Asphalt mixtures with bauxite residue as a partial replacement for fine aggregates: technical, economic, and...

The generation of waste is inherent to production systems, necessitating proper management to mitigate environmental and economic impacts. In the mining sector, bauxite residue (BR), a byproduct from alumina production, presents significant environmental challenges due to its contaminant potential but also offers opportunities for reuse. This study evaluates the incorporation of BR in asphalt mixtures as a partial replacement for fine aggregates, assessing mechanical performance, environmental aspects, and economic impact. The methodology involved three stages: (i) physical, chemical, and environmental characterization of BR and aggregates; (ii) production of asphalt mixtures with 5%, 10%, and 15% BR, and mechanical characterization before and after long-term thermal aging (LTOA), including indirect tensile strength (ITS), moisture-induced damage, resilient modulus (RM), dynamic modulus (DM), fatigue life, and permanent deformation resistance; and (iii) economic and environmental evaluation, including leaching tests to assess the mobility of soluble metals and cost analysis for storage and disposal by the mining company. Results indicated that BR incorporation increased fine content, improving stiffness and performance in ITS, RM, DM, and permanent deformation resistance, both before and after LTOA. However, soluble metals in BR led to higher moisture susceptibility, requiring mitigation strategies. From an environmental perspective, BR reduced soluble metal mobility, indicating potential for residue encapsulation. Economically, partial BR substitution reduced storage and disposal costs for the mining company. These findings suggest that using bauxite residue in asphalt mixtures can be a sustainable, economically viable solution for the mining industry.