Extended Research on Microwave Heating-Healing Capacity of Asphalt Mixture: Asphalt Flow Analysis Combining Capillary Flow Test with Temperature Distribution

Abstract

Asphalt pavement faces the threats of load-induced cracks. The cracks result in several diseases and shorten the service life of the pavement. In the pavement, the asphalt binder can heal cracks via its self-healing capacity. The self-healing capacity can mitigate the negative impact of the cracks. Thus, the capability has the value of being strengthened. As a maintenance measurement, microwave heating has been used to improve the healing capacity. The existing research on microwave heating and healing can be extended in two ways. First, the correlation between temperature and asphalt flow state needs further clarification. Second, the healing state judgement method with average temperature is not comprehensive because temperature distribution is not considered. This research studied these two aspects in three steps. First, the temperature data of asphalt mixture were obtained with an infrared camera. The second step was to investigate the correlation among temperature, flow state, and healing state of asphalt binder. The crucial temperature values were determined using a dynamic shearing rheometer (DSR) and capillary flow test. The third step was to include temperature distribution in the judgement of heating and healing states. The correlation determined in the second step and the temperature data from the first step were integrated with an analysis of area proportion. The area proportion corresponds to certain temperature ranges. Corresponding to the two researched issues, the main results can be summarized in two aspects. First, the initial temperature of capillary flow is over 40°C higher than that of Newtonian flow. Second, the area proportion is influenced by heating time and admixture content. The increase in heating time and admixture content changes the asphalt flow states between Newtonian flow and capillary flow, and is accompanied by variation of healing promotion modes.