Rheo-viscoelastic behavior and viscosity prediction of calcium sulphoaluminate modified Portland cement pastes

In this study, the rheo-viscoelastic behaviors of calcium sulphoaluminate (CSA) modified Portland cement (PC) pastes were investigated. The shear stress, apparent viscosity, frequency sweep and time sweep curves of composite pastes with different PC and CSA volume fractions were analyzed, and the minimum apparent viscosity (η_min) of PC-CSA pastes were predicted. Results show that with the increase of PC and CSA volume fractions, η_min, critical strain and flow strain of pastes increase at both 5 min and 60 min resting time, and the phase angle varies under different time spots. The accuracy of viscosity prediction models for 5 min and 60 min are both relatively high. Meanwhile, the reason why the prediction accuracy of 5 min is higher than 60 min is that with the prolongation of resting time, the relationships between particle volume fractions and rheological properties are affected by early microstructure formed by flocs and hydration products, thus affecting their original functional relationship at 5 min.