to be processed in the planning and flattening integrated machine immediately. If the interval time is too long, the temperature of the bamboo slices will decrease too much, which will lead to an increase in the hardness and a decrease in the plasticity of the bamboo slices. As a result, undesirable cracking will occur when the cooled bamboo slices enter the flattening machine. Figure 7a shows the schematic diagram of the non-notched planing and flattening integrated machine. The integrated machine is divided into three parts: the shaping part, the step-by-step unfolding part, and the flattening part. As we know, the bamboo culm wall is thin, its center is empty, and the cross-section is irregular, which makes the arcs of the sliced bamboo sheets irregular. Therefore, it is necessary to roll and shape the softened bamboo slices in the shaping part. By rolling arc rollers with fixed radian, the arc of the softened bamboo slice can be adjusted slightly to make the resulting radian consistent with the preset radian of the rollers. In this process, the outer and inner layers can also be planned, and finally, the arc-shaped bamboo slices with different shapes can be trimmed into a unified and regular shape. Figure 7b shows the physical pictures of four shaping rollers at the beginning of the shaping part. As can be seen, the shaping rollers are spherical. And the surface of the rollers is evenly distributed with scattered and rectangular protrusions, which are used to release the internal stress generated during shaping. Then, several groups of planning mechanisms are used to remove the outer (Fig. 7c) and inner layers (Fig. 7d). In this way, the inner layer of bamboo, which is easy to crack, and the outer layer, with high density, can be removed, being conducive to flattening. At the same time, it can simplify the traditional process of removing the outer and inner layers and improve production efficiency. As shown in Fig. 7a, the inner and outer layer planing mechanisms appear alternately. And there are many groups of arc-shaped unfolding rollers between the planning mechanisms. The physical photos of the unfolding rollers are shown in Fig. 7e. Different from the previous four shaping rollers, although these unfolding rollers are also evenly distributed with protrusions on the surface, their corresponding height is very small so as to avoid damaging the bamboo flesh with mechanical functions. These protrusions mainly play a role in unfolding the arc-shaped bamboo slices after removing their inner and outer layers. To be mentioned, these protrusions can cause slight damage to the smooth surface of the inner layer softened by high temperature and high humidity, which is beneficial to the subsequent milling processing. And the shaping rollers can crush the bamboo inner joints and bamboo partitions during the rolling and conveying processes, so

Bamboo Flattening Technique

201

as to remove most bamboo partitions and facilitate subsequent milling processing. Afterward, the bamboo slices are transported to the progressive flattening part. This part consists of several groups of gradually flattened arc-shaped rollers, as shown in Fig. 7f. It is observed that the unfolding rollers are composed of a pair of upper and lower rollers, and an arc unfolding gap corresponding to the shape of bamboo slices is formed between these two rollers. The radian of such gaps decreases step by step. Finally, the unfolded bamboo slices enter at least one group of flattening rollers. The gap formed between the upper and lower rollers of the flattening part is a plane, which is mainly used for flattening the unfolded slices. As a result, the arc-shaped bamboo slices are unfolded and flattened step by step in the non-notched planing and flattening integrated machine until they are completely flattened. As described, the non-notched flattening method can flatten arc-shaped bamboo slices without any grooves, nails, or guidelines. This method has the advantages of a simple process and low cost, and the obtained flattened board can be as long as 3.00 m. The flattened bamboo boards can be applied to the processing and manufacturing of bamboo-based laminated timber flooring, planing veneer, furniture, beams and columns, and so on. The yield of this crack-free flattening production technology is as high as 80–90%. This technology can increase the utilization rate of bamboo resources of traditional bamboo lumps to 55% and reduce the requested amount of adhesive by 30%, which is of practical significance for the development of new bamboo products [43]. At present, the technology has been popularized in domestic bamboo growing areas, and more than 10 production lines are built in Zhejiang, Jiangxi, Fujian, Hunan, and other provinces in China.

(a)

(b)

(c)

(d)

(c)

(d)

(e)

(f)

Fig. 7 a Schematic diagram of the non-notched planing and flattening integrated machine. b The physical picture of the shaping rollers at the initial stage of the shaping component. c, d are the physical presentative pictures of the inner layer planing mechanism and outer layer planing mechanism in (1) side view and (2) top view, respectively. e Physical picture of unfolding rollers. f Progressive flattening component with gradually flattened arc-shaped rollers

202

Z. Lou et al.

4 Drying Treatment of Flattened Bamboo Board The drying process of bamboo involves many physical parameters, including specific heat capacity, thermal conductivity, fiber saturation point, equilibrium moisture content, glass transition temperature, and so on [113]. Due to the anisotropy of bamboo and its inherent internode structure, the drying behaviors of bamboo are different in position and orientation [114]. Researches show that the radial shrinkage of bamboo without knots is greater than that of corresponding tangential shrinkage, but the drying speed in the longitudinal direction is larger than that in tangential and radial directions. However, the radial shrinkage of bamboo knots is less than that in the tangential direction, and the corresponding radial drying speed is larger than that in longitudinal and tangential directions. In addition, the shrinkage of knots is less than that of node-less parts of bamboo [115]. Therefore, improper drying methods and parameters are easy to cause cracks and other defects in the flattened bamboo boards. On the other hand, the resulting moisture content of the flattened bamboo boards, which are pre-softened by saturated steam as mentioned above, can reach 50–80%. As a result, during the drying processes, the deformation and bending of the flattened bamboo boards should happen due to natural characteristics such as accumulated internal stress, growth stress, density gradient, hygroscopicity, and dehumidification. Thus, it is necessary to shape the flattened bamboo boards to release their internal stress and prevent them from rebounding and bending during cooling [116]. The flattened bamboo boards of small sizes can be directly stacked and dried in a tunnel kiln. However, for the flattened bamboo boards with large sizes, there are two drying methods according to their characteristics.

4.1 Collaborative Treatment of Roller-Involved Cooling and Drying For the flattened bamboo boards obtained by the non-notched flattening method described above, rebounding and deformation easily appear due to the presence of internal stress non-completely released. Therefore, in the actual production, the method of roller-involved cooling and shaping, followed by stacking drying, is used to treat the flattened bamboo boards. Direct stacking and drying may cause transverse cracking on the surface of the inner layer of bamboo boards due to excessive shrinkage. On the contrary, using roller-involved cooling and shaping machine (Fig. 7b) to quickly cool and shape the flattened bamboo board can improve the flatness of the obtained board and reduce the cracking ratio in the later stacking process. To be mentioned, the roller-involved cooling and shaping machine can be equipped with cooling devices such as water cooling, atomization, or cold air, which are connected to the water storage tank. By doing this, the temperature of the bamboo board should gradually decrease under the condition of wetting so as to achieve the efficient release of the generated stress. During the roller-involved cooling process,

Bamboo Flattening Technique

203

the upper and lower rollers exert pressure on the inner and outer layers of the bamboo boards, respectively. As a result, the surface of the flattened bamboo board is smooth finally. The roller-involved cooling and shaping are suitable for the thinner flattened bamboo boards while the thicker boards are easy to crack during such process due to the larger generated internal stress. Thus, the thicker boards should be processed in roller-involved cooling and shaping machines quickly at a higher temperature. After being cooled and shaped, the flattened bamboo boards are dried by a pressure stacking method. In detail, the flattened boards are first sawed to a uniform width, followed by being stacked in the way of the inner surface to the inner surface or outer surface to the outer surface. Bamboo strips or stainless-steel strips with a width of 2.5 cm and a thickness of 0.5–1 cm are added between each pair of flattened bamboo boards as spacer strips (Fig. 7a). The corresponding drying temperature should be lower than 70 °C to prevent the deformation and cracking of the flattened boards caused by the high drying speed at a higher temperature. At the same time, in the drying process, the upper part of the stack is always pressed with heavy objects to prevent the warpage and deformation of the boards. Alternatively, controllable pressure equipment is also suggested to gradually relieve part of the pressure intermittently during the drying process to facilitate moisture removal and free shrinkage of the bamboo boards. By doing this, the moisture evaporation is accelerated, and the transverse cracking due to the lack of timely release of drying shrinkage stress is prevented. The drying temperature is requested to increase at a rate of 3–5 °C every 8–12 h. When the dry-bulb temperature reaches 60 °C, and the moisture content of bamboo boards reaches about 10%, the steam injection rebound treatment begins. After that, the boards are cooled to room temperature and removed from the drying kiln for curing. After the moisture content is balanced, the flattened bamboo boards are taken out from the stack, and their surface is sanded or planed. Finally, the crackfree flattened bamboo boards can be used to fabricate a series of bamboo-based products such as multi-layer bamboo boards or bamboo/wood composite. Figure 7c displays the physical picture of the obtained non-notched flattened bamboo board after the cooling, shaping, and drying processes. Compared with the board obtained by the notched flattening method in Fig. 5f, there are no diamond notches or nail holes on the inner surface of the non-notched board.

4.2 Collaborative Treatment of Cold Pressing, Water Boiling, and Drying According to Fig. 7b, roller-involved cooling and shaping machine have the disadvantage of occupying large spaces. Besides, the steam injection rebound treatment is time-consuming, and the corresponding energy consumption is large. Comprehensively considering, the collaborative treatment of roller-involved cooling and drying is a high cost in actual production. Therefore, some factories in China try to use the method of cold pressing instead of roller-involved cooling and then use the method

204

Z. Lou et al.

of water boiling instead of steaming rebound so as to simplify the cooling, shaping, and drying processes. In detail, the flattened bamboo boards are directly placed on a multi-layer press equipped with a water-cooling system for cold pressing treatment for 5–7 min. During this process, the upper and lower pressing plates of the press are cooled by circulating water through the water-cooling system. By doing this, the bamboo boards are gradually cooled and shaped under the action of pressure. The cold pressing pressure is generally set as 1–2 MPa to prevent the bamboo boards from being crushed due to the excessive pressure or being excessively compressed in the thickness direction in order to ensure the mechanical properties and the yield of the treated boards. After that, the flattened bamboo boards are taken off the press, stacked, and water-boiled at 60–80 °C for 1 h. Water-boiling treatment can not only make the bamboo board rebound 0.3–0.5 mm in thickness and width but also remove the polysaccharide degradation products in the boards after high temperature and high humidity treatment. As a result, the color of the treated bamboo boards is more uniform, and the corresponding weather ability is further improved. After being dried, a crack-free flattened bamboo board is obtained. This method is suitable for the drying and shaping of notched flattened bamboo boards with wide sizes.

5 Conclusion Bamboo flattening technology is an efficient way of bamboo utilization. The truncated bamboo tube is first treated by outer and inner layer removal and slotted through axially or longitudinally dissected by a bamboo dissector to fabricate arc-shaped bamboo slices. Then, the slotted bamboo tubes or arc-shaped bamboo slices are softened by heat treatment at high temperatures and high humidity. Finally, flattened bamboo boards are obtained by the one-step pressure flattening method, sectional pressure flattening method, and continuous flattening technology. According to the different techniques and surface morphology, the obtained flattened boards can be divided into cracked bamboo flattened board and crack-free flattened boards. And the latter can be further divided into notched crack-free flattened boards and non-notched crack-free flattened boards. This technology can realize the utilization of the whole bamboo, which plays a positive role in promoting the development of resource-saving and high-added value utilization of bamboo resources and improving the scientific and technological content of the bamboo industry. China has independent intellectual property rights in both the technology and equipment involved in the production of the bamboo flattened board, which provides strong scientific and technological support for improving the quality and efficiency of the bamboo processing industry in China. With the development of biomass-based building materials and bamboobased structural materials in China, bamboo flattening technology should enter a rapid development stage.

Bamboo Flattening Technique

205

References 1. Xie DY (2013) Analysis to situation and countermeasure of wood manufacture industry of our country. For Investig Des 3:85–92. https://doi.org/10.3969/j.issn.1673-4505.2013.03.038 2. Li YJ, Xu B, Zhang QS, Jiang SX (2016) Present situation and the countermeasure analysis of bamboo timber processing industry in China. China For Sci Technol 1:2–7. https://doi.org/ 10.13360/j.issn.2096-1359.2016.01.001 3. Fenning TM, Gershenzon J (2002) Where will the wood come from? Plantation forests and the role of biotechnology. Trends Biotechnol 20:291–296. https://doi.org/10.1016/S0167-779 9(02)01983-2 4. Peng Z, Lu Y, Li L et al (2013) The draft genome of the fast-growing non-timber forest species moso bamboo (Phyllostachys heterocycla). Nat Genet 45:456–461. https://doi.org/10.1038/ ng.2569 5. He M-J, Zhang J, Li Z, Li M-L (2016) Production and mechanical performance of scrimber composite manufactured from poplar wood for structural applications. J Wood Sci 62:429– 440. https://doi.org/10.1007/s10086-016-1568-1 6. Yong C, Guan MJ, Zhang QS (2012) Selected physical and mechanical properties of bamboo and poplar composite OSB with different hybrid ratios. KEM 517:87–95. https://doi.org/10. 4028/www.scientific.net/KEM.517.87 7. Li T, Cheng D, Wålinder MEP, Zhou D (2015) Wettability of oil heat-treated bamboo and bonding strength of laminated bamboo board. Ind Crops Prod 69:15–20. https://doi.org/10. 1016/j.indcrop.2015.02.008 8. Sharma B, Gatóo A, Ramage MH (2015) Effect of processing methods on the mechanical properties of engineered bamboo. Constr Build Mater 83:95–101. https://doi.org/10.1016/j. conbuildmat.2015.02.048 9. Sun ZJ, Fei BH (2019) Opportunities and challenges for the development of bamboo industry in China. World Bamboo Rattan 17:1–5. https://doi.org/10.13640/j.cnki.wbr.2019.01.001 10. Shi JY, Zhou DQ, Ma LS, Yao J, Zhang DM (2020) Diversity and important value of bamboos in china. World Bamboo Rattan 18:55–65, 72. https://doi.org/10.12168/sjzttx.2020.03.010 11. WangG IJL, Dai S, He G (2008) Achieving sustainable rural development in Southern China: the contribution of bamboo forestry. Int J Sust Dev World 15:484–495. https://doi.org/10. 3843/SusDev.15.5:9 12. Flynn A, Chan KW, Zhu ZH, Yu L (2017) Sustainability, space and supply chains: the role of bamboo in Anji County, China. J Rural Stud 49:128–139. https://doi.org/10.1016/j.jrurstud. 2016.11.012 13. Habibi MK, Samaei AT, Gheshlaghi B, Lu J, Lu Y (2015) Asymmetric flexural behavior from bamboo’s functionally graded hierarchical structure: underlying mechanisms. Acta Biomater 16:178–186. https://doi.org/10.1016/j.actbio.2015.01.038 14. Chaowana P, Barbu MC, Fruhwald A (2015) Bamboo—a functionally graded composite material. For Prod J 65:S48–S53 15. Zhang QS (1993) Status and discussion of bamboo processing and utilization in China. J Southwest For College 4:289–292 16. Zhang QS (1989) Study of bamboo plywood—III. Physical and mechanical properties of bamboo plywood. J Nanjing For Univ (Natural Science Edition) 2:13–18 17. Qi JQ, Xie JL, Huang XY, Yu WJ, Chen SM (2014) Influence of characteristic inhomogeneity of bamboo culm on mechanical properties of bamboo plywood: effect of culm height. J Wood Sci 60:396–402. https://doi.org/10.1007/s10086-014-1429-8 18. Hou HT, Sun YF, Zhou J, Lv ZL, Li JJ (2013) Design and application of lightweight steel residential house. AMM 353–356:2851–2856. https://doi.org/10.4028/www.scientific.net/AMM. 353-356.2851 19. Zhu FM, Chen LS, Zhu SX, Zhang QS, Xia JH, Shi BH (1991) Design and research of high-strength glued formwork for steel frame plywood formwork. Build Technol 6:26–31

206

Z. Lou et al.

20. Chugh S, Kandya A, Chaaruchandra K, Sudhakar P (2012) Experimental study of twin round bamboo concrete infill parabolic tied arch. Key Eng Mater 517:208–212. https://doi.org/10. 4028/www.scientific.net/KEM.517.208 21. Huang Y, Ji Y, Yu W (2019) Development of bamboo scrimber: a literature review. J Wood Sci 65:25. https://doi.org/10.1186/s10086-019-1806-4 22. Huang Y, Qi Y, Zhang Y, Yu W (2019) Progress of bamboo recombination technology in China. Adv Polym Technol 2019:1–10. https://doi.org/10.1155/2019/2723191 23. Lou ZC, Yuan CL, Li YJ, Shen DH, Yang LT, Liu J, Zhang AW (2020) Effect of saturated steam treatment on the chemical composition and crystallinity properties of bamboo bundles. China For Sci Technol 5:29–35. https://doi.org/10.13360/j.issn.2096-1359.201905014 24. Li YJ, Hu SH, Lv RJ, Zhang AW, Liu HZ, Wang XZ, Chen LC (2018) Production technology of outdoor reconstituted bamboo. China Wood-Based Panels 25:9–13. https://doi.org/10.3969/ j.issn.1673-5064.2018.06.003 25. Li YJ, Liu ZK, Du CG, Mao SF, Lin Y (2003) Preliminary analysis on development and application of shaving super bamboo. Wood Process Mach 14:25–26. https://doi.org/10.3969/ j.issn.1001-036X.2003.05.007 26. Cheng R, Zhang Q (2011) A study on the bonding technology in sliced bamboo veneer manufacturing. J Adhes Sci Technol 25:1619–1628. https://doi.org/10.1163/016942411X55 8996 27. Li YJ, Shen YC, Wang SQ, Du CG, Wu Y (2012) A dry-wet process to manufacture sliced bamboo veneer. For Prod J 62:395–399. http://forest.ckcest.cn/d/hxwx/AVkJddC349MUqoK BNnyS.html. Accessed 31 July 2020 28. Nugroho N, Ando N (2001) Development of structural composite products made from bamboo II: fundamental properties of laminated bamboo lumber. J Wood Sci 47:237–242. https://doi. org/10.1007/BF01171228 29. Zhang QS, Sun FW (1997) Several ways of industrial utilization of bamboo in China. China For Sci Technol 3:13–14 30. Chen F, Li M, Xin W, Zhou H, Smith LM, Wang G, Fei B, Ye L (2019) Development of bamboo winding composite pipe (BWCP) and its compression properties. BioResources 14:5875–5882 31. Fei BH, Chen ML, Wang G, Ye L, Chen Q (2018) Status and role of bamboo winding technology in national economic development. World Bamboo and Rattan 16:1–4. https:// doi.org/10.13640/j.cnki.wbr.2018.04.001 32. Sharma B, Gatóo A, Bock M, Ramage M (2015) Engineered bamboo for structural applications. Constr Build Mater 81:66–73. https://doi.org/10.1016/j.conbuildmat.2015.01.077 33. Jiang SX (2002) Research and development of bamboo industry utilization. China For Sci Technol 16:5–6. https://doi.org/10.3969/j.issn.1000-8101.2002.03.002 34. Sun FW (1996) Current production situation and development direction of bamboo plywood. China For Sci Technol 4:14–16 35. Zhang QS (1988) Research on bamboo plywood——I. Softening and flattening of bamboo. J Nanjing For Univ (Natural Science Edition) 4:13–20 36. Zhang QS (1995) Industrial utilization of bamboo in China. China Forestry Publishing, Beijing 37. Zhang QS (1989) Research on bamboo plywood—II. Hot pressing process of bamboo plywood. J Nanjing For Univ (Natural Science Edition) 1:32–38 38. Okahisa Y, Kojiro K, Kiryu T, Oki T, Furuta Y, Hongo C (2018) Nanostructural changes in bamboo cell walls with aging and their possible effects on mechanical properties. J Mater Sci 53:3972–3980. https://doi.org/10.1007/s10853-017-1886-8 39. Ren D, Yu Z, Li W, Wang H, Yu Y (2014) The effect of ages on the tensile mechanical properties of elementary fibers extracted from two sympodial bamboo species. Ind Crops Prod 62:94–99. https://doi.org/10.1016/j.indcrop.2014.08.014 40. Huang XY, Xie JL, Qi JQ, Hao JF, Zhou N (2014) Effect of accelerated aging on selected physical and mechanical properties of Bambusa rigida bamboo. Eur J Wood Prod 72:547–549. https://doi.org/10.1007/s00107-014-0796-6

Bamboo Flattening Technique

207

41. Hou LY, Zhao RJ, Ren HQ, An Z (2012) Analysis of surface color and wettability and chemical composition of different age Phyllostachys pubescens. J Nanjing For Univ (Natural Science Edition) 36:159–162. https://doi.org/10.3969/j.issn.1000-2006.2012.02.033 42. Liu HZ, Wang XZ, Li YJ, Xu B, Chen LC, Zhang NH (2018) Manufacturing technique of crack-free flattened bamboo tube. China For Prod Ind 45:40–44. https://doi.org/10.19531/j. issn1001-5299.201805009 43. Li YJ, Lou ZC, Jiang YJ, Wang XZ, Yuan TC, Yang FM (2020) Flattening technique without nicked in curved bamboo strips. For Mach Woodworking Equip 48(28–30):34 44. Stamm AJ, Tarkow H (1947) Dimensional stabilization of wood. J Phys Chem 51:493–505. https://doi.org/10.1021/j150452a016 45. Kim JS, Lee YY, Kim TH (2016) A review on alkaline pretreatment technology for bioconversion of lignocellulosic biomass. Biores Technol 199:42–48. https://doi.org/10.1016/j.bio rtech.2015.08.085 46. Taherzadeh M, Karimi K (2008) Pretreatment of lignocellulosic wastes to improve ethanol and biogas production: a review. IJMS 9:1621–1651. https://doi.org/10.3390/ijms9091621 47. Song J, Chen C, Zhu S et al (2018) Processing bulk natural wood into a high-performance structural material. Nature 554:224–228. https://doi.org/10.1038/nature25476 48. Behera S, Arora R, Nandhagopal N, Kumar S (2014) Importance of chemical pretreatment for bioconversion of lignocellulosic biomass. Renew Sustain Energy Rev 36:91–106. https:// doi.org/10.1016/j.rser.2014.04.047 49. Kim TH, Kim JS, Sunwoo C, Lee YY (2003) Pretreatment of corn stover by aqueous ammonia. Biores Technol 90:39–47. https://doi.org/10.1016/S0960-8524(03)00097-X 50. Carlquist S (1982) The use of ethylenediamine in softening hard plant structures for paraffin sectioning. Stain Technol 57:311–317. https://doi.org/10.3109/10520298209066729 51. Wang SG, Hua YK (1994) The effect of softening process conditions on the properties of bamboo and its reconstituted wood. J Nanjing For Univ 1:57–62 52. Cheng R, Zhang Q, Sui S (2006) Improvement of softening treatment technology of bamboo. Wood Sci Technol 40:327–335. https://doi.org/10.1007/s00226-005-0034-9 53. Wang ZB, Wang SQ, Tong HT, Zhou J, Qian J (2015) Effect of different treatment on softening of bamboo culm. J Zhejiang For Sci Technol 35:58–62. https://doi.org/10.3969/j.issn.10013776.2015.06.011 54. Fu DJ, Zhao RY, Sun T (2009) The effect of softening treatment on bamboo water content and compression strength. J Bamboo Res 28:42–45. https://doi.org/10.3969/j.issn.1000-6567. 2009.03.010 55. Huang MX, Zhang WB, Zhang XC, Yu WJ, Li WZ, Dai CP, Wang SG (2016) Dynamic mechanical analysis of moso bamboo timber. J Nanjing For Univ (Natural Sciences Edition) 40:123–128. https://doi.org/10.3969/j.issn.1000-2006.2016.01.020 56. Cheng RX (2005) Applications of dynamic mechanical analysis in wood processing industry. China Wood Industry 19:28–30. https://doi.org/10.3969/j.issn.1001-8654.2005.04.009 57. Liu Z, Jiang Z, Cai Z, Fei B, Yu Y, Liu X (2012) Dynamic mechanical thermal analysis of moso bamboo (Phyllostachys heterocycla) at different moisture content. BioResources 7:1548–1557 58. Nakajima M, Furuta Y, Ishimaru Y (2008) Thermal-softening properties and cooling set of water-saturated bamboo within proportional limit. J Wood Sci 54:278–284. https://doi.org/ 10.1007/s10086-008-0952-x 59. Nakajima M, Furuta Y, Ishimaru Y, Ohkoshi M (2009) Cooling set and its recovery in watersaturated bamboo under large bending deformation. J Wood Sci 55:100–106. https://doi.org/ 10.1007/s10086-008-1002-4 60. Yang M, Wang F, Zhou S, Lu Z, Ran S, Li L, Shao J (2019) Thermal and mechanical performance of unidirectional composites from bamboo fibers with varying volume fractions. Polym Compos 40:3929–3937. https://doi.org/10.1002/pc.25253 61. Liu W, Chen T, Xie T, Lai F, Qiu R (2015) Oxygen plasma treatment of bamboo fibers (BF) and its effects on the static and dynamic mechanical properties of BF-unsaturated polyester composites. Holzforschung 69:449–455. https://doi.org/10.1515/hf-2014-0097

208

Z. Lou et al.

62. Back EL, Salmen L (1982) Glass transitions of wood components hold implications for molding and pulping processes. Tappi J 65:107–110 63. Chow S-Z, Pickles KJ (2007) Thermal softening and degradation of wood and bark. Wood Fiber Sci 3:166–178 64. Takamura N (1968) Studies on hot pressing and drying process in the production of fibreboard. III. Softening of fibre components in hot pressing of fibre mat. Mokuzai Gakkaishi 14:75–79 65. Hillis WE (1984) High temperature and chemical effects on wood stability. Wood Sci Technol 18:281–293. https://doi.org/10.1007/BF00353364 66. Placet V, Passard J, Perré P (2008) Viscoelastic properties of wood across the grain measured under water-saturated conditions up to 135 °C: evidence of thermal degradation. J Mater Sci 43:3210–3217. https://doi.org/10.1007/s10853-008-2546-9 67. Shrestha B, le Brech Y, Ghislain T, Leclerc S, Carré V, Aubriet F, Hoppe S, Marchal P, Pontvianne S, Brosse N, Dufour A (2017) A multitechnique characterization of lignin softening and pyrolysis. ACS Sustain Chem Eng 5:6940–6949. https://doi.org/10.1021/acssuschemeng. 7b01130 68. Jiang HB, Peng YG (2007) Bamboo softening technology and equipment. For Mach Woodworking Equip 35:53–54 69. Zhao RY, Fu DJ, Sun T (2009) The effect of different softening treatment methods on quality of bamboo. J Jiamusi Univ (Natural Science Edition) 28:637–640. https://doi.org/10.3969/j. issn.1008-1402.2009.04.054 70. Huang YW, Wu XH, Qian J (2015) The comparison of mechanical properties of the softening treated bamboos at various position and different age. J Bamboo Res 34:40–46. https://doi. org/10.3969/j.issn.1000-6567.2015.02.008 71. Hsu WE, Schwald W, Shields JA (1989) Chemical and physical changes required for producing dimensionally stable wood-based composites. Wood Sci Technol 23:281–288. https://doi.org/ 10.1007/BF00367742 72. Starke R, Rosenthal M, Bues C-T, Bremer M, Fischer S (2016) Thermal modification of African alpine bamboo: mass loss, chemical composition and impact resistance. Eur J Wood Prod 74:901–903. https://doi.org/10.1007/s00107-016-1092-4 73. Li WX (2007) Production method of softening and flattening floor of round bamboo tube: China, CN200710077726.5, 2007-09-12 74. Jiang SX (1995) Research on chain conveyor bamboo softening machine. J Nanjing For Univ 19:53–58 75. Cheng RX, Zhang QS (2006) Effect of softening treatment at high temperature on property and veneer quality of bamboo. Scientia Silvae Sinicae 42:97–100. https://doi.org/10.3321/j. issn:1001-7488.2006.11.018 76. Chen XZ, Niu SH, Jiang NC. Wang XZ, Wang L, Li YJ (2019) Effects of high temperature hydrothermal treatment on color and equilibrium moisture content of bamboo. J Anhui Agric Univ 46:815–819. https://doi.org/10.13610/j.cnki.1672-352x.20191122.011 77. Wu YF, Liu HZ, Li YJ, Xia L, Xu B (2016) Effect of softening of bamboo specimen treated by steam. J Zhejiang For Sci Technol 36:36–39. https://doi.org/10.3969/j.issn.1001-3776.2016. 05.007 78. Wang Q, Wu X, Yuan C, Lou Z, Li Y (2020) Effect of saturated steam heat treatment on physical and chemical properties of bamboo. Molecules 25:1999. https://doi.org/10.3390/ molecules25081999 79. Song LL, Ren HQ, Wang XZ, Ma JM, Li YC, Li YJ, Xu B (2018) Effect of high temperature saturated steam treatment on bamboo properties. China For Sci Technol 3:23–28. https://doi. org/10.13360/j.issn.2096-1359.2018.02.004 80. Huang RF, Lv JX, Cao YJ, Zhao X, Zhao YK, Zhou YD, Wu YZ (2010) Impact of heat treatment on chemical composition of Chinese white poplar wood. J Beijing For Univ 32:155– 160 81. Norimoto M, Wada H, Hasegawa K, Iida I (1980) Wood bending utilizing microwave heating. Nihon Reoroji Gakkaishi (J Soc Rheol, Japan) 8:166–171. https://doi.org/10.1678/rheology1 973.8.4_166

Bamboo Flattening Technique

209

82. Norimoto M, Gric J (1989) Wood bending using microwave heating. J Microw Power Electromagnet Energy 24:203–212 83. Norimoto M (1993) Large compressive deformation in wood (in Japanese). Mokuzai Gakkaishi 39:867–874 84. Iida I (1986) The thermal softening of green wood evaluated by its young’s modulus in bending. Mokuzai Gakkaishi 32:472–477 85. Ozarska B, Daian G (2010) Assessment of microwave bending capabilities for Australian wood species. For Prod J 60:64–68 86. Gasparik M, Gaff M (2013) Changes in temperature and moisture content in Beech wood plasticized by microwave heating. BioResources 8:3372–3384 87. Gasparik M, Barcik S (2014) Effect of plasticizing by microwave heating on bending characteristics of Beech wood. BioResources 9:4808–4820 88. de Peres ML, de Ávila DR, Gatto DA, Beltrame R (2016) Mechanical behavior of wood species softened by microwave heating prior to bending. Eur J Wood Prod 74:143–149. https://doi. org/10.1007/s00107-015-0978-x 89. Hao RM, Liu WJ, Chen XY (2014) Investigation on bamboo chip bending process by microwave-heating softening. J Central South Univ Fores Technol 8:111–113. https://doi. org/10.3969/j.issn.1673-923X.2014.08.023 90. Shen LL, Liu JL, Wang CG (2007) Study on hot compressing process for compressed bamboo. China Wood-based Panels 14:8–10. https://doi.org/10.3969/j.issn.1673-5064.2007.01.004 91. Lv H-F, Ma X-X, Zhang B, Chen X-F, Liu X-M, Fang C-H, Fei B-H (2019) Microwavevacuum drying of round bamboo: a study of the physical properties. Constr Build Mater 211:44–51. https://doi.org/10.1016/j.conbuildmat.2019.03.221 92. LvH CX, Liu X, Fang C, Liu H, Zhang B, Fei B (2018) The vacuum-assisted microwave drying of round bamboos: drying kinetics, color and mechanical property. Mater Lett 223:159–162. https://doi.org/10.1016/j.matlet.2018.04.038 93. Xie LS, Zhang ZL (2000) Manufacturing technique of new type bamboo plate. Wood Process Mach 2:10–13 94. Azadeh A, Ghavami K (2018) The influence of heat on shrinkage and water absorption of Dendrocalamus giganteus bamboo as a functionally graded material. Constr Build Mater 186:145–154. https://doi.org/10.1016/j.conbuildmat.2018.07.011 95. Chen CZ, Huang XD, Zhao GY (2013) Processing method and equipment for continuous development of Bamboo: China, CN201210416447.8[P]. 2013-01-16 96. Ding DA, Sun XD, Tu J, Chen WM, He HG, Bu HK (2012) The “mutually cutting and spreading out” technology for cambered bamboo sheets. Hunan Fores Sci Technol 39:25–28 97. Yang ZH (2015) A kind of scraper assembly for removing inner segment: China, CN201510402174.5[P]. 2015-10-07 98. Yang ZH (2015) A kind of internal knot machine: China, CN201520494107.6[P]. 2015-11-11 99. Wu YQ, Jiang YJ (2015) A kind of horizontal internal joint plane: China, CN201520133827.X[P]. 2015–08–05 100. Yang ZH (2019) A kind of bamboo deqing machine: China, CN201610994064.7[P]. 201902-19 101. Lin H, Jiang YJ (2014) Bamboo Deqing cutter assembly and its bamboo Deqing device: China, CN201210257812.5[P]. 2014-02-12 102. Wu YQ, Jiang YJ (2015) A kind of Maozhu Deqing machine: China, CN201520134076.3[P]. 2015-08-05 103. Yang ZH (2016) A bamboo Deqing cutter assembly and a bamboo Deqing cutter: China, CN201520495488.x[P]. 2016-01-20 104. Huang HL, Zhao M, He Q, Dong LJ, Mei YC (2011) Study on the change trend of bamboo static MOE in cross direction during its planishing process. China For Prod Ind 38:12–15. https://doi.org/10.3969/j.issn.1001-5299.2011.06.003 105. Qian J, Ye LM, Li WZ (1999) A preliminary study on the flattening of moso bamboo. J Bamboo Res 18:23–26

210

Z. Lou et al.

106. Zhao Z (2015) Analysis of Zhuzhanping patent technology. Agric Dev Equip 7:51. https:// doi.org/10.3969/j.issn.1673-9205.2015.07.044 107. Zhang QS, Jie ZH (1988) Manufacturing method of bamboo plywood: China, CN87100368[P]. 1988-08-24 108. Huang HL, Zhao M, Lu XN, Xue LD (2007) Flattening method of original bamboo arc-shaped bamboo slices: China, CN200610097854.1[P]. 2007-05-23 109. Wu YW, Kuang P, Yang Z, Huang LT, Li ZP, Deng JH, Wu LZ (2008) The utility model relates to a device for flattening bamboo: China, CN200720041215.3[P]. 2008-07-02 110. Ling H, Fu MY, Tan QL (2010) Round bamboo flattener: China, CN200920121598.4[P]. 2010-05-26 111. Ling H (2012) Bamboo flattening method: China, CN102794805A[P]. 2012-11-28 112. Yang FM (2019) A bamboo spreading device: China, CN201811550360.3[P]. 2019-03-29 113. Yi SL, Zhang BG, Liu W, Wang JM (2001) Study on the drying of bamboo flooring during production. Newslett Wood-Based Panels 8:12–13. https://doi.org/10.3969/j.issn.1673-5064. 2001.08.003 114. Sun ZB, Tian Y, An SZ (2006) Status of study on bamboo timber drying technology. World For Res 19:41–44. https://doi.org/10.13348/j.cnki.sjlyyj.2006.06.009 115. Sun ZB, Gu LB (2004) Preliminary study on drying properties of Dendrocalamus giganteus. J Northwest For Univ 19:107–111. https://doi.org/10.3969/j.issn.1001-7461.2004.02.032 116. Zhang W, Yue K, Xie CF, Liu J, Lu XN (2009) Effects of heat treatment process on rebound of arc-bamboo strip flattened. China For Sci Technol 23:26–28. https://doi.org/10.3969/j.issn. 1000-8101.2009.01.007

A Century-Old Tradition and Sustainable Technique to Protect Natural Bamboo Through Smoke Treatment—Advantages and Limitations Raviduth Ramful

Abstract The ancient traditional and sustainable technique of smoke treatment is a proven technique that has been considered for protecting bamboo against natural degradation. This unconventional technique, which is environmentally friendly and derived from a combustion smoke of organic matter and steam, has been slightly modified and adapted to meet the specific requirements in various parts of the world. The rise in people’s awareness about the harmful effects of chemical compounds used to treat natural wood and bamboo products is creating a demand and new opportunities for alternative greener treatments. This book chapter aims to outline the consideration of smoke treatment to protect natural bamboo by considering recent findings in this field from the author’s own work and from past literature. In the former section, the effect of smoke treatment on the mechanical behavior of bamboo, namely its flexural strength, will be discussed. The influence of smoke treatment on another peculiar aspect of bamboo, namely its antibacterial trait, will be also covered in that section. Finally, from past literature, an overview of the benefits and limitations of the established traditional treatment methods as well as the latest techniques to improve the efficiency of smoke treatment methods will be reviewed. Limitations pertaining to premature failure in smoke-treated bamboo will be further discussed, and means to suppress such failure will be outlined. The noteworthy benefits obtained from the traditional smoke treatment of bamboo could be an inspiration for alternative means of treating natural materials. Keywords Smoke treatment · Bamboo · Hierarchical structure · Mechanical properties · Physical changes · Shrinkage · Thermal modification · Antibacterial resistance

R. Ramful (B) Mechanical and Production Engineering Department, Faculty of Engineering, University of Mauritius, Réduit 80837, Republic of Mauritius e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 F. L. Palombini and F. M. Nogueira (eds.), Bamboo and Sustainable Construction, Environmental Footprints and Eco-design of Products and Processes, https://doi.org/10.1007/978-981-99-0232-3_8

211

212

R. Ramful

1 Introduction The utilization of natural materials for practical and useful applications, such as in construction has been considered by mankind for centuries [1]. Bamboo has been widely considered for structural applications owing to its noteworthy geometrical, physical, and mechanical characteristics. The constant challenge posed by the consideration of such materials by builders has been their limited durability. Being a natural material, untreated bamboo can only last a few months prior to degradation when subjected to environmental conditions such as sun and rain [2, 3]. The challenge is still present today, and much attention is being provided to come up with a sustainable solution for durability preservation. The smoke treatment is one natural preservation technique that has shown proven results to protect bamboo against natural degradation. Smoke treatment is a well-regarded treatment known to substantially improve the durability of bamboo against hygrothermal effects and enhance its resistance against fungal decay and termite attack [4, 5]. This efficient method of bamboo modification has been employed over the centuries in the construction industry to treat bamboo materials used in Japanese houses. It is also considered a sustainable alternative to conventional chemical treatments.

1.1 Smoke Treatment From the outline of bamboo preservation methods in Fig. 1, smoke treatment is categorized as a heat-based treatment that has been derived and inspired by traditional practice. From the literature, two main types of smoke treatments have been considered to protect bamboo, namely conventional and accelerated smoking treatments commonly referred to as traditional smoke and modern smoke treatments, respectively.

1.1.1

Traditional Smoke Treatment

Traditional smoke treatment consists of smoke that is derived from the incomplete combustion of organic matter such as dry wood, bamboo, leaves, and trunks, among others. As depicted in Fig. 2, smoke treatment penetrates the culm structure through the outermost layer. In Japan, for instance, traditional smoke treatment as employed by local craftsmen involved the storing of fresh bamboo culms above a fireplace over a long period of time. The effect of heat generated from partial pyrolysis as well as the deposition of soot on its outermost surface was found to impart notable improvement in bamboo durability. This method was found to greatly improve the durability of bamboo culms which could last over 50 years if utilized under a controlled environment [4]. Given

A Century-Old Tradition and Sustainable Technique to Protect Natural …

213

Fig. 1 Outline of bamboo preservation methods

Fig. 2 a Schematic illustration of smoked treatment and b longitudinal sliced section of smoked bamboo culm

its efficacy in protecting bamboo, the method of smoke treatment, as employed in Japan, has been modified to speed up the process.

214

1.1.2

R. Ramful

Modern (Artificial) Smoke Treatment

Modern smoke treatment is based on the same principle of traditional smoke treatment, but one which is conducted at an accelerated rate for improved output productivity. To meet the increasing demand for natural materials in construction, in particular for esthetic embellishment and for traditional applications in Japan, an accelerated version of the traditional smoke treatment has been devised over the last decades [6]. To replicate the partial pyrolysis process on the outermost surface of bamboo culms while concurrently suppressing the lengthy time of treatment, modified smoke treatment was conducted inside a furnace environment at an elevated temperature. Vertically stacked bamboo culms were subjected to a mixed treatment consisting of the combustion smoke of wood and bamboo plus steam at a temperature of around 150 °C over a 24-h period [6]. The treatment was found to yield satisfactory results through effective replication of the partial pyrolysis on the outermost surface of bamboo culms. In Colombia, for instance, an alternative method for smoke treatment of bamboo culms on a larger scale is considered based on the same original principle. In that setup, a large-scale furnace that can accommodate large numbers of vertically stacked bamboo culms is utilized to apply smoke treatment to semi-dry culms. The smoke, which is generated over a period of 15–30 days at a temperature of 55 °C, is maintained until the moisture content was reduced to 12% [4]. The smoke was also derived from the combustion of organic matter such as dry leaves, wood, and bamboo waste materials. The utilization of natural waste materials such as bamboo culms and dry bamboo leaves as a source of combustion fuel in accelerated smoke treatment spanning over a period of 6–8 h was found to yield satisfactory results [7]. The continuous flow of smoke inside the combustion chamber was found to be essential for the treatment to be efficient [7].

1.2 Mechanism of Smoke Treatment Smoke treatment, which is derived from the combustion of organic compounds, is applied to bamboo material via the air medium and mainly affects the outermost surface of the culm structure, as highlighted in Fig. 2. During combustion, an insoluble compound known as soot, which is resistant to atmospheric agents and light, is produced and gives smoked bamboo a pale brown coloration [8]. The changes to the outermost culm surface also occur due to the effect of heating from the smoke treatment, which leads to partial pyrolysis of the bamboo outer surface. Despite affecting the outermost surface, the effect of smoke treatment implies both the physical and mechanical attributes of bamboo material. Partial carbonization of bamboo culms through smoke treatment affects their physical properties as the moisture content in the outermost periphery of the culm is reduced.

A Century-Old Tradition and Sustainable Technique to Protect Natural …

215

The heat generated by smoke treatment was found to lead to a decrease in moisture content by up to approximately 70% [7, 8]. The resistance of bamboo against insect degradation is assumed to be improved through smoke treatment. Firstly, the heat of smoke and soot generated during pyrolysis was found to lead to a reduction in the starch content by 35% of the parenchyma cells. Secondly, anti-insect resistance was assumed to be improved by the action of elevated temperature, which resulted in the de-polymerization of carbohydrates [7, 8]. Moreover, an improvement in the mechanical strength of smoke-treated bamboo was observed due to the action of heat. The heat of smoke treatment above 120 °C was found to be high enough to alter the structure of lignin, thereby leading to poly-condensation reactions [7, 9]. The in-depth mechanisms of the effect of smoke treatment on both the physical and mechanical properties of bamboo are explained in further sections of this chapter.

2 Influence of Smoke Treatment on Mechanical Properties of Bamboo A proper understanding of the changes to the physical and mechanical properties of bamboo as a result of administered treatments is necessary for safety and reliability in construction. In this study, the effect of smoke treatment on the flexural strength of Madake bamboo’s (Phyllostachys bambusoides) hierarchical structure was investigated [6]. Moreover, the corresponding alterations to its chemical structure were also investigated through microscopy analysis and Fourier transform infrared (FTIR) analysis. For comparison purposes, the result obtained was compared with similar bamboo species preserved of any treatment modification.

2.1 Materials and Sample (Method) The Madake bamboo (P. bambusoides) specimens used in this study were harvested from the Kameoka and Ohara in the western and northern regions of Kyoto, Japan, respectively. The materials were handled and prepared by Kyoto craftsmen. A modified traditional smoke treatment was considered and applied to minimize the lengthy duration of the conventional treatment. Smoke treatment was applied by subjecting dried bamboo culms to an organically derived combustion smoke consisting of wood and bamboo over a 24-h period at a temperature not exceeding 150 °C. The treatment parameters were carefully monitored through a controlled environment inside a furnace. Prior to the mechanical characterization test, the physical properties of specimens, which were conditioned at room temperature of 25 °C and relative humidity

216

R. Ramful

Fig. 3 Untreated bamboo specimen in a 3-point bending test in a Mode A and b Mode B

below 20%, were measured [6]. Density was measured through the mass and volume method [10], while moisture content was measured by the EXTECH MO280 pinfree moisture meter (FLIR Commercial Systems Inc., Extech, Nashua, NH, USA). The density, which was chosen from various culm lengths, ranged between 600 and 900 kg/m3 . Moisture content varied in accordance with treatment type and ranged between 12.4% in untreated bamboo and 4.5% in smoked bamboo. Mechanical characterization through a three-point bending test was conducted on the Shimadzu EZ-S (Shimadzu Corporation, Kyoto, Japan) fitted with a load cell of 500 N [6]. A cross-head speed of 2 mm/min and a distance between supports of 80 mm were considered throughout all tests. The radii of the puncher and supports were 2.5 mm. Given the inhomogeneous nature of the plant structure across the wall thickness, two configurations were selected to evaluate bamboo specimens in flexural tests. These were Modes A and B, in which perpendicular loads were applied to the outermost and innermost layers of bamboo, as shown in Fig. 3a, b, respectively. The modulus of elasticity (MOE) and the flexural strength, which was assumed to be the same as the modulus of rupture (MOR), was termed apparent MOE and apparent MOR, respectively. The apparent MOR, the apparent flexural strain, and apparent MOE were considered as the calculated results were determined by the following equations based on an assumption of a homogeneous material with the neutral axis being at the center: σf =

3F L 2bt 2

εf =

6Δt L2

Ef =

F L3 4Δbt 3

A Century-Old Tradition and Sustainable Technique to Protect Natural …

217

Fig. 4 Determination of specific energy absorption from the stress–strain curve

where σ f is the flexural strength (MPa); F is the force capacity (N) of the bending test jig; εf is the apparent flexural strain; E f is the apparent flexural modulus (MPa); Δ is the deflection of the center of the beam; and L, b, and t represent the length (m) between supports, breadth, and thickness of the specimen, respectively. The specific energy absorption, U s , which is another important mechanical property, was also calculated to further assess the effect of smoke treatment on bamboo’s hierarchical structure. The specific energy absorbed gives a measure of the energy absorbed per unit mass during deformation [11, 12] and was determined from the area under the stress–strain curve up to the maximum flexural strain, ε1 as indicated in Fig. 4 [6]. The following equation was considered: 1 Us = ρ

∮ε1 σf (εf )dεf 0

where U s is the specific energy absorbed (J/kg), σ f is the flexural stress (MPa), and ρ is the density (kg/m3 ). The fractured surface of smoked bamboo was further observed by using the scanning electron microscope (SEM) (JSM-6010LA SEM; JEOL Ltd., Tokyo, Japan) [6]. The digital microscope Keyence VHX VH-Z20R (Keyence Corporation of America, Itasca, IL, USA) was also considered to observe the effect of treatment modification on the microstructure [6]. Chemical analysis by Fourier transform infrared spectroscopy (FTIR) was selected to probe into the effect of smoke treatment on bamboo’s cellular structure [6]. FTIR spectroscopy was performed by using the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR, FTIR-4700 with ATR PRO ONE fitted with a diamond prism; Jasco Co., Tokyo, Japan) at 100 scans with a resolution of 4 cm−1 . The FTIR analysis will also be considered to qualitatively assess the extent of treatment modification on the mechanical performance of smoked bamboo.

218

R. Ramful

2.2 Results and Analysis 2.2.1

Mechanical Test Results

The flexural test results of smoked bamboo are displayed in Fig. 5. Each curve in Fig. 5 was computed from the arithmetic mean of multiple stress– strain curves obtained from each batch of bamboo specimens. In comparison with untreated bamboo, smoke-treated specimens were found to display higher average maximum flexural stress in both Modes A and B. Moreover, the distinct non-linear region up to the fracture point was found to be two times larger in Mode B as compared to Mode A. This observation corresponded to the ones observed in the literature [13, 14]. The discrepancy between the two results was assumed to result from the hierarchical arrangement, whereby the outermost section of concentrated fibers was found to withstand greater tensile loads. Further, mechanical analysis results of smoke-treated bamboo were plotted in terms of MOE and MOR against density as displayed in Fig. 6. A general observation in terms of a linear increase in both mechanical parameters was observed with increasing density. From Fig. 6, the gradient of the trend lines for both MOE and MOR results of smoke-treated specimens was found to be greater with a steeper slope in comparison with untreated bamboo. The same trend was observed in both Modes A and B. In untreated bamboo, however, the slope of trend lines of MOE and MOR results was found to be steeper in Mode A as compared to Mode B, which was consistent with the literature [13, 14]. Further, mechanical analyzes involving the specific energy absorption, specific strength, and specific stiffness were discussed, as presented in Fig. 7.

Fig. 5 Arithmetic mean of multiple stress–strain curves of untreated and smoked bamboo specimens

A Century-Old Tradition and Sustainable Technique to Protect Natural …

219

Fig. 6 Correlation between the modulus of elasticity and density in a Mode A and b Mode B; correlation between modulus of rupture and density in c Mode A and d Mode B

Fig. 7 Comparative study of the a apparent flexural strain; b specific energy absorbed; c specific strength; and d specific modulus of untreated and smoked bamboo specimens in bending Modes A and B

220

R. Ramful

Table 1 Mechanical properties of smoked and untreated bamboo specimens, including their standard deviations and coefficient of variance Specimen Mode n MC (%) ρ (kg/m3 ) tested

MOR (MPa)

MOE (GPa)

Us (J/kg × 104 )

Mean COV Mean COV Mean COV Mean COV Untreated A

0.04

185

0.04

12.6

0.05

0.292

0.08

4.5

661

0.03

173

0.06

12.1

0.05

0.263

0.15

5 12.4

851

0.01

174

0.02

14.6

0.03

0.641

0.07

Smoked

5

875

0.03

202

0.04

16.3

0.08

0.490

0.07

B

8

677

Untreated B

Smoked

A

8 12.4

4.5

From Fig. 7, the specific energy absorption, which was a function of flexural strain, was found to be twice as large in Mode B as compared to Mode A for both specimen types. Similar results were observed between the specific strength of untreated and smoked bamboo in Mode A, while the latter displayed slightly greater specific strength in Mode B. Moreover, a similar trend was observed in the variation of specific stiffness in untreated bamboo, while smoke-treated specimens were found to exhibit an increase in specific stiffness in Mode B. This overall increase was attributed to the narrow linear region of the stress–strain curve exhibited in Mode A [6]. In line with the results in Fig. 7, the specific energy absorption parameter and the corresponding flexural strain values were considered as indicating properties (IPs) as they were determining to discuss the changes in mechanical properties and FGM structure due to treatment modification. The large variation observed among the specific energy absorption parameter in Mode B was attributed to the method of smoke treatment, which predominantly targeted the outermost surface of bamboo culms. The microstructural changes in that section further impaired the flexibility of the fibers [15]. The MOE and MOR results obtained in Fig. 6 were compared to the material property chart of modulus versus specific strengths by Ashby et al. [16]. The results corresponded to a material performance index which allowed large, recoverable deformation. Table 1 summarizes the determined mechanical properties of smoked and untreated bamboo specimens, including their standard deviations and coefficient of variance.

2.2.2

Microscopy and FTIR Test Results

From SEM observations, crack propagation was found to predominantly vary as a function of the hierarchical bamboo structure. Radial crack propagation, which resembled a zigzag crack propagation pattern, was observed across the layers in Mode A and corresponded to similar observations by Song et al. The fiber-phase was found to display better resistance to transverse crack propagation in comparison with the softer matrix component. Fiber debonding was also observed as the softer matrix component was found to display inferior resistance to transverse crack propagation in

A Century-Old Tradition and Sustainable Technique to Protect Natural …

221

Fig. 8 SEM observations of fracture modes of untreated bamboo in: a, b, c Mode A and d Mode B [6], Author is Copyright owner

comparison with the fiber-phase. From Fig. 8a, c, side debonding of the parenchyma matrix can be clearly seen to occur from the main fiber bundles [6]. Besides, resistance to transverse crack propagation was found to be improved due to the arresting effect caused by the intertwining of fiber pull-out. In contrast, crack propagation in Mode B propagated in an orthogonal direction to the original crack leading to delamination in the outermost layers as a result of the disproportionate volume fraction of fibers to the parenchyma matrix. Moreover, Mode B displayed an improved ability to absorb large bending deformation while reducing large-scale buckling due to the tightly arranged parenchyma cells in the outermost section [6]. The foam-like structure of parenchyma cells is assumed to absorb large deformation, as observed by the large non-linear deformation regime prior to fracture in the stress–strain curves [13, 15]. Extensive delamination, which was found to be promoted by rapid crack propagation at the interface as a result of inferior interfacial strength between the fibers and parenchyma matrix, was further evidenced by the serrations observed in the fracture region of the stress–strain curves in Fig. 5. From Fig. 9, further observation by digital microscope of the radial delamination across the layers of Mode B-tested specimens showed that delamination affected approximately 40% of the specimen thickness in smoked bamboo. The ability to bear greater tensile load by the outermost layers in bending Mode B was thus affected by smoke treatment, as indicated by the decrease in mechanical properties of specific energy absorption and flexural strain. The marked increase in toughness in Mode B, however, was attributed to the increase in parenchyma content in the compressive region [15], while the overall stiffness contribution was associated with the increase in volume fraction of fibers (E f = 46 GPa, ρ f = 1160 kg/m3 ) [17]. A qualitative assessment of the effect of smoke treatment modification on the microstructure of bamboo was obtained from FTIR results as shown in Fig. 10.

Fig. 9 Microscopy analysis of the fractured surface of bamboo by digital microscope Keyence VHX VH-Z20R (magnification ×30) in: a, c Mode A and b, d in Mode B

222

R. Ramful

Fig. 10 FTIR spectra of the a outer and b inner layers of untreated and smoked bamboo

The analysis of FTIR results proved decisive in elucidating the corresponding effect of treatment modification on the mechanical properties of bamboo material. The FTIR spectra in the range of 400 to 1800 cm−1 were considered to demonstrate the prevailing difference which exists between the cellular structure of the outer and inner layers of bamboo as displayed in Fig. 10a, b, respectively. Table 2 shows the characteristic bands of FTIR spectra of bamboo samples ranging between the frequency intervals from 400 to 1800 cm−1 . An increase in the FTIR spectra at peak 1114 cm−1 in smoked bamboo corresponding to C–H functional group, assigned to guaiacyl and syringyl (lignin) [18], was noticeable from Fig. 10a. This increase was attributed to oxidation as bamboo culms were exposed to the elements of air and ultraviolet light over a year of natural drying. After this, further heat treatment was applied to remove oil from its hard waxy outermost surface. The elevated temperature of smoke treatment was assumed to further increase the lignin content [18]. Table 2 Characteristic bands of FTIR spectra in the frequency interval from 400 to 1800 cm−1 Frequency (cm−1 ) Functional group Assignment 896

C–H

References

Bending vibration of β-glucosamine bond [19] in cellulose

1051

C–O, C–H

Primary alcohol, guaiacyl (lignin)

[20]

1114

C–H

Guaiacyl and syringyl (lignin)

[18]

1159

C–O–C

Carbohydrate

[21]

1375

CH

CH deformation in cellulose and hemicellulose

[18]

1460

C–H

Asymmetric bending in CH3 (lignin)

[22]

1657

C=O

Quinines and quinine methides, adsorbed water

[23]

1737

C=O

Carbonyl groups in lignin

[24]

A Century-Old Tradition and Sustainable Technique to Protect Natural …

223

The formation of new alcohols and esters linked to lignin was assumed to decrease the number of free hydroxyl groups, hence affecting the hygroscopicity of bamboo. The decrease in hygroscopicity of bamboo, which is known to improve its dimensional stability and durability, was further confirmed by the decrease observed in the peak at 1657 cm−1 [18]. As detailed in Table 2, the peak at 1657 cm−1 corresponds to the C=O functional groups interacting with adsorbed water at the surface [23]. Furthermore, oxidation is assumed to lead to an increase in carbonyl groups in lignin, as indicated by the increase in peak at 1737 cm−1 in smoked bamboo [24]. Additionally, compared to other components, the cellulose decomposition was found to be much lower, given its crystalline structure [25].

2.3 Mechanics of Smoke Treatment Smoked bamboo was found to display substantial asymmetrical bending behavior, given the notable difference which prevailed in the mechanical properties of modified bamboo in terms of specific energy absorption. The asymmetric behavior occurred as a result of the hierarchical graded structure, and the effect of treatment modification was found to be more pronounced in Mode B, corresponding to a region of fibers with an excellent load-carrying capacity [17]. The marked reduction in the mechanical properties of smoke bamboo was linked to its non-uniform method of treatment, which affected the outermost layers of concentrated fibers. Moreover, both the physical and mechanical properties of bamboo were further affected by the heat of smoke treatment, which altered its chemical constituents, namely lignin [7, 19]. Based on microscopy analysis, the effect of smoke treatment, which principally affected the outer surface of bamboo, was further amplified in that section by bamboo’s graded structure. As schematically displayed in Fig. 9, the denser region of fibers in the outer periphery, which was mainly affected, plays a vital structural role as the fibers have a high tensile load-bearing capacity. The heat of smoke treatment thus led to a significant change in the mechanical characteristics of the fiber-rich areas as a result of alteration to their chemical composition [6]. The mechanisms of smoke treatment in terms of its effect on the chemical structure of bamboo are further discussed. Above a temperature of 150 °C, an increase and decrease in lignin and free hydroxyl groups, respectively, as evidenced by FTIR results, are observed [18, 19, 24]. Lignin content is increased as it undergoes further cross-linking due to poly-condensation reactions at elevated temperatures (> 120 °C) [7, 9]. A schematic outline of the poly-condensation reaction is shown in Fig. 11. Lignin has a significant structural contribution in plant materials such as bamboo, namely in the matrix phase, as it accounts for approximately 21% of the material’s chemical composition [17]. The increase in MOE was also attributed to an increase in lignin content in the outermost periphery of the wall tissues. Moreover, a reduction in toughness followed by an increase in brittleness is observed with further crosslinking of the lignin network, which also led to a notable reduction in water absorption [26, 27].

224

R. Ramful

Fig. 11 Schematic outline of the polymerization process of coniferyl alcohol by condensation reaction to the formation of complex lignin structure

The duration and thermal intensity of smoke treatment are thought to lead to a degradation of hemicellulose followed by transformation into a hydrophobic network, hence affecting bamboo’s affinity to water [9, 26, 28]. From past studies, the effects of a reduction in MC on the mechanical characteristics of bamboo have been thoroughly reported [29–32]. The above-mentioned changes in the cellular constituents of bamboo, cement the experimental observations made about the increase in hardness and brittleness characteristics observed in smoke bamboo.

3 Influence of Thermal Effects of Smoke Treatment on Shrinkage Behavior of Bamboo Once harvested, natural materials are likely to experience some form of natural degradation, such as shrinkage behavior as their conducting vessels cease to transport water. Further investigation to probe into the influence of smoke treatment, namely due to its thermal effect, on the hygroscopic changes and corresponding shrinkage behavior of bamboo material was conducted. The study was conducted by investigating the hygroscopic changes and shrinkage behavior with respect to bamboo’s orthotropic nature in small clear specimens following thermal modification [33]. For comparison purposes, the result obtained was compared with untreated bamboo specimens, and the corresponding alterations to its cellular structure due to thermal contraction were evidenced via Fourier transform infrared (FTIR) analysis.

3.1 Materials and Sample (Method) Moso bamboo specimens (Phyllostachys edulis) were selected for this study and were procured from Kyoto, Japan. All specimens had a maturity of 2 years and were sized from the intermodal section of bamboo culm [33].

A Century-Old Tradition and Sustainable Technique to Protect Natural …

225

A specific internodal section was considered to minimize microstructural and growth variation at various length scales. The corresponding intermodal section, from which the specimens were processed, had an approximate culm diameter and a wall thickness of 15 cm and 1.5 cm, respectively. Two specific batches, each comprising a total of 10 specimens, were considered and prepared for the test. The first batch comprised specimens without the outermost epidermis with average dimensions of 15 mm (longitudinal) × 14 mm (tangential) × 14 mm (radial). The second batch of specimens, in contrast, was unmodified and had average dimensions of 15 mm (longitudinal) × 14 mm (tangential) × 15 mm (radial) [33]. Prior to the shrinkage test, the specimens were subjected to a pre-treatment conditioning phase. The conditioning was conducted inside a laboratory environment by subjecting all specimens to drying at an ambient temperature of 25 °C and humidity of 60% followed by oven drying for 72 h at a temperature of 60 °C. The remaining moisture content was absorbed by storing the conditioned specimens in a desiccator fitted with a humidity absorber for a 1-week period. Moreover, the original dimensions of the conditioned specimens prior to the shrinkage test were carefully measured by using a Vernier caliper having a precision of ± 0.02 mm [33].

3.1.1

Determination of Heating Range

To prevent complete thermal degradation, the heating range was determined by considering the thermal gravimetric analysis (TGA) [33]. TGA analysis comprising the TGA curve and differential thermo-gravimetric (DTG) curve was conducted on the TGA machine (Discovery TGA, TA Instruments). A heating rate of 10 °C/min in an air atmosphere was selected. The TGA test results of Moso bamboo are given in Fig. 12. The weight loss percentage of Moso bamboo with respect to temperature is given by the solid curve represented in Fig. 12. The dotted line in Fig. 12, also commonly referred to as the first derivative curve, gives an indication of the weight

Fig. 12 Determination of heating range for Moso bamboo via thermal gravimetric analysis (TGA)

226

R. Ramful

loss concerning time. As can be clearly discerned from Fig. 12, the degradation in Moso bamboo through noticeable weight changes was observed to occur from 150 °C onwards [33]. As well reported in the literature, the thermal effect of heat treatment has an impact on the main cellular constituents of natural materials such as wood, which comprises cellulose, hemicelluloses, and lignin [26, 27, 34]. Bamboo material, which has a similar chemical composition, undergoes major changes in terms of decomposition at temperatures above 200 °C [35, 36]. The cellulose component in the cellular structure, however, has been reported to have improved resistance to thermal degradation as a result of its crystalline structure [25]. As this study investigates the hygroscopic changes and shrinkage behavior with respect to bamboo’s orthotropic nature, the temperature range within the TG plateau was considered. The heating range for bamboo specimens was thus determined as 25, 100, 150, and 200 °C [33].

3.1.2

Shrinkage Test

The shrinkage test was conducted at four different temperatures based on the determined heating range over a 24- and 48-h duration. For a given temperature and test duration, the changes in weight and dimensions of specimens, grouped in sets of 3, were measured by using a Vernier caliper [33].

3.1.3

FTIR Analysis

FTIR analysis was considered to assess the corresponding changes of thermal modification on the cellular constituents of bamboo. FTIR analysis was conducted by the attenuated total reflection Fourier transform infrared spectroscopy method (ATRFTIR, FTIR-4700 with ATR PRO ONE connected with a diamond prism; Jasco Co., Tokyo, Japan) [33]. A resolution of 4 cm−1 and 100 scans were used in the FTIR analysis.

3.2 Results and Analysis 3.2.1

Effect of Thermal Modification on Physical Changes

The experimental results following the shrinkage test can be visualized in Fig. 13. The effect of thermal modification on physical changes was first conducted by considering weight changes. The weight measurement results showed a non-linear increase in percentage weight loss with increasing temperature, as displayed in Fig. 14a [33]. A notable increase in percentage weight loss occurred after 150 °C, while the discrepancy observed between the 24-h and 48-h period was relatively small. The

A Century-Old Tradition and Sustainable Technique to Protect Natural …

227

Fig. 13 Visual changes following heat treatment in test specimens

Fig. 14 a Percentage weight loss and b dimensional changes due to shrinkage in radial, tangential, and longitudinal directions following heat treatment at three different temperatures for a 24- and 48-h duration

228

R. Ramful

variation between the percentage weight loss and the temperature was modeled by the following expression: W = Ae BT where W stands for the weight loss (%), T is the temperature (°C), and coefficients A and B are obtained via curve fitting. In terms of dimensional changes, similar observations based on a non-linear increase in shrinkage with increasing temperature were observed to occur principally in the radial and tangential directions, as shown in Fig. 14b [33]. A marked increase in the rate of dimensional changes in the two mentioned directions was observed to occur after 150 °C. Compared to results observed in the radial and tangential directions, shrinkage in the longitudinal direction was found to be notably lower. Moreover, the ratio of shrinkage in the radial and tangential directions to that in longitudinal direction could be deduced to further increase with temperature, as shown in Fig. 14b [33]. In contrast, the corresponding sets of results between the 24- and 48-h treatment periods showed negligible difference as substantial shrinkage occurred within the first 24 h. The mean and coefficient of variation (COV) of weight loss and dimensional changes following the 24- and 48-h treatment periods are summarized in Table 3.

3.2.2

FTIR Analysis

The corresponding changes of thermal modification on the cellular constituents of bamboo were evidenced by FTIR results in the range of 400–1800 cm−1 , as shown in Fig. 15a [33]. The decrease in intensity of peaks 3 (897 cm−1 ) and 9 (2945 cm−1 ), which correspond to C–H deformation of glucose ring in cellulose and hemicellulose, indicated a degradation of cellulose content as temperature increased from 150 to 200 °C. A similar trend in peaks 4 (1039 cm−1 ) and 6 (1242 cm−1 ), which are associated with guaiacyl units in the lignin molecule of bamboo, was observed as the temperature exceeded 150 °C. Degradation of hemicellulose above 150 °C also took place as evidenced by the flattened peaks 5 (1160 cm−1 ), 6 (1242 cm−1 ), 7 (1730 cm−1 ), and 9 (2945 cm−1 ), which correspond to hemicellulose molecule in bamboo. Notable changes observed in the physical characteristics of bamboo were substantiated by FTIR results which showed distinct degradation among its main chemical constituents, namely cellulose, lignin, and hemicellulose between 150 and 200 °C [33]. Moreover, degradation in cellulose and lignin is assumed to directly affect the mechanical properties of bamboo, as they account for approximately 44 and 20% in terms of the chemical composition of bamboo, respectively [37]. From FTIR results shown in Fig. 15b, substantial alterations to the physical characteristics of bamboo specimens could be further evidenced by peak 10 (3400 cm−1 ), which was associated with weakly bound water [38]. As reported in the literature, an increase

0.03

3.3

9.9

41

100

150

200

0.03

0.04

CV

Mn

CV

50

15

3.3

0.03

0.03

0.03 17

1.3

0.7

Mn

0.03

0.12

0.31

CV

24 h

23

2.7

1.1

Mn

48 h

Radial shrinkage/%

24 h

48 h

Weight loss/%

Mn

Temp/°C

0.01

0.20

0.10

CV

18

1.7

1.0

Mn

24 h

0.08

0.13

0.17

CV

23

2.8

1.2

Mn

48 h

Tangential shrinkage/%

0.12

0.04

0.13

CV

0.6

0.1

0.2

Mn

24 h

0.52

0.50

0.82

CV

Longitudinal shrinkage/%

1.1

0.9

0.3

Mn

48 h

Table 3 Weight and dimensional changes of Moso bamboo specimens (Mn and CV represent the mean and coefficient of the variance, respectively)

0.10

0.07

0.43

CV

A Century-Old Tradition and Sustainable Technique to Protect Natural … 229

230

R. Ramful

Fig. 15 FTIR spectra of untreated and thermally-modified bamboo corresponding to the range of a 400–1800 cm−1 and b 2280–3600 cm−1 . Adapted from Ramful et al. [33], License CC BY

in the desorption of water content is also assumed to occur with an increased amount of adsorbed carbon dioxide, which was evidenced by peak 8 between the range of 2320–2370 cm−1 .

4 Influence of Thermal Effects of Smoke Treatment on the Antibacterial Characteristics of Bamboo As a natural material that grows unblemished in nature, bamboo possesses notable antibacterial characteristics which enable it to withstand the rough conditions posed by its environment. The resistance to abiotic and biotic factors could have beneficial usage if rightly exploited in bamboo-derived products. A study was conducted by considering the non-extraction method to verify whether thermally-modified Japanese bamboo can fully preserve its antibacterial characteristics following treatment modification such as by smoke treatment [39]. For comparison purposes and to establish the antibacterial mechanism in bamboo, the results were compared with natural bamboo.

4.1 Materials and Sample (Method) In this study, the two most popular species of bamboo in Japan were selected for investigation, namely Moso bamboo (P. edulis) and Madake bamboo (P. bambusoides) [39]. The former was obtained from the Kyoto and Kyushu regions of Japan, while Madake bamboo was obtained from the Kyushu region only.

A Century-Old Tradition and Sustainable Technique to Protect Natural …

231

To investigate the antibacterial characteristics via the non-extraction method, the ground bamboo culm was processed into powder form. In the first preparation stage, the coarse sieved powder was subjected to a preparatory heat treatment of 60 °C for 24 h to remove the remaining moisture content. The second preparation stage involved a thorough sieving process until a particle size of 106 μm was achieved. The thermally-modified samples were prepared by subjecting the fine bamboo powder to a heat treatment of 150 °C for a 48-h duration [39]. Following similar methods used in the previous studies [40, 41], the antibacterial efficacy of thermally-modified bamboo was investigated by testing 0.02 g of finely sieved and thermally-treated bamboo.

4.1.1

In Vitro Bacteria Culture

The in vitro cultured bacteria technique was selected as part of the sample characterization process to test for antibacterial efficacy. Two species of bacteria, namely Staphylococcus aureus (NBRC 13276) and Escherichia coli (E1 NBRC 3972), which correspond to gram-positive and gram-negative bacteria, were cultured in a lab environment through the streak plate method [39]. The bacteria culture consisted of bacteria beads installed in agar-containing plates, which were incubated for a period of 24 h under 37 °C. Further preparation after 24 h involved mixing the colony with 5 mL of Luria Broth (LB Broth, Sigma-Aldrich, Tokyo, Japan) followed by thorough mixing in a shaking incubator (Southwest Science, Hamilton, NJ, USA) set at 37 °C and 175 rpm for a 24-h period. The second plate was prepared by considering the four sector quadrant streaks based on the colony obtained from the first plate. Finally, repeated dilution steps of the bacteria solution were conducted until an optical density of 0.3 was achieved [39].

4.1.2

Pre-characterization of Bacterial Culture

To estimate the concentration of bacteria during various growth stages of bacterial culture, the optical density was measured with the mini photo 518R photometer (TAITEC CORPORATION, Tokyo, Japan) equipped with a wavelength of 660 nm (OD660nm ) [39]. Four growth stages, ranging from lag, log, and stationary phases, were recorded. From the measured results of microbial growth count, a clear indication of microbial activity could be obtained.

4.1.3

Antibacterial Efficacy

Sample characterization in terms of antibacterial efficacy was conducted by using finely sieved-bamboo powder in both natural and heat-treated conditions. A summary of the various types of antibacterial agents used in this study and their corresponding

232

R. Ramful

Table 4 Types of antibacterial agents used in this study and their corresponding abbreviations following location, species, and treatment modification Types of antibacterial agents of bamboo specimens subjected to treatment modification Location

Kyoto

Kyushu

Kyushu

Species

Moso (Phyllostachys edulis)

Moso (Phyllostachys edulis)

Madake (Phyllostachys bambusoides)

Treatment modification Stage I—natural

KM

KyM

KyMa

Stage II—heat treated

KMH

KyMH

KyMaH

abbreviations in accordance with location, species, and treatment modification is displayed in Table 4. 0.02 g of each specimen was added into small-sized Eppendorf tubes (2 mL), followed by 100 μL of LB Broth and by either 100 μL of E. coli or 100 μL S. aureus bacteria solution. An Eppendorf shaker, set at a speed of 1000 rpm and 37 °C for 24and 48-h, was utilized, followed by a High-speed Refrigerated Centrifuge, CR-GIII (Hitachi Ltd., Tokyo, Japan) set at 4 °C and 10,000 rpm for a 10-min duration. 100 μL from the supernatant solution produced was diluted to 10–5 by serial dilution, and 100 μL of the solution was added to an LB agar plate for incubation at 37 °C for 24 h [39]. The number of colony-forming units, CFU/mL, could be calculated using the following expression: CFU/mL = (no. of colonies × dilution factor) × 10

4.1.4

FTIR

The effects of thermal modification on the antibacterial trait of bamboo were further explored by looking into the corresponding changes to its chemical constituents via the Fourier transform infrared spectroscopy (FTIR) technique [39]. The ATR-FTIR, FTIR-4700, and ATR PRO ONE fitted with a diamond prism (Jasco Co., Tokyo, Japan) set at a resolution of 4 cm−1 , and 100 scans were used for this purpose.

4.2 Results and Analysis The CFU counting results for bamboo specimens tested against E. coli are displayed in Fig. 16.

A Century-Old Tradition and Sustainable Technique to Protect Natural …

233

Fig. 16 Colony-forming units of various types of antibacterial agents of bamboo specimens following in vitro testing with E. coli for a 24 h and 48 h duration (* statistically significant difference, NS = no significant difference). Adapted from Ramful et al. [39], License CC BY

The results indicated that all six types of bamboo specimens displayed good effectiveness against E. coli bacteria when compared with control specimens. Higher effectiveness was notably observed in natural Kyoto-Moso and Kyushu-Madake bamboo in the first 24-h period, and no statistically significant difference could be discerned after the 48-h period. The remaining specimens, however, showed maximum antibacterial characteristics after a 48-h period. Moreover, a statistically significant difference could be observed in the antibacterial activity of heat-treated Kyoto-Moso, Kyushu-Moso, and Kyushu-Madake specimens between the 24- and 48-h periods [39]. The CFU counting results for bamboo specimens tested against S. aureus are displayed in Fig. 17. Similar to the previous observations and with respect to the control specimens, all six types of bamboo specimens displayed good effectiveness against S. aureus bacteria. Kyushu-Moso bamboo, in both natural and heat-treated forms, was found to display higher effectiveness in the first 24-h, and no statistically significant difference could be discerned after the 48-h period. From general observations, most specimens were found to display maximum antibacterial characteristics after a 48-h period except natural Kyoto-Moso and Kyushu-Madake specimens. In addition, a statistically significant difference between the antibacterial activity of heattreated specimens in the 24- and 48-h period could only be observed in heat-treated Kyushu-Madake specimens [39].

234

R. Ramful

Fig. 17 Colony-forming units of various types of antibacterial agents of bamboo specimens following in vitro testing with S. aureus for a 24 h and 48 h duration (* statistically significant difference, NS = no significant difference). Adapted from Ramful et al. [39], License CC BY

FTIR Analysis The discrepancy observed in the antibacterial activity of natural and heat-treated specimens was further explored by considering the results of FTIR analysis in the range of 400–1800 cm−1 as shown in Fig. 18. The molecular footprint of natural bamboo powder, which corresponded to previous FTIR analyzes involving solid bamboo samples [6, 18, 33], was found to be identical to thermally-modified ones. Distinct changes in the characteristic bands of FTIR spectra at peaks 1045 and 1737 cm−1 could be discerned in thermallymodified bamboo. The peak at 1045 cm−1 corresponded to C–O and C–H primary alcohol group in guaiacyl lignin [20] while the peak at 1737 cm−1 was associated with C=O carbonyl groups in lignin [24].

4.3 Discussion and Antibacterial Mechanism The CFU results of various types of antibacterial agents of thermally-modified bamboo specimens following in vitro testing with S. aureus for 24- and 48-h periods were found to correlate with FTIR results. The notable increase in lignin, observed by the surge in peak 1045 cm−1 in both heat-treated Kyoto-Moso and Kyushu-Madake bamboo, is assumed to lead to a marked reduction in the CFU counting results for

A Century-Old Tradition and Sustainable Technique to Protect Natural …

235

Fig. 18 FTIR spectra of three different types of untreated and thermally-modified bamboo specimens in the range 400–1800 cm−1 . Adapted from Ramful et al. [39], License CC BY

the corresponding antibacterial agents. In contrast, however, the antibacterial agents of heat-treated bamboo were found to be less effective against E. coli in the first 24-h period [39]. Based on the above correlation, it was concluded that the effect of thermal modification does affect the antibacterial performance of bamboo powder. The lignin component, specifically the C–O and C–H functional groups, corresponding to the primary alcohol group in guaiacyl lignin, was identified as the chemical constituent

236

R. Ramful

responsible for the antibacterial efficacy in bamboo. The correlation established in this study is related to the observations made in the previous studies, whereby the origin of antibacterial characteristics in bamboo was linked to lignin [40]. In lignin, the sugar content is assumed to promote its adhesion to the bacterial membrane [42], given the interaction between the peptidoglycan layer of bacterial cell walls and the glucan content and polysaccharide of the sugar molecules [43]. Besides, numerous other compounds present in lignin, namely phenolic compounds, carboxylic acid containing OH-group, and methoxyl and epoxy functional groups containing oxygen, were reported to affect the antibacterial property of bamboo [42]. Moreover, the amounts of phenolic carboxylic acids and lignin-containing fragments were found to increase following thermal modification [44], which was also evidenced by FTIR results based on an increase in peak at 1737 cm−1 [24, 44–47].

5 Advantages and Limitations of Smoke Treatment Methodology Based on the key findings of the research discussed in this chapter, the numerous benefits provided by smoke treatment are evident. In summary, the treatment was found to affect the physical, mechanical, and antibacterial characteristics of bamboo culms. In terms of physical properties, the treatment provided an improved hygroscopicity and was found to be effective at restraining the moisture content in the outermost layers of bamboo culms. The transformation of the cellular constituent following smoke treatment led to an enhancement in the mechanical properties of bamboo which displayed greater rigidity, hardness, and strength. Besides changes to the physical and mechanical attributes, the thermal effect of smoke treatment was found to considerably alter the antibacterial and anti-insect repellency of smoke bamboo due to changes in its cellular constituents. Despite the noteworthy benefits of smoke treatment on the physical and mechanical traits, high levels of the treatment tend to result in an adverse and undesirable effects. Lengthy duration and exposure to the elevated temperature of the treatment accentuate the reduction in moisture content. Further drying and shrinkage at elevated temperature result in changes in its mechanical and geometrical features, respectively. Bamboo tends to become harder and brittle at temperatures exceeding 150 °C, while uncontrolled shrinkage can yield premature failure due to crack formation.

A Century-Old Tradition and Sustainable Technique to Protect Natural …

237

6 Conclusion 6.1 Influence of Smoke Treatment on Mechanical Properties of Bamboo In the first part of the investigation about the influence of smoke treatment on the mechanical properties of bamboo, the effect of smoke treatment was found to be more pronounced when loading was applied in the less fiber-dense section. This observation corresponded to the non-uniform treatment application method, which predominantly targeted the outer layers of concentrated volume fraction of fibers, thus affecting fibers with high tensile load-bearing capacity. Consequently, smoke treatment was found to lead to an increase in the modulus of elasticity and modulus of rupture at the expense of a marked reduction in specific energy absorption (U s ) and maximum flexural strain (ε1 ). Besides, alterations to the chemical constituents of bamboo in its outermost surface at high temperature led to an improvement to its dimensional stability due to an increase in lignin and reduction in free hydroxyl groups which in turn improved the strength while reducing the hygroscopicity, respectively. To further exploit the full potential of bamboo-based materials, smoke treatment could be considered as an excellent alternative to enhance its dimensional stability and durability, while further research investigations will be required to relieve excessive brittleness in order to reduce its propensity to cracking.

6.2 Influence of Thermal Effects of Smoke Treatment on Shrinkage Behavior of Bamboo Secondly, despite its beneficial ability to improve dimensional stability, the associated effects of heat treatment led to internally induced forces due to shrinkage, which could result in a sudden split. Being an orthotropic material, the experimental observations made about the dimensional changes during shrinkage showed a good correlation in the three principal directions. Similar trends were observed in dimensional and weight changes, whereby the measurement results observed in the radial and tangential directions significantly exceeded the ones observed in the longitudinal direction. Moreover, changes between a temperature of 150–200 °C in the cellulose and lignin components in bamboo, which account for 44 and 20%, respectively, in terms of its chemical constituent [37], were found to lead to significant alterations to both its physical and mechanical properties.

238

R. Ramful

6.3 Influence of Thermal Effects of Smoke Treatment on the Antibacterial Characteristics of Bamboo From antibacterial test results, antibacterial agents derived from thermally-modified bamboo powder, such as heat-treated Kyushu-Moso bamboo, were found to be more efficient when tested against S. aureus. Correlations between FTIR results and past studies have identified the lignin component as accountable for the antibacterial trait in both natural and thermally-modified bamboo powder. In lignin, the C–O and C–H functional groups, which correspond to the primary alcohol group in guaiacyl lignin, were specifically considered as the chemical constituents responsible for the antibacterial efficacy in bamboo. The beneficial aspects of the antibacterial characteristics in bamboo could be further exploited in naturally bamboo-derived products ranging from laminates to fabrics.

References 1. Ghavami K (2016) Introduction to nonconventional materials and an historic retrospective of the field. In: Nonconventional and vernacular construction materials. Woodhead Publishing, pp 37–61 2. Correal FF (2020) Bamboo design and construction. In: Nonconventional and vernacular construction materials. Woodhead Publishing, pp 521–559 3. Trujillo DJA, Ramage M, Chang WS (2013) Lightly modified bamboo for structural applications. Proc Inst Civ Eng Constr Mater 166(4):238–247 4. Liese W (2018) Protection of bamboo in service. World Bamboo Rattan 1(1):29–33 5. Kaur PJ, Satya S, Pant KK, Naik SN (2016) Eco-friendly preservation of bamboo species: traditional to modern techniques. BioResources 11(4):10604–10624 6. Ramful R, Sakuma A (2021) Effect of smoke treatment on flexural strength of bamboo hierarchical structure. BioResources 16(1):387 7. Kaur PJ, Satya S, Pant KK, Naik SN, Kardam V (2016) Chemical characterization and decay resistance analysis of smoke treated bamboo species. Eur J Wood Wood Prod 74(4):625–628 8. Liese W (2005) Preservation of a bamboo culm in relation to its structure. World Bamboo Rattan 3(2):17–21 9. Boonstra MJ, Van Acker J, Kegel E, Stevens M (2007) Optimisation of a two-stage heat treatment process: durability aspects. Wood Sci Technol 41(1):31–57 10. Dixon PG, Gibson LJ (2014) The structure and mechanics of Moso bamboo material. J R Soc Interface 11(99):20140321 11. Priem C, Othman R, Rozycki P, Guillon D (2014) Experimental investigation of the crash energy absorption of 2.5 D-braided thermoplastic composite tubes. Compos Struct 116:814–826 12. Mou HL, Zou TC, Feng ZY, Xie J (2016) Crashworthiness analysis and evaluation of fuselage section with sub-floor composite sinusoidal specimens. Latin Am J Solids Struct 13:1186–1202 13. Habibi MK, Samaei AT, Gheshlaghi B, Lu J, Lu Y (2015) Asymmetric flexural behavior from bamboo’s functionally graded hierarchical structure: underlying mechanisms. Acta Biomater 16:178–186 14. Chen M, Ye L, Li H, Wang G, Chen Q, Fang C, Dai C, Fei B (2020) Flexural strength and ductility of moso bamboo. Constr Build Mater 246:118418 15. Obataya E, Kitin P, Yamauchi H (2007) Bending characteristics of bamboo (Phyllostachys pubescens) with respect to its fiber–foam composite structure. Wood Sci Technol 41(5):385– 400

A Century-Old Tradition and Sustainable Technique to Protect Natural …

239

16. Ashby MF, Gibson LJ, Wegst U, Olive R (1995) The mechanical properties of natural materials. I. Material property charts. Proc R Soc Lond Ser A: Math Phys Sci 450(1938):123–140 17. Amada S, Munekata T, Nagase Y, Ichikawa Y, Kirigai A, Zhifei Y (1996) The mechanical structures of bamboos in viewpoint of functionally gradient and composite materials. J Compos Mater 30(7):800–819 18. Meng FD, Yu YL, Zhang YM, Yu WJ, Gao JM (2016) Surface chemical composition analysis of heat-treated bamboo. Appl Surf Sci 371:383–390 19. Wang X, Cheng D, Huang X, Song L, Gu W, Liang X, Li Y, Xu B (2020) Effect of hightemperature saturated steam treatment on the physical, chemical, and mechanical properties of moso bamboo. J Wood Sci 66(1):1–9 20. Pandey KK (1999) A study of chemical structure of soft and hardwood and wood polymers by FTIR spectroscopy. J Appl Polym Sci 71(12):1969–1975 21. Kotilainen RA, Toivanen TJ, Alén RJ (2000) FTIR monitoring of chemical changes in softwood during heating. J Wood Chem Technol 20(3):307–320 22. Colom X, Carrillo F, Nogués F, Garriga P (2003) Structural analysis of photodegraded wood by means of FTIR spectroscopy. Polym Degrad Stab 80(3):543–549 23. Huang X, Kocaefe D, Kocaefe Y, Boluk Y, Pichette A (2012) Study of the degradation behavior of heat-treated jack pine (Pinus banksiana) under artificial sunlight irradiation. Polym Degrad Stab 97(7):1197–1214 24. Hoseinzadeh F, Zabihzadeh SM, Dastoorian F (2019) Creep behavior of heat treated beech wood and the relation to its chemical structure. Constr Build Mater 226:220–226 25. Zaman A, Alen R, Kotilainen R (2000) Thermal behavior of Scots pine (Pinus sylvestris) and silver birch (Betula pendula) at 200–230. Wood Fiber Sci:138–143 26. Tjeerdsma BF, Boonstra M, Pizzi A, Tekely P, Militz H (1998) Characterisation of thermally modified wood: molecular reasons for wood performance improvement. Holz als Roh-und Werkstoff 56(3):149–153 27. Boonstra MJ, Tjeerdsma B (2006) Chemical analysis of heat treated softwoods. Holz als Rohund werkstoff 64(3):204–211 28. Tang T, Zhang B, Liu X, Wang W, Chen X, Fei B (2019) Synergistic effects of tung oil and heat treatment on physicochemical properties of bamboo materials. Sci Rep 9(1):1–11 29. Chen G, Luo H, Yang H, Zhang T, Li S (2018) Water effects on the deformation and fracture behaviors of the multi-scaled cellular fibrous bamboo. Acta Biomater 65:203–215 30. Ota M (1953) Studies on the properties of bamboo stem (part 9). On the relation between compressive strength parallel to grain and moisture content of bamboo splint. Bull Kyushu Univ For 22:87–108 31. Jiang Z, Wang H, Tian G, Yu Y (2012) Sensitivity of several selected mechanical properties of moso bamboo to moisture content change under the fibre saturation point. BioResources 7(4):5048–5058 32. Xu Q, Harries K, Li X, Liu Q, Gottron J (2014) Mechanical properties of structural bamboo following immersion in water. Eng Struct 81:230–239 33. Ramful R, Sunthar TP, Zhu W, Pezzotti G (2021) Investigating the underlying effect of thermal modification on shrinkage behavior of bamboo culm by experimental and numerical methods. Materials 14(4):974 34. Tjeerdsma BF, Militz H (2005) Chemical changes in hydrothermal treated wood: FTIR analysis of combined hydrothermal and dry heat-treated wood. Holz als roh-und Werkstoff 63(2):102– 111 35. Khalil HA, Bhat IUH, Jawaid M, Zaidon A, Hermawan D, Hadi YS (2012) Bamboo fibre reinforced biocomposites: a review. Mater Des 42:353–368 36. Azadeh A, Ghavami K (2018) The influence of heat on shrinkage and water absorption of Dendrocalamus giganteus bamboo as a functionally graded material. Constr Build Mater 186:145–154 37. Taylor D, Kinane B, Sweeney C, Sweetnam D, O’Reilly P, Duan K (2015) The biomechanics of bamboo: investigating the role of the nodes. Wood Sci Technol 49(2):345–357

240

R. Ramful

38. Emmanuel V, Odile B, Celine R (2015) FTIR spectroscopy of woods: a new approach to study the weathering of the carving face of a sculpture. Spectrochim Acta Part A Mol Biomol Spectrosc 136:1255–1259 39. Ramful R, Sunthar TP, Kamei K, Pezzotti G (2022) Investigating the antibacterial characteristics of Japanese bamboo. Antibiotics 11(5):569 40. Afrin T, Tsuzuki T, Kanwar RK, Wang X (2012) The origin of the antibacterial property of bamboo. J Text Inst 103(8):844–849 41. Xi LX, Qin DC (2012) The antibacterial performance of natural bamboo fiber and its influencing factors. In: Proceedings of the 55th international convention of society of wood science and technology, pp 1–8 42. Alzagameem A, Klein SE, Bergs M, Do XT, Korte I, Dohlen S, Hüwe C, Kreyenschmidt J, Kamm B, Larkins M, Schulze M (2019) Antimicrobial activity of lignin and lignin-derived cellulose and chitosan composites against selected pathogenic and spoilage microorganisms. Polymers 11(4):670 43. Navarre WW, Schneewind O (1999) Surface proteins of gram-positive bacteria and mechanisms of their targeting to the cell wall envelope. Microbiol Mol Biol Rev 63(1):174–229 44. Díez-Pascual AM (2020) Antimicrobial polymer-based materials for food packaging applications. Polymers 12(4):731 45. Xu G, Wang L, Liu J, Wu J (2013) FTIR and XPS analysis of the changes in bamboo chemical structure decayed by white-rot and brown-rot fungi. Appl Surf Sci 280:799–805 46. Veiga TRLA, Lima JT, Dessimoni ALDA, Pego MFF, Soares JR, Trugilho PF (2017) Different plant biomass characterizations for biochar production. Cerne 23:529–536 47. Sikora A, Kaˇcík F, Gaff M, Vondrová V, Bubeníková T, Kubovský I (2018) Impact of thermal modification on color and chemical changes of spruce and oak wood. J Wood Sci 64(4):406–416

A Critical Review on Finite Element Models Towards Physico-Mechanical Properties of Bamboo Fibre/Filler-Reinforced Composite Materials Ranjan Kumar, Sujeet Kumar Mishra, and Kaushik Kumar Abstract Bamboo is nowadays considered one of the most promising alternative substitutes to synthetic fibre composites. In addition to being affordable, having a quick growth cycle, being easily accessible, environmentally benign, extremely flexible, simple to develop, and biodegradable characteristics, it also has higher strength and stiffness with low density. Their natural abundance, lower cost, lightweight, and strength-to-weight ratio characteristics have compelled us to consider bambooreinforced composites as the most sustainable and suitable composites for wide industrial applications. Researchers are deeply involved in investigating such natural fibre-reinforced composites (NFRCs) for the wider arena of industrial applications that have identified their reliability and accessibility for being involved in aircraft, automotive, and marine equipment as well as in various engineering disciplines. In this regard, various researchers have gone through modelling and simulation approaches in order to determine the performance characteristics of such bambooreinforced composites (BRCs). The present work is a noble attempt to illuminate the readers regarding the comprehensive review and summary of the finite element method (FEM) approach that has been carried out in terms of their modelling and simulation (M&S), model type, simulation parameters, and performing platforms, their research outcomes based on the applicable theories and popular methods in this area. The work is also expected to let more experts know about the current status of research in this area which would definitely prove to be a resourceful work for sustainable guidance for relevant researchers. Keywords Bamboo composite · Bio-composite · Bamboo sustainability · Finite element modelling · Finite element method · Bamboo modelling and simulation · Bamboo composite modelling · Natural fibres-reinforced composites (NFRCs)

R. Kumar · S. K. Mishra · K. Kumar (B) Birla Institute of Technology, Mesra, Ranchi, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 F. L. Palombini and F. M. Nogueira (eds.), Bamboo and Sustainable Construction, Environmental Footprints and Eco-design of Products and Processes, https://doi.org/10.1007/978-981-99-0232-3_9

241

242

R. Kumar et al.

1 Introduction In many structural and non-structural applications, composites are being utilized and taking the place of traditional materials. Reinforcing and matrix are two phases that are typically present in any composite material. Fibres or particulates make up the reinforcing phase. Typically, reinforcing fibres are either short or long/continuous. Continuous fibre-reinforced composites have a poor production rate as a result of their inherent processing challenges; as a result, they are seldom taken into consideration by huge applications, particularly in case of the mass manufacturing. Contrarily, short-fibre polymer composites (SFPCs) are rarely considered for crucial structural applications because they lack the high stiffness and strength of continuous fibre composites [1, 2]. Growing environmental consciousness in recent years has demonstrated the significance of producing composite materials that are biodegradable, recyclable, and environmentally friendly [3–5]. Due to their attractive assortment of properties, natural fibres including “kenaf, silk, jute, palm, leaf spring, sisal, flax, and hemp” can be considered an alternative to synthetic fibres [6–8]. These fibres possess notable qualities that include strength [9, 10], toughness, flexibility, and stiffness [10–15]. They are also sustainable and renewable [16], and they have a high availability [17]. A few of their benefits deserve to be mentioned, including “low density, minimal cost, outstanding energy recovery, vibration dampening, less skin and respiratory irritation, and less equipment abrasion.” However, the reinforcement of such natural fibres is mostly dependent upon their fibre length, reinforcing orientation, interfacial interactions with matrix, aspect ratio, etc.; during the material selection of any potential application, it is necessary to investigate their mechanical properties [1]. Out of many mechanical properties, the tensile modulus is one of the most important material characteristics used for the selection of material depending upon the stiffness required for that particular application [18]. The tensile or Young’s modulus of a material provides an estimation for their deformation response on the application of the uniaxial applied loading. The high stiffness of the material is due to its high modulus, and relatively, the material is known to be less deformable. Such materials are most useful in the domain of application where the designing of components requires high load-bearing capacity. In the production of such components, the injection moulding and the extrusion process as well as any other composite manufacturing techniques have provided the ease of processing and bulk production for such SFPCs that have been emerging as a viable alternative for semi-structural components and low load-bearing applications [19]. Further, there are two ways of estimating the material properties such as prediction based on a mathematical model or prediction of material properties using any computational tool. However, prior to the experimentation, it is advisable to solve and estimate the material behaviour based on their modelling using any computation tools available nowadays because the experimental synthesis and characterization demand a lot more sophistication which cost consuming as well as time-consuming. But nowadays, the available computational tools produce the most accurate results, which can

A Critical Review on Finite Element Models Towards …

243

be approximated against the experimentation, but still, further experimental validation for the same is quite necessary and important for actual material behaviour characterization [20]. The predictive model produced by composite modelling leads towards estimating the macroscopic properties of the material, which can be further optimized using the parametric analysis of constituents incorporated in composite modelling. The term “modelling” refers to mathematical analysis or computer-based simulation used to estimate the behaviour or characteristics of a material [1]. Two approaches, such as the macromechanics’ approach and the micromechanics approach, can be used to model composites. In micromechanical modelling, the material/model is seen at a macroscopic level or on a global scale, which is the orientation of constituent materials and internal boundaries. Macromechanics regards composite as anisotropic in the linear elastic domain, and the associated anisotropic elastic constants are established empirically. The response of the composite structure under various loading situations could be studied using a finite element analysis (FEA)-based approach that uses experimentally established anisotropic elastic constants [21], whereas the micromechanics deals at the microlevel and considers each constituent that takes part in composite development considering the internal boundaries and orientation of individual constituents. Therefore, various models have been developed to understand the behaviour of the prepared composites. These estimations of material properties are pretty accurate in the case of micromechanical modelling [22, 23]. The micromechanics focusses on the assessment of elastic moduli of the composite system. These elastic moduli are interpreted in terms of their elastic properties. Whilst dealing with the micromechanics of anelastic composite material, the elastic constants can be predicted and further utilized directly as parametric inputs in finite element simulation purposes through which the modelling and simulation can be performed to estimate the behaviour of the material [1, 20, 24]. The present work is a noble attempt to illuminate the readers with the stateof-the-art review of the establishment of different mathematical models developed, and the FEM approaches incorporated for analyzing the behaviour of natural fibres or bamboo fibre composites. This review article emphasizes the important methods/approaches that may be used to examine the properties of bamboo fibresreinforced composites analytically and numerically whilst taking into account the validity of each model and the effectiveness of the employed techniques. Its focus is on recent research on natural fibre composites (NFCs). The varieties of natural fibre and matrix, model and analysis types, simulation parameters and platforms, and model/method accuracy have all been gathered and compared from various studies.

2 Analytical Modelling Approach Through assigning matrix and reinforcement characteristics as input parameters using the concepts of macromechanics, analytical models are basically the computational or mathematical approach to compute a specific property of a finally prepared composite system. For instance, during computational modelling, we generally

244

R. Kumar et al.

require theories that deal with micromechanics. The main inputs of micromechanics basics include the “volume fraction, shear modulus, Poisson’s ratio, and elastic modulus” of each component of the composite system. In some models, additional characteristics, such as “fibre orientation, aspect ratio, density, orthographic features, and viscoelastic behaviour,” may be needed. In comparison with continuous fibre composites, predicting the properties of woven fibre composites is far more complex. The rule of mixtures (ROM) is one of the theoretical models available that provides one of the simplest ways to numerically determine and study the elastic characteristics of a fibre-reinforced composite and is only utilized in the case of continuous and unidirectional fibre [25]. Various micromechanical models are available nowadays which have been summarized below.

2.1 Micromechanical Modelling Micromechanical modelling is essential in estimating the macroscopic behaviour of the composite material based on the macroscopic behaviour of the constituent materials. Since there is a mechanical interaction between the fibres and matrix material, where stress and strain experienced by the laminate are homogenous, we may expect that deformation will occur if a load is applied to the composite laminate. The total volume of a composite is defined as the sum of the volume of fibre and the volume of a matrix; also, the mass of a composite is defined as the sum of the mass of fibre and the mass of matrix and is given as follows: Vc = Vf + Vm

(1)

Mc = Mf + Mm

(2)

Further, the volume fractions of fibres and matrix are related as follows: Vf Vf = Vc Vf + Vm   1 − Vfr( f ) Vf Vm = Vfr( f )

Vfr( f ) =

(3)

(4)

Here, Vfr( f ) denotes the volume fraction of fibres. Also, by involving the density ratio, Mf/A Mf = Vf/A Vf

(5)

Here, Mf/A and Vf/A denote the mass of fibres and volume of fibres determined using the Archimedes principle. And also, the mass of fibres M f and volume of fibres V f

A Critical Review on Finite Element Models Towards …

245

are determined using the following relation given as follows: V f = Vfr Vc Mf =

Mf/A Mf/A Vf = (Vfr Vc ) Vf/A Vf/A

(6) (7)

Further, knowing the density of matrix (ρm ) material, the mass of matrix material for composite development can be expressed using the expression as follows: ρm =

Mm , and Mm = ρm Vm Vm

(8)

Typically, the composition of short-fibre composites is based on mass fraction because it is simple to measure the weight of individual ingredients whilst mixing. The relation between the volume fraction, mass fraction, and density is given as follows: Vf =

Wf ρm Wf ρm + Wm ρf

(9)

Also, the densities of the composites system using the individual volume fractions and densities of fibres and matrix components are given as follows: ρc = ρf Vf + ρm Vm

(10)

It is worth noting here that mass fraction and volume fraction are not equal; mismatch can result in a drastic variation in densities of individual constituents (i.e. fibre and matrix).

2.2 Calculation of Elastic Modulus Einstein and Guth made some of the earliest attempts at modelling composites using micromechanics. The proposed model turned out to be quite successful for composites with lower particulate concentrations. Furthermore, based on the linear relationship between the modulus of individual constituents present in composite, their effective modulus can be calculated using such models.

246

R. Kumar et al.

2.3 Einstein Modelling Approach Einstein’s model for the prediction of the effective modulus of a two-phase composite system is given as follows: E c = E m (1 + 2.5Vf )

(11)

2.4 Guth and Modified Guth Modelling Approach   E c = E m 1 + 2.5Vf + 14.1Vf2

(12)

Further, the Guth model was modified by introducing the term “S” which describes the length-to-width ratio of reinforcement or particulates in the composite material, and the related modified Guth model was given by the “Cohan” equation which is given as follows:   E c = E m 1 + 2.5SVf + 14.1S 2 V f2

(13)

2.5 Rule of Mixtures In the year of 1889, an analytical model was proposed by “Voigt.” The primary presumption for this Voigt-model was that both of the material’s phases undergo the same strain in response to axial stress. Later, the examined assumption in the Voigtmodel was known as the “Voigt-assumption,” and the Voigt-model itself became known as the “rule of mixing” (ROM). According to the proposed Voigt-model, the elastic modulus of a two-phase composite material is given as follows: E 1 = E f Vf + E m Vm

(14)

2.6 Inverse Rule of Mixtures In 1929, another predicted model was reported by “Reuss.” In this model, the prediction of the lower bound can be effectively done using the inverse of the rule of mixtures, and the absolute value could be known by keeping the assumption in mind that equal stress is experienced by both individual constituents in the composite

A Critical Review on Finite Element Models Towards …

247

material [26]. Later on, this predicted model came to be known as the “inverse rule of mixtures” and is given as follows: 1 Vm Vf = + Ec Em Ef

(15)

2.7 Halpin–Tsai Modelling Approach Further, the prediction of the elastic characteristics of a composite system was carried out by Affdl and Kardos [27] through a proposed known as the “Halpin–Tsai model.” The model is useful in approximating the “effective stiffness properties” of the composite material system as a function of the aspect ratio of the fibre or filler reinforcements and volume fractions [28]. The estimation of the modulus properties of a composite using the Halpin–Tsai model is given as follows:

2.8 Eshelby’s Modelling Approach The solution to the problem of stress–strain inside a composite system can be solved using Eshelby’s model. The proposed model is solved for an ellipsoidal volume cut out, which further undergoes the stress-free Eigen strain ε* and is given as follows: ε(x) = ξ(I, C0 ) : ε∗

(16)

Here, the term ξ (I, C 0 ) indicates the Eshelby Tensor, and ε* shows the Eigenstrain. The strain depends upon the stiffness matrix, shape, and orientation of the inclusion of ellipsoidal cutout.

2.9 Mori–Tanaka Modelling Approach Further, similar to the Eshelby model, in 1973, Mori and Tanaka also proposed their M–T model to assess the elastic modulus of a composite system having random fibre distribution. The Mori and Tanaka method (M–T method) simulates the interaction between inhomogeneities that occurred in the fibres distribution and helps in determining the practical characteristics of a single inhomogeneity contained inside an infinite matrix. “The M–T model is particularly efficient in calculating the effective properties in two-phase composites with smaller volume fractions of reinforcement.” The M–T model of a fibre-reinforced composite system is determined in terms of stress and strain as follows:

248

R. Kumar et al.

σ = M(ε)

(17)

The effective elastic modulus M is given as follows: M = (Vm Mm + Vf Mf A)(Vm I + Vf (A))−1

(18)

where I denotes the fourth-order identity tensor, M m and M f show the fourth-order elasticity tensor of fibre and the matrix material. V f and V m denote the volume fractions of fibre and matrix material [29].

3 Finite Element Modelling Approach Finite element modelling (FEM) or finite element analysis (FEA) is a mathematical modelling and simulation (M&S) tool that helps in predicting the behaviour of the material in real-life scenarios for their end-use application. This is achieved by incorporating the required material properties as well as defining the necessary boundary conditions for the same. The FEM or FEA approach is a tool that provides in developing a virtual experimentation strategy for estimating the behaviour of the material or product in a real-time scenario. The estimated simulation results are obtained in the form of various graphs and charts that is easily understandable by end users [30–32]. The most accurate solution can be achieved by incorporating multiple iterations, and this leads to the downfall in product development time and enhancements in product lifetime [33, 34]. The finite element simulation is carried out in three stages, such as (i) preprocessing, (ii) solution, and (iii) post-processing. The associated sections under these stages can be seen the Fig. 3.

Fig. 3 Schematic of associated stages in finite element modelling and simulation

A Critical Review on Finite Element Models Towards …

249

The preprocessing stage is the most important stage in any FE simulation procedure. This stage is responsible for the quality of the simulation and the accuracy of the results. Here, the geometry modelling assigns material properties. Selection of elements for geometry discretization under meshing the geometry is done. Further, the load is assigned to the geometrical model, and the associated constraints and boundary conditions, as well as the required output parameters, are defined as per the requirement of geometry analysis [35]. In the solution step, the finite element calculations are made based on the defined parameters under the preprocessing stage. On the basis of the defined preprocessing parameters, “the finite element software module assembles all the governing equations in matrix form and calculates the values of the primary variables that are further substituted and computed to calculate other variables.” Further, in the last stage of post-processing, the final results are obtained through the FEA procedure. Here, the various components of the software module are responsible for various sorting and plotting of solutions results [36].

4 Finite Element Modelling of Natural Fibres Composite Various properties estimations and the materials’ performance prediction can be made using the finite analysis approach. In the modern research scenario, diversified modelling and simulations are performed under various analysis types, namely “multi-physics analysis electromagnetic analysis, electrical analysis, buckling analysis, electromagnetic analysis, heat transfer analysis, fluid analysis, thermal analysis, structural analysis, and acoustic.” However, even if any product is manufactured and tested through virtual simulation still mechanical testing is equally essential for its performance under real-time scenario. Hence, in modern research practice, many researchers are focussed on analyzing the mechanical behaviour of the end product. Therefore, as composite manufacturing is replacing traditional materials in end-use application due to their enhanced and diversified mechanical and physical characteristics, researchers are focussing on finite element modelling and simulation of natural fibre composites [37–43]. In the FEM procedure, the accuracy of results also depends upon the types of geometry created. However, one can analyze the one, two, or threedimensional geometry in FE simulation software, but three-dimensional geometry gives comparatively better and more accurate results. Further, the matrix and natural fibres are required to be fed into the M&S software to specify the types of analysis needed to perform [44, 45]. For analyzing the mechanical behaviour of a natural fibre-reinforced matrix composites, certain inherent mechanical properties such as Young’s modulus, density, Poisson’s ratio, shear modulus, elongation at break etc. are to be considered. These mechanical parameters are fed with the types of material (i.e. orthotropic or isotropic), and we are interested to analyze [1]. However, it is difficult to define the orthotropic characteristics of a newly formed natural fibre composite. Hence, many researchers consider their material isotropic for ease of modelling and simulation.

250

R. Kumar et al.

In the present scenario of computer-aided research based on modelling and simulation approach, FEA has played a vital role. Various FEA tools, such as “ANSYS, NASTRAN, ABAQUS, COMSOL, LS DYNA, IDEAS, NX, and SIEMENS PLM”, are available commercially as well as for their academic use. MATLAB nowadays has become one of the finest tools that provide a fantastic numerical modelling environment with ease of optimization solvers. ABAQUS possesses a very sophisticated capability in geometry modelling, a huge library of different materials, and limited support and provides judicious control in geometry meshing during preprocessing stage [46]. Similarly, ANSYS workbench and other ANSYS analysis modules produce a user-friendly environment towards ease of applications and analysis. It also provides a very sophisticated material library and includes automated meshing and thin-sweep meshing options for better accuracy of results. A comparison of the capabilities of different modules in ANSYS and ABAQUS software packages can be systematically found in [47]. Therefore, every software package is associated with various modules that are capable of solving problems differently. In this context, using multiple S&M software packages, various NFRCs have been numerically solved in terms of their associated physicomechanical characteristics estimations.

5 Representative Volume Element (RVE) In a composite structure, the microstructures can be visualized using a “volume element” known as the representative volume element (RVE). Through RVE, the entire microstructure can be represented via a small virtual specimen. It can be utilized in the characterization of computational micromechanics [48]. RVE entails analyzing the performance of a unit cell natural fibre composites or a composite structure at the nanoscale, microscale, or macroscale. The “periodic boundary condition (PBC), homogeneous boundary condition (HBC), and displacement boundary condition” are the three main 3D RVE boundary conditions [34]. The simulation outputs characterize a macrostructure with repeating periodical cells when PBC is chosen. The simulation results, however, will regard the RVE itself to be the macrostructure and will take into account its micro-components if HBC is chosen [49]. The boundary conditions for the problems related to electrical conductivity include “an applied voltage on one face and a ground on the opposite.” This resulted in some current density within the RVE model, and the overall conductivity of the composite is calculated using that “current density, Ohm’s law, and the dimensions of the RVE.” The RVE of NFRCs is now being studied using a variety of tools, including “EasyPBC in ABAQUS and material designer in ANSYS” [50]. Further, in order to solve the RVE model and automatically define the associated RVE dimensions, mesh type, and most practicable mesh size, these tools need inputs from the end user in the form of material characteristics, fibre size, and volume percentage.

A Critical Review on Finite Element Models Towards …

251

6 Need for Bamboo and Bamboo Fibre Composites Natural fibres like jute, sisal, banana, flax, hemp, bamboo, etc., are preferred over synthetic fibres because they are more advantageous from an economic and environmental standpoint. Most bio-applications use biodegradable polymers like starch, protein, and cellulose [51–53]. Amongst many natural fibres occurring in nature, bamboo is considered one the most needful biomaterial that has been utilized since ancient times in many ways by humankind.

6.1 Environmental Concerns and Sustainability of Bamboo Bamboo offers several benefits in terms of sustainability because of the way it naturally grows and is harvested. Bamboo may grow in areas where timber cannot, such as on steep hillsides. Products made with bamboo have lower environmental costs than tropical hardwood. Compared to timber, bamboo produces a far higher output, particularly when used to make biofuel. Additionally, using bamboo instead of tropical hardwoods helps lessen the strain on those regions’ forests [54]. Bamboo may be harvested significantly more often than timber because of its quick growth [55]. In addition, bamboo absorbs carbon during growth and stores it when it is harvested. Given that bamboo can withstand the environment for 30–40 years when properly cared for, the sequestered carbon will be kept in check and will not be released into the atmosphere for the whole lifespan of the bamboo product [56]. Due to the manufacturing processes involved, traditional building materials like steel and concrete have large embodied energy [56]. It is obvious that the widespread utilization of bamboo as a building material would improve the sustainability of the globe.

6.2 Structural Importance of Bamboo The inherent variety in “raw culms and the anisotropic” characteristics of bamboo, which makes it challenging, are two of the key issues preventing the extensive utilization of bamboo in the building sector. Bamboo-reinforced composites can be developed to address these drawbacks. In this regard, Sharma and coworkers [57] reported that both bamboo scrimber and laminated bamboo (LB) exhibit extremely comparable qualities in “tension, compression, and shear parallel to the grain, with LB surpassing bamboo scrimber (BS)” in the ability to withstand post-peak load deformation. The two designed bamboo products are extremely comparable when comparing the qualities perpendicular to the grain. However, BS is twice as powerful when compressed. The BS exhibits excellent strength characteristics in every direction except the shear direction that is parallel to the grain. The investigation also indicates that the LB possesses an appreciable flexural strength-to-density ratio.

252

R. Kumar et al.

Stepping ahead in analyzing the mechanical characteristics of engineered bamboo, Sharma and coworkers investigated and reported the mechanical characteristics of laminated composites under various processing techniques. They employ two processing techniques: bleaching and caramelization. Previously, literature shows very limited studies that have been carried out to analyze the impact of processing on bamboo that largely focussed on using full-culm raw bamboo outside of structural applications. The specimens are put through “compression, tension, shear, and flexion tests. Specimens include Sitka spruce, Douglas fir, raw bamboo, bleached bamboo, semi-caramelized bamboo, and caramelized bamboo.” Although the specimens’ compressive and shear strengths rise with processing and treatment, their tensile strength decreases. Further processing and treatment also significantly boost the bending modulus. Further, the hydrothermal characteristics of bamboo were also examined by Huang et al. [58] and reported in relation to wood metrics that are commonly available in databases. According to their findings, bamboo resembles hardwood more closely than the softwood that is most frequently used in wood-based panels. The investigation findings reveal that bamboo surpasses wood in terms of heat storage and vapour resistance. However, bamboo does not conduct heat, as well as lumber does. In hotter or more temperate temperatures, such as those found in areas where bamboo is naturally found, research has shown that bamboo performs better than timber for lightweight construction. As a result, the research that is now accessible highlights the promising qualities of modified bamboo, which demonstrates how its processing can alter the specimens for specific needs. However, the majority of the test subjects were laminates, panels, and boards made for flooring and surface applications. Currently, bamboo is more well-established for these applications; nonetheless, there are still few technical applications of bamboo in load-bearing structural components [59].

7 Finite Element Modelling and Analysis of Bamboo Fibres Bamboo is one of the significant renewable lignocellulosic materials. Around 2.5 billion people worldwide rely on bamboo for a variety of goods and means of their survival. Compared to wood, bamboo has recently become a significant “source of renewable natural lignocellulosic fibre for high-value products.” The world is home to more than 1250 different species of bamboo, all of which are tropical or subtropical with the exception of Europe and West Africa. In tropical and subtropical regions, bamboo makes up about 25% of the total biomass. Bansal and Zoolagud [60] reported the growth and availability of bamboo in India. About a billion people reside in bamboo homes around the world. The culm of bamboo is comparable to a tree’s trunk, which possesses a hollow interior region known as the cavity. The thickness of the wall is what distinguishes the cavity from the culm. Diaphragms, nodes on the outside of the culms, divide the cavities from one another. An internode is the section of culm that lies between two nodes. For many decades, humankind has been using bamboo

A Critical Review on Finite Element Models Towards …

253

as their primary source of structural materials, and many researchers have established the relations between the structural properties and behaviour of bamboo. Hence, it is important to investigate the mechanical properties of bamboo fibre or bamboo fibresreinforced composite materials for end-use applications. As far as we are concerned about the mechanical estimation behaviour of bamboo fibres-reinforced composites through the finite element modelling and simulation (FEMS) approach. Stepping ahead to this approach, Chand and coworkers [61] have reported the investigation of the tensile strength of bamboo fibres having the orientation of fibres “parallel and perpendicular to the fibre direction.” The investigation was carried out in both experimental and simulation modes. The FEMS tool ABAQUS was employed to calculate the “stress and strain values of bamboo under the action of tensile loads, and failure load patterns” have been developed and examined. Experimentally determined results of flexural strength and deflection of bamboo fibres appreciably match the values produced by the FEM. A similar simulative study was carried out to estimate the tensile properties of bamboo yarn and is reported by Li and coworkers [62]. In the study, the tensile properties were analyzed at varying tensile speeds. The study observed that at varying tensile speeds in the range of 100–3000 mm/min, the increasing trend in the breaking strength of the yarn was found, but the tensile strength was found to be at a significantly decreasing trend. Further, a similar study was carried out to estimate the tensile elastic properties of engineered bamboo boards. Li and coworkers [63] investigated and reported the tensile elastic properties of an engineered bamboo panel (EBP). The analysis was carried out through an image information system of bamboo strips. The work contains the geometrical modelling as the representative volume element using micromechanics definition. Based on the geometric information and elastic parameters, the mechanical properties of the said bamboo composite were modelled using the finite element modelling approach. The ultimate aim of this investigation was to develop a fast and efficient practical method to determine the mechanical properties of commercially available bamboo boards. In many research applications, strength and stiffness characteristics are the prime importance during the development of engineering parts. Abhilash et al. [1] reported the tensile elastic modulus and strength of bamboo-reinforced polypropylene composite. The article discusses various micromechanical theoretical models in order to establish a correlation between the best possible model with the performed experimentation. Here, the elastic modulus values obtained experimentally and those anticipated by the “Halpin–Tsai” model agreed closely. Strength as determined using the “Kelly–Tyson” model, likewise closely matched the actual results. The findings are compared with experimentally obtained values for the “micromechanics-based semi-analytical “Mori–Tanaka” model in Digimat-MF (mean-field homogenization) and the numerical finite element modelling (FEM) of BPC utilizing the concept of representative volume element (RVE).” Stepping ahead towards the finite element modelling analysis of bamboo fibre composite structures, Eskezia et al. [64] have evaluated the FEA-based results for an internal door panel of a car and reported its performance. The work contains the transient dynamic structural analysis through the FEM procedure in terms of stress and

254

R. Kumar et al.

displacement analysis. The work contains the 3D model of the door panel developed in the CATIA V5 R20 environment and imported under the ANSYS 15.0 workbench analysis environment. The self-inertial weight produced due to the acceleration field was utilized for assigning the load. Finally, the equivalent stress and displacement were noted to investigate the comparative study with the previous literature. Much research on bamboo composite in terms of their structural importance has been regarded as the prime focus of researchers and the scientific community. In this regard, Richardson and coworkers [59] have reported the nonlinear modelling of the bamboo composites and carried out the buckling analysis to determine the response of the composite under axial loading conditions. The investigation contains the finite element modelling and simulation of advanced bamboo composite-based column structure in the ABAQUS software package. Bamboo-reinforced composite structures possess inherent significant mechanical properties comprising a certain degree of engineering processing. The work comprises different numerical modelling to estimate the behaviour of bamboo composite under axial compressive loading. Different modelling “elements and imperfection parameters” were considered and implemented in several FEA models. Insights about the potential of results that can be acquired through numerical modelling are provided by comparing the results to empirical findings. This made it possible to assess the model’s assumptions and methodology. Only slight variations were found between the load at rupture and displacements calculated by the computational model and the experimental results. A similar study on buckling and post-buckling analysis of bamboo-reinforced composite (BRCP) plates was evaluated and reported by Kasim and coworkers [65]. The analysis was carried out first for the linear bucking analysis under the action of compressive load. The determined critical load was further utilized in the nonlinear post-buckling analysis. During both linear and nonlinear analysis, the effect of BRCP thickness under the cross-ply and angle-ply orientations of fibres was also considered. The results produce an appreciable agreement with the past results, and the investigation found a significant increase in aspect ratio as well as highlights the increased value of the critical load. Since bamboo is a naturally occurring material that possesses a very complex surface structure than man-made composite. In order to improve the “bonding strength between layers and prevent non-uniformity in stress concentration,” it can be anticipated that the change in characteristics along the thickness of the culm will follow a smooth transition due to optimization. As a result, biological structures are complex and possess gradient structures. Therefore, a realistic model that can accurately represent bamboo’s mechanical performance will be useful in developing strong, multipurpose composites in the future, keeping this view, Askarinejad and coworkers [66] did their research. The experimental and numerical findings of the torsional (shear) characteristics of bamboo are presented in this work. Laser scanning and atomic force microscopy (AFM) were utilized to show the hierarchical and multiscale structure of bamboo as well as the dispersion of microscale fibres. In order to examine the mechanical performance of bamboo under torsion and to calculate the shear modulus of bamboo along the fibre’s direction, this data was incorporated

A Critical Review on Finite Element Models Towards …

255

into a finite element modelling procedure. Moreover, it was found that the presence of water content and humidity produce a significant effect on the mechanical characteristics of bamboo during the torsion test. Further, because of degradation caused by many factors like corrosion, poor detailing, failure of bonding between beam-column joints, rise in service loads, etc., many old reinforced concrete structures worldwide urgently require rehabilitation, repair, or reconstruction. Therefore, natural fibre-reinforced composite has gained wide acceptance as a possible alternative for maintaining and strengthening the RCC structures. In this regard, bamboo fibre-reinforced composites have attracted special interest amongst many other natural fibres because they have excellent impact strength in addition to having moderate tensile and flexural capabilities. In this way, Sen et al. [67] have carried out a nonlinear finite element analysis in order to assess how well bamboo fibre-reinforced polymer performs in structural retrofitting when used to repair a plain concrete block. Compared to controlled specimens, the reinforced specimens show a notable improvement in strength, stiffness, and stability. Further, for establishing a material’s heat-insulating value in specialized applications such as walls, partitions, roofs, etc., thermal conductivity is one of the key qualities. A number of polymer composites filled with metallic fillers and inorganic fillers have had their thermal conductivity studied. It has been shown that the thermal conductivity of composite materials is significantly lower than that of metals and ceramics. In order to get composites for appropriate applications, several researchers have focussed on predicting the heat conductivity of composites. To test the heat conductivity of polymer composites, many experimental procedures, such as the hot-wire method and Lee’s disc method, are available. The simplest way is the Lee disc method, which is employed with poor conducting materials. In this regard, Jena and coworkers [68] investigated and reported the thermally insulated property of cenosphere-reinforced bamboo fibre composite material. In this work, the author has incorporated the varying weight fraction of cenosphere, which is a mixture of alumina and silicon-rich industrial wastes obtained from thermal power plants during the burning of pulverized coal, as a filler material in composite manufacturing. The thermal insulating property of such fillers has gained enormous attention in their utilization in the insulating property. The author reported the thermal conductivity of these composites through the finite element approach that established an appreciable agreement with the carried experimentation. In another study, Chandana and Altaf Hussian [69] reported the thermal conductivity of the bamboo-reinforced epoxy composites developed by the traditional hand layup techniques. In the article, the experimental procedure was carried out to determine the thermal conductivity, as well as the results obtained were further validated by the rule of mixtures, E-S composite modelling, and the FEM approach. Thus, various finite element modelling and simulation procedures have been adopted to estimate the various mechanical and thermal characteristics of the bamboo fibres-reinforced composite materials.

256

R. Kumar et al.

8 Results and Discussion Various models were adopted for investigating the behaviour of natural fibre composites theoretically discussed in much research literature that has been published in the past. The analytical approach mostly discusses the one-dimensional and three-dimensional models. The literature survey highlights that various models such as “Tsai–Wu, Tsai–Hill, Mendels et al. stress transfer, fatigue-life (S–N) curves, and Hirsch were used to study stiffness, elastic modulus, strength, and fatigue-life response. However, a variety of analytical theories were also involved in the analysis of the mechanical, thermal, and acoustic properties” of NFRCs. Due to the FEA and RVEs’ excellent accuracy in predicting the characteristics of composite materials, these methods are typically used in numerical analytic research. Other than using numerical techniques, several studies have used analytical theories, including the ROM, Chamis model, Fick’s law, Hamilton’s principle, Halpin–Tsai model, and Hashin and Rosen model. Numerous research mostly focussed on numerically assessing the mechanical characteristics of NFRCs. Further, different composite modellings, such as the rule of mixtures, Halpin–Tsai, and Eshelby model, were adopted to predict mechanical behaviour, such as tensile elastic properties and physical properties of the NFRCs. Many works of the literature suggest that out of many modelling approaches, the Halpin–Tsai model exhibited appreciable and higher accuracy than the micromechanical modelling model [25, 50, 70–74]. The FEA and RVEs were heavily applied in NFRCs numerical investigations. However, few studies also employed analytical methods in addition to the FEA. As a result, ANSYS, with its solisd and shell components, is the most widely used FEA tool for performing M&S of NFRCs. Many boundary conditions were taken into account, including PBCs in RVE, simply supported, clamped, and free boundary conditions. ANSYS has been employed for numerical solutions and is found to be the most promising tool. The majority of researchers studied the 3D solid model, which includes a variety of element types, such as “wedge elements (C3D6), linear hexahedral elements (C3D8R), quadratic tetrahedral elements (C3D10), SHELL 181, Solid 95, Solid 185, Solid 186, and Solid 187.” Several optimization methods were introduced, such as the “genetic algorithm, TOPSIS, parametric optimization, and APDL.” The application of these approaches demonstrated their dependability and efficacy. Very few studies have included the design of experiments (DOE) using the Taguchi optimization approach for selecting the various parameters at various levels. In this regard, the study of the physical and abrasive wear characteristics has been analyzed and reported by Eagala and coworkers [75]. A similar algorithm has also been incorporated by Prabhu et al. [76] in order to investigate the alkaline treatment in fibre length on the mechanical properties of short bamboo fibres-reinforced composites. More mechanical performance may be examined by FEA at a cheaper cost than experimental testing. For instance, Davoodi et al. [77] used the Catia and Abaqus platforms to numerically analyze the impact characteristics of a hybrid compositebased automobile bumper.

A Critical Review on Finite Element Models Towards …

257

9 Conclusion The present article provides a comprehensive review and includes various works carried out in recent scenarios to estimate the mechanical and thermal properties of bamboo fibres-reinforced composites. The present study found that various experiments and analytical methods have been adopted in the past to estimate the properties of natural fibre composites as well as bamboo fibre composites. Further, the estimated results in experimentation and through the analytical procedure are further validated through the finite element analysis approach. Most studies, taking into account both numerical and analytical investigations, concentrated on the mechanical characteristics of NFRCs, such as tensile, flexural, and impact. In contrast, only a small number of studies considered took into account moisture absorption, thermal, and acoustic properties. Various works have taken place to estimate the mechanical properties of bamboo composites, considering them a structural material. However, most of the works on NFRCs have been carried out in the past in terms of their theoretical modelling, and very few studies in bamboo composites through the finite element approach occurred. Most numerical modelling and FEM simulation approaches were adopted to predict the thermal, mechanical, and acoustic behaviour of bamboo composites or NFRCs.

References 1. Abhilash RM, Venkatesh GS, Chauhan SS (2021) Micromechanical modeling of bamboo short fibre reinforced polypropylene composites. Multiscale Multidiscip Model Exp Des 4(1):25–40. https://doi.org/10.1007/s41939-020-00081-3 2. Kim HG, Kwac LK (2009) Evaluation of elastic modulus for unidirectionally aligned short fibre composites. J Mech Sci Technol 23(1):54–63. https://doi.org/10.1007/s12206-008-0810-1 3. Ashwini K, Mohan Rao CV (2018) Design and analysis of leaf spring using various composites—an overview. Mater Today Proc 5(2):5716–5721. https://doi.org/10.1016/j.matpr.2017. 12.166 4. Koronis G, Silva A, Fontul M (2013) Green composites: a review of adequate materials for automotive applications. Compos Part B Eng 44(1):120–127. https://doi.org/10.1016/j.compos itesb.2012.07.004 5. AL-Oqla FM, Sapuan SM (2014) Natural fibre reinforced polymer composites in industrial applications: feasibility of date palm fibres for sustainable automotive industry. J Clean Prod 66:347–354, Mar 2014. https://doi.org/10.1016/j.jclepro.2013.10.050 6. Singh S, Deepak D, Aggarwal L, Gupta VK (2014) Tensile and flexural behavior of hemp fibre reinforced virgin-recycled HDPE matrix composites. Procedia Mater Sci 6:1696–1702. https:// doi.org/10.1016/j.mspro.2014.07.155 7. Sailesh A, Arunkumar R, Saravanan S (2018) Mechanical properties and wear properties of Kenaf—Aloe Vera—Jute fibre reinforced natural fibre composites. Mater Today Proc 5(2):7184–7190. https://doi.org/10.1016/j.matpr.2017.11.384 8. Alves C et al (2010) Ecodesign of automotive components making use of natural jute fibre composites. J Clean Prod 18(4):313–327. https://doi.org/10.1016/j.jclepro.2009.10.02 9. Naresh Kumar S, Venkatesh D, Subbaratnam B, Shekar M (2020) Mechanical testing and numerical analysis of flax/glass epoxy hybrid composite material. IOP Conf Ser Mater Sci Eng 998(1). https://doi.org/10.1088/1757-899X/998/1/012032

258

R. Kumar et al.

10. Kiruthika AV (2017) A review on physico-mechanical properties of bast fibre reinforced polymer composites. J. Build. Eng. 9:91–99. https://doi.org/10.1016/j.jobe.2016.12.003 11. Mallampati M, Raju BN, Krishna TM (2018) Evaluation of mechanical properties of rice straw fibre polypropylene composites. AIP Conf Proc 1980:10–14. https://doi.org/10.1063/1. 5044282 12. Madival AS, Doreswamy D, Handady SA, Hebbar KR, Lakshminarayana SK (2022) Investigation of the mechanical and liquid absorption properties of a rice straw-based composite for ayurvedic treatment tables. Materials (Basel) 15(2). https://doi.org/10.3390/ma15020606 13. Safri SNA, Sultan MTH, Jawaid M, Jayakrishna K (2018) Impact behaviour of hybrid composites for structural applications: a review. Compos Part B Eng 133:112–121. https://doi.org/10. 1016/j.compositesb.2017.09.008 14. Vigneshwaran S et al (2020) Recent advancement in the natural fibre polymer composites: a comprehensive review. J Clean Prod 277:124109. https://doi.org/10.1016/j.jclepro.2020. 124109 15. Ku H, Wang H, Pattarachaiyakoop N, Trada M (2011) A review on the tensile properties of natural fibre reinforced polymer composites. Compos Part B Eng 42(4):856–873. https://doi. org/10.1016/j.compositesb.2011.01.010 16. Fan J, Grande CD, Rodrigues DF (2017) Biodegradation of graphene oxide-polymer nanocomposite films in wastewater. Environ Sci Nano 4(9):1808–1816. https://doi.org/10.1039/C7EN00 396J 17. Alvarez-valencia D, Dagher HJ, Roberto A, Davids WG, Gardner DJ (2009) Behavior of natural-fibre/thermoplastic sheet piling, pp 1–16 18. El-Sabbagh A, Taha I, Taha R (2011) Prediction of the modulus of elasticity of short fibre reinforced polymer composites by finite element modelling. Polym Polym Compos 19(9):733– 742. https://doi.org/10.1177/096739111101900903 19. Xiong X, Shen SZ, Hua L, Li X, Wan X, Miao M (2018) Predicting tensile behaviors of short flax fibre-reinforced polymer–matrix composites using a modified shear-lag model. J Compos Mater 52(27):3701–3713. https://doi.org/10.1177/0021998318769128 20. Jagath Narayana K, Burela RG (2019) Multi-scale modeling and simulation of natural fibre reinforced composites (Bio-composites). J Phys Conf Ser 1240(1). https://doi.org/10.1088/ 1742-6596/1240/1/012103 21. Agarwal BD, Broutman LJ, Chandrashekhara K (1992) Analysis and performance of fibre composites (second edition). 151(1) 22. Chen XL, Liu YJ (2004) Square representative volume elements for evaluating the effective material properties of carbon nanotube-based composites. Comput Mater Sci 29(1):1–11. https://doi.org/10.1016/S0927-0256(03)00090-9 23. Sheng N, Boyce MC, Parks DM, Rutledge GC, Abes JI, Cohen RE (2004) Multiscale micromechanical modeling of polymer/clay nanocomposites and the effective clay particle. Polymer (Guildf) 45(2):487–506. https://doi.org/10.1016/j.polymer.2003.10.100 24. Schmachtenberg E, Brandt M (2006) Mechanical design of injection moulded parts made of short-fibre reinforced thermoplastics by means of integrative simulation. J Polym Eng 26(2–4), May 2006. https://doi.org/10.1515/POLYENG.2006.26.2-4.179 25. Facca AG, Kortschot MT, Yan N (2006) Predicting the elastic modulus of natural fibre reinforced thermoplastics. Compos Part A Appl Sci Manuf 37(10):1660–1671. https://doi.org/10. 1016/j.compositesa.2005.10.006 26. Haghighat M, Zadhoush A, Khorasani SN (2005) Physicomechanical properties of α-cellulosefilled styrene-butadiene rubber composites. J Appl Polym Sci 96(6):2203–2211. https://doi.org/ 10.1002/app.21691 27. Affdl JCH, Kardos JL (1976) The Halpin-Tsai equations: a review. Polym Eng Sci 16(5):344– 352. https://doi.org/10.1002/pen.760160512 28. Tucker CL III, Liang E (1999) Stiffness predictions for unidirectional short-fibre composites: review and evaluation. Compos Sci Technol 59(5):655–671. https://doi.org/10.1016/S02663538(98)00120-1

A Critical Review on Finite Element Models Towards …

259

29. Budarapu PR, Zhuang X, Rabczuk T, Bordas SPA (2019) Multiscale modeling of material failure: theory and computational methods, 1st ed, vol 52. Elsevier Inc 30. Zhong B, Li C, Li P (2020) Modeling and vibration analysis of sectional-laminated cylindrical thin shells with arbitrary boundary conditions. Appl Acoust 162:107184. https://doi.org/10. 1016/j.apacoust.2019.107184 31. Liu T, Wang A, Wang Q, Qin B (2020) Wave based method for free vibration characteristics of functionally graded cylindrical shells with arbitrary boundary conditions. Thin-Walled Struct 148:106580. https://doi.org/10.1016/j.tws.2019.106580 32. Gao W, Qin Z, Chu F (2020) Wave propagation in functionally graded porous plates reinforced with graphene platelets. Aerosp Sci Technol 102:105860. https://doi.org/10.1016/j.ast.2020. 105860 33. Li C, Li P, Zhong B, Wen B (2019) Geometrically nonlinear vibration of laminated composite cylindrical thin shells with non-continuous elastic boundary conditions. Nonlinear Dyn 95(3):1903–1921. https://doi.org/10.1007/s11071-018-4667-2 34. Rahman MZ (2017) Mechanical performance of natural fibre reinforced hybrid composite materials using finite element method based micromechanmincs and experiments. J Chem Inf Model 53(9):1689–1699 35. Yu W (2016) An introduction to micromechanics. Appl Mech Mater 828:3–24. https://doi.org/ 10.4028/www.scientific.net/AMM.828.3 36. Poudel A (2019) Finite element method: introduction and steps of finite element analysis. https://geniuserc.com/finite-element-method-introduction-and-steps-of-finite-element-ana lysis/. Accessed on 25 Oct 2022 37. Abu Seman SAH, Ahmad R, Md Akil H (2019) Experimental and numerical investigations of kenaf natural fibre reinforced composite subjected to impact loading. Polym Compos 40(3):909–915, Mar 2019. https://doi.org/10.1002/pc.24758 38. Bazli M, Ashrafi H, Jafari A, Zhao XL, Raman RS, Bai Y (2019) Effect of fibres configuration and thickness on tensile behavior of gfrp laminates exposed to harsh environment. Polymers (Basel) 11(9):1401, Aug 2019. https://doi.org/10.3390/polym11091401 39. Chen Y, Xin L, Liu Y, Guo Z, Dong L, Zhong Z (2019) A viscoelastic model for particlereinforced composites in finite deformations. Appl Math Model 72:499–512. https://doi.org/ 10.1016/j.apm.2019.03.033 40. Dong C (2019) Mechanical properties of natural fibre-reinforced hybrid composites. J Reinf Plast Compos 38(19–20):910–922. https://doi.org/10.1177/0731684419856686 41. Hu D, Dang L, Zhang C, Zhang Z (2019) Mechanical behaviors of flax fibre-reinforced composites at different strain rates and rate-dependent constitutive model. Materials (Basel) 12(6):854. https://doi.org/10.3390/ma12060854 42. Alioua T, Agoudjil B, Boudenne A (2019) Numerical modelling and experimental study of heat and moisture properties of a wall based on date palm fibres concrete. E3S Web Conf 85:02009, Feb 2019. https://doi.org/10.1051/e3sconf/20198502009 43. Su J, Zheng L, Deng Z (2019) Study on acoustic properties at normal incidence of threemultilayer composite made of glass wool, glue and polyurethane foam. Appl Acoust 156:319– 326. https://doi.org/10.1016/j.apacoust.2019.07.016 44. Qin J-L, Qiao W-G, Lin D-G, Zhang S, Wang J-Y (2019) Mechanical properties and numerical analyses of basalt fibre crumb rubber mortars in soft rock roadways. Adv Civ Eng 2019:1–13. https://doi.org/10.1155/2019/5159094 45. Ma P, Jin L, Wu L (2019) Experimental and numerical comparisons of ballistic impact behaviors between 3D angle-interlock woven fabric and its reinforced composite. J Ind Text 48(6):1044– 1058. https://doi.org/10.1177/1528083718754903 46. Sun X et al (2019) Fracture performance and numerical simulation of basalt fibre concrete using three-point bending test on notched beam. Constr Build Mater 225:788–800. https://doi. org/10.1016/j.conbuildmat.2019.07.244 47. Meyghani B, Awang MB, Emamian SS, Mohd Nor MKB, Pedapati SR (2017) A comparison of different finite element methods in the thermal analysis of friction stir welding (FSW). Metals (Basel) 7(10):1–23. https://doi.org/10.3390/met7100450

260

R. Kumar et al.

48. Fr˛acz W, Janowski G (2019) Predicting effect of fibre orientation on chosen strength properties of wood-polymer composites. Compos Theory Pract 19(2):56–63 49. Jiang W-G, Zhong R-Z, Qin Q, Tong Y-G (2014) Homogenized finite element analysis on effective elastoplastic mechanical behaviors of composite with imperfect interfaces. Int J Mol Sci 15(12):23389–23407. https://doi.org/10.3390/ijms151223389 50. Adeniyi AG, Adeoye AS, Ighalo JO, Onifade DV (2021) FEA of effective elastic properties of banana fibre-reinforced polystyrene composite. Mech Adv Mater Struct 28(18):1869–1877. https://doi.org/10.1080/15376494.2020.1712628 51. Fragassa C (2016) Effect of natural fibres and bio-resins on mechanical properties in hybrid and non-hybrid composites, p 020118. https://doi.org/10.1063/1.4949693 52. George J, Sreekala MS, Thomas S (2001) A review on interface modification and characterization of natural fibre reinforced plastic composites. Polym Eng Sci 41(9):1471–1485. https:// doi.org/10.1002/pen.10846 53. dos Santos D, Tavares LB, Batalha G (2012) Mechanical and physical properties investigation of polyurethane material obtained from renewable natural source. J Achieve Mater Manuf Eng 54(2):211–217 54. Vogtländer J, van der Lugt P, Brezet H (2010) The sustainability of bamboo products for local and Western European applications. LCAs and land-use. J Clean Prod 18(13):1260–1269. https://doi.org/10.1016/j.jclepro.2010.04.015 55. Asif M (2009) Sustainability of timber, wood and bamboo in construction. In: Sustainability of construction materials, Elsevier, pp 31–54 56. Manandhar R, Kim J-H, Kim J-T (2019) Environmental, social and economic sustainability of bamboo and bamboo-based construction materials in buildings. J Asian Archit Build Eng 18(2):49–59. https://doi.org/10.1080/13467581.2019.1595629 57. Sharma B, Gatóo A, Bock M, Ramage M (2015) Engineered bamboo for structural applications. Constr Build Mater 81:66–73. https://doi.org/10.1016/j.conbuildmat.2015.01.077 58. Huang Z, Sun Y, Musso F (2017) Assessment of bamboo application in building envelope by comparison with reference timber. Constr Build Mater 156:844–860. https://doi.org/10.1016/ j.conbuildmat.2017.09.026 59. Richardson C, Mofidi A. Non-linear numerical modelling of sustainable advanced composite columns made from bamboo culms, pp 169–187, 202 60. Bansal AK, Zoolagud SS (2002) Bamboo composites: material of the future. 1(2):119–130 61. Chand N, Shukla M, Kumar M (2014) Analysis of mechanical behaviour of bamboo (Dendrocalamus strictus) by using FEM. Nov 2014, pp 37–41. https://doi.org/10.1080/154404708019 28970 62. Li L (2012) Tensile properties of regenerated bamboo yarn. 1(90):20–22 63. Li Z, Zhang J, Xiao D, Xiao Y (2020) Estimation on tensile elastic properties of engineered bamboo boards with image information. In: The 2020 world congress on the 2020 structures congress (Structures 20), pp 25–28 64. Eskezia E, Abera A, Tilahun D (2017) Finite element analysis of internal door panel of a car by considering bamboo fibre reinforced epoxy composite. J Appl Mech Eng 6(1):1–6. https:// doi.org/10.4172/2168-9873.1000247 65. Mat Kasim FA, Roslan SAH, Rasid ZA, Yakub F, Hassan MZ, Yahaya H (2021) Post-buckling of bamboo reinforced composite plates. IOP Conf Ser Mater Sci Eng 1051(1):012040. https:// doi.org/10.1088/1757-899X/1051/1/012040 66. Askarinejad S, Kotowski P, Shalchy F, Rahbar N (2015) Effects of humidity on shear behavior of bamboo. Theor Appl Mech Lett 5(6):236–243. https://doi.org/10.1016/j.taml.2015.11.007 67. Sen T, Reddy HNJ (2011) A numerical study of strengthening of RCC beam using natural bamboo fibre. 3(5):707–713 68. Jena H (2017) Effect of cenosphere on thermal conductivity of bamboo fibre reinforced composites. Adv Mater Proc 2(2):97–102. https://doi.org/10.5185/amp.2017/207 69. Chandana E, Altaf Hussian D (2013) Thermal conductivity characterization of bamboo fibre reinforced in epoxy resin. IOSR J Mech Civ Eng 9(6):7–14

A Critical Review on Finite Element Models Towards …

261

70. Alhijazi M, Zeeshan Q, Qin Z, Safaei B, Asmael M (2020) Finite element analysis of natural fibres composites: a review. Nanotechnol Rev 9(1):853–875. https://doi.org/10.1515/ntrev2020-0069 71. Shinde SS, Salve AV, Kulkarni S (2017) Theoretical modeling of mechanical properties of woven jutefiber reinforced polyurethanecomposites. Mater Today Proc 4(2):1683–1690. https://doi.org/10.1016/j.matpr.2017.02.008 72. Rajkumar DR, Santhy K, Padmanaban KP (2021) Influence of mechanical properties on modal analysis of natural fiber reinforced laminated composite trapezoidal plates. J Nat Fibers 18(12):2139–2155. https://doi.org/10.1080/15440478.2020.1724230 73. José da Silva L, Hallak Panzera T, Luis Christoforo A, Miguel Pereira Dur L, Antonio Rocco Lahr F (2012) Numerical and experimental analyses of biocomposites reinforced with natural fibres. Int J Mater Eng 2(4):43–49. https://doi.org/10.5923/j.ijme.20120204.03 74. Joffre T, Miettinen A, Wernersson ELG, Isaksson P, Gamstedt EK (2014) Effects of defects on the tensile strength of short-fibre composite materials. Mech Mater 75:125–134. https://doi. org/10.1016/j.mechmat.2014.04.003 75. Eagala RY, Gopichand A, Raghavendra G, Ali S (2012) Abrasive wear behaviour of bambooglass fibre reinforced epoxy composites using Taguchi approach. Int J Adv Eng Technol 5(1):2231–1963 76. Prabhu R, Mendonca S, D’Souza R, Vas JP, Bhat T (2019) Application of Taguchi techniques to study the effect of alkaline treatment and fibre length on mechanical properties of short bamboo fibre reinforced epoxy composites. AIP Conf Proc 2080. https://doi.org/10.1063/1. 5092902 77. Davoodi MM, Sapuan SM, Ahmad D, Aidy A, Khalina A, Jonoobi M (2011) Concept selection of car bumper beam with developed hybrid bio-composite material. Mater Des 32(10):4857– 4865. https://doi.org/10.1016/j.matdes.2011.06.011

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo Raviduth Ramful

Abstract Being a natural material of complex and orthotropic nature, the fracture displayed by bamboo remains widely unsolved to date. The fracture of natural bamboo is contingent on several external factors ranging from environmental to physical ones such as maturity and humidity. To elucidate the intricate fracture mechanisms in bamboo, there is a need to suppress numerous variables observed in natural materials, namely natural defects, geometry, and other physical and mechanical characteristics. One proven technique, which has shown numerous benefits to probing further into the fracture mechanisms of natural composite materials like bamboo, is the finite element method (FEM). This chapter focuses on the state-of-the-art research involving FEM simulation which has been considered to elucidate the fracture mechanisms in whole culm bamboo. The contents of this chapter will also comprise research findings from recent studies conducted by the author in this field. The research findings, in the first instance, will cover the effects of contributing factors such as material inhomogeneity, thermal modification, and direction of loading on the fracture mechanisms of bamboo. Under-researched areas involving the associated effects of physical and geometrical factors on the fracture of bamboo requiring further application of FEM techniques are also covered. Despite its wide usage over the last decades, the advent of high-end FEM simulation capabilities could exert a key role in elucidating the complex fracture mechanisms in bamboo products and bamboo-inspired structures. Besides, FEM can as well be considered to optimize the material structure of similar bio-inspired and advanced composites in further research. Keywords Bamboo · Inhomogeneity · Orthotropic nature · External loading · Thermal modification · Finite element method (FEM) · Fracture mechanisms · Crack propagation

R. Ramful (B) Mechanical and Production Engineering Department, Faculty of Engineering, University of Mauritius, Réduit 80837, Republic of Mauritius e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 F. L. Palombini and F. M. Nogueira (eds.), Bamboo and Sustainable Construction, Environmental Footprints and Eco-design of Products and Processes, https://doi.org/10.1007/978-981-99-0232-3_10

263

264

R. Ramful

1 Introduction Natural materials still have wide considerations in our modern society as nonconventional materials for construction as well as in numerous other practical applications. Natural materials are sustainable, with significantly lower environmental impacts and a reduced carbon footprint, in comparison to conventional ones like steel and concrete. On the downside, the durability of these materials is impacted by their inherent nature which is prone to both natural degradation and limited strength due to load-induced cracks as outlined in Fig. 1. Materials in nature have unique structures given their diversity based on genus and species. Moreover, plant species tend to develop unique structure, which varies in terms of growth factors such as maturity and density, as they adapt to specific locations and climate conditions. The specific traits in the material structure result in complex and unique behaviour in the deformation behaviour of such materials. Comparably, the fracture mechanisms in bamboo are intricate and distinctive owing to its unique geometrical features and structural attributes [1–5]. The geometrical features of bamboo are unique, consisting of nodes, tapered wall sections, and internodal culm sections of varying wall thickness [6]. Besides, the structural attribute of

Fig. 1 Factors affecting bamboo quality

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

265

bamboo is distinct as it possesses a graded distribution of vascular bundles across its wall thickness. In contrast to conventional metallic materials with a homogeneous structure, natural materials display complex and diverse fracture behaviour. Evaluating the complex fracture behaviour through the experiment is limited to specific plant characteristics such as maturity, species, and location amongst others. The advent of high-end computational techniques in the past decades is enabling to solve complex investigations in material science which would have been otherwise lengthy and inefficient to solve conventionally. One such powerful computational technique is the finite element method (FEM).

1.1 Finite Element Modelling (FEM) Technique The finite element modelling is a proven technique that is widely employed in material science to investigate and elucidate the material deformation behaviour and fracture mechanisms of advanced materials, respectively.

1.2 Benefits of FEM Techniques Investigation of the complex deformation behaviour and failure mechanisms in natural composite materials tends to be limited by experiments given their nonlinearity and intricate nature [7, 8]. The FEM technique provides numerous benefits to investigate the durability limitations as a result of load-induced cracks in natural composite materials. FEM techniques enable the suppression of numerous variables observed in natural materials, namely natural defects, geometry, and other physical and mechanical characteristics. Moreover, the use of FEM to investigate natural materials can also be extended to investigate and predict the behaviour of advanced engineered materials such as laminates. This chapter aims to highlight key areas of concern whereby the application of FEM techniques can be impactful in elucidating otherwise unknown mechanisms about the durability of natural materials.

2 Investigating the Effect of Material Inhomogeneity on the Fracture Mechanisms of Bamboo by the Finite Element Method Natural materials like bamboo are susceptible to various modes of failure as a result of load-induced cracks as outlined in Fig. 1. Load-induced cracks can emerge from

266

R. Ramful

both internal and external modes of loading. Internal and external modes of loading, namely self-weight and wind, respectively, have a significant influence on the failure modes of bamboo as their mechanical characteristics are stretched to their limit. From past studies, the fracture mechanisms through the microstructure of bamboo have been widely investigated [9–13]. In contrast, only, sparse information is available on the effect of material inhomogeneity and distinctive geometrical features on its macroscopic fracture mechanisms. This study highlights key findings obtained from the investigation of material composition and geometrical attributes on the fracture mechanisms of bamboo culm in various modes of loading by FEM [14]. The investigation in this study was facilitated by the FEM to enable the investigation of intrinsic material composition, such as variation in orthotropic properties, which would have been otherwise tedious to achieve experimentally.

2.1 Determination of the Optimized Transverse Isotropy in Bamboo Culm 2.1.1

Material and Model

Information about the inherent characteristics for which bamboo is well renowned for resisting flexural deformation is limited in the literature. Numerical simulation was conducted in the first place to determine the optimized transverse isotropy developed in bamboo to resist bending loads [14]. FEM simulation was conducted on LS-DYNA (Livermore Software Technology, Livermore, CA, USA), in implicit mode. The maximum principal strain criterion, one of the fundamental criteria for evaluating material failure, was adopted to analyse the flexural deformation in bamboo. Prior to simulation, the elastic modulus in the longitudinal direction, E L , was determined experimentally by evaluating small clear specimens in a 3-point bending test on the Shimadzu EZ-S table-top universal testing instrument (Shimadzu Corporation, Kyoto, Japan) as shown in Fig. 2. Small clear specimens of Madake bamboo (Phyllostachys bambusoides) with average dimensions of 100 mm (longitudinal) × 8 mm (tangential) × 3 mm (radial) were considered. The distance between supports was fixed at 80 mm, and the supports and punch had radii of 2.5 mm. The experimental tests were conducted in a controlled environment at a temperature of 25 °C and relative humidity below 20%. An average modulus of elasticity of E L of 15 GPa was calculated following the evaluation of 10 specimens in a 3-point bending test at a cross-head speed of 2 mm/min, as shown in Fig. 3 [14]. From the literature, the approximate orthotropic specification of bamboo in terms of longitudinal-to-transverse bending stiffness ratio (E L –E T ) was taken as 100:1 [1, 15–17]. The corresponding modulus of elasticity in the tangential direction, E T , was first approximated from this ratio. Given the negligible difference prevailing between

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

267

Fig. 2 3-Point bending test setup in the Shimadzu EZ-S table-top universal testing equipment

Fig. 3 Results of modulus of elasticity, E L

the radial and tangential directions, the orthotropic material model was simplified into a transversely isotropic model. Similar material constants in the radial and tangential directions were thus considered. For a Poisson’s ratio, ν L of 0.3 taken from past literature [18], ν T , GL , and GT were calculated based on the following isotropic material formulations: νi j ν ji = , i, j = L , T (i /= j ) Ei Ej The relationship between ν L and ν T in transversely isotropic material is given by the following expressions:

268

R. Ramful

Table 1 Material parameters corresponding to the longitudinal-to-transverse bending stiffness ratio (E L –E T ) of 100:1 Elastic material parameters

Orthotropic material parameters

Elastic modulus (MPa)

Poisson’s ratio

Elastic modulus (MPa)

Poisson’s ratio

Shear modulus (MPa)

E

ν

EL

ET

νL

νT

GL

15,000

0.3

15,000

150

0.3

0.003

147

√ −1 < νT < 1, −

√ EL < νL < ET

E L E T VL2 1 − νT , < ET EL 2

Finally, GL and GT were determined by considering the following expressions: Gi j =

Ei E j , i, j = L , T (i /= j ) E i + E j + 2E j νi j GT =

ET 2(1 + νT )

The material parameters corresponding to the longitudinal-to-transverse bending stiffness ratio (E L –E T ) of 100:1 for a material density of 700 kg/m3 are summarized in Table 1. Moreover, the deformation behaviour of the inhomogeneous material model was compared with a similar geometrical model and was assigned isotropic elastic material parameters. The isotropic elastic model was referred to as a homogeneous material model, and their corresponding material parameters are summarized in Table 1 [14].

2.1.2

Geometrical Modelling and Boundary Conditions

The numerical simulation to determine the transverse isotropy in bamboo was conducted by considering an internodal portion of the culm section. The physical model of the internodal section was constructed based on the morphological data of Madake bamboo. The outer diameter, wall thickness, and internodal length were taken as 100, 12, and 450 mm, respectively, which corresponded to an internode count of 18. A half-solid cylindrical model was considered based on symmetry to reduce the computational load. The node was taken as a rigid section and was consequently assigned material parameter settings of high elasticity. Figure 4 shows the outline of the test setup in bending mode to determine the optimized transverse isotropy developed in bamboo culm [14]. A localized displacement of 5 mm, aligned with the fibre direction, at the bottom corner of the rigid section, was applied to simulate the bending behaviour. Other

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

269

Fig. 4 a Bending deformation due to external loading in natural bamboo; b boundary condition in bending mode setup. Adapted from Ramful and Sakuma [14], License CC BY

Fig. 5 a Longitudinal-radial and b radial-tangential sectional views of FE meshed model

boundary conditions involved restraining the movement at the wall end in the zdirection and applying a node constraint in the radial direction at the neutral axis to simulate the curvature due to bending in the internode section. The final model was meshed on finite element modelling and post-processing software (FEMAP) (Siemens Digital Industries Software, Plano, TX, USA), by applying a hexahedral mesh solid. The model was discretized into 53,951 nodes and 47,100 elements, as shown in Fig. 5 [14].

2.1.3

Results

The deformation behaviour of both material models, as shown in Fig. 6 in terms of their maximum principal strain distribution, was selected at the same specific state.

270

R. Ramful

Fig. 6 Fringe component of maximum principal strain in: a homogeneous model; b inhomogeneous model [14]

From Fig. 6, both models displayed distinctive variations in the circumferential distribution of maximum principal strain. From Fig. 6b, ovalization due to bending could be observed in the inhomogeneous model. This led to the highest maximum principal strain distribution at the neutral axis of the outermost surface and at the inner surface of both the convex and concave sides of the model. In contrast, the original shape of the homogeneous model was found to be preserved, and maximum principal strain distribution was found to mainly occur on the outermost convex section of the model [14]. The inhomogeneous material model in Fig. 6b is assumed to accentuate the compression of the cross-section during bending. During bending, inward forces, which were generated by longitudinal tensile and compressive strains on the convex and concave sides, respectively, are assumed to contribute to this effect. Further analysis of the resistance to bending deformation by the innermost and outermost layers of the inhomogeneous model was conducted. The maximum principal strain ε1 distribution in the inner and outer layers was plotted against a varying longitudinal-to-transverse bending stiffness ratio, as shown in Fig. 7 to reveal the optimized longitudinal-to-transverse bending stiffness ratio developed in the bamboo culm. A mixed mode of failure was observed from the analysis of results in Fig. 7, which corresponded to a longitudinal-to-transverse bending stiffness ratio of 100:4.5 [14]. The intersection point of both lines indicated the cross-point at which both the innermost and outermost layers had equal resistance to bending deformation. The optimized stiffness corresponding to equal distribution of deformation resistance between the layers was thus taken as 100:4.5, which enabled bamboo to withstand high external loadings. Moreover, additional bending toughness observed in bamboo during bending is attributed to the reduction in transverse strength of the inhomogeneous model, as shown by the shift in maximum deformation from the outermost to innermost layers. The optimized longitudinal-to-transverse bending stiffness ratio of 100:4.5, as obtained from Fig. 7, correlated to a large extent to experimentally determined modulus of elasticity values, which ranged between 15 to 20 GPa longitudinally

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

271

Fig. 7 Distribution of maximum principal strain ε1 measured from the inner and outer layers of bamboo model [14]

and 0.5 to 0.8 GPa transversely [1, 15–17]. From the literature, the ratio of transverse to longitudinal tensile strength was found to range between 1/50 and 1/24 in orthotropic materials. The substantial difference prevailing between these two principal directions was attributed to the difference in chemical bond energy as cellulose chain molecules are connected by C–C and C–O in the axial direction and by C–H and H–O in the radial direction [19]. Unlike woody plant materials, which have cambium in the radial direction [3], bamboo derives its strength in the longitudinal direction as its primary growth is restricted axially. The optimized transverse isotropy observed in bamboo is one of several features which has been developed in its structure to enable it to withstand external forces at multiple length scales [20].

2.2 Investigating the Fracture Mechanisms in Bamboo Culms Due to External Modes of Loadings In the next phase of the investigation, the atypical deformation behaviour observed in bamboo due to external modes of loadings was further enlightened by considering FEM investigation techniques. FEM techniques were found to be appropriate to elucidate the complex fracture behaviour exhibited by bamboo material given their inherent inhomogeneous nature [1, 3–5, 7, 21–23]. Four principal modes of loading, namely bending, compression, shear, and torsion, were considered as part of the investigation of fracture mechanisms in bamboo culm. As a natural and inhomogeneous material, bamboo displays a complex deformation behaviour when exposed to external loading conditions [1, 3, 7, 21, 22]. This

272

R. Ramful

study mainly focuses on the effect of orthotropic material characteristics on the fracture patterns in bamboo culms in external loading modes while suppressing other influential factors such as maturity, moisture content, and microstructural variations [14]. Numerical simulation by considering the FEM software of LS-DYNA was found to be appropriate for this purpose. Moreover, the maximum principal stress and strain criteria were found to be suitable for assessing failure in hard and brittle materials like bamboo [24]. The maximum principal strain criterion, which was previously used to investigate the failure mechanism in engineered bamboo and timber products [25], was found to be appropriate given the nature of failure in bamboo culms comprising of sudden split and instantaneous crack propagation. The crack initiation stage and mode of propagation were investigated by applying an element erosion technique in the numerical model. The maximum principal strain at failure, εmax , was selected as the failure criterion in the element erosion setting and was defined as 30% less than the value of the maximum principal strain. The simulation was conducted in implicit mode.

2.2.1

Material Parameters, Geometrical Modelling, Boundary Conditions, and FE Mesh

The corresponding engineering constants based on the optimized longitudinal-totransverse isotropic ratio determined in the precedent section are displayed in Table 2. For comparison purposes, a homogenous material model assigned with elastic properties, as displayed in Table 1, was considered. The geometrical models for bamboo culms in all test conditions were sized as per the morphological data of Madake bamboo. To minimize computational time, the models have been accordingly refined with respect to their loading test setup [26]. In compression, torsion and shear loading modes, a full internodal length of 450 mm was selected, while only a half-internodal length of 225 mm was selected in the bending mode. Besides, a full cylindrical model and quarter cylindrical models were selected in torsion and compression loading modes, while semi-cylindrical models were considered in bending and shear investigations only [14]. Moreover, the node was assumed as a full solid and rigid section of 75 mm in length in all modes of loading except in bending and shear investigations whereby a length of 150 mm was considered. The detailed boundary conditions corresponding Table 2 Material parameters corresponding to the longitudinal-to-transverse bending stiffness ratio (E L –E T ) of 100:4.5 Orthotropic material parameters Elastic modulus (MPa)

Poisson’s ratio

EL

ET

νL

νT

GL

15,000

675

0.3

0.0135

630

Shear modulus (MPa)

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

273

Fig. 8 Detailed boundary conditions of bamboo model in: a bending, b torsion, c compression, and d shear modes of loading. Adapted from Ramful and Sakuma [14], License CC BY

to each mode of loading are shown in Fig. 8. Deformation in the bamboo model was simulated by applying a displacement of 5 mm in bending, compression, and shear modes, while an angle of twist of 5.73° was applied in torsion mode [14]. Two models were considered in each mode of loading, namely (1) hollowhomogeneous and (2) hollow-inhomogeneous models. Hexahedral mesh solid was applied throughout all models in FEMAP software, while the internodal section was refined with finer mesh.

2.2.2

Strain Field Analysis

The strain field analysis for each mode of loading is presented in Fig. 9. General observations obtained from Fig. 9 have shown that the location of crack initiation tends to vary with respect to geometrical features, material properties, and mode of loading [14]. As reported in a previous study, crack initiation in the hollowtype models in the shear mode, for instance, was found to significantly differ from solid-type models which displayed break-point crack initiation [14]. Similarly, a notable difference in crack initiation in compression mode was observed between hollow- and solid-type models [14]. In contrast to the observation made in Fig. 9c, d, cracks in solid-type models were reported to initiate closer to the internode midsection [14]. In subsequent analyses, key observations made about the crack initiation and propagation in each mode of loading of the hollow-inhomogeneous model corresponding to bamboo culm are highlighted. Firstly, in bending mode, cracks were found to initiate from the lower innermost wall section of the culm, followed by longitudinal and radial propagation in the outward direction. The crack propagation corresponded to a splitting-like pattern [14].

274

R. Ramful

Fig. 9 Fringe plots of the maximum principal strain of hollow-homogeneous and hollowinhomogeneous models in: a bending, b compression, c torsion, and d shear modes of loading [14]

Secondly, in compression mode, cracks, which originated from both the outermost wall of the node-internode sections, followed a diagonal pathway towards the middle of the internode before moving radially inwards. In torsion mode, crack initiation was predominantly observed to occur in the peripheral wall section of the prescribed end, while further propagation was found to affect both the outermost wall section and the node-internode section of the fixed end. Finally, in shear mode, a similar splitting-like pattern observed in bending mode could be discerned as cracks, which initiated at the innermost wall of the internode middle section, propagated radially outwards [14].

2.2.3

Analysis of Bamboo Fracture Mechanisms

In accordance with FEM results, the fracture mechanisms prevailing in bamboo culms were further established. From fringe plots of maximum principal strain, the crosssectional deformation observed, which resembled cross-sectional flattening to a large extent, was assumed to occur as a result of poor transverse strength. Cross-sectional flattening also known as Brazier’s effect has been widely reported in the deformation theory of tubular section. The geometrical changes and corresponding stress distributions are assumed to be caused by inward-induced forces due to longitudinal tensile and compressive stresses on the convex and concave sections, respectively, which eventually led to the ovalization of the cross-section [3–5, 27]. Conjointly, associated effects linked to ovalization of the cross-section lead to cracking at four vertices [17,

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

275

28], as illustrated in Fig. 9a, as well as splitting in the compressive region of the culm section due to crushing of fibres during bending [1]. Shear failure, which occurred along distinct shear planes around the neutral axis, resembled a large-extent fracture observed in bamboo culms during a 4-point bending test [1]. The transverse strength in bamboo is also assumed to be undermined by the inferior interlaminar strength prevailing between fibre bundles within the culm structure [9, 11, 29], which was partially taken into account in the transversely isotropic model. Moreover, despite the longitudinal stiffness being 20 times greater than the radial and tangential stiffness, the notable ability developed by bamboo culms to withstand buckling due to transverse shear and bending loads originates from the arrangement of longitudinal fibres which are bound by a non-cellulose component. Additionally, both experimental and numerical results about bending and shear simulations have demonstrated that the optimized strength developed by bamboo to resist transverse fracture is partly due to its unique cross-sectional arrangement. The optimized structure developed in bamboo culms enables it to display a relatively high strength-to-weight ratio to resist elevated bending loads in snow and wind, thereby compensating for the high aspect ratio of length to diameter observed in bamboo culms. In compression mode, crack mechanisms were associated with shear band formation [22]. Similar to this formation, cracks were found to initiate from the outermost wall of the node-internode section, followed by propagation at an angle of 45°. In previously reported findings, larger axial strain induced by the loading platens on both ends tends to cause the section in the middle of the culm to bulge out prior to splitting [21]. The results obtained in torsion mode however differed from the remaining modes as maximum principal strain distribution was observed on its outermost surface. A similar observation has been reported in another study whereby maximum principal stress distribution was found to occur on the outermost surface of bamboo culms in torsion mode [7]. Moreover, the variation of Von Mises stress was found to vary over a wider range in the inhomogeneous model of bamboo in torsion mode as compared to the homogeneous isotropic model [30].

3 Assessing the Transverse Fracture Mechanisms in Bamboo with Respect to Grain Direction by the Finite Element Method As seen in the previous section, natural materials like bamboo inherit a unique inhomogeneous structure which is predominantly reinforced in the longitudinal direction. Besides, the influence of inhomogeneity on the limited strength of bamboo to resist fracture in external modes of loading, the direction of loading with respect to its three principal axes exerts an equally critical role. Structural plant features,

276

R. Ramful

namely the grain size, graded arrangement, and interlaminar strengths, are additional contributing factors which have been reported to influence the fracture mechanisms in bamboo material. This research investigation is focused on investigating the fracture mechanisms in bamboo material by taking into account their structural arrangement, namely grain distribution and orthotropic material characteristics [31]. FEM techniques were selected for this investigation given the relative ease to suppress omitted variables not investigated in this study ranging from geometrical features to natural defects.

3.1 Materials and Methods The fracture mechanisms with respect to grain distribution and orthotropic variations were investigated through FEM by evaluating single-edge-notched bending (SENB) test specimens in a 3-point bending test. In the recent past, FEM techniques have been applied to elucidate the fracture mechanisms in a multitude variety of artificial and natural composite materials [14, 32–37]. In this study, the same FEM software of LS-DYNA (Livermore Software Technology, Livermore, CA, USA), as utilized in the previous section, was considered for numerical simulation. The simulation was conducted in implicit mode, and amongst the numerous failure criteria available to evaluate fracture in composite materials, the maximum principal strain criterion was selected in this study. The selected criterion was found to be appropriate to assess failure in hard materials like bamboo as it corresponded to a large extent to the selection of the maximum principal stress criterion used in similar investigations [14, 24]. Both the maximum principal strain and the maximum principal stress criteria have been widely adopted as failure criteria in previous studies to evaluate failure mechanisms in bamboo culm, engineered bamboo, and timber materials [18, 21, 25]. Given the insignificant variation of mechanical properties in the radial and tangential directions as compared to the longitudinal direction, bamboo was simplified into a transversely isotropic model to replicate its orthotropic nature partially. Bamboo was modelled by considering a longitudinal-to-transverse stiffness ratio of 100:4.5 [14]. Each layer in the transverse section was assigned a specific stiffness parameter in an attempt to replicate the graded distribution of the volume fraction of fibres in the bamboo model, as displayed in Fig. 10 [31]. To further the understanding of to investigate the material deformation behaviour with varying orthotropic characteristics, other material models having longitudinalto-transverse stiffness ratio in the range between 100:100 to 100:1 were selected. As a control, a purely homogenous material with elastic material characteristics was selected. The corresponding engineering constants for the various material models are given in Table 3. A similar methodological approach was selected for investigating both LR and LT SENB specimens in numerical simulation [31].

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

277

Fig. 10 Graded distribution of modulus of elasticity in the radial direction across bamboo’s wall thickness

Table 3 Elastic and orthotropic material parameters (corresponding to the outermost layer of the bamboo model) used in FEM Elastic material parameters

Orthotropic material parameters

Elastic modulus (MPa)

Poisson’s ratio

Elastic modulus (MPa)

Poisson’s ratio

Shear modulus (MPa)

E

v

EL

ET

vL

vT

GL

15,000

0.3

20,000

900

0.3

0.0135

840

3.1.1

Geometrical Modelling, Boundary Conditions, and FE Mesh

The SENB bamboo specimens were replicated by considering a directionally reinforced laminate model [38]. As an anisotropic material, bamboo, which is composed of fibres and parenchyma matrix as main constituents, was simplified into an orthotropic material model [39]. The outline of the SENB specimen is illustrated in Fig. 11 [31]. In terms of geometrical sizing, the breadth and height were reduced by 50% to address geometric nonlinearities which may originate across the thickness. The final SENB specimen, as displayed in Fig. 11, had dimensions of 100 mm (span) × 2 mm (breadth) × 5 mm (height) [31]. Moreover, a puncher and supports having dimensions

Fig. 11 Outline of SENB LR-bamboo specimen in third angle projection [31]

278

R. Ramful

of 2.5 mm in diameter and spanning across the full breadth of the beam were selected to simulate SENB specimens in 3-point bending. To reduce shear stresses during numerical simulation, a span-to-depth ratio of 20 was selected [12, 40]. The models in this study were designed and meshed by considering hexahedral mesh solid on the finite element modelling and post-processing software (FEMAP) (Siemens Digital Industries Software, Plano, TX, USA) [31].

3.2 Numerical Results of Strain Field Analysis Figure 12 shows the numerical simulation results of each type of SENB specimen of the bamboo model which has been arranged in accordance with their increasing orthotropic characteristics [31] From Fig. 12, the change in fracture patterns in both LR and LT SENB specimens with respect to varying orthotropic characteristics could be clearly discerned. Firstly, in the homogeneous material model with highly elastic characteristics, transverse fracture predominantly took place as a crack followed an initial transverse propagation pathway. The type of failure observed in this model was linked to the brittle mode of fracture typically observed in hard isotropic elastic materials [31]. In contrast, however, the fracture pattern observed in the inhomogeneous material model with highly orthotropic characteristics displayed distinctive fracture patterns. For instance, at a longitudinal-to-transverse stiffness ratio of 100:1, the crack tip deviated from their original direction and propagated in an orthogonal pathway, a mode of failure which was associated with the prevalence of delamination in layered and fibrous composite materials. Moreover, further observations have shown that the transition prevailing between the two modes of crack propagation in LR and LT specimens occurred between orthotropic material of 100:50 and 100:4.5 [31]. Similar analyses conducted on wood specimens have revealed interesting results [31]. The LR-type specimen displayed, to a large extent similar fracture patterns

Fig. 12 Fringe plots of the maximum principal strain of SENB: a LR- and b LT-bamboo specimens corresponding to varied orthotropic characteristics. Reprinted with permission from Ramful [31], Copyright 2022, Springer Nature

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

279

observed in bamboo, unlike the LT-type specimen, whereby the fracture patterns could be seen to gradually vary from 0° to 90° between the highly elastic and orthotropic models, respectively. The inferior transverse strength in wood-based material was assumed to promote unrestricted crack propagation transversely [31]

3.2.1

Analysis of Transverse Fracture Mechanisms in Bamboo

In accordance with the FEM results of various bamboo-type specimens, besides the grain distribution, the observed fracture patterns were found to be influenced by intrinsic mechanical characteristics such as the orthotropic nature and corresponding stiffness. In comparison to LR specimens, the brittle-like fracture displayed by LT specimens, which is typically observed in hard solid materials, is assumed to occur as a result of a more homogenous arrangement of its fibres [31]. The FEM results were found to have a large correlation with experimental results [31]. For instance, results from the scanning electron microscope (SEM) showed that the crack propagation across LR-bamboo specimens was easier in comparison to LT-bamboo specimens as a result of the softer parenchyma component [31]. In nature, the discrepancy prevailing between the fibre-matrix strength was linked to accentuating the effect of interfacial delamination leading to rapid crack propagation. The physical and mechanical properties of the parenchyma section were reported to be inferior to the directionally reinforced fibrous component [41, 42]. The density of parenchyma was found to be 50% lower than that of the fibrous component, while their modulus of elasticity was found to be 20 times lower [43]. Moreover, the soft and foam-like structure of parenchyma in LR-bamboo specimens was reported to prevent large-scale buckling by absorbing large deformation and extending the nonlinear deformation stage [44, 45].

4 Evaluating the Underlying Effects of Thermal Modification on Shrinkage-Induced Cracks in Bamboo Culms by the Finite Element Method Besides load-induced cracks, which can emerge in various modes of loading as previously seen, premature failure in bamboo culms can also occur, given their susceptibility to natural degradation following harvest. Once harvested, bamboo is conventionally dried in an oven or via natural means to achieve a moisture content below the fibre saturation point (FSP) [46]. To improve dimensional stability, further drying below the FSP is conducted thereby affecting the bound water in plant cell walls. The reduction in weakly bound water in plant cell walls eventually results in further physical changes in the weight and dimensions of the bamboo culm. The onset of shrinkage in a material with peculiar geometrical features, such as bamboo, gives rise to unprecedented stress distributions which often result in crack formation.

280

R. Ramful

The fracture mechanism in bamboo culms due to the shrinkage phenomenon is not well documented in the literature. To the author’s knowledge, the use of FEM techniques to probe into the crack growth emanating from climatic variations in bamboo material is sparsely available in literature as compared to similar techniques involving the macro-structural behaviour of bamboo culms. This study is focused on the investigation of the fracture mechanisms in bamboo culms due to shrinkage behaviour resulting from the thermal effect via FEM [47]. The FEM model proposed in this study to simulate shrinkage behaviour via thermal effect is conducted by considering the variation in a gradient of thermal expansion coefficient across its wall thickness.

4.1 Materials and Methods The detailed numerical steps and parameters required to simulate shrinkage behaviour in the full-culm bamboo model are described in this section. In comparison to previous research investigations, whereby the effective stress or Von Mises stress was considered to investigate the deformation mechanisms in numerically simulated bamboo models, the effective strain distribution was specifically considered in this study to investigate the deformation due to thermal contraction [47]. To replicate the orthotropic nature of bamboo culms, shrinkage variation with respect to the three principal directions, as reported in previous literature data [46, 48, 49], was considered. The graded distribution of vascular bundles across the cross-section was taken into account by selecting a shrinkage model based on an exponentially varied coefficient of thermal contraction. For comparison, two additional shrinkage models based on a linear and constant variation in the coefficient of thermal contraction were considered, as shown in Fig. 13 [47].

4.1.1

Material Model

The shrinkage model was set up based on the theory of thermal expansion and by considering dimensional changes in the three principal axes as obtained in a previous study [47]. In accordance with the equation below, the coefficient of thermal expansion for the corresponding dimensional changes was calculated by selecting a factor of 5 to simulate an accentuated shrinkage behaviour in the internodal section. A temperature change of 200 °C was selected in this direction [47]. [ ] 1ΔL α= LΔT where α is the coefficient of thermal expansion in K–1 , L is the original length, ΔL is the change in length, and ΔT represents the change in temperature.

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

281

Fig. 13 Variation of coefficient of thermal expansion in constant, exponential, and linear shrinkage models

Table 4 Thermal expansion parameters to simulate shrinkage behaviour in bamboo Thermal expansion parameters Internode Radial Change in 2.17 length ΔL (%) Coefficient of thermal expansion α (K–1 )

− 1.08 × 10–4

Node Tangential

Longitudinal

Radial

Tangential

Longitudinal

1.67

0.17

1.73

1.33

0.13

− 8.33 × 10–5

− 8.33 × 10–6

− 8.67 × 10–5

− 6.67 × 10–5

− 6.67 × 10–6

In past literature, shrinkage behaviour in the nodal section was reported to be more restricted as compared to the internodal section [48]. In line with this observation, an incremental factor of 1.25 was maintained between shrinkage in the internodal and nodal directions. A summary of the thermal expansion parameters derived for the bamboo culm model is outlined in Table 4 [47]. Besides the shrinkage simulation parameters, the material data used to replicate the orthotropic mechanical characteristics in bamboo culm is given in Table 5 [47].

4.1.2

Geometrical Modelling, Boundary Conditions, and FE Mesh

Similar to the previous section in this chapter, the morphological data of Madake bamboo was considered, and outer diameter, wall thickness, and internodal length of 100, 12, and 450 mm were selected [26]. The boundary conditions and the distinct geometrical features of bamboo culm, which was modelled as a thick-walled cylindrical section, are displayed in Fig. 14 [47].

282

R. Ramful

Table 5 Material parameters used to replicate bamboo’s orthotropic nature Orthotropic material parameters Internode

Node

Elastic modulus Poisson’s ratio (MPa)

Shear modulus (MPa)

Elastic modulus Poisson’s ratio (MPa)

Shear modulus (MPa)

EL

ET

νL

νT

GL

EL

ET

νL

νT

GL

15,000

675

0.3

0.0135

630

30,000

1350

0.3

0.0135

1260

Fig. 14 Dimensional outline of bamboo geometrical model in third angle projection

The 3D model was designed on the finite element modelling and post-processing (FEMAP) software (Siemens Digital Industries Software, Plano, TX, USA). A hexahedral mesh solid was selected, and the 3D model was discretized into 101,556 nodes and 89,280 elements, as shown in Fig. 15. Finally, to investigate the effect of thermal contraction on shrinkage behaviour, numerical simulation was conducted on the FEM software of LS-DYNA (Livermore Software Technology, Livermore, CA, USA).

4.2 Strain Field Analysis of Bamboo Shrinkage Model The fringe plots of effective strain distribution for the three shrinkage models, namely exponential, linear, and constant models, are outlined in Fig. 16 [47]. A displacement scale factor of 10 has been assigned in the displayed models to highlight the noticeable shrinkage observed in the material. General observations obtained from Fig. 16 have shown that the variation in effective strain distribution occurred mainly as a result of the change in the gradient of the thermal expansion coefficient. As displayed in Fig. 16a, b, distinct regions of strain concentration in both exponential and linear shrinkage models could be

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

283

Fig. 15 Meshed model of bamboo internodal culm section using hexahedral mesh solid

Fig. 16 Fringe plots of effective strain distribution in: a exponential, b linear, and c constant bamboo shrinkage models. Adapted from Ramful et al. [47], License CC BY

clearly discerned [47]. The narrowed region of strain concentration observed from the exponential shrinkage model, as shown in Fig. 16a, corresponded to a large extent to previously reported research findings about the longitudinal split observed in bamboo culms [50].

4.2.1

Analysis of Effective Strain Distribution

A qualitative assessment of the various shrinkage models was conducted by analyzing the effective strain distribution in the outermost periphery of the internodal culm section. The effective strain distribution was plotted against the azimuthal angle θ, taken as clockwise in reference to the vertical axis, at four specific locations in the model’s cross-section, as shown in Fig. 17 [47].

284

R. Ramful

Fig. 17 Distribution of effective strain at transverse sections 1, 2, and 3 in: exponential-, linear-, and constant-type of shrinkage models. Adapted from Ramful et al. [47], License CC BY

The onset of initial crack formation during shrinkage was associated with the marked increase in peaks located at 0° and 180° in both exponential and linear gradient models. Moreover, the similarity observed in the variation of effective strain distribution across sections 1–3 in both shrinkage models, indicated an aligned region corresponding to strain concentration. This specific region along the culm length is assumed to originate from the inducement of internal forces, namely tensile and compressive forces as a result of the graded nature of both shrinkage models, which could eventually lead to a sudden split [47]. Interestingly, the strain distribution in the outermost section of the constant shrinkage model was found to be approximately constant in the transverse section 2, corresponding to the middle portion of the culm section. Given the absence of strain concentration in the middle portion of the culm section, the constant thermal gradient model was thus assumed to reduce the susceptibility of bamboo culms to premature failure by longitudinal split [47].

4.2.2

Analysis of Fracture Mechanisms in Bamboo Culm Due to Thermal Contraction

Further discussion about the fracture mechanisms originating from the exponential model is presented in this section. As illustrated in Fig. 18, the discrepancy observed between the innermost and outermost layers of the culm model in terms of thermal contraction as a result of the non-uniform thermal gradient was found to lead to a tensile stress build-up in the latter [47]. The non-uniform shrinkage model was found to promote residual stress build-up within the culm structure as the shrunk outermost layer would exert a restraining effect. As illustrated in Fig. 18a, the stages from crack initiation to propagation could be visualized by implementing the element erosion technique on LS-DYNA.

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

285

Fig. 18 Analysis of fracture mechanisms in bamboo culm due to thermal contraction: a fringe plot of effective strain distribution in the bamboo model; b distribution of internally-induced forces due to thermal contraction and c longitudinal crack propagation in thermally modified bamboo. Adapted from Ramful et al. [47], License CC BY

As previously reported by Hone et al. [50], compressive and tensile forces, which were induced at the innermost and outermost layers of the node-internode section, respectively, led to the longitudinal split in the bamboo culm. The outermost layer at the node-internode section was thus considered to be the critical location of crack initiation. Moreover, from FTIR results, major changes to the cellular constituents of bamboo, namely cellulose, hemicellulose, and lignin, occurred between 150 and 200 °C. The cellular constituents, which also account for its high mechanical strength, were found to contribute to its susceptibility to split. A noticeable shrinkage effect could be observed as a result of weight loss by a reduction in weakly bound water at elevated temperatures. The shrinkage effect was accentuated by the reduction in moisture content during the thermal degradation of hemicellulose, which led to an increase in brittleness as a result of an increase in the arrangement of crystalline cellulose [51, 52].

5 Conclusion Given the constrained time span and limited scope of this research investigation, the primary target of this study was to mainly focus on the investigation of load- and thermally induced cracks in bamboo culm section in order to propose an alternative solution for improving its durability performance.

286

R. Ramful

5.1 Investigating the Effect of Material Inhomogeneity on the Fracture Mechanisms of Bamboo by the Finite Element Method In the first part of the investigation, bamboo was observed to develop a unique orthotropic material structure which was optimized to enable it to resist extensive deformation predominantly during bending and shear loadings. Distinct fracture patterns were observed in the culm section of bamboo following numerical simulation in various modes of loading. Both the type of geometrical structure and material model were found to exert a noticeable influence on the fracture mechanisms. Splitting patterns could be clearly discerned in bending and shear modes in the hollow-inhomogeneous model representing the cylindrical and directionally reinforced bamboo model. The location of split, on the other hand, was found to occur at specific positions inside the culm section, namely on the inside-lowermost section and on the outside-centre position corresponding to bending and shear modes, respectively. The findings of this study could be further considered to shed light on the deformation mechanisms in artificial composites and bio-inspired structures based on the bamboo geometrical-material model.

5.2 Assessing the Transverse Fracture Mechanisms in Bamboo with Respect to Grain Direction by the Finite Element Method Secondly, one area requiring further research investigation, namely the fracture mechanisms in natural composites with respect to their structural arrangements, such as grain distribution and orthotropic material characteristics, was further explored by considering numerical simulation techniques. The numerical simulation results were found to exhibit good correlations with experimental observations regarding the fracture patterns obtained in longitudinal-radial (LR) and longitudinal-tangential (LT) specimens. The crack tip in both specimen types was observed to deviate from their original direction at highly orthotropic material characteristics starting from a longitudinal-totransverse stiffness ratio of 100:4.5 onwards. This failure mode was associated with the prevalence of delamination in layered and fibrous composite materials, which showed contrasting differences with the homogeneous material model whereby transverse fracture predominantly took place. From this study, it was concluded that the underlying factors affecting the crack initiation and its growth patterns in natural composite materials besides the grain distribution were the orthotropic nature and corresponding stiffness.

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

287

5.3 Evaluating the Underlying Effects of Thermal Modification on Shrinkage-Induced Cracks in Bamboo Culms by the Finite Element Method Finally, the use of FEM to investigate other causes of fracture in bamboo was further discussed by analyzing the underlying effect of thermal modification on the shrinkage behaviour of bamboo culms. Successful replication of the shrinkage model in bamboo culm was realized by considering the variation in the gradient of thermal expansion in accordance with its graded hierarchical structure to simulate shrinkage behaviour across the wall thickness. The noticeable longitudinal crack propagation, which occurred along the internodal length of bamboo culm, as observed from the exponential thermal gradient model, gave a clear indication of the influence of the graded structure across the wall thickness on shrinkage mechanisms of bamboo culms. The findings of this study showed that, in addition to the beneficial effects that can be induced by thermal modification, such as smoke treatment to enhance dimensional stability in natural materials, it can also lead to adverse effects on the physical characteristics of such material, making it prone to premature failure by a longitudinal split.

6 Direction for Future Work A substantial amount of interest has been expressed in the last decades in the use of natural materials with enhanced durability traits for sustainable development in large-scale applications. Despite much research having been conducted on the material’s physical and mechanical characteristics, the durability aspect of natural-based material remains widely unsolved owing to diverse factors. Both the physical and mechanical characterization of natural materials and natural-based composites are governed by their intricate structural composition. The structure of plant materials tends to be inhomogeneous and diverse due to their natural evolution and the influence of external factors, respectively. Addressing the mentioned variables all at once is unfeasible and inefficient as they are conditional and subject to change over time. The long-term goal is to combine the predictive modelling techniques available through FEM simulation with artificial intelligence (AI) technology to enhance the assessment and monitoring capacity of natural-based structures. Other identified areas requiring further research attention to address additional durability challenges affecting bamboo material, namely fatigue over its service lifetime and premature failure due to mechano-sorptive creep, could be further researched and modelled through numerical simulation techniques. Besides, the use of FEM techniques enumerated in this chapter can be of great significance when applied to the investigation of bamboo-inspired bionic design. There are great prospects for improving the strength of advanced composites through a modelling approach to further support experimental findings [53, 54]. Moreover,

288

R. Ramful

alternative methods to conventional experiments are required to study and replicate the naturally optimized structure of bamboo in artificially crafted composites structure based on similar attributes consisting of axially reinforced fibres.

References 1. Trujillo D, Jangra S, Gibson JM (2017) Flexural properties as a basis for bamboo strength grading. Proc Inst Civ Eng Struct Build 170(4):284–294 2. Ribeiro RAS, Ribeiro MGS, Miranda IP (2017) Bending strength and nondestructive evaluation of structural bamboo. Constr Build Mater 146:38–42 3. Kappel R, Mattheck C, Bethge K, Tesari I (2004) Bamboo as a composite structure and its mechanical failure behaviour. WIT Trans Ecol Environ 73 4. Huang YS, Hsu FL, Lee CM, Juang JY (2017) Failure mechanism of hollow tree trunks due to cross-sectional flattening. R Soc Open Sci 4(4):160972 5. Spatz HC, Niklas KJ (2013) Modes of failure in tubular plant organs. Am J Bot 100(2):332–336 6. Trujillo DJ, López LF (2020) Bamboo material characterisation. In: Nonconventional and vernacular construction materials. Woodhead Publishing, pp 491–520 7. Askarinejad S, Kotowski P, Shalchy F, Rahbar N (2015) Effects of humidity on shear behavior of bamboo. Theor Appl Mech Lett 5(6):236–243 8. Qiu Z, Fan H (2020) Nonlinear modeling of bamboo fiber reinforced composite materials. Compos Struct 238:111976 9. Shao ZP, Fang CH, Tian GL (2009) Mode I interlaminar fracture property of moso bamboo (Phyllostachys pubescens). Wood Sci Technol 43(5):527–536 10. Askarinejad S, Kotowski P, Youssefian S, Rahbar N (2016) Fracture and mixed-mode resistance curve behavior of bamboo. Mech Res Commun 78:79–85 11. Shao Z, Wang F (2018) Introduction to the application of the fracture mechanics in wood and bamboo. In: The fracture mechanics of plant materials. Springer, Singapore, pp 1–10 12. Chen M, Dai C, Liu R, Lian C, Yuan J, Fang C, Fei B (2020) Influence of cell wall structure on the fracture behavior of bamboo (Phyllostachys edulis) fibers. Ind Crops Prod 155:112787 13. Chen Q, Dai C, Fang C, Chen M, Zhang S, Liu R, Liu X, Fei B (2019) Mode I interlaminar fracture toughness behavior and mechanisms of bamboo. Mater Des 183:108132 14. Ramful R, Sakuma A (2020) Investigation of the effect of inhomogeneous material on the fracture mechanisms of bamboo by finite element method. Materials 13(21):5039 15. Nugroho N, Bahtiar ET (2017) Structural grading of Gigantochloa apus bamboo based on its flexural properties. Constr Build Mater 157:1173–1189 16. Nogata F, Takahashi H (1995) Intelligent functionally graded material: bamboo. Compos Eng 5(7):743–751 17. Sharma B, Harries KA, Ghavami K (2013) Methods of determining transverse mechanical properties of full-culm bamboo. Constr Build Mater 38:627–637 18. Keogh L, O’Hanlon P, O’Reilly P, Taylor D (2015) Fatigue in bamboo. Int J Fatigue 75:51–56 19. Xu YM (2006) Wood science. China Forestry Publishing, Beijing, China, p 181 20. Cui J, Qin Z, Masic A, Buehler MJ (2020) Multiscale structural insights of load bearing bamboo: a computational modeling approach. J Mech Behav Biomed Mater 107:103743 21. Gauss C, Savastano Jr H, Harries KA (2019) Use of ISO 22157 mechanical test methods and the characterisation of Brazilian P. edulis bamboo. Constr Build Mater 228:116728 22. Zhang X, Li J, Yu Z, Yu Y, Wang H (2017) Compressive failure mechanism and buckling analysis of the graded hierarchical bamboo structure. J Mater Sci 52(12):6999–7007 23. Deng J, Chen F, Wang G, Zhang W (2016) Variation of parallel-to-grain compression and shearing properties in moso bamboo culm (Phyllostachys pubescens). BioResources 11(1):1784–1795

Review of FEM Simulations to Elucidate Fracture Mechanisms in Bamboo

289

24. Moss DR (2004) General topics. In: Pressure vessel design manual. Elsevier, pp 1–36 25. Reynolds T, Sharma B, Harries K, Ramage M (2016) Dowelled structural connections in laminated bamboo and timber. Compos B Eng 90:232–240 26. Ghavami K (2016) Introduction to nonconventional materials and an historic retrospective of the field. In: Nonconventional and vernacular construction materials. Woodhead Publishing, pp 37–61 27. Brazier LG (1927) On the flexure of thin cylindrical shells and other “thin” sections. Proc R Soc Lond Ser A 116(773):104–114 28. Moran R, Webb K, Harries K, García JJ (2017) Edge bearing tests to assess the influence of radial gradation on the transverse behavior of bamboo. Constr Build Mater 131:574–584 29. Wang F, Shao Z, Wu Y (2013) Mode II interlaminar fracture properties of Moso bamboo. Compos B Eng 44(1):242–247 30. Silva ECN, Walters MC, Paulino GH (2006) Modeling bamboo as a functionally graded material: lessons for the analysis of affordable materials. J Mater Sci 41(21):6991–7004 31. Ramful R (2022) Investigation of the transverse fracture mechanisms of bamboo by the finite element method. J Mater Sci 57(11):6233–6248 32. Vasic S, Stanzl-Tschegg S (2007) Experimental and numerical investigation of wood fracture mechanisms at different humidity levels 33. Schoenmakers JCM, Jorissen AJM, Leijten AJM (2010) Evaluation and modelling of perpendicular to grain embedment strength. Wood Sci Technol 44(4):579–595 34. Qiu LP, Zhu EC, Van de Kuilen JWG (2014) Modeling crack propagation in wood by extended finite element method. Eur J Wood Wood Prod 72(2):273–283 35. Bienia´s J, Dadej K (2020) Fatigue delamination growth of carbon and glass reinforced fiber metal laminates in fracture mode II. Int J Fatigue 130:105267 36. Monticeli FM, Daou D, Pekovi´c O, Simonovi´c A, Voorwald HJC, Cioffi MOH (2020) FEA simulation and experimental validation of mode I and II delamination at the carbon/glass/epoxy hybrid interface: physical-based interpretation. Compos Commun 22:100532 37. Khan Z, Yousif BF, Islam M (2017) Fracture behaviour of bamboo fiber reinforced epoxy composites. Compos B Eng 116:186–199 38. Meyers MA, Chawla KK (2008) Mechanical behavior of materials. Cambridge University Press 39. Youssefian S, Rahbar N (2015) Molecular origin of strength and stiffness in bamboo fibrils. Sci Rep 5(1):1–13 40. Dixon PG, Gibson LJ (2014) The structure and mechanics of Moso bamboo material. J R Soc Interface 11(99):20140321 41. Ramful R, Sakuma A (2021) Effect of smoke treatment on flexural strength of bamboo hierarchical structure. BioResources 16(1):387 42. Lilholt H, Talreja R (1982) Fatigue and creep of composite materials. In: Proceedings of the 3rd Risø international symposium on metallurgy and materials science. Risø National Laboratory 43. Amada S, Munekata T, Nagase Y, Ichikawa Y, Kirigai A, Zhifei Y (1996) The mechanical structures of bamboos in viewpoint of functionally gradient and composite materials. J Compos Mater 30(7):800–819 44. Habibi MK, Samaei AT, Gheshlaghi B, Lu J, Lu Y (2015) Asymmetric flexural behavior from bamboo’s functionally graded hierarchical structure: underlying mechanisms. Acta Biomater 16:178–186 45. Obataya E, Kitin P, Yamauchi H (2007) Bending characteristics of bamboo (Phyllostachys pubescens) with respect to its fiber–foam composite structure. Wood Sci Technol 41(5):385– 400 46. Azadeh A, Ghavami K (2018) The influence of heat on shrinkage and water absorption of Dendrocalamus giganteus bamboo as a functionally graded material. Constr Build Mater 186:145–154 47. Ramful R, Sunthar TP, Zhu W, Pezzotti G (2021) Investigating the underlying effect of thermal modification on shrinkage behavior of bamboo culm by experimental and numerical methods. Materials 14(4):974

290

R. Ramful

48. Huang P, Chang WS, Ansell MP, Bowen CR, Chew JY, Adamaki V (2018) Thermal and hygroscopic expansion characteristics of bamboo. Proc Inst Civ Eng Struct Build 171(6):463– 471 49. Yu HQ, Jiang ZH, Hse CY, Shupe TF (2008) Selected physical and mechanical properties of moso bamboo (Phyllostachys pubescens). J Trop For Sci:258–263 50. Hone T, Cahill L, Robinson A, Korde C, Taylor D (2020) The splitting of bamboo in response to changes in humidity and temperature. J Mech Behav Biomed Mater 111:103990 51. Boonstra MJ, Van Acker J, Kegel E, Stevens M (2007) Optimisation of a two-stage heat treatment process: durability aspects. Wood Sci Technol 41(1):31–57 52. Tang T, Zhang B, Liu X, Wang W, Chen X, Fei B (2019) Synergistic effects of tung oil and heat treatment on physicochemical properties of bamboo materials. Sci Rep 9(1):1–11 53. Palombini FL, de Araujo Mariath JE, de Oliveira BF (2020) Bionic design of thin-walled structure based on the geometry of the vascular bundles of bamboo. Thin-Walled Struct 155:106936 54. Zhang T, Wang A, Wang Q, Guan F (2019) Bending characteristics analysis and lightweight design of a bionic beam inspired by bamboo structures. Thin-Walled Struct 142:476–498

Performance Assessment Methods and Effects of Bamboo-Based Envelopes in Buildings Under Hot and Humid Conditions Miguel Chen Austin, Thasnee Solano, Cristina Carpino, Carmen Castaño, and Dafni Mora

Abstract The increment in the average global temperature and the lack of resources for the built environment are leading researchers to look for alternative construction materials and building design approaches based on nature. Bamboo-based materials have been attracting significant interest in the design and construction of sustainable buildings because of their fast-growing, appropriate thermal and mechanical properties and effectiveness in CO2 absorption. Thus, this chapter systematically analyzes the methods employed over the years to assess the thermal and energy performance of bamboo-based constructive systems as part of the building’s envelope (either by relevant thermal properties, comfort indicators, or energy indicators) under hot, humid, and tropical conditions. The interest in studying bamboo-based composites coupled with advanced assessment methods is considered a current and trending topic. Most M. C. Austin · T. Solano · C. Carpino · C. Castaño · D. Mora (B) Research Group in Energy and Comfort in Bioclimatic Buildings (ECEB), Faculty of Mechanical Engineering, Universidad Tecnologica de Panama, Ciudad de Panama 0819-07289, Panama e-mail: [email protected] M. C. Austin e-mail: [email protected] C. Carpino e-mail: [email protected] C. Castaño e-mail: [email protected] M. C. Austin · D. Mora Centro de Estudios Multidisciplinarios en Ciencias, Ingeniería y Tecnología (CEMCIT-AIP), Ciudad de Panama 0819-07289, Panama Sistema Nacional de Investigación (SNI), Clayton, Panama City 0816, Panama C. Carpino Department of Mechanical Energy and Management Engineering, University of Calabria, Via P. Bucci, 87036 Arcavacata, Rende, Cosenza, Italy C. Castaño Faculty of Industrial Engineering, Universidad Tecnológica de Panama, Ciudad de Panama 0819-07289, Panama © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 F. L. Palombini and F. M. Nogueira (eds.), Bamboo and Sustainable Construction, Environmental Footprints and Eco-design of Products and Processes, https://doi.org/10.1007/978-981-99-0232-3_11

291

292

M. C. Austin et al.

studies, including experimental analysis, are not performed at the building scale, but rather at a local scale that struggles to consider the thermal dynamics the envelope system could experiment. The latter was investigated through four case studies under the tropical climates of Panama for March and October. Here, common bamboobased envelope elements were assessed and compared to conventional envelope elements with different insulation and thermal mass degrees via parametric analysis based on dynamic simulations. Results demonstrated comparable energy and thermal performance to other conventional envelope elements and, in some cases, successfully outstanding recommended envelopes in the local regulation. Finally, including bamboo envelope elements in buildings help increase energy efficiency by reducing electricity consumption for cooling, not so regarding the thermal comfort in merely naturally ventilated buildings. Keywords Bamboo envelopes · Buildings · Energy performance · Dynamic simulation · Hot climate · Humid climate · Parametric analysis · Tropical

1 Introduction Both the demand for non-renewable building materials and the total energy consumption of buildings are increasing considerably worldwide, causing negative effects on the environment. In recent years, sustainable construction has begun to be required in the cities’ development, promoting environmentally friendly building materials [1], such as bamboo. Bamboo grows naturally and responds favorably under tropical climate conditions. Implementing bamboo in architecture in regions such as Indonesia has comfortably influenced the microclimate [2, 3]. As so in non-tropical climates, there are more and more successful applications of bamboo in the construction sector worldwide, such as the bamboo ceiling at Madrid International Airport in Spain, the Tokyo Dong Wu Department in Japan, the bamboo floors in the Clinton Library in the United States, and IBM headquarters in Germany [4]. Hence, it is relevant to study its applications in design and its effects on energy performance. Many governments worldwide have already introduced several policy measures to promote the application of bamboo as a building material. In Europe, several programs to encourage bamboo materials have been introduced, for example, “Sustainable management and quality improvement of bamboo and products [5] and “New bamboo engineered biomaterial for sustainable building components” [6] in countries such as the UK, Germany, Belgium, and Italy. The Indian government launched the “National Bamboo Mission” in 2006 [7]. The Chinese government has been promoting bamboo-based materials by introducing a series of guidance documents [8], for example, the “Replacing Wood with Bamboo” program published in 2005. It included producing and using bamboo as a building material as a key research area in China’s 13th Five-Year Plan [8]. Moreover, Bamboo is considered worldwide as a green construction material [8], outperforming wood due to its rapid growth, reduced carbon emissions, and high

Performance Assessment Methods and Effects of Bamboo-Based …

293

mechanical and structural properties, making it an alternative element to replace commonly used materials such as concrete and steel [9, 10]. Bamboo can replace up to 70% of the steel used in a building and reduce 40% of the cost [11]. Besides, construction standard codes are available [11], such as ISO 22156: 2004 Bamboo structural design, ISO 22157: 2004 Bamboo physical and mechanical properties, and IS 9096: 1979 Code of practice for conservation of bamboo for structural purposes. Today, bamboo-based materials (also called bamboo composites) are very homogeneous in quality, can be tested and calculated in the same way as wood constructions, and have better strength and termite-resistant quality than untreated bamboo [9], also called biocomposites, can be divided into three categories [12]: (i) Conventional biocomposites: chipboard and flakeboard, plywood and laminate boards, medium density fiberboard, hybrid biocomposites. (ii) Advanced polymer biocomposites: thermoplastic-based bamboo composites, thermoset-based bamboo biocomposites, elastomer-based biocomposites. (iii) Inorganic-based biocomposites: inorganic binders—gypsum, portland cement, and magnesium cement. In this matter, a recent study developed eco-friendly building materials with improved thermal and mechanical performances using red clay and biochar produced from rice husk, coconut shell, and bamboo. The C-Therm’s analyzer was used to measure thermal conductivity, and infrared experiments were performed to quantify heat transfer. The thermal conductivity of these composites incorporating bamboo was found to vary between 0.143 and 0.223 W/mK. The 10% bamboo weight percentage of the mixture was the most effective combination that allowed for the optimization of thermal properties and mechanical strength [13]. Additionally, unlike other woods, bamboo can be harvested after three to four years after planting and annually after that. Annual harvesting of bamboo keeps the bamboo clump or forest healthy. Because when bamboo is harvested, the root system is not damaged and is ready to produce more shoots, allowing for a sustainable harvest of bamboo [14]. Thus, it is important to know where it will be used, whether as a structure, in interior spaces, or as a building envelope, since the way the material is processed influences its density, composition, morphology, and mechanical properties, which vary among different species. Furthermore, the benefits of bamboo application as a green building material can be classified into five categories. (i) Large-scale and fast-growing bamboo is one of the fastest-growing and widely distributed plants on Earth [15]. It is mainly distributed in three regions: Asia–Pacific, America, and Africa, and Asia–Pacific is the largest in terms of materials volume. According to Escamilla et al. [16], there are more than 180,000 km2 of bamboo forests in Asia (half the size of Germany). Bamboo also exhibits a short rotation age. It has a higher accumulation rate than timber and can be harvested every three to five years. Besides, harvesting bamboo is more acceptable to the general public than harvesting timber [17]. (ii) Lightweight and high strength, bamboo, also known as “vegetable steel” due to its lightweight and high-strength characteristics, is stronger than steel in tension and bending in certain cases [15]. It has been used to construct millions of houses worldwide over the past thousands of years although these homes are largely in simple structures [18, 19]. Besides, bamboo is often used as an alternative to wood and plastic for

294

M. C. Austin et al.

drainage pipes and storage facilities, offering resilient structures that can withstand natural phenomena such as high-velocity winds [20] and earthquakes [11, 20]. (iii) Low cost, the cost of bamboo raw materials, is low [8], also known as “poor man’s wood” in vulnerable areas of the world [18]. In India, for example, there are lowcost houses with prefabricated bamboo reinforcements and wall panels [18]. (iv) Eco-friendly and environmentally friendly: the application of bamboo as a building material can reduce the depletion pressure of non-renewable building materials and contributes to energy savings, reduction of CO2 emissions, and increased carbon storage [20]. Besides, bamboo planted on sloping agricultural land positively affects water conservation and soil erosion control [15]. Finally, (v) socially beneficial and economically underdeveloped areas where bamboo resources exist, its application can help local workers to have greater job opportunities and increase their income. In summary, the above-discussed benefits of using bamboo can contribute to the promotion of sustainable construction. Architects and engineers are encouraged to explore the world of possibilities offered by this environmentally friendly material. But for this, we must familiarize ourselves with the various bamboo species and the properties that each possesses. Hence, this chapter gathers and analyzes information related to the methods to assess the thermal and energy performance of bamboo-based constructive systems (either by relevant thermal properties, comfort indicators, or energy indicators) as part of the buildings’ envelope under hot and humid conditions.

2 A Systematic Literature Review on Bamboo-Based Envelopes’ Thermal Performance Evaluation Methods This section is dedicated to gathering and analyzing relevant information related to the methods employed to assess the thermal and energy performance of bamboo-based constructive systems as part of the buildings’ envelope under hot and humid conditions. The literature concerning these methods, either based on numerical, experimentation, or a combination of both, is systematically analyzed to present past and new trends highlighting the potential of bamboo. To retrieve information from the vast literature concerning bamboo implementation in buildings, the search was limited to the range of years from 2012 to 2022 within the Google Scholar, SCOPUS, and Web of Science databases. More than a few thousand references were encountered, where only 309 are strictly related to this chapter’s subject. Figure 1 shows the generating keywords and keyword combination strategy followed. These 309 references were first treated with the VOSviewer 1.6.17 software [21] to highlight current knowledge interests and trends. Figure 2 shows a network map of the keywords found and their relationship by term frequency threshold (only considering keywords appearing three times). This led to 1780 keywords being found, but only 73 met the term-frequency threshold. Results showed eight clusters (represented by different colors in Fig. 2). The keyword “bamboo” is the most frequent term, with

Performance Assessment Methods and Effects of Bamboo-Based …

295

Fig. 1 Flow followed to generate keywords and keyword combinations

98 occurrences, followed by “mechanical properties” with 40 occurrences, which highlights the main topics of interest in this literature review. Although eight clusters are identified by color, some clusters are concatenated. For instance, the only cluster appearing to stand alone is the red cluster gathering

Fig. 2 Network map by keywords and by three-times term occurrence

296

M. C. Austin et al.

keywords related to direct building application interests. However, the turquoise, olive, green, purple, and brown clusters can be considered a combined cluster since they gather keywords related to the physical properties, i.e., hygrothermal, chemical, mechanical, and treatments to the bamboo fiber. Here, the bamboo species appearing as most frequent are as follows: Phyllostachys edulis (known as bamboo Moso or winter bamboo from China), Guadua (from tropical regions in America), and Bambusa vulgaris (known as the common bamboo from China). The orange and blue clusters gather more general studies interested in bamboo and its effect on sustainability and climate change. Moreover, Fig. 3 shows that interest in direct bamboo application in buildings has been diminishing since 2018. The interest in studying bamboo’s physical properties and assessment methods has remained active until recently (2019–2020), when exploring bamboo-based composites coupled with advanced assessment methods may be considered the current and trending topic (2021-current).

Fig. 3 Overlay map by keywords and by three-times term occurrence

Performance Assessment Methods and Effects of Bamboo-Based …

297

2.1 Most Frequent Bamboo-Based Envelope Systems and Characteristics A total of 1575 bamboo species are found in the world [12], with 1200 species of woody bamboo [22]. Of these, only 20–38 species are useful in construction, Moso bamboo (P. edulis), Guadua (Guadua angustifolia Kunth), and giant bamboo (Dendrocalamus asper) the most important, being the strongest and largest of all [23]. Bamboo’s resistance depends on the species since it depends on age, diameter, wall thickness, load position, the radial position from outside to inside, and water levels [12]. Knowing that bamboo is a natural material, susceptible to natural degradation, if properly treated and industrially processed, components made of bamboo can have a useful service life of 30–40 years. However, the natural durability of bamboo varies according to the species and types of treatments [24]. Moreover, various applications of bamboo in the construction sector can be identified based on the characteristics of the material and the function it is required to perform. It can be used to construct the load-bearing structure of buildings, the external envelope (walls or roof), or the separation elements (internal horizontal or vertical partitions). Other uses are attributable to the production of accessory building components such as screens, railings, floors, coverings, and various types of furniture. In general, the use of bamboo in construction can be connected into four categories (Fig. 4). Raw bamboo refers to the use of materials obtainable from the bamboo plant in its original form (culm, stems, and foliage) or subjected to primary transformations to obtain, for example, strips, curtains, chips, etc., in their natural state or treated for improved durability. Bamboo in the form of fabric or non-woven fabric is a particular category that finds application not only in the construction sector but also in the automotive industry. Eco-sustainable and bio-compatible insulation based on bamboo are widely used in the construction industry and have already captured a good share of the market in a scenario that has increasingly turned to green goals. Engineered bamboo is the broadest category, which includes a range of products made artificially from bamboo by various processes and fabrications. Figure 5 shows a list of engineered bamboo products used in construction. However, what is attracting the most attention is the possibility of using bamboo in composite products (as also found in the analysis of Fig. 3). Positive properties can be enhanced by processing and

Raw bamboo

Engineered bamboo

Non-woven and bamboo textile

Fig. 4 Main categories of bamboo used in construction

Bamboo insulation infills

298

M. C. Austin et al.

Laminated bamboo sheet Bamboo mat board

Bamboo composites

Bamboo scrimber

Bamboo fiberboard Engineered bamboo building products

Bamboo particleboard

Plybamboo

Bamboo laminated lumber

Flattened bamboo panel

Bamboo oriented strand board (bamboo OSB)

Fig. 5 Engineered bamboo building products

incorporating the raw material with other materials, helping eliminate or minimize negative features. Several studies are being carried out in this direction, proposing alternative construction systems based on bamboo. Important aspects of bamboobased envelopes in most recent studies are summarized in Table 1.

2.2 Performance Assessment Methods of Bamboo-Based Envelope Systems In the literature, the performance of bamboo-based envelope systems is either assessed via experimental studies [25, 27, 28, 35, 36, 40, 41, 44, 46–55], numerical analysis (including simulation) [42, 56], or a combination of both [1, 43, 45,

Bamboo Moso (Phyllostachys pubescens “Mazel”)

Phyllostachys, Dendrocalamus,Bambusa, Guadua, and Gigantochloa

Madake bamboo (Phyllostachys bambusoides)

Moso bamboo (Phyllostachys pubescens)

Zhejiang, China

Various

Kyoto, Japan

Taiwan

Lin’an, Moso bamboo (Phyllostachys pubescens) Zhe-jiang, China

Species of bamboo

Place

Study the mechanical properties of woven bamboo fiber-reinforced (WBF) polypropylene (PP) composites Explore how high-temperature hydrothermal treatment affects the integral properties of bamboo

Bamboo + high-temperature hydrothermal treatment

Investigate the effect of smoke treatment on the hygroscopic characteristic of smoke-modified bamboo

Oven bamboo fiber (WBF) + reinforced polypropylene (PP) composites

• • • •

Bamboo untreated Bamboo smoked Bamboo dried Bamboo Dyed

Laboratory experiments

Laboratory experiments

Laboratory experiments

A review of the Collection of existing knowledge of most relevant the mechanical information properties of laminated bamboo lumber

Bamboo + PF Bamboo + MUF Bamboo + HPA Bamboo + PVA

• • • •

Identify the properties Laboratory of heat-treated oriented experiments bamboo fiber mats for their applications in structural and floor systems

Bamboo + phenol formaldehyde resin

Methodology

Research objective

Bamboo-based envelope system

Table 1 Aspects of most recent studies: species, envelope systems, and methods

• High-temperature hydrothermal treatment • Swelling Test

Universal material testing machine (AG-250/300KNX, Shimadzu corporation, Japan)

Spectroscopic techniques

Detailed, selective, and critical study

• Universal testing machine • FTIR-ATR spectroscopy

Technique implemented

(continued)

2022 [29]

2022 [28]

2022 [27]

2022 [26]

2022 [25]

Year Reference

Performance Assessment Methods and Effects of Bamboo-Based … 299

Species of bamboo

Moso bamboo (Phyllostachys pubescens)

Undefined

Place

Various

Anhui Province, China

Table 1 (continued) Methodology

• Highlight the Laboratory similarities and experiments differences between wood and bamboo characteristics pertaining to adhesive interactions and bonding processes • Elucidate techniques to improve the surface properties and bonding performance of bamboo • Identify challenges and knowledge gaps in engineered bamboo manufacturing, testing, and performance

Research objective

Bamboo + wood + stud + Determine how Mathematical fiberglass insulation + climate affects models gypsum board + paint building materials over time and determine actions needed to prevent deterioration of materials and extend the useful life of buildings

Bamboo-based composites: • Bamboo + PF • Bamboo + polymeric methylene diphenyl diisocyanate (pMDI) Bamboo + EPI • Bamboo + PUR • Bamboo + wood

Bamboo-based envelope system

RC machine learning method with AHC

• Chemical and steam treatments • Surface modification using physical methods

Technique implemented

(continued)

2022 [31]

2022 [30]

Year Reference

300 M. C. Austin et al.

Makino bamboo (Phyllostachys makinoi) Moso Bamboo (Phyllostachys pubescens)

• • • • • • •

Yushania alpina

Taiwan

Malaysia

Ethiopia

Bambusa blumeana Bambusa vulgaris Balanocarpus levis Dendrocalamus asper Gigantochloa scortechinii Gigantochloa levis Koompasia malaccensis

Species of bamboo

Place

Table 1 (continued)

Bamboo fibers

Expand the knowledge of the mechanical, thermal, and chemical properties of alkali-treated Ethiopian Yushania alpine bamboo fiber

Compile the trends of physical, mechanical, and thermal properties of bamboo fiber-reinforced thermosetting and thermoplastic polymers, hybrid composites, and their application

Bamboo fiber + Thermoplastic polymer Composites

Experimental study

Collection of most relevant information

Evaluate the physical Laboratory and flexural properties experiments of Bamboo Sticks Boards and Veneers Bamboo Sticks Boards treated at different vacuum treatment temperatures and their dimensional soaking capacity for 24 h

Bamboo sticks + bamboo veneers + PF resin

Methodology

Research objective

Bamboo-based envelope system

• Universal testing machine • Design Expert® 11

Detailed, selective, and critical study

Heat Treatment under Vacuum

Technique implemented

(continued)

2022 [34]

2022 [33]

2022 [32]

Year Reference

Performance Assessment Methods and Effects of Bamboo-Based … 301

Species of bamboo

Moso bamboo (Phyllostachys pubescens)

Phyllostachys iridescens

Various

Various

Place

An Hui Province, China

Anhui province, China

Asia Pacific región, North, Central and South America

Unspecified

Table 1 (continued) Methodology

A critical review of the Compilation of mechanical relevant studies performance of bamboo fiber-reinforced polymeric composites (BFRP) to determine possible structural applications

Bamboo + polymer composites

Experimental study

Review of the key Collection of aspects of bamboo as a most relevant construction material information

Evaluate the stability of bamboo to deformation and provide important guidelines for its industrialization

Investigate the Experimental mechanical properties study of bamboo scrimber (BS) in its three main load directions and understand its mechanical differences from other bamboo or engineered wood products

Research objective

• Full/half culm bamboo • Engineered bamboo • Bamboo-reinforced concrete

Bent Bamboo

Bamboo scrimber

Bamboo-based envelope system

Critical analysis

Detailed, selective, and critical study

SilviScan analysis

• Extensometer • Mathematical equations

Technique implemented

(continued)

2022 [38]

2022 [37]

2022 [36]

2022 [35]

Year Reference

302 M. C. Austin et al.

Bamboo culms

Bamboo-based composite panel

Moso bamboo (Phyllostachys edulis)

Moso bamboo (Phyllostachys heterocycla)

Hunan Province of China

China

Improve the Experimental mechanical properties study of the bamboo-based panel, extend its service life, and improve the quality of its application and comprehensive utilization of bamboo materials for future use in structural construction

Explore the dynamic Experimental changes of chemical study and mechanical properties and their relation to the soluble sugar and starch contents of bamboo after storage in water to provide a theoretical basis and references for large-scale industrial processing

Summarize and further Compilation of discuss the accumulated achievements of knowledge bamboo bolts, including their classification, mechanical properties, and anchoring performance

Bamboo + anchoring adhesive

Bambú Moso (Phyllostachys edulis)

China

Methodology

Research objective

Bamboo-based envelope system

Species of bamboo

Place

Table 1 (continued)

• Box–Behnken model design • Data analysis Static bending strength (MOR) • Elastic modulus (MOE) • Hot pressing equipment: LB-D1.00MN • Universal mechanical testing machine: WDW-100

• Ultraviolet spectrophotometer • Testing Methods according to the Chinese National Standards (GB/T 15,780–1995)

• Universal testing machine • Tensile test device • Engineering inspection • Theoretical analysis

Technique implemented

(continued)

2021 [41]

2021 [40]

2022 [39]

Year Reference

Performance Assessment Methods and Effects of Bamboo-Based … 303

Perform a thermal Experimental energy analysis and evaluation and assess the life cycle simulation GHG emissions of different wall configurations using biological mortars produced with bamboo particles (EMB) Evaluate the thermal Field Test and acoustic performance of a building envelope made with aerated cement fiber panels and bamboo composite Study the thermal performance of a new steel-bamboo composite wall for use in residential buildings in different climatic regions

• Bamboo particles (BP) + fine earth fractions • Hydrated lime • Portland cement • Metakaolin • Fly ash

Bamboo + cement plaster + steel wire mesh

Bamboo + steel

Bambusa chungii

Bamboosa balcooabamboo

Undefined

Brazil

Roorkee, India

China

Field Test and simulation analysis

Simulation

Present an overview of the problem of overheating and thermal comfort of the envelopes of buildings to promote bamboo as a building material for prefabricated lightweight systems

• Steel + bamboo • Brick, and bamboo-Expanded Polystyrene (EPS)

Moso bamboo (Phyllostachys edulis)

Hungary

Methodology

Research objective

Bamboo-based envelope system

Species of bamboo

Place

Table 1 (continued) Year Reference

• • • •

Software EnergyPlus Patrol check device Heat flux meter Temperature sensor

• Infrared thermometer Fluke 64 MAX • Sound level meter Class I, CESVA SC-420 • Lux meter

• DesignBuilder software • GHG emissions life cycle modeling • Scanning electron microscope (SEM) • C-Therm equipment, model TCi

2020 [45]

2021 [44]

2021 [43]

• Therm version 7.7.10 2021 • DesignBuilder version [42] 6

Technique implemented

304 M. C. Austin et al.

Performance Assessment Methods and Effects of Bamboo-Based …

305

57–64]. Here, envelope systems refer to the integral consideration of all three envelope elements: external and internal walls, roof, and floor. Most studies, including experimental analysis, are not performed at the building scale [45, 53, 55, 63], but rather at a local scale that struggles to consider the thermal dynamics the envelope system could experiment with. Such local experimental studies are often performed under controlled conditions using probes or individual envelope elements, e.g., walls. In these cases, the performance is assessed by the (i) thermal conductivity [47, 50, 54, 60, 61, 65], via the transient plane source method [65], the steady-state guarded hot-plate method [47, 57, 60, 64], guarded heat flow meter method [50], (ii) specific heat capacity [60, 66] via the differential scanning calorimetry [51, 57, 60, 66], (iii) radiative properties (emissivity, reflectivity) [67] and surface morphology [51], via the scanning electron microscope [51], and (iv) how they are affected by the humidity content [29, 48, 58, 59] via the thermogravimetric analysis [51, 60], experimental tests in climate chamber [58]. Most studies focusing on thermal conductivity found a strong insulation-like characteristic of all bamboo-based composites analyzed, with values between 0.0423 [61] and 0.3760 W/mK [57] among all composites analyzed, where lower values relate to the dry bamboo. Although the local assessment methods of bamboo-based composites are not the main focus of this chapter, such studies are fundamental to conducting analysis at the building scale. In the latter, performance assessment studies often need to incorporate parameters such as the transmittance value (U) and heat capacity of each bamboo composite, where the bamboo layer is only a part of the envelope element. This led researchers to combine experimental and numerical analysis. In such analyses, the criteria used for performance assessment are electrical consumption [45, 60] due to cooling needs [45, 56], indoor thermal comfort [42, 60], acoustic comfort [44], hygrothermal [58, 59, 61], and time lag and decrement factor [63].

3 Case Study: Parametric Analysis of Bamboo-Based Envelopes Effect in Buildings Energy Performance Under Panama’s Tropical Climate To assess the performance of the bamboo-based envelope systems encountered, the tropical conditions of Panama were selected as a case study along with four building typologies (Table 2). Each case study has been evaluated in previous studies under conventional envelope conditions and scenarios. Here, a parametric analysis is performed to compare such conventional envelopes containing different degrees of insulation and thermal mass with the bamboo-based envelope in terms of comfort, heat gains, and electricity due to cooling; Fig. 6 presents the overall methodology followed. Among the evaluated conventional envelopes are the envelope characteristics proposed by local Panama regulations and Bio-PCM envelopes. The latter is only in case 4.

306

M. C. Austin et al.

Table 2 Building typology and characteristics of the cases of the evaluated studies Case study

Building typology

Characteristics

Climate type, location

Reference

1

Conventional residence

One story, multizone

Awi, Chitré

[68]

2

Residence

One elevated story, multizone

Awi, Diablo—Panama City

[69]

3

Dwelling

Four stories, multizone

Awi, Panama City

[70]

4

Office

One story, multizone

Awi, Panama City

[71]

Input: Dynamic simulation for March and October

Occupants behavior

Output:

Cooling (electricity)

1

Discomfort hours Envelope materials

2

Envelope systems tested

Bamboo

3

Meterological data

Envelope heat gains

EPS

Steel

4

Systems

Conventional Chinesse Bamboo

Insulation degree

Thermal mass degree

Envelope systems tested Case studies

Parametric study

Assessment criteria

Fig. 6 Overall methodology followed for each case study analysis was performed using the DesignBuilder software

The first case study corresponds to an existing 55 m2 residence located within a neighborhood in Chitré. The neighborhood construction ended in 2019, so the residences were built with the design and materials typical of current architecture without considering the criteria of the sustainable building regulations. External walls and partitions are constructed of 0.1016-m-thick concrete blocks with a 0.0127-m mortar layer on both sides. The ceiling is of the suspended type, made of 7-mmthick gypsum sheets. The gable roof of the building is made of 26-gauge zinc sheets (0.44 mm thick) with a 30° slope. As for the openings, the exterior and interior doors are made of medium-density fiberboard (MDF) with a thickness of 0.030 m, except for the rear door, which is made of cast iron (gray iron), also with the same thickness. These have dimensions of 1 m wide by 2.10 m high. The wood doors have the following thermal properties: a U-value of 1.40 W/m2 K, a thermal conductivity of 0.14 W/mK, a specific heat of 1700 J/kgK, and a density of 600 kg/m3 . On the other hand, the iron door has a U-value of 5.836 W/m2 K, a thermal conductivity of 56 W/mK, specific heat of 530 J/kgK, and a density of 7500 kg/m3 . The windows are 1.20 m wide by 1.00 m high and are single-glazed with 3-mm glass. The thermal properties of this glass are as follows: U-value of 3.835 W/m2 K, the conductivity of 0.90 W/mK, solar gain coefficient (SGHC) of 0.768, direct solar transmission (g-value) of 0.741, and a light transmission coefficient of 0.821 [68].

Performance Assessment Methods and Effects of Bamboo-Based …

307

In the second case, an existing house of such type was taken as reference (144.06 m2 ), where its envelope is mostly constituted out of heavyweight wood as part of the floor, external walls, and internal partitions (of 0.20 m thickness), whit classic type of single windows (with a 50% of WWR). External walls (0.665 W/m2 K), windows (6.121 W/m2 K), floor (0.648 W/m2 K), and roof (0.670 W/m2 K) [69]. The roof is composed of standard concrete tiles, and the floor is elevated 3 m away from the ground. The third case corresponds to a fictional four-story dwelling (400 m2 per story, 3.3 m height) with envelope characteristics established by local regulations. The flat roof is made of 200-mm concrete, 67.1-mm insulation, 200-mm air gap, and 10mm plaster (0.459 W/m2 K), and internal floors are made of ceramic 10 mm, cast concrete 200 mm (2.864 W/m2 K) [70]. Exterior walls and partitions are made of cement 100 mm, and plaster (×2) 5 mm (2.534 W/m2 K). Finally, the fourth case corresponds to a fictional one-story office building of 375 m2 . For the external walls (3.859 W/m2 K), a 0.01-m mortar layer was followed by a 0.1-m heavyweight concrete layer and a 0.01-m mortar layer. For the internal partitions (2.618 W/m2 K), there was a 0.01-m mortar-cellular-cement layer followed by a 0.1-m heavyweight concrete layer and a 0.01-m mortar-cellular-cement layer. Both layouts were chosen based on the local standard construction tendency. For the floor (3.487 W/m2 K), there was 0.1-m cast dense concrete as the external layer and 0.016-m granite as the internal layer. The roof (1.486 W/m2 K) was a 0.2-m concretebased slab followed by a 0.5 m air gap and a 0.02-m gypsum-plasterboard layer and solar-gray double-layer windows (1.96 W/m2 K) [71]. Each envelope element and system were assessed through a parametric analysis in the software DesignBuilder v7.0.1.006. Typical meteorological data was acquired from Solargis CLIMdata® . The input data for the parametric analysis consists of the dynamic behavior of the buildings under specific climatic conditions, the conventional envelopes containing different degrees of insulation and thermal mass (from Panama and default incorporated in the software), and bamboo-based envelope systems from Al-Rukaibawi et al. [42]. For the latter, the bamboo-based envelope systems evaluated are the modified steel bamboo, bamboo with EPS, and the original Chinese bamboo with steel [42] (Table 3). Table 3 Bamboo envelope elements used in the parametric analysis

Envelop component [42]

U (W/m2 K)1 ID (-)2

Modified steel-bamboo composite wall 0.186

0.477

Bamboo composite roof

0.131

0.5878

Bamboo partition

0.412

0.8451

Slab on the ground with bamboo

0.34

0.8720

External wall (Bamboo-EPS)

0.181

0.9282

Chinese bamboo steel

0.300

0.700

1 Transmittance 2 Insulation

[72]

calculations from DesignBuilder degree (ID) calculation procedure from Araúz et al.

308

M. C. Austin et al.

Average simulation results from March (the hottest month) and October (the rainiest month) were used as input data for the parametric analysis. Daily averages were used for cases 1, 2, and 4, and monthly averages for case 3. The latter helped speed up the analysis due to the massive building without losing accuracy. The performance criteria used to evaluate such building envelopes are the electricity consumption due to cooling (conditioned to the specific case study), average thermal discomfort hours at the building level (based on the ASHRAE 55, adaptive 80% of acceptability), and the envelope element ability to manage the heat gains. For case study 1, the three criteria were used to evaluate the performance of the bamboo-based envelope. In this case study, not all houses have air-conditioned zones, and some are entirely naturally ventilated. For those houses with air-conditioned zones, Fig. 7a shows significant variability in the electricity consumption among the envelope systems assessed. The greater changes are presented when using the original external walls (309.81 kWh, reference case) and superinsulated brick/block external walls, resulting in about 15.5% reduction (the lowest cooling values encountered). All bamboo-based external walls appeared to perform similarly when combined with a steel-bamboo composite roof, with a cooling reduction of 14.2% for Chinese steel-bamboo composite, steel-bamboo composite, and bamboo EPS. However, the Chinese steel-bamboo composite appeared to work best with a heavyweight energy code standard roof, reaching a reduction of 15.5% in electricity for cooling (just like the superinsulated wall). Similar results were found in [3, 45, 73], where the greater the insulation degree, the lower the cooling electricity consumption. This highlights the bamboo insulation-like behavior tendency. On the contrary, high insulation degree envelopes in buildings without air conditioning in tropical climates can significantly affect thermal comfort. This is observed in Fig. 7b via the discomfort hours (DH). Here, the original walls present the best results (137 h) when combined with the bamboo roof as the original roof. On the other hand, depending on the type of roof, bamboo walls behave differently: (i) steel-bamboo composite with medium-weight energy-standard roof increases the DH by about 12%, but combined with bamboo roof, DH increases up to 60% concerning the original case. (ii) bamboo-EPS walls with a bamboo roof yielded the same results as the steel-bamboo composite wall. However, the DH only increases by about 12% when bamboo-EPS is combined with a lightweight energy-standard roof. (iii) Chinese bamboo also attained about a 12% increase in DH when combined with a clay tiles roof. However, the DH increased by about 53% when combined with a bamboo roof. Moreover, Fig. 7c shows the external walls’ heat gains variability, similar to Fig. 5a, suggesting these heat gains dominate the cooling needs, which again highlights the insulating characteristics of bamboo, resulting in an average of about 86% heat gain reduction concerning the original walls when the bamboo roof is combined with any bamboo wall. On the other hand, case study 2 does not possess any air-conditioned zones. Here, as suggested by the bioclimatic architecture for tropical climates [74], envelopes with low insulation and thermal mass degrees perform best. The lowest discomfort hours are presented with uninsulated lightweight external walls, with a difference of

Performance Assessment Methods and Effects of Bamboo-Based …

309

Fig. 7 Parametric results regarding roofs and external walls for case study 1: a Electricity due to cooling, b discomfort hours, and c wall gains

310

M. C. Austin et al.

Fig. 7 (continued)

about 6% with respect to the original walls (216 h) (Fig. 8a). However, the combination of uninsulated lightweight external walls with the steel-bamboo composite roof appeared as the best option, achieving a reduction of about 21% with respect to a combination of a bamboo-based roof with bamboo-based walls. Slightly better than the RES roof (based on new local regulations). Note here that negative values refer to a contribution to reducing the indoor environment temperature. Bamboo-based walls reduce this contribution almost to zero. Moreover, Fig. 8b shows the advantages of low insulation degree as similar values are found with a combination of uninsulated walls and roof, and the original walls have an uninsulated roof. Figure 8c, similar to Fig. 8a, shows that bamboo-based roof presents the lowest heat gains. This leads to the state that attention should be paid to the envelope combination rather than only choosing to modify one envelope element. For instance, in terms of discomfort hours, steel-bamboo roof only appears to work with uninsulated lightweight walls (Fig. 8a). Still, from the point of view of the roof heat gains, the steel-bamboo roof works indistinguishably well when combined with any type of wall (resulting in about 91% reduction) (Fig. 8c). The latter was also pointed out in Araúz et al. [72]. The envelope should be treated as a system (including internal partitions) rather than independent elements; this is at least for tropical climates. Conversely, since case study 3 corresponds to a four-story dwelling, roof materials may only affect the highest story. Thus, instead of presenting the variability in roof heat gains, as roof-ceiling sections could be assumed adiabatic, internal partitions are chosen instead

Performance Assessment Methods and Effects of Bamboo-Based …

311

Fig. 8 Parametric results regarding the external walls and partition constructions for case study 2: a Discomfort hours, b wall gains, and c roof gains

It can be observed that internal partitions have no significant influence on cooling and external wall heat gains as the latter (Fig. 9a, b), respectively). Similar to case study 1, the cooling is dominated by the external walls’ heat gains, where bamboo, as well as other walls with insulation degrees, performs best. Besides, lower roof heat gains are achieved when using bamboo; about 15% reduction is achieved with

312

M. C. Austin et al.

Fig. 8 (continued)

bamboo-based partitions together with bamboo external walls, with respect to the original walls and partitions. Similar to previous cases, bamboo does not seem to be the best choice regarding discomfort hours. The highest discomfort hours result from a combination of bamboo partitions and external walls. Please note that the air conditioner was set to 24/7 active in three of five zones (the living rooms and the two bedrooms). The parametric analysis with simulation results from October showed no significant differences from those from March. Regarding case study 4, Fig. 10 shows the parametric analysis results. Note that all zones are air-conditioned. Conversely to the results obtained in Austin et al. [71], where all preferable walls and roofs for such a case were based on PCM layouts to reduce cooling needs significantly, Fig. 10a shows that PCM-based external walls with steel-bamboo composite roofs perform better (achieving near 51% (788.21 kWh) reduction with BioPCM Dupont Energain wall). Besides, similar results can be achieved when the RES roof is combined with “brick air hollow concrete blocks and phenolic foam and lightweight plaster” wall (near 48% reduction). The original walls have the lowest performance, even if combined with any type of roof. However, both combinations reach higher discomfort hours than the original walls and roof (similarly with the RES roof). Note here that the air conditioner is only turned on when occupied. Regarding the wall (Fig. 10c) and roof heat gains (Fig. 10d), the roof heat gains appeared to dominate the cooling electricity consumption (Fig. 10a), contrary to the previous cases where the wall heat gains dominated. This may be due to the west–east extended building leading to a larger roof surface area than the wall surface area.

Performance Assessment Methods and Effects of Bamboo-Based …

313

Fig. 9 Parametric results regarding the external walls and partition constructions for case study 3 in March: a Electricity due to cooling, b wall gains, c roof gains, and d discomfort hours

Even if there is no apparent distinction among the type of walls, greater heat gains reduction is achieved: about 93% with the BioPCM Dupont Energain roof (481.70 kWh) and about 95% with the steel-bamboo composite roof (389.57 kWh). Similar behavior was found in October regarding all performance criteria. Bamboo EPS external walls coupled with BioPCM M27Q25 roof Dupont Energain show good performance. However, Chinese steel-bamboo composite walls display similar levels

314

M. C. Austin et al.

Fig. 9 (continued)

of discomfort when combined with any of the roofs. Regarding the cooling, steelbamboo composite roof combined with any walls excels as the lowest option with a reduction from 48.11% (with heavyweight energy-standard walls) to 50.02% (with superinsulated walls). This is followed by BioPCM Dupont Energain walls (49.68%) and bamboo EPS walls (49.17%), concerning the original walls and roof (1744 kWh).

Performance Assessment Methods and Effects of Bamboo-Based …

315

Fig. 10 Parametric results regarding the external walls and roof constructions for case study 4: a Electricity due to cooling, b discomfort hours, c wall gains, and d roof gains

316

M. C. Austin et al.

Fig. 10 (continued)

4 Final Discussion and Conclusions After analyzing the information related to the assessment methods for thermal and energy performance of bamboo-based constructive systems, although the interest in direct bamboo application in buildings has been diminished since 2018, the interest in bamboo’s physical properties and assessment methods remains active, where exploring bamboo-based composites coupled with advanced assessment methods may be considered as a trending topic.

Performance Assessment Methods and Effects of Bamboo-Based …

317

Results provided by the parametric analysis helped highlight the insulationlike characteristics of bamboo-based envelopes when used in buildings under tropical climates, as obtained in Huang et al. [61] and hot and humid climates [3]. Including bamboo envelope elements in buildings help increase energy efficiency by reducing electricity consumption for cooling as encountered in [3, 45, 63, 73], comparable to conventional type of walls [46]. Conversely, in general, the bamboo envelope elements assessed here are not adequate when the buildings are merely naturally ventilated since discomfort hours tend to increase compared to recommended envelopes for such climates, e.g., uninsulated or low degree of insulation. Comparing these results for different building typologies under tropical climates to results found in [42, 60], significant differences are encountered. In fact, following the insulation degree (ID) indicator in [72], the properties of steel bamboo composite wall yield an ID of 0.4770, placing it far away from the superinsulated external walls with an ID of 0.9176, which implies sufficient low (ID lower than 0.39 [72]) applicable to such climates. Dynamic simulation results of bamboo-based envelope elements demonstrated comparable energy and thermal performance to other conventional envelope elements and, in some cases, successfully outstanding local regulation envelopes. These findings could impact the cost not only in new buildings construction but also in buildings retrofit, with a lower ecological footprint (carbon and water). The carbon footprint of such envelopes with a conventional high insulation degree tends to be higher than bamboo-based envelopes [20] due to the bamboo content, which could be considered low [13]. Difficulties may arise if good maintenance of such bamboo envelope systems is not provided due to the thermal properties change with humidity content. For example, water infiltration or condensation problems, common to humid climates, could increase thermal conductivity, lowering the overall performance.

References 1. Shanmugam S, Sun C, Chen Z, Wu YR (2019) Enhanced bioconversion of hemicellulosic biomass by microbial consortium for biobutanol production with bioaugmentation strategy. Bioresour Technol 279:149–155. https://doi.org/10.1016/j.biortech.2019.01.121 2. Apsari DP, Dewi OC (2021) Bamboo as a structural element of architectural buildings in tropical climates. IOP Conf Ser: Earth Environ Sci 3. Caroline OS (2018) Implementing bamboo research into holistic architecture design for creating thermally comfortable interior environment in Gili Meno, Indonesia. IOP Conf Ser: Earth Environ Sci 4. Bamboo ceiling in Madrid International Airport—MOSO® Bamboo specialist. https://www. moso-bamboo.com/bamboo-inspiration/madrid-international-airport/?lang_selected=true. Accessed 4 Nov 2022 5. Sustainable management and quality improvement of bamboos and products. Project | Fact Sheet | FP4 | CORDIS | European Commission. https://cordis.europa.eu/project/id/IC1897 0176. Accessed 4 Nov 2022

318

M. C. Austin et al.

6. New BAMboo ENGineered bio-material for sustainable building components. BAMBENG Project | Fact Sheet | H2020 | CORDIS | European Commission. https://cordis.europa.eu/pro ject/id/663477. Accessed 4 Nov 2022 7. Lahiry S (2022) India’s national bamboo mission. http://www.millenniumpost.in/opinion/ind ias-national-bamboo-mission-308107. Accessed 4 Nov 2022 8. Shen L, Yang J, Zhang R, Shao C, Song X (2019) The benefits and barriers for promoting bamboo as a green building material in China—an integrative analysis. Sustain 11. https://doi. org/10.3390/su11092493 9. Nor AFM, Sultan MTH, Jawaid M, Abu Talib AR, Azmi AMR, Harmaen AS, Asa’ari AZM (2018) The effects of multi-walled CNT in bamboo/glass fibre hybrid composites: tensile and flexural properties. BioResources 13:4404–4415. https://doi.org/10.15376/biores.13.2.44044415 10. Shu B, Xiao Z, Hong L, Zhang S, Li C, Fu N, Lu X (2020) Review on the application of bamboo-based materials in construction engineering. J Renew Mater 8:1215–1242. https://doi. org/10.32604/jrm.2020.011263 11. Syeda A, Shrujal B, Kumar J (2014) A case study on bamboo as green building material. Int J Eng Adv Technol 2249–8958 12. Manandhar R, Kim JH, Kim JT (2019) Environmental, social and economic sustainability of bamboo and bamboo-based construction materials in buildings. J Asian Archit Build Eng 18:52–62. https://doi.org/10.1080/13467581.2019.1595629 13. Yang S, Wi S, Lee J, Lee H, Kim S (2019) Biochar-red clay composites for energy efficiency as eco-friendly building materials: thermal and mechanical performance. J Hazard Mater 373:844–855. https://doi.org/10.1016/j.jhazmat.2019.03.079 14. Asif M (2009) Sustainability of timber, wood and bamboo in construction. Woodhead Publishing Limited 15. Lu HF, Cai CJ, Zeng XS, Campbell DE, Fan SH, Liu GL (2018) Bamboo vs. crops: an integrated emergy and economic evaluation of using bamboo to replace crops in south Sichuan Province, China. J Clean Prod 177:464–473. https://doi.org/10.1016/j.jclepro.2017.12.193 16. Escamilla EZ, Habert G, Daza JFC, Archilla HF, Echeverry Fernández JS, Trujillo D (2018) Industrial or traditional bamboo construction? Comparative life cycle assessment (LCA) of bamboo-based buildings. Sustain 10. https://doi.org/10.3390/su10093096 17. Chang FC, Chen KS, Yang PY, Ko CH (2018) Environmental benefit of utilizing bamboo material based on life cycle assessment. J Clean Prod 204:60–69. https://doi.org/10.1016/j.jcl epro.2018.08.248 18. Rosse Caldas L, Bernstad Saraiva A, Andreola VM, Dias Toledo Filho R (2020) Bamboo bio-concrete as an alternative for buildings’ climate change mitigation and adaptation. Constr Build Mater 263. https://doi.org/10.1016/j.conbuildmat.2020.120652 19. Salzer C, Wallbaum H, Lopez LF, Kouyoumji JL (2016) Sustainability of social housing in Asia: a holistic multi-perspective development process for bamboo-based construction in the Philippines. Sustain 8. https://doi.org/10.3390/su8020151 20. Farah S, Whaley D, Saman W, Boland J (2019) Integrating climate change into meteorological weather data for building energy simulation. Energy Build 183:749–760. https://doi.org/10. 1016/j.enbuild.2018.11.045 21. VOSviewer—Visualizing scientific landscapes. https://www.vosviewer.com/. Accessed 3 Nov 2022 22. Nurdiah EA (2016) The potential of bamboo as building material in organic shaped buildings. Procedia—Soc Behav Sci 216:30–38. https://doi.org/10.1016/J.SBSPRO.2015.12.004 23. Benton A (2015) Priority species of bamboo. Springer, Cham, pp 31–41 24. Gichohi RN (2014) Factors influencing the use of Bamboo as a flooring construction material: a case of garden city project–Nairobi County. University of Nairobi, Kenya 25. Li X, Li L, Li N, Bao M, Bao Y, Wu Z, Wang J, Rao F, Chen Y (2022) Sustainable production of engineered bamboo scrimber composites for construction and flooring applications. Constr Build Mater 347:128615. https://doi.org/10.1016/j.conbuildmat.2022.128615

Performance Assessment Methods and Effects of Bamboo-Based …

319

26. Dauletbek A, Li H, Lorenzo R, Corbi I, Corbi O, Ashraf M (2022) A review of basic mechanical behavior of laminated bamboo lumber. J Renew Mater 10:273–300. https://doi.org/10.32604/ jrm.2022.017805 27. Ramful R, Sunthar TPM, Marin E, Zhu W, Pezzotti G (2022) Investigating the effect of smoke treatment on hygroscopic characteristics of bamboo by FTIR and Raman spectroscopy. Materials (Basel) 15. https://doi.org/10.3390/ma15041544 28. Wang BJ, Bin YW (2022) The natural fiber reinforced thermoplastic composite made of woven bamboo fiber and polypropylene. Fibers Polym 23:155–163. https://doi.org/10.1007/s12221021-0982-1 29. Li X, Peng H, Niu S, Liu X, Li Y (2022) Effect of high-temperature hydrothermal treatment on chemical, mechanical, physical, and surface properties of moso bamboo. Forests 13. https:// doi.org/10.3390/f13050712 30. Nkeuwa WN, Zhang J, Semple KE, Chen M, Xia Y, Dai C (2022) Bamboo-based composites: a review on fundamentals and processes of bamboo bonding. Compos Part B Eng 235. https:// doi.org/10.1016/j.compositesb.2022.109776 31. Wang X, Li H, Zhu Y, Peng X, Wan Z, Xu H, Nyberg RG, Song WW, Fei B (2022) Using machine learning method to discover hygrothermal transfer patterns from the outside of the wall to interior bamboo and wood composite sheathing. Buildings 12. https://doi.org/10.3390/ buildings12070898 32. Yang YH, Chung MJ, Wu TL, Yeh CH, Yang TC (2022) Characteristic properties of a bamboobased board combined with bamboo veneers and vacuum heat-treated round bamboo sticks. Polymers (Basel) 14. https://doi.org/10.3390/polym14030560 33. Radzi AM, Zaki SA, Hassan MZ, Ilyas RA, Jamaludin KR, Daud MYM, Aziz SA (2022) Bamboo-fiber-reinforced thermoset and thermoplastic polymer composites: a review of properties, fabrication, and potential applications. Polymers (Basel) 14. https://doi.org/10.3390/pol ym14071387 34. Ebissa DT, Tesfaye T, Worku D, Wood D (2022) Characterization and optimization of alkalitreated yushania alpina bamboo fiber properties: case study of ethiopia species. SN Appl Sci 4. https://doi.org/10.1007/s42452-022-04965-6 35. Wu M, Mei L, Guo N, Ren J, Zhang Y, Zhao Y (2022) Mechanical properties and failure mechanisms of engineering bamboo scrimber. Constr Build Mater 344. https://doi.org/10.1016/ j.conbuildmat.2022.128082 36. Wang X, Ma J, Xu W, Fei B, Lian C, Sun F (2022) Effect of bending on radial distribution density, MFA and MOE of bent bamboo. Sci Rep 12. https://doi.org/10.1038/s41598-022-126 75-7 37. Fahim M, Haris M, Khan W, Zaman S (2022) Bamboo as a construction material: prospects and challenges. Adv Sci Technol Res J 16:165–175. https://doi.org/10.12913/22998624/149737 38. Nurazzi NM, Norrrahim MNF, Sabaruddin FA, Shazleen SS, Ilyas RA, Lee SH, Padzil FNM, Aizat G, Aisyah HA, Mohidem NA, Asyraf MRM, Abdullah N, Sapuan SM, Abdan K, Nor NM (2022) Mechanical performance evaluation of bamboo fibre reinforced polymer composites and its applications: a review. Funct Compos Struct 4. https://doi.org/10.1088/2631-6331/ac5b1a 39. Li X, Zhou J, Meng X, Yan L, Zhao S, Ji X (2022) Research and prospects of bamboo bolts in China: state of the art. Eur J Wood Wood Prod. https://doi.org/10.1007/s00107-022-01834-2 40. Zhan H, Niu Z, Yu L, Li M, Wang C, Wang S (2021) Dynamic changes of chemical and mechanical properties of moso bamboo (Phyllostachys edulis) culms under different storage conditions. J Renew Mater 9:1031–1043. https://doi.org/10.32604/jrm.2021.014109 41. Li Q, Liu R, Chen X, Lin H (2021) Box-Behnken design for process parameters optimalization of bamboo-based composite panel manufacturing. Wood Res 65:989–1000. https://doi.org/10. 37763/WR.1336-4561/65.6.9891000 42. Al-Rukaibawi LS, Szalay Z, Károlyi G (2021) Numerical simulation of the effect of bamboo composite building envelope on summer overheating problem. Case Stud Therm Eng 28:101516. https://doi.org/10.1016/j.csite.2021.101516 43. Paiva RLM, Caldas LR, Martins APS, de Sousa PB, de Oliveira GF, Filho RDT (2021) Thermalenergy analysis and life cycle ghg emissions assessments of innovative earth-based bamboo plastering mortars. Sustain 13. https://doi.org/10.3390/su131810429

320

M. C. Austin et al.

44. Singh S, Chourasia A, Bisht RS, Yadav S (2021) Thermal and acoustic performance of cement fibreboard and bamboo buildings. Indian J Eng Mater Sci 28:462–471 45. Shan Q, Tong K, Zhang X, Li Y (2020) Field test and simulation analysis of thermal performance of bamboo steel composite wall in different climate regions. Adv Civ Eng 2020. https://doi. org/10.1155/2020/8854156 46. Bambi G, Ferraz PFP, Ferraz GAS, Pellegrini P, Di Giovannantonio H (2019) Measure of thermal transmittance of two different infill wall built with bamboo cultivated in Tuscany. Agron Res 17:923–934. https://doi.org/10.15159/AR.19.130 47. Kiran MC, Nandanwar A, Naidu MV, Rajulu KCV (2012) Effect of density on thermal conductivity of bamboo mat board. Int J Agric For 2:257–261. https://doi.org/10.5923/J.IJAF.201202 05.09 48. Liu R, Li Y (2015) Bamboo-steel composite structures. Futur Archit Res 49. Lv Q, Wang W, Liu Y (2019) Study on thermal insulation performance of cross-laminated bamboo wall. J Renew Mater 7:1231–1250. https://doi.org/10.32604/jrm.2019.08345 50. Mounika M, Ramaniah K, Ratna Prasad AV, Rao KM, Hema K, Reddy C (2012) Thermal conductivity characterization of bamboo fiber reinforced polyester composite. J Mater Environ Sci 3:1109–1116 51. Pu H, Shu C, Dai R, Chen H, Shan Z (2022) Mechanical, thermal and acoustical characteristics of composite board kneaded by leather fiber and semi-liquefied bamboo. Constr Build Mater 340. https://doi.org/10.1016/j.conbuildmat.2022.127702 52. Shah AUM, Sultan MTH, Jawaid M, Cardona F, Talib ARA (2016) A review on the tensile properties of bamboo fiber reinforced polymer composites. BioResources 11:10654–10676. https://doi.org/10.15376/BIORES.11.4.10654-10676 53. Sujatmiko W, Suhedi F, Rumiawati A (2017) Thermal resistance measurements of building envelope components of the minang traditional house using the heat flow method. In: Proceeding—2016 international seminar on sensors, instrumentation, measurement and metrology, ISSIMM 2016, pp 88–92. https://doi.org/10.1109/ISSIMM.2016.7803729 54. Wang C, Zuo Q, Lin T, Anuar NIS, Mohd Salleh K, Gan S, Yousfani SHS, Zuo H, Zakaria S (2020) Predicting thermal conductivity and mechanical property of bamboo fibers/polypropylene nonwovens reinforced composites based on regression analysis. Int Commun Heat Mass Transf 118:104895. https://doi.org/10.1016/J.ICHEATMASSTRANS FER.2020.104895 55. Yu Y, Long E, Shen Y, Yang H (2016) Assessing the thermal performance of temporary shelters. Procedia Eng 159:174–178. https://doi.org/10.1016/j.proeng.2016.08.152 56. Huang Z, Sun Y, Musso F (2019) Hygrothermal performance optimization on bamboo building envelope in hot-humid climate region. Constr Build Mater 202:223–245. https://doi.org/10. 1016/j.conbuildmat.2019.01.039 57. Cui Z, Xu M, Chen Z, Xiang J (2018) Experimental study on thermal performance of bamboo scrimber at elevated temperatures. Constr Build Mater 182:178–187. https://doi.org/10.1016/ j.conbuildmat.2018.06.124 58. Huang P, Chew YMJ, Chang WS, Ansell MP, Lawrence M, Latif E, Shea A, Ormondroyd G, Du H (2018) Heat and moisture transfer behaviour in Phyllostachys edulis (Moso bamboo) based panels. Constr Build Mater 166:35–49. https://doi.org/10.1016/j.conbuildmat.2018.01.092 59. Huang Z, Sun Y (2021) Hygrothermal performance comparison study on bamboo and timber construction in Asia-Pacific bamboo areas. Constr Build Mater 271. https://doi.org/10.1016/j. conbuildmat.2020.121602 60. Huang Z, Sun Y, Musso F (2017) Assessment of bamboo application in building envelope by comparison with reference timber. Constr Build Mater 156:844–860. https://doi.org/10.1016/ j.conbuildmat.2017.09.026 61. Huang Z, Sun Y, Musso F (2018) Hygrothermal performance of natural bamboo fiber and bamboo charcoal as local construction infills in building envelope. Constr Build Mater 177:342– 357. https://doi.org/10.1016/j.conbuildmat.2018.05.071 62. Li NP, Long JB, Lin S, Li W, Shan Z (2012) Experimental and theoretical study on thermal and moisture characteristics of new-type bamboo structure wall. J Cent South Univ 19(3):600–608. https://doi.org/10.1007/S11771-012-1045-Y

Performance Assessment Methods and Effects of Bamboo-Based …

321

63. Li Y, Yao J, Li R, Zhang Z, Zhang J (2017) Thermal and energy performance of a steel-bamboo composite wall structure. Energy Build 156:225–237. https://doi.org/10.1016/j.enbuild.2017. 09.083 64. Wang JS, Demartino C, Xiao Y, Li YY (2018) Thermal insulation performance of bambooand wood-based shear walls in light-frame buildings. Energy Build 168:167–179. https://doi. org/10.1016/j.enbuild.2018.03.017 65. Shah DU, Bock MCD, Mulligan H, Ramage MH (2016) Thermal conductivity of engineered bamboo composites. J Mater Sci 51:2991–3002. https://doi.org/10.1007/s10853-015-9610-z 66. Huang P, Zeidler A, Chang W shao, Ansell MP, Chew YMJ, Shea A (2016) Specific heat capacity measurement of Phyllostachys edulis (Moso bamboo) by differential scanning calorimetry. Constr Build Mater 125:821–831. https://doi.org/10.1016/J.CONBUILDMAT. 2016.08.103 67. Huang Z, Sun Y (2021) Experimental study on the surface light and thermal properties of bamboo. J Build Eng 37. https://doi.org/10.1016/j.jobe.2020.102126 68. de León L, Chen Austin M, Carpino C, Mora D (2021) Towards zero energy districts developments base on bioclimatic strategies: a numerical study in a developing country. In: E3S web of conferences. EDP Sciences, p 02017. https://doi.org/10.1051/e3sconf/202131202017 69. Chen Austin M, Castillo M, De Mendes Da Silva Á, Mora D (2020) Numerical assessment of bioclimatic architecture strategies for buildings design in tropical climates: a case of study in Panama. In: E3S web of conferences, pp 1–10 70. Austin Ortega D, Jiménez U, Mora D, Chen Austin M (2021) Influence of arborization in building energy consumption and thermal comfort: a numerical study in tropical climate. In: 19th LACCEI international multi-conference for engineering, education, and technology: “prospective and trends in technology and skills for sustainable social development” “leveraging emerging technologies to construct the future.” Argentina 71. Austin MC, Araúz J, Mora D (2022) Numerical assessment of different phase change materials as a passive strategy to reduce energy consumption in buildings under tropical climates. Build 12:906. https://doi.org/10.3390/BUILDINGS12070906 72. Araúz J, Mora D, Austin MC (2022) Assessment of different envelope configurations via optimization analysis and thermal performance indicators: a case study in a tropical climate. Sustain 14:2013. https://doi.org/10.3390/SU14042013 73. De León L, Student E, Cedeño M, Mora D, Chen Austin M (2021) Towards a definition for zero energy districts in panama: a numerical assessment of passive and active strategies. In: 9th LACCEI international multi-conference for engineering, education, and technology: “prospective and trends in technology and skills for sustainable social development” “leveraging emerging technologies to construct the future” 74. Olgyay V (2015) Design with climate: bioclimatic approach to architectural regionalism: new and expanded edition. Princeton University Press

New Bamboo-Based Materials Yihua Ren and Yingwu Yin

Abstract Bamboo is a fast-growing plant that can be utilized sustainably. It serves as a potential biomass storage facility, with benefits for carbon neutrality and ecological restoration. Because of its high productivity, strength, and abundant resources, bamboo is a competitive option for wood and synthetic materials. The anisotropic and hollow construction, however, limit its functional applicability. The development strategy is to reassemble new bamboo-based materials such as bamboo-plastic composites, bamboo integrated materials, and recombinant bamboo to enhance the material density and reduce the coefficient of variation. A novel method is to disassemble and depolymerize the raw bamboo to the brown pulp, brown paper, or cellulose skeleton before reassembling it to high-density fiberboard, paper-based composite laminate, and high-strength profiles and integrated materials, which could significantly improve the strength, the interface compatibility, and productivity. To address the low utilization rate of raw bamboo materials, ease of mildew and cracking, and high cost, new varieties of aldehyde-free, high-strength, waterresistant, and flame-retardant materials are being developed, which would help to build the ecological bamboo industrial chain and reduce global warming. Keywords Bamboo processing · High performance · Bamboo fiber-reinforced composites · Bamboo engineering materials · 1D · 2D · 3D fiber-based materials · Modified lignin · Mechanical interlocking · Interfacial interaction

Y. Ren Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institute, Chinese Academy of Sciences, Xiamen 361021, China e-mail: [email protected] State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China Y. Yin (B) School of Materials Science and Engineering, University of Jinan, Jinan 250024, China e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 F. L. Palombini and F. M. Nogueira (eds.), Bamboo and Sustainable Construction, Environmental Footprints and Eco-design of Products and Processes, https://doi.org/10.1007/978-981-99-0232-3_12

323

324

Y. Ren and Y. Yin

1 Introduction Bamboo is one of the fastest-growing and most ecological plants in the world. The species is advantageous in compensating for rapid deforestation, which leads to biodiversity loss and soil erosion. With its high-efficiency carbon and water fixation, energy storage, and oxygenation, it reduces climate change and improves the ecological environment. Bamboo products have been part of our lives and culture since ancient times. It profoundly affects the material and spiritual lives of people. The British scholar Joseph Lee wrote in his book “History of Chinese Science and Technology” that China was “the land of bamboo civilization.” Bamboo has been used in China to record history as a raw material for food, building materials, medicine, furniture, paper, clothing, and chemicals, and it has been incorporated into every aspect of people’s daily lives. Since papermaking is one of the four ancient inventions of China, paper made from bamboo has been extended from a vessel of culture to one of the necessities of everyday life that bring great convenience. Asia has the most bamboo, followed by Africa and Latin America[1]. Globally, bamboo forests cover 30,538.35 ha, and Asia is home to the largest bamboo forests, accounting for 56.88% of the total area. China has the largest bamboo forest in the world, with 6.42 million hectares, representing 36.18% of Asia and 20.58% of the world[2]. Furthermore, China owns all bamboo genera in the Asia–Pacific bamboo region, known as the “Kingdom of Bamboo.” Over 150 million tons of bamboo are produced yearly in China, but only about 40 million tons are utilized. As opposed to the 5-year life cycle of wood, bamboo matures in only 2 years, and its growth rate exceeds that of tropical rainforests. Bamboo has remarkable environmental benefits, each bamboo can fix 6 m3 of soil, and each hectare of bamboo forest can absorb over 12 tons of carbon dioxide and store 1000 tons of water. It sequesters 1.33 times more carbon than tropical rainforests and releases 35% more oxygen than wood. For these reasons, bamboo forests are advantageous biomass resources as they have large stocks and low exploitation rates, and provide many ecological, environmental, economic, and social benefits. Two thousand years ago, talented craftsmen in China employed bamboo to build the Ganquan Shrine Palace for Emperor Wu of Han. The minority Dai people continue to use bamboo structures. The Bank of China Tower, a 70-story, a 315-m-high skyscraper designed and built by I. M. Pei and inspired by Zheng Banqiao’s “Orchid and Bamboo,” proudly stands in the typhoon-prone city of Hong Kong as a “bamboo masterpiece.” In recent years, more and more countries have placed a high priority on the development and utilization of bamboo resources and the development of the bamboo industry. According to the report [3], the global bamboo market size was estimated at USD 59.30 billion in 2021 and is expected to expand at a compound annual growth rate (CAGR) of 4.5% from 2022 to 2030. North America accounted for 33.9% of the global revenue share in 2021, the Asia Pacific led with the largest revenue share of 78.8% in 2021, Central and South America is expected to grow at a CAGR of 2.7%, the demand for bamboo is increasing in Europe. In China, the forestry industry

New Bamboo-Based Materials

325

achieved a total output value of USD 1 trillion in 2019, of which nearly USD 42 billion is derived from bamboo production. Bamboo industrialization is low-carbon, resource-rich, and environmentally favorable. Bamboo fiber is the fifth largest environmentally friendly natural fiber after cotton, hemp, silk, and wool due to the separation of natural fibers directly from bamboo, which involves mechanically separating, chemically or biologically degumming process. With its characteristics of sustainability, renewable, low pollution, low energy consumption, biodegradability, and good mechanical properties, it has been widely used for a variety of applications such as spinning, textile, nonwoven, transportation, building panels, home, and sanitary products. Today, bamboo is also used widely in the manufacturing of various products, including bamboo fiberboards, bamboo plywood, composite boards with high strength, bamboo shredded boards, handicrafts, and bamboo furniture. Using bamboo instead of wood can help reduce deforestation, enhance carbon sequestration, and protect the ecological environment. It has a higher specific strength and specific modulus than glass fiber, second only to carbon fiber, and lower manufacturing costs than stainless steel and aluminum alloy, making it a better substitute. It also possesses all the advantages of other natural materials, such as the absence of shielding signals, a lack of electromagnetic interference, and low thermal conductivity. The material has a wide range of applications, including wind power, construction, shipbuilding, aviation, automotive, environmental protection, and industrial structural materials.

2 Structure of Bamboo The bamboo cell walls are hierarchical assemblies of different types of fibrils including macrofibrils, microfibrils, and elementary fibrils [4, 5]. Bamboo has a complex structural composition, with parenchyma cells serving as the matrix and vascular bundles serving as reinforcement [6]. It is the morphological structure, chemical composition, and fiber strength which determine the mechanical properties of bamboo. Bamboo is a highly anisotropic natural porous material made of macroscopically arranged cells[3], and has a hollow structure with varying wall thicknesses. The vascular bundle is made up of thick-walled bamboo fibers (30–50%) that are scattered in parenchyma cells (40–60%), resulting in a two-phase composite with an “island structure” [6]. Bamboo fibers are the foundation of bamboo’s mechanical strength, and thin-walled cells serve as a load transfer and buffer between vascular bundles (the remainder are around 5% ducts and post-growth xylem, etc.) [6]. Radial density gradients of the vascular bundles increase continuously from the interior to the exterior, resulting in the flexural rigidity of the material [4]. Water and nutrients are transported by sieve tubes, vessels, and pits in the inner wall and parenchyma cell. Bamboo has a fiber content of 40.8%, a tube content of 6.1%, and vessel and parenchyma cells of 52.8%. The length of these pore channels varies, such as sieve tubes 300–1200 µm long and 60–120 µm in diameter, parenchyma cells 50–300 µm long and 30–60 µm in diameter, pits 500 nm–5 µm in diameter, and nanoscale and

326

Y. Ren and Y. Yin

molecular-level porosity in fiber cell walls [7–9]. It is these unimpeded nutrient network networks that ensure the nutrient requirements for the rapid growth of bamboo [5]. Bamboo is made up of cellulose fibers embedded in a lignin–hemicellulose matrix, where cellulose serves as the skeleton, lignin as the natural glue, and hemicellulose as the link between cellulose and lignin. Based on van der Waals’ force and cellulose molecules’ intra- and inter-chain hydrogen bonds between the OH and O groups, cellulose molecular chains aggregate into primary protofibrils (elementary fibrils) with high axial stiffness and distribute in ordered (crystalline) and disordered amorphous structures (amorphous). Bamboo’s cell wall comprises around 55% cellulose, 20% hemicellulose, and 25% lignin. Additionally, bamboo has alkaline extracts, ash, silica [10], minor organic components (resins, tannins, pigments, pectin, and proteins, etc.), and inorganic salt components (potassium, sodium, calcium, phosphorus, and magnesium, etc.). It has been shown that the total cellulose content of bamboo varies little between ages, carbohydrate content is an important factor in the durability and longevity of bamboo, and the structure and composition of bamboo are closely related to its durability against mold, fungal attack, and moth attack.

3 Mechanical Properties of Bamboo Fibers Similar to wood, bamboo is a non-homogeneous and anisotropic material. Adult moso bamboo has a tensile strength of 186 MPa, a bending modulus of elasticity of 16.0 GPa, and a horizontal shear strength of 22 MPa. The mechanical properties of bamboo are influenced by species, moisture content, density, age, and bamboo height [11]. Bamboo grown for less than two years has poor mechanical properties, bamboo grown for four to six years has improved mechanical properties, and bamboo grown for more than seven years is fragile and has poor mechanical properties. Furthermore, the mechanical properties of bamboo are influenced by its height, position, and orientation, and its physical and mechanical properties vary greatly in the radial, tangential, and longitudinal directions [6], demonstrating excellent strength properties along with fiber extension. The strength and stiffness of bamboo increase with specific gravity and density. Because the vascular bundles are denser along the outer side of the bamboo stem wall than the inner side, the outer side is stronger, and strength increases from the bottom to the top as the density of the bamboo stem wall increases. Compared to bamboo stems, bamboo nodules have different physical and mechanical properties, and their tensile strength is lower. Bamboo fibers are thick-walled fibers with fiber lengths ranging from 1.49 to 2.28 mm, diameters ranging from 12.24 to 17.32 m, length-to-diameter ratios ranging from 122 to 165, wall thickness ranging from 3.90 to 5.25 m, and wall cavity ratios ranging from 4.20 to 7.50 [12]. Aside from its low density, bamboo has high strength, toughness, impact resistance, low friction coefficients, tensile outer surfaces, and compressive internal surfaces. The bamboo parts of outer ring hoops and inner cross partitions increase bearing area while simultaneously increasing lateral bearing

New Bamboo-Based Materials

327

capacity, allowing it to withstand hurricanes while trees could not. Because bamboo has more than three times the bending strength of a tree of the same weight, it can be utilized to cast cement buildings instead of steel. Bamboo, however, has a small diameter, wide fluctuations within individual portions, and a hollow shell structure, making it impossible to plane directly, and its mechanical qualities are not as stable as wood. Because bamboo joints produce anisotropic discontinuities, the coefficient of variation can be decreased using a recombination process similar to that employed in wood composites [13]. Therefore, recombinant bamboo engineering materials have a great deal of potential in the construction industry, which might lead to the promotion of “bamboo instead of wood,” “bamboo instead of steel,” and “bamboo instead of plastic.”

4 Resource Utilization of Bamboo 4.1 Bamboo Fiber-Reinforced Composites Natural bamboo fibers have several advantages, including being lightweight, having high specific strength, having superior mechanical qualities, having low manufacturing costs, using less energy in production, and being green and sustainable. Because of technological advancements in advanced composite processing, they can stimulate the development of natural fiber-reinforced polymer composites. The three primary chemical components of plants, cellulose, hemicellulose, and lignin, have varied effects on plant strength, biodegradability, hygroscopicity, and heat and UV deterioration [14]. Cellulose is the primary component that defines fiber strength and contributes to the stability of the plant cell wall; cellulose crystals have the poorest water absorption properties; lignin is the most thermally stable, least degradable, and has poor water absorption properties. As a result, the three principal polymer materials can be disassembled and depolymerized, modified, and reconstituted to improve performance, minimize production costs, and meet users’ expectations. Bamboo fibers have a higher lignin content, which improves their water resistance and thermal stability [15]. They disintegrate at temperatures ranging from 290 to 370 °C [16], making them more stable during thermal processing. As a result, bamboo has developed into a superior alternative to wood and has significant potential as a reinforcement in composite materials [17]. By using the melt method, Jiang et al. [18] prepared a composite made from poly3-hydroxybutyrate, 3-hydroxyvalerate (PHBV8), and bamboo pulp. In this study, the tensile strength was 39.0 MPa, and the flexural strength was 57.2 MPa at 20% bamboo pulp fiber addition, respectively, which was increased by 42 and 91%. The tensile modulus of bamboo fibers was 4.6 GPa, and the flexural modulus was 3.9 GPa, representing an increase of 142% and 111%, respectively, probably due to the large aspect ratio of bamboo fibers. In fiber-reinforced composites, tensile

328

Y. Ren and Y. Yin

stresses are generated by shear stresses transmitted through the polymer/fiber interface, which have an irregular distribution along the fibers. As a result, there exists a critical fiber length exceeded which the tensile stresses in the fibers are capable of reaching their maximum value. According to Wibowo et al. [19, 20] for the same fiber weight ratio, small-diameter fibers have a larger total surface area than largediameter fibers. They found that smaller-diameter bamboo fibers resulted in a larger interfacial area between the PHBV8 matrix and the bamboo pulp, which facilitated the transfer of stresses at the interface, resulting in better reinforcement. It was found that the impact strength of the composites increased with an increase in bamboo pulp content and that this increase was twofold at a bamboo pulp content of 10 wt%. Sheldon et al. [21] attributed the toughening effect due to fiber debonding, stress redistribution, and the additional energy required to create a new surface in the fiber pull-out region. Using injection molding, Bari et al. [22] produced giant bamboo composites containing 40 wt% bamboo in high-density polyethylene (HDPE), lowdensity polyethylene (LDPE), and polypropylene (PP). In the study, an increase in bamboo content significantly affected flexural properties and tensile strength but did not impact strength or moisture behavior. By preparing green composites of bamboo-coconut shell/PLA and kenaf-bamboo-coconut shell/PLA. Yusoff et al. [23] found that the mixed fibers could compensate for the deficiencies of the single fibers. The tensile strength of kenaf-bamboo-coconut shell/PLA reached 187 MPa. Bamboo and kenaf fibers have high-strength, and coconut shell fibers have high ductility. Combining both properties improves the tensile and flexural strength of the composite. According to Ismail et al. [24], hybrid bamboo/red hemp composites are less porous and have improved tensile, friction, and acoustic properties. A study by Ali et al. [25] investigated bamboo mats/glass/unsaturated polyester composites, tested bullets for ballistic impact, and concluded that green composites might replace synthetic composites in some manufacturing processes. Kumar et al. [26] prepared short bamboo fiber/polypropylene composites with treated hollow glass microspheres and found that bamboo fibers greatly enhanced the mechanical properties of polypropylene, demonstrating the capability of this new composite to meet the future needs of lightweight and high-strength engineering equipment in the automotive and aerospace industries. In general, extrusion or injection molding procedures are used to manufacture natural fiber-reinforced composites; nevertheless, dispersion uniform and the high fiber ratio are significant issues. The features, form, length, and aspect ratio of the additional fibers [27–31], composition [31], processing technology [32–35], and the design of the mold section [36–38] all have a significant impact on the product’s mechanical and thermal qualities. In addition, cellulose fibers contain a large number of polar hydroxyl groups (OH), which makes them easy to absorb moisture and agglomerate, and difficult to disperse uniformly in PP, PE, and PVC as well as other weakly polar polymer materials, resulting in poor interfacial adhesion, surface stress transfer, an additional amount of less than 50%, and composite material with low strength [22, 36, 39–45]. Several

New Bamboo-Based Materials

329

methods have been proposed to address the problems of poor fiber-resin compatibility, including physical pretreatment [30, 46], alkali treatment, esterification, etherification, carbon dioxide pretreatment, coupling agent treatment, graft copolymerization, oxidation, etc. [46–50]. Overall, the research work in the past decades has focused on improving the interfacial compatibility of various types of bamboo fibers with the substrate and has proposed mechanical interlocking mechanisms, reactive binding mechanisms, and solubilization infiltration mechanisms.

4.1.1

Theory of Mechanical Interlocking

In 1925, McBain and Hopkins proposed the Theory of Mechanical Interlocking [51], stating that mechanical joints can only be achieved using porous materials, as adhesives enter pores and voids in these materials and are used to cover irregular surfaces, such as interlocking occurs. The theory has been applied to the development of dental [52], plastic plating [53], pavement applications [54], and organic-based composite coatings [55–57]. It has provided useful theoretical guidance for the development of thermoplastic composite materials with a wide variety of substrates (textile fabrics, porous materials, pulp paper, and clay-coated papers) [58]. Further studies have shown that the degree of interlocking is determined by the porosity of the material, the viscosity of the molten binder, the bonding pressure and holding time [59], the low surface tension, and the high spreading coefficient. The mechanical interlocking theory explains well the bonding mechanism of porous materials such as wood and textiles [60], fibers have groove structures on their surfaces after treatment, the rough surfaces interlock mechanically when they come into contact with each other, and frictional forces result in greater bonding between the surfaces [61–63]. Therefore, the surface area of fibers increases with roughness, porosity, or specific surface area, thereby improving composite properties in a small way. However, a number of viscous liquids cannot flow into the pores, causing interfacial debonding and stress concentration. When fillers are added to the composite, stresses are transferred under the action of external forces, which ultimately improves the mechanical strength of the composite. A selection of fillers with excellent mechanical properties, together with surface modification to ensure their uniform dispersion in the matrix, will contribute to regular fiber distribution and effectively limit fiber movement [64]. Fillers crack and absorb the energy generated by external forces, resulting in a reduction in the frequency of stress concentration [65]. Several fillers have been reported to be more effective at improving the performance of the applications, including elorite carbon nanotubes [65–68], nanosilica [65, 69–72], nanoceramics [73–77], nano calcium carbonate [78, 79], and graphene oxide [80–84]. Zuo et al. [71] proposed a crystallization process for composites with the same matrix material, setting the extrusion temperature at 160 °C, speed at 80 rpm, and time at 10 min, and adding 1.5% nanosilica to optimize the interfacial compatibility and obtain the best moisture resistance, flexural strength, and tensile strengths, the improvement in flexural strength being achieved by transferring pressure through the large aspect ratio of HNT. The tensile strength is improved by distributing

330

Y. Ren and Y. Yin

the stress concentration effect formed by the composite around the nanoparticles when subjected to external forces, which results in cracks and energy absorption. Wang and colleagues [84] conducted research on graphene oxide-reinforced bamboo fiber/polypropylene composites. When the graphene oxide content was 0.05–0.1 wt%, it generated more hydrogen bonds with fibers. Graphene oxide-reinforced composites showed some advantages; however, commercial acceptance remains challenging due to their high cost. Besides the addition of fillers, physical structure modifications can also affect the properties of composites. Some researchers designed finite element models and showed that altering the physical structure of composites can improve mechanical properties [85, 86]. Using a composite material model with bamboo poles as the skeleton, Zhao et al. [87] investigated the effect of uneven size and hollow structure of bamboo fiber on composite characteristics. Gu et al. [88, 89] employed film stacking to produce multi-layer composites of bamboo viscose fiber-reinforced maleic anhydride grafted polypropylene with flexural strength up to 52.93 MPa. The fibers were better bound to the polypropylene matrix, and the surface strength was increased by multi-layer film stacking.

4.1.2

Reaction Binding Methods and Mechanisms

In composite materials, chemical reactions can be used to create strong interfacial bonding. There are two main methods to improve interfacial lipophilicity: the reactive material acting as a bridge linking the polymer and the bamboo fiber at the same time and reducing the number of hydroxyl groups of the bamboo fiber through a reaction between the substance and the bamboo fiber. Reactive coupling agents, epoxy resins, isocyanates, acid anhydrides, polymers, acid and alkali salts, plasma, ozone, etc. are commonly used as treatment reagents. The coupling agent treatment reaction mechanism is that coupling agents convert the hydrophilic surface of fibers to more hydrophobic and improve strength by forming a chemical bridge between the bamboo fiber and polymer [90, 91]. Silane, aminoethyl-aminopropyltrimethoxysilane [92–94], is most commonly used because of its low cost, ease of reaction, and high efficiency. Other coupling agents can be chosen depending on the mechanism of the reaction of hydroxyl groups with functional groups such as carboxyl, hydroxyl, and phenyl [95]. Under certain conditions, the acid anhydride found in ethylene propylene rubber reacts with bamboo fiber to form carboxyl groups, which provide interfacial bonding via esterification and hydrogen bonding. The phenyl [96] graft on fiber can also improve the compatibility of bamboo fiber with MDPE. The benzylated bamboo fiber/MDPE composite has better mechanical properties than the untreated bamboo fiber/MDPE composite [97]. In addition to the use of coupling agents, the fibers can also be treated simultaneously by physical and chemical reactions [64]. The most typical procedure is alkali pretreatment [98, 99]. It involves removing the bamboo’s wax and lipid components, breaking cross-linked bonds between hemicellulose and lignin, reducing the number of hydroxyl groups, dissolving the lignin, modifying the surface, increasing porosity

New Bamboo-Based Materials

331

and the effective contact area between bamboo fibers and the matrix, and finally strengthening the mechanical interlocking effect. Suwan et al. [100] found that when waste bamboo was treated with potassium hydroxide, the C/O ratio of the bamboo fibers reduced, indicating that the alkali treatment modified the bamboo surface. Das and colleagues [101] used varying amounts of sodium hydroxide solution to pretreat bamboo chips. They discovered that when the fiber addition was 25%, the mechanical properties of the composites improved as the alkali concentration increased until the alkali concentration reached 20%. The biggest improvement in reinforcing material qualities was obtained when the bamboo fibers were treated with 16–20% soda, with a flexural modulus of 2200 MPa, but no noticeable improvements in mechanical properties were observed at alkali concentrations over 20%. Organic acids have also been employed to modify bamboo fibers. Fajardo et al. [102] employed tricarboxylic, cetyl, and dodecanoic acids to remove lignin and hemicellulose from the industrial waste bamboo powder. The researchers then created bamboo/polypropylene composites that demonstrated a 190% increase in tensile strength due to the esterification of acidic rosin in a non-homogeneous system. The research presented above offers novel methods for producing more bamboo-based materials. The plasma, which is an ionized gas consisting of positive, negative, and neutral particles, is another method for improving the interfacial compatibility with which bamboo fibers react chemically and change their surface properties. By applying plasma treatment conditions (Ar, CH4 , etc.) to fibers [15, 103, 104], better roughness and hydrophobicity are achieved. Due to the breaking of molecular bonds on the surface of bamboo fibers, many fractures, pits, and small particles are present on the surface, increasing the roughness of the fibers and enhancing the physical bonding. In recent years, the high reactivity of ozone treatment has enabled the removal of lignin from bamboo fibers without destroying the cellulose [105, 106]. Even though ozone is an efficient and waste-free method of removing impurities, it poses safety and environmental concerns, as well as its susceptibility to decomposition during the process or destruction in the end process [107, 108]. As a result, ozone is rarely applied to fiber surface modification. Other methods are available to improve the compatibility of bamboo fibers and substrates, such as maleic anhydride [109] and polyester amide polyols [110–112], which can improve the mechanical properties of the composite. In summary, alkali-treated bamboo fibers are most suitable for industrial applications, and coupling agents, as well as nanofillers, are also promising. Increasing the interfacial bonding, addressing uneven filler dispersion, and reducing the cost of modification are the key challenges involved in developing high-strength composites, which require innovative approaches.

332

Y. Ren and Y. Yin

4.2 Development and Application of Bamboo Engineering Materials Figure 1 demonstrates the various process of bamboo engineering materials based on current technological and structural features [113]. Bamboo is frequently processed into various constituent parts, including shavings, chips, gabions, bundles, and tubes (as shown in Table 1 [114]). Sizing, drying, and pressing are then used to manufacture a regular composite material with stable physical and mechanical properties. Table 2 shows the standard values for each type of lumber in China and the USA. Some of the major technological advances of bamboo material include the preservation of the natural structure of bamboo, the removal of the greenish outer skin and knot, heating to remove water and small molecule components, filling the pores with adhesive, drying, hot-pressing, and pressure-holding. In 2021, China published

Fig. 1 Scheme of technology of engineered bamboo

Table 1 Different types of bamboo constituent units [114]

Constituent unit

Utilization ratio of raw bamboo (%)

Rectangular bamboo strip ~30 Arc bamboo strip

60–80

Tangential bamboo strip

~65

Radial bamboo strip

~90

Bamboo fiber mat

45–50

Bamboo bundles

~90

Bamboo particle

~95

Flattened bamboo board

66–60

Crushed bamboo

~55

12.0

1900

0.45

8.0

Flexural modulus/MPa

Internal bonding strength/MPa

Thickness swell rate/%

16.0

1.20

3800

42.0

10.0

0.36

1700

11.0

USA Particleboard

Particleboard

High-density fiberboard

China

Flexural strength/MPa

Properties

10.0

0.75

2400

24.0

Medium-density fiberboard

Table 2 Standard value of modulus and strength of grade-engineered bamboo materials [115–120]

25.0

0.90

/

41.4

Hardboard

6–12

/

15,000

80.0

Engineering bamboo E16.0

New Bamboo-Based Materials 333

334

Y. Ren and Y. Yin

Table 3 Comparison of properties of laminated veneer bamboo with other wood [121] Materials

Density/g‧cm−3

Compressive strength/MPa

Flexural strength /MPa

Glued laminated bamboo

0.64–0.80

66.4

100–160

Pterocarpus santalinus

0.55–0.75

44.1–59.0

88.1–118.0

Quercus

0.57

64.7

139.6

Cupressus funebris

0.60

53.3

98.6

T/CECS 10138-2021, “engineering bamboo materials” [115], which specifies the engineering strength, stiffness, and durability parameters of bamboo engineering timber to meet engineering criteria. “Glued Laminated Bamboo” and “Bamboo Scrimber” are particularly well-represented and skillfully applied. Glued laminated bamboo [121] is a bamboo composite material manufactured by gluing and pressing bamboo sheets, a semi-mechanical process that is widely used in industries. The product retains the mechanical features of natural bamboo; it is sturdy, stiff, and has twice the tensile strength of wood. It also dries faster than the original material, is abrasion resistant, shrinks less, effectively protects against insects and mildew, and has a long service life. Furthermore, the recombination approach is more adjustable and may be altered to generate varying widths based on customer needs, allowing more alternatives for building modern panel furniture. It is considered one of the most preferred green materials in the modern furniture industry (see Table 3 [121]). It serves as a construction structure for beams, columns, load-bearing walls, one-way panels, and other materials [122]. However, it should be noted that the bamboo constituent unit grading standard does not take into account how natural structure influences bamboo performance, such as the difference between part and overall, node and internode. Both the jointing and assembling equipment limit the jointing process of bamboo constituent pieces, and it also needs a manual operation, which has a low production efficiency and cannot ensure stable performance [122]. As a result, the time-consuming, limited mold life, high energy consumption, and lengthy processing cycle [123] issues should be solved. Bamboo scrimber is another important bamboo profile invented by the Chinese Academy of Forestry. Bamboo veneers or bamboo bundles are used as the basic constituent unit and are subsequently molded in the direction, glued, and pressed. Firstly, the natural bamboo section is broken up into pieces by a bamboo breaking machine. Then pressed into bundles after removing the greenish outer skin, yellowish inner skin, and bamboo nodes by peeling and knotting machine, thus, the flatness and surface roughness of the bamboo increase. Secondly, the protein and small molecules are removed by thermal decomposition under high temperatures resulting in increased internal porosity. Thirdly, the bundles are dried and gum dipped with phenolic resin or urea–formaldehyde resin and dried repeat. Fourthly, the glued

New Bamboo-Based Materials

335

bundles are manually formed into shape before being released from thermal stress after ten days of holding pressure at ambient temperature. Finally, after about two months of production, the “bamboo scrimber” produced with mechanical strength 2–3 times that of the original bamboo can be widely used in indoor flooring, furniture, container floor [124], wind power blades, wind turbine blades, building structures [125], outdoor materials, and so on. Because the bamboo fiber arrangement is maintained during the preparation, bamboo scrimber manufactured by neosinocalamus affinis has strong mechanical qualities, high weather resistance, flame retardant, long service life, and so on. The composites have a flexural strength of 350 MPa, a flexural modulus of 30GPa, a tensile strength of 360 MPa, a compressive strength of 140 MPa, and a thickness swell rate of 5%. Although the high-temperature process removes small molecules of nutrients and water from bamboo, it also causes some issues, such as the loss of bamboo raw materials, the release of VOC, formaldehyde emissions, vinegar, and waste gas pollution, and residual decomposition in the material also causes mold and cracking of the product. On the other hand, irregular defibering of bamboo bundles will result in uneven glue distribution, while problems of high labor costs, and a long product manufacturing cycle still exist. These issues must be addressed to lower production costs, increase product durability, and limit formaldehyde release through technical innovation [126].

4.3 1D, 2D, 3D Fiber-Based High-Strength Materials Bamboo cell walls are graded fiber aggregates created by elementary fibrils modified by hemicellulose and wrapped around lignin, according to a microstructure study. After the lignin is removed, nanofibers and nanopores in the cell wall are exposed, which can shorten diffusion distances and fine-tune product qualities [127]. Scientists have done excellent work in recent years by applying lignin removal procedures to generate functioned nanowood or nanobamboo. Song et al. [128] used a NaOH/Na2 SO3 pulping process to remove lignin, hemicellulose, and other soluble components of bamboo while retaining the natural structure, followed by 24 h of hot-pressing to eliminate pores of the fiber and form strong hydrogen bonds, resulting in high performance densified bamboo. Its static flexural strength and modulus can reach 327 MPa and 38.5 GPa, respectively, significantly exceeding bamboo, conventional metal, and synthetic materials. This research continues to provide inspiration for bamboo engineering. However, the delignification process takes 12 h, and the delignified bamboo must be immersed in boiling water many times to dissolve the lignin and hemicellulose, which requires a significant quantity of water and energy. By modifying the surface of the cellulose bundles by in-situ lignin precipitation, Yin et al. [129] developed a new approach to make pulping without black liquor pulp, avoiding the degradation of lignin and hemicellulose macromolecule structure. The approach improves fiber lipophilicity, reuses recovered lignin, and significantly

336

Y. Ren and Y. Yin

increases pulp production and quality. As shown in Fig. 2, the length of the fiber is 1.5– 2.5 mm, the longest one can be more than 5 mm, the diameter is 13–16 µm, the fiber aspect ratio is 62.0, and the strength of the fiber with minimum damage is maintained well. The alkaline lignin extracted from bamboo (Fig. 3) has an average molecular weight of up to 770 kD. The content of lignin covered on the fiber is up to 10–14%, with a C/O of 1.67 due to a higher content of aliphatic or aromatic hydrocarbons [130]. Because of this, the fiber has a higher lipophilicity, which can significantly increase the interfacial compatibility between fiber and synthetic resin. The amount of lignin can be controlled and modified, as well as the surface lipophilicity and adhesive content, depending on the needs of the product. By using the aforementioned modified brown pulp as bamboo units, the bamboo pulp/PVC composite is prepared and replaces traditional urea–formaldehyde resin or phenolic resin with synthetic resins such as PVC [131]. The mechanical property of the composite is 2–8 times stronger than the current man-made fiberboard, with a flexural strength of 107 MPa, a flexural modulus of 7.6 GPa, and an internal bonding force of more than 4.0 MPa. It has a limit oxygen index of 32%, a 24-h thickness Fig. 2 Morphology of bamboo pulp fiber (LM × 500)

Fig. 3 SEM of alkaline lignin extracted from bamboo

New Bamboo-Based Materials

337

swell rate of 4–5%, and does not emit formaldehyde. The characteristics are further enhanced when hydrated calcium silicate is added. The obtained loose fiber can withstand thermal stress without prolonged cold-pressing, which ultimately leads to good performance. This process also removes water-soluble nutrients to prevent mold at the source and shortens processing cycle times. This straightforward procedure increases the full utilization of bamboo resources, opens new markets for the product, improves production quality, decreases manufacturing costs, and develops a variety of new applications. Further measurement of brown paper of 80 g/m2 made of the above pulp showed that the tear index is 10.0–15.0 mN‧m2 /g, the bursting index is 3.60–4.20 kPa‧m2 /g, the folding endurance is 50–150 times, and the tensile index is 51.0–72.0 N‧m/g, all of which meet the Chinese standard for A-grade kraft paper (breaking index 3.8 kPa‧m2 /g, tearing index 11.25 mN‧m2 /g). It possesses a sustainable network structure with numerous pores as well as a high number of hydrogen bonds in the two-dimensional plane. By hot/cold-pressing of paper-PVC film stacking, brown paper/PVC composite is produced with strong strength and fire resistance [130]. Their tensile strength, flexural strength, and flexural modulus of paper /PVC composite are 133 MPa, 183 MPa, and 10.4 GPa, respectively, which are 2.5, 1.7, and 1.4 times that of pulp/PVC composites, respectively. The properties greatly surpass that of the original bamboo and PVC profiles, 5–10 times higher than that of man-made boards, superior to that of glass fiber-reinforced PVC composites, and demonstrated significant advantages of high strength and low cost. With the benefit of numerous evenly distributed micro “tongue and rivet” mechanical interlocking structures, the hydrogen bonds of cellulose fibers in the plane of the paper, higher lipophilicity due to the high content of lignin, effective interfacial bonding between the paper and PVC is realized. Furthermore, polyethylene glycol is added to avoid the strength fluctuation caused by moisture fluctuation. The research team also made progress in the development of “bamboo steel” recombinant materials: by treating bamboo with mild conditions, partially removing lignin, hemicellulose, and soluble cellular nutrients while retaining the threedimensional bamboo skeleton, filling lignin to the pore by acidifying the black liquid; then finally hot-pressing after drying. Thus the green “bamboo steel” with specific strength exceeding that of steel is obtained [132]. By effectively removing soluble and low-molecular-weight components and nutrients, the method solves the problem of mildew and cracking at the source while fully utilizing lignin to increase the raw material utilization and decrease adhesive usage. The addition of polyhydroxy polyvinyl alcohol strengthens the hydrogen bonding and improves the properties of the product finally. The “bamboo steel” has a static flexural strength of 394 MPa, a flexural modulus of 25 GPa, and an impact toughness of 62 kJ/m2 , which are 3.7, 3.3, and 11.9 times of the aforementioned pulp/PVC composites, respectively. The new material can be used as a replacement for wood and metal materials and has a wide range of potential applications in construction materials, train cars, flooring, furniture, etc. Table 4 compares the performance and cost of various types of bamboo-based materials. The one-dimensional pulp/PVC composites, two-dimensional paper/PVC

338

Y. Ren and Y. Yin

composites, and three-dimensional “bamboo steel” materials have the advantages of high strength, flame retardant, water resistance, mold resistance, and low cost, which have effectively solved the technical and economic issues that limit the bamboo industry. The simple method removes the nutrient to prevent mildew, recycles lignin to maximize the usage of raw bamboo, and expands the PVC and other polymer materials as adhesive. Additionally, the bamboo brown paper maintains antibacterial properties like natural bamboo and does not contain any toxic and harmful additives, it can be developed with paper film to replace plastic agricultural film. Furthermore, the co-production of a bio-based water-soluble fertilizer can be used for soil conditioning, water retention, and fertilization. This approach establishes a followup fertilizer for bamboo and resolves the problem of reusing pulp black liquor. The associated technology establishes the technical, product, and market underpinnings of an improved ecological industry chain based on bamboo (Fig. 4). Table 4 Comparison of properties and cost of bamboo-based material Materials

Tensile strength /MPa

Flexural strength /MPa

Flexural modulus /GPa

Internal bonding strength /MPa

Impact strength /KJ·m−2

Cost /$·T−1

PVC board

39

39

2.3

/

7.8

1000–1300

GB/T 31765-2015

/

42

3.8

1.2

/

600–800

A135.4–2012

21

41

/

0.9

/

600–800

Natural fiber-reinforced PVC composites [31, 32, 38, 49, 133]

20–32

23–40

2.8–6.7

/

5–8

700–1000

Nanoinorganic reinforced PVC composites [134–136]

32–44

40–60

3.6–6.0

/

14–53

900–1300

Glass fiber-reinforced 24–45 PVC composites [36, 49, 50, 137]

40–100

2.5–5.8

/

4–15

1000–1400

Bamboo scrimber E18.0

80

80

15.0

/

/

900–1200

Pulp/PVC

53

107

7.6

> 4.0

5.2

700–1000

Paper/PVC

133

183

10.5

2.6

15.8

800–1000

“Bamboo steel”

196

376

26.0

/

81.9

700–1000

New Bamboo-Based Materials

339

Fig. 4 Industrial chain designed based on bamboo-based materials

5 Summary In summary, bamboo, a biomass resource that grows quickly, is a valuable biomass resource. The key points of the bamboo industry include raising the utilization rate, enhancing product flame retardant and mildew resistance, raising labor efficiency, lowering processing costs, and expanding the application areas. By utilizing the rapid growth, abundant supply, and low-cost nature of bamboo while adopting the processing technology of deconstruction and reorganization, innovating the product structure, and utilizing synthetic resin, such as PVC, instead of glue that contains aldehydes, we could develop bamboo-based composites and engineering materials according to the market demand. It would contribute significantly to the growth of the regional economy and environmental efforts, provide a major boost to combat resource scarcity and global warming, and eventually achieve “carbon neutrality.”

References 1. Kang X, Hu Y (2011) Bamboo species map of Shanghai. Shanghai Jiaotong University Press, Shanghai 2. Du H, Mao F, Li X et al (2018) IEEE J Sel Top Appl Earth Obs Rem Sens 11:1458. https:// doi.org/10.1109/jstars.2018.2800127 3. Global bamboos market size & share report, 2022–2030 (2022) Grand View Research, GVR2-68038-819-0. https://www.grandviewresearch.com/industry-analysis/bamboos-market

340

Y. Ren and Y. Yin

4. Wegst UG, Bai H, Saiz E, Tomsia AP, Ritchie RO (2015) Nat Mater 14:23. https://doi.org/ 10.1038/nmat4089 5. Moon RJ, Martini A, Nairn J, Simonsen J, Youngblood J (2011) Chem Soc Rev 40:3941. https://doi.org/10.1039/c0cs00108b 6. Shao Z (2012) Fracture mechanics of bamboo and wood. China Science Publishing, Beijing 7. Lian C, Liu R, Xiufang C et al (2019) Holzforschung 73:629. https://doi.org/10.1515/hf-20180236 8. Yu Y, Huang Y, Zhang Y, Liu R, Meng F, Yu W (2018) Polym Compos 40:1463. https://doi. org/10.1002/pc.24885 9. Tang T, Zhang B, Liu X, Wang W, Chen X, Fei B (2019) Sci Rep 9:12824. https://doi.org/10. 1038/s41598-019-49240-8 10. Chen Y, Qin W, Li X, Gong J, Gong N (1985) Proceedings of the international bamboo workshop, Hangzhou, China 11. Akinlabi ET, Anane-Fenin K, Akwada DR (2017) Bamboo—the multipurpose plant. Springer International Publishing AG, Germany 12. Fu X (2022) World Bamboo Rattan 20:54. https://doi.org/10.12168/sjzttx.2022.01.011 13. Rogerson A, Edi Suhaimi B, Jegatheswaran R, Awangd KB (2016) Pertanika J Scholarly Res Rev 2:64. https://doi.org/10.13140/RG.2.1.1939.3048 14. Faruk O, Bledzki AK, Fink H-P, Sain M (2014) Macromol Mater Eng 299:9. https://doi.org/ 10.1002/mame.201300008 15. Faruk O, Bledzki AK, Fink H-P, Sain M (2012) Prog Polym Sci 37:1552. https://doi.org/10. 1016/j.progpolymsci.2012.04.003 16. Jawaid M, Chee SS, Asim M, Saba N, Kalia S (2022) J Clean Prod 330:129938. https://doi. org/10.1016/j.jclepro.2021.129938 17. Chaowana P (2013) J Mater Sci Res 2:90. https://doi.org/10.5539/jmsr.v2n2p90 18. Jiang L, Huang J, Qian J et al (2008) J Polym Environ 16:83. https://doi.org/10.1007/s10924008-0086-7 19. Wibowo AC, Mohanty AK, Misra M, Drzal LT (2004) Ind Eng Chem Res 43:4883. https:// doi.org/10.1021/ie030873c 20. Oksman K, Clemons C (1998) J Appl Polym Sci 67:1503. https://doi.org/10.1002/(sici)10974628(19980228)67:9%3c1503::Aid-app1%3e3.0.Co;2-h 21. Sheldon R (1982) Composite polymeric materials. Applied Science Publishers, London 22. Bari E, Morrell JJ, Sistani A et al (2018) Polym Compos 40:2834. https://doi.org/10.1002/pc. 25097 23. Yusoff RB, Takagi H, Nakagaito AN (2016) Ind Crops Prod 94:562. https://doi.org/10.1016/ j.indcrop.2016.09.017 24. Ismail AS, Jawaid M, Naveen J (2019) Materials (Basel) 12:2094. https://doi.org/10.3390/ ma12132094 25. Ali A, Adawiyah R, Rassiah K et al (2019) Defence Technol 15:282. https://doi.org/10.1016/ j.dt.2018.09.001 26. Kumar N, Mireja S, Khandelwal V, Arun B, Manik G (2017) Compos B Eng 109:277. https:// doi.org/10.1016/j.compositesb.2016.10.052 27. Zheng YT, Cao DR, Wang DS, Chen JJ (2007) Compos A Appl Sci Manuf 38:20. https://doi. org/10.1016/j.compositesa.2006.01.023 28. Xu K, Li K, Zhong T, Guan L, Xie C, Li S (2014) Compos B Eng 58:392. https://doi.org/10. 1016/j.compositesb.2013.10.056 29. Sombatsompop N, Chaochanchaikul K, Phromchirasuk C, Thongsang S (2003) Polym Int 52:1847. https://doi.org/10.1002/pi.1386 30. Rocha N, Kazlauciunas A, Gil MH, Gonçalves PM, Guthrie JT (2009) Compos A Appl Sci Manuf 40:653. https://doi.org/10.1016/j.compositesa.2009.02.022 31. Kazi MK, Eljack F, Mahdi E (2020) Compos Struct 254:112885. https://doi.org/10.1016/j. compstruct.2020.112885 32. Li YY, Wang B, Wang B, Ma MG (2018) J Appl Polym Sci 135:46090. https://doi.org/10. 1002/app.46090

New Bamboo-Based Materials

341

33. Deka BK, Maji TK (2011) Compos A Appl Sci Manuf 42:686. https://doi.org/10.1016/j.com positesa.2011.02.009 34. Deka BK, Maji TK (2010) Compos Sci Technol 70:1755. https://doi.org/10.1016/j.compsc itech.2010.07.010 35. Bakar NA, Chee CY, Abdullah LC, Ratnam CT, Ibrahim NA (2015) Mater Des (1980–2015) 65:204. https://doi.org/10.1016/j.matdes.2014.09.027 36. Jeamtrakull S, Kositchaiyong A, Markpin T, Rosarpitak V, Sombatsompop N (2012) Compos B Eng 43:2721. https://doi.org/10.1016/j.compositesb.2012.04.031 37. Hasan M, Kumar R, Barakat MA, Lee M (2015) RSC Adv 5:14393. https://doi.org/10.1039/ c4ra16043f 38. Abu Bakar A, Baharulrazi N (2008) Polym Plastics Technol Eng 47:1072. https://doi.org/10. 1080/03602550802367300 39. Xian Y, Wang C, Wang G, Ren W, Cheng H (2016) J Appl Polym Sci 133:43053. https://doi. org/10.1002/app.43053 40. Tan W, Hao X, Fan Q et al (2019) Polym Compos 40:4619. https://doi.org/10.1002/pc.25329 41. Sobczak L, Lang RW, Haider A (2012) Compos Sci Technol 72:550. https://doi.org/10.1016/ j.compscitech.2011.12.013 42. Faludi G, Dora G, Renner K, Móczó J, Pukánszky B (2013) Compos Sci Technol 89:77. https://doi.org/10.1016/j.compscitech.2013.09.009 43. Diaz CA, Afrifah KA, Jin S, Matuana LM (2011) Compos Sci Technol 71:67. https://doi.org/ 10.1016/j.compscitech.2010.10.007 44. Bakar N, Chee CY, Abdullah LC, Ratnam CT, Azowa N (2014) Compos A Appl Sci Manuf 63:45. https://doi.org/10.1016/j.compositesa.2014.03.023 45. Abdul Khalil HPS, Bhat IUH, Jawaid M, Zaidon A, Hermawan D, Hadi YS (2012) Mater Des 42:353. https://doi.org/10.1016/j.matdes.2012.06.015 46. Huang Z, Wang N, Zhang Y, Hu H, Luo Y (2012) Compos A Appl Sci Manuf 43:114. https:// doi.org/10.1016/j.compositesa.2011.09.025 47. He P, Bai S, Wang Q (2016) Compos B Eng 99:373. https://doi.org/10.1016/j.compositesb. 2016.06.006 48. Qian S, Wang H, Zarei E, Sheng K (2015) Compos B Eng 82:23. https://doi.org/10.1016/j. compositesb.2015.08.007 49. Khan RA, Sharmin N, Khan MA et al (2011) Polym-Plast Technol Eng 50:153. https://doi. org/10.1080/03602559.2010.531422 50. Mongkollapkit N, Kositchaiyong A, Rosarpitak V, Sombatsompop N (2010) J Appl Polym Sci 116:3427. https://doi.org/10.1002/app.31882 51. Mcbain JW, Hopkins DG (2002) J Phys Chem 29:188. https://doi.org/10.1021/j150248a008 52. Jialanella GL (2010) Advances in structural adhesive bonding. Woodhead Publishing Limited, UK 53. Jennings C (1972) J Adhes 4:25. https://doi.org/10.1080/00218467208072208 54. Omar HA, Yusoff NIM, Mubaraki M, Ceylan H (2020) J Traffic Transp Eng (English Edition) 7:600. https://doi.org/10.1016/j.jtte.2020.07.001 55. Zeng R, Liu Z, Zhang F et al (2015) Trans Nonferr Metals Soc China 25:1917. https://doi. org/10.1016/s1003-6326(15)63799-2 56. Zeng RC, Cui L, Jiang K, Liu R, Zhao BD, Zheng YF (2016) ACS Appl Mater Interfaces 8:10014. https://doi.org/10.1021/acsami.6b00527 57. Tan JKE, Balan P, Birbilis N (2021) Appl Clay Sci 202:105948. https://doi.org/10.1016/j. clay.2020.105948 58. Parbhoo B, O’hare LA, Leadley SR (2002) Adhesion science and engineering. Dow Corning Ltd., UK 59. Comyn J (2006) Adhesives and sealants-general knowledge, application techniques, new curing techniques. Dow Corning Ltd., Barry, UK 60. Khelifa M, Celzard A, Oudjene M, Ruelle J (2016) Int J Adhes Adhes 68:283. https://doi.org/ 10.1016/j.ijadhadh.2016.04.007

342

Y. Ren and Y. Yin

61. Cai M, Takagi H, Nakagaito AN, Li Y, Waterhouse GIN (2016) Compos A Appl Sci Manuf 90:589. https://doi.org/10.1016/j.compositesa.2016.08.025 62. Zhang K, Wang F, Liang W, Wang Z, Duan Z, Yang B (2018) Polymers (Basel) 10:608. https:// doi.org/10.3390/polym10060608 63. Zhang S, Yao W, Zhang H, Sheng K (2018) Polym Compos 39:E640. https://doi.org/10.1002/ pc.24805 64. Liu L, Yuan Z, Fan X, Pan C, Li X (2021) Cellulose 29:83. https://doi.org/10.1007/s10570021-04242-6 65. Sliwa F, El Bounia N, Charrier F, Marin G, Malet F (2012) Compos Sci Technol 72:1733. https://doi.org/10.1016/j.compscitech.2012.07.002 66. Abdullah ZW, Dong Y (2019) Front Mater 6:58. https://doi.org/10.3389/fmats.2019.00058 67. Smith RJ, Holder KM, Ruiz S et al (2018) Adv Func Mater 28:1703289. https://doi.org/10. 1002/adfm.201703289 68. Ye H, Wang Q, Sun Q, Xu L (2020) Colloids Surf, A 606:125495. https://doi.org/10.1016/j. colsurfa.2020.125495 69. Bino Prince Raja D, Shakthi Prasad M, Ramanan G (2020) Mater Today: Proc 24:1498. https:// doi.org/10.1016/j.matpr.2020.04.469 70. Zhou Z, Du C, Yu H, Yao X, Huang Q (2020) Wood Res 65:693. https://doi.org/10.37763/ wr.1336-4561/65.5.693704 71. Zuo Y, Chen K, Li P, He X, Li W, Wu Y (2020) Int J Biol Macromol 157:177. https://doi.org/ 10.1016/j.ijbiomac.2020.04.205 72. Sinha RK, Sridhar K, Purohit R, Malviya RK (2020) Mater Today: Proc 26:3183. https://doi. org/10.1016/j.matpr.2020.02.657 73. Wang C, Cai L, Shi SQ, Wang G, Cheng H, Zhang S (2019) Renew Energy 134:436. https:// doi.org/10.1016/j.renene.2018.09.051 74. Adamu M, Rahman MR, Bakri MKB, Md Yusof FAB, Khan A (2020) J Vinyl Addit Technol 27:147. https://doi.org/10.1002/vnl.21792 75. Adamu M, Rahman MR, Hamdan S, Bakri MKB, Yusof FABM (2020) Constr Build Mater 258:119693. https://doi.org/10.1016/j.conbuildmat.2020.119693 76. Chee SS, Jawaid M, Alothman OY, Yahaya R (2020) RSC Adv 10:21686. https://doi.org/10. 1039/d0ra02126a 77. Chee SS, Jawaid M, Sultan MTH, Alothman OY, Abdullah LC (2020) J Market Res 9:5871. https://doi.org/10.1016/j.jmrt.2020.03.114 78. Essabir H, Bensalah MO, Rodrigue D, Bouhfid R, Qaiss A (2017) Constr Build Mater 134:549. https://doi.org/10.1016/j.conbuildmat.2016.12.199 79. Srivabut C, Ratanawilai T, Hiziroglu S (2018) Constr Build Mater 162:450. https://doi.org/ 10.1016/j.conbuildmat.2017.12.048 80. Chen L, Li Y, Du Q et al (2017) Carbohyd Polym 155:345. https://doi.org/10.1016/j.carbpol. 2016.08.047 81. Lu C, Lu Z, Li Z, Leung CKY (2016) Constr Build Mater 120:457. https://doi.org/10.1016/ j.conbuildmat.2016.05.122 82. Reale Batista MD, Drzal LT (2020) Polym Compos 42:1135. https://doi.org/10.1002/pc.25888 83. Wang J, Li J, Zhuang X et al (2018) R Soc Open Sci 5:180173. https://doi.org/10.1098/rsos. 180173 84. Wang Q, Zhang Y, Liang W, Wang J, Chen Y (2020) Polym Compos 41:3615. https://doi.org/ 10.1002/pc.25648 85. Md Shah AU, Sultan MTH, Jawaid M (2019) J Sandwich Struct Mater 23:47. https://doi.org/ 10.1177/1099636218822740 86. Penellum M, Sharma B, Shah DU, Foster RM, Ramage MH (2018) Constr Build Mater 165:241. https://doi.org/10.1016/j.conbuildmat.2017.12.166 87. Zhao Z, Sui X, Liu X, Sun W, Gong X (2018) In: 2018 International conference on computer modeling, simulation and algorithm (CMSA 2018), Atlantis Press, China 88. Gu F, Zheng Y, Zhang W et al (2018) Ind Crops Prod 121:372. https://doi.org/10.1016/j.ind crop.2018.05.025

New Bamboo-Based Materials

343

89. Sharmin N, Hasan MS, Parsons AJ, Rudd CD, Ahmed I (2016) J Mech Behav Biomed Mater 59:41. https://doi.org/10.1016/j.jmbbm.2015.12.011 90. Abdelmouleh M, Boufi S, Belgacem MN, Duarte AP, Ben Salah A, Gandini A (2004) Int J Adhes Adhes 24:43. https://doi.org/10.1016/s0143-7496(03)00099-x 91. Bogoeva Gaceva G, Avella M, Malinconico M et al (2007) Polym Compos 28:98. https://doi. org/10.1002/pc.20270 92. Kim BJ, Yao F, Han G, Wu Q (2012) Polym Compos 33:68. https://doi.org/10.1002/pc.21244 93. Panaitescu DM, Nicolae CA, Vuluga Z et al (2016) J Ind Eng Chem 37:137. https://doi.org/ 10.1016/j.jiec.2016.03.018 94. Liew FK, Hamdan S, Rahman MR, Rusop M, Khan A (2020) Polym Compos 41:4830. https:// doi.org/10.1002/pc.25755 95. Jin X, Zhang X, Xu C, Nie S (2019) J Appl Polym Sci 136:47533. https://doi.org/10.1002/ app.47533 96. Chen T, Wu Y, Qiu J, Fei M, Qiu R, Liu W (2020) Compos A Appl Sci Manuf 138:106066. https://doi.org/10.1016/j.compositesa.2020.106066 97. Sun E, Sun F, Zhang Z, Dong Y (2016) Surf Interface Anal 48:64. https://doi.org/10.1002/ sia.5889 98. Teli MD, Terega JM (2018) J Text Inst 110:496. https://doi.org/10.1080/00405000.2018.149 2321 99. Ku H, Wang H, Pattarachaiyakoop N, Trada M (2011) Compos B Eng 42:856. https://doi.org/ 10.1016/j.compositesb.2011.01.010 100. Suwan A, Sukhawipat N, Uthaipan N, Saetung A, Saetung N (2020) Prog Org Coat 149:105899. https://doi.org/10.1016/j.porgcoat.2020.105899 101. Das M, Pal A, Chakraborty D (2006) J Appl Polym Sci 100:238. https://doi.org/10.1002/app. 23028 102. Fajardo Cabrera de Lima LDP, Chamorro Rodriguez CD, Mina Hernandez JH (2021) Polymers (Basel) 13:2007. https://doi.org/10.3390/polym13122007 103. Scalici T, Fiore V, Valenza A (2016) Compos B Eng 94:167. https://doi.org/10.1016/j.com positesb.2016.03.053 104. Sinha E, Panigrahi S (2009) J Compos Mater 43:1791. https://doi.org/10.1177/002199830 9338078 105. Mamleeva NA, Kharlanov AN, Chukhchin DG, Bazarnova NG, Lunin VV (2021) Russ J Bioorg Chem 46:1330. https://doi.org/10.1134/s1068162020070080 106. Pujokaroni AS, Ohtani Y, Ichiura H (2020) J Appl Polym Sci 138:e49610. https://doi.org/10. 1002/app.49610 107. Sever K, Erden S, Gülec HA, Seki Y, Sarikanat M (2011) Mater Chem Phys 129:275. https:// doi.org/10.1016/j.matchemphys.2011.04.001 108. Cubero MTG, Coca M, Bolado S, Benito GG (2010) Chem Eng Trans 21:1273. https://doi. org/10.3303/CET1021213 109. Chattopadhyay SK, Khandal RK, Uppaluri R, Ghoshal AK (2011) J Appl Polym Sci 119:1619. https://doi.org/10.1002/app.32826 110. Saxena M, Gowri VS (2003) Polym Compos 24:428. https://doi.org/10.1002/pc.10041 111. Guan M, Yong C, Wang L (2013) J Appl Polym Sci 130:1345. https://doi.org/10.1002/app. 39256 112. Hong G, Cheng H, Meng Y et al (2018) Polymers (Basel) 10:461. https://doi.org/10.3390/pol ym10040461 113. Li X, Cheng S, Li X, Su G, Liu X, Li T (2022) Standard Pract 602:183. https://doi.org/10. 3969/j.issn.1002-5944.2022.05.025 114. Huang B, Fang C, Liu H, Chen L, Tao R, Fei B (2021) China For Prod Ind 58:43. https://doi. org/10.19531/j.issn1001-5299.202109008 115. CECS (2021) Engineered bamboo. T/CECS 10138-2021 116. ANSI (2009) Particle board. ANSI A208.1-2009 117. ANSI (2009) Medium Density Fiberboard. ANSI A208.2-2009 118. ANSI (2012) Basic Hardboard. ANSI A135.4-2012

344

Y. Ren and Y. Yin

119. 120. 121. 122.

AQSIQ, SAC (2015) High density fibreboard. GB/T 31765-2015 AQSIQ, SAC (2015) Particleboard. GB/T 4897-2015 Lin J, Qin Y (2021) Light Ind Sci Technol 37:87 Tao J, Xie L, Liu J, Shen M (2020) China For Prod Ind 57:16. https://doi.org/10.19531/j.iss n1001-5299.202012003 Liu Y, Zhou J, Fu W, Zhang B, Chang F, He W (2020) Scientia Silvae Sinicae 56:131. https:// doi.org/10.11707/j.1001-7488.20200815 Yu Y, Meng F, Yu W (2013) Scientia Silvae Sinicae 49:116. https://doi.org/10.11707/j.10017488.20130316 Li K (2019) Urban Arch 16:115. https://doi.org/10.19892/j.cnki.csjz.2019.26.037 Yu W (2019) World Bamboo Rattan 17:1. https://doi.org/10.13640/j.cnki.wbr.2019.03.001 Berglund LA, Burgert I (2018) Adv Mater 30:e1704285. https://doi.org/10.1002/adma.201 704285 Song J, Chen C, Zhu S, et al. (2018) Nature 554: 224. https://doi.org/10.1038/nature25476 Yin Y, Yu H, Li H et al. Preparation of high performance pulping with high yield from plant: China, 201010227219.7 [P/OL]. 2014-01-22 Ren Y, Zhang D, Yin Y et al (2022) Compos Sci Technol 226. https://doi.org/10.1016/j.com pscitech.2022.109544 Yingwu Y, Ren Y, Zhao S et al. New cellulose based profile and a processing process thereof: China, 202010179204.1 [P/OL]. 2022-06-30 Yin Y, Ren Y, Zhao S et al. A new natural cellulose skeleton based “Bamboo Steel” and preparation method therefor: China, 202010179352.3 [P/OL]. 2020-03-13 Bahari SA, Grigsby W, Krause A (2017) Eur J Wood Wood Prod 75:147. https://doi.org/10. 1007/s00107-016-1148-5 Lu Y, Zhao C, Khanal S, Xu S (2020) Compos A Appl Sci Manuf 135:105926. https://doi. org/10.1016/j.compositesa.2020.105926 Chen N, Wan C, Zhang Y, Zhang Y (2004) Polym Testing 23:169. https://doi.org/10.1016/ s0142-9418(03)00076-x Lu Y, Wu C, Xu S (2018) Compos A Appl Sci Manuf 113:1. https://doi.org/10.1016/j.com positesa.2018.07.012 Lee J, Park SB, Lee JS, Kim JW (2017) Mater Res Exp 4:075303. https://doi.org/10.1088/ 2053-1591/aa76fa

123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. 137.