PERFORMANCE EVALUATION OF EXPANDED POLYSTYRENE AS PARTIAL REPLACEMENT OF COARSE AGGREGATE IN CONCRETE MIX STRENGTHENED BY SP430

Concrete is one of the most widely used construction materials, but its weight often poses challenges in structural design. Expanded Polystyrene (EPS), a lightweight, recyclable material, has gained attention as a potential partial replacement for coarse aggregate in concrete. This study was undertaken to investigate how the inclusion of EPS, combined with SP430 super-plasticizer, affects the fresh and hardened properties of concrete. The aim was to determine whether EPS-modified concrete could achieve reduced density while maintaining acceptable strength and durability for practical applications. To achieve this, concrete cubes were produced with varying EPS replacement levels of 0%, 10%, 15%, 20%, and 50% by volume of coarse aggregate, and cured in water. Standard laboratory tests were conducted to evaluate workability (slump test), water absorption, density, and compressive strength at curing ages of 7, 14, 21, and 28 days. The use of SP430 was incorporated to improve mix cohesion and workability, ensuring fair comparison across all replacement levels. The results revealed that slump decreased slightly with EPS addition, though SP430 minimized loss of workability. Water absorption remained low overall, with marginal increases at higher EPS levels due to porosity. Density showed a steady reduction with increasing EPS, classifying 0–15% as normal-weight concrete and 20–50% as lightweight concrete. Compressive strength decreased with higher EPS replacement, yet up to 20% replacement still met the requirements for structural lightweight concrete, while 50% was suitable only for non-structural applications. These findings demonstrate that EPS, at moderate replacement levels, can produce lighter, durable concrete suitable for both structural and non-structural purposes, while contributing to sustainability through waste material recycling.