Incorporation of plastic waste into road pavements: Performance of SMA mixtures containing flakes of low-density polyethylene

The study presented in this article contributes to the existing research on incorporating flakes of low-density polyethylene (LDPE) plastic waste into stone mastic asphalt (SMA) mixtures. Specifically, it evaluates the feasibility of incorporating waste plastic, with no commercial value, into the mixture and using conventional bitumen to replace the usual SMA polymer-modified bitumen. Marshall and volumetric properties were analyzed to define the most suitable mixtures for further study. The performance of a reference mixture and a plastic-modified mixture was evaluated in terms of water sensitivity, workability, rutting, stiffness, and fatigue resistance. Both mixtures performed well in all aspects. Compared to the reference mixture, the mixture with waste LDPE presented an excellent performance against rutting with almost no accumulated deformation and a slightly reduced behaviour against fatigue cracking. A mechanistic-empirical analysis was also conducted, showing that waste plastic-modified mixtures can enhance the pavement's structural behaviour. All in all, this study showed that it is possible to produce an SMA mixture using conventional bitumen incorporating waste LDPE, thereby contributing to a circular economy for plastics and helping to mitigate the problem related to their disposal.