Since the late 80s, monolithic strip foundations filled with ready-mix concrete BSG (ready-mix concrete) have become increasingly popular among the population. 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 foundation, 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 the construction of 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 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, the concrete monolithic foundation is subject to different loads 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 are 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 level groundwater, 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 a higher grade should be used when pouring the foundation of a 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 in this case– F25, and the highest – 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 the next one is 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-mix concrete, 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.
What concrete is best to buy for the foundation of a private house?
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 about 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. The filler for the concrete mixture in this case is gravel, limestone or granite crushed stone.
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 the installation of 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. The 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.
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. It 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. The following types of cement grades M 400-M 500 are popular in individual construction:
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. 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 topicThe foundation is the basis of any building, regardless of its size and purpose. The foundation bears the load from all structures located above. The reliability of the foundation depends on many factors, the main one of which is the strength of the foundation concrete. Except physical characteristics(width and depth), the grade of concrete for the foundation of a private house must correspond to the loads. In this article we will tell you how to correctly determine the grade of concrete for a foundation, what types of foundations exist, and what grades of concrete are used for constructing certain types of foundations.
The following types of foundations are distinguished:
Especially often used in private construction. Suitable for heavy houses made of concrete and brick. It is a reinforced concrete strip of calculated width and depth, arranged under load-bearing walls buildings, usually with basements.
The depth of the strip foundation exceeds the depth of soil freezing. Shallow strip foundations are sometimes installed under light (usually wooden) houses.
Pillar supports at the corners of the building and at the intersections of walls.
Built on stable soils for lightweight buildings. The lintels between the pillars can be brick, concrete, or rubble. Basements are not expected with this type of foundation. This type of foundation is cheaper than a strip foundation, but has limitations in use.
Used on highly compressible soils for light (wooden) structures.
In case of soil movement monolithic slab prevents the structure from collapsing. Construction is done without the use of equipment, and planning possibilities are unlimited. The disadvantage is the impossibility of constructing a basement and the high cost.
It is installed on weak moving soils for structures with high loads. The piles are predominantly reinforced concrete with a load-bearing load of 2 - 5 tons per unit.
The head parts of the piles are connected to form a support. Convenient in dense urban areas. Reliable and durable, does not depend on groundwater levels. The method is expensive and is not used in private construction.
Member of the group monolithic foundations. The base of such a foundation is the floor of the house.
The foundation is expensive, it is arranged only for small houses. The characteristics correspond to a monolithic foundation.
Such a foundation protects the building from ground deformations.
It is installed on waterlogged, weak-bearing and bulk soils.
Member of the group pile foundations– the pile in this case is a pipe with a blade.
It is used on flooded construction sites, on heaving soils, unstable soils with complex terrain.
The type of foundation chosen depends on the characteristics of the building under construction and the conditions of the construction site. The foundation is selected according to:
The criteria by which the type of foundation is determined are set out above. If exists finished project object, then it indicates the selected type, its characteristics and the grade of concrete for the construction of the foundation. Each type of building and structure under construction corresponds to the grade of concrete that is used in the construction of the foundation.
M100 is used for footings in preparatory stages construction. A foundation made of this brand of concrete can be built for wooden houses, garages, fences, and farm buildings.
M150 is used for preparatory work, for pouring shallow foundations of strip type, small one-story houses, houses made of aerated concrete, foam concrete and cinder block. Can be used for foundations for garages and agricultural buildings.
· M200 is used in the construction of private houses up to two floors with light floors. Concrete of this grade is classified as structural and is used for the production of reinforced concrete products.
M250 and M300 are used for the construction of large foundations individual houses. Concrete M300 is suitable for monolithic floors.
· M400 is used for the construction of foundations for multi-story construction and floors.
Some of the most important characteristics influencing the choice of concrete for the foundation.
A characteristic that reflects the ability of concrete to withstand compressive loads. M (concrete grade) is the average value of the maximum pressure per 1 sq. cm that a concrete sample can withstand 28 days after mixing. B (concrete class) - more modern version strength characteristics taking into account a variation of 13%. The higher the M and B values, the stronger the concrete.
It is impossible to check what brand of concrete it is. With a special device Using a sclerometer, you can determine the quality of the mixture directly when pouring concrete into the formwork, but this requires specialists.
Characteristics of the flowability or workability of concrete. Index P from 1 to 5 determines the ability of the solution cone to settle by a certain amount. The higher the mobility of concrete, the more liquid concrete used for filling. In the foundations under individual houses Concrete with mobility P-2 or P-3 is used. For ease of installation, do not add to the mixer more water- this inevitably reduces the strength of concrete and can be dangerous for the foundation of the house.
The index (W) is indicated by numbers from 2 to 20 and is called the water resistance coefficient. The water resistance of the prepared concrete can be increased by using special hydrophobic additives in the production of concrete mixture for the foundation.
It is designated by the index F and has values of 25 – 1000. Characterizes the ability of water-saturated concrete to withstand “freeze-thaw” cycles while maintaining strength characteristics. Coefficients F100 – F200 are typical for individual construction. The value depends on the construction conditions (climate, humidity, type of soil), as well as the quality of the foundation waterproofing work.
Concrete contains four components: cement, crushed stone, sand, and water. The main thing is that the concrete must exactly match its brand in terms of strength. Briefly, the requirements for each material:
Active component of concrete. For foundation concrete, cement M400 or M500 is used (not to be confused with the brand of concrete!).
The selected cement must have a minimum shelf life (after a month of storage at a temperature of 20 o C indoors, M400 cement loses its properties by a quarter, and by half when stored outdoors).
A filler that provides strength to concrete. For a reinforced structure, which is the foundation, according to the standards, a crushed stone fraction of up to 40 mm is required. To choose the desired faction, you need to take into account the minimum distance between the reinforcing bars. The selected crushed stone of the maximum fraction should not exceed this distance by more than ¾.
It is preferable to use granite crushed stone or crushed gravel 5 - 20 mm for pouring the reinforcement frame and 20 - 40 mm for pouring on the ground. Crushed limestone can only be used to prepare concrete for foundations on dry soils.
Will do quarry sand- it must be washed and sifted with a minimum amount of clay impurities.
River sand is finer and usually contains a lot of clay, which is undesirable for concrete production. If there is no choice, then river sand should be thoroughly sifted and washed.
Pure water without biological inclusions, petroleum products, oils. Tap water is usually used.
The ratios of components of concrete mixtures of various brands are shown in the table:
You can watch the video for making concrete at home.
The choice of concrete grade is dictated performance characteristics And economic feasibility. A strong foundation, if it is not necessary, will lead to unjustified construction costs, so it is important to correctly determine what grade of concrete is needed. As a rule, private housing projects in Russia offer strip foundations (more than 70% of the total are being built). To determine the grade of concrete for a strip foundation, you need to take into account everything that affects the foundation.
To determine the grade of concrete for building a foundation, you need to use the recommendations outlined, then take into account additional construction conditions and, depending on them, make a final decision on the grade of concrete.
What kind of concrete is needed for the foundation of a house? updated: November 25, 2016 by: Artyom
