Effect of fly ash content on the performance of hardened cement-based materials suffered from high temperatures

Fire resistance is an important performance for cement-based materials used in constructions and buildings. In this work, the properties of the hardened cement pastes (HCP) and mortars blended with 0–50% fly ash (FA) suffered from high temperatures were investigated, including mass loss, mechanical strength, deformation, and the evolution of mineral phase, micromorphology and pore structure. Results showed that the increase of FA content did not change the mineral phase evolution of HCP during continuous heating. According to the mass loss, crack temperature, and microstructure evolution of HCP suffered from high temperatures, it was concluded that the increase of FA content effectively improved their resistance to high temperatures. However, this positive effect of FA was not reflected in the mortars exposed to high temperatures, as the crystal transformation of quartz played a critical role.