Mechanical and thermal properties of lightweight concrete with recycled expanded polystyrene beads

Recycled expanded polystyrene (EPS) beads were used as a partial replacement for concrete mix components to develop lightweight concrete mixes with good thermal insulation properties. The replacement ratios were 50, 55, and 60% of the total mix volume. Workability, compressive, flexural, splitting tensile strengths, and thermal conductivities were evaluated. Two casting methods were investigated (with and without compaction). The results showed that using the recycled EPS beads significantly reduced the density, thermal conductivities, and mechanical properties of the mixes. Compared to the control mix, the decrease in the density ranged between 37% and 46% for the compacted samples and between 52% and 60% for the un-compacted samples. The thermal conductivities decreased by about 63% to 74% for the compacted samples and by about 78% to 85% for the un-compacted samples, which makes them efficient in thermal insulation applications. The decrease in the compressive strength ranged from 87% to 94% for the compacted samples and from 97% to 98% for the un-compacted samples. The test results revealed that the compacted samples with 50% and 55% of EPS achieved compressive strengths of 7.2 and 5.1 MPa, respectively. This makes them suitable for environmentally friendly non-structural applications with good thermal insulation properties.