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The polyether modified silicone oil was prepared by using methyl hydrogen silicone oil, F-6 type unsaturated polyether and ethylene glycol monovinyl ether. Polyether modified silicone oil, dimethyl silicone oil and MQ silicone resin were used as main raw materials to prepare concrete defoamer X-1 under high-speed shearing of emulsifier HA and emulsifier. The effects of different emulsification time, shear rate and polyether modified silicone oil on the performance of concrete defoamer X-1 were investigated. The test results showed that compared with the commercially available defoamer X-2, X-1 could effectively improve concrete 0.5h slump retention performance and bulk density, and 7d and 28d compressive strength. [ABSTRACT FROM AUTHOR]

In this paper, three kinds of viscosity modifying admixtures for concrete (VMA) including cellulose/ether type (VMA-1), propylene type (VMA-2) and warm wheel rubber (VMA-3) were studied for the influence of the rheological properties of the cement paste with PCE and the performance of the concrete with PCE. The results showed that the plastic viscosity of the cement paste could be improved by the three kinds of VMA, and the viscosity-increasing effect of VMA-1 was the best. The addition of VMA could improve the dispersibility, dispersion retention and workability of concrete. But they also would reduce the early strength of the concrete. [ABSTRACT FROM AUTHOR]