Enhanced mechanical and axial resilience of recycled plastic aggregate concrete reinforced with silica fume and fibers

The rapid increase in plastic waste due to urbanization and population growth is causing significant environmental and health concerns. Simultaneously, the high demand for concrete in infrastructure projects is depleting natural resources. To address both challenges, many studies have explored using recycled plastic waste in concrete, primarily for non-structural applications. Although plastic waste generally reduces concrete's mechanical properties, various additives like fly ash and silica fume have been used to improve strength. However, limited research exists on the structural performance of concrete with recycled plastic coarse aggregate (PCA). This study examines the mechanical and axial behavior of recycled plastic aggregate concrete (RPAC) reinforced with silica fume, steel fiber (SF), and polypropylene fiber (PPF). Results reveal a significant increase in mechanical and axial properties for RPAC mixes modified with silica fume and fibers. The RPAC mix (M3) with 20% PCA, 20% silica fume, and 0.75% steel fiber (SF) achieved the highest compressive strength (CS) of 17.9 MPa, split tensile strength (ST) of 1.81 MPa, and flexural strength (FL) of 2.96 MPa. Similarly, an enhanced ultimate load capacity of approximately 927 kN was achieved, significantly reducing the load capacity loss from 18.2% (RPAC with only 20% PCA) to just 4.83%. Additionally, columns containing PCA exhibited an improved ductility index compared to the control column without PCA, with a maximum enhancement of approximately 59.1% observed in RPAC columns (M3) modified with silica fume and SF. Overall, M3 with 20% PCA, 20% silica fume, and 0.75% SF exhibited excellent performance with enhanced mechanical, axial, and ductility behavior.