Thermal conductivity of concrete: features, coefficient and table

One of the most important characteristics of concrete, of course, is its thermal conductivity. Change this indicator for different types of material can be significant. теплопроводность бетона, п режде всего, от вида использованного в нем наполнителя. The thermal conductivity of the concrete depends , first of all, on the type of filler used in it. The lighter the material, the better insulator it is from the cold.

What is thermal conductivity?

When building buildings and structures, different materials can be used. Residential and production buildings in the Russian climate are usually warmed. That is, during their construction special insulators are used, the main purpose of which is to maintain a comfortable temperature inside the premises. When calculating the required amount of mineral wool or expanded polystyrene, the thermal conductivity of the basic material used for the erection of the enclosing structures is necessarily taken into account.

Very often, buildings and structures in our country are built from different types of concrete. ю тся кирпич и дерево. Also, for this purpose, brick and wood are used. Actually, the very heat conductivity is called the ability of a substance to transfer energy in its thickness due to the motion of molecules. A similar process can take place, both in the solid parts of the material, and in its pores. In the first case it is called conduction, in the second case convection. Cooling of the material goes much faster in its hard parts. Air filling the pores, delays the heat, of course, better.

What determines the indicator

Conclusions from all of the above can do the following. еплопроводность бетона, дерева и кирпича, как и любого другого материала, от их : The conductivity of concrete, wood and brick, like any other material, depends on them :

• Density;
• Porosity;
• Humidity.

With increasing density of concrete , the degree of its thermal conductivity also increases. The more in the pore material, the better insulator from the cold it is.

Types of concrete

In modern construction, a variety of types of this material can be used. However, all existing concrete on the market can be classified into two large groups:

• Heavy;
• Light foamy or with a porous filler.

Thermal conductivity of heavy concrete: indicators

Such materials are also divided into two main groups. Concrete can be used in construction:

• Heavy;
• Especially heavy.

In the production of the second type of material, fillers such as metal scrap, hematite, magnetite, barite are used. Used especially heavy concretes usually only in the construction of objects, the main purpose of which is protection from radiation. This group includes materials with a density of 2500 kg / m ³ .

Conventional heavy concretes are made with the use of filler types such as granite, diabase or limestone, made on the basis of rock crushed stone. In the construction of buildings and structures a similar material with a density of 1600-2500 kg / m ^{3 is used} .

теплопроводность бетона? What is the thermal conductivity of concrete in this case ? представленная ниже, демонстрирует показатели, характерные для разных типов тяжелого материала. The table below shows the indices typical for different types of heavy material.

Thermal conductivity of cellular lightweight concrete

Such material is also classified into two main varieties. Very often in construction concrete is used on the basis of a porous filler. As the last applied clay, tuff, slag, pumice. In the second group of lightweight concrete filler, the usual one is used. But in the process of kneading such a material foams. As a result, after ripening, many pores remain in it.

еплопроводность бетона легкого очень низкая. The thermal conductivity of concrete in the lung is very low. . But at the same time and in terms of strength characteristics, this material is inferior to the heavy one . Use lightweight concretes most often for the erection of various kinds of residential and household buildings that are not subject to serious stress.

Classify lightweight concretes not only by the method of manufacture, but also by purpose. In this regard, there are materials:

• Heat-insulating (with a density of up to 800 kg / m3);
• Structural and heat-insulating (up to 1400 kg / m3);
• Structural (up to 1800 kg / m3).

легкого разных видов представлена в таблице. Thermal conductivity of cellular lightweight concrete of various types is presented in the table.

Thermal insulation materials

Such concrete blocks are usually used for the lining of walls, collected from a brick or filled from a cement slurry. теплопроводность бетон а этой группы может варьироваться в достаточно большом диапазоне. As can be seen from the table, the thermal conductivity of concrete a of this group can vary in a fairly large range.

Concretes of this variety are often used as insulation materials. But sometimes they also erect various insignificant enclosing structures.

Structural and heat-insulating and structural materials

Of this group in construction, foam concrete, slag-pomber-concrete, slag-concrete are most often used. Вт/(м°С) также могут быть отнесены к этой разновидности. Some types of claydite concrete with a density of more than 0.29 W / (m ° C) can also be attributed to this variety.

бетон с низкой теплопроводностью используется непосредственно в качестве строительного материала. Very often such concrete with low thermal conductivity is used directly as a building material. But sometimes it is also used as an insulator that does not let the cold pass.

How does the thermal conductivity of moisture

Everyone knows that almost any dry material isolates from the cold much better than the wet one. This is primarily due to the very low degree of thermal conductivity of the water. бетонные стены, полы и потолки помещения от пониженных уличных температур , как мы выяснили, в основном благодаря наличию в материале пор, заполненных воздухом. Protect the concrete walls, floors and ceilings of the room from low street temperatures , as we found out, mainly due to the presence of pores filled with air in the material. When wet, the latter is displaced by water. коэффициент теплопроводности бетона. And, consequently, the coefficient of thermal conductivity of concrete considerably increases . In the cold season, the water that gets into the pores of the material freezes. теплосохраняющие качества стен, пола и потолков снижаются еще больше. The result is that the heat-retaining qualities of walls, floors and ceilings are reduced even more.

The degree of moisture permeability in different types of concrete may not be the same. According to this indicator, the material is classified into several grades.

Tree as an insulator

к оторого низкая, конечно же, очень популярны е и востребованные вид ы строител ьных материал ов . And the "cold" heavy, and lightweight concrete, the thermal conductivity to low is, of course, a very popular and sought-after type of building material . цементного раствора в смеси с щебнем или бутовым камнем . In any case, the foundations of most buildings and structures are erected precisely from the cement slurry in a mixture with crushed stone or rubble stone .

б етонную смесь или же изготовленные из нее блоки и для возведения ограждающих конструкций. Apply a concrete mix or blocks made of it and for erecting enclosing structures. But often enough for the assembly of floors, ceilings and walls, and other materials, for example, wood. The beam and the board differ, of course, much less durable than concrete. However, the degree of thermal conductivity of a tree is, of course, much lower. Вт/(м°С). In concrete, this figure, as we found, is 0.12-1.74 W / (m ° C). In a tree, the coefficient of thermal conductivity depends, in particular, on a given concrete breed.

In other breeds, this indicator may be different. Вт/(м°С) . It is believed that, on average, the thermal conductivity of the wood across the fibers is 0.14 W / (m ° C) . It is best to isolate the space from the cold cedar. Its heat conductivity is only 0.095 W / (m C).

Brick as an insulator

Next, for comparison, consider the characteristics of the thermal conductivity and this popular building material. кирпич не только не уступает бетону, но зачастую и превосходит его. According to strength properties, brick not only does not concede to concrete, but often surpasses it. The same applies to the density of this building stone. к лассифицируется на керамический и силикатный. All the brick used today for the erection of buildings and structures is classified for ceramic and silicate.

Both these varieties of stone can in turn be:

• Full-bodied;
• With voids;
• . Slotted .

Of course, solid bricks retain heat worse than hollow and crevice.

аким образом, практически одинакова. The thermal conductivity of concrete and brick, therefore, is almost the same. Both silicate and ceramic stone isolate the premises from the cold is rather weak. Therefore, houses constructed from such material should be additionally insulated. As insulation during the plating of brick walls, as well as those filled from ordinary heavy concrete, polystyrene or mineral wool is most often used. You can also use porous blocks for this purpose.

How is the coefficient of thermal conductivity calculated

This figure is determined for different materials, including concrete, according to special formulas. In total, two methods can be used. The thermal conductivity of concrete is determined by the Kaufman formula. It looks like this:

• 0.0935x (m) 0.5x2.28m + 0.025, where m is the mass of the solution.

(0,196 + 0,22 m2) 0,5 – 0,14 . For wet (more than 3%) solutions Nekrasov's formula is used: (0,196 + 0,22 m2) 0,5 - 0,14 .

ерамзитобетон плотностью 1000 кг/м3 имеет массу 1 кг. The frame of concrete with a density of 1000 kg / m3 has a mass of 1 kg. к примеру, по Кауфману в данном случае получится коэффициент 0,238. Accordingly, for example, according to Kaufman in this case, the coefficient will be 0.238. The thermal conductivity of concretes is determined at a mixture temperature of +25 C. In cold and heated materials, its performance may vary slightly.