Cracking and Rutting Performance of Asphalt Mixtures Incorporating RAP and RAS

Abstract
The use of recycled materials in hot-mix asphalt (HMA) has been encouraged by transportation agencies across Canada and elsewhere to save construction costs, preserve natural resources and reduce impact on the natural environment. Reclaimed asphalt pavement (RAP) has now become feasible source of acceptable quality and cost-effective recycled material in pavement construction that contributes to sustainable growth by reducing the consumption of virgin aggregates and asphalt binder as well as reduction in carbon footprints by reducing fuel consumption from that required for the equivalent quantities of virgin aggregates and virgin asphalt binder production. Some agencies have also started to use the recycled asphalt shingle (RAS), at least on a trial basis, while some others started to explore the potential use. Nevertheless, highway agencies, like Manitoba, require performance evaluation of HMA mixtures containing both RAP and RAS or RAS only to allow them as acceptable materials and/or to determine the acceptable proportions for pavement construction. The objective of this study is to investigate the performance of HMA mixtures in Manitoba containing both RAP and RAS for a potential move to allow RAS in the HMA to advance sustainability in pavement construction. In the experimental phase of this project, three local asphalt mixtures including a virgin mix, a mix that contains RAP only, and a mix that contains both RAP and RAS were assessed in terms of cracking and rutting performance as well as moisture susceptibility. Cracking resistance was evaluated using the Illinois Flexibility Index Test, while rutting and moisture resistance were evaluated using the Hamburg Wheel-Tracking Test. Results showed that RAP and RAS combination improved both rutting and moisture resistance but led to a more brittle behaviour with low cracking resistance of asphalt mixtures.

Keywords:
Hot-mix asphalt (HMA), reclaimed asphalt pavement (RAP), recycled asphalt shingles (RAS), Illinois Flexibility Index Test (I-FIT), Hamburg Wheel-Tracking Test (HWTT).