Adding Effects of CaF2 and TiO2 as Mineralizers on the Sintering Temperature and Hardening Properties of Calcium Sulfoaluminate Cement

• Published in: Journal of Advanced Concrete Technology 2021/12/23, Vol.19(12), pp.1309-1317
• Main Authors: Wang, Kai, Dong, Jingliang, Zhang, Tingting, Deng, Xiaohan, Ren, Liang
• Format: Article
• Language: English
• Subjects: Calcium fluoride; Compressive strength; Hydration; Setting (hardening); Sintering; Sulfoaluminate cement; Titanium dioxide
• ISSN: 1346-8014; 1347-3913
• DOI: 10.3151/jact.19.1309

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 (C4A3 S ) 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 C4A3 S from 1300 to 1100°C. The addition of appropriate amounts of CaF2 and TiO2 promoted hydration and significantly improved the compressive strength of C4A3 S 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 C4A3 S as a mineraliser are 0.5 and 0.2 wt.%, respectively.