Engineering properties, microplastics and emissions assessment of recycled plastic modified asphalt mixtures

The use of recycled plastic in asphalt is raising interest since contributing to increase the sustainability of roads pavements. The engineering performance of such roads are commonly assessed but scarcely correlated to the environmental impacts of incorporating recycled plastic in asphalt. This research encompasses an evaluation of the mechanical behaviour and environmental impact of introducing low melting point recycled plastics, low density polyethylene and commingled polyethylene/polypropylene, to conventional hot mix asphalt. While this investigation reveals a reduction in moisture resistance between 5 and 22 % contingent on the plastic content, the benefits include a significant 150 % enhancement in fatigue resistance and 85 % improvement in rutting resistance when compared with conventional hot mix asphalt (HMA). From an environmental perspective, high-temperature asphalt production with higher plastic content resulted in decreased gaseous emissions for both types of recycled plastics up to 21 %. Further comparison studies indicate that microplastic generation from recycled plastic-modified asphalt is comparable to that from commercial polymer-modified asphalt products, long employed by the industry. Overall, the use of low melting point recycled plastics as an asphalt modifier is promising since offering both engineering and environmental benefits when compared to conventional asphalt.