What kind of concrete is suitable for the foundation. Types of foundations and common brands of concrete. Which concrete is better for the foundation of the house - selection of the brand of concrete solution

27.01.2022

In individual housing construction, strip foundations are used most often. This type of foundation consists of a monolithic concrete casting placed along the perimeter and under the internal load-bearing walls of the facility. It is technically simple in execution, available for execution by a home master, which determines its popularity.

The depth of the structure during the implementation of capital construction should be higher than the level of soil freezing, which increases labor costs, the cost of work, and the consumption of concrete casting. If we are talking about low-rise construction, you can build a monolithic shallow foundation.

Strip foundation - the main properties of concrete

To understand what brand of concrete is needed for the foundation of a summer house, bathhouse or garage, you need to familiarize yourself with its characteristics.

Avoiding high financial costs will allow the arrangement of individual concrete poles

Strength - the ability to resist compressive loads:

the minimum figure is 100 kg / cm². The upper limit used in private housing construction is 400 kg / cm²;
strength parameters determine the class, brand and cost of reinforced concrete;
when selecting a material, it is necessary to calculate the load that will be transmitted to the structure under the weight of the structure;
the maximum level of loads on the support is calculated based on the weight of floors, engineering systems, walls and a number of additional loads, such as snow;
the resulting value is divided by the area of \u200b\u200bthe support, so the calculated load is displayed.

Concrete grade

The working solution is formed on the basis of cement, additives and filler. The filler is crushed stone and sifted building sand. Additives increase resistance to moisture (multiple wetting and drying), frost resistance.

The brand of reinforced concrete determines the strength of the finished structure. It is denoted by the letter "M" and a numerical indicator. The figure indicates what level of pressure in kg can withstand 1 cm² of the finished casting. What brand of concrete is needed for the strip foundation? For such structures, the indicator should not be lower than M300.

additional characteristics

The choice of material is based on data obtained after studying the composition of the soil and its characteristics. . Professionals recommend paying attention to the following guidelines:

dacha construction in regions with cold climatic conditions involves the use of concrete that is resistant to freeze / thaw cycles. This marking is indicated by the letter "F", and the numerical value tells how many times the casting can be thawed and frozen without loss of performance. For the implementation of work in the middle lane, it is enough to use concrete F200;
in soils with a high occurrence of groundwater, it is recommended to use concretes that are resistant to such effects (marking "W"). The numerical indicator characterizes the maximum allowable water pressure and can vary from 2 to 20.

High fluidity and mobility of concrete are necessary if the mixer cannot be brought directly to the work area and with frequent laying of reinforcing rods. This indicator is regulated by the amount of water introduced into the working solutions.

What brand of concrete is needed for a strip foundation

The brand is selected based on the following characteristics:

design load on the base. If the structure is two-story, then the load increases. The properties of the material depend on the type of cement used: if it is necessary to obtain M300 concrete, M500 cement should be selected;
climate conditions and soil characteristics - concrete parameters are regulated by additional additives;
the method of pouring the mixture into the formwork, the design features of the frame.

The maximum allowable load of concrete must be higher than the design indicator

How to mix concrete

The standard proportions are as follows:

cement - 10.00 kg;
sand - 30.00 kg;
gravel of fine fraction (up to 2 cm) - 40.0-50.0 kg;
water - 40.0-45.0 l.

All components must be dry. If the mass is too dense, it is slightly diluted with water.. You should not buy cement long before the start of construction work, it will quickly absorb moisture and deteriorate.

How much cement in a cube of concrete

When calculating the amount of material, you can be guided by tabular data.

What reinforcement is needed for a strip foundation

The strength of the tape system forms a metal space frame. It provides resistance to tensile, compression, bending loads, compensating for soil movements.

All characteristics are based on the correct selection of fittings:

the diameter of longitudinal rods in foundations with a length exceeding 3 m should not be less than 10 mm;
the diameter of the transverse rods can vary from 6 to 8 mm;
if the length of the base exceeds 3 m, the value should be 12 mm.

To build a foundation, a four- or six-bar reinforcement scheme can be used for laying.

How to make a foundation for a house

Shallow construction (up to 60 cm) is used in low-rise construction and reduces financial costs. The easiest and fastest way to perform work is to fill a monolithic base. At the preparatory stage, a site is organized, tools and materials are prepared.

markup

Work progress:

the area where the foundation will be placed is freed from the soil layer;
according to the design data, markings are made with the help of pegs and cords: the perimeter is marked, beacons are placed in the corners, the diagonals between the corners are adjusted. An auxiliary blind area is constructed along the beacons, on which the cords are fixed.

Soil extraction

Sequencing:

focusing on the markup, trenching is carried out;
work starts from the lowest angle, the rest of the horizontal plane is aligned along it;
walls must be strictly vertical;
in the presence of loose soils, the side faces are reinforced with props.

Pillow

An additional layer is formed as follows:

geotextile is laid out at the bottom of the channels, the edges of which must exceed the calculated height of the sand cushion;
layer-by-layer dressing of crushed stone and coarse sand is carried out;
each layer is moistened and compacted;
the height of the substrate depends on the type of soil: if it is sandy and sandy soils, 20 cm is enough; on clays and loams, the layer should reach 50 cm;
between the casting and the pillow, it is better to install a layer of waterproofing.

formwork

The structure is set up like this:

boards are a continuation of the walls of the trench;
fixation is carried out using self-tapping screws or nails, preventing them from entering the formwork, which can complicate further dismantling;
the system is fixed with props with a step of 600 mm;
markings are applied to the formwork, which regulates the level of pouring concrete. Control is carried out by the building level.

Reinforcement

If the height of the shallow foundation exceeds 30 cm, the reinforcement is laid in several layers. When fixing wire and rods, welding is not recommended. Corrosion-resistant zones appear in such areas, the system loses its tensile strength.

Sequencing:

rods are cut in longitudinal and cross sections and assembled into a lattice using wire knitting;
all joints and corners are reinforced with perpendicular rods, which will ensure tensile strength.

The reinforcing mesh can be laid on the starting layer, which is 30% of the height of the structure. This will help protect the metal from moisture and create a level surface for placement.

fill

Concrete must be poured in a uniform layer, otherwise vertical seams will appear, weakening the base:

the base layer is evenly distributed over the formwork. To remove air voids, the mass is pierced in several places with a probe;
each subsequent level is poured until the previous one sets;
the last fill layer is aligned to the markup using the rule;
with the help of a sieve, the base is sprinkled with dry cement, which eliminates cracking during drying and leads to a stronger setting.

Reinforced concrete matures for about 28 days which depends on weather conditions. When light objects are being erected, work on the formation of walls can begin after 14-15 days. If the creation of a brick house is meant, the ripening period must be completely exhausted.

What brand of concrete is needed for the blind area

The formwork is removed after 6-7 days. Further, the casting is processed with bituminous mastic, the sinuses from the formwork are covered with sand, compacted and a blind area is constructed. The work is carried out on the basis of concrete grade M200 and higher, but it will also cost more. To prepare the mixture, you can take 3.7 parts of crushed stone, 1 part of M300 cement, 1.9 parts of sand.

Price

The cost of concrete depends on the brand of cement used: the higher it is, the more expensive the material will cost. M300 concrete, the cost of which starts at 3800/cube, is optimally suited for strip structures. The remaining costs are added up based on the area of the base, the cost of additives, reinforcement, formwork. The price range for arranging a strip foundation varies from 2800 to 7000 r / m².

How to practically make a foundation for a house from concrete of a given brand and what kind of reinforcement is needed for a strip foundation? - about this in the video:

The basis of a reliable home is a solid foundation, and the strength of the foundation is largely determined by the sufficient margin of safety of concrete, as well as its other characteristics: frost resistance, and at a high level of groundwater - water permeability. In order for the house to stand for a long time and without problems, you need a correctly calculated brand of concrete for the foundation. What it is and how to define it will be discussed further.

The composition of concrete for the foundation

Astringent. Most often it is cement (Portland cement). There is also non-cement concrete, but it is not used for foundations.
Placeholders:
- sand;
- rubble or gravel.
Water.

The brand of concrete is determined by the proportions of all these components, as well as the conditions of its hardening (setting). Optimal conditions for concrete to gain strength are created at a temperature of +20°C. Under such conditions, the process is very active in the first 7 days. During this time, concrete gains about 50% strength. With these parameters, it is already possible to continue construction further. The design strength, which is taken as 100% during design, is gained under such conditions in 28-30 days. In reality, the process continues further, but at a very slow speed. The strength gained after 30 days is not taken into account anywhere - it goes "to the reserve".

When the temperature drops, the setting time increases significantly (at +15°C it takes about 14 days to reach 50% strength). At a temperature of +5°C, the process practically stops, and under such conditions, winter concrete is already needed - with appropriate additives and / or measures to increase the temperature (wrap, heat in a mixer, use heating through the formwork or heat directly by attaching heating cables to the formwork from the inside ).

Cement

Various types of Portland cement are used to make concrete. The most common are:

Any of these types of binder can be used to prepare concrete. Only you will need to take into account the setting time of the mortar - you need to lay and vibrate it before the start of hardening.

Placeholders

Aggregates also affect the quality of concrete. It is necessary to adhere not only to the recommended proportions, but also to quality indicators - moisture and granularity.

Sand

Depending on the size of the grains, the following types of sand are distinguished:

For backfilling, mainly large and medium are used, less often - small. The sand must be clean - not contain any foreign inclusions - roots, stones, plant debris, pieces of clay. Even the content of dust and silt is standardized - they should not be more than 5%. If you decide to “mine” the sand yourself, check the amount of contaminants.

To test 200 cu. centimeters of sand are poured into a half-liter container (jar, bottle), filled with water. After a minute and a half, the water is drained, poured again and the sand is shaken. The procedure is repeated until the water is clear. If there are 185-190 cubic meters of sand left. cm, it can be used - its dust content does not exceed 5%.

You need to pay attention to the moisture content of the sand. All proportions are based on dry ingredients. Even dry and loose sand has a moisture content of at least 1%, ordinary - 5%, wet - 10%. This must be taken into account when dosing water.

Crushed stone and gravel

Crushed stone is obtained by crushing rocks. Depending on the size of the fragments, the following fractions are distinguished:

For the preparation of concrete, several fractions are used - so the distribution of crushed stone by volume is more uniform, and strength increases. The size of the largest fragments is normalized: it should not be more than 1/3 of the smallest size of the structure. In relation to foundations, the distance between the reinforcement bars is taken into account. SNiP also determines the amount of small gravel: it must be at least 1/3 of the total volume.

Gravel has approximately the same fractions and sizes, but when using it, the water-cement ratio (water / cement or w / c) increases by 0.05 (5% more water needs to be poured).

Water

For the preparation and watering of concrete, drinking water is used. Including the one that can be drunk after boiling. Sea water can be used with Portland and alumina cement. Any other technical water is not suitable.

Brand of concrete and its choice of strength

Depending on the characteristics of concrete, it is divided into compression classes and their corresponding grades. This correspondence is shown in the table.

Compressive strength class of concrete	Compressive strength of concrete kg/cm2	The closest brand of concrete in terms of strength
AT 5	65.5	M75
B7.5	98.2	M 100
B10	131.0	M 150
B 12.5	163.7	M 150
B15	196.5	M 200
B20	261.9	M 250
B22.5	294.4	M 300
B25	327.4	M 350
B30	392.9	M 400
B35	458.4	M450
B40	523.5	M 500

The compressive strength of concrete is determined during testing. This parameter reflects the load that this concrete can endure without signs of destruction during prolonged exposure. According to this characteristic, concrete is selected depending on the load that the house will create (it depends primarily on the weight of the walls and ceilings, but a lot of factors are also taken into account, including snow loads).

When designing the foundation and determining its dimensions, the load from the building is calculated. This figure is one of the brand selection parameters. Find in the middle column of the table a value close to the calculated load and determine the brand.

Grade of concrete for the foundation, depending on the materials of the walls and soils

Projects and calculations are not always carried out. During the construction of dachas or baths, developers prefer not to spend money, and develop the structures themselves. And although there are many brands of concrete, in private housing construction, three are mainly used for the foundation:

Still need to make adjustments, taking into account the type of soil under the foundation and the level of groundwater. If the soils are sandy or rocky, and the water is below the freezing depth, then all recommendations remain valid. If the groundwater level is high and the soils are heaving, the concrete grade is taken a step higher: the conditions are more difficult and a larger margin of safety is required.

Selection based on the type of foundation

Other characteristics

In addition to the main characteristic - strength, concrete has a number of other indicators that can affect the choice of grade under special construction or operating conditions.

As for workability, it affects how comfortable you will be with the mortar. For foundations, concrete with characteristic P2 is most often used (with frequent reinforcement, P3 is used). It is permissible to use P1 with the obligatory treatment with a vibrator for concrete - it settles the solution well, making it more homogeneous.

Type of one-story house	Slightly loose soil	Fluffy soil
Panel, frame house	M-200 (P3 F100 W4)	M-250 (P3 F150 W4)
House made of timber and logs	M-250 (P3 F150 W4)	M-300 (P3 F150 W6)
House made of aerated concrete, foam concrete, expanded clay concrete	M-300 (P3 F150 W6)	M-350 (P3 F200 W8)
Brick, monolithic house	M-350 (P3 F200 W8)	M-400 (P3 F200 W8)

Remember that when building a two-story house, the concrete grade increases by one step from those shown in the table.

Proportions of components for concrete

In the formulations of the preparation of concrete are given by weight or volume. Moreover, cement is always taken as 1, and all other components are taken in relation to it. Proportions for commonly used brands are shown in the table.

As you can see, the same concrete can be obtained using different brands of cement. What it is, fall asleep like that, only adhering to the recommended mass (or volume) fractions. Basically, when pouring foundations, Portland cement M400 and M500 are used. When composing the mixture, remember that if gravel is used instead of crushed stone, 0.05 more water is added.

How to decipher table instructions? For example, let's take the Grade of concrete M250, it will be made of Portland cement M400. Let's focus on mass. Then select the corresponding row in the third column: 1/2.1/3.9. This means that for one kilogram of M400 cement, we take 2.1 kg of crushed stone and 3.9 kg of sand. The amount of water can be taken from the table below - it is 0.65 kg for crushed stone backfill.

If we make the same concrete, focusing on volume, for example, a 10-liter bucket, then we take the proportions from the fourth column: 10/19/34. This means that for 1 bucket of cement, we put 1.9 buckets of sand, 3.4 buckets of crushed stone. The water/cement ratio remains the same: 0.65 pails.

The proportions of concrete per cubic meter. The mass of the components is indicated in kilograms, parts are given in brackets.

Another table summarizes the data on the consumption of M400 and M500 cement per cubic meter of the most popular concrete grades in the construction of the foundation.

The right brand of concrete for the foundation is the key to its strength. But high-quality compositions are very expensive. If, according to all the above recommendations, you need to use the M300 and higher, it is better to order, which will confirm or refute your assumptions. The cost of this service is about $100-150, and it can save thousands if you need a lower brand.

Any building will serve for a long time if the builders have laid a quality foundation -. And its strength, in turn, is directly dependent on the properties of the building materials used.

Most individual buildings are built on monolithic structures.

In private construction, several types of foundations are used:

- for brick and block one-two-story houses;
- for frame-type and wooden houses;
- for the construction of massive buildings and other buildings erected on soft soils.

Since the choice of the type of foundation is influenced by two factors - the mass of the above-ground part and the condition of the soil, we can say that they are decisive when choosing a brand of concrete.

In the general case, you can be guided by the following rule: the brand of concrete for the foundation of a house, designed in the form of a monolithic tape, is taken lower than for a pile.

Influence of the state of the soil on the choice of brand of concrete mix

Without having a conclusion on the characteristics of the soil at the construction site, it is impossible to correctly determine what kind of concrete is needed for the foundation of the house ().

If we focus only on the weight of the above-ground part of the building, we can draw the following conclusion:

M150 - quite a suitable brand of concrete for the foundation of a house made of foam concrete (one-story);
M200 - will withstand a one-two-story () building with light ceilings;
M300 and M250 - able to carry a large load from multi-storey cottages;
M350 and above - reasonably used only in the construction of high-rise buildings.

However, all these statements are true only when the house is built on rocky or sandy soil. If the developer encounters clays or loams, the situation changes dramatically.

What brand of concrete for the foundation of the house should be used so that it is not squeezed up? A monolithic tape for a light frame house will have to be erected from a mixture of M250. And if the walls are planned to be made of brick, then concrete must be chosen not lower than M300.

Groundwater has a great influence on the durability of the underground part of the building. With their high level, it is desirable to use concrete of high grades with good water resistance.

How to calculate the volume of concrete mix

Brands of concrete under the foundation of the house do not affect its consumption. The amount of the mixture is calculated based on the geometric dimensions of the structure.

There are several simple formulas that can be used to easily calculate how much ready-made concrete will be needed for pouring.

Strip foundation

The calculation of the need for concrete in this case comes down to calculating the volume of the tape ().

We denote the foundation parameter as follows:

a is the length of the building;
b - the width of the building to the inner perimeter;
d is the width of the tape;
h is the height of the tape.

So, the volume of the monolith V = 2d x h (a+b)

In the presence of internal load-bearing walls, the volume of these sections of the foundation is calculated in the same way. The results obtained are summarized.

slab

The volume of a monolithic slab is calculated by multiplying three values:

length;
width;
height.

Columnar

The volume of a round post can be calculated using the formula:

V = (3.14D 2 /4) x H, where

D is the column diameter;

H is its height.

The volume of a rectangular or square support is determined as follows:

V = a x b x H, where

a is the width of the support section;

b is the section length;

H is the height of the column.

In all cases, the resulting volume must be increased by 10% (that is, multiplied by a factor of 1.1). Thus, you will insure yourself in case of unforeseen circumstances.

How to prepare concrete of the desired grade

Private developers do not always buy ready-made mixtures of factory production. It is more convenient for them to prepare concrete directly at the construction site: it is cheaper and more in line with the pace of individual construction ().

So, you have decided on the brand of concrete for the foundation of the house. Now you need to choose the right proportions of the components of the concrete mixture. All concretes, regardless of brand, are prepared on the basis of cement grades M400 or M500.

For example, consider the preparation of concrete M250.

If you decide to use M400 cement, then the proportions of the mixture will be as follows:

cement - 1 kg;
sand - 2.1 kg;
crushed stone - 3.9 kg;
water - 0.56 kg.

The total output of one portion of concrete will be 7.56 kg.

It is worth replacing the M400 cement with M500, and the proportions will change:

more sand will be required - 2.6 kg;
the amount of crushed stone will also increase - up to 4.5 kg;
more will have to be poured in and water - 0.64 kg.

At the output, you will receive 8.74 kg of concrete mix. The difference in the price of cement of the above brands is small - it is 10-20 rubles for a fifty-kilogram bag. Do not be lazy, calculate the cost of raw materials in both cases. This way you will understand which option will cost less.

But first you need to calculate how much raw materials you need. This is done simply: the volume of the foundation structure is multiplied by the specific gravity of the concrete, and the result is divided by the total mass of one portion of the mixture. Now you just have to multiply the amount of each component by the number of servings received.

The density of concrete mixtures is different. If, according to calculations, you need a brand of concrete M250 for the foundation of a one-story house, its density is 2348 kg / cu. m. A cubic meter M350 weighs 2502 kg.

Although builders often operate with an average density of concrete equal to 2400 kg / cu. m.

All calculations are rounded up. Thus, the amount of concrete shrinkage is compensated - it is unrealistic to calculate it on your own. When buying ready-mixed concrete, you can use the shrinkage factor specified by the manufacturer.

Pay attention to water quality. The fluid must not contain oils or biological impurities. So a stagnant swamp is not suitable as a source of water for concrete preparation. It is best to use ordinary drinking water for kneading.

How to determine the brand of concrete without the help of a laboratory

How to check which brand of concrete for the foundation of a private house you received? To check the quality of the concrete mix, there is a special device - a sclerometer.

But it is unlikely that you will rush to buy it, since it costs 11-35 thousand rubles. You can make samples and send them to the laboratory, but this pleasure also significantly hits the pocket.

It remains to use home methods. First, take a close look at the concrete mix. The higher its quality, the bluer the tint. If there is a yellowish tint in the cement milk, it can be concluded that the concrete contains clay impurities or slag additives. The thicker the milk, the higher the brand of concrete.

Now try to explore the pre-made concrete cube. Prepare a hammer weighing 400-800 g and a chisel. Place a chisel against the surface of the cube and hit it with a hammer. The impact force should be medium.

If you managed to drive the tip of the chisel to a depth of 1 cm or more, you got concrete M 75, 0.5 cm - M150. A small dent indicates that the brand of concrete for the foundation of a wooden house is quite suitable - it is in the range of M200-250. If, after the impact, only a small mark remains, you managed to prepare high-quality concrete of the M350 brand.

Conclusion

Asking what kind of concrete is needed for the foundation of a one-story house, a private developer must have accurate information about the soils on his site, the total mass of the building, snow and wind loads in a given climatic zone.

But in any case, experts advise sticking to the golden mean: do not use concrete of high grades (above M350) and low grades (below M200). The first - because there will be unreasonably high costs for the construction of the foundation, the second - based on considerations of reliability and durability of the building.

Concrete grades below M200 can only be used for the construction of low-responsibility structures - fences, sites for the installation of household equipment, gazebos or small cabins.

Video about what kind of concrete is needed for the foundation.

During the construction of a private house, in most cases, a monolithic strip foundation is structurally adopted. It consists of a reinforcing cage and concrete. The choice of both components is approached through engineering calculations, however, when building cottages, this stage is often skipped. Nevertheless, there are rules and recommendations on which brand of concrete to choose for the strip foundation of a private house, as well as for pouring the grillage of a pile or column base, we will describe further.

What determines the brand of concrete

Every concrete mix contains:

cement is the main binding component;
sand - fine binder;
crushed stone enhances the strength of the finished stone;
water.

The brand is an indicator of the maximum load on the test sample, measured in kgf / cm 2, that is, the ultimate strength of the structure without a margin. The brand is influenced by the proportions of the components used, to a greater extent this value is determined by the amount and brand of binder. In most cases, Portland cement is used for mixing, sometimes Portland slag cement.

In order to save expensive cement, if necessary, strengthen the concrete, plasticizer additives are used:

water repellents (for foundations serving in conditions of high soil moisture or in the presence of groundwater);
hardening accelerators for rapid construction;
plasticizers to increase grade strength reduce cement consumption when obtaining concrete of the desired grade without loss of quality.

There are also additives that prolong the life of the solution, sealants and other additives, but they do not always affect the brand.

Along with the brand, builders use the concept of concrete class - this is an indicator with a margin of safety. The brand and class values are interrelated, so the marking for structures in projects is mainly paired:

The use of concrete in the construction of foundations

To carry out the stages of foundation construction, you will need different grades of concrete:

M75 and M100 are the so-called "weak" concretes of low strength. Their use is possible when installing an underlying cushion under the foundation.
M150 - a solution of a more durable stone than M100. This can be used as a foundation for light structures - a small porch, a fence, a greenhouse. M150 is suitable for arranging garden paths and laying platforms for a car (filling the floor in a garage, a place under a canopy, an entrance to the site).
M200 is taken for arranging structural elements of a house that do not take significant constant loads (stairs, blind areas, entrance groups, porches of varying complexity), grillage and tape can be poured with mortar under one-story lightweight frame-type houses.
M300 is actually the most versatile type of concrete used in private construction. It is suitable for pouring the foundation body, manufacturing prefabricated structures, monolithic construction of a two-story and three-story cottage, laying a reliable paving on the site.
M350 and M400 are high-strength concretes, they are used mainly for the manufacture of precast hollow-core slabs, crossbars and some floor beams. This material can be used in the construction of cottages in earthquake-prone regions, it is preferred by lovers of high reliability and durability for centuries.
M500 and above are practically not used in private housing construction due to the high cost and inappropriate use. These are special-purpose concretes for the construction of bank vaults, hydraulic and complex structures and other objects of increased responsibility and complexity.

Thus, for the construction of one foundation, it may be necessary to manufacture several types of concrete solutions (cushion, tape body).

But this does not mean that you have to purchase different cement.

What kind of cement is needed

As already mentioned, the grade of concrete is affected by the grade of cement or its concentration. To calculate the required amount of material for the purchase, we present the conditional dependence of these values in the table:

For convenience, these values can be taken as unity. For example, you need to get concrete M200, take 0.55 parts (from the whole) of cement M300 and take it as a unit.

Preparation of concrete solution

When the required brand of concrete has been determined and a sufficient amount of cement has been purchased, it is possible to start mixing the solution.

To prepare the working mixture, in addition to cement and water, you will need sand and crushed stone. Next, you need to calculate the volumes of these components. For convenience, here is a table with concrete formulas:

It is more convenient to consider the cubic capacity of the finished solution not in m 3, but to transfer them to buckets. There are about 80-85 twelve-liter buckets in 1 cube. Thus, it is convenient to take the volume of the components if you are going to make the mixture yourself. When ordering concrete from the factory, of course, it is more convenient to count cubic meters and the supplier will deliver exactly the required amount.

Attention to the quality of the components

The number of components taken according to the formula does not guarantee the expected quality of the mixture. The ingredients, as the quality of the finished mortar, must comply with the requirements of GOST 26633-2012 "Concrete heavy and fine-grained."

The cement must be fresh. The closer to the date of manufacture, the better.
Crushed stone should be taken with a large fraction and square flakiness (stones are convex, not flat).
Sand must be clean with a minimum amount of organic impurities. It is optimal to order it at the procurement base, where they produce additional enrichment of its quality.
Certain requirements are also imposed on water: it should not be highly mineralized or polluted. It is optimal to take liquid from the central water supply - its composition is stabilized at water intake stations.

You should also pay attention to the labeling of cement. The substance can be pure (D0) or with additives, the amount of which is indicated in percent (D20). Also, cements with additives already added can be useful for the foundation:

"PL" - frost-resistant compositions;
"B" - fast-hardening cement;
"GF" - for hydrophobic concrete, resistant to wetting, thermal expansion and temperature changes.

Plasticizer c3 will help save on the amount of cement without losing the quality of the concrete mixture. It increases the strength of the stone and improves the plasticity of the mixture, frost resistance. It must be added according to the instructions.

As you know, the durability and strength of any structure depends on the quality of the foundation on which it is based. In private construction, as a rule, 3 types of structures are used, these are columnar or pile, slab and the most common tape, which we will talk about. The brand of concrete for the strip foundation of a private house is the most important indicator of its quality.

What is strip foundation

The tape type of foundation structures is considered the most common.

It is a reinforced concrete strip buried in the ground and passing in a closed loop under all load-bearing walls and piers of the building.

Instructions for arranging this type of structure is not very difficult. A trench is dug, a reinforcing iron frame is laid in it, and all this is poured with liquid concrete.
But, despite the seeming simplicity, perhaps the most difficult moment here is the correct determination of which brand of concrete to use for the strip foundation. This choice is influenced by a number of factors.

What factors influence the choice of brand composition

Unfortunately, there are no universal recipes, the price is not always a fundamental factor. After all, even expensive formulations have their own recommendations and restrictions on use.

Dependence on the weight of the building

If you want to build a house with your own hands, but you do not have a ready-made project with written recommendations, then, first of all, you should pay attention to the total weight of the building. This is the first indicator from which they start when choosing a brand of composition.

A prefabricated panel house with a height of 2 floors, in most of our country, will comfortably stand on a reinforced concrete foundation, filled with the M200 brand.
For 2 - 3-storey log buildings, as well as for houses built of foam concrete, gas silicate blocks or other cellular concrete, grades M200 - M300 are recommended.
For heavy, capital buildings built of brick, cast concrete structures or other heavy materials, it is recommended to use a grade of M300 and higher.

Soil characteristics

Much depends on the geology of the soils in a given area, their composition and how deep the groundwater is.

The most favorable are sandstones and rocks. They can be poured concrete M200 - M250.

Clay soils and loams are a rather big problem. The fact is that these soils are prone to heaving when freezing. That is, they do not freeze evenly and are able to squeeze out a shallow-buried strip foundation in some places, which leads to a general deformation.
In this case, you can do it in two ways.

First, to deepen the structure to a level exceeding the average total soil freezing in the region.
Secondly, it is possible to equip a tape-column, well-reinforced foundation. This is when at key points they are poured to a considerable depth, which stabilize the entire structure.

If we talk about what brand of concrete is needed for a strip foundation laid on clay, then experts recommend taking a brand an order of magnitude higher, approximately M250 - M300.

Important: it should also be noted that starting from the M200 grade, if necessary, cutting of reinforced concrete with diamond wheels is already used, and diamond drilling of holes in concrete is used for deepening.

Common brands of concrete

In the production of concrete of different grades for foundations, cement M 400 is most often used, but in different proportions.

M100 - used as an underlayment in the construction of roads, laying deep foundations or pouring floor screed.
M200 - suitable for shallow foundations based on stable soils. They fill basements and all sorts of open areas.
M250 - used for casting fences, various kinds of stairs and strip-column structures.
M300 - is considered the most popular brand for pouring the foundation. It is successfully poured into the vast majority of known foundation structures, and can be used in a humid environment.
M400 - used for pouring underwater structures, bridges and other capital structures. It is applied to construction of houses in extreme conditions.
M500 - used for pouring sheer structures, repairing roads and structures, or as an additive.

Important: the quality and strength of concrete is greatly influenced by the so-called shrinkage coefficient - the lower it is, the stronger the structure will be.
You can lower it with the help of special additives.
When using vibrators, more rigid and dry compositions can be poured.

What else is worth paying attention to

There is also a marking characterizing the strength class of the hardened composition. It is denoted by the letter "B", characterizes the margin of compressive strength and is measured in megapascals.

Important: The strength of concrete can change over time.
Active curing takes place within 28 days from the moment of pouring.
Further, these processes slow down significantly, but do not stop.

The level of strength and brand of concrete indicators are related.
According to GOST, each brand of concrete corresponds to its own, here are some key indicators:

B7.5 corresponds to M100
B15 corresponds to M200
B20 corresponds to M250
B22.5 corresponds to M300
B25, B27.5 correspond to M350
B30 corresponds to M400
B35 corresponds to M450

For our country, the frost resistance indicator is also relevant, it is marked with the letter "F" and a certain number after it. The number indicates how many times the structure can freeze through. For more of the country's territory, F200 is enough, the more thaws in winter, the higher this figure.
It is also worth paying attention to the indicator of resistance to high humidity. It is indicated by the letter "W" and the number after it.

Conclusion

It is worth considering the fact that the higher the class, quality and of course the price of concrete, the faster it will set. Experts advise pouring high-quality compositions within 1 day. Accordingly, it will be problematic to quickly fill such a foundation with your own hands, so it is better to resort to the services of construction companies. You can find more information in the posted video in this article.