Valorization of Fibrous Mineral Waste via Bauxite-Enhanced Milling: A Pathway to Sustainable Cement and Geopolymer Binders

The increasing accumulation of mineral wool waste, especially from construction and demolition sources, presents a major environmental burden. This study investigates a scalable grinding enhancement strategy using bauxite and glass cullet additives to improve the comminution of glass wool, rock wool, and mixed mineral wool waste. Mechanical grinding assisted with the use of 10 wt% and 20 wt% of hard mineral additives reduced milling time by up to 50% compared to unmodified samples, with bauxite consistently outperforming glass cullet. Laser diffraction confirmed a marked reduction in particle size, reaching sub-50 µm targets essential for alkali activation, while SEM analysis revealed smoother, fractured surfaces conducive to improved geopolymer reactivity. Energy consumption estimates suggest substantial efficiency gains; however, upstream impacts such as additive production and transport warrant further evaluation. Compared to conventional thermal and chemical pretreatments, this abrasive-assisted approach demonstrates a lower-energy pathway for producing geopolymer-compatible powders. The findings also offer guidance for developing standardized protocols and open avenues for testing these powders in future binder formulations.