is a compound (e.g., CA, CA₂, C₁₂A₇) produced by calcining limestone and bauxite/alumina at high temperatures (1300–1450°C). Characterized by high melting points, high porosity, and strong chemical reactivity, it is primarily used as an efficient desulfurizer in steelmaking to deeply remove sulfur from molten steel. It also serves as a raw material for calcium aluminate cement and refractories. The sintering process offers cost-effectiveness and scalability, though moisture protection is required (some phases are hygroscopic).