Petrographic and thermal evaluation of dolomites for the manufacture of magnesium oxychloride cement

In the preparation of magnesium oxychloride cement from MgO and MgCl 2 .6H 2 O solution, MgO is sometimes replaced by partially calcined dolomite, MgO.CaCO 3 . In this paper, the suitability of dolomites for this purpose was studied by use of petrographic, d.t.a. and X ‐ray diffraction techniques. It is shown that for making good oxychloride cement, the dolomite should be compact and microcrystalline. Impurities such as siderite, haematite, magnetite and clayey matter which are generally present in dolomites, form a coating over the MgO particles during partial calcination at 750° and make the fired material less reactive and generally unsuitable for making oxychloride cement.