Investigation into the mechanical and thermal properties of lightweight mortar using commercial beads or recycled expanded polystyrene

The addition of recycled expanded polystyrene (EPS) in cement mortar is a key to enhancing buildings’ insulation and reducing energy consumption. The main objective of this study is to improve the thermal conductivity of lightweight mortar (LWM) by using the EPS. Also, to overcome the segregation problem when increasing the EPS proportion by more than 70% by volume, slurry sand was used. To achieve that, more EPS waste is required to produce an LWM with less cement and natural resources (sand) content. The effect of different percentages and particle sizes of the EPS either virgin or grated on the workability, density, compressive, flexural strength, and thermal conductivity were investigated by using the EPS with the range of 0, 75, 80, and 85% by mortar’s volume. The results exposed that LWM with grated EPS waste had greater physical and mechanical properties than with EPS beads because it has low void content and suitable distribution. In addition, mortar with 85% grated EPS had similar properties than that with 75% EPS beads. Accordingly, EPS should be grinded to increase its volumetric percentage in the mixture. Also, electron microscopy was used as an integral technique to study surface morphology between mortar components and the EPS.