Leaching Mechanism of Metals from Recycled Concrete Aggregates (RCA) and Potentially Environmental Issues

Recycled concrete aggregates (RCA) is one of the most prevalent construction waste products what is regularly used in the road construction industry. Besides many advantages, substances leaching from RCA are emphasised as the most involving the environmental problem. The research investigated metals leaching characteristics from RCA by carrying out a detailed experimental method with many influential factors to grasp the most influencing factors on the metal leaching regime. Research outcomes disclosed that the integrated influences of factors are changed to RCA, while individual metals released are also influenced following to varied ways. Liquid-to-solid ratios (L/S) significantly affect leaching metals from RCA controlling saturated conditions, facilitating high metal concentrations in the leachate. Interestingly, the larger degree of compaction leading to increasing density of materials displayed the highest negative influence on metal leachability, suggesting that the metal release can considerably decrease, especially when the RCA is used for the sub-base road layers with a high degree of compaction. However, the use of recycled construction materials under field conditions should be further studied as there is an increasing concern of metal leaching from RCA with respect to recreational and drinking water thresholds.