Investigating the utilization of waste EPS as aggregate in mortar

Nowadays, the energy consumed for heating and cooling buildings represents a significant portion of total energy usage, which makes the development of alternative construction materials essential to improve energy efficiency and reduce environmental impacts. In the construction sector, the conservation of natural resources and the utilization of waste materials as inputs have become increasingly important for sustainability. In this study, the mechanical and physical performance of cement-based mortars in which natural river sand and pumice were partially replaced with modified EPS (MEPS) and raw waste EPS (HEPS) aggregates at various ratios was investigated. The mixtures were prepared with a constant water-to-cement ratio of 0.40 and 1% of the cement was replaced with silica fume. The aggregate composition consisted of 35% sand and 65% pumice, and three main groups of mixtures were prepared with different proportions of MEPS and HEPS. For each mixture, a total of 264 specimens were produced for 7 and 28 day curing periods, including 96 cubic specimens (5×5×5 cm) and 36 prism specimens (4×4×16 cm). Fresh-state properties such as workability, unit weight, and mass loss were measured, while hardened-state properties included compressive and flexural strength, ultrasonic pulse velocity (UPV), water absorption, void ratio, density, and thermal conductivity. Additionally, SEM analyses were conducted to evaluate the microstructural characteristics of the mortars. The results demonstrated that the use of EPS aggregates significantly reduced the density of the mortars and decreased their thermal conductivity. Although mechanical strengths decreased with increasing EPS content, acceptable performance levels were maintained at certain replacement ratios. These findings confirmed the potential of recycled EPS as a sustainable construction material, offering an environmentally friendly, energy-efficient, and cost-effective alternative for building applications.