Performance and cost efficiency of plastic-modified asphalt pavements: a multi-criteria approach

The utilization of post-consumer plastic waste in asphalt pavements offers a sustainable alternative to conventional materials. This study evaluates the mechanical performance, moisture resistance, and economic feasibility of incorporating polyethylene terephthalate (PET), high-density polyethylene (HDPE), and low-density polyethylene (LDPE) as waste plastic modifiers in asphalt mixtures using the dry process. In this approach, shredded plastic particles coat the heated aggregates before bitumen addition, enhancing aggregate–binder interaction and mixture performance. Modified mixes were assessed for volumetric properties, Marshall stability and flow, indirect tensile strength (ITS) under dry and wet conditions, and tensile strength ratio (TSR). PET- and HDPE-modified mixes showed improved density and reduced air voids, with maximum Marshall stability values of 14.9 kN and 16.1 kN, respectively, compared to 12.1 kN for the control mix. LDPE-modified mixes exhibited superior moisture resistance, achieving TSR values above 89%, while all modified mixes satisfied the minimum TSR requirement of 80%. Economic analysis indicated cost savings ranging from 4.7 to 8.0%. Analysis of Variance (ANOVA) confirmed the significant influence of plastic type on stability and TSR, and multi-criteria decision-making analysis identified the HDPE-modified mix as the optimal solution. The results support the sustainable and cost-effective use of waste plastics in asphalt pavement construction.