The thermal conductivity of the foam block is due to the fact that it has a cellular, that is, porous structure. It is due to this that a low coefficient of the specified parameter is created. It is possible to obtain a porous structure of the material due to the fact that a foaming material is added to the composition. The amount of this additive depends on the number of pores, 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 value of this parameter.
What is thermal conductivity? Foam concrete grades
Start with what is thermal conductivity and why is it so important. This is an indicator that characterizes how much heat a material is able to give off in 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 density of the foam block and its humidity.
Currently, there are three types of raw materials:
- structural foam concrete;
- heat-insulating foam block;
- structural and heat-insulating material.
Structural and thermal insulation block
Start with a building block. It differs in that its density is the largest among all types, 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 of 0.29-0.38 W / m K. Most often, such material is used only for the construction of the foundation and load-bearing structures of buildings. But at the same time, it must be understood that, due to the high coefficient of heat conductivity, it will be necessary to lay additional heat-insulating materials. To date, such foam concrete is available in grades from D900 to D1200.
As for the thermal conductivity of the foam block of the 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 from this that the structure contains the largest number of cells, that is, pores. Because of this, strength is worse than that of the other two species. It is not allowed to build a house from such a foam block. It can only be used as a heat-insulating material for an already finished structure. The building 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 has 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 this material that is most often used for the construction of a warm house. The main field of application is the private construction of residential buildings. As for the marking, this includes foam blocks from D500 to D800.
Block properties and masonry features
It is worth saying that choosing the right brand of foam block for building a house will not be enough. It is very important to properly lay the building material. A serious difference is that you cannot use a conventional 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 a 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 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 that will have the correct geometric shape. Another important rule is that it is possible to build a warm house from foam concrete only if you immediately purchase the required 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 thermal insulation will be lost.
Processworkmanship
Since the foam block is a kind of concrete with a cellular structure, some raw materials are the same, but there are some nuances. The main materials for the production of such a block:
- cement, water, sand;
- additives designed to improve performance;
- synthetic type blowing agents.
Currently, there are three main ways to produce foam blocks.
The simplest and most classic method is to feed the foaming agent into the already prepared cement mixture using a device such as a foam generator. The finished mixture must be well mixed, after which it is placed in a special chamber that will maintain the right temperature for the material to harden.
There is a method of dry mineralization, which differs in that the foaming agent is introduced into the dry mixture, all the ingredients are mixed and only then water is added. Foam blocks made in this way have good strength, but thermal conductivity deteriorates. This method is best suited for continuous production.
The last method is barotechnology. It implies mixing the foaming agent first with the liquid, and only after that all the 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 averages can be givenindicators. The density of the material is from 600 to 1000 kg/m3, the thermal conductivity is within 0.14-0.22 W/m K, the strength is 15-25 kgf/cm 2, water absorption - from 10 to 16% of the mass of the block, frost resistance is determined in cycles and on average starts from 35 cycles. For the middle climate zone, the acceptable thickness of a foam block wall 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 reduces the amount of material needed and reduces the time for erecting walls.
One of the minuses is that such material is quite fragile and it will not work to mount heavy hinged structures on such walls.
