Compressive and flexural strength of mortar and concrete facings with expanded polystyrene and particle board cores sandwich panels

Lightweight sandwich panels are mainly utilized in the aerospace and automobile industries, and are increasingly explored for sustainable construction. This study investigates the mechanical performance of sandwich panels composed of mortar and concrete facings with expanded polystyrene (EPS) and particle board (PB) cores. Mortar facings were a 1:3 mix of cement and sand, a 0.65 water-cement ratio, and a 1:2:4 mix of cement, sand, and granite for the concrete, with a 0.5 water-cement ratio. Cube (75 × 75 × 75 mm3) and prism (100 × 100 × 400 mm3) samples were fabricated with 15 mm facings and 45 mm cores, then cured and tested for compressive and flexural strength at 7, 14, 21, and 28 days in line with BS EN 12390-3:2019 and ASTM C293. At 28 days, concrete-faced PB-core panels achieved a compressive strength of 8.18 N/mm², approximately 17% higher than 6.96 N/mm2 of EPS-core. Mortar-faced PB-core panels reached 6.44 N/mm², 64.13% compared to 4.13 N/mm² for mortar-faced EPS panels. Flexural strength followed similar patterns: concrete-faced PB-core panels increased by 96% from 9.18 N/mm² at 7 days to 9.48 N/mm² at 28 days, while EPS-core panels improved by 87.9% from 6.56 N/mm² to 7.46 N/mm². ANOVA (α = 0.05) confirmed statistically significant differences between core types, with PB consistently outperforming EPS due to higher stiffness and improved core–facing bonding. EPS and PB core panels remain suited for non-load-bearing applications.