Keywords

3.1 Introduction

The traditional and most common material used in civil infrastructures is concrete [1]. Although it is weak in tension, it is more potent in compression. As a result, steel bars are common reinforcement members, which provide the tensile strength for concrete. However, using steel as a reinforcing material has significant drawbacks, including increased cost and non-renewability [2]. In addition, steel production is a noticeable contributor to emissions of greenhouse gases. Thus, efforts are being undertaken by a few scientists and academicians to suggest a low-cost, ecofriendly alternative to steel by employing materials that are readily available locally. Several studies have examined using agriculture-based fibers as concrete reinforcement in this area. Jute, coir fiber, sisal, palm leaves, and bamboo are a few common natural fibers that have been investigated in the past [3]. However, despite the positive outcomes of most of these investigations, bamboo still has a distinct edge over other renewable reinforcing materials [4].

Fast-growing bamboo, which resembles wood, is a member of the Poaceae family of grasses. It takes just a couple of years to reach its peak strength and 5 years to reach perfection [5]. The maximum tensile strength of certain bamboo species is equal to the elastic modulus of mild steel. As a result, bamboo can withstand tension and compression loads like steel bars, while many other plant-based reinforcing materials cannot. Moreover, bamboo requires 50 times less energy to manufacture one cubic meter of material per unit of tension than steel [6]. These characteristics of bamboo have attracted the interest of numerous studies for use as concrete reinforcement [6, 7].

Amin et al. [8] conducted an experimental study to evaluate the feasibility of using bamboo as reinforcement in cement mortar as a woven mesh. The results demonstrated that adding bamboo mesh considerably improved the tensile, flexural, and impact strengths of mortar while also providing the ductility and toughness. To reduce water absorption by bamboo, Harelimana et al. [9] coated it with bitumen and sand before utilizing it as reinforcement in beam and column components.

Experimental evidence presented by Govindan et al. [10] showed that bamboo-reinforced concrete specimens exhibited four times higher ultimate load-carrying capacity compared to unreinforced concrete. However, the study also revealed that the bond interface between bamboo and cement mortar was weaker due to the smooth bamboo surfaces and moisture content, resulting in reduced tension-carrying capacity [11]. Ramesh et al. [12] provided a concise overview of the construction usage of bamboo as a tensile element in concrete members, including beams, slabs, panels, blocks, and components subjected to stress-strain.

Chithambaram and Kumar [13] reported bamboo-reinforced concrete panels to construct affordable houses in mountainous regions. Bitumen-treated strips and sand-blasted bamboo sheets were employed for constructing wall and roof components. A cement plaster with a uniform thickness of 10 mm on each face was applied to enhance the structure’s strength against static and impact loads [6, 14]. Load tests were done to assess the performance of composite members better.

Himasree et al. [15] evaluated prefabricated bamboo-reinforced concrete wall panels as an alternative to clay and brick masonry for constructing low-cost homes in villages. Bui et al. [16] studied the durability of bamboo and mentioned that extensive exposure to wetting and drying cycles did not affect its tensile strength or Young’s modulus, which are crucial requirements for any reinforcement members embedded in concrete sections. Mali and Datta [17] assessed the structural strength of bitumen-coated bamboo-reinforced concrete columns, while Qaiser et al. [18] examined the performance of bamboo-based concrete beams. Meanwhile, Schneider et al. [19] investigated the flexural load-carrying capacity of beams reinforced with bamboo using stirrups and bamboo as the primary reinforcements. Previous studies have indicated that the weak bond between bamboo strips and cement mortar is the main reason for member failure [20].

However, limited literature is available on the most effective treatment methods to enhance the interface contact between bamboo and cement mortar. Hence, the current chapter aims to strengthen the bond at the bamboo and cement concrete composite matrix. The efficiency of the treated bamboo behavior can be found through the performance of bamboo-reinforced concrete beams. Compressive and tensile tests were conducted on steel-reinforced and bamboo-reinforced concrete beams to compare their load-carrying capacity, deflection, ductility, stiffness, and energy absorption.

3.2 Possibility and Potential for Bamboo

In Asia, while India possesses a much greater bamboo reserve than China, the latter’s exports surpass India’s significantly [21]. However, there are several challenges that the Indian bamboo industry needs to address effectively, including lack of awareness, unregulated harvesting in extensive bamboo-bearing areas, absence of standardized bamboo farming policies, restrictions in transportation, inadequate knowledge regarding the suitable species selection based on the environment and cultivation age, limited market access, failure to meet global standardization requirements, poor quality management, and non-compliance with quality standards [22].

The total bamboo-covered area in India exceeds the estimated value of 8.96 million hectares, reaching 13.96 million hectares [23]. This substantial coverage indicates a remarkable increase in bamboo yield within India. Figure 3.1 [23] illustrates the state-wise distribution of bamboo production in India, visually representing the bamboo industry’s productivity across the country.

Fig. 3.1
A pie chart has the following values. Central region states, 27. Northeastern states, 28. East Coast states, 29. West Coast states, 16.

Bamboo production percentage in India region-wise

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Only a very few of the 160 species in India have DNA bar-coding and sequencing, which might be beneficial for their identification and research of structural patterns. Additional difficulties include the industry’s preference for traditional furniture design and the strong demand for contemporary design but insufficient supply. Furthermore, the area where bamboo is grown is far from an enterprise that uses bamboo.

Additional difficulties include culm splits, bamboo drying that lowers the market value, culm weakening from too much moisture, and fungal invasion. For rural residents in many Indian States who depend on bamboo, plantation diversity of bamboo is particularly crucial. Forty-eight million households reside in grass, thatch, or bamboo-walled homes in India, according to data from the 2012 census [23]. More than 60% of the populace resides in homes with bamboo walls in regions like Arunachal Pradesh and Assam. Bamboo wall weaving methods may be found all over the world. However, other regions worldwide use bamboo infill walling systems with different building methods [23]. Bamboo is currently being considered as a building material that can aid in sustainable development [25]. Because of its advantages for the environment, society, and economy, it is exceptionally desirable.

3.3 Methodology

Bamboo was employed instead of steel in this experimental investigation on concrete beams. The locally accessible Muli Bamboo (Melocanna bambusoides) culms adhere to specific standards, such as being a maximum of 5 years old, representing a brownish look, and having been harvested before spring season. The lathe machine then cut bamboo strips into the required sizes from bamboo stems. Next, the bamboo sample’s ultimate strength and elastic modulus were assessed using tensile testing. Next, the bamboo samples were treated twice for strengthening. First, bamboo samples were submerged in water for 24 h. The samples were then covered in a layer of lime. After that, the samples must dry for 30 days because immersion could cause them to absorb up to 32% of their weight in water. Afterward, these samples were given a bitumen coating on one set and an epoxy resin coating on the other. Finally, the samples were covered in a layer of dry sand to strengthen the binding between bamboo and cement mortar.

This study employed ordinary Portland cement (53 grade) with local market availability and standard requirements (IS 12269-1987) [25]. Sand and aggregate with the respective specific gravity values of 2.64 and 2.69 were utilized. The mixed design method described in IS 10262 and IS 456 was applied [25]. M20 grade concrete was used throughout the trial. Cement, fine aggregate, and coarse aggregate proportions for 1 m3 of concrete were 365 kg, 670 kg, and 1250 kg, respectively. The water-cement ratio of the blends was kept constant at 0.5 for the concrete mix. Since cement was employed in the concrete mix, the bamboo-reinforced concrete members were intended for structural elements to be used in low-cost housing developments. Concrete of the experiment met the minimal cement content requirements and had no admixtures. Concrete was made to be pourable into cages made of bamboo beams. With a proportion of 70:30, coarse aggregate was divided into 20 mm and 10 mm size aggregates. The strength and other crucial characteristics of concrete made from this blend were also evaluated. At 28 days, the average cube strength for each concrete mix batch was 27 MPa. The 15 × 15 × 70 cm concrete prism samples were cast and tested for 28 days. The flexural strength was determined under the recommendations provided by IS 516-2004 [25]. Figure 3.2 shows the bamboo treatment and casting and testing of the bamboo-reinforced concrete beams.

Fig. 3.2
Two sets of 3 views of the bamboo-reinforced beam. In the first set, the bamboo is cut into the required size. In the second set, the bamboo is installed within the beam.

Bamboo-reinforced concrete beams: (a) bamboo treatment, (b) casting and testing of bamboo-reinforced concrete beams

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3.4 Results of Tested Bamboo-Reinforced Concrete Beams

To determine the bamboo reinforcement’s ultimate strength and elasticity properties, tensile tests were performed on locally sourced bamboo strips. For this reason, a total of three samples were tested. Figure 3.3 displays the effect of nodes on the tensile strength of the bamboo strips with varying nodes.

Fig. 3.3
A grouped column chart of the tensile strength versus nodes, has columns for with bark and without bark. The columns are the tallest for with bark.

Tensile strength of bamboo strips with and without bark

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According to the investigations, bamboo is more prone to node failure [6]. Three different places on the specimen were measured for breadth and thickness, and the average value was used to estimate the strength. The tests demonstrated that splitting caused samples to fail, most commonly at nodes. The bamboo strip had an average tensile strength of 171.22 N/mm2.

3.4.1 Results of Pullout Tests

The effectiveness of different types of treated bamboo in increasing the interface strength between the treated bamboo and cement mortar was compared. Five cylinders were cast for comparison purposes: plain bamboo, bitumen-coated bamboo, epoxy resin-coated bamboo, bitumen-coated bamboo with sandblasting, and epoxy resin-coated bamboo with sandblasting.

At a depth of 100 mm, bamboo strips were put into the concrete cylinders. As per Agarwal et al. [6], the specimen’s bond stress was computed. According to Table 3.1, the bitumen with sandblast-coated bamboo and epoxy resin with sandblast-coated bamboo concrete specimens exhibited the highest average bond strength. The bond force between bar deformations and the surrounding concrete was established through the mechanical interlock, chemical adhesion, and friction. However, it is essential to note that the chemical adhesion was typically less strong and could be easily overcome. Thus, it is often disregarded in the context of bond force. The remaining elements, namely the mechanical interlock and friction, work together to create a cohesive bond.

Table 3.1 Results of pullout tests
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In analyzing the resulting stress, it is essential to distinguish between its longitudinal and radial components. The mechanical interlock mechanism is paramount as it is the critical factor in generating the binding force for distorted bars. Therefore, considering the mechanical interlock mechanism is crucial when studying this phenomenon.

In the case of other beam investigations, different materials were selected to explore their effectiveness. For instance, bitumen with sandblast-coated bamboo and epoxy resin with sandblast-coated bamboo concrete were chosen for their respective properties and potential benefits. Furthermore, these materials were specifically selected to assess their performance and suitability in the given context.

3.4.2 Load-Deflection Behavior of Bamboo-Reinforced Concrete Beams

All beams underwent full-scale testing, and the behavior was recorded as load-deflection curves. Table 3.2 lists the ultimate failure loads, ultimate failure moments, ultimate deflections, and first cracking loads of the beams.

Table 3.2 Load and deflection test results
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Table 3.2 demonstrates that each bamboo-reinforced concrete specimen exhibited higher first crack loads and ultimate loads when compared to the control specimen. This was primarily due to the improved action of the bamboo-concrete composite, which produced a constant load distribution between the two components in contact. Also, the bamboo-reinforced concrete specimens with epoxy resin treatment had better flexural strength than those with bitumen coating. This was because the epoxy resin’s stronger adhesive nature enhanced the friction between treated bamboo and concrete mortar.

3.4.3 Ductility, Stiffness, and Energy Absorption of Bamboo-Reinforced Concrete Beams

The ductility, stiffness, and energy absorption of the beams are all important mechanical properties that influence how the beams react to stresses. Results for the initial first crack load (Pi), ultimate load (Pu), deflection at the first crack (Δx), deflection at the final crack (Δy), ductility index, initial stiffness, and final stiffness are presented in Table 3.3. The ductility index largely determines the mechanical properties of a material and its suitability for construction and infrastructure development. The ductility index of the bamboo-reinforced concrete beams was less than that of the control reinforced concrete beam (Table 3.3). The observed low tensile strength of the used bamboo could impact how ductile the concrete mix was. For other applications, such as low-bearing buildings, where increased ductility is not necessary, this is not a big problem.

Table 3.3 Ductility and stiffness behavior results
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Stiffness is a term used to describe a material’s resistance to deformation under load. In reinforced concrete beams, stiffness is frequently estimated as the slope of the load-deflection curves up to the yield point. Up to the first fracture load, Table 3.3 displayed that the control steel-reinforced concrete beam was more rigid than the bamboo-reinforced concrete beams. This illustrated how adding bamboo made concrete stiffer. For applications where stability and deflection control are crucial, a beam with high stiffness can support weights without exhibiting excessive deflection.

An energy absorption value can be calculated by dividing the area under the load-deflection curves up to the ultimate load by the area under the load-deflection curves up to the first crack load. Data on the energy absorption of the control steel-reinforced concrete and bamboo-reinforced concrete specimens are shown in Fig. 3.4. In comparison to the control beam, the bamboo-reinforced concrete beams (B1 and B2) exhibited higher energy absorption. This might result from the treated bamboo with sandblasting having superior energy-dissipation characteristics and effective load transfer between reinforcing bamboo (sandblasting roughened the surface) and concrete.

Fig. 3.4
A bar graph of energy absorption versus mixes has the following values. (C, 5.84), (B 1, 17.18), and (B 2, 11.12).

Energy absorption of control steel-reinforced concrete and bamboo-reinforced concrete beams

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Even though the treated bamboo-reinforced concrete beams (B1 and B2) had higher initial deflection than the control beam, they can still be an acceptable substitute for steel-reinforced concrete beams in some situations. However, carefully evaluating bamboo treatment’s unique requirements and characteristics is necessary to improve its performance and longevity further.

3.5 Conclusions

To determine the possibility of employing bamboo as reinforcement in concrete, experimental research on various beams was conducted in this study.

The tensile strength of bamboo strips with bark was higher than those without bark. Moreover, strips with two nodes were more durable than those with one or no nodes.

Pullout tests revealed that, when compared to the other samples with adhesives alone, the sandblasted bamboo-reinforced concrete beams had higher interface resistance at the surface of the bamboo concrete composite.

The bitumen-coated bamboo-reinforced concrete beams with sandblasting exhibited better energy absorption than the epoxy resin-coated bamboo-reinforced concrete beams with sandblasting or the control steel-reinforced concrete beam. The bamboo-reinforced concrete beams started to break between the loads 11 kN and 18 kN.

For temporary and lightweight residential houses, as well as in underdeveloped nations where steel for use as reinforcement members is either rare or too expensive, it is believed that bamboo may be utilized as a substitute for steel. However, reinforcement bars can only be replaced when more research is done on the best way to use the bars to maximize its potential as a composite-resistant material.

In the future, a total cost comparison of utilizing local versus conventional building materials for a specific region might also be beneficial. Research is required to determine how bamboo-reinforced concrete walls made of locally produced blocks operate in regions where bamboo is easily accessible and can be used as an alternative to steel.