Technical feasibility of bauxite-enhanced vitrification for utilizing AOD slag as a supplementary cementitious material

The utilization of bauxite-vitrified argon–oxygen decarburization (AOD) slag as a supplementary cementitious material is explored as an alternative approach for recycling unmanageable AOD slag and reducing the CO₂ emission levels. The results demonstrate that AOD slag can be effectively vitrified by incorporating 15wt% bauxite as the alumina source, facilitating the formation of a stable glass phase. The resulting vitrified product exhibits excellent properties, such as initial and final setting times of 337 and 437 min, respectively, good soundness (<0.05 mm), and a compressive strength of 88.7 MPa. In particular, the robust cementitious matrix effectively encapsulates and immobilizes the Cr ions, thus reducing the total chromium leaching concentration to 0.09 mg/L, which is significantly below the regulatory limit (0.15 mg/L) specified by the HJ/T 301—2007 industrial standard. The leached Cr³⁺ ions can be easily oxidized in a liquid environment with a pH > 11 at a positive oxidation–reduction potential. The carbonation reaction inhibits the conversion from trivalent chromium to hexavalent chromium, thereby lowering its concentration. These findings suggest that vitrifying AOD slag using Al₂O₃-rich solid waste as a supplementary cementitious material is a promising and environmentally sustainable method.