Each developer knows what building materials are used to build a house or a bath. In this case, it would be useful to ask what kind of sand is needed for the foundation? And who wondered why this ingredient is better than the other?
Sand as fine aggregate
Mixing sand-cement mortar Everyone knows the components of concrete, where one of the components is sand. What is its feature? Is it better to replace or do without it?
The fact is that cement acts as an astringent in concrete, which, in interaction with water, seizes and hardens. In this case, the deformation of the volume occurs - shrinkage, accompanied by internal stress and the occurrence of cracks. In order to avoid these phenomena, aggregates are added to the cement - sand, crushed stone and others, which level out internal deformations, reduce shrinkage, and increase the strength of concrete. The flowability and density of sand allow it to fill voids and hold together crushed stone, which is the basis of concrete.
Classification of fine aggregates
- natural sand;
- sand from crushing screenings.
It is they that are used as a fine aggregate for the production of concrete, mortars, the manufacture of dry mixes, etc. And if the first type does not need explanations, then the second type is the same bulk material, but it is obtained during the development of rocks, from enrichment waste iron ore and other ores.
All technical and quality indicators of fine aggregate are regulated by GOST 8736-93. It applies to sand with a grain density of 2000 to 2800 kg/m3.
By quality, this bulk material is divided into classes I and II and its criteria are:
- grain composition;
- the content of dust and clay particles;
- mineralogical and petrographic composition;
- radiation-hygienic characteristics.
By grain size, sand is divided into groups from “very coarse” (over 3.5) to “very fine” (up to 0.7). When calibrating, sieves of different cell sizes are used.
The mineralogical and petrographic composition is established during the geological exploration of the deposit and is indicated by the sand manufacturer in the quality certificate, as well as all other indicators.
Depending on the radionuclide contamination, the use of sand is delimited:
- for housing and civil construction;
- construction of industrial buildings and roads within the city limits;
- for road construction outside settlements.
Types of sand
Natural sand, depending on the origin, is quarry, river and sea.
Career
Mining takes place in open pit mines. In addition to organic, it contains many other impurities and inclusions. Washing and screening is always required. The grains are quite large. The cheapest price.
River
This material originates from the riverbed mainly by hydromechanical means. It is much cleaner than quarry and without impurities, but sifting is carried out, and sometimes washing. The grain composition is smaller.
Nautical
It is extracted from the seabed and the grain composition is similar to river sand. Undergoing cleaning. Due to the high costs of this mining method, it is the most expensive of the sands.
When choosing sand, attention should be paid to the grain composition and purity from impurities.
Fine aggregate requirements
There is one more moment to find out which sand for the foundation is better. This will make it possible to make knowledge of the requirements for fine aggregate in the production of concrete, which are contained in GOST 26633-91. In the video you will see how to choose the right sand for construction.
According to clause 1.6.11 of this GOST, the choice of fine aggregate is made according to technical and quality indicators (considered above in GOST 8736-93). Specific figures are given in clause 1.6.12, where the lower limit of sand size is indicated - 1.5 and the upper limit - 3.25. Now we can confidently say that the following groups of sands are used for the production of concrete:
- small 1.5–2.0 mm;
- average 2.0–2.5 mm;
- large 2.5–3.0 mm.
Ingredients for mixing the solution Moreover, if the grain composition does not correspond to the specified parameters, then a coarsening additive is applied to fine and very fine sands - coarse sand, and vice versa: to coarse sand - an additive that reduces fineness.
In concrete grades M50, M100, the use of very fine sands is allowed.
The conclusion is simple. Sand is a consumer product, a construction material that meets certain standards and is subject to control. Its use in construction is indispensable.
If we talk about residential and industrial housing construction, then the origin of the sand does not matter for the construction of the foundation.
And that's why:
- Compaction of concrete occurs with the help of vibrators.
- Chemical additives are used to improve the properties of concrete, and special aggregates are used to reduce cement consumption.
- The workability of concrete mixtures is regulated by the addition of plasticizers.
Although even without this, the quality of the foundation will not suffer.
Which is better: career or river
As for individual construction, the load on the foundation is disproportionately lower here. The use of a group of fine sands is not capable of violating the integrity of the foundation. Consequences are possible in case of inconsistency of soils, violation of technology or non-compliance with proportions. In the video you will see how to properly mix the mortar with cement and sand.
And yet there is one caveat in answering the question of quarry or river sand is better for the foundation. The trick is that the grains of river sand have a rounded shape, the grains of quarry sand are rough faceted. Rounded grains fill voids in crushed stone faster and more densely, so concrete mixed on river sand settles immediately and shrinks less than on quarry sand.
Conclusion! The best choice for the foundation is washed river sand.
In modern construction, sand is used very actively and almost everywhere. At the same time, there are about 10 different varieties of this material, but in the practice of Russian builders, two types are most common: quarry and river. Naturally, each type has those properties that determine its advantages and disadvantages as a building or finishing material. Therefore, non-professionals who decide to build some kind of structure on their own often face a choice:
Quarry sand - advantages and disadvantages
Quarry is called sand, mined in quarries, from huge layers located at a certain depth underground. The quality of such sand is largely determined by its origin. The fact is that such underground sand is formed as a result of weathering of rocks. This process has been going on for centuries, decay products are deposited underground, eventually turning into caked masses of sand.
The formation of sand deposits results from the weathering of rocks such as mica, quartz, feldspar and partly limestone. The composition and characteristics of the sand depend on which rocks prevail in a particular area.
What must be taken into account when deciding which sand is better than quarry or river sand is the possible presence of impurities in the total mass of natural material. Clay contamination for quarry sands is a common phenomenon and only the concentration of foreign matter differs depending on the deposit.
Another important characteristic is the heterogeneity of fractions. In the mass of quarry sand, there are both very small and very large particles, often fragments come across in it, which, in terms of size, can be attributed to fine gravel. However, in the case of using sand for construction purposes, this property cannot be called a minus. The fact is that the heterogeneity of sand fractions and the presence of various impurities in it causes higher binding characteristics of sand.
So let's sum it up. Quarry sand is characterized by increased surface roughness of the particles, as well as the angularity of their shape.. This makes it excellent for use as an additional bonding agent for binders in mortars. There are also construction areas in which it is recommended to use quarry sand. It makes an excellent pillow for a deepened strip foundation. From this point of view, no other variety can be compared with quarry sand.
River sand - pros and cons
Now let's look at the main characteristics and properties of river sand in order to try to answer the question of which sand is better than quarry or river sand by comparison. River sand, as its name suggests, is mined from riverbeds. This circumstance is due to extremely low content of various impurities in it especially clay rocks and loams. They are simply washed away by the current, which provides natural cleaning of the sand.
Also, the constant exposure to water to which river sand is exposed leads to the fact that it the particles are approximately the same size and almost perfectly rounded shape. Due to this, this material is actively used in landscape design to create the desired decorative effect.
One of the advantages of the material is the fact that for the arrangement of children's sandboxes or volleyball courts, it is imperative to use river sand.
If we talk about construction, then the main properties of river sand, in addition to shape and size, should be recognized as a low ability to absorb and retain moisture, as well as environmental cleanliness and safety.
Given all this, river sand is used mainly for decorative finishing materials. For example, if it is planned to arrange a cement screed on the floor in the house, then river sand is better suited for these purposes. It will not accumulate moisture in itself, and will also help to obtain a more even and smooth surface of the coating.
For the same reasons, river sand is the preferred material for making paving slabs. In Krasnoyarsk, it is also used in the construction of drainage and filtering systems.
In fact, the only, but very significant minus of river sand as a building material is high price. The process of its extraction is associated with the use of complex expensive equipment; special barges and powerful hydraulic pumps are required to lift rock layers from the bottom of the channel and subsequently flush it. As a result, the cost of the final product is very high.
It is precisely because of the significant cost that when deciding which sand is better than quarry or river sand, builders often prefer the first. The issue of price becomes especially relevant when carrying out rough construction work, for example, arranging the foundation, creating open areas for cars, etc. But for finishing work, especially internal, it is recommended not to save and choose river sand, the use of which provides a better result.
Our company is engaged in retail and wholesale deliveries of river and quarry sand in Krasnoyarsk. For more information and ordering delivery, call the phone number listed on the "" page.
You will be interested in the following materials:
Looking at a pile of sand brought to the site, two builders will behave differently.
The newcomer will cast an indifferent glance at her and take up the shovel.
An experienced builder will first pick up a handful of sand, look at it carefully and rub it in his palms. After that, he will issue a verdict: it is suitable for concrete, but it will not work for plaster and masonry.
What is the secret of construction sand, which requires such a careful assessment? We will analyze this issue in more detail.
Physical and mechanical characteristics
Volume weight
It shows the mass of 1 m3 of sand in its natural state (wet, with all impurities). On average, the volumetric weight of this material is from 1500 to 1800 kg.
The composition of building sand is evaluated according to the following parameters:
- Granulometric;
- Mineral;
- Chemical.
Granulometric shows the percentage of grains of different sizes. To determine it, the sand is sieved through calibrated sieves (from 0.16 mm to 10 mm).
A sieve with a hole size of 5 and 10 mm reveals gravel granules. GOST allows the presence of grains 1 cm in size. At the same time, their number should be no more than 0.5% of the total mass of sand.
Granules larger than 5 mm are normalized in this way:
- The maximum content is up to 10% in natural;
- up to 15% in crushed;
- up to 5% in enriched sand.
Mineral composition
Chemical composition
It plays an important role in determining the suitability of bulk material in various areas of construction. Red, yellow, and orange shades indicate the presence of oxidized metals. Green and blue colors are characteristic of river sand, which contains aluminum salts.
Types of building sand
The classical definition says that sand is a mixture of mineral particles (quartz, mica, limestone) formed as a result of natural or artificial destruction of rocks.
"On the shelves" the most important properties of sand are laid out by GOST 8736-93. According to this standard, sand is divided into two classes:
- I class - very large, then comes sand of increased size, large, medium and fine;
- Class II - very large, oversized, large, medium, small, very small, thin and very thin.
The main difference between these classes is that lower quality sand (second class) includes three additional fractions. Fine dusty particles are an undesirable component of mortars. They impair the bond between the large sand granules that the cement binds.
In real production there is no such fine gradation.
Here, the extracted sand is conditionally divided into three fractions:
- 0.5-1 mm - small;
- 1.5-2 mm - medium;
- 2.5-3.5 mm - large.
Sands with a fineness modulus of 2-2.5 mm are used for the production of concrete and reinforced concrete structures. Bulk material with a size of 1.5-2 mm is used for the manufacture of bricks. The finest sand is used for the preparation of dry building mixtures.
Having taken into account the GOST classification, let's move on to the practical aspects of the origin and use of building sand.
According to the type of production, they distinguish:
- Career;
- River;
- Nautical;
- Quartz (artificial) sand.
Career
The name clearly indicates the origin of the sand. Clay and stones are found in it, so quarry material is used to a limited extent: for site planning, pouring under concrete screeds or foundations.
To improve the properties, quarry sand is washed with water right at the place of extraction, freeing it from dust particles and clay. This is how alluvial (washed) sand is obtained. It is suitable for plaster and masonry mortars. In addition, sieving can be used to remove clay.
Important practical conclusion: if you are offered to buy quarry (ravine) sand, do not forget to clarify whether it has been cleaned (washed, screened) or not.
Areas of application for washed (sifted) quarry sand:
- cement screed, masonry and plaster mortars;
- Finishing work;
- brick production;
- foundation device;
- concrete preparation.
river sand
This building material is mined by a dredger from the bottom of the river. River sand contains no clay particles and very few stones. This allows you to use it without restrictions for concrete work.
It is very valuable that river sand of medium size (1.8-2.2 mm) practically does not shrink. Therefore, it is optimally suited for masonry and plastering.
Quarry sand is more difficult to use in this capacity. In the solution, it sits on the bottom and has to be periodically mixed.
Areas of application for river sand:
- concrete production;
- brick production;
- masonry work and cement screed;
- preparation of asphalt concrete;
- drainage device;
- filler for paints and grouts.
Sea sand is similar in properties to river sand. It is also highly valued in the construction industry for its high purity and uniform particle size distribution.
Quartz sand
This material is obtained as a result of mechanical crushing of quartz-containing rocks. It is homogeneous in structure, chemically inert and pure.
The main field of application of this type of sand is the building materials industry. It goes into dry building mixtures, sand-lime bricks, blocks and concrete, and is used to prepare grinding compounds. Landscaping, expensive interior and facade plasters also cannot do without quartz sand.
It is impossible to unequivocally answer the question which sand is better, since each material is designed for certain types of work.
Nevertheless, the main conclusions are already clear:
- for brick and large-block masonry, it is better to take river sand. If you mix it with a small amount of unwashed quarry sand, the solution will become more plastic (due to clay particles);
- coarse or medium river sand is better suited for concrete (you can add a little fine washed quarry sand to it);
- for plaster, washed quarry sand with a small addition of river sand or without it is better.
Estimated prices
Obviously, the cost of sand is the higher, the more manipulations had to be done with it during extraction and cleaning.
The cheapest is quarry unwashed and not seeded. Its price per cube is from 300 to 400 rubles. Quarry sand cleaned with water or sifted for construction work will cost from 550 to 700 rubles per 1 m3 with delivery.
River sand is significantly more expensive than quarry sand. Its price starts from 750 rubles and ends at 950 rubles/m3.
Fractionated quartz sand is the most expensive. When buying from 10 tons (1 KAMAZ), its price with delivery is from 4,500 rubles per cubic meter.
Concrete is made up of sand, cement, gravel and water. Each of these components has its own role both in the manufacture of a concrete structure and in its subsequent operation.
Sand for concrete is a fine aggregate that covers the voids that form between the rubble. It allows you to evenly distribute internal stresses during concrete hardening and reduce the final cost of the mortar by reducing the amount of cement to be kneaded.
The main thing is to take into account all the requirements for preparing the solution, choose those components that are best suited, and observe the appropriate proportions.
Particle size
Bulk material is divided into two classes depending on the particle size: I and II class. As part of a higher quality class I, there are no very small, thin and very thin groups, which are undesirable components for mortars. If they are present, the relationship between larger fractions worsens. Therefore, when preparing the solution, it is better to use class I sand.
Fraction classification
According to GOST 8736-93, in terms of fineness modulus, division can be:
- very large;
- increased size;
- large;
- average;
- small;
- very small;
- thin;
- very thin.
In reality, the division is usually conditional. May be:
- small;
- average;
- large.
To prepare a high-quality durable solution, it is better to use a large fraction. Preferably with a particle size of 2-2.5 mm. With a smaller size, the cost of the prepared solution will increase significantly, and the quality will decrease.
Mining place
The place of extraction has a significant impact on the composition and properties of the material. It is customary to distinguish river, quarry, sea and quartz. Sand is mined in an open pit.
Career
In the quarry there are impurities of clay and stones, so it can be used exclusively as a backfill for foundations or concrete screeds. In the preparation of concrete, quarry sand can only be used after washing with water, carried out at the place of extraction. When performing such an operation, clay and dust particles are removed.
River
River sand initially no longer contains clay. It may contain a minimum of stones. It is actively used in construction work, allowing you to get a better solution. It is distinguished by the ability of natural precipitation, therefore, when preparing the solution, it must be constantly mixed.
It should be borne in mind that the cost of river material is slightly higher than quarry material. When choosing, you should analyze what is better: reducing the cost of manufacturing a concrete structure or ensuring sufficient strength.
Marine and quartz
Marine in its characteristics is close to the river. Differs in purity and uniformity of granulometric structure. May require additional cleaning due to possible shell content.
Quartz is the result of mechanical crushing of rocks containing quartz. Homogeneous, pure and chemically inert. Obtained artificially.
Processing method
Depending on the processing method, there may be:
- alluvial, obtained by washing;
- seeded, obtained by sifting the feedstock to remove large particles and debris.
Specifications
The requirements for sand used in the preparation of concrete are reflected in the relevant regulatory documents. Some characteristics can be checked exclusively in the laboratory, others can be checked directly on the construction site.
Volume weight
An indicator that reflects the mass of 1 m³, which is in its natural state. A cube of wet sand with all impurities weighs on average about 1500 - 1800 kg. The smaller value is preferred.
Compound
The composition may be:
- granulometric, which reflects the ratio (in percent) of grains of different sizes;
- mineral: quartz, dolomite, feldspar and limestone;
- chemical, depending on the elements present in the composition, a possible area of \u200b\u200buse is determined.
Example of particle size distribution:
Example of a chemical composition:
| Sl02 | Al2O3 | Fe203 | Ti02 | CaO | MgO | SO3 | K2O | Na2O | P.P.P. 1000C |
Sum | Content CO2 |
CaCO3 |
| 78,26 | 6,48 | 1,45 | 0,12 | 5,89 | 0,70 | 0,12 | 0,96 | 0,64 | 5,35 | 99,97 | 4,92 | 11,2 |
Mineral composition example:
Humidity
As a rule, this characteristic is equal to 5%. If the mixture is dried, the indicator will decrease to 1%. When moistened by precipitation, the value can increase up to 10%. The amount of water added to the solution at this humidity should be reduced.
Moisture requirements are important, since the amount of water added to the solution depends on it. Humidity is determined by calcining a kilogram of the mixture. The indicator will be equal to the difference in the weight of wet and dried.
At the construction site, the humidity level can be checked as follows. If the sand is compressed into a lump, it will have to crumble. If this does not happen, the humidity is more than 5%. Although this indicator is still better to control in the laboratory.
| Sand volume, cm3 (ml) | Moisture content of sand, %, at the density of sand particles, g/cm3 | ||
| 2,6 | 2,65 | 2,7 | |
| 448 | 2 | 2,9 | 4,1 |
| 450 | 2,6 | 3,5 | 4,7 |
| 452 | 3,3 | 4,2 | 5,3 |
| 454 | 4 | 4,8 | 6 |
| 456 | 4,6 | 5,5 | 6,6 |
| 458 | 5,3 | 6,1 | 7,3 |
| 460 | 5,9 | 6,7 | 8 |
| 462 | 6,5 | 7,4 | 8,6 |
| 464 | 7,2 | 8 | 9,3 |
| 466 | 7,8 | 8,7 | 9,9 |
Porosity coefficient and bulk density
The porosity coefficient reflects the ability of sand and, accordingly, the ability of concrete to pass moisture in the future. Can only be determined in the laboratory.
The average value of bulk density is considered to be 1.3 - 1.9 t / m3. 1.5 t / m3 is considered optimal. A lower value may indicate the presence of undesirable impurities, a higher value may indicate excessive moisture. The necessary information must be written in the accompanying documents.
Which one to give preference?
To understand what kind of sand is needed for concrete of a particular brand, it is necessary to take into account the upcoming type of work.
masonry
Brick and large-block masonry is best done using river. If it is necessary to increase the plasticity of the prepared solution, a small amount of unwashed quarry can be added to the river one, which will also help reduce costs.
Concrete
For the preparation of concrete, it is preferable to use medium or coarse river sand, to which a little washed quarry sand can be added. It should be noted that grains of quarry sand, in contrast to river and sea sand, have an irregular shape and a rough surface. Under the influence of an aqueous medium, the surface of the particles is polished, which significantly impairs adhesion to the remaining components of the solution.
However, it is not always possible to completely remove clay by washing a quarry. Therefore, when preparing a concrete mixture, it is preferable to use river sand. He's already washed. The particles are approximately the same size. It does not contain clay, which significantly reduces the strength characteristics of the prepared solution.
Criterias of choice
Thus, when choosing sand, you need to focus on:
- cost - river and sea will cost more than a quarry.
We prepare concrete, maintaining proportions
To obtain high-quality concrete, it is necessary to properly maintain the ratio of sand and cement. The optimal ratio of components (c - cement (M400, M500); u - crushed stone: p - sand) of the solution is as follows:
| Concrete brand | Mass ratio: c:shch:p (kg) |
| 100 | 1:7:4,6 (1:8,1:5,8) |
| 150 | 1:5,7:3,5 (1:6,6:4,5) |
| 200 | 1:4,8:2,8 (1:5,6:3,5) |
| 250 | 1:3,9:2,1 (1:4,5:2,6) |
| 300 | 1:3,7:1,9 (1:4,3:2,4) |
| 400 | 1:2,7:1,2 (1:3,2:1,6) |
| 450 | 1:2,5:1,1 (1:2,9:1,4) |
The brand of concrete is important. If it is below M300, it is better to take sand with a particle size of less than 2.5 mm. Such concrete is traditionally used for pouring the foundation for a garage, one-story buildings, and outbuildings. For grades above M350, used in the construction of multi-storey buildings, floor slabs, armored belts, it is worth taking a river grade with a grain size of 3 mm or more.
In the most general case, when preparing a solution, you can use the following data:
| Concrete brand | River sand particle size, mm | Volumetric composition per 10 l: sand: crushed stone (l) | Mass ratio: cement: crushed stone: sand (kg) |
| 100 | up to 2.5 | 41:61 (53:71) | 1:7:4,6 (1:8,1:5,8) |
| 150 | 32:50 (40:58) | 1:5,7:3,5 (1:6,6:4,5) | |
| 200 | 25:42 (32:49) | 1:4,8:2,8 (1:5,6:3,5) | |
| 250 | 19:34 (24:39) | 1:3,9:2,1 (1:4,5:2,6) | |
| 300 | 17:32 (22:37) | 1:3,7:1,9 (1:4,3:2,4) | |
| 400 | from 3.5 | 11:24 (14:28) | 1:2,7:1,2 (1:3,2:1,6) |
| 450 | 10:22 (12:25) | 1:2,5:1,1 (1:2,9:1,4) |
A reliable foundation of the building is the key to its strength and durability. Laying is based not only on the choice of high-quality concrete and competent piping of reinforcement, but also on the correct filling of the foundation pit. When choosing sand for the foundation, it is necessary to take into account the varieties, breeds and nuances of using the material.
Functions of the sand cushion
Quartzite fractions are used to create a fundamental foundation and organize backfilling during construction. In the latter case, sand copes with several tasks:
- levels dense soils, evenly distributing the load of the building;
- compensates for the increase in the volume of frozen water on heaving soils. The material eliminates deformation, reduces the risk of cracking;
- eliminates damage to organic rocks - peatlands, increases the bearing capacity of the substrate.
A well-equipped layer will act as a barrier in conditions of close groundwater and absorb the weight of a multi-storey building.
What is the need for embankment?
The residential building must be built on a solid capital foundation. A monolithic structure located on a special bulk support has good strength indicators. After preparing the territory (clearing debris, marking), determining the depth, digging a pit, a pillow of sand is lined. When is the best time to build it? Sprinkling is recommended in the following cases:
- when building a dwelling on heaving soils. The sandy layer prevents destruction and deformation of the structure during freezing and thawing;
- with uneven ground. The embankment ensures the distribution and leveling of the construction site;
- with increased dampness from passing groundwater. The layer acts as a barrier;
- with a possible settlement of the building. The cushion resists the compressive forces in the soil;
- when building a building with several floors. The topping is lined to cushion the structure.
Sand under the foundation is laid in uniform layers, to a depth of no more than 20 cm, followed by tamping and watering each. 
What type of material is poured under the base?
Proper arrangement of the bottom of the pit in accordance with the norms and rules of SNiP 3.02.01 - 87 "Earth structures, foundations and foundations" requires the use of a loose mixture to ensure the reliability of the structure. It is worth choosing what kind of sand is needed for the foundation - river or quarry, focusing on the product line of modern manufacturers.
The building materials market sells sedimentary rock for foundation construction in 2 types: quarry and river. Which one is better to use for a pillow? Answering this question, you should decide on the nuances of using each. 
Quarry sand: characteristics, application features
Raw materials are extracted from a quarry formed by the destruction of rocks. It is of low quality due to the large volumes of impurities from clay and other substances. It is used for arranging pits, but not in its natural form. Before use, for the construction base, it is washed, dried and sifted from impurities. Popularity is due to the low cost of raw materials.
A pillow from a quarry embankment should have an important factor that determines the reliability and strength of the future structure - moisture. Its percentage in raw materials should be 1-5%. 
Varieties of material
According to the type of processing, quartz raw materials are divided into:
- washed. It is extracted with the help of hydromechanical equipment from flooded deposits. The technology allows to obtain a composition without impurities and various components. Alluvial type is used in the production of bricks, concrete, reinforced concrete products, paving slabs and roads;
- seeded. Obtained as a result of technical-mechanical screening from stones and large particles. It is used in the casting of stone products, the preparation of masonry mortars and for the formation of a mass of plaster;
- sandy soil. It is a crude mixture with many impurities. They, as a rule, fall asleep trenches and level the relief of summer cottages.
Career crumb, offered in the construction markets, has exceptional quality in accordance with GOST 8736-93. Materials mined in quarries are cheap. To check the quality, i.e. humidity, it is recommended to weigh wet sand and keep it in the sun for about 30 minutes, and then re-weigh. Humidity is calculated as the mass of raw materials after heating, from which the mass of the container was subtracted by dividing it by 100. The optimal moisture indicator is from 1 to 5%. 
River sediment is a versatile material
A universal type of quartzite raw material is mined from the bottom of freshwater rivers. The composition is considered a natural, pure product, designed for multi-purpose use in accordance with GOST - 8736-93. It rarely contains impurities and other organic compounds. Thanks to natural polishing, river rock fractions have an ideal shape. Experts note the fact that it is better to use it for the construction of foundations.
The fine fraction product is relevant for interior and exterior decoration, for brickwork and wall plastering, as well as for creating a drainage system. 
breed gradation
Raw materials extracted from the bottom of the river are characterized by heterogeneity. When choosing the right size of pebbles for the base, it is worthwhile to deal with fractional diversity.
There are the following types of river bulk material:
- Washed - is a medium-sized grain of sand, gray or yellow. They contain oxides of silicon and iron.
- Coarse-grained - mined in the beds of dry rivers. It has an unobtrusive neutral color. It is used for decoration and interior decoration.
- Large - pebbles reach sizes up to 5 mm. It is obtained on specialized crushing and grinding equipment, by splitting the rock.
River bulk material can be of several fractions. Sizes range from 0.7 mm to 3.5 mm. A pillow equipped with a mound of fine grains of sand is intended only for lightweight buildings. Fine-grained filling is strongly compacted and shrinks. 
Positive characteristics of river sand
For residential capital buildings, it is better to use crumbs of medium and large size - 2-3 mm, and for multi-storey buildings, only the large fraction type is used.
River sedimentary rock has a number of positive qualities:
- meets aesthetic and technical requirements;
- has increased moisture resistance;
- not exposed to aggressive environment, does not rot;
- characterized by excellent soundproofing qualities;
- environmentally friendly and safe.
It is popular not only on construction sites. Loose rock is used for arranging playgrounds, for the manufacture of concrete products, landscaping, in decorating rooms and in landscaping. 
Fractions of sand material
Career and river varieties are classified according to the size of the elements. Experts identify several fractions of quartz rock:
- very thin. Sand grains with a size of 0.7 mm are unsuitable for building a foundation. They can be used in the arrangement of children's play areas;
- thin. The sizes of grains reach 0.7-1 mm. Loose sand is not suitable as a base component, but is good for creating lean concrete;
- very small. The elements are 1.5 mm, but it is not enough to fill the foundation;
- small. It is characterized by the presence of fractions of 1.5 - 2 mm. The use of this type of material increases the consumption of the cement mixture;
- average. Grains from 2 to 2.5 mm in diameter are suitable as a component of standard concrete;
- large. Sand grains up to 3 mm in size - ideal for making high-quality concrete mix intended for large-scale construction;
- a composition of increased size with grains of sand up to 3.5 mm is needed to cushion the foundation and distribute the mass of the structure over it.
For pouring, only particles with sharp edges are needed, which increase the adhesion of the concrete dough to the surface. 
Features of the construction of a sand cushion
For the construction of a reliable foundation, it is necessary to properly make an embankment and level the surface of the pit. The arrangement of the embankment implies the following indicators:
- The pillow is constructed at 1/3 of the width of the foundation. The depth of the embankment layer should not exceed 20 cm.
- Before the flooring, geotextile sheets are laid on the bottom of the pit. It will provide additional drainage and keep the embankment from mixing with the soil.
- The embankment is laid in parts. After laying each layer of bulk material, it must be well moistened and compacted. It is better to tamp the sand with a vibrating plate.
- Tamping sand under the foundation is carried out until then. Until footprints remain on the surface.
- Upon completion of the filling, the level of the surface should be checked. It must be even. The correctness of the subsequent construction of the building depends on this indicator.
After backfilling the bottom, a reinforcement piping is arranged, formwork is laid and concrete is poured.
To build a good and reliable foundation, it is necessary, first of all, to take care of the arrangement of the sand cushion. It plays an important role in the construction of the foundation, especially on heaving soils.