Rules for backfilling the foundation. Sand and gravel cushion for the foundation. Subtleties of constructing a shallow foundation.

Sand and gravel mixture is one of the most common inorganic materials, used in the construction industry. The composition of the material and the size of the fractions of its elements determine what type the extracted mixture belongs to, what its main functions are, and where it is more suitable for use.

Sand-gravel mixture is used in construction for filling in the lower layers various reasons , for example, asphalt or other road surface, and for the manufacture of various mortars, for example, concrete with added water.

Peculiarities

This material is a universal ingredient, that is, it can be used in different types activities. Since its main components are natural materials (sand and gravel), this indicates that the sand-gravel mixture is an environmentally friendly product. Also, ASG can be stored for a long time - there is no expiration date for the material.

The main condition for storage is to keep the mixture in a dry place.

If moisture does get into the ASG, then when using it, a smaller amount of water is added (for example, when making concrete or cement), and when the sand-gravel mixture is needed only in dry form, you will first have to dry it thoroughly.

Due to the presence of gravel in the composition, a high-quality sand-gravel mixture should have good resistance to temperature changes and not lose its strength. One more interesting feature This material lies in the fact that the remnants of the used mixture cannot be disposed of, but can be further used for their intended purpose (for example, when laying a path to a house or when making concrete).

Natural sand and gravel mixture is low cost, while enriched PGS has high price, but this is compensated by the durability and quality of buildings made from such environmentally friendly material.

Specifications

When purchasing a sand-gravel mixture, you need to pay attention to the following technical indicators:

• grain composition;
• the volume of sand and gravel in the mixture;
• grain size;
• impurity content;
• density;
• characteristics of sand and gravel.

Technical characteristics of sand and gravel mixtures must comply with accepted standards state standards. General information You can learn about sand-gravel mixtures from GOST 23735-79, but there are also others regulatory documents regulating technical specifications sand and gravel, for example, GOST 8736-93 and GOST 8267-93.

The minimum size of sand fractions in ASG is 0.16 mm, and gravel - 5 mm. The maximum value for sand according to the standards is 5 mm, and for gravel this value is 70 mm. It is also possible to order a mixture with a gravel size of 150 mm, but not more than this value.

In enriched ASG, the amount of gravel content is on average 65%, the clay content is minimal - 0.5%.

Based on the percentage of gravel content in enriched ASG, materials are classified into the following types:

• 15-25%;
• 35-50%;
• 50-65%;
• 65-75%.

Important characteristics of the material are also strength and frost resistance. On average, PGS should withstand 300-400 freeze-thaw cycles. Also, the sand and gravel composition cannot lose more than 10% of its mass. The strength of the material is affected by the number of weak elements in the composition.

Gravel is divided into categories based on strength:

• M400;
• M600;
• M800;
• M1000.

Gravel of the M400 category has low strength, and M1000 has high strength. Intermediate level strength is present in gravel of the M600 and M800 categories. Also, the amount of weak elements in gravel of category M1000 should contain no more than 5%, and in all others - no more than 10%.

The density of PGS is determined in order to find out which component in the composition is contained in more, and decide on the scope of use of the material. On average specific gravity 1 m3 should be approximately 1.65 tons.

Has great value not only the size of the sand, but also its mineralogical composition, as well as the fineness modulus.

The average compaction coefficient of the ASG is 1.2. This parameter may vary depending on the amount of gravel content and the method of compacting the material.

The Aeff coefficient plays an important role. It stands for the coefficient of total specific activity efficiency of natural radionuclides and is available for enriched PGS. This coefficient indicates the rate of radioactivity.

Sand and gravel mixtures are divided into three safety classes:

• less than 370 Bq/kg;
• from 371 Bq/kg to 740 Bq/kg;
• from 741 Bq/kg to 1500 Bq/kg.

The safety class also determines which area of ​​application a particular ASG is suitable for. The first class is used for small construction activities, such as manufacturing products or repairing a building. The second class is used in construction automotive coatings in cities and villages, as well as for the construction of houses. The third safety class is involved in the construction of various sites with high load(these include sports and children's playgrounds) and large highways.

The enriched sand-gravel mixture is practically not subject to deformation.

Species

There are two main types of sand and gravel mixtures:

• natural (PGS);
• enriched (OPGS).

Their main difference is that an enriched sand-gravel mixture cannot be found in nature - it is obtained after artificial processing and the addition of large quantity gravel.

Natural sand and gravel mixture is mined in quarries or from the bottom of rivers and seas. Based on place of origin, it is divided into three types:

• mountain-ravine;
• lake-river;
• sea

The difference between these types of mixture lies not only in the place of its extraction, but also in the area further application, the amount of volumetric content of the main elements, their sizes and even shapes.

Main features of natural sand and gravel mixtures:

• the shape of the gravel particles - the mountain-ravine mixture has the most pointed corners, while the sea ASG does not have them (smooth rounded surface);
• composition - a minimum amount of clay, dust and other polluting elements is contained in the marine mixture, while in the mountain-ravine mixture they predominate in large quantities.

The lake-river sand-gravel mixture has intermediate characteristics between the sea and mountain-ravine AGS. Silt or dust can also be found in its composition, but in small quantities, and its corners have a slightly rounded shape.

In OPGS, gravel or sand can be excluded from the composition, and crushed gravel can be added instead. crushed gravel- this is the same gravel, but in processed form. This material is obtained by crushing more than half the original component and has sharp corners and roughness.

Crushed gravel increases the adhesion of building compounds and is perfect for the construction of asphalt concrete.

Crushed stone compositions (sand-crushed stone mixtures - SSH) are divided according to the particle fraction into the following varieties:

• C12 – up to 10 mm;
• C2 – up to 20 mm;
• C4 and C5 – up to 80 mm;
• C6 – up to 40 mm.

Compositions with crushed stone have the same characteristics and features as compositions with gravel. Most often, a sand-crushed stone mixture with a fraction of 80 mm (C4 and C5) is used in construction, since this type provides good strength and stability.

Scope of application

The most common types of construction in which sand and gravel mixtures are used are:

• road;
• housing;
• industrial.

Sand-gravel mixtures are widely used in construction for backfilling pits and trenches, leveling the surface, building roads and laying a drainage layer, producing concrete or cement, laying communications, filling foundations for various sites. They are also used in the construction of railway tracks and landscaping. This one is affordable natural material participates in the construction of one-story and multi-storey buildings(up to five floors), laying the foundation.

The sand-gravel mixture, as the main element of the road surface, ensures the road’s resistance to mechanical impact and performs water-repellent functions.

When producing concrete (or reinforced concrete), in order to eliminate the possibility of the formation of empty spaces in a structure, it is enriched ASG that is used. Its factions various sizes They perfectly fill voids and thereby ensure the reliability and stability of structures. The enriched sand-gravel mixture makes it possible to produce several grades of concrete.

The most common type of sand-gravel mixture is ASG with a gravel content of 70%. This mixture is highly durable and reliable; it is used in all types of construction. Natural ASG is used much less frequently, since its strength properties are reduced due to the content of clay and impurities, but it is ideal for backfilling trenches or pits due to its ability to absorb moisture.

Most often, natural ASG is used for arranging the entrance to a garage, pipelines and other communications, constructing a drainage layer, garden paths and landscaping of homestead areas. The enriched composition is used in the construction of high-traffic highways and houses.

How to make a foundation cushion from a sand-gravel mixture, see below.

The ISO Altair company offers to buy a sand and gravel mixture that meets the requirements of GOST 23735-2014. We deliver with our own fleet of vehicles, 7 days a week, without holidays or weekends. We supply up to 2000 cubic meters of sand and gravel mixture per day.

To order, we will make the required ratio of sand and gravel.
The price of PGS according to your parameters is discussed individually. Call!

Price for sand and gravel mixture

The table below shows base prices ISO Altair company for sand and gravel mixture.

ISO "Altair" is equipped with a fleet of vehicles. Therefore, the vehicle with the cargo is sent from the warehouse immediately after payment for the order. The transport department and order department operate around the clock. The client receives the sand and gravel mixture at the specified address within a few hours after placing the order. Each batch of ASG is certified.

This material is a mixture of gravel and sand. The fractionation of the sand-gravel mixture is heterogeneous: the diameter of the grains of sand and pebbles is not the same.
Sand and gravel mixture is an environmentally friendly natural material. Mined open method in quarries using excavators. This mortar rough, its use is limited. ISO "Altair" among non-metallic building materials sells sand and gravel mixture in Moscow and the region.

Characteristics of ASG

The ratio of sand and gravel in a sand-gravel mixture is not the same.

• Natural ASG is a coarse material with impurities. No additional processing of the mass after its extraction is done. This mixture is divided, depending on the place of extraction, into mountain-ravine, lake-river or sea. Natural ASG is used in land reclamation and road construction for adding a drainage layer. The company supplies the natural mixture to customers in the form in which the raw materials were extracted from the quarry. The size of the pebbles in this mixture exceeds 5 mm in diameter, and their number is total mass is no more than 10%.
• The enriched sand and gravel mixture is artificial material, consisting of sand and granite chips of a given size. The quality of the material depends on this. Mixture varieties differ in the ratio of sand to gravel and the size of the pebbles. A popular brand of ASG is one in which the content of granite chips is 70% and sand - 30%.

Enriched ASG is divided into 5 types:

• Group 1 - from 15 to 25% gravel;
• Group 2 - from 25 to 35% gravel;
• Group 3 - from 35 to 50% gravel;
• Group 4 - from 50 to 65% gravel;
• Group 5 - from 65 to 75% gravel.

Application of PGS

Sand-gravel mixture is used when laying communication lines, when carrying out foundation works, when filling pits, as well as in construction and road laying. It is purchased for adding highways, laying drainage manifolds and even sometimes for preparing mortars. True, the latter are made only using enriched ASG.
The Moscow region is very rich in deposits of this natural material. Its extraction here is well established, and therefore the cost of natural gas is low. It is difficult to find prices for PGS cheaper in the region than at Altair.

5 reasons to buy PGS from ISO Altair

1. The ASG is delivered to the customer on the day of payment, since a sufficient number of dump trucks and loading and unloading equipment are provided for this. In addition, there is a stock of this material at the transshipment bases.
2. The company sells only certified ASG.
3. There is a system of discounts for regular and wholesale customers on an ongoing basis.
4. The company's departments operate around the clock and seven days a week.
5. ISO "Altair" offers the cheapest price for ASG in the region and accepts payment in a convenient way for the buyer.

The set of rules for foundations and earthen structures SP 45.13330 regulates the backfilling of foundations. Technical standards TR 73-98 provide rules for compacting the materials used. General principle is to apply inert materials from the outside, any from the inside.

The question of how to fill the foundation inside is relevant both for floors on joists and for floors on the ground. The choice of material and compaction technology depends on the following factors:

• type of operation - in buildings permanent residence heating is year-round, the soil under the base of the house does not freeze, so you can even fill it with clay, which will not swell in the absence of moisture and freezing;
• ceiling/floor construction - if the project includes a ceiling on beams, it is cheaper to fill inner part clay; for the footing of a floating floor on the ground, sand is necessary to level the base at least in the upper level (minimum 10 cm layer);
• the height of the base part - for large volumes it is more rational to use soil from the building site, taken out of the trenches; to fill the concrete footing, the very top should be filled with sand;
• GWL level – at high groundwater It is preferable to fill with crushed stone, if the aquifer (“upper water”) is 1 m from the base of the foundation, sand should be used to save the construction budget.

Attention: Clay castles prohibited outside, although the technology was described in the old SNiP. Clay does not allow moisture to pass through, but absorbs intensely, which is dangerous due to uneven swelling, not only when freezing, but also when swelling.

When backfilling, layer-by-layer (20 cm) soil compaction is required.

Don't neglect filling out internal space cells strip foundation when making floors using joists:

• the underground is too low for normal operation;
• the soil inevitably releases vapors that are harmful to power structures buildings;
• ventilation is required, heat loss through the floor of the lower floor increases;
• Harmful radon is often released from pits, from which the home will have to be protected with foil materials.

Backfilling before the ceiling will allow you to solve all the problems comprehensively and improve the quality of operation.

Materials

Almost any soil is allowed in the internal backfill, but large stones (more than 25 cm) must be excluded from them and, if necessary, longitudinal drains must be laid, including them in the general contour located around the perimeter of the house (only with high groundwater level). Depending on the heating mode, groundwater level, freezing depth, the width of the shell of non-metallic material around concrete structures is:

• heating is constant - there are no restrictions; with proper compaction, backfilling with clay is allowed;
• periodic heating - a 20 cm layer of sand or ASG is enough interior walls foundation;
• freezing 1 m, no regular heating - sinuses 20 cm filled with inert material;
• freezing 1.5 m, without heating - 30 cm layer of non-metallic material near the tape;
• freezing 2.5 m – width of the sinuses 50 cm minimum.

The depth of filling the sinuses is calculated from the planning mark (usually the blind area), and is ¾ of the depth of the base of the strip foundation.

Technologies

Compaction of clay, sand, sandy loam and other materials is not required inside the foundation tape in the only case - when making floors on joists. If you plan to pour a screed, any of these materials must be compacted to a density of 0.95 units. To do this, you need to use manual rammers or vibrating plates.

You can determine the quality of the compaction visually - as soon as traces are no longer imprinted on the soil, you can pour 5-10 cm of the “concrete footing” screed. It is not recommended to spill sand, sandy loam, or loam with water, so as not to saturate the underlying horizons. Instead, the backfill material is moistened to the following values:

• 15 – 23% heavy soils (including dusty ones), waterlogging no more than 1%;
• 12 – 16% – light loams, waterlogging coefficient Kp 1.15%;
• 9 – 14% – light sandy loam, Kp 1.25%;
• 7 – 12% – coarse sandy loam, Kp 1.35%.

You can pour the screed after the soil has completely dried. When filling any monolithic foundation footing is used. This structural element allows:

• reduce the height of the protective layer;
• prevent the leakage of cement laitance into the lower layer with high drainage characteristics;
• protect the waterproofing layer of the foundation base.

Therefore small sand layer on top of loam, sandy loam, crushed stone or clay will further level the base and reduce concrete consumption.

Backfilling outside

Unlike the internal perimeter, which cannot freeze (in a heated building), the soil adjacent to the outer edges of the foundation is not protected from the cold. It swells unevenly and tends to pull out the concrete structure by tangential forces. The problem is solved by the following methods:

• backfilling of the foundation cavities with non-metallic material (minimum 20 cm sand, crushed stone shell);
• insulation of the blind area - 60 - 1.2 m tape around the building pushes back the freezing zone;
• sliding-creased thermal insulation – rigid fixation of extruded polystyrene foam high density EPPS to the outer walls of the foundation, covering with two layers of a plinth fixed at the level polyethylene film, installation of sheets of PSB 25 (minimum density of polystyrene) vertically close to the film without fastening (held by sand powder).

When heaving forces occur, soft polystyrene crumples and rises up a perfectly smooth film without causing damage to the underlying layer of thermal insulation. In the spring, structural elements arrive original appearance after reducing the soil volume.

Materials

The possibility of freezing of the soil adjacent to the foundation from the outside is always present. Therefore, despite the insulation of the blind area, the sinuses of the trenches are filled from the outside with sand, ASG or crushed stone, depending on the groundwater level. For normal operation of concrete structures, a shell density of 0.95 units is required, so non-metallic materials are poured in layers of 10 - 20 cm, compacted with a vibrating plate, hand tools. Spilling sand is not recommended, because... there is a danger of erosion of the lower layers (relevant for silty soils).

Therefore, when backfilling with sand, it is necessary to moisten the material abundantly before placing it in the sinuses. Natural shrinkage takes time, so it is better to rent or make a vibrating plate yourself, reducing the compaction time to a minimum.

If the groundwater level is high or there is a possibility of its seasonal rise, crushed stone should be used. The gravel material is inferior to this non-metallic product in terms of its main characteristic - flakiness. Therefore, shrinkage during operation is possible, leading to deformation of the blind area.

Technologies

Filling the sinuses from the outside with sand or crushed stone allows you to completely eliminate swelling of the layer adjacent to the foundation. However, all non-metallic materials have excellent drainage properties. Therefore, ring drains at the level of the foundation base are prerequisite normal operation.

Scheme of ring drainage around the base of the foundation.

When filling the sinuses, it is necessary to ensure that there is no shrinkage during operation. This is only possible by compacting materials with vibrating plates and hand rammers. The maximum effect is observed when preventing mutual penetration of inert materials and neighboring soils. The technology looks like:

• laying geotextiles or dormite on the walls of the sinus;
• backfilling the outside with sand or crushed stone in a 10–20 cm layer;
• compaction with a tamper or vibrating plate.

If a deep foundation strip is being poured, horizontal thermal insulation (5 cm sheets of high-density extruded polystyrene foam) must be laid at an area of ​​30–40 cm from the surface, after which the work must continue.

In MZLF tapes, the depth usually does not exceed the specified level, so thermal insulation is laid outside along the bottom of the trench by default. Backfilling is done on top of it.

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