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 obtained by 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 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

Knead the composition automatically. Then it is poured into molds (approximately up to half). As it thickens, the mass itself rises to the brim, it takes about an hour or two. After that, aerated concrete is cut into blocks using special equipment, and sent to an autoclave oven for twelve hours. There, at an elevated 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 bricks);
• good sound insulation;
• resistance to moisture, mold;
• the correct form, which allows you to make even masonry, 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 carefully handle the material during loading and unloading, transportation and direct laying). Also, to work with such walls, special fasteners are required, ordinary dowels, screws, self-tapping screws are not helpers here.

Conclusion. Aerated concrete that has been "hardened" in an autoclave is good and relatively inexpensive alternative traditional building materials. It is produced in the factory, which provides for quality control of finished blocks. However, as experts note, their installation must be carried out correctly, in compliance with the technology.

natural curing

Compound

The composition of non-autoclaved lightweight concrete includes:

• Portland cement;
• sand (pure or with an additive in the form of fly ash remaining after combustion at solid fuel 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 involves the same chemical reaction with the release of bubbles. The resulting mass with pores is also poured into molds, but left to solidify on its own, in natural conditions. To give the material greater strength, a steaming chamber is often used. For the same purposes, with the non-autoclave method of hardening, “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 the autoclaved one, only they differ not for the better. So, lower thermal insulation performance is inherent. It is not so strong, it gives a large one, therefore it is not used in load-bearing structures.

Unlike its “brother” in class, non-autoclave material does not stand out with ideal geometric shapes - when laying it, the solution layer will be thicker, and surface leveling will be more difficult.

Initially, the technology for creating aerated concrete provided for its production only in high-tech production. But over time, the demand for this material increased so much that autoclaved aerated concrete began to be used equally with a similar type of cellular material produced without additional heat and moisture treatment. And if an unprepared beginner dives into the abyss of a huge selection of aerated concrete, he can easily drown in the flow of information provided about him. So what is the difference between autoclaved aerated concrete and non-autoclaved aerated concrete and which one is best to buy? You will find answers to these burning questions in our publication.

Aerated concrete production technology

Before talking about significant differences in the properties and quality of autoclaved aerated concrete and naturally aged blocks, let's consider their component composition, which is absolutely identical:

• additive-free Portland cement grades M300, M400, sometimes M500 is used;
• clean sand of fine fractions - from 2.0 to 2.5 mm.
• water of medium hardness without chemical impurities;
• blowing agent - aluminum powder or paste;
• a substance that triggers chemical swelling reactions - lime, the type, condition and dispersion of which depends on the method of production;
• modifiers that improve the quality of the final product are added at will and are not mandatory components.

Another similarity that unites autoclaved and non-autoclaved aerated concrete is the principle of mortar production.

At the first stage, in accordance with the technology, an ordinary cement-sand mortar of the required consistency is prepared. The resulting mixture is distributed over the formwork. After that, aluminum powder and lime are introduced into it. It is the reaction of these components that provides the formation of gas, the solution swells, forming pores.

Further technologies diverge at the stage of curing and processing of aerated concrete. With natural curing ready solution poured into the formwork, forming blocks of the desired size. After curing, the products are demoulded and sent to the finished product warehouse.

When using an autoclave for aerated concrete, this step is a little more complicated. Namely, the mixture is poured into a monolithic formwork. After its swelling and gaining minimum strength, the aerated concrete block is cut into products of the required dimensions and sent for additional firing to an autoclave, where the temperature is maintained within 200 0 C and a pressure of 10 bar. Such conditions activate the processes of cement hydration to the maximum and allow removing excess moisture from concrete.

As a result, it turns out that products of natural drying are just a hardened expanded cement-sand mixture, when autoclaved gas blocks in the process of firing, they form a new synthetic component - tobermorite, which qualitatively improves the characteristics of the final product.

Properties of non-autoclaved and autoclaved aerated concrete

The resulting blocks, made using two different technologies, are so different both in appearance and in their characteristics that even an inexperienced layman can distinguish them from each other.

External indicators

The first thing the buyer faces when choosing is the appearance of the materials. It would seem, what difference does it make how the wall blocks look, which subsequently still need to be plastered. However appearance- the most accurate visual characteristic that will help weed out low-quality products.

Geometric dimensions

If we compare gas blocks by the criterion of geometry, then the products autoclave are more accurate. This is partly due to autoclaving and, of course, cutting technology. Even GOSTs regulate deviations linear dimensions from nominal in different ways, depending on the method of production used.

These data only underscore the fact that AAC has a precise finished product geometry that prevents:

• freezing of the walls due to the thickening of the masonry joint, which compensates for the shortcomings in the form of blocks;
• overspending masonry adhesive, leading to an increase in the cost of it.

Color

When buying blocks, pay attention to their color. Of course, it will be gray in the case of products of natural hardening and almost white in autoclaved aerated concrete. The difference in the shades of the blocks and the heterogeneity of the color indicates changes in manufacturing process which often lead to performance degradation.

Autoclaved aerated concrete production equipment reduces any errors to zero, which is initially considered a guarantee of quality and durability. In addition, such large-scale workshops are supplemented by their own construction laboratory, timely testing in which inconsistencies in technology or recipes are identified.

Physical and mechanical properties

Aerated concrete blocks differ not only in external indicators and color, but also in physical and mechanical properties.

Strength

Aerated concrete is represented by a rich range of strength grades - from B1 to B7.5. They are widely used not only as a creation load-bearing structures but also for wall insulation. If we compare aerated concrete produced using different technologies, then autoclaved ones are more durable at the same density as non-autoclaved ones.

For example, blocks with a density of D600 should have a strength class of B3.5. If for autoclave products the indicator is observed, then with naturally aged products the strength class hardly reaches half the norm. Things are even worse with the strength characteristics of self-made aerated concrete. If you want to see this for yourself, buy a block and test it in an independent building laboratory. The results will be on the face.

Thermal conductivity

The thermal conductivity of aerated concrete directly depends on the density of this material. The lower the brand in terms of block density, the better its heat capacity qualities. It is wiser to purchase products of lower density, but with higher strength characteristics, thereby reducing the thermal conductivity of the walls.

Shrinkage

The weakest side of any cellular concrete is its shrinkage after the walls are erected. When using the wrong construction technique, cracks may appear and the plaster layer will peel off. The processes of shrinkage of naturally aged aerated concrete can last up to several years, when autoclaved blocks are practically devoid of such a drawback, since during heat and moisture treatment they have already reached brand strength and complete drying.

Moreover, sustained aerated concrete blocks under natural conditions, they are far from ideal indicators, which negatively manifests itself in the form of shrinkage. This not only leads to a violation of the linear dimensions, but also to the destruction of the structure.

Summing up, we can easily conclude that autoclaved aerated concrete blocks have undeniable advantages over naturally aged products. But in any case, when buying such a wall material, always ask for documents certifying its quality.

Autoclaving aerated concrete

What is the difference between autoclaved aerated concrete and non-autoclaved aerated concrete?

Recently, due to the growing popularity of cellular concrete building blocks, the question often arises: what is the difference between autoclaved aerated concrete and non-autoclaved materials (foam concrete and non-autoclaved aerated concrete)? We will try to answer this question in this article.

Several terms are common for building materials made of cellular concrete - aerated concrete, foam concrete, in addition, there are such characteristics as autoclave and non-autoclave. Let's take a look at the definitions. Cellular concrete- this is the general name of all lightweight concretes, which are characterized by the presence of many pores (cells) in their structure, which give improved physical and mechanical properties to the material.

According to the method of pore formation, cellular concretes are divided into foam concrete And aerated concrete. As the name suggests, one material uses chemical foam, and in the other gas.

Foam concrete is a cement-sand mortar that has hardened in a porous state. The cellular structure in it is formed due to the introduction and "whipping" of chemical foaming agents. As a rule, a shop for the production of foam concrete (“plant” is extremely difficult to call this factory), small in area with a predominance of manual labor and unqualified personnel. The volume of production is extremely small, the turnover of funds is low, therefore, in such production, one has to save literally on everything, which clearly does not contribute to improving the quality of the finished product.

Saturation of concrete with gas released during the reaction of lime and aluminum paste is a rather complicated process and requires careful control over the dosage of these components. It is possible to ensure this only in large plants with high-quality automated equipment, and until recently the term "aerated concrete" already by default meant the presence of autoclave processing. So gradually a stable and completely objective opinion was formed in the mind of the consumer: foam concrete is cheap and with mediocre characteristics; aerated concrete - a little more expensive, but much better quality and stable properties.

In the competition for the buyer, foam concrete manufacturers, instead of reducing the price or improving the quality of their products, decided to simply get away from the completely discredited term “foam concrete”, replacing it with a more harmonious one - NON-autoclaved aerated concrete. In essence, the material has not changed, now a little blowing agent is added to the same chemical foam, then everything is also poured into the formwork and the mortar gains strength in the open. For the end consumer, apart from increasing the price of the product, this renaming does nothing.

What is autoclaving and why is it needed?

Autoclaving - steaming in metal capsules (autoclaves) with high pressure(12 atm.) and high temperature(191 ° C) - allows you to get a material with properties that cannot be obtained in normal conditions. Aerated concrete is autoclaved not only to speed up the curing process of the mixture. The main point is that in the autoclave in the structure of aerated concrete, changes occur at the molecular level, and a new mineral with unique performance characteristics is formed - tobermorite. That's why autoclaved aerated concrete- This artificially synthesized stone, A non-autoclaved concretes- actually frozen in a porous state cement-sand mortar.

Autoclaved aerated concrete and non-autoclaved materials fundamentally differ in a number of parameters, ranging from composition and ending with physical, technical and operational characteristics. And to be more precise, autoclaved aerated concrete surpasses them in everyone indicators.

Consider the main indicators:

1. Quality stability of autoclaved aerated concrete

Autoclaved aerated concrete It is manufactured only in large-scale production and gets to the construction site in the form of finished blocks. The production of autoclaved aerated concrete in artisanal conditions is impossible, since during the manufacture it is necessary to control several dozens of processes and parameters simultaneously. Modern autoclaved aerated concrete plants have a high degree of automation (about 95%) and practically exclude the influence of the human factor on the production process.

Autoclaved aerated concrete is produced in accordance with modern GOST 2007, which is confirmed by test reports, the products have a quality certificate, and the client can be sure of the proper quality.

The production of foam concrete and non-autoclaved aerated concrete does not require a large plant and huge capital investments, which provides a low threshold for entering this business. In practice, this means that with a small concrete-mortar plant, formwork and a couple of low-skilled workers, it is possible to organize a handicraft production with unstable quality indicators, proudly calling it a plant or building materials factory. It is almost impossible to ensure the stability of the product characteristics under such conditions, since the dosing of the components is done manually and, as a rule, “by eye”, and the old GOST, which is more than a quarter of a century old, allows the production of such products.

2. Strength

Cellular concretes are produced in different densities: from 400 to 800 kg/m3 with compressive strength class from B1.5 to B7.5. Densities D500 and D600 are the most popular, while autoclaved aerated concrete at these densities has a compressive strength class of B2.5 and B3.5, respectively.

Non-autoclaved materials, on the other hand, lose significantly autoclaved aerated concrete physical properties and strength at the same density. For example, at a density of D600, they have a compressive strength two times lower than that of autoclaved aerated concrete! In addition, manufacturers of non-autoclaved materials simply cannot produce building blocks with a density below D600, because these blocks have no strength at all, and it is unacceptable to use them in construction.

3. Possibility of fastening

Autoclaving significantly increases the strength characteristics of aerated concrete. At the base of autoclaved aerated concrete you can fix not only cabinets and shelves, but also boilers, air conditioners, ventilated facades. Moreover, hinged facades can be made of both light composite and heavy porcelain stoneware. For this, anchors with polyamide expandable elements are used. For example, one 10x100 anchor can withstand an axial pull-out load of up to 700 kg, which is quite comparable with solid bricks or heavy concrete.

It is simply not necessary to talk about fastening in foam concrete or NON-autoclaved aerated concrete. A nail or screw is simply pressed into the wall by hand, so the use of conventional mechanical fasteners is not possible here. You can use an expensive two-component chemical anchor to attach non-heavy objects, such as mirrors or coat hooks, which gives at least some illusion of reliability. But when hanging on the wall kitchen set even the use of "chemistry" will not help, because. under the weight of the cabinet with dishes, the non-autoclave material will be destroyed at the attachment point and a piece of the block will simply fall out of the wall.

4. Uniformity

In production autoclaved aerated concrete gas formation occurs simultaneously in the entire volume of the material. In parallel with gas formation, curing occurs. As the array grows, special vibrators fixed on it periodically give an impulse to the formwork, which “shakes” the array, expelling large gas bubbles from it and excluding the presence of shells and air sacs in the finished blocks. As a result, the pores are of the same size and evenly distributed throughout the volume of the material. Building blocks from autoclaved aerated concrete obtained as a result of cutting a large array, which guarantees the perfect and the same quality of all blocks.

Non-autoclaved aerated concrete and foam concrete obtained by introducing into the concrete mass of foam, blowing agents and mixing it. As a result, it often happens that bubbles, as the lighter components of the mixture, float up, and heavier fillers settle down. It turns out uneven distribution of pores in the block, and due to this it is not possible to achieve uniform characteristics on different blocks. The technology for the production of non-autoclaved aerated concrete eliminates the possibility of shaking the array, so the presence of bubbles with a diameter of 50-70 mm is a common thing. In such material, colder sections of the wall often appear with condensation on the surface, as well as cracks - in places where the masonry is weakened by large air bubbles.

5. Dry shrinkage

The strength gain of non-autoclaved cellular concrete is accompanied by its significant shrinkage, which, in turn, leads to cracking of the finished masonry. Very often one has to see how multiple cracks appear on a newly built and finished building, the finishing layer peels off, and the plaster falls off. These processes can take place over a period of several years - the same period while the "set of strength" is underway.

Moreover, the blocks are dotted with cracks even before they are laid in the masonry. It is possible to get rid of shrinkage and cracks only by autoclaving, but in conditions of handicraft production this is impossible. Therefore, the sellers of foam concrete and non-autoclaved aerated concrete are marketing ploys by adding fiber (paper impregnated with a solution of sulfuric acid and calcium thiocyanate) and calling it "reinforced foam concrete" that is resistant to cracking. For the end user, again, apart from increasing the cost, the fiber does not give anything, because any person, not even connected with the construction industry, understands that if you add paper to concrete, then no miraculous properties promised by foam concrete sellers, the material will not appear.

It should be noted that the lighter (and as a result, warmer) the material, the greater the shrinkage. Construction experience shows that walls made of non-autoclaved cellular concrete cannot simply be puttied and painted - inside they have to be covered with plasterboard, and for external decoration, hinged facades with fastening to the ceiling or bricks are used.

Autoclaved aerated concrete fully gained strength already in the process of production and autoclaving, so shrinkage deformation does not threaten it.

For example, for autoclaved aerated concrete the shrinkage index does not exceed 0.4 mm/m, while for non-autoclaved materials it is 10 times higher - up to 5 mm/m.

6. Environmental friendliness

Autoclaved aerated concrete is an absolutely environmentally friendly and breathable material. Therefore, in a house made of autoclaved aerated concrete, there is always a favorable microclimate for living, similar to the climate wooden house. Aerated concrete is made from mineral raw materials, therefore it is completely not subject to decay, and due to the ability to regulate the humidity of the air in the room, the likelihood of fungi and mold on it is completely excluded.

Foam concrete can be made from the cheapest local raw materials: sand, crushed stone production waste, in addition, chemical additives are used as foaming agents, which undoubtedly reduces the environmental friendliness of a foam concrete house. Also, chemical components are introduced into the block with fiber impregnated with acids, chlorides and thiocyanates. Even present in small quantities, these substances can be released and accumulate in the air of residential premises.

7. Geometry

The accuracy of the geometric dimensions of the blocks from autoclaved aerated concrete regulated by modern GOST, permissible deviations - in length up to 3 mm, in width up to 2 mm, in thickness - up to 1 mm. Blocks are obtained by cutting a large array of autoclaved aerated concrete with strings and it is simply impossible to cut unevenly on such equipment.

Non-autoclaved aerated concrete and foam concrete are poured into formwork with limited use cycles. In view of the same savings, the formwork is used several times longer than its standard service life, and since the formwork is collapsible, due to its deformation and wear, it becomes more and more difficult to assemble it correctly every time - hence the deviations in the geometry of the blocks. For non-autoclaved aerated concrete and foam concrete, deviations in geometric dimensions are allowed much more - they can reach 5 mm in thickness (old GOST 1989).

A large run-up in the geometric dimensions of blocks made of non-autoclaved materials leads to a deterioration in all masonry indicators:

• - the thickness of the mortar layer increases, leading to an increase in the cost of masonry
• - the shrinkage of the masonry increases, because in addition to the blocks, thick mortar joints also shrink
• - cold bridges are formed due to thick mortar joints
• - time-consuming leveling of the vertical surface of the walls is required
• - the consumption of cement-sand mortar is 5-6 times higher than that of masonry adhesive
• - increase in thickness and complexity finishing works
• - the strength of the masonry is reduced

8. Thermal insulation properties

The density of foam concrete or aerated concrete directly affects their thermal insulation properties and the denser the material, the lower the thermal insulation. Foam concrete or low-density non-autoclaved aerated concrete is an excellent thermal insulation material, but its strength is extremely low and cannot be used for masonry walls. As a constructive, especially for bearing walls, a higher density is required, which means that the material will be “colder”. For example, for the Irkutsk region, when using non-autoclave materials, the density of cellular concrete should be at least 700 kg / cu. meter. The already outstanding thermal insulation properties are significantly worsened by masonry on a cement-sand mortar with thick seams. This means that the thickness of a wall made of foam concrete or non-autoclaved aerated concrete with a density of D700 for normal thermal insulation without the use of insulation should be about 65-70 cm.

Wall of autoclaved aerated concrete provides the same results thermal protection and durability at thicknessonly 40 cm, while the density D400-D500 is sufficient. Objectively autoclaved aerated concrete has better than non-autoclave materials, indicators of strength and thermal insulation with less weight.

Summing up

• - Autoclaved aerated concrete surpasses non-autoclave materials in terms of physical and technical properties due to autoclave processing.
• - Autoclaved aerated concrete produced only on modern factories with stable guaranteed quality at the level of world standards.
• - Autoclaved aerated concrete differs from non-autoclaved materials in higher strength with less weight.
• - Autoclaved aerated concrete does not shrink during operation.
• - Blocks of autoclaved aerated concrete differ in exact dimensions and uniform density of the array.
• - Autoclaved aerated concrete is an artificial natural mineral, which determines the highest level of its environmental friendliness.
• - Application autoclaved aerated concrete allows you to build a heat-efficient house with a homogeneous wall of 400 mm, which does not require insulation.

Building houses from non-autoclaved materials is cheaper only at first glance. If we take into account the poor geometry of non-autoclaved materials, worse thermal insulation and strength compared to autoclaved aerated concrete, the need for more masonry and leveling materials, then there is no benefit in building from non-autoclaved materials.

Aerated blocks obtained by processing in autoclave ovens have gained popularity and taken their rightful place in industrial and residential construction. The material has a lot of advantages over traditional, including natural, building materials. Automation of gas block production technology allows to obtain products with specified controlled characteristics. First of all, we are talking about the high strength of the product and its low thermal conductivity, which is especially important against the background of the constant rise in the cost of energy resources.

Compound

Aerated concrete gets its amazing properties due to: limestone, Portland cement, calcium silicate, aluminum pastes (suspensions), calcium chlorides, water, etc., which are included in its composition in a strictly defined percentage with each other (to form products with specified density characteristics etc.). The calculation of the components is in kilograms to obtain 1 m3 of the finished mixture. The binder can be lime, cement, slag, gypsum, both by themselves and in various mixtures. The most common base is cement with pieces of lime. Additional additives allow the production of blocks different color and give the product specific properties.

Material advantages

Autoclaved aerated concrete has a number of technological, operational and production advantages. The blocks are light in weight, which is convenient when building walls. One unit of the product can replace up to 20 masonry bricks, which speeds up construction. Factory products have high manufacturing accuracy, which reduces the consumption of solutions, ensures the formation of smooth surfaces.

Low ensures the preservation of heat in buildings without additional thermal insulation. Provides sound insulation and has the right degree of gas permeability (similar to wood). When heated, the material does not emit gases hazardous to health, and has a high fire resistance. It is also a neutral environment for microorganisms. Blocks are easily drilled and sawn even with a hand saw.

Material processing is carried out by any tool. Products with a structural and heat-insulating density of the substance (from 500 kg / m3) are intended for the erection of walls of buildings from 3 floors and above. The durability of products is tens of years. The cost of construction is lower than from other materials.

Flaws

High-tech material (blocks) has the ability to absorb moisture from the environment and direct precipitation, so it needs additional waterproofing. After installation, the construction of walls made of gas blocks already has lower thermal insulation due to cold bridges, which are created by fastening mortars, armored belts, metal mortgages, masonry joints, lintels, etc. Blocks of non-factory production do not have standard characteristics for this material.

Areas of use

Autoclaved aerated concrete is widely used in the construction of industrial buildings, residential and commercial real estate. Exterior walls are built from autoclave gas blocks, which can be single-layer, combined and two-layer. Such internal walls designed to take on the load of the upper floors.

It is important to lay the first row perfectly even.

Autoclave blocks can form partitions and walls of fire-prevention rooms, and also be a filler of frames made of steel or concrete. A separate area of ​​​​use is the formation of floor slabs (density of autoclaved aerated concrete 800-1000 kg / m3) in structures. Material with a lower density (plates) is used for thermal insulation of basements, attics, etc.

Autoclaved aerated concrete has been used in the production of wall panels for residential, public and industrial buildings. This applies to reinforced strip cut panels. For standard projects of large-panel buildings, such panels consist of several standard sections.

Production

High-quality autoclaved aerated concrete is produced in the conditions of industrial enterprises. All processes at the production sites are automated, which makes it possible to form aerated concrete products of various formulations with the required characteristics. Production is easily reconfigured for the manufacture of products at the request of customers.

Preparing the Components

For the production of autoclaved aerated concrete, not quartz sand itself is used, but a product of its processing, obtained by wet grinding in ball mills. Further, the sand sludge is additionally processed to the desired consistency in the sludge pools. The compacted material is fed by pumps to the installations that form the required weight proportions of the components.

Dosing and mixing

For this, special automated modules are used, with a capacity of up to 40 cubic meters of products per shift. A fairly wide range of mixing ratios source materials allows you to form autoclaved aerated concrete with specified characteristics. The dosed components of future products are mixed with water, aluminum suspension and lime (Portland cement, etc.) in a mixer according to a given program.

The molds with the mixture are transported to the maturation and pre-hardening chamber.

The addition of gypsum slows down the process of thickening the mass. After the mixture reaches the density of pouring sour cream, it is poured into molds up to half the level. The regulation of the amount and ratio of aluminum and lime determines the volume of hydrogen gas released and, as a result, different density aerated concrete. Impact loads on molds accelerate chemical processes replacement of hydrogen in aerated concrete in voids with air, increasing the volume of material and filling forms with it. There is a primary aging and hardening of the material.

Currently, the demand for building blocks made from cellular concrete is growing rapidly and one can often hear the question: “what is the difference between autoclaved and non-autoclaved aerated concrete?”. Within the framework of this article, the main differences and indicators of these products will be considered.

Material characteristics

First, we need to clarify the terminology. Cellular concretes are understood to mean all lightweight concretes 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 pressure and a temperature above 190 degrees Celsius in apparatuses called autoclaves, one obtains 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 naturally cured or steam-cured concrete, but under normal atmospheric pressure mortar with pores, while autoclaved aerated concrete is an artificially created stone. They are fundamentally different in many respects. They have a different composition 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 doubt, since its production is extremely complex and impossible in artisanal conditions. technological process. 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 the technology due to human fault. Production, as a rule, takes place at large factories and the material is brought to the construction site already in the form of ready-made building blocks. The technology is described in the modern GOST of 2007 and must be confirmed by test reports and product certificates. For the manufacture of foam blocks and aerated concrete, such capacities are not required, and at first glance this seems to be a plus. After all, the product is cheaper. But can you eliminate the risk of low-quality production or even handicraft? When buying autoclaved aerated concrete, this question will not arise, because you can always be 100% sure of its quality.

Uniformity

Non-autoclaved aerated concrete is produced by adding a blowing agent to the concrete mass and mixing it. As a result, there are cases in which the bubbles, having a smaller weight, float up, and the fillers, on the contrary, settle down. As a result, finished products in the form of building blocks are heterogeneous and may even have different 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 evenly throughout the volume of the produced material. As a result, the pores in the finished material are distributed evenly and after the completion of the stage of cutting the finished material into building blocks, they are of perfect quality and uniform structure.

Mounts

Since aerated concrete is very durable, it is possible to fix heavy materials and equipment on it. For example, ventilated facades, made not only of light materials, but also heavy porcelain stoneware. In order for the fastening to be reliable, anchor bolts with polyamide expandable elements are used. As a result, when using, for example, a 10x100 anchor, a pull-out load along the axis of up to 700 kg is maintained, which is very close to the values ​​of a solid brick.

Shrinkage

When curing, 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, it is impossible to only putty and paint the walls, as a rule, more complex work is required. Inside, you have to finish with plasterboard, and outside, use brick or hinged facades. Such problems do not arise when using autoclaved aerated concrete, since it gains its strength even during the production process. For comparison, the shrinkage rate of autoclaved aerated concrete is 0.5 mm / m, but non-autoclaved from 1 to 3 mm / m.

Production precision

In the production process for non-autoclaved materials, they rely on the indicators of permissible values ​​​​from the old GOST, as a result, finished building blocks have a large difference in geometric characteristics. There are no such problems for autoclaved aerated concrete blocks, since all production is carried out in accordance with modern GOST and the discrepancies in the parameters of the finished product are minimal. Due to the large error in geometric dimensions, a number of problems arise when using non-autoclaved aerated concrete:

• is increasing required amount solution and, as a consequence, the cost of construction.
• Cold bridges form due to thick seams.
• Leveling the surface of the walls becomes a rather laborious process.

thermal insulation

The level of thermal insulation of both materials is very good. But you can consider this issue from the side 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 lower the thermal insulation performance of the building blocks will be. For example, to use the material as a constructive, 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 desired level of strength, autoclaved aerated concrete with a density level of 500 kg / m3 can be used and the wall thickness will already 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 needed to eliminate them, this plus comes to naught. Autoclaved aerated concrete is superior to non-autoclaved in almost all respects.