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 technology, autoclaved aerated concrete of various shapes, sizes and colors can be found.
Autoclaved aerated concrete consists of three main components:
- cement;
- silica sand;
- gas formers.
Structure
It contains pores up to three millimeters in size.
It is considered a type of
cellular concrete. Common in the concrete mix is a cementitious base, filler and water. Aerated concrete can be classified by the type of binder in the base, it can be:
Cement-based autoclaved aerated concrete is widely used together with lime.
To achieve a porous structure, a chemical reaction is created in concrete in which gas is released.
To create such a process,
aluminum powder or paste is used. If you need to give the material special properties, additional substances are introduced into its composition.
Manufacturing methods
You can get autoclaved aerated concrete in this way: a thin mixture of concrete is poured into special forms to half the volume. At the same time, a shock load acts on it. In this case, heat is released due to the extinguishing of lime. The temperature of the autoclave increases to 80 degrees.
After this, lime reacts with aluminum, from which oxygen is released. Due to this, the mass of concrete rises to the edge of the mold. Pressure, like temperature, increases. Under the influence of these quantities, cement hardens, while the pores remain, and inside them is air instead of hydrogen. Thus, the formation of a concrete structure occurs, the pores of which occupy up to 80 percent of the volume. You can influence the percentage of porosity by changing the amount of aluminum powder.
After a couple of hours, the hardened mass is removed from the autoclave and cut into segments of the desired size. Then the finished blocks are sent again to the autoclave, where full hardening will be achieved only after 12 hours. In this case, the temperature regime should not be lower than 190 degrees at a pressure of 1.2 MPa.
Typically, the volume of cement concrete is not more than 20%, and more often use Portland cement.
In a larger volume, autoclaved aerated concrete consists of
quartz sand (approximately 60%). Lime as well as cement, not more than 20%. The aluminum content can be no more than one percent.
Manufacturers of autoclaved aerated concrete at their enterprises ensure that pressure and temperature make a special mineral - tobermorite from the component. It is due to this formation that the material has high strength and is not subject to shrinkage. Another important point of artificial conditions is that the time for production is reduced, which allows us to produce large batches.
The production cycle
The accuracy in the structure of the production process depends on what type of cellular concrete is made. The general processes are as follows:
- preparation of the required number of components;
- preparing the mixture and introducing a blowing agent into it;
- fill in forms;
- removal of excess mixture;
- time delay.
Dimensions
Like any building material, aerated concrete has standardization.
The sizes of such blocks are much larger than bricks. Everything is connected with a smaller mass. Building blocks have dimensions:
- length - 625 mm;
- width varies from 100 to 400 mm;
- height - from 200 to 250 mm.
Naturally, the increased size allows you to simplify and speed up the speed of their installation. And their insignificant weight will not interfere with manual work with it.
The production of autoclaved aerated concrete has a huge advantage, and this is the form of blocks. They have a perfect shape, the angles and ribs of which are even and smooth. Block sizes do not change over time. Even different batches of blocks have insignificant errors in their size - only 1.5 mm. For blocks of the lowest category, this parameter may be 3 mm, but in comparison with the whole block this indicator is insignificant.
The properties
Autoclaved aerated concrete has a small 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 production method 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 an increase, its strength decreases, but the thermal insulation properties increase. A decrease in this indicator leads to the opposite effect.
The change in porosity leads to the fact that concrete is divided into three main classes:
- Heat insulating. The density of the material in this class is 400 kg / m³. Its purpose is areas with cold climatic conditions, but buildings from it can be constructed low.
- Constructional. This aerated concrete has the highest density - 700 kg / m³. It can be used for the construction of high-rise buildings or for the construction of load-bearing structures. When used in residential buildings, it must be covered with an additional layer of thermal insulation.
- Structural and heat insulating. This aerated concrete with an average density value (500 kg / m³) is widespread, as it has good strength and sufficient thermal insulation.
Manufacturing differences
There are two ways of producing aerated concrete: in an autoclave and without it. There is aerated autoclaved and non-autoclaved aerated concrete. How to understand the difference?
Both species have the same production structure - by gas evolution as a result of a chemical reaction.
But these are fundamentally different schemes. The way in which the blocks harden gives differences in the properties of aerated concrete.
Non-autoclaved aerated concrete in its composition has a large percentage of Portland cement. The mixture is left to dry naturally, without the use of a special furnace - an autoclave. This type of cellular concrete has minimal production costs. But in its properties, it is much inferior to aerated concrete obtained using a furnace.
Only a large autoclaved aerated concrete plant is capable of producing large quantities of such blocks, while foam blocks can be produced even in a small enterprise.
Benefits
Its dimensional stability allows laying blocks on a mortar with a minimum thickness (about 3 mm). This advantage provides a high degree of protection against external temperature. Since the masonry mortar has a lower degree of heat protection, its insignificance will be only a plus. Due to the fact that the ribs and angles are even, the appearance of the masonry will be noble.
Another advantage may be its compliance with any construction tool. Autoclaved aerated concrete blocks can be planed, cut, drilled and warped. You can easily screw a screw into it or hammer a nail into it.
Building a house from this material
For a person who is just about to build a house, the main criteria for selecting materials will be their reliability, durability, environmental friendliness and comfort. In the face of economic problems, the criterion of profitability is also important. All of the above signs will correspond to such material as autoclaved aerated concrete.
This is an artificial stone, but it is made from natural ingredients. The microclimate of such a 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 despite the porous structure, hygroscopicity (moisture absorption) is within the normal range.
Its percentage is not more than 5%. If we compare this indicator with the hygroscopicity of some wood species, then the percentage there will be several times higher. It is easier to heat a house from aerated concrete than that of a brick one. This will significantly save energy.
The thickness of the walls of aerated concrete is only 1 block, this will be enough for thermal insulation. Whereas for brick an additional layer is required. Therefore, the cost of such walls will be minimal.
Humidity in rooms made of aerated concrete cannot lead to mold or mildew. In such houses, the process of decay and decay is excluded. The use of innovative technologies has allowed to reduce the thickness of the walls, while not reducing their strength. It is profitable to build a house from autoclaved aerated concrete due to minimal labor costs. Even a beginner can cope with the installation of such a wall.
Fire safety
Another advantage of the material can be its absolute fire safety. Autoclaved aerated concrete walls do not heat up even when exposed to open fire. Since it is not capable of burning, it cannot excrete hazardous substances. The construction of such a house will be carried out in terms much lower than those that can be spent on other types of materials.
Stacking blocks
Installation of wall blocks from aerated concrete can be done using a solution of warm or cement-sand, but a special glue would be the best option. It can be applied in a thin layer, which eliminates the bridges of cold. The first row of blocks must be laid on a well-prepared horizontal surface. Reinforcement of such masonry is carried out according to the project. The first row of blocks, the lower window and supporting surfaces of the jumpers must be reinforced.
Wall decoration
A properly made aerated concrete wall does not require plastering.
The outer surface does not have to be trimmed, but you can do this to give a beautiful appearance. 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 roof drains and visors and provide protection for the base.
When choosing an exterior finish, it should be noted that it should also be permeable, like aerated concrete. A well-made 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 everything can be finished without preliminary processing of the internal walls.
Decorating can be done directly on the blocks. Pre-plastering the walls is not necessary, especially since a simple putty will be enough. In rooms with high humidity should be vapor barrier.