Concrete is an artificial buildingmaterial obtained during the formation and further solidification of a rationally selected and compacted mixture. It consists of cement or other astringents, as well as small and large aggregates with the addition of water. In some cases where special density of concrete is needed, for example, in asphalt concrete technology, water is not added, but special additives are used.
Its main advantages areecological compatibility, as well as the availability of a huge resource base. It is possible to use it in different operating conditions. It can be called a universal material, which is intensively used in all areas and sectors of construction. It is chemically and heat-resistant, sound-absorbing and does not conduct nuclear radiation.
Mixing of sand, cement, water and crushed stone allowsto obtain the required density of concrete. The ratio will depend on the moisture content of the rubble and sand, cement grade and fractions. In some cases, it will affect the amount and composition of additives: water repellents, plasticizers, etc. For example, to obtain a density of M200 concrete, 400 cement is used.
One of the important characteristics of this materialwater-cement ratio. There is a direct dependence of water / cement. That is, the smaller this ratio, the stronger the concrete. A material having a density of 200 has a considerable mass (this is its only "minus"). It reaches 2,400 kg / m3. This concrete is excellent for load-bearing structures, columns, crossbars, etc. With too little water, the concrete density is high and has low ductility. It is used as a basis for equipment, a blind area around the house, etc.
There is one mistake that is oftenkneading the solution. In cottage industry, too much water is often added, which reduces the density of concrete and increases its mobility. This in turn significantly reduces its strength.
For concrete there is a classification thatis made by appointment, types of aggregates and binders, the conditions of hardening and its structure. By appointment, it is possible to distinguish the usual (for civil and industrial buildings) and special (road construction, heat-insulating, hydraulic and decorative works) concrete.
According to the types of binding agent, it can be plaster,silicate, cement, slag-alkaline (asphalt concrete, plastic or polymer concrete). Types of its fillers are also different: porous, dense and special, and its content is lean, fat and commodity. Also, in its structure, concrete can be dense, porous, cellular and coarse-porous. The conditions for hardening are as follows: natural, heat and moisture treatment at atmospheric or autoclave pressure.
The main indicator in the characteristics of concrete isits compressive strength. It defines the class of concrete. For example, the density of concrete B25. This means that in 95% of cases this class will withstand a pressure of 25 MPa. That is, the letter "B" and the numbers indicate the pressure that concrete can sustain in megapascals. When calculating the strength index, it is required to take into account the coefficients of the normative compressive strength. This is suitable for the density of concrete B25. Age of concrete, based on its class, will be determined by compressive strength and axial tension, which is assigned at the design stage. The possible methods of erection and design loads on the structure, as well as the conditions for hardening the concrete, are taken into account.
The density of concrete B 25 is ideal for slabsoverlapping, monolithic foundations, pool basins. This is the material most often used for these purposes. In addition, builders use this material for other structures of responsible use. The density of concrete B 25 makes it possible to guarantee the excellent quality of finished structures, provided, of course, that the purchased goods fully comply with the declared characteristics.
