Laboratory and Field Performance Characterization of Recycled-Plastic-Modified Asphalt Mixtures at the National Center for Asphalt Technology Test Track

Abstract

This study evaluated the performance of two recycled-plastic-modified (RPM) asphalt mixtures versus a nonplastic control mixture through laboratory performance testing, FlexPAVE™ simulations, and accelerated pavement testing at the National Center for Asphalt Technology (NCAT) Test Track. One RPM mixture used the wet process of adding linear low-density polyethylene (LLDPE) for asphalt binder modification, and the other the dry process of adding LLDPE for mixture modification using a drop-in approach. The nonplastic control mixture used a binder modified by styrene-butadiene-styrene. Each mixture was produced in an asphalt plant and placed as a single-lift asphalt layer of a structural test section at the NCAT Test Track. Laboratory performance testing showed that the wet plastic mixture had comparable properties to the control, while the dry plastic mixture had significantly higher stiffness, better rutting resistance, but worse cracking resistance than the control mixture. Using a representative pavement structure and layer properties as inputs, FlexPAVE™ simulations predicted that the dry plastic section would have the best fatigue-cracking performance, followed by the control and wet plastic sections, respectively. In situ pavement structural characterization data showed the control section had lower asphalt layer moduli, higher granular base and subgrade moduli, and lower measured strain at the bottom of the asphalt layer than the two plastic sections. Through 10 million equivalent single axle loads of trafficking, all three test sections showed steady smoothness and comparable rutting and friction performance. The dry plastic section had 3.5% surface cracking, while the control and wet plastic sections remained intact with no cracking.