The thermal conductivity of expanded clay and its dependence on various factors

By Admin | Construction Materials
26 April 2016

Thermal insulation properties of expanded clay are well known and are largely determined by the raw material from which it is produced.The thermal conductivity of expanded clay - one of its main characteristics, which, together with a low specific weight and strength, determines the widespread use of this material in construction.

Heat-conducting properties of expanded clay


  1. What affects the thermal conductivity of expanded clay
  2. Production processes affecting the thermal conductivity of expanded clay

What affects the thermal conductivity of expanded clay

For materials that performprotective functions, thermal conductivity - a particularly important characteristic.For expanded clay, as a natural material, it depends on the combination of its various qualities.

Firstly, the thermal conductivity characteristic of expanded clay depends on the fraction (grain size): the larger granules, the greater the need of insulation.Influence on the

thermal conductivity for example, characteristics such as humidity and expanded clay porosity.The average coefficient of thermal conductivity of expanded clay is not easy to determine because of the many variations.In the references you can find the value of the data that it is in the range 0,07-0,16 W / mK.

should choose a concrete block with a minimum thermal conductivity.The higher the thermal conductivity, the greater the number of passes through the heat insulating layer for a certain time, and so, consequently, lower the heat shield.Thus, the larger expanded clay porosity, the lower the density and thermal conductivity.

Keramzit hygroscopic: with increasing humidity, it increases its thermal conductivity and insulation loses its properties, and weight gain also increases the load on the ceiling.High-quality waterproofing of expanded clay is necessary to preserve the properties, ensuring conservation of heat in your home.

So, concrete block has a thermal conductivity which depends on its fractions: a decrease in the size of the expanded clay grain decreases its emptiness, increased bulk density and thermal conductivity increases.

The size of expanded clay granules are divided into expanded clay gravel, crushed stone and sand.

Expanded clay gravel

obtained from expanded by crushing weight of expanded clay.

Expanded clay gravel

clay gravel

round or oval particles obtainable in a rotary kiln mild swelling clay.It possesses strong dense surface so often used as filler in concrete.It has the lowest thermal conductivity.For example, expanded clay gravel 10-20 mm mark on the bulk density of the M350 and P125 brand strength (3.1 MPa) has a thermal conductivity of 0.14 W / (m ° C).

Clay gravel

Expanded clay sand

Has fraction up to 5 mm, and is most commonly used for insulation.

Production processes affecting the thermal conductivity of expanded clay

According to the research, the characteristics of the thermal conductivity of expanded clay depend on the presence of quartz in it at some stage of production and, to a lesser extent, the density and porosity of the material.This suggests that the quality of expanded clay affects the method of its production, as it appears glassy quartz in the production process.

Note that single crystal quartz itself has a high thermal conductivity (6,9-12,2 W / m), which is entirely dependent on the characteristics of raw materials.Clay having good swelling in phase quartz glass formation is obtained, the thermal conductivity is higher than that of quartz from the worst swelling clay.This relationship also extends to the properties of expanded clay.

matters as production technology.Contained in Leca silica enhances thermal conductivity, and other oxides, on the contrary, it is reduced.It does not apply to gases that are formed when heated to the temperature of the mass of clay swelling.It is found that when the content of the pores from 55% of H2 + CO keramzita thermal conductivity is twice that when filled with air.

on the thermal conductivity is also influenced by the size of micropores: the smaller the pores, the lower the thermal conductivity.At the same time, she porosity while significantly on this characteristic is not affected.

above listed characteristics mainly depend on the production method.The usual method of production, as a rule, does not significantly change the quality of expanded clay.However, modern methods of production (Plastic mode or "joint firing") can significantly increase the thermal insulation properties of expanded clay.

When compared to the total performance of expanded clay and foam are preferred expanded clay, although the thermal conductivity of the foam is very low - 0,038-0,041 W / m.

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