Investigation of the impacts of aging and RAP percentages on effectiveness of asphalt binder rejuvenators

• Five different asphalt binder rejuvenators were evaluated.
• Two mixtures containing RAP were utilized in the study.
• Binder grading testing was also conducted according to AASHTO M320.
• Rejuvenators help in lowering the true grade of aged binders.

In this study, the ability of five asphalt binder rejuvenators to restore low and high temperature true performance grades of aged binders was investigated. The rejuvenators considered in this study included a Naphthenic Oil, a Paraffinic Oil, an Aromatic Extracts, a Tall Oil, and an Oleic Acid. Several sets of asphalt mixtures containing different percentages (i.e. 25% and 45%) of RAP materials were prepared using PG 76-22 polymer-modified asphalt binder blended with rejuvenators at manufacturers’ recommended dosage. Control mixtures not including the rejuvenators were also prepared. All mixtures were loose mix aged for two hours and six hours to evaluate the impact of aging on the effectiveness of the different rejuvenators. After aging and compaction, the asphalt binder contained in each of these mixtures was extracted and recovered. The true low and high temperature grades of the extracted binders were determined using the Dynamic Shear Rheometer (DSR) and the Bending Beam Rheometer (BBR) tests. The recovered binders were considered RTFO aged due to the mixture aging used in this study. The DSR shear modulus master curves were also utilized to examine the impact of using different rejuvenators on rutting and fatigue cracking. Furthermore, a multi-factor Analysis of Variance (ANOVA) was conducted to evaluate the statistical significance of the differences between results. The results showed that all rejuvenated binders had lower performance grade than that of the control binder without rejuvenation. In addition, rejuvenator’s effectiveness was not affected by aging (from 2 to 6 h) and increasing the amount of RAP materials (up to 45%). The rejuvenators were also found to improve the fatigue resistance without substantially influencing rutting performance.