Applicability of rheological properties of superabsorbent polymer cement-based materials using apparent viscosity

Superabsorbent polymer (SAP) is usually used as an internal curing agent for concrete, while its water absorption and desorption properties could affect the rheology of cement-based materials. In this paper, the effects of different SAP particle size, content and extra water on the apparent viscosity of cement paste over time were studied. Further, the correlation between plastic viscosity, yield stress and apparent viscosity was evaluated. The results show that the SAP particle size had a significant impact on the apparent viscosity of cement paste, and the larger the particle size of SAP, the more obvious the change of water absorption and desorption. The addition of SAP and extra water would reduce the plastic viscosity and yield stress of the cement paste to promote its fluidity. At the same time, the correlation coefficients of apparent viscosity, plastic viscosity and yield stress of SAP cement paste with different content and particle size were all above 0.93. Therefore, apparent viscosity not only could explain the water absorption and desorption kinetics of SAP in cement paste well, but also could be used as an evaluation index for the rheological properties of cement-based materials cured in SAP.