Effect of pH-Responsive Superabsorbent Polymers on the Self-Healing of Cement-Based Materials

Self-sealing cement-based materials utilize the swelling properties of superabsorbent polymers (SAPs) to repair cracks without requiring additional labor. SAPs have been the subject of numerous studies as self-sealing materials for cementitious materials to repair fissures. The goal of this research project is to use pH-responsive SAPs to enhance cementitious material’s capacity for self-sealing. To achieve this, two SAPs were used: one consisting of sodium acrylate and the other of an acrylic acid/acrylamide copolymer. Each SAPs had a distinct particle size distribution, and its concentration was adjusted between 0.5% and 1% based on the binder weight. The swelling capability of sodium polyacrylate-type SAPs decreased with increasing pH, with the maximal absorption capacity occurring at pH 7, as determined by a pH-sensitive assay. On the contrary, the swelling potential of acrylic acid and acrylamide copolymer type SAPs exhibited a positive correlation with pH levels, culminating in the attainment of their peak absorption capacity at pH 12. The occurrence can be ascribed to the intermolecular forces among ions present in the polymeric constituents as well as the density of crosslinks. For the purpose of determining the sealing effect, the cumulative mass adsorbed and water permeated were measured following the curing of various pH solutions. The results indicate that the incorporation of the SAPs significantly enhances the self-healing effect of the cementitious materials, and the difference in self-healing varies with the change in pH value. In addition, SEM test results indicate that the addition of environmentally responsive SAPs has increased the number of microcracks at the crack interface to a certain extent, effectively enhancing the binding effect of the healing products and the expanded SAPs.