Investigation into the Evolution of Structural Characteristics of Asphalt by Aging at Microscale and Macroscale

Abstract

The surface morphology and micromechanical behavior of asphalt are significantly affected by aging, affecting the macroscopic characteristics of asphalt mixtures. This study investigates the evolution of the nanoscale microstructure of asphalt, with a focus on quantitative characterization. Key parameters such as the characteristic group index, beelike structure, roughness, force curves, complex modulus (G*), and phase angle (δ) of asphalt before and after aging were analyzed both quantitatively and qualitatively. A gray correlation analysis was employed to establish the relationship between asphalt nanoscale microstructure and macroscale rheological properties. Results indicate that aging leads to an increase in carbonyl, sulfoxide, and aromatic indices for both types of asphalt, while the isoprene index in styrene-butadiene-styrene (SBS)-modified asphalt decreases. As aging progresses, the number and area proportion of beelike structures on the asphalt surface decrease, but the average area of individual beelike structures increases. The SBS modifier reduces the roughness parameters of SBS-modified asphalt compared with matrix asphalt. Aging decreases both the adhesion work and surface energy of asphalt, with the most significant decline observed during long-term aging. The G* of the asphalt increases with aging, whereas δ decreases. The grey correlation coefficients for carbonyl index and surface energy are 0.6979 and 0.6666, respectively, indicating that characteristic group and surface energy are primary factors influencing macroscopic rheological performance.