When choosing the brand of concrete that will be used on the site, they are usually guided by two principles. The first is the expected load. This factor depends on criteria such as the weight of the future structure, vibration, the frequency of mechanical stresses, etc. The second factor is the economic feasibility of the substance used. Thus, grades of raw materials from M300 and higher are used for critical facilities. For ordinary use concrete B20 (M50, M250).
General description of the brand of substance
The use of concrete of this brand is the most optimal option in terms of price / quality ratio if the concrete casting process of a monolithic frame structure, the arrangement of paths, sites is underway, the construction of buildings is carried out, regardless of how many floors are planned to be built. Buy this mixture is also not difficult. The price per 1 m 3 will vary depending on what quantity, quality and which impurities were used as additional components. Concrete B20 is quite simple in terms of mixing even at home. The only thing that is important to consider is the change in proportions, since these raw materials are quite sensitive to them.
Substance composition
The composition of the brand of raw materials is the simplest - cement, sand, gravel, water. However, it is important to note here that the type of coarse aggregate can change, due to which the density of the final composition can vary between 1800-2300 kg / m 3 . Concrete will have the lowest density if expanded clay is used as aggregate. The composition, which includes B20 slag concrete, has an average density. The composition with granite crushed stone as a filler is characterized by the highest density.
Concrete B20 is a standard concrete grade that belongs to the mobility class P2-P4. The standard strength set for this brand is 28 days. It is also worth adding here that some manufacturers of this product replace a certain part of the solid filler with mineral additives. This makes the final composition more plastic, but it also increases the cost of the finished product.
Features
It is worth saying that concrete b20 is an intermediate composition. It is slightly better than the M200 brand, which is considered cheap raw materials and is not used for the construction of long-term facilities. But at the same time, the M250 (M50) is somewhat worse in its characteristics, and therefore can not be used as a foundation for objects characterized by high load, like the M300. Among the advantages of the M250 brand, it can be distinguished that it successfully combines the optimal ratio of substances. If the fraction of solid aggregate is large enough, then the maximum tensile pressure that it can withstand after solidification is 20 MPa. However, it is cheaper, and also more flexible and lightweight than premium brands.
Material Technical Parameters
Concrete grade B20 is characterized by the following technical characteristics. The strength level of raw materials M250 is 260 kg / cm 2 . Resistance to frost in concrete is in the range of F150-200. It is worth adding here that this parameter can be increased artificially if you add more crushed stone from hard rocks to the composition, as well as introduce some strengthening additives. If we talk about the permeability of the material, then it is in the range from W2 to W8. For example, there may be concrete B20 W6. You can also change this parameter artificially if you enter the necessary additives. As mentioned earlier, the density, as well as the weight of the substance will directly depend on the selected solid aggregate. The mobility of the substance is P2-P4.
Where is the composition used
Characteristics of concrete B20 led to the fact that its main purpose was to fill in monolithic foundations of any type. It is also successfully used for arranging gangways, flights of stairs, lightly loaded walls and ceilings. The parameters of the material do not allow using it as a foundation, on which a high load is expected in the future. However, if a good reinforcement is carried out, then columns, foundation rings, and wells can be erected. The possibility of building the last building is possible due to the fact that concrete b20 w4 is characterized by good resistance to moisture and other aggressive environments, which is the main quality for the material used in the construction of the well. In addition, the use of this concrete is considered optimal if it is necessary to build a high-rise building. With its help, a monolithic foundation foundation is poured. Another application is the manufacture of reinforced concrete products, however, for this it is necessary to use granite crushed stone as the main solid aggregate for the composition.
How to mix concrete M250
The solution is prepared either in the factory or at home using gravity concrete mixers. In the production of concrete M50 , it is characteristic that the proportion of the knitting element decreases, and at the same time, the volume of the liquid being sealed increases. For this reason, in order to achieve the necessary strength of concrete, B20 will have to be mixed thoroughly. In this regard, factory products always have an advantage over domestic ones. When preparing the mixture, it is best to use the following proportion 1: 2.5: 4.6 (cement: sand: coarse aggregate). Naturally, the basis for the solution is cement. To prepare a quality mixture, it is best to take cement of grade I / II 32.5 (the proportion of slag should be small).
An alternative is Portland cement, which can also be used. The main requirement for any type of cement is freshness. If we talk about sand filler, then it is best to use river material with a particle size of 2 or 2.5.
All the above proportions correspond to GOST 27006, which regulates the quality of the mixture M250 (M50, b20). Generally speaking, for the preparation of 1 m 3 of the mixture 536 kg of sand, 360 kg of cement, 1141 kg of crushed stone and 133 l of water will be needed.
Benefits and other metrics
The undoubted advantages of the composition include the following points:
- Using the composition allows you to make prefabricated and monolithic structures for various buildings.
- The level of material costs for manufacturing is quite low, since local ingredients are used.
- There is the possibility of mechanization or automation of the manufacturing process of the solution.
- Differs in high durability and fire resistance. Other important indicators can be increased depending on the requirements, by changing the composition.
Another important factor that is often overlooked is the ease of laying concrete. This factor plays a decisive role when using a concrete pump for laying. However, it is worth noting here that you will have to use only that concrete b20, which belongs to the class P4 in its mobility.