Cracking resistance evaluation of epoxy asphalt mixtures with 100% reclaimed asphalt pavement (RAP)

Despite the recycling of reclaimed asphalt pavement (RAP) providing great economic and environmental benefits, conventional technologies exhibit poor cracking resistance and cannot achieve high RAP content. The major objective of this paper is to evaluate the cracking resistance of recycled mixtures containing 100% RAP using epoxy asphalt, and to determine an optimal production method. In this paper, the effects of temperatures, epoxy proportions, and gradations on cracking resistance of epoxy-recycled mixtures with 100% RAP were explored through semi-circular bending (SCB) tests, and the mechanism was explained by laser scanning confocal microscopy (LSCM) tests. Subsequently, the validity of SCB parameters was examined using statistical analysis, and a new index (Cracking Resistance Comprehensive Score, CRCS) for evaluating the cracking resistance of epoxy-recycled mixtures was proposed through principal component analysis (PCA). The results indicate that the graded mixture with an epoxy proportion of 30% could be the best solution to recycle 100% RAP, which can restore the cracking resistance to the level of virgin mixtures, outperforming the conventional recycling technique. Statistical analysis shows that temperatures and epoxy proportions have significant effects on SCB parameters, and the fracture energy until failure (Gf1) or crack resistance index (CRI) is valid for characterizing the cracking behavior of epoxy asphalt mixtures. Moreover, CRCS contains over 90% of the original information and effectively identifies the effects of temperatures, epoxy proportions, and gradations, which can be applied to evaluate and rank the cracking resistance of epoxy-recycled mixtures.