Characterization of surface roughness and adhesive mechanism of asphalt and mineral aggregate based on atomic force microscopy method

The 2-D picture and 3-D topography for asphalt and mineral aggregate were firstly scanned with the tapping mode of atomic force microscope (AFM). Then the surface energies of asphalt and mineral aggregates were measured with the force-curve mode of AFM and calculated to represent their physical bonding performance. The results indicate that the asphalt binders made with various crude oils have different chemical compositions and surface roughness. The asphalt binder with bee-structure has a larger roughness compared with asphalt binder without bee-structure. Ageing can reduce the surface roughness and surface energy of asphalt, then weaken the adhesive bonding between asphalt and mineral aggregate. Finally the relationships among the surface roughness and surface energies of asphalt and mineral aggregate, and the adhesive tensile strength of asphalt/mineral aggregate system were analyzed, based on the adhesive tensile test results at the macro-scale. It is found that the roughness of asphalt and mineral aggregate play a key role in determining their adhesion, when the asphalt has bee-structures. However, for the asphalt which has no bee-structures, the adhesion between asphalt and mineral aggregate is more dependent on the surface energies of materials, which actually represents the physical bond performances of materials.