Toward understanding the surface morphology and microscopic mechanical properties of asphalt after experiencing tensile and compressive stress.

[Display omitted] • Novel tension–compression device reveals asphalt's asymmetric mechanical properties. • Atomic force microscope and molecular dynamics simulations show lower compressive strength compared to tensile strength. • Tensile stress decreases roughness and increases adhesion; compression has the opposite effect. • Different migration rates of asphalt components change surface morphology under stress. • Findings enhance theoretical support for improved asphalt pavement design and maintenance. Load-induced stress is a one of the major causes of asphalt pavement failure. It is, therefore, necessary to understand the changes in stress on the microscopic mechanical properties of asphalt in improving pavement design. While much research been carried out concerning effects brought about by tensile, the effects that compressive stress would have on the microscopic mechanical properties of asphalt remains less explored. In the current study, a custom-designed tension–compression device was developed and atomic force microscopy (AFM), complemented by molecular dynamics (MD) simulations, to investigate the microscopic properties of asphalt in both undeformed and deformed states. The findings reveal that asphalt exhibits significantly weaker compressive strength compared to tensile strength. Under tensile stress, the various components in asphalt align loosely in the direction of tension, while asphaltenes are affected the least. These changes in apparent morphology reflect different migration rates of the various components. Under compressive stress, the asphalt surface is more compact, and this reduces the area of the "bee" structure. Under varying stress conditions, asphalt exhibits a smoothing of the rough region with an associated loss in adhesion. Specifically, increased tensile strain leads to smoother topography and increased adhesion, while increasing compressive strain has the opposite effect. These results provide valuable theoretical insights for the design and maintenance of more durable asphalt pavements. [ABSTRACT FROM AUTHOR]