Impact of using recycled polystyrene foam in place of natural coarse aggregate on concrete performance

The extensive use of conventional concrete intensifies environmental degradation through high natural aggregate consumption and carbon emissions. Concurrently, polystyrene waste remains a persistent yet underutilized pollutant. This study examines recycled polystyrene foam (RPS) as a partial replacement for coarse aggregate (0–40 vol.%) in concrete, focusing on fresh, mechanical, durability, and thermal properties. Increasing RPS content improved workability and reduced density but led to significant strength and durability losses. However, mixtures with up to 20% RPS maintained compressive strength above 17 MPa and acceptable ultrasonic pulse velocity, while thermal conductivity decreased markedly (62.4%), enhancing insulation. These findings suggest RPS incorporation can yield sustainable, lightweight, and energy-efficient concretes suitable for non-structural applications, advancing both waste valorization and environmental performance.