RAP-Added SMA Mixtures: How Do They Fare?

Abstract

Stone matrix asphalt (SMA) is a highly rut-resistant gap-graded asphalt mixture. The inclusion of supplementary materials such as fiber, filler, and polymer-modified bitumen (PMB) makes the layer more expensive to construct. This study examined the rutting and fatigue behavior of SMA mixture by partially replacing virgin aggregates and bitumen with reclaimed asphalt pavement (RAP), thus enhancing sustainability. The study compared the laboratory performance of 20%, 30%, and 40% RAP-added SMA mixtures with that of a conventional SMA mixture. The virgin binders were infused with RAP binder at different proportions and were subjected to rheological testing to evaluate miscibility and performance. The results indicated an improvement in rutting and a decrease in fatigue life, with crumb rubber–modified bitumen (CRMB) offering a higher degree of miscibility than styrene-butadiene-styrene (SBS) PMB when infused with RAP binder. From this study, it can be concluded that in a high-quality SMA surface layer, 20% is the most acceptable amount of RAP content. However, if SMA with CRMB60 binder is used as a binder layer, then 30% of RAP can be used to improve performance.