Laboratory Evaluation of Asphalt Containing Recycled Plastic as a Bitumen Extender and Modifier

: Recent interest in recycling and reuse of waste plastic has resulted in a dramatic increase in the evaluation of waste plastic as an extender and/or modifier of bituminous binder for asphalt production. Although significant field trials of waste plastic modified asphalt have been reported in Australia since 2017, no laboratory evaluation of the effects of these products on the engineering properties of binder and asphalt has been published. In this research, two commercially available recycled waste plastic products were evaluated in the laboratory. One product is intended to be plastomeric while the other is intended to be elastomeric in nature. Compared to unmodified viscosity grade bitumen and acid modified multigrade, the recycled plastic products increased the viscosity and softening temperature of the binder and introduced significant elastic recovery. Following dry-mixing into asphalt, the recycled plastic products were associated with improved mixture deformation resistance and increased mixture stiffness. However, the mixtures containing recycled plastic were also associated with an increase in moisture susceptibility and their fatigue lives were not significantly different to those of the control mixtures. Further research is recommended to better understand the modest reduction in moisture damage resistance associated with recycled plastic, as well as the digestion of recycled plastic via the dry-mixing process.