Type: Research Essays
Sample donated: Darryl King
Last updated: September 13, 2019
When I was inShang-ri-la in Yunan, China, I realized that many buildings in the villages andeven the town were made of dried earth bricks, without much reinforcement butsupporting wooden pillars. This led me to think about how bricks could bereinforced with materials easily available in these rural regions such as driedvines and bamboo. Being a scout, I knew the usefulness of bamboo in buildingstructures such as towers, especially the flexible and strong nature of thematerial. As such, I realized that bamboo could make a good reinforcement forbricks as they provide reinforcement against shear and tensile forces which thebricks are weak against.
This led to me wondering if bamboo fibres couldreplace steel fibres as reinforcement for bricks allowing cheaper constructioncosts in poorer regions of East Asia where bamboo is abundant. Bamboo has seenwidespread applications in early eastern civilizations and still enjoyextensive use in modern society. The flexible nature of bamboo as a material isevident especially in the field of construction engineering. Bamboo has beenthe baseline for many structures in ancient eastern civilizations such asChina.
The reason for this is due to the fact that bamboo is extremely durableand flexible, allowing it to be implemented in many construction applications.One example of such constructions are rammed earth walls used in sections ofthe Great Wall of China, which had straw and crushed bamboo placed horizontallybetween rammed earth to act as reinforcement to prevent collapse (En.wikipedia.
org, 2017). In modernconstruction, steel has become the main material for reinforcements for reasonsvery much like bamboo, that is, that they are strong and flexible, allowing forwidespread application in construction. However, Steel is costly to produce andrequires many processes to be produced at a suitable quality for use inconstruction reinforcement. This makes it unviable for rural areas in largecountries which are cut off from developed industries such as India and China,resulting in these rural areas having inadequate reinforcement in structuresand being limited to small structures with low height clearance so as toimprove survivability in an earthquake .
The purpose of thisinvestigation is to explore bamboo as a green alternative to the use of steelas reinforcement in rural construction. This is due to bamboo being extremelyeasy to grow in underdeveloped countries in Asia as well as the fact that thecarbon emissions of producing and transporting bamboo compared to steel islikely significantly lower, helping third world countries reduce their carbonemissions which is difficult in a developing industry while also reducing thecost of construction drastically. The fast-growing nature of bamboo alsoensures that the rural regions will have abundant supply of reinforcementmaterial. The use of bamboo in construction will help reduce the level ofindustrial development required for constructing buildings and optimizing landuse in rural areas, allowing more land to be used for agricultural and othereconomic activities. In this paper I will explore the relationship of bambooreinforcement to the amount of load the reinforced bamboo brick is able towithstand before failure. Literature ReviewNatural bamboo growsin large abundance in Asia. It has many advantages, especially its high rate ofgrowth of 4-5 years as well as its high strength and low density.
Many recentstudies have investigated the development of naturally growing fibers asreinforcement for many applications, such as biodegradable plastics,investigating their mechanical properties. Bamboo is atubular-shaped plant with a cross sectional area smaller than that of wood.However, its strength is twice stronger than that of wood due to the internalstructure of the bamboo. The sheath of the vascular bundles in bamboo containmany fibers made up of cellulose, with diameters 10-20 micrometers. Celluloseis a natural polymer with a long chain of linked sugar molecules. When theglucose forms form lie next to eachother, the OH groups in between the chains bond with the O groups forming aHydrogen bond.
These beta linkiages in cellulose give the polymer a flat andrigid structure and allows cellulose molecules to stack on top of each othergiving it its strength and flexibility. A study discovered that bamboo fiberand bamboo powder composite materials could replace traditional plastics suchas polycetal, having tensile and flexural strengths exceeding general purposeplastics. The high specific strength ofbamboo compared to its weight is due to its fibers being longitudinally alignedwith its body1. The most common bamboo in China is thePhyllostachys Eduilis, and has an average compressive strength of 1143kg/cm3and a tensile strength of ~2200kg/cm3 when tested parallel to thebamboo fiber2.
This means that bamboo outperforms many othermaterials, with some papers suggesting that it outperforms mild steel intensile strength by weight. The bamboo also grows extremely quickly, meaningthat large amounts of carbon dioxide is absorbed by the plant forphotosynthesis to obtain the energy necessary for such rapid growth, accountingfor 9-12% of all human CO2 emissions3.This makes bamboo an extremely environmental alternative as seen in figure 1. Moreover,the cost of bamboo makes it also extremely attractive as it can be implementedwithout much additional cost to the brick unit. The ancient concept ofcombining different materials to create a new composite material has longexisted. A composite material is a material composed of two or more distinctmaterial on a macro scale with different properties to form a new material thatis different from its constituent materials property-wise. This compositematerial system gives the material properties that cannot be attained by anindividual constituent of the composite, offering a flexible design. Naturalfibers have been used as reinforcement materials for more than 3000 years suchas flax, hemps straw, wood and bamboo.
One example of acomposite is a paper-concrete composite. In a recent research, a composite wasmade by mixing wastepaper turned to paper sludge with concrete. This was donedue to the presence of cellulose within the wastepaper which could combine withthe concrete to create a new composite material. The results of the experimentshowed that the bricks were a potentially ideal material for earthquake proneareas. Through an extensiveliterature review, it has been observed that although the literature is rich inthe study of fiber reinforced structures, the exact effect of bamboo reinforcedbricks on mechanical properties has hardly been investigated. As such, thescope of this research was narrowed to determining the effect of fiberreinforcement on the reinforced bricks. Fiber is the reinforcing phase of thecomposite material. In fiber reinforced composites, the fiber used may be ofdifferent sizes depending on its application and the type of property to beimparted to the composite.
The mechanicalbehavior is mainly influenced by the volume fraction of fibers, the length offibers, aspect ratio, fiber matrix adhesion, fiber orientation. The better thebonding between the fibers and their matrice, the better the mechanicalbehavior of the composite. Since load can be easily transferred to fibers bythe matrix, mechanical properties should increase. One ancient concept ofconstructing earth structures was Adobe4whereby bricks were made using moulds and left to be sundried before beingjoined together by a mortar. This method is still prevailant in ruralconstruction in undeveloped nations, making it a viable subject for the use offiber reinforcement. The purpose of using bamboo fiber as reinforcement servesto act as a binding agent for soil tobind to increasing compressive strength and shear strength.
Due to the limitationsof lack of equipment in the lab, the approach to investigating the mechanicaleffects had to be investigated for it to be able to be carried out within labconditions. The approach for investigatingshear strength is to use a cantilever setup with a fulcrum and a support whileloading a point load on the other end of the brick. Load is to be loaded untothe brick until failure occurs. When failure occurs the mass can be obtainedand the shear force is equivalent to the mass loaded.
The bending moment canalso be attained for reference. Morel and Pklaproposed an approach to compressive strength which could be carried out withoutthe use of advanced machinery. This is the 3-point bending test which couldroughly estimate the compressive strength of the brick in question. Accordingto Morel and Pkla, the equation governing the compressive strength in such atest isWhere l I the width ofthe brick, p is the force of the applied weight, L is the distance between the bottomsupport bars, 2h the thickness of the arch and e the distance between the bottomand top bars. This test is an indirect method for obtaining compressivestrength as it does not derive from (will explain in more detail after draft). The assumption made is thatthe beams receive uniform stress due to P and rupture before brik failurebegins at point M, claiming that compressive stresses are primarily transmittedto the lower support bars through an arch effect as shown in the figure above.