Effect and Mechanism of Sodium Fluosilicate on Setting Time of Cement

Abstract:

Sodium fluosilicate (Na₂SiF₆) is prepared from by-product of phosphate fertilizer production. According to a certain percentage of Na₂SiF₆ mixed in the cement, the influence of different dosages on the setting time of cement under different water-cement ratio was discussed, and the effect of different forms of fluoride compounds on the setting time of cement were compared. The effect and mechanism of sodium fluosilicate on the hydration products of cement were researched by using the X-ray diffraction analysis and micro electron microscope. Experimental results show that the retarding effect of sodium fluosilicate on the coagulation time had a critical effect, and beyond a certain value, it sharply decreased the setting time. The critical dosage increased with the increase of water-cecment ratio. Compared with the retarding effect of Na₂SiF₆、MgSiF₆、NaF and CaF₂ on the coagulation time of cement, Na₂SiF₆ was the best. The incorporation of Na₂SiF₆ does not change the types of the hydration products, the main function of FN is hydrolyzed with Ca²⁺ ions to form CaF₂ with a very low solubility.

• Periodical: Materials Science Forum (Volume 898)
• Pages: 1978-1983
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.898.1978
• Online since: June 2017
• Authors: Hai Wang*, Qian Jin Mao, Yue Gao, Zi Ming Wang, Su Ping Cui
• Keywords: Hydration, Setting Time, Sodium Fluosilicate

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