Expanded clay gravel is a building material obtained from clay by firing and is a rounded fragment with pores inside and a melted surface.

The document regulating the requirements for expanded clay gravel: technical parameters, acceptance rules, test methods, transportation and storage is the Interstate Standard GOST 32496-2013 “Porous Aggregates for Lightweight Concrete. Specifications”.

The production of expanded clay gravel is carried out in special drum ovens, where the raw material, which is montmorillonite and hydromicaceous clays, is brought to a certain structural state, after which it is cooled.

Production

The production process is divided into several stages:

1. Preparation of raw materials.
2. Burning.
3. Cooling.

Schematically, the production process looks like this:

The requirements for the raw materials from which expanded clay gravel is made are determined by three parameters, these are:

1. The content of quartz should be no more than 30%, silicon oxide - no more than 70% and minerals - no less than 12%.
2. Low melting point - firing temperature should not exceed 1250˚С;
3. Swelling interval - must meet the requirements.

The preparation of raw materials can be carried out using several technologies. This is dry preparation - when the clay rock is crushed to the required grain size, followed by division into fractions. Plastic preparation - the formation of grains is carried out by kneading the feedstock in a special machine (clay mixer) and molding the granules, followed by drying. Powder - plastic preparation - the process is carried out similarly to the preparation according to the plastic method, with the only difference being that in this case, the raw material is initially converted into powder. Wet (slip) preparation - clay is mixed with water in special devices (clay mashers), where a clay solution, called slip, is obtained, which is fed into the furnace. Furnaces, with this technology, are equipped with special curtains of chains, which heat up during operation. The slurry is fed to the chains, where it is broken into pieces, which are subsequently fired.

Roasting takes place in special furnaces of various designs:

• Rotary, one- and two-drum kilns - with this design, the prepared raw material is fed into the upper part of the drum, which is placed at a certain angle to the ground surface. At the bottom of the drum there is a nozzle that provides heating of the internal space of the device. Clay granules roll down the walls of the drum and are subjected to heat treatment, during which the clay boils and swells, its upper layer melts.
• Ring - the production of expanded clay is carried out by the method of thermal shock. Finished granules are 25-40% lighter than when fired in drums.
• Vertical, aerofountain - expanded clay is produced in an upward flow of hot gases. With this design, thermal shock also occurs, which causes active swelling in the clay.

Cooling takes place in several stages with a gradual decrease in temperature: 1st stage - at the end of swelling of the clay - to a temperature of +800-900°C, 2nd stage - for 20 minutes, until a temperature of +600 - 700°C is reached and 3 th stage - final cooling.

In accordance with GOST 32496-2013, gravel is produced in three fractions, these are:

1. Fine fraction - the size of fragments (grains), ranges from 5.0 to 10.0 mm;
2. Medium fraction - grain size is from 10.0 to 20.0 mm;
3. Large fraction - grain size is from 20.0 to 40.0 mm.

The main technical parameters of expanded clay gravel are:

• Bulk density (bulk density).

It is measured in kg per m3, 11 grades are produced - from grade M150 to M800, the most in demand are M450, M500, M600.

The true density (bulk density) is 1.5-2 times greater than the bulk density.

• Strength.

The strength of the material is measured in MPa (N / mm2), 13 strength grades are produced - from P15 to P400.

There is a connection between expanded clay grades in terms of density and strength - an increase in density leads to an increase in strength.

• Compaction coefficient - the value (K=1.15) is used to take into account the compaction of the material mass during transportation or storage.
• Soundproofing. Expanded clay has increased sound insulation.
• Frost resistance.

Expanded clay has sufficiently high frost-resistant properties. It is characterized by a loss in the mass of the material, measured in%.

• Thermal conductivity is the most important indicator.

Measured in W/m*K. It characterizes the ability of a material to retain heat. As the density increases, the thermal conductivity increases.

• Water absorption.

Measured in mm. Determines the amount of moisture that expanded clay can absorb. Expanded clay refers to relatively resistant materials to moisture.

• The number of radionuclides.

Specific effective activity of radionuclides should not exceed 370 Bq/kg.

In accordance with GOST 32496-2013, the grade of expanded clay gravel should be according to:

• Strength, depending on the brand:

Gravel grade	Strength, MPa
	Up to 0.5	0,5 – 0,7	0,7 – 1,0	1,0 – 1,5	1,5 – 2,0	2,0 – 2,5	2,5 – 3,3	3,3 – 4,5	4,5 – 5,5
By strength	P15	P25	P35	P50	P75	P100	P125	P150	P200

• According to the bulk density, it must correspond to the strength grade, namely:

Gravel grade
By bulk density	M150	M200	M250	M300	M350	M400	M450	M500	M600	M700	M800
By strength	P15	P25	P25	P35	P50	P50	P75	P100	P125	P150	P200

The frost resistance of the material is also normalized by GOST - the mass loss of expanded clay gravel should not exceed 8%.

Thermal conductivity depends on the technology of preparation and composition of raw materials, the design of the firing furnace and cooling conditions. Depending on the density of the material obtained and the manufacturing technology, the thermal conductivity ranges from 0.07 to 0.18 W/m*K.

The ability of expanded clay to absorb moisture (moisture absorption) is also an important parameter that characterizes this building material. Moisture absorption coefficient for different grades is from 8.0 to 20.0%. The ability to absorb moisture, in relation to the mass of the material, for 1 hour, should be no more than, for grades:

• Up to M400 - 30%;
• M450 - M600 - 25%;
• M700 - M800 - 20%.

The total moisture content of the shipped batch of material should not exceed 5.0% of the total mass of gravel.

After expanded clay is made, the finished material is sent for sale, in the form of a bulk or in a certain package, while the number of damaged (split) grains should not exceed 15% of the total mass of the material produced.

In addition, in the production of expanded clay gravel, the shape of the grains is controlled, which is determined by the shape factor. The form factor should be no more than 1.5, and the number of grains exceeding this indicator should also be no more than 15% of the total amount in the batch of material.

When selling in bulk and using containers, the selling organization must have certificates of conformity, test results and waybills for the material. When sold in containers (packaged), the products are marked on the packaging. The marking indicates: the name of the filler, the manufacturer's data, the date of manufacture, the value of thermal conductivity, the amount of filler, test results and the designation of the standard.

For packing, paper, polypropylene and fabric bags are used, which must comply with the requirements of GOST for this type of container. Marking is applied to each bag, in accordance with the requirements for labeling the goods indicated above.

The quality control of the material is carried out by the manufacturer, while the control is carried out from the moment of receipt of raw materials, until the end of the production process (input, operational and acceptance control), data on which are recorded in special journals and drawn up in protocols.

When conducting acceptance tests, the following are determined:

• grain composition in each batch;
• bulk density;
• strength;
• grain shape coefficient;
• the content of split grains in the gravel;
• humidity.

With long-term storage of the finished material, periodic tests are carried out, which are carried out:

• once every two weeks - the loss of mass on ignition and the content of lightly burned grains are checked;
• once a quarter - the mass loss during boiling is checked;
• once every six months - frost resistance and softening coefficient are checked;
• once a year - the specific effective activity of natural radionuclides and thermal conductivity are checked.

At the start of production and every time a change in raw materials, tests are performed to check for radionuclides and the thermal conductivity of expanded clay.

Expanded clay prepared for sale is shipped, while the amount of material is measured by volume or its mass, taking into account the compaction coefficient (K = 1.15).

Advantages and disadvantages

Advantages of use:

1. Sufficient strength of the material.
2. Low thermal conductivity, and as a result - good thermal insulation properties.
3. It is a good sound insulator.
4. High fire resistance, defines this material as non-combustible, fireproof. When exposed to an external fire source, it does not support combustion, and does not emit harmful substances into the surrounding space.
5. Frost resistance.
6. Low specific gravity - allows you to use, if necessary, to reduce the weight of the building structures under construction.
7. Unaffected by weather conditions (humidity, temperature changes).
8. Inert to chemical attack.
9. Does not rot and is not subject to decomposition.
10. Long terms of operation.
11. It is an environmentally friendly material.
12. Ease of installation work.
13. Low cost, in comparison with other heat-insulating materials.

The disadvantages are:

1. When laying in a horizontal plane, laying the underlying layer is necessary.
2. In case of poor quality manufacture or in the manufacture without the formation of a surface crust, it absorbs moisture, after which it cannot be used as a heat insulator.
3. When used as a heater, it occupies a large volume, thereby reducing the space in the insulated room.

Due to its positive properties, expanded clay gravel is widely used in various types of construction work, such as:

• monolithic construction - used as a filler;
• thermal insulation is roofs, floors and ceilings of buildings, structures and structures;
• thermal insulation of various systems - "warm floor", water pipes, external heating pipes and other pipe systems.
• protection against noise of the internal space of the premises;
• production of concrete and building blocks;
• thermal insulation of the foundation - allows you to reduce the depth of laying the foundation;
• road construction - used for thermal insulation and water drainage in the construction of embankments for roads and in construction in wetlands.

Expanded clay is also used in the creation of landscape design of the site (creating alpine slides and terraces), if necessary, thermal insulation of the soil (when growing plants) and in crop production - to create drainage for the root system of plants.

When choosing ceramic gravel, it is necessary to follow the selection criteria, which are:

• Material quality.
• Availability of a certificate of conformity.
• Storage conditions of the finished material.
• The integrity of the fragments (grains) of the material.
• Color and presence of a crust on expanded clay grains.

Expanded clay gravel, due to its positive properties, has been widely used in various industries and economy, both in our country and abroad.

Every year, new building and cladding materials appear on the market. The improvement of production technologies allows creating materials that are characterized by low weight, good strength parameters and thermal insulation characteristics. Expanded clay meets even the highest requirements for building and facing products, therefore it is increasingly being used in various fields. The technical characteristics of this material will be discussed below.

Main features - structure and types of modern expanded clay

Expanded clay is made from clay by firing blanks in high-temperature furnaces. The outer layer of clay conglomerates melts under the influence of high temperature, which provides expanded clay with its specific color and smooth surface. During firing, gas is released from the clay, due to which the finished products acquire a porous structure.

Clay is the basis of a large number of different building materials. This is cement, and brick, and many others. Such an active use of clay is due to its excellent natural strength characteristics, which are transferred to the materials made from it. The properties that ensure the high popularity of expanded clay in the modern market, it acquires precisely during the processing of clay. The porous structure provides a low weight of the products and their good thermal insulation qualities.

Depending on how and from what expanded clay is produced, its shape, appearance and other important parameters are determined. In total, there are three types of such products:

1. 1. Gravel. Expanded clay gravel is oval pellets or granules of red-brown color. It is widely used in the construction industry.
2. 2. Rubble. Large fragments of split conglomerates of baked clay with sharp edges and angular shape. Such crushed stone is usually added to the composition of concrete solutions.
3. 3. Screening. The smallest particles of fired clay, which are usually a by-product of production (firing and crushing). Used in construction as a porous filler.

The first two types of products have sizes from 40 to 10 mm. Particles smaller than 5 mm already belong to screenings. The smallest elements of expanded clay sand are often used outside the construction industry. For example, today it is customary to use such material in the manufacture of water purification filters.

The use in cleaning systems once again confirms the environmental friendliness of expanded clay. The material is completely non-toxic, which endlessly expands the ways of its use in everyday life.

Expanded clay - technical characteristics and properties that determine its popularity

Fired clay products have many important characteristics that are not constant and depend both on the type of product and on its main purpose. Among the main parameters of the material, the bulk density of expanded clay is necessarily distinguished. There are seven different grades of material on the market in terms of density: from the lightest density of 250 kg / m3 to the heaviest - with a density of up to 850 kg / m3. In the open sale, you can find brands of products from 250 to 600 kg / m3, brands 700 and 800 are made by manufacturers by direct order from the buyer.

The true density of materials can be 1.5 and even 2 times higher than the bulk density. Expanded clay density is a parameter that describes the weight of a cubic meter of granules, without taking into account the gaps between them and voids in individual conglomerates. That is, if the bulk density is 350 kg / m3, the true density can reach 700 kilograms per cubic meter.

When choosing materials, it is necessary to take into account not only the volumetric weight of the brand, but also strength. There are 13 types of gravel in terms of strength and 11 types of crushed stone on the market. The strength of such products of the same brand may vary. For example, crushed stone of the P100 brand has a strength of up to 1.6 MPa, while gravel of the same brand can have a strength of up to 2.5 MPa. The strength and density of expanded clay are interrelated: the higher the density, the higher the strength will be.

Another important characteristic of the material is the level of thermal conductivity. The range of thermal conductivity levels for various baked clay products is rather narrow. This is due to the ability of expanded clay to reliably retain heat. For different brands, this value varies between 0.10-0.18 W / (m * C). The higher the density of the material and its weight, the higher the thermal conductivity.

Expanded clay is resistant to moisture, its water absorption level is from 8 to 20% for different grades. Low water absorption provides clay products with high characteristics of resistance to low temperatures.

When choosing building materials, owners are usually interested in how much a cube of expanded clay weighs, how much it costs and what its advantages are, but they forget about the disadvantages, although they also exist. The first of them is that expanded clay crushed stone and gravel are prone to high dust formation, therefore, personal protective equipment, including a respirator, must be used to work at home. The second drawback is the lengthy time it takes for the material to dry completely when wet.

Where is expanded clay used?

Most often, materials are used to make lightweight concrete. Such a solution allows you to build lightweight monolithic walls, pour rough screeds and perform other important work. A light mortar is simply indispensable if you need to lay a large screed in an old apartment building in which the floors are not in the best condition and cannot withstand a significant increase in load. The small specific gravity of expanded clay makes it possible to create lightweight building structures without investing a lot of money in them. The walls created in this way are distinguished by excellent hygienic and sanitary characteristics, they are durable and affordable.

Those who are interested in what expanded clay is and where to use it at home usually find recommendations on the use of such material for insulating private houses. However, it is not possible to carry out such work on your own. Only experienced specialists will be able to carry out calculations to determine the required density of products for insulation, choose the most suitable brand and correctly install the insulation layer. By the way, from a practical point of view, using expanded clay for insulation is not always rational, since the material may require falling asleep a heat-insulating layer 30-40 cm thick.

In a completely different way, it is possible to perform insulation and cladding of a residential facility if you use not bulk material, but expanded clay concrete blocks made from it. They are characterized by high density and allow effective and attractive cladding of modern ventilated facades.

The excellent properties of expanded clay led to its widest use in the construction of foundations for residential and non-residential facilities. Due to its resistance to moisture and frost, it can be used to significantly reduce the required depth of the foundation by almost 2 times. For example, if without the use of special gravel the estimated depth of the foundation is 1.5 meters, with the help of baked clay it can be reduced to 80 cm.

Expanded clay granules are quite unusual and attractive, which allows them to be used not only in construction, but also in the design of home gardens. For example, they allow you to create quite aesthetic paths on the land, which will not get wet and will not lose their visual characteristics over time.

STATE STANDARD OF THE UNION OF THE SSR

GRAVEL, STONE AND SAND
ARTIFICIAL POROUS

TECHNICAL CONDITIONS

GOST 9757-90
(ST SEV 5446-85)

USSR STATE CONSTRUCTION COMMITTEE

STATE STANDARD OF THE UNION OF THE SSR

Introduction date 01.01.91

This standard applies to artificial porous gravel (expanded clay, shungizite, agloporite), crushed stone (slag-pumice, agloporite, expanded clay) and sand (expanded clay crushed and roasted, shungizite, agloporite, slag-pumice), used as aggregates in the preparation of lightweight concrete according to GOST 25820 and silicate concrete according to GOST 25214, as well as heat-insulating and sound-proof fillings.

This standard does not apply to expanded vermiculite and perlite thermolite.

Classification, terms and definitions - according to GOST 25137.

1. TECHNICAL REQUIREMENTS

1.1. Artificial porous gravel, crushed stone and sand (hereinafter referred to as gravel, crushed stone and sand) should be produced in accordance with the requirements of this standard according to technological regulations approved in the prescribed manner.

1.2. Main dimensions

from 5 to 10;

from 10 to 20;

from 20 to 40 mm.

By agreement between the manufacturer and the consumer, it is allowed to produce gravel and crushed stone from 2.5 to 10 mm and a mixture of fractions from 5 to 20 mm, and for heat-insulating backfills - from 5 to 40 mm.

1.2.2. Sand, depending on the grain composition, is divided into three groups:

1 - for structural and heat-insulating concrete;

2 - for structural concrete;

3 - for insulating concrete.

By agreement between the manufacturer and the consumer, it is allowed to produce a sand-gravel mixture with the largest grain size up to 10 mm.

1.2.3. The grain composition of gravel and crushed stone of each fraction must correspond to that indicated in Table. .

Table 1

Note. D, d- respectively, the largest and smallest nominal diameters of the control sieves.

In gravel and crushed stone of a fraction from 2.5 to 10 mm and a mixture of fractions from 5 to 20 mm, the content of grains with a size of 5 to 10 mm should be from 25 to 50% by weight.

1.2.4. The grain composition of the sand must correspond to that indicated in Table. .

table 2

	Total residue on test sieve, by volume, for sand groups
			Not standardized
Pass through a sieve 0.16

In a sand-crushed stone mixture with a grain size of up to 10 mm, the content of crushed stone of a fraction from 5 to 10 we should be no more than 50% by volume.

1.3. Characteristics

1.3.1. Depending on the bulk density, gravel, crushed stone and sand are divided into grades given in Table. .

Table 3

	Bulk density, kg / m 3
	Up to 250 included
	St. 250 to 300 "

1.3.2. The limit values ​​​​of grades for bulk density for various types of porous gravel, crushed stone and sand must correspond to those given in table. . At the same time, the actual grade in terms of bulk density should not exceed the maximum value, and the minimum values ​​are given as reference.

Table4

	Bulk density grades
	minimum	maximum
Gravel and crushed stone expanded clay
shungizite gravel
Aggloporite gravel
Aggloporite crushed stone
Crushed slag-pumice stone
Expanded clay and shungizite sand
Aggloporite sand
Slag-pumice sand

Note. It is allowed, by agreement between the manufacturer and the consumer, for the preparation of structural lightweight concrete of classes B20 and above, the production of expanded clay gravel and crushed stone of grades 700 and 800.

Compressive strength in the cylinder, MPa

expanded clay and shungizite gravel

expanded clay crushed stone

aggloporite

slag-pumice rubble

Note. The ratio between the filler grade in terms of strength and compressive strength in the cylinder can be specified on the basis of testing in concrete according to GOST 9758.

Strength grade, not less

expanded clay gravel and crushed stone

shungizite

aggloporite

slag-pumice rubble

Note. For heat-insulating backfills, it is allowed to produce gravel and crushed stone with a strength grade lower than indicated in the table, but not less than grade P15.

1.3.6. In gravel, crushed stone and sand used as aggregates for reinforced concrete, the content of water-soluble sulfur and sulfate compounds in terms of SO 3 should not exceed 1% by weight.

1.3.7. The structure of aggloporite gravel and crushed stone and slag-pumice crushed stone must be resistant to silicate decay. Weight loss when determining resistance to silicate decomposition should be, %, not more than:

5 - for slag-pumice rubble;

8 - for agloporite gravel and crushed stone.

1.3.8. The mass loss during boiling should be, %, not more than:

5 - for expanded clay gravel and crushed stone;

4 - for shungizite gravel.

1.3.9. Loss of mass during ignition should be, %, not more than:

3 - for agloporite gravel and crushed stone;

5 - for aggloporite sand.

8 - for agloporite gravel, crushed stone and sand from the ashes of the thermal power plant.

5 - for agloporite gravel and crushed stone;

3 - for expanded clay sand obtained in fluidized bed furnaces.

1.3.11. For gravel and crushed stone used for heat-insulating backfills, the requirements of paragraphs. - do not apply.

1.3.12. Gravel, crushed stone and sand intended for the preparation of heat-insulating and structural-heat-insulating lightweight concretes must be subjected to periodic tests for thermal conductivity.

in newly built and reconstructed residential and public buildings with A eff up to 370 Bq/kg;

in the construction of industrial buildings and structures with A eff over 370 Bq/kg up to 740 Bq/kg.

If necessary, in the national norms in force on the territory of the state, the value of the specific effective activity of natural radionuclides can be changed within the limits indicated above.

2. ACCEPTANCE

2.1. Gravel, crushed stone and sand must be accepted by the technical control of the manufacturer.

2.2. Gravel, crushed stone and sand are accepted in batches.

A batch is considered to be the amount of gravel and crushed stone of the same fraction and of the same brand in terms of bulk density and strength, simultaneously shipped to one consumer in one train, but not more than 300 m 3. The batch is considered the amount of sand of one group and brand by bulk density, simultaneously shipped to one consumer, but not more than 300 m 3.

When shipped by road, a batch is the amount of material that is simultaneously shipped to one consumer during the day.

2.3. Compliance of the quality of gravel, crushed stone and sand with the requirements of the standard is established according to the data of input, operational and acceptance control. The results of incoming, operational and acceptance control must be recorded in the relevant journals of the laboratory, Quality Control Department or other documents.

The procedure for carrying out, the volume and content of the input and operational control are established in the relevant technological documentation.

Acceptance control is carried out in accordance with the requirements of this standard by conducting periodic and acceptance tests.

2.4. Periodic testing of finished products is carried out:

once every two weeks to determine:

mass loss during calcination of aggloporite gravel, crushed stone and sand;

once a quarter to determine:

resistance against silicate decay of slag-pumice crushed stone and aggloporite gravel and crushed stone;

weight loss during boiling expanded clay gravel and crushed stone, shungizite gravel;

once every six months to determine frost resistance of gravel and crushed stone;

once a year,as well as every time the raw material is changed to determine the content of natural radionuclides and the thermal conductivity of gravel, crushed stone and sand.

(Revised edition, Rev. No. 1).

2.5. Acceptance tests of gravel, crushed stone and sand of each batch are carried out to determine:

grain composition;

bulk density;

strength (only for gravel and crushed stone).

Subject to the rules for separate storage of gravel, crushed stone and sand by grade, it is allowed to carry out acceptance control of the quality of aggregates during the production process and to carry out spot sampling on production lines in accordance with paragraphs. 2.2 and 2.3 GOST 9758.

The combined sample is used to determine all quality indicators of gravel, crushed stone or sand. The bulk density of the material is also determined in each incremental sample.

The volume of samples and the procedure for their selection are taken according to GOST 9758.

2.7. The results of periodic tests are considered satisfactory if the values ​​of the quality indicators of the combined sample meet the requirements of paragraphs. -.

If the results are unsatisfactory, the production of gravel, crushed stone and sand should be stopped until measures are taken to ensure compliance with the established requirements.

2.8. A batch of gravel, crushed stone and sand is considered accepted based on the results of acceptance and periodic tests if the values ​​of the quality indicators of the combined sample comply with the requirements of paragraphs. -, and the values ​​of the bulk density of each incremental sample, in addition, do not exceed the maximum value established for this grade by more than 5%.

(Revised edition, Rev. No. 1).

4. TRANSPORT AND STORAGE

Gravel, crushed stone and sand are transported in railway wagons in compliance with the requirements of GOST 22235 and the Rules for the Transportation of Cargoes and the technical conditions for loading and securing cargoes approved by the Ministry of Railways. Wagons should be loaded taking into account the full use of their carrying capacity.

4.2. Gravel and crushed stone should be stored separately according to fractions and grades according to bulk density and strength, sand - according to grades.

4.3. During storage, gravel, crushed stone and sand should not be clogged.

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the State Association "Soyuzstroymaterialov"

DEVELOPERS

V. P. Petrov,cand. tech. sciences (topic leader); L. S. Burlakova; V. Ya. Argunova; V. G. Dovzhik, cand. tech. sciences; B. A. Verskain; S. G. Vasilkov, Dr. tech. sciences; S. V. Ronshina, cand. tech. sciences; F. M. Shukhatovich, cand. tech. sciences; R. I. Khodskaya, cand. tech. sciences; D. N. Kurolapnik, cand. tech. sciences; V. E. Yurovsky, cand. tech. sciences; M. Ya. Levitin, cand. tech. sciences; I. E. Putlyaev, Dr. tech. sciences; R. K. Zhitkevich, cand. tech. sciences; V. I. Savin, cand. tech. sciences; N. Ya. Spivak, cand. tech. sciences; N. S. Strongin, cand. tech. sciences; T. N. Kyiv; V. V. Eremeeva; T. A. Fironova

The production of expanded clay is based on the firing of fusible clay rocks under certain temperature conditions, as a result of which the clay swells, and expanded clay granules are obtained. Depending on the clay processing mode, the density of expanded clay will differ. There are the following processing modes:

• dry;
• wet;
• powder-plastic;
• plastic.

Since the density of expanded clay does not differ in high rates, the strength of expanded clay concrete blocks and other building materials made from it is also at a lower value compared to analogues. True, the mechanical strength does not depend on low strength, therefore expanded clay of any brand is distinguished by high mechanical strength.

The most important characteristic when choosing expanded clay, as a light porous material, is the bulk density.

How is the bulk density of expanded clay determined and what does it affect?

The density of expanded clay gravel is determined by weighing this material in containers, after which the result is divided by the volume of containers used. This is how the bulk density of expanded clay is obtained, while the lower it is, the higher its quality indicators. Depending on the density of expanded clay in accordance with GOST 9757-90, they are divided into several grades:

Its density indicates that in one cubic meter of volume, the weight of expanded clay is, for example, for the M250 brand - 250 kg. Grades with higher bulk density are available on request. This gradation is valid for expanded clay gravel, while for expanded clay sand, the density is indicated, starting from the minimum M500 grade and ending with the maximum M1000. With the same size of fractions and the same volume, the quality will be higher for the expanded clay, which will have less weight. The claydite quality indicators will be influenced by the grades of clay used in the production process and the accuracy of observing the technological process for manufacturing this material. Therefore, when choosing expanded clay, the density and weight of a cubic meter will be of decisive importance, even if expanded clay is purchased in bags.

It is necessary to distinguish between the true density of expanded clay and its specific gravity. The true density of expanded clay shows the mass per unit volume in a dense state, it is used to determine the specific density of a given bulk building material. The true density is a constant value, while the specific density of expanded clay is a variable. For expanded clay gravel it ranges from 450 to 700 kg/m3, for expanded clay gravel it varies between 600 and 1000 kg/m3, and for dry expanded clay concrete mixture it is 800 kg/m3.

Expanded clay technical characteristics fractions 20-40 and 10-20 has different. Consider in this article its properties and varieties, application in construction and in the production of building materials. Despite the emergence of new materials for thermal insulation, this insulation is still in demand. It is impossible to imagine modern construction without the use of expanded clay.

Expanded clay is a natural and environmentally friendly heat-insulating material with a fraction of 10 to 40 mm. The material is obtained by firing special types of clay in high-temperature furnaces. This clay swells when heated sharply, resulting in a durable bulk heat-insulating material with low weight, but with a low coefficient of thermal conductivity - this property applies to all fractions from 10 to 40 mm.

Expanded clay has some advantages in comparison with mineral wool. Most mineral insulators decompose and cake over time. Expanded polystyrene emits harmful substances, while being a fire hazardous material. Expanded clay is environmentally friendly, does not decompose, is resistant to moisture and open flame, has good heat and sound insulation.

This porous material is one of the most effective for thermal insulation, which is in great demand in the production of building materials (expanded concrete, lightweight concrete, etc.) and in the insulation of residential buildings (, floors on the ground floor of a house, etc.). The main properties are: grain fraction, bulk density and strength. See the photo below for material usage.

Varieties of expanded clay

Expanded clay sand has a fraction size from 0.14 to 5 mm. It is used as a filler for concretes and mortars, for thermal insulation of floors and interfloor ceilings with a small backfill thickness (up to 50 mm).

Expanded clay gravel has a size of fractions from 5 to 40 mm. It is used as a filler in the production of lightweight concrete, for thermal insulation of horizontal surfaces on the roof and on the floors.

Expanded clay crushed stone has a size of fractions from 5 to 40 mm. The material is obtained by additional crushing of large pieces of expanded clay, because of this, the crushed stone has an irregular and angular shape.

Specifications of expanded clay

In its appearance, expanded clay is a granule of a porous material of a rounded shape of various sizes. It is used in construction today extremely widely, the main purpose of the material is the insulation of structures during construction, as well as reducing the weight of building materials during their production without loss of strength. See the characteristics of bulk insulation in the table below.

Expanded clay thermal conductivity by fractions

Expanded clay is subdivided into fractions of gravel: 5-10 mm; 10-20 mm; 20-40 mm and sand (0-5 mm). By density and strength, gravel is divided into grades from M300 to M700. These figures indicate the bulk density, but do not indicate the strength of the material or its thermal conductivity. Specifications of expanded clay for strength and bulk density:

• Fraction 20-40 mm (M300 - M380) - gravel strength grade P50 - P75
• Fraction 10-20 mm (M400 - M450) - gravel strength grade P75 - P100
• Fraction 5-10 mm (M500 - M550) - gravel strength grade P100 - P125
• Fraction 0-5 mm (M600 - M700) - gravel strength grade P50 - P75

Expanded clay thermal conductivity characteristics

Application in the construction of expanded clay

1. Thermal insulation of floors, ceilings, attics, basements;
2. Thermal insulation of strip foundations and blind areas of houses;
3. Thermal insulation of flat roofs, creating a slope on the roof;
4. Production and lightweight concrete;
5. Thermal insulation of the soil - lawns and drainage on the site;
6. , in case of repair, expanded clay is reused;
7. Hydroponics, expanded clay creates an optimal microclimate for plant roots.

When laying expanded clay, it should be protected from getting wet and absorbing moisture with a waterproofing film (polyethylene, roofing material, etc.).

As you can see, the scope of this insulation in construction and in the household is diverse, which is explained by the excellent indicators of thermal conductivity, environmental safety and durability of the insulation. In addition, the material is free-flowing and takes any shape, it can fill any medium. When used correctly, it can reduce heat loss in the room by 50-75%.