Interactions between superabsorbent polymers and cement-based composites incorporating colloidal silica nanoparticles

The relatively new applications of superabsorbent polymers (SAPs) in cement based materials call for investigations regarding their behaviors in relation to other constituents in the system. Colloidal silica nanoparticles (CS) are becoming increasingly important for the improvement of strength and durability of cement based materials. In this study, a poly (AA-co-AM) SAP was synthesized by free radical polymerization, and its behaviors in cement based composites incorporating CS were investigated. These included swelling behavior, setting time, mechanical performance in different curing conditions, and rheological properties of fresh pastes. The observation of an unusual reduction in swelling, revealed the role of SAP in precipitation of calcium carbonate from the cement paste filtrate, and provided evidence for the less than expected reduction in workability and setting times. Combinations of the SAP and CS increased the compressive and decreased the flexural strengths, respectively, which is supported by changes in the microstructure as observed by SEM.