Mechanical performance, water and chloride permeability of hybrid steel-polypropylene fiber-reinforced recycled aggregate concrete

Environmental impact and inherit brittleness of conventional concrete can be reduced simultaneously by utilising recycled aggregates instead of natural ones and fiber-reinforcements. In this research, the effect of incorporating single steel fiber (SF) and polypropylene fibers (PPF) and hybrid SF-PPF was studied on the performance of recycled aggregate concrete (RC). Both single fibers and hybrid fibers were used at the volume fraction of 1%. Examined properties included compressive strength-f(cm), flexural strength-f(bm), ultrasonic pulse velocity-UPV, water absorption-WA, and rapid chloride permeability-RCP. The results revealed the use of single SF and hybrid SF-PPF in incredibly advanced the flexural performance of RC. Single SF-reinforced-RC or hybrid SF-PPF-reinforced RC showed markedly higher flexural strength than that of the conventional plain NC. The optimum compressive and flexural strength were obtained when plain NC and RC were reinforced with 0.85%SF-0.15%PPF. Flexural strength of RC reinforced with 0.85%SF-0.15%PPF was 26% higher compared to that of the plain-NC. The use of hybrid SF-PPF also reduced the water permeability capacity of RC better than the use of single SF or PPF. Hybrid fiber-reinforced RC has implications for cheaper and eco-friendly concrete than single SF-reinforced concrete.