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

Ceramics-Silikáty 57, (1) 45 - 52 (2013)


INFLUENCE OF POZZOLANA ON THE HYDRATION OF C4AF RICH CEMENT IN CHLORIDE ENVIRONMENT
 
Barauskas Irmantas
 
Faculty of Chemical Technology, Kaunas University of Technology, Radvilenu str. 19, LT-50254, Kaunas, Lithuania

Keywords: Brownmillerite, Pozzolana, Chloride, Friedel’s salt
 

This study investigated the influence of natural pozzolana - opoka additive on the hydration of C4AF rich cement and the effects of chloride ions on the hydrates formed. In the samples, 25 % (by weight) of the sintered C4AF rich cement and OPC was replaced with pozzolana. The mixtures were hardened for 28 days in water, soaked in a saturated NaCl solution for 3 months at 20oC. It was estimated that under normal conditions, pozzolana additive accelerates the hydration of calcium silicates and initiates the formation of CO32-–AFm in the Brownmillerite rich cement. However, the hydration of Brownmillerite cement with opoka additive is still slower to compare with hydration of Portland cement. Also, opoka decreases total porosity and threshold pore diameter of Brownmillerite cement paste after two days of hydration. After 28 days of hydration threshold pore diameter became smaller even to compare with threshold pore diameter of Portland cement. Opoka additive promotes the formation of Friedel’s salt in Brownmillerite samples treated in saturated NaCl solution, because CO32-–AFm affected by saturated NaCl solution become unstable and takes part in reactions producing Friedel’s salt.


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