Expanded clay

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Expanded clay balls
Leca pellets.jpg

Expanded clay is a building and material with various uses.


Low-lime clay with finely divided organic components is used as the raw material . This is ground, granulated and fired in a rotary kiln without any further additives at around 1200 degrees Celsius . Finely ground limestone is used as a release agent . The organic additives in the spheres burn and the material puffs up into a spherical shape due to the carbon dioxide produced during combustion . Expanded clay reaches four to five times the original volume. The core is closed-cell, the surface is sintered .


The first attempts to manufacture expanded clay were made in 1917 in a brickworks in Birmingham / USA. SJ Hayde is considered the inventor, which is why the material is still referred to as Haydite in the USA today . The procedure was taken up and further developed in Denmark. The brand name Leca was introduced here as an abbreviation for lightweight expanded clay aggregates (German for "light, expanded clay") . The Netherlands, Great Britain, Sweden (Sillit) and the USSR (Keramsit) followed . In Germany, the first expanded clay plant was put into operation in 1955 in Hennstedt (Dithmarschen) .


Because of its spherical shape with a diameter of up to 40 millimeters, expanded clay is suitable as an aggregate in mortar , concrete and loam . It is therefore used in the production of dense and pore-like lightweight concrete . Expanded clay is also used more and more in massive system shell construction due to its good properties. Here, entire walls are prefabricated in the factory from the special lightweight concrete and put together on the construction site in the shortest possible time. Grains with a diameter of up to four millimeters are used in masonry, plaster and screed mortar. In particular, the low weight as well as the good thermal insulation properties of the expanded clay are used. Expanded clay can be installed as a heat-insulating and room-stable fill without further processing or treatment.

Pore-filled expanded clay lightweight concrete wall

In gardening and landscaping , expanded clay is used for soil improvement , for green roofs and for hydroponics . Expanded clay is used in substrates for hydroponics. Since expanded clay does not bind nutrients, the nutrient content of the soil can be easily controlled by adding to the water.

Special applications

Expanded clay lightweight concrete precast wall

In addition to these standard applications, there are other areas of application for expanded clay:


Expanded clay is not identical to the aerated concrete, which is sometimes referred to as expanded concrete .


On the early historical development:

  • Siegfried Reinsdorf: Lightweight concrete . Volume 1: Lightweight concrete made from porous aggregates. VEB Verlag für Bauwesen, Berlin 1961.

On structural properties of the surcharge :

  • K. Wesche: Building materials for load-bearing components . Volume 2: concrete, masonry. 3. Edition. Bauverlag, Wiesbaden / Berlin 1993, ISBN 3-7625-2681-8 .

Web links

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Wiktionary: Expanded clay  - explanations of meanings, word origins, synonyms, translations