Microstructure tailoring of internal curing agents: modified cement particles/superabsorbent polymers composites balancing strength and shrinkage mitigation

Superabsorbent polymers (SAPs) are widely studied as internal curing agents in high-performance concrete, but their adverse effects on pore structure remain a challenge. This study introduces an innovative cement-integrated SAP (CiSAP) by modifying the interface, using KH570-modified cement (KMC) as the functional core. By optimizing KMC content, the microstructure was improved, leading to enhanced performance. Structural characterization confirmed that KMC was successfully embedded into the polymer network. CiSAP30 reduced shrinkage by 61.4 % due to its excellent desorption efficiency. The 28-day strength retention of CiSAP in cement-based materials varied from 93.4 % to 99.6 %, compared to the reference group without CiSAP. MIP and fractal dimension analysis indicated that CiSAP refined the microstructure by reducing large capillary pores and filling macropores. The sustained water release from CiSAP, along with KMC hydration, promoted long-term densification and controlled autogenous shrinkage. This study provides a novel strategy for designing internal curing agents for high-performance cement-based materials.