Compaction, CBR, and microstructural performance of lateritic soil stabilized with recycled concrete aggregate

The continued reliance on energy-intensive hydraulic binders for soil stabilization presents a significant environmental challenge, prompting the need for sustainable, low-carbon alternatives. This study investigates the technical, microstructural, and environmental performance of Recycled Concrete Aggregate (RCA) as a stabilizer for brown lateritic soil. A multi-scale experimental program was conducted, integrating microstructural characterization (X-ray Diffraction [XRD] and Scanning Electron Microscopy [SEM]) with macroscopic geotechnical evaluations (compaction and California Bearing Ratio [CBR]) at RCA replacement levels of 0–25%. Mineralogical analysis revealed the laterite to be a quartz-dominant ferruginous soil, while the RCA introduced calcium-rich anorthite and fibrous anthophyllite phases. SEM imaging showed that RCA addition promoted a rigid granular skeleton with mechanical interlocking and partial void infilling by fine particles. Geotechnical testing indicated that soil performance peaked at 20% RCA replacement, where Maximum Dry Density increased from 1.98 to 2.11 g/cm³, Optimum Moisture Content decreased from 9.5% to 8.0%, and soaked CBR improved from 30% to 41%. Replacements exceeding 20% led to performance declines attributed to matrix disruption and high-water absorption of the residual mortar. Environmental and cost analyses suggested that the optimized 20% RCA mixture can achieve a substantial reduction in CO₂ emissions (approximately 93%) compared to traditional 5% cement stabilization within the system boundary considered in this study. These findings indicate that RCA offers a promising circular-economy approach for improving the short-term mechanical properties of this lateritic soil, contributing to more sustainable road infrastructure development.