Nano-sized morphology of asphalt components separated from weathered asphalt binders

Aging of an asphalt binder results in the changes in its structure and percentage of every component of the asphalt binder. The aim of the research was to explore the change in nano-sized micro-structure of the four common asphalt components by atomic force microscope (AFM) technologies, and the change in quantity of the component during an aging process. In this study, an open-graded friction courses (OGFC) mixture was at first weathered by an accelerated weathering machine (AWM). Weathered asphalt binders were then recovered from the weathered mixtures by the Abson method, consequently separated into four common components, i.e., saturate, aromatic, resin and asphaltene (SARA). The test results indicated as follows: 1) the four components appeared different nano-sized morphology images: “moon-like spots” were found for asphaltene; “small irregular spots” for resin, “micro-particle structures” for aromatic component while “membrane-like structures” for saturate; 2) weathering caused the changes in the morphology of the components in different way and at different speed; 3) AFM index R_q of the four asphalt components all became bigger as the weathering time increased, although that the R_q of asphaltene and aromatic increased much faster than that of the other two.