RAPID AND SIMPLE METHOD FOR BINDER OXIDATIVE AGING

A rapid and simple method for simulating binder aging is presented. Using the eight Strategic Highway Research Program (SHRP) core asphalts, treating neat asphalt with microwave radiation for 7 hr and 20 min at 143 deg C and 440 psi (3034 kPa) yields a residue equivalent to that of "RTFOT + PAV." To test ability of microwave energy (dielectric heating) to simulate "RTFOT + PAV" aging (conductive heating), six different tests were used to compare physical, chemical, and physicochemical changes resulting from the two modes of aging. The six tests are: intermediate-temperature stiffness, low-temperature stiffness, asphaltene content, high-performance size exclusion chromatography (HPSEC), asphalt relative total polarity, and infrared spectroscopy. Conductive heating (PAV, with or without RTFOT) under the conditions of microwave treatment (7 hr and 20 min at 143 deg C and 300 psi (2069 kPa) - for safety, 440 psi (3034 kPa) could not be used with PAV) yields a residue that shows clumping in the pan, and nonhomogeneity that prevented rheological testing. Therefore, conductive heating cannot replace dielectric heating for rapid aging. Alternatively, applying dielectric heating at the Superpave conditions of 20 hr at 100 deg C and 300 psi (2069 kPa), gives rheological changes equivalent to those produced by both the RTFOT plus the 20 hr of PAC at similar conditions. Thus, dielectric heating enhances oxidation even at 100 deg C. The enhancement is more pronounced at higher temperatures (143 deg C) with a 70% saving of time.