Fabrication of Microcapsule-Type Long-Lasting Phosphorescent Sensor for Concrete Crack Monitoring

The generation and expansion of cracks in concrete structures reduce the durability and safety of structures. In order to detect cracks in concrete structures, a long-lasting phosphorescent microcapsule coating is proposed in this study. The microcapsule-based sensor is pasted on the surface of cement-based materials and solidified. The microcapsules become ruptured and cause the core material to flow out when the microcracks occur on the material, which emits strong phosphorescence at the cracked position under UV irradiation. The results indicate that the successful encapsulation of microcapsules could enhance the thermal stability of phosphorescent dye. The excitation wavelength of the phosphorescent microcapsules is also investigated. The phosphorescent microcapsules could effectively highlight unnoticeable cracks by a long-lasting phosphorescence response in the cracking region. The mechanical properties of microcapsules/epoxy resin composite coatings were studied, and the optimal content of microcapsules in the coating was determined. The as-fabricated phosphorescent microcapsules have good damage-sensing effects in conditions of different light and temperatures. The method proposed in this study will assist in the further development of damage-sensing material in the field of concrete crack monitoring.