cement manufacturing process& quality .pptx

1. CEMENT

2. DEFINITION
Cements are materials that exhibit
characteristic properties of setting and
hardening when mixed to a paste with
water. This makes them join rigid masses
into coherent structures. It is powdery
bonding material having adhesive and
cohesive properties.
Chemically it is a finely ground mixture of
calcium silicates and aluminates which set
to a hard mass when treated with water.
These are called as Hydraulic Cements
(Portland Cement) and those setting in air
Non Hydraulic cements (Ordinary Lime).
It was first made by Joseph Aspdin in 1824
in England.

3. CLASSIFICATION OF CEMENT
• Natural Cement: Obtained by
calcinating and pulverizing natural
cement rock of argillaceous and clay
with limestone. It does not have
sufficient strength and is cheap and
quick setting & have hydraulic
properties.
• Pozzolana Cement: Volcanic ash
containing silicates of calcium, iron
and aluminum when mixed with lime
and heated produces this cement.
• Slag Cement: Mixture of blast
furnace slag (Ca and Al Silicates) and
hydrated lime. Sometimes
accelerators like clay, salt, caustic
soda are added to hasten hardening
process.
• Portland Cement: It consists of
compounds of lime, silica, alumina
and iron. When mixed with water it
forms a paste which binds the rock,
sand and gravel to form concrete.

4. PORTLAND CEMENT COMPOSITION
Lime (CaO) 60-6% Exces reduces strength
and make cement
disintegrate and in Les
amount reduces strength
and makes it quick seting.
SiLica(SiO2) 17-25% Provides strength to cement
ALumina(AL2O3) 3-8% HeLps inquick seting
CaLciumSuLpha
te (Gypsum)
Enhances initiaL setingof
cement
IronOxide 2-6% Gives coLor, Strength and
hardnes.
SuLphur
trioxide (SO3)
1-3% Provides soundnes
ALkaLi Oxides
(Na2O and
K2O)
0.5-
1.5%
inexces makes cement
efLorescent
MagnesiumOxi
de (MgO)
1-5%

5. RAW MATERIALS
• Calcareous Materials : Supplies Lime to cement
Lime Stone (65-80% CaCO3), Marl, Chalk, Shale,
Calcite, Alkali waste. It should contain less than 3.3%
of MgO and 3-4% of SiO2, Fe2O3, and AlO2 combined.
• Argillaceous Materials : Supplies Silica, Alumina and
Iron Oxide. Clay, Marl, Shale, Blast Furnace Slag, sand
etc. Here Silica provides strength, Alumina imparts
quick setting, iron provides color, strength and
hardness.
• Gypsum: increases setting time.
• Powdered Coal and Fuel Oil: For generating required
temperatures.

6. MANUFACTURE OF PORTLAND CEMENT
•
•
•
•
•
•
Crushing Mixing(Wet Proces)
Mixing(DryProces)
Grinding(BaL Mi L and TuBe Mi L)
Storage of Ground MateriaLs Burning
–
–
–
DryingZone
CaLcinationZone
CLinkeringZone
• Grinding
–
–
–
Retarder DispersingAgent Water
Proofing
• Packaging

7. CRUSHING
• This is the first step in the manufacture
of Portland Cement.
• Jaw crushers of various sizes are
employed for the crushing purpose.
• Raw materials are crushed by crushers
till the size of the raw material reduces
to ¾ of an inch.
• It is than send for either Wet process or
Dry process. Wet process is universally
employed.

8. MIXING WET PROCESS
•
•
•
•
Calcareous materials are crushed, powdered and stored in bins.
Argillaceous materials is mixed with water and washed. This removes
any adhering organic impurities.
• Powdered Calcareous and Washed Argillaceous materials are mixed in
proper proportions to get a slurry.
Chemical composition is analyzed and corrected if necessary by addition
of the deficient materials.
This slurry is then fed into the rotary klin.

9. MIXING DRY PROCESS
• Hard raw materials like cement rock
or blast furnace slag are first
crushed to 50mm pieces in ball mill,
then dried and stored.
• Crushing
crushers
is done by
and drying is
gyratory
done by
rotary driers.
• Separate powdered ingredients are
mixed in required proportions to get
the raw mix which is then fed to
rotary klins.

10. GRINDING
Grinding can be done in two stages
• Ball Mill
– Consists of cast iron drum
containing iron and steel balls of
different sizes. The principle used in
ball mill s impact and shear
produced by large no. of tumbling
and rolling balls.
• Tube Mill
–
– Ball mill grinding is followed by tube
mill grinding. Tube mill is conical at
the discharge end with separate
inlet and outlet.
Slower is the feeding speed finer is
the product coming out of the tube
mill.

11. STORAGE OF GROUND MATERIALS
• The ground materials containing 30 – 40% of water is
stored in separate tanks equipped with agitators.
• This step is followed by process of burning.

12. BURNING
• Slurryisburnt inrotaryklinwhere actual chemical changestakesplace.
• KLin is Long steL cyLinder 30-40meter in Length, 2-4meter in diameter, Lined
ByrefractoryBricks. It is incLined at gradient of 0.5-0.75inch and can Be rotated at the
desired sp ed.
• The materiaL isintroduced inthe kLinfromthe upper end asthe kLinrotatesmateriaL
pasessLowLytowardsthe Lower end.
•
KLinis heated ByBurningpuLverized coaL or oiL and temperature ismaintained at aBout
1400-150°C. At cLinkeringtemperature actuaL chemicaL reactions take pLace.

13. BURNING ZONE
A. DRYING ZONE
The upper part of the klin is known as drying zone.
The temperature is about 200-500°C.
Most of the water gets evaporated from the slurry by means of hot gases.
•
•
•
B. CALCINATING ZONE
• This the middle zone of the klin with temperature around 1000°C.
• Organic matter burns away and CaCO3 decomposes to quick lime and CO2
escapes out. The material forms small lumps called as nodules.

14. BURNING ZONE
C. CLINKERING ZONE
This is lowest portion of Klin with a temperature of about
1400-1600°C. Lime and clay nodules melts with chemical
fusion and gives calcium aluminates and silicates. These
silicates and aluminates then fuse together to form small
hard stones called Clinkers which than fall down from
lower end of the Klin.
– CaCO3  CaO + CO2
– 2CaO + SiO2  Ca2SiO4
– 3CaO + SiO2  Ca3SiO5
– 3CaO + Al2O3  Ca3Al2O6
– 4CaO + Al2O3+Fe2O3  Ca4Al2Fe2O10
Calcium Oxide
Dicalcium Silicate
Tricalcium Silicate
Tricalcium Aluminate
Tetracalcium Aluminoferrite

15. CONSTITUTION OF CLINKERS
Clinkers are cooled under controlled condition to produce a definite
degree of crystallization.
Clinker Constitution
– Ca2SiO4
– Ca3SiO5
– Ca3Al2O6
– Ca4Al2Fe2O10
– MgO
– Cao
Dicalcium Silicate
Tricalcium Silicate
Tricalcium Aluminate
Tetracalcium Aluminoferrite
Magnesia
When burning is incomplete

16. GRINDING
Clinkers are finally grinded in ball mill and tube mill to a
fine powder. Additives added are as follows.
Retarder
Gypsum CaSO4.2H2O or Plaster of Paris CaSO4.½H2O
acts as retarder to prevent quick setting. After initial
setting gypsum retards the dissolution of tricalcium
aluminate by forming tricalcium sulphoaluminate
(3CaO.Al2O3.xCaSO4.7H2O).
Dispersing Agent
Sodium salts and polymers of condensed napthlene or
sulphonic acid are added to prevent the formation of
lumps and cakes in the cement.
Water proofing agents are also added.

17. PACKAGING
powder is
The ground
packed by automatic
machines in a 50kg bag.
This is then dispatched
to the markets where it
is sold for constructions
of cities.

18. CHEMICAL COMPOSITION OF
PORTLAND CEMENT
– Ca2SiO4 Dicalcium Silicate 25% 28 days 420KJ/Kg
– Ca3SiO5 Tricalcium Silicate 45% 7 days 880KJ/Kg
– Ca3Al2O6 Tricalcium Aluminate 1% 1 day 879KJ/Kg
– Ca4Al2Fe2O10 Tetracalcium Aluminoferrite 9% 1 day 418KJ/Kg
– MgO Magnesia 4%
– Cao Incomplete burning 2%
– CaSO4 Calcium Sulphate 5%

19. SPECIFICATIONS OF PORTLAND
CEMENT
Lime saturation fraction = CaO / 2.8 SiO2 + 1.2 Al2O3 + 0.65 Fe2O3
= 0.66. To 1.02
The ratio of Al2O3 / Fe2O3 < 0.66
SiO2 / Al2O3 = 2.5 to 4.0
Weight of insoluble residue < 1.5%
Weight of Magnesia < 5%
Total sulphur content calculated as SO3 < 2.75%
Total loss of ignition should be less than 4%

20. OTHER SPECIFIC REQUIREMENTS
Fineness generates lot of heat quickly hence cement
mortar or concrete is likely to develop cracks.
Setting time initially - 30 minutes and finally not mare
than 600 minutes.
Tensile Strength after 3 days  300lbs.sq. inch and
after 7 days  375 lbs/sq. inch.
Compressive Strength after 3 days  300lbs.sq. inch
and after 7 days  375 lbs/sq. inch.
Heat of Hydration within 7 days  65 cal/gm and in 28
days  75 cal/gm.
Soundness is the ability of a cement to maintain stable
volume after setting. A sound cement resists cracking
and disintegrating.

21. VERTICAL SHAFT KLIN TECHNOLOGY
Vertical shaft klin technology has been successfully
employed by mini cement plants. The VSK have pan
noduliser or pelletiser. The uniform pellets so formed
can be fed into the vertical shaft Klin and the cement
can be produced. Proper proportions of raw material
must be taken to get good quality of clinkers.
– Black Metal Process : Raw materials are ground
along with coal and then converted into pellets with
about 15% water.
– Fuel Slurry Process: Raw materials are dry ground
and coal is wet ground separately and then mixed to
get pellets which move down VSK.

22. ADVANTAGES OF VERTICAL SHAFT KLIN
• Vertical Shaft Klin has following advantages:
– No dust discharge in the atmosphere due to pellets.
– Clinker clogging is avoided because no low
constituents are formed.
melting
– Wearing of grinder machinery and cost of grinding is removed
– Plant is quite compact.

23. CHEMISRTY OF SETTING
Cement forms paste like mass with water resulting in
hydration of compounds of cement. This mass then
becomes stiff and hard. This change of fluid to solid is
known as setting of cement.
The process of solidification comprises of three stages:
– Initial Setting – It is mainly due to the hydration of
tricalcium aluminate and gel formation of tricalcium
aluminoferrite. Dicalcium silicate also contributes to
initial setting.
– Final Setting – mainly due to the formation of
tobermonite gel and crystallization of calcium
hydroxide and hydration of tricalcium aluminate. The
concrete can neither be moulded into any shape nor it
can be remixed.

24. CHEMISRTY OF HARDENING
During hardening the solid cement
material begins to gain strength. It
depends upon the chemical
combination of cement and water.
Hardening starts with great speed but
finally its speed reduces. The
hardening of concrete stops and it is
dried out.
The hydration reactions are
exothermic and the volume of cement
increases with hydration.
Hydrated cement dissociates on
heating by destroying the bond which
held the mass together.

25. REACTIONS INVOLVED
2(3CaO.SiO2)+ 6H2O 3CaO.2SiO2.3H2O+ 3Ca(OH)2
2(2CaO.SiO2)+ 4H2O 3CaO.2SiO2.3H2O+ Ca(OH)2
3CaO.AL2O3 + 30H2O+ 3(CaSO4.2H2O) 3CaO.AL2O3.3CaSO4.36H2O
4CaO.AL2O3.Fe2O3 + 10H2O+ 2Ca(OH)2  6CaO.AL2O3.Fe2O3.12H2O
Decay of cement : Cements are susceptiBLe to
atack BysaLtywater and acidic soLutions