Connections between the Rheological and Chemical Properties of Long-Term Aged Asphalt Binders

AbstractAsphalts aged in laboratory conditions have been extensively studied, but those aged in hot-mixed asphalt (HMA) mixtures in the field receive less attention. Particularly missing are the aging characteristics of asphalts in long-life HMA pavements. In this study, the rheological and chemical properties of asphalts that were aged in HMA pavements for 7 and 36 years were examined, including the variations of these properties with pavement depth and their interrelationships. The analysis results suggest that (1) severe asphalt binder aging occurred at the deepest pavement layer, (2) material type and pavement depth affect aging rate, (3) asphalt binder from the deepest layer showed a loss of saturates, (4) binders’ two important rheological properties are well related to asphaltenes content and ketone formation, and (5) age hardening apparently is affected more by the increase of dispersion volume and size than by the viscosity of the suspension medium. These findings not only prove that asphalt bind...