Investigation of the Influence of Aging on the Nanoscale Adhesion of Asphalt from the Perspective of AFM-IR–Based Chemical Properties

Abstract

Investigation of the adhesion mechanism during the aging process of the asphalt-aggregate interface from a microscopic point of view contributes to the solution of water damage of asphalt pavements. So far, some work has been done to reveal the influence of aging on the adhesion strength of the asphalt from the nanoscale factors. However, due to the lack of direct chemical analysis means to test the chemical composition of asphalt at the nanoscale, the inferences made among different scholars are somewhat controversial. The objective of this study is to reveal the evolution of adhesion characteristics of the asphalt binders during the aging process based on their chemical components. Five asphalt binders at different aging degrees were prepared via laboratory simulated aging procedure. State-of-art technologies, atomic force microscopy–based infrared spectroscopy (AFM-IR) and AFM PF-QNM (peak force quantitative nanomechanical mapping) mode, were adopted to analyze the nanoscale adhesion and chemical components of the prepared asphalt. And binder bond strength (BBS) testing was performed to interpret and verify the nanoscale mechanism of asphalt adhesion behavior from macroscale. The results of the AFM test indicated that both sulfoxide and carbonyl functional group content contribute to the adhesion force of the asphalt binders. Compared with the carbonyl group, the sulfoxide content affects the nanoscale adhesion force more significantly. Meanwhile, the results of the BBS test are found in accordance with the AFM trends. Finally, an estimation model was established to roughly estimate the nanoscale adhesion force of asphalt at varying aging conditions based on these two functional groups.