During aging process physio-chemical changes occur in asphalt. As a result, many serious distresses evolve in pavement. The changes occur in asphalt from aging should have deep relation with its intrinsic properties. The surface free energy is a fundamental property of a solid and liquid. A PG 64-24 binder was aged to simulate aging that occurs during construction and in-service state. The binder’s surface tension property, i.e., the contact angle between the binder and three liquids were measured by a sessile drop device. This property was then used to estimate surface free energy (SFE) components of control binder, differently aged binders and binders with two rejuvenators, using Good-van-Oss-Chaudhury’s postulation. Cohesive and adhesive bond energies of asphalt-aggregate mixture system were also analyzed. Aggregates considered in adhesion analysis consists of limestone and granite based aggregates that have different moisture affinity. The data shows as asphalt ages the contact angle between a liquid (distilled water) and asphalt surface exhibits increasing pattern, however for other two liquid no pattern was observed. For the SFE components of the control, differently aged and binder with rejuvenators, it was noticed that the contribution from Lifshitz-Waals components are comparatively much higher than the acidic and basic components. The energy requires to initiate a cohesive failure or crack reduces is observed. The rejuvenators are seemed to be effective to improve the cohesive energy of asphalt binder suggesting that the softening agents enhance resistance to moisture damage by water diffusion process through the binder film itself in the asphalt-aggregate mixture. When the combination between binder and aggregate type is evaluated, the results clearly demonstrate that limestone based mixture continued to have a higher moisture damage resistance after different types of aging comparing to granite based mixture.
Contributors: Hossain S M K, Karakas A, Singhvi P, Ozer H, Al-Qadi I.
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