Thermal properties of calcium sulfoaluminate cement-based mortars incorporated with expanded perlite cured at cold temperatures

•An energy-efficient and environmentally-friendly building material was developed.•For the first time, the thermal properties of CSA-based materials were reported.•Expanded perlite effectively reduced the thermal conductivity of CSA-based mortars.•Curing temperatures scarcely affected the thermal properties of CSA-based mortars. Reducing the thermal conductivity of cement-based building materials can alleviate the energy consumption and carbon dioxide (CO2) emissions that are related to space heating in buildings. The objective of this study is to incorporate expanded perlite into calcium sulfoaluminate (CSA) cement-based mortars to develop a novel building material that has low thermal conductivity for applications in cold regions. These mortars were cured at 23 °C and cold temperatures (0 °C and −10 °C), and experiments were conducted for thermal properties (i.e., thermal conductivity, thermal diffusivity, and heat capacity), unconfined compressive strength (UCS), density, ultrasonic pulse velocity (UPV), and thermogravimetric analysis (TGA). The results showed that CSA cement-based mortars gained UCS rapidly even at −10 °C owing to a fast hydration reaction, and an exponential decrease was found in UCS with an increase of the aggregate replacement ratio by expanded perlite. Thermal properties of CSA cement-based mortars were mainly affected by aggregate replacement ratios, while curing temperatures and ages had a negligible influence. For example, thermal conductivity decreased exponentially from 0.97 ± 0.01 to 0.13 ± 0.002 W/mK when the aggregate replacement ratio increased from 0% to 100%. It is of note that the thermal conductivity of CSA cement-based mortar without expanded perlite was 0.97 W/mK, being 47% lower than that of ordinary Portland cement-based mortar (1.83 W/mK). In summary, incorporating expanded perlite into CSA cement-based mortars reduced their thermal conductivity, showing their huge potential as energy-efficient and environmentally-friendly building materials.