Expanded-clay aggregate, or "exclay", is a lightweight ceramic

Ceramic

A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...

 aggregate

Aggregate (composite)

Aggregate is the component of a composite material that resists compressive stress and provides bulk to the composite material. For efficient filling, aggregate should be much smaller than the finished item, but have a wide variety of sizes...

 ("LWA"), used in construction and hydroponics

Hydroponics

Hydroponics is a method of growing plants using mineral nutrient solutions, in water, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel, mineral wool, or coconut husk.Researchers discovered in the 18th...

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It is produced by processing natural clay

Clay

Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...

 which is finished to the shape of round pellets. The clay is expanded by thermal treatment in a rotating kiln

Kiln

A kiln is a thermally insulated chamber, or oven, in which a controlled temperature regime is produced. Uses include the hardening, burning or drying of materials...

 operating at temperatures about 1100 °C. Exclay lightweight aggregates are available in various densities and grades between 3-32 mm (0.8-8.1 inches). It packaged in sacks of 25-50 liters. The density of exclay pellets is approximately 350 kg/m³.

Exclay has the advantage of high durability, heat retention and excellent sound insulating properties. It is also an environmentally friendly product composed of mostly of naturally occurring clay and has a long life span. The pellets can be compressed into solid lightweight blocks of LWA. Exclay is the main aggregate used for LECA blocks. LWAs are also frequently used in water filtration systems due to their high surface area

Surface area

Surface area is the measure of how much exposed area a solid object has, expressed in square units. Mathematical description of the surface area is considerably more involved than the definition of arc length of a curve. For polyhedra the surface area is the sum of the areas of its faces...

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Fuels such as used oil and different kinds of petroleum gas oils are used in the manufacture of exclay. Such fuels may leave toxic residues in the final product.