Nanoscale evolution of rubber-oil modified asphalt binder after thermal and UV aging

Thermal oxidation and ultraviolet exposure cause complex micro-scale chemical changes in asphalt binders, leading to severe deterioration of pavements. The aging-induced evolution of nanoscale domains in asphalt binders was investigated using multiple nanoscale characterizations. This in turn provides insights to develop means of alleviating the aging of asphalt binders to extend pavement service life. The chemical composition, surface topography, and mechanical properties of four asphalt binders (base asphalt and modified asphalt with bio-oils and crumb rubber) are investigated by atomic force microscopy during thermal aging and UV aging and a combination thereof. It was shown that the three domains in the asphalt binder react differently to aging. Abundant carbonyl and sulfoxide compositions are observed in the aged base asphalt binder, which is mainly generated and concentrated in the para domains. The addition of rubber and bio-modified rubber reduces the formation of aging-related compositions in para domains, thereby enhancing the aging resistance of asphalt binder. Aging also significantly changes the surface roughness and domain structures of asphalt binders. Furthermore, it was shown that the domain stability during thermal aging and UV aging can be enhanced by crumb rubber and bio-oils, respectively. Nano-mechanical characterization shows the surface of asphalt binders becomes stiffer, and its adhesion is reduced after aging. Significant reduction (up to 26%) in latter aging indicators was observed with the bio-modifier used in rubberized asphalt. This paper provides insights pertaining to the aging-induced evolution of asphalt binders while examining the efficacy of bio-modification of rubberized asphalt to delay aging. It is recommended to include hybrid aging in future studies and to test bio-modified rubberized asphalt at a larger scale.