In the manufacture of concrete, as well as other binders of construction solutions, special astringent building materials are used. Have such materials with one important feature – they freeze under the influence of water or in the air. Thus, all astringent materials are divided into 2 categories: hydraulic and air.
The most famous hydraulic astringent is cement, since it begins to harden in the air, and its hardening continues even under the influence of water. Cement is used in the manufacture of construction solutions, as well as in the construction of concrete ceilings. In the manufacture of cement, clay, slag, gypsum and sand are used. It should be noted that several types of cement are distinguished, depending on which additives were included in its composition. Cement is marked in accordance with its strength, which is set in laboratory conditions. For this, a cube is made from cement with a side of 100 millimeters and put it under the press. If the cube withstands a load of 400 kilograms, respectively, its marking will be 400. The most durable cement is 600 and 700, it is used for the manufacture of concrete slabs for the runways at airfields, as well as for spacecraft platforms. The most common in everyday life are 350 and 500 markings. The process of hardening cement begins 45 minutes after applying the solution and lasts about 12 hours, as for the visible part of the entire hardening process. The full stagnation of cement ends after 28 days.
Gypsum cement is made by adding chopped gypsum stone. It should be noted that in the process of grinding, the gypsum crumb passes through the firing stage and thanks to this gypsum in the composition of the cement becomes the same as it was in the source. Gypsum cement has fiery resistance: when exposed to fire, a water crust is formed on it that does not allow the penetration of open fire into deep layers of the solution. Grinding clinker and gypsum with the addition of mineral additives is the process of manufacturing Portland cement. This material has increased strength and strength, inferior only to steel. Portland cement manufacturers guarantee one hundred percent quality of their products, since the material undergoes a serious test in laboratories. For example, the material is immersed in an autoclave, where under the influence of various temperatures, they check how much it changes in size, because it depends on this expansion when setting. Such tests found that the proportion of Portland cement on average is 3.1 g // Water, then you can get a solution of special strength, which will be higher than that of Portland cement. The strength of such a cement in some cases can be compared with the strength of ceramics.
Air materials include, for example, clay, which is easily diluted with water and at the same time becomes very plastic. Any shape can be sculpted from clay, however, when exposed to high temperatures and fire, clay freezes and the fortress becomes akin to the stone. In case the clay is exposed to very high temperatures, then it will acquire a vitreous state.
Clay is used for the manufacture of bricks, the structure of clay walls, laying clay roof using straw. There is a special refractory clay that can withstand temperatures up to 1,500 degrees. Such clay, as a rule, is used for laying furnaces. An interesting feature of clay is that absorption of water is carried out to a certain level, after which clay becomes a waterproofing. Thanks to this feature, clay is used in the construction of various embankments, which are designed to insulate water.
Another air astringent material is lime, which can be ineffective and ground. Increased lime is obtained when firing limestone and is used for the manufacture of special solutions for concrete and masonry, as well as for silicate brick. Before use, the unsuccessful lime is extinguished with water, then it is kept for two weeks and used only after that to prepare a lime solution, be sure to mix it with sand. Unexpected lime is a fire hazardous substance.
Hydratic lime turns out in a different way: the negative material is crushed, mix it with water, then turn into powder. To work with such lime, you also need to mix it with sand. However, it is believed that the solution prepared on the basis of the negative lime is more elastic. The lime solution hardens only in the air, the water on such a solution acts destructively.
