The aging characteristics of 20 asphalts were investigated by using the thin film oven test (TFOT) and rolling thin film oven test (RTFOT) at three temperature levels. Infrared absorption spectroscopyand the Schweyer rheometer test as well as penetration and absoluteviscosity tests were used to evaluate the characteristics of the asphalts before and after the TFOT and RTFOT. Data from the field werealso used to compare with the laboratory results. On the basis of percent penetration retained and absolute viscosity ratio, the RTFOT was found to be a more severe aging process than the TFOT for oven temperatures of 285 degrees F and 325 degrees F. On the basis of low-temperature constant power viscosity, the effects of TFOT and RTFOT are not significantly different at any of the three levels of temperature. As a rough estimate, the TFOT or RTFOT procedure performed at365 degrees F, 3 months of natural weathering of compacted Marshallspecimens, and 6 to 9 months of aging in a pavement would result inapproximately the same hardening effects on a typical paving grade asphalt used in Florida. From the results of this study, it appears feasible to use TFOT or RTFOT at higher temperature to simulate the aging process on the asphalt binder in asphalt paving mixtures in service, as well as that of the hot-mixing process.
Abstract