Influence of SiO2 content on the CA2–CA6 transformation and mechanical behavior of calcium aluminate cement

Silica is an essential component for improving the workability and fluidity of calcium aluminate cement (CAC). Therefore, phase and volume changes have been measured as a function of silica content and temperature, and investigated the resulting mechanical stability. XRD measurements of specimens containing 0.26-4.0 wt.% SiO 2 sintered at 1500 °C showed that the CA 6 fraction increased from 9.8 to 28.6 wt.% with increasing SiO 2 . Phase fraction and three-point flexural strength were further evaluated after three thermal cycles at 1500 °C. The 2.0 wt.% SiO 2 composition exhibited the highest initial strength but experienced significant degradation after cycling. In contrast, the 4.0 wt.% SiO 2 specimen demonstrated improved strength after cycling due to enhanced CA 6 formation. The CA 6 phase impeded crack propagation through deflection and bridging, while SiO 2 -induced liquid phases facilitated densification. These results demonstrate that adjusting the SiO 2 content is an effective approach to improve the long-term thermal stability of CAC-based refractories.