Investigation of Contamination Levels of Surface Runoff From Asphalt Pavements Designed With Waste Materials

The integration of waste materials into asphalt pavements provides sustainability advantages but presents issues with water contamination from surface runoff and infiltration. This study assessed the short-term leaching characteristics of asphalt mixtures using crumb rubber (CRM), recycled asphalt pavement (RAP), recycled concrete aggregate (RCA), and oil-contaminated sand (OCS), in comparison to traditional hot-mix asphalt (HMA). Cylindrical specimens were submerged in water for durations ranging from 30 min to 24 h, and the resulting leachates were examined for turbidity, color, pH, conductivity, nitrates, phosphates, and chlorides. The results indicated that RCA and OCS combinations demonstrated the largest pollutant emissions, with chloride and color identified as the most sensitive indicators. Welch's ANOVA revealed statistically significant variations among mixes for chloride (p = 0.0011), although Kruskal-Wallis tests suggested a near-significant trend for color (p ≈ 0.066). Risk quotient analysis (RQ < 1) indicated no immediate ecological concern; nevertheless, cumulative consequences may develop under repeated wetting and drying cycles characteristic of tropical regions. The results emphasize the environmental compromises associated with utilizing recycled materials in asphalt pavements and show the necessity for mitigating techniques, including pre-treatment, optimum substitution ratios, and prolonged field validation. This study offers novel perspectives on reconciling sustainability objectives with water quality preservation in pavement design.