Research on Effect of Polymer Repair Agent on Self-Healing Performance of Concrete Cracks Based on Different Humidity Environments

The damage deterioration law and crack repair mechanism of concrete under different humidity environments were systematically studied by the changes of apparent morphological characteristics, gas permeability, moisture transport and compressive strength, and the incentive mechanism of environmental responsive polymeric repair agents on the self-healing of damaged concrete under different humidity environments was revealed; meanwhile, the microstructure and evolution mechanism of crack self-healing were studied by combining scanning electron microscopy, energy spectrum analysis and X-ray diffraction. The microstructure and evolution mechanism of crack self-healing were also investigated by combining scanning electron microscopy, energy spectrum analysis and X-ray diffraction. The results showed that the natural air and 30% relative humidity curing environment were not conducive to the self-healing behavior of concrete cracks; with the increase of curing humidity, the concrete crack repair rate increased continuously, and the humid environment was favorable for the environmentally responsive polymeric repair agent to give full play to the stimulating effect, promote the crack self-healing characteristics, and prolong the service life; the best repair effect of polymeric repair agent was achieved under the water immersion environment, and the crack healing rate could reach 70.38%, the durability and compressive strength of the repaired concrete were significantly better than those of plain concrete.The main reason for crack healing was that the repair agent absorbed water and swells, and a large amount of gel precipitates such as calcium carbonate and calcium alumina filled the cracks; the self-healing performance of concrete cracks was the result of both physical and chemical changes.