Research on Rapid-Response Self-Healing Cement Mortar Based on SAPs and Crystalline Admixture

The cracking problem of cement-based materials seriously threatens their mechanical properties and durability. This study innovatively develops a fast-response self-healing capsule based on superabsorbent polymers (SAPs) and crystalline admixture to enhance the crack self-healing ability of cement mortar. The study systematically investigates the release and migration behavior of healing agents within cracks, with a particular focus on the influence of environmental humidity, as well as the effects of different capsule dosages on the pore structure and hydration heat of the mortar. In addition, the enhancing effects of the capsules on crack self-healing performance, including healing width and volume filling rate, and on impermeability performance, including permeability coefficient and plugging air leakage rate, are evaluated. The results indicate that environmental humidity significantly raises the release behavior, migration area, and migration distance of healing agents. Increasing the capsule dosage moderately increases the porosity of the mortar and reduces the total hydration heat release. A key finding is that the incorporation of the capsules significantly improves the self-healing efficiency of the mortar, as the maximum crack healing width reaches 453 μm, the internal volume filling rate reaches 90.25%, and the permeability coefficient is significantly reduced by 92.62%. In contrast, the air permeability is reduced by 93.34%. Microscopic analysis confirms that the healing products within the cracks are mainly composed of calcium carbonate (CaCO₃), calcium hydroxide (Ca(OH)₂), SAP residues, and hydrated calcium silicate (C-S-H) gel. This study provides an important theoretical and practical basis for the development of efficient self-healing cement-based materials.