Concrete m 250 - the composition of the solution, the scope

If you do not take such an exotic type of construction as wooden architecture, then any other building is built using concrete structures. The range here is large enough and for each object a professional will be able to choose the desired brand of concrete. At present, brand 250 has become widely spread, and using this brand as an example, we will tell you what to look for when choosing a composition.

The composition of the solution

Classically, the composition of concrete M 250, as in most other brands, includes 4 main components, these are cement, sand, crushed stone and, of course, water. The solution can be made of cement M 400 and M 500. The technology is governed by GOST R 7473.

The proportions of ingredients in the solution are given in the table.

But not everything is so simple, the quality of the final product strongly depends not only on the brand of cement, but also on what rubble and sand was used, and how accurately manufacturers comply with the production technology.

• In particular, water should have low acidity, sand should comply with GOST 8736-93, and large aggregate can be 3 types, crushed lime, gravel or granite. Where the most mediocre characteristics are lime material, and granite crushed stone for concrete is considered to be the most preferred and qualitative.
• In addition, the use of various additives can make major adjustments. With their help, you can significantly increase the plasticity, frost resistance, shrinkage rate and other basic characteristics of the material. The price, of course, will increase, but the quality will be appropriate.

Scope of application

This brand of concrete is widely used in the construction of industrial and residential buildings with a small number of floors.

• Concrete brand 250 is well suited for the manufacture of monolithic slab bases. In private construction it can be stoves for stoves or fireplaces. In production, this composition can be poured over covered workshops with a relatively small load on the base.
• Specifically, the characteristics of concrete M 250 make it possible to use it when setting up playgrounds.. Regulatory documents it is allowed for the installation of a concrete base for the construction of sidewalks, parking lots and other road construction objects.
• In private construction M250 can be used almost everywhere. In particular, they can pour strip and strip-column foundations. Including on the ground with close groundwater storage.
• On its basis it is allowed to install objects located in an aggressive environment or in places with complex soil geology.

Material characteristics

In addition to the actual stamp of the composition, in our case M250, a number of alphanumeric designations are indicated in the accompanying documents, then we will try to understand them.

Brand or class

• Let's start from the very first, the composition mark characterizes the amount that a prototype can withstand, matured in a humid environment, at a temperature of +20? C for 28 days. Measured in kilograms per cm ?. For М250, the value is 260 - 262 kg / cm ?.
• As for the class of the composition, in order to understand how it differs from the brand one needs to be an expert, it is measured in MPa. And although, according to ST SEV 1406, it is the class that must be indicated in the regulatory documents, the vast majority of organizations prefer to order the brand. Mark M250 corresponds to class B20.

Tip: if the builders concreted the object to you, the documents indicate a certain grade of concrete, and you doubt it. Now there are a lot of independent experts who, without sampling, ultrasound or other method, will be able to confirm or refute your doubts.

Mobility Characteristics

In different sources, this value may have different names:

• Mobility, cone sludge or workability, all this is denoted by the letter "P" and a factor of 1 - 5. The cone sludge is measured in cm.
• If you move away from engineering terms, this ratio means how fluid the solution is. Most of the existing formulations are released with fluidity of P-2 and P-3. For casting of complex structures and thin columns, concrete is taken with P-4 or P-5 fluidity. M250 can be dispensed with flowability from P-2 to P-4, depending on the amount of plasticizer.

Important: a gross violation of all rules and regulations is diluting the solution with water to increase fluidity. If the workers you hire are engaged in this, then know that from your M250, even with a slight dilution with water, you will get M100 or M150. Cement will take a strictly defined amount of moisture, the rest of the water will gradually dry, leaving micro voids.

Frost resistance

This coefficient is marked with the letter “F” and numbers from 25 to 1000.

It characterizes the number of cycles of freezing and thawing of the monolith.

• Everyone knows that freezing water breaks pores. This does not mean that the monolith will fall apart further; just within the limits of a given value, the characteristics will be acceptable for operation.
• Do not be alarmed to see that frost resistance is not too high, remember that this is laboratory data that is obtained under extreme conditions. In life, as a rule, the monolith is protected by waterproofing, blind area, hydrophobic additives, etc.
• As for the M250, a lot depends on the filler. For limestone, the coefficient will be F-50, and already using granite rubble, it will increase to F-200.

Water Resistance Level

It is also called the coefficient of water resistance. It is indicated by the letter “W” and a digital factor of 2–20. Simply put, it is the ability of the monolith to get wet or pass water through itself, which is regulated according to GOST 12730.5-84.

You can increase this value with the help of hydrophobic additives.

• For private construction, this factor is important from the point of view of economy, if the composition has an increased value of water resistance, then the foundation of concrete will not be afraid of groundwater, and if the soil is dry, you can save on waterproofing.
• Concrete brand 250 on granite rubble has a rather high coefficient W-8, but already on limestone rubble the coefficient drops to W-2.

Important: even if all the proportions of concrete M 250 are observed correctly, it is desirable to work out the composition within an hour, maximum two. If you do it yourself, it's easy. But if you buy, then pay attention to the mixer time on the way, otherwise the solution can be brewed directly in the mixer.

The video in this article shows some subtleties in the selection of concrete.

Conclusion

In conclusion, I would like to note that the instructions for laying concrete M250, without fail, require additional compaction of the composition, preferably with the help of vibration. For those who do everything with their own hands, you can simply pierce.