Foam: to be or not to be?

By Admin | Recommendations
18 April 2016

forumhouse.ru Regular readers know very well how difficult it is to choose a wall material for the construction of the house.

necessary to take into account the many nuances.Often the choice is complicated because a lot of conflicting information.How not to get confused when choosing?It is necessary to consider all the pros and cons of a particular material and then form their own opinion.

about how to do this, we will explain the example of foam.

Among the advantages of this material may be noted:

  • fast installation and easy handling;foam well sawn, milled and drilled;
  • environmental friendliness;cellular concrete blocks does not allocate toxic substances;
  • good thermal insulation properties due to the fact that the pores in the block filled with air;
  • insulation - why foam is often used when installing internal partitions in the building.

main disadvantages of foam:

  • fragility;during transport of the blocks is often damaged;
  • long gaining the necessary strength;in violation of production
    technology in the material eventually undergo structural changes which can result in shrinkage and cracks in the walls;
  • insufficient bearing capacity;to hang heavy objects on the walls of foam concrete, it is necessary to use a special fixture;
  • hygroscopic;foam may accumulate water, which requires its protection against atmospheric and soil moisture;
  • purchasing nedosushennyh blocks or blocks with poor geometry;discrepancies may reach from 1 to 3 cm, which eliminates foam laying on adhesive solution.

So whether or not to build a house out of foam, and there are some features of this material?Referring to the experience of members of the forum.

Features

foam properties and quality of the foam is directly dependent on the characteristics of its production.Let us examine them in detail.

Cepera:

- Foam - an artificial stone material of mineral binder and kremnezёmistogo component with uniformly distributed over the volume of the pores.

foam concrete block consists of a mixture of sand, cement, water and foaming agent.

Technology of foam is as follows: in the cement-sand mixture is added a foaming agent and a pressure in the chamber is mixed.

After mixing the components of the resulting mixture is shaped different building products: wall panels, walls, bridges and slabs.

In conditions of artisanal, so-called "garage" of production, the workers poured the mixture into the prepared mold.

This great influence of the "human factor".If the mixture is unevenly stir it gives shrinkage.Blocks made in violation of the technology have uneven density, they have broken geometry and strength characteristics of the material is considerably reduced.

In the natural drying process must be not less than 28 days to foambloc scored the required strength.

many novice developers often confused with each other two materials - foam concrete and aerated concrete.

Leo060147:

- there are concrete blocks, silicate blocks and there.Technology of production of these blocks are different, which affects the properties of these materials.

the production of aerated concrete or gazosilikata using autoclave technology.This requires large investments of money that the small-scale production uneconomic.

Autoclave - a special oven, which for a long time maintained a high temperature and pressure.

In autoclave processing technique blocks are cooked by steam in an autoclave at high temperature and pressure.Autoclave treatment accelerates the curing mix, due to which increases the strength of the unit and reduce its shrinkage.

In the manufacture of foam is most commonly used simpler - non-autoclaved technology.Therefore, the production of foam blocks is cheaper than production of silicate blocks and foam block has a lower price.

thermal properties of foam concrete

Properties wall material directly affect the level of comfort of living in the house.Due to the constant rise in energy prices still more widespread construction of energy-efficient homes.Can the foam serve as a basis for a homogeneous wall structure that meets all the requirements of thermal properties?

Leo060147:

- exterior building envelope, including walls, should have a thermal resistance equal to or greater than normable resistance to heat transfer to the area where the building is constructed.

For example, for Moscow and Moscow region value Rreq = 3,15 square meters * C / W.

Rreq - the coefficient of heat transfer resistance to normalized walling.

value of heat transfer from the walls of the foam block is dependent on the volumetric weight of the unit.

Volumetric weight of the unit can be from 300 to 1000 kg / m³.Most often it sold the unit volume weight of 400 or 600 kg / cubic meter.

unit volume weight 400 kg / cubic meter.and a thickness of 300 mm has Rreq = 2,158 sq.m. * C / W, which is less than required by the standards.

If volumetric weight of the unit is in the range 600 kg / cubic meter, the thermal resistance of the wall thickness of 300 mm has Rreq = 1,312 square meters * C / W, which is also not enough.

Note that the data is correct, if the unit is well-dried.If the block is waterlogged, it adversely affects its insulating properties.

According to calculations, to meet the thermal specifications, homogeneous wall thickness of foam blocks should be at least 500-600 mm and corrected for the percentage of moisture blocks.

In reality a wall of foam is not monolithic and heterogeneous structure.Masonry joints armpoyasa, reinforced concrete frames - all this cold bridges, to increase the performance of the thermal conductivity.Therefore, to achieve acceptable performance wall thickness must be increased even more.

Irkutsky:

- The higher the density of the blocks, so it is stronger in compression (ie it can be used for masonry bearing walls).Typically such blocks have a density of 600-900 kg / m3.And the higher the figure, the stronger the block, but above its thermal conductivity.

such density units are commonly used for the construction of one- and two-storey house.

Yuri From:

- to meet all heat engineering standards, the thickness of bearing walls of the house of foam stamps D800 for Moscow should be 1150 mm, which is very expensive.

Conclusion: not economically feasible to increase the thickness of the wall of the foam, and further insulate it.

For example, use a block D600- D800 thickness of 400 mm and a layer of mineral wool (outside) 100 mm.

If you take a brand D300, then the norms of the wall thickness of 400 mm, but this unit has a low load-bearing capacity and is suitable only as a material for building envelope, not bearing structures!

Features of building a house of foam

Depending on the construction and design of the house, you must select the appropriate brand of foam.

There are three types of foam:

1. Insulation - D200-D500.It is used for thermal insulation of load-bearing walls.


In this case, the blocks are used as filler reinforced concrete frame, for example, in the construction industry.

2. Heat-insulating-structural - D600-D800.It is used for masonry bearing walls with sufficient thermal insulation performance.

3. Structural - D800-D1200.It is used for masonry bearing walls, often requiring additional insulation.

have quality foam pores on fracture have a homogeneous structure, their diameter must not exceed 3 mm.High-quality foam water resistance.

The structural strength of concrete blocks, as a rule, increases the addition of sand.In addition to strength characteristics, it is necessary to pay attention to frost indicator of foam concrete blocks.

Irkutsky:

- The average value of frost in blocks of 25 cycles.

This figure suggests that the blocks withstand 25 cycles of freezing and thawing in the natural moisture without loss of original characteristics.Then the blocks, though not begin to fail, but will lose their properties.

25 cycles obtained during tests in the mother's laboratory.Ieunit filled with water up to the limit, and then frozen at a certain temperature, then thawed and look when it will begin the process of destruction.

to the house, built of foam concrete, get quality, you can use the tips with the nickname forumchanin usa:

- To avoid the appearance of cracks in the foam concrete:

1. Do not use "fresh" units.The unit must stand at a temperature of + 10C or higher for two or three weeks.The unit must be packed in foil.

2. When masonry blocks required to use masonry grid three, but better - in two series.

3. Plaster walls of the foam can be 3-4 months after completion of masonry, as the unit gives a certain shrinkage.

foam is best suited for the construction of one- and two-storey houses with wooden beams.

Also, special attention in the construction of houses made of aerated concrete should be paid to the construction Laying nets.

Laying nets - a reinforced concrete frame to distribute the load on the perimeter of the building, for example, between the first and second floor.

Laying nets necessary becauseBlocks do not like to point load, and in the absence of foam block may crack and crumble.

Maxsmax:

- In order to foam block is not destroyed by the pressure of RC slabs, including through Laying nets under Laying nets, I suggest putting a few rows of bricks.

Laying nets having uneven pressure on a relatively large foam concrete blocks, which can lead to cracks.Brick also distribute the load more evenly.

believed that the foam block is difficult to attach heavy items or equipment.For this purpose, use the special anchors, anchor bolts and fasteners.For example, for attaching the metal door grilles on the windows or on the perimeter of the opening can be installed metal corners.

summarize.The quality of foam and hence the walls depends on compliance with the technical regulations in its manufacture.Therefore foam should buy only from trusted manufacturers.In addition, the house of foam is necessary to build strictly on the project, with careful calculation of loads and the choice of the appropriate unit of strength.

Learn more about the construction of stone houses forumhouse.ru users can in this section of our forum.A detailed story about the construction of our new posts House of foam here.Discussion of the material from which to build the wall, is conducted here.

Detailed description of all stages of the construction of the house of reinforced foam is available at this link.

And acquainted with this article's accompanying video, you will learn how to approach the construction of houses of aerated concrete.