The Role of Brownmillerite in Preparation of High-Belite Sulfoaluminate Cement Clinker

High-belite sulfoaluminate cement (HBSC) clinker containing brownmillerite was prepared using the industrial raw materials limestone, aluminum tailings, aluminum ore waste rock, and anhydrite. The effect of brownmillerite on clinker sintering and clinker minerals and the mechanical performance of HBSC was investigated using thermal analysis, petrographic analysis, and quantitative X-ray diffraction (QXRD). Results indicated that brownmillerite promoted the formation of clinker minerals and stabilized calcium sulfoaluminate (C(4)A(3)$) through the substitution of Fe3+ for Al3+ in C(4)A(3)$, which increased the actual C(4)A(3)$ content and decreased the brownmillerite content compared to that of the designed theoretical mineral composition. However, the early compressive strength of HBSC pastes decreased with the increase in brownmillerite content due to the decrease in the total amount of early-strength clinker minerals. Brownmillerite also influenced belite (C2S) structures and increased the gamma-C2S content with poor hydration activity, thus inhibiting the strength development of HBSC pastes. The proper amount of brownmillerite in HBSC clinker can ensure the early strength and strength development of HBSC pastes.