Microstructural characterization and mechanical properties of lightweight polymer concrete exposed to elevated temperatures

Abstract

In the present study, effect of elevated temperatures on the microstructure and mechanical characteristics of lightweight polymer concrete (LPC) was investigated. To manage this aim, LPC mix proportions were prepared by combination of polyester resin in five ratios ranged from 15 to 27% with lightweight expanded clay aggregate (LECA) and natural river sand. Provided specimens, then, were exposed to various temperatures up to 400 °C for 3 h. The microstructural analysis consists of petrographic inspection and SEM observation was performed at various temperatures. In addition, mechanical tests (mass and volume changes, compressive strength, and module of elasticity) were conducted to confirm the microstructural observations. Results indicate that LPCs have a decent performance versus raising the temperature to less than 150 °C. Reducing the mechanical properties commenced at 200 °C due to the proximity of the thermal resistance of polymeric binder to the test temperature. By increasing the temperature by more than 250 °C, a significant reduction in the properties of LPCs was observed, where LPC with 24% resin (optimum mix) lost 59 and 85% of its strength at 300 and 400 °C, respectively. Petrographic and SEM observations, also, showed that creation and widespread of cracks in the polymer matrix and the interfacial transition zone (ITZ) is the main reason for reducing the properties of LPCs. In addition, some discolorations were observed on the surface of aggregates in high temperatures.