Concrete is perhaps the most demanded building material, widely used in the construction of both private houses and large multi-storey buildings. There are many brands of this material designed for use in a variety of purposes. One of the most popular is concrete B15 (class) or M200 (grade).
General Features
Concrete B15 (grade M200) belongs to the group with an average strength of 196 kgf/sq.cm. It is produced in accordance with GOST standards on modern equipment, on automated lines. The result is a very high quality material suitable for the construction of a wide variety of structural elements of buildings.
Use area
Production of durable durable floors - the main scope of this material. Its resistance to adverse weather conditions is at an average level. And therefore it is more expedient to use it indoors. The screed using this material is very reliable and durable. In addition, B15 concrete is a brand,used when:
- construction of foundations (mainly outbuildings);
- filling walls;
- concrete paths and curbs;
- fill blind area;
- construction of stairs and porches;
- creating precast concrete products;
- filling columns;
- to create a substrate for roadworks.
Concrete grade B15: composition
Produce standard B15 concrete using the following ingredients:
- Cement (30 kg).
- Small aggregates (40 kg). It is allowed to use sand with a particle size of 0.15 to 5 mm. Its density should be 1790 kg/m3.
- Crushed or gravel (90 kg). The grain size of this filler ranges from 6 to 70 mm. When erecting massive structures, it is allowed to use crushed stone with a fraction size of up to 140 mm.
Dry ingredients are pre-mixed thoroughly and then diluted with water in an amount of 20% of the total volume. Sometimes manufacturers add various kinds of minerals, plasticizers, etc. to improve the quality of the finished product.
Concrete grade B15 (GOST 7473-2010) is made exclusively from high-quality cement. Most often it is a product of the M400 brand. The mass ratio of cementsandcrushed stone in proportions will be as follows: 12, 84, 8.
Varieties
Currently produced several types of concrete of this class. They differcan, for example, by the type of filler used. It can be lime, granite or gravel crushed stone. There are also varieties of this material with an unequal degree of mobility and rigidity.
Brand to class ratio
Contrary to popular belief, concrete does not stop gaining strength after 28 days. This process can last all the time of operation of the structure erected from it. The brand of concrete is determined depending on the amount of cement used in its manufacture. This indicator plays a decisive role in the ability of concrete to resist compression and expansion. It is measured in kgf/cm3. Thus, the M200 concrete grade shows that the compressive strength is 200 kgf/cm3.
In addition to the brand, concrete is also divided into classes. This indicator determines the maximum pressure that the finished material can withstand in megapascals. In relation to B 15, this is 15 MPa (in 95% of cases). The class of concrete itself is indicated by the letter "B".
Previously, the strength of concrete was judged mainly by the grade. Now this material is classified mainly by classes. However, in order to make it more convenient for people who are used to focusing on the brand, special tables have been created in which the correspondences of these two indicators are given.
Concrete grades by other indicators
Strength is not the only parameter that you should pay attention to when buying a mixture. A very important indicator is also the brand of mortar for frost resistance. It is denoted by the letter F and numbers starting from 25. In practice, in private housing construction, concrete with a frost resistance grade of F100-200 is usually used.
Another important parameter is the water resistance of concrete. In this case, the material can be marked as W2, W4, W6, W8 and W12. The numbers show the water pressure at which a concrete cylinder 15 cm high does not let water through at a certain pressure. Concrete grade B15 has very good characteristics in this regard.
Also, when buying concrete, you should pay attention to such an indicator as the draft of the cone. This parameter determines such a characteristic of the material as mobility. This indicator is marked in the data sheet of the mixture with the letter "P". Most often, concrete with mobility P-2 and P-3 is used in construction. Solutions P-4 and above are used if it is required to fill hard-to-reach places. Plastic concretes are also used when pouring is done using a pump.
Specifications
What specific properties are different concrete B15 (grade M200), can be found in the table below.
| Indicator | Parameters |
| Frost resistance | F100 (if you freeze and thaw the material 100 times, the loss of strength will be no more than 5%) |
| Waterproof | W6 (prevents the penetration of water at pressures up to 0.6 atm) |
| Mobility | R3 |
Material cost
Prices for concrete class B15 (grade M200) depend mainly on the variety of crushed stone used in the manufacture. For example, if it is granite, you will have to pay about 3,850 rubles per cubic meter of B15 concrete (data for 2015). For the option with gravel filler - approximately 3600 rubles.
Making at home
In this case, you can get a high-quality mixture only by using a concrete mixer. Manually, good concrete of class B15, grade M200, cannot be kneaded. The procedure for preparing the solution is as follows:
- Sand and cement are thoroughly mixed beforehand. At the same stage, you can add an additive that increases frost resistance (for 20 kg of cement 2 kg).
- Water is added, then gravel.
- The resulting mass is mixed for at least three minutes.
In volume ratio, concrete B15 (grade M200) is prepared in the following proportions: 19 liters of sand and 33 liters of crushed stone are taken for 10 liters of cement. Therefore, in ten-liter buckets, the ratio will be something like this: 1x2x3, 5.
During the manufacture of concrete of this grade, deviation from the specified quantitative ratios by no more than 1% is allowed.
Example of kneading
For one element of a columnar foundation with a volume of 0.11 m3 you will need approximately 19 kg of cement, 41 kg of sand, 78 kg of crushed gravel, and 9 kg of water. A similar ratio is valid when using cement brand M400. Forpouring the column will need to be done approximately two such batches.
Concrete of other grades
Very often in private housing construction, high-quality concrete grade M250 (B20) is also used. This variety is somewhat stronger than class B15 and can also be used for pouring floors that are not subjected to serious loads. Concrete grade M300 (class B22, 5) is most often used for the construction of strip foundations. For pouring slab solid foundations for houses, mortar M350 (class B25) is more often used.
Concrete B15 is a brand, in terms of strength, therefore, it is quite suitable for the construction of most objects in private housing construction. Very good technological characteristics, combined with low cost, make it advisable to use it both for pouring screeds and floors, and for building foundations (outbuildings) and partitions.
