What is the thermal conductivity of a foam block: what is it and how to calculate it correctly?

Foam block

When planning the construction of a house, any developer tries to choose the most practical and durable material. The modern market is rich in variety and making a choice sometimes becomes extremely difficult.

Some materials are superior to analogues in one respect, but may be significantly inferior in other respects. So what should you pay special attention to?

In this article we will talk about the significant quality of products intended for the construction of walls, on which, first of all, the building’s ability to retain heat will depend. Thermal conductivity of foam block: what is it and why are the numerical indicators of this quality so important?

Foam block production technology

To make foam blocks at home, you do not have to organize a complex technological chain.
A solution of cement and sand is immersed in a mixing tank, where foam in an aqueous solution is added. Auxiliary admixtures are intended to increase strength and frost resistance. In addition, they determine the thermal conductivity coefficient and the degree of shrinkage during solidification.

The production process is carried out in 2 ways:

1. Autoclaved.
2. Non-autoclave.

Technology has both pros and cons.

Autoclaved

Autoclave technology uses more sand than cement. Then the workpiece is processed under high temperature and pressure in special chambers - autoclaves.

As a result, the adhesion of the components of the material occurs better, and the percentage of defects is reduced.

When making blocks, the cement mixture is combined with additional admixtures. They are needed to obtain a porous structure inside structures.

Processing blocks in an autoclave.

Non-autoclaved

The non-autoclave type of foam concrete is characterized by the following advantages:

1. Low cost. For 1 cubic m of foam block you will need to pay less than for a cube of aerated concrete made using autoclave technology. Therefore, if you need to build a garage, shed or other utility room, it is better to choose this type.
2. Minimal thermal conductivity. Rooms based on such materials are quite warm.
3. Vapor permeability. Due to this feature, non-autoclaved foam blocks allow you to maintain a comfortable microclimate in your home without accumulating condensation.

Non-autoclave manufacturing method.

Foam concrete manufacturing technology

Representing a cellular variety of classic concrete, this building material is made from the following components:

• cement;
• water;
• sand;
• synthetic foaming agent;
• additives that improve the performance properties of the material.

Currently, three technologies for producing foam concrete are used.

The classic method involves supplying foam to the cement mortar using a special device - a foam generator. The resulting mixture is thoroughly mixed, then placed in a special chamber to harden, ensuring the specified temperature. The result is cellular concrete, which is considered to be of the highest quality, reliable, and durable.

To create foam concrete at home, you will have to spend a lot on the necessary equipment, and it will also take a lot of time

When using the dry mineralization method, foam is added to the dry mixture, and only after thorough stirring is water added in the required proportions. Typically this method is used in continuous production. Cellular concrete obtained in this way is more durable, but its thermal conductivity characteristics are inferior.

The barotechnology method is characterized by the fact that the foaming agent is first mixed with water, and only then the remaining components are added to the resulting mixture. To obtain foam blocks of acceptable quality, pressure chambers are used, which ensure the mixing process at excess pressure. The hardening process does not require heating, but generally lasts much longer, and shrinkage and even cracking of the material is possible.

Regardless of the manufacturing method used, each individual block is characterized by a closed air pore structure, which ensures its excellent thermal insulation properties.

Dependence of thermal conductivity on density

Air is an effective natural thermal insulation material. Foam blocks have a cellular structure, due to which this block building material has a low thermal conductivity coefficient. The indicator is much lower than that of concrete or brick and is equal to 0.08 W/mS. For ordinary users, these indicators do not mean anything, so we will give a comparative example. To get a wall that will have a thermal conductivity of 0.18 W/m0 C, you will need foam concrete blocks of the D700 brand (dimensions 588x300x188). To achieve the same thermal conductivity for cinder blocks, you will need to make the wall thickness 108 cm, and for red brick 140 cm.

Important! When calculating the heat transfer coefficient, it is necessary to take into account the density, which is indicated by the letter D. For example, the marking D 900 means that 1 cubic meter of foam concrete blocks weighs 900 kg

The thermal conductivity coefficient of foam concrete varies depending on the density and strength of the material. The lightest blocks with less strength are used for thermal insulation of building walls and construction of interior partitions. Blocks with a density of 400-500 kg/m3 are suitable for this. Foam concrete with high density is produced - 1000-1200 kg/m3. By reducing the size of the cells inside the blocks, the structure becomes more dense. This building material is suitable for constructing load-bearing walls of 1-2 storey buildings, but retains heat less well. Foam blocks of average density 600-700 kg/m3 are heat-resistant and can withstand the load of floors.

Types of foam concrete blocks by thermal conductivity

Depending on the density values, foam blocks are combined into three subgroups:

• thermal insulation (grades from D300 to D500);
• structural (grades from D900 to D1200);
• structural and thermal insulation (grades from D600 to D800).

Additional Information . D - designation of material density in kg/cubic meter.

Foamed concrete of the first type has a thermal conductivity from 0.08 to 0.12, W*m* degrees C. Products of these brands serve only for thermal insulation of structures (as an additional layer for the insulating contour of walls), since they have the most porous structure of all types of blocks.

The second type of foam concrete - structural - has a thermal conductivity in the range from 0.24 to 0.38 W*m* degrees C.

They are characterized by a weak ability to store thermal energy, but at the same time they are a very durable material and also have an increased compression strength.

Due to these properties, structural blocks are used more often for the construction of multi-story buildings, foundations and load-bearing walls and partitions, underground, underground garage boxes. In order to maximize strength, blocks can be reinforced with fiber fibre.

The third type of foam concrete blocks is characterized by average values ​​of thermal conductivity - it varies from 0.11 to 0.18 W * m * degrees C., and also has good thermal insulation properties. The place of its use is load-bearing fencing.

Pros of a foam block house

Cellular concrete materials (foam concrete, aerated concrete) have a unique porous structure, making them good heat insulators.

Light weight

Depending on what brand of foam concrete blocks are used, the weight is 1 cubic meter. ranges from 300 to 1200 kg. This leads to more lenient requirements for the foundation and, in practice, results in the opportunity to save on materials for the foundation of a foam block house.

Minimum hygroscopicity

In the process of producing foam concrete, a method is used to form blocks by pouring them into molds. This affects the geometry of the block, but promotes the formation of closed pores. It is thanks to this that foam concrete does not absorb moisture from the environment. A simple test, immersing foam concrete in a container of water, can demonstrate the block's resistance to water absorption.

Durability of foam concrete

This is due to the fact that concrete, which forms the basis of foam concrete, gains strength during operation. That is, the longer the house stands, the stronger the foam concrete will be.

Resistance of foam concrete to fire

In terms of fire safety class, foam concrete is one of the safest building materials, since it does not burn and does not support combustion.

Environmental friendliness of foam concrete

To make foam blocks, water, sand, cement and foaming agents are used. The latter can be of two types: natural and synthetic. Even if synthetic foaming agents are used, their specific gravity is no more than 0.5% of the total mass, which allows us to confidently declare the environmental friendliness of the material.

High speed of construction of a house from foam blocks

Installing one block is faster than laying bricks of the same square footage. Plus, the installation error will be significantly lower.

The ability to implement any architectural style

Foam concrete is easy to process. Cutting, drilling, and grinding the block is not difficult and does not require the use of special tools. Thanks to this, even a beginner with no experience in construction can remove the box of a foam block house.

Convenience of laying communications in foam concrete

Dictated by the flexibility of the blocks for processing, they are easy to groove for laying pipes, wiring, etc.

No finishing requirements

A house made of foam concrete can be used for a long time without additional finishing. As a rule, cladding is performed purely for aesthetic reasons. The most popular option is decorative plaster.

A foam concrete house can be finished with any of the existing materials; it is important that they are designed for foam concrete blocks and do not have a negative impact on the microclimate in the building. Otherwise, the ability of the house to “breathe”, which is due to its porous structure, may deteriorate.

Easy to decorate

Thanks to its smooth surface, foam concrete can be plastered or finished with any other finishing material with minimal effort in preparation for finishing.

Relatively low price of foam block

Despite the fact that in absolute terms, foam concrete (35-39 rubles/piece) costs more than brick (6-10 rubles/piece). But to cover the same area, you will need one foam block (35-39 rubles/piece) and 13.5 bricks (13*6=78 rubles). The benefit is obvious. And taking into account the fact that the house does not need insulation and a strong foundation, savings can reach up to 30%.

Low cost of laying foam blocks

This aspect is relevant for those who do not plan to build a house from foam blocks with their own hands.

What is foam concrete

First, let's understand the characteristics of the material itself, and on this basis, analyze the factors influencing the thermal conductivity coefficient.

Main characteristics

Foam concrete is a type of cellular concrete. It is distinguished by the presence of a porous structure, which gives the product qualities that are different from other materials.

Foam concrete structure

Swelling of the solution occurs as a result of adding a foaming agent to the composition. In addition to it, sand, cement, water and specialized additives are used, which can be varied, but we’ll talk about this a little later (see Composition of foam blocks and their production).

So what is foam concrete in technical terms, and what properties does it have?

For clarity, consider the table: Table 1. Characteristics of foam concrete in accordance with GOST and SNiP

Classification

Foam concrete can be of different types, depending on certain factors. Let's look at them.

According to density, foam concrete is distinguished:

• Thermal insulation. This type of foam concrete has a density of 300-400. It is used exclusively as a material for insulation, since it is not able to withstand any significant loads. Has the lowest thermal conductivity coefficient.
• Structural and thermal insulation. More durable material. Characterized by a density of 500-900, it is the most popular among private developers. Used for the construction of walls and partitions.
• Structural. The most durable of all types. Strength indicators vary from 1000 to 1200.

They are used in the construction of frame buildings up to 12-15 meters high. Such products can withstand significant loads.

It is worth mentioning the existence of foam concrete of even greater density. They are called structurally porous. The numerical indicator of its density is not standardized by GOST, and the production of products is limited to individual orders.

Depending on the hardening method, foam concrete is distinguished:

• Autoclave. They differ in that at the last stage of manufacturing, the products are processed in special equipment - an autoclave under high pressure and temperature. It is also called synthetic hardening foam concrete.
• Non-autoclave, or hydration-hardening foam concrete . Such products achieve technical strength in a natural way. Sometimes the process is accelerated by heating to a temperature not exceeding 100 degrees.

Note! Non-autoclaved foam concrete can be made independently with your own hands. To do this, you will need a minimum set of equipment, raw materials and instructions.

Ready-made blocks also differ from each other, the differences boil down to the following:

• Autoclave products are more durable. If we talk about the strength-thermal conductivity ratio, then synthetic hardening blocks benefit significantly.
• External differences: the autoclave is white, and the non-autoclave is grayer.
• Fragility is more characteristic of a non-autoclave.
• One of the main disadvantages of hydration-hardening foam concrete is the presence of a large number of handicraft industries, due to the simplicity of the production process.

Another classification of foam concrete and products made from it is based on the content of the silica component, on which the thermal conductivity of products also depends.

In accordance with this, foam concrete can be used for:

1. Pesce;
2. On the ashes;
3. On other secondary industrial products.

Depending on the type of binder, foam concrete is distinguished:

• On lime binder;
• On cement;
• On ash;
• On slag;
• On mixed.

The content of the main component in the above types varies from 15 to 50%.

It is also worth noting that, depending on geometric deviations, certain categories of finished products are distinguished:

• Blocks of the first accuracy category are distinguished by minimal deviations. Acceptable values: up to 1.5 mm – along the length, up to 2 mm – along the diagonal. It is recommended to lay the products using specialized adhesive for cellular concrete blocks.
• Blocks of the second category of accuracy. The following deviations are typical for such products: up to 2 mm in size, up to 4 mm in diagonal. Chips up to 5 mm are allowed, no more than 2 chips on one product. It is recommended to lay masonry using mortar (in accordance with GOST), but using glue is also allowed.
• Blocks of the third category have the greatest deviations. They can reach 4 mm in size, 7-8 mm diagonally. Chips and broken corners – up to 1 cm.

The latter type is usually used in the construction of outbuildings, for example, a barn or garage. This can be explained simply: the solution consumption is high, the seams are thick, and these are additional cold bridges. In this regard, the room will either be cold, or it will need to be insulated, and considerable costs will have to be incurred.

There are also foam blocks with a facing side. They do not require further finishing. The price for them, of course, is higher, but the savings on facade cladding are obvious.

Foam block with cladding

Foam concrete is used not only in the form of building blocks. No less popular is its use in liquid form in the construction, for example, of monolithic structures, screed installation (or the base for a heated floor). Lower density material is sometimes used for roof insulation.

Table for determining the thermal conductivity coefficient of aerated concrete blocks

To determine the level of thermal resistance of materials, use a special table.

Aerated concrete is an excellent material for laying walls, with a low ability to transfer heat. Thus, structures made from aerated blocks perfectly maintain a comfortable temperature regime. Aerated concrete floor slabs are described here.

https://www.youtube.com/watch?v=plUs3Z6cFy8

Technical characteristics of blocks

Some characteristics of gas-foam concrete

Cellular concrete is produced:

• with compressive strength grades from B 0.35 and B 0.5 ending with B 17.5 and B 20;
• with medium density grades - from D 200 and D 250 to D 1000, D 1100 and even D 1200;
• with thermal conductivity - determined only in a dry state and specified by a coefficient, measured in W/(m ∙ °C)№;
• with vapor permeability in a dry state, specified by a coefficient, measured in mg/(m ∙ h ∙ Pa);
• with shrinkage formed during drying;
• with frost resistance - measured by the number of freezing/defrosting cycles, marked “F”, for example, F 15, varies from F 15 to F 100.

The coefficients of thermal conductivity and vapor permeability in connection with the density grade are given in the table below.

According to their intended purpose, cellular concrete, including foam concrete, must be:

1. Thermal insulation. The compressive strength is not less than B 0.35, and the density is not more than D 400. They are used for external thermal insulation of the house. For masonry, it can only be used for unloaded partitions.
2. Structural and thermal insulation. Compressive strength class higher than B 1.5, average density up to D 700. Can be used both in internal partitions and external walls. If the wall thickness is appropriate, no additional thermal insulation is required.

Compressive strength

Strength characteristics have a direct impact on the scope of application of cellular concrete. If thermal insulation grades of foam concrete, having low compressive strength and low thermal conductivity, are used only as a thermal insulation layer, then structural and thermal insulating blocks are strong enough to withstand slabs and floor beams of low-rise buildings, and structural ones can be used in the construction of multi-story buildings.

Comparative table of different brands of foam concrete

Compressive strength of foam block brands (kg/sq. cm):

• D400 – 9;
• D500 – 13;
• D600 – 16;
• D700 – 24;
• D800 – 27;
• D900 – 35;
• D1000 – 50;
• D1100 – 64;
• D1200 – 90.

An equally important property of cellular concrete is the presence of internal voids and the accuracy of the geometric dimensions of the blocks. The consumption of masonry mortar depends on the last parameter: when using uneven blocks, the thickness of the seam has to be increased from 3 to 10 mm, which leads to the appearance of “cold bridges” and a decrease in the energy efficiency of the structure.

The main competitor of the foam concrete block is blocks made of autoclaved aerated concrete.

The white porous blocks that you might see on construction sites are autoclaved aerated concrete or gas silicate. Autoclaved aerated concrete is the main competitor of foam concrete. Externally, it is very similar to foam concrete. The main difference between autoclave materials is the composition of the raw materials. If foam concrete is made on the basis of cement, then autoclaved materials are made on the basis of lime. And since lime is white, aerated concrete blocks are also white. The beautiful white color is of course an interesting, but practically useless feature of aerated concrete. What is the difference between non-autoclaved foam concrete and autoclaved aerated concrete?

Cement non-autoclaved foam concrete hardens at any positive temperature, and lime aerated concrete only in an autoclave, at a pressure of 8 atmospheres and a temperature of 200 degrees. Cement foam concrete, unlike lime-based materials, is not afraid of water, and practically does not get wet in water. Lime aerated concrete from an autoclave quickly absorbs water, losing its strength and ability to store heat. If structural foam concrete floats in water indefinitely and does not get wet, then aerated concrete sinks after a few hours, having absorbed water. To sum it up briefly, let's say that aerated concrete is generally slightly stronger than foam concrete (as it hardens in an autoclave). At the same time, aerated concrete has significantly less durability than foam concrete. Foam concrete gains strength over time, while aerated concrete loses strength.

Thermal conductivity of foam concrete blocks

One of the most important characteristics of any building material is its thermal conductivity.
This indicator indicates the ability to transfer heat. The higher the value of the thermal conductivity coefficient, the faster heat will leave the house or any other building in winter and the faster the building will heat up in summer. When making a foam block, a special foaming agent is added to the mixture of water, sand and cement. Thanks to this, foam concrete blocks have a porous structure. In the next photo you can see how the block will be smoothed inside. The pores distributed evenly throughout the volume contain air, which has a fairly low thermal conductivity. This is what explains the ability of foam concrete to retain heat.

If we compare this indicator for several building materials, cellular concrete is significantly superior to ordinary concrete and brick, and is only slightly inferior to wood. The low thermal conductivity coefficient of the foam block, its relatively low cost, strength and durability have brought it to one of the leading positions for use in construction.

Table

You can see a comparison of the thermal conductivity of various building materials in the table below.

Construction process - building walls

And now, as promised, instructions for the construction of external walls, taking into account all the factors affecting the material:

• First, you need to prepare the foundation for work: clean it from dust and dirt, level it if there are unevennesses.
• Afterwards, calculate the required amount of materials: foam blocks and adhesive solution. To make it easier for you to navigate, there are about 30 blocks in one cubic meter measuring 200x300x600 mm (we chose them so that the wall thickness was 300 mm). The glue calculation can be taken as an approximate amount - about 30 kg per 1 m3 of wall, so the main thing is to find out the total area of ​​​​the walls being built.

Large reinforced concrete blocks must be installed above the openings

• When all the materials and tools are in place, you can begin to prepare the solution, unless, of course, you bought a ready-made mixture.
• Initially, the glue is applied to the surface of the foam block, which is placed on the foundation or floor slab.
• Before the adjacent block is laid, the end is thoroughly coated with glue so that there are no empty gaps between the products.

Use a notched trowel as shown in the photo.

• To remove excess glue from under the foam concrete, tap it with a mallet.
• The second row is laid out with the materials shifted so that the vertical joints do not coincide; to do this, you need to cut one block in half and start laying from half.

There are blocks that have a recess on the horizontal surface for mortar - this increases adhesion, or you can make such a recess yourself

Since foam concrete products are easy to process, you should not have any problems with making holes for window and door openings.

Now all that remains is to finish and insulate the façade of the foam block house:

• To finish with brick, several rods of thin reinforcement should be fixed in the foam concrete wall, between the blocks, this is necessary in order to connect the inner wall with the brickwork. However, first you need to install polystyrene foam boards using disc nails.
• If you use only plaster, then initially, on top of the finished wall, you should fix the reinforcing mesh. Then you need to apply a thick layer of heat-insulating plaster so that it hides the mesh underneath. The finishing layer is a decorative finish that protects the inner layer from ultraviolet radiation and moisture.

The first layer of plaster does not need to be leveled to zero

Foam block laying technology

Even if glue is used during masonry work, the first row is laid using cement-sand mortar, and the surface of the base is covered with roll waterproofing. Initially, blocks are installed in the corners, then a cord is pulled along them, which serves as a guide. During the work, the masonry is constantly checked using a level, and leveling is carried out using a rubber mallet. Reinforcement is required for every 4th row of masonry (for this, mesh or reinforcement made of metal or fiberglass is used). The reinforcement is placed in special grooves that are created on the surface of the masonry. In the future, these grooves need to be filled with masonry adhesive.

To correctly lay foam block walls, it is recommended to follow certain rules:

• Mixing of masonry adhesive is carried out in small portions, which are used for 30-60 minutes.
• The second and subsequent rows of masonry are performed with dressing in half a block.
• The optimal temperature for masonry work is 5-25 degrees. At higher temperatures, foam blocks require additional moisture.
• Masonry adhesive is applied with a notched trowel, facilitating the formation of smooth, uniform seams along the entire length.
• If necessary, the block is adjusted to size by cutting (a regular hacksaw is used for this).
• Using a plumb line, an accurate check of the vertical position of the masonry is carried out.

The importance of values ​​when building walls

Information about their weight is relevant for anyone who is going to engage in new construction, repair and construction work, redevelopment or restoration using this material.

Knowing the mass of porous concrete before the start of construction work allows you to select the right type of foundation, having previously calculated the load on it, solve logistics, organize loading and unloading operations and carry out installation.

Thus, if you do not know the weight of these materials when laying enclosing and separating structures, it may turn out that the bearing capacity of the selected foundation is not designed for this load and it will begin to collapse, which can lead to the complete unsuitability of the structure being built for its intended purpose.

Basic properties of foam concrete.

Density is the weight of 1 cubic meter of material. Foam concrete can weigh from 200 to 900 kg/m3. Thus, it is clear that any foam concrete floats in water, so it is lighter than it (the density of water is 1000 kg/m3.) In GOST, foam concrete is standardized according to density classes, the density class is designated by the letter D. Class D600 means that a cubic meter of such foam concrete is dry weighs 600 kilograms. Please note that the class indicates the weight of the dry material, and when shipped from the factory, foam concrete contains up to 20% process water. This means that a cubic meter of such foam concrete is 20% heavier and weighs not 600 kilograms, but 600 * 1.2 = 720 kilograms.

Strength is the ability of foam concrete to withstand load. It is measured in kilograms per square centimeter. Thus, a strength of 25 kg/cm2 means that foam concrete will collapse if the load per 1 cm2 exceeds 25 kg. The strength of foam concrete ranges from 2 to 50 kg/cm2. Sometimes strength is indicated in megapascals (MPa). To convert strength from kg/cm 2 to MPa, the numerical value in kilograms must be divided by 10. Thus, a strength of 25 kg/cm 2 is equal to 2.5 MPa.

Thermal conductivity is the ability of foam concrete to retain heat. Preserving heat is the main purpose of foam concrete, its “trick”. Thermal conductivity is measured in Watt/meter*degree. The thermal conductivity of foam concrete can vary from 0.045 W/m*deg to 0.2 W/m*deg. A thermal conductivity coefficient of 0.1 W/m*deg means that with a temperature difference of one degree, 0.1 Watt of thermal energy will pass through 1 square meter of a wall 1 meter thick. The lower the thermal conductivity coefficient, the warmer the material. Foam concrete has a thermal conductivity from 0.045 to 0.2 W/m*degree. For comparison, the thermal conductivity of ceramic brick is 0.56 W/m*deg. As you understand, brick is 3-12 times colder than foam concrete!

Naturally, the lighter the foam concrete, the warmer it is. But the lower its strength. This determines the areas of application of foam concrete. Light foam concrete is used for thermal insulation, while “heavy” foam concrete is used for the construction of house walls.

Thermal conductivity

Air is the most effective natural thermal insulation material. The presence of a large number of air-filled pores in the structure of the foam concrete block made it possible to reduce its thermal conductivity to the level of 0.08 W/m°C, which is an order of magnitude lower than that of concrete or brick.

The key factor when choosing a material is thermal conductivity

For the average user, this digital indicator doesn’t mean much, so here are the comparative characteristics of foam concrete, ceramic bricks and cinder blocks: to get a wall with a thermal conductivity of about 0.18 W/m°C, you need a layer of D700 foam concrete 300 mm thick. For cinder blocks, the wall thickness will be 1080 mm, for red brick – 1400 mm.

What is the thermal conductivity coefficient of foam concrete?

Figure - 1 foam concrete blocks
Each wall material has a different structure, which affects strength, density and energy saving, characterized by the rate of transfer of thermal energy. This indicator determines how long the heat will be retained in the house, so when choosing a building material, this property should first be taken into account. Today, walls and internal partitions are built from foam concrete, the thermal conductivity of which depends on the porosity of the structure and the saturation with air bubbles.

Determining the thickness

Now let's conclude from the above, the recommended thickness of external walls made of foam blocks for areas with moderate winters is 300 mm with a density of D600 and a layer of thermal insulation.

• This, so to speak, is the golden mean, which is suitable for almost all regions of Russia. Additional thermal insulation on the outside of the house allows you to survive the winter without feeling the cold in the living space.
• As for strength, even if the house is planned to be two-story, the maximum load on the walls of the first floor will not exceed 20 tons (together with the roof, floor slabs and furnishings). And from the technical characteristics we know that every 100 mm of foam block can withstand a load of up to 10 tons.

On the other hand, you can clearly use an example to find out what thickness a wall made of foam blocks should be.

Thermal conductivity calculations

You should know that the heat transfer resistance of the external wall (with all finishing materials) must exceed 3.5 degrees per m2/W.

To determine the thickness, let's take a closer look at this process based on the different densities of foam concrete:

• From the technical characteristics you can find out that the D600 and D800 blocks have coefficients of 0.14 and 0.21 deg * m2 / W, respectively.
• The finishing materials used are facing brick (0.56 deg*m2/W) and decorative plaster (0.58 deg*m2/W).

Let's start the calculation:

• First, let's determine the thickness of the brickwork and plaster; usually (for facades without thermal insulation materials) the brick is laid in two rows, that is, 120 mm.
• Now let’s convert this into meters and divide by the thermal conductivity coefficient of the facing material, we get a resistance of 0.21.
• We do the same with plaster and as a result the resistance is 0.03.

Now all that remains is to substitute all our numbers into a simple formula:

• Foam concrete with a density of 600 = 3.5 (total heat transfer resistance) – 0.21 (brick) – 0.03 (plaster) and all this is multiplied by 0.14 (foam block coefficient). As a result, we get about 450 mm (don’t forget to convert from meters). This is exactly the thickness that a wall with the materials described above should be.
• Foam concrete with a density of 800 - (3.5 - 0.21 - 0.03) * 0.21 = about 680 mm.

As you can see, in the second case you will need a thicker wall, which means there will be more costs. On the other hand, add polystyrene foam (the most common insulation) and the thickness of the facade will be significantly reduced.

Cinder blocks do not have a pleasant appearance, but they have good thermal insulation properties

Foam concrete blocks

Foam concrete is a type of cellular concrete.
It is created by uniformly distributing air bubbles throughout the entire mass of concrete. Unlike aerated concrete, foam concrete is obtained not through chemical reactions, but through mechanical mixing of pre-prepared foam with a concrete mixture. New technologies make it possible to obtain non-autoclaved foam concrete with a reduced water-solid ratio, due to which its release humidity and, accordingly, the thermal conductivity coefficient will be lower than that of autoclaved cellular concrete at equal average densities. The main positive qualities of non-autoclave-hardening cellular concrete are its low cost, environmental friendliness, high fire resistance, simplicity of technology compared to autoclaved cellular concrete, and even more so compared to traditional building materials.

A material such as foam concrete brings us closer to the level of countries with similar natural and climatic conditions (Canada, Sweden, etc.) in terms of energy consumption standards for home heating. As a result, houses and apartments become competitive products that meet the standards accepted in developed countries.

physical characteristics

Foam can be produced either using a foam generator or in a pressure unit. Here we will look at the main characteristics of foam concrete and compare it with other materials.

Concrete is divided into CLASSES: VO.5, B2.5. B60, which are determined by the value of the guaranteed compressive strength. During production, it is important to know the average strength - GRADE, which come in M5. M600 and above.

You can approximately convert the CLASS of concrete to GRADE by dividing the class by 0.77, multiplying the result by 10 and rounding to 5 in the last digit. For example, B1 = M15. There is also GOST 25192-82 for brands and classes.

Now we look at the plate above and see that for foam concrete grade 600 the average class for compressive strength is set to B2, i.e. (2/0.77)* 10=26. Thus, the foam concrete grade M26 is obtained.

Brand is an indicator of strength, designated “M” with a digital value. The numbers show how much load per 1 cm2 the product can withstand. For example, brand 100 (M100) means that the product is guaranteed to withstand a load of 100 kg per 1 cm2. We find that foam concrete with a density of 600 can withstand a load of 26 kg per 1 cm2.

Frost resistance of concrete is the ability to retain its properties during repeated alternating freezing and thawing. The frost resistance of concrete is characterized by the corresponding frost resistance grade F - this is the minimum number of cycles of freezing and thawing of concrete samples.

Thermal insulation of foam concrete walls and options for their construction

Foam concrete, as a building material, became in demand in Russia after SNIP 2-3-79 came into force.
It defined new standards for the thermal insulation of walls, according to which, for example, the minimum thickness of a brick wall should be about 2 meters. Naturally, it is not economically profitable to build houses with such walls, and builders began to look for material to replace brick. This material had to provide good thermal insulation, be environmentally friendly and durable. Foam concrete meets all these requirements, and for this reason the demand for this material is currently continuously growing.

So, in this article we will calculate the required thickness of the outer wall when constructing it using one of the 2 most popular options: brick-foam concrete or plastered foam concrete. Foam concrete in the wall can be of different densities; we will calculate wall options for densities of 600, 800 and 1000 kgcub.m. Also, based on the example of calculating the required wall thickness in this article, you will be able, in the future, to calculate the thickness of any wall, from any materials, yourself.

What you need to know to calculate

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1. Thermal characteristics of all materials that will make up the wall: Each building material has thermal characteristics. This is thermal conductivity or heat transfer resistance (the reciprocal of thermal conductivity). These coefficients, necessary for calculating heat loss, show how much power is lost by each square meter of the outer surface of the structure when its thickness is 1 m and the temperature difference between the outer and inner surface is 1 degree (kt = watt/(m*t)). Data for many materials are given in SNIP 2-3-79.

2. GSOP (degree-days of the heating period, degrees C per day) This indicator can be calculated using the formula from SNIP 2-3-79, or you can simply take it from the reference book. For example, for Moscow and St. Petersburg it is less than 6,000.

3. Wall resistance to heat transfer It depends on GSOP and is taken from SNIP. In our case, with GSOP 6000, the heat transfer resistance at the wall should be at least 3.5 (deg.S*sq.m./W).

So, our wall must have a total heat transfer resistance of at least 3.5 (deg.S*sq.m./W), because Each layer has its own resistance to heat transfer, then the resistance of the entire wall, according to SNIP 2-3-79, is measured as the sum of the resistances of the layers. We also need the thermal conductivity coefficient W/(m*deg.C) of all materials used for the wall:

1. facing brick M-150 – 0.56 2. foam concrete density 600 – 0.14 3. foam concrete density 800 – 0.21 4. foam concrete density 1000 – 0.29 5. plaster – 0.58

Below is the calculation of the foam concrete layer for 2 wall options: 1st wall option: facing brick (250x120x65) + foam concrete (x mm) + plaster (20mm)

Let's calculate what thickness of foam concrete is needed. The thickness of the brick in the wall, during normal installation, is 120mm. Let's divide the thickness in meters by thermal conductivity 012/0.56 and get the heat transfer resistance of the brick layer 0.21. The thickness of the plaster is 20mm, therefore its heat transfer resistance is 0.02/0.58=0.03.

Let's calculate the thickness of the foam concrete layer:

2nd wall option: plaster (20mm) + foam concrete (x mm) + plaster (20mm) The thickness of the plaster (total) is 40mm, therefore its heat transfer resistance is 0.06. Accordingly, the thickness of the foam concrete layer should be:

Here the required wall thickness is calculated to comply with thermal conductivity according to SNIP 2-3-79, taking into account various wall laying options. If you don’t understand something or have any questions, write to the forum.

For the calculation, the coefficients were taken in the dry state.

The calculated coefficient for density 600 is 0.22, for density 800 is 0.33, then the wall thickness according to calculations is equal to: density 600 (3.5-0.21-0.03) x0.22= 0.717 m density 800 (3.5-0.21-0.03) x0.33= 1.076 m

Comparison with other materials

Below is a table that provides comparative data on the thermal conductivity of foam concrete and other building materials.

Foam concrete blocks can be placed on glue, this reduces “cold bridges” and, accordingly, heat loss.

Advantages of foam concrete

Foam concrete is an ageless and almost eternal material, not subject to the effects of time. It does not rot and has the strength of stone. Increased compressive strength allows the use of products with a lower volumetric weight in construction, which further increases the thermal resistance of the steppe.

Due to their high thermal resistance, buildings made of foam concrete are able to accumulate heat, which during operation can reduce heating costs by 20-30%.

Foam concrete prevents significant heat loss in winter, is not afraid of dampness, helps to avoid too high temperatures in summer, regulates air humidity in the room by absorbing and releasing moisture, thereby helping to create a favorable microclimate (microclimate of a wooden house).

The low density and lightness of foam concrete, the large size of the blocks compared to bricks make it possible to increase the speed of masonry several times. Ease of processing and finishing allows you to quickly cut channels and holes for electrical wiring and pipe sockets. Simplicity of masonry is achieved by high accuracy of linear dimensions, the tolerance is +/- 1 mm.

Foam concrete has a relatively high ability to absorb sound. In buildings made of cellular concrete, the current requirements for sound insulation are met.

During operation, foam concrete does not emit toxic substances and is second only to wood in its environmental friendliness. For comparison: the environmental coefficient of cellular concrete is 2; wood - 1; bricks - 10; expanded clay blocks - 20.

Thanks to its good workability, foam concrete can be used to make various shapes of corners, arches, pyramids, which will give your home beauty and architectural expressiveness.

High geometric dimensional accuracy of the products allows for laying blocks with glue, avoiding “cold bridges” in the wall and significantly reducing the thickness of internal and external plaster. The weight of foam concrete is up to (87%) less than that of heavy concrete. Significant weight reduction results in significant savings on foundations.

Products made from foam concrete reliably protect against the spread of fire and meet the highest degree of fire resistance, which is confirmed by relevant tests. Thus, it is well suited for use in fire-resistant structures. When a heat source, such as a blowtorch, is applied to the surface of the concrete, it will not splinter or explode, as happens with heavy concrete. As a result, the fittings are protected from heating. Tests show that 150mm thick foam concrete protects against fire for 4 hours.

The favorable ratio of weight, volume and packaging makes foam concrete convenient for transportation and allows full use of the capacity of both road and rail transport.

Foam concrete can be used not only in the form of blocks, but also to fill roofs, floors, insulate pipes, and make prefabricated blocks and panels. Also, higher-density foam concrete can be used to fill floors and foundations.

What products does the market offer?

For a long time, foam blocks were produced in almost a single size: 200*300*600 mm. The parameters were considered standard, and the foam block was called universal and was used equally for the construction of both external and internal partitions of the house.

Today there are no standard sizes as such. The specified “station wagon” is still the most popular, but the production of foam blocks with other parameters made it possible to divide the products into groups.

For the construction of the external walls of a house, experts recommend using larger blocks. On the one hand, this makes the builder’s work easier, especially since the outer walls of the building must consist of two rows of foam blocks; on the other hand, large sizes reduce the number of vertical seams, which in turn contribute to the formation of cold bridges. Product parameters: 250*400*600 mm, 250*375*600 mm. Which dimensions are optimal is determined by the builder himself.

The large dimensions of the block not only speed up the construction of the house, but also help reduce other costs. To attach it, you will need less cement, and for finishing, less plaster. The alignment process is also simplified since fewer elements need to be adjusted. If the dimensional parameters do not match, the blocks are very easy to correct: the material is sawn and polished without the slightest difficulty using mechanical tools.

For internal partitions, foam blocks of smaller dimensions are used: 100*250*600 mm or 125*250*600. As a rule, blocks with a minimum height of 75*250*600 mm are used for walls in bathrooms. This is due to the fact that the internal walls of the house are much thinner than the external ones, but at the same time they should have a smoother surface.

The video demonstrates the use of foam blocks.

Density and thermal insulation

An equally important issue when building a house is the thermal conductivity of the material, which is related to its density. Which foam blocks to choose for construction depends on the purpose of the building and the area of ​​residence.

Material with a density of up to 500 kg/sq. m. is a good heat insulator and is recommended for carrying out relevant work. However, its strength is insufficient and it is impossible to construct a load-bearing wall from it.

• Foam block with a density in the range of 500–900 kg/sq. m. can withstand very significant loads and can be used for the construction of external walls of a house.
• Product with a density from 900 to 1200 kg/sq.m. m. applies without restrictions. However, its thermal insulation properties leave much to be desired. The photo shows samples of materials with different densities.

The dimensions of the foam block determine not only the heat resistance of the walls. The dimensions of the foam concrete blocks determine the parameters of the foundation grillage, and even the speed of construction of the structure itself. Therefore, any builder, as well as the customer of construction work, should know the standard block size.

Scope of application

In the West, foam concrete has been actively used for several decades, but in our country it appeared relatively recently, but has already acquired an excellent reputation as a worthy alternative to classic building materials. The only significant drawback can be considered lower strength, therefore, in multi-story construction, concrete and brick remain uncompetitive.

It is recommended to use foam concrete when building a house no higher than two floors

The use of a combination of “concrete frame + foam blocks” makes it possible to erect buildings more than two floors high, but this option is rare. The main area of ​​use of foam concrete is low-rise construction: houses, garages, utility rooms, commercial and industrial buildings.

Planning of load-bearing walls and options for foam block structures

When planning the load-bearing surfaces of any construction project, the question arises of what building material to choose and what thickness should be.

For help, you need to turn to the regulatory documents that regulate all construction standards.

It turns out that the thickness of a foam block wall does not depend on the multi-story building, the main parameter is thermal conductivity. The thermal conductivity value of walls depends on the design of the wall and the material used. It turns out that the thicker the wall, for example, brick, the greater the thermal conductivity. Today builders use the following wall designs:

1. The material is laid in two layers with additional brick finishing;
2. In one layer of foam blocks with a plaster finish;
3. Three layers with thermal insulation material and ventilated facade;
4. In two layers with a plaster finish and thermal insulation.

Very often, thanks to the use of insulation, you can save on building materials and make the wall thinner. But a wall that is too thin means poor load-bearing capacity, so builders do not try to make walls smaller than 45 cm; this is precisely the thickness that turns out to be the minimum and generally accepted in modern construction. If you use foam concrete with grade 600, then in terms of its thermal conductivity it will be absolutely no worse than a brick wall with a width of 2 meters.

If you need more accurate data, engineering calculations, then construction reference books and SNiP will help you carry out any calculations according to the required dimensions. But even builders calculate and plan the width of the wall, depending on the brand of foam block.

For example, if you chose a wall foam block with grade 600, then the width of the wall should be no narrower than 45 cm. And this takes into account the fact that your wall covering will be decorated with finishing bricks.

If external plaster is planned on a wall made of foam block grade 1000 from a single-layer masonry, then the supporting structure should be 1 meter.

Types of foam blocks

Foam concrete is produced using a single technology by mixing the main components, pouring the mixture into molds, drying under pressure and high temperature in an autoclave, further cutting and storing. Production is carried out using the same technology, but the composition of the filling solution may be different. The less foaming agent is added to the mixture, the more dense and durable and heavy the material will be.

But due to the reduced number of pores, the ability to retain heat in such a material decreases in proportion to the decrease in the number of voids in the structure. Based on the level of density (and therefore weight, strength, thermal conductivity), foam concrete is divided into three main categories - for thermal insulation, construction and combined type.

Main types of foam concrete blocks:

1. Structural (grades D900-1200) - density and weight, maximum strength due to the small number of pores in the structure, the material can be used for laying foundations, creating basement floors, load-bearing structures. Thermal conductivity is the highest, in the range of 0.29-0.38 W/m*K. The blocks require mandatory thermal insulation measures.

1. Structural and thermal insulation (grades D500-800) - blocks demonstrate average thermal conductivity, density, and strength. Used for laying load-bearing walls and internal partitions. The most popular material on the market, which is most often used in construction, especially residential buildings. The ability to retain heat is average - thermal conductivity ranges from 0.15 to 0.29 W/m*K.
2. Thermal insulation (grades D100-400) - used exclusively for the purpose of insulation, the least dense and durable, with the lowest thermal conductivity value (indicator at the level of 0.09-0.12 W/m*K). The structure of the material contains the maximum number of air cells. It is impossible to build buildings and lay walls from the material; it acts only as a thermal insulation layer.

Summarizing

• If you have chosen foam blocks as a building material for your home, then even before selecting and constructing the foundation you need to decide on the size and weight of the foam blocks for the external and internal walls. The larger the size and the higher the density, the heavier the blocks and the higher their cost. Accordingly, a more powerful and expensive foundation is required.
• Foam blocks with a density of at least 600 units are suitable for external walls. The most common material is with a density of 900.
• For internal walls and partitions, materials with a density of 100-300 are used. Usually these are blocks measuring 10*30*60 cm.
• Blocks with a density of less than 600 are used only for the heating circuit of the house. They cannot be used as carriers.
• Frost resistance also plays a role. It is necessary to take into account the climatic features of the place of life when purchasing blocks. The house should be warm and comfortable in any weather and temperature.

Thermal conductivity and frost resistance of various brands of foam blocksSource kladka-info.ru

• Check the quality of foam concrete, its color, structure. Request a quality certificate from the seller, which indicates the results of the laboratory test.
• Buy from large sellers of building materials. Reputation is very important for them and it is almost impossible to “run into” counterfeit goods here. If there are only small manufacturers nearby, then all the nuances must be checked especially carefully.
• Price also plays a role in the choice. A price that is too high or too low should be a deterrent. Too low indicates low quality components or cheap technology. Poorly mixed foam concrete will disrupt the bubble structure, the pores will be interconnected, which means the hardness of the material will be impaired and moisture absorption will increase.

About the test purchase of foam blocks, watch the video:

Types of foam blocks

When making blocks from foam concrete, the same technology is used, but the composition of the mixture may vary. The less special foaming agent it contains, the denser and stronger the resulting building material will be. However, in the most durable foam blocks with a high density solution, the number of pores is much lower, and accordingly the ability to conduct heat increases. According to their performance characteristics, all brands of foam blocks are divided into the following types:

• ·Structural. A material with the highest density and the best strength characteristics, which can be used for laying foundations, load-bearing structures, and basement floors. This group includes brands D 1100, D1200.

• ·Structural and thermal insulation. They have medium density and are most often used for laying walls and partitions. The group includes the following brands: D600, D700, D800, D1000. This group is the most popular in the building materials market, as it combines fairly high strength and the ability to retain heat.
• ·Thermal insulation. This type is the least durable and is used only for building insulation. The group includes blocks marked D400, D500.

Below is a table in which all brands of foam concrete are distributed according to purpose groups and the strength class and similar marking of concrete are indicated.

Main characteristics of cellular concrete

Depending on the density, the following grades of foam concrete are distinguished:

• Thermal insulating cellular concrete is represented by grades D300-D500. Low density (about 300-500 kg/cubic meter) provides blocks of standard sizes with low weight (12-19 kg) and low thermal conductivity. Since the strength of such foam blocks is low, they are used exclusively to form a thermal insulation layer;

Comparison table between foam concrete and other materials

• Structural-thermal-insulating foam concrete (grades D600-800), having the appropriate density and block weight in the range of 25-35 kg, is characterized by an optimal strength-thermal conductivity ratio, therefore this particular brand is the predominant one in low-rise construction;
• Structural cellular concrete is blocks of grades D900-1200, characterized by a weight of 40-47 kg and a density of 900-1200 kg/cubic meter. They are moderately strong and resistant to compression, therefore (with certain restrictions) they can be used in multi-story construction, requiring an additional layer of insulation;
• Structural porous foam blocks (grades D1300-1600) are distinguished by their high strength, allowing the construction of objects of unlimited number of storeys, but they are not produced on an industrial scale.

What affects thermal conductivity

1. The size of the internal voids - air bubbles inside the block help retain heat. The smaller they are, the better the thermal insulation properties of the material;
2. Thermal conductivity is affected by the density of the building material - the fewer pores inside, the worse the foam block will retain heat. But dense blocks are more durable, so they are used for the construction of load-bearing structures;
3. The indicator of real thermal conductivity may differ from that specified by the manufacturer; the value of the coefficient is influenced by the geometric accuracy of the manufacturing of the blocks and how thick the seam is made during laying (10-12 mm seams turn into cold bridges and lead to the formation of condensation and heat loss).