Research on the Microscopic Aging Characteristics of Asphalt Binder Based on Atomic Force Microscopy

To deeply analyze the difference between styrene-butadiene-styrene (SBS)-modified asphalt and base asphalt in ultraviolet (UV) aging performance, an atomic force microscope was used to carry out an accurate analysis of the bee structural characteristic parameters of two kinds of asphalt experiencing different UV aging time duration. With the advantages of the Levenberg-Marquardt (LM) algorithm and universal global optimization (UGO) algorithm, the relationship between the microscopic characteristic value and the performance index of asphalt under UV aging was constructed. The results show that the physical parameters of the bee structure of asphalt are closely related to the macroscopic properties of asphalt materials. Because the number of bee structures of SBS-modified asphalt is significantly more than that of base asphalt, and in the process of UV aging, the absolute height and area of the bee structure fluctuate less, and the adhesion force fluctuates with aging time. The decreasing trend makes SBS-modified asphalt significantly better than base asphalt in anti-UV aging performance. Under different UV aging time durations, the penetration and aging index (AI) of the two kinds of asphalt showed an excellent linear relationship with the microscopic indexes measured by atomic force microscope (AFM). Through the nonlinear optimization algorithm, the prediction equations of the morphology height and adhesion force of the two kinds of asphalt under different aging stages were successfully derived. The research results can provide theoretical support for the optimization and improvement of the UV aging performance of SBS-modified asphalt.