A grade of concrete for the foundation of a private house. Concrete of what brand is needed for the foundation
Concrete is a modern buildingmaterial, in strength, competing with natural stone. Its high operational properties 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, gravel 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 concretemixture can be different, depending on the brand of cement, the moisture content 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 reinforcing cage used in the foundation provides also strength in the transverse direction when the soil moves.
The choice of concrete for the foundation depends on the construction of the erected building. There are various 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 mark M100
Refers to light concretes, low inthe maintenance of cement. 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
According to its characteristics, this brand of concrete is notis very different from 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 is often used forerection 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. Soil is allowed only sand, 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 durable 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 the production of monolithic ceilings. It is used when pouring pools. Concrete of these grades can be used in the arrangement of the foundation 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 has a long declared life.
Suitable for erecting multi-storey buildings,It is used in the construction of consoles, ceilings and other critical structures. When erecting a foundation, concrete grade M350 is acceptable for a single-storey brick house. Suitable for difficult clay 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 field of application is the erection of multi-storey buildings (up to 20 storeys in height).
What concrete is needed for the foundation?
Concrete of a lower grade is cheaper, howeverbuilding a foundation 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 high density, and consequently, moisture will penetrate through it worse, and the base will be more dry. 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 what is neededbrand of concrete 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,
- water resistance (protection against 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: tape, pile or some other.
Each of the factors listed above affects how much concrete is needed for the foundation, the choice of concrete grade, taking into account its special characteristics, etc.
On a concrete monolithic foundation actmultidirectional forces 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 select the depth of the deposit with some reserve. Reliance on a soil base that is not susceptible to freezing saves the band foundation against deformations of frost heaving.
For the basement base, lowerbrand concrete, but the pile, on the contrary, requires higher and more durable. 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 and mixing
Despite similar designations, the brand of concrete and the brand of cement are completely different concepts. The number in the cement brand means the strength of the cement slurry.
Because the foundation design impliesits reinforcement in order to provide transverse strength, it is optimal to choose gravel or gravel of the middle fraction. The grinding granite gravel provides the best grip.
As for sand, in theory it is recommendedsea, but also suitable, the usual, from the sand 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 useconcrete mixers, 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 slabs, stripsribbon foundation, pillars, which are then summed. 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 soil and future foundation.
