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close this bookAsbestos Overview and Handling Recommendations (GTZ, 1996)
close this folderPart II. Asbestos
close this folder4. Application areas of Asbestos materials and Asbestos products
View the document4. 1 Introduction
View the document4.2 The meaning of composite fibrous materials
View the document4.3 Asbestos in the building construction area

4.3 Asbestos in the building construction area

The quantitatively most important use of Asbestos is without a doubt in building construction materials. There it is differentiated between tightly bound Asbestos (nonfriable Asbestos) and weakly bound Asbestos (friable Asbestos). In Asbestos cement products, Asbestos is tightly bound by cement, and the Asbestos fraction is generally < 15 %). In sprayed Asbestos and similar Asbestos products, Asbestos is only weakly bound with at the same time a relatively high weight fraction of up to > 60 wt -% Due to this weak binding, Asbestos fibers can be released to the environment in relatively high amounts from weathering or even light mechanical impacts.

4.3.1 Asbestos in Housing Construction

The use of sprayed Asbestos and similar Asbestos products with a very high fraction of Asbestos (generally > 60 wt.-%) is particularly problematic. Large amounts of Asbestos fibers can be released from these sources. Preferred areas of application for these materials were or are: (UBA-Report 5/91)

· fire protection, e.g.
wood wrappings, fill between ceilings, electrical wiring shafts, inner coatings for roofs,
ceilings, and walls, covering of openings, wrapping of air shafts and ventilation pipes
near fire shutters, etc.

· vibration protection, e.g.
ceilings and wall coatings, inner coatings of ventilation pipes

· thermal protection and humidity protection, e.g.
coatings of ceilings, fire extinguishing blankets, wrappings of steam and water pipes
and boiler units

· other uses, e.g.
gaskets, safety curtains, storage masses in heat recovery units, ventilation pipes made
of sheets, hot pads for pots

Products made of friable Asbestos are considered the greatest source of risk and are largely no longer permitted in the construction sector. Therefore, in the following, only nonfriable Asbestos materials are considered, which in particular are used in the form of roofing. The most important of these products are Asbestos cement corrugated sheets and Asbestos cement sheets.

Due to the high tensile strength of Asbestos fibers, which is achieved in spite of their fineness, Asbestos fibers are a favored reinforcing material for cement products. The resistance to tearing of e.g. chrysotile is like that of iron wire. Asbestos fibers are hollow, which accounts for their insulation capacity and the good attachment with all binding materials. Asbestos fibers do not burn, have a high melting point and are largely insensitive against chemicals. They are resistant to alkalis, salts, alcohols, mineral oils, and tar, and do not corrode and are resistant to dry gases.

Asbestos cement products show in general a limited resistance against moss formation, fungus accumulation or moulding. They are not resistant to acids, vegetable oils and fats, solutions of magnesium salts, sulfates, ammonium salts, iron chloride, warm distilled water and hot condensed water. Other harmful agents are chlorine, sulfur dioxide and smoke over long periods.

4.3.2 Asbestos in Water Mains

In water mains Asbestos cement pipes are particularly relevant due to their many technical properties. Asbestos cement pipes are normed for DN 65-600 and up to PN 16. The high tensile strength of Asbestos fibers ( 750-2250 N/mm² ) permits their use as reinforcing material in cement pipes.

The deciding criteria in the use of Asbestos cement pipes are the resistance against inner and outer corrosion for most soils and waters, the low weight for small nominal diameters, the simple manufacturing of the pipe joint, the mobility lengthwise, the bendability in the sockets and also the smooth pipe wall. The inner pressure of Asbestos cement pipes is generally 10 bar, or a maximum of 16 bar.

Aside from the health hazard, other negative aspects to be mentioned are: the low bending tensile strength, the very low breaking elongation, and the sensitivity against additional stresses primarily for small nominal diameters. In addition, special care is required for the transport and bedding of the pipes, and the pipeline fittings are partly made of other materials. Special measures are needed to take up the axial forces, and an additional effort arises for the processing of cut pipe ends, since the equipment must be permitted (prevention of Asbestos dust).

The application areas for Asbestos cement pipes are primarily in soils with relatively high corrosiveness and in rural areas. However, Asbestos cement pipes are not more resistant to corrosion than concrete pipes. In developing countries, primarily the H2S-corrosion of cement-bound materials needs to be considered.

<TOC5>> 4.4 Other application areas

Aside from the structural elements and other construction products, the so-called friction products are an important application area for Asbestos. These are primarily in the form of Asbestos containing brake and clutch linings, which are to some extent still found in numerous countries.

The many mechanical, physical and chemical properties of Asbestos have generated many additional application forms. Table 14 presents an overview of these Asbestos containing products. In total, Asbestos manufacturing (manufacturing of Asbestos containing products) amounts to about 30 - 40 million tons per year (1985).

Table 14: Summary of Asbestos Containing Products

Product

Average percent Asbestos

Binding Agent

Period of Use

Friction products

50

various polymers

1910 - present

Plastic products




Floor tile and sheet

20

PVC, asphalt

1950 - present

Coatings and sealants

10

Asphalt

1900 - present

Rigid plastics

< 50

Phenolic resin

? - present

Cement pipe and sheet

20

Portland cement

1930 - present

Paper products




Roofing felt

15

Asphalt

1910 - present

Gaskets

80

Various Polymers

? - present

Corrugated paper pipe wrap

80

Starches, sodium silicate

1910 - present

Other paper

80

Polymer, starches, silicates

1910 - present

Textile Products

90

Cotton, wool

1910 - present

Insulating and decorative products.




Sprayed coating

50

Portland cement, silicates, organic binders

1935 - 1978

Trowelled coating

70

Portland cement, silicates

1935 - 1978

Preformed pipe wrap

50

Magnesium carbonate, Calcium

1926 - 1975

Insulation hoard

30

silicate


Boiler insulation

10

silicate

unknown



Magnesium

1890 - 1978



carbonate, calcium silicate


Other Uses

< 50

Many types

1900 - present

Source: US-EPA Asbestos Waste Management Guidance - Generation. Transport, Disposal; 1985

Comment: The stated dates are to be taken relatively and can vary depending on the country; the term "present" indicates that these products can still be found.

Due to the combination of material properties, Asbestos is also used in street construction, in the manufacturing of rubber and tires and in the production of vehicles, airplanes and ships.

Table 15 shows the main uses of chrysotile Asbestos and their typical trade classifications.

Table 15: Usual Trade Classification of Chrysolite Asbestos

Classification*

Description

Primarily used for:

1

Crude 1

Woven textile, protective clothing, gasket

2

Crude 2

High quality It-sheets

3

Spun fiber

Pressure pipes, filters, etc.

4

Slate fiber

It-sheets, Asbestos cement sheets, pipes and formed pieces of pipe, gasket, Asbestos paper, spraying Asbestos, etc.

5

Long cardboard fiber

Asbestos cement sheets, Asbestos pipes, Asbestos singles, Asbestos cardboard for example for cushion-vinyl-lining, brake lining and clutch lining

6

Cardboard fibers

Clutch lining

7

Short fibers

Asbestos cardboard, friction lining, PVC-floor lining, and for casing of welding electrodes, etc.

8

Sand and waste


*) Classes 1 and 2 refer to hand-picked unprocessed Asbestos pieces with fibers of more than 19 mm (Crude 1) and of cat 9.5 to 19 mm lengths (Crude 2); Classes 3-8 refer to Asbestos qualities according to mechanical processing (milled fibers): Classification according to normed sifling methods of the QAPA (Quebec Asbestos Producers Association).

Source: Frank, K.: Asbestos Hamburg 1952, (cited from the UBA-Report 1180)