Study of High-Strength Concrete Reinforced with Bamboo Fibers

H. Soto, R. Marrero, F. Benítez, C. Medina, O.M. Suárez
University of Puerto Rico,
Puerto Rico

Keywords: bamboo, fiber reinforced concrete, flyash, nanosilica

Summary:

Concrete is the most used construction material worldwide and, as a consequence, has a significant environmental impact. Cement fabrication accounts for 5 to 10% of the global carbon emission. This has driven scientists to create innovative alternatives with smaller carbon footprint. Therefore, scientists and researchers are studying additions and material replacements to raise the concrete’s performance so as to reduce its consumption thus lowering the overall environmental impact. As it is well known, concrete reinforcement is needed to raise approximately 10% of the material compressive strength. These reinforcements help sustain tensile stress generated in a given structural element and prevent or limits crack propagation. Concrete has been reinforced with rebar, fibers, and mesh from different types of materials such as steel, carbon fiber, and polyvinyl chloride. Some studies show that steel produces 85 times carbon impact on the environment in the production process than bamboo. Various researches are replacing concrete components with natural and recycled materials as well as nano materials to confront this problem. They are studying the replacement of steel reinforcement with natural materials such as jute, coconut coir, sisal, babadua, date palm, raffia palms, bamboo, and bamboo fibers. Although researchers have used bamboo as a reinforcing material for concrete, they utilized the entire bamboo pieces or bamboo chunks; only a few used bamboo fibers. The principal objective for the substitution from steel to bamboo is to preserve or enhance the mechanical and durability properties while minimizing environmental effects. Of all potential alternatives, we selected bamboo fiber (Guadua angustifolia) for this study, since preliminary research indicated this natural fiber can better bond strength with minimal fiber degradation. Smaller bamboo elements achieved a higher contact area with the concrete matrix and this increases the bond between the two materials. Also using fiber reinforced concrete the time and cost of construction can be reduced by the low reinforcement cost. These fiber reinforced concrete (FRC) structures possess both durability and cost effectiveness. The FRC is a composite material made of Portland cement, aggregate, and different types of fibers aligned in one direction or randomly distributed. The role of randomly distributed discontinuous fibers is to bridge across the cracks that develop upon concrete fracture. The fibers lower the crack propagation rate, which increases the deformation of a given concrete element before its final failure. On this research we evaluated the effect of adding 1% of bamboo fibers to the concrete mix to better understand the mechanical properties. The samples also contained different amounts of fly ash and nanostructured silica as partial replacements of cement. The concrete samples were tested at three different ages; 7, 14, and 28 days. The results evinced higher compressive and tensile resistance in the specimens that contained the bamboo fibers. Compressive and tensile strength increased approximately 22% and 17%, respectively compared to concrete strength without fibers. Thus, this research furthered the understanding of natural fibers and cementitious materials interactions and opens the path to design concrete with a higher loading capacity and more environmentally friendly.