Effect of Aging on the Rheological and Molecular Weight Distribution of Asphalt Binder Treated with Polyphosphoric Acid

Asphalt binder behaves as a viscoelastic material and its inherit performance is dominated by rheological and chemical properties. Aging of asphalt binder is a prominent distress for long-term in-service asphalt pavement. In this work, the effect of aging on base asphalt modified by polyphosphoric acid (PPA) has been investigated. For the objective, virgin asphalt binder was modified by various dosages of PPA, styrene-butadiene-styrene (SBS), and PPA/SBS compound modification. The short- and long-term aging processes were simulated by Rolling Thin-Film Oven Test (RTFOT) and Pressure Aging Vessel (PAV) procedure. Rheological property of five aged modified binders was evaluated by the Dynamic Shear Rheometer (DSR). Meanwhile, gel permeation chromatography (GPC) was conducted to measure the molecular weight distribution and dispersion coefficient during the aging process. The high-temperature stiffness of PPA polymer binders is slightly higher than that of SBS and PPA/SBS compound modified asphalts. The aging ratio and molecular weight analysis verify the lower thermal-oxidative susceptibility of PPA/SBS compound modified asphalts. This study offers an understanding for the promotion and application of PPA modifier.