A critical review on the utilization of coir (coconut fiber) in cementitious materials

Environmental problems such as the depletion of natural raw materials and the discarding of solid and gaseous wastes into the atmosphere drive modern communities towards green construction. Artificial fibers like steel, glass, and polypropylene have been used in concrete due to their unique advantages, such as a crack-arresting mechanism and enhanced toughness. Large-scale production of artificial fibers causes adverse environmental impacts due to CO2 emissions. Therefore, significant efforts are being made to appraise other eco-friendly fiber alternatives such as waste and natural fibers. Coir is a natural lightweight fiber having the highest toughness among all-natural fibers. It is one of the most widely investigated natural fibers in cementitious materials compared to other natural fibers (i.e., jute fiber, sisal fiber, and banana fiber). In this review article, the findings of different research articles have been collected and analyzed to observe the possible benefits and drawbacks of using coir as fiber reinforcement in cementitious materials. The effect of coir was studied for the different properties of concrete, including workability, fresh density, hardened density, water absorption, compressive strength, modulus of elasticity, splitting tensile strength, flexural behavior, impact toughness, and ultrasonic pulse velocity. This review summarizes the published literature and identifies future research gaps on the behavior of coir-reinforced composites for civil engineering applications.