Asbestos

Topics: Asbestos, Mesothelioma, Thermal insulation Pages: 5 (1492 words) Published: June 13, 2013
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Asbestos- Assignment 1

Asbestos has been used for over 2000 years and during the 20th century more than 3000 products contained asbestos. The chemical properties of asbestos are extremely desirable, especially in the construction industry. Asbestos is resistant to heat and most chemicals, non flammable and extremely workable. Mining of asbestos began in 1880 in Australia and nearly one third of every domestic dwelling build between 1945 and 1987 is thought to contain asbestos. Australia had the highest per capita use of asbestos in the world from the 1950s until the 1980s until manufacturing was eventually banned in 1983, although it was still in use until 2002. Despite the bans, Australia’s residents are still exposed to asbestos in many buildings that contain asbestos cement and other asbestos products, especially when they are demolished . Products which contain asbestos can generate fibres when they are damaged, weathered, old or demolished which can cause air borne fibres to be released into the atmosphere where they can be harmful to humans.

Asbestos is a set of six naturally occurring silicate minerals that have been exploited commercially for their desirable physical and chemical properties. In nature they generally occur in metamorphic or igneous rocks, and it has been estimated that asbestos can be found in two thirds of the rocks in the earth's crust. Naturally, there are some forms which haven't been altered by extreme pressure and heat and present no effects on human health.

Asbestos is resistant to heat and most chemicals, the fibres do not evaporate in air and they are insoluble in water. It is non-flammable and has a tensile strength which is stronger than steel. It has tremendous thermal and electrical resistance, and once combined with other insulating materials, creates an ideal material for construction use. There are three main types of asbestos used commercially, Chrysotile, Crocidolite and Amosite. Chrysotile, commonly known as white asbestos, has the most flexible fibres of any asbestos. They can withstand extreme heat but are so soft and flexible that they can be spun like cotton. Chrysotile was the most widely used of all asbestos types, with it's workability leading to prominent use in reinforcing and strengthening materials, such as cement sheeting. Products containing chrysotile tend to age better than those containing crocidolite or amosite in similar conditions. Crocidolite, which is also known as blue asbestos, possesses thin, needle-like fibres which are the strongest of all asbestos fibres and due to the high bulk volume of crocidolite, it is suitable as a sprayed insulation, where it was most prominently used. It has a high resistance to acids and is the most dangerous of all asbestos types. Amosite is also known as brown asbestos, and has coarse, spiky fibres which have good tensile strength and a strong resistance to heat. It's was prominently used in thermal insulation, concrete slabs and pipes. Amosite and crocidolite have been used extensively for commercial use over the years and are now considered to be extremely hazardous, while chrysotile is considered to be the least hazardous to humans.

The building industry is responsible for the vast majority of asbestos use and it can be found almost anywhere in buildings that were constructed between the 1950s and 1980s. It's commercial uses include pipe insulation, asphalt floor tile, vinyl sheet flooring, acoustical and decorative plaster, cement products (wallboard, siding, pipes, panels, facings, extruded products, ducts, sheets, shingles), heating and electrical ducts, textured paints, roofing shingles and felt, wallboard blown in insulation, spray applied insulation, vinyl wall coverings, and all sorts of sealants (Asbestos, its Chemical and Physical Properties, 2004).

Human ingestion of asbestos fibres has severe implications, once ingested the fibres can often cause asbestosis, a disease which causes progressive...

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