Rheological behavior of calcium sulfoaluminate cement paste with supplementary cementitious materials

•The plastic viscosity of CSA paste is remarkably higher than that of OPC paste.•CSA paste exhibits shear thickening behavior.•SF can significantly reduce the plastic viscosity of CSA paste.•With the effect of SCM, CSA pastes exhibit shear thinning behavior. Calcium sulfoaluminate (CSA) cement has the potential to become the ‘future cement’ given its excellent characteristics, such as low carbon, energy saving, and low shrinkage. However, compared with ordinary Portland cement (OPC) paste, with the same water–to–cement (w/c) ratio and similar fluidity, the plastic viscosity of the CSA cement paste increases remarkably and exhibits significant shear thickening behavior, which is unconducive to the formulation and application of CSA cement concrete. Rheological behavior of CSA cement paste with supplementary cementitious materials (SCMs) is systematically studied. Results show that silica fume (SF) can significantly reduce the maximum shear stress and plastic viscosity of CSA cement paste, but the yield stress increases evidently. The incorporation of fly ash and blast-furnace slag can substantially eliminate the negative effect of the increase in the yield stress of the paste caused by the SF. As the w/c ratio decreases, the plastic viscosity of the CSA cement paste increases significantly. Under the action of the SCMs, the plastic viscosity of CSA cement paste with low water–to–binder (w/b) ratio is reduced, and the plastic viscosity of the high w/b CSA cement paste is increased, all CSA cement pastes exhibit shear thinning behavior.