The concept and characteristics of expanded clay gravel (expanded clay). What are the fractions of expanded clay gravel? What is expanded clay gravel

Expanded clay is a light porous material of a cellular structure in the form of gravel, less often in the form of crushed stone, obtained by firing low-melting clayey rocks that can be pushed in when they are quickly heated to a temperature of 1050 - 1300 C for 25-45 minutes. The quality of expanded clay gravel is characterized by its grain size, bulk density and strength. Depending on the grain size, expanded clay gravel is divided into the following fractions: 5 - 10, 10 - 20 and 20 - 40 mm, grains less than 5 mm are classified as expanded clay sand. Depending on the volumetric bulk weight (in kg / m3), gravel is divided into grades from 150 to 800. Water absorption of expanded clay gravel is 8–20%.

Expanded clay is used as a porous filler for lightweight concrete, as well as a heat-insulating material in the form of backfills.

Expanded clay gravel

Rounded particles with melted surface and pores inside. Expanded clay is obtained mainly in the form of expanded clay gravel. Its grains have a rounded shape. The structure is porous, cellular. On its surface there is often a denser crust. The color of claydite gravel is usually dark brown, in a break it is almost black. It is obtained by swelling during firing of fusible clays in rotary kilns. Such gravel with a grain size of 5 - 40 mm is frost-resistant, fire-resistant, does not absorb water and does not contain impurities harmful to cement. Expanded clay gravel is used as a filler in the manufacture of lightweight concrete structures.

Expanded clay crushed stone

Expanded clay rubble - aggregate for lightweight concrete of arbitrary shape, mostly angular with grain sizes from 5 to 40 mm, obtained by crushing large pieces of expanded expanded clay mass. (Crushed stone is crushed gravel, crushed stone has sharp angular edges, gravel is crushed into crushed stone for better adhesion concrete)

Some clays swell when fired. For example, in the production of clay bricks, one of the types of marriage - burnout - is sometimes accompanied by swelling. This phenomenon is used to obtain a porous material - expanded clay from clays.

Swelling of clay during firing is associated with two processes: gas evolution and the transition of clay to a pyroplastic state.

The sources of gas evolution are the reactions of reduction of iron oxides during their interaction with organic impurities, oxidation of these impurities, dehydration of hydromica and other water-containing clay minerals, dissociation of carbonates, etc. Clays pass into the pyroplastic state when a liquid phase (melt) is formed in them at high temperature ), as a result of which the clay softens, acquires the ability to plastic deformation, at the same time becomes gas-tight and swells with released gases.

For the manufacture of expanded clay concrete products, not only expanded clay gravel is needed, but also fine porous aggregate.

Expanded clay sand (expanded clay screening- other name ) - filler for lightweight concretes and mortars with a particle size of 0.14 to 5 mm is obtained by firing clay fines in rotary and shaft kilns or by crushing larger pieces of expanded clay, as well as screening waste in the production of expanded clay.

Innovative technologies have already reached building materials. Expanded clay gravel became one of the innovations. It is made from clay of natural origin. It undergoes rapid firing in furnaces (about 30 minutes), while the temperature reaches 1300 degrees. Clay swells in a special way. As a result, clay grains (fractions) with a light porous structure and dark brown color are obtained at the output. If you break the granule, then inside the color will be almost black. Depending on the degree of processing, a dense crust forms on the surface of the granules. After cooling, the granules are sorted. GOST, provides for granule sizes of 5-10, 10-20 and 20-40 mm. The number of granules of the wrong size should not exceed 5%.

Characteristics of the building material

The advantages of this material are undeniable. They completely change the idea of ​​building materials. Expanded clay gravel is very light, but at the same time it perfectly retains heat, is moisture resistant and fireproof, and can withstand very low temperatures. Does not deform when they are dropped. Provides excellent sound insulation, does not rot at all, does not smell of anything. With completely environmentally friendly material. After all, it only contains clay.

Application in various fields

Russia is considered one of the largest producers of this product. In recent years, the production of gravel in our country has increased by 30%, the demand for it is constantly growing. Expanded clay gravel is indispensable for home insulation. The foundation, floor, external floors, insulation of water supply networks - all this can be insulated with expanded clay gravel. Lightweight but bulky, it retains heat well and is durable. In order to carry out high-quality work on insulation with expanded clay, you need to take it into account. The smaller the “grains” of gravel, the greater its density per 1 sq. m. Efficiency will be higher if the height of the embankment is at least 15 cm. Gravel will help keep the heat in the house by more than 60%. The construction of new roads is no longer complete without this material. It is used to divert water when working in wet and swampy areas. For utilities, expanded clay gravel is also an assistant. It is used to maintain the desired temperature and sound insulation. In addition, it can be used repeatedly, which is especially important for emergency work.

Expanded clay is a porous lightweight building material. It is obtained by firing a special low-melting clay, which swells rather quickly when the temperature rises to 1300 ° C. At the same time, the surface of the granules melts, thereby creating a hermetic shell.

Externally, expanded clay gravel, the price of which is affordable, resembles oval (round) cellular vitreous granules covered with a shell. Accordingly, its characteristics depend on the following factors:

• strength;
• bulk density;
• thermal conductivity;
• water absorption;
• the class of clay that is used as the initial product.

The production of expanded clay gravel involves the following operations:

• preparation and selection of raw materials;
• the process of creating granules;
• firing (blowing) of granules:
• cooling process;
• selection of granules by fractions.

At the same time, depending on the characteristics of the raw material, there are several methods for preparing it for firing.

1. Expanded clay gravel: fractions.

Depending on the parameters of the grains, expanded clay gravel is divided into several fractions:

• 5-10 mm;
• 10-20 mm;
• 20-40 mm.

Grains with a size of less than 5 mm are classified as expanded clay sand.

2. Water absorption of expanded clay.

The water absorption of expanded clay gravel is from 8–20%, frost resistance is at least 25 cycles.

3. Expanded clay gravel: grades.

Expanded clay gravel is produced in 10 grades (from 150 to 800), each of which depends on the bulk density (kg/m³).

4. Expanded clay gravel: density.

The bulk density of this building material is determined by fractions in special vessels. The larger the expanded clay, the lower its density.

5. Thermal conductivity of expanded clay.

The amount of heat that passes through the wall depends on the thermal conductivity of the building material. To date, in this area, GOST does not set certain requirements for expanded clay. Accordingly, one should choose the product whose thermal conductivity is lower.

6. Expanded clay strength.

High-quality expanded clay, having optimal strength, is characterized by closed, relatively small and evenly spaced pores. It contains enough glass for the normal binding of particles into a dense building material. If you saw the granules, then the edges are preserved in them and the crust is clearly visible.

Operational properties of expanded clay gravel

• ease;
• fire safety;
• environmental friendliness;
• water resistance;
• strength;
• it does not contain toxic impurities;
• increased sound and moisture insulation;
• frost resistance;
• chemical inertness;
• long service life;
• vapor permeability;
• resistance to temperature changes;
• does not rot;
• retains its properties during repeated freezing and thawing.

Expanded clay gravel: application

Used for:

• production of building blocks;
• improvement of paths in the garden;
• thermal insulation of baths;
• due to the light weight of expanded clay gravel, it is used to create a concrete screed, drainage system;

• insulation of engineering thermal and plumbing systems;
• production of lightweight concrete;
• backfilling of the foundation;
• thermal insulation of attics, roofs, basements, ceilings, walls, floors, etc.

Clay was used by man in ancient times, even then it was known about its hardening properties under the influence of hot air. Today expanded clay is widely used in construction and repair work. Expanded clay is a clay rock burned in kilns, which, when rotated in a kiln, swells from the gases inside.

Expanded clay gravel is the most popular building material, unlike expanded clay gravel or sand. Expanded clay gravel has a rounded oval shape, it is used for installation of floor screed and thermal insulation of houses, communications. Bricks or slabs for construction can be made from such material.

Expanded clay gravel has a number of positive characteristics:

• almost does not absorb water, because there is a protective shell;
• has good heat and sound insulation due to its porous structure;
• non-flammable, provides fire safety;
• the strength of the material allows it to be used in construction, it can withstand loads (if mixed with concrete);
• blends well with concrete;
• withstands frost and the adverse effects of atmospheric factors;
• has a small weight;
• does not rot or corrode;
• expanded clay is available in price.

Marking

Depending on the weight of expanded clay gravel per 1 cubic meter, it is divided into 10 main grades. The M250 brand means that there are 250 kilograms of expanded clay gravel per 1 cubic meter. Its strength and density depend on its weight. The most durable expanded clay gravel is M800, it is used for the manufacture of building materials. When buying gravel, the marking is the main feature. Expanded clay can be bought both in bags and machine standards in terms of the number of cubic meters. According to GOST, expanded clay gravel is divided into large (10-20 mm), small (5-10 mm) and medium (10-20 mm) fractions in size.

Application for floor screed installation

They are used when installing floor screeds, when it is necessary to level the floors in the room or make thermal insulation. Due to its low weight, even a screed 15-20 centimeters thick will not put pressure on the ceiling. Expanded clay gravel is poured and leveled, and then poured with concrete milk. There is another technology for installing a screed using expanded clay - when a ready-made mixture of expanded clay with concrete is laid.

Application for roof insulation

Expanded clay gravel is used in conjunction with polystyrene foam to insulate the roof, filling various cavities on the roof with this mixture. These can be as specially made wooden trays, or other cavities. Expanded clay gravel is also used to insulate a flat roof; for this, a protective layer is made on top.

Wall insulation

You can insulate the walls with expanded clay gravel by filling it between the walls of the building.

Warming of communications

So that communications do not freeze in winter, they make a special shaft into which pipes are laid and covered with expanded clay gravel.

Construction

Slabs or bricks are made from expanded clay gravel, from which you can build a house or any industrial premises. Expanded clay is used in the construction of baths to ensure a sufficient level of moisture. At the same time, the use of expanded clay together with a film for waterproofing in the construction of the foundation will protect against moisture penetration.

Use in horticulture

Expanded clay gravel is widely used in horticulture, it is mixed with the soil in which plants are planted. It maintains the necessary level of moisture and heat, helps to let air through the soil. Rodents do not start in expanded clay, it even protects plants from them.

Expanded clay is a material produced from low-melting sedimentary clay by firing at high temperatures. Due to the peculiarities of the structure, it is very useful in construction: it is filled with wooden and concrete structures. Service life - not less than 25 years.

Outwardly expanded clay gravel resembles vitreous granules with a smooth shell. The following factors influence the determination of its characteristics:

• bulk density;
• water absorption;
• clay structure;
• thermal conductivity;
• mechanical strength of the granules.

The starting material is placed in an oven preheated to 1050°C. For a certain period of time (20–40 min), the temperature rises to 1300°C. Under the action of heat treatment, the surface of the raw material is melted, forming a sealed smooth shell. During the firing (expansion) gases are released, which make the internal structure of the granules porous. The finished product is cooled and sorted into fractions.

Varieties

Granules, depending on the size, configuration and production process, are divided into the following types (fractions).

1. Expanded clay gravel. The form, indispensable in the construction industry, is produced more often than others. Oval, almost round granules are red-brown in color. The grain sizes are divided into several groups: 5-10, 10-20 and 20-40 millimeters.

2. Expanded clay crushed stone. Obtained by crushing large pieces of expanded clay, its particles are distinguished by sharp edges and an angular shape. Use in construction is limited to adding to concrete. The crushed stone fraction is 5–40 mm.

3. Expanded clay sand (screening). Get it in several ways. Most often on roller crushers, when crushing large pieces of gravel. To get 0.5 cubic meters of sand, you need to use 1 cubic meter of expanded clay. May be a by-product of foaming and splitting crushed stone. The size of sand particles is 0–5 mm. This species is used as a porous filler.

Technical indicators

One of the most important characteristics is the bulk density, that is, the density of the material, which does not take into account the gaps between the particles (kg/cubic meter). It is found empirically with the help of measuring vessels.

The indicators vary from 250 to 800 kg / m3 and determine the brand. If the density is 250 kg / m3 or less, the grade of gravel or crushed stone is M250. Usually the maximum value is M600, but by individual agreement with the customer, they can produce a material with a higher density. Sand is marked with slightly different indicators - from 500 to 1000 kg per cubic meter. Moreover, only the maximum characteristics are obligatory for fulfillment, the minimum ones are usually reference.

Based on strength (it is determined by squeezing particles in a cylinder), there are 13 grades of gravel and 11 grades of crushed stone. They are designated the same for both fractions, but differ in density. Density and strength of grades are interrelated, an increase in one parameter leads to an obligatory increase in another. The higher the strength index of gravel, the greater will be its cost, which can be found out.

The thermal conductivity coefficient of expanded clay is determined by the number and size of air pores. The range of values ​​is small - from 0.10 to 0.18 W / m - which indicates the high thermal insulation qualities of the raw material.

Water absorption indicates how expanded clay behaves when exposed to water. A coefficient of 8–20% characterizes the high resistance of the material to moisture. Small water absorption and clay, as raw materials, make gravel frost-resistant. Moreover, only the indicators of stones containing expanded clay in their composition are normalized by the standards.

Areas of use

Due to environmental friendliness and special qualities, expanded clay is often used:

1. in construction, as a concrete filler;

2. when insulating roofs, a heat-insulating pillow is made of gravel;

3. in landscape design when creating terraces or alpine slides;

4. as a layer of thermal insulation, when laying the foundation and erecting the floor;

5. in the construction of roads in wet and swampy areas;

6. as a filter in small sewage treatment plants;

7. as drainage when planting indoor plants.

Price

It is more profitable to buy expanded clay at a factory engaged in its production. So you can avoid the markup of intermediaries and get the original quality at a lower price.

The table shows the average price per m3 in Moscow.

This material has become widespread due to its relatively low cost, variety of fractions and well-established production technologies that allow obtaining particles of the desired size and porosity.