Size optimization and self-healing evaluation of microcapsules in asphalt binder

Adding self-healing microcapsules into the asphalt binder seems to be an effective way to autonomously repair the micro-cracks in asphalt concrete, slow fatigue cracks growth rate, restore original mechanical properties, and further enlarge the fatigue life. Size including the diameter of the capsules and the thickness of the shell wall is one key parameter significantly determining the properties of microcapsules. Eleven microcapsule samples fabricated under different stirring rates with different core/shell thickness ratio are prepared. An optimal set of parameters suitable for introduction into asphalt is studied based on the microscope observation, component identification, and thermogravimetric estimation. The self-healing capability of the selected microcapsules is further evaluated based on the fatigue life recovery test. From testing results, it is shown that microcapsules fabricated under the 800 rpm stirring speed with 1:1 core/shell thickness ratio have a much more satisfactory size and shell structure, and present superior capability to improve the healing behavior of asphalt.