Advances in Self-Healing Ordinary Portland and Geopolymer Cement Systems: A Comprehensive Review of Stimuli-Responsive Polymer Mechanisms and Performance

Stimuli-responsive polymers (SRPs) provide a promising path towards self-repair of cracks in cementitious materials. This review critically synthesizes SRP-based self-healing in Ordinary Portland Cement (OPC) and alkali-activated/geopolymer systems, based on polymers with moisture, pH, and thermo-responsive properties, including superabsorbent polymers (SAPs), hydrogels, shape memory polymers, and microcapsules. Literature that was published from 2000 to 2025 was screened from the major databases of information. More than one hundred and four relevant studies were chosen for comparative assessment. Quantitative performance indicators such as crack-closure efficiency, mechanical recovery, permeability reduction, and swelling behavior are used to investigate the reported healing performance and to understand the importance of differences in pore-solution chemistry of OPC and geopolymers on polymer activation and durability. The synthesis shows that the current evidence is mostly OPC-centric, while geopolymer applications are still limited in number and have not long-term tested for durability, standardized testing methods are unavailable, and the field-scale validation of these materials is lacking. Key research priorities are identified to facilitate durable polymer design and support more rapid translation of SRP-enabled self-healing systems to sustainable cementitious infrastructure.