3. 7 Summary
The fiber substitute technique has not yet reached the standard of quality of Asbestos fiber reinforcement. Deficiencies, such as frost uplifting and fine fissures from thinning of fibers, occurred particularly with corrugated SFC products.
Aside from several disadvantages which SF have over Asbestos fibers, such as reduced binding and higher price, the new SFC products also have advantages, such as higher elasticity and easier processing.
The mechanical resistance of fibrous cement products is dependent on the mixture of ingredients, which is different for each application area, and on the particular manufacturing process. The maximum temperature resistance lies around 150°C.
As with Asbestos fiber products, SFC products have generally limited resistance against moss formation, fungus collection and mold. This is true to the same extent for Asbestos containing and Asbestos-free products. They are also impaired by acids, vegetable oils and fats, magnesium salt solutions, sulfates, ammonium salts, iron chloride, warm distilled water and hot condensed water. Chlorine, sulfur dioxide and smoke also act destructively over long periods.
SFC products, however, resist alkalis, salts, alcohols, mineral oils (bitumen), and tar. They do not corrode and resist dry gases.
Cement contains free unbound alkali metals, which partly separate during the hardening process, and lead to the formation of hydroxyl ions in aqueous medium. (Cement reacts as an alkaline substance).
These characteristics also apply for housing construction and water pipelines, with the limitation that no adequate SFC pipe products have been found for high pressure requirements.
Aside from SF substitutes, other fiber-free substitutes are usable in the building area, and their application is especially gaining importance in housing construction and water pipeline construction. Their possible applications are therefore discussed in the next two sections.
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