Characterization of Adhesion and Healing at the Interface Between Asphalt Binders and Aggregate Using Atomic Force Microscopy

The adhesion damage and healing in asphalt mixture have been studied at the macroscale for decades. This study investigated the adhesive performance and adhesion-healing property of asphalt binder aggregate interface at the microscale. The study employed atomic force microscopy (AFM) to measure the adhesion force between asphalt binder [one base asphalt and one styrene butadiene styrene (SBS) modified asphalt] and silicon nitrite tip. In addition, two probes were selected for the AFM test, and the influences of the probe parameters on the test results were analyzed. On the basis of measurement of the adhesion forces, adhesion work was calculated, and the adhesive performance and adhesion-healing ability of the two asphalt binders were studied. The results showed that a relatively soft probe was suitable for measurement. With a combination of surface free energy data and,AFM test results, SBS modified asphalt was found to have better adhesive performance and adhesion-healing ability. Also, the addition of SBS polymer induced an obvious contrast in phase separation behavior, which was responsible for the change in adhesion forces. This study provided fundamental research in the investigation of asphalt binder aggregate interface and useful guidance for probe selection in the AFM test.