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Concept
Expanded clay aggregate
Summary
Lightweight expanded clay aggregate (LECA) or expanded clay (exclay) is a lightweight aggregate made by heating clay to around in a rotary kiln. The yielding gases expand the clay by thousands of small bubbles forming during heating producing a honeycomb structure. LECA has an approximately round or potato shape due to circular movement in the kiln and is available in different sizes and densities. LECA is used to make lightweight concrete products and other uses.
LECA was developed about 1917 in Kansas City, Missouri, to the production in a rotary kiln of a patented expanded aggregate known as Haydite which was used in the construction of SS Selma, an ocean-going ship launched in 1919. Following in the USA was the development of a series of aggregates known as Gravelite, Perlite, Rocklite, etc. In Europe, LECA commenced in Denmark, Germany, Netherlands, and UK.
LECA is usually produced in different sizes and densities from up to , commonly 0–4 mm, 4–10 mm, 10–25 mm and densities of 250, 280, 330, and 510 kg/m3. LECA boulder is the biggest size of LECA with 100–500 mm size and 500 kg/m3 density.
Some characteristics of LECA are lightness, thermal insulation by low thermal conductivity coefficient (as low as 0.097 W/mK), soundproofing by high acoustic insulation, moisture impermeability, being incompressible under permanent pressure and gravity loads, not decomposing in severe conditions, fire resistance, a pH of nearly 7, freezing and melting resistance, easy movement and transportation, lightweight backfill and finishing, reduction of construction dead load and earthquake lateral load, being perfect sweet soil for plants, and as a material for drainage and filtration.
Common uses are in concrete blocks, concrete slabs, geotechnical fillings, lightweight concrete, water treatment, hydroponics, aquaponics and hydroculture.
LECA is a versatile material and is utilized in an increasing number of applications. In the construction industry, it is used extensively in the production of lightweight concrete, blocks and precast or incast structural elements (panels, partitions, bricks and light tiles).
Official source
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