Effects of Fineness of Raw Materials on the Qualities of Sulfated Slag Cement

Experiments were carried out with view to find the influence of the fineness of the raw materials on the properties, especially on the strength of sulfated slag cement. The higher the fineness of slag and calcium sulfate, the greater the mechanical strength and the setting time became shorter to some extent. It is desired for slags having basisity (CaO+MgO+Al2O3)/SiO2 of about 2.0, that their grain size distribution be narrow and that their specific surface as well as that of calcium sulphate to be admixed should not be less than 5000cm2/g on measurement by Blaine's apparatus. The required amount of portland cement clinker as an alkaline exciter lies in a certain narrow range, but the effect of its fineness is not so significant. The slag is 5 or alternatively 2 times harder to be ground than sulphate or clinker respectively. Because sulphate powder is adhesive, its grindability decreases in course of grinding. separate grinding is preferable because it gives somewhat stronger cement than by a combined grinding to the same specific surface.