Workability and strength of recycled aggregate concrete reinforced with nylon fibers

Abstract

The demolishing waste generated due to demolishing of the structures has proved difficult to handle due to scarcity of the dumping space particularly in urban areas. Its use in new concrete solves the problem to some extent but developed products differ in properties both at fresh and hardened states. To overcome the deficiency nylon fibers are proposed in this work. The compressive and tensile strength of the proposed concrete at a hardened state and workability as fresh properties of concrete are studied. Conventional and recycled aggregates were used in equal proportions. Nylon fibers of 1 mm diameter and 25 mm length were used from 0.25% to 2% with a 0.25% increment in each successive batch were used. Using 1:2:4 mix with water cement ratio equal to 0.5, a total of 10 mixes were designed. The workability of each mix was evaluated by the slump cone test. Water curing for 28 days was used for five samples in each batch. Compressive and tensile strength were computed from the crushing load determined in the universal testing machine. Comparison of the results with those of control concrete revealed that 1.5% of nylon fibers along with 50% recycled aggregates produce maximum compressive strength of 930.16 (MPa) with 24% more than conventional concrete (24.16 MPa) and 56% more than recycled aggregate concrete (19.27 MPa) without nylon fibers. The tensile strength of the proposed concrete (3.66 MPa) was noticed 22% and 55% higher than the conventional concrete (3.0 MPa) and recycled aggregate concrete (2.36 MPa) at optimum dosage. Hence the impact of optimized doze of the nylon fiber shows improved strength properties of the concrete.