The thermal conductivity of the foam block is due to the fact that it has a cellular, that is, a porous structure. It is thanks to this that a low coefficient of the indicated parameter is created. It is possible to obtain the porous structure of the material because a foam-forming material is added to the composition. The number of pores depends on the amount of this additive, and hence the coefficient of thermal conductivity of the foam block. The dependence in this case is quite simple: the more pores, the lower the indicator of this parameter.
What is thermal conductivity? Foam concrete brands
To begin with, what is thermal conductivity and why is it so important. This is an indicator that characterizes how much heat is able to give the material for a certain period of time. In other words, how much heat will go through the wall per unit of time. It becomes clear why this indicator is very important for building material. The main indicators that affect the formation of thermal conductivity are the foam block density and its humidity.
Currently, there are three types of raw materials:
- structural foam concrete;
- thermal insulation foam block;
- structural and heat-insulating material.
Structural and insulation block
It’s worth starting with the building block. It differs in that its density is the highest among all species, and the number of pores is minimal. Because of this, the thermal conductivity of this type of foam block is the highest and is in the range 0.29-0.38 W / m · K. Most often, such material is used only for the construction of the foundation and supporting structures of buildings. But at the same time, you need to understand that due to the high coefficient of heat conductivity, laying of additional thermal insulation materials will be required. To date, such foam concrete is available from D900 to D1200.
As for the thermal conductivity of the foam block heat-insulating type, it is, of course, the best. The numerical indicator of this characteristic is 0.09-0.12 W / m · K. However, it follows that the structure contains the largest number of cells, i.e., pores. Because of this, durability is worse than that of the other two species. Building a house from such a foam block is not allowed. It can be used only as a heat-insulating material for an already finished structure. Construction material of this group is marked from D300 to D500.
Combination material
The third type is a structural and heat-insulating block. From the name it follows that he possesses the qualities of both previous groups. However, they have an average indicator of both strength and thermal insulation - 0.15-0.29 W / m · K. But, despite this, it is precisely such material that is used most often for the construction of a warm house. The main scope is private construction of residential buildings. As for marking, this includes foam blocks from D500 to D800.
Block properties and masonry features
It is worth saying that the right choice of a foam block brand for building a house will not be enough. It is very important to correctly lay the building material. A serious difference is that you can not use ordinary cement-sand mortar. This is due to the fact that its use will reduce the thermal conductivity of the blocks. To avoid such a defect, use special glue. Another very important point is the thickness of the seam. It should not exceed 2-3 mm. If the seam is thicker, then the so-called cold bridges will form due to the properties of the foam block. A significant part of the heat will go through them, which is unacceptable.
In order to achieve the most even masonry and the exact thickness of the seam, it is very important to purchase high-quality foam blocks, which will have the correct geometric shape. Another important rule - to build a warm house of foam concrete is possible only if you immediately purchase the necessary amount of building material from one manufacturer. Purchasing in different places or at different times does not guarantee the most accurate convergence in size, because of which the masonry will be broken, the seam will change and a significant part of the insulation will be lost.
Manufacturing process
Since the foam block is a type of concrete with a cellular structure, some of the raw materials coincide, but there are some nuances. The main materials for the production of such a unit:
- cement, water, sand;
- additives designed to improve performance;
- synthetic foaming agents.
Currently, there are three main methods for the production of foam blocks.
The simplest and most classic method is to supply a foaming agent to an already prepared cement mixture using a device such as a foam generator. The finished mixture should be well mixed, after which it is placed in a special chamber, which will maintain the desired temperature so that the material hardens.
There is a method of dry mineralization, which is characterized in that the foaming agent is introduced into the dry mixture, all the ingredients are mixed and only then water is added. The foam blocks made in this way are notable for their good strength, but the thermal conductivity is deteriorating. This method is best suited for continuous manufacturing.
The final method is barotechnology. It involves mixing the foaming agent with the liquid first, and only then all other components are added. Also, special pressure chambers are used here, which support the process of mixing substances at the required overpressure.
Reviews and characteristics of the foam block
As for the characteristics of this material, the following average indicators can be given. The density of the material is from 600 to 1000 kg / m 3 , the thermal conductivity is in the range 0.14-0.22 W / m · K, the strength is 15-25 kgf / cm 2 , the water absorption is from 10 to 16% by weight of the block , frost resistance is determined in cycles and on average starts at 35 cycles. For an average climate zone, an acceptable wall thickness of a foam block with such characteristics is 0.6 m.
As for the reviews, many highlighted the following advantages: significant savings in the construction of the foundation, the shape of the blocks is large, which allows to reduce the amount of material needed and to reduce the time of building walls.
Of the minuses, the fact that such a material is quite fragile and it will not work to attach heavy hinged structures to such walls.