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What is Asbestos?
Asbestos is a naturally-occurring fibrous silicate
mineral found predominantly in metamorphic rock. Asbestos minerals crystallize
in narrow veins as parallel bundles of tiny fibers. These fibers are very small,
and may remain airborne for several hours when broken-up and dispersed into the
air. Asbestos is very resistant to acids, fire, and heat. Asbestos is also known
for it's high tensile
strength.
There are two categories of asbestos: serpentine and amphiboles. The serpentine
group is comprised of chrysotile, also known as "white asbestos." Chrysotile
fibers are hollow and pliable. Over 95% of all asbestos used in the United
States is the chrysotile variety. The amphibole group is comprised of amosite
and anthophyllite, crocidolite also known as "brown" or "blue" asbestos as well
as actinolite, tremolite, and anthophyllite. Amphibole fibers are hard and
straight.
How Was Asbestos Used?
Asbestos’ resistance to chemicals and heat, high tensile strength, and low cost
made it a very attractive ingredient in thousands of building and thermal
insulation products. Some typical uses of asbestos include transite pipes, floor
tiles, sheet floorings, drywall, drywall texture, drywall joint compound, insulation, automotive brakes and clutches, electric wiring
insulation, transite siding, structural fireproofing and roof shingles.
In the late 1970’s, the U.S. began banning the use of asbestos in most building
products due to studies confirming the harmful health effects caused by exposure
to airborne asbestos. Manufacturers were allowed to deplete their existing
stocks of asbestos materials, so some asbestos products were still being
installed in buildings in the 1980's.
The last ban on manufacturing with asbestos building products was stayed by the
U.S. Supreme Court in the late 1980’s. This makes it possible for certain
building materials such as mastics, adhesives, and wall texturing to be made
with asbestos. With the advent of the North American Free Trade Agreement
(NAFTA), other asbestos-containing building products are currently being shipped
into the U.S. from Mexico and Canada.
What is Asbestos Abatement?
Asbestos abatement is the removal, repair, encapsulation, enclosure, or clean-up
of asbestos-containing materials (ACMs). Abatement is performed in academic and
non-academic buildings and utility tunnel systems to assist departments with a
planned renovation or maintenance activity, and to ensure compliance with
federal and state regulations. On some occasions, unplanned, emergency abatement
is performed to remove asbestos materials from mechanical equipment to allow
critical repairs to be performed, or to clean-up an area contaminated by
asbestos when a building system suddenly fails (e.g. roof leaks, steam system
failures).
Asbestos in raw form
Asbestos under a polarized light microscopy
Industrial usage of asbestos
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