Low-Temperature Calcination of Belite-Calcium Sulphoaluminate Cement Clinker and the Hydration Process

To reduce the calcination temperature of belite (β-C2S)-calcium sulphoaluminate (C4A3$) cement clinker, hydrothermal curing was applied to mixed raw materials before calcination. The influences of calcination temperature on the mineralogical composition of cement clinker were investigated, and the optimum β-C2S/C4A3$ ratio was deduced. The phase and microstructure evolution of the hydrated paste were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The compressive strength development was also tested. The results showed that after hydrothermal curing at 95°C, the belite-calcium sulphoaluminate cement clinker can be prepared with a low-temperature calcination of 1,200°C. When the β-C2S/C4A3$ ratio reached 50%/50%, the cement pastes had the highest 3- and 28-day compressive strengths of 37.34 and 62.94 MPa, respectively. The main hydration product formed in the cement paste was ettringite.