What is the compaction coefficient of sand? What is the compaction coefficient of bulk materials? Sand-gravel mixture compaction coefficient Natural sand-gravel mixture compaction coefficient

Sand (K upl) is known not only by specialists working in design organizations, but also operators whose main activity is construction. It is calculated in order to compare the actual density in a certain area with the value prescribed regulations. Compaction factor bulk materials- This important criterion, which evaluates the quality of preparation for the main types of work on construction sites.

What it is?

To compaction characterizes the density that the soil has in a particular area; it refers to the same indicator of the material that has undergone standard compaction under laboratory conditions. It is this figure that is used when assessing the quality of work performed. This coefficient determines how well the soil on the site complies with the requirements of GOST 8736-93 and 25100-95.

At various works sand may have different indicator density. All these standards are prescribed in SNiP 2.05.02-85, table 22. They are also usually indicated in project documents; in most cases this figure ranges from 0.95 to 0.98.

What causes the density coefficient to change?

If you do not understand what sand compaction is, then it is almost impossible to correctly calculate the amount of material during construction. After all, you need to clearly know how various manipulations affected the soil. What coefficient of relative sand compaction we will ultimately obtain may depend on many factors:

• on the method of transportation;
• how long the route was;
• whether mechanical damage has appeared;
• the presence of foreign inclusions;
• moisture ingress.

Naturally, if you ordered sand, you simply must check it on the spot, because late complaints will be completely inappropriate.

Why take into account the relative coefficient when building roads

This indicator for a sand cushion must be calculated, and this is explained by a common physical phenomenon that is familiar to any person. To understand this, remember how loosened soil behaves. At first it is loose and voluminous. But after a couple of days it will settle and become much denser.

The same fate awaits any other bulk material. After all, its density increases in the warehouse under the pressure of its own weight. Then, during loading, it is loosened, and directly at the construction site, the sand is again compacted with its own weight. In addition, moisture affects the soil. The sand cushion will be compacted during any type of work, be it the construction of a roadway or backfilling of the foundation. For all these factors, the corresponding GOSTs (8736-93 and 25100-95) were calculated.

How to use a relative indicator

For any construction work ah, one of the most important stages The preparation of estimates and calculations of coefficients is considered. This is necessary in order to correctly draw up the project. If it is important to find out how much sand will compact when transported in a dump truck or railway car, just look in GOST 8735-88 required indicator, and divide the required volume by it.

It is also necessary to take into account what kind of work is ahead. Are you going to make a sand cushion under the roadway, or backfill the foundation. In each situation, compaction will proceed differently.

For example, when backfilling sand, a dug pit is filled. Tamping is done using various equipment. Sometimes compaction is done with a vibrating plate, but in some cases a roller is required. Accordingly, the indicators will be different. Keep in mind that the soil changes its properties during excavation. So the amount of backfill must be calculated taking into account the relative indicator.

Table of compaction coefficient values ​​depending on the purpose of sand.

The need to know the exact density of bulk building materials arises during their transportation, compaction, filling containers and pits, and selecting proportions when preparing mortars. One of the indicators taken into account is the compaction coefficient, which characterizes the compliance of the laid layers with regulatory requirements or the degree of reduction in the volume of sand during transportation. The recommended value is indicated in project documentation and depends on the type of structure being built or type of work.

The compaction coefficient is a standard number that takes into account the degree of reduction in the external volume during the process of delivery and laying followed by compaction (you can find information on compacting crushed stone). In a simplified version, it is found as the ratio of the mass of a certain volume taken during sampling to a reference parameter obtained in laboratory conditions. Its value depends on the type and size of filler fractions and varies from 1.05 to 1.52. In the case of sand for construction work, it is 1.15; it is used as a starting point when calculating building materials.

As a result, the actual volume of sand supplied is determined by multiplying the measurement results by the compaction rate during transportation. Maximum permissible value must be specified in the purchase agreement. The opposite situations are also possible - to check the integrity of suppliers, the volume is found at the end of delivery, its quantity in m 3 is divided by the sand compaction coefficient and compared with the delivered one. For example, when transporting 50 m 3 after compaction in the back of a car or wagons, no more than 43.5 will be brought to the site.

Factors influencing the coefficient

The given number is the statistical average, in practice it depends on the set different criteria. These include:

• Sand grain sizes, purity and other physical and Chemical properties, determined by the place and method of extraction. The characteristics of the source may change over time; as the material is removed from the quarries, the looseness of the remaining layers increases; to eliminate errors, the bulk density and related parameters are periodically checked in laboratory conditions.
• Conditions of transportation (distance to the facility, climatic and seasonal factors, type of transport used). The stronger and longer the vibration affects the material, the more efficiently the sand is compacted; maximum compaction is achieved when it is moved by vehicles, slightly less - during rail transportation, minimal - during sea transportation. At the right conditions transportation exposure to humidity and subzero temperatures reduced to a minimum.

These factors should be checked immediately; the values ​​of the indicators are acceptable natural humidity and bulk density are specified in the passport. Additional volumes of bulk solids due to losses during transportation depend on the delivery distance and are taken equal to 0.5% within 1 km, 1% beyond this parameter.

Using the coefficient in the preparation of sand cushions and road construction

A characteristic feature of any bulk building materials is a change in volume when unloading into a free area or compacting it. In the first case, the sand or soil becomes loose; during storage, the particles settle and adhere to each other with virtually no voids, but still do not meet the standards. On last stage– when laying and distributing compositions at the bottom of the pit, the coefficient of relative sand compaction is taken into account. It is a criterion for the quality of work carried out during the preparation of trenches and construction sites and varies from 0.95 to 1, exact value depends on the purpose of the layer and the method of backfilling and compaction. It is determined by calculation and must be indicated in the design documentation.

Compaction of the soil backfilled is considered the same mandatory action as when laying a sand cushion under the foundations of buildings or when arranging a road surface. To achieve the desired effect, special equipment is used - rollers, vibrating plates and vibrating stamps; in its absence, tamping is carried out hand tools or feet. The maximum permissible thickness of the treated layer and the required number of passes refer to the table values, the same applies to the recommended minimum of bedding on top of pipes or communications.

During the process of compacting sand or soil, their bulk density increases, and the volumetric area inevitably decreases. This must be taken into account when calculating the amount of material purchased, along with the total losses due to weathering or the amount of stock. When choosing a compaction method, it is important to remember that any external mechanical influences affect only the upper layers, in order to obtain a coating with the required quality vibration equipment required.

High pace of construction, accelerated development of residential areas, office buildings makes you think about the quality characteristics of concrete. Lasting, strong foundation without concrete mortar impossible to create. Concrete is the main connecting material, construction material in construction. The quality of concrete directly affects the strength and service life of structures. The solution can be prepared from sand and gravel mixtures, paying attention to the source of occurrence and observing the required ratio of components.

Purpose of PGS

The sand-gravel mixture, or in other words ASG, consists of gravel. The composition is prepared in two ways:

• natural;
• artificial.

The resulting mixture is in great demand and is used in industrial, road, and housing construction:

• For ;
• for the manufacture of monolithic, reinforced concrete structures;
• as a drainage layer of the road surface;
• landscape leveling.

Types, mixture structure

The proportional content of sand and gravel in the mixture is: main criterion gravmass. Gravel should not be more than 75% of the total mass. Great importance is paid to the size of components, and they are also checked for compliance with standards. Based on the proportional content of components, two types of sand and gravel are distinguished:

• Natural (pgs). The ratio of gravel as a percentage relative to the total mass is no less than 10 and no more than 95 - 1/5 of the total composition. Additional processing the classic composition is not exposed. The gravel mass is extracted from a quarry and immediately shipped to the buyer. Basically, the gravel content is 10-20% of the bulk. The percentage can rise to 30 if the mixture was mined in reservoirs. The size of the elements reaches from 10 to 70 mm. By separate agreement with the buyer, the size may be larger than stated, the maximum value is 10 cm.
• Enriched (OPGS). The proportions of the components are as follows: sand 30%, gravel up to 70%. 3/4 of the entire enriched mass is gravel.

The enriched composition can be obtained through special preparation. Observing certain proportions, the necessary components are mixed. The result is opgs. Considering percentage gravel, five groups of enriched mixture are distinguished.

• 1 group. The percentage of gravel from the total mass is 15-25%.
• 2nd group. The amount of gravel is 25-30%.
• 3rd group. The component content is from 35 to 50%.
• 4th group. The percentage of gravel is 50-65%.
• 5 group. Gravel in quantities from 65 to 75%.

The greater the percentage of gravel contained in the solution, the harder the mass is. Depends on the amount of gravel specifications solution, operating parameters. The final cost of concentrated gravel compounds is influenced by the amount and percentage of content natural stone.

Based on the deposit and initial source of formation, natural gravel mixtures are divided into:

• Gully (mountain) are characterized by an admixture rocks, the shape of the natural stone is acute, the size varies. The heterogeneity of the structure of this type does not allow the use of the ravine-mountain type for the production of concrete. The mixture is widely used as drainage during the repair of highways, filling pits and pits.
• River (lake) A small amount of clay and shell rock is observed. The shape of the elements is rolled.
• Marine. Impurities are contained in small quantities or absent. The shape of the stones is round and dense.

Lake-river and sea gravel mixtures are used to make concrete mortar, necessary for buildings of special strength, and for pouring foundations.

Features of mass selection

In all branches of construction: preparation of structures, pouring any type of foundation, concrete is required. A responsible approach to the production of concrete mortar ensures reliability and strength of structures. An important role in technological process plays the ratio of components.

The main point is to buy high-quality products correctly; you should not save. The concrete reflects the method of extraction of the material. Pay attention to various impurities; the structure of the mass should not contain them. The absence of foreign components increases the adhesion between the gravitational mass and other components of the solution.

To work with the foundation, enriched mixtures are used, since the amount of gravel in them exceeds the sand content, which increases the density and reduces the looseness of the solution.

Compaction degree

Transportation of a bulk substance leads to its compaction. Compression is controlled by regulatory building standards. The exponential value that determines the amount of reduced volume is called the compaction coefficient. Compaction standards are set at the state level.

Compacting the material is a natural process; the coefficient depends on the mass of the batch. Important points are the quality of the material and the method of transportation. The average compaction index is 1.2, according to the standards. For example, for sand the compaction index is 1.15, for crushed stone - 1.1.

Compression Rate - important point in construction. At the beginning of work it is carried out preparatory stage, during which the thickness, level, quantity and other indicators necessary for subsequent work are determined. The acceptance of the final result is influenced by the compaction coefficient.

When compacting soil using the tamping method, the main rules are followed. Differences in the depth of the dug trench are leveled out by compaction from the highest elevations, gradually moving to lower ones. Compaction is carried out until the density required by the standards is achieved. When working with the mixture, freezing of materials is not allowed; humidity is normal. The process is considered complete when the number of strikes does not exceed the specified limits. The so-called “two control strikes” rule.

Concrete preparation process

During individual construction The mixture is prepared by hand. For small construction volumes, there is no need to hire expensive construction equipment. Before starting work, it is worth determining the structure, calculating the mass, and preparing the appropriate components.

To mix it yourself you will need the following: consumables and tools:

• stock of cement of the required brand;
• clean warm water;
• opgs;
• kneading container;
• (concrete mixer);
• bucket.

Correctly matched components influence the quality result. For an enriched look, it is worth making the ratio of parts 8 to 1, where the first is the mixture, the second is cement. This coefficient was determined by trial and error and is still actively used today. experienced craftsmen. How much water to add is an individual matter. It is worth focusing on the dryness of the components, gradually adding liquid until the desired consistency of the solution is achieved.

Cement for mortar is used of those brands that provide the required strength. These are M300, M500, M600. Recently, Portland cement has become popular because it has excellent astringent properties. For a small amount of work, M400 concrete is used, taking into account the fact that ready mixture worth using within two hours.

On quality concrete made from PGS affects the size of the natural stone. The solution acquires the required strength when the gravel size is 8 cm. The required proportions are maintained: 6 - mixture, 1 - cement.

The compaction coefficient of crushed stone is a dimensionless indicator that characterizes the degree of change in the volume of the material during compaction, shrinkage and transportation. It is taken into account when calculating the required amount of filler, checking the weight of products delivered to order and when preparing the bases for bearing structures along with bulk density and other characteristics. Standard number for specific brand determined in laboratory conditions, the real is not a static quantity and equally depends on a number of inherent properties and external conditions.

The compaction coefficient is used when working with bulk building materials. Their standard number varies from 1.05 to 1.52. The average value for gravel and granite crushed stone is 1.1, expanded clay - 1.15, sand-gravel mixtures - 1.2 (read about the degree of sand compaction). The actual figure depends on the following factors:

• Size: the smaller the grain, the more efficient the compaction.
• Flakiness: needle-shaped crushed stone and irregular shape compacts less well than cube-shaped filler.
• Duration of transportation and type of transport used. The maximum value is achieved when gravel and granite stones are delivered in dump truck bodies and railway cars, the minimum value is achieved in sea containers.
• Conditions for filling into a car.
• Method: manually achieving the desired parameter is more difficult than using vibration equipment.

In the construction industry, the compaction coefficient is taken into account primarily when checking the mass of purchased bulk material and backfilling foundations. The design data indicates the density of the structure skeleton. The indicator is taken into account in conjunction with other parameters building mixtures, humidity plays an important role. The degree of compaction is calculated for crushed stone with a limited volume of walls; in reality, such conditions are not always created. A striking example the foundation or drainage cushion being filled in serves (the fractions extend beyond the boundaries of the interlayer), an error in the calculation is inevitable. To neutralize it, crushed stone is purchased with a reserve.

Ignoring this coefficient when drawing up a project and carrying out construction work leads to the purchase of an incomplete volume and deterioration performance characteristics constructed structures. With the correct degree of compaction selected and implemented, concrete monoliths, building and road foundations can withstand the expected loads.

Degree of compaction on site and during transportation

Deviation in the volume of crushed stone loaded and delivered to the final point – known fact, the stronger the vibration during transportation and the further the distance, the higher its degree of compaction. To check the compliance of the amount of material brought, a regular tape measure is most often used. After measuring the body, the resulting volume is divided by a coefficient and checked with the value indicated in the accompanying documentation. Regardless of the size of the fractions, this indicator cannot be less than 1.1; if there are high requirements for delivery accuracy, it is negotiated and specified in the contract separately.

If this point is ignored, claims against the supplier are unfounded; according to GOST 8267-93, the parameter does not apply to mandatory characteristics. By default for crushed stone it is taken equal to 1.1, the delivered volume is checked at the receiving point, after unloading the material takes up a little more space, but over time it shrinks.

The required degree of compaction when preparing the foundations of buildings and roads is indicated in the design documentation and depends on the expected weight loads. In practice, it can reach 1.52, the deviation should be minimal (no more than 10%). Tamping is carried out layer by layer with a thickness limit of 15-20 cm and the use of different fractions.

The road surface or foundation pads are poured onto prepared sites, namely with leveled and compacted soil, without significant level deviations. The first layer is formed from coarse gravel or granite crushed stone; the use of dolomite rocks must be permitted by the project. After preliminary compaction, the pieces are separated into smaller fractions, if necessary, even to the point of filling with sand or sand-gravel mixtures. The quality of work is checked separately on each layer.

The compliance of the obtained tamping result with the design one is assessed using special equipment– density meter. The measurement is carried out provided that there is no more than 15% grains with a size of up to 10 mm. The tool is immersed 150 mm strictly vertically, maintaining the required pressure, the level is calculated by the deflection of the arrow on the device. To eliminate errors, measurements are taken at 3-5 points in different places.

Bulk density of crushed stone of different fractions

In addition to the compaction coefficient, to determine the exact amount of material required, you need to know the dimensions of the structure being filled and specific gravity filler. The latter is the ratio of the mass of crushed stone or gravel to the volume it occupies and depends primarily on the strength of the original rock and size.

The specific gravity must be indicated in the product certificate; in the absence of accurate data, you can find it yourself empirically. To do this, you will need a cylindrical container and a scale; the material is poured without compaction and weighed before and after filling. The quantity is found by multiplying the volume of the structure or base by the obtained value and by the degree of compaction specified in the design documentation.

For example, to fill 1 m2 of a 15 cm thick cushion of gravel with a fraction size in the range of 20-40 cm, you will need 1370 × 0.15 × 1.1 = 226 kg. Knowing the area of ​​the base being formed, it is easy to find the total volume of filler.

Density indicators are also relevant when selecting proportions for cooking concrete mixtures. For foundation structures recommended to use granite crushed stone with a fraction size in the range of 20-40 mm and a specific gravity of at least 1400 kg/m3. Seal in in this case is not carried out, but attention is paid to flakiness - for the manufacture of reinforced concrete products, a cube-shaped filler with a low content of grains of irregular shape is required. Bulk density is used when converting volumetric proportions to mass proportions and vice versa.