Physical and mechanical properties of expanded vermiculite (EV) embedded foam concrete subjected to elevated temperatures

Expanded vermiculite (EV) is an innovative alternative to conventional fire-resistance material due to exceptional thermal performance and non-combustible property. In this study, the effect of elevated temperatures on microstructure, mechanical and physical properties of foam concrete containing EV as lightweight aggregates (LWA) was investigated. Foam concrete samples with 10%, 15% and 20% EV as sand replacement were developed and exposed to 300 ℃, 600 ℃, and 900 ℃. Scanning electron microscopy (SEM) test was conducted to identify microstructure changes in the cement matrix and fine aggregates after elevated-temperature exposure. The enhanced close-fitted bond in the interfacial transition zone (ITZ) of EV-based foam concrete was observed in SEM, which might be due to the higher water absorption of EV granules. Residual compressive and flexural strength, relative porosity and water sorptivity coefficient of foam concrete were also obtained. The 15% EV reduced compressive strength loss of samples by 1.84%, 11.68% and 69.1% at 300 ℃, 600 ℃ and 900 ℃, respectively, compared with that of the reference as 9.81%, 33.7%, and 72.28%, respectively. Enhanced sorptivity-related durability and lower residual porosity were also obtained at elevated temperatures when 15% EV was added.