(190al) Time-Temperature Superposition Analysis of Asphalt Complex Modulus

Complex modulus data available from experiments described in the literature were reinterpreted using time-temperature superposition of tan delta as the main criterion. Shift factors in moduli G' and G" (usually notated b_T) were required in addition to the more typical relaxation time shift factors (a_T). The former spanned approximately an order of magnitude over 5-70 C, while the latter spanned the usual many orders of magnitude and were consistent with the WLF equation. Results were fit using a multicomponent Maxwell model. The resulting frequency distribution was used to interprent the changes in relaxation times that occur as a result of the Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV) tests that are used to model asphalt oxidation in the lab. Changes in WLF dependence of the a_T shift factor and in relaxation time dependence differed among asphalts, though the cause could not be attributed between crude oil source vs. polymer modifier.