Mechanical, thermal and environmental performance of expanded polystyrene beads modified mortar for sustainable building applications

Abstract In this study, a novel energy-efficient mortar is developed by incorporating expanded polystyrene beads (EPBs) into the mixture to reduce density and enhance thermal efficiency while mitigating the associated strength degradation. To achieve this, EPBs were surface-coated with silica fume using epoxy and incorporated as partial replacements for sand at 0%, 25%, 50%, and 75% by volume. Afterwards, Workability, physico-mechanical, thermal, and environmental performances were evaluated in accordance with relevant ASTM standards, while phase composition and microstructure were analyzed using XRD, SEM, and EDS. Energy efficiency was assessed through ASHRAE-compliant simulations of a mid-rise residential building using DesignBuilder, and the resulting energy savings were used to estimate CO₂ emission reductions. The results showed improved fresh and mechanical properties, with the highest compressive strength achieved at 25% EPB. Microstructural analysis confirms EPB fragmentation with epoxy-enhanced matrix bonding and thermal performance. In addition, the energy analysis revealed that 75% EPB use can reduce the energy demand up to 10%, eventually saving up to 263,775 kg CO₂-e over the lifetime of the building.