Almost similar properties and the scope has a cement grade M 500 - D20, in addition to good water resistance and cold in this type of cement has a low resistance to corrosion. It is used as cement brand PC 400 - D20 for construction, as well as it is suitable for plastering, masonry and other construction and repair works and the manufacture of various mortars. Cement mark M 500 - A0 introduced into the concrete, gives the latest features such as: increased frost resistance, water resistance, durability. It is indispensable in industrial construction, particularly for emergency and reconstruction. The construction of buildings, one way or another associated with exposure to fresh or saline water, to use cement brand PC (M) 400 - A0. Without it, not do in the manufacture of concrete structures using thermal-moisture treatment. Also this is good for the manufacture of cement concrete and mortar. Another important characteristic of the cement is hardening its time. This process takes place in several stages: first - seizure (beginning of curing) of cement. It takes 40 - 50 minutes. Second - the end of solidification. It comes in 10 - 12 hours. TECHNOLOGIES FOR MANUFACTURING CEMENT Cement production involves two stages: first - obtain the clinker, the second - to bring the clinker powder conditions with the addition thereto of gypsum or other additives. The first stage of the most expensive, is it accounted for 70% of the cost of cement. This happens as follows: First stage - this production of raw materials. The development of limestone deposits are usually drift, ie, part of the mountain "toppled down, thus opening up a layer of yellowish-green limestone, which is used for cement production. This layer is typically at a depth of 10 m (up to this depth it occurs four times), and the thickness reaches 0.7 m. Then the material is sent by conveyor to the grinding up of pieces equal to 10 cm in diameter. After that dried lime, and the process of grinding and mixing it with other components. Further, this raw material mixture is subjected to roasting. So get clinker. The second stage also consists of several stages. These are: clinker grinding, drying of mineral additives, gypsum crushing, grinding clinker with gypsum and active mineral additives. However, we must bear in mind that raw material is not always the same, and the physical and technical characteristics (such as strength, humidity, etc.) from various raw materials. Therefore, for each type of raw material was developed by their mode of production. In addition, it helps ensure a good uniform grinding and complete mixing of components. The cement industry uses three methods of production, based on various technological methods for the preparation of raw material: wet, dry and combined. Wet method of production used in the manufacture of cement from chalk (calcareous components), clay (silicate component) and iron supplementation (converter sludge, ferric product, pyrite candle-ends). Humidity clay at the same time should not exceed 20%, and the humidity Cretaceous - 29%. Wet this method is called because the grinding of raw mix produced in the aquatic environment, the output is a blend of an aqueous slurry - slurry humidity 30 - 50%. Then the sludge enters the kiln, which reaches a diameter of 7 m, and length - 200 m or more. When firing from the raw material of carbon dioxide. Then clinker-balls, which are formed at the exit from the oven, ground to fine powder, which is cement. The dry method consists in the fact that the raw materials prior to milling or in the process dried. And the raw batch comes in the form of finely ground powder. In the dry method, which probably belongs to the future of cement production, to meet the burning gases serves no sludge, and milled into powder raw materials: limestone, clay, slag. This saves fuel, which in a wet method is spent on evaporation. Combined method, as the name implies, involves the use and dry and wet method. Combined method has two varieties. The first assumes that the raw material mixture is prepared by the wet method in the form of sludge, it then dehydrated to a moisture content of the filters 16 - 18% and sent to the kiln in the form of semi-dry mass. The second option is making exactly the opposite to the first: first using the dry method to produce the raw mix, then add 10 -14% of water, granulating, the grain size is 10 - 15 mm and is fed to roasting.