Perlite


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perlite

[′pər‚līt]
(geology)
A rhyolitic glass with abundant spherical or convolute cracks that cause it to break into small pearllike masses or pebbles, usually less than a centimeter across; it is commonly gray or green with a pearly luster and has the composition of rhyolite. Also known as pearlite; pearlstone.

Perlite

A lightweight, expanded mineral bead; highly flame resistant and with good insulating value.

Perlite

 

an acid volcanic glass with fine, concentric cracks along which a specimen breaks into small pebbles that sometimes have a pearly luster; such cracks are characteristic of perlitic structure.

The composition of perlite resembles that of acid lavas, for example, liparite and dacite, which are chiefly composed of 65 to 75 percent SiO2 and 10 to 15 percent Al2O3 and which also include admixtures of Fe2O3, CaO, MgO, SO3, and R2O in proportions that range from fractions of a percent to single percentage units. Perlite can also contain as much as 3 to 6 percent constitutional water, that is, water which is bound into hydrated crystals. When crushed perlite is rapidly heated, the enclosed water evaporates, thus swelling the softened rock and increasing the specimen’s volume ten to 20 times. The swelling temperature of perlite, which depends on the water content and chemical composition, ranges from 850°C to 1000°C and sometimes reaches 1200°C. Expanded perlite grains have a low density that ranges from 70 to 600 kg/m3; they are thus suitable for use as sand or rubble in aggregates for lightweight concrete as well as in heat-insulating products, for example, those made from perlite and bitumens, perlite and silicates, and perlite and ceramics. Expanded perlite is also used in the chemical, petroleum-refining, food, and pharmaceutical industries and in glassmaking and agriculture.

Perlite is widely used in many countries throughout the world. The USSR has aggregate geological reserves of perlite that are estimated at approximately 500 million m3. More than 600,000 m3 of perlite was extracted in 1974, including 427,000 m3 from the Aragats deposit in the Armenian SSR, 110,000 m3 from the Beregovo deposit in the Ukrainian SSR, and 66,000 m3 from the Mukhor-Tala deposit in the Buriat ASSR.

V. M. BORZUNOV

perlite

A siliceous volcanic rock; under heat it expands to 15 to 20 times its original volume, forming an excellent lightweight aggregate; used in plaster or gypsum wallboard, as loose-fill thermal insulation, and as an aggregate in concrete.
References in periodicals archive ?
Perlite aggregate consists of expanded perlite, sized for use in lightweight fire retardant (resistant up to four hours) insulating concrete, replacing sand or gravel.
Next, cut a piece of window screen to fit over the top of the perlite.
Expanded perlite that is supplied to Saudi industries and other Gulf and African markets includes insulite for building and insulation; looslite for insulation of walls; cryolite for industrial purposes, and agrilite for agricultural purposes and as a soil conditioner.
For potting the herbs a good potting soil is fine or you can mix the soil with compost, perlite, or vermiculite.
Cathedral Cast Products created test bricks with perlite as a part replacement while Teesside University looked at fascia brick and threshold product standards.
When raw perlite reaches temperatures of 850-900[degrees]C, it softens due to its glass properties.
The disinfected plastofoam pots were filled with different ratios of perlite: cocopeat (sole perlite, 75% perlite + 25% cocopeat, 50% perlite + 50% cocopeat, 25% perlite + 75% cocopeat, and sole cocopeat).
Four substrates were used as cultivation media: A) Perlite (P): it is a substrate widely used in the preparation of compost from different cultures.
Nursery plants are grown in containers filled with a soil-less potting media, formally called "substrate," which typically consists of Canadian peat moss, perlite (heat-expanded volcanic rock), vermiculite (heat-expanded silicate mineral), and pine bark.
Summary: Riyadh, June 21, 2010, SPA -- The Minister of Commerce and Industry, Abdullah bin Ahmed Zainal Ali Reza has approved the transformation of Saudi Perlite Industries Company from limited liability company into a closed joint stock company and the establishment of Company of Integration Capital.
The Perlite particles within the paste start out coarse and gradually break down into smaller particles as you clean, resulting in less abrasion to the dentin and enamel.