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Asbestos cement, genericized as fibro, fibrolite (short for "fibrous (or fibre) cement sheet"; but different from the natural mineral fibrolite), or AC sheet, is a composite building material consisting of cement and asbestos fibres pressed into thin rigid sheets and other shapes.
Asbestos (/ æ s ˈ b ɛ s t ə s, æ z-,-t ɒ s / ass-BES-təs, az-, -toss) [1] is a group of naturally occurring, toxic, carcinogenic and fibrous silicate minerals.There are six types, all of which are composed of long and thin fibrous crystals, each fibre (particulate with length substantially greater than width) [2] being composed of many microscopic "fibrils" that can be released into ...
Chrysotile is resistant to even strong bases (asbestos is thus stable in high pH pore water of Portland cement), but when the fibres are attacked by acids, the magnesium ions are selectively dissolved, leaving a silica skeleton. It is thermally stable up to around 550 °C (1,022 °F), at which temperature it starts to dehydrate.
In time it became a generic term for other companies' similar asbestos-cement products, and later an even more generic term for a hard, fireproof composite material, fibre cement boards, typically used in wall construction. It can also be found in insulation, siding, roof gutters, and cement wallboard. The more prevalent transite found in wall ...
In Finland anthophyllite asbestos was mined in two mines, the larger one Paakkila in the Tuusniemi commune started in 1918 and closed in 1975 due to the dust problems. The smaller mine, Maljasalmi in the commune of Outokumpu, was mined from 1944 to 1952. The anthophyllite was used in asbestos cement and for insulation, roofing material etc.
Higher concentrations of airborne asbestos fibers are reported in urban areas where there is more ACM (asbestos containing materials) and mechanisms of release (vehicles braking and weathering of asbestos cement materials); concentrations in the range of 1–20 ng/m 3 have been reported. Fibers longer than 5μm are rarely found in rural areas.
Asbestos shingles are roof or wall shingles made with asbestos cement board. They often resemble slate shingles and were mass-produced during the 20th century as these were more resilient to weathering than traditional slate shingles for the reason that slate is very soft and prone to weathering.
The most common asbestiform mineral is chrysotile, commonly called "white asbestos", a magnesium phyllosilicate part of the serpentine group. Other asbestiform minerals include riebeckite, an amphibole whose fibrous form is known as crocidolite or "blue asbestos", and brown asbestos, a cummingtonite-grunerite solid solution series.
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