Comparing asphalt modified with recycled plastic polymers to conventional polymer modified asphalt

Abstract

As sustainable infrastructure solutions become a focus of societies and governments, the interest in recycling plastic into asphalt mixtures will continue to increase. There are many forms of plastic that can be added to asphalt, but those plastics that partially replace the bituminous binders, as well as improve the mechanical properties of the asphalt mixture, are the most valuable. The effects of 6% (of bitumen mass) of two commercially available recycled plastic products were compared to the effects of 2-6% conventional elastomeric and plastomeric polymers, within a typical dense graded asphalt mixture. The Marshall stability associated with recycled plastic was comparable to that for 2-3% conventional polymer content, while indirect tensile stiffness and deformation resistance were comparable to 4-6% conventional polymer content. In contrast, workability, Marshall flow and moisture damage resistance were not significantly different for recycled plastic and conventional polymers, regardless of the conventional polymer content. It was concluded that the recycled plastic products used in this research should be thought of as sustainable polymers for asphalt mixture modification, rather than as simple extenders of the bituminous phase in asphalt production. However, further work is required to understand the ageing, leaching and fuming of asphalt mixtures modified with recycled plastic, compared to conventional polymers.