Layering of autoclaved aerated concrete. What is non-autoclaved aerated concrete. The difference between aerated concrete and autoclaved aerated concrete in terms of technical characteristics

In connection with the increased interest in aerated concrete blocks, many are interested in what is the difference between aerated concrete and autoclaved aerated concrete. And although they receive new material from the same components, there are differences in the use of material, quality, strength and density of the block. Depending on the hardening conditions, autoclaved and non-autoclaved aerated concrete have different performance characteristics. Non-autoclave products are characterized by high shrinkage, and autoclave products are characterized by dimensional stability.

The difference between autoclaved aerated concrete and non-autoclaved in production technology and application

Despite the popularity of aerated concrete products, not everyone knows how autoclaved and non-autoclaved aerated concrete is made. Many people not associated with construction industry, aerated concrete is associated with non-autoclave technology. However, aerated concrete products are also produced by the autoclave method. Depending on the selected production method, the necessary equipment for making and solidifying blocks.

Performance characteristics differ between autoclave and non-autoclave aerated concrete

Aerated concrete composites, depending on the method of solidification, are divided into the following types:

Autoclave materials

Portland cement mixed with quartz sand, lime and water is used as a raw material. Aluminum powder is introduced into the working mixture, which, interacting with lime, promotes the formation of air pores.

In the process of the gas-forming reaction, the volume increases due to the uniform formation of many pores inside the aerated concrete mass round shape with a diameter of no more than 3 mm. After filling according to the molds, the products are placed in autoclave chambers. At temperatures exceeding 200 degrees Celsius and a pressure of 10-12 atmospheres, the material hardens, acquiring working properties;

Non-autoclave products

It is manufactured from the same components as the autoclave units. In the manufacture of aerated concrete by the non-autoclave method, there is no need to use autoclaves. Uncomplicated technology makes it possible to produce aerated concrete at small enterprises or in a construction site.

After preparation of the working solution, the molding containers are filled. The aerated concrete mixture hardens in natural conditions. By reducing the energy consumption of production, the cost of non-autoclave blocks is significantly reduced. However, at ambient temperatures, the drying time increases to a month.

Features of manufacturing technology affect the structure and properties of the material. Autoclave blocks with cells evenly distributed inside the array have increased strength. Non-autoclave products also have a porous structure, however, the air cavities are unevenly located within the blocks. This negatively affects strength.

The structure and properties of the material are influenced by the features of the manufacturing technology

The use of non-autoclaved and autoclaved aerated concrete is different:

• blocks obtained by autoclave technology are used to build residential buildings of various storeys, cottages and summer cottages;
• non-autoclaved material is used for construction utility rooms and technical facilities.

The strength of buildings made of non-autoclaved aerated concrete is lower than that of buildings made of autoclaved building materials. Various production technologies that determine the operational characteristics of the material are the main difference between autoclaved aerated concrete and non-autoclaved.

Basic properties of non-autoclaved and autoclaved aerated concrete

Let us consider the properties of heat-treated and hardened in natural conditions aerated concrete. Main characteristics of materials:

• increased thermal insulation properties. Due to the air cells located inside the aerated concrete massif, the material retains heat well. The energy-saving properties of gas blocks allow you to maintain a favorable temperature in the building all year round, as well as reduce the cost of heating the room;
• soundproofing characteristics. Aerated concrete walls make it difficult for street noise to enter living quarters. Effective noise insulation is provided due to the saturation of the array with air pores that absorb extraneous sounds... Sound-absorbing properties provide a comfortable living environment;

The material retains heat well due to the air cells located inside the aerated concrete mass

• resistance to negative temperatures. Frost resistance of aerated concrete depends on the concentration of moisture that accumulates inside the air cells. Under the influence of negative temperatures, the liquid crystallizes and, increasing its volume, tries to destroy the gas block. Plastering the surface of blocks increases frost resistance;
• light weight. From block aerated concrete, characterized by a reduced mass and increased volume, they are quickly erected different kinds buildings. For transportation of light gas blocks, no vehicles with increased carrying capacity are required. Masonry products are supplied by hand, and aerated concrete walls do not exert an increased load on the foundation;
• workability. There is no need to use special equipment to change the size of gas blocks during masonry. The material is easily cut with a hand saw or grinder. If it is necessary to make holes or cavities inside the aerated concrete block, this operation is easy to perform using an electric drill.

Aerated concrete blocks are also characterized by:

• correct form;
• exact dimensions;
• rough surface;
• ecological cleanliness;
• fire safety;
• affordable price.

When planning to build a box of your own house or summer cottage from aerated concrete blocks, you should choose the right material and figure out how autoclaved aerated concrete differs from non-autoclaved one. Let's dwell on this point in more detail and compare the properties of materials produced using different technologies.

The frost resistance of aerated concrete depends on the concentration of moisture accumulating inside the air cells.

The difference between aerated concrete and autoclaved aerated concrete in terms of technical characteristics

For the construction of buildings, autoclaved and non-autoclaved aerated concrete is used. What is better to use for the construction of a specific structure? To answer this question, you must compare the characteristics.

Autoclaved and non-autoclaved aerated concrete - which is better in quality

Technology plays a decisive role in product quality:

• autoclave materials are produced in industrial conditions on modern technological equipment with a high degree of automation. The influence of the human factor in production process reduced to a minimum. Quality control is carried out in special laboratories;
• non-autoclaved aerated concrete manufactured using a simplified technology that does not require special equipment. Using a concrete mixer, formwork and ancillary workers, it is not difficult to make blocks in an artisanal way. Under such manufacturing conditions, it is difficult to talk about the stability of product quality.

Thinking about the durability of the future structure, give preference to industrial products manufactured in accordance with the requirements of the current standard.

Differences in strength of aerated concrete

The strength properties of aerated concrete are related to its density. If equal specific gravity the load capacity of autoclaved concrete and non-autoclaved composite is significantly different:

It is easy to cut the material with a hand saw or grinder

• heat-insulating aerated concrete with a specific gravity of 0.4 t / m3, made by the autoclave method, has a strength class up to B2.5;
• a similar material, hardened at natural temperature and pressure, has a strength class reduced to B0.75.

The popular D600 gas block, steamed in autoclaves, has a compressive strength of B3.5. The strength of the same block, manufactured by a non-autoclave method, is B2. The heterogeneity of the structure of handicraft blocks made negatively affects their strength.

Shrinkage of non-autoclaved and autoclaved building materials

Aerated concrete blocks have different shrinkage. For this indicator, the value is regulated by the standard:

• shrinkage of autoclaved materials per meter of masonry does not exceed 0.5 mm;
• the analogous figure for non-autoclave blocks reaches 3 mm.

To prevent cracking of the walls, use a reinforcing mesh and plaster the surface of aerated concrete.

How does the technology of creating aerated concrete affect the porous structure?

Depending on the production method, the homogeneity of aerated concrete changes:

• air pockets in autoclave products are evenly distributed throughout the volume;
• cells within non-autoclave blocks are concentrated at the outer surface.

The production of non-autoclaved aerated concrete without compaction of the material causes unevenness in the structure, which negatively affects the performance.

The homogeneity of aerated concrete changes depending on the production method

Block making precision

Aerated concrete products made by various methods are distinguished by geometry accuracy and dimensional stability:

• thanks to the use of precision equipment for the production of autoclave products, the error of the blocks does not exceed 1 mm;
• the use of inexpensive equipment and different shapes for the manufacture of non-autoclave blocks increases the dimensional tolerance up to 5 mm.

With stable dimensions and precise tolerances, the consumption of glue is reduced, which can be applied in a layer of 1-2 mm.

We compare the properties of materials for thermal conductivity

Both types of aerated concrete have increased thermal insulation characteristics, but there are certain differences:

• autoclaved aerated concrete provides heat protection with reduced product thickness;
• to provide thermal insulation for a building made of non-autoclaved blocks, increased wall thickness is required.

Autoclave blocks are superior to non-autoclave building materials in thermal insulation properties.

We compare the frost resistance of aerated concrete blocks

The durability of buildings depends on the frost resistance of the blocks:

• walls built of non-autoclaved aerated concrete can withstand no more than 50 freezing cycles;
• structures made of autoclaved aerated blocks are not subject to destruction for 100 cycles.

When choosing material for a residential building, it is important to take into account its frost resistance.

We estimate the fire resistance of aerated concrete

Both types of aerated concrete are equally fireproof. No toxic substances are released when the material is heated. Aerated concrete is used for the construction of fire-resistant structures, where there is a high probability of exposure to high temperatures.

Conclusion

Having analyzed the difference between autoclaved aerated concrete and non-autoclaved aerated concrete, it is easy to choose a building material for solving specific problems. It is important to comprehensively assess the properties of the material. It is preferable to use high-quality aerated concrete, characterized by increased strength.

To understand how autoclaved concrete differs from 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 foundation and floors), the possibility of laying thin, but warm and reliable walls.

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

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

Aerated concrete production technology

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

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

First, an ordinary cement-sand mortar is kneaded, poured into a special mold, then aluminum powder is added. As a result of the reaction of powder and lime, carbon dioxide appears, due to which the mass increases in volume, swelling and forming a porous structure. The outgassing 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, foam concrete is created, which is a variety. Indeed, 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 - due to chemicals.

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

Further, the technology for the production 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 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 released from the material). Autoclaving of aerated concrete allows: to accelerate the hardening of the material, to increase its strength characteristics, to reduce shrinkage in the future, to make the structure homogeneous, and to improve the geometry of the finished blocks.

Non-autoclaved aerated concrete gains strength not in a furnace, but in the natural environment - without the influence of temperature and pressure to evaporate moisture. Moreover, often for the production of this type of material, not large molds are used with further cutting of gas blocks, but molds for casting individual elements.

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

Properties of non-autoclaved and autoclaved aerated concrete

Aerated concrete autoclave hardening and non-autoclave - completely different materials at the exit. They differ both in appearance (so you can immediately determine by eye which concrete is in front of you) and in operational characteristics.

External indicators

Blocks of a cellular structure, cut from solid wood, usually differ in greater compliance with the design dimensions. Of these, it is easier to carry out masonry, less time, effort and materials is spent on sealing the seams, the thickness of the interlayer seams is much smaller (and cold bridges, respectively, too), the building is easier to finish.

Aerated concrete of non-autoclaved production turns out to be gray, autoclaved - almost white. If the shade is non-uniform and various inclusions in the structure are visible, 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 - concrete is simply mixed, formwork is used for pouring, 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, compressive strength is in the range B1.5-B5, but non-autoclaved aerated concrete gives a maximum strength of B3. Shelves and cabinets, air conditioners, speakers and other devices, which are far from always able to withstand non-autoclaved aerated concrete, can be fixed on walls made of fired blocks.

One of the main differences between materials is shrinkage - there is moisture in unbaked aerated concrete, which provokes the appearance of cracks on the walls. And the density plays an important role - with its decrease, the shrinkage coefficient increases during the residual strength gain. The process takes about 5-10 years. Autoclaved aerated concrete shrinks by about 0.5m / mm, unbaked - by 2-3mm / m.

Thermal conductivity indices also differ - the property depends on 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 values \u200b\u200band lower density.

Differences: the pros and cons of materials

Autoclave aerated concrete blocks quite noticeably differ in various respects from the material that has not been fired. Due to their different properties, blocks are used to perform different tasks, they are relevant for certain types of construction. Before using this or that 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 the autoclave for aerated concrete contributes to the speedy passage of the curing process (accelerates hundreds of times), therefore, after processing with steam at high temperatures, the strength of autoclaved concrete is one and a half to two times higher than the analogue without firing.

So, for example, autoclave grades D500 and D600 show a strength indicator at the level of B2.0-B3.5, a non-autoclave of a similar brand will give B2 class at best.

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 (bathhouse, garage or residential building), the more accurately the blocks are made, the higher the quality of the masonry. Indeed, in which case the difference in level is leveled with glue or mortar, cold bridges are created, and thermal insulation properties decrease.

Thick seams have a negative effect on 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 a flat autoclaved aerated concrete and erect a building from it.

Uniform 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. Autoclaved aerated concrete blocks have a more homogeneous structure, since they are created quickly, harden immediately, and then the blocks are cut into separate blocks.

Non-autoclaved aerated concrete is produced in a different way - foam and blowing agents can be distributed unevenly: often bubbles float up, heavy elements fall down. This has a bad effect on construction - strength decreases in places of large accumulation of bubbles, cold bridges appear in places of a small number of bubbles. The characteristics are unstable.

Mountable

Autoclaved aerated concrete is a durable material on which even very heavy devices and elements can be fixed. There is a possibility of attaching facades made of light expanded clay or even heavy porcelain stoneware. So, the anchor 10x100 can easily withstand the axle pull-out load of about 700 kilograms. That is, you can fix shelves, cabinets, boilers, air conditioners without fear that all of 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 with your hands. No mechanical fasteners are used, light objects are attached to an expensive two-component chemical anchor.

Drying shrinkage

When choosing autoclaved blocks for masonry, one can hope for minimal shrinkage in 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.

Strong shrinkage of buildings made of non-autoclaved aerated concrete can cause a lot of troubles - cracking of masonry, cracks, peeling of finishing, plaster. All this can go on for several years until the concrete takes all its strength.

Sustainability

Autoclaved aerated concrete is absolutely environmentally friendly, breathes well, allows the building to breathe and contributes to the creation of an optimal microclimate. Aerated concrete is created from mineral raw materials, so it is not afraid of decay, 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 house over time.

Thermal insulation properties

Heat retention characteristics are directly related to density. Here, foam concrete demonstrates the best performance, the disadvantage of using it in the construction of which is its low strength. For masonry walls, denser materials are used - the density of kg / m3 should be at least 700 kilograms per cubic meter... And if you use non-autoclaved aerated concrete of this density, then because of the cold bridges of thick seams, the characteristics are even lower.

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

It can be concluded that autoclaved aerated concrete is superior to non-autoclaved blocks in many areas and indicators. We are talking about both geometry and physical and mechanical properties. Autoclave units are created in a factory, with strict adherence to regulations and standards. It is easier and simpler to build from such concrete, the buildings are more durable and of high quality. Completely safe and environmentally friendly material can withstand any stress and guarantees the best operational properties of the structure.

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 technology for the production of autoclaved aerated concrete, its advantages and disadvantages.

Composition

Autoclaved aerated concrete is obtained by firing blocks in special autoclave furnaces, 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 in comparison with conventional non-autoclave blocks. In the process of firing, the molecular structure of the material changes and as a result, aerated concrete is obtained, resembling the volcanic rock tobermorite.

Autoclaved aerated concrete is obtained by firing the material in special furnaces 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.

In the manufacture of 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.

Material advantages

Convenient dimensions of autoclave hardening make work easier. They allow building elements to be laid faster than conventional bricks. Gas silicate complies with standards fire safetysince it does not highlight harmful substances during burning and does not catch fire 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, the owners can significantly save on additional heating.
2. Low weight of the blocks. This makes it easier to work with the material and reduces the load on the base of the building.
3. High sound insulation of the material. Is an good advantage when choosing an apartment in a multi-storey building.

disadvantages

1. Poor compressive and tensile strength. It is applied during construction, which reduces the likelihood of cracking in the walls of the building.
2. High block cost. Gas silicate is practically not produced in small industries due to the need for autoclave furnaces. Large production involves the release of 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 them, which makes them difficult to use in bathrooms.
4. Increased fragility of blocks. Air bubbles create a porous structure, and the material is easily exposed to mechanical damage.

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

Areas of use

The environmental friendliness of the composition made autoclave blocks generally available both in mass and in individual construction. They are used in many areas, and because of 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 you to quickly erect a building, which is very convenient in the design of multi-storey buildings. They are often used in the construction of the walls of the premises, as well as in the restoration of old buildings. Aerated concrete blocks are often used in the construction of summer cottages, country houses, garages and outbuildings to the house.

Production

Non-autoclave blocks require about a month of curing time before use. The autoclave oven reduces the setting time of the material. Firing blocks are often produced by large manufacturers ( autoclave gas blocks produced only in factories), since this requires expensive equipment and large premises. The production technology complies with GOST, therefore, when firing in autoclaves, specialists strictly observe certain temperatures and pressure in the furnace.

Preparation of components

All consumables delivered to the plant by road and stored in special bunkers. Before use, quartz sand and other components undergo special processing. The quartz sand is fed by belt conveyors to a ball mill, where it is finely ground into a powder-like mass. The mass is stored in large slurry tanks equipped with an agitator, 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 plants for the production of autoclaved aerated concrete is automated

Dosage and mixing

The dosage of the components is carried out according to a proven and proven recipe. With the help of automation, each component is accurately weighed and fed into the mixer. Before feeding aluminum powder, it also undergoes preliminary processing. This material is explosive, therefore, the premises comply with all required fire safety standards.

The components are mixed on special conveyors. The components are mixed with water until a sour cream consistency is formed. Automated mixing is carried out at high speed for 4–5 minutes. After mixing, the mixer is cleaned with water and filled with the next batch.

Slicing into blocks

After mixing, the mass is poured into large steel molds for half of 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 ripen and gain the required strength. The ripening time of the mixture is determined by the recipe and the external conditions in the room. After that, the material is fed for slicing. Cutting of aerated concrete is carried out on automated lines special strings. In a given sequence, aerated concrete material lends itself to vertical, horizontal cutting using a trimmer.

Aerated concrete is cut into blocks on special lines with wire strings

Autoclave treatment

Autoclaving changes the molecular structure of the blocks, allowing them to finally mature. The products are placed in an autoclave oven for an average of 12 hours. After the oven is closed, the temperature automatically rises to 190 ° C. With the created vacuum inside the furnace, the pressure gradually rises to 12 bar. On modern factories autoclaves are installed 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 packing

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

The removed blocks are placed on wooden pallets and wrapped in foil. The finished pallets are transported by a loader to the finished product warehouse. So they are stored, protected from moisture. From the warehouse, the goods are delivered to specialized stores.

Ready-made aerated concrete blocks are stacked on pallets and packed with special foil

Reinforce or not?

When building residential and public buildings from gas blocks, it is necessary to perform reinforcement. This eliminates the longitudinal deformation of the walls resulting from temperature differences and shrinkage of the material. The installed fittings will take on additional loads and increase the durability of the erected building.

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

• on structures with increased load;
• under the window openings;
• after the construction of the foundation during the laying of the first row of blocks;
• in each 3-4 row of wall masonry.

The reinforcement of aerated concrete walls takes up 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 the thermal insulation characteristics of aerated concrete blocks. Such grooves are cut with a manual chasing cutter and, before laying the rods, they are cleaned of dust with a construction hairdryer. It is best to use intermittent reinforcement with a diameter of 8 mm.
2. "?" There are many advantages and disadvantages in the construction of aerated concrete bath. Such blocks have high thermal insulation properties, are economical, easy to work with, they do not rot and are completely environmentally friendly. Unlike wooden bath, such a bath during construction requires additional costs for waterproofing and interior decoration, since this material has a 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 autoclaved aerated concrete, which contains lime, and it matures in autoclaves. The main material of ordinary non-autoclaved aerated concrete is and hardens by natural exposure to fresh air for a month. The production technology and the different composition of materials also affect the differences in color between these blocks (gas silicate has white color, aerated concrete - gray tint).

findings

Autoclaved aerated concrete has high quality indicators and is used for the construction of various types of buildings. Like all materials, it has its advantages and disadvantages, which must be familiarized with before carrying out construction work. The advantage of autoclave blocks over non-autoclave ones is that the first ones are produced at large automated factories and more often correspond to GOST and quality standards.

Comments:

Autoclaved aerated concrete is bright representative porous concrete and has proven itself quite well in many countries of the world. Such materials are now widely used in the construction of residential and industrial facilities.

The main components of autoclaved aerated concrete: cement, quartz sand and special blowing agents.

Currently, many companies are engaged in the manufacture and sale of the material. Autoclaved aerated concrete on the building materials market is presented in a wide range: different shapes, sizes and colors. One thing is invariable - high performance characteristics that distinguish it from other products.

Material structure

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

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

Air pores in the structure are created by a chemical reaction with the release of gas. To initiate such a 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 the remains of aluminum powder. Additives can be added as needed 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 got its name from the method of hardening of the concrete mass, after a chemical reaction with the release of gas. A diagram of the complete cycle of material production is shown in Fig. one.

The manufacture 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 for half the volume, while an impact load is applied to the mixture, at which the lime slaking process takes place with the release of heat. Since all this takes place in an autoclave, the temperature rises to 80 degrees.

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

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

Autoclave hardening of the mass is carried out within 1-2 hours. Then the autoclave lid is removed and the aerated concrete is cut into blocks of the required size, while the complete hardening of the concrete is not yet achieved. When cutting, 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 with the formation of a durable mineral. The final hardening and crystallization occurs within 12 hours. Usually the concrete mixture is prepared in the following proportion: cement (usually Portland cement) - 20%, quartz sand - 60%, lime - up to 20%. Remains of aluminum - no more than 1%.

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

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Basic material properties

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

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

Based on this relationship, autoclaved aerated concrete is divided into 3 categories: heat-insulating, structural and structural-heat-insulating. Autoclaved concrete with a density of up to 400 kg / m³ belongs to the heat-insulating type and is intended for private low-rise buildings 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 of several floors, but it will have to be additionally covered with thermal insulation. Optimal properties have structural and heat-insulating concretes with a density of 500 kg / m³, which, with a 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. Aerated concrete building blocks are 625 mm long, 200 and 250 mm high, and 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 manual movement and laying.

An important advantage of autoclaved concrete is the accuracy and stability of the geometry of the building elements (blocks). Autoclave hardening of the concrete mass in the mold allows for clearly defined edges and corners, an even smooth surface of the edges, very high dimensional stability that hardly changes over a long production time. If we take blocks from different production lots, then the deviation is possible only within 1.5 mm in all directions (the first category of accuracy) or up to 3 mm for the third category. Very strict standards have been established for the stability of the ribs and angles.

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Other properties of aerated concrete

Autoclaved aerated concrete has high vapor permeability. According to its air permeability, it belongs to the "breathing" building materials, ie. able to remove steam from the room. This property excludes the formation of mold or mildew in places of steam condensation.

The porous structure provides enhanced 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 in an insignificant amount and in a bound state), which excludes harmful emissions, both during construction and during operation. The environmental friendliness of the composition does not even violate the effect of high temperatures and other climatic factors. Aerated concrete can be considered unique in its fire safety and fire resistance. Even prolonged exposure to open flame and thermal stress does not ignite or destroy the material.

The primary task of every developer is to the right choice building material. Of all the variety on the market, it has proven itself well fake diamond - autoclaved aerated concrete, which is a type of cellular concrete (aerated concrete, aerated concrete). Considering that the material is gaining popularity in private construction, it is worth figuring out what it is and what properties it has. Also, you need to know how non-autoclaved aerated concrete differs.

Characteristics

Aerated concrete blocks have a porous structure, which is formed due to the presence of spherical pores. The air particles are 1 to 3 mm in size. The quality of the building material directly depends on the uniformity of the distribution of pores throughout the volume of the stone and their closure.

The raw material composition of aerated concrete produced by autoclave and non-autoclave methods is completely identical. The mixture contains the following components:

The reaction for the formation of pores does not take place during the mixing stage, but directly in the molds. Hydrogen released as a result of a chemical reaction permeates the entire filled mass and ensures the formation of air particles of almost the same size with their uniform distribution. Despite the identity of the components, there is a difference: the physicochemical composition of the artificial stone changes under the influence of high pressure and humidity. Global changes in strength take place inside the stone. When solidified under natural conditions, the strength of the blocks is much lower.

Types and scope of application

Aerated concrete blocks are classified into 3 categories:

• Heat insulating,
• Constructional.
• Structural and thermal insulation.

Autoclave gas block with density up to 400 kg / m2 is heat-insulating and is used for construction low-rise buildings in areas with very cold climates. Artificial stone with a density of 700 kg / m2 belongs to the structural type and is designed to create load-bearing structures and buildings no higher than 3 floors. Such material requires additional thermal insulation. Structural and heat-insulating blocks with a density of 500 kg / m2 are universal: they have sufficiently high strength and good thermal insulation.

Low weight building blocks available in larger sizes. Length is 625 mm, height - 200, 250 mm, width - 100-400 mm. Large parameters contribute to a significant acceleration of the construction of buildings, and simplify the laying of walls.

Differences

What are the main differences between the two types of aerated concrete blocks? It is most convenient to compare materials using a table.

Characteristics of autoclaved aerated concrete	Characteristics of non-autoclaved aerated concrete
Artificial synthesized stone.	Cured mortar with pores in a natural way or using steam at normal atmospheric pressure.
The structure of the finished block is the same in terms of characteristics and properties at any point.	Properties and characteristics differ within the same batch.
There are no shrinkage deformations at all. The required strength is achieved during production and autoclaving. The shrinkage index does not exceed 0.4 mm / m.	The shrinkage index is 10 times higher - up to 5 mm / m.
Cutting into blocks is carried out on specialized equipment using strings. As a result, such mechanical processing the wall material of the ideal geometric shape is obtained. The sizes are regulated by GOST. The permissible deviations are up to 3 mm in length, up to 2 mm in width, and up to 1 mm in thickness. Artificial stone is laid on a glue mortar, which creates a thinner layer compared to the cement-sand option. The adhesive composition gives the structure solidity, increases the thermal insulation properties and eliminates the formation of "cold bridges". The minimum deviation rate helps to save masonry adhesive.	For the manufacture of blocks, demountable formwork with limited cycles of use is used. Significant deviations in geometric dimensions are allowed - up to 5 mm in thickness (GOST 1989). Due to the large run-up in geometry: the consumption of cement-sand mortar increases - 5-6 times more in comparison with masonry glue; the thickness of the mortar joint increases, which leads to an increase in the cost of masonry work; together with the blocks, a thick masonry layer undergoes shrinkage; cold bridges are created at the seams; laborious leveling and wall decoration is performed; masonry strength indicators deteriorate.
Blocks with a thickness of only 40 cm and a density of D400-D500 have the necessary requirements for thermal protection and strength.	To provide the necessary thermal insulation without the use of insulation, the thickness of the stone should be about 65-70 cm. The density of aerated concrete is at least D700.
Frost resistance, (cycles) - F20	Frost resistance index - F15 -F35
The period of operation is 200 years.	The operational period is 50 years.
Strength according to GOST - B2.5-B5	Strength according to GOST - B1.5-B2.5
High indicators of environmental friendliness.	Environmentally friendly material.

Autoclavableaerated concrete has improved physical and technical properties and appearance.

Technology

The high quality of building material can only be guaranteed by an enterprise with specialized equipment, where production takes place in strict compliance technological processes at all stages. The technology of production by autoclaving provides for the use of a sealed chamber, where a frozen solution with pores is given by heat treatment under high pressure. This technology makes it possible to obtain construction material with improved properties and characteristics that cannot be achieved in normal conditions... Changes in the structure of the artificial stone are carried out at the molecular level. At modern plants of autoclaved aerated concrete, products meet European quality standards.

The proportions of non-autoclave and autoclave product are regulated and recommended in the following ratio of components:

• Portland cement - from 35 to 49%.
• Quicklime - from 12 to 26%.
• Calcium silicates - about 2.6%.
• Calcium chloride - from 0.18 to 0.25%.
• Aluminum powder - from 0.06 to 0.1%.
• Unsalted water, up to 100% volume.

The percentage of components and composition is established empirically. Depending on the strength and hardening conditions, the indicators vary over a wide range. When using autoclaving, excess moisture is removed from the product and the hardening process is completed.

Production

The production of autoclaved aerated concrete takes place in a certain sequence:

• Sand and water are combined, after which the particles are crushed into sand slurry.
• Further, the remaining components are introduced step by step - cement, lime, table salt. The mixing time lasts 5 minutes and the ready-made mortar is poured into the prepared formwork, the surface of which is oiled.
• In the form, the main cycle of a chemical reaction takes place with the participation of highly dispersed aluminum. As a result of the hydrogen reaction, bubbles are formed, foaming the solution and creating a porous structure that takes up to 80% of the total volume. The concrete mass increases in volume, filling the entire mold.
• The ripening and hardening time lasts approximately 2-3 hours.
• The solidified mass is cut with industrial strings into blocks of appropriate sizes.
• The final stage of processing includes steaming the workpieces in an autoclave at a temperature of 180-200 ° and under a pressure not exceeding 1.2 MPa. The crystallization process continues for 12 hours.

In order to make a non-autoclave gas block at home, you will definitely need a concrete mixer. Before preparation, the components are weighed in separate containers: for one part of aluminum powder, 50 parts of water are taken and washing powder is added. The resulting mixture is thoroughly mixed until no metal particles remain on the surface. When filling out the forms, take into account the geometry of the non-autoclaved concrete. When the foam begins to form inside the product, surfaces that are not limited by the formwork rise up. Therefore, in the upper plane, a so-called "hump" is formed, the dimensions of which can reach 7% of the total volume of the block. Such swelling must be removed.

The increased demand for artificial stone led to the formation of a national association of autoclaved aerated concrete manufacturers. The problems of the industry associated with the production of aerated concrete are solved at a professional level. Modern requirements for the quality of building materials are being developed.

Benefits

The main advantages of autoclaved aerated concrete are:

• environmental friendliness - there are no harmful impurities in the composition;
• increased refractoriness and ability to keep the combustion process for 7 hours or more;
• low thermal conductivity;
• accurate and stable geometry of blocks, which allows you to create even and smooth surfaces of the edges, to design the outer and inner corners;
• increased vapor and air permeability, due to which the walls of buildings "breathe" and the formation of condensation is excluded;
• light weight - as a result of low density;
• resistance to moisture, the effects of microorganisms and decay processes;
• ensuring an optimal indoor climate regardless of the season.

The advantages of autoclaved aerated concrete include the presence in the composition of the mineral formation - tobermorite. Under the influence of high temperature and pressure, the stone acquires increased mechanical strength and shrinkage. Thanks to the created conditions, the solidification of the mass is significantly accelerated, which is an important point in large-scale production.

Wall mount attachments, furniture is carried out using special anchors that can withstand up to 350 kg.

Application

Autoclave production has significantly expanded the scope of aerated concrete products. The material is in high demand among individual developers. Cottages and low-rise buildings made of autoclaved aerated concrete, industrial and commercial buildings are being erected.