Effect of RAP Source on Cracking Resistance of Asphalt Mixtures with High RAP Contents

This paper summarizes the results of a research study that used microscale and macroscale tests to examine the effects of reclaimed asphalt pavement (RAP) source and RAP percentage on the cracking resistance of asphalt mixes with high RAP content. Atomic force microscopy (AFM) was used to study the microstructure and the adhesion properties of binders of two different RAP sources. In addition, asphalt mixes with three RAP percentages were designed using the two RAP materials considered. The low-temperature cracking resistance and fatigue cracking resistance of the designed mixes were evaluated. The results of the AFM experiments indicated that the microstructure of the RAP binders was different from that of the virgin asphalt binders. While the adhesive properties of RAP binders were statistically different from each other, both RAP binders had significantly lower adhesion than the virgin asphalt binders used. The results of macroscale tests indicated that the RAP source has a significant effect on the fatigue cracking resistance of RAP asphalt mixes, particularly those with more than 30% RAP. This might be attributed to differences in the adhesive properties of the RAP binders. Therefore, it is very important to determine the adhesive properties of the RAP binders. The results also indicated that using a virgin asphalt binder with appropriate low-temperature performance grade can help ensure satisfactory low-temperature cracking resistance of mixes with up to 50% RAP.