Cement-Plant-Chemistry-Manufacturing-Process.ppt

Chemistry and Manufacturing Process of Portland Cement

The manufacturing process of Portland cement, the most common type of cement, is fundamentally a high-temperature chemical process that transforms simple raw materials into complex, cementitious compounds known as clinker.

2. Who –
Joseph Aspdin,
 In 1824.
Foundation for today's portland cement industry.
A British stone mason.
Obtained a patent for a cement he produced in his kitchen.
How –
Aspdin heated a mixture of ground limestone and clay in his kitchen and
ground the mixture into a powder creating a hydraulic cement –
Heat Ground
Ground Limestone + Clay ------- Mixture -------- Powder (P / C)
(N Stone,Portland in England)
Powder + Water ------------------------ Hard Object
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3. First Use –
First engineering use, was in a tunnel under the Thames River in 1828.
The first portland cement manufactured in the US was produced at a plant
in Coplay, Pennsylvania in 1871.
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4. 10/07/2012 5Cement Chemistry by M.L.Suthar

5. First –
Adhesive substances containing compounds of lime as their principal
constituent and are capable of uniting fragments of solid matters to a
compact mass.
Second –
1.Hydraulic Cement is the cement which continuously develops its strength
when kept in contact with water.
Third –
Portland Cement, is a finely ground material consisting mainly of
components like CaO, SiO2, Al2O3, Fe2O3 and Gypsum.When mixed with
water, it forms a paste that hardens and binds other materials called
aggregates together.The final product is a hard strong mass called
concrete.
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6. •Quarrying – Raw materials
•Crushing
•Grinding
•Mixing
•Calcine (900 - 1100C)
•Burned (1200 - 1400C)
•Clinker is produced
•Inter-ground with 5% gypsum (1-100 m)

- most reactive ( <50 m)
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7. Several types of Portland Cement are recognised having different
characteristics.
The most important variables are -
The Rate of Hardening.
Heat evoluation during hydration.
The resistance of the hardened cement to attack by sulphate solution.
These characteristics are influenced by the mineralogical and chemicaL
composition of the cement as well as physical factors such as fineness on
grinding.
Indian Standard Specification cover 14 types of Cement and of these 9 are
commercially produced.
Mainly is Ordinary Portland Cement (OPC), Portland Pozzolana Cement
(PPC) and Portland Slag Cement (PSC).
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8. 1. Ordinary Portland Cement -
 Cement obtained by grinding Portland Clinker with the possible
addition of a small quantity of Gypsum, and not more than five percent
of Air Entraining Agents or other agents or Improvers.
 This type of cement is further divided into three categories i.e.
 33 Grade OPC (IS:269-1987),
 43 Grade OPC (IS:8112-1989)
 53 Grade OPC (IS:12269 - 1987).
2. Portland Pozzolana Cement (IS:1489-1991 Part I & Part II) -
 An Inter-ground mixture of Portland clinker and pozzolana with the
possible addition of gypsum and uniform blend of fine pozzolana.
 The proportion of pozzolana addition varies from 15 to 35%. Such
cement has a much lower heat of hydration and is also fairly sulphate
resistant. It is particularly useful in marine structures.
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9. 3.Supersulphated Cement (IS:6909-1990)
 A hydraulic cement having Sulphuric anhydride (SO3) more than 5% and
made by inter-grinding a mixture of atleast 70% granulated blast
furnace slag, Calcium Sulphate and a small amount of Lime or Portland
Clinker. (Max. – 6.00 %)
 This type of cement is resistant to a variety of aggressive agents such as
acids, linseed oil and sea water which generally damage OPC and PSC.
4.High Alumina Cement (IS:6452-1989)
 High Alumina Cement is the cement obtained by grinding high Alumina
clinker.
 This type of cement is - Very rapid rate of development of strength and
approaches closely to its final strength in twenty four hours after
gauging.
 It is basically a refractory cement. Due to high heat of hydration and
high early strength, it may be used as a structural material in cold
regions.
 This cement is also used for emergency repairs.
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10. 5.Rapid Hardening Cement (IS:8041-1976)
 This cement is produced using high C3S clinker combined with very fine
grinding.
 Such cements are used where high early strength is necessary like pre-
cast concrete, for quick release of moulds, repair work and construction
where the form work is to be removed quickly.
6.Portland Blast Furnace Slag Cement (IS:455-1989)
 Mixture of Portland Clinker and Granulated Blast Furnace Slag with
addition of Gypsum and permitted additives or an intimate and uniform
blend of Portland Cement and finely ground blast furnace slag.
 The proportion of slag varies from 25% to 65%, depending upon the
Quality of Slag/Clinker.
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11. 7.Masonry Cement (IS:3466-1988)
 Product obtained by inter-grinding of Portland Clinker with
Pozzolanic materials, inert materials such as limestone, and waste
materials like carbonate sludge etc., Gypsum and an air entraining
plasticiser in a suitable proportion.
 It is characterised by certain physical properties, such as slow
hardening, high workability, and high water retentivity.
 It is chiefly intended for use in masonry mortars for brick, stone and
concrete block, and for plastering work.
8.Oil Well Cement (IS:8229-1989)
 Hydraulic cement suitable for use in high pressure and
temperature, in sealing water and gas pockets and setting casings
during drilling and repair of oil wells.
 Oil Well cement is generally used by the petroleum industries for
cementing gas and oil wells at high temperature and pressure.
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12. 9.Sulphate Resistant Portland Cement (IS:12330-1988)
 Portland cement with its C3A content not more than 5%, 2C3A + C4AF
not more than 25% and specific surface not less than 225 m2/kg. are
known as Sulphate Resistant Portland Cement.
 Such cements are highly resistant to sulphatic action and beneficial
where concrete is exposed to the risk of deterioration due to sulphate
attack.
10White Portland Cement (IS:8042-1976)
 In White Portland Cement, content of Fe2O3 is less than 1%. Also the
presence of other colouring agents is restricted to very small amount.
 This cement is used for
 Architectural purpose, pastel finishing and
 Decorative work in concrete.
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13. Ordinary Portland Cement (OPC) is mainly consisting of basic compounds of
Calcium Oxide (CaO), Silicon Di-oxide (SiO2), Aluminum Oxide (Al2O3),
Ferric Oxide (Fe2O3). The prevailing general chemical composition of OPC
is as follows :

GENERAL
LOI(%): 2 to 4
IR(%) : 2 to 4
SO3(%): 2 to 3
SiO2(%): 18 to 20
Al2O3(%) : 3 to 5
Fe2O3(%) : 2.5 to 3.5
CaO(%): 58 to 60
MgO(%): 2 to 3
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14. In addition to the above major components, some minor constituents like
Alkalis (Na2O & K2O), Chlorides (Cl -), Titanium Oxide (TiO2), Phosphorus
Penta-oxide (P2O5), Manganese Oxide (Mn2O3) are also present in minor
proportions.
In our cement these compounds fall in following proportions :

Na2O(%) : 0.37 to 0.47
K2O :0.44 to 0.54
Cl - :0.015 to 0.022
TiO2(%): 0.40 to 0.50
P2O5(%) : 0.15 to 0.25
Mn2O3(%) : 0.02 to 0.09

These minor components may cause major effects during burning of raw
mix and also on the quality of cement.
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15. During clinkerisition, the oxides are converted into clinker phases and
change the mineralogical structure of the material. The resultant clinker
mainly consists of following mineral compounds :
Tri-calcium Silicate (C3S) : 45 to 52
Di-calcium Silicate (C2S) : 22 to 28
Tri-calcium Aluminate(C3A) : 7 to 9
Tetra-calcium Alumino Ferrite (C4AF): 11 to 13
These clinker minerals are not pure compounds but mixed crystal phases.
Each phase has its significant effect on the Quality of cement.
The basic properties of these compounds are as follows :
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16. 1Tri-calcium Silicate (C3S)
 Tri-calcium Silicate contains all the essential properties of Portland
Cement.
 Its hydration is rapid and it undergoes an initial and final set within few
hours after gauging.
 C3S attains the greater part of its strength in early ages.
2.Di-calcium Silicate (C2S)
 Di-calcium Silicate exhibits no definite setting time and the gauged mass
sets very slowly over a period of few days.
 C2S produces little strength at early ages but gains steadily in strength
at letter ages.
3Tri-calcium Aluminate (C3A)
Tri-calcium Aluminate gives much heat.
It gives some strength at one day but shows no subsequent development
of strength.
The presence of C3A increases the rate of hydration and strength
development of C3S.
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17. 4. Tetra-calcium Alumino ferrite (C4AF)
1.Tetra-calcium Alumino ferrite hydrates rapidly but its contribution to
strength still remains uncertain.
The setting occurs in a few minutes after gauging, Some heat is also
evolved. It imparts the colour of cement.
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18. 1.STRENGTH
Strength may be define as resistance to failure and collapse under
external load.
The strength in cement is due to the cohesion of the particles of the
cement and to their adhesion to the grains of sand or other aggregates
with which they are mixed.
The development of strength depends upon many factors such as grading
of sand or aggregates,
The property of water used, the degree of mixing and the temperature
and humidity of atmosphere and above all on the chemical composition of
cement.
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19. 1Water / Cement ratio (WC)
2Degree of compaction
3.Curing conditions
4 Atmospheric Conditions
 For testing purposes, it is necessary to define all the above conditions,
and in all standard specifications,
 This is done as closely as possible.
 A specification test for strength has to fulfill two requirements. First, it
must give reproducible results when tests are carried out on the same
material in different laboratories, and secondly the result of the test
must bear some reasonable relation to the strengths that will be
developed in the actual use.
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20. 2SOUNDNESS
 Soundness of cement signifies the volume stability in the sense that
once the cement is applied on any surface, it should neither undergo
shrinkage nor expansion in volume.
 The volume stability of structure made of Portland cement is affected
by a large number of physical and chemical parameters.
 The parameter affecting the soundness are as follows :
1.Rawmix Composition
2.Mineralogical Characteristics of Rawmix
3.Burning conditions
4.Cooling Schedule
5.Clinker composition
6.Fineness of Cement
 Volume instability is termed as unsoundness and the primary causes of
unsoundness are the presence of free CaO and MgO contents beyond
certain limits.
 Le- Chatelier and Autoclave expansion tests are required to detect it.
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21. 3SETTING TIME
 Initial - The time interval between the gauging and partial loss of
plasticity is known as Initial setting time.
As soon as this ‘time’ has elapsed, the mass becomes friable and if it is
re-mixed with water, the plasticity is not restored.
Final - The time required for a gauged cement to harden and to acquire
sufficient firmness to resist a certain definite pressure is called Final
Setting Time.
Factors affecting the Setting of cement are as follows :
1.The Quantity and Quality of water used
2.The Atmospheric Conditions
3.The sulphur from the fuel used
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22. 4.FALSE SET
When the cement is mixed with water and gauged for a short time, the
material appears to set. Further working breaks up the set and the
material then exhibits a normal setting time. This phenomenon is known
as False set.
Why False set - The prime cause of the false set is the dehydration of
gypsum caused by the high temperature attained during grinding the
cement.
How - When cements showing false set are mixed with water, there is an
immediate super-saturation of the solution with CaSO4 to a much larger
extent than with normal cements.
This is indicative of presence of a dehydrated form of gypsum.
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23. Fineness -
Fine grinding of cement is valuable in two ways : first, a fine powder is
able to coat the surface of grains of sand or other material more
completely than a coarse one, so that more intimate contact of the
components of mortar is assured.
Second, the surface of solid particles. Hence, more finely ground a
cement, and greater the surface exposed in proportion to its mass, the
more rapid is the rate of hydration and the greater is the proportion of
cement which reacts.
More finely a cement is ground, the greater is the strength. The effect of
increase in fineness is proportionally much greater at early than at later
age. Increase in fineness beyond 500 m2/kg rather decreases the strength
at all ages
Equal rise in W/C ratio.
An increase in fineness also increases the gypsum requirement to control
setting and to give optimum strength.
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24. Gypsum -
Gypsum influence the rate of formation of the coagulational and
crystallisational hydration products.
Gypsum act as setting time retarter -
A cement without gypsum quickly forms a coagulational structure which
stiffens by rapid crystallisation of hydrated calcium aluminate from the
supersaturated solution resulting in quick setting.
When the gypsum is added, the Calcium Sulphoaluminate coating formed
on the anhydrous cement particles acts as a protective coating which
delays the coagulation process.
Gypsum retards the hydration of aluminates but it accelerates the
hydration of silicates so that in a properly retarded cement, the framework
of the hydrated cement paste is established by the C-S-H gel and the
resultant strength development is uniform.
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25. 5.HEAT OF HYDRATION
The reactions which are responsible for setting and hardening of cement
are accompanied with the liberation of heat. This liberated heat is known
as Heat of Hydration.
The C3A, C3S and C4AF phases mainly dominate the heat development
characteristics because their hydration reactions are very fast and are
combined with highest specific heat development.
The heat of hydration can be an important factor in concrete technology. It
can be helpful in cold weather concreting, or can be troublesome in mass
concreting work.
Reaction during Hydration -
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26. 2C
3S + 11H C
3S
2H
8 + 3CH H = -500 J/g
2C
2S + 9H C
3S
2H
8 + CH H = -250 J/g
Calcium silicates (C
3S or C
2S) + water
Calcium silicates hydrate (C-S-H) + calcium hydroxide
•Amount of CH depends on proportion of C
3
S and C
2
S
•CSH - amorphous in nature, is an inexact composition,
And is extremely fine (Colloidal).
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27. C
3A + H
2O  reacts very fast
C
3
A + H
2
O + CSH
2
(Gypsum)  reacts much slower
C
3A + 3CSH
2 + 26H  C
6AS
3H
32 H = -1350 J/g
Tricalcium Aluminate + Gypsum + Water
Ettringite
Once CSH
2 is depleted:
C
6AS
3H
32 + 2C
3A + 4H  3C
4ASH
12
Ettringite + Tricalcium Aluminate + Water
 Monosulfoaluminate
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28. •Forms same reaction as C
3A but to a lesser degree
•Uses small amount of gypsum
C
4
AF + 2CH + 14H  C
4
(A,F)H
13
+ (A,F)H
3
Ferrite + Calcium Hydroxide + Water
 Tetracalcium Hydrate + Ferric Aluminum Hydroxide
 like monosulfoaluminate amorphous
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29. 1029869C
4AF
324311212C
3
A
594212C
2S
12210458C
3
S
13 years90 days3 daysCompound
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30. Rate of heat evolution during the hydration of portland cement

31. A small change in the chemical composition of clinker may change the
Quality of cement.
Effects of chemical compounds on the quality of clinker as well as on the
quality of cement are as follows :
Lime (CaO)
Principle component of cement and it is combined with all major
components of clinker.
An increase in the proportion of lime to a certain limit, provides increased
compressive strength at early ages. If the amount of lime is further
exceeded beyond which no more lime can be combined, it may result into
increase of free lime in the resultant clinker and it causes unsoundness in
the cement.
Silica (SiO2)
The Silica in a Portland cement forms with the lime the essential
cementing components C3S and C2S. Any change in the silica content
affects the proportion of C3S and C2S which will affect both the early and
later strength of cement.
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32. Alumina and Ferric Oxide (Al2O3 & Fe2O3)
The Alumina and Ferric Oxide contents in a cement need to be
considered together. These oxides form the compounds C3A and C4AF
which are not true hydraulic cement and their value is mainly confined
to their effect in rendering burning possible at kiln temperature. They
probably make no direct contribution to the cementing action other
than accounting for the initial set and adding to the early strength. The
relative proportion of these two compounds depends upon the ratio of
Alumina and Ferric Oxide.
Magnesia (MgO)
Magnesia is a deleterious constituent of cement. The proportion of MgO
in OPC is restricted to maximum of 6% in the Indian Standard
specification. Due to slow rate of hydration, the higher content of MgO
leads to long term unsoundness of Cement.
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33. The relationship between the water/cement ratio and porosity.

34. Pictoral representation of Cement Grain