The feasibility of using copper slag in asphalt mixtures for base and surface layers based on laboratory results

Abstract

This study aims to assess the feasibility of using copper slag (CS) in asphalt mixtures in both the surface and base layers of road pavements. For this purpose, two sets of asphalt mixtures with different CS content (15 and 30%) and fraction sizes (0/8 and 0/16 mm) were prepared. The optimal binder content of each mixture was determined using the Marshall mix design method. Their laboratory performances were investigated and compared with the properties of reference asphalt mixtures, i.e. mixtures consisting exclusively of virgin materials. Test results showed that adding CS to the mixture for the surface layer improved stiffness and rutting resistance and had almost no negative impacts on the remaining properties apart from cracking resistance. Further, the addition of CS to the base-layer mixture improved cracking resistance, but negatively affected stiffness, rutting and fatigue resistance. In both cases, adding CS did not influence the strength, water sensitivity or freeze–thaw resistance. From a leaching perspective, the results showed that leachates gathered from the asphalt mixtures designed for the surface layer did not contain heavy metals. Overall, it can be concluded that CS has a potential to be used as an appropriate aggregate substitute for virgin aggregates in asphalt mixtures for both surface and base layers.