Nanoscaled characteristics of recovered asphalt binders from weathered asphalt mixtures

The nanoscaled properties including morphology and mechanics of recovered asphalt binders from open-graded friction course (OGFC) asphalt mixtures weathered in a laboratory were measured by atomic force microscopy. In addition, specific functional groups and molecular size distributions of the recovered binders were tested by Fourier infrared spectroscopy and gel permeation chromatography (GPC), respectively. The OGFC mixtures were weathered in an accelerated weathering machine for various durations of 0, 1,000, 2,000, and 3,000 h. The results showed that (1) as the weathering degree increased, the root mean square of morphology increased, and both the number of the “bee-structures” and the adhesion decreased; (2) as the weathering degree increased, the carbonyl and sulfoxide indexes increased, whereas the butadiene-based index decreased; and (3) the large molecular size groups from GPC tests increased, whereas the small molecular size groups decreased, as the weathering time increased. The changes of the molecular size groups had fairly good linear correlations with the weathering time.