Evaluation of Oxidization of Crumb Rubber–Modified Asphalt during Short-Term Aging

Abstract

Asphalt binder is subjected to aging during the construction process and service life of pavement. Aging substantially changes the chemical composition and physical properties of asphalt and leads to premature distresses on pavement. It is speculated that crumb rubber modifier (CRM) reduces the susceptibility of asphalt to aging, but its mechanism is not fully understood. Also, the impact of interaction parameters and exchange of components on the aging behavior of a crumb rubber–modified binder is not fully understood. In this study, the effect of CRM on the short-term aging of asphalt was investigated through an analysis of the distinctions between the impact of different CRM activities (e.g., swelling and dissolution) on the oxidization process of asphalt. The crumb rubber–modified binder and its extracted liquid phase were aged with the use of a rolling thin-film oven. Physical and analytical tests (e.g., dynamic shear rheometer, Fourier transform infrared spectroscopy) were performed before and after aging. The results revealed that CRM affected the short-term aging behavior of asphalt in two ways. First, CRM retarded asphalt oxidization through the release of antioxidants. Second, CRM continued to interact with asphalt during its aging through absorption of aromatics and swelling. The results indicated that, through the accurate control of the interaction conditions, a modified asphalt could be produced with antiaging behavior superior to that of neat asphalt. Moreover, the results showed that an increase in the mixing and compaction temperature of hot-mix asphalt was not a good remediation of the high-temperature workability problem with the crumb rubber–modified binder because it significantly affected the nature of the composite.