ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 34, (3) 247 - 255 (1990)


STUDY OF THE EFFECT OF CHEMOGYPSUM AS SETTING RETARDER ON THE PROPERTIES OF CEMENT PASTES
 
Šauman Zdeněk
 
Technical University, Department of Building Materials Technology, Gorkého 7, 622 38 Brno

Waste gypsum from chemical works contains various proportions of impurities according to the character of the respective production technology. If the chemogypsum is used as a setting retarder in portland cement, the hexafluorosilicates present exhibit considerable additional retarding effects with respect to early strength, whereas the fluorides, such as CaF₂ , do not influence the hydration processes to any substantial degree. 'l'he early strengths of cement are mostly affected by Na₂SiF₆.


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