IMPROVING HYDRATION RESISTANCE OF MAGNESIA-DOLOMA REFRACTORIES BYIRON OXIDE ADDITION

Abstract: There have been lots of studies to control the poor hydration resistance of dolomite refractories one of themost effective solutions has been the addition of magnesia to doloma. Using a co-clinker of magnesia-doloma as astarting material would provide more homogeneity in the properties of the product and has been published recently.On the other hand, addition of iron oxide to doloma has been found to increase the hydration resistance. In this paper,the effect of iron oxide addition on hydration phase analysis and microstructure of two different magnesia- dolomasamples, one with CaO content of ۲۵ wt% and the other one with that of ۳۵ wt% has been investigated. Ten sampleswere prepared by pressing followed by firing at ۱۷۵۰ ºC for ۳hrs. Results showed that the hydration resistance of thesamples improved by decreasing the CaO content, because CaO is much more prone to hydration comparing to MgO.Besides, iron oxide addition lead to the formation of iron-containing phases which increased the hydration resistanceof the samples both by capsulating the CaO and MgO grains and by promoting the liquid phase sintering.

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Keywords: Magnesia-doloma ، Iron oxide ، CaO content ، Hydration resistance.