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

Ceramics-Silikáty 54, (1) 47 - 52 (2010)


THE INFLUENCE OF POZZOLANA TO THE TRICALCIUM ALUMINATE HYDRATION AND THE EFFECTS OF CHLORIDE IONS TO FORMED HYDRATES
 
Kaminskas Rimvydas, Barauskas Irmantas
 
Faculty of Chemical Technology, Kaunas University of Technology, Radvilenu str. 19, LT-50254, Kaunas, Lithuania

Keywords: Tricalcium aluminate, Chloride, Pozzolana
 

Influence of natural pozzolana additive to the hydration of tricalcium aluminate and the effects of chloride ions to formed hydrates was investigated. In the samples 25 % C₃A mass weight was replaced by pozzolana and they were hardened for 28 days at normal conditions, soaked in saturated NaCl solution, and stored there for three months at 20 °C. It is estimated that at normal conditions the additive of pozzolana has no substantial effect on the course of C₃A hydration, but a part of amorphous SiO₂ penetrates into the structure of aluminium hydrates. Regular C₃A hydrates and CO₃²⁻ - AFm affected by NaCl becomes unstable and takes part in reactions producing Friedel’s salt and a complex compound - hydrocalumite - Ca₈A₁₄(OH)₂₄(CO₃)Cl₂(H₂O)1,6·(H₂O)₈. Pozzolana additive reduces the penetration of Cl⁻ ions to the structure of C₃A hydrates and impedes the formation of aluminium chloride hydrates. In samples with pozzolana additive a part of cubic aluminium hydrates, CO₃²⁻ - AFm and C₃A hydrate substituted with Si⁴⁺ affected by chlorides remained stable.


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