Classification of concrete is carried out according to three main characteristics: by purpose, by average density, and also by the type of binder in the mixture. By its purpose, this material is actually divided into many subclasses. For example, in some conditions, increased heat resistance is required, in others, shock resistance, etc. In each case, the optimal composition is selected that will not allow the structure to collapse during operation.
In general, the following classification of concrete is built for the purpose:
- materials for special purposes (used in conditions of increased radiation, in acidic environments, etc.);
- mixes for sidewalks, roads, airfields;
- ordinary concrete (foundations, floors, various reinforced concrete structures are made of it);
- hydrotechnical samples (used to create sewers, dams, channels, etc.).
Classification of concrete by density depends on which large aggregates are included in the composition. If the mixture contains pumice, tuff and other porous components, then it can weigh from 0.5 to 1.8 tons per cubic meter (lightweight concretes, including slag concrete, pumice concrete, expanded clay concrete). In order to obtain particularly heavy samples (more than 2.5 tons / cubic meter), steel sawdust is introduced into concrete. Such mixtures are used to create protective structures. Heavy concrete (1.8-2.5 tons / cubic meter) incorporates diabase, granite or limestone.
Classification of concrete also emits ultralight mixtures, such as aerated concrete, foam concrete or foam silicate. Their weight per cubic meter is less than half a ton. Concretes of this class, due to increased cellularity, have low thermal conductivity, but also low strength. Therefore, they are mainly used as facing materials.
The classification of concrete by type of binders is more than extensive. The most common substances today are silicates with the method of hardening in an autoclave. Also infrequently found are mixtures based on liquid glass, glass-glass components, which are necessary for the formation of heat-resistant concrete.
The most common are gypsum-based materials from which the trim elements, internal partitions, and also mixtures for waterproof coatings are made. In addition, there are widely used cement concretes (such as Portland cement), slag-alkali (a relatively new product on the construction market), polymer-cement compositions.
Classification and properties of concrete are necessary in order to determine the main indicators of the mixture and future construction. In particular, for such compositions, such characteristics as mobility (the ability to spread under its own weight), water resistance (at which a sample pressure of 0.15 meters does not pass water) and, which is very important for Russia, frost resistance are distinguished. For example, concrete labeled F1000 can withstand a thousand cycles of thawing and thawing, which is especially important in regions with unstable weather, and sample F50 can only withstand 50 such cycles.