Sustainable valorization of mine-derived solid wastes into cementitious pavement materials: Mechanical performance and microstructural insights

Blasting slag and neutralized dreg are mine-derived solid wastes commonly stockpiled in open-pit mining areas, posing long-term environmental risks while remaining underutilized resources. This study presents a short-term, material-level and field-validated evaluation of a composite solid waste (CSW)-amended blasting slag/neutralized dreg mixture (BN) composed entirely of recycled materials for use as sustainable cementitious pavement materials. The mechanical performance of the material was evaluated through compaction characteristics, strength development, immersion stability, and resistance to wetting-drying cycles, followed by field validation and environmental safety assessment at a gold mining site. Results indicated that the BN with a blasting slag-neutralized dreg ratio of 5:5 achieved a maximum dry density of 2.09 g/cm 3 . Increasing CSW content significantly enhanced compressive strength, immersion stability, and durability, with >9% CSW met the reference strength requirement for cement-stabilized pavement base materials. Microstructural analyses using scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP) revealed that strength improvement originated from pore refinement and the formation of stable cementitious phases. Field application demonstrated that the CSW-amended material (15% CSW) significantly reduced pavement deflection compared with rock and soil bases, indicating superior deformation resistance satisfying the reference design criterion. Leaching tests confirmed low environmental risk, with Cd, Hg, and Cr concentrations of 0.007 mg/L, 0.00003 mg/L, and 0.02 mg/L, respectively, met the groundwater Ⅳ standard. A simplified cradle-to-gate life cycle assessment further showed that the proposed material can reduce carbon emissions by over 50% compared to cement- and fly ash-stabilized materials.