Mesostructural analysis of damage and healing of fine-aggregate mixtures containing recycled asphalt

This study evaluates the damage and healing characteristics of fine aggregate mixtures (FAM). Some FAM samples comprised only of virgin aggregate and asphalt binder, while others included reclaimed asphalt (RAP) and a recycling agent (REC). Sample damage was characterized using continuous shear cyclic loading, while the healing response was studied by including rest periods. To corroborate these mechanical analysis results, X-ray microtomographic (μCT) images were captured for FAM samples before and after applying cyclic loading and rest periods. Critically, mechanical analysis demonstrated that adding RAP increased the rate of FAM damage, while using REC or higher binder content improved its healing capability. μCT analysis revealed that FAM composition influenced pore geometry; samples with high binder content (B2, B2.RA) formed spherical pores, while those with low binder content and RAP (B1.RA) developed elongated interconnected pores. These elongated pores coalesced into microcracks under load, reducing healing potential and increasing damage susceptibility.