Chrome waste utilization in base layers: Mechanical strength and environmental risk assessment

This study investigates the partial substitution of natural aggregate (Na) with chrome mine waste (Crw) in highway base layers, focusing on mechanical performance and environmental safety. Crw-Na mixtures with contents from 0 % to 100 % were tested using CBR, cyclic plate loading, chemical, and leachate tests. The 15 % Crw-85 % Na mixture achieved the highest CBR (287.4 %) with limited deformation (37 mm). Although the 60 % Crw blend also met the required strength level (156.6 %), it showed higher settlement (50 mm) and three times greater vertical strain. SEM-EDX and chemical results indicated increased magnesium content and mineral changes at higher Crw ratios. Leachate tests confirmed compliance with TS266 and international water standards; all samples were categorized as neutral drainage with low metal risk. The findings show that Crw improves strength without causing environmental risk. Among tested mixtures, 15 % Crw offered the most balanced outcome in terms of field stability and performance.