Oxygen diffusion coefficients of asphalt mixtures and their impacts on mixture aging

Abstract

The oxidative aging of asphalt binder affects the long-term performance of flexible pavement. Apart from the intrinsic property of asphalt binder, binder aging in an asphalt mixture is also affected by the mixture’s oxygen transport efficiency, which can be characterized by the oxygen diffusion coefficient. In this study, the diffusion coefficients (Dₛ) of compacted asphalt mixtures of different designs were determined. The same mixture samples were also aged in one dimension for a relatively long period of time. Asphalt binders from different slices of the aged specimens were extracted and recovered, and their aging states were determined. Influences of Dₛ and air void content on binder aging gradient and binder aging extent in the mixture samples were systematically examined and compared. The results indicate that, as compared with air voids, Dₛ is more closely related to the aging susceptibility of asphalt binders in asphalt mixtures. It may serve as a useful and convenient parameter in mixture design optimization, modeling and prediction of in situ pavement aging, and quality control and quality assurance (QC/QA) in pavement construction.