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Uses and applications of asbestos - an extract from a film by Parsons Brinckerhoff
An extract from Asbestos Awareness - an informative guide to asbestos produced by Parsons Brinckerhoff.
Asbestos was used in building materials up until 1990, and in some items of plant and equipment up until 2003. However, if you are not sure whether a material contains asbestos, presume that it does.
This film gives general information about where asbestos containing materials are commonly found in domestic and commercial buildings.
PRESENTER 1: Asbestos has played a role in human culture for at least four and a half thousand years. In what is now Finland, in 2500 BC, Asbestos fibre was used to reinforce the walls of clay jars. At about the same time, the Egyptians were using it to wrap embalmed pharaohs. In classical Cyprus, there's evidence of a variety of uses including lamp wicks, cremation cloths, hats and shoes.
The ancient Greeks supplied the name from the word 'Amiantus.' They used asbestos for tablecloths and napkins, which could be tossed into a fire for cleaning.
The Romans were impressed, and helped themselves to the idea as they built their empire. Fast-forward to the late 17th Century, where Peter the Great of Russia initiated paper making using chrysotile or white asbestos fibres from the Ural Mountains.
While in the New World, Benjamin Franklin had a purse of asbestos.
In the Industrial Age, paint containing asbestos adorned some of the world's most famous buildings.
While in the late 19th Century, fire proof asbestos stage curtains lured back the patrons after a rash of disastrous theatre fires.
Its uses have been many, varied, and sometimes quite spectacular.
PRESENTER 2: When asbestos consumption peaked in industrialised nations, it was being used in around 3000 products or applications. Because of recent restrictions and market changes, most of these applications have been abandoned.
Where asbestos is still used, conditions for use are tightly regulated. So, what are the properties of asbestos which have made it so valuable through the ages?
PRESENTER 1: Asbestos fibres have high tensile strength, making them an excellent binding agent. It has thermal stability, enabling it to resist heat, and low thermal conductivity, enabling it to reduce heat loss. It has low electrical conductivity, ideal for electrical applications. It is chemically inert, so resistant to attack by acids or other active chemicals. Asbestos has low biodegradability; it lasts a very long time. It absorbs noise, so it's an excellent acoustic insulator. And it has excellent wearing and friction properties.
PRESENTER 2: In Australia, the most common use of asbestos was in asbestos cement sheeting. Fibro, or AC sheet, was widely used in home and commercial building applications until the mid 1980s.
PRESENTER 1: Fibro is the common or generic name for fibro cement sheet. The name refers to the fibre used to bind the cement, in a similar way to reinforcing steel in concrete.
Since 1985, the once common asbestos has been replaced by cellulose fibre, from wood pulp. So as a rough guide, fibro used in buildings before 1985 was likely to contain asbestos, however, some post-1985 buildings could still contain asbestos cement fibro if the material had been stored for a lengthy time between manufacture and use.
PRESENTER 2: Asbestos was so versatile that it can be found in a whole range of building locations from the roof down.
PRESENTER 1: The asbestos containing materials used in these applications fall into two broad categories. The first, friable or loosely bonded ACMs, and the second, bonded or firmly bound ACMs.
Friable, or loosely bonded ACMs have a greater potential to release asbestos fibres than bonded or firmly bound ACM's. This is significant as it is an indicator of risk to health.
Asbestos cement roof sheeting was commonly known by the manufacturer's trade name 'Super Six.' The paint coating applied to Super Six roofs will have deteriorated with age, and they now appear grey in colour.
Also on the roof, there's asbestos in the ridge capping, and the barge capping which seals the roof ends. Often, the bituminous seal around the roof screws also contains asbestos. As AC roofs weather, asbestos fibres can collect in gutters along with leaves, soil and other debris. The asbestos fibres in this situation are typically loose so it's important to follow the safe work procedure outlined on the DVD when cleaning gutters.
Occasionally, you'll also find cast asbestos cement down pipes and even gutters. Asbestos cement sheets were used in other overhead applications including gable ends, fascia panels and eaves or soffit linings.
You might find AC sheet used for eaves lining where there's no other AC structure. Elsewhere, small pieces of AC sheet may have been used for packing between timber supports. Semi-circular pieces of moulded AC were often used as form work for downpipe collars and overflow relief gullies.
Sometimes, concrete spilled over the top of this formwork, making it harder to establish the presence of asbestos.
PRESENTER 2: Stable, strong, and easy to work with, asbestos cement sheeting was ideal for a whole range of wall applications, both inside and out.
PRESENTER 1: Outside, AC sheet was generally flat with AC cover strips used to finish over joints between the sheets. It also came in the shadow-line profile, in a plank form, which provided an inexpensive and robust alternative to weatherboard, and infrequently, in a brick patterned finish.
Sometimes, Super Six was used in external wall applications, particularly in sheds, and occasionally it was used as a decorative fencing.
The most common use of asbestos cement in wet areas like bathrooms, toilets, laundries and kitchens was a product commonly known as Tillux because of its great ability to repel water. When renovations were undertaken in the 60s, 70s and early 80s, asbestos cement was widely used in other internal locations including walls and ceilings.
Suspended compressed sheet floors could also contain asbestos. So, extensions to all types of houses from weatherboard to brick could contain asbestos.
Common extension work from this period include; enclosing verandas, and building rumpus rooms.
AC sheet could also be found in the infill panels above or below windows and doors in brick homes.
PRESENTER 2: Other domestic applications for asbestos could include insulation in the ceiling cavity. Asbestos was also widely used in commercial buildings.
PRESENTER 1: Asbestos cement panels were used on a steel grid support system to create easily installed ceilings. You might also see AC castings to concrete support columns in larger buildings.
AC panels were widely used for housings around hot items such as water heaters and boilers. Sprayed fire proof insulation applied to beams and other areas for fire proofing has a fibrous and matted appearance. Trade names for sprayed asbestos insulation include limpet, which contained amesite; chrysotile or chrasydolite, asbestosspray, cafco and silbestos, which contain chrasydolite; and monokote, which contained chrysotile.
Vinyl floor coverings were both widely used in domestic and commercial applications, and both can contain significant asbestos levels. The backing material to vinyl sheet floor coverings can contain as much as 100 per cent chrysotile. This material crumbles easily when ripped and should only be removed with appropriate procedures in place.
Vinyl floor coverings can be found under carpet, newer vinyl layers, or even under floors of masonite and compressed sheet. Older vinyl tiles which were often used in the high-traffic areas of commercial buildings, sometimes contained asbestos which was used as a binding agent.
PRESENTER 2: We mentioned earlier that asbestos has very low electrical conductivity properties. For this reason, some electrical systems need to be treated as an asbestos risk.
PRESENTER 1: Older, black electrical switchboards with brand names like 'Zelemite' and 'Miscolite' were manufactured from coal tar pitch and asbestos usually chrysotile.
The timber box sometimes installed behind the board can also contain an AC lining.
The outer lining to electrical cables may also contain asbestos.
Old hot water systems may be lined with asbestos, and the electrical panel on the system can sometimes be separately lined with asbestos impregnated paper.
Similarly boilers may have asbestos insulation.
Hot water pipes may be lagged with insulation containing asbestos to minimise heat loss. If the lagging is damaged there may be asbestos fibres present in ceiling and sub-floor areas.
Air conditioning duct work was lined with asbestos millboard around electric heater elements and fire dampers to provide thermal insulation.
PRESENTER 2: For more than four and a half thousand years, asbestos has been a part of our lives. And it's still around today, in a wide variety of locations and applications. We now know of the health hazards posed by asbestos. Knowing where it commonly occurs and how to spot it will help you to deal with it safely.