Enhancing self-healing properties of microcrack on aged asphalt incorporating with microcapsules encapsulating rejuvenator

Self-healing microcapsules encapsulating asphalt rejuvenator were synthesized by in-situ polymerization. Micromorphology, chemical structure, thermal stability and salt resistance of microcapsules were characterized by Environmental scanning electron microscope (ESEM), Fourier transform infrared (FTIR), Thermogravimetric analyzer (TGA) and Electron microscope (EM). Conventional performance was studied by three major indicators (the penetration, softening point and ductility) experiments, self-healing rate was studied by ductility experiment and self-healing behavior was studied by Laser scanning confocal microscopy (LSCM), respectively. The results showed that microcapsules had regular spherical shape, rough surface, good salt resistance, and remained stable at 160 similar to 180 degrees C of asphalt mixing temperature. With the increase of microcapsule content, the conventional performance of aged asphalt would be improved. For neat asphalt, the maximum self-healing rate was 75.6% when microcapsule content was 3 wt%. For Rotated thin film oven test (RTFOT) asphalt, the maximum self-healing rate was 69.0% when microcapsule content was 2 wt%. For Pressure aging vessel (PAV) asphalt, the maximum self-healing rate was 64.0% when microcapsule content was 4 wt%. The self-healing time of microcrack on neat asphalt, RTFOT asphalt and PAV asphalt was 50 min, 70 min and more than 70 min, respectively. Asphalt rejuvenator in microcapsules had high fluidity, and released rejuvenator could quickly fill the microcrack, then promote the diffusion of asphalt molecules toward microcrack and winding, thus repairing the microcrack. The surface of aged asphalt had many folds and hindered the diffusion of rejuvenator on the microcrack. The aged asphalt increased the time for rejuvenator to accelerate the diffusion rate of asphalt molecules.