Blending of Virgin and RAP Binder for Asphalt Mixes with High RAP Contents: A Pilot Study

Reusing reclaimed asphalt pavement (RAP) presents an opportunity to reduce environmental burdens and encourage sustainable development. However, a concern exists about blending RAP binder and virgin asphalt binder. While RAP mixtures assume complete blending between these binders, the actual extent of this blending remains uncertain. Lower blending percentages can reduce the total binder content of the asphalt mixture, potentially leading to cracking failure. From this perspective, the present study quantifies the effect of blending between the RAP and virgin asphalt binders, considering various influential factors such as mixing temperatures, RAP gradation, and RAP source. Three different blending scenarios (0%, 50%, and 100%) were hypothesized in this study, and their impact on the performance of asphalt mixtures and binders was evaluated through semi-circular bend and rheological tests, respectively. To find the blending efficiency, the asphalt mixtures were also prepared using actual RAP (coated with RAP binder) and virgin aggregates. Results revealed that the amount of RAP binder in the final mix greatly influenced the cracking resistance. Even though the gradation and design binder content of two RAP mixtures are the same, differences in their cracking resistance highlight the important role of active binder content in the final mix. The findings emphasize the critical role of blending in determining the cracking resistance of RAP mixes. With the increase in blending levels between the RAP and virgin binder, the asphalt mixtures exhibit higher cracking resistance. Considering all the aspects, an average blending of 56.5% was recommended for the RAP mix design.