Life Cycle Assessment of Recycled Plastic Modified Asphalt Pavements: A Case Study in Virginia

Abstract

This study presents a life-cycle-assessment-based investigation of the environmental impacts of recycled plastic modified (RPM) asphalt mixtures compared with conventional unmodified and polymer-modified mixtures in Virginia, U.S. The types of recycled plastic used as a modifier via the dry process were polyethylene terephthalate and a combination of high- and low-density polyethylene. A “cradle-to-grave” analysis, using real material properties and simulated lifespan, was performed. This analysis revealed that the content of reclaimed asphalt pavement and the type and amount of recycled plastic incorporated had a significant influence on the environmental impact of mixtures during the raw materials extraction stage. The projected performance life of the evaluated mixtures was determined by means of mechanistic-empirical simulations using FlexPave^TM and AASHTOWare® Pavement ME software. The improved performance of RPM mixtures resulted in 14% to 65% increase in the lifespan of surface layer, depending on the pavement structure and traffic considered. This increase correlated with extended duration between rehabilitation intervals, thereby decreasing environmental impacts during the use stage; however, these benefits were offset by incremental increases in vehicle emissions arising from change in roadway roughness, which accumulated over the selected study period to a value 20 times higher than emissions from all other life cycle stages combined for the study period. Results from this study illustrate how changes occurring over all stages of the pavement life cycle influence overall performance. Overall, incorporation of recycled plastics into pavement results in significant diversion of waste from landfills with no significant increase in other measured environmental impacts.