Evaluating fire resistance of calcium sulfoaluminate cement-based lightweight mortar: A comparative analysis of raw and expanded vermiculite

This study examined the impact of direct fire exposure on the engineering properties of calcium sulfoaluminate cement (CSA) mortars with substitutions of vermiculite, either raw or expanded, at 10%, 20%, and 30% replacement ratios by volume. Specimens measuring 40x40x160 mm were cured for 28 days, dried, exposed to fire, and subsequently cooled. Various tests were conducted before and after exposure to evaluate the fire's impact on the mortars. Results indicated that increasing the vermiculite content significantly diminished both compressive and flexural strength across all replacement levels, with reductions persisting after fire exposure. Additionally, thermal properties were notably affected; for instance, the thermal conductivity after fire exposure decreased from 1.47 ± 0.01 W/mK to 0.85 ± 0.002 W/mK for raw vermiculite and to 0.31 ± 0.001 W/mK for expanded vermiculite at a 30% replacement ratio. Mortars containing expanded vermiculite exhibited considerably lower thermal conductivity compared to those with raw vermiculite, highlighting the potential of expanded vermiculite in producing energy-efficient and sustainable CSA mortars. This volumetric replacement approach not only reduces thermal conductivity but also contributes to enhanced heat and sound insulation, as well as moisture regulation in buildings.