The duration of operation of the foundation determines the life of the housing, and depends on the specified strength of the concrete, which is present in the foundation structure, and the strength determines the foundation of a private house. Concrete parameters such as frost resistance and water permeability also have a fairly large impact on the strength of the concrete base. But, since these indicators are included in the operational properties of concrete inherent in its grade, then when building a foundation, the fundamental factor of reliability is the grade strength of concrete.
The concrete solution is mixed from proportionally added bulk substances and water. Consists of a mixture of binder (Portland cement), gravel or crushed stone (fillers), purified or river sand. The dry mixture is mixed with water. When the ratios of components change, the grade of concrete for the foundation also changes. The determination of the grade is also influenced by the setting conditions of the solution, for example, the street temperature, which should be equal to ≈ +20 0 C. When the temperature deviates in one direction or another, the grade strength decreases.
Concrete gains its design strength in 28 days, and concrete gains up to half its strength in the first 5-7 days. Thus, without waiting for full strength gain, you can proceed to further construction work in a week. With the correct composition of concrete, strength increases throughout the entire service life of the concrete structure. But the basis for brand strength is its value for the first four weeks.
Concrete grade
M100 M200 M250 M300
Demotion outside temperature up to +15 0 C, the setting time to 50% strength increases from 5 to 14 days. If the outside temperature drops to +5 0 C, the solution stops hardening. Therefore, for such temperatures, brands of winter concrete have been developed, to which special plasticizers, hardeners and anti-frost additives are added. Also during winter construction concrete structure heated, and for this there are different methods - from tents to laying a heating cable.
Concrete is prepared on the basis different brands Portland cement. IN individual construction The following types of cement grades M 400-M 500 are popular:
Any of listed types based on concrete.
The strength of concrete is affected by aggregates and their proportions in the solution, as well as granule fractions and humidity. bulk material. Sand is divided by size into:
To arrange the cushion and backfill, you need to use sand of coarse and medium fractions, purified and free of impurities in the form of stones, clay and dirt. The presence of dust and silt should not exceed 5% of the total volume of sand.
Rational grades of concrete for pouring foundations of various classes (grades of cement according to GOST 10178)
| Design class of concrete | Cement brands | |
| Featured | Allowed | |
| B 3.5-B 7.5 | 400 | 300 |
| B 12.5-B 15 | 400 | 300; 500 |
| B 20 | 400 | 500; 550 |
| B 22.5 | 500 | 400; 550; 600 |
| B 25 | 500 | 550; 600 |
| B Z0 | 550 | 500; 600 |
| B 35 | 550 | 500; 600 |
| B 40 | 600 | 550 |
To check the degree of contamination of sand at home, you need to take 200 cm 3 of sand and pour it into a 500 ml container, then pour clean water. After a few minutes, drain the water, add a new portion, and shake the container. The operation of changing the water is repeated until the water becomes clean and transparent. After this, the remaining volume of sand is measured: if 185-190 cm 3 remains, then the sand has 5% dust content, which means it is suitable for preparing durable concrete. 
The sand for mixing the loaf solution should be as dry as possible. There are certain standards for determining humidity: if the humidity does not exceed 1%, then the sand is considered dry and can be used in solution. At a humidity of ≈ 5%, sand can not be dried, but added to the solution less water. If the sand moisture content exceeds 10%, the sand must be dried.
Gravel and crushed stone are the result of crushing rock minerals. The crushed fractions of these rocks are as follows:
To prepare durable concrete, it is recommended to add different fractions to the mixture so that the grains different sizes filled the air pores in the solution as tightly as possible, making it denser, and therefore stronger. The largest one should not exceed 30% of the grain size of the largest small fraction. In this case, the volume of crushed stone of the smallest fraction should not be more than 30% of the total volume of the solution.
If the concrete solution is prepared with the addition of gravel, then the VC parameter (the ratio of water and cement in the solution) must be increased by 0.05, which in practice means: 5% more water must be added than in a solution with crushed stone. To prepare durable concrete for the foundation of a fence or house, you only need to add to the solution drinking water. Marine or process water will spoil the strength characteristics of concrete.
Concrete is divided into grades and classes in accordance with its characteristics, and the table shows what grade of concrete is needed to obtain a durable structure:
| Concrete strength class | Concrete strength kg/cm2 | Nearest brand of concrete |
| B 5 | 65,5 | M 75 |
| B 7.5 | 98,2 | M 100 |
| B 10 | 131 | M 150 |
| B 12.5 | 163,7 | M 150 |
| B 15 | 196,5 | M 200 |
| B 20 | 261,9 | M 250 |
| B 22.5 | 294,4 | M 300 |
| B 25 | 327,4 | M 350 |
| B 30 | 392,9 | M 400 |
| B 35 | 458,4 | M 450 |
Strength is calculated on test benches; research results show the load that the tested concrete will withstand without deformation or destruction in the long term.
In private construction, developers rarely make costly strength calculations using practical experience and using the three most common grades of concrete:
To accurately determine which brand of concrete to choose for arranging a strip foundation, you need to conduct a study of the site, and if the groundwater lies deeper than 2 meters, then the following brands are recommended:
The slab foundation needs to be laid concrete slabs grade M 350. Bored piles are filled with concrete M 200 - M 250.
The workability of concrete mortar affects the speed and ease of working with the material. When pouring the foundation, it is recommended to use grades P 1 and P 2. Taking into account the given data, the following grades of concrete are recommended for the foundations of private houses:
When increasing the number of storeys in a building, the grade of concrete also needs to be increased, as shown in the table above.
What brand of concrete is needed for the foundation of a house? updated: October 2, 2017 by: zoomfund
Read on topicWhat concrete is best to buy for the foundation of a private house?
The construction of an industrial complex or multi-story building necessarily begins with pouring a reliable foundation. It will directly depend on the quality of the foundation, as well as on the technology of its pouring. further fate upcoming architectural project. Well, the reliability of the foundation is ensured by the pouring material from which it is made. We are talking about high quality concrete. Next, we will consider which one is better to buy or do it yourself, so that the foundation of the building is considered as reliable as possible in accordance with GOST.
Brand of concrete for the foundation
The first thing to note is the brand. If we're talking about on the construction of bridge structures, hydraulic structures and industrial buildings, it is recommended to take ready-made, grade M400, that is, high density, which includes all kinds of plasticizers, as well as granite crushed stone. What kind of foundation concrete is useful in civil engineering? For the strip foundation of a house, you can also use a lower density of the commodity, characteristic of the premium brands M200 and M350. M200 is a universal, low-cost, high-consumption brand that is recommended for use in the construction of foundations for residential buildings. Concrete mix filler in this case gravel, limestone or granite crushed stone appears.
The next thing we pay attention to is the predicted load on residential or industrial building. Any builder should remember this. What kind of concrete is needed for a strip foundation used in the construction of prefabricated panel houses? As a rule, this is the M200 brand. For the foundation of a multi-story stone building, it is better to use more reliable option– brand M350. This brand is recommended for arranging floor slabs and load-bearing walls. Regarding concrete for stairs, lightly loaded floors and wooden buildings, then here you can opt for the M250 brand, the strength of which is slightly less than that of the M300 and M400 brands. The cost of delivering such concrete in a machine such as a concrete mixer will be most optimal for residential construction.
Soil properties
Many people place advertisements in newspapers like “I’ll buy concrete,” without even thinking about the fact that you need to pay no less attention to the properties of the soil than to the previous parameters. Rocky soil is a continuous mass of quartzite, granite, and sandstone. It is resistant to moisture, as a result of which the W-2 grade can be used when constructing buildings on rocky and sandy soils. As for clay soil, it is very susceptible to compression. The moisture content of clay soil will determine bearing capacity. Which brand is suitable in this case? To erect a building on such soil, it is better to resort to grades W-8 and W-12.
Cement brand
Before you think about where to buy concrete with delivery, take into account the fact that the brand of cement used in preparation will to a large extent determine its quality. The higher the grade of cement, the higher the quality of the concrete mixture and its price. If it is necessary to obtain concrete that is resistant to prolonged frosts, then PC 500-DO cement plus antifreeze additives is recommended. The final one will be durable and waterproof. PC-500 DO cement can be actively used for repair and restoration work. The amount of cement can be calculated either manually or using a special online calculator.
Porosity of concrete
Porosity, which also determines its quality, can be open or closed. In the first case, we are talking about capillary pores, microcracks and open cracks. In the second case - about the pores of the gel. Large open porosity can negatively affect technical specifications building material, including resistance to chemicals, moisture, low temperatures. Concrete with closed porosity is much more preferable in terms of properties.
Composition of concrete for foundation with impurities
Impurities or additives on the cube can have a significant impact on performance concrete composition and its quality. There are both individual admixtures on sale and concrete with already added admixtures, for which you don’t need to think about how to make and calculate correct composition. Dynamic properties of dry and liquid concrete can be increased through the use of superplasticizers, which make it more dense, fire-resistant and strong, plus eliminate the penetration of moisture. If a building is being built at a temperature of -15...-25 degrees, then the composition and proportions must contain frost-resistant components. To protect the concrete solution from corrosion, special proportions are used for the foundation with modifiers that reduce the resistance of the building material to low temperatures and moisture.
Certification
Certification is common in manufacturing around the world, but in Russian Federation it is not required. And yet, when thinking about how to choose concrete, we strongly recommend paying attention only to certified products with documents in the appropriate form, or at least to those manufacturers who have a good reputation in the region.
Regardless of which building is planned to be built (skyscraper made of glass and metal, dacha, cottage, fence, garage), its basis will be the foundation. The responsibility that falls on construction specialists in the process of producing the foundation is quite high. When calculating and choosing a concrete grade for the foundation of a house or other building, one should take into account a large number of parameters on which the durability, stability, and safety of the structure being built depend.
One of the components of the foundation is concrete. The result of all work on the construction of the facility will depend on how correctly the solution is selected and ultimately used.
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To decide what brand of concrete you will need for the foundation, you need to take into account several parameters, including:
The expected load is the most important indicator when choosing.
When calculating the load, it is clear that a structure made of reinforced concrete will be much larger in weight compared, for example, with a prefabricated panel building. This may lead to the fact that in the first case it is necessary to take a mixture of concrete with increased strength and viscosity characteristics. For buildings that have a lot of weight, we can recommend a brand from M350 and above. Grade up to M350 should be used for light buildings.
The next parameter is soil properties. Soil characteristics significantly influence. Resistance to possible deformations (which may be caused by displacement, for example, sandy, loamy or other similar types soil) can be achieved by selecting a special one for the foundation. If the soil is sandstone or rocky, grade M200 or M250 may be sufficient. If there are clay deposits in the area, then M350 may be a more suitable brand.
One of the problems with clay is heaving. If the foundation is built shallow, during the process of freezing in winter period over time, an uneven rise of the soil will be observed, which depends on the speed and degree of saturation with water.
Before you start building a house, you need to choose the type of foundation and determine what concrete will be needed to pour it.
There is 1 piece of advice on this matter. In such cases, you will need not only to choose the right brand of concrete, but also to dig much deeper than the frost line in order to avoid possible problems further.
The next parameter is groundwater. The proximity of groundwater will influence the search for it. Water impermeability is a criterion that should be taken into account primarily when groundwater is close to each other.
Please note that you will definitely need to keep in mind the seasonal changes in the existing area. They can lead not only to rising waters, but also to their emergence to the surface. This may entail negative impacts on the foundation.
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In order for the structure to maintain its integrity in the event of possible danger associated with groundwater, the following recommendations should be followed:
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Cement. When determining what composition and grade of concrete is needed for the selected type of foundation, you should know that there is a fairly large number of varieties of cement, including: without additives and with additives, Portland cement, normalized, quick-hardening, waterproof, plasticized, frost-resistant, resistant to aggressive environments and etc.
For the foundation, the M300 brand is most suitable, but builders recognized the M500 brand as optimal.
Fittings. Speaking about which reinforcement is most suitable for the foundation, it is worth knowing that experts advise choosing a cage structure with perpendicularly connected rods. Reinforcement bars for foundations are distinguished by a corrugated surface, which gives the concrete the opportunity to completely envelop the element that is embedded in the foundation.
It is important to note that the reinforcement must be completely included in the thickness of the base, without reaching the bottom.
Solution. When choosing a brand of mortar for foundations, you need to know that, in addition to cement, clay and lime can be added to the mortar, and therefore the choice expands. Mortars can be cement with different ratios of incoming components, cement-lime, cement-clay, which are used for foundations on dry soil. If the soil moisture increases, you will need to increase the amount of cement included in the composition.
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The grade of cement for a strip-type foundation for manual laying can be as follows:
Since the late 80s, monolithic strip foundations, filled with ready-mix concrete BSG (ready-mixed concrete). began to give way to the practical and convenient monolithic casting of foundations. Not only strip foundations are cast, but also various combinations of structures: pile-transom, bored piles and others.
Thanks to a wide selection constructive solutions With the use of monolithic casting, the choice of builders is increasingly choosing this technology. This raises the question: “ What kind of concrete is needed for the foundation?" Our managers answer this question quite often and without much difficulty, however, for a competent answer you will need information about the construction of the facility and other data.
Concrete grade M100 suitable for initial stages construction, pouring concrete. A foundation made of concrete grade M100 is suitable for fences, wooden houses, small garages and agricultural buildings.
Concrete grade M150 suitable for light strip foundations, preparatory concrete works. Concrete grade B7.5 is used for foundations of small one-story residential buildings made of cinder block, foam concrete and aerated concrete. Suitable for foundations of garages and agricultural buildings.
Concrete grade M200 used very often in the construction of residential single- and two-story houses with a light type of overlap. This brand of concrete mixtures is classified as structural in its strength characteristics and is used in production reinforced concrete products.
Concrete grade M250 and M300Suitable for foundations of large private residential buildings. Brand M300 is used for pouring the foundations of cottages with a height of up to 5 floors. Concrete grade M300 is the first in strength, which is recommended for use for monolithic floors.
Concrete grade M400used in construction multi-storey buildings up to 20 floors high.
If your construction project has a ready-made engineering design and it defines necessary materials for construction, you don’t need to think too much. Projects usually indicate the required grade of concrete for the foundation and other characteristics of the concrete mixture. The characteristics of concrete mean its mobility (plasticity), frost resistance and water resistance (water resistance coefficient W).
Having settled on one of the foundation laying designs, you need to choose grade of concrete for the foundation. Among other questions, the question also arises: “where to get concrete?” The answers are simple. The first option, from the factory; the second is to hire labor and mix it yourself. In 99% of cases it will be correct at the factory.
I wonder why? Read our review “7 advantages of concrete from the manufacturer.”
We have already come to the conclusion that concrete should be ordered from the factory. When choosing, you need to consider following parameters designs.
1) The weight of the structure and the load on the foundation, the number of storeys of the future building, the presence or absence of a basement.
2) Geological research land plot. Determination of the nature of soils, groundwater levels, etc.
3) The type of foundation used and its base part: strip, pile or other.
Each of these points influences to varying degrees the choice of concrete grade for the foundation. Let's look at each of them in more detail.
Foundation load prediction- one of the most important parameters when choosing a concrete mixture. Based only on the load, then in most cases, M200 class B15 concrete is suitable for 1-2 storey buildings. This grade of concrete belongs to structural mixtures and is also used in the production of reinforced concrete products. There are often known cases of using concrete grade M150 B12.5 for the construction of foundations of private buildings, agricultural buildings and garages. When using bricks (ordinary, silicate, hyper-pressed, etc.), gas blocks, expanded clay concrete blocks, as masonry materials, as well as reinforced concrete slabs floors, we recommend using grades no lower than B20. In the construction of multi-storey buildings using precast concrete or monolithic construction it is necessary to use the grade of concrete for the strip foundation M300 - and higher.
Soil characteristics. In the case of sandy or rocky soils, for a strip foundation and a 1-2 floor building, you can safely choose low ones - M200. Alas, such soils are not found very often, and in most cases you have to work with clays, loams and other soils. In such cases experienced builders highly recommend using ready concrete for foundation.
Be careful, clay! Its main problem is a lot of heaving. When the temperature drops environment Clay can expand in volume. Shallow foundation structures due to this effect in winter time are subject to deformation. Relative deformation movements can reach several tens of millimeters. In addition, such deformations are characterized by unevenness, which is associated with to varying degrees saturation with groundwater.
Thus, on concrete monolithic foundation different loads are applied along its entire perimeter. That is why all foundations are laid below the freezing level (freezing depths are determined for different latitudes). The freezing depth for the latitudes of Ukraine is about 1 m. different regions specialists, for one reason or another, choose a foundation depth of 0.7 - 1.2 m. Relying on non-frozen soils relieves strip foundations from frost heaving deformations.
Types of foundation. A strip foundation implies the use of lower grades, but a pile foundation involves the use of higher grades (but not always). Pile foundations often used in construction high-rise buildings, where concrete is poured into piles using special drill-injection machines. The grades of concrete used there are no lower and all requirements for concrete are set by design engineers.
The choice of concrete can also be influenced by the groundwater level, proximity to reservoirs, rivers and the presence of a basement in the house. Let's discuss the water resistance coefficient W. Water resistance is the ability of a concrete mixture not to allow water under pressure to pass through from outside. Very important parameter for hydraulic structures. The water resistance coefficient W can vary from W2 to W20, indicating the pressure in kgf/sq.cm. For high waterproofness of the foundation, you can use external coating waterproofing or purchase a higher grade of concrete in which this coefficient is 100% higher than that of lower grades. For this parameter we recommend choosing -25.
The cost of concrete for a foundation is determined by its strength characteristics. The larger and higher your house is, the more durable concrete and the higher grade should be used when pouring the foundation of the future building. High grades of concrete use more cement to create the required strength. Concrete prices depend on its grade strength (higher grade - more cement).
In this review, we examined only some of the parameters and touched on the train of thought regarding the choice of concrete for the foundation. In each specific case of choosing the type of foundation, concrete and design of the structure as a whole, you need to approach it individually with the involvement of professional builders.
The durability and stability of any type of foundation depends on many factors. The most important are the quality and grade of concrete. The success of all construction cycles directly depends on how well it matches the type of house structure, the quality of the soil and the chosen type of foundation.
In the presence of project documentation, the main criteria have already been outlined by professional architects. Consequently, the task of builders is to strictly follow the developed project, in which the grade of concrete has already been determined. However, what to do if you plan to independently arrange the foundation?
Before deciding whether to purchase a concrete mixture or produce it yourself on site, you need to understand what basic properties should be taken into account.
Any concrete consists of three main components; the quality of the concrete mixture itself depends on their percentage in cement.
Water acts as a solvent for the fillers present. Fillers such as crushed stone, gravel, sand and other bulk additives reduce the stress of the hardening foundation and can significantly reduce the cost of the foundation being built. Cement is the connecting link between the two components listed above.
Concrete mixture, as a material for construction, is usually divided according to the following main characteristics: according to its purpose and use, type of connecting component, medium density, strength characteristics, water resistance and frost resistance.
These may be the most different conditions, such as resistance to stress (including vibration and shock), fire resistance and resistance to sulfates. Here we can highlight the following types concrete:
Production different types concrete depends on what conditions and for what reinforced concrete structures it will be used.
The astringent component included in the solution determines its fundamental characteristics. Main types:
This category includes decorative mixtures different colors. The most expensive of them is white. This group contains concrete mixtures based on alumina, non-shrink and prestressing cement;
The first indicator means the ability of the mixture to not allow water to pass under pressure. According to it, the concrete grade is classified from W2/4/6/8/12. IN Lately the letter F was replaced by B.
The indicator of resistance to frost in GOST is designated by the letter F and indicates the number of maximum possible freezing and thawing with a decrease in weight and strength by a certain amount. The better the density of concrete, the higher its frost resistance. The lowest grade of concrete in this case is F25, and the highest is F1000.
After determining the type of future foundation, you need to decide which brand is suitable for laying the foundation of a private house. When determining the proportions of components, it is necessary to take into account:
Based general information given at the beginning of the article, it follows that the higher the load, the higher the grade of concrete should be. For example, for a lightweight wooden or prefabricated panel cottage, concrete mortar M200 or M250 is suitable, and the construction of a strip foundation for a brick house will require the use of M300.
When determining the composition of the mixture, the structure of the soil and the characteristics of the climatic zone in which construction is being carried out should be taken into account. The grade of concrete is selected depending on the level of water rise and seasonal freezing.
The necessary parameters, namely water resistance, mobility, rigidity, frost resistance, depend on Portland cement. In accordance with established and justified requirements, its grade should be 2 times higher than the finished concrete solution.
So, for concrete with an index of 300, the M600 brand is suitable. However, this ratio can be reduced to 1.5 or to 1.0 for rocky or sandy soils. But, in the presence of clayey or swampy soils, the quality of concrete will have to be increased by 50 or more units.
Self-production cement mortar for foundation
For self-made concrete, attention should be paid to the purity of the additional components:
In order for the solution to obtain the required strength, you should choose the required brand and strictly adhere to the water ratio. General proportion concrete mortar is as follows - 1: 3: 5 (for one part of cement you need to add 3 parts of sand and 5 crushed stone).
To mix the solution you will need Portland cement M 400 per 1 m³ in the following proportions:
Experts say that even if all proportions are observed, there is no guarantee that as a result the builder will receive an M200 grade mixture. The properties of a concrete mixture largely depend on the moisture content of the components, the quality of mixing the solution and the order in which it is laid in the structure.
Ready concrete mixture, as well as components for self-production on site, should be purchased only from trusted manufacturers.
The grade of concrete for the construction of the foundation of a house must exceed the declared characteristics by 30 to 40%. Following this principle will ensure the reliability of the foundation and the entire structure during operation.
