Paving roads with recycled plastics: Microplastic pollution or eco-friendly solution?

Although plastic-modified roads are a promising approach to reducing the amount of landfilled and incinerated plastic and improving asphalt pavement performance, the contribution of plastic-modified roads to microplastic pollution is unknown. This study aimed to develop a new abrasion procedure to quantify the release of microplastics from recycled plastic-modified asphalt depending on environmental factors, the type and content of plastic used, and the incorporation method in bitumen/asphalt. A Wet Track Abrasion machine was used to simulate road traffic abrasion on a plastic-modified asphalt sample, and a novel microplastic extraction procedure was designed to extract the generated microplastics. Incorporating recycled plastic as a polymer modifier in the bitumen matrix resulted in an early release of microplastics compared to its addition as a synthetic aggregate substitute in the asphalt mix. Cold temperatures and low pH values favoured the generation of microplastics from plastic-modified asphalt. Due to the lack of universal thresholds for the release of microplastics into the environment, environmental agencies and local authorities could benefit from this novel laboratory-based microplastic assessment procedure to foster the sustainable use of recycled plastic in roads.