Environmental Impact of Construction Waste Mixture Containing Heavy Metals Pollutants Cadmium (Cd) and Arsenic (As) Used in Highway Engineering

Abstract

The benefits of using mixed-CDW (construction and demolition waste) in highway construction was a recent hot topic. In this study, the analysis of the pollutant content of 49 sets of the mixed-CDW samples from 11 construction waste treatment plants found that the content of heavy metals Cd and As exceeded the standard. The release characteristics of Cd and As pollutants in the mixed-CDW under different conditions were studied by leaching experiments. The results show that the particle size, pH and liquid-to-solid ratio of the mixed-CDW have a greater impact on the leaching pollutants of Cd and As. When the particle size of the mixed-CDW with over-standard Cd and As is less than 0.3 cm, pH is 4, liquid–solid ratio (L:S) is 0.4, the concentrations of Cd and As in the leachate still meet the relevant environmental protection standards in China and Europe. From an environmental perspective, it is feasible for the mixed-CDW with over-standard Cd and As to be used in highway projects, which further expands the application scope and scale of the mixed-CDW.