Autoclaved aerated concrete

AAC (formerly Concrete; brand name eg international Ytong, levers, H H Celcon and also in Germany, for example, under Greisel, Lemga, Porit, Hansa, Solbet, Turrit and Domapor ) is a relatively easier highly porous, mineral building material on the basis of lime, lime or cement mortar, which is made ​​porous by swelling and basically subjected to steam curing.

Classification

The term aerated concrete is misleading: it is in no way to concrete in the sense of the definition. AAC does not contain any aggregate such as sand or gravel. The finely ground quartz containing sand (sand flour), which is used as raw material, is a component that takes part in this case to a large extent on the chemical reactions. AAC belongs to the so-called steam-cured materials. Despite its name, it is not a concrete variant, also because the special steam treatment with saturated steam is essential.

The finished product is in accordance with the steam curing process of a crystalline phase, which corresponds to the naturally occurring mineral tobermorite, a balance of silica sand, which has not reacted in the reactions during the preparation, as well as some anhydrite and still other phases ( mainly CSH (I ) ). From the raw materials cement and lime is nothing more to be found in the product, since they are fully implemented in CSH phases.

The closest related material to AAC is also the steam -cured sand-lime brick building material. Similar to the porous concrete is still concrete foam (or expanded concrete ), a pored by foaming or swelling of normal concrete.

Production

Aerated concrete is a steam- cured, solid building material with a bulk density of 300 to 800 kg / m³ and is made from the raw materials lime, water and quartz sand. The sand must be finely ground flour, and can be completely replaced by fly ash from coal-fired power plants. First, the raw materials are turned on in the ratio of 1:1:4, for example, the addition of water to a mortar mix. In the finished suspension, a small amount of aluminum powder or paste is usually added. The mortar mixture is poured into tubs, where the metallic, finely divided aluminum developed in the alkaline mortar suspension hydrogen gas. It caused a lot of small gas bubbles which foam the mixture gradually ansteifende. After 15 to 50 minutes, the final volume is reached, there are now blocks of three to eight meters in length, one in front and one-half meters wide and 50 to 80 cm in height. This cake only fixed blocks are cut by wires to the desired stone or component sizes. By curing in particular steam pressure vessels, the autoclave at temperatures of 180 to 200 ° C in water vapor under saturated steam pressure of 10 to 12 bar, the material obtained after 6 to 12 hours its final properties. Chemically corresponds to the porous concrete at the end of the large proportion of the natural mineral tobermorite, but in synthetic form.

By curing the aerated water vapor requires a comparatively small amount of energy during production. The manufacturing process also allows for an optional production of reinforced and non-reinforced components. The reinforcement, usually in the form of reinforcement cages, is to protect them from corrosion, covered with varnish.

Non-reinforced cellular concrete

The uniform distribution of the pores and be typical high porosity make this building material because of its low weight versatile even in larger formats, universal and static boundary regions. These are referred to as plan stones or blocks. Then there are the good thermal insulation capacity and high load-bearing capacity of aerated concrete plan stone masonry ( in terms of its low bulk density ) as an important feature. These properties and its better compressive strength are also considered in the DIN 1053 as a basic standard for the calculation and execution of masonry.

The compressive strength classes are also characterized color for better representation ( usually on some stones a pallet ). It is here:

• Strength class 2: green
• Strength class 4: blue
• Resistance Class 6: red
• Strength class 8: black

The full name consists of the following data (example ):

• DIN V 4165 - PPW 2 - 0.40 to 624 × 300 × 249

Increasing use of this building material learned with the introduction of the Thermal Insulation Ordinance 1995 ( WSV 95) and in force since 2002 and the guidelines worsening Energy Saving Ordinance ( ENEV ). Please refer to here is very low computational values ​​of the thermal conductivity λ (in W / (m · K) ) of 0.11 at PPW 2 to 0.18 are the PPW 6 Attempts to improve these low values ​​still (eg PPW 2 0.09 W / ( m · K) ), have now led to material of 0.08 W / ( m · K), but other properties such as the compressive strength, may be adversely affected.

Another advantage of aerated concrete precision blocks is achieved already by production high dimensional accuracy, which allows processing in thin-bed method in which the joints reach a thickness of 1 to 3 mm, thus minimizing thermal bridges in the joint area and the compressive strength of the masonry is increased. The practical handle aids allow a compliant processing. Plan stones have a weight of 7 to a maximum of 25 kg.

Thus, the walling is also the artisan skilled laymen possible.

Components with reinforcement

Components made of autoclaved aerated concrete included as components of reinforced concrete reinforcement, which can absorb tensile forces. Precast Aerated concrete are used as wall panels, wall, ceiling and roof panels in the industrial, residential and municipal construction used here as a simple solution for high thermal insulation. This storey-high wall panels and for non- load-bearing walls wall panels are produced for load-bearing walls. Aerated concrete wall panels are used variably in conjunction with supporting structures of steel, concrete or wood. The different component sizes and the horizontal or vertical way laying open many paths in facade design and give the opportunity to create any building envelope assembly contractors. The installation is usually done by specialized installation company. The services range from creating installation plans and structural calculations, about the installation, through to disposal and surface treatment ( coating, clothing).

Aerated concrete wall components, also called system wall elements shown in their combination a complete and therefore efficient mounting system.

Roof panels made ​​of aerated concrete can be used for flat and pitched roofs and are placed on the design part. With appropriate connection or anchoring elements for the stiffening of the building can be counted as a roof panel.

Fire and complex partitions made ​​of aerated concrete are employed in industrial due to its high fire resistance for up to 360 minutes one of their main applications. The high temperature damping leads even after six hours of fire up to 1200 ° C on the unexposed face only to about 50 ° C surface temperature and that even for a wall thickness of 175 mm.

F90 fire walls made ​​of aerated concrete mounting components are possible in the minimum wall thickness of 175 mm, both between and in front of or behind the supports of the support structure of the building. In contrast, the minimum wall thickness of complex partitions F180 from aerated concrete building panels is 250 mm.

Use

For aerated concrete masonry units (block, flat blocks, plan block elements ) and prefabricated components (wall, roof and floor slabs ) manufactured. Although the low density of the material causes an equivalent compared to brick wall with thermal insulation effect, but the sound insulation is also rather moderate. Aerated concrete is used for masonry for external walls and internal walls. Especially as a monolithic outer wall are its advantages (insulation and homogeneous solid material ) advantage. Its disadvantages are unfavorable behavior at low moisture absorption and sound insulation. Because of the light and versatile processability of the material, the use of the individual interior design and for objects of sculptural art is popular.

History

The historical development of the building material aerated concrete, which began in the 19th century, goes back to the laboratory tests of the Swedish architect Axel Erikson in the years 1918-1923. The process was patented in 1924. In 1929, production started in the Swedish Yxhult. From " Yxhults Anghärdade Gasbetong " the first registered brand building material in the world was later Ytong .. The second major international brand AAC lever goes back to the company's founder and technicians Josef lever from Memmingen. In 1943, the first lever - plant was opened in Germany ..