Moisture Regulation, Performance Influence, and Synergistic Strategies of Superabsorbent Polymers in Cement-Based Materials: A Comprehensive Review

Superabsorbent polymers (SAP) can absorb and subsequently release large amounts of water, with uptake reaching several hundred times their dry mass under aqueous conditions. Together with a space-occupying pore-forming mechanism, these features enable internal curing, volumetric stability, and microstructural refinement throughout the mixing–setting–hardening stages of concrete. A systematic review is provided of the absorption–desorption behaviors of different SAP types under varied environments and of their effects on cement-based materials, including micro-morphology, pore structure, rheology, mechanical properties, volume stability, and durability. The use of SAP in combination with chemical admixtures and mineral admixtures is also assessed. The sorption–desorption behavior of SAP is governed by dosage, particle size, crosslink density, ambient temperature and humidity, and ionic effects. In representative systems, alkali-labile dual-crosslinked SAP has been reported to complete suppression of autogenous shrinkage within 7 days, while nano-SiO 2 -modified SAP exhibits a swelling capacity about 1.49 times that of commercial SAP and reaches more than 95% of its maximum uptake within 5 min. The relative amounts of adsorbed water and capillary water within SAP constitute the key factors controlling the release period. Consequently, the sorption–desorption characteristics of SAP govern the internal moisture distribution in concrete. When combined with other chemical admixtures, SAP's effectiveness has in many reported systems been improved under suitable conditions. Synergistic interactions with materials including accelerators, superplasticizers, and rice husk ash can strengthen internal curing, increase the degree of hydration, refine the pore structure, and partly compensate for strength loss or improve mechanical performance. The microstructure and macroscopic properties of SAP internally cured concrete are influenced by SAP characteristics, the service environment, additional mixing water, and the presence of chemical and mineral admixtures. When used appropriately, SAP can refine the pore structure, increase density, enhance mechanical properties, and improve durability. However, current studies remain limited by the lack of in situ quantitative tracking of SAP morphological evolution and water-release pathways in real cementitious matrices, insufficient kinetic models that couple ionic effects, temperature, humidity, and confinement, and limited cross-validation among characterization techniques. Future research should therefore prioritize dynamic multi-scale monitoring and coupled kinetic–transport modeling for the refined design of SAP internally cured concrete.