190al Time-Temperature Superposition Analysis of Asphalt Complex Modulus

Joseph V. Badami and Michael L. Greenfield. University of Rhode Island, Dept. of Chemical Eng., 205 Crawford Hall, Kingston, RI 02881

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 bT) were required in addition to the more typical relaxation time shift factors (aT). 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 aT shift factor and in relaxation time dependence differed among asphalts, though the cause could not be attributed between crude oil source vs. polymer modifier.