By: Dr. Shamshad Ahmad
LECTURE NO. 2
MANUFACTURING OF PORTLAND CEMENT
Objectives:
• To explain the raw materials used in
manufacture of Portland cement
• To explain briefly the manufacturing process
of cement
By: Dr. Shamshad Ahmad
INTRODUCTION
• Portland cement was invented in 1824 by Joseph Aspdin,
an English mason
• Joseph Aspdin named his patented product as “Portland
cement” because it produced a concrete that resembled
the color of the natural limestone quarried at Portland in
England
Natural limestone
obtained from a
quarry in Portland
A cylinder of
concrete made
using cement
By: Dr. Shamshad Ahmad
INTRODUCTION
• Portland cements are hydraulic cements
composed of hydraulic calcium silicates
primarily
• Hydraulic cements set and harden by reacting chemically
with water
• Most of the hydration and strength development take
place within the first month of mixing, but they continue,
though more slowly, for a long time
By: Dr. Shamshad Ahmad
RAW MATERIALS USED IN MANUFACTURE OF
PORTLAND CEMENT
•
The raw materials are generally a mixture of calcareous
(calcium oxide, CaO) and argillaceous (silica SiO2 and alumina
Al2O3).
•
The raw materials used in manufacture of Portland cement
contain appropriate proportions of the following:
•
Calcium oxide or Lime (CaO), Sources: Limestone, Shale, Marl,
Calcite, Argonite, Clay, Chalk, etc.
•
Silica (SiO2), Sources: Clay, Marl, Shale, Sand Fly ash, Calcium
silicate, etc.
•
Alumina (Al2O3), Sources: Aluminum-ore refuse, Clay, Fly ash,
Shale, etc.
•
Iron oxide(Fe2O3), Sources: Iron ore, Clay, Mill scale, Shale, etc.
•
Magnesia (MgO), Sources: Cement rock, Limestone, Slag, etc.
•
Gypsum
(CaSO4.2H2O),
Anhydrite,Gypsum, etc.
Sources:
Calcium
sulfate,
By: Dr. Shamshad Ahmad
RAW MATERIALS USED IN MANUFACTURE OF
PORTLAND CEMENT
By: Dr. Shamshad Ahmad
RAW MATERIALS USED IN MANUFACTURE OF
PORTLAND CEMENT
By: Dr. Shamshad Ahmad
RAW MATERIALS USED IN MANUFACTURE OF
PORTLAND CEMENT
By: Dr. Shamshad Ahmad
RAW MATERIALS USED IN MANUFACTURE OF
PORTLAND CEMENT
By: Dr. Shamshad Ahmad
RAW MATERIALS USED IN MANUFACTURE OF
PORTLAND CEMENT
By: Dr. Shamshad Ahmad
RAW MATERIALS USED IN MANUFACTURE OF
PORTLAND CEMENT
By: Dr. Shamshad Ahmad
RAW MATERIALS USED IN MANUFACTURE OF
PORTLAND CEMENT
By: Dr. Shamshad Ahmad
STEPS USED IN MANUFACTURE OF PORTLAND CEMENT
1. Raw materials stones in appropriate proportions are first crushed to
5-in. size, then to ¾ in., and stored
By: Dr. Shamshad Ahmad
STEPS USED IN MANUFACTURE OF PORTLAND CEMENT
2.
3.
Crushed raw materials are ground to powder so that approximately
80% of the raw materials pass a No. 200 sieve
The powdered raw materials are either blended in dry condition
(dry process) or mixed with water to form slurry and blended (wet
process)
By: Dr. Shamshad Ahmad
STEPS USED IN MANUFACTURE OF PORTLAND CEMENT
4.
After blending the raw materials the same is sent to a rotating kiln
for burning at a temperature in the range of 2600ºF to 3000ºF
(1427°C to 1649°C).
By: Dr. Shamshad Ahmad
STEPS USED IN MANUFACTURE OF PORTLAND CEMENT
5.
Mixing the raw materials while burning in the kiln leads to the
removal of water from raw materials and chemical reactions
between oxides of the raw materials by fusion, forming cement
clinkers.
• Diameter of clinkers is around ¾
inch
• Clinkers should approximately
contain: 65% lime, 21% silica, 5%
alumina, and 3% iron oxide
6.
The clinkers are cooled to about 150°F (51°C) and then pulverized.
During this operation, a small amount of gypsum (2 to 5%) is
added to regulate the setting time of the cement.
By: Dr. Shamshad Ahmad
STEPS USED IN MANUFACTURE OF PORTLAND CEMENT
7.
Clinker with gypsum is ground to a desirable fineness (< 45 μm
diameter) of cement. This grounded product is the Portland
cement.
+
Clinkers
Gypsum
Portland cement
By: Dr. Shamshad Ahmad
STEPS USED IN MANUFACTURE OF PORTLAND CEMENT
8.
Final product of cement is packed in bags with quantity usually 50
kg per bag.
•
•
Bulk density of cement is around 1500 kg/m3
Specific gravity of cement is around 3.15
By: Dr. Shamshad Ahmad
CHEMICAL COMPOUNDS IN THE FINAL PRODUCT OF
PORTLAND CEMENT
The final product of a Portland cement contains the following four
principal chemical compounds:
(C = CaO, S = SiO2, A = Al2O3, F = Fe2O3)
By: Dr. Shamshad Ahmad
CHEMICAL COMPOUNDS IN THE FINAL PRODUCT OF
PORTLAND CEMENT
Oxide and Compound Composition and Fineness of Some Typical
Cements:
C3S and C2S together constitute around 75% of the cement
A rule of thumb: C3S + C2S = 70%
C3A + C4AF = 20%
By: Dr. Shamshad Ahmad
CHEMICAL COMPOUNDS IN THE FINAL PRODUCT OF
PORTLAND CEMENT
Characteristics of Major Constituents of Cements
1. C3S Phase
•
•
Hydrates and hardens rapidly and is largely
responsible for initial set and early strength
Early strength of cement is higher with increased
percentages of C3S
By: Dr. Shamshad Ahmad
CHEMICAL COMPOUNDS IN THE FINAL PRODUCT OF
PORTLAND CEMENT
Characteristics of Major Constituents of Cements
1. C3S Phase-----contd.
By: Dr. Shamshad Ahmad
CHEMICAL COMPOUNDS IN THE FINAL PRODUCT OF
PORTLAND CEMENT
Characteristics of Major Constituents of Cements
2. C2S Phase
•
•
•
•
Hydrates and hardens slowly (it is the slowest
reacting substance in cement)
It is the lowest heat generating substance (60 cal/g)
Contributes to strength at ages beyond one week
It generates half of the Ca(OH)2 and about 133%
C-S-H as those generated by C3S
By: Dr. Shamshad Ahmad
CHEMICAL COMPOUNDS IN THE FINAL PRODUCT OF
PORTLAND CEMENT
Characteristics of Major Constituents of Cements
3. C3A Phase
• Its quantity varies from 2 to 14% depending on the type of
cement
• It does not contribute to strength (some controversy exists)
• It accelerates the hydration of C3S
• It is the first reacting substance in cement and generates highest
amount of heat
• Gypsum is added to the cement to slow down the hydration rate
of C3A for regulating the time of setting
• Cements with low percentages of C3A are especially resistant to
soils and waters containing sulfates
• Cements with high percentages of C3A are resistant to
reinforcement corrosion
By: Dr. Shamshad Ahmad
CHEMICAL COMPOUNDS IN THE FINAL PRODUCT OF
PORTLAND CEMENT
Characteristics of Major Constituents of Cements
4. C4AF Phase
• Its quantity varies from 7 to 10% with 8% as average
• Its characteristics does not differ structurally very much from
C3A, however, it is generally less reactive than C3A and does not
play any significant role on hydration
By: Dr. Shamshad Ahmad
CHEMICAL COMPOUNDS IN THE FINAL PRODUCT OF
PORTLAND CEMENT
Characteristics of Minor Constituents of Cements
1. Gypsum (CaSO4.2H2O)
By: Dr. Shamshad Ahmad
CHEMICAL COMPOUNDS IN THE FINAL PRODUCT OF
PORTLAND CEMENT
Characteristics of Minor Constituents of Cements
2. Free (Uncombined) Lime (CaO)
By: Dr. Shamshad Ahmad
CHEMICAL COMPOUNDS IN THE FINAL PRODUCT OF
PORTLAND CEMENT
Characteristics of Minor Constituents of Cements
2. Magnesium Oxide (MgO)
By: Dr. Shamshad Ahmad
CHEMICAL COMPOUNDS IN THE FINAL PRODUCT OF
PORTLAND CEMENT
Characteristics of Minor Constituents of Cements
3. Alkalis (Na2O + K2O)
By: Dr. Shamshad Ahmad
CHEMICAL COMPOUNDS IN THE FINAL PRODUCT OF
PORTLAND CEMENT
Determination of the Content of Major Constituents of Cements from the
Oxide Composition
CaO: C
SiO2: S
Al2O3: A
Fe2O3: F
SO3:
S