Combined effect of silica fume and expanded vermiculite on properties of lightweight mortars at ambient and elevated temperatures

•We studied effect of vermiculite and silica fume on mortar properties.•Silica fume increase mechanical properties of mortar.•Vermiculite increased thermal properties of mortar.•Silica fume and vermiculite combinations increased durability against elevated temperature.•Expanded vermiculite turns out to be a good fire resistant material.

In this study, properties of cement based mortars produced with vermiculite and silica fume were investigated at ambient and elevated temperatures. Physical, mechanical, thermal and micro structure properties of mortars produced were determined. Mortars were produced at 4, 6 and 8 expanded vermiculite/cement ratio (V/C) by volume. Silica fume was used at the ratios of 0%, 5%, 10% and 15% under each V/C ratio. In total, 114 mortar specimens with 40 × 40 × 160 mm were investigated. Specimens were subjected to 300, 600 and 900 °C for 6 h. It was observed that new formulations with silica fume increased both strength and durability at elevated temperatures of mortars with vermiculite. Unit weights of mortars at hardened state range between 1200 and 780 kg/m3. Water absorption values range between 24.2% and 40.6%. Strengths of mortars vary between 3.9 MPa and 16.4 MPa at ambient temperature. Thermal conductivity coefficient of mortars indicated a decrease depending on V/C ratio of mortar up to 0.257 W/m K which means 58.2% increment in thermal performance. Mortars produced using expanded vermiculite aggregate shows a good performance in terms of preservation of mechanical strength to elevated temperature. This means that expanded vermiculite turns out to be a good fire resistant material.