Microstructural Evaluation and Void Topology Analysis of Cold Asphalt Mixtures Containing Recycled Concrete and Reclaimed Asphalt Pavement

The microstructural behaviour and pore structure of cold-mix asphalt mixes made with bitumen emulsion and partially recycled aggregate are examined in this work. Limestone served as the reference aggregate, while 20%, 40%, and 80% volumetric replacement ratios of recycled concrete (RC) and recycled asphalt (RAP) were employed as substitute materials. All mixes were treated with the ideal quantity of bitumen emulsion, which the researchers had previously established. Marshall tests were performed to assess mechanical behaviour, and advanced imaging methods such as computed tomography (CT-scan) and scanning electron microscopy (SEM) were employed to examine the samples' microstructure, aggregate-bitumen bond, and pore distribution. While CT imaging of the control, RC-40%, and RAP-40% mixes showed notable changes in pore topology with depth, SEM examination showed varying bond characteristics based on the aggregate type. The findings support the use of partial replacement in sustainable pavement applications by showing that it can improve microstructural performance, especially when combined with RAP.