Experimental Investigation on the Strength Behavior of Hybrid Fibre-Reinforced Recycled Aggregate Concrete

The study provides a systematic experimental examination of mechanical and durability performance of hybrid fibre reinforced recycled aggregate concrete (HFRRAC). The mix was prepared by replacing natural coarse aggregate with recycled coarse aggregate (RCA) as a partial replacement at the percentage levels of 0%, 10%,20%,30%,40% and 50% respectively by volume corresponding to M25 grade. A hybrid mix of polypropylene and nylon fibres were added at total fibre contents of 0.5%, 1.0% and 1.5% by volume to the concrete. The microstructural observations indicated the good physical and mechanical characteristics of the optimized blend, which were confirmed using compressive strength, split tensile strength and flexural strength tests for the mechanical properties, while water absorption and acid resistance tests exhibited their durability characteristics. The results show that the increased RCA reduces strength, but addition of hybrid fibres compensates for this reduction effectively. Based on the tests, optimum performance was obtained with 30% RCA replacement and hybrid fibre content of 1% (0.5% polypropylene + 0.5% nylon); 28 day compressive strength exceeding 25 MPa with significant increases in tensile and flexural strength also observed. Durability analysis indicated lower water absorption and enhanced acid attack resistance for the fibre reinforced mixtures. The results show that with optimized RCA and hybrid fibre content HFRRAC can be a durable sustainable alternative of conventional concrete and can provide necessary contribution towards conservation of resources and circular economy based construction practices.