BBR and DSR Testing of Aging Properties of Polymer and Polyphosphoric Acid–Modified Asphalt Binders

This work evaluated the effect of polymer and polyphosphoric acid (PPA) on the aging resistance of different asphalt binders with pressure-aging-vessel (PAV) aging. Two base asphalt binders, three polymers, one recycled crumb rubber, and one PPA were used to produce the modified binders. The tested aging resistance included failure temperature, fatigue factor ($G^{*}·\sin \delta$), phase angle by dynamic-shear-rheometer (DSR) testing, stiffness ($S$), and creep rate ($m$-value) by beam-bending-rheometer (BBR) testing. The $G^{*}·\sin \delta$ values of the modified binders produced by 2% oxidized polyethylene or propylene–maleic anhydride and 0.5% PPA are lower than that of the modified binders produced by 3% oxidized polyethylene or propylene–maleic anhydride. Similarly, the modified binders produced by 2% styrene butadiene styrene (SBS) and rubber and 0.5% PPA show a lower fatigue factor value than those produced by 3% SBS and rubber. The asphalt binders blended with 0.5% PPA show lower phase-angle values than those produced by 3% oxidized polyethylene, propylene–maleic anhydride, or SBS. Moreover, the phase-angle value of the modified binder containing 2% SBS and 0.5% PPA is the lowest. The low-temperature stiffness and failure of modified asphalt with PPA is reduced to 23, 18, and 20°C. Compared with the polymer-modified asphalt, the difference between the stiffness of modified-asphalt binder with PPA at the test temperature of $-18°\mathrm{C}$ decreased by 16.67, 25, 4.17, and 4.17%, respectively. The results showed that using 0.5% PPA as 1.0% polymer replacement has a positive influence on the aging properties of binders. Moreover, the polymers, PPA, and binder sources can obviously influence the fatigue resistance of the binders.