What crushed stone is needed for the foundation of a house: choice of material, recommendations for use

The foundation is the element that is actually built first. A lot depends on him. If the roof becomes leaky or even collapses, it can be restored; If the walls are cracked, they can also be rebuilt on the same foundation. But a foundation that doesn’t hold up can force you to build everything from the very beginning. Therefore, everything is important here, and this applies not only to calculations, but also to correctly selected material and even its components.

Typically, this structure is built from concrete. To prepare it you need cement, sand, water and coarse aggregate. The role of the latter is often played by crushed stone. It is he who increases the strength of the foundation, therefore, as you understand, his choice should not be any. What kind of crushed stone is needed for a concrete foundation? Let's talk about this.

Contents of technical characteristics of crushed stone

About the meaning of purity

The purity of materials for a crushed stone foundation is one of the parameters of its high quality. Foreign inclusions get into it. When choosing a material, you need to familiarize yourself with the product quality certificate, which shows the percentage of inclusions. Crushed stone should not have impurities (more than the norm allowed by the standard) that provoke corrosion. It is unacceptable for inclusions harmful to its strength to get into the solution:

• phosphorites, chlorites, apatites;
• shale, coal, acids;
• asbestos fibers.

The presence of inclusions is allowed in the standard volume. They cannot occupy more than 0.1 to 15%. Their content above this indicator destroys the concrete monolith.

What you need to know about the flakiness of crushed stone

This parameter gives an idea of ​​the relationship between stones of different shapes. There are 4 main varieties:

• cubic grains;
• acute-angled;
• wedge-shaped;
• flaky.

Flakiness indicates the presence of lamellar and needle-like fragments. The higher the percentage of flakiness, the lower the quality of the crushed stone. Cuboid stones are considered the most durable. Concrete made from them has a uniform high density. When constructing a housing foundation, granite stone is used. According to the flakiness, crushed stone has the following varieties:

1. The first of them consists of cube-shaped grains used for the base of buildings.
2. The second group, which contains 10-15% of other types of material, is also suitable for these purposes.

Group 3 - limestone rocks, including 15-50% substandard crushed stone. Stones have weak adhesion, so they are not suitable for constructing the foundation of buildings. It is acceptable to use them under a cushion and for a foundation made of crushed stone, the flaky fraction of which is 25-35% of inferior material. Stones belonging to groups 1 and 2 are most suitable for making the base of buildings.

About the influence of frost resistance

The measurement of frost resistance is the number of cycles of complete freezing and thawing of the stone without loss of technical qualities. It is designated by the letter “F” (from English “frost” or frost). Crushed stone made from various materials has the following frost resistance parameters:

• from limestone – F25÷F100;
• concrete – F50÷F75;
• slag – F75÷F200;
• gravel – F200÷F300;
• granite – F300÷F400.

For the foundation of houses, crushed stone is used, the frost resistance coefficient of which is F250-300.

Crushed stone strength grades

Varieties of material have a strength grade, established by determining the coefficient of high loads, abrasion, pressure, crushing:

• M200 - crushed stone of very low strength;
• M300 and M600 - low strength;
• M600 and M800 - medium strength;
• M800 and M1200 - optimal strength;
• M1200 and M1400 - high strength.

The pillow is made on the basis of the M800 brand. It is recommended to pour the foundation with the M1200 grade of stone.

About the factionality of crushed stone

The stones are fractionated during sifting. Before deciding which fraction of crushed stone is needed for the foundation of a house, it is advisable to familiarize yourself with its types:

1. The European standard material, calculated in millimeters, has fractions: 3÷8, 5÷10, 10÷15, 15÷20, 20÷40, 40÷80.
2. Crushed stone with non-standard shapes, ordered by the consumer.

For the construction of the base of buildings, the optimal fractions will be: 5 -10 mm, 10 -20 mm and 20-40 mm.

Classification

Crushed stone can be different. But it will not be possible to consider it from one point of view, because many of its components are important. And, in order to create a real strong foundation from crushed stone, you need to pay attention to:

1. Material . The pebbles that strengthen the base are made from different materials. In one case, crushed stone may not be strong enough, in another you will simply overpay;
2. Frost resistance . This is a very important point, since concrete must withstand low temperatures;
3. Strength. I think comments will be superfluous here;
4. Faction. Knowledge about size will also not be superfluous. For example, in order not to choose a non-standard crushed stone fraction;
5. Flakiness. This interesting word also plays an important role. Thus, stones of the wrong flakiness can cause voids to appear in concrete.

As you can see, there are a lot of points. And in order to build a foundation, they must be taken into account, because correctly selected crushed stone, due to its characteristics, will reliably strengthen the structure, and unsuitable stones will simply ruin it. Well, in order not to make a mistake in our choice, we will consider all these points in more detail.

By material

Crushed stone is, in fact, stones that are not obtained from a single specific rock. Based on origin, the material is divided into:

1. Granite.
2. Gravel.
3. Limestone.
4. Slag.
5. Secondary.

The most durable is the granite type. However, you should not immediately pay attention to it. Yes, it is just right for heavy, large-scale houses.

But, if you are building a small one-story building, such crushed stone will simply be of no use, since the loads will be small, but the cost of the material is high.

In such cases, it is best to choose the gravel option, which is both cheaper and quite durable.

In addition to residential buildings, other buildings such as sheds, car garages or gazebos can be erected in the yard. Limestone crushed stone is well suited for them, the strength of which is lower than gravel, as is, in fact, the price.

Particular attention should be paid to waterproofing here, since limestone tends to wash out.

You can also use the slag type, which is obtained by crushing blast furnace waste.

True, its strength varies greatly, so it is also suitable for residential buildings. But the secondary analogue is not suitable here, since its strength reaches only medium. True, for a fence that has a foundation, it is quite enough, especially since the cost of such stones is quite low (for example, a granite analogue costs twice as much).

According to frost resistance

Quite an important characteristic of crushed stone, especially for places with harsh climates. What does this frost resistance mean? This is the ability to freeze and thaw a certain number of times without serious loss of quality. To achieve this, crushed stone undergoes freezing and thawing processes.

The minimum frost resistance of crushed stone is F50, the maximum is F400 (in increments of 50). What crushed stone will be optimal for foundation concrete? The answer is simple: one that can withstand at least 300 cycles. Be sure to pay attention to this parameter, otherwise a stone with less durability will ruin your foundation.

By strength

Any base supports a structure, be it a fence wall with columns and a roof. Therefore, concrete always receives a certain load that it must withstand. In other words, the material must be strong enough. And crushed stone, as we have already mentioned, ensures this indicator at the proper level.

The strength of crushed stone has several levels, as a result of which the stone is assigned one of the following grades:

1. High strength (M 1200 - M 1400).
2. Durable (M 800 - M 1200).
3. Medium strength (M 600 - M 800).
4. Low strength (M 300 - M 600).
5. Very weak strength (M 200).

To build the foundation of a residential building, you need to use particles of a grade of at least M 1200. That is why limestone stones are not suitable for these purposes, because their maximum grade is M 800, and their frost resistance also only reaches F150. And the secondary analogue does not have any strength above average.

By faction

This word refers to the average grain size. Crushed stone fractions are as follows:

1. Fine grain (from 3 x 8 to 5 x 20 mm). Such stones are used for the manufacture of various concrete structures (for example, reinforced concrete slabs).
2. Medium grain (from 20 x 40 to 25 x 60 mm). It is also used to create reinforced concrete structures. Foundations are also included.
3. Coarse grain (from 20 x 70 to 40 x 70 mm). Such stones are also part of the foundations, but of heavy and industrial buildings.

There is another type of crushed stone, namely a non-standard fraction (for example, 70 x 120 mm). It is not suitable for foundations, and in fact it is not used in construction.

But this stone has found its place in landscape decoration. The same applies to small particles measuring 3 x 8. If you, for example, want to sprinkle a path, crushed stone of this fraction is quite suitable.

What stone is chosen for the foundation? The optimal sizes are 5 - 10 mm, 10 - 20 mm and (probably especially) 20 - 40 mm. It all depends on which part of the material will be used. We will also talk about this later.

By flakiness

This beautiful word denotes the percentage of flake stones present in the overall crushed stone composition.

In general, you need to choose cube-shaped stones for the foundation. But flat and oblong ones are undesirable. They are called flaky.

Such crushed stone complicates compaction; this results in too many voids, which results in more binder material being consumed.

Of course, you are unlikely to be able to use only cube-shaped crushed stone. The best option involves the presence of 10 percent flakier stones. Such crushed stone belongs to the first group of flakiness, called cuboid. The second - improved - contains from 10 to 15% of such components. The last three groups are called ordinary, each of which contains up to 25, 25 and, finally, 50% flakier particles. Of course, it is not recommended to use such compositions.

Which crushed stone is best for the foundation?

Crushed stone is a bulk material made from stones of different sizes, widely used in modern construction. Due to its good adhesion to concrete, crushed stone of different fractions is used as a filler when pouring concrete and reinforced concrete structures, monolithic sections and foundations.

This allows you to significantly increase the strength of structural elements of buildings and structures.

Therefore, if you are planning to build a bathhouse, garage or house on a country plot, you should know what crushed stone has its characteristics and how to choose exactly the material that is best suited for construction, providing the necessary strength and durability, but will not require you to large financial costs

Let's figure out which crushed stone is best to use for the foundation, for the foundation pad, for concrete preparation for a slab foundation and for pouring the blind area.

Blind area and monolithic foundation

And if you need to equip a blind area, then what kind of crushed stone should be poured under the foundation and under the blind area? It must be a building material of one fraction, and the remaining requirements for crushed stone of the blind area are minimal, since there is no soil pressure on its surface. Therefore, crushed limestone is the best cheap option, but if granite or gravel crushed stone has already been purchased, the quality of the blind area will only improve.

Granite cube-shaped crushed stone of grade M 900-M 1200, with a grain size of 20-40 mm and a flakiness of ≤ 10%, is used as a concrete aggregate for a monolithic base. Such crushed stone will make the structure as durable as possible. Crushed gravel has a smoother surface, so its adhesion to concrete mortar will be worse. Crushed stone grade M 900-M 1200 can also be used in the manufacture of FBS (wall foundation blocks). In addition to foundation blocks made from heavy concrete grades, for the construction of a prefabricated foundation based on blocks or slabs, it is allowed to use expanded clay concrete building blocks or cinder blocks with a filler made not of crushed stone, but of expanded clay or slag.

General recommendations for choosing crushed stone

Once the required strength, frost resistance and degree of flakiness have been determined, you need to pay attention to a number of properties. The high-strength material has increased radioactivity, unlike crushed stone M600

Ideally, it is recommended to check the delivered lot using radiometric instruments

The high-strength material has increased radioactivity, unlike M600 crushed stone. Ideally, it is recommended to check the delivered lot using radiometric instruments.

Visually assess the quality of the crushed stone surface. For the foundation, the best material is a cube-shaped rough material with a pronounced ribbed structure.

Builders often make the mistake of using river gravel instead of high-quality building materials. This solution has quite good strength, a low percentage of crushed stone and flakier grains. However, the main disadvantage of the material is its perfectly smooth surface. As a result, it will not be possible to achieve good contact of the binder with the building material in question.

But if you can’t purchase cube-shaped material, then you can pay attention to mountain gravel, which has sufficient grain roughness

It is important to remember that crushed stone grains in concrete form a macroframework, which bears the main load from the building, while cement and sand play the role of void filler and fastening agent

It is important to remember that crushed stone grains in the concrete form a macroframework, which bears the main load from the building, while cement and sand play the role of void filler and fastening agent. To summarize the article, we note that the choice of crushed stone must be made based on the scale of the project being built

The material fraction is also determined depending on the project requirements. In most cases, it is recommended to use cube-shaped crushed stone as the highest quality material

To summarize the article, we note that the choice of crushed stone must be made based on the scale of the project being built. The material fraction is also determined depending on the project requirements. In most cases, it is recommended to use cube-shaped crushed stone as the highest quality material.

Tips for using crushed stone in the construction of a foundation structure

Now you understand that choosing crushed stone for making concrete mortar for the foundation is not as trivial as it might seem at first glance. To choose it correctly, you need to take into account a serious list of characteristics. But that's not all.

In order for the house to stand for decades and not create problems, it is necessary to pour a good foundation for it. And for this you will have to take into account some points that are usually associated with the specifics of building a private house.

1. If your plans are to build a stone house with thick walls and powerful ceilings, then to form the foundation you will need granite crushed stone of the highest quality.
2. If it is decided to erect a lightweight structure on the site, then a concrete solution mixed with lime crushed stone is suitable for the foundation structure.
3. If the concrete will be mixed by hand, then you should not add large material to it. The optimal granule size should be within 20 mm.
4. If a mesh with small cells is used as a reinforced frame for the foundation, then the crushed stone fraction should be smaller than the size of these cells.
5. For the foundation cushion, crushed stone of medium strength is suitable, which is filled with a thickness of at least 30 cm and must be compacted.

Crushed stone for the foundation

Therefore, different crushed stones are also used for the foundation. Therefore, it is impossible to say unambiguously which crushed stone is best to purchase for the foundation.

Footing

To fill the foundation, preparation for it is often used. This is done in order to prevent the leakage of moisture and cement laitance. Sometimes its role is played by a layer of crushed stone filled with liquid bitumen, and sometimes by a “footing”, that is, a 10-centimeter concrete layer.

When calculating sand and crushed stone, the choice of stone is made. In the case of “concrete footing”, fine crushed stone of a fraction of 10 - 20 mm is used. But with the option using bitumen, the crushed stone fraction for a concrete foundation can be 40 - 70 mm. Although the above-mentioned small particles are also used here. That is, choosing crushed stone for the foundation in this case will be easier.

Sealing pad

This is the first layer from which everything begins. When choosing a material for backfilling a foundation (sand or crushed stone), as a rule, they settle on both, since a sand bed, although it will be cheaper, will not be as durable. This is especially true in cases where the soil is weak-bearing. Thus, the construction of a pillow under the foundation includes two materials, each of which plays an important role.

Sand for the pillow is suitable from a quarry; its size should be about 2.2 - 2.5 mm. But the crushed stone fraction in this layer should be medium-grained (for example, 20 x 40). Strength is also important - it should not be less than average (that is, M 600). Crushed limestone is not used in such pillows because it is prone to shrinkage.

Blind area

This element is made along the entire perimeter of the foundation to prevent moisture from approaching

In this design, it is important to make a good drainage system, for which crushed stone and sand are used

For the blind area, you can purchase both recycled and limestone crushed stone. The building is not being erected on it, so it will not experience large loads. The fraction may be fine-grained: such stones are easier to compact than larger ones.

Preparing the soil for the foundation - general rules

Numerous types of soil, as well as various weather conditions, influence the composition and technology of laying the foundation. For accurate calculations in construction, a number of rules, formulas and reference values ​​are used to determine the required parameters of the materials and work used. In addition, when constructing buildings, they are guided by GOST standards for building crushed stone.

The foundation is never installed on black soil. Even during the construction of non-critical buildings (shower stall, toilet or storage room for equipment), a foundation located on top of black soil will cause a dangerous distortion of the entire structure in a few years. The fertile and unstable layer of soil is small in thickness - up to 30-50 cm. Removing it manually is not difficult, but it will reliably protect you from negative consequences. The surface of the foundation pit or trench must be horizontal. The reason lies not only in the excess consumption of materials when leveling the slope, but also in the strength gradient of the resulting substrate. In its thinnest place, defects are most likely to occur. To prevent the transition of sand from the bottom of the substrate into clay, it is desirable to use geotextile materials. The time interval between excavation and laying of the foundation should not be prolonged. Otherwise, the work will be hindered by the soil, which constantly rolls into a pit or trench when it dries. The compaction of the cushion under the foundation should be done using a special vibrating plate, also called a “vibrating heel”. After compaction, you can walk on the crushed stone bed without disturbing the surface.

Types of crushed stone

The main division of crushed stone is as follows:

• natural material;
• artificial material (recycled).

A regulatory document that includes the classification of crushed stone and gravel is GOST 8267-93*. Based on it, the following division of natural material can be given:

• from igneous and metamorphic rocks;
• from sedimentary rocks;
• from gravel (obtained by crushing mountain gravel) and gravel (natural origin);
• from boulders.

Natural crushed stone

It is made by crushing durable rocks. Depending on the raw materials for production, there are:

Granite (from metamorphic rocks). It is one of the most durable. Made from natural granite by crushing. Provides the concrete mixture with high performance parameters. The grade of crushed granite is in the range of 1200-1400, and in terms of frost resistance, the material can withstand up to 400 cycles of alternating freezing and thawing (that is, theoretically, the service life can be up to 400 years). Such crushed stone is used in the production of concrete mixtures for especially critical structures. The disadvantage is the highest cost compared to other types of coarse aggregate.

Granite crushed stone is the strongest, but very expensive.

Gravel. To make it, gravel is crushed, which is mined in two ways: quarrying and from the bottom of rivers. At the bottom, gravel is part of the sand-gravel mixture, so it is cleaned before use. If you answer the question, which crushed stone is better for the foundation, then the answer will be gravel as the best option. For buildings with a normal level of responsibility, there is no point in spending large sums on materials with increased strength: the loads during operation are negligible compared to those that granite can withstand. In addition, gravel material benefits in terms of cost.

Crushed gravel is the most suitable.

Limestone (from sedimentary rocks). Used for low-rise private construction. Has low strength and cost

When used for foundations, it is important to know that limestone dissolves with water over time. If you still decide to use it, you need to take care of reliable waterproofing of the foundation

Limestone crushed stone is highly undesirable to use for foundations.

Advice! Sometimes it can be difficult to understand the concepts of crushed stone and gravel. It must be remembered that crushed stone has a more uneven shape with torn edges, since it is produced by crushing by human forces. Gravel is the result of many years of natural destruction of rocks, so its surface has a smoother shape. Crushed stone is more suitable for concrete, because... its uneven edges have better adhesion to the solution.

Artificial crushed stone

Produced by crushing:

• concrete;
• bricks;
• foam concrete;
• slag.

Artificial crushed stone from construction and production waste.

The advantages include accessibility and the lowest cost. Disadvantage: dubious origin. The buyer cannot say with certainty that the material is safe. When producing crushed stone from industrial waste, GOST “Crushed stone and sand from slags of ferrous and non-ferrous metallurgy for concrete” and GOST “Crushed stone and sand from slags of thermal power plants for concrete” are also followed.

Brands and strength classes

Concrete is marked with the letters M and V. M is a grade of material that indicates the average load per square centimeter that a given sample can withstand when compressed until complete destruction.

In construction, grades from M100 to M500 are mainly used:

1. M400-M500 is concrete used for the construction of bridges, tunnels, hydraulic structures and other large objects with increased strength requirements.
2. M400 is a material intended for industrial construction and the construction of foundations for low-rise buildings on wet and soft soils.
3. M350 – used in the construction of swimming pools, multi-storey buildings, and various high-rise structures.
4. M300 - used in the creation of reinforced concrete structures, as well as for the arrangement of road slabs and staircases.
5. M200 – concrete for private construction. Used for the construction of light foundations and interior work.
6. M100 is an auxiliary material used for preparing the foundation base, arranging drainage drains, and thin screeds.

B is the concrete class. It indicates the actual compressive load that the species can withstand.

The strength class is determined by destroying a cube of hardened concrete with a side of 15 cm using a special press.

Brand and class are not the same thing. But each class has a grade that is as close as possible in strength. This is shown in the table:

The brand and class of concrete - what are the differences, the video will tell you:

Frost resistance

This indicator is marked with the letter F. It determines how much freezing and thawing concrete can overcome without suffering more than 5% destruction.

Different brands of concrete can undergo from 30 to 300 freezing cycles.

Waterproof

The letter W is used to indicate water resistance. It shows how much water pressure a concrete coating can withstand without allowing water to pass through the pores.

To determine the compliance of water resistance and frost resistance of concrete with grades and classes, a special table is used:

Indicators of workability of the solution

Workability is the ability of concrete to fill the mold evenly when poured and, after compaction, to form a homogeneous dense mass.

There are three classes of concrete for workability:

• P – spreading mixtures;
• P – mobile;
• F - hard.

Within each class there is a division according to the degree of manifestation of characteristics. Thus, spreading mixtures are divided into categories from P1 to P6. The higher the indicator, the higher the ability of the material to self-fill the mold without compaction by vibration.

Mobility is indicated by the letter P. There are 5 degrees of mobility of concrete. Mobility is determined by placing concrete in a mold with a cone with a height of 30 cm, a lower diameter of 30 cm and an upper diameter of 10 cm.

The higher the number, the greater the mobility. After removing the cone, the concrete gradually loses its shape. The degree of shrinkage of the mold determines the mobility of the mixture.

Depending on how mobile the mixture is, its purpose is determined:

Fractional description

Crushed stone is a loose, granular building material obtained mainly through the process of crushing rocks. The crushed stone fraction is the size of the grains of this building material. Fractions are divided into small, medium, large. Small fractions include crushed stone of the following sizes (mm):

• 3 x 8 (European standard);
• 5 x 10;
• 10 x 20;
• 5 x 20.

Scheme of a crushed stone foundation.

Fine fractions are used for the production of concrete, concrete structures, floor slabs, and bridge decks in the construction of bridges.

Average fractions (mm):

• 20 x 40;
• 25 x 60.

The scope of application of medium fractions is the production of concrete and reinforced concrete products, the construction of roads, railways, tram tracks, laying foundations, and the construction of industrial facilities.

Large fractions (mm):

• 20 x 70;
• 40 x 70.

Area of ​​use: construction of industrial buildings, construction of large-scale reinforced concrete structures, construction of bridges.

Non-standard fractions (mm):

• 70 x 120;
• 120 x 150;
• 150 x 300.

Building materials of non-standard fractions are used extremely rarely. Scope of application – decor: finishing of ponds, fences, swimming pools, plinths, etc.

Granite and gravel seeds, which are smaller in size than Eurocrushed stone, are also used for decorative purposes (for landscape design needs) and for sprinkling paths and platforms.

Size of fractions.

Which fraction of crushed stone is better for the foundation of a house?
The size of crushed stone fractions may also differ; the bulk product is divided into several types:

1. Fine – grain size 3×8, 5×10, 10×20, 5×20. This type is considered a European standard, therefore it is used by builders when constructing concrete slabs, floors, walls and bridges.
2. Medium – 20×40, 25×60. The most popular option among most owners of private houses when arranging the foundation. The foundation will support reinforced concrete buildings, railway tracks and powerful production workshops.
3. Large – has a size of 20×70, 40×70. Suitable for powerful structures with heavy weight.
4. Non-standard view – 70×120, 120×150, 150×300. Professionals prefer this crushed stone when finishing swimming pools, the basement of a house, and fences.

Choose a medium fraction for the foundation of a private house; fine is suitable only if the construction involves a small object in a seismically stable region with groundwater running underground at a considerable depth.

Material of origin crushed stone

The properties of crushed stone vary depending on the material of origin

Almost all other criteria for evaluating the material depend on which mineral is the basis of the rock of origin. It is customary to divide the filler:

1. Granite. Characterized by the highest levels of mechanical strength. Obtained by processing rocks.
2. Gravel. There are 2 types: crushed and natural. It is rarely used in the construction of concrete foundations. Usually used for making blind areas.
3. Dolomite. The forming rock is limestone. It has weak strength and a low level of frost resistance. Not used in foundations.
4. Slag. A product of processing waste from blast furnaces. Used as a filler for concrete bases.
5. Secondary. It is obtained in the process of processing obsolete or low-quality crushed concrete products. The most economical type of filler. According to building codes, the material is allowed to be used when filling foundations for one-story buildings in areas with stable soils.

Documents regulating the quality of bulk materials

To equip a foundation cushion, you must use only crushed stone that complies with building codes and regulations. State standards regulate the selection of other bulk materials.

Main regulatory documents:

1. GOST 8267-93 - determines the characteristics of crushed stone from rocks;
2. GOST 8267-87 – characterizes crushed stone for a natural stone foundation;
3. GOST 32495-2013 - describes bulk materials from crushed concrete.

The documents contain all the necessary information about crushed stone and other bulk materials used in construction. The permissible amount of impurities is taken into account, and methods for controlling the quality of the product and its acceptance are described.

There are other standards that regulate the use of crushed stone. But many documents are difficult for the average person to perceive, since professional terminology was used to write them. But you can find a simpler decoding of the standards.

Peculiarities

Crushed stone is one of the most common fillers for concrete mixtures, without which no modern construction of a house or other facility can be completed. This building material has many classifications and is endowed with different characteristics and features, on which the quality of the future construction, the strength of the concrete, and the strength of the foundation directly depend. Despite its low cost as a building material, crushed stone combines all the qualities that are irreplaceable in construction.

Crushed stone has the following features:

• high degree of strength - when compared with all fillers for concrete mixtures, the most durable of all types of crushed stone is granite material;
• moisture resistance - crushed stone does not react to moisture at all;

• excellent tolerance to temperature changes - frost and heat, as well as resistance to environmental influences. Crushed stone can withstand up to three hundred changes in temperature cycles;
• high adhesion - thanks to the rough surface and acute angular shape, the adhesion of the material to concrete is significantly enhanced;
• reduction of settlement and creep of concrete, which minimizes the occurrence of cracks and various types of deformations in the constructed building;
• ease of use;
• high performance properties.

In addition, due to the variety of types of crushed stone, you can always choose the one that suits not only its technical characteristics, but also its cost.

High-quality crushed stone must be selected based on the following technical characteristics:

• Flakiness is a characteristic of the flatness of a material. In total, crushed stone has 4 categories of flakiness: rounded, cuboidal, improved and normal;
• degree of strength - the stronger the material, the better. Two types of crushed stone are endowed with the highest strength indicators: granite and gravel;
• Radioactivity is an important characteristic that depends on the deposit of the building material. High-quality crushed stone is certified for radioactivity. This indicator does not affect the strength of the material, however, the level of environmental friendliness depends on it;
• frost resistance - this characteristic indicates the number of seasons that a foundation made of a given material will withstand. According to the level of frost resistance, crushed stone can be divided into stable, unstable and highly resistant;
• compaction coefficient - the density of crushed stone ranges from 1.2 to 3 g/cm³. This coefficient depends on the type of origin of the material. Crushed stone with a high degree of density is universal and has an unlimited scope of application. The density and strength of this building material are directly proportional.

Adviсe

When purchasing gravel, be sure to find out as much as possible about all the properties listed above; for greater confidence, ask for any documentary evidence of the seller’s words. Otherwise, you may be deceived. It is also best to purchase from today’s popular construction stores, since they will not risk their reputation because of one buyer and will most likely show you the necessary documentation. If possible, carefully examine the packaging material of the bag where the crushed stone is poured. Detailed characteristics and composition are often written there.

Selection of crushed stone

All necessary recommendations for selection are given in GOST 8267-93* and SP “Load-bearing and enclosing structures” (hereinafter GOST and SP). It is required to consider each selection criterion separately.

Purity and radioactivity

These requirements will affect not only the reliability of the foundation structure, but also its safety. Compliance must be checked especially carefully when using recycled crushed stone from construction and industrial waste. The content of dust and clay particles, as well as clay in lumps, is given in tables 9 and 10 of GOST.

According to paragraph 4.8 of GOST, material extracted and manufactured by any method must be resistant to decay of any kind, negative environmental influences and the effects of alkalis. Resistance to decay must satisfy Table 11 of GOST, which shows the maximum percentage of mass loss during decay for materials of various grades of crushability.

In addition, a radiation-hygienic assessment is mandatory. Based on its results, the possibility of application for the construction of residential buildings is determined. The total specific effective activity of natural radionuclides should not exceed 370 Bq/kg.

Fraction and brand

Crushed stone of various fractions.

An important factor in the construction of foundations will be the particle size of the coarse aggregate. The requirements of the joint venture can be summarized in one table:

You also need to correctly select the grade of material for strength, depending on the required grade of concrete. Concrete grades higher than B25 are rarely used for foundations, since this is not economically viable.

A competent choice of aggregate for concrete will ensure its high strength and reliability of foundations.

Which is better: crushed stone or gravel or other material

Crushed stone is used in drainage systems to form a drainage layer, the equipment of which can be made using various materials, each with its own advantages and disadvantages:

Crushed stone and gravel. Photos of Soil Trucks

Gravel is a material obtained naturally from rocks, most often it has a smooth surface, and as a result does not retain dirt well in drainage. This drawback can be eliminated through additional crushing, but this requires special equipment. The main advantage of gravel is its low cost, the disadvantage is that the strength of the material is lower than that of some high-strength types of crushed stone: basalt, granite, diorite.

Screenings are a by-product of crushed stone production; the grain size does not exceed 10 mm. Small fractions of screenings can be washed away by water. As a result, over time, the drainage layer becomes thinner and performs its own functions worse. Therefore, it is recommended to use the material to fill the outer layer around the pipe.

Sand visually resembles screenings and has a similar disadvantage: it can be washed away by water and poorly perform its own function. Filtration properties depend on particle size, presence and percentage of clay impurities. In drainages, it is recommended to use sand together with fine crushed stone or screenings.

Expanded clay is a material produced artificially by firing clay. It has a porous structure and low weight, has sufficiently high strength, allows water to pass through well and performs filtration. Recommended for use in septic tanks and sewer drains.

Rocky soil (or rocky soil) is a material obtained through the natural or artificial destruction of rock masses; as a result, collapsible or explosive soils are distinguished. The characteristics of the material, in particular frost resistance and strength, depend on the type of rock.

Dropout 0-10. Photos of Soil Trucks

As disadvantages of the soil, it is possible to note the heterogeneous grain composition, as well as contamination with clay or loam. As a result, water absorption increases and the filtration coefficient decreases. The advantage over crushed stone is the lower cost of soil. And it is possible to get rid of impurities; the material must be sifted or washed; doing this with your own hands will not be difficult.

SGS (sand-gravel mixture) is a building material that is a mixture containing sand and gravel. There are two types of ASG: natural and enriched. The former often contains clay impurities, so it is not best suited for drainage. Enriched ASG with crushed gravel grains, coarse sand and a clay content of no more than 3% performs an excellent filtration function, and is also sold at a low cost, so it is suitable for a drainage layer.

PShchS is a complex material of natural origin, which is a mixture of sand and crushed stone of different fractions. The mixture contains practically no particles or lumps of clay, the surface of the grains is rough. The cost of PShchS is lower than that of crushed stone, and its characteristics are superior to ASG.

Recently, drainage systems without crushed stone, in which the natural material is replaced by polystyrene foam or polystyrene foam, have been of great interest. This technology has several advantages over traditional solutions using bulk materials.

PShchS granite. Photos of Soil Trucks

As a result, the choice depends on the client’s budget and the role of the material in the drainage system. However, despite the variety of materials, crushed stone is still in high demand, as it successfully performs several functions.

How to make a pillow

First, the trench or pit is lined with river sand, preferably coarse, 10-15 cm thick. There are no organic inclusions in it, which eliminates the processes of decay.

The sand should completely cover the bottom of the pit. The surface is leveled and compacted. To prevent the soil from mixing with the sand layer and being washed out by groundwater, a substrate is made of geotextile or roofing felt.

A crushed stone layer up to 20-25 cm high is laid on top of the sand. The greater the load of the building on the base, the thicker the substrate is made. The crushed stone is leveled and compacted with a special roller or vibrating plate. Compaction is required to eliminate voids and ensure a tighter fit of components to each other. The ideal density of the finished pillow is from 1.6 t/m³.

The bedding is poured and compacted until its surface is located at the level of the edge of the pit.

The covering is made with mortar and cement 15-20 cm thick from the ground level. If there is an area with nearby groundwater, it is better to increase the height of the crushed stone layer. During installation, constantly check the evenness of the surface and correct flaws in a timely manner. The reinforcement cage helps to strengthen the foundation.

Filling device

Before laying the foundation for a house, many actions are performed that precede a serious process, the so-called preparation. At the same time, it is necessary to comply with all norms and rules in order to avoid future distortions of window and door frames, the appearance of cracks on the walls and drafts. The key to a quality foundation is bedding.

To carry it out, it is necessary to use high-quality building materials that have the following features:

• are not heaving;
• do not lose properties due to temperature changes;
• perform drainage functions during compaction;
• do not contain flammable impurities.

As a rule, the bedding (pillow) is made from a building mixture, which includes concrete, sand, and crushed stone. The thickness of such a pillow can be from 25 cm to 60 cm. The bedding can be sand, or it can be made of crushed stone. The sand option is budget-friendly and quite common.

The technology for constructing a crushed stone lining (pillow) should be carried out by observing the following steps:

• a trench is dug, the bottom of which is covered with fine crushed stone or coarse river sand. The layer should be 10–15 cm;
• further, there is a layer of crushed stone. According to SNiP, compacted crushed stone or a thin layer of concrete is needed, in which cement makes up at least five percent. The thickness of such a layer is 20–25 cm;
• The crushed stone is well leveled and compacted using a vibrating saw. All free space must be eliminated. The addition of crushed stone should reach the level of the edge of the trench. It is from this mark that the foundation will begin.

A sand cushion is the best option for people who are short on funds allocated for the foundation. It is made using coarse sand. Before backfilling, it is necessary to cover the bottom of the trench with roofing felt or geotextile to prevent sand from mixing with the soil. In this procedure, dense compaction is also important, which can easily be done using a roller. After careful preparation and creation of the cushion, the foundation slab is laid.

Frost resistance of the material

Under existing conditions, it must be borne in mind that low temperatures can have an extremely negative impact on the condition of the foundation. In this case, we need to use frost-resistant crushed stone. As for the immediate essence of this characteristic, we are talking about the freezing/thawing cycles of the material. If the crushed stone is truly frost-resistant, then even dozens of such cycles will not affect its condition in any way.

In this situation, there are also grades of crushed stone, the minimum is f15, and the maximum is f400. Again, granite crushed stone has a high level of frost resistance, so it is more advisable to purchase it for owners working on creating a structure in Eastern Europe, as well as the central and eastern parts of Russia. In these areas, extremely low temperatures can turn into heat waves in record time. Accordingly, excellent frost resistance is required from crushed stone here. You can choose some average value (by brand of material), and this will be the best solution.

If in your region the temperature remains virtually unchanged throughout the year, then the issue of frost resistance fades into the background. In this situation, you can safely take any crushed stone that meets all the requirements in construction in terms of strength.

Concrete base

The most expensive and reliable type of underlying layer. A concrete pad can even be used for the foundations of apartment buildings. The technology for its implementation is quite simple and accessible for independent work. The process consists of several stages:

• leveling the bottom of the excavation;
• adding crushed stone with a layer of 10 cm and tamping;
• installation of formwork to the height according to the project;
• waterproofing flooring;
• installation of reinforcement;
• pouring concrete mortar;
• gaining monolith design strength;
• dismantling formwork.

To ensure strong adhesion of the base to the foundation, steel rods protruding above the surface are installed in the cushion. They serve as connecting anchors, maximizing the strength of the underground structure.

Fraction and amount of crushed stone

Scheme of crushed stone production.

To lay the base of a residential building, it is most preferable to use granite crushed stone of a medium fraction of 20 x 40 mm, cube-shaped. The use of just such a building material will ensure a high compaction density of the filler and the absence of air inclusions. Consequently, concrete will have high strength, reliability, and durability. In seismically inactive areas, areas characterized by deep groundwater, the use of fine fractions for laying the foundations of small houses is common.

Gravel has high strength characteristics. It can also be used in the construction of small buildings. The preferred particle size is 20 x 40 mm.

To lay a monolithic foundation, it is necessary to prepare a mixture of crushed stone, cement, river sand, and water. Cement is the binding material, crushed stone and sand are the fillers. The amount of crushed stone and other building materials needed to lay a solid foundation must be calculated based on the following ratio: for 1 part of cement you need 3 parts of sand, 1.5 parts of water, 5 parts of crushed stone.

The information collected here will be useful in the future not only for laying the foundation of a building, because we are talking about a very popular building material with a wide range of applications.

Flakiness indicators

A specific characteristic is the flakiness of the crushed stone. It determines the amount of stone of different shapes as a percentage. You need to know what fraction and size of crushed stone for the foundation is used for a private house.

Common forms of crushed stone:

• Cuboid version;
• Sharp stone;
• Wedge-shaped;
• Flaky.

Typically, grains are divided into flat and sharp. In sharp versions, the length exceeds the width, and in flat ones, vice versa. The lower the flakiness, the better the quality of the material. The strongest fragments have a cuboid shape. It is this sand and crushed stone that is recommended to be used for the foundation.

The best flakiness is observed in granite crushed stone. It is from such crushed stone that the most durable material with the correct shape is obtained, which is suitable for pouring the base.

BEST CHOICE – CRUSHED GRAVEL

Usually, when making a foundation, it is important to use crushed gravel. It is quite durable and expensive compared to granite crushed stone. But if you plan to build a heavy and large object, for example, a residential building, then the best option would be to use expensive granite crushed stone. And if you are planning light buildings, such as garages, gazebos, sheds, then an excellent, suitable option would be to use inexpensive limestone crushed stone.

The most important advantage inherent in crushed gravel is its significantly low radioactive background. Other materials are inferior to it in this regard.

If we talk about flakiness, then this criterion measures the flatness of the elements. Crushed stone will be compacted better if the largest number of pebbles have a shape that is close to cuboid. But if the material contains the largest number of needle-shaped and plate-shaped stones, then in the process of mixing concrete for building a foundation, cement costs will increase significantly.

Specifications

What crushed stone is needed for the foundation is determined based on the main characteristics of individual batches.

Strength

Based on the results of laboratory tests, which are carried out for each large batch, crushed stone is assigned a strength grade:

• M1200…M1400 – high strength;
• M800...M1200 – durable;
• M600...M800 – medium strength;
• M300...M600 – weak strength;
• M200 and less – very weak strength.

Frost resistance

The ability to maintain properties under conditions of temperature changes, in particular destructive frosts. Frost resistance of crushed stone of different types:

• Gravel – F15…F200;
• Granite – F300 and more;
• Limestone – F25…F

For crushed stone cushions and pouring foundation walls, especially those located above the soil freezing level (in shallow strip foundations, in columnar structures), stones with a frost resistance index of at least F200 are required.

Fraction

During production, crushed stone is sorted by grain size into groups:

Flakiness

The shape of the stones plays no less important than the strength indicator and fraction - the ability of crushed stone to adhere to concrete mortar depends on the flakiness.

Conventionally, screening can be divided into 3 groups according to the form of the constituent components:

• cuboid is the best solution for filling concrete mixture. It is evenly distributed in volume and provides uniform adhesion to concrete. The name “cuboid” does not mean that all stones in the screening are cube-shaped. The definition hides the convex shape of the stones;
• improved - this is crushed stone, into the batch of which a cubic type of filler has been artificially added to improve the general properties of the material;
• the usual one is a mixture of stones of different shapes and qualities. The flatter the individual elements, the worse the adhesion and load distribution. In addition, when mixing flaky crushed stone, voids may form in concrete, which is extremely undesirable for critical load-bearing structures.

Radioactive background

Mined rocks may have a radioactive background, especially granite. Background is measured in Bq/kg (becquerel per kilogram); for residential buildings, stones of no more than 370 Bq/kg can be used.

Summarizing

Crushed stone is not the only material used when arranging a cushion under the base of a building. Lightweight structures with strip foundations can be erected on an inexpensive sand base. Capital multi-storey and other objects require the installation of an expensive concrete pad.

In private housing construction, both in terms of price and quality, the best choice would be either a substrate made entirely of crushed stone or a substrate combined with sand. The main thing is to use the correct fraction of bulk material, carry out high-quality leveling and compaction, and maintain the thickness of the layers being constructed, taking into account the maximum level of groundwater rise.

When is concrete preparation required?

The footing is a layer of thin cement laid between a layer of gravel or crushed stone and the body of the foundation. As a rule, the thickness of the pillow does not exceed 1 dm.

Thanks to it, the building rests securely on a stable foundation. This is what is most lacking in these situations:

• loose soils;
• existence of seismic hazard;
• close proximity to slopes, slopes and embankments;
• high compressive load from the building.

In addition to the basic purpose - a strong support for the structure - foundation preparation facilitates many stages of the process:

1. Installation of prefabricated structures on a leveled surface is more convenient, and the results are accurate.
2. High-grade concrete is consumed more economically when it is laid out on a flat, compacted base made of cheap material.
3. On concrete it is easier to install a frame of reinforcement with maximum precision to make a monolithic foundation. A crushed stone cushion will not give such an accurate result.
4. A special coating is created that prevents the penetration of moisture.
5. Protection of concrete from loss of grade due to leakage of cement laitance, complete hydration of binder grains.

Advantages and disadvantages of sand bedding

This bedding has an affordable price; it is often used when they want to save on materials.
Waterproofing can be laid on it without damaging the integrity of the carpet. It can be used for buildings that do not carry a large load (one-story buildings, bathhouses, barns, and so on). But it is washed away by water, so a drainage layer is provided for it. Thus, if the groundwater level is below the base of the foundation, then sand backfill can be used. Since when swelling this material turns into a shapeless mass and its design resistance to construction decreases. This is one of its shortcomings.

But there is also a feedback here: the sand swells evenly and with a sharp increase in the groundwater level, the base of the building will also begin to rise evenly without distortion of the building. With the correct construction of a sand cushion, it performs all the functions assigned to it.

We recommend watching a video on how to properly use sand to fill the base.

Watch this video on YouTube