Performance Evaluation of Asphalt Mixtures Modified with Recycled Polyethylene via the Wet Process

Abstract

The plastics and asphalt pavement industries have shown increasing interest in recycling waste plastics in asphalt because of potential environmental benefits. One approach to incorporating recycled plastics in asphalt is the wet process, which requires mechanical blending of recycled plastics into the asphalt binder as polymer modifiers. This study was aimed at exploring the use of recycled polyethylene (rPE) and a reactive elastomeric terpolymer (RET), which was used as a potential compatibilizer to rPE, for asphalt modification. Moreover, the study evaluated the impact of both modifiers on the bond strength characteristics of asphalt-aggregate systems as well as on the rutting and cracking resistance of asphalt mixtures. To this end, a battery of laboratory performance tests was conducted on asphalt mixtures containing binders: one neat; two rPE modified; and one styrene-butadiene-styrene modified. One rPE modified binder was formulated by adding 3% rPE to a PG 58-28 neat binder, while the other was modified with 3% rPE, RET, and polyphosphoric acid. Test results indicated that the rPE-plus-RET modified binder yielded an asphalt-aggregate system with enhanced moisture resistance, before and after oxidative aging. When compared with the control mixture, using rPE alone or rPE plus RET for asphalt modification significantly improved the rutting resistance. However, the rPE and rPE-plus-RET modified mixtures were found to be more susceptible to intermediate-temperature fatigue cracking at both short-term and long-term aging conditions. Finally, adding rPE or rPE plus RET did not have a significant impact on the mixture reflective cracking and thermal cracking resistance after long-term aging.