en Research Paper Research Paper Abstract: There have been lots of studies to control the poor hydration resistance of dolomite refractories one of the<br>most effective solutions has been the addition of magnesia to doloma. Using a co-clinker of magnesia-doloma as a<br>starting material would provide more homogeneity in the properties of the product and has been published recently.<br>On the other hand, addition of iron oxide to doloma has been found to increase the hydration resistance. In this paper,<br>the effect of iron oxide addition on hydration phase analysis and microstructure of two different magnesia- doloma<br>samples, one with CaO content of 25 wt% and the other one with that of 35 wt% has been investigated. Ten samples<br>were prepared by pressing followed by firing at 1750 ºC for 3hrs. Results showed that the hydration resistance of the<br>samples improved by decreasing the CaO content, because CaO is much more prone to hydration comparing to MgO.<br>Besides, iron oxide addition lead to the formation of iron-containing phases which increased the hydration resistance<br>of the samples both by capsulating the CaO and MgO grains and by promoting the liquid phase sintering. Keywords: Magnesia-doloma, Iron oxide, CaO content, Hydration resistance. 34 40 http://ijmse.iust.ac.ir/browse.php?a_code=A-10-3-152&slc_lang=en&sid=1 F. Kashaninia 180031947532846001221 180031947532846001221 No H. Sarpoolaky * hsarpoolaky@iust.ac.ir 180031947532846001222 180031947532846001222 Yes A. R. Bagheri 180031947532846001223 180031947532846001223 No R. Naghizadeh 180031947532846001224 180031947532846001224 No M. Zamanipour 180031947532846001225 180031947532846001225 No