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ABSTRACT Asphalt binders have the self-healing ability to repair fatigue cracking automatically, and therefore the fatigue life can be extended. The extended fatigue life depends on the coupling effect between [...]

In order to distinguish the wetting healing stage and the molecular diffusion healing stage during the self-healing process of asphalt binders, the fluorescence microscope (FM) together with the image processing technique was employed. The healing index was put forward based on the variation of crack area. On the basis of the established capillary diffusion theory, the Two-Stage Model was built to fit the healing curves characterizing the healing index variation with healing time. It is found that the established method is quite suitable to identify the wetting and the diffusion stages. The wetting healing occurs firstly, during which the asphalt molecules spontaneously wet the both faces of crack. Although the strength recovery is not distinct at this stage, SBS modified asphalt shows greater wetting healing strength than the other neat asphalt binders. Once the wetting process is nearly finished, the molecular diffusion healing ratio accelerates significantly, and the descending order of the molecular diffusion rate is: SBS > PEN 100 > PEN 70 > PEN 50 > PEN 20. The test results also show that the disappearance of visible crack does not indicate that the strength has been fully recovered. Here, the tensile strength test is developed to identify the strength recovery rate after the crack is fully closed, which implies that the strength regeneration is a long process. Keywords: Asphalt Self-healing Two-Stage Model Wetting healing Molecular diffusion healing, 1. Introduction The failure process of composites is normally preceded by the coalescence of interacting micro cracks to form a fatal crack. The formation of micro cracks with a length [...]

ABSTRACT Self-healing, as a very valuable characteristic, should be considered when selecting and designing constitutions of asphalt materials. It is necessary to develop a fundamental and universal healing evaluation indication [...]