Investigation of Synergistic Effects of Warm Mix Asphalt and High Fractionated Reclaimed Asphalt Pavement for Safe, Environmentally Sustainable Highway
To increase RAP materials by up to 75% by binder replacement, a fractionation method was applied to the RAP stockpile by discarding RAP materials passing No. 16 sieve. This fractionation method was effective in improving volumetric properties of the HMA mixture with high RAP contents. The mix designs were then performed for both HMA and WMA with varying fractionated RAP amounts accounting for a replacement of 20, 30, 40, 50 and 75% of the mixture’s optimum asphalt binder content. All mix designs met the Iowa DOT mix design requirements except the one with 75% RAP materials by binder replacement due to the excessive amount of dust content. Hamburg Wheel Tracking (HWT) test was used to evaluate the rutting and moisture susceptibility of both HMA and WMA mixtures with varying RAP amounts. Overall, HMA mixtures performed better than WMA mixtures and the mixes with higher RAP amounts performed better except the mix with 30% RAP materials by binder replacement. Both HMA and WMA mixes with 75% RAP materials by binder replacement (90% by weight replacement) performed the best by exhibiting very little deformation ranging between 2 and 4 mm after 20,000 repetitions.
In order to evaluate the performance of WMA mixtures in the field, test sections were constructed in Iowa and Ohio. The average densities of the HMA and WMA test sections in Iowa were 94.3% and 93.9%, respectively, and those of the HMA and WMA test sections in Ohio were 94.6% and 95.2%, respectively. Significantly less emission and smoke were observed during construction of WMA mixtures, which confirmed the environmental benefits of using WMA technologies while meeting both Iowa and Ohio DOT’s density requirements. Both HMA and WMA mixes from Iowa met Hamburg testing requirement by exhibiting very little deformation of 3 mm and 5 mm, respectively, after 20,000 repetitions. HMA mix from Ohio met Hamburg testing requirement by exhibiting very little deformation of 4 mm after 20,000 repetitions whereas WMA mix exhibited 15 mm deformation after 20,000 repetitions.