Concrete grade for the foundation of a private house. Concrete of what brand is needed for the foundation

Concrete is a modern building material, competing with natural stone in strength. Its high operational properties have provided him with popularity in the manufacture of all types of construction work, including the construction of a foundation. If lightweight structures can use columnar foundations, capital structures require a high-quality belt or pile foundation, the characteristics of which directly depend on the choice of concrete grade, skilful batch and carefully selected composition.

In this article, we will consider which concrete to use for the foundation.

Mixture composition

In the concrete mixture, two main components can be distinguished:

• Fractional filler (sand, crushed stone or gravel) is a "power" element that perceives all loads. The volume fraction in the composition is up to 80%.
• An astringent, resulting from the contact of the cement mixture and water. The volume fraction in the composition is up to 30%.

The ratio of the listed substances in the concrete mix can be different, depending on the brand of cement, moisture of the filler, the presence of additives. The foundation is the load-bearing part of the building, therefore, to ensure the resistance to design loads, it is necessary to select the composition of the concrete mix correctly. Concrete works perfectly for compression, which allows the foundation to successfully withstand the pressure of the ground structure. The reinforcement frame, used in the foundation, also provides strength in the transverse direction during soil motions.

The choice of concrete for the foundation depends on the construction of the erected building. There are different requirements to the foundation, which causes the use of a wide range of concrete grades in practice.

To answer the question, what brand of concrete for the foundation of a private house is suitable, let's consider the main types.

Concrete of the brand M100

Refers to lightweight concrete, low in cement content. The main application is in the preparatory steps of construction work, when pouring concrete preparation. M100 is quite cheap, but its strength characteristics limit the use of non-capital buildings, such as fences, frame houses, sheds.

Concrete of the brand M150

By its characteristics, this brand of concrete is not much different from the M100. The main application is preparatory construction work. From concrete M150 it is possible to fill only the lightest ribbon foundations of single-storey light houses made of wood or hollow blocks, garages and sheds. This brand of concrete for the foundation of a private house is only permissible if the rocky soil acts as a reliable base. Deepen the foundation is not due to the danger of groundwater, otherwise it is mandatory to use waterproofing (liquid rubber).

Concrete of the brand M200

This concrete is already stronger and often used in the construction of low-rise (up to two floors) buildings and structures with wooden or metal ceilings. Of concrete grade M200 it is allowed to produce reinforced concrete products, for example, piles or slabs. The main area of application in residential construction is the foundation casting for frame-panel houses. The soil is allowed only sandy, and groundwater should not rise to the freezing height, and their seasonal fluctuations should be taken into account.

Concrete brand M250 and M300

The cement content is average. Used M250-I brand of concrete for the foundation of the house (for pouring) to three floors. Mark M300 - more solid concrete, it is used in the foundations of cottages with a height of up to five floors. According to construction standards, M300 concrete is allowed to be used for making monolithic ceilings. It is used when pouring pools. Concrete of these grades can be used for foundation construction on sandy soils, as well as on gravel or rubble ground with a relatively high level of groundwater.

Concrete of the brand M350

One of the most popular in the construction of concrete grades. Significantly superior to the M300 not only in strength, but also in frost resistance. It is characterized by a long stated life.

Suitable for erecting multi-storey buildings, is used in the construction of consoles, ceilings and other responsible structures. When erecting a foundation, concrete grade M350 is permissible for a single-storey brick house. Suitable for difficult clayey soils and places where there is a high level of groundwater. Loams and clay soils are the most common. Freezing, clay increases in volume, which can lead to deformation of the foundation in case of incorrectly selected brand of concrete.

Concrete brand M400

This brand is characterized by extremely high strength characteristics due to the large content of cement and specially selected filler.

Used this brand of concrete for the foundation of a private house. Also, the permitted area of application is the erection of multi-storey buildings (up to 20 floors in height).

What concrete is needed for the foundation?

Concrete of a lower grade is cheaper, however, when constructing a foundation it is better to provide some margin of safety, especially for those cases when it is planned to make a basement residential. What concrete is needed for the foundation? Concrete of M350, M400 grades is characterized by increased density, and consequently, moisture will penetrate through it worse, and the cap will be drier. Sometimes, when building unreasonable structures on bad ground, it makes sense to calculate that it is more profitable to use a higher grade of concrete or to use concrete cheaper, but to treat the foundation with waterproofing to protect it from groundwater.

The easiest way to determine which brand of concrete is needed for the foundation of the house, which brand to choose is to make a preliminary order of the design estimates to the designer. It identifies suitable concrete grades for each type of work, including the foundation, and the additional properties that the solution must satisfy, such as:

• density,
• Watertightness (protection from groundwater),
• Frost resistance (the higher, the more suitable for severe climate),
• Fluidity,
• Fire resistance.

However, the concrete grade for the foundation of a private house can be selected independently. For this, it is necessary to take into account the following features of the constructed structure:

• Weight of the structure, number of storeys, presence or absence of the basement,
• Geological survey of the site: determine the type of soil and the depth of groundwater,
• Type of foundation: belt, pile or some other.

Each of the factors listed above affects what concrete is needed for the foundation, the choice of concrete grade, taking into account its special characteristics, etc.

On the monolithic concrete foundation, multidirectional forces operate along the entire perimeter. The foundation should be deepened to the ground so that it is below the freezing level. Specific values of the depth of freezing vary widely, depending on the soil and climatic conditions. In general, for mid-latitudes the freezing level is 0.9-1.5 m. It is recommended to choose the depth of the deposit with some reserve. Reliance on the soil base, which is not subject to freezing, saves the band foundation from deformations of frost heave.

For the basement base, lower grades of concrete will fit, but the pile, on the other hand, requires higher and stronger concrete. Pile foundations are used in the construction of capital multi-storey buildings. Belt foundations equip for low-rise construction.

Selection of the composition of the concrete solution and mixing

Despite the similar designations, the brand of concrete and the brand of cement are completely different concepts. The number in the cement brand indicates the strength of the cement slurry.

Since the foundation design implies its reinforcement in order to provide transverse strength, it is optimal to choose gravel or gravel of the middle fraction. The clay granite gravel provides the best grip.

As for sand, in theory it is recommended to use sea, but it will be suitable for a normal one, from a sandy quarry. It is important to note that the sand should first be filtered to exclude clay and other undesirable inclusions.

To the water there are no special requirements, ordinary tap is suitable. The cement-water ratio is 2: 1.

The preferred method is to use a concrete mixer, but it is also possible to manually mechanically mix the solution. This requires a volumetric tank, in which sand, gravel or crushed stone and cement are added in a certain ratio. Mixing the dry ingredients well, you can gradually pour water, stirring constantly until a uniform mass is formed. It is important not to overdo it with the amount of water.

Calculation of the required amount of concrete

An incorrect calculation threatens with a shortage of material or the formation of surpluses, which is also undesirable.

Separate volumes of a plate, strips of a tape base, columns which are then summarized are separately calculated. The calculated value is multiplied by the concrete shrinkage factor, the value of which is taken from the passport. Since the reinforcement also occupies a certain volume in the formwork, to account for this, it is necessary to divide the volume of concrete by a factor of 1.05. The resulting value is rounded up.

What concrete is needed for the foundation

Selection guide:

• Carefully calculate the weight of the structure;
• To allocate safety margin due to possible error or unforeseen circumstances;
• To determine the depth at which groundwater flows;
• Determine the interaction of the soil and the future foundation.