<p>The rise in the generation of construction and demolition wastes has prompted the use of recycled concrete aggregate (RCA) as a sustainable alternative in pavement construction. However, the presence of mortar in RCA results in higher porosity, density, and reduced mechanical strength. The present work aims at evaluating the efficiency of the accelerated carbonation method in improving the properties of RCA for pavement construction. The RCA specimens were exposed to 10%, 15%, and 20% CO₂ concentrations for 3 and 7 days of exposure time. To determine the optimal carbonation condition (OCC), physical and mechanical parameters such as specific gravity, water absorption, aggregate impact value, and aggregate crushing value were determined. Based on the findings for the physical and mechanical parameters, a 15% CO₂ treatment for 7 days was optimal. Further engineering properties of RCA treated under OCC were carried out by performing compaction and California Bearing Ratio (CBR) tests. Microstructural studies of RCA treated under OCC were carried out using XRD and SEM-EDX techniques. The dry density was found to have increased from 1.98&#xa0;g/cc to 2.06&#xa0;g/cc under OCC. The optimum moisture content was reduced from 8.8% to 7.9% under OCC. The CBR value was found to have increased from 62.4% to 72.0%, indicating an increase in load-carrying capacity. Microstructural studies have also shown that calcite formation has taken place in RCA under OCC. Based on the results, carbonated RCA demonstrates strong potential as a substitute material for unbound pavement applications.</p>