Tuesday, January 4, 2011

Asbestos and Asbestos Cement Products

Asbestos is a naturally occurring mineral found in underground rock formations. For commercial purposes, it is recovered by mining and rock crushing. Fine fibres, invisible to the eye, are present in the air and water in every region of the globe. Hence, all of us may be inhaling and also ingesting them through drinking water every day. There are two different varieties of asbestos (i) Chrysotile variety and (ii) Amphibole variety. Amphibole variety comprises of Crocidolite, Amosite, Tremolite, etc. Only Chrysotile variety is in production and use for the past two decades.

Only Chrysotile variety (white asbestos) is in commercial use now. Indian asbestos cement sheet and pipe manufacturers import all their requirements of chrysotile fibres from Canada, Brazil, Russia, Zimbabwe and Kazakhstan for production of AC sheets and pipes. Chrysotile asbestos is also mined in India in very small and insignificant quantities which are of no consequence or relevance to our asbestos-cement production. The other varieties of asbestos known as amphiboles (crocidolite, amosite, tremolite, etc) which were considered rather unsafe, have been prohibited all over the world including in India. Wherever asbestos is produced or used in products, only Chrysotile variety is permitted now. 

Chrysotile asbestos fibre, (composed mainly of magnesium and silica), is a great reinforcing agent. While its tensile strength is greater than steel, it has other rare and highly valued fire-retardant, chemical-resistant and heat-insulating qualities. In fact it is a magic mineral.

Asbestos Cement Products

AC products are made with a mix of chrysotile fibres (about 8-9%), cement (about 40%), Fly Ash (about 30%), the rest being wood pulp and water. Over 90% of asbestos fibre imports of India go in to AC sheet and pipe production.

AC Sheets have been used in India for over 70 years. Being weather-proof and corrosion resistant, these sheets are practically ageless and maintenance free, whereas metal sheets corrode and deteriorate with age and exposure. (See chart for comparison).

AC Sheets have also proven to be the most cost effective, easy-to-install, strong and durable roofing material for warehouses, factories, low-cost housing, and practically any structure needing a roof. Apart from India, Russia, China, Thailand, Brazil are some of the largest users of AC Sheets.

AC sheets and pipes, being corrosion and erosion-free, once properly laid and jointed, need no maintenance or replacement. They are also very cost effective

AC products, which consume low energy in manufacture and do not in any way deplete the natural resources, meet the needs of the country in its developing economy in the context of rapidly rising population and limited resources.

AC products are manufactured under (ISI) licence strictly conforming to the standards of Bureau of Indian Standards. IS 459/1992 for Corrugated Roofing Sheets, IS 2098/1997 for Building Boards, IS 2096/ 1992 for Flat Sheets and IS 1626 (Part III)/ 1994 for Roofing Accessories. AC Pressure Pipes are covered by IS 1592/1989.

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