Cement is a fine gray powder, which when mixed with water and materials such as sand, gravel,
pebble, etc., forms a paste which binds other together.
* For the manufacture of cement clay and calcium carbonate are taken in the ratio 1:2.These two are
then powdered and mixed with water to form a paste called slurry. The slurry is then put into a rotary
furnace called kiln and heated to 16000 0 C. After heating a mixture of calcium aluminate and calcium silicate is formed which is called cement clinker. Finally 1-2% gypsum is added & the mixture is grinded to form cement.
* Chemically cement is a mixture of calcium silicate and calcium aluminate
* During manufacture of cement when slurry is heated in the furnace, it changes into lump of chemical which is called cement clinker. By grinding the cement clinker with gypsum salt (1-2%) cement is made.
Uses of cement are
a. A mixture of cement, gravel, pebble and water is called concrete, which is used fior roofing
and flooring.
b. A thick paste of cement, sand and water is called mortar which is used for plastering walls
and to join bricks, stones etc.
c. Cement is used in the construction of buildings, roads, bridges etc.
d. Gypsum is added in the manufacture of cement to increase the setting time of cement. It makes
convenient to use the cement.
Artificial fibers
a.Man made fibers is called artificial fibers. They are of two types
o Recycled or Regenerated fibers
o Synthetic fibers
b. Rayon is an artificial silk made from cellulose of cotton and wood pulp. It is recycled fiber. Rayon is used in making fabrics, tyres cords, carpets, etc
c. Fibres made by chemical process are called synthetic fibers. Nylon, terylene, polyester, accryline,
olefin, etc are its examples.
d. Nylon is the first synthetic fiber because it is manufacture by polymerization of adipic acid and
hexamethyne-diamide.
e. Nylon fiber is widely used as
o In making socks, ropes, tyre cords, bristles for tooth brush, nets etc.
o In making fabrics in textiles.
f. Nylon fiber melts at low temperature , absorbs less water, therefore, quickly dry up when washed A polymer of ester molecule is Terylene fiber or polyester.
g. Terylene fibers are used in making fabrics, sails for boats, conveyor belt etc.
h. The common properties of synthetic fibers are
o They are fine, light, strong, durable and not eaten by insects.
o They absorb less water and therefore dry up quickly.
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