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.
• vibration protection, e.g.
• thermal protection and humidity protection, e.g.
• other uses, e.g.
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.
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