Preparation, Hydration Characteristics, and Carbon Footprint Assessment of Sulfoaluminate Cement Prepared by Co-Utilization of Industrial Solid Wastes and Bauxite

This study evaluates the technical feasibility, environmental sustainability, and economic viability of producing sulfoaluminate cement (SW-SAC) by co-utilizing bauxite and industrial solid wastes—phosphogypsum, calcium carbide residue (CCR), and red mud—with the solid wastes accounting for approximately 75% of the raw meal. CCR replaces limestone as the primary CaO source, releasing H2O instead of CO2, while phosphogypsum supplies SO3; the raw meal is directly calcined in a single step at 1300–1350 °C, 100–150 °C below that of ordinary Portland cement (OPC). Calcination temperature and holding time were optimized through phase analysis, microstructural observation, free lime (f-CaO) determination, and strength testing. SW-SAC meeting the 42.5 strength class was then prepared using phosphogypsum as a setting regulator and phosphorus slag or limestone powder as Supplementary materials. X-ray diffraction (XRD), thermogravimetry (TG), and scanning electron microscopy (SEM) were used to examine hydration products and microstructural evolution. The optimized clinker was dominated by ye’elimite (C4A3S̄) and belite (C2S). Phosphorus slag favored the formation of gel-like products at later ages, whereas limestone powder promoted ettringite (AFt) stabilization and monocarboaluminate (Mc) formation. SW-SAC exhibited a lower carbon footprint than both Type P·I Portland cement and conventional SAC, and a lower production cost than conventional SAC. These results demonstrate a promising low-carbon route for high-value utilization of industrial solid wastes.