Perlite: main properties and applications
Perlite is one of the most universal and effective natural materials. This is a natural material of volcanic origin, which contains 70-75% of silicon dioxide SiO2 and 2-5% of water Н20. The main points of extraction of this mineral are located close to dead volcanos: the major part of perlite is extracted in USA and Greece.
Perlite is practically not used in its natural form, but gets its unique properties during thermal treatment. Perlite rock expands during heating forming light granules: in the form of crushed rock of different fractions, sand or powder (filter perlite powder). The resulting highly efficient heat- and soundproof porous raw material has high sorption properties, fire resistance and chemical passivity. Due to its special characteristics, it is widely used in different areas: agriculture, construction, metallurgy, medicine, energy, etc.
- low bulk density;
- high air porosity (70-90%) and light weight;
- thermal resistance (fire resistance rating А1);
- resistance to moisture, decay and vermin;
- high values of heat- and soundproofing;
- hygroscopic materials: increased waterproofing values;
- durability: perlite does not lose its properties or deteriorate over time;
- environment friendly material: non-toxic and does not cause allergy, no problems in recycling and disposal.
Main properties of foamed perlite:
Perlite applications
- Construction (2/3 of the total volume used)
- Agriculture and gardening
- Auxiliary perlite filter for chemical, pharmaceutical and food industry
- Perlite insulation of freezers
- Perlite in metallurgy
The classical application of perlite is filling ceiling and roof cavities: loose granules are used for heat insulation, soundproofing and height adjustment. For example, perlite is able to reduce heat insulation thickness by several times as compared to commonly used keramzit.
Perlite is also used as filler and additive to plasters, plaster base, mortar or screed improving their characteristics greatly. For comparison: 3 cm layer of warm plaster with perlite components has the same heat insulation properties as 15 cm brickwork. In addition, due to such properties of the material as inflammability and fire resistance (can withstand temperature up to 1260 оС), special fire resistant plasters can be made. Moreover, heat-insulated floor with perlite filler proved to save up to 30% of heat-transfer agent with ceiling height up to 3 m: and the higher the ceiling, the lower the heating costs.
Perlite is used as a basis for manufacturing numerous heat-insulation products: perlite insulation panels, blocks and bricks for walling.
When added to soil, perlite has positive effect protecting the soil from excessive compaction and thus improving air permeability, and preventing bogging up. Perlite serves for even distribution of roots around the plants. It protects roots from freezing and overheating. At the same time, perlite has proved to be a good substrate for growing plants without soil. Perlite contains useful microelements necessary for life of plants and animals.
Perlite is the most widespread auxiliary filtering material meeting all requirements. Unlike other filtering materials, it is environment friendly and health safe: filtering perlite has neutral рН from 6.5 to 7.5, is chemically inactive, very stable and almost insoluble. In addition, it has neutral taste, odor and color. Filtering perlite is used in different industries, such as chemical, pharmaceutical and food industry. For example, it is the most common filtering material used in clarification of apple juice concentrate, brewing, production of vegetable oil and various non-alcohol drinks. Due to its basic properties, perlite is also used in wastewater treatment, and filtering of chemical and pharmaceutical products.
Due to its unique properties, perlite is used as insulation material for tanks used for storage and transportation of extremely cold gases in liquid state. For example, perlite is used in shipbuilding for insulation of tanks in construction of liquefied gas tankers, and in refrigerating equipment manufacturing as a filler for cooling chambers in air separation units.
Perlite is used in iron and steel casting for insulation of surface of metal in ladles. Foamed perlite with diameter up to 5 mm is thrown into the melting pool in paper or polypropylene bags. On contact with the molten metal, the bag bursts and burns, while foamed perlite scatters over the molten metal. The resulting insulation layer prevents rapid cooling of the molten metal and improves its quality.
Conclusion
The wide spread of perlite is dictated by its unique properties and characteristics making it highly competitive to other similar materials. Perlite is environment friendly raw material used not only in construction and agriculture, but also in landscape design and even cosmetology.