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

Ceramics-Silikáty 31, (4) 299 - 307 (1987)


II. Reactivity with Water

Drábik Milan, Smrčok Ľubomír, Števula Ladislav, Kaprálik Ivan,
Institute of Inorganic Chemistry, Centre of Chemical Research, Slovak Academy of Sciences, 842 36 Bratislava

X-ray diffraction methods and thermal analysis were used to determine the changes in phase composition of the systems C₄AF-H*) and C₄AF-CSH₂-H in the course of hydration of brownmillerite (C₄AF) synthesized by solid state reactions. The reactivity of substance in question was assessed on the basis of the time dependence of relative representation of the individual phases determined semiquantitatively from the diffractometric data. Reactions of C₄AF with water give rise to a Fe-substituted hydrogarnet phase, C₃(A.F)H₆, while the so-called AFm phase is formed in the presence of CSH₂. Under identical reaction conditions, the relative contents of C₄AF found are lower than the values reported for C₄AF synthesized from melt. The increase in the rate of the heterogeneous reactions is ascribed to the effect of the amorphous component and to that of the small crystals of C₄AF present after the synthesis in solid state on increasing the density of reaction centres at the brownmillerite-water boundary.

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