Degassed expanded polystyrene in concrete mixes: enhanced performance and sustainable construction

The construction sector urgently requires sustainable alternatives that reduce natural sand consumption while enabling the reuse of plastic waste. This study investigates concrete mixes in which expanded polystyrene (EPS) from post-consumer food containers underwent a thermal degassing process prior to being incorporated as a partial sand replacement (2.5%, 5%, and 10% by mass). The degassing treatment modified the EPS microstructure—increasing its density, reducing deformability, and producing particles with a morphology closer to that of natural sand. These transformations enhanced adhesion to the cementitious matrix and allowed the incorporation of 5% degassed EPS without significant loss of compressive strength or unit weight compared with conventional concrete. The findings demonstrate the technical feasibility of this innovative approach and its strong alignment with sustainable construction practices, particularly in reducing CO2 emissions, promoting circular economy principles, and advancing environmental objectives consistent with the United Nations Sustainable Development Goals (SDGs) and the ESG agenda.