Experimental Characterization of Self-Healing of Asphalt Materials

Several efforts have been made by the research community to identify proper laboratory testing methods and develop various analytical interpretations to estimate the healing performance of asphalt materials at the binder, mastic, mortar, and mixture scales. Depending on the considered scale and the testing approach, the evaluation of healing can capture two distinct mechanisms: adhesive healing and cohesive healing. While adhesive healing considers the phenomenon at the binder-aggregate interface, cohesive healing refers to the rebonding action of the binder medium itself. The assessment of crack healing can be derived from a variety of testing modes used to induce damage in the material and allow for the self-healing phenomenon to manifest itself when the material is left at rest. In such a context, damage can be based on both fatigue or fracture modes, requiring different experimental protocols and theoretical approaches. When focusing on the rest phase, the testing methods can be generally classified as storage, intermittent and hybrid healing tests, depending on how rest period(s) are introduced in the overall testing protocol. Following these considerations, several healing parameters can be introduced to measure the healing performance of the asphalt materials.