Aerated concrete is the material that combines most of the technical properties that are required of building material. Aerated concrete offers sufficient compressive strength for external walls, excellent fire protection, and has already integrated effective thermal protection. Exterior walls made of aerated concrete no longer have to be additionally insulated against heat loss. Aerated concrete has to make compromises in terms of space requirements, sound insulation, and, above all, weather protection.
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What is an aerated concrete block?
Aerated concrete is, as its name suggests, a building material made of a heavily foamed material. It is made by adding aluminum shavings to a cement-lime powder slurry. They react with the setting cement and release hydrogen in the process. This hydrogen in turn ensures the formation of the bubbles and pores for which aerated concrete is known. After the reaction with the hydrogen, an approximately dough-solid mass is formed. Only in an autoclave, in which the mass is treated with steam at 200 ° C, does the mass harden to form aerated concrete.
Advantages of aerated concrete block
The aerated concrete has the following advantages:
- excellent insulation protection
- excellent fire protection
- very precise dimensional accuracy
- easy to manufacture and process
- easy to transport
- very suitable for processing by laypeople.
The thermal insulation protection of outer walls can hardly be increased sensibly with aerated concrete. The many bubbles create an excellent insulation effect that can only be achieved with KSV, concrete, or solid bricks with a complex and expensive additional insulation layer. Aerated concrete blocks are not only easier and faster to process. As an inorganic material, they are also very insensitive to the formation of mold. The aerated concrete also tolerates damage to weather protection reasonably well. Moistened aerated concrete forms a thermal bridge that can cause structural damage inside the building. However, the aerated concrete does not rot but regains its full functionality after it has dried out. This is especially true as long as no frost has frozen the sucked in water to ice. But even flaking due to the formation of ice in the aerated concrete can usually be easily repaired. Nevertheless, aerated concrete must always be well protected against the effects of the weather
When it comes to fire protection, aerated concrete is one of the best materials available. A wall that is only 17.5 cm thick can be exposed to over 1500 ° C, while only 50 ° C can reach the other side of the wall, and this for hours if necessary.
Aerated concrete is processed cold. The shaping is done with thin wires. The degassed pre-mass is cut into the desired stone formats before steaming. There is almost no waste. The hardened stone can be easily adjusted by sawing. Simple hand saws are well suited for this. However, the saw blade of a hand hacksaw quickly becomes dull when working with aerated concrete. Special aerated concrete hand saws, on the other hand, can be used permanently. Particularly precise results can be obtained by using a band saw. The use of circular saws or cut-off grinders for processing aerated concrete is not recommended due to the generation of dust. The material is so soft that slots and recesses can be made very quickly with a hammer and chisel.
Aerated concrete has a very low density. Packed watertight, an aerated concrete block can float. This makes it very popular in terms of handling, as even large stones can be moved and set easily by only moderately strong people.
Aerated concrete blocks are not bricked up in a thick bed, but glued in a thin bed. The craftsmanship of being able to put a straight layer of brick is not necessary when working with stones made of aerated concrete. The adhesive is simply applied with a notched trowel, the aerated concrete blocks are butted vertically and horizontally – done. Even laypeople can quickly master building with aerated concrete blocks and get good results.
The prerequisite for a straight wall erected using the adhesive process is an absolutely straight first layer. The thin-bed mortar adhesive can no longer create any height compensation. That is why the straightness of the first layer is particularly important when working with aerated concrete blocks. Kimmsteine made of lime sand or aerated concrete is recommended for this purpose. They have been specially developed for this purpose and provide excellent results. In addition, the dimensionally accurate chimney stones have effective thermal protection, so that they cannot create a thermal bridge on the base of an aerated concrete wall.
Disadvantages of aerated concrete blocks
The aerated concrete block has significant disadvantages
- reduced sound insulation
- high sensitivity to moisture
- low compressive strength
- high space requirement
Good sound insulation can only be achieved with dense solid material. Because of its light, open-pore structure, aerated concrete does not have the same sound-insulating effect as solid material made of concrete, KSV, or clay bricks.
The open-pored structure of aerated concrete makes it very absorbent against all liquids. The compressive strength of aerated concrete is additionally reduced by penetrating water. When processing aerated concrete, special attention must therefore be paid to long-term protection against the ingress of moisture.
Aerated concrete is very sensitive. You can leave thumbprints in the material just by gripping it vigorously. The low compressive strength makes it necessary to make load-bearing outer walls made of aerated concrete very wide. This affects the usable area inside the house.
Dimensions and prices for aerated concrete blocks
The price for aerated concrete blocks depends on their thermal conductivity. The lower this is, the more expensive the stone is, but the better the insulation properties. The values vary between 0.06 W / mK and 0.21 W / mK
Conversely, the bulk density, compressive strength and even sound insulation increase with increasing thermal conductivity, but only in a theoretical range.
In the production of aerated concrete blocks, however, the use of aluminum powder is driving up prices. The more of it is added, the higher the proportion of pores. This in turn is responsible for the thermal insulation properties.
The width of the stone is always the same as the width of the wall that can be created with this stone.
The prizes are awarded differently. In the hardware stores, you can find the price information either in “per piece” or in “square meters”. In the building materials trade, however, you can also see information in euros per cubic meter for pallet acceptance.
|width||Prices / piece|
|50 mm||€ 1.10 to € 1.30|
|75 mm||€ 1.25 to € 1.90|
|100 mm||€ 1.60 to € 2.20|
|115 mm||€ 1.80 to € 2.90|
|150 mm||€ 2.40 to € 3.50|
|175 mm||€ 2.75 to € 3.95|
|200 mm||€ 3.20 to € 4.40|
|240 mm||€ 3.60 to € 4.95|
|300 mm||€ 4.50 to € 5.90|
|365 mm||€ 5.50 to € 7.10|
Conclusion: The price differences arise on the one hand from different purchase quantities and on the other hand from online trade vs. hardware store. For smaller quantities, I recommend purchasing in regional stores, as the costs for delivery still have to be added to the online prices. For really large quantities, buying on the Internet is a good alternative and saves money.
Aerated concrete – flow concrete combinations
The combination stones, which allow the inclusion of flowing concrete, are particularly interesting. The combination of flowing concrete and aerated concrete block results in a material mix that has the highest static as well as sound and heat-insulating properties. The manufacturers offer formwork blocks and U-block shells for this purpose.
The shuttering block is a hollow block with a circular opening on the top. It is large enough to accommodate vertical reinforcement. The stone is filled with concrete through this opening. In combination with the reinforcement, the formwork blocks can be used to create excellent corner connections, which make very stable buildings possible, especially in areas at risk of earthquakes.
The U-shell is used to produce ring anchors. They are walled up dry end to end, provided with reinforcement, and filled with concrete. You thus create the necessary transverse and longitudinal stability of a house. U-shells are specified in the price per meter.