The document provides a comprehensive overview of cement, detailing its definition, composition, types, and historical development. It explains the manufacturing processes of cement, focusing on the differentiation between natural and artificial (including Portland) cements, and addresses the chemical reactions involved during hydration that lead to setting and hardening. Additionally, it includes insights into the function of gypsum in cement and the hydration processes that develop strength over time.

1. CEMENT
From desk of :
Y S G GOVIND BABU

2. CEMENT
• It can be defined as material having adhesive and cohesive
properties which make it capable of bonding material fragments
in to a compact mass.
• Cement is obtained by burning together, in a definite proportion,
a mixture of naturally occurring calcareous (containing calcium
carbonate or lime) and argillaceous (containing alumina)
material to be partial fusion at high temperature about 1450◦c.
• The product obtained on burning called clinker, is cooled and
ground to the required fineness. During grinding of clinker
gypsum (CaSO4) is added to it to adjust the setting time and to
improve the soundness of cement.

3. Introduction
“A cement is a binder, a substance that sets and hardens and can bind other materials
together. It principal constituents for constructional purpose are compounds of
Ca(calcareous) and Al + Si (argillaceous)”
The cements have property of setting
and hardening under water, by virtue
of certain chemical reaction with it
and are called ‘hydraulic cements’
Chemical Composition of Cement
Lime 63%
Silica 22%
Alumina 06%
Iron oxide 03%
Gypsum 01 to 04%

4. Classification Of Cements
• 1. Natural cement
- burning limestone containing 20-40 % clay and crushing it to
powder.
- brown in colour and sets very quickly when mixed with water.
2. Artificial cement
(i) portland cement - ordinary portland cement
- rapid hardening cement
- low heat cement
(ii) special cements – quick setting cement
- high alumina cement
- blast furnace cement
- calcium chloride cement
- white cement
- coloured cement
- expanding cement
- super sulphate cement
- sulphate reisting cement

5. Early History of Cement
• In ancient times, Romans, Egyptians and Indians used some kind
of cementing materials in their construction
• Egyptians used burnt gypsum (CaSo4) as cementing materials, the
analysis of mortar used in Great pyramid showed that it contained
81.5% of calcium sulphate and about 9.5% of calcium carbonate
• Not much is known about the cementing materials used by
Indians in the construction of cities of Harappa and Mohenjo-
Daro.
• Early Romans & Greeks used cementing materials obtained by
calcinations (burning) of lime stone.
• Latter Romans & Greeks learnt that cementing materials may be
obtained by mixing volcanic ash and tuff with lime stone, sand and
water.

6. Early History of Cement……
• In the absence of natural volcanic ash, Romans used powdered
pottery or tiles as pozzolona,
• In India Surkhi (brick powder) has been used as pozzolona in
mortar
• Romans added milk, blood & lard in the mix to improve the
workability
• The blood Hemoglobin is a powerful air entraining agent and
plasticizer.
• After 1756, John Smeaton carried out extensive experiments to
find out the best material to withstand severe action of sea water.
• In 1796 hydraulic cement was produced by burning the nodules of
argillaceous lime stones
- in 1800 it was given the name Roman cement
- it was in use till 1850 then OPC was introduced

7. Portland Cement
“An extremely finely ground product by calcinising together , at above 1500oC , an
intimate and properly proportioned mixture of argillaceous (clay) and calcareous
(lime) raw materials, without the addition of anything subsequent to calcination ,
excepting the retarder gypsum”
Clinker CCN Mass %
Tricalcium silicate (CaO)3 · SiO2 C3S 45–75%
Dicalcium silicate (CaO)2 · SiO2 C2S 7–32%
Tricalcium aluminate (CaO)3 ·
Al2O3
C3A 0–13%
Tetracalcium aluminoferrite
(CaO)4 · Al2O3 · Fe2O3
C4AF 0–18%
Gypsum CaSO4 · 2 H2O 2–10%
Calcium Oxide - CaO
2%
Magnesium Oxide - MgO 4%
Pile of Portland cement
Chemical Composition of Portland Cement

9. Raw materials
Oxide % Function
Lime, CaO 60-65 Bulk to cement,
Lesser - sets quickly and reduction in strength
More - unsound, expansion & disintegration
Silica, SiO2 17-25 Imparts strength
Alumina, Al2O3 3-8 Setting, imparts quick setting, excess make weak
Iron oxide, Fe2O3 0.5-6 Grey colour, strength to cement & hardness
Magnesia, MgO 0.5-4 soundness
Sulphur trioxide,
SO3
1-2 Reduce the setting time, combined with lime
gives calcium sulphate
Soda(Na2O) and
Potash (K2O)
(alkalis)
0.5-1 react with agg. Cause disintegration of concrete,
affect the rate of gain of strength

10. Raw materials of Portland Cement and it’s use
Calcareous materials, CaO [eg.
Limestone ]
• Principal Constituent and its proportion can
be regulated
• Excess of lime reduces the strength and
makes the cement expand & disintegrate
• Lesser amount of lime also reduces the
strength by quick setting
Argillaceous materials, Al2O3 and SiO2
[eg. Clay ]
• Imparts strength
• Makes quick setting
• Excess of alumina weakens the cement
Powdered Coal or fuel oil
• For burning
Gypsum (CaSO4 2H2O)
• Retards and enhances quick setting
.

11. History of OPC
• Invented in 1824 by Joseph Aspdin, a brick layer of Leeds
(Yorkshire) England, Prepared by heating a mixture of finely
divided clay and hard lime stone in furnace until CO2 had been
driven off.
• In 1845 – modern cement was made by Issac Johnson
• In India,OPC was first manufactured in 1904 near madras Bet’n
1912 & 1913, the India cement Co. was established at Porbander
produced 1000 tons(1914).
• By 1918 three more cement factories were established in India
and produced about 8500 tons every year
• During 1951 -56 production rose from 2.69 million tons to 4.6
million tons.
• By 1969 the production of cement in India was 13.2 million tons
(9th place in the world USSR being the first with production of
89.4 million tons)

13. Manufacturing Cement
1. Mixing and Crushing of raw materials
a) Dry process
a) Wet process
2. Burning
3. Grinding
4. Storage and Packing

14. Manufacturing of Portland cement
Agillaceous
materials
Callareous
materials
Is Wet
process
Crushing &
Grinding
NO
Washing
Basin
Silos
Grinding
Slurry
Correcting Basin A
Rotary Klin
Hot Clinkers
Water
Powdered
coal + air
Cooler
Grinding in Ball
Mill
Storage Silos
Packing
2 -4 %
Gypsum
A
Flow Chart of Portland cement manufacturing process
YES

15. Mixing and Crushing: a) Dry Process
1. Mixing
2. Burning
3. Grinding 4. Storage &
Packing
• Raw materials are crushed , powdered
and mixed in right proportion ( Dry
Raw mix )
• Stored in silos
• Burning of dry raw mix is
carried out in rotary kiln
• Klin rotates at speed of 1
RPM and is slightly inclined
in position of 5 – 6 o C
Hot clinkers are cooled with atmospheric air
and pulverized together with 2-3% of gypsum
in ball mills

16. Mixing and Crushing: b) Wet Process
Figure showing manufacturing of cement using wet process
• Limestone is crushed,
powdered and stored in silos
• Clay is washed with water to
remove organic matter and
stored in basin
• Both these materials are mixed
in grinding mill to form slurry
• Slurry contains 38-40% water
stored in correcting basin

17. Burning Process : View of complete setup
Cold
Clinker
Hot Air
5 to 6o inclined
refractory-lined rotary
kin
Air
Rollers
Powdered
Coal
Ball
mill
Gypsum
Cement to strong and
packing bags
Slurry
Slurry Tank
Hot clinker
Fig. Rotary Cement Klin
Air
Blast

18. Burning Process : Zones of Rotary Klin
5 to 6 o inclined
SlurryRotary Klin
• Upper part of the kiln
• About 400 0C
• Most of the water in the slurry
gets evaporated
• Center part of the kiln
• About 700oC – 1000oC
• Lime gets decomposed into CaO
and CO2
• Lower part of the kiln
• About 1250oC - 1500oC
• Reacts with clay to form various
bouge compounds

19. Burning Process : Chemical Reactions in Rotary Klin Zones
• Calcination Zone :
CaCO3 CaO + CO2
• Clinkering Zone :
2CaO + SiO2 Ca2SiO4 ( Dicalcium silicate – C2S )
3CaO + SiO2 Ca3SiO5 ( Tricalcium silicate – C3S )
3CaO + Al2O3 Ca3Al2O6 ( Tricalcium aluminate – C3A )
4CaO + Al2O3 + Fe2O3 Ca4Al2Fe2O10
(Tricalcium aluminoferrite – C4AF)

20. Grinding and Packaging
• Cooled clinkers are ground to fine powder in
ball mills
• At final stages of grounding about 2-3% of
powdered gypsum is added.
(This is to avoid setting of cement quickly when it comes in
contact with water)
Grinding
Packaging
• Ground cement is stored in silos
• From silos they are automatically packaged into bag which are about 50 Kg
• Gypsum acts as a retarding agent for early setting of the cement
3CaO + Al2O3 + x CaSO4 . 7H2O 3CaO . Al2O3 . xCaSO4 . 7H2O
After initial set Gypsum Tricalcium sulphoaluminate (Insoluble)

21. Properties of cement : Setting and hardening
 When the cement is mixed with water, hydration and hydrolysis reactions of
Bogue compounds of cement begin, resulting in formation of gel and crystalline
products.
 These products have the ability to surround inert materials liks sand , bricks ,
crushed stones, etc.
“ Setting is the stiffening of original plastic mass due to the formation of
tobermonite gel”. It can be divided into 2 stages a) Initial Set b)Final Set
 Initial Set is when paste being to stiffen
 Final Set is when the paste beginning to harden and able to sustain some
loads
“ Hardening is the development of strength due to formation of crystals”

22. Setting and hardening
Unhydrated Cement
Hydration
Metastable Gel
Crystalline hydration
products
Stable Gel Crystalline products
Figure showing setting and hardening of cement

23. Sequence of changes during setting and hardening
Cement
+
Water Paste
Hydration of
C3A and C4F
Gelation of
C3S
Gelation of
C2S and C3S
1st day 7th day 28th day

24. Hydration of cement
• Upon hydration, both C3S and C2S give the same product called calcium silicate
hydrate (C3S2H3) and calcium hydroxide (Ca (OH)2)
2 C3S + 6 H --------> C3S2H3 + 3 Ca (OH)2
(100) (24) (75) (49)
2 C2S + 4 H ------ > C3S2H3 + Ca (OH)2
(100) (21) (99) (22)
Note:C3S2H3 – mainly responsible for strength for bond and strength
Ca (OH)2 is responsible for sulphate attack , to compensate this add poz.mat
• Tricalcium silicate(C3S ) giving a faster rate of reaction accompanied by greater heat
evolution develops early strength.
• On the other hand, dicalcium silicate (C2S) hydrates and hardens slowly and
provides much of the ultimate strength.
• C3S and C2S need approximately 24% and 21% water by weight respectively for
chemical reaction but C3S liberates 2 times as much calcium hydroxide on hydration
as C2S. however C2S provides more resistance to chemical attack.
• The amount of Ca(OH)2 is not a desirable product in the concrete mass as it is
soluble in water and may get leached out making the concrete porous, weak and not
durable.

25. • Ca(OH)2 also reacts with sulphates present in water or soil to form calcium
sulphates which further reacts with C3A and cause deterioration of concrete
• The only advantage of calcium hydroxide is that it being alkaline in nature,
maintains the Ph value of water around 13 in the concrete which reduces the
corrosion of reinforcement.
• The reaction of C3A with water is very rapid and produces enormous heat. The
hydrated product obtained is calcium alumina hydrate (C3AH6) which will bind
the materials.
The approximate reaction being
C3A + 6 H -----> C3AH6
(100) (40) (140)
The reaction of C4AF with water gives a product called calcium ferrite hydrate
(CFH) in addition to calcium alumina hydrate. It does not contribute any
strength to concrete. The calcium ferrite hydrate shows a comparatively higher
resistance to attack of sulphate than the hydrates of calcium aluminates. The
reaction being
• C4AF + 7 H -----> C3AH6 + CFH

26. Setting and Hardening : Day Wise
Day 1 :
• When cement is mixed with water, hydration of tricalcium aluminate (C3A)
takes place within a day
• The paste becomes rigid, which is known as Initial set or Flash set
• To avoid early setting of C3A , gypsum is added which acts as retarding
agent
3CaO . Al2O3 + 6H2O 3CaO . Al2O3 . 6H2O + 880 kJ/Kg
C3A + 6H2O C3A . 6H2O + 880 kJ/Kg
[OR]
Tricalciumaluminate Hyderated tricalcium aluminate (Crystalline)
C3A + 3CaSO4 . 2H2O C3A . 3CaSO4 . 2H2O
Caclium sulpho aluminate

27. Setting and Hardening : contd…
Day – 2 to 7 :
• After hydration of C3A, C3S beings to hydrate to give tobermonite gel and
crystalline Ca(OH)2, which is responsible for initial strength of the cement
• The hydration of C3S gets completed within 7 days
2[3CaO .SiO2] + 6H2O 3CaO.2SiO2 . 3H2O + 3Ca(OH)2 + 500 kJ/Kg
Tricalcium silicate Tobermonite gel Crystalline
2C3S + 6H2O C3S2 . 3H2O + 3Ca(OH)2 + 500 kJ/Kg
[OR]
Tobermonite gel possesses a very high surface area and very high adhesive property

28. Setting and Hardening : Chemical Reactions contd…
Day – 7 to 28 :
• Dicalcium silicate (C2S) reacts with water very slowly and gets completed in 7
to 28 days
• Increase of strength is due to formation of tobermonite gel and crystalling
Ca(OH)2 of both C2S and C3S
2[2CaO . SiO2 ] + 4H2O 3CaO .2SiO2 . 3H2O + Ca(OH)2 + 250 kJ/Kg
2C2S + 4H2O C3S2 . 3H2O + Ca(OH)2 + 250 kJ/Kg
Dicalcium silicate Tobermonite gel Crystalline
[OR]

29. Setting and Hardening : Chemical Reactions contd…
• After initial hyderation of tetracalcium alumino ferrite (C4AF) , hardening takes place
through crystallization , along with C2S
4CaO . Al2O3 . Fe2O3 + 7H2O 3CaO . Al2O3 . 6H2O + CaO . Fe2O3 . H2O + 420 kJ/Kg
Tetracalcium alumino ferrite Crystalline Gel
C4AF + 7H2O C3A . 6H2O
[OR]
Graphical representation of development of compressive strength
“Hydration and Hydrolysis of Bogue
compounds causes cement to develop
compressive strength”(Shown in the
figure )

31. Function of Gypsum (CaSO4·2H2O ) in cement
• Tricalcium aluminate (C3A) combines with water very rapidly with the evolution
of large amount of heat
• After the initial set, the paste becomes stiff.
• Adding gypsum retards the dissolution of C3A by forming insoluble calcium
sulpho-aluminate
• The above reaction shows how gypsum retards the early initial set of cement
C3A + 6H2O C3A . 6H2O + Heat
3CaO . Al2O3 . xCaSO4 . 7H2O

32. Major compounds of cement
Tricalcium silicate (3CaO.SiO2) C3S 54.1%
Dicalcium silicate (2CaO.SiO2) C2S 16.6%
Tricalcium aluminate (3CaO.Al2O3) C3A 10.8%
Tetra calcium alumino ferrite
(4CaO. Al2O3.Fe2O3) C4AF 9.1%
The calculation of main compounds in cement
C3S = 4.07(CaO) - 7.6(SiO2) - 6.72(Al2O3) - 1.43(Fe2O3) - 2.85(SO3)
C2S = 2.87(SiO2) - 0.754(C3S)
C3A = 2.65(Al2O3) - 1.69(Fe2O3)
C4AF = 3.04(Fe2O3)

33. Heat of Hydration of Cement
• When cement is mixed with water, hydration , hydrolysis an
gelation reaction starts and some heat is liberated
• On an average of 500 kJ/Kg of heat is evolved during complete
hydration of cement
Bogue Compounds Heat of hydration (kJ/kg)
C3A 880
C3S 500
C4AF 420
C2S 250
Heat of hydration of Bogue compounds

37. Applications
▫ Hydraulic structures
▫ Mass concreting works
▫ Marine structures
▫ Masonry mortars and plastering
▫ Under aggressive conditions.
▫ All other application where OPC is used.

38. Sulphate Resisting Portland Cement (SRC)
C3A is restricted to less than 5 %
2 C3A + C4AF lower than 25%
use of SRC is particularly beneficial in such
conditions where the concrete is exposed to the risk
of deterioration due to sulphate attack.
Ex: in contact with soils and ground waters
containing excessive amounts of sulphates as well as for
concrete in seawater or exposed directly to seacoast.

39. Sulphate attack
• The Ca(OH)2 react with sulphate gives calcium
sulphate resulting in the formation of gypsum
(CaSO4.2H2O) with an increase in volume of solid
phase by 124%
This calcium sulphate reacts with hydrated product of
C3A and C4AF forms calcium sulpho aluminate which
causes expansion of cement ( increase the solid phase
by 227%), hence the disintegration of concretee
This increase in volume by any type of reaction is
called g* attack.

40. Applications
▫ Foundations, piles
▫ Basements and underground structures
▫ Sewage and Water treatment plants
▫ Chemical, Fertilizers and Sugar factories
▫ Food processing industries and Petrochemical projects
▫ Coastal works.
▫ Also for normal construction works where opc is used .

43. Physical Characteristics of OPC (BIS Requirement)
grade
of
cement
Fineness
(sq.m/kg)
Min
Soundness
Le Chate Auto
-lier Clave
Max Max
Setting Time
(Minutes)
Initial Final
Min Max
Compressive Strength
(MPa)
3day 7day 28day
53 225 10 mm 0.8 % 30 600 27 37 53
43 225 10 mm 0.8 % 30 600 23 33 43
33 225 10 mm 0.8 % 30 600 16 22 33

44. Portland Pozzolana Cement (PPC)
OPC clinker along with gypsum and pozzolanic
materials in certain proportions either inter-grinding or
grinding separately and thoroughly blending
Pozzolana is a natural or artificial material containing
silica in a reactive form, no cementitious properties,
chemically react with calcium hydroxide to form stable
calcium silicates which have cementitious properties.
PPC produces less heat of hydration and offers greater
resistance to the attack of aggressive waters