Expanded clay aggregate
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LECA (Lightweight Expanded Clay Aggregate) is an aggregate made by expanding clay at average 1200 C° in rotary kiln. The Yielding gases are expanded by thousands of small bubbles during this temperature and those will provide many voids and honeycombs in this aggregate by shell structure when melted material become cold. Leca has approximately round shape externally or potato shape due to circular movement on rotary kiln production line.
The clays and shales expanded were developed about 1917 in Kansas City, Missouri, to the production in a rotary kin of a patented expanded aggregate known as Haydite which was used in the construction of USS Selma, an ocean-going ship launched in 1919 year. There following in the USA the development of a series of aggregates known as Gravelite, Perlite, Rocklite, etc. In Europe, LECA commenced in Denmark, Germany, Holland (Netherlands), UK and Middle East.
LECA is usually produced from 0.1 mm up to 25 mm and supplied in various rang sizes, which some of the commons grades are (0-4) mm, (4-10) mm, (10-25) mm and 0-25 mm which has 510 , 330 , 250 and 280 kg/m3 average density. LECA boulder is a the bigger size of LECA with 100-500 mm size and 500 kg/m3 density.
Some of the important advantages of LECA aggregate are: lightness, thermal insulation by low conductivity coefficient, soundproofing by high acoustic resistance, moisture impermeable, incompressible under permanent pressure and gravity loads, non–decomposition against severe condition, fire resistant, 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, perfect sweet soil for plants, best material for drainage and filtration.
LECA is an incredibly versatile material, and is utilized in an ever-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. LECA used in structural backfill against foundations, retaining walls, bridge abutments etc., in additional it can reduce earth pressure by 75% compared with conventional materials, and also increases ground stability while reducing settlement and land deformation. LECA can drainage the surface water and groundwater to control ground water pressure. LECA grout can be used for flooring (finishing) and roofing with thermal and sound insulation. LECA is also used in water treatment facilities for the filtration and purification of municipal wastewater and drinking water as well as in other filtering processes, including those for dealing with industrial wastewater and fish farms. LECA has many advantage for agriculture and landscapes, it is used as a growing medium in Hydroponics systems, and blended with other growing mediums such as soil and peat to improve drainage, retain water during periods of drought, insulate roots during frost and provide roots with increased oxygen levels promoting very vigorous growth. LECA can mix with normal sweet soil in order to reduce the weight of plants and landscapes soils.
- Tor Arne, Hammer; Klaas van Breugel; Steinar Helland; Ivar Holand; Magne Maage; Jan P. G. Mijnsbergen; Edda Lilja Sveinsdóttir (2000). "Materials for Buildings and Structures". Euromat 99. EUROMAT 99 6: 18. doi:10.1002/3527606211.ch3. ISBN 3527301259.