Adding Effects of CaF<sub>2</sub> and TiO<sub>2</sub> as Mineralizers on the Sintering Temperature and Hardening Properties of Calcium Sulfoaluminate Cement

The influences of CaF2 and TiO2 as a mineraliser on the sintering temperature, phase formation, setting times, and the mechanical and hydration properties of calcium sulfoaluminate (C4A3S) were investigated. The results showed that the addition of CaF2 and TiO2 by 0.5 and 0.2 wt.% can reduce the sintering temperature of C4A3S from 1300 to 1100°C. The addition of appropriate amounts of CaF2 and TiO2 promoted hydration and significantly improved the compressive strength of C4A3S cement (CSC). The compressive strength and hydration speed of CSC containing 0.5 wt.% CaF2 increased with an increase in the TiO2 contents from 0 to 0.2 wt.% at all curing ages. However, when the TiO2 content was increased to 0.25 wt.%, a significant reduction in the compressive strength of CSC was observed. The initial and final setting times of CSC containing 0.5 wt.% CaF2 both decreased with increasing TiO2 content. Compared with the control paste, the 15-h and 28-d compressive strength of CSC containing 0.5 wt.% CaF2 and 0.2 wt.% TiO2 increased from 30.4 and 79.2 MPa to 46.2 and 88.3 MPa, respectively. The hydration speed of CSC containing 0.5 wt.% CaF2 and 0.2 wt.% TiO2 was almost three times that of CSC without CaF2 and TiO2. Therefore, the optimum amounts of CaF2 and TiO2 that should be added to C4A3S as a mineraliser are 0.5 and 0.2 wt.%, respectively.