Utilization of Atomic Force Microscopy (AFM) in Characterizing Microscopic Properties of Asphalt Binders: A Review

Atomic force microscopy (AFM) is a powerful tool that can effectively reveal the intricate relationship between the microstructure and micromechanical properties of asphalt binders, as well as their subsequent influence on macro-level performance. Thus, it plays a crucial role in the design and development of new asphalt materials. The objective of this review is to analyze the literature on the microscopic characterization of asphalt binders using AFM and to provide a reference for designing high-performance asphalt materials based on micromechanisms. This review begins by discussing various AFM-based characterization techniques for asphalt binders, such as morphology imaging, tip modification, atomic force microscopy-infrared (AFM-IR), nanorheological tests, and in situ tests. Next, the sample preparation methods and their impact on the test results are discussed. Then the composition-structure-mechanics relationship of asphalt binders, including the chemical composition of bee structures, surface and bulk microstructures, and macroproperties of asphalt binders are analyzed. Furthermore, we summarize the current applications of AFM in asphalt studies. Lastly, we discuss the challenges and future directions of AFM-based characterization methods of asphalt binders, emphasizing the research prospects of nanorheological testing methods.