Phase assemblages of seawater-mixed model cement modified by in-situ polymerization

Abstract

In-situ polymerization of organic monomers in seawater cement is an effective method to mitigate the erosion of cement hydrates. Understanding the effects of in-situ polymerization on the hydration products of model cement holds promise for extending the service life of seawater concrete. Herein, we conducted a series of experiments combined with Density Functional Theory (DFT) calculations to investigate the impact of in-situ polymerization of sodium acrylate (SA) on the phase assemblages of seawater-mixed model cement. Our findings reveal that in-situ polymerization of SA enhances the stability of hydration products. This improvement is attributed to the carboxylic acid groups of polyacrylic acid (PAA), which form stable coordination bonds with Ca²⁺ and Mg²⁺, anchoring onto the surface of hydration products and weaving an organic-inorganic interpenetrating network structure that strengthens interfacial bonding and inhibits erosion from external ions, thereby reducing calcium dissolution. However, the physical barrier effect of PAA on mineral surfaces and its chemical adsorption behavior towards Ca²⁺ collectively alter the aqueous chemical environment, thereby inducing nucleation poisoning effects in C-S-H while reducing precipitation rate of other hydrates. Notably, PAA significantly lowers the decalcification risk of the C-S-H structure by enhancing its erosion resistance. These findings are expected to deepen the understanding of the role of in-situ polymerization in cement-based materials and promote the design of durable seawater-mixed concrete.