The demand for ultrafine cement is increasing, and our main object in the present invention is to devise a new and improved method of manufacturing it. Broadly stated the method of the invention is an improvement in the manufacture of ultrafine cement in which cement clinker is ground to a fineness of ordinary Portland cement,<a href="http://www.sellercrusher.com/project/slag-crushing-plant.html">slag crushing plant</a> the ground clinker is cooled and then the cooled cement is ground in a mill with the use of grinding bodies having a maximum average weight of about 6 grams.
Ordinary Portland cement is a hydraulic cement generally consisting of various silicates of calcium which when mixed with water, sand and gravel or other substance forms the common material of construction. It has a fineness which usually corresponds to a specific surface of from 3,000 to 5,000 cm.2 /g. measured by the Blaine method, is readily available and constitutes a very suitable starting material in the production of ultrafine cement. Because the preliminary grinding of the clinker to a fineness corresponding to that of Portland cement is performed in another mill, and not in that in which the ultrafine grinding takes place,<a href="http://www.sellercrusher.com/project/coal-crusher-machine.html">coal crusher machine</a> heat developed in the preliminary grinding does not increase the temperature attained in the final grinding. Cooling the starting material before feeding it to the mill in which the ultrafine cement is produced means that less cooling is needed during the grinding and so a higher mill output is obtainable.
In grinding clinker such very small grinding bodies would have no effect as their individual weights would be too small compared to the weight of the pieces of clinker, but in grinding Portland cement to an ultrafine cement they are found to have excellent grinding efficiency. It is also found that such very small grinding bodies do not become coated to any appreciable extent even in the absence of grinding aids.