Study on effect of high speed dispersion on rheological behavior of cement-based paste
In order to study the influence of parameters such as high-speed dispersion rate and time length on the theological behavior of cement-based paste,eddy current high-speed dispersion equipment was used to get different rates and time lengths.Cement-based paste with different water-binder ratios and different silica fume contents were dispersed respectively,and the theological properties of the paste were tested by rheometer.The results showed that the influence of dispersion velocity on the yield stress and thixotropy of paste with lower water-binder ratio was greater than that of paste with higher water-binder ratio.The plastic viscosity of cement paste samples with different water-binder ratios decreased rapidly with the increase of dispersion velocity,and then tended to be stable.The turning point of plastic vis-cosity change occured roughly at the dispersion rate from 1 000 rpm to 1 500 rpm.The addition of silica fume significantly increased the yield stress,plastic viscosity and thixotropy of each paste,but the difference of theological parameters between the samples tended to de-crease when the paste was dispersed at a higher rate.It was suggested that the dispersion time of cement-based paste mixed with ultrafine powder such as silica fume should be controlled at about 2 min.
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