Expanded clay, the thermal conductivity of which is largely determined by the raw material, also has a low specific gravity, as well as high strength. It is these qualities that determine the wide field of use of this material in construction.
Thermal conductivity
For those materials that are designed to perform a protective function, the characteristic of thermal conductivity is especially important. Expanded clay acts as a natural material, which is why this parameter depends on many qualities.
Among the first, the size of the granules should be highlighted. The more impressive the fraction, the more insulation will be needed. Expanded clay porosity and humidity will also affect thermal conductivity. The average coefficient of thermal conductivity is quite difficult to determine, because there are many deviations. Expanded clay, the thermal conductivity of which in the reference literature is indicated in the range from 0.07 W / m, has a high hygroscopicity. But it would be fair to indicate the maximum value of thermal conductivity - it reaches the level of 0.16.
It is important to choose the right material. If the thermal conductivity is higher, the amount of heat that passes through the insulator layer will be impressive. This indicates that thermal protection is reduced. You should also pay attention to the porosity of expanded clay, which affects the density and thermal conductivity. The higher the first parameter, the lower the last two.
What affects the main characteristic of expanded clay
Studies show that the thermal conductivity of expanded clay is determined by the absence of quartz, but only at a single stage of production. Technologists must take into account the features of production. After all, the silica contained in expanded clay increases thermal conductivity, while other oxides lower this value.
This does not apply to gases generated when heated to a swell temperature. It was found that if the pores contain H 2 + CO in a volume greater than 55%, then the thermal conductivity of expanded clay will be 2 times higher than if the filling is carried out by air. Micropores can also affect thermal conductivity. The smaller they are, the lower the thermal conductivity will be, but porosity does not affect this characteristic.
Basic properties
Expanded clay, the thermal conductivity of which was mentioned above, has certain properties, among them:
- high strength;
- frost resistance;
- durability;
- fire resistance;
- optimum ratio of quality and cost.
Considering this material, it is impossible not to distinguish good heat-insulating qualities, acid resistance and chemical inertness. Expanded clay is considered a natural material and is an environmentally friendly heat insulator.
Key Features
Expanded clay, the thermal conductivity of which you need to know before purchasing this material, has excellent qualities. It is made of slate and clay and is suitable for environmentally friendly and modern housing construction.
Expanded clay is also used for decorative purposes, and at home it is suitable for solving problems of growing cultivated plants. Using this material, it is possible to exclude increased evaporation of moisture, which helps to control the water balance of plants.
Specifications
Expanded clay thermal conductivity is established by state standards 9757-90, as well as other technical characteristics, among them the fractional composition should be distinguished. On sale you can find material in three fractions:
One cannot fail to mention another category of fractions, which is rarely used in construction work. This can include expanded clay crushed stone and granules, the sizes of which vary from 2.5 to 10 mm. Quite often, when buying, a consumer is interested in bulk density, in this issue there are 7 values for brands:
- up to 250 kg / m 3 - grade 250;
- from 250 to 300 kg / m 3 - grade 300;
- similarly - brands 350, 400, 450, 500, 600.
For wide sale, the following two brands are not available; they are made only with the agreement of the consumer. Expanded clay, the characteristics whose thermal conductivity are mentioned in the article and should be interesting to the consumer, has a certain compaction coefficient, which is agreed individually, but this value does not exceed 1.15. An important parameter that determines the behavior of expanded clay when exposed to moisture is water absorption. It can vary from 8 to 20%.
Comparison of the thermal conductivity of expanded clay with some other materials
Expanded clay, thermal conductivity (a comparison of this characteristic with other materials should also be done before making the choice of material) which has already been mentioned above, is often preferred by consumers of mineral wool or expanded perlite. In the first case, the coefficient is 0.04, this indicates that with the same thickness of the cotton wool will release less heat compared to expanded clay.
Another alternative is expanded perlite. Its water absorption is lower than that of expanded clay and is only 5%, while the thermal conductivity is only 0.04.
Expanded clay, properties whose thermal conductivity sometimes makes it an indispensable material during work, is sometimes compared with expanded vermiculite. It is the most optimal option, which could replace expanded clay, and is produced from rock, which makes it environmentally friendly. The thermal conductivity of expanded vermiculite is 0.08, which is 2 times less compared to mineral wool. If you use this material, you can form a thinner layer of backfill, which will load the overlap less. This suggests that this insulation can also be used as the basis for screed.
Conclusion
Thermal conductivity acts as one of the important characteristics of expanded clay. But it is highly independent of the mode of production. If you use conventional technology, then changing the quality of expanded clay is not particularly possible. However, when applying modern techniques such as co-firing or plastic method, it is possible to increase the thermal insulation properties of expanded clay.