Mechanical Performance and Microstructural Analysis of Cold Asphalt Mixtures with Recycled Aggregates and Optimized Emulsion Content

The potential of employing recycled asphalt pavement (RAP) and recycled concrete aggregate (RCA) as partial substitutes for natural aggregate in cold asphalt is examined in this study. Assessing the mechanical, microstructural, environmental, and financial effects of employing recycled materials at varying replacement levels (20%, 40%, and 60%) was the goal of this study. Marshall stability, flow, density, and air spaces were assessed in laboratory experiments, and the interior microstructure and bitumen-aggregate interactions were examined using scanning electron microscopy (SEM). Because of its superior compatibility with emulsified bitumen and asphalt pavement, RAP outperformed RCA, obtaining the maximum stability (5.95 kN) at 40% replacement. SEM imaging verified that RCA mixes were more porous and showed weaker bonding, particularly at 60% replacement. Nevertheless, performance can still be maintained while using up to 40% RCA. The study also emphasizes the financial and environmental ad-vantages, such as less dependency on raw resources, less building costs, and encouragement of environmentally friendly infrastructure techniques. Ac-cording to the findings, cold asphalt with 40% RAP offers the best combination of sustainability, durability, and mechanical strength, making it a good option for creating ecologically friendly pavements, particularly in settings with limited resources or urban regeneration initiatives.