China Nonferrous Metallurgy

Barium slag is widely used as a mineralizer for cement clinker. Numerous scholars have explored the influence of BaSO₄ on the structure and properties of cement clinker. However, as a hazardous waste, there is currently no literature investigating its impact on the mineral composition of clinker and the environmental safety of cement products. This study used barium slag as an additive to prepare ordinary Portland cement clinker, and analyzed the mechanism by which barium slag regulates the phase composition, microstructure, and hydration performance of cement clinker. It also explored the distribution form of Ba²⁺ in cement clinker and the mechanism of Ba²⁺ leaching from silicate cement clinker. The introduction of barium slag reduced the high-temperature viscosity of the liquid phase, promoting the formation of C3S, thereby promoting the formation of highly hydration-active 2BaO·SiO₂ (B2S), significantly improving the hydration performance of silicate cement clinker; Ba²⁺ replaces Ca²⁺ and dissolves in β-C₂S, stimulating its hydration activity and promoting the formation of highly hydration-active α-C₂S phases; the introduction of barium slag significantly enhances the compressive strength of cement mortar. After adding 4.5% barium slag, the compressive strengths of the specimens at 3 days, 28 days, and 90 days increased to 37.55MPa, 58.47MPa, and 73.55MPa, respectively; the cement mortar containing barium slag has a dense structure, which inhibits the penetration of acid solution into the sample interior through pores to leach out Ba²⁺, and BaO·SiO₂·H₂O and Ba(OH)₂ are physically encapsulated by hydrated calcium silicate gel, while hydrated calcium silicate can chemically bind Ba²⁺. The synergistic effect of these two mechanisms inhibits Ba²⁺ leaching, resulting in soluble Ba²⁺ levels in the mortar samples below the limit specified in the “Criteria for the Identification of Hazardous Wastes by Leaching Toxicity” (GB 5085.3—2007) (100mg·L-1). This study provides a basis for the clean and harmless utilization of barium slag.