SHP f
2w
Acid-resistant asbestos comprises crocidolite asbestos, anthophyllite asbestos, amosite asbestos,
actinolite asbestos and tremolite asbestos. The group of non-acid-resistant asbestos is represented
by chrysotile asbestos only, which is of great industrial importance. In chemical composition
chrysotile asbestos (theoretical) is a magnesium hydrosilicate 3MgO.2SiO 2. 2H 2 O.
Asbestos molecules are strongly bound together only in one direction, whereas the lateral
bond with adjacent molecules is quite weak. This property explains the very high tensile
strength of asbestos along the fibres and its good fluffing ability and ready transversal
(across the fibres) splitting. Diameter of chrysotile-asbestos fibres lies between 0.00001 to
0.000003 mm, but in practice chrysotile-asbestos can be fluffed to fibres of a mean diameter of
0.02 mm, and, therefore, such a fibre is actually a bunch of numerous elementary fibres. On the
average, the tensile strength of asbestos fibres is 3000 N/mm^2 , but since the fibres are subjected
to compression, impact and other types of action in the process of fluffing, their strength drops
to 600–800 N/mm^2 which corresponds to the strength of high-quality steel wire.
Asbestos has a good absorption capacity. When mixed with Portland cement and wetted by
water, it absorbs, i.e., retains firmly on its surface, the products of cement hydration, which
bind the asbestos fibres, and, therefore, asbestos-cement can be considered a finely reinforced
cement stone. Chrysotile-asbestos is incombustible, however, at about 110°C it begins to lose
absorption water and its tensile strength drops by 10 %; at 368°C all of the absorption water
evaporates and asbestos strength decreases by 25–30%. However, after asbestos is cooled, it
readsorbs from the air the moisture it has previously lost and regains its original properties.
When asbestos is heated to over 550°C, chemically bound water is removed, asbestos loses
elasticity and strength, becomes brittle and fails to restore its properties on cooling. Chrysotile-
asbestos melts at a temperature of about 1550°C.
Asbestos has low heat and electric conductivity, high resistance to alkali and poor resistance
to acids. The quality of asbestos-cement items depends greatly on that of asbestos and on
fineness of cement.
Asbestos is used to make sheets (A.C. sheets) and boards for roofing, false-ceilings,
paneling, partitions, wall linings, door panels, window panes, sign boards, wardrobes, etc. In
the form of pipes it is used to drain rain water, soil water, etc. It is also used for making paints.
PIQ2vsxyvi w
It is a plastic material obtained by oxidizing linseed oil into a rubber like substance mixed with
ground cork, wood flour and pigments. The resulting material is pressed upon a backing of
burlap.
Linoleum is classified as plain, printed and inlaid. It is available in the form of tiles and rolls.
The plain linoleum of a uniform colour is available in thickness 2–4.5 mm. The printed linoleum
has a pattern printed on it in oil paints. Its thickness ranges from 1.25–2 mm. The inlaid
linoleum has small units of linoleum in different colours and shapes patterned and pressed on
a burlap back.
Linoleum floors are durable, resilient, quiet and comfortable. They are cheap easy to install and
maintain.
This is most suitable decorative floor covering for wood and concrete floors.