Concrete b25 - material for high-strength structures:

Concrete brand B25 is almost not familiar to a wide range of craftsmen involved in private construction. The reason is quite simple: for the construction of low-rise buildings, the strength that this composition provides is simply not needed.

However, those who plan to design structures with a large margin of reliability and high mechanical performance, should get acquainted with this material.

Strength and brand

Before analyzing the composition itself, we need to understand what the concrete grade B25 actually means?

• A brand is an indicator that characterizes the resistance of a material to a compressive load.. Typically, the brand is indicated by the index M with a digital designation of the tensile strength of concrete in kgf / cm². Thus, if we, for example, use the composition of M 400 (it is also a very popular concrete C25 30), then we can talk about the strength of 400 kgf / cm².
• Recently, however, the brand is used to denote the properties of the material less and less.. She was replaced by such a parameter as a class. This value is a measure of compressive strength (in MPa), guaranteed in 95% of cases.

Note! The definition of the class and grade of material is carried out experimentally. To this end, cubes of 150x150x150 mm are cast from a reference solution with precisely maintained proportions, dried for 28 days and subjected to pressure testing.

• Today, GOST 26633-91 establishes the ratio between the grades and classes of concrete used in construction (the table is given in the article below). If we take into account these characteristics - concrete B25 corresponds to the brand M350 (strength - 25 MPa or 327 kgf / cm²).

Concrete description

Composition and preparation

In the manufacture of building solutions with their own hands, it is very important that their parameters match the design requirements for strength of other items. This can be achieved only if the ratio of the mixture components: cement, sand, gravel, and water is precisely observed.

These ratios are different for different material classes.

So, if we need one cubic meter of concrete M400 (B25), then the instruction recommends taking:

• Cement brand M500 - 400 kg.
• Sand (sifted and purified from organic impurities) - 755 kg.
• Crushed stone or gravel from crushed quartzite -1000 kg.
• Water - 0.18 m³.

Note! One of the most important technical requirements for a solution is its homogeneity. Poorly mixing the components, we will significantly reduce the strength of the finished structure, since the density of the stiffened concrete will be very heterogeneous.

Significantly facilitate the process of cooking can also buy ready-made mixture, but the savings will be minimal. It is easier to order ready-made concrete with the necessary parameters in a large enterprise.

With a centralized purchase (for example, if we need to fill in a large amount at once) the price of such a solution will be about 4 - 4.5 thousand rubles per cubic meter. Factors that can cause a rise in the cost of the mixture are modifiers (hardeners or plasticizers), as well as the use of more durable granite aggregate. In the latter case, the cost will increase by about 10%.

Basic properties

For concrete brand B25 characterized by the following performance:

• Compressive strength, as follows from the marking -25 MPa. This is quite a lot, which allows you to use this material for the construction of highly loaded structures with high responsibility.
• Density - from 2200 to 2500 kg / m³. The material belongs to the group of heavy concretes.
• Mobility - from P2 to P4. This parameter is determined by the degree of precipitation of the mortar cone, and is typical of most concrete used in construction.

Note! If you need to increase the mobility parameter, then plasticizers are added to the material. Most often this is practiced when casting monolithic structures of complex shape.

• Material frost resistance - F This figure tells us that the design and after 200 cycles of freezing and thawing under conditions of full moisture saturation will lose no more than 5% of compressive strength. High resistance to cold allows the use of concrete B25 in the construction in northern latitudes.

• The material is water resistant to W8 class, which is quite a lot. In addition, high resistance to moisture is directly related to cold resistance, because the foundations on the basis of the B25 solution can be laid in soils with a high level of occurrence of water and periodic freezing.

Tip! Despite all these qualities, additional waterproofing in such difficult conditions does not hurt.

Scope of application

High strength and good performance against the background of acceptable (naturally, in its class of materials) cost make concrete grade B25 very popular.

As a rule, this composition is used for arranging such facilities:

• Monolithic and strip foundations of concrete with high bearing capacity.
• Pile bases with steel reinforcement.
• Rostverki for pile foundations of various types.
• Monolithic floors and walls.
• Elements of reinforced concrete structures.

Note! The high content of high-quality cement allows pouring hollow core blocks without significant loss of concrete strength. Due to this, the mass of prefabricated structures and the load on the base are significantly reduced.

• The bodies of piles, columns, beams, beams and other reinforced concrete products with a compressive load.
• Airfield plates pavement (PAG).

In addition, the waterproofing properties of the material allow the use of B25 when pouring bowls of pools, tanks for industrial water, drainage systems, etc.

Conclusion

As you can see, the characteristics of B25 concrete make its use in low-rise construction irrational: the composition is expensive, and the strength provided by it will be clearly excessive. At the same time, in the construction of commercial real estate, as well as multi-storey residential buildings, this material is one of the most popular. After studying the video in this article, you will gain additional information about the properties and scope of such concretes.