introduction to cement raw material

1. 1
CHAPTER - 1
1. RAW MATERIALS.
The process of the cement manufacturing consists in the incorporation of the raw materials to
form a homogeneous mixture. The Portland Cement manufacture is prepared by burning of
the raw materials mixture in the rotary kiln to form the clinker.
The raw materials for the cement industry are minerals of the natural origin. The production
of the cement clinker depends on the selected standard used by the cement factory which
includes the chemical specification for the clinker and for the cement, in addition to the
physical properties and the requirement for the used cement.
The production of the high quality of the Portland cement requires a good raw material. The
basic ingredients for the production of the Portland cement clinker consists of the Limestone,
Marble, Chalk, Shellac, Clay, Sand and Iron Ore or other additive materials. The number of
the raw materials depends upon the composition of these materials and the types of the
cement to be produced. The main constituents of the Portland cement raw materials based on
their chemical composition which consists mainly of the four major chemical compositions :
Calcium Oxide ( CaO) or Lime, Silica Dioxide (SiO2), Aluminum Oxide ( Al2O3) and Ferric
Oxide (Fe2O3). The other minor components, to some extent, which can be incorporated in
the raw materials are SO3, MgO, K2O, Na2O, CL, TiO2, MnO3, P2O5 and Cl which are in
small quantity.
The concentration of the individual chemical components have to be adjusted carefully in
order to obtain the requested raw mix suitable for the production of the Portland cement
clinker. The proportion of the components needed for the production can not be found in one
raw material, therefore it is necessary to select and to incorporate other raw material and to
have an homogenous mixture to met the requirement for a good burning in the kiln to form
the clinker.
1.1 The Calcareous Components.
Usually the calcareous components are distinguished by its chemical composition, it means
by its content of the carbonate. The carbonate content of the calcareous components used in
the cement manufacturing is higher than 75 %. A great variety of the rocks which are
classified as calcareous are such as Limestone, Marl, Chalk etc. which can have the same de-
carbonisation ( Titration) value determined by the chemical analysis. We have to notice that
the method for the determination of the Carbonate includes in all the carbonate is not
identical with Ca CO3 content, but it includes other Carbonates such as MgCO3, FeCO3, and
Na CO3 etc.
1.1.1 Limestone.
The Calcium Carbonate (CaCO3) is wide spreaded in the nature. The calcite is the essential
constituent of the limestone. The calcite is the purest grades of the limestone and it is found
in the nature in form of veins. May be the calcium Carbonate is the main component of the
High Limestone. Other than the Limestone, the Marble and the Chalk have also the common
form of the calcium carbonate.

2. 2
The limestone having 53 % or more CaO is a high quality limestone. The limestone having
more than 10 % or more MgCO3 is called dolomitic limestone, and when the MgCO3
level reach 45 % or more, the limestone is known as dolomite.
The limestone is of a predominantly fine grained crystalline structure. The hardness of the
limestone depends on its geological age. Usually , the limestone is more hard for the older
geological formation.
Limestone deposit is found in many areas of the worlds. Most of the limestone used as a raw
material for clinker production have a certain percentage of other sediments like the Clay
substance, the Iron compound, the sand, the Quartz. Also it may be mixed or contaminated
with other sediment rocks of the surrounding area.
For the evaluation of the Limestone quality for the cement clinker production, it is advised
for the calculation to use the lime saturation factor LSF, while it gives a very clear figure in
respect of the chemical composition, because in addition to the lime, the Silica, the Alumina
and the Iron content are considered in this factor. The CaCO3 content is not sufficient to
decide whether the limestone is a suitable quality to produce a good clinker or not. The table
( 1.1 ) presents the main composition of the typical High Limestone and Table (1.2) presents
the main composition of the typical Low Limestone in the cement Production.
1.1.2 Marl.
The Marl is a sedimentary rocks developed by the sedimentation of the Calcium carbonate,
the Clay and the Shellac or Schist substance. The composition of the Marl is widely varied
and depends from one location to the other, therefore it is frequently used for the cement
clinker production. The Marl is softer than the Limestone, it means that the hardness of the
Marl is lower than that of the Limestone and it is easy to crush. The Marl is an excellent raw
material for the clinker production.
The Marl has a high water absorption factor which can reach 25 % by weight of the Material.
Table (1.3) shows the chemical composition of a certain types of the Marl used for the
production of the Portland Cement Clinker.
1.1.3 Dolomite.
The dolomite is a Calcite limestone which become dolomitized by the action of the
Magnesium bearing solution. The dolomitization of the limestone may happen during the late
diagnoses of the consolidated rocks under the influence of the pore solution. The dolomite is
used as magnesium limestone when the content of the Mg CO3 is not exceed 25 %.
Table (1.4) shows the Chemical composition of a certain types of the dolomite of low and
medium content of MgO.

3. 3
Table - 1.1 Typical High Limestone Composition.
Components 1 2 3 4 5 6 7 8 9
SiO2 0.25 5.04 2.16 0.70 6.29 3.98 2.07 1.71 2.16
AL2O3 0.15 1.27 1.09 0.68 1.35 1.01 0.20 0.35 1.09
Fe2O3 0.13 0.79 0.54 0.08 1.28 0.56 0.08 0.11 0.54
CaO 55.31 52.28 52.72 54.54 46.57 52.12 51.77 51.58 52.72
MgO 0.40 0.01 0.68 0.59 0.78 0.50 2.02 1.88 0.68
K2O 0.04 0.17 0.26 0.01 0.30 0.15 0.02 0.08 0.26
Na2O 0.03 0.25 0.11 0.16 0.20 0.14 0.19 0.09 0.11
SO3 0.02 0.44 0.02 0.25 0.26 0.12 0.34 0.06 0.02
LOI 43.66 40.41 42.39 42.90 41.34 41.45 43.53 44.12 42.39
Balance 0.01 -0.66 0.03 0.09 -1.07 -0.03 -0.22 0.02 0.03
Total 100 100 100 100 100 100 100 100 100
Table - 1.2 Typical Low Limestone Composition.
Components 1 2 3 4 5 6
SiO2 20.00 13.23 17.32 15.98 15.40 15.40
AL2O3 7.71 4.87 4.41 7.03 6.75 6.28
Fe2O3 3.17 2.27 2.80 2.79 1.92 3.00
CaO 35.87 42.12 41.48 37.76 42.60 38.17
MgO 1.30 0.90 0.78 3.21 1.16 1.60
K2O 0.82 0.30 0.32 0.38 0.31 0.60
Na2O 0.20 0.13 0.18 0.22 0.17 0.16
SO3 1.71 0.06 0.75 0.08 0.15 0.50
LOI 29.22 35.72 33.41 32.45 31.62 34.88
Balance - 0.40 -0.19 0.10 -0.08 -0.59
Total 100 100 100 100 100 100
Table - 1.3 Marl.

4. 4
Components 1 2 3 4 5 6 7 8 9
SiO2 1.83 2.8 4.44 3.12 21.32 16.86 19.14 27.98 32.01
AL2O3 0.29 0.17 0.01 0.48 4.14 3.83 4.15 10.87 7.31
Fe2O3 1.09 0.09 0.04 0.21 1.64 1.11 3.58 3.08 4.83
CaO 52.09 51.0 52.38 51.49 39.32 42.58 37.28 30.12 30.22
MgO 2.38 2.8 1.04 2.28 0.75 0.62 3.00 1.95 0.66
SO3 0.08 0.01 0.22 0.06 0.04 0.08 0.25 0.70 0.2
K2O 0.07 0.01 0.08 0.05 0.06 0.66 0.44 0.20 0.12
Na2O 0.03 0.03 0.03 0.03 0.08 0.12 0.82 0.33 0.25
LOI 42.10 42.7 41.7 42.82 32.62 34.66 31.28 24.68 24.37
Balance 0.04 0.39 0.06 0.08 0.03 -0.52 0.06 0.09 0.03
Total 100 100 100 100 100 100 100 100 100
1.2 Argillaceous Component.
The constituents of the calcareous component don’t contain the proportion needed for the
production of the good clinker quality. The addition of the argillaceous component is
necessary to cover the deficiency of the calcareous component. The argillaceous component
basically supply SiO2 , Al2O3 and Fe2O3.
A large number of the argillaceous materials types are considered as potential raw materials
for the cement clinker production, such as Clay, Claystone, Mudstone, Shale etc.
1.2.1 Clay.
The other important raw materials for the production of the cement clinker is the clay. It is a
mixture of different components such as the Alumina, Silicate and other Chemical
constituents. The primary clay sediments contains clay minerals - Kaolinite, calcite, and
Quartz. The chemical composition of the clay may vary from one soil bearing to the other,
from those close to pure clay to that containing a variety of chemical admixture such as Iron
Hydroxide or Iron Sulfide.
The SiO2 is present in combination with Alumina, Iron Ore and other elements in form
Silicates or Aluminates. The silt, the clay or the shale are used in the cement clinker
production as raw materials components. It contain a certain amounts of Quarts, calcite and
other varieties of sand and calcareous components.
The percentage of the Iron Oxide content in the Clay is an indication for the color of the clay,
but there are other Organic matters which give the clay different colors.

5. 5
Table (1.5) shows the chemical composition of the various Schist / Schist which is similar to
the clay material whereas the Table (1.6) shows the typical chemical composition of various
clays used for the Portland cement clinker production.
Table - 1.4 Chemical Composition of the Dolomite.
Components 1 2 3 4 5 6 7 8
SiO2 4.93 7.51 14.74 7.40 8.47 9.2 2.76 7.90
AL2O3 2.11 1.93 0.92 0.80 0.85 0.67 0.35 0.69
Fe2O3 0.22 0.28 0.75 0.33 0.33 0.26 0.15 0.26
CaO 34.18 31.09 30.28 35.77 35.77 31.00 43.90 31.00
MgO 17.43 15.66 16.34 14.33 14.33 16.7 12.94 16.70
SO3 0.10 0.11 0.35 0.09 0.09 0.01 0.03 0.01
K2O 0.60 0.41 0.58 0.11 0.11 0.05 0.13 0.05
Na2O 0.02 0.01 0.03 0.01 0.01 0.01 0.02 0.01
TiO2 0.01 0.01 0.01 0.04 0.04 0.05 0.03 0.05
MnO2 0.03 0.03 0.04 0.05 0.05 0.04 0.03 0.04
P2O5 0.11 0.11 0.10 0.13 0.13 0.09 0.08 0.09
LOI 40.20 42.75 35.78 40.00 40.00 41.9 39.55 41.90
Balance 0.06 0.1 0.08 0.94 -0.18 0.02 0.03 1.30
Total 100 100 100 100 100 100 100 100
1.2.2 Mica.
The Mica is a cleavage and Glossy mineral. It is abundant in the eruptive and metamorphic
rocks. The Mica is formed from the Aluminum Silicate and of Potassium. The Muscovite is
commonly called white Mica. The thin films muscovite ore usually greenish, brown or
reddish color. Mica is a good resistant to heat. The Mica film are not only impervious to the
fire, water, acid, but it is also constant in volume under the high heat or under the extreme
cold. The Mica is distinguished from other platy mineral by the flexibility of the sheets.
The Mica is one of the most difficult mineral to grind, but the strong heating or the excessive
weathering make the Mica easier to grind.
Table - 1.5 Chemical Composition of Various Schist / Schist / Shale / Shellac.

6. 6
Components 1 2 3 4 5 6 7 8
SiO2 59.90 55.44 77.29 55.67 61.55 60.9 71.10 57.29
AL2O3 16.66 17.83 12.02 21.50 16.50 17.7 12.70 18.43
Fe2O3 5.84 7.00 2.62 9.00 6.70 6.7 3.90 7.05
CaO 1.94 5.87 1.24 0.89 2.17 1.2 1.50 5.23
MgO 2.28 2.60 0.36 2.81 2.8 3.0 1.94 2.37
SO3 0.8 0.6 0.3 - 0.46 0.12 0.01 0.13
K2O 2.48 1.65 1.88 4.56 2.00 2.2 3.2 1.57
Na2O 1.00 0.43 1.57 0.82 0.68 0.47 3.10 1.39
Cl - - 0.1 0.1 0.01 0.03 0.01 0.01
TiO2 - - - - 0.01 0.89 0.53 0.66
MnO2 - - - - 0.02 0.03 0.07 0.56
P2O5 - - - - 0.06 0.15 0.01 0.04
LOI 9.10 9.18 1.13 4.65 7.00 6.5 2.4 5.27
Balance - -0.60 - - 0.04 0.11 -0.47 -
Total 100 100 100 100 100 100 100 100
1.2.3 Chalk.
The chalk is a sedimentary rock. Geologically it is a young formation consisting of
essentially of calcareous shells. The chalk is a soft earthy limestone of organic origin,
friable, fine grained , light colored. Due to the property quality, the chalk is selected as a raw
material for the cement production. For the chalk quarrying, the rocks blasting is not required
also the crushing process is abundant which reduce considerably the cement production cost.
In some deposits the content level of the calcium carbonate reach 98 - 99 %. The content of
the SiO2, AL2O3 and MgO is very low. Table (1.7) shows a typical chemical composition of
the Chalk.
1.2.4 Feldspars ( Silicate Aluminum)
The feldspars are a compound of the Silica and Aluminum basis. It is the common mineral in
igneous and metamorphic rocks such a granites. The feldspars are the most abundant
minerals in the crust of the earth, its particles show smooth surface. The smooth cleavage
shows fine parallel lines. The alkali of the feldspar consists of the potassium or Sodium
which acts as a mineralize and flux. The hardness of the feldspars is lower than that of the
Quartz. The various members of the feldspars groups is differentiated by the chemical
composition and crystallographic properties of each group.
Table - 1.6 Chemical Composition of Various Clay.

7. 7
Components 1 2 3 4 5 6
SiO2 52.97 60.08 60.48 48.59 67.29 51.28
AL2O3 14.57 21.42 17.79 17.59 8.97 16.58
Fe2O3 6.72 6.78 6.77 8.42 4.28 7.51
CaO 5.28 0.05 1.61 7.17 7.27 5.67
MgO 3.41 1.86 3.10 3.40 1.97 3.41
SO3 1.48 1.98 0.21 1.15 0.32 1.40
K2O 2.53 3.40 2.61 0.75 1.20 0.72
Na2O 1.26 0.85 0.74 0.38 1.52 0.50
LOI 11.44 5.10 6.65 12.30 7.19 12.57
Balance 0.34 -1.52 0.04 0.25 -0.01 0.36
Total 100 100 100 100 100 100
Table – 1.7 Chemical composition of the Chalk
Compo-
nents SiO2 AL2O3 Fe2O3 CaO MgO SO3 K2O Na2O LOI
% 1.14 0.28 0.14 54.64 0.48 0.07 0.04 0.09 43.04
Since the feldspar is a compound of Aluminum - Silicate, therefore, it is another source for
the Silica (SiO2) which can be used in the Portland cement clinker production.
The feldspar which the alkali constituents are present in its structure, it acts as flux and
lowering the temperature required to promote the silica availability to combine with the
clinker compound during the sintering.
1.3 Additive Materials.
Some raw materials for the Portland cement production don’t have a sufficient constituents
for the prosper composition of the raw mixture to conform to the standard of the cement
specification. To compensate the deficiency of the constituents, it is necessary to add some
corrective ingredients.
Using the corrective materials means increasing the production cost, because these corrective
materials, in case of not availability in site, will be transported / imported from outside the
factory. For that the poor composition in the raw materials should be concentrated at high
level in the corrective materials.

8. 8
The corrective ingredient added to the raw mix will improve the material burnability, the
clinker fluidity, it will reduce the clinker balls formation in the Kiln etc.. or to produce a
special cement.
The most corrective materials used to correct the deficiency of the raw mix are :
- Iron ore or pyrite which have a concentration of Fe2O3 more than 60 %.
- Bauxite which have a concentration of AL2O3 more than 40 %.
- Quartz sand or Sandstone which have a concentration of SiO2 more than 60 %.
1.3.1 Iron Ore.
The ferric Oxide Fe2O3 content in the Portland Cement occur in small amount. The ferric
Oxide is present in the limestone, in the Clay and in the shellac. The presence of the Fe2O3 is
of a great importance, because its character in the process technology is similar to the
Alumina and act as an acid radical in the cement clinker. In many case and may it is
frequently that the presence of the ferric Oxide in the limestone, the Clay or the Shellac does
not satisfy the requirements of the raw mix for the good pyro-process of the cement clinker
production, therefore and for better burnability of the raw mix, it will be necessary that the
Fe2O3 level in the raw mix to be supplemented by a material which is rich in the ferric Oxide
constituent such as the Iron Ore (Table 1.8).
The ferrous oxide is soluble in CaO, and may also growth of large CaO under reduction.
Table - 1.8 Chemical Composition of Iron Ore.
Components 1 2 3 4 5 6 7 8
SiO2 20.11 34.06 18.25 9.17 17.19 18.56 36.15 16.35
AL2O3 5.05 6.12 5.04 6.64 4.58 3.69 3.48 6.06
Fe2O3 63.41 47.72 63.52 69.40 65.95 64.85 48.98 65.40
CaO 1.40 0.92 2.02 1.74 1.51 1.48 1.09 2.05
MgO 0.30 0.53 0.31 0.60 0.32 0.38 0.22 0.4
SO3 0.05 0.25 0.10 0.04 0.10 0.02 0.1 0.05
K2O 0.03 0.10 0.04 0.16 0.12 0.05 0.08 0.10
Na2O 0.25 0.19 0.30 0.25 0.27 0.22 0.17 0.12
TiO2 0.01 0.13 0.11 0.15 0.20 0.18 0.21 0.20
Mn2O3 0.05 0.12 0.09 0.20 0.15 0.10 0.20 0.08
P2O5 0.01 0.07 0.05 0.09 0.10 0.12 0.19 0.11
Cl 0.03 0.05 0.07 0.16 0.12 0.08 0.11 0.09
LOI 9.37 9.71 10.14 11.4 9.37 10.24 8.94 9.16
With the partial reduction of the iron that is followed by a subsequent re-oxidation which has
not penetrated to inside the clinker granulated surface, the clinker color is black outside but it
is yellow or brown in the interior of the clinker grain.
1.3.2 Sandstone.

9. 9
The sandstone is a material component used in the cement clinker production (Table 1.9) to
supply the raw mix by the pure silica where there is in need. The sandstone is very poor of
the Aluminum and of the Iron ore.
Table – 1.9 Chemical composition of the Sandstone.
Components 1 2 3 4 5 6 7 8 9
SiO2 50.85 87.28 82.15 79.04 83.62 86.61 81.12 85.41 83.37
AL2O3 7.95 3.58 6.25 9.7 6.26 4.52 8.34 5.22 6.21
Fe2O3 3.78 4.32 6.42 2.35 3.84 4.44 3.26 2.95 3.12
CaO 11.65 1.48 1.34 3.55 2.34 1.37 3.29 2.46 2.92
MgO 2.10 0.40 0.80 1.65 0.82 0.49 0.45 0.77 1.20
SO3 1.46 0.07 0.10 0.10 0.10 0.10 0.08 0.09 0.16
K2O 3.77 0.03 0.03 0.02 0.08 0.07 0.19 0.01 0.12
Na2O 0.64 0.13 0.10 0.14 0.13 0.12 0.11 0.12 0.15
TiO2 0.40 0.09 0.10 0.06 0.07 0.04 0.08 0.07 0.06
Mn2O3 0.08 0.02 0.01 0.02 0.01 0.01 0.01 0.01 0.01
LOI 17.29 2.50 2.69 2.95 2.72 2.15 3.09 2.87 2.73
The sandstone is a substance very hard to burn, therefore it is necessary to be fine grinded.
But the Sandstone is also a very abrasive material and wear out very fast the grinding media
balls, the rollers of the roller press, and the tires and the turn table of the vertical roller mills.
For that it is recommended to use the minimum possible amount of the sandstone in the raw
mix.