Examining relationships between properties of weathered asphalt mixtures and nano-sized morphology of their recovered binders

The objective of this study was to examine the relationship between the properties of weathered asphalt mixtures and the nano-scaled morphology of their recovered asphalt binders. Firstly, asphalt mixtures of open-graded friction course (OGFC) were weathered in an accelerated weathering machine (AWM) and then tested for selected properties. Secondly, the asphalt binders were recovered using an Abson method and investigated for their nano-scaled morphology by an atomic force microscopy (AFM). Finally, the relationships between the selected properties of the weathered mixtures and the nano-scaled morphology of their asphalt binders were established. The results revealed that (1) the increasing height roughness and wrinkle degree of the nano-morphology of the recovered asphalt binder could be well exhibited by the increasing AFM indexes: image surface area difference (ISAD), height root-mean-square (R _q) and the difference between maximum and minimum height (R _max), a clear demonstration of how asphalt binder surfaces stiffen with age; (2) the cracking-resistance at low temperature, the rutting resistance and the splitting strength of the weathered OGFC mixtures decreased, while the AFM indexes of the nano-sized morphology increased as the weathering time increased; (3) There was a linear relationship between the properties of the weathered mixtures and the three AFM indexes.