The main differences between autoclaved and non-autoclaved aerated concrete blocks: properties, characteristics, application. What is the difference between autoclaved aerated concrete and non-autoclaved aerated concrete? Autoclaved concrete

Aerated concrete is a popular building material, the main application of which is the construction of buildings 1-3 floors high. Low density and high thermal resistance make it possible to build walls from aerated blocks, the weight of which is 3-4 times lower than the weight of similar brick walls. Today, this is the only building material suitable for the construction of durable and warm walls minimum thickness.

This article discusses two types of aerated concrete - natural and autoclave hardening materials. We will study their raw material composition and production technology, get acquainted with the differences, advantages and disadvantages, and also determine which cellular concrete is better.

Autoclaved aerated concrete is superior to natural hardening material in all performance characteristics. Let's look at its main advantages:

1. Stable quality. The production of autoclaved aerated concrete is possible only in large-scale production conditions, while a non-autoclaved analogue can be made even at home, which is why blocks of dubious quality often end up on the market.
2. Strength. Autoclaved aerated concrete is produced in densities D400-800, its compressive strength varies between B1.5-B5, while the maximum strength of non-autoclaved material does not exceed B3. On a wall made of thermally hardened blocks, you can mount not only cabinets and shelves, but also heavier objects - speakers, air conditioners, the weight of which non-autoclaved cellular concrete cannot withstand.
3. No shrinkage during operation. Shrinkage associated with the evaporation of moisture contained in the material is the main reason for the appearance of cracks on walls made of aerated blocks. The lower the density of the material, the more it shrinks during the process of residual strength gain, which continues for 5-10 years after the production of the blocks. Atoclaved aerated concrete shrinks by an average of 0.5 m/mm, while non-autoclaved aerated concrete shrinks by 2-3 mm/m.
4. Geometry. Blocks cut from solid wood always have smaller deviations from the design dimensions than products formed by injection molding methods in separate molds. Size mismatch cellular concrete natural hardening leads to an increase in the thickness of masonry joints (cold bridges are formed) and problems when finishing the building facade.

For comparison, here are the characteristics of both materials:

Based on the totality of operational characteristics, it is much better to use autoclaved aerated concrete for the construction of residential buildings, while its analogue can be used for the construction of technical buildings - garages, animal sheds, gazebos. The difference in the price of materials is about 15-20%.

About 90 large factories and countless small enterprises are engaged in the production of cellular concrete in Russia. Among the verified suppliers, we note the following companies:

• Aerok;
• Bonolite;
• AeroStone.

The largest manufacturer in Russia is Aerok, whose supply volume exceeds 400 thousand m 3 of aerated concrete throughout the year. It was Aerok who introduced into circulation blocks with strength B2.5 and density D400 in 2005, which subsequently became the standard in the field of low-rise construction.

The company's product range includes the following types of blocks:

• thermal insulation: EcoTerm (D400) and EcoTerm + (D300);
• structural: Classic (D500) and Hard (D600);
• lintels and U-shaped blocks.

The company supplies all common block sizes. The quality of its products is confirmed by full compliance production process requirements of GOST No. 31360.

As an analogue to Aeroc aerated concrete, it makes sense to consider the products of Bonolit, the second most popular manufacturer in Russia. First of all, the company is known for its line of autoclaved aerated concrete Bonolit40, which is designed specifically for the Russian climate and performs ideally at temperatures from -40 to +40. In addition to supplying products, the company offers turnkey construction services for cellular concrete houses.

To understand the difference between autoclaved concrete and non-autoclaved concrete, it is necessary to consider the main features of both types of aerated concrete. The popularity of aerated concrete in construction is growing every day, which is explained by its positive properties: good strength, low density, high quality, low weight (which generally reduces the cost of foundations and floors), the ability to lay thin, but warm and reliable walls.

Autoclaved and non-autoclaved concretes differ in their production method and, accordingly, in their performance characteristics. Initially created exclusively in conditions industrial production, but they soon found a way to produce cellular material without additional heat and moisture treatment.

Autoclaved aerated concrete is more stable, but non-autoclaved aerated concrete involves shrinkage. But if we consider their differences in more detail, it becomes clear: both types of aerated concrete are relevant for repair and construction work, it is important to know their characteristics and choose the right one for specific tasks.

Aerated concrete production technology

Autoclaved and non-autoclaved aerated concrete are produced using the same technology; the differences lie only in the accuracy of the technology and in the final stages of processing the material. The raw materials are used identically and in the same proportion.

• Fine sand 2-2.5 millimeters
• Portland cement grades M300 and M400
• Lime
• Aluminum powder or paste with an active metal content of 90-95%
• Various additives and modifiers (not necessarily introduced, but needed to improve various performance properties)
• Water

First, an ordinary cement-sand mortar is mixed, poured into a special mold, then aluminum powder is added. As a result of the reaction of powder and lime, carbon dioxide, due to which the mass increases in volume, swelling and forming a porous structure. The gas release reaction must be completed before the cement sets; to intensify the process, the mold is processed on a vibrating platform. But this process is only relevant for large factories.

In small workshops they create foam concrete, which is a type. After all, according to the method of foam formation, concrete is divided into gas and foam concrete. And if in the first case the foam is created by gas, then in the second - by chemicals.

The cellular structure is created by adding and whipping special chemical foaming agents. Shops are usually small, with a small number of employees, predominantly manual labor. The production of aerated concrete is more expensive, but such a material is also more stable and has better properties.

Further, the production technology of autoclaved and non-autoclaved aerated concrete suggests differences. If autoclaved aerated concrete is produced, after pouring the mixture into the mold and starting the reaction, wait a certain time, allowing the mixture to partially harden and gain sufficient strength to remove the mass from the formwork and cut it into blocks.

The cut blocks are sent to an autoclave and fired at a temperature of +190-200 degrees, the pressure is 8-10 Bar (so that moisture is completely removed from the material). Processing aerated concrete with an autoclave allows you to: accelerate the hardening of the material, increase its strength characteristics, reduce shrinkage in the future, make the structure homogeneous, and improve the geometry of the finished blocks.

Non-autoclaved aerated concrete gains strength not in the oven, but in natural environment– without exposure to temperature and pressure to evaporate moisture. Moreover, often for the production of this type of material they do not use large forms with further cutting of gas blocks, and molds for casting individual elements.

Autoclaved and non-autoclaved aerated concrete are produced in accordance with the following regulatory documents: GOST 21520 "", GOST 25485 "Cellular concrete", as well as GOST 31360 and GOST 32359.

Properties of non-autoclaved and autoclaved aerated concrete

Autoclaved and non-autoclaved aerated concrete – absolutely different materials at the exit. They differ as appearance(therefore, you can immediately determine by eye what kind of concrete is in front of you), and by performance characteristics.

External indicators

Blocks of a cellular structure, cut from solid wood, are usually distinguished by greater compliance with the design dimensions. They make masonry easier, less time, effort and materials are spent on sealing the seams, the thickness of the inter-masonry joints is much smaller (and cold bridges, respectively), and the finishing of the building is simpler.

Aerated concrete is not autoclave production turns out gray, autoclaved - almost white. If the shade is uneven and various inclusions are visible in the structure, most likely the quality of such material is not very good.

The production of non-autoclaved aerated concrete is often carried out practically in artisanal conditions - the concrete is simply mixed, formwork is used for pouring, and after hardening in natural conditions, the material is supplied for construction. All this negatively affects the quality of the final material and its basic properties.

Physical and mechanical properties

Autoclaved aerated concrete shows a density of D400-800, the compressive strength is in the range of B1.5-B5, but non-autoclaved aerated concrete gives a maximum strength of B3. On walls made of fired blocks, you can attach shelves and cabinets, air conditioners, speakers and other devices that non-autoclaved aerated concrete is not always able to withstand.

One of the main differences between the materials is shrinkage - unfired aerated concrete contains moisture, which causes cracks to appear on the walls. And density plays an important role - as it decreases, the shrinkage coefficient during residual strength increases. The process lasts about 5-10 years. Autoclaved aerated concrete shrinks by approximately 0.5 mm/mm, unburnt - by 2-3 mm/m.

Thermal conductivity indicators also vary - the property depends on the density: the lower the density, the more heat-intensive the material. To reduce the thermal conductivity of walls, it is best to choose aerated concrete with high strength and lower density.

Differences: pros and cons of materials

Autoclaved aerated concrete blocks differ quite noticeably in various indicators from material that has not been fired. In view of different properties blocks are used to perform different tasks and are relevant for certain types of construction. Before using a particular material in your work, you first need to study all the specifications, advantages and disadvantages.

Strength

Naturally hardened aerated concrete is less durable, especially if it is completely fresh. It takes a lot of time to gain strength. But an autoclave for aerated concrete helps speed up the process of strength gain (it speeds up hundreds of times), so after steam treatment at high temperatures, the strength of autoclaved concrete is one and a half to two times higher than its counterpart without firing.

For example, autoclave grades D500 and D600 demonstrate a strength indicator at the level of B2.0-B3.5, non-autoclave grades of a similar grade best case scenario will give class B2.

Block geometry

During the construction process, the evenness of the blocks and their compliance with the specified parameters are very important. Regardless of what kind of object is being built (a bathhouse, a garage or a residential building), the quality of the masonry is higher, the more accurately the blocks are made. Indeed, if something happens, the difference in level is leveled out with glue or mortar, cold bridges are created, and the thermal insulation properties are reduced.

Thick seams negatively affect shrinkage during the process and cracks may appear. To avoid this, the difference in levels is removed, the usual hand saw. But the time and labor costs in this case are simply enormous. It is much easier and cheaper to immediately buy smooth autoclaved aerated concrete and build a building from it.

Uniformity of structure

The uniformity of the structure is determined by the number of bubbles in the material and the uniformity of their distribution. The more homogeneous the material, the better it is - this has a positive effect on quality. Aerated concrete blocks autoclave hardening have a more uniform structure, since they are created quickly, harden immediately, and then the arrays are cut into separate blocks.

Non-autoclaved aerated concrete is produced differently - foam and gas-forming agents may not be distributed evenly: often bubbles float up, heavy elements fall down. This has a bad effect on construction - strength decreases in places large cluster bubbles, cold bridges appear in places with a small number of bubbles. Characteristics are unstable.

Possibility of fastening

Autoclaved aerated concrete is durable material, on which you can attach even very heavy devices and elements. It is possible to mount facades made of light expanded clay or even heavy porcelain stoneware. Thus, a 10x100 anchor can easily withstand an axle pullout load of about 700 kilograms. That is, you can attach shelves, cabinets, boilers, air conditioners, without fear that all this will fall with a piece of the wall and fasteners.

Non-autoclaved aerated concrete is much less durable - sometimes you can even press screws or nails into it by hand. No mechanical fasteners are used; lightweight objects are secured with an expensive two-component chemical anchor.

Drying shrinkage

When choosing autoclaved blocks for masonry, you can hope for minimal shrinkage during the process. Under firing conditions, concrete has already gained strength and gives a shrinkage rate of a maximum of 0.5 mm/m, while non-autoclaved aerated concrete gives about 5 mm/m - the difference is significant.

Severe shrinkage of buildings made of non-autoclaved aerated concrete can cause a lot of troubles - cracking of masonry, appearance of cracks, peeling of finishing and plaster. This can continue for several years until the concrete takes on all its strength.

Environmental friendliness

Autoclaved aerated concrete is absolutely environmentally friendly, allows air to pass through well, allows the building to breathe and helps create an optimal microclimate. Aerated concrete is created from mineral raw materials, so it is not afraid of rotting, moisture and mold.

In the case of the production of non-autoclaved aerated concrete, chemical additives are used to form foam, which already reduces the level of safety of its operation. Often, chemical components are introduced into a block with fiber impregnated with special thiocyanates, chlorides and acids, which is even more dangerous, since these substances can be released and accumulate in the air of the home over time.

Thermal insulation properties

Heat retention characteristics directly depend on density. Here the best performance is demonstrated by foam concrete, the disadvantage of using it in construction is its low strength. For laying walls they use more dense materials– the density kg/m3 must be at least 700 kilograms per cubic meter. And if you use non-autoclaved aerated concrete of such a density, then due to the cold bridges of thick joints, the characteristics are further reduced.

Autoclaved aerated concrete provides the same properties, but with a smaller wall thickness and with smaller cold bridges, which ultimately provides better performance.

We can conclude that autoclaved aerated concrete is superior to non-autoclaved blocks in many areas and indicators. It's about both about geometry and physical and mechanical properties. Autoclave blocks are created in a factory environment, with strict adherence to regulations and compliance with standards. It is easier and simpler to build from such concrete, the buildings are more durable and of higher quality. Completely safe and environmentally friendly material withstands any load and guarantees the best operational properties buildings.

With the increasing pace of construction activities, non-autoclaved aerated concrete has gained popularity among builders. The growing need for materials for construction requires an increase in production volumes and changes in technology.

In construction, professional terminology associated with types of raw materials is common. Autoclave and non-autoclave production methods are known. What are their features?

The tested technological process involved obtaining products using an autoclave method. This narrowed the scope of application of the resulting concrete mass and made it possible to produce only standard elements - lintels, blocks. Manufacturing methods have improved. The result is the production of raw materials made without autoclaving. This expanded the scope of use and allowed it to be used in the construction of monolithic structures.

A wide range of building materials sold allows you to choose the concrete most suitable for specific conditions

Distinctive features

Let's figure out what is the main difference between autoclaved aerated concrete and non-autoclaved aerated concrete? These are the conditions for the hardening of concrete mortar. They are divided into the following types:

• artificial, in which the hardening of the concrete mixture is carried out under pressure exceeding atmospheric pressure, with an increased concentration of saturated vapors;
• natural, hardening naturally, using electrical heating or atmospheric pressure, getting saturated with steam.

Non-autoclaved aerated concrete differs from autoclaved aerated concrete in the features of its manufacturing technology. It can be obtained quite simply without the use of autoclaves. This is a simple method carried out at a factory or landfill. To do this, a mixture consisting of lime, cement, gypsum, aluminum powder is poured into special forms. It hardens at normal conditions. This manufacturing method reduces costs electrical energy. No operation required special equipment. The resulting block is cut into finished fragments.

Autoclaved aerated concrete is produced by autoclaving. This is a complex operation that requires maintaining a steam pressure of 12 atmospheres and a temperature of up to 200⁰ C, at which the aerated concrete is “hardened” and acquires operational characteristics. Due to its high strength and durability, autoclaved aerated concrete is widely used in the construction of various objects: country houses, garages, cottages. Offices, high-rise buildings, and industrial facilities are no exception.

Aerated concrete is concrete with air or gas pores evenly distributed in it.

How are properties improved?

The characteristics of the composition produced without steaming in containers are increased as follows:

• Modifying components are added - microsilica, semi-aqueous gypsum.
• Hardening is accelerated by introducing calcium chloride.
• Bringing strength closer to parameters artificial material. For this purpose, dispersed reinforcing fibers of natural origin are introduced - basalt fiber, asbestos, as well as artificial ones - fiberglass or polymer components.
• They are strengthened by introducing acidic ash with a total volume of 10% of the cement mass.

The naturally hardened solution has high thermal insulation properties. The blocks obtained from it are quality characteristics are not inferior to traditionally produced ones, hardening in autoclaves.

Technological features, properties

As a result chemical reaction Using aluminum powder with alkali, which promotes gas formation, a synthetic gas-filled composite is obtained. A uniformly distributed porous structure is formed by hydrogen bubbles. Strength characteristics can be improved by adding modifiers. There are reagents that accelerate the hardening process. Experts believe that using composites reduces construction costs by 10 to 20%. This depends on the proportion of the mixture among the total range of items used. The energy-saving indicators achieved during use are also important.

Non-autoclaved aerated concrete matures under natural conditions or under certain exposure to temperature and moisture, but at normal atmospheric pressure

If we compare it with the widely used brick, then natural concrete reduces the need for energy resources. When operating objects built from it, energy costs are reduced by 20-25%.

Difficulty of choice

Which composition is better? There are three fundamental points related to the characteristics of concrete solutions. Let's take a closer look:

• The first is the amount of shrinkage of concrete compositions. The natural mixture, which hardens naturally, has an increased shrinkage of 2-3 millimeters per meter of pouring depth. Autoclaved aerated concrete shrinks significantly less. The layer reduction is 0.3 mm/m. This does not affect the quality of construction of monolithic objects. During hardening and shrinkage, the solution spreads under the influence of its weight, which compensates for the change linear dimensions. This disadvantage manifests itself in the production of prefabricated structures.
• The next factor is the time required for curing. U ordinary material it takes more time to acquire the necessary strength properties.
• Strength factors are important. Autoclaving technology promotes the formation of a special mineral - tobermorite, which increases strength. This substance is not formed during the traditional method. This limits the scope of use of naturally curing composites. Scope of application: structures operating under light loads.

You can determine the difference between each type of concrete by considering autoclaving.

Non-autoclaved aerated concrete has a large number of pores with a diameter of up to 3 mm, evenly distributed throughout its volume

Production Features

Autoclaving is the operation of steaming a concrete composition in special metal containers called autoclaves. Concrete mortar at given parameters (temperature, pressure) acquires high strength properties that cannot be achieved in the usual way. This treatment not only reduces the hardening time of the mixture. The main feature is changes at the molecular level. The result is that the composition acquires unique strength characteristics. Aerated concrete produced in an autoclave is synthesized. This is an artificially obtained stone. It differs from cement-sand concrete, which hardens porous.

Products obtained in various ways have their own performance characteristics, composition, and physical and technical parameters. The main indicators of the produced concrete are quite high. Manufacturing features and parameters are regulated by various regulatory documents. Innovative technological methods used by Europeans are gradually replacing ineffective, outdated production methods.

Important Details

Let's look at how each material differs. The scope of application is determined by:

• Quality. The synthesized product is produced at large enterprises. It is transported to construction site ready-made blocks. It is impossible to make this gas concrete by hand. Many parameters are controlled during its manufacture. Enterprises equipped with autoclaves have a high automation rate of 95%. Human factor has virtually no effect on production. Quality is confirmed by certificates of conformity. Natural compositions do not require major investments and are inexpensive.

• Strength factors. Cellular composites differ in density and strength class. With equal density, conventional products are inferior in terms of physical characteristics and strength.
• Fastening properties. The synthesized composite makes it possible to secure heavy equipment: ventilation systems, air conditioners, heaters. For this purpose, an expansion type anchor is used.
• Stable density. Gas formation using the autoclave method occurs throughout the entire environment. At the same time, the mixture hardens, the pores are uniformly distributed throughout the volume. The formation of blocks from the resulting mixtures is carried out by cutting the hardened mass. This is a guarantee of the quality of the blocks. When producing naturally hardening concrete, foam with gas-forming agents is introduced into the solution. During mixing, light components float and heavy fillers settle. Uneven distribution of cavities occurs. The density of different blocks is different. Stability of indicators is associated with homogeneity, which affects strength.
• Environmental friendliness. Synthetic is completely safe for others gas composition. This affects the microclimate of the building, which is favorable for living. The mineral components used do not rot. This ensures that mold and fungi cannot form. The decrease in the environmental friendliness of foam concrete is due to the use of waste from the production of crushed stone, local sand, and chemical fillers. This negatively affects the microclimate of the room.
• Compliance with dimensions. Standards regulate deviations in the length, width, and thickness of blocks obtained in autoclaves. The tolerance value does not exceed 3 millimeters. Naturally hardening concrete products are characterized by large dimensional deviations - up to 5 mm. Tolerances in the geometry of the blocks worsen the masonry: more mortar is required, labor intensity increases, and costs increase.

Comments:

Autoclaved aerated concrete is a prominent representative of porous concrete and has proven itself quite well in many countries around the world. Such materials have now been found wide application in the construction of residential and industrial facilities.

The main components of autoclaved aerated concrete: cement, quartz sand and special gas generators.

Currently, many companies are engaged in the production and sale of the material. Autoclaved aerated concrete on the market building materials presented in a wide range: different shapes, sizes and color. One thing remains the same - high performance characteristics, which distinguish it from other products.

Material structure

Aerated concrete is a type of cellular concrete in which air pores measuring 1-3 mm are located throughout the entire volume. It is based on a concrete mixture of binder, filler and water.

In general, the class of aerated concrete includes (divided by type of binder composition) cement-based aerated concrete, gas silicate concrete with lime as a binder, slag-based aerated concrete and gas gypsum. Like autoclaved aerated concrete, the most widely used material is cement-based with the addition of lime.

Air pores in the structure are created due to a chemical reaction with the release of gas. To initiate this reaction, aluminum powder or paste is added to the mixture. Thus, the composition of aerated concrete, in general, is a mixture of cement, lime, sand, water and aluminum powder residues. If necessary, additives can be added to impart specific properties. Accordingly, the structure of autoclaved concrete is a hardened concrete mass with numerous small pores evenly distributed throughout the volume.

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Manufacturing Features

Autoclaved aerated concrete gets its name from the method of hardening the concrete mass after a chemical reaction with the release of gas. A diagram of the complete material production cycle is shown in Fig. 1.

The production of such aerated concrete is carried out in an autoclave in the following order. The concrete mixture is mixed to the consistency of sour cream and poured into molds to half the volume, while a shock load is applied to the mixture, during which the process of slaking lime occurs with the release of heat. Since all this happens in an autoclave, the temperature rises to 80 degrees.

Figure 1. Scheme of the full production cycle of autoclaved aerated concrete.

An active reaction of aluminum and lime begins with the release of hydrogen. The concrete mass increases in volume and fills the entire form. Pressure rises in the autoclave. Under the influence of temperature and pressure, cement hardens, clogging the pores inside its volume. During the reaction, air displaces hydrogen from the pores, filling them. In this way, a concrete structure is formed in which air pores occupy up to 80% of the total volume. By changing the mode and amount of introduced aluminum powder, the pore concentration can be changed over a wide range.

Autoclave hardening of the mass is carried out within 1-2 hours. Then the lid of the autoclave is removed and the aerated concrete is cut into blocks the right size, while complete hardening of the concrete has not yet been achieved. When cutting, the end elements of block engagement are formed (if necessary). After cutting, the blocks are again placed in an autoclave, where they are moistened at a temperature of about 190 degrees and a pressure of up to 1.2 MPa. Under this influence, the mass finally crystallizes to form a durable mineral. Final hardening and crystallization occur within 12 hours. Typically, the concrete mixture is prepared in the following proportion: cement (usually Portland cement) - 20%, quartz sand - 60%, lime - up to 20%. Aluminum residues - no more than 1%.

The main advantage of the autoclave hardening method is that when exposed to high temperature and pressure, cellular aerated concrete forms a special mineral formation - tobermorite, which has an increased mechanical strength and is not subject to shrinkage. In addition, such artificial conditions significantly accelerate the hardening process of the mass, which is very important in industrial production.

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Basic properties of the material

Due to its porous structure, aerated concrete has a low specific gravity (from 300 to 700 kg/m³) and high thermal insulation properties. The autoclave production method also provides high compressive strength, up to 50 kg/cm².

By varying the pore volume, the density of aerated concrete changes; At the same time, strength and thermal conductivity change. At the same time, changes in the main parameters occur in different directions. A decrease in density (increase in porosity) leads to an increase in thermal insulation properties and a decrease in strength, and an increase in density leads to the opposite effect.

Based on this dependence, autoclaved aerated concrete is divided into 3 categories: thermal insulation, structural and structural-thermal insulation. Autoclaved concrete with a density of up to 400 kg/m³ is a thermal insulation type and is intended for private low-rise houses in areas with a fairly cold climate. Aerated concrete with a density of 700 kg/m³ is structural and is used in load-bearing structures and houses with several floors, but it will have to be additionally covered with thermal insulation. Structural and thermal insulating concrete with a density of 500 kg/m³ has optimal properties, which, with sufficiently high strength, provide good thermal insulation.

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What are the block sizes?

The low weight of porous concrete makes it possible to use building elements with increased dimensions. Building blocks made of aerated concrete are 625 mm long, 200 and 250 mm high, 100-400 mm wide. Such dimensions make it possible to significantly speed up and simplify the laying of walls, while the weight of the block remains within reasonable limits for its manual movement and laying.

An important advantage of autoclaved concrete is the accuracy and stability of the geometry of building elements (blocks). Autoclave curing of the concrete mass in the mold allows for clearly defined edges and corners, even smooth surfaces of the edges, very high dimensional stability, which remain almost unchanged over a long production time. If you take blocks from different production batches, then deviation is only possible within 1.5 mm in all directions (first category of accuracy) or up to 3 mm for the third category. Very strict standards have also been established for the stability of ribs and corners.

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Other properties of aerated concrete

Autoclaved aerated concrete has high vapor permeability. In terms of its breathability, it belongs to “breathable” building materials, i.e. capable of removing steam from the room to the outside. This property prevents the formation of mold or fungi in areas of steam condensation.

The porous structure provides increased sound insulation properties.

The material will gain wide popularity in Europe due to its environmental friendliness. The composition of aerated concrete does not contain any harmful impurities (even aluminum is found in small quantities and in a bound state), which eliminates harmful emissions both during construction and during operation. The environmental friendliness of the composition is not disrupted even by exposure to high temperatures and other climatic factors. In its own way fire safety and fire resistance, aerated concrete can be considered unique. Even long-term exposure open flame and thermal load does not ignite or destroy the material.

Aerated concrete happens autoclave and non-autoclave, and many builders are wondering what the differences are between them.

Let's figure this out together, but looking ahead, let's say that autoclaved aerated concrete is a much higher quality material, and then we will tell you why.

What is autoclave processing of aerated concrete?

Autoclave processing – stage of processing aerated concrete with high temperature (190°C) under high pressure during 12 hours. Autoclaves are called metal containers, into which cut gas blocks are placed.

Autoclaving is done for the following purposes:

1. acceleration of aerated concrete hardening;
2. increased strength;
3. reduction of shrinkage;
4. improvement of structure homogeneity;
5. improvement of block geometry.

The autoclave also changes the structure of aerated concrete at the molecular level, forming new material – tobermoritis. This synthesized stone has properties that cannot be obtained under normal conditions at standard pressure and temperature.

Let us repeat that non-autoclaved aerated concrete hardens under natural conditions, and its production is expensive and modern equipment not required. In other words, many manufacturers stamp gas blocks in their garages, which does not inspire much confidence.

Now let’s take a closer look at the differences between aerated concrete, and we’ll start with strength.

Comparison of autoclaved and non-autoclaved aerated concrete

It is important to note that the video tests non-autoclaved aerated concrete, to which fiber fiber has been added; it significantly increases the strength of the blocks. But we note that in reality, not everyone uses fiber in the production of non-autoclaved aerated concrete, since it is quite expensive.

Strength

Aerated concrete without an autoclave is less durable, especially when it is fresh. After all, like ordinary concrete, it still needs time to gain strength, and autoclave curing accelerated hundreds of times thanks to high-temperature steam treatment. But even with complete hardening of both materials, the strength of the autoclave is higher by half or more.

For example, autoclaved grades of aerated concrete D500 and D600 have a strength class of B2.5 - B3.5, while a non-autoclaved analogue of the same brand achieves, at best, class B2.

Shrinkage

Large shrinkage of blocks can create multiple cracks in the masonry; moreover, cracks can appear over the course of a year or more. To keep such processes to a minimum, block shrinkage should be minimal.

The shrinkage of non-autoclaved aerated concrete is from 3 to 5 mm per meter, while that of autoclaved aerated concrete is ten times less. That is, autoclaved aerated concrete practically does not produce shrinkage cracks when laid correctly.

Block geometry

The geometry of the blocks is also very important, and the smoother the blocks are to each other, the better. After all, if the blocks differ from each other by 5 mm, then the difference in level must be leveled with glue, and these are cold bridges that greatly worsen thermal insulation characteristics masonry

Moreover, thick seams cause greater shrinkage, which again can cause cracks. Experienced builders I will say that the difference in levels can be leveled with a float on aerated concrete, but imagine how much time it will take.

Now let’s think about where the geometry of the blocks will be better, on high-tech factory equipment with autoclaves, or in garage conditions? The answer is obvious!

Most builders believe that the best and most even blocks are obtained from AEROC. The average price per cubic meter of their aerated concrete is 4,000 rubles.

Uniformity of structure

Uniformity refers to the number of voids (bubbles) that are distributed in a certain way in aerated concrete, and the more uniform they are, the better. Autoclaved aerated concrete technology guarantees an ideal distribution of voids, due to the fact that bubbles form and harden immediately, and individual blocks are obtained after cutting one large block.

Non-autoclaved aerated concrete is made completely differently. IN concrete mixture foam and blowing agents are added. As a result, bubbles can rise closer to the surface, while heavier elements fall down. As a result, the distribution of bubbles will be uneven.

Now let's think about what this threatens. Firstly, where there are fewer bubbles, there is less strength, and where there are few bubbles, there is a cold bridge through which heat will escape faster. That is, the strength and thermal conductivity of non-autoclaved aerated concrete are very unstable.

Thermal conductivity

Smoothly moving from the topic of structure uniformity to thermal conductivity, we will say that the uneven structure of bubbles worsens the average thermal conductivity of the block, and naturally, in autoclaved aerated concrete, the uniformity of bubbles is better and, therefore, the thermal insulation is also better.

Conclusion

Autoclave and non-autoclaved aerated concrete differ greatly from each other in a number of parameters, and we can say with confidence that autoclave material surpasses its brother in all respects except one - price. Yes, non-autoclaved aerated blocks are cheaper, but if you count how many problems arise when laying them, how many additional materials, work and time will have to be done, we advise you to think carefully when making your choice.

It’s better to build a house correctly once, from quality material, and be sure that it will last for many years without problems.