Magnesium Oxide Content in Portland Blast-Furnace Slag Cement

The deleterious effect of delayed expansion of MgO present in Portland Cement led to the introduction of limits for total MgO content in cement specifications, all over the world. In manufacturing Portland Cement with limiting MgO content of 6.0% as per Indian Standard, only limestone of high quality (low magnesia) can be used. But in our country the reserve of low magnesia limestone is limited and hence for proper quality of limestone raising for cement production, the quarry operations have to be done with much care involving rejection of dolomite stones and hence the cost goes up.