Only for CBPBU UG Syllabus

1. Cement
Cement is the general term given to the
powdered materials which initially have
plastic flow when mixed with water or other
liquid, but has the property of setting to a
hard solid structure in several hours with
varying degree of strength and bonding
properties
Classification of Cements: Portland Cement, High
Alumina Cement, Slag Cement, Acid resisting cements,
Super sulphate cement, White cement, Colored cement
Sorel’s Cement, Roman Cement, Pozzolan Cement, Blended
Portland cement
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2. Ingredients and their role:
Ingredients
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3. Ingredients and its role
Ingredient Percentage in cement
Lime 60-65
Silica 17-25
Alumina 3-8
Magnesia 1-3
Iron oxide 0.5-6
Calcium Sulfate 0.1-0.5
Sulfur Trioxide 1-3
Alkaline 0-1
Functions of Cement Ingredients:
Lime:
•Lime is calcium oxide or calcium hydroxide.The
presence of lime in a sufficient quantity is required to
form silicates and aluminates of calcium.
•Deficiency in lime reduces the strength of the property
to the cement.
•Deficiency in lime causes the cement to set quickly
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4. Ingredients and its role
Silica:
A sufficient quantity of silica should be present in
cement to dicalcium and tricalcium silicate.
Silica imparts strength to cement.
Silica usually presents to the extent of about 30
percent cement.
Alumina:
Alumina imparts quick setting property to the cement.
Clinkering temperature is lowered by the presence of
the requisite quantity of alumina.
Excess alumina weakens the cement.
Magnesia:
Magnesia should not be present more than 2% in
cement.
Excess magnesia will reduce the strength of the cement.

5. Ingredients and its role
Iron oxide:
Iron oxide imparts color to cement.
It acts as a flux.
At a very high temperature, it imparts into the chemical
reaction with calcium and aluminum to form tricalcium
alumino-ferrite.
Tricalcium alumino-ferrite imparts hardness and
strength to cement.
Calcium Sulfate:
This is present in cement in the form of
gypsum(CaSO4.2H2O)
It slows down or retards the setting action of cement.
Sulfur Trioxide: Chemical formula is SO3
It should not be present for more than 2%.
Excess Sulfur Trioxide causes the cement to unsound.
Alkaline:
It should not be present more than 1%.
Excess Alkaline matter causes efflorescence
.

6. Manufacturing process of cement:
Flowchart for cement manufacture

7. Manufacturing process of cement:
Reaction involves in manufacturing process:
The reactions that take place (after evaporation of free water) between the reactants in
the kilning phase of cement making process are as follows:
Clay Decomposition:
Si2Al2O5(OH)2 → 2 SiO2 + Al2O3 + 2 H2O (vapor)
KAlSi3O8 (orthoclase) + 0.5 SO2 + 0.25 O2 → 3 SiO2 + 0.5 Al2O3 + 0.5 K2SO4
Dolomite Decomposition:
CaMg(CO3)2 → CaCO3 + MgO + CO2
KMg3AlSi3O10(OH)2 + 0.5 SO2 + 0.25 O2 → 0.5 K2SO4 + 3 MgO + 0.5 Al2O3 + 3 SiO2 + H2O
(vapor)
Low-Temperature Calcite Decomposition:
2 CaCO3 + SiO2 → Ca2SiO4 + 2 CO2
2 MgO + SiO2 → Mg2SiO4
Ca5(PO4)3OH + 0.25 SiO2 → 1.5 Ca3(PO4)2 + 0.25 Ca2SiO4 + 0.5 H2O (vapour)
Alumina and Oxide Reaction:
12 CaCO3 + 7 Al2O3 → Ca12Al14O33 + 12 CO2
4 CaCO3 + Al2O3 + Fe2O3 → Ca4Al2Fe2O10 + 4 CO2
4 CaCO3 + Al2O3 + Mn2O3 → Ca4Al2Mn2O10 + 4 CO2
The reaction of Remaining Calcite:
CaCO3 → CaO + CO2
Sintering:
Ca2SiO4 + CaO → Ca3SiO5

8. Setting of Cement
When water is mixed with cement, a smooth paste is produced
that remains plastic for a short time. During this period, the
paste can be disturbed and remixed without injury. As the
reaction between water and cement continues, the plasticity of
the cement paste is lost. This early period in the hardening of
cement is known as ‘Setting of Cement’.
Reaction involving during the setting of cement

9. Notes on Special type of Cement
White Cement: The color of the ordinary Portland cement is
grayish-black due to the presence of iron oxide present as one of
the constituents. If iron oxide can be avoided by suitable selection
of raw materials, it is even possible to get white cement. Hence, if
low iron feldspar, limestone and gypsum are fused together at
900C and then leached with water, the fusion of the leached
product at 1400C gives white cement. This is mainly used in
decorative construction
Colored Cement: Colored cement can be obtained by mixing
white or grey Portland cement with suitable colored pigments,
which must have fine state of subdivision, color and chemical
composition not destroyed by the components of the cement. For
getting blue, green, black and red cements, the pigments that are
respectively added are cobalt blue, chromium oxide, carbon black
and iron oxide.

10. Notes on Special type of Cement
Pozzolan Cement: To save on Portland cement, a universal but expensive
cement, mixed cement is made, which can only be used with certain
limits. Pozzolanic cements are mixtures of portland cement and a
pozzolanic material that may be either natural or artificial. The natural
pozzolanas are mainly materials of volcanic origin but include some
diatomaceous earths. Artificial materials include fly ash, burned clays, and
shales. Portland-pozzolana cement shall be manufactured either by
intimately inter-grinding Portland cement clinker and fly ash or by
intimately and uniformly blending Portland cement and fine fly ash. The
fly ash constituent shall not be less than 10 percent and not more than 25
percent by mass of Portland-pozzolana cement.
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