Autoclave aerated concrete: production, scope, material features

This type of porous concrete has been on the list of the first building materials for a long time. Therefore, many factories and companies are engaged in its manufacture. With the development of technologies, one can find autoclaved aerated concrete of various shapes, sizes and colors.

Autoclaved aerated concrete consists of three main components:

• Cement;
• Quartz sand;
• Blowing agents.

Structure

It contains pores up to three millimeters in size. It is considered a variety of cellular concrete. The common in a concrete mix is an astringent base, a filler and water. Aerated concrete can be classified according to the type of binder in the base, it can be:

• cement;
• lime;
• slag;
• Gas gypsum.

A high prevalence of autoclaved aerated concrete based on cement with lime.

To achieve a porous structure, a chemical reaction is created in concrete in which gas is released. To create such a process, use aluminum powder or paste. If you want to give the material special properties, additional substances are added to its composition.

Production methods

Get autoclave aerated concrete in this way: a thin mixture of concrete is poured into special molds for half the volume. At the same time, the shock load acts upon it. At the same time, heat is generated by quenching the lime. The autoclave temperature increases to 80 degrees.

After this, the lime reacts with aluminum, from which oxygen is released. Due to this, the mass of concrete rises to the edge of the mold. The pressure, like the temperature, increases. Under the action of these quantities, cement hardens, while the pores remain, and inside them there is already air instead of hydrogen. Thus, the formation of a concrete structure takes place, the pores occupying up to 80 percent of the volume. The percentage of porosity can be influenced by changing the amount of aluminum powder.

After a couple of hours, the hardened mass is extracted from the autoclave and cut into segments of the correct size. Then the finished blocks are sent back to the autoclave, where complete hardening will be achieved only after 12 hours. In this case, the temperature regime should be at least 190 degrees at a pressure of 1.2 MPa.

Usually in the volume of concrete cement is not more than 20%, and more often portland cement is used. In a larger volume, autoclaved aerated concrete consists of quartz sand (approximately 60%). Lime as well as cement, no more than 20%. The aluminum content can not be more than one percent.

Manufacturers of autoclaved aerated concrete in their enterprises achieve the fact that pressure and temperature make a special mineral from the component - the tobermorite. It is due to this formation that the material has high strength and is not subject to shrinkage. Another important moment of artificial conditions is that the production time is shortened, which allows producing large lots.

Production cycle

The accuracy in the structure of the production process depends on what type of cellular concrete is manufactured. The general processes are as follows:

• Preparation of the required number of components;
• Preparation of the mixture and introduction of a blowing agent into it;
• Pouring into shapes;
• Removal of surplus mixtures;
• Time exposure.

Dimensions

Like any building material, aerated concrete has standardization. The size of such blocks is much larger than bricks. Everything is connected with a smaller mass. Blocks for construction have the following dimensions:

• Length - 625 mm;
• Width varies from 100 to 400 mm;
• Height - from 200 to 250 mm.

Naturally, the increased dimensions make it possible to simplify and accelerate the speed of their laying. And their light weight will not interfere with the manual work with it.

The production of autoclaved aerated concrete has a huge advantage, and this is a form of blocks. They have an ideal shape, the corners and edges of which are smooth and smooth. The dimensions of the blocks do not change with time. Even different batches of blocks have in their size insignificant errors - only 1.5 mm. For blocks of the lowest category this parameter can be 3 mm, but in comparison with the whole block this indicator is insignificant.

Properties

Autoclaved aerated concrete has an insignificant weight with a large volume - this is the most important positive property of such a material. Its specific gravity is not more than 700 kg / m³. Also due to the method of production in an autoclave, the compressive strength increases significantly - up to 50 kg / cm².

If you change the porosity of concrete, this can lead to a change in thermal conductivity and strength. With increasing its strength decreases, but the thermal insulation properties increase. Reducing this indicator leads to the opposite effect.

The change in porosity leads to the fact that concrete is divided into three main classes:

1. Heat-insulating. The density of the material in this class is 400 kg / m³. Its destination - areas with cold climatic conditions, but the construction of it can be constructed low.
2. Constructional. This aerated concrete has the highest density - 700 kg / m³. It can be used to build high-rise buildings or for structures of load-bearing structures. When used in residential buildings, it must be covered with an additional layer of thermal insulation.
3. Structural and heat-insulating. This aerated concrete with an average density (500 kg / m³) is widely used because it has good strength and sufficient thermal insulation.

Differences in production

The way of production of aerated concrete is two: in an autoclave and without it. There is autoclaved aerocrete and non-autoclaved aerated concrete. How to understand the difference?

Both species have the same production structure - by releasing gas as a result of a chemical reaction. But these are fundamentally different schemes. The way the blocks harden, gives differences in the properties of cellular concrete.

Non-autoclaved aerated concrete in its composition has a high percentage of Portland cement. The mixture is left to dry naturally, without using a special oven - autoclave. This kind of cellular concrete has a minimum cost of production. But in its properties, it is much inferior to aerated concrete, obtained with the help of a furnace.

To produce in large quantities such blocks are capable only of a large plant of autoclaved aerated concrete, while foam blocks can be produced even in a small enterprise.

Benefits

Its dimensional consistency makes it possible to lay blocks on a solution with a minimum thickness (about 3 mm). This advantage gives a high degree of protection from external temperature. Since the masonry solution has a lower degree of heat protection, its insignificance will be only a plus. Due to the fact that the edges and corners are even, the appearance of the masonry will be noble.

Another advantage can serve as its compliance to any construction tool. Blocks of autoclave aerated concrete can be cut, cut, drilled and jarred. In it you can easily screw in the screw or hammer a nail.

Building a house from this material

For a person who is only going to build a house, their main criteria for selecting materials will be their reliability, durability, environmental friendliness and comfort. In conditions of economic problems, the criterion of economy is also important. All the above characteristics will be matched with such material as autoclaved aerated concrete.

This is an artificial stone, but it is made of natural ingredients. The microclimate of this house is the same as in a house made of wood. All due to the fact that the structure of the blocks is porous, this allows the building to "breathe".

Even in spite of the porous structure, hygroscopicity (absorption of moisture) is within the normal range. Its percentage is no more than 5%. If we compare this indicator with the hygroscopicity of some species of wood, then there the percentage will be several times higher. It is easier to heat a house of aerated concrete than a brick one. This will significantly save energy costs.

The thickness of the walls of aerated concrete is only 1 unit, this will be enough for thermal insulation. While for brick an additional layer is required. Therefore, the cost of such walls will be minimal.

Humidity in aerated concrete premises can not lead to the formation of mold or fungi. In such houses, the process of decay and decomposition is excluded. The use of innovative technologies allowed to reduce the thickness of the walls, while not reducing their strength. To build a house from autoclave aerated concrete is advantageous because of minimal labor costs. Even a beginner can cope with the installation of such a wall.

Fire safety

Another plus of the material is its absolute fire safety. Walls made of autoclaved aerated concrete do not heat up even when exposed to open flames. Since it is not capable of burning, it can not release dangerous substances. The erection of such a house will be made at a time much lower than what can be spent on other types of materials.

Block laying

You can install wall blocks from aerated concrete using a solution of warm or cement-sand, but the best option is a special glue. It can be applied in a thin layer, which will eliminate cold bridges. The first row of blocks should be laid on a well-prepared horizontal surface. Reinforcement of such masonry is made according to the project. The first row of blocks, the lower window and supporting surfaces of the jumpers are to be reinforced necessarily.

Wall decoration

Correctly executed wall of aerated concrete does not require finishing with plaster. The outer surface does not need to be trimmed, but to make it look beautiful, you can do it. In bad weather conditions, the blocks can get wet and absorb moisture, but not more than two centimeters. In order to avoid this, you need to properly make plums and roofs and protect the socle.

When choosing an exterior finish, it should be noted that it must also be permeable, like aerated concrete. A beautifully executed ventilated facade from any available materials will look beautiful. You can use, for example, autoclaved aerated concrete, user reviews about which are only positive. Users note that it is possible to finish everything without preliminary processing of internal walls.

You can decorate the premises directly on the blocks. Pre-plastering the walls is not necessary, the more it will be enough simple putty. In rooms with high humidity it is necessary to make a vapor barrier.