2. 2
Cement Technology Course
CEMENT TECHNOLOGY COURSE NO 58
CHEMISTRY OF PORTLAND CEMENT CLINKER
0930 - 10.15 PART 1 Graeme Moir
1015 - 10.35 INTRODUCTION TO CHEMISTRY
OF CEMENT (RESUME) Andrew Rogers
10.35 - 10.50 COFFEE
10.50 - 11.45 PART 2 Graeme Moir
11.45 - 12.30 SYNDICATE WORK
12.30 - 1315 LUNCH
3. 3
Cement Technology Course
Chemistry of Portland Cement Clinker
• Nature of Portland Cement.
• Clinkering reactions
• Control ratios (LSF, SR,AR)
• Raw mix mineralogy and homogeneity
• Minor constituents
• Determination of chemical and compound
composition
•Special clinkers
4. 4
Cement Technology Course
The nature of cement
• Cement manufacture is a basic chemical
process industry.
• It is relatively impure material and the
impurities can have a marked influence on
properties.
• It is seen as a relatively “cheap” commodity.
• Customers have increasingly sophisticated
expectations.
• Consistency of properties is vital.
6. 6
Cement Technology Course
Precalciner process developed
High efficiency separator introduced for cement grinding
X-ray fluorescence ( XRF) rapid chemical analysis
1920
1940
1960
1980
2000
Automatic kiln control using expert systems (Linkman)
Suspension preheater process introduced
Lepol (nodule) process introduced
Introduction of pneumatic blending silos for raw meal
First electrostatic precipitator installed on cement works
Paper sacks introduced for cement
High pressure roll press for cement pregrinding
New horizontal cement mill technology
LANDMARKS IN PORTLAND CEMENT PRODUCTION (CONT)
Multistage combustion - emission control
8. 8
Cement Technology Course
OUTLINE OF CEMENT MANUFACTURING PROCESS
STACK
DUST
REMOVAL
RAW
MATERIAL
STORAGE
RAW MIX
GRINDING
BLENDING
&
STORAGE
GYPSUM
CLINKER
STORAGE
CEMENT
GRINDING
MILL
PACKING
PLANT
ROTARY
KILN
BAG &
BULK
CLINKER
COOLER
PREHEATER
FAN
COAL
MILL
Pulverised
coal
Air
COAL
CEMENT
STORAGE
SILOS
Clinker
DUST
RETURN
TO
PROCESS
LIMESTONE
QUARRY
CRUSHING SHALE
QUARRY
Blue Circle
Cement
9. 9
Cement Technology Course
Sources Of Cement “Chemicals”
The sources of the basic chemicals required for
cement production are normally described as :
• Primary or calcareous for the main source of
Calcium.
• Secondary or argillaeous for the source of the
other main three.
•Tertiary for purchased chemical “adjusters”.
13. 13
Cement Technology Course
Cement Chemist’s Notation
For simplicity, cement chemists tend to
use a “shorthand” when describing the
chemical formulae of the compounds
present in cement clinker.
14. 14
Cement Technology Course
Cement Chemist’s Notation
The four principal elements are
described thus:
C Ca (Calcium)
S Si (Silicon)
A Al (Aluminium)
F Fe (Iron)
16. 16
Cement Technology Course
C
O
M
P
O
S
I
T
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.
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s
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o
r
t
h
a
n
d
2
2
2
3
3
F
I
G
U
R
E
4
20. 20
Cement Technology Course
Principal Compounds
The four major components of cement
clinker are:
C3S or Tri-Calcium Silicate or Alite
C2S or Di-Calcium Silicate or Belite
C3A or Tri-Calcium Aluminate
C4AF or Tetra-Calcium Alumino-Ferrite
21. 21
Cement Technology Course
Al
O O O
Al
Ca O Ca O
Ca O
Ca Al O
3 2 6
or
3CaO. Al O
2 3
or
C A
3
O O O
Fe
O O
O O
O O
Ca Al Fe O
4 2 2 10
or
4CaO. Al O . Fe O
2 3 2 3
or
C AF
4
PROPORTIONS OF CALCIUM, ALUMINIUM, IRON
AND OXYGEN ATOMS IN C3A AND C4AF
Note. the arrangement of the atoms shown does not attempt
to illustrate the actual crystalline structure.
C A
3
C AF
4
One formula unit consists of :
3 atoms of calcium (Ca)
2 atom of aluminium (Al)
6 atoms of oxygen (O)
One formula unit consists of :
One formula unit consists of :
4 atoms of calcium (Ca)
2 atoms of aluminium (Al)
2 atoms of iron (Fe)
10 atoms of oxygen (O)
FIGURE 7
O
O O
O
O
Ca Si O
3 5
or
3CaO.SiO2
or
C S
3
O
O
Si
O O
Ca Si O
2 4
or
2CaO.SiO2
or
C S
2
PROPORTIONS OF CALCIUM, SILICON AND
OXYGEN ATOMS IN C3S AND C2S
Note. the arrangement of the atoms shown does not attempt
to illustrate the actual crystalline structure.
One formula unit consists of :
3 atoms of calcium (Ca)
1 atom of silicon (Si)
5 atoms of oxygen (O)
C S
C S
3
2
One formula unit consists of :
2 atoms of calcium (Ca)
1 atom of silicon (Si)
4 atoms of oxygen (O)
FIGURE 8
Ca
Ca Ca
Ca Ca
O
Al Al
Al Al
Fe
Ca
Ca
Ca
Ca
Si
24. 24
Cement Technology Course
1 1 4
1 3
4 2
4
8 1
6
1 2 5
9 1
8
A
l
l
t
h
e
c
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:
-
C
4
A
F
1
p
a
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C
3
A
1
p
a
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t
C
2
S
2
p
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C
3
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1
6
p
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t
%
t
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s
c
o
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s
p
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d
s
t
o
:
-
C
4
A
F
1
0
%
C
3
A
6
%
C
4
A
F
C
3
A
C
2
S
C
3
S
F A C S
C
2
S
8
%
C
3
S
7
6
%
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
S
SS
S
S
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R
1
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N
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A
T
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R
A
T
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D
M
I
X
ILLUSTRATION OF OXIDE PROPORTIONS IN A
TYPICAL RAW MIX
25. 25
Cement Technology Course
1 1 4
1 3
5
4 1
8
2 6
1 1
8
T
h
e
a
d
d
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:
-
C
4
A
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1
p
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C
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p
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8
p
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%
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p
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d
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:
-
C
4
A
F
1
0
%
C
3
A
6
%
C
4
A
F
C
3
A
C
2
S
C
3
S
F A C S
C
2
S
n
i
l
C
3
S
8
4
%
1
ILLUSTRATION OF OXIDE PROPORTIONS IN A
TYPICAL RAW MIX
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
S
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L
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T
S
O
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L
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(
C
)
A
D
D
E
D
C
C
26. 26
Cement Technology Course
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
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C
C
C
C
C
C
C
C
C
C
C
C
C
C
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C
C
C
C
C
C
C
C
C
C
S
S S
S
S
S
S
S
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S
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S
S
S
S
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A
AF
L
S
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1
0
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S
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0
A
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1
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3
C
.
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F
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F
L
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(
C
)
A
D
D
E
D
C
C
C
C
1 1 4
1 3
5
4 1
8
1 2 6
3 1
8
T
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p
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p
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r
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s
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:
-
C
4
A
F
1
p
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C
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A
1
p
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t C
3
S
1
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p
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%
t
h
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s
c
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s
p
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d
s
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o
:
-
C
4
A
F
1
0
%
C
3
A
6
%
C
4
A
F
C
3
A
C
2
S
C
3
S
F A C S
C
2
S
n
i
l
C
3
S
8
2
%
C
(
F
r
e
e
l
i
m
e
) 2
F
r
e
e
l
i
m
e
2
%
T
h
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e
i
s
n
o
s
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l
i
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e
.
ILLUSTRATION OF OXIDE PROPORTIONS IN A
TYPICAL RAW MIX
29. 29
Cement Technology Course
limestone
CaCo3
silica
SiO2
shale/clay
(Al2O3 and SiO2)
iron oxide
Fe2O3
SCHEMATIC ILLUSTRATION OF RAW MIX
PRIOR TO HEAT TREATMENT
50 MICRONS (0.05 mm)
Note, for clarity this schematic illustration only shows
relatively large particles. In an actual raw mix a much higher
proportion of finer particles would be present.
30. 30
Cement Technology Course
FIGURE 16
SEQUENCE OF FORMATION OF CALCIUM SILICATES IN A ROTARY KILN
MATERIAL TEMPERATURE
600
800
1000
1200
1400
1600
T C
0
C S
C S
FREE LIME
QUARTZ
CaCO 3
3
2
CALCINING ZONE BURNING ZONE
MOLTEN FLUX
APPEARS
CRYSTALLISATION OF FLUX
TO YIELD C A & C AF
3 4
MOVEMENT OF MATERIAL
RELATIVE
WEIGHT
COOLING ZONE
31. 31
Cement Technology Course
SCHEMATIC ILLUSTRATION OF REACTIONS
FOLLOWING HEAT TREATMENT TO 1000 DEG C
Reaction at point of contact
between CaO and silica
to form C2S
Reaction between shale and
CaO to form C12A7 and C2S
Reaction between CaO and
iron oxide to form C2F
(ferrite) 50 MICRONS (0.05 mm)
Decarbonated limestone (CaO)
note cracks/porosity introduced
as a result of ~ 50% loss in mass
and other intermediate compounds
which are not found in the final clinker.
33. 33
Cement Technology Course
C
3
S U
n
r
e
a
c
t
e
d
C
2
S
M
o
l
t
e
n
C
3
A
a
n
d
C
4
A
F
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s
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0
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D
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C
5
M
I
C
R
O
N
S
(
0
.
0
0
5
m
m
)
p
o
r
e
34. 34
Cement Technology Course
T
Y
P
I
C
A
L
C
O
M
B
I
N
A
B
I
L
I
T
Y
C
U
R
V
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S
0 1 2 3 4 5
1
,
3
5
0
1
,
4
0
0
1
,
4
5
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1
,
5
0
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1
,
5
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F
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b
i
l
i
t
y
C
o
m
b
i
n
a
b
i
l
i
t
y
35. 35
Cement Technology Course
I
N
F
L
U
E
N
C
E
O
F
R
A
W
M
I
X
F
I
N
E
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S
S
0 1 2 3 4 5
1
,
3
5
0
1
,
4
0
0
1
,
4
5
0
1
,
5
0
0
1
,
5
5
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R
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L
I
M
E
%
T
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P
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R
A
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D
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C
5
%
P
L
U
S
9
0
M
I
C
R
O
N
S
1
5
%
P
L
U
S
9
0
M
I
C
R
O
N
S
2
5
%
P
L
U
S
9
0
M
I
C
R
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t
e
m
p
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r
a
t
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e
C
o
m
b
i
n
a
b
i
l
i
t
y
36. 36
Cement Technology Course
SCHEMATIC ILLUSTRATION OF CLINKER AT 1400 DEG C
50 MICRONS (0.05 mm)
C3S Free lime cluster C2S cluster
Clinker flux
(molten C3A and C4AF)
37. 37
Cement Technology Course
SCHEMATIC ILLUSTRATION OF CLINKER FIRED TO 1400 DEG C
AND COOLED TO AMBIANT TEMPERATURE
C3S Free lime cluster C2S cluster
C4AF (Ferrite) C3A (aluminate)
Note, the well formed and relatively large C3A and C4AF crystals
indicate that the clinker has been relatively slowly cooled
50 MICRONS (0.05 mm)
45. 45
Cement Technology Course
For optimum clinker quality:-
• The kiln feed chemistry must be of low
variability
•The raw meal must be adequately ground
•The coal ash must be uniformly
incorporated into the clinker
•The clinker must be rapidly cooled from
the burning zone temperature
47. 48
Cement Technology Course
Control Ratios
The three principal ratios used in the
cement industry are:
LSF or Lime Saturation factor
SR or Silica Ratio
AR or Alumina Ratio
48. 49
Cement Technology Course
Lime Saturation Factor
Lime Saturation Factor is a
means of describing the capacity
of the other three major elements
to totally use up the lime
(Calcium).
52. 53
Cement Technology Course
Silica Ratio
Silica Ratio is a method of describing
the amount of Silica that is present in
the mix with respect to the amounts of
Alumina and Iron
59. 60
Cement Technology Course
SENSITIVITY OF CLINKER PARAMETERS AND
MINERAL PROPORTIONS TO CHANGES IN CHEMISTRY
S
A
F
C
LSF
SR
AR
TARGET
MIX
20.9
5.6
3.0
65.7
97.8
2.43
1.87
( -0.2)
(+0.2)
MINOR
VARIATION
20.7
5.5
3.0
65.9
98.9
2.41
1.87
( -0.5)
(+0.5)
MAJOR
VARIATION
20.4
5.6
3.0
66.2
100.6
2.37
1.87
C S
C S
C A
C AF
67
9
10
9
69
7
10
9
73
3
10
9
Potential phase composition
3
2
3
4
FIGURE 26
64. 65
Cement Technology Course
•Requirement of national customers
(RMC Ltd, Tarmac, Pioneer etc.) for
cement to have the same properties
throughout the UK
•Optimisation of kiln operation
(particularly dry process/precalciner
kilns)
WHY HAS LSF AND SR
RANGE NARROWED?
65. 66
Cement Technology Course
CLINKER OXIDE RATIOS AND COMPOUND COMPOSITION OF UK AND US WORKS
DATA FOR JANUARY TO DECEMBER 1997
94 96 98 100
1.5
2
2.5
3
3.5
4
LSF
SR
92
CLINKER LSF AND SR
40 45 50 55 60 65 70
6
8
10
12
14
C3S
C3A
ABERTHAW
CAULDON
COOKSTOWN
DUNBAR
HOPE
MASONS
NORTHFLEET
PLYMSTOCK
WEARDALE
WESTBURY
ATLANTA
HARLEYVILLE
TULSA
ROBERTA
RAVENA
CLINKER C3S AND C3A
ATLANTA
HARLEYVILLE
TULSA
ROBERTA
RAVENA
ABERTHAW
MASONS
PLYMSTOCK
CAULDON
NORTHFLEET
HOPE
COOKSTOWN
DUNBAR WEARDALE
WESTBURY
BOWMANVILLE
ST MARYS
BOWMANVILLE
ST MARYS
FIGURE 28
66. 67
Cement Technology Course
9
4 9
6 9
8 1
0
0
1
.
5
2
2
.
5
3
3
.
5
4
L
S
F
S
R
9
2
C
L
I
N
K
E
R
L
S
F
A
N
D
S
R
P
L
A
N
T
S
O
U
T
S
I
D
E
U
K
A
N
D
U
S
D
A
T
A
F
O
R
2
0
0
0
E
W
E
K
O
R
O
S
A
G
A
M
U A
S
H
A
K
A
R
A
W
A
N
G
K
A
N
T
H
A
N
L
A
N
G
K
A
W
I
M
I
L
A
K
I
V
O
L
O
S
H
A
L
K
I
S
F
O
R
T
U
N
E
R
E
P
U
B
L
I
C
I
L
I
G
A
N
A
L
E
X
A
N
D
R
I
A
U
K
P
L
A
N
T
S
U
S
P
L
A
N
T
S
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Cement Technology Course
FIGURE 30
1.5 2 2.5 3 3.5 4 4.5
1350
1400
1450
1500
1550
SR
COMBINABILITY
TEMPERATURE
C
1.5 2 2.5 3 3.5 4 4.5
1350
1400
1450
1500
1550
SR
(b)
(a)
VARIATION OF COMBINABILITY TEMPERATURE OF WORKS MATERIALS WITH SILICA RATIO
LSF 96%, residue on 90 micron sieve 8%.
AR ratios between 1.1 and 2.8 AR ratios between 1.8 and 2.2
0
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Cement Technology Course
• Portland cement consists mainly of
calcium silicates
•The main (primary) raw material is a
source of lime such as limestone or chalk
•Secondary (and tertiary) materials provide
silica, alumina and iron oxide
•The raw mix must be ground to a fineness
which is appropriate for the raw materials
and thoroughly blended - coarse silica
particles must be avoided
SUMMARY
88. 89
Cement Technology Course
SUMMARY (cont)
•The fuel must be ground to the required
fineness and absorbed uniformly in the clinker
• Reducing conditions must be avoided
•The clinker should be cooled rapidly from the
burning zone
•Portland cement contains 4 minerals in the
following typical proportions:
C3S 50 - 60% C3A 7 - 12%
C2S 14 - 24% C4AF 7 - 10%
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Cement Technology Course
SUMMARY (cont)
•The raw mix and clinker chemistry is
controlled using the ratios of LSF, SR and AR
• Differences in clinker chemistry between
works have reduced over the years
•C3S is more reactive than C2S and is mainly
responsible for strength development up to 14
days
•The levels of certain minor constituents must
be closely controlled to optimise production
and ensure satisfactory cement properties
•The potential environmental impact of raw
materials must be considered
