Survival and activation behavior of microcapsules in self-healing asphalt mixture

Microcapsule technology exhibits great potential in improving the healing efficiency of asphalt mixture and prolonging the service life of the pavement. The capsule should be kept intact in the mixing and compaction process of asphalt mixture, whereas broken to release the healing agents in time when cracks encounter it. This paper aims to investigate the survival and activation behavior of microcapsules in asphalt mixture during construction and service period. By means of the in situ polymerization method, the microcapsules of various sizes were prepared and their particle size distribution, core material content, shell permeability, and other properties were characterized. Based on the quantitative analysis principle of Fourier transform infrared spectrometer (FTIR), the influence of microcapsule size and mixing temperature on the survival rate of microcapsules was analyzed. Meanwhile, the morphology and size distribution of surviving microcapsules was obtained via fluorescence microscope (FM). In addition, the morphologies of microcapsules before and after the bitumen bond strength (BBS) test and dynamic shear rheological (DSR) test were observed by FM to examine the releasing behavior of microcapsules. Finally, the fatigue-rest-fatigue test was performed to investigate the influence of microcapsule size on the healing efficiency of aged asphalt mastic. The results showed that the survival rate could be improved by reducing the construction temperature and the microcapsules size. The loss of microcapsules was more likely to happen in the mixing process rather than in the compaction process. Microcapsules with larger sizes were easier to be activated to remarkably enhance the healing efficiency of the aged asphalt mastic. Notably, the microcapsules with appropriate size are recommended to be added to the mixtures to ensure that the microcapsules survive in the construction process and are activated when cracks appeared. (C) 2020 Elsevier Ltd. All rights reserved.