It is quite difficult to imagine any construction process without the use of crushed stone. It is used when creating a foundation, mixing concrete mortar, formation garden paths, organizations landscape design, laying access roads and highways. This article will discuss the basics of crushed stone compaction.

The rock crushing product is used to create a so-called cushion, which performs the following functions:

• leveling the base before further work;
• imparting hardness to weak-bearing soils;
• protection of buildings from negative impact moisture;
• increased durability under high loads.

In any case, the quality of the crushed stone base directly depends on the physical and technical characteristics of the material. Determine by appearance characteristics will not work; they are indicated in the accompanying documents and certificates.

Type of crushed stone

This bulk material produced by passing boulders through crushing equipment. The output is stone of various fractions from 0*5 to 40*70 mm. The size determines the scope of application. For domestic construction, crushed stone of 5*20 and 20*40 mm is mainly used.

The type of building material is:

• granite. It is characterized by high natural strength and the ability to withstand multidirectional loads;
• limestone. In terms of hardness, it is practically not inferior to granite crushed stone. However, it costs much less. Ideal for housing construction;
• slag This material is obtained from metallurgical waste. The cost is much lower than the above types of gravel. But due to harmful impurities in its composition, the scope of application is quite limited;

• secondary. Crushed stone is produced from construction waste (fragments of brick, asphalt or concrete). Of course, recycling of the material does not have high rates, and therefore is not suitable for all types of work.

Before purchasing, you should pay attention to such a parameter as flakiness. A large percentage of lamellar-shaped grains significantly reduces the strength of the finished base during the construction of objects for any purpose. Therefore, the lower this parameter, the better.

Crushed stone compaction coefficient

At self-construction Everyone has faced such a problem as a shortage or excess of material. Ability to calculate the required quantity - important aspect any process. For domestic needs, average values ​​are often used.

To calculate the volume you need to know:

• the required thickness of the cushion after compaction. Typically this figure is 0.2 or 0.25 m;
• compaction of crushed stone with a compaction coefficient - 1.3. The parameter is correct for most fractions compacted by mechanized means;
• specific gravity bulk material, which is indicated in the certificate. For ease of calculation, let’s take a weight of 1.5 t/m. cube, characteristic of ordinary crushed stone.

So, knowing all the components of the equation, we calculate the material for 1 square meter laying: 0.25x1.3x1.5=0.4875 t.

As with any calculation, the result is rounded up. This means that for backfilling 1 sq.m. An area of ​​25 cm thick crushed stone layer will require 490 kg. Well, calculate the volume for 10-20 square meters. m. it will be much easier.

Why do you need to compact the base with crushed stone?

The question of compaction is asked by all newcomers to the construction business. After all, in theory, the stone itself is a durable material and it is quite enough to level it and you can move on to next stage works However, everything is not so simple.

• Crushed stone is obtained by crushing, during which the edges of the grains acquire a free shape. When filling the material between each element, air voids are formed, reducing the level of resistance under load.
• The tight fit of individual fragments reduces the risk of them “walking.” After all, after compacting the soil with crushed stone, the voids disappear or are significantly reduced in volume. This creates an additional safety margin for the foundation.

• As an exception, we can consider rocky soil, which serves as the basis for construction. In this case, it is quite enough to level the crushed stone embankment for subsequent work: laying tiles, pouring concrete mixture, etc.
• In other conditions, the gravel should not just lie on the ground, but be compacted, forming a single plane. Densely filling the space between the grains with soil particles will give the necessary solidity.
• The thickness of the compacted layer can vary from 50 to 250 mm. The safety factor for crushed stone compaction is determined by the subsequent load on the base (passing vehicles, pedestrians, weight of the building, etc.).
• Separating the crushed stone base can be highlighted as a separate line. The method consists of several stages - using gravel of different fractions. First, they take large material and compact it, then pour in smaller crushed stone and compact it again, last layer fine-grained material emerges and the final rolling of the surface is carried out.

Compacting crushed stone with a manual tamper

In the absence of special vibration equipment, folk craftsmen use products made with their own hands. Of course, with such compaction good physical preparation is necessary. Manual tamping is relevant for small volumes of work.

• There are many options for how to make a device. Of these, the most primitive is 100x100 mm timber. You can take wood with a larger cross-section, thus increasing the area covered for compaction.
• The length of the beam is selected based on ease of use, most often the human chest is taken as the basis. The lower end of the tool is lined with a galvanized sheet. Handles made of wooden pegs or metal rods are mounted in the upper part on both sides.
• The way it works is quite simple. The beam is lifted by the handles to the maximum height and forcefully lowered onto the crushed stone base. Repeating these movements multiple times in a certain direction will lead to the desired result.

• If a zealous owner has a metal head, then it is fixed to a thinner wooden base, such as a log. The device will become much lighter, which means tamping will be more fun.
• A device made entirely of metal (stand and sole) has a more durable design. True, this material creates a lot of vibration, which wood perfectly absorbs. In this case, the solution is to use special gloves.

Compacting crushed stone with a vibrating plate

The use of a vibrating plate or vibrating rammer is relevant for global volumes. With the help of technology, the process can be carried out in hard to reach places, and in areas located near the walls of buildings.

• The equipment is compact, reliable and mobile. Easy Operation and high efficiency allow us to complete work with maximum quality in a short time. For domestic needs, vibrating plates weighing from 60 to 120 kg are used.
• The principle of operation is the vibration of the plate produced by rotating eccentrics. Tamping occurs by transferring shock vibrations and energy from the support shoe to the crushed stone.
• The presence of shock absorbers allows you to dampen mechanical vibrations in the top part equipment, thus providing protection to both the engine and the operator. The equipment is equipped with a speed shift lever, which makes it possible to regulate the travel power.

• Based on the method of movement, there are single-pass and reversible (with reciprocating movements) devices. The latter option is characterized by increased functionality and efficiency. With their help, tamping is carried out without cyclic movement along the surface being treated.
• The engine can run on liquid petroleum products (gasoline or diesel fuel) or by connecting to electrical network. Units with an electric motor are lightweight (up to 100 kg). They are widely used in jobs where high requirements for material compaction are not required.
• Such equipment can be purchased in specialized stores or second-hand, as they say. The most profitable option is to rent equipment, which will cost much less.
• In any case, it is important to comply with operating conditions that will extend the service life and prevent failure. Before starting, you should carefully study the instructions for use and familiarize yourself with the safety rules.
• Regular lubrication of individual elements and cleaning air filter, changing the oil will help keep everything technical indicators equipment.

Alternative crushed stone compaction options

For these purposes, you can also use homemade devices with operating principles similar to mechanized equipment. Here you will need an old metal trough, a pipe, sand and a welding machine.

• A handle from a piece of pipe is welded to the container at an angle, and perpendicular fittings are fixed to the upper part. It is advisable to further strengthen the bottom of the trough by welding a sheet of iron to it.
• By filling the device with sand, we end up with a universal hand tool like an asphalt roller. The device is moved by the handle in a given direction, and due to its considerable weight, the crushed stone is compacted. It is quite simple to operate, but will require some skill and, again, physical strength.
• The second method is relevant for compacting bulk material on a spacious area devoid of green spaces, gazebos, fences or other obstacles. The technology requires the presence of a vehicle, which is used to compact sand and crushed stone.
• A layer of gravel is distributed over the entire surface with a shovel or rake. Then we get behind the wheel and begin to methodically drive around the prepared area in various directions (lengthwise, across and diagonally) until we get the required result.
• If a rut is formed during the process, then crushed stone is added to this area, so some material must be left for backfilling. Then compaction continues using the above method. Of course, this method cannot be called manual, but compaction is still carried out on our own without involvement construction crews or purchasing special equipment.
• Control of compaction of crushed stone is important for any construction work, carry it out for show and especially should not be neglected. This gives reliability and stability to buildings or road surface, and also ensures safety during operation.
• At the end of the work, the compaction of crushed stone is determined using a special device.

• A soil analysis should be carried out in advance, the level of the groundwater. The quality of work depends on this information. Otherwise, even with the most effective compaction, one cannot be sure that subsidence will not occur in the future, which, in turn, will lead to unpredictable consequences.

Before proceeding with the construction of various buildings and structures, it is necessary to carry out a number of mandatory calculations in order finished building could be used for a long period. It is necessary to decide on the materials used to lay the foundation of the structure. Their quality characteristics directly depend on the production method. One of the main building materials, often used in construction, considered crushed stone. How to determine the compaction coefficient of crushed stone 20 40?

Application

Crushed stone is produced through quarrying. By crushing large rocks into small components. The size of granules in crushed stone can vary from small 5-15 mm to large 120-150 mm.

Application:

• when laying the foundation;

• when laying road surfaces, major highways or railway tracks;

Most builders prefer granite crushed stone due to a number of advantages:

• high resistance to frost;
• moisture absorption by the material is very low;
• strength of the material.

When selecting the fraction of crushed stone, it is worth considering for what purpose it will be used.

For more information about granite crushed stone 20 40, watch the video:

Kinds

Used in construction work different kinds crushed stone All of them are divided into several types:

• crushed stone made from granite deposits;

• crushed stone or gravel made from stone material;

• limestone crushed stone;

• recycled crushed stone.

Each type has its own characteristics and areas of application. The first way they differ from each other is quality; the higher it is, the higher the cost of crushed stone.

The secondary product is the cheapest due to the way it is produced. It is made from old pieces of used or asphalt, as well as fragments of bricks.

Granite crushed stone is considered high in price and, accordingly, in quality. Therefore, it is mainly used for the construction of high-rise buildings and laying railway tracks.

And in any construction where the main aspect is quality, this type of crushed stone is used.

What is the compaction coefficient of crushed stone during compaction?

This coefficient is a dimensionless quantity, which indicates the degree of compaction, and therefore the reduction in the visual volume of crushed stone during delivery or during construction work.

The value of this parameter depends on the material from which the crushed stone is made, and varies from 1.05 to 1.52. If we take granite crushed stone as an example, the average value is 1.1.

In addition to the actual volume and degree of compaction, also consider external factors like temperature and humidity of air and soil.

Why do we need a compaction indicator?

So why is it necessary to take into account the compaction coefficient of crushed stone? This parameter applies:

• when calculating the amount of material required;
• when calculating shrinkage during construction.

If you know the compaction coefficient of crushed stone 20 40, you can calculate. To do this, you need to multiply the available volume of any object for storage or transportation, be it a train car or a car body, by and the compaction coefficient.

It is worth remembering that the level of compaction of the material depends on the size of the crushed stone granules. If we take 5 20, it will be significantly less than n.

Calculations must be carried out at the construction site.

What does the compaction index depend on?

The compaction of crushed stone material is influenced by additional indicators. Which primarily take into account these characteristics of crushed stone.

• factional data;
• the material from which the crushed stone was made.

Since the essence of the compaction coefficient is a reduction in the volume of material during compaction, its indicator also changes due to the following factors:

• how crushed stone is loaded into transport, height matters here;
• what kind of transport is used when transporting crushed stone. Distance also matters, because during transportation the crushed stone gradually settles, thereby reducing its volume;
• size of crushed stone granules and the percentage of finer fractions in the purchased crushed stone;
• The coefficient is also affected by granules. So, for example, needle-shaped stones settle much less than cube-shaped granules.

The more accurately the crushed stone compaction coefficient is determined, the higher the strength of the future building.

The problem with most builders is insufficient experience or outright hackwork. According to construction standards, each layer of crushed stone must be rolled and parameters measured separately.

But some builders do not do this and only compact upper layer crushed stone The consequence of such incompetence will be the gradual settlement of an already completed building, which will lead to the formation of cracks in the structure and its gradual destruction.

Another serious point when calculating compaction is to measure where compression occurs without lateral expansion, and the limiter is the walls, which prevent it from spreading.

Compaction index

During transportation

It is difficult to accurately determine the degree of compaction of crushed stone during the acquisition of material, since standard value No. The supplier himself can indicate it in the documents accompanying the goods, but it is not required to be included.

Of course, when purchasing and transporting large volumes of goods, there is often a serious difference in volume between loading and receiving crushed stone at the warehouse.

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For such cases, the supply contract concluded between the supplier and construction company, an additional clause is added, which specifies the correction factor, which is referred to at the point of receipt of the goods.

According to GOST, the correction indicator cannot be higher than 1.1. Therefore, suppliers take this into account when loading and make a small reserve so that the goods are not returned.

The delivered crushed stone is measured at the time of delivery, before it is unloaded. The reason for this is that the order is made not in tons, but in cubic meters. As soon as the transport arrives at the construction site, the loaded body is measured from the inside with a tape measure.

This is how the volume of crushed stone brought is calculated, and after it multiplied by a factor of 1.1. Thus

At the construction site

Natural compaction of crushed stone differs significantly from mechanical compaction, which is carried out on construction site. Therefore, the compaction coefficient of crushed stone 20 40 can reach a parameter of 1.52. And the workers who will carry out the work need to know the seal readings for sure.

Necessary digital value indicated in construction project. But if a specific figure is not indicated, then an approximate value is used.

So for fractions with the parameter 5 20, 20 40 the indicator is not set. Because these types of crushed stone are most often used for decluttering the load-bearing layer at the top, where grains are used.

Laboratory indicator

Laboratory measurements are considered the most accurate. because they are calculated using various ways tampers. And the check is carried out using different devices.

Here are some of the commonly used methods:

• volume substitution according to GOST 28514 – 90;
• layer-by-layer compaction of crushed stone in accordance with the GOST standard 22733 - 2002

Quick options for densitometer calculations are used:

• static type;
• water balloon;
• dynamic view.

Results are provided within four days, maybe sooner. This depends on the specific study. The cost of a standard sample will cost 2,500 rubles, and you will need at least five of them in total.

Using express methods helps to obtain data within a day, but the cost, of course, is higher.

This will require a sample from ten places, and each will cost 3,000 rubles. Such studies are necessary when developing large objects, in order to comply with all formalities and a documentary conclusion.

During home construction

You can determine the meaning at home yourself. This is very convenient and there is no need to call specialists, because it is quite expensive. First of all, the potential builder should know exactly the bulk of the selected material. This is usually indicated in the documentation that you can ask the supplier for.

It is worth remembering that the indicator is influenced by the composition of crushed stone and the amount of foreign impurities, as well as the size of the granules.

Once you know the bulk density, you can proceed to calculating the compaction factor. To do this, roll the crushed stone to the condition that you need during construction.

Then take measurements with a tape measure. Then the following formula is applied:

Compaction coefficient = mass of crushed stone / per volume.

As a result, you get two different density values ​​before and after compacting the material.

How to correctly determine the compaction coefficient of crushed stone fraction 20 40

For accurate measurements, laboratory testing will be required. Because with the use of special equipment, the reliability of the data obtained increases.

To determine the level of compaction, a special tip is inserted into the area under study and by how far the tip entered the dense crushed stone, as well as what it was like resistivity and the level of crushed stone compaction is determined.

The coefficient depends on what material the research is carried out with. The tip can be a regular cone or a truncated one. The degree to which the indicator arrow deviates during ring deformation determines the crushed stone compaction coefficient.

There is no particular difficulty in determining the density indicator of crushed stone. To do this, the density meter must be held vertically. Then plunge the tip firmly into the dense mixture.

After this, the device is removed and all readings are recorded in a special journal. For each selected location, the density meter must be immersed at least 5 times. The distance between the points should be up to 15 centimeters.

After this, all readings are compared with each other and the average reading is displayed. The documentation for the density meter contains a special graph, thanks to which the crushed stone compaction coefficient is determined.

Conclusion

Crushed stone today has become an indispensable material in construction work. Its use helps to achieve better results, This is especially true for the construction of monolithic high-rise buildings.

Through intelligent use different types crushed gravel durability increases and the weight of the final structure decreases. This is a definite plus, especially if the construction of skyscrapers is planned. Of course, before purchasing crushed stone material, you should decide what it will be used for.

After all, each type of crushed stone has its own characteristics, and most importantly, cost. Also, types of crushed stone have their own compaction coefficient. It should definitely be taken into account when designing a future structure.

The compaction coefficient is a dimensionless number that shows the degree of reduction in the external volume of bulk granular building material during transportation or compaction. Used for sand and gravel mixtures, sand, crushed stone, and soil.

Each type of crushed stone has its own marking, indicated in the accepted standard (GOST 8267-93). It also describes methods for determining the compaction coefficient. Manufacturers must indicate this parameter in the labeling of crushed stone of one type or another. The degree of compaction is also determined by experts experimentally. Results can be received within 3 days. The amount of crushed stone compaction is also measured using express methods. For this purpose, static and dynamic density meters are used. The cost of measuring the coefficient value in laboratory conditions is significantly lower than directly on the construction site.

Why do you need to know the value of the compaction coefficient?

Knowledge of the exact value of Ku (crushed stone compaction coefficient) is required to determine: a) the mass of the purchased building material; b) the degree of further shrinkage of crushed stone during construction work. In both cases, errors cannot be made.

The mass of crushed stone (in kg) can be calculated by multiplying the values ​​of 3 quantities:

• filling volume (in m3);
• specific gravity (in kg/m3);
• compaction coefficient (in most cases ranges from 1.1 to 1.3).

Experts use tables of the average mass of crushed stone depending on the fraction. For example, in 1 m3 crushed stone fits 1500 kg fraction 0-5 mm and 1470 kg fraction 40-70 mm.

Working with bulk materials is also associated with such a value as bulk density. Its consideration is mandatory in the process of decluttering, laying crushed stone, and calculating the composition of concrete. Its value is determined empirically using special vessels (volume up to 50 l). To do this, the difference in mass between an empty and a vessel filled with crushed stone is divided by the volume of the vessel itself.

Rasklintsovka— dense laying of the crushed stone base using grains of various fractions. The essence of the technology is to fill large voids between large grains with small pieces.

Tamping- one of mandatory conditions strengthening the base of roads or building foundations. It is carried out using special equipment (mechanical roller, vibrating plate) or manual rammer. The quality of the seal is controlled by a special device. The amount of compaction (tamping) can be determined by several methods. In particular, using the dynamic sensing method.

Compaction factor also used when calculating the required amount of bulk materials for leveling a site with crushed stone. Let the laying thickness be 20 cm. How much screening do we need for 1 m2 of area? Multiplying the volume of the area by the specific gravity (1500 kg/m3) and the compaction coefficient (1.3), we get 390 kg.

It should be remembered that different fractions of crushed stone have different compaction coefficients. This parameter becomes of great importance when performing design work based on crushed stone.

Main characteristics and areas of application of crushed stone

Crushed stone is a granular building material. In nature, it is formed as a result of the weathering of rocks. It occurs in the form of clusters (loose and weakly cemented). Or it is obtained by mechanically crushing rocks and stones into pieces. Soft nonmetallic rocks (gravel, boulders, limestone) are also used for its production. Rubble has a number physical properties(strength, bulk density, radioactivity and others). Depending on the type of material, it is divided into several types: granite, gravel, limestone, slag and secondary.

Granite, produced by crushing granite (hardened magma). Technological process receiving crushed granite includes 3 stages:

• blocks are formed from monolithic rocks by explosion;
• lumps are crushed using special machines;
• the resulting pieces are sifted into fractions. The following types of granite crushed stone are distinguished depending on the maximum particle sizes.
• Screenings, particle sizes up to 5 mm, is used as a decorative finishing material, for filling country paths, sports grounds and other purposes.
• Fine, consists of two fractions (5-10 and 10-20 mm). A very valuable material in construction. Used in the production of concrete, laying bridges and road surfaces.
• Medium (20-40 mm).
• Large (40-70 mm).
• Extra large. This includes pieces of size 7-120 and 120-150 mm. Produced by agreement between the manufacturer and the consumer.

Gravel, can be obtained by sifting quarry rocks or by crushing natural stone. It is inferior in strength to crushed granite. However, it has some advantages: low radioactivity and price. It exists in the form of crushed stone (natural or crushed) and rounded pebbles (gravel).

Limestone is made from sedimentary rock (limestone) by crushing it. Finds wide application in construction installation work (road construction, production of reinforced concrete products).

Slag, made from metallurgical slag and slag melts. Used for the production of slag concrete.

Secondary, formed from construction waste (concrete, bricks, asphalt). In some respects it is inferior to crushed rocks, but is widely used in many construction works.

Crushed stone is a common building material that is obtained by crushing hard rock. Raw materials are extracted by blasting during quarrying. The rock is divided into appropriate fractions. In this case, the special compaction coefficient of crushed stone is important.

Granite is the most common, as its frost resistance is high and water absorption is low, which is so important for any building structure. The abrasion and strength of granite crushed stone meets the standards. Among the main fractions of crushed stone we can note: 5-15 mm, 5-20 mm, 5-40 mm, 20-40 mm, 40-70 mm. The most popular is crushed stone with a fraction of 5-20 mm; it can be used for various works:

• construction of foundations;
• production of ballast layers for highways and railway tracks;
• additive to construction mixtures.

The compaction of crushed stone depends on many indicators, including its characteristics. Should be considered:

1. The average density is 1.4-3 g/cm³ (when compaction is calculated, this parameter is taken as one of the main ones).
2. Flakiness determines the level of plane of the material.
3. All material is sorted into fractions.
4. Frost resistance.
5. Radioactivity level. For all work, you can use crushed stone of the 1st class, but the 2nd class can only be used for road work.

Based on such characteristics, a decision is made which material is suitable for certain type works

Types of crushed stone and technical characteristics

Various crushed stones can be used for construction. Manufacturers offer different types of it, the properties of which differ from each other. Today, based on the type of raw material, crushed stone is usually divided into 4 large groups:

• gravel;
• granite;
• dolomite, i.e. limestone;
• secondary.

To make granite material, the appropriate rock is used. This is a non-metallic material that is obtained from hard rock. Granite is solidified magma that is very hard and difficult to process. Crushed stone of this type is manufactured in accordance with GOST 8267-93. The most popular is crushed stone having a fraction of 5/20 mm, as it can be used for a variety of works, including the manufacture of foundations, roads, platforms and other things.

Crushed gravel is a bulk construction material that is obtained by crushing stony rock or rock in quarries. The strength of the material is not as high as that of crushed granite, but its cost is lower, as is the background radiation. Today it is common to distinguish between two types of gravel:

• crushed type of crushed stone;
• gravel of river and sea origin.

According to the fraction, gravel is classified into 4 large groups: 3/10, 5/40, 5/20, 20/40 mm. The material is used for preparing various building mixtures as a filler; it is considered indispensable for mixing concrete, building foundations, and paths.

Crushed limestone is made from sedimentary rock. As the name implies, the raw material is limestone. The main component is calcium carbonate, the cost of the material is one of the lowest.

The fractions of this crushed stone are divided into 3 large groups: 20/40, 5/20, 40/70 mm.

It is applicable to the glass industry, in the manufacture of small reinforced concrete structures, in the preparation of cement.

Recycled crushed stone has the lowest cost. It is made from construction waste, for example, asphalt, concrete, brick.

The advantage of crushed stone is its low cost, but in terms of its main characteristics it is much inferior to the other three types, therefore it is rarely used and only in cases where the strength of great importance does not have.

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Compaction factor: purpose

The compaction coefficient is a special standard number determined by SNiP and GOST. This value shows how many times crushed stone can be compacted, i.e. reduce its external volume during compaction or transportation. The value is usually 1.05-1.52. According to existing standards, the compaction coefficient can be as follows:

• sand and gravel mixture - 1.2;
• construction sand - 1.15;
• expanded clay - 1.15;
• crushed gravel - 1.1;
• soil - 1.1 (1.4).

An example of determining the compaction coefficient of crushed stone or gravel can be given as follows:

1. It can be assumed that the mass density is 1.95 g/cm³; after compaction was carried out, the value became 1.88 g/cm³.
2. To determine the value, you need to divide the actual density level by the maximum, which will give a crushed stone compaction coefficient of 1.88/1.95=0.96.

It is necessary to take into account that the design data usually does not indicate the degree of compaction, but the so-called skeleton density, i.e. During calculations, it is necessary to take into account the level of humidity and other parameters of the building mixture.

To install crushed stone layers (bases and coverings), the following work is performed: removing crushed stone for the lower layer and distributing it with self-propelled spreaders (as an exception, distribution of crushed stone by a bulldozer or motor graders may be allowed); compaction of crushed stone with simultaneous watering; removal of crushed stone for the top layer and its distribution; compaction of crushed stone with watering; removal of crushed stone for clearing and its distribution using mounted distributors with sweeping by mechanical brushes; compaction with watering; removal of crushed stone for final wedging of coatings, its distribution and final compaction with watering.
In the lower and middle layers of crushed stone bases, crushed stone of fractions 40-70 and 70-420 mm is used; in the upper layers of bases and coatings - 40-70 mm; for wedging - 5-10, 10-20 and 20-40 mm.
For foundations laid using the “wedge” method, fractionated crushed stone of natural rocks, crushed stone from mining waste and low-active crushed stone from ferrous metallurgy slag are used. They also use cast slag crushed stone chemical industry (phosphorus), containing predominant amounts of calcium oxides (CaO) and silica (SiO2), the content of oxides (Al2O3, FeO, MnO, MgO) is lower than in ferrous metallurgy slags. A distinctive feature of these slags is the presence of CaF2 and P2O5 compounds. The strength of crushed stone must comply with current SNiPs.
Requirements for strength and frost resistance of standard (up to 70 mm) and large (70-120 mm) fractions of crushed stone from natural rocks and from slag for foundations, depending on the category highways and climatic conditions are indicated in table. 50.

The removal and distribution of crushed stone is carried out taking into account the compaction coefficient of 1.25-1.30. The maximum thickness of the compacted layer should not exceed 18-20 cm.
To distribute crushed stone, two types of self-propelled crushed stone spreaders can be used: I - for laying crushed stone or gravel layers on sand layer(the paver is loaded by dump trucks moving along the side of the road); II - for laying crushed stone or gravel layers on a solid base (material is loaded from the base side).
Crushed stone from a dump truck usually enters the distributor hopper of the crushed stone spreader, the output of which is controlled by valves. The thickness of the leveled layer is regulated by a screed bar, and the width is fixed by side stops. The leveled layer of crushed stone (gravel) is compacted by vibrating plates with vibrators installed on them.
If the base is sandy and there are no self-propelled spreaders, crushed stone can be unloaded at the edge of the compacted crushed stone layer and then moved onto it with a bulldozer. In the trough, the crushed stone is leveled with a motor grader or bulldozer.
When rolling crushed stone in a trough, it is necessary to create a reliable side stop, for which a strip of side stones is laid along the edges of the trough before the crushed stone is scattered, or temporary stop boards 5-6 cm thick are placed along the edges of the roadway on the edge. The side strips or boards on the side of the roadside are sprinkled with soil. with careful compaction.
Compaction of crushed stone is the most important part of the work on constructing a crushed stone layer. During the compaction process, movement, convergence and mutual jamming of crushed stones occur, and significant vertical and horizontal forces arise. Compaction is carried out by motor rollers with metal rollers, rollers on pneumatic tires, vibratory rollers and vibrating plates. The entire compaction cycle can be divided into three periods: sedimentation of crushed stone, compaction, creation of a dense surface crust.
The first period is characterized by the compaction of the placer, the movement of individual crushed stones, which continues until they occupy the most stable position. This period is characterized by the presence of mainly residual deformations, which decrease significantly towards the end of the period.
The second period is characterized by complete convergence and mutual jamming of crushed stones with filling of the gaps with broken off particles; As a result of this process, a rigid, stable skeleton with a porous (porous) surface is obtained. By the end of the second period, there should be practically no residual deformation.
In the third period, the formation of a dense crust in the upper part of the layer should be achieved by wedging its surface with fine crushed stone.
To obtain a dense and durable crushed stone layer, it is very important to ensure the correct mode of watering during compaction. The initial compaction of crushed stone of normal sizes does not require watering, since in a loose placer the individual crushed stones are relatively easily distributed and mutually moved. In the first period, watering is carried out only when compacting crushed stone of low-strength rocks larger than 70 mm in size. Once the initial settlement of the layer has been achieved, further compaction requires overcoming friction between the crushed stones. In this case, water facilitates compaction, and partly also goes into the formation of a cementitious paste from the fines obtained from breaking off the edges of crushed stone. During the formation of a dense surface crust, the cementing dough from the seedings can stick to the rollers of the roller and contribute to tearing out the crushed stones from the coating, so watering is stopped at the last stage of coating formation. On average, 15-25 liters of water per 1 m2 are required in the second period and about 10-12 liters per 1 m2 of coating in the third rolling period.
Watering is carried out immediately before compaction from tank trucks equipped with a distribution system. If there is a lack of water, the compaction time will be prolonged, and if there is too much water, the underlying layer may become waterlogged.
Compaction begins with light rollers from the edges to the middle of the coating. Compaction of crushed stone with rollers with metal rollers begins from the roadside in three to four passes along one track, followed by the roller passes approaching the road axis, overlapping the previous tracks by 1/3 of the width and reducing the number of passes along the road axis to one. Having reached the axis, the roller again moves to the edge and moves from the edge to the axis.
Roll with a light roller until it leaves a noticeable mark. Then compaction is continued with heavier rollers with mandatory watering to reduce friction when the crushed stones jam against each other. If subsidence occurs, it is necessary to immediately level it by adding fresh crushed stone.
When rolling the top layer, the first passes compact the area, the axis of which is the curb (the edge of the placer) with partial grips of the shoulders, which are poured out of stable soils during the installation of the base layer by layer and over the entire width. This creates a stop that prevents the spread of crushed stone during rolling. With subsequent passes, the roller, alternately moving from one side to the other, approaches from the edges to the middle.
Compaction of crushed stone in the second period requires the largest number of passes of the roller along one track, and it is very important to determine the end of rolling, since overcompaction can lead to rounding and crushing of crushed stone and to the breakdown of the compacted layer,
Before the third rolling period, to fill the voids in the upper layer of the crushed stone skeleton, crushed stone is distributed over the surface for wedging using mounted distributors at the rate of 1.5-2 m3 per 100 m2 of coating, depending on the size of the crushed stone. Signs of the end of compaction of the top layer in the second and third periods are: absence of a trace - precipitation from the passage of a 12-ton roller, immobility of crushed stone, disappearance of a wave, crushing of crushed stone thrown under the roller.
When installing crushed stone coverings, it is also necessary to scatter stone fines (1 m3 per 100 m2 of covering), sweeping it over the surface and rolling it with a heavy roller. Before rolling the wedge and stone chips, the coating is watered with water.
The number of passes of the roller along one track depends on the quality of the crushed stone and is approximately 3-6 for the first compaction period; second - 10-35; third - 10-15 passes. In each specific case, the number of passes should be determined by experimental compaction of the area.
When compacting crushed stone pavement, it is necessary to periodically check the longitudinal and transverse profiles. If individual unevenness and waves are formed during rolling, the crushed stone in these places must be loosened and the excess must be moved to low places, or the subsidence must be leveled with crushed stone of the same size, followed by rolling with light rollers.
At the end of rolling, the top layer should be smooth and uniform; a heavy roller leaves no trace on such a layer. It is advisable to control the evenness of the coating using a mobile two-support folding rail PKP-5 designed by Soyuzdornia.
For getting flat surface The base mixture should be laid using special laying machines or motor graders with a tracking system.
The vertical evenness of the layers of road structures is achieved by using tracking systems to ensure evenness: stabilizing (according to the DS-515 grader scheme), tracking (D-699, D-700), and software.
The basis of stabilizing systems is the principle of ensuring a gap, no more than permissible, under a rail of a certain length. An effective remedy To reduce the amplitude of unevenness of the leveled surface and expand the range of leveled wavelengths, the long-base leveler DS-515, made according to a grader scheme with a reduced ratio of the distance from the axis of the rear support to the working body to the base of the leveler, can be used.
Tracking systems installed on pavers and motor graders ensure that a given level is achieved by moving the working element in accordance with changes in the vertical marks of a real reference longitudinal profile, called a copier.
The following can be used as a copier: a compacted and profiled base or an adjacent strip of coating; rigid metal copier made of slats 1.5-4.0 m long; a wire or cable stretched along the covering with supports installed every 5-15 m; beam (light, laser, etc.) with the placement of radiation sources every 10-400 m, depending on the longitudinal profile of the road.
The domestic industry produces asphalt pavers D-699, D-700, concrete paver DS-510 with a tracking system, as well as systems. "Profile-1" and "Profile-2" for the motor grader.
Software systems set the vertical marks of the surface of the base or coating through the appropriate installation of the working element, and the control value software system is a program or record of commands for changing the position of the working body.
The moment of completion of rolling can be accurately determined using a dynamometer by Ya. A. Kaluzhsky. This device is installed on a motor roller and records the value of the rolling resistance coefficient (the ratio of traction force to the mass of the roller). After the disappearance of residual deformations, the value of the coefficient becomes minimal and stabilizes. This shows that further compaction with this roller is impractical.
The speed of the roller is of great importance for the efficiency of rolling. You should roll especially carefully at the beginning, when there is a significant wave in front of the roller rollers. In this case, the speed should not exceed 1.5-2.0 km/h (for rollers with metal rollers).
When choosing types of rollers, you need to take into account not only the rolling period, but also the strength of the stone material being rolled. For low strength stone materials Lighter rollers should be used (Table 51).

When working on three-drum two-axle rollers, it should be borne in mind that they compact mainly with rear rollers, which provide a large amount of pressure, and therefore the roller passes must be taken into account in strips corresponding to the width of these rollers.
If it is impossible to achieve the required compaction (or it is necessary to open traffic on the crushed stone base), the following measures can be taken: wedging the base with fine crushed stone or sand treated in installations with organic binders; pouring bitumen or tar (2-3 kg/m2) before scattering crushed stone or distributing a wet mixture of cement and sand (1:4) at the rate of 7-10 kg of cement per 1 m2; replacing propping small crushed stone with another one that has good cementing properties (limestone); replacement of highly rounded crushed stone with sharp-edged one.
Crushed stone, crushed stone-sand or cement-sand mixtures for wedging are distributed with mounted distributors at the rate of 2-3 m3 per 100 m2 of base, depending on the size and compactability of the crushed stone.
In the first 10-15 days of operation of the crushed stone coating, it is necessary to organize care for its formation: correct partial minor damage and sweep up scattered small items. In Fig. 43 shown technology system crushed stone layer devices.
Road bases made of coarse crushed stone. Crushed stone materials with maximum size up to 120 mm are used for the construction of lower crushed stone layers; pieces about 16 cm high of the appropriate shape can in some cases be used for the construction of pakage bases or bridges.

The construction of foundations made of coarse crushed stone of low-strength limestone and sandstone has the appearance of features. Careful management of the work is required to ensure the cleanliness of the crushed stone and its minimum crushability during movement, leveling and, most importantly, during compaction. It is advisable to transport very large crushed stone into piles placed perpendicular to the axis of the road. The crushed stone is leveled and leveled with a bulldozer or motor grader equipped with a special blade. When moving forward, the blade moves the crushed stone to the required place, and then, after setting it to a given height, in reverse motion it levels this layer. Bulldozers should be used with low or medium power (preferably with pneumatic tires), since heavy machines crush crushed stone and press it into the sand layer.
With a design thickness of up to 20 cm, it is advisable to arrange the base in one layer of crushed stone with a size of 40-120 mm, and for wedging, use crushed stone with a size of 25-40 mm. When the thickness of the base is over 20 cm, it is arranged in two layers, and crushed stone with a size of 70-120 mm is used for the bottom layer.
Due to the fact that the bulldozer performs only rough leveling, to obtain the required profile, it is advisable to lay crushed stone of fractions 40-70 or 25-70 mm on a layer of coarse crushed stone; This crushed stone can be leveled with a motor grader.
If the surface of the base is too porous, you can use crushed stone with a particle size of 15-25 mm. This crushed stone is distributed by trailed crushed stone spreaders. The scattering of each fraction must be compacted.
To compact layers of low-strength crushed stone, machines that do not destroy crushed stone should be used (planar vibrators, self-propelled rollers on pneumatic niches). When compacting large crushed stone of low strength, the forces required to move the crushed stone exceed the forces expended on breaking off the edges.
This can explain the significant crushability of crushed stone already in the first period of compaction. To reduce crushability, large crushed stone must be watered with water from the very beginning of compaction. The amount of water should be such as not to cause severe weakening and crushing of crushed stone. When vibrating compaction, the crushed stone must be dry.
The technological scheme for constructing foundations made of coarse crushed stone on a drainage sand layer consists of the following operations.
- removal by dump trucks of crushed stone of fractions 70-120 mm and unloading it into piles at the edge of the placer; leveling crushed stone with bulldozers;
- compaction of crushed stone with rollers on pneumatic tires (with watering) or vibration machines (without watering);
- removal by dump trucks of crushed stone with a particle size of 40-70 mm and its distribution by self-propelled crushed stone distributors;
- compaction of crushed stone with light rollers on pneumatic tires (with watering) or vibrating machines (without watering), removal by dump trucks and distribution of crushed stone with a particle size of 15-40 or 25-40 mm in the case of a porous surface using trailed distributors;
- compaction of crushed stone with light rollers on pneumatic tires (with watering) or plane vibration machines (without watering).
The given technological scheme can be modified depending on the thickness of the base, the size and class of crushed stone, the presence of compaction means and crushed stone distributors.