3. OUT LINE
History
About Cement
Raw materials
Description
Manufacturing Process
Manufacturing Steps
Process Scheme
Uses
4. History
Cement was first invented by the Egyptians.
Cement was later reinvented by the Greeks
and the Babylonians who made their mortar
out of lime.
About ninety-nine percent of all cement used
today is Portland cement.
5. PORTLAND CEMENTS
Cement is a material with adhesive and cohesive
properties which make it capable of bonding
minerals fragments into a compact whole.
It helps to join the materials like
stones,sand,bricks,building stones etc…
PORTLAND – Island in English
6. What is Cement?
Cement is a fine grayish powder which, when mixed with water, forms a thick
paste. When this paste is mixed with sand and gravel and allowed to dry it is called
concrete.
The term cement is commonly used to refer to powdered materials which develop strong
adhesive qualities when combined with water.
Gypsum plaster, common lime, hydraulic lime, natural pozzolana, and Portland cements
are the more common hydraulic cements.
7. RAW MATERIALS :
Calcareous Material : Such as limestone or chalk ,
as a source of lime .
Clayey Material : Such as clay or shale(soft clayey
stones), as a source of silica and alumina .
9. WET PROCESS :
Grinding and mixing of the raw materials
the existence of water.
DRY PROCESS :
Grinding and mixing of the raw materials
their dry state
10. Manufacturing Process
The production of cement takes place with several steps:
• Quarrying of limestone and shale
• Dredging the ocean floor for shells
• Digging for clay and marl
• Grinding
• Blending of components
• Fine grinding
• Burning
• Finish grinding
• Packaging and/or shipping
11. Manufacturing Steps
The most common way to manufacture Portland cement is through a
dry method.
The first step is to quarry the principal raw materials, mainly
limestone, clay, and other materials. After quarrying the rock is
crushed. This involves several stages.
The first crushing reduces the rock to a maximum size of about 6
inches. The rock then goes to secondary crushers or hammer mills for
reduction to about 3 inches or smaller.
12. Manufacturing Steps
The crushed rock is combined with other
ingredients such as iron ore or fly ash and ground,
mixed, and fed to a cement kiln.
The cement kiln heats all the ingredients to about
2,700 degrees Fahrenheit in huge cylindrical steel
rotary kilns lined with special firebrick.
In its simplest form, the rotary kiln is a tube up to
200 meters long and perhaps 6 meters in
diameter, with a long flame at one end.
13. Manufacturing Steps
The material formed in the kiln is described as 'clinker' and is
typically composed of rounded nodules between 1mm and
25mm across.
After cooling, the clinker may be stored temporarily in a clinker
store, or it may pass directly to the cement mill. The cement
mill grinds the clinker to a fine powder.
A small amount of gypsum - a form of calcium sulfate - is
normally ground up with the clinker. The gypsum controls the
setting properties of the cement when water is added.
17. SETTING AND HARDNING
STAGES OF SETTING
FIRST STAGE :
C3A + 6H2O → C3A.6H2O
SECOND STAGE :
2C3S + 6H2O → C3S.3H2O + 3Ca(OH)2
THIRD STAGE :
2C2S + 4H2O → C3S2.3H2O + C(OH)2
FOURTH STAGE :(Hardening)
C4AF + 7H2O → C3A.6H2O + CF.H2O
18. FACTORS AFFECTING THE SETTING
WATER/CEMENT RATIO : Setting time increases with
the increase of W/O ratio .
TEMPERATURE AND RELATIVE HUMIDITY : Setting
time decreases with a rise in temperature .
FINENESS OF CEMENT : Setting time decreases with a
rise in fineness of cement .
