Mechanical and Microstructural Performance of Concrete Incorporating Expanded Polystyrene as Partial Coarse Aggregate Replacement

The increasing demand for lightweight and sustainable construction materials has led to the search for alternative aggregates in the production of concrete. This current study investigates the performance assessment of concrete strength with expanded polystyrene (EPS) as a partial coarse aggregate replacement. Concrete mixes were prepared with 5, 10, 15, 20, 25, and 30 varying percentage replacement of granite with EPS. Fresh and hardened properties were assessed through the slump, compressive, split tensile, and flexural tests at both early and late ages. Microstructural characterization was conducted using Scanning Electron Microscopy (SEM) and EDX to evaluate the interfacial transition zone (ITZ) and pore distribution. The results obtained showed that the addition of EPS at varying percentages produced a lightweight concrete usable for non-structural and some structural applications. An inverse relationship was observed between strength performance and EPS content, with higher replacement levels resulting in reduced strength. The optimal strength level was achieved at 5% EPS replacement. SEM and EDX analysis revealed weaker bonding in the ITZ at higher EPS contents, contributing to a reduction in strength, but also demonstrated improved energy absorption and ductility. It was concluded that EPS can be used in lightweight concrete production while promoting waste recycling and sustainable construction practices.