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Autoclaved aerated concrete: advantages of the material and where it is used. Which is better, non-autoclaved or autoclaved aerated concrete? Non-autoclaved aerated concrete

Autoclaved aerated concrete: advantages of the material and where it is used. Which is better, non-autoclaved or autoclaved aerated concrete? Non-autoclaved aerated concrete

Currently, the demand for building blocks made from cellular concrete and you can often hear the question: “what is the difference between autoclaved and non-autoclaved aerated concrete?” This article will discuss the main differences and performance indicators of these products.

Material characteristics

First, we need to clarify the terminology. Cellular concrete refers to all lightweight concrete, during the manufacturing process of which cells (pores) are formed in the structure. In turn, it is divided into foam concrete and aerated concrete, depending on the technology for creating pores. The next stage of division occurs depending on the hardening process - autoclave or non-autoclave.

Autoclaving

When steaming the mixture necessary for the production of aerated concrete at a pressure above 12 atmospheric and a temperature above 190 degrees Celsius in devices called autoclaves, new material with characteristics that cannot be obtained under normal conditions - this process is called autoclaving. As a result, the structure of concrete changes at the molecular level and a new material with completely unique characteristics is obtained, called tobermorite.

Non-autoclaved concrete is concrete that has hardened naturally or with the use of steam, but under normal atmospheric pressure solution with pores, while autoclaved aerated concrete is an artificially created stone. They are fundamentally different in many respects. They have different compositions and different physical and technical parameters, which are an order of magnitude higher for autoclaved aerated concrete.

Main characteristics of materials:

Quality

The quality of autoclaved aerated concrete is always beyond any doubt, since its production is an extremely complex technological process that is impossible to implement in home-made conditions. During production, it is necessary to simultaneously control many processes and parameters; for this, in modern factories the degree of automation reaches 95 percent and practically eliminates the possibility of non-compliance with technology due to human fault. Manufacturing, as a rule, takes place in large factories and the material is brought to the construction site in the form of finished building blocks. The technology is described in modern GOST from 2007 and must be confirmed by test reports and product certificates. For the production of foam blocks and aerated concrete, such capacities are not required and at first glance this seems to be a plus. After all, the products are cheaper. But can you eliminate the risk of poor-quality production or even handicraft? When purchasing autoclaved aerated concrete, this question will not arise, because you can always be 100% sure of its quality.

Uniformity

Non-autoclaved aerated concrete produced by adding a gas-forming agent to the concrete mass and mixing it. As a result, there are cases in which the bubbles, having less weight, float up, and the fillers, on the contrary, settle at the bottom. As a result, the finished product in the form of building blocks is heterogeneous and may even have various parameters. In the case of the production of autoclaved aerated concrete, everything is completely different. The process of gas formation and hardening occurs simultaneously and proceeds uniformly throughout the entire volume of the produced material. As a result, the pores in the finished material are distributed evenly and after completing the stage of cutting the finished material into building blocks, they are of ideal quality and uniform structure.

Fastenings

Since aerated concrete is very durable, it is possible to secure heavy materials and equipment on it. For example, ventilated facades made not only of lightweight materials, but also heavy ones of porcelain stoneware. To ensure reliable fastening, use anchor bolts with polyamide expansion elements. As a result, when using, for example, a 10x100 anchor, an axial pullout load of up to 700 kg is maintained, which is very close to the values ​​of a solid brick.

Shrinkage

As it gains strength, significant shrinkage of non-autoclaved aerated concrete occurs, as a result of which cracks appear in the finished masonry, plaster falls off, or the finishing layer peels off. All this lasts for 3-5 years until the material reaches its strength. Often, when using such materials, walls cannot simply be puttied and painted; as a rule, more complex work is required. The inside has to be finished with plasterboard, and the outside has to be used with brick or curtain facades. Such problems do not arise when using autoclaved aerated concrete, since it gains its strength during the production process. For comparison, the shrinkage rate of autoclaved aerated concrete is 0.5 mm/m, but that of non-autoclaved aerated concrete is from 1 to 3 mm/m.

Precision production

During the production process for non-autoclave materials, they rely on the permissible values ​​​​from the old GOST; as a result, the finished building blocks have a big difference in geometric characteristics. For autoclaved aerated concrete blocks such problems do not exist, since all production is carried out in accordance with modern GOST and there are discrepancies in parameters finished products minimal. Due to the large error in geometric dimensions, a number of problems arise when using non-autoclaved aerated concrete:

  • Increases required amount mortar and, as a result, the cost of construction.
  • Cold bridges form due to thick seams.
  • Leveling the surface of the walls becomes a rather labor-intensive process.

Thermal insulation

The level of thermal insulation of both materials is very good. But we can consider this issue from the point of view of efficiency of use different materials and costs to achieve the same effect. The level of thermal insulation, among others, is influenced by such an indicator as the density of the material. The higher the density level, the more low performance The building blocks will have thermal insulation. For example, for using the material as a constructive material, and even more so for load-bearing walls, high strength is required. To achieve the desired performance using non-autoclaved aerated concrete, a density of at least 700 kg/m3 is required. This means that for high-quality thermal insulation, the wall thickness should be about 65 cm. Under the same conditions, to achieve the required level of strength, you can use autoclaved aerated concrete with a density level of 500 kg/m3 and the wall thickness will be about 40 cm.

Results

At first glance, when building houses, it seems obvious that the price advantage is not in favor of autoclaved aerated concrete. But in the end, taking into account all the shortcomings of non-autoclave materials and the amount required to eliminate them, this plus comes to naught. Autoclaved aerated concrete is superior to non-autoclaved aerated concrete in almost all respects.

Refers to artificial building materials. It has a porous structure and is highly popular in the construction of residential and industrial buildings. Depending on the production method, aerated concrete is divided into autoclave and non-autoclave. This article will help you understand the production technology of autoclaved aerated concrete, its advantages and disadvantages.

Compound

Autoclaved aerated concrete is produced by burning blocks in special autoclave ovens, where they are subjected to high pressure up to 12 atm. and a temperature of 191 °C. This allows not only to speed up the curing process of the material, but also to obtain a material with improved strength characteristics compared to conventional non-autoclaved blocks. During the firing process, the molecular structure of the material changes and the result is aerated concrete, reminiscent of the volcanic rock Tobermorite.

Autoclaved aerated concrete is produced by burning the material in special ovens in which it is exposed to high pressure and temperature

Aerated concrete obtained by autoclave firing is often called gas silicate. Its composition includes:

  1. Portland cement.
  2. Quartz sand.
  3. Lime.
  4. Aluminum powder.
  5. Gypsum.
  6. Water.

When producing gas silicate, the exact proportions of these materials are observed. Gypsum is added so that the mass does not immediately thicken, and aluminum powder helps the process of forming many bubbles.

Advantages of the material

Convenient dimensions of autoclave hardening make work easier. They allow you to lay building elements faster than laying conventional bricks. Gas silicate meets the standards fire safety, since it does not highlight harmful substances during combustion and does not ignite quickly.


Aerated concrete blocks are resistant to harmful microorganisms and mold, as they are made from mineral raw materials

Aerated concrete - pros and cons

Advantages

  1. High thermal insulation performance. Houses made of gas silicate blocks reliably retain heat. With their help, owners can save significantly on additional heating.
  2. Light weight blocks. This makes it easier to work with the material and reduces the load on the base of the building.
  3. High sound insulation material. Is good advantage when choosing an apartment in a multi-storey building.

Flaws

  1. Poor compressive and tensile strength. During construction, it is used, which reduces the likelihood of cracks forming in the walls of the building.
  2. High cost of blocks. Gas silicate is practically not produced in small industries due to the need for autoclave ovens. Large production involves the release quality products and compliance with production standards, but such work will have to pay a lot.
  3. Low moisture resistance. Due to the porous structure of the blocks, moisture quickly penetrates into them, which does not allow their use in bathrooms.
  4. Increased fragility of blocks. Air bubbles create a porous structure, and the material is easily subject to mechanical damage.

Mortar joints and armored belts reduce the thermal insulation of autoclaved aerated concrete blocks

Areas of use

The composition is environmentally friendly autoclave blocks publicly available both in mass and individual construction. They are used in many areas, and due to their good thermal insulation properties, such blocks are used in the construction of schools, government agencies and hospitals. The large dimensions of the block allow the building to be quickly erected, which is very convenient in the design of multi-storey buildings. They are often used in the construction of room walls, as well as in the restoration of old buildings. Aerated concrete blocks are often used in the construction of summer houses, country houses, garages and extensions to the house.

Production

Non-autoclaved blocks require about a month of curing before use. Processing with an autoclave oven allows you to reduce the setting time of the material. The production of kiln blocks is often carried out large manufacturers(autoclaved gas blocks are produced only in factories), since this requires expensive equipment and large rooms. The production technology complies with GOST, therefore, when firing in autoclaves, specialists strictly observe certain temperatures and pressure in the furnace.

Preparing the Components

All Consumables are delivered to the plant by road and stored in special bunkers. Before use, quartz sand and other components are tested special treatment. Quartz sand is fed by belt conveyors into a ball mill, where it is finely ground into a powder-like mass. The mass is stored in large sludge basins equipped with a mixer, which brings the raw material to the desired consistency. The prepared material is fed into machines that form the required proportions of each component.


All work at factories for the production of autoclaved aerated concrete is automated

Dosing and mixing

The dosage of components is carried out according to a proven and proven recipe. Using automation, each component is accurately weighed and fed into the mixer. Before feeding aluminum powder, it also undergoes pre-treatment. This material is explosive, so all required fire safety standards are observed in the room.

Mixing of components occurs on special conveyors. The components are mixed with water until the consistency of sour cream is formed. Automated mixing is carried out at high speed within 4–5 minutes. After kneading, the mixer is cleaned with water and filled with the next portion.

Cutting into blocks

After mixing, the mass is poured into large steel molds to half its volume, since after swelling of the material it will fill the mold to the brim and become porous. Before cutting into blocks, the material is left for 2.5 hours to mature and gain the required strength. The maturation time of the mixture is determined by the recipe and external conditions created indoors. After this, the material is fed for cutting. Cutting of aerated concrete is carried out on automated lines using special strings. In a given sequence aerated concrete material Can be cut vertically or horizontally using a trimmer.


Cutting aerated concrete into blocks occurs on special lines using wire strings

Autoclave processing

Autoclave processing changes the molecular structure of the blocks, allowing them to finally ripen. Products are placed in an autoclave oven for an average of 12 hours. After closing the oven, the temperature automatically rises smoothly to 190 °C. When a vacuum is created inside the furnace, the pressure gradually increases to 12 bar. Modern factories have autoclaves in which excess steam is automatically transferred from one oven to another.


Maintaining the created temperature is maintained in the oven for 6 hours

Sorting and packaging

After processing the blocks in the ovens, they are unloaded using special equipment. The blocks move out on the grates one after another, and the crane removes them from the grates to load the next batch of blocks onto them.

The removed blocks are placed on wooden pallets and packed in film. Finished pallets are transported by forklift to the finished product warehouse. They are stored this way, protected from moisture. From the warehouse, goods are delivered to specialized stores.


Finished aerated concrete blocks are stacked on pallets and packed with special film

To reinforce or not?

During the construction of residential and public buildings Reinforcement must be made from aerated blocks. This eliminates longitudinal deformation of the walls that occurs due to temperature changes and shrinkage of the material. The installed reinforcement will take on additional loads and increase the durability of the constructed building.

The need for reinforcement is foreseen by specialists during the design of the building. Most often, reinforcement is used:

  • on structures with increased load;
  • under window openings;
  • after erecting the foundation while laying the first row of blocks;
  • in every 3-4 rows of wall masonry.

Armature aerated concrete walls bears tensile loads

Many non-professional builders are concerned about the question:

  1. "How ?" The rods are laid on both sides of the block in specially made grooves (grooves), they do not increase the thickness of the masonry joints and do not reduce thermal insulation characteristics aerated concrete blocks. Such grooves are cut with a hand wall chaser and cleaned of dust before laying the rods construction hairdryer. It is best to use periodic reinforcement with a diameter of 8 mm.
  2. "?" There are many advantages and disadvantages when building a bathhouse from aerated concrete. Such blocks have high thermal insulation properties, are economical, easy to work with, do not rot and are completely environmentally friendly. Unlike wooden bath, such a bathhouse during the construction process requires additional costs for waterproofing and interior decoration, since this material has low moisture resistance. For reliable waterproofing of aerated concrete, you can use fiberglass, and insulate the walls and floor with mineral wool.
  3. “What is the difference between aerated concrete and gas silicate?” Gas silicate is an autoclaved aerated concrete that contains lime and matures in autoclaves. The main material of conventional non-autoclaved aerated concrete is and it hardens naturally by curing for fresh air for a month. Production technology and different composition of materials also affect the differences in color of these blocks (gas silicate has White color, aerated concrete – gray shade).

conclusions

Autoclaved aerated concrete has high quality indicators and is used for construction different types buildings. Like all materials, it has its advantages and disadvantages, which you need to familiarize yourself with before carrying out construction work. The advantage of autoclave units over non-autoclave units is that the former are produced in large automated factories and more often comply with GOSTs and quality standards.

There are quite a lot of debates about which aerated concrete is better - autoclaved or non-autoclaved. Manufacturers lead comparative characteristics, specialists conduct research and make calculations various designs from these materials. But one thing remains unchanged: it is quite possible to master the technology for producing non-autoclaved foam concrete at home, and autoclave blocks can only be purchased.

What is non-autoclaved aerated concrete? This is the same foamed concrete, but hardened under normal conditions - without overpressure and with standard thermal and humidity treatment. It differs from “kiln” concrete in that its main component acts as a binder. For aerated concrete using a non-autoclave curing method, it is always cement; lime-containing gas silicate is obtained in autoclaves.

Sometimes blast furnace slag or gypsum is added to the composition, resulting in fundamentally new materials - gas-slag concrete and gas-gypsum, but in our country they are not in great demand.

Characteristics

Like all cellular concrete, non-autoclaved porous materials with high strength are characterized by low weight - 4-6 times less than that of a conventional monolith. Thanks to this, blocks from aerated concrete can be made very big size, which ensures faster work with less labor costs. This is what determined the popularity among developers that non-autoclaved and autoclaved aerated concrete has gained.

Another advantage of porous blocks is their good resistance to heat transfer - the numerous air capsules of which they are composed work as thermal insulators. The energy-saving characteristics of concrete are almost an order of magnitude higher than its dense “parent” and clinker brick. This allows you to save on additional insulation, reducing construction costs to a minimum.

A pleasant bonus for everyone who is used to building on their own - aerated concrete is well processed by any electric and even hand tools. This facilitates not only the construction of the box, but also the laying engineering systems, for which you need to cut grooves or drill holes in the walls.

Comparison with autoclaved aerated concrete

Still, it would be fairer to consider non-autoclaved concrete, comparing it with its autoclaved relative. In this section, normally hardening material has its advantages:

1. The ability to produce structures from aerated concrete of any size, up to continuous pouring into formwork for monolithic construction.

2. Simplified manufacturing scheme, which allows you to make non-autoclave products even at home.

3. Slightly higher resistance to moisture and frost, although they are far from optimal.

4. Relatively low production cost due to minimal energy consumption. The price for a cube of normal-hardening aerated concrete ranges from 2,800 to 3,200 rubles; for the same blocks from a kiln, the cost only starts at 3,200 rubles/m3.

At the same time, non-autoclaved foam concrete is inferior to gas silicate in terms of shrinkage by 7-10 times and almost twice as much in strength (class B 1.5 versus B 2.5). However, this is enough for the construction of private houses of 2-3 floors. Non-autoclaved aerated concrete has slightly higher thermal conductivity – about 0.17 W/m×°C. Because of this, the thickness of the walls has to be made 40% more.

Compound

In order to produce any amount of aerated concrete on your own, you will need to stock up on raw materials:

1. Portland cement - in solution it will take up about 50-60% of the total mass. The most common brands of cement are suitable: M400 D0-D20 and M500 D0-D20.

2. Fillers – ash from thermal power plants, crushed limestone, blast furnace slag (40-50% of the total mass).

3. Blowing agent - this can be aluminum powder PAP (138-195 rubles/kg) or ready-made additives like POS-15 (150 rubles/kg). For 1 m3 of mixture you will need from 1,700 to 2,800 grams. The greater the porosity of aerated concrete is required, the higher the concentration of the blowing agent should be.

4. Modifiers - these additives are not mandatory, but they can be used to improve the characteristics of foamed concrete.

The modifiers are microsilica, calcium chloride, and semi-aqueous gypsum. Instructions for home production allows their replacement with table salt (0.2% of dry weight) or household washing powder (0.01%).

By the way, microsilica, like fly ash, introduced in a ratio of 1:10 or 1:20 to the mass of cement, slightly increases the strength class of foamed products. To zoom in specifications aerated concrete to the performance of more durable autoclave blocks, reinforcing fibers are also introduced into the solution: basalt, polymer, asbestos.

Proportions for preparing formulations of different densities (in kg):

From the given number of components, 1 m3 of aerated concrete is obtained.

Production scheme

Foaming of a composition that has not yet hardened occurs due to the reaction of the alkaline components of the solution with the foaming agent. As a result, hydrogen is released, which forms numerous pores in the concrete body. This is the most critical stage in the production technology of a porous monolith, the flow of which will determine its final characteristics.

The manufacturing scheme itself is no different from conventional concrete work:

  • preparing the solution;
  • pouring into formwork;
  • TVO on initial stage hardening;
  • final hardening.

In order to make aerated concrete with your own hands, you will need a regular concrete mixer, a shovel and buckets. All dry components can be weighed in a separate container before mixing in order to convert the mass proportions of the solution into volumetric ones. Only blowing agent and modifiers (salt or washing powder) will need to be accurately weighed and divided into equal portions for each batch.

Is our quick guide will help you cook aerated concrete mixture and form it into blocks or a solid monolithic structure:

1. Install removable formwork the right size, treat the internal surfaces with oil.

2. In a separate container, add 50 parts water to 1 part aluminum powder, add washing powder.

3. Pour aluminum powder into the resulting composition and mix thoroughly so that no metal particles remain on the surface.

4. Pour the calculated volume of water into the mixer and start the unit.

5. Add the required amount of filler, then add cement.

6. After 2-3 minutes of mixing, you can add lime, if it is present in the “recipe,” and aluminum suspension.

7. At the fourth minute, table salt is added, and already at the fifth minute the solution is quickly poured into the formwork.

In a month, when the concrete gains strength, it will be possible to cut off the top, dismantle the frame and make aerated concrete blocks with your own hands, cutting the monolith into pieces of the required size.

Consider geometry features non-autoclaved concrete– during the process of foaming inside the cement paste, surfaces not limited by the formwork will heave. As a result, the so-called hump will grow at the top. Its size can reach 7% of the total volume of the structure, but this bubble will still have to be removed.

Sometimes it is necessary to speed up the hardening process of non-autoclaved pouring in order to quickly release the formwork and slightly mitigate the shortcomings of foam concrete. To do this, in the first 24 hours the structures provide a constant temperature in the range of +30-50 °C. But the level of humidity and pressure according to the instructions must correspond to normal environmental conditions. It is on these days that porous concrete gains about 50-60% of its strength.

Today, builders are increasingly resorting to the use of modern, lightweight materials that are not inferior to traditional ones. These include aerated concrete. Blocks are produced using two methods - non-autoclave and autoclave. What is the difference, how do the materials differ, and most importantly, which one is better to prefer?

Which one is preferable?

Fake diamond

  • cement;
  • lime;
  • quartz sand;
  • aluminum powder (as a result of the reaction of its aqueous suspension with lime, hydrogen is released, due to which bubbles appear in aerated concrete).

A small amount of gypsum is also added to slow down the thickening of the mixture.

Technology

The composition is mixed automatically. Next, it is poured into molds (approximately half). As the mass thickens, it rises to the edges, this takes about an hour or two. After this, the aerated concrete is cut into blocks using special equipment and sent to an autoclave oven for twelve hours. There, at an increased pressure of 12 atmospheres, it is treated with water vapor heated to a temperature of 190°C, acquiring the required strength.

Features and benefits

Autoclave production of blocks gives them a number of special advantages. Among them:

  • high thermal insulation properties (several times better than conventional brick);
  • good sound insulation;
  • resistance to moisture, mold;
  • correct shape, which allows for smooth masonry and finishing;
  • ease of processing, speed of installation;
  • minimal shrinkage during construction.

Flaws

The disadvantages of autoclave blocks include their certain fragility (it is necessary to handle the material carefully during loading and unloading, transportation and direct installation). Also, to work with such walls, special fasteners are required, ordinary dowels, screws, self-tapping screws - there are no helpers here.

Conclusion. Aerated concrete, “hardened” in an autoclave, is a good and relatively inexpensive alternative to traditional building materials. It is produced in a factory, which provides for quality control of finished blocks. However, as experts note, their installation must be done correctly, in compliance with technology.

Natural hardening

Compound

Composed of non-autoclaved lightweight concrete include:

  • Portland cement;
  • sand (pure or with an additive in the form of fly ash remaining after combustion of solid fuel at thermal power plants);
  • aluminum powder (as in autoclave production, it is used as a blowing agent);
  • calcium chloride (accelerates the hardening process);
  • various additives.

Technology

Non-autoclave production assumes the same chemical reaction with the release of bubbles. The resulting mass with pores is also poured into molds, but left to harden on its own, under natural conditions. To give the material greater strength, a steaming chamber is often used. For the same purposes, with a non-autoclave hardening method, “additional mixing” of additives with reinforcing properties (for example, polymer fiber, glass fiber) is also practiced.

Flaws

The finished block has virtually the same properties as an autoclave one, only they differ not in better side. Thus, they have lower thermal insulation properties. It is not so durable, it gives more, therefore it is not used in load-bearing structures.

Unlike its “brother” in the class, non-autoclave material does not have ideal geometric shapes - when laying it, the layer of mortar will be thicker, and leveling the surfaces will be more difficult.

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