Salt-alkali resistant semi-interpenetrating network SAP for internal curing of concrete: A combined experimental and molecular dynamics study

J Sun and ZQ Jin and ZX Du and XY Zhang and B Pang and J Iran and W Zhang, CONSTRUCTION AND BUILDING MATERIALS, 500, 144157 (2025).

DOI: 10.1016/j.conbuildmat.2025.144157

To address the low salt-alkali resistance and poor sustained-release performance of conventional superabsorbent polymers (SAPs) in marine concretes, this study developed a semi-interpenetrating network SAP by integrating 2acrylamido-2-methylpropane sulfonic acid (AMPS) and polyvinyl alcohol (PVA) into polyacrylic acid networks. Laboratory tests, molecular dynamics (MD) simulations, and marine field test were combined to clarify the saltalkali resistance mechanisms of SAPs and the macro-micro performance of SAP-modified concrete. Experimental results demonstrated that PVA/(AA-co-AMPS) achieved an outstanding absorption of 22.79-30.13 g/g (3-5 times higher than that of commercial SAPs) and slowly released water in cement filtrates. This is attributed to the weak interaction between -SO3H groups in PVA/(AA-co-AMPS) and Cat , which mitigates the Ca bridging effect and thereby inhibits the water diffusion within the SAP network. In SAP-modified concrete, the PVA/(AA- coAMPS) improved the internal relative humidity, reduced the autogenous shrinkage of concrete by 58.8 %, and improved the concrete durability. Furthermore, MD simulations revealed the H-bonds network formed by -SO3H (from AMPS) and -OH (from PVA) groups in PVA/(AA-co-AMPS) with water molecules, leading to a 61 % increase in SAP-water interaction energy. This enhanced interaction explains the exceptional water retention and salt-alkali resistance of PVA/(AA-co-AMPS), offering a theoretical basis of SAPs design for high-salinity and highalkalinity environments.

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