Lightweight concrete: composition, density and application in construction

general information

Lightweight concrete began to appear in the construction industry relatively recently. Despite this, it quickly gained great popularity and became widely used for a wide variety of tasks. Today, based on such raw materials, high-quality buildings for various purposes are created.

Thanks to its significant advantages, lightweight concrete allows you to achieve better acoustic and thermal insulation performance during the construction of premises, and its minimal weight guarantees significant cost savings and a reduction in the final cost of the project.

Currently, the material is especially in demand in difficult conditions with high seismic activity, since heavy concrete cannot be used in such places.

The innovative building material can be used in the construction of thermal insulation and load-bearing structures, as well as play a decorative role. With its help, you can achieve a reduction in the overall load on the foundation and a reduction in financial costs for labor and delivery of material to the site. In terms of thermal insulation quality, it is in no way inferior to classic brick, and at the same time costs much less. The advantages of the material also include:

Moisture resistance.
Frost resistance.
Excellent density.

Lightweight concrete: material characteristics and application in construction

Lightweight concrete is an identical material in a dry state with a density of less than 1800 kg/m3. Such a dense state is obtained due to the fact that various lightweight fillers are used in its manufacture, or through the process of porousization of the binder. By reducing the density of concrete, it is possible to reduce the weight of any building structure or structure, as well as increase the thermal insulation characteristics.

Recently, the production of lightweight concrete has become a huge achievement in the construction industry. Today, in the production of such concrete, consumables have been significantly reduced and the development process has been reduced. This is due to the presence of modern technological equipment, as well as the use of additional substances in manufacturing.

Despite the fact that the material used in construction is called lightweight concrete, it has the same characteristics as ordinary concrete. The only difference is the appearance: it looks more like a simple pumice stone.

In accordance with GOST of the Russian Federation, the composition of a lightweight concrete solution is determined by the presence of the following fillers:

When making concrete, one or two mineral porous fillers are used (expanded clay, vermiculite, algoporite, perlite).
Organic fillers are used.

Depending on the stage of construction, a certain type of lightweight concrete is used. So, when installing the foundation of a building or flooring, a mortar with expanded clay is used, and the walls are laid with concrete blocks (foam or aerated concrete, wood concrete, etc.). Any ceiling is insulated using polystyrene concrete.

Lightweight concrete includes the following building materials: aerated concrete, foam concrete and polymer concrete. Let's look at their main advantages:

The relative lightness of reinforced concrete structures.
High heat resistance.
Convenience when installing building structures.
Cost-effective materials.
High heat resistance.
Plastic.

Despite its advantages, lightweight concrete also has its disadvantages:

Installation of additional reinforcement to increase the strength of the material.
If concrete blocks are exposed to uneven loads, this can lead to the formation of various cracks in the material.
Difficulty in interior and exterior decoration.
High degree of moisture absorption.
Excellent sound transmission.

Lightweight concrete can also be used in the manufacture of various decorative elements in homes where gypsum is traditionally used. This will provide the structure with heat resistance and low moisture absorption. At the same time, the structure will be manufactured in a short time and will be easy to use.

Using lightweight concrete, you can reconstruct old buildings and premises, provide additional insulation, make screeds for floors, use them in low-rise and road construction, and much more.

On the market, the cost of lightweight concrete is determined per 1 m3 and varies depending on the brand, additional fillers, and transportation costs. For example, in Moscow the cost ranges from 3 to 5 thousand rubles. As a rule, enterprises engaged in the production of lightweight concrete have the necessary modern technological equipment, as well as their own fleet of vehicles for timely delivery.

Of course, you can prepare a mixture of lightweight concrete yourself. The main point: you need to decide on the brand of filler, installation of fittings and other actions.

For example, granulated foam glass can be used for thermal insulation of floors. To produce 1 m3 of a mixture with a density of 600 kg/m3, 250 kg of M-500 cement will be required. First you need to mix cement with a certain amount of water in a ratio of 0.4:1. Then add a little more water for the next kilogram, namely 0.45 liters. This will require about 110 liters of water, and be sure to add 0.5 kg of superplasticizer mixture to it. In a concrete mixer, mix this mixture with the following components: 100 kg of river sand, 180 kg of foam glass mixture, 0.5 kg of polypropylene fiber. The temperature must be at least 5°C. It will take about 4 weeks for the solution to obtain the required strength.

In addition, you can make lightweight and inexpensive sawdust concrete yourself. You can use it to build walls. In order to obtain similar concrete at home, you will need 50 kg of sawdust, 50 kg of cement powder and 100 liters of water. This mixture will be convenient to use, quick to manufacture and easy to install.

Thus, due to its structure, lightweight concrete is very popular in the modern construction field. At the same time, it meets the requirements and standards of heat conservation.

Contact form

Main types of lightweight concrete

Experienced builders know that high-quality material meets all state standards, while according to GOST 25192 it can have a different structure. Depending on this characteristic, concrete can be:

Dense . The material contains small and large particles, an astringent component and liquid, which create a thick consistency and completely fill the voids. The air content inside the composition does not exceed six percent.
Large porous . The binder components of this concrete are capable of enveloping the aggregate grains, while the air content is equal to ¼ of the total volume. To achieve better thermal insulation, wall structures must be treated with plaster on both sides.
Cellular . It has low density and poor thermal conductivity. The pores of this concrete resemble small cells in the shape of a sphere, the diameter of which is 1-3 millimeters. Among the advantages of the variety are low weight but excellent strength. In addition, the material does not require complex installation and is very cheap, which allows us to call it the most suitable building material for erecting walls and carrying out roofing work.

When choosing a suitable brand of concrete, you need to make sure that it complies with the state GOST standard. In addition, the products must remain environmentally friendly and not contain harmful components.

The main component of concrete is crushed stone, which is often diluted with limestone, dolomite and other particles. The name of the material depends on the type of filler, so modern craftsmen distinguish:

Slag concrete.
Expanded clay concrete.
Pumice concrete.
Agloporite concrete.
Perlite concrete.
Azerite concrete.
Vermiculite concrete.
Thermozitic concrete.

And several other varieties.

The material can contain both mineral and organic binder components. In the first case it is:

Cement.
Lime.
Liquid glass.
Lime.
Mixed particles.

Also, the grades of concrete available on the market can be divided depending on their purpose. There are these types:

Structural. They are characterized by low density, which is 1400-1800 kg/cm3, with strength indicators from M50 and frost resistance F 15.
Structural and thermal insulation. The density of lightweight concrete of this type is 500-1400 kg/m3, and the strength is not lower than M35. Most often this variety is used for load-bearing structures.
Thermal insulation. They have an average density in an air-dry state. On their basis, thermal insulation boards and many other useful elements are created.
Heat resistant. Used in extreme conditions with abnormally high ambient temperatures or a high risk of ignition.
Chemical-resistant. Effective in plants and factories where work with chemicals is carried out.

Types of lightweight concrete and their application

In private and professional construction the following are used:

Porous concrete. Perlite concrete, expanded clay concrete, agloporite concrete. Cellular concrete. Aerated concrete and foam concrete. Concrete mixtures with organic aggregates. Bonfire concrete, polystyrene concrete and wood concrete.

Lightweight concrete with porous aggregates

They are widely used in private construction, including as the basis for the construction of one-story buildings.

Expanded clay concrete

A building material containing cement, sand and filler (expanded clay). Basic proportions:

1 part cement; 2 parts fine-grained filler; 3 parts coarse-grained filler.

Air-entraining additives (saponified tree resin) must be added to the mixture.

Expanded clay is a porous material, with a specific volumetric gravity of 300-600 kilograms per cubic meter. A distinctive feature is the ability to strongly absorb and store water. Specifics of preparing concrete mixture:

1 part cement, 1 part water and 2 parts sand are poured into a container or concrete mixer, after which the ingredients are thoroughly mixed. The mixture is supplemented with expanded clay - 3 parts of coarse filler.

During the re-mixing process, the finished solution should be wet. If expanded clay absorbs a lot of water, then it is necessary to additionally pour in liquid in portions of 5-7 liters without stopping mixing until the granules of the substance are covered with a cement “glaze” on all sides.

The above scheme is used to create brick blocks with a mass of 15-20 kilograms. If a screed is made on the basis of expanded clay concrete, then you need to add significantly more water so that the concrete mixture, when mixed, resembles a “sour cream-like” essence. The poured floor is isolated from rigid structures and other types of concrete using multilayer polyethylene film.

Currently reading: Lighting poles made of reinforced concrete

Advantages of the material:

High speed of construction work; Effective interaction with various finishing materials; No need to pour a heavy foundation for construction and expanded clay concrete blocks; Low coefficients of water absorption and thermal conductivity after hardening of the mixture; Lack of mold and low cost of blocks compared to similar materials of the same strength.

Perlite concrete

The density of such concrete mixtures in the hardened state is 600-1200 kilograms per cubic meter. The basis of the material is expanded perlite, which is a finely dispersed material obtained from crushed volcanic rocks by direct firing.

Features of perlite concrete:

Lightness and fire resistance; Easy to use and breathable; Environmentally friendly; High degree of water absorption.

In private construction, perlite concrete is used to lay out fireplaces, create “warm” plaster, and as a basis for decorative work.

Agloporite concrete

The basis of the concrete mixture is a combination of processed clay mixture and ash-cereal waste from coal enrichment.

The products have a low compressive strength class - B2.5-B7.5. In a dry state, the relative density is 1000-1500 kilograms per cubic meter. Thermal conductivity coefficient is 0.3-0.6.

Agloporite concrete is used in the construction of internal walls of low-rise structures or the foundations of outbuildings.

Concrete with lightweight organic aggregates

The filler of this type of concrete is a variety of organic matter.

Arbolit

Shredded wood in a splinter-like state is used as a filler. Mineralizer - calcium chloride, liquid glass, aluminum sulfate or other components that neutralize the negative effects of organic matter on cement.

The relative density of wood concrete is 400-850 kilograms per cubic meter. The hardened mixture has high bending strength, absorbs sounds, does not burn and is convenient for any type of processing. Other parameters:

Water absorption - 50-80 percent when mixing; Frost resistance - 40-50 freezing/thawing cycles; Shrinkage - 0.4-0.5 percent; Elasticity - 1000-2300 MPa.

Arbolite is used in the construction of low-rise buildings for commercial and residential purposes, and the creation of external enclosing structures.

Kostrobeton

The organic filler of the concrete mixture is woody parts of the stems of cultivated hemp. A mandatory additive is calcium chloride, alumina sulfate or lime, which helps to avoid deterioration of the adhesive properties of cement.

Bonfire concrete is not subject to rotting and is unattractive to rodents and insects. Volumetric mass – 400-700 kilograms per cubic meter. The product has low thermal conductivity and sound conductivity, and is easy to machine. It is used for secondary work in private construction - thermal and sound insulation, internal partitions of residential premises.

Polystyrene concrete

A common composite material. Porous filler - foamed polystyrene granules, which are the main product of polymerization of vinylbenzenes.

Advantages:

Good sound insulation and heat insulation properties, comparable to the identical characteristics of mineral wool, foam glass and polystyrene. Cost-effectiveness and low load on the foundation. Environmental friendliness and low water absorption. High coefficient of frost resistance. Minimum level of shrinkage and balanced adhesion to the plaster mixture. Low vapor permeability.

The relative density of polystyrene concrete is 200-600 kilograms per cubic meter.

Scope of use:

Monolithic and classic private housing construction. Filling the space inside critical and secondary structures - load-bearing walls, fences, concrete grillages. Alternative insulation of premises. Comprehensive measures to reduce the load weight on various structures - swimming pools, profiled decking, watercraft.

Cellular concrete

The basis of concrete mixtures of this type is siliceous aggregates, which form spherical or oval voids as a result of reactions.

Foam concrete

This type of concrete mixture is created on the basis of cement-sand mortar, water and foaming agent. The latter forms small, medium and large pores, acting as a substitute for classical aggregates.

Depending on the specific composition, the lightweight type of foam concrete can be thermal insulating, structural-thermal insulating, or structural. The main feature of the material is its long-term strength gain. It reaches nominal parameters within 20-40 days after filling (depending on climatic conditions) and over the course of 2-3 years its characteristics gradually improve.

The relative strength of foam concrete is 10-90 kilograms per square centimeter. The material is used in monolithic and classical construction of houses, as complex thermal and sound insulation of ceilings, floors, walls, and roofs. Thanks to simple production technology, foam concrete products are cheaper than conventional concrete. Low weight and ease of processing make it possible not only to reduce transportation costs, but also to use the products in any type of construction.

Disadvantages of foam concrete:

bends, gives significant shrinkage, mechanically fragile.

Aerated concrete

Classic cellular concrete is made from quartz sand, cement and gas-forming agents.

The gas-forming agent is finely dispersed aluminum. Once it is combined with lime mortar or highly alkaline cement, a chemical reaction is formed to form calcium aluminates and hydrogen gas. The latter foams the solution, creates closed spores of spherical or oval shape communicating with each other, reaching a diameter of 4 mm.

Gas-forming additives are represented by aluminum pastes and suspensions, since in dry bulk form the substance generates a lot of dust.

The scope of application of aerated concrete is commercial, residential and industrial construction. The material is used to make wall partition blocks, internal floor slabs, lintels, including reinforced ones. The advantages and disadvantages of the material are identical to foam concrete.

Porous material

It's no secret that one of the most popular materials for modern construction is lightweight concrete. The composition of such a product is selected depending on the type and complexity of the work to be performed.

And among the above varieties, porous materials are especially popular.

In addition to frost resistance and a long service life, the raw materials remain resistant to moisture and are relatively inexpensive. In addition, it consists of mineral components, which guarantees compliance with all modern norms and environmental standards. It is these properties that make porous concrete very popular and in demand for construction.

It should be noted that the prototype of the porous material was used in ancient Rome several thousand years ago. It was created from natural ingredients, such as pumice, ceramics or clay from dishes.

However, the material began to be in wide demand only in the second half of the 20th century, when artificial fillers appeared on the market, including expanded clay, slag pumice, etc. Currently, both natural and artificial components are used. And if the first is pumice, lava, limestone or rocks, then the second is a complex porous product that is created on the basis of natural materials with the addition of chemical additives. Artificial fillers can have different bulk densities, strength and grain composition, moisture and frost resistance.

Properties of aerated concrete

The use of lightweight concrete in construction has been known since ancient Rome. However, the material received its current form after many years of research and many changes. Modern aerated concrete is created from a cement mixture with the addition of lime, a siliceous component and liquid, which is introduced into an already mixed mixture of a gas-forming agent - aluminum powder, perhydrol, etc.

Only one aluminum powder can be used. The creation of the gas is accomplished by chemical contact of aluminum with calcium hydroxide. The release of hydrogen causes swelling of the cement, as a result of which it hardens, but retains its characteristic cellularity.

The initial components of aerated concrete include cement, lime, ground sand and water. All components are thoroughly mixed with each other in a special container, after which the solution is diluted with aluminum powder and stirred again.

Ultimately, the resulting consistency must be poured into a metal mold and filled completely.

After waiting for the aerated concrete to mature, it must be further processed in actoclaves for accelerated hardening. The autoclave processing method guarantees maximum strength of the final product, and also reduces cement costs due to complete or partial replacement with lime.

Due to its low cost, minimal weight and many other advantages, aerated concrete is considered an extremely popular building material, without which it is difficult to imagine modern construction. The scope of application of raw materials is very wide, since aerated concrete can be used for the construction of houses, for arranging walls, and for solving various decorative problems.

Light and heavy concrete

Many people have heard more than once that in addition to the usual classification by grades and classes, concrete is also given a “degree of severity.” We will try to determine what light and heavy concrete are, and what are their fundamental differences.

Basic Concepts

Lightweight concrete is considered to be a construction concrete mixture made from water, cement, sand and large porous aggregates. Due to its relatively low density, such building material has a specific gravity of one “cube” of less than 1.8 tons. When it comes to lightweight concrete, this concept should be understood as slag concrete and expanded clay concrete. Also included in the category of lightweight concrete are high molecular weight products: aerated concrete, foam concrete, polystyrene concrete and even polymer concrete. Lightweight concrete is distinguished not only by its excellent heating properties and excellent porosity, but also by its most important advantage - the low weight of structures made from it.

In turn, heavy concrete is a concrete mixture of the same cement and water. Only it uses both large (gravel, granite, limestone, diabase) and small aggregates, which significantly increases the density of the material. This allows the specific gravity of one cube to reach from 1.8 to 2.5 tons. In this case, sand concrete or fine-grained concrete will be called a type of heavy concrete, where a mixture of large and small fractions of sand is used as a filler. Some types of heavy concrete have a specific gravity of 1 cubic meter. up to 7 tons. Such concrete is called especially heavy, used for the construction of structures and buildings of a high level of responsibility: nuclear reactors, nuclear power plants, etc. High density in especially heavy concrete is achieved through the use of substances with high molecular weight as fillers - barite, hematite, magnetite, and metal scrap.

Application area

Monolithic lightweight concrete slabs are used to create expanded clay concrete floors, as well as in the construction of the lower floors of buildings without basements. The use of such materials makes it possible to reduce heat loss in the room, significantly saving in the future on high-quality and inexpensive heating of the building. It is for this reason that lightweight concrete products are also used for attic floors. Due to their low weight, lightweight concrete reinforced concrete products are used in monolithic high-rise buildings. At the same time, there is no need to worry about the strength of buildings - it is provided by the reinforcement located in the reinforced concrete frame.

Lightweight concrete is used in the manufacture of enclosing structures, as well as masonry wall materials such as expanded clay concrete, slag concrete, foam concrete and aerated concrete products. However, the reduced strength and load-bearing capacity of lightweight concrete limits their use, and therefore lightweight concrete without metal frames and reinforced belts is practically not used for capital construction. However, by constantly changing the forms and types of lightweight concrete, in the near future scientists will certainly be able to minimize the disadvantages, which will make this product one of the main building materials of the future.

Heavy concrete is used everywhere and is by far the most durable and widespread type of concrete. All monolithic elements of buildings and structures are made of heavy concrete. Excellent strength properties, unpretentiousness when feeding and laying, affordable price - all these serious advantages make heavy concrete practical and popular. Heavy concrete is less effective only for constructing walls and light floors, i.e. where it is necessary to reduce heat loss due to the materials used.

Subtleties of production technology

As is known, the technology for producing light weight concrete differs significantly from the production of heavy concrete. To create a high-quality product, the porous element must be placed in dry conditions where there is no moisture. In this case, the fractions should not be mixed, but separate. Otherwise, the composition of the product will differ from the required one.

It is also important to transport the aggregates carefully to the production site. Any disruption, moisture penetration or mixing will significantly damage the consistency. In most cases, light mixtures are created in specialized mixers, where the possibility of separation of the components is eliminated. Water is continuously supplied to the container until loading is complete. The mixing time is determined by the operation of the mixer, the speed of rotation and the density of the mixture.

Vibration technology is used to compact the structure. It is through vibration that the material acquires one unique feature. At the end, the light grains float to the top, and the cement ends up at the bottom.

Products made from the described building material can often be further processed in an environment with saturated steam. To speed up the hardening of concrete, it is better to use steamless heating in an environment with low humidity. It is this approach that guarantees complete purification of the material from moisture without compromising the strength characteristics.

Advantages of buildings

As is known, lightweight concrete differs from heavy material by the presence of small and large pores in the filler grains. It is inferior in strength to cement stone, but due to its specific structure it demonstrates excellent adhesion.

When choosing a building material, it is important to pay attention to its density. The fact is that this parameter is one of the primary indicators of quality. Moreover, density indicators vary depending on the state of the material. So in a dry state they are different than in a wet state. The main factors affecting density are:

Permeability.
Thermal conductivity.
Strength.

There are many grades of concrete available on the market: from D200 to D2000.

As for reliability, it is determined by the quality of the raw materials and solidification conditions. If you add porous components to concrete, this will have a bad effect on strength. Also, the presence of coarse aggregate with a porous structure in the composition plays a special role.

In terms of water resistance and resistance to frost, lightweight concrete is not inferior to ordinary concrete. However, it costs much less than its classic brother. According to information from the manufacturer, the frost resistance of lightweight concrete varies in the range F 25-F 100. For extreme climatic conditions, grades with indicators F 200, F 300, F 400 are produced.

As for resistance to moisture, it is indicated by the letter W. Today on sale you can find the following brands: WO 2, WO 4, WO 6, WO 8, W 1, W 1.2.

According to the builders, when constructing wall structures from lightweight concrete, labor costs are reduced by 20 times, and the cost of the future project becomes 30% cheaper. Among the advantages of such materials for walls are:

Environmental cleanliness and compliance with all cleanliness and safety requirements.
Minimum weight.
Plastic.
Beautiful appearance, allowing the use of concrete for decorative wall decoration.
Resistance to moisture, due to which the material is widely used for the construction of baths.
Fire resistance and frost resistance.

Types of lightweight concrete

The role of aggregates in lightweight concrete is crushed stone, which can be based on dolomite, porous limestone and other components.

Depending on the type of coarse-grained porous aggregate, the material can be divided into slag-expanded clay-pumice and agloporite concrete.

Lightweight concrete class table.

According to structural indicators, such concrete can be divided into types, including materials made on the basis of binders, fillers of different fractions and liquids. The volume of air that is involved in the mixture is small as a percentage and does not exceed 6% of the volume of the product. Another type of lightweight concrete, distinguished by a special structure, is called sandless or large-porous. Such concretes contain grains of coarse aggregate coated with a slight layer of cement, while the space between the grains is empty. The large-porous structure contains more than 25% of voids that contain air. There are also porous type concretes, which are made on the basis of a binder and a blowing agent. The structure of this material contains cells that provide increased porosity of the solution. This causes a decrease in the density of the mixture.

Scheme of expanded clay production.

Lightweight concrete can also be distinguished by its purpose. So, they can be thermally insulating; their average density is 500 kg/m3, while thermal conductivity does not exceed 0.25 W/(m.K). Such concretes are usually used to produce slabs and other products with thermal insulation properties. There is also a variety of structural and thermal insulating concrete, the average density of which can reach 1400 kg/m3, and the thermal conductivity does not exceed 0.6 W/(m.K), while the strength is M35 and higher. Such concretes are successfully used in the construction of self-supporting and load-bearing elements, including walls and ceilings. Another type of lightweight concrete for structural purposes, their average density is equal to the limit of 1400-1800 kg/m3, strength M50, and frost resistance level starts from F15. Such concretes are applicable in the construction of load-bearing structures.

Lightweight concrete can also differ in the type of binders; they can be lime, gypsum, cement, liquid glass based or using a mixed binder.

In the production of lightweight concrete using the non-autoclave method, ordinary, quick-hardening or pozzolanic Portland cement, as well as slag Portland cement, are used.

Types of aggregates

In the production of lightweight concrete, porous stone components can be used, which are of artificial or natural origin, the quality characteristics of which determine the final characteristics of the material.

Table of thermal conductivity of lightweight concrete.

Natural aggregates can be obtained by crushing and grain selection of porous rocks, including lava, volcanic tuff and pumice. The leaders in efficiency among them are the last two positions; they have high and almost closed porosity, which determines their low water absorption rate.

Some types of concrete are made using artificial aggregates, which are industrial waste and processing of natural rocky components. Those aggregates that are called industrial waste are metallurgical and fuel slags, in addition, they can be slags of chemical origin.

Among the fillers obtained by processing rocky materials and industrial waste, one can distinguish expanded clay, agloporite, vermiculite, etc., expanded during the firing of clays.

Expanded clay is obtained from clay raw materials, which have the ability to swell effectively under the pressure of firing. The resulting clay mass makes it possible to obtain granules that undergo a drying stage before the firing process. The granules are fired in the body of the furnace, and a high temperature is maintained throughout the entire procedure, which can reach 1200°C. Expanding allows the granules to increase in volume up to 17 times. This allows you to obtain expanded clay gravel.

Classification of lightweight concrete based on the characteristics of expanded and coarse porous aggregate.

Perlite is a porous non-natural material based on igneous polymer rocks. Exposure to high temperatures, which reach a limit of 1100-1300°C, causes rocks to swell, which contributes to the formation of crushed stone.

Vermiculite is a product of weathering rock. The process of short-term temperature increase makes it possible to achieve swelling and increase in volume of the material up to 40 times, the swelling condition is a temperature regime of up to 900°C.

Agloporite is a material that has the appearance of sand and crushed stone; it can be obtained by sintering clay rock and substances formed during the extraction, processing and subsequent combustion of fossil coals.

Features of lightweight concrete

The density of concrete is largely determined by the density of the aggregate, grain composition, amount of liquid and binder that were used during the production process. The ratio of the bulk density of coarse-grained porous aggregate to the density of the building mixture prepared on its basis for ordinary lightweight concrete is 0.5, and in the case of porous and low-sand materials this ratio reaches 0.6.

Diagram of the relationship between components in a concrete mixture.

The level of thermal conductivity characteristic of the described concrete varies widely, 0.07-0.7 W/(m.K). The level of this characteristic is significantly influenced by the density, porosity of concrete and other factors. If the density of lightweight concrete increases, the level of thermal conductivity becomes greater.

Lightweight concrete with thermal insulation characteristics and thermal conductivity that does not exceed 0.2 W/(m.K) can be produced by adding extremely light aggregates to the composition, which can be expanded perlite.

The strength characteristics of concrete are affected by the strength of the cement stone and the aggregates used; the strength of the latter is significantly lower compared to the strength of the aggregates that form the basis of traditional concrete. If the strength of the coarse aggregate is insignificant, the separation of the integrity of the building mixture can begin with the destruction of the aggregate, which will not be affected by the density of the cement stone. Concrete, which has a high density, is used to reinforce the structure. This entails a cement consumption of 200 kg per 1 m3, moreover, the amount of consumption indicated is the minimum.

Classification scheme for cellular concrete.

The frost resistance of the concrete described is determined by the volume and type of binder. It is also important what frost resistance indicator the filler has. Concrete made on the basis of Portland cement is distinguished by more outstanding frost resistance qualities, which improve with increasing volume of cement. If the concrete contains lightweight aggregates, including agloporite, pumice or expanded clay, then this makes it possible to produce a lightweight building material with a frost resistance index of F100. This type of concrete is used in the construction of external structures of buildings.

Cellular lightweight concrete

Cellular concrete, which acts as a type of lightweight concrete, is produced using a mixture of binder and additives, which can be foaming or gas-forming. The latter are devoid of coarse aggregates. These types of concrete may also be devoid of fine aggregate, which is sand. After the process of hardening the mixture with the described composition, a stone building material is obtained, which is characterized by high porosity. The air pores are evenly distributed, and their volume can reach 85% of the total volume. Pores are closed cells that contain gas or air inside.

The main disadvantage of cellular concrete is low fracture strength.

The presence of gas or air in the pores determines the type of lightweight concrete, which is called aerated concrete or foam concrete. Aerated concrete is obtained by swelling the concrete mixture with the introduction of a blowing agent, while in the second option a foaming agent is introduced. The pores formed in the process have a diameter limited to 1-2 mm; between them there are thin walls based on the building mixture.

Foam concrete is obtained by mixing a solution, which can be replaced with cement paste, with foam prepared in advance. After the mixture hardens, it is possible to obtain a material based on cells. Foam is obtained by actively mixing a liquid with a foaming agent. The last are liquid compositions of rosin soap, which contains animal glue or an aqueous solution of saponin.

The foam concrete mixture is prepared in special purpose mixers. Then the composition is in steel molds and enters autoclaves, instead of which steaming chambers can be used.

Comparative table of characteristics of foam concrete and ordinary concrete.

The mixture is exposed to constant temperature conditions in the range of 180-190°C and high steam pressure in the range of 0.8-1.3 MPa. These conditions promote the active interaction of the silica component and calcium hydroxide. The end result is calcium hydrosilicate, its features include excellent strength and high durability.

Aerated concrete is made from a mixture of cement, silica and water. In some cases, lime is added to the composition. As soon as the mixture is thoroughly mixed, a gas-forming agent is added to it; it is aluminum powder, perhydrol, etc. Among the most popular gas-forming agents is the first option, which is represented by a fine powder. In this case, gas formation occurs due to the interaction of aluminum and calcium hydroxide. Hydrogen produced during the chemical reaction promotes swelling of the cement paste. The latter becomes hard and retains its porous structure.

Technological diagram for the production of foam concrete.

After preparation, the aerated concrete mixture ends up in the internal space of steel forms. They are filled using such technology that after swelling is completed, the forms are filled to the brim. Aerated concrete undergoes a ripening stage while in molds, after which it is subjected to an accelerated hardening process using autoclave processing. This approach makes it possible to obtain products that are characterized by high strength; in addition, the technology helps to significantly reduce cement consumption, which is ensured by its partial or complete replacement with lime. If you completely use lime instead of cement, you will be able to obtain gas silicates. Each type of cellular concrete lends itself perfectly to any type of processing. Thus, products can be sawed or drilled if necessary.

Installation of internal walls using aerated concrete blocks is carried out using special adhesive mixtures. As a rule, they are prepared from cement, sand and component additives. Dry ingredients must be mixed first in dry form, and then liquid should be added to them. Laying is done along a cord, which should be pulled between two blocks laid at the corners.

Installation diagram of aerated concrete walls.

In the second row, laying can be done without using a cord, but using a level. You can adjust the position of the products using a rubber hammer, which you should gently tap on the product until its position reaches the ideal level. The spaces between the seams should be carefully filled with adhesive, making sure that no voids are formed. This condition is mandatory, otherwise they may cause a change in the specified position of the wall, which will lead to the destruction of the entire structure. The seams should not be too large; their width varies from 1 to 3 mm.

The construction of partitions should be carried out in parallel with the reinforcement, which should be transverse. Reinforcement is recommended to be carried out in certain directions, one of them is the floor level, the other is wall joints and blind areas.

Application in construction and decoration

Recently, lightweight materials have begun to be actively used for decorative elements. With their help, you can decorate a beautiful arch or columns in the Greek style, frame windows, or perform any other decorative task.

With the right approach, almost anything can be made from the material, including the most bizarre designs of designers. In addition, you can complete most tasks yourself, since there are no difficulties.

Without a doubt, lightweight concrete is a unique material that has virtually no competitors on the market. In a short period of time, you can build a full-fledged structure from this material, as well as turn the decor into a real work of art.