One of the popular materials in modern construction is concrete, without which it is impossible to imagine any construction. This material has high strength, versatility, environmental friendliness. It includes four main components – cement, sand, gravel and water. In the manufacture, a certain ratio of these components is observed (1: 2: 4: 1/2). It should be noted that depending on a number of factors, the proportions may be different. Since the main components are cement and water, which provide the connection of the rest of the components, in the production process it is impossible to violate their balance. Here, in addition to the amount of water in concrete, the decisive humidity is the humidity of the aggregates, their level of absorption of moisture, etc. P. Sand and crushed stone are added so that during hardening the mixture, cracks do not form. In addition, these components reduce the shrinkage of concrete to a minimum, make it stronger and relatively cheaper. Large aggregates are also used – granite, limestone and gravel. Granite provides maximum strength, limestone – frost resistance, and gravel is considered the cheapest aggregate.
The properties of concrete mixtures are conditionally marked by the letters M, B, P, W – brand, class, mobility, water resistance, respectively. The brand indicates the amount of cement in the mixture (M100 – M500), as well as the average strength indicator. Class (B3.5 – B80) focuses guaranteed strength. Concrete mobility varies from P1 to P5, and water resistance – from W2 to W20. The letter F is also used – frost resistance (F 25 – F 1000).
There are many varieties of concrete. Divide them based on the density, purpose and type of binding substance. By the type of astringent, the types of concrete are divided into: gypsum, silicate, polymer -cement, cement, special and slag -bush, the delivery of concrete should be carried out very quickly so that it does not have time to harden.
The density, which is the main indicator of the resistance of concrete to the loads, is determined by the type of aggregates. In this vein, concrete is light, heavy and especially heavy. It is also classified for its intended purpose: ordinary, fast -hardening, hydraulic, special, high -strength, cast and for road work.
In order for concrete to get certain qualities, special additives or modifiers are used that affect mobility, plasticity, frost resistance, moisture powers, corrosion resistance, etc. P.