Accelerated Aging of Asphalt by UV Photo-Oxidation Considering Moisture and Condensation Effects

Abstract

To understand the long-term performance degradation of asphalt, ultraviolet (UV) photo-oxidation has been used to accelerate the aging process. Three types of asphalt binders extracted from reclaimed asphalt pavements (RAPs) and one extracted from fresh hot-mix asphalt (HMA) were aged under continuous UV exposure and UV/moisture/condensation exposure. After accelerated aging tests, the weight percentage of oxygen (WPO) in all samples were measured by using energy-dispersive X-ray (EDX) spectroscopy. The testing results indicate that the aging rates of the asphalt binder under both UV and UV/moisture/condensation are fast at the beginning and stabilize after a certain period. Experimental results were also modeled by two classic asphalt aging models, namely, the fast rate–constant rate (FRCR) and nonlinear differential dynamic (NDD) models. Although the NDD model exhibits acceptable agreement with the experimental results from both the UV aging and UV/moisture/condensation aging samples, the FRCR model fits the UV/moisture/condensation aging better and thus is recommended for future UV/moisture/condensation aging performance prediction. Additionally, although exposed under UV for the same time, the WPO in samples after UV/moisture/condensation aging were lower than those in samples after continuous UV aging. This indicates that condensation and moisture reduce the UV-induced photo-oxidative aging rate.