Evaluation of the Rheological Properties and Activation Energy of Virgin and Recovered Asphalt Binder Blends

In this study, the rheological properties and activation energy (AE) of unaged and aged asphalts blended with different percentages of binder, recovered from three reclaimed asphalt pavement (RAP) sources, were investigated. Superpave asphalt binder tests were used to evaluate the effects of the recovered asphalt binder source and content. The results indicated that the addition of recovered binder from each source increased the viscosity, $G^{*}/\sin \delta$, and $G^{*}\sin \delta$. The increase in viscosity per 1% recovered binder was evaluated using non-dimensional viscosity index ($\nabla {\eta }_{\mathrm{RAP}}$). In addition, the increase in $G^{*}/\sin \delta$ and $G^{*}\sin \delta$ per 1% recovered binder were investigated using relative Superpave rutting gradient (RSRG) and relative $G^{*}\sin \delta$ gradient (RG) factors, respectively. The results indicated that the $\nabla {\eta }_{\mathrm{RAP}}$, RSRG, and RG depended on recovered binder source, content, aging, and test temperature. The interpretation of the AE results depended on the physical phase of the asphalt blends, irrespective of the recovered binder source and content. The AE increased when the physical phases of the asphalt blends were in liquid and semiliquid (high phase angle) states over the range of temperatures tested compared with the control asphalt binder. However, the AE decreased when the physical phase of the asphalt blend samples was solid (low phase angle).