A direct characterization of interfacial interaction between asphalt binder and mineral fillers by atomic force microscopy

The property of asphalt mastic directly affects the service performance of asphalt mixtures and pavements. Previous studies have demonstrated that the interaction between asphalt binder and mineral fillers has a significant effect on the performance of asphalt mastics. However, the interaction hasn’t been characterized by direct tests. In this study, an adsorption–separation test of asphalt binder on surface of mineral fillers was conducted to separate the structure asphalt binder and free asphalt binder. Atomic force microscope (AFM) PeakForce QNM mode was used to characterize the morphology and mechanical property of asphalt binder at different distances to filler surface. Results show that the effected thickness of binder–filler interaction was around 1 μm. Within this specific thickness, the “bee” structure of asphalt surface disappears gradually, and the modulus increases significantly when the tested samples are closer to the aggregate surface.