Influencing factors of rheological properties and prediction of rheological behavior of fresh low water-to-cement ratio cement pastes

The poor stability and complex control methods of rheological properties of high performance concrete are one of the important factors that affect its popularization and application in civil engineering construction. Based on the measurements of packing density, rheological properties, and total organic carbon adsorption, the influence and mechanism of the content of mineral additives on the rheological properties of cement paste with low water-to-cement ratio were investigated. The results show that, when the volume content of mineral powder and fly ash is between 0% and 15%, with the increase of the volume, the packing density of the composite cementing material system will be increased, and the yield stress and plastic viscosity of the cement slurry will be reduced. Moreover, the above rheological parameters increase with the increase in PCE dosage and the replacement ratio of mineral additives. Through adopting the particle packing model and recently developed rheological models, the adsorption-desorption equilibrium rate constant on the surface of the cementitious material is only related to the nature of the water reducing agent, and the fitted value is 12 for the water reducing agent used in this test. It is concluded that the change in rheological properties by blending mineral additives is mainly due to the changes in the colloidal interactions and relative packing density of the cementitious particles. Based on the above findings, an approach for predicting and optimizing the rheological properties of low water-to-cement ratio cement paste applicable to the cement-slag and the cement-fly ash microbeads system is proposed.