Influence of Aging Temperature on Rheological and Chemical Properties of Asphalt Binders

Four asphalts used in field pavements were aged at a laboratory in a pressure-aging vessel (PAV) at several temperatures for various lengths of time. The chemical (infrared spectra) and rheological properties of these aged asphalts were compared. Results showed that the same PG graded asphalts from different crude sources had significant differences in their rheological behavior and chemical properties after long-term oxidative aging. Asphalt per se had approximately the same aging rheological pattern regardless of aging temperature. Laboratory PAV aging at 80°C for 504 h was found to produce stiffer material than the same material subjected to the same PAV aging at 100°C for 100 h. The plot of G * complex modulus versus phase angle was found particularly useful for characterizing the asphalt binder rheology in terms of long-term aging characteristic. Additionally, the aging shift factor, generated from the aging master curve, was used to characterize the modulus changes with respect to aging and to compare effects of aging on different materials. Furthermore, results indicated a linear relationship between the change of rheological property and the change of chemical property (carbonyl index) with respect to long-term aging. It was verified that sulfoxide was formed easily with aging. However, sulfoxides also decomposed at longer aging times.