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asbestos cement[as′bes·təs si‚ment]
building material made from a watered mixture of cement and asbestos. To 100 parts (by mass) of type 500 and higher Portland cement are mixed from 12 to 20 parts of asbestos, primarily of the lower grades. Because of the reinforcing effect of the asbestos fibers, asbestos cement, even before it has become bonded, possesses enough tensile strength and plasticity to allow products of various shapes to be formed from a sheet 5–10 mm thick. In its hardened state asbestos cement possesses high physical and mechanical properties. Its strength limit in bending ranges up to 30 meganewtons (MN) per m2 (300 kilograms-force [kgf] per cm2) and in compression to 90 MN/m2; its impact strength is within the limits of 1,800–2,500 joules per m2 (1.8–2.5 kgf • cm/cm2). Asbestos cement is long-lasting and frost-resistant (losses in strength amount to no more than 10 percent after 50 cycles of freezing and thawing); it is practically waterproof and fireproof and has a high degree of chemical stability, as compared to concrete products. The density of asbestos cement ranges from 1,550 to 1,950 kg/m3. The shortcoming of asbestos cement is that it is subject to brittle destruction and deformation under conditions of changes in humidity. This characteristic can be reduced by waterproofing and additional reinforcement.
Asbestos cement is manufactured in plants on sheet-forming machines; there are also prospective methods for continuous rolling, semidry forming, and other processes.
Asbestos cement is usually produced without any additional coloring (it itself is gray in color), but sometimes a dye is used, either added to the mass or applied on the surface. Coatings of protective film may also be applied.
REFERENCESSokolov, P. N. Tekhnologiia asbestotsementnykh izdelii, 3rd ed. Moscow, 1960.
Blokh, G. S., and A. N. Litvinov. Asbestotsementnye materialy i konstruktsii i ikh ekspluatatsionnye kachestva. Moscow, 1964.
L. N. PITSKEL’