Ordinary portland cement

MANUFACTURING
ORDINARY PORTLAND
CEMENTPresented by
Aglaia

Definition of OPC
 Cement can be defined as the bonding material having cohesive &
adhesive properties which makes it capable to unite the different
construction materials and form the compacted assembly.
 Ordinary/Normal Portland cement is one of the most widely used type
of Portland Cement.
 The name Portland cement was given by Joseph Aspdin in 1824 due to
its similarity in colour and its quality when it hardens like Portland
stone.
 Portland stone is white grey limestone in island of Portland, Dorset.

Production & Manufacturing
 Today, Ordinary Portland cement is the most widely used building
material in the world with about 1.56 billion tones produced each
year.
 Annual global production of Portland cement concrete is around 3.8
million cubic meters per year.

Manufacturing Raw Materials
1. Calcareous (material having content of lime)
2. Argillaceous (material having contents of silica & alumina)
3. Gypsum

Process
 Cement is usually manufactured by two processes:
1. Wet process
2. Dry process
 There are five stages in manufacturing of cement by wet process:
1. Crushing and grinding of raw material
2. Mixing the material in proportion
3. Heating the prepared mixture in rotary kiln
4. Grinding the heated product known as clinker
5. Mixing and grinding of cement clinker with gypsum

Crushing and Grinding
 In this phase, soft raw materials are first crushed into
suitable size.
 This is done usually in cylindrical ball or tube mills
containing the charge of steel balls

Mixing the Material
 In this part, the powdered limestone is mixed with the clay paste in
proper proportion (75%=lime stone; clay=25%).
 The mixture is then grounded and made homogeneous by mean
of compressed gas.
 The resulting material is known as slurry having 35-40% water.

Heating the slurry in rotary kiln:
 Slurry is then introduced in rotary kiln with help of conveyor.
 The rotary kiln consists of large cylinders 8 to 15 feet in diameter &
height of 300-500 feet.
 It is made with steel & is usually lined inside with firebricks.
 Kiln rotates at the rate of 1-2 revolution per minute.
 In rotary kiln, slurry is passed through different zones of temperature.
 This whole process in kiln usually covers 2 to 3 hours.

 Different temperature zones are as under:
Preheating Zone
 In this zone, temperature is kept at 500 degree Celsius & usually the
moisture is removed & clay is broken into silica, aluminum oxide, iron
oxide.
Decomposition Zone
 Temperature is raised up to 800 degree Celsius. In this zone lime stone
decomposes into lime and CO2.
Burning Zone
 In this zone temperature is maintained up to 1500 degree Celsius and the
oxides formed in above zones combine together and form respective
silicate, aluminates & ferrite.
Cooling Zone
 This is last stage where the whole assembly cooled is up to 150 to 200
degree Celsius.

Clinker Formation
 The product which is obtained from the rotary kiln is known as the
cement Clinker.
 Clinker is usually in the form of greenish black or grey colored
balls.

Grinding the Clinker
 The Cement Clinker is then air cooled.
 The required amount of Gypsum (5 %) is ground to the fine
powder, and then mixed with the Clinker.
 Finally cement is packed in bags and then transported to the
required site.

Setting and Hardening:
 When ordinary Portland cement is mixed with water its chemical
compound constituents undergo a series of chemical reactions that
cause it to set.
 These chemical reactions all involve the addition of water to the basic
chemical compounds.
 This chemical reaction with water is called "hydration".
 Each one of these reactions occurs at a different time and with different
rates.
 Addition of all these reactions gives the knowledge about how Ordinary
Portland cement hardens and gains strength.

 Those compounds and their role in hardening of cement are as
under:
 Tri-calcium silicate (C3S)
 Hydrates and hardens rapidly and is largely responsible for initial set
and early strength. Ordinary Portland cements with higher
percentages of C3S will exhibit higher early strength.
 Di-calcium silicate (C2S)
 Hydrates and hardens slowly and is largely responsible for strength
increases beyond one week.

 Tri-calcium aluminate (C3A)
 Hydrates and hardens the quickest.
 It liberates a large amount of heat almost immediately and contributes
somewhat to early strength.
 Gypsum is added to Ordinary Portland cement to retard C3A hydration.
 Without gypsum, C3A hydration would cause ordinary Portland cement to
set almost immediately after adding water.
 Tetra-calcium alumino-ferrite (C4AF)
 Hydrates rapidly but contributes very little to strength.
 Most ordinary Portland cement color effects are due to C4AF.

Uses of OPC (Ordinary Portland Cement)
 It is used for general construction purposes where special properties
are not required.
 It is used for the reinforced concrete buildings, bridges, pavements,
and where soil conditions are normal.
 It is used for most of concrete masonry units and for all uses where
the concrete is not subject to special sulfate hazard or where the heat
generated by the hydration of cement is not objectionable.
 It has great resistance to cracking and shrinkage but has less
resistance to chemical attacks.

Thank you
For more…. Mail to aglaiaconnect2018@gmail.com

Ordinary portland cement

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