What determines the coefficient of thermal conductivity of

The ability of various concretes to retain heat in a room primarily depends on their density or internal structure, that is, the material is divided into classes, for example, B20 or B25. In addition, the composition of the solution may include various fillers, on which the thermal transfer of the finished product also depends.

Thermal conductivity of materials

All of this we will discuss below, as well as show you on our topic video in this article.

Effect of density and aggregates on thermal properties

Heat conductivity diagram of materials

Explanation. The thermal conductivity of a material is called its ability to transfer internal energy from hot to cold regions through the chaotic movement of molecules. This concept is the opposite of thermal resistance, which means the ability of the upper layers of material to prevent the spread of heat.

What are the concrete

Note. Concrete is called artificial stone, obtained by mixing and hardening of the binder component (in this case - cement), water, sand and larger aggregate (crushed stone, gravel, expanded clay, plastic). Its price depends on the density of the material and method of manufacture.

Monolithic RC walls
  1. Concretes are primarily classified according to their density, so they are: 1) especially light, where the density is less than 500kg / m3; 2) lungs - from 500kg / m3 up to 1800kg / m3; 3) heavy - from 1800kg / m3 up to 2500kg / m3; 4) especially heavy - from 2500kg / m3 and higher.
  2. Also, the material is classified by structure and is: 1) coarse-grained; 2) cellular; 3) porous; 4) dense. The coefficient of thermal conductivity of reinforced concrete, which belongs to the fourth class, is the highest and ranges from 1.28 W / m * K to 1.51 W / m * K, that is, the higher the density, the easier and faster internal energy ( heat) is transferred to colder areas.
  3. Concretes can be classified by the type of binder:
  • cement;
  • silicate;
  • plaster;
  • slag alkaline;
  • polymer concrete;
  • polymer cement.

Of course, polymers have the lowest thermal conductivity, so the thermal conductivity of polystyrene concrete is the lowest - from 0.057W *? C to 0.2W *? C (depending on density), that is, it can be used to warm the room.

  1. And, of course, all concrete products are classified by purpose and are:
  • constructional;
  • конструкционно-heat insulating;
  • heat insulating;
  • hydrotechnical;
  • road;
  • chemically resistant.

In this case, we are interested in the 2nd and 3rd points, where the reinforced concrete structures with a relatively small thickness can provide not only the carrying capacity, but also retain heat in the room. For example, the coefficient of thermal conductivity of foam concrete depending on the filler (sand, ash) and destination ranges from 0.08W *? C to 0.29W *? C, and the coefficient of thermal conductivity of aerated concrete, taking into account the same parameters, from 0.072W *? C to 0.183 W *? C.

Строительство

Precast Reinforced Concrete
Aggregate Mass (kg / m3) Average coefficient of thermal conductivity (W / m *? C)
Studded concrete (cement 165kg / m3)
Puma 775 0,193
Lump porous and blast furnace granulated slag 1045 0,324
Boiler slag 1190 0,314
Sand, boiler slag 1450 0,461
Sand, brick rubble 1660 0,620
Sand, gravel 2055 1,319
Rammed concrete (cement 165kg / m3)
Puma 864 0,24
Lump porous and blast furnace granulated slag 1140 0,327
Boiler slag 1258 0,335
Sand, boiler slag 1340 0,393
Sand, brick rubble 1560 0,544
Sand, gravel 1816 0,733
Rammed concrete (cement 245kg / m3)
Puma 885 0,262
Lump porous and blast furnace granulated slag 1165 0,317
Boiler slag 1300 0,348
Sand, boiler slag 1375 0,42
Sand, brick rubble 1820 0,7
Sand, gravel 2127 1,372

Table of heat conductivity of concrete in a dry form

The walls of foam blocks. A photo
Mass (kg / m3) Average number of cells / cm2 (pieces) Average cell diameter (mm) Average coefficient of thermal conductivity (W / m *? C)
253 221 0,63 0,069
282 53 1,28 0,087
314 23 1,86 0,101
368 201 0,64 0,088
373 161 0,71 0,088
366 88 0,97 0,098
370 60 1,17 0,102
415 186 0,66 0,096
415 123 0,81 0,102
420 42 1,38 0,112
563 284 0,51 0,129
539 202 0,61 0,11
559 145 0,71 0,127
580 94 0,89 0,14
611 300 0,49 0,14
633 70 1,07 0,154
620 22 1,79 0,158
913 313 0,41 0,217
927 58 0,96 0,234
956 22 1,53 -

Heat conductivity table of foam concrete in dry form

Lightweight aggregate masonry

В настоящее время, благодаря изобилию материалов на строительном рынке, при строительстве дома своими руками можно выбрать наиболее «тёплые» элементы для кладки, что в дальнейшем скажется на стоимости эксплуатации (меньший расход энергоносителей для отопительных приборов). Например, коэффициент теплопроводности керамзитобетонных блоков с плотностью 1000кг/м3 is 0.41W / m? C, which is half the brickwork rate!

But the thermal conductivity coefficient of lightweight aggregate with a density of 1200 kg / m3 there will be more - 0.52W / m? C and so on, but any of these units is suitable for low-rise construction, therefore, this material is the best fit for the private sector.

Of course, there may be a problem because of the higher cost, but you can also use cheaper cellular blocks with other foam, gas or slag concrete fillers. Of course, it is very important to take into account the ability of the material to absorb oxen - the bigger it is, the worse, because wet masonry perfectly conducts heat and in such cases additional facial finishing with a hydro-barrier is required.

Conclusion

When choosing materials for building a house, you can focus on the tables given in this article, and this will be your instruction on thermal conductivity. But, nevertheless, for the design we need general calculations, which take into account not only the ability of the walls to hold heat, but also the average annual air temperature in the region and the type of heating that you will use when operating the building.

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