MAIN TITLE Asbestos
Article Title Uses of Asbestos
Asbestos has been used in literally hundreds of products. Collectively, these are frequently referred to as asbestos-containing material (ACM). Asbestos gained wide spread use because it is strong, it conducts heat and electricity poorly, and it is impervious to chemical corrosion.
Asbestos proved well suited for many uses in the construction trades. One of the most common uses for asbestos is as a fireproofing material, It w as sprayed on steel beams used in construction of multi-storied buildings. This application prevented these structural
members from warping or collapsing in the event of fire. Chrysotile w as the commonly used asbestos constituent in sprayed-on fireproofing. Asbestos comprised 5-95% of the fireproofing mixture, and was used in conjunction with materials such as vermiculite, sand, cellulose fibers, gypsum and a binder such as calcium carbonate. These materials are soft and may be fluffy in appearance and to the touch. They vary in color from w hite to dark gray, occasionally they have been painted or encapsulated w ith a clear or colored sealant. The material may be exposed or concealed behind a suspended ceiling. The application to structural members (beams and columns) often resulted in some material being sprayed on w alls and ceilings as w ell. This is referred as over-spray. Asbestos is added to a variety of building materials to enhance strength. It is found in concrete and
concrete-like products. Asbestos cement products generally contain Portland cement, aggregate, and chrysotile fibres. The asbestos content may vary up to 50% by w eight depending on the use of the product. Asbestos cement products are used as siding and roofing shingles; as wallboard; as corrugated and flat sheets for roofing, cladding, and partitions; and as pipes. Asbestos has also been added to asphalt, vinyl and other materials to make products like roofing felts, exterior siding, floor tile, joint compounds and adhesives. Fibres in asbestos cement, asphalt and vinyl are usually firmly bound in the cement and will be released only if, the material is mechanically damaged, for example by drilling, cutting, or sanding. Roofing shingles and siding may also show slow deterioration due to weathering.
As an insulator, asbestos received wide spread use for thermal insulation and condensation control. It was usually spray applied, trowel applied, or manually installed after prefabrication. Asbestos proved valuable as a component of acoustical plaster. The material was applied by trowel or by spraying on ceilings and sometimes w alls. It varies in colour from white to grey-rarely it was painted, as a noticeable loss of acoustical value occurs. Similarly as a decorative product, asbestos was mixed with other materials and sprayed on ceilings and walls to produce a soft, textured appearance.
FRIABLE AND NON-FRIABLE ACBM
The U.S. Environmental Protection Agency (EPA) and others distinguish between friable and non-friable forms of ACBM.
All things being equal, friable ACBM is thought to release fibres into the air more readily.
How ever, many types of non-friable ACBM can also release fibres if disturbed.
CATEGORIES OFASBESTOS-CONTAININGBUILDINGMATERIALS (ACBM)
EPA identifies three categories of ACBM used in buildings:
Surfacing Materials
Members for acoustical, decorative, or fireproofing purposes. This includes plaster and
fireproofing insulation.
Thermal System Insulation - pipes, boilers, tanks, ducts, and various other components of hot and cold water systems and heating, ventilation, and air conditioning (HVAC) systems. This includes pipe lagging, pipe wrap, gaskets and ropes.
Miscellaneous Materials
ceiling tile, roofing felt, concrete pipe, outdoor siding, and fabrics.
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