CEMENTS... Flashcards
is a building material. It is applied in the form of a soft paste with sand and water and later its sets into a hard mass.
CEMENT
CEMENT It is a mixture of
calcareous material and argillaceous material.
silicates of calcium and aluminium
paste of cement with water on setting and hardening gave a hard mass whose colour and hardness were similar to those of stones from Portland in England
PORTLAND CEMENT
1.These materials supply lime Examples: Limestone, chalk, marble
CALCEROUS MATERIALS
2.these materials supply silica Example: Clay
AGRILLAEOUS MATERIALS
The powdered limestone and wet clay are mixed and made into a paste in a grinding mill. This paste is known as slurry. The slurry contains
30 TO 40 PRCENT WATER
is made of steel plates lined with fire bricks.
ROTARY KILN
In the upper part of the kiln(_______) where the temperature is 400°C, the slurry loses all its water.
drying zone)
Then the charge enters lower portion of the kiln ______where the temperature is about 1400°C. Lime and clay combines to form calcium silicates and aluminates called ____
(burning zone)
clinker.
When water is added to cement, sudden setting of cement occurs (flash set). The hardening of cement by the addition of water is known as
setting of cement
ne of the main applications of ceramics is
WHITE POTTERY
are inorganic non-metallic materials that are processed at high temperature and subsequent cooling.
CERAMICS
They are ceramic materials of china clay which is in white colour after firing is called white wares. They consist of a refractory body and glossy coating.
WHITE POTTERY
Uses of White ware
They are used for the preparation of
1.Spark plugs
2.Electrical insulators
3.Laboratory equipments
Crucibles, dishes, insulators sanitary wares etc.
is the process of giving a smooth, glossy, non-porous surface on the articles using glazes.
GLAZING
There are two methods of glazing
1.Salt glazing
2.Liquid glazing
common salt (sodium chloride) is used for getting glossy films over articles. The process consists of throwing sodium chloride into furnace, when the article is in red-hot condition.
Salt glazing
Slurry of glaze is prepared by mixing Feldspar, silica and boric oxide with water. Now the articles are dipped into the slurry of glaze and then fired. Now a smooth, glossy and non-porous surface is formed on the articles
Liquid glazing
may be defined as the substance which reduces the friction between the two moving surfaces or parts of a machine.
LUBRICANT
Characteristics of a lubricant
1.It should have enough viscosity and oiliness.
2.It should have flash and fire points higher than the operating temperature of the machine.
3.It should be chemically inert.
4.It should not come out of the surface under pressure.
5.It should not evaporate easily.
6.It should stick on the surface.
7.It should leave low carbon residue.
8.It should not form emulsion with water.
9.It should have cloud and pour points lower than the operating temperature of the machine.
10.The volatility of the lubricating oil should be low.
11.It should possess a higher resistance towards oxidation and corrosion.
Classification of lubricants
Lubricants may be broadly classified as follows.
1.Solid lubricants
2.Semi-solid lubricants
3.Liquid lubricants
is a mixture of mineral oil and soap
GREASE
Solid lubricants
The most widely used solid lubricants are
graphite and molybdenum sulphide.
EXAMPLE OF SEMI SOLID LUBRICANT
GREASE
