Concrete compressive strength: limits, grades and brands,

25-08-2018

Building

Strength is the most important parameter of concrete. This characteristic is the main one when choosing a solution of one class or another, if this material is chosen as the main one for the future object.

In the photo - laboratory work to determine the state of frozen material

Strength Characteristics

Immediately it should be said that due to the peculiarities of its structure, concrete is most resistant to compression deformation. That is why the facilities where the use of cement mortar, as the main building material, is envisaged, are designed in such a way that it is primarily the compressive loads that are transmitted to it.

Note! Characteristics such as tensile strength in bending, or ordinary tensile strength, are taken into account quite rarely.

Limits

A conversation about the state of the material, such as the limit, can be depicted in several parts, and list the basics, and these will be:

It should always be remembered that with all the technical and practical advantages of this building material, the tensile strength is from 5 to 10% of the values that reach the ultimate compressive strength of concrete.
Flexural strength reaches a maximum of 15% of the compressive strength
Brand or class of solution is determined at the age of 28 days. They determine the compressive strength.

Testing the finished unit for compression performance, without which construction is impossible

Strength can be determined at the age of three, seven and even sixty days.
Values obtained as a result of measurements shall not exceed the ultimate compressive strength of concrete, corresponding to the brand or class of more than 15%. It is important to emphasize that such a value is set in order to save cement.

Classes and brands

The following classes of concrete exist: Bb1; Bb1,5; Bb2; B2.5; Bb3.5; Bb5; Bb7,5; Bb10; Bb12,5; Bb15; Bb20; Bb25; Bb30; B35; Bb40; Bb50; B55; Bb60.

Note! The class of concrete for compressive strength, in fact, is its guaranteed strength, measured in MPa, with a security equal to 0.95.

There is also a division by brand. About the brand say, mainly when it comes directly to the heavy types of material. The following brands are distinguished: Мb50; M75; M100; M150; M200; M250; M300; M350, Мb400; Mb450; Mb500; Mb600; Mb700; Mb800.

The brand of this material is a normalized value of the average strength of concrete. This value is measured in kgf cm2, and in order to be clear, we will clarify that this means the effect of one kilogram of forces per square centimeter of area.

The simplest vacuum gauge that plays an important role in allowing the material to work

Naturally, the higher the strength characteristics of the solution, the higher its price, since these concepts are almost interconnected.

Note! In the preparation of project documentation often indicate the class of compressive strength of concrete. Mark is indicated only in some cases when it is really necessary.

Guests

GOST on the brand of concrete for compressive strength establishes the correspondence between the classes and brands. To understand how to determine the strength of the solution by its alphabetic and numerical designation, it is necessary to consider a specific example.

For this fit such a common class of material, as B25. The strength of concrete B25 in compression means that concrete of this class can withstand a pressure of 25 MPa in 95% of cases.

An example of the construction expertise, which is determined by the guest

Gas concrete

Separately, it should be noted such material as aerated concrete and its strength characteristics. The fact is that there is a perception of the fragility of this building material. This is not true.

Факты говорят о том, что прочность на сжатие газобетона с плотностью D500 (35 кг/м2), позволяет применять его для строительства двухэтажных домов. Gas concreteные блоки с плотностью D600 уже могут использоваться для пятиэтажных строений.

A good example of the density of aerated concrete

Self check

According to GOST, compressive strength is tested in the laboratory. However, it is possible to check the conformity of the brand and independently. To do this, you must perform the following steps, which we present in the table.

Form preparation	You can prepare, for example, wooden forms with a size of 100x100x100 mm.
Mixture intake	Take a small sample of the concrete mix from the mixer tray and pour a few cubes into the molds.
Compaction	Condense the composition with your own hands, knocking the shape of a hammer.
Exposure	Maintain cubes at a humidity of 90% and an ambient temperature of + 20 ° C. To exclude hit of direct sunshine on cubes.
results	Transfer samples to the laboratory after 28 days. Some samples can be transferred at intermediate stages of solidification (3rd, 7th, 14th days) for preliminary examination.

If the above instructions are followed, then with high accuracy it will be possible to determine whether the mortar on the construction site is the same as that ordered for construction.

Looks like this for laboratory analysis cubes.

Conclusion

All complex calculations are carried out in laboratory conditions and are necessary in the construction of multi-storey buildings. As for low-rise construction, the video in this article will demonstrate how to achieve excellent results in the preparation of the solution.