On the factors affecting the swelling behavior of superabsorbent polymers in cement-related environment

Abstract

Superabsorbent polymer (SAP) has water absorption and release behavior and can be used as internal curing or self-healing additive in cement-based materials. However, SAP has complicated and changeable swelling behaviors in cement-based materials, which has not been fully investigated. In present work, an AA-AM co-polymerized SAP was synthesized, and potential factors related to cement-based materials, including water-cement ratio and binder type, superplasticizer content, early hydration time, mixture stirring rate, temperature and pressure, were systemically investigated. Results indicated that maximum absorptivity of SAP decreased gradually with hydration time. SAP presented the highest absorptivity in FA and GGBS blended cement binder, and the lowest absorptivity in geopolymer, although the water-binder ratio is the same. The swelling behavior of SAP is related to the PCE content, and maximal SAP absorptivity first rises and then falls as PCE content increases. As the stirring rate increases, SAP's maximal absorptivity increases, due to the “Bernoulli's effect”. In addition, the absorptivity of SAP showed temperature and pressure sensitivity, which was improved by the increased temperature or decreased external pressure. The findings in present work suggest that potential factors related to cement-based environment should be comprehensively considered for practical application of SAP in concrete engineering.