Autoclaved aerated concrete (AAC) – the story of a low-weight material

aac story


AAC is attractive on the world market. The production is growing by some 5 Mm3 per year, while the total demand will reach 100 Mm3 in the year 2010, according to H. Bagheri (2006). It is a high-class building material made of simple or even waste ingredients (sand and/or fly ash), with a limited amount of mineral binders (lime, cement). Foaming is generally activated by aluminium powder. The elevation to a higher level is an example of the current trend towards material economy, activated through a well-adapted, low-temperature manufacturing process. The pressurized autoclaving (180-200°C, at about 1 MPa for around 10 h) converts the minerals chemically into a strong crystal structure of torbermorite. And the level of embodied energy is relatively low. Cutting with wires is very accurate, which allows for precise block geometry and masonry with thin bed (1-3 mm) mortar.

In practice AAC now appears in dry densities from 275-400 kg/m3 (insulating densities) to 450-750 kg/m3 (structural qualities). It is used for plain masonry or insulating purposes and for reinforced components such as lintels, roof/floor and wall panels. The creep factor increases with lowering the material density. This may have an important influence on load-bearing walls with a low content of reinforcement. In practice, the density 500 kg/m3 is a good compromise in such cases. Horizontal members have reinforcement also on the compressed side, which make them less sensitive to long-term effects. Investigations of up to 70 year-old horizontal elements confirm to this fact. A lower density is compensated by more steel, which has a fourfold purpose, to resist tension, compression, shear and supply anchorage.

The span limit of a horizontal member was traditionally 6 m. The amount of steel was then still moderate. Increasing the span led to a rapid increase of steel. Siporex, a Swedish producer, expanded the mould to 8.0 m, but in practice the limit was held at 7.2 m with densities 500 or 600 kg/m3, (Lättbetonghandboken, 1993). One factor of critical importance was the deflection under dead weight – a test member of 8 m span had a substantial hang.


A completely different solution to the span problem is given by the BCE technology, originally suggested by one of the authors in the early 1990s, (Hellers B.G. & Lundvall O., 1992). It is a hybrid combination of AAC (PFA or sand), and HPC (High Performing Concrete) and has a special attraction to a block producer, who wants to expand his production to a complete building system. The basic idea behind BCE was to expand the capacity of AAC into 9 m for floor panels and 12 m for roof panels. The units are composed of blocks, stacked in vertical or horizontal directions in a second production stage. The compatibility is secured by pre-stressing, which is carried by the HPC-component, while AAC is an "in-fill" component, building up the body of the structure. The pre-stressing is designed to eliminate the dead weight deflection. This production is well adapted to CAD/CAM conditions, applied to a specific project. The combination is material saving in that concrete is used for compression but also for shear and anchorage of the reinforcement. Three out of four requirements on steel in a genuine AAC-panel are eliminated. Typically, coming from the AAC-side, 75% of the steel is saved, while 75% of the concrete and half the embodied energy is saved (Aroni, 1993), if you come from the pure concrete side (HDelements, hollow core decks). It indicates that going from concrete to BCE, half the emission of carbon dioxide is saved. A complication comes from handling two different concretes. The BCE project is still being developed.


– The embodied energy of AAC is comparatively low, 1.0 GJ/m3 (one third of concrete).
– The density of AAC varies between 275 (insulating quality) and 750 kg/m3 (structural quality).
– The conductivity (W/mK) of insulating materials is in practice 0.08 (275), 0.09 (350), 0.10 (400).
– The characteristic compressive strength (N/mm2) of AAC is 2.3 (450), 3.0 (500), 5.0 (600), 10.0 (750) (sand recipe).
– The characteristic compressive strength (N/mm2) of AAC is 2.9 (460), 3.6 (600), 7.3/8.7 (750) (PFA recipe).
– The creep factor is 0.5 (750), 0.7 (600), 1.0 (500), 1.5 (450) (sand recipe).
– Reinforced panels in practice are made of genuine AAC up to 6.0/7.2 m span (sand recipe). Reinforced members cannot be made with a genuine PFA-recipe.
– Reinforced panels are made in hybrid technology (HPConcrete/AAC:PFA recipe or sand recipe) up to 9.0 m span (roof panels up to 12.0 m).
– The modulus of elasticity (N/mm2) is 1 200 (450), 1 700 (500), 2 500 (600), 4 000 (750).


It all began in 1923, when a Swedish architect, J Axel Eriksson, almost by chance, discovered the possibility to use an autoclaving process to stabilize a mix of slate and burnt lime, foamed by aluminium powder. It had very limited moisture-depending shrinkage (in older literature (Ytong, 1942), it is claimed that its shrinkage is nil!). A patent was granted in 1924, but it took a full five years, until 1929, before the invention was commercially exploited, by Yxhults stenhuggeri AB, a natural stonemasonry, converting to a producer of artificial stone blocks. It was a daring step by the industrialist, Carl August Carlén, soon paying off, since the market was anxiously looking for an insulating masonry material. Sweden had experienced a serious energy shortage after WW1. Ytong, as the material was named after 1940, was widely accepted for its combination of desirable properties, load bearing, heat and sound insulating, fire proof and durable, resisting moisture rot and insects. Reinforced components wereproduced after 1933/34 (Ytong, 1954). The reinforcement in lintels was embedded in ordinary concrete, which was covered on both sides by AAC (Ytong, 1942). To our knowledge, this is the first case of hybrid combination of two concretes, an idea now recurring in the BCE-system, previously introduced. Still, Ytong has remained, first of all, a block producer.

The immediate success of Eriksson´s product soon attracted domestic competition. In the case of Carlsro kalkbruk at Skövde, the competition was of a friendly kind, built on exchange of experience. The competitor had a reputation for producing plain foamed concrete blocks since 1924 (Rönnow, 1948) and it later invested in autoclaves, following the example from Yxhult, in order to stabilize the product. The modernized production of AAC started in 1932. The company name was changed to Skövde Gasbetong AB in 1943 and again to AB Durox in 1964/65, taking the company name from its AAC product. The Durox name is now related to a Dutch group, still producing AAC in more than ten plants around the world, of which nine are in Europe.

A much more severe situation arose, when Siporit (from 1937 Siporex) was launched on the Swedish market in 1934, (Rosenborg, 1998). This material was made of a full cement-based recipe, developed as an alternative to the older slate/lime composition, used by Eriksson and others. The original purpose of Siporex was to form a complete building system, including plain blocks and reinforced products. Lintels were available from the start and roof elements the year after (1935). Typically, the proportion of reinforced products from Siporex exceeded 60% (1964), whereas Ytong´s proportion was always far less. On a European scale, the relation has remained low, 16 % in 1991 (Dubral, 1992), which indicates that AAC as a material was generally approached on a rather low level. It is believed that the current tendency is much in favour of reinforced material, forming components of complete building systems, a higher level of approach. Also, present architecture favours a free hand in choosing components, which are designed to project, beside any standard of sizes.

A Danish group, H+H A/S (Henriksen og Henriksen Aktieselskab) was formed in 1937. Later, it has merged with the British company Celcon Ltd. and it is currently expanding into Eastern Europe, through buy-out of production facilities, where PFArecipes were established after WW2. Celcon had initiated the use of PFA, replacing siliceous sand, in their products, already after 1955.

The spread of AAC technology around the world indicates that the market has been ripe for this kind of product and that maintaining patent rights has been difficult, indeed. It was long tried by Ytong AB, opposing Siporex AB, which ended in an agreement, based on a modus vivendi. Meanwhile, other producers, such as H+H A/S, tried their luck on the market with a long-term success.


Another recipe for making AAC, the third to appear and probably inspired, like Siporex (Rosenborg, 1998), by the German material Mikroporit, was developed at the technical universities in Aachen and Stuttgart after 1942 (Schramm, 2005). It is more than likely that an inspiration came from the Siporex patent of 1937. Whether the rights were in fact violated under the war conditions is still an open question. But the researchers were certainly aware of the sensitivity of traditional wooden floorings by war actions – in 1942 the bombing of German cities started causing devastating firestorms, fed by an extensive use of wood material in buildings, especially in floorstructures, all the way from medieval times up until 1935 (Berg, 2006). (Some roof structures are still made of wood, e.g. in Scandinavia.) The walls and chimneys were normally brick structures, which remained standing after all that could burn had disappeared (Friedrich, 2002). Under war conditions, it was concluded that a new building material must be fireproof and be made of simple materials in a process of low stress on resources. This is a fully modern aspect, important in our times, when we must, for climate reasons, favour efficient solutions to building material supply, measured by some sharp resource or energy index. AAC has a low embodied energy compared to most other products.

Josef Hebel, a Bavarian contractor of high reputation since 1926, was informed about the new material, AAC, through the Generalbaurat of Munich, Hermann Giesler, who organized a meeting with important contractors of Southern Germany, on request from the Reichsregierung (L Hebel, 2008)! J Hebel was commissioned some time in 1941-42 to visit the new AAC-factories (Siporex) in the Baltics (Tallinn and Riga) to learn about reinforced panel production (Rosenborg, 1998). This is a surprising piece of information, not that a capable engineer was assigned to industrial espionage, although with Swedish consent (Jönsson, 2009), but that this happened in war-time, when the German industry, by Führerbefehl, was fully geared to belligerent production. In fact, it was a downright crime to engage in anything beside the purpose of warfare itself. Obviously, the in-house and the public policies did not match! Some kind of accepted disobedience must have characterized the Wirtschaftsministerium, where a man like Otto Ohlendorf was open to long term planning for Germany, despite the prohibition (Herbst, 1982). It is not known whether there was in fact a connection between Ohlendorf and Giesler, but it is a sign of common sense that there were good people in the time of the Third Reich, who were preparing for other conditions than the current. Or were they so convinced that the war would be won, one-way or the other? Not until the 9th of Sept 1943, was the dangerous situation altered by the Führererlass allowing the production of emergency housing for the many unfortunate people, victimized by the bombing. It is highly probable that the Hebel production of AAC at Memmingen, starting in March 1943, was part of the programme. Josef Hebel expanded his business by acquiring an abandoned silicate brick factory at Emmering later that year, which had operative autoclaves, ready for use. His office in Memmingen (since 1921) was bombed to pieces in 1945, just before the end of the war. He had then developed his production into reinforced panels, cut in shape from soft material by thin wire. Wire cutting was an old technology, used e.g. on cheese, but now subject to patent application by Ytong (1942), (Byttner, 1968). It is very likely that Hebel knew about this application.

Josef Hebel was a capable engineer but not a true inventor himself. The technology that he applied in the production, starting again in 1948 at Emmering, was a wise selection of available procedures. The AAC recipe was German, but the reinforcement and the cutting technologies came from Sweden. The initial money came from the Marshall aid to Germany. Hebel specialized in reinforced panels and elements, a profile close to that of Siporex. In 1961 the first home was built by Hebel and the next year another division, Hebel House, was formed to concentrate on residential projects throughout Germany. Hebel has since then swallowed the Siporex plants on several markets. As late as in the 1980s, (Wittmann, 1992/Pytlik & Saxena) the number of production sites was about equal, or 35, between the two companies. In 1994, there were 45 plants named Hebel. In 2002 (Charleston RBJ, 2002) the number of Hebel plants was 115, growing by on average with 4 new plants per year. The identity ofSiporex has eventually been lost to Hebel. The success of Hebel´s brand of AAC, throughout the world, is a proof of his high engineering status, combined with superior management. The total number of plants in the world was exceeding 300 in 2004 (Budwell, 2004), of which Hebel had a 40% share. His name has become a brand in itself.


The AAC material, combined with reinforcing steel, forms a building system, to be used exclusively or in combination with steel, concrete and sometimes wood. The composition of AAC has been refined to include waste materials (already in the 1950s, based on patents from the 1930s !), such as PFA (Pulverized Fuel Ash), class F, replacing part of the sand commercially, or being the only source of siliceous matter, eliminating the grinding process. This is an environmental friendly step, working well with lower densities. At present, it is being tried to use such compositions with reinforced products. According to available experience (Siporex), it was not possible to replace more than 70% of the sand in order to avoid longitudinal cracking, but this conclusion is being questioned by other producers, such as H+H Celcon. A way of avoiding such cracking is to include calcinated magnesium oxide in the recipe. To our knowledge, Hebel is not using PFA anymore, after serious problems with a test facility in 1986.

The production of integral panels, up to say 30 m2 is possible with a one-way prestressing, in the vertical direction. Such a technology is inspired by G Dahl's development of Integral walls (Rosenborg, 1998). The BCE-system is semi-heavy building technology – characteristically, it carries a live load double its dead weight, while massive concrete carries only half.

It is believed that the BCE technology helps overcome some of the drawbacks of the traditional AAC-technology. This is rather wasteful with steel, like the HDtechnology (not to mention massive concrete on-site structures) is wasteful with concrete. This material is not to be approached as a free commodity in our modern world, due to a large embodied energy, related to cement, and severe restrictions on natural gravel. Similar restrictions will possibly be extended to crushed rock, now substituting natural gravel on Scandinavian markets. And, why destroy nature, if not absolutely necessary? In the long perspective, we feel that the prefab concrete industry will also need to approach the BCE-technology. Either way of approach, the new technology is more efficient than the origin.

Bo G. Hellers, Bo R. Schmidt, Autoclaved Aerated Concrete (AAC)-the story of a low-weight material, - Materials of 5th International Conference on Autoclaved Aerated Concrete "Securing sustainable future", Bydgoszcz, Poland, 2011, - p. 63-68.

  • Видение и миссия +

    Видение компании ЮДК заключается в том, чтобы предоставить украинским застройщикам материал премиум-класса, который позволяет улучшить качество жизни, а также:

    • Помогает экономить благодаря уменьшению затрат при строительстве и сберегает энергоресурсы при эксплуатации;
    • Помогает сделать жилье более комфортным благодаря прекрасным физическим характеристикам автоклавного газобетона;
    • Помогает сохранить окружающую среду:  
      • В производстве используется очень мало природных энергоресурсов;
      • Токсичные отходы не загрязняют атмосферу;
      • Только природные сырьевые материалы используются для производства 100% природного конечного продукта.

    Миссия компании ЮДК – это концепция устойчивого развития в экономической, социальной и экологической составляющих нашей деятельности.

  • Основные ценности +

    ЮДК является социально ответственной компанией. Мы ценим длительное и взаимовыгодное сотрудничество с нашими работниками, клиентами, поставщиками. Наше производство является экологически-чистым и не загрязняет окружающую среду. Наш кодекс правил:


    Сотрудники: Компания ЮДК строит честные и согласованные взаимоотношения с сотрудниками и выполняет все юридические обязательства перед ними. Кроме того, ЮДК предоставляет своим сотрудникам хороший социальный и экономический пакет.


    Клиенты: Своим клиентам компания ЮДК предлагает строительные блоки из автоклавного газобетона наивысшего качества, которые производятся с использованием новейшей технологии на современном оборудовании. Компания ЮДК понимает всю ответственность того, что из нашего строительного материала возводятся дома клиентов, поэтому мы обязуемся предоставлять нашим клиентам честную и достоверную информацию и оказывать техническую поддержку на всех стадиях строительства и эксплуатации здания.


    Поставщики: Со своими поставщиками компания ЮДК строит длительные партнерские отношения, что обеспечивает поставку сырья наилучшего качества. Главными критериями отбора наших поставщиков являются профессиональная этика, честность и экологическая чистота поставляемой продукции.


    Окружающая среда: Автоклавный газобетон – это экологически чистый продукт. Благодаря превосходным теплоизоляционным свойствам использование газобетона помогает снизить расходы потребления энергии, что в свою очередь помогает сохранить окружающую среду. Кроме того, для производства газобетона требуется значительно меньше затрат энергии и сырья, чем для производства других строительных материалов. Более того, производство является экологически чистым, вредные токсические отходы не выбрасываются в атмосферу. Команда ЮДК будет продолжать свою миссию по сохранению окружающей среды!

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  • Vision and Mission +

    Vision Company UDK is to provide Ukrainian developers of premium material that improves the quality of life, as well as:

    • It helps to save costs by reducing the construction and saves energy during operation;
    • It helps to make housing more comfortable thanks to the excellent physical properties autoclaved aerated concrete;
    • It helps to save the environment:
      • The production uses very few natural energy resources;
      • Toxic waste is not released into the atmosphere;
      • Only natural raw materials are used for the production of 100% natural final product.

    The company's mission UDK - is to maximize profits for shareholders in accordance with our values and vision.

  • Core values +

    UDK is a socially responsible company. We value long-term and mutually beneficial cooperation with our employees, customers, suppliers. Our production is environmentally-friendly and non-polluting. Our Code of Conduct:


    Empoleyrs: Company UDK build honest and consistent relationships with the staff and fulfills all legal obligations to them. In addition, UDK provides its employees with good social and economic package.


    Customers : The company offers customers UDK provides the building blocks of autoclaved aerated concrete of the highest quality, which are made using the latest technology with modern equipment. Company UDK understands the responsibility that from our building materials to build houses yet, so we are committed to providing our customers with honest and accurate information and provide technical support at all stages of construction and operation of buildings.


    Suppliers : the company with its suppliers UDK builds long-term partnerships that ensure the supply of raw materials of the best quality. The main criteria for the selection of our suppliers are professional ethics, honesty and environmental safety of products supplied.


    Environment : Autoclave aerated concrete - this is an environmentally friendly product. Due to the excellent thermal insulation properties of aerated concrete use helps reduce the cost of energy consumption, which in turn helps save the environment. Furthermore, for the production of aerated concrete requires considerably less energy and raw materials to produce than other building materials. Moreover, production is environmentally friendly, not harmful toxic waste released into the atmosphere. UDK team will continue its mission to preserve the environment!

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  • Properties
  • Product dimensions
The average density of the dry material 500 kg / m3
Thermal conductivity (λ) 0,12 W/(m·K)
Concrete class C2,0; C2,5
Frost-resistance F50; F100
Block sizes Number of units
on pallet (1,8 m3)
The number
of blocks in 1 m3
Length × height Thickness
* Blocks D500 can be produce only by pre-order
  • Properties
  • Product dimensions
The average density of the dry material 400 kg / m3
Thermal conductivity (λ) 0,10 W / (m · K)
Concrete class C2,0; C2,5
Frost-resistance F50; F100
Block sizesNumber of units
on pallet (1,8 m3)
The number
of blocks in 1 m3
Length × heightthickness
600 × 20010015083,3
600 × 20015010055,6
600 × 2002506033,3
600 × 2003005027,8
600 × 2003754022,2
600 × 20040040* 20,8
600 × 2005003016,7
* The volume of pallets 1,92 м3
  • Expense
  • Properties
The thickness of the block (the wall), mm Consumption in kg / m² of masonry Consumption kg/m³ brickwork
100 2,5 25
150 3,8
200 5,0
250 6,3
300 7,5
375 9,4
400 10,0
500 12,5
Color Grey
Compressive strength At least 5 MPa
The amount of mixing water 0,17-0,21 liters per 1 kg of dry adhesive mixture
Time suitability mortar Not less than 2 hours.
Waiting time and adjustments About 15 min.
Frost-resistance At least 50 cycles
Water retention Not less than 95%
Density of mortar 1,55±0,05 kg/dm³
Application temperature From 5 to +30°С
  • Work productivity while using UDK TBM +

    UDK TBM thin bed mortar for aerated concrete is an ideal alterrnative to the traditional cement and sand based mortar and differs in its plastics, applying convenience, less consumption. It also decreases labor intensity, work execution terms in comparison with traditional methods and has high adhesion to mineral surfaces.
  • To reduce heat loss using UDK TBM +

    Heat loss through traditional mortar joints can influence significally the total heat loss through the walls. While using UDK TBM thin bed mortar the joint thickness is 2-3 mm instead of 10-15 mm joint of traditional mortar.Due to the thin joints it is easy to eliminate so called "cold bridge" and decrease heat loss through the walls by 30%.
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  • icon Economical Efficiency
  • icon High Strengts
  • icon Light Weight
  • icon Thermal Insulation
  • icon Versatility
  • icon Fire Resistance
  • icon Seismic Design
  • icon Healthy Room Climate

Economical Efficiency

Saving time, labor-hours and building material cost are the things real estate customers are increasingly demanding from their builders, contractors and developers. UDK wall blocks play an important part in the economy and speed essential to economical and profitable construction projects.
8 blocks/m2
height: 200 mm
length: 600 mm
128 pcs/m2
height: 65 mm
length: 250 mm
UDK wall blocks have larger sizes, are precise in dimensions and weigh remarkably little compared to traditional building materials.
They have hand grips and tongue and groove joints which make them easier to use and lay.
The diagram on the bottom shows clearly that apart from the fact that considerably fewer blocks are required for 1 m2 of wall, a worker can lay a certain number of high-speed building bricks a day and just as many UDK blocks and therefore build a much greater area of wall. Construction crews can complete their work faster saving time and money.
Since walls built with UDK wall blocks together with UDK TBM© will be built much faster, following works such as installation of floors and roofs, as well as plastering, infrastructure (electric cables, water pipes) installations and partitioning will start and progress faster, saving labour and time.
UDK wall blocks are 3 to 4 times lighter than the equivalent volume of traditional construction materials (approximately 75% lighter than concrete) which means transport capacity is maximized and freight cost reduced. Below is a comparison of building material transported on a 20 ton truck:
Ttruck Load (20 tons) Aerated Concrete Blocks Shell Stone Blocks Silicate Bricks
Wall Size 96 m2 32.5 m2 34 m2
Wall Thickness 375 mm 400 mm 380 mm
Product Volume 36 m3 13 m3 13 m3
The cost of 1 m2 wall built with UDK wall bolcks will be less than walls built with other materials:
Comparative price for 1 m2 Aerated Concrete Blocks Shell Stone Blocks Silicate Bricks Ceramic Bricks
Cost Wall Material, % 58 51 80 77,8
Cost of Mortar, % 2,3 9,5 9,3 12
Cost of Labor, % 16,5 21,4 24 28,7
Insulation Cost, % 0 47,5 47,5 47,5
Internal Plaster, % 6,7 9,3 8,5 8,5
External Plaster, % 16,5 16,5 16,5 16,5
Total Cost, % 100 155 186 191
Productivity per Shift (8 hours) 15 m2 7,4 m2 7,4 m2 7,4 m2
All cost calculations in % is based on average prices of popular building materials.

High Strengts

Autoclaved aerated concrete has high thermal insulation properties. 375-400 mm walls built with AAC blocks do not require additional insulation. UDK wall blocks are solid, robust and can safely be used in load bearing walls.

During manufacture autoclaved aerated concrete is steam-cured in a pressurized autoclave (190°С, 12 Bar). The concrete actually turns to rock, forming microscopic crystals of calcium silicate hydrate. It is the analogue of natural stone mineral that gives to AAC its high strength.

UDK Gazbeton AAC blocks are divided into Classes by Strengts B2,0 and B2,5 which is confirmed by Conformity and Test Certificates.

UDK AAC blocks can be applied for construction of load bearing walls of private houses with several floors as well as for construction of non-bearing and bearing walls of high-rise framehouses with no limitation to the number of floors.

Light Weight

Density is one of the main technical characteristics of autoclaved aerated concrete. Density (ρ, kg/m3) is the weight of 1m3 of dry material. 60% of AAC is a porous mass (air porosity). For example, AAC with density D500 (average density kg/m3) is 75% a porous mass. AAC with density D400 has an even higher porosity.

Due to low density, the weight of AAC wall is three times less than the weight of a respective brick wall and 1,7 times less than the weight of ceramsite concrete wall.

In terms of volume, one UDK GAZBETON block can replace 10 bricks and can be installed at one laying, which makes building speed faster and saves labor. AAC blocks have hand grips, which is very convenient. Tongue and groove also makes quality laying of blocks very easy even for inexperienced builders. The light weight of UDK wall blocks means less weight and less pressure on the structure and foundations of a building which means proportional saving along the line: shipment-building-use of building. This makes UDK blocks ideal for use in multi-story buildings as well as in building private homes.

Here are the savings you get while using light-weight UDK wall blocks:

- Save on shipment of blocks to the building object (a truck can take a larger volume of the product);

Truck (20 tons) AAC Blocks Shell Limestone Silicate Bricks
Wall Size 96 m2 32,5 m2 34 m2
Wall Thickness 375 mm 400 mm 380 mm
Volume of Product 36 m3 13 m3 13 m3

- Lower weight of 1 m2 of walls and partitions leads to lower weight of the building as a whole, which consequently lowers load on the foundation;

- Good thermal insulation of frame structure leads to savings on heating each 1 m2 of the building.

Thermal Insulation

Buildings constructed with UDK wall blocks will be warmer in winter and cooler in summer.

High thermal insulation is one of the determining characteristics of autoclaved aerated concrete. Its cellular structure gives it a thermal insulation characteristic several times higher than that of concrete and сlay or silicate bricks.

thermal insulation

A wall built with UDK wall blocks and UDK TBM© thin bed mortar provides solid insulation without thermal bridging associated with most conventional brick and mortar walls. By using UDK TBM© additional savings are made on laying blocks, heating and cooling, and additional insulation materials are not needed.

Thermal Conductivity Comparison
Wall Type
(W/m K)
UDK Block 400
Shell Limestone
Silicate Brick
Ceramic Brick

In summer, the exterior of buildings are subject to high fluctuations in temperature. In order to create cool, comfortable microclimate in buildings, tempertaure fluctuations inside buildings must be minimized. Thanks to effective combination of thermal insulation, thermal inertia and thermal mass characteristics, walls made with UDK wall blocks provide for minimum temperature fluctuations inside the building when the outside temperature fluctuates significantly.

thermal insulation


AAC Versatility

The high level of performance achieved by autoclaved aerated concrete means UDK blocks can be used in a variety of building applications:

UDK wall blocks are ideal for the constructing of all types of external and internal walls in a most economical way, whether load bearing, solid or self-supporting walls. Significant savings in cost and time are possible by using 375 or 400 mm thickness UDK wall blocks in a single row without additional insulation.

UDK wall blocks are a tried and tested, fast and efficient way of constructing external single row solid walls. They are produced in most economical sizes to suit the builder’s requirements

AAC Versatility

UDK blocks can be used for the construction of the inner rows of two or three row cavity walls in combination with a brick external row, with ventilation or thermal insulation material.

Quallity control ensures high precision of dimensions of UDK wall blocks. It allows to build faster and save building materials. Due to minimal tolerances (±1 mm) of blocks, building with UDK wall blocks is economic, precise and fast.

AAC Versatility

UDK wall blocks can be easily shaped. AAC is can be sawed, drilled and filed with the help of an ordinary hand instrument. Blocks of necessary shape can be used for constructing walls, partitions, fencing of balconies, fireplaces, ladders and even for construction of various architectural elements. For rigidity of construction it is better to use blocks with tongue and groove. Large-sized blocks have grips for easy mounting.

Fire Resistance

UDK wall blocks are non-combustible, will prevent the spread of fire, endure high temperatures over long periods of time and can be used in buildings requiring all classes of fire resistance.

fire resistance

Fire separation walls built with UDK wall blocks are:

  • Noncombustible;
  • Will limit temperature rise on the unexposed side of a wall;
  • Do not emit combustion gasses.

Walls built with UDK wall blocks do not transmit smoke and will contain fire. In case of afire, no poisoning gasses are releases.

AAC buildings have proven that even after a fire their walls did not collapse and only renovation of the finish were required to repair the impact of fire.

Seismic Design

Low density of UDK wall blocks in filler structures means less load on the foundation and building frame. It in turn leads to lower material consumption and lower weight of the building. Due to low density combined with high strength, buildings from AAC blocks have proved to have good earthquake resistance.

The table below compares post-earthquake data of a 16-storey building:

Building using AAC Blocks

External Walls (30 cm) 720 m2 360 t
Internal Walls(12,5 cm) 680 m2 340 t
Total 1400 m2 700 t
Horizontal seismic impact equals 40% of vertical load
Horizontal Load 700 t х 40% 280 t

Building using Bricks

External Walls (30 cm) 720 m2 720 t
Internal Walls (12,5 cm) 680 m2 680 t
Total 1400 m2 1400 t
Horizontal seismic impact equals 40% of vertical load
Horizontal Load 1400 t х 40% 560 t

This way, vertical load on building foundation of AAC walls is 360 tons less and horizontal load is 280 tons less. Bearing capacity of the foundation increases and horizontal load on the building during seismic activity decreases.

Healthy Room Climate

Healthy room climate of a buildings has become vitally important nowadays. While designing a new building, we realize that any building should not only be functionally and aesthetically appealing, but also ecologically clean and environmentally friendly.

healthy room climate

European Declaration on Environment pays great attention to building ecologically clean and healthy housing. Thus, viewing impact on the environment while applying AAC for building: raw material-production-application in building-use of building-recycling-utilization and storage, it can be characterized as ecologically clean material.

Another positive aspect is long term of use of buildings from AAC. This is the advantage of using building materials produced on the mineral basis.

Good thermal insulation qualities of AAC play a great role in maintaining energetic balance, warmth and clean air in the building. These component form microclimate that is so important for people’s health.

Comfort and Clean Air

Feeling of comfort is a very important criterion of microclimate. Comfort depends, first and foremost, on the temperature and humidity inside the building.

Low thermal conductivity of AAC makes temperature of internal surface of walls equal to air temperature inside the building, which results in temperature comfort. Temperature of wall surface can differ insubstantially from air temperature inside the building, which eliminates air drafts so typical for poorly insulated buildings.

UDK wall Blocks possess high vapor permeability, which makes process of drying faster and maintains heat and humidity comfort. Good air permeability of AAC helps create healthy and comfortable microclimate in the building.

UDK wall Blocks are resistant to rodents, insects and vermin. The walls will not decay with time.

Low Radioactivity

Low radioactivity is another important requirement to building materials.

According to radiation and hygienic assessment that estimates content of total natural radioactivity, UDK wall Blocks belong to the 1-st and highest class of building materials (according to standard ДБН В.1.4-1.01-97) and can be applied for all types of buildings without any restrictions.

  • Who can apply? +

    • Representatives of construction brigades
    • Construction managers
    • Representatives of building companies
  • How is master class carried out? +

    Training is either done on a specially-equipped training ground of an authorized regional distributor of "UDK", or at "UDK" LLC factory.
    • Training is carried on the rolling basis as soon as the group is formed
    • The average number of persons in a group: 9-12 persons (3-4 brigades, 3 persons in each)
    • Duration: 5-6 hours
    • Those participants who successfully complete practical assignment and pass theoretical testing obtain Certificate of UDK Gazbeton ® Professionals
    • List of participants who receive training and obtain certificates will be published on the website
  • Master Class Program +

    Theoretical part:
    • About "UDK" LLC factory
    • Main properties of AAC
    • UDK Gazbeton ® Products
    • Comparison of existing types of walls
    • Advantages of building walls with UDK Gazbeton ®
    • Building walls with UDK Gazbeton ®
    • Variants of finishing internal and external walls
    • Objects built with UDK Gazbeton ® blocks
    Practical part:
    • Preparing UDK Gazbeton ® thin bed mortar
    • Laying first row
    • Laying next rows
    • Linking walls
    • Cutting and filing blocks
    • Anchoring
    • Practical assignment of building part of wall
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  • Where to buy UDK product? +

    UDK company has wide distributorship chain. Visit "Where to buy" website page and choose on the map the location according to your construction. If you have any questions please contact UDK LLC Heads of sales department of the region directly.
  • How long has UDK company been present on Ukrainian market? +

    UDK LLC has been selling from its factory in Dnepropetrovsk city own-manufactured product under UDK Gazbeton brand since autumn, 2009.
  • What does В2,0 and В2,5 etc. marking mean in aerated concrete strength characteristics? +

    AC compression strength class (B) is nondimensional value but it characterizes material strength including variability index. According to the construction regulation base it is calculated laying compression strength of the blocks with certain strength class.
  • Can we build bearing walls from D400 В2,0? +

    Autoclaved aerated concrete with D400 density class is referred to construction thermal insulating materials with B1,5 and more strength class .Modern technologies can provide D400 aerated concrete density class with В2,0 and В2,5 strength class. It enables to use AAC in different bearing constructions but after necessary construction calculations.
  • Are there any materials with better thermal transmittance/strength coefficient? +

    There are construction materials with less density and thermal transmittance (thermal insulating materials), and higher strength (construction materials). Autoclaved aerated concrete has low density and thermal transmittance and quite high strength that makes it unique construction thermal insulating wall material.
  • What is the main distinсtion between foam concrete and aerated concrete? +

    The main distinсtion is method of pore formation. In the first case it is added foam agent to the concrete mix and cellular structure is formed while its mixing. In the second case there is a pore formation process in the mix as the result of interaction of foaming agent and calcium hydroxide. Foam concrete, as a rule, is aging material, which is produced at the small factories. Aerated concrete is the material of autoclaved industrial production (but there also exists non-autoclaved concrete). Curing method influences the physical and mechanical characteristics – while equal material density autoclaved concrete has higher strength.
  • How to achieve the strength if there is little cement in aerated concrete? +

    Compared to non-autoclaved cellular concrete where material strength is provided by hardened porous cement-sand mortar, autoclaved cellular concrete strength is achieved while autoclave curing (at 195 C temperature and 12 atm pressure). During this process there are formed new materials such as hydrated calcium silicate that provide interpore partition and so the material itself with higher strength.
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