A new superabsorbent based on the poly(itaconic acid)/poly(sodium allyl sulfonate) polymer network for application in concrete as an internal curing agent

The eco-friendly and low-cost poly(itaconic acid)/poly(sodium allyl sulfonate) (PIA/PSAS) new superabsorbent polymers (SAP) were prepared based on the monomers of itaconic acid (IA), sodium allyl sulfonate (SAS) and the cross-linking agent of N,N′-methylene bisacrylamide (MBA) by aqueous solution process. Moreover, the expanded vermiculite (EV) particles were used as reinforcement for SAP. The absorption behaviour of SAP in different liquids were studied by the teabag method, including deionized water, 0.9% NaCl solution and cement filtration. The results showed that SAP could reach the optimal liquid adsorption state under certain experimental conditions such as the molar ratio of IA/SAS as 2:1, the IA neutralization degree of 70%, the cross-linker dosage of 0.6%, and the EV content of 2.0%. The morphology and structure of the synthetic SAP were characterized. Furthermore, the effects of SAP type and content on concrete properties were evaluated. Results showed a reduction in shrinkage and revealed SAP particles acted as miniature reservoirs lead to cure concrete internally by supplying water during hydration. The EV particles reinforced SAP composite slightly and alleviated the negative influence on the compressive strength of concrete relative to PIA/PSAS. This designed SAP showed its potential to be used as an internal curing agent for concrete due to its ability to provide comprehensive protection against shrinkage and fracture.