Thermal Characteristics of Hollow Block Masonry Units Incorporating Expanded Polystyrene Wastes

The increasing demand for energy-efficient and sustainable building materials has driven research into lightweight and thermally insulating construction units. This study aims to enhance the thermal performance of hollow masonry blocks by partially replacing sand in cement mortar with varying percentages of expanded polystyrene (EPS). The primary objective is to evaluate the effect of EPS incorporation on the thermal conductivity of both mortar mixtures and hollow blocks. The thermal conductivity (k value) of the mortar was measured experimentally, while the thermal behavior of three-dimensionally modeled EPS hollow blocks was analyzed using ANSYS Fluent software under four heat transfer scenarios: conduction only, conduction and radiation, conduction and convection, and combined conduction–convection–radiation. Experimental results showed that increasing the EPS content significantly reduced the thermal conductivity of mortar, with values ranging from 1.8 W/m·K for the control mix to as low as 0.16 W/m·K. Numerical simulations yielded similar trends for hollow blocks, with k values ranging from 1.43 W/m·K (control) to between 1.27 and 0.25 W/m·K for EPS blocks across the different heat transfer modes. These findings confirm the potential of EPS as an effective additive for improving the thermal insulation of masonry units.