Light clay

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Light clay is a building material made from building clay and light organic or mineral aggregates .

Composition and properties

The proportion of clay should be at least 30%, the bulk density can be between 400 and 1,200 kg / m³. Most of the time, however, light clay is produced in bulk densities of 600 - 800 kg / m³. This puts them in the same weight class as porous bricks or aerated concrete .

Organic aggregates can be, for example, chopped straw , wood chips , wood shavings, sawdust, hemp fibers or shavings or granulated cork . The fabrics must not be sensitive to moisture. Natural or artificial rocks with a high pore content are suitable as mineral aggregates . Expanded clay , expanded slate, expanded glass , perlite or pumice are examples of lightweight mineral aggregates.

Pure clay is classified as "non-flammable" according to DIN 4102 (fire behavior of building materials and components). With mineral aggregates, the light clay remains non-combustible because it is a mixture of two non-combustible substances. Because the organic aggregates are flammable, in the case of such an admixture, the light clay is classified as "hardly inflammable" (B1 or B2 according to DIN 4102) depending on the type and amount of the aggregate.

The heat-insulating properties of light clay are comparable to those of bricks with the same gross weight. Its thermal conductivity is around 0.25 - 0.45 W / K m.

Manufacturing and processing

A slurry or pulp is made from clay, possibly sand and water, and the aggregates are poured over, dipped or mixed with the clay in a compulsory mixer . The light clay is then placed in a formwork or mold and dries there. Since there is seldom strong compression and usually no visible surface is required, the requirements for stability and surface quality of the formwork are not high. Boards or formwork panels are just as possible as "lost formwork" made of reed mats. Closed formwork elements must be removed for the component to dry completely - the lost formwork remains in the component and is z. B. plastered over (hence the term "lost").

The material can either be processed “wet” on the construction site or prefabricated components are used “dry” in the factory. There are different formats for the prefabricated components made of light clay: in addition to the usual stone formats (3 DF - 12 DF), panels up to floor-to-ceiling wall elements are also manufactured, some with wooden frames.

Both non-load-bearing (e.g. infill of a half-timbered wall) and load-bearing components can be built from light clay .

literature

  • Volhard, Franz, with the assistance of Ute Schauer: Leichtlehmbau. Old building material - new technology , 5th edition 1994, Verlag CF Müller, Karlsruhe 1983. ISBN 3-7880-7511-2
  • Dahlhaus, Ulrich, Kortlepel, Uwe, (Eds.): Lehmbau, current planning manual for earth building , 4th edition 2004, Manudom Verlag, Aachen 1997. ISBN 3-9807245-0-6