Mechanical and Circularity Analysis of Asphalt Mixtures Produced with Bauxite Residue and RAP

Abstract Industrialization and urbanization generate significant waste volumes, demanding sustainable solutions in sectors like mining and infrastructure. This study evaluates the technical and environmental feasibility of incorporating 5% bauxite residue (BR) and 20% Reclaimed Asphalt Pavement (RAP) into asphalt mixtures. The research integrated physical characterization, mechanical performance testing, and a circularity assessment using the Material Circularity Index (MCI). Mechanical results showed that the combined use of RAP and BR significantly enhanced stiffness and rutting resistance, increasing the Resilient Modulus by 79.79% and the Flow Number (resistance to permanent deformation) from 301 to 800 cycles compared to the reference mixture. Despite higher stiffness, the recycled mixture maintained a Retained Indirect Tensile Strength (ITSR) of 93%, well above the technical requirement of 70%. Aging, intensified by RAP, reduced moisture susceptibility but increased surface wear vulnerability, while mixtures with RAP and bauxite residue demonstrated fatigue performance equivalent to the reference mixture. Regarding circularity, evaluated through two distinct utility factor methodologies, the mixture with 20% RAP and 5% BR demonstrated superior resource efficiency. It achieved an MCI of 0.93 (Method 1) and 0.91 (Method 2), significantly outperforming the conventional mixture, which presented an MCI of only 0.10. Furthermore, these mixtures exhibited superior circularity, reducing virgin material consumption and mitigating environmental impacts across the pavement life cycle, demonstrating a sustainable, efficient approach.