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Autoclaved Aerated Concrete files/Brochure... · 2011-01-18 · Autoclaved Aerated Concrete The Manufacture and Application of Autoclaved Aerated Concrete For many years, aerated

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Autoclaved Aerated Concrete

The Manufacture and Application

of Autoclaved Aerated Concrete

For many years, aerated concrete was known in Germany as "Gas-

beton" (gas concrete). Simply on the basis of the construction material

it quickly becomes clear that "gas concrete" is not only an erroneous

description but also a misleading name, which has led to confusion

in the past. The German expression "Porenbeton" conforms to the

English "Autoclaved Aerated Concrete" and all of the usual linguistic

descriptions from other countries such as "Cellenbeton" in Dutch and

"Béton Celulaire" in French.

1

The Development

of Autoclaved Concrete

1800

� The first attempts go back to Zernikov, who "boiled" calcium sand-

based cement in high-tension steam but achieved little stability

and firmness. W. Michaelis followed a similar line but used

reduced water content. The result was a hard and waterproof

calcium hydro silicate for which he was granted a patent in

1880. This is the basis of all steam-cured building materials.

1924

� The Swedish architect A. Eriksson combined the process of pore-

formation with steam-curing and thus became the first to create

the modern aerated concrete. In 1924 Eriksson was granted a

patent for this invention.

1929

� The industrial production of aerated concrete items began in

Sweden. In the early 30s, further plants had to be built in order to

cover the demand for the aerated concrete products.

2

The Manufacture

of Autoclaved Aerated Concrete

and its Main Constituents

ground

sand =

< 0,05 mm

water

aluminium

as paste

or powder

cement

lime/

quicklime

3

Autoclaved Aerated Concrete

Autoclaved aerated concrete is manufactured with the

raw materials of quicklime, cement and siliceous sand. The sand

must be finely ground. A proportion of the sand may be replaced

with quick ash. First the ingredients are mixed using a ratio of, (for

example), 1:1:4, then water is added and a mortar mix is created. A

small amount of aluminium powder is then mixed into the resulting

suspension. The mortar is poured into a tub, where the metallic, fine

particled aluminium develops hydrogen gas in the alkaline mortar

mixture. Many small gas bubbles are created, which expand the

gradually stiffening mixture. After 15 - 50 minutes, the final volume is

achieved and blocks of between 3 and 8 metres long, up to 1,5

metres wide and 50 - 80 cm high are created. These doughy blocks

are cut into the required building element sizes with wire. After 8 -

12 hours the aerated concrete attains its final properties via curing

in special autoclaves (high-pressure steam boilers) at

temperatures of 180° - 200° C in steam under saturated vapour

pressure of 10 - 12 Bar. The autoclaved aerated concrete

corresponds chemically to the mineral tobermorite, which can be

found in natural environments. The production takes place in a

sealed cycle and thus no pollutants to water, air or ground are

released. Via the curing with steam, the autoclaved aerated

concrete avoids a great deal of potential energy waste.

4

Production

of Autoclaved Aerated Concrete

5

Production

of Autoclaved Aerated Concrete

and its Technology

� From the main

constituents

� Movable curing

vehicles and static

moulds

� Via the creation of hydrogen

(lime and aluminium), the

compound is forced from a

height of 20 to around 80 cm

6

Mixing

Process

Pouring

process into

pre-lubricated

moulds

Fermentation

process

Production

of Autoclaved Aerated Concrete

and its Technology

� The raw "cakes”

are cut with steel

wire before the

steam-curing

� The cut cakes are

cured at a temperature

of around 200°C and a

pressure of 13 Bar for

ca. 8 hours

� After curing the stones

are packaged and stored

in the warehouse

7

Cutting

Curing

by steam in

autoclaves

Packaging

The Properties

of Autoclaved Aerated Concrete

� Autoclaved aerated concrete, being a natural, non-combustible, solid building material, possesses the best possible fire-protection properties

� Solid building materials are proven to provide very good sound insulation values

� For example, the lightweight autoclaved aerated concrete compares favourably in terms of sound insulation with other equally heavy walls made from other types of stone. This is because the pore structure aids internal sound muffling

� Autoclaved aerated concrete is produced with a compressive strength of between 2 and 6 N/mm2

� The bulk density of the autoclaved aerated concrete is crucial to good thermal conductivity

� The upshot is, the lighter the material, the higher the thermal conductivity

8

Fire

protection

Sound

isolation

Fermentation

process

The Benefits

of Autoclaved Aerated Concrete

� The simple technique for using the material ensures that an

absolutely straight and smooth wall is achieved with the shaped

brick. This wall can be finished with a thin coating of plaster

prior to being wallpapered or painted.

� Thanks to the balance between thermal insulation and thermal

storage, the autoclaved aerated concrete provides for a pleasant

room climate.

� On the other hand, tiles can be applied directly to the smooth

surface of the autoclaved aerated concrete wall. Adhesion slits

are manually scratched into the stone, using a special groove-

cutter, and plug and switch sockets can be created where

required using a dry-wall socket drill.

� Ceramic tiles or flagstones can be simply and economically

applied to all autoclaved aerated concrete walls as an interior

room cladding. In most cases the surfaces are already suitable

even for application using the thin-bed method.

9

The Benefits

of Autoclaved Aerated Concrete

� Among the outstanding properties of autoclaved aerated

concrete are a high level of stability and a relatively low

bulk density. As a result of the low bulk density, autoclaved

aerated concrete is a solid building material with excellent

thermal insulation properties. Furthermore, the sound

insulation and fire protection are of the highest level. In the

end, autoclaved aerated concrete can really only be

characterised by the sum of its properties.

� Many coordinated building elements

� Ease of use and application

� Good ecological structure and biological building properties

� A high level of heat protection in summer thanks to the exellent

heat-storage properties together with the cooling characteristics.

10

The Application

of Autoclaved Aerated Concrete

� Because of the way autoclaved aerated concrete is applied in the

thin bed mortar system, a valuable but inexpensive masonry is

created.

� Fundamental features are a constant thermal insulation without

the need for thermal bridges, a high compressive strength and

especially flat, even wall surfaces. This facilitates all follow up

tasks such as plastering, tiling and wallpapering.

� Among the very important advantages of the thin bed system are

the fast application and the low amount of water used. Thus

only very little damp can penetrate the brickwork. The grouting

cement volume for the thin bed system is - depending on the

stone format - between 6 and 10 litres per cubic metre.

� If the bricks have tongue and groove joints, where grouting

cement is only applied to the horizontal joints, the mortar

consumption is reduced to 5 litres per cubic metre.

� The reduced grouting of the butting joints leads to a substantial

saving on time as well as cost, when compared to bricks which are

laid in "normally" grouted brickwork.

11

Autoclaved Aerated Concrete Bricks

� The advantages of autoclaved aerated concrete - namely the

extremely small tolerances, precise surfaces and low thermal

conductivity - can be especially exploited by its use in brick form.

� Length = 332, 339, 499, 599 and 624 mm

� Height = 199 and 249 mm

� Thickness/Width = 115, 150, 175, 200, 240, 300 and 365 mm

� Characteristic strength = 0,2 mm/m of material shrinkage

stability class bulk density thermal conductivity

• 2,0 N/mm2 = 0,4 kg/dm

2 = 0,09 W/(m*K)

• 4,0 N/mm2 = 0,6 kg/dm

2 = 0,13 W/(m*K)

• 6,0 N/mm2 = 0,7 kg/dm

2 = 0,15 W/(m*K)

12

The Application

of Autoclaved Aerated Concrete

� Owing to the use of the thin-bed system, grouts with a maximum

thickness of 1 mm are created. The adhesive is applied with a

mortar trowel.

� The cost-sinking use of the thin-bed system reduces the building

dampness significantly. The brickwork achieves the outstanding

thermal insulation properties of autoclaved aerated concrete

rapidly, avoiding the need for a lengthy drying out process.

13

The Application

of Autoclaved Aerated Concrete

� Cuts can be quickly and precisely made using a band-saw.

� Using a band-saw, even round cuts can be effected.

� Band-saws are provided by many autoclaved aerated concrete

suppliers as a complementary service.

14

The Uses

of Autoclaved Aerated Concrete

� U-forms are supplied by the autoclaved aerated concrete

manufacturers

� U-forms are used for the construction of ring bracing

� U-forms can also be utilised in Lintels for windows and doors

15

The Process of Working

with Autoclaved Aerated Concrete

� The material allows an easy application.

� Cutting of autoclaved aerated concrete with band-saw.

� Channeling for electric cables with scraping tool.

� Drilling of switches and sockets with dry wall countersinking

accessories.

The entire mechanical process of working with autoclaved

aerated concrete can best be compared to working with

wood.

16

Autoclaved Aerated Concrete

in External Walls

� Autoclaved aerated concrete is used in the construction of

dwellings and businesses.

� Autoclaved aerated concrete is used preferentially in external

walls because of its outstanding insulation properties.

� Autoclaved aerated concrete is used in multi-storey construction

up to a level of around 5 stories.

17

Autoclaved Aerated Concrete

in Many Residential Areas

� Entire residential areas are built using autoclaved aerated

concrete.

� A very big reason for this is the ease of application, even for the

non-professional, thus enabling a high level of personal

contribution and resulting in a reduction of building costs.

18

Autoclaved Aerated Concrete

in Internal Walls

� Autoclaved aerated concrete can also be used for internal walls.

� Because the walls are so level, they can be finished with a very

thin coat of plaster (3 - 5 mm).

� Use of adhesive considerably reduces dampness in the brickwork.

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Autoclaved Aerated Concrete

as Shelving !

Autoclaved aerated concrete has the advantage that it can be shaped

with saws, files and rasps. It is nevertheless very stable and thus

suitable for load-bearing and non-load-bearing elements alike.

Autoclaved aerated concrete is supplied in a variety of formats and

compressive strength grades. Constructions should be planned as

much as possible around the standard formats, in order to avoid too

much cutting and shaping. Slabs come with a length of 50 cm, a

height of 25 cm and thicknesses of 7,5; 10; 12,5; 15; 17,5; 20; 25;

30 and 37,5 cm. Additionally there are special formats which can be

used for the construction of shelving elements and compartments.

These have a length of 62,5 m, a height of 25 cm and thicknesses

of 5; 7,5; 10; 12,5; 15; 17,5 and 20 cm. In 75 cm lengths with a height of

50 cm, autoclaved aerated concrete bricks are available in the

thicknesses of 7,5; 10 and 12,5 cm, which are especially suitable

for worktops and shelving.

20

Autoclaved Aerated Concrete

for Fireplaces

Because of its low weight, autoclaved aerated concrete enables the

construction of a fireplace as an add-on after the initial loads have

been calculated without leading to significant extra stress on

ceilings with standard load-bearing properties. For the combustion

chamber itself, only fireproof materials can be used. The cladding

and plinth must also be made of non-combustible and heat-resistant

materials. Autoclaved aerated concrete fulfils these demands as a

non-combustible, solid, A1-classified building material. Because of

its low thermal conductivity, the temperature increase on the outer

surface is very low.

21

Autoclaved Aerated Concrete

for the Kitchen

� The advantage for the tenant is that such a kitchen can easily be

removed without damage to the surroundings. We have used

thicker stones for the tile border and stuck them to the existing

PVC floor covering. Cross-grouting is thus avoided ! We have

located the architrave under the duct, so that a gapped butt joint to

the wall is established which can be used for cables and pipes.

Additionally, hardly any bricks have to be cut.

� A typical, cheap handsaw is quickly blunted by a great deal of

cutting, although a more expensive specialised autoclaved

aerated concrete saw is longer-lasting.

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