Cement (Chapter 3)

Adigrat University
Engineering and Technology Collage

Chemical Engineering Department
Process Industries-II
Lecture Note
Chapter -3
Prepared By: Basha Mekonnen
INTRODUCTION
• Cement is a fine gray powder, when it reacted with water hardens
to form a rigid chemical mineral structure which gives concrete
with high strength. Cement is in effect the glue that holds concrete
together.
• Portland cement ( often referred to as OPC ) is the most common

type of cement in general use around the world.
• Basic Raw materials needed for cement production are:

Limestone( CaCO3), Sand (SiO2), Shale/clay ( SiO2, Al2O2, Fe2O3)
Iron Ore (Fe2O3) AND Gypsum.

INTRODUCTION
• Limestone is a common sedimentary rock exposed on the surface

of the earth surface. It is mainly chemically composed of CaCO3
and trace amount .of SiO2, Al2O3,Fe2O3 & MgO.
• Physical Property of limestone: pure limestone has white color and

gray color, but limestone with impurities will have yellowish color,
blackish and redish.
• Physical property of clay, shale: has brown color, and has 45-55 %
SiO2 and should have proper water absorption characteristics.
Cement Manufacturing Process
• The main operation involved in the manufacturing of cement are:
1. Quarrying Limestone and cement rock ( clay) from their source
2. Grinding and crushing of those raw materials separately
3. Raw Mix Preparation
4. Burring and Killing of the grind raw mix in kiln to get clinker
5. Mixing of gypsum and Grinding of the mixture of gypsum and
clinker to produce cement in powder form.

• In cement manufacturing technology, there are two types of
processes namely: Wet and Dry processes.
• Wet process: Clay limestone and water will mix together in the
wash mill tank to further pulverized to prepare the raw mix. The
main feature of this process is water is added during the milling
process in addition to limestone and clay.
• Dry Process: Only clay and limestone are fed together in to a mill
to reduce the size of the raw mix to appropriate size.
• N.B in both cases additional minerals or additives may be added

to the raw mix during milling process.
Manufacturing process has six basic steps;
1. Quarrying: the raw material for cement manufacture should be
mining from their source and stored separately.
• 80 % Lime stone ( CaCO3 ) and 20 % clay/shale ( SiO2, Al2O3 and
Fe2O3) should supply to the factory. So the reserves must be
according to the consumption.
• Basically the lime and silica provides the main strength of the
cement, while iron reduces the reaction temperature and gives
the cement it gray color.
• since lime stone is the most predominant raw material the plant
should be located near to the lime quarrying site.
2. Raw Milling (Raw Mill Preparation): this step is involved based on
the process used. If we use wet milling, limestone, clay and water are
mixing together and mill to give raw mix fed to the next process.
But if we use dry process only clay and limestone will mix together
and further mill to give raw mix.
Raw mill preparation has the following basic aims:
1. to obtain the correct chemical composition
2. to achieve the desired/ proper particle size to ensure optimum

fuel efficiency in the cement kiln and strength in the final concrete
product.
3. Pyro processing ( Kilning): This is the process that give the
characteristics of cement.
The finely ground material is dried, heated ( to enable the sintering

reaction to takes place) .
The raw mill is exposed at various temperature in the kiln and various
chemical reaction takes place to form major mineral constituents of
the cement.
The slurry from the wet process contains too much water to be
successful dried in a pre heater tower to remove much of water
before the kiln process.
Reaction Zones in the kiln(pyro-processing)
Zone 1: → Reaction Time is 0-35 min.
→ Temperature is between 800-1100 O
→ At this zone decomposition of lime (CaCO3) and formation of
tricalcium Aluminate (3CaO.Al2O3) according to the follwing reactions.
CaCO3 Heat CaO + CO2 …………………………….(1)
CaO + Al2O3 Heat 3CaO.Al2O3 ( Tricalcuim Aluminate) ………..(2)
Zone 2: → Reaction time 35-40 min
→ Temperature 1100-1300 oC
→ Exothermic reaction and the formation of secondary silicate phase (

Dicalcuim silicate, 2CaO.SiO2), According to the following reaction
2CaO + SiO2 2CaO.SiO2 ( dicalcuim silicate)……………………….(3)
Zone 3: → Reaction Time 40-50 min.
→ Temperature 1300-1450
→ Formation of tricalcuim silcate and teteracalcuim

alomuno ferrate according to:
2CaO.SiO2 + CaO Heat 3CaO.SiO2 ………………(4)
3CaO. Al2O3 + CaO + Fe2O3 Heat 4 CaO.Al2O3.Fe2O3 …..(5)
Zone Four: →Time 50-60 min and temperature is 1000-1300 oC
→ cooling and crystallization of various mineral phase formed in the kiln.

• The Major constituents (composition) of clinker/cement are:
Compound Chemical Formula Typical concentration

abbreviation (%)
Tricalcium Silicate C3 S 3CaO.SiO2 60-70%
Dicalcium Silicate C2 S 2CaO.SiO2 10-20%
Tricalcium Aluminate C3 A 3CaO.Al2O3 5-10%
Teteracalcium Alumino C4AF 4CaO.Al2O3.Fe2O3 3-8%

ferrate
4. Clinker Cooling: Immediately following the kiln there is a large
cooler used to drop the temperature of the clinker from 1000 – 150
o C.
This is achieved by forcing air through a bed of clinker in the base of

the cooler. After cooling it will discharged and transported to the
storage tank.
5. Cement Milling: At this stage the cooled clinker is mix with the
gypsum (CaSO4.H2O) or natural anhydrite is added to regulate the
setting time of the final cement, and introduce into the milling
machine in order to make cement with powder form.
6. Packing: this is the final operation,

Cement (Chapter 3)

Uploaded by

Copyright:

Available Formats

Cement (Chapter 3)

Uploaded by

Document Information

Original Description:

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Cement (Chapter 3)

Uploaded by

Copyright:

Available Formats

Adigrat University

Engineering and Technology Collage

• Portland cement ( often referred to as OPC ) is the most common

• Basic Raw materials needed for cement production are:

Iron Ore (Fe2O3) AND Gypsum.

• Limestone is a common sedimentary rock exposed on the surface

• Physical Property of limestone: pure limestone has white color and

• The main operation involved in the manufacturing of cement are:

1. Quarrying Limestone and cement rock ( clay) from their source

2. Grinding and crushing of those raw materials separately

3. Raw Mix Preparation

5. Mixing of gypsum and Grinding of the mixture of gypsum and

clinker to produce cement in powder form.

• N.B in both cases additional minerals or additives may be added

Raw mill preparation has the following basic aims:

1. to obtain the correct chemical composition

2. to achieve the desired/ proper particle size to ensure optimum

The finely ground material is dried, heated ( to enable the sintering

Zone 2: → Reaction time 35-40 min

→ Exothermic reaction and the formation of secondary silicate phase (

Zone 3: → Reaction Time 40-50 min.

→ Formation of tricalcuim silcate and teteracalcuim

3CaO. Al2O3 + CaO + Fe2O3 Heat 4 CaO.Al2O3.Fe2O3 …..(5)

Zone Four: →Time 50-60 min and temperature is 1000-1300 oC

→ cooling and crystallization of various mineral phase formed in the kiln.

Compound Chemical Formula Typical concentration

Tricalcium Silicate C3 S 3CaO.SiO2 60-70%

Dicalcium Silicate C2 S 2CaO.SiO2 10-20%

Tricalcium Aluminate C3 A 3CaO.Al2O3 5-10%

Teteracalcium Alumino C4AF 4CaO.Al2O3.Fe2O3 3-8%

This is achieved by forcing air through a bed of clinker in the base of

You might also like