Effects of Aging and Rejuvenation on Surface-Free Energy Measurements and Adhesion of Asphalt Mixtures

Abstract

This paper presents the results of a study that was conducted to understand the impacts of aging and rejuvenation on fundamental properties of asphalt binders. A Performance Grade (PG) 64-22 binder was aged to simulate the aging of asphalt mixes during construction and in-service conditions. The binders' surface tension property, i.e., contact angles between binder and three probe liquids, was measured using a sessile drop device. This property was then used to estimate surface free energy components of the control binder, aged binders, and rejuvenated binders using the Good-van Oss-Chaudhury postulation. Cohesive and adhesive bond energies of asphalt-aggregate systems under dry and wet conditions were also analyzed. The aggregates considered in this study were limestone and granite; these aggregates have different moisture affinities. The data showed that as asphalt ages, the contact angle between a liquid (distilled water) and the asphalt surface increases; however, for the other two probe liquids (formamide and glycerol), no pattern was observed. For the surface free energy components of the control binder, the aged binders, and the binders with rejuvenators, the contribution from Lifshitz-van der Waals components were comparatively much higher than those from acidic and basic components. The rejuvenators seemed to be effective at improving the cohesive energy of asphalt binder, suggesting an improvement in the water damage resistance of the mix. In general, the limestone-based asphalt concrete mixture showed a higher moisture damage resistance than the asphalt concrete mixture with granite. (C) 2019 American Society of Civil Engineers.