A Comprehensive Review of Water-Absorbing Superabsorbent Polymers for Enhancing Concrete Performance
Sarvesh Kumar *
Department of Civil Engineering, School of Engineering &Technology, CT University, Ludhiana-142024, Punjab, India.
Abhilash Thakur
Department of Civil Engineering, School of Engineering &Technology, CT University, Ludhiana-142024, Punjab, India.
*Author to whom correspondence should be addressed.
Abstract
Superabsorbent polymers (SAPs) have become one of the most promising materials for improving the mechanical, durability, and functional performance of modern cementitious systems. This comprehensive review synthesizes findings from existing high-impact literature and studies to provide a unified understanding of SAP behavior in concrete. SAPs exhibit exceptional water absorption and controlled release capabilities. These features directly influence hydration kinetics, internal curing efficiency, shrinkage mitigation, microstructural refinement, and long-term durability. The review examines SAP impacts on compressive and tensile strength, shrinkage (plastic, autogenous, drying), water–cement ratio sensitivity, and ultrasonic pulse velocity (UPV) as an indicator of internal homogeneity. Extensive findings from microstructure analysis reveal that SAPs refine hydration products, modify gel porosity, and influence the interfacial transition zone (ITZ). Moreover, SAP beads (>1 mm) called as water absorbing beads act as spherical internal reservoirs that provide prolonged water release, improving self-desiccation resistance while functioning as intentional lightweight inclusions that adjust density, thermal conductivity, and insulation capacity. SAP-modified concretes show improved resistance to chloride penetration, carbonation, salt-scaling, and mechanical degradation, particularly under low-humidity or sealed-curing environments. Thermal analyses demonstrate dual roles: (1) SAP voids enhance insulation by reducing conductivity; (2) SAP-driven microstructural refinement improves thermal mass stability for building energy applications. This review presents insights into SAP behavior and optimal dosages. The optimal dose of fine granular SAP (<1mm) is recommended as 0.15–0.35% by cement weight in dry form and is 8–12% by volume of coarse aggregates in expanded form for SAP beads (>1mm). Critical research gaps are identified regarding field-scale validation, SAP beads, thermophysical behavior, and multi-physics modeling. Recommendations for mix design, curing protocols, and performance prediction models are presented to support the integration of SAPs into advanced, durable, and sustainable concrete.
Keywords: Superabsorbent Polymer (SAP), shrinkage, durability, microstructure, concrete, insulation, heat transfer