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. Depends thermal conductivity of concrete, Pmost likely, from species the filler used therein. The lighter the material, the better insulator it is from the cold.
When erecting buildings and structures,used different materials. Residential and production buildings in the Russian climate are usually warmed. That is, in 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. Also for this purpose, usingYubricks and a tree. Actually the most thermal conductivity is calledThe ability of a substance to transfer energy in its thickness due to the motion of molecules. A similar process can occur, both in solid parts of the material and in its pores. In the first case it is called conduction, in the second case it is called convection. Cooling of the material goes much faster in its solid parts. The air filling the pores delays the heat, of course, better.
Conclusions from all of the above can do the following. Depends tthermal conductivity of concrete, wood and brick, as well as any other material, from their:
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.
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:
Such materials are also divided into two main groups. Concrete can be used in construction:
In the production of a second variety of materialsuch fillers as metal scrap, hematite, magnetite, barite are used. Used especially heavy concretes usually only in the construction of facilities, the main purpose of which is protection from radiation. This group includes materials with a density of 2500 kg / m3.
Conventional heavy concretes are manufactured withthe use of such filler types as granite, diabase or limestone, made on the basis of mountain crushed stone. In the construction of buildings and structures, a similar material with a density of 1600-2500 kg / m3.
What can be in this case thermal conductivity of concrete? Table, The information presented below demonstrates the indices characteristic for different types of heavy material.
Type of concrete | Especially heavy | Heavy for reinforced concrete structures | On the sand |
The heat conductivity index W / (m ° C) | 1,28-1,74 | With the density 2500kg / m3 - 1,7 | At a density of 1800-2500 kg / m3 - 0.7 |
Такой материал также классифицируется на две basic varieties. Very often in construction, concretes based on a porous filler are used. 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.
Tthermal conductivity of concrete lung is very low. But at the same time, and in terms of strength characteristics, such material is inferior to heavy. 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:
Thermal conductivity of cellular concrete different types of light in the table.
Type of concrete | Heat-insulating | Structural and heat-insulating | Structural |
Maximum allowable thermal conductivity W / (m ° C) | 0,29 | 0,64 | Not standardized |
Such concrete blocks are usually used for the lining of walls, assembled from a brick or filled with cement mortar. As can be seen from the table, thermal conductivity concretea This group can vary in a fairly large range.
Material | Aerated concrete | Expanded clay concrete |
Coefficient of thermal conductivity W / (m ° C) | 0,12-0,14 | 0,23-0,4 |
Concretes of this variety are often used as insulation materials. But sometimes they are also built of all kinds of insignificant fencing structures.
Foam concrete, slag concrete and slag concrete are most often used in construction from this group. Some types of lightweight aggregate with a density greater than 0.29 W / (m ° C) can also be attributed to this species.
Material | Foam concrete | Shlakopemzebeton | Slag concrete |
Coefficient of thermal conductivity | 0,3 W / (m ° C) | Up to 0.63 W / (m ° C) | 0,6 W / (m ° C) |
Very often such concrete with a low thermal conductivity is used directly as building material. But sometimes it is used as an insulator, which does not let the cold through.
Everyone knows that almost any dry material insulates from the cold much better than a wet one. This is due primarily to a very low degree of thermal conductivity of water. Protect concrete walls, floors and ceilings premises from low street temperatures, as we found out, mainly due to the presence of air-filled pores in the material. When wet, the latter is displaced by water. And, therefore, and significantly increased coefficient of thermal conductivity of concrete. In the cold season, water entering the pores of the material freezes. The result is that the heat preservation qualities of walls, floors and ceilings are reduced even more.
The degree of moisture permeability of different types of concrete may not be the same. According to this indicator material is classified into several brands.
Brand of concrete | HF | Lb | AT 8 | W10-W14 | W16-W20 |
Water / cement ratio (not more) | 0,6 | 0,55 | 0,45 | 0,35 | 0,30 |
And “cold” heavy, and lightweight concrete, thermal conductivity toexpensively low of course, highly are populare and sought after views buildernyh materiala. In any case, the foundations of most buildings and structures are built precisely from cement slurry mixed with rubble or rubble stone.
Apply ban eton mixture or blocks made from it andfor the construction of enclosing structures. But often enough other materials are used to assemble the floor, ceilings and walls, for example, wood. Timber and board differ, of course, much less strength than concrete. However, the degree of thermal conductivity of a tree, of course, is much lower. In concrete, this figure, as we found out, is 0.12-1.74 W / (m ° C). In a tree, the coefficient of thermal conductivity depends, including on this particular breed.
Wood type | Pine | Linden, fir | Spruce | Poplar, oak, maple |
Coefficient of thermal conductivity W / (m ° C) | 0,1 | 0,15 | 0,11 | 0,17-0,2 |
In other breeds, this indicator may be different. It is believed that the average thermal conductivity of wood across the fibers is 0.14 W / (m ° C). It best isolates the space from cold cedar. Its thermal conductivity is only 0.095 W / (m C).
Further, for comparison, we consider the characteristics with respect to thermal conductivity and this popular building material. For strength properties brick not only not inferior to concrete, but often surpasses it. The same goes for the density of this building stone. All used today in the construction of buildings and bricks tolassified into ceramic and silicate.
Both of these types of stone in turn can be:
Of course, solid bricks retain heat worse than hollow and slotted.
Brick | Full body silicate / ceramic | Silicate / ceramic with voids | Slit Silicate / Ceramic |
Coefficient of thermal conductivity W / (m ° C) | 0.7-0.8 / 0.5-0.8 | 0.66 / 0.57 | 0.4 / 0.34-0.43 |
Thermal conductivity of concrete and bricks, thow practically the same.Both silicate and ceramic stone isolate rooms from the cold rather weakly. Therefore, houses built from such material should be further insulated. When insulating brick walls as well as poured from ordinary heavy concrete, expanded polystyrene or mineral wool are most often used. Porous blocks can also be used for this purpose.
Определяется этот показатель у разных материалов, including concrete, according to special formulas. In total, two techniques 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.
For wet (more than 3%) solutions, the Nekrasov formula is used: (0.196 + 0.22 m2) 0.5 - 0.14.
TOEramzit concrete with a density of 1000 kg / m3 has a mass of 1 kg. Respectively, for example, according to Kaufman in this case, the coefficient will be 0.238. The thermal conductivity of concrete is determined at a mixture temperature of +25 ° C. In cold and heated materials, its performance may vary slightly.
