Properties and mechanism of self-healing cement paste containing microcapsule under different curing conditions

This paper used the grouting method to maintain the cracks of subsea tunnel lining concrete, and the grouting materials was given the self-healing capacity by Urea-Formaldehyde/Epoxy (UF/E) microcapsules. The prop-erties and mechanism of grouting slurry and hardened paste body exposed to seawater were investigated. Firstly, the microcapsule was synthesized by means of an in-situ polymerization method. Then the fluidity and dispersion of microcapsules were investigated. Besides, the mechanical properties and pore structure of the composites were measured. Meanwhile, the strength and porosity recovery rates were calculated after pre-damage treatment. Finally, the self-healing mechanism of microcapsule was researched through Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS). The results indicated that the microcapsule had a negative effect on the mechanical properties and porosity. With the increasing microcapsule dosage, the self-healing capacity first increased and then decreased, and the highest capacity was achieved with 1% dosage. Mean-while, the self-healing capacity decreased with the increased pre-damage level. The SEM and EDS analysis showed that the microcapsule could repair the micro-cracks within the cement paste.