Cement

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CEMENT
On completion of this class, you would be able to
• Know the history of cement
• Know the chemical composition of cement
• Describe the manufacturing process of cement (Dry process)
 Define Hydration of cement
 State the water requirement of Hydration of cement
 State the different types of cement
 State the uses of each type of cement
• Know the different types of tests on cement
(a) Consistency test
(b) Initial and final setting time tests
(c) Soundness test
• Know the grades of cement and their compressive strength
• Blended cement and their types

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Property
variety
Low cost
Plasticity Simple process
Durability
Bonding well
with bar
Hydraulicity
Advantages
of Cement
Advantages of cement

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• Cement is a fine, soft, powdery-type substance
• It is made from a mixture of elements that are found in natural
materials such as limestone, clay, sand and/or shale
• When cement is mixed with water, it can bind sand and
aggregates into a hard, solid mass called concrete
Cement

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History of Cement
• In 1824, Joseph Aspdin, a British stone mason, heated a mixture of
finely ground limestone and clay in his kitchen stove and ground
the mixture into a powder to create a hydraulic cement—one that
hardens with the addition of water.

5
• He took a patent for this cement
• A variety of sandstone is found in abundance in Portland in
England
• Hence it is called as “ ORDINARY PORTLAND CEMENT “
• In India, the first cement factory was installed at Tamil Nadu
(1904) by South India Industry Limited
History of Cement (contd)

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• Four essential elements are needed to make cement. They are
Calcium, Silicon, Aluminum and Iron
• Calcium (which is the main ingredient) can be obtained from
limestone, whereas silicon can be obtained from sand
• Aluminum and iron can be extracted from bauxite and iron ore,
and only small amounts are needed
History of Cement (contd)

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Chemical Composition of Cement
• The raw materials used for the manufacture of cement consist
mainly of lime, silica, alumina and iron oxide
• These oxides interact with one another in the kiln at high
temperature to form more complex compounds
• The relative proportions of these oxide compositions are
responsible for influencing the various properties of cement, in
addition to rate of cooling and fineness of grinding

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Oxide Percent content
CaO (Lime)
SiO2 (Silica)
Al2O3 (Alumina)
Fe2O3 (Iron oxide)
MgO (Magnesia)
Alkalies(K2O,Na2O)
SO3 (Sulphur trioxide)
60-67%
17-25%
5-8%
0.5-6%
0.1-4%
0.2-1.0%
1-3%
Chemical Composition of Cement

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Functions of Ingredients of Cement
Lime (CaO)
• Major ingredient of cement
• Excess quantity of lime makes the cement unsound
• If it is less, it decreases the strength and allows the cement to set
quickly

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Silica (SiO2)
• An important ingredient which gives strength to cement
• If it is in excess silica allows the cement to set slowly
Functions of Ingredients Cement (contd)

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Alumina(Al2O3)
• This imparts quick setting time to the cement
• If it is in excess quantity, it weakens the cement
• It also lowers the temperature of clinkers
Functions of Cement Ingredients (contd)

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Iron Oxide (Fe2O3)
• It helps the fusion of the raw materials during
burning stage
• It gives colour, strength and hardness to
cement

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Magnesium Oxide (MgO)
• If present in small quantities, MgO imparts hardness
and colour to cement
• If becomes excess quantity, weakens the cement

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Sulphur Trioxide (SO3)
• A very small quantity is required in the manufacturing
of cement
• If it is in excess, SO3 makes the cement unsound

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Alkalies
• A small quantity are required
• Alkalies and other impurities present in raw materials are
carried by the flue gases during heating
• If it is in excess quantity, efflorescence is caused

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Manufacturing of Portland Cement
• The raw materials required for manufacturing of cement are
calcareous materials, such as lime stones or chalk, and
argillaceous materials such as shale or clay
Lime Stone Shale

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• There are two processes known as ‘wet’ and ‘dry’ processes
depending upon whether the mixing and grinding of raw
materials is done in wet or dry conditions
Dry Process
In this process the following operations are involved
1. Mixing of raw materials
2. Burning
3. Grinding
4. Packing and Distribution
Manufacturing of Portland Cement (contd)

Production and Composition
of Portland Cement
Process to Produce Portland Cement
Grinding
Iron ore
powder PⅡ
PⅠ
Mixing
materials
Limestone
Clay
Bleeding
Grinding
1450℃
Raw material Clinker
Gypsum

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Flow chart of the manufacture of cement

Traditional Manufacture of
Portland Cement
1. Stone is first reduced to 125 mm (5 in.)
size, then to 20 mm (3/4 in.), and stored.

2. Raw materials are ground to powder and blended.
or
2. Raw materials are ground, mixed with water to form slurry,
and blended.

3. Burning changes raw mix chemically into cement clinker.

3. Burning changes raw mix chemically into clinker. Note
four stage preheater, flash furnaces, and shorter kiln.

4. Clinker is ground with gypsum into portland cement and
shipped.

Grinding
• Clinker is ground with gypsum
(calcium sulfate) to produce
portland cement
• Fine grinding is necessary for
high early strength
– 85-95% -325 mesh (45
microns)
– ~ 7 trillion particles per
pound
• Gypsum absorbs water and
prevents setting of C3A during
shipment

Source: van Oss and Padovani, 2002

Source: MacLaren and White, 2003

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• Limestone is taken from a quarry. It is the major
ingredient needed for making cement
• Smaller quantities of sand and clay are also needed
• Limestone, sand and clay contain the four essential
elements required to make cement
• The four essential elements are oxides of calcium, silicon,
aluminum and Iron
Manufacturing of Cement (contd)

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2.) Boulder-size limestone rocks are transported from the
quarry to the cement plant and fed into a crusher which
crushes the boulders into pieces

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• The limestone pieces then go through a blender where
they are added to the other raw materials in the right
proportions
3. Mixing of raw materials

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• The raw materials are ground to a powder. This is
sometimes done with rollers that crush the materials
against a rotating platform
4. Grinding of Raw Materials

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Tube Mill
The tube mills are used to have preliminary grinding of
raw materials or mixture of raw materials or clinkers

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5. Sintering
• Everything then goes into a huge, extremely hot rotating furnace to
undergo a process called "sintering“
• Sintering means: to cause to become a coherent mass by heating
without melting. In other words, the raw materials become sort of
partially molten
• The raw materials reach about 2700° F (1480°C) inside the furnace
• This causes chemical and physical changes to the raw materials and
they come out of the furnace as large, glassy, red-hot cinders called
"clinker"

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cooler

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Rotary Kiln

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• The clinker is cooled and ground into a fine powder
in ball mills
• A small amount of gypsum is also added during the
final grinding. It is now the finished product -
Portland cement
• The cement is then stored in silos (large holding
tanks) where it awaits distribution
6. Grinding of clinkers and storing

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Ball Mill The ball mills are used to carryout
final grinding of clinkers

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Bogue Compounds
• During the manufacturing of cement, various constituents combine
in burning and form certain compounds
• These compounds formed during burning, react with water help in
setting and hardening of cement
• These compounds are called bogue compounds they are
Compound symbol
1.Tricalcium silicate C3S
2.Dicalcium silicate C2S
3.Tricalcium aluminate C3A
4.Tetracalcium alumino
ferrite
C4AF
Hydration of Cement

Properties of Mineral Compounds
Mineral
types
Tricalcium
silicate
Dicalcium
silicate
Tricalcium
aluminates
Tetracalcium
aluminoferrite
Abbreviation C3S C2S C3A C4AF
Content (%) 37-60 15-37 7-15 10-18
Hydration
speed
fast slow fastest fast
Hydration
heat
much little most more
Strength high
early low
later high
low low
Anti-
corrosion
good fine poor excellent
Shrinkage middle better big small

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Hydration of Cement (contd)
• When water is added to cement a chemical reaction starts
between active components of cement (C4AF,C3A,C3S andC2S)
and water which is exothermic in nature and liberate a significant
amount of heat
• This is known as hydration and the liberated heat is called heat of
hydration

When mixed with water,
Portland cement hydrates
and forms heat
3CaO·SiO2+H2O CaO·2SiO2·3H2O+Ca(OH)2
Triealcium silicate hydrates rapidly and forms
earlier strength and earlier heat of hydration.
Tricalcium silicate is formed in a kiln when the
charge contains an abundance of lime, and hence the
greater amount of CaO in the reaction.
Hydration Mechanism

Dicalcium silicate hydrates slowly and is
responsible for strength increase in concrete
at later ages. The heat of hydration is
liberated slowly.
More dicalcium silicate is formed when the
raw materials contain less lime.
2CaO·SiO2+H2O
3CaO·2SiO2·3H2O+Ca(OH)2
Hydration Mechanism

Tricalcium aluminate hydrates rapidly
and liberates a large amount of heat.
If this reaction were not controlled,
concrete would set so rapidly (flash set)
that it could not be used in modern
construction.
3CaO·Al2O3+H2O 3CaO·Al2O3·6H2O
Hydration Mechanism

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• About an average 23 percent of water by weight of cement is
required for complete hydration of Portland cement
• This water combines chemically with the cement compounds
• Some quantity of water, about 15 percent by weight of cement
, is required to fill the cement gel pores
• A total of 38 percent of water by weight of cement is required
to complete the chemical reaction
Water Requirement for Hydration

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• If excess water is present, it will lead to capillary cavities
• In a month’s time 85 to 90 % of the cement gets hydrated and
cement attains almost its full strength
• Hydration still continues and cement grows stronger with time
• Total 50% of water by weight of cement is required for
complete hydration
Water Requirement for Hydration (contd)

Fineness and Properties
Fineness
Surface area
touching with
water
Setting and
hardening
speed
Properties
Small
D < 40μ
Great High
Strength
High
Too small Easily Great Cost High
Large
D >100μ
Low Low Low
Fineness related to the surface area touching with
water, so it influences the setting/hardening speed
and the properties of cement.
Fineness and Properties of Cement

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1. Ordinary Portland Cement(OPC)
2. Rapid Hardening Cement
3. Sulphate Resisting Cement
4. Quick Setting Cement
5. Low heat Cement
6. Portland Pozzolana Cement
7. High Alumina Cement
8. White Cement
9. Coloured Cement etc..,

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Ordinary Portland Cement(OPC)
• It is a common variety of cement
• It is suitable for the construction of all civil engineering works except under
water constructions
Uses of Ordinary Portland Cement
• Used in all important structures where great strength is required such as heavy
buildings and bridges light houses, docks, reservoirs, etc,.
• Foundations in wet places, and structures subjected to the action of water
such as
• Retaining walls
• Watertight floors
• Cement mortar for plastering, pointing etc
• Plain concrete

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• For making
• Reinforced cement concrete for laying floors ,roofs, lintels, beams,
etc,.
• Reinforced brick work
• In drainage and water supply works like water storage tanks, septic,
tanks, etc,.
• For protecting the external faces of buildings or engineering
structures from weathering action
• For thin masonry works, where strength is required
• Making joints for drains, pipes etc,.
• Manufacturing of precast pipes, piles, garden benches, fencing posts,
flower pots, etc,.
• Preparation of foundations, watertight floors, footpaths, etc,.
Uses of Ordinary Portland Cement (contd)

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Quick Setting Cement
• As the name indicates, it sets very fast
• The early setting property is brought out by reducing the
amount of gypsum during the grinding process
• This cement is costlier than ordinary Portland cement
• Initial setting time starts within 5 minutes, after adding water
• Final setting time: within 30 minutes
• It is ground much finer than OPC

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Advantages
• It is used in construction of structures under water, in water
logging areas, rivers, in running water like canals and streams
and pipe lines etc,.
• It is also used in emergency circumstances where quick
setting of cement is needed.
Quick Setting Cement (contd)

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White Cement
• Raw materials like china clay and pure lime stone are used to get
pure white colour
• It is a variety of OPC
• It is prepared from such materials which are practically free from
colouring oxides of iron and manganese
• For burning of this cement, the oil fuel is used instead of coal
• It is white in colour

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Uses
• It is used for floor finish, plaster work, ornamental work,
etc
• It is also used to fill the small holes during sanitary, water
supply fittings, wall tiles etc
White Cement (contd)

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Laboratory Tests on Cement
1. Consistency of cement
2. Setting times of cement
3. Soundness of cement
4. Compressive strength test
5. Fine ness of cement
6. Tests for chemical composition of cement

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Normal consistency of cement
Normal consistency is defined as the percentage of
water required to produce a cement paste of standard
consistency

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Normal Consistency Test of Cement
1. Take 300gm of cement sample and place at on a non-
absorbent plate
2. Take 25% of water by weight of cement as first trial and
mix it thoroughly with cement using gauging trowels.
Ensure that the time of gauging shall be within 3 to 5
minutes. The time of gauging shall be reckoned from the
instant water is added to cement to that paste is filled in the
mould

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3. Keep mould on a non absorbent plate. Apply a thin coat of oil
inside the mould
4. Fill the vicat’s mould with cement paste at a stretch and tamp the
mould so as to make the cement spread uniformly in the mould.
Strike off the excess cement plate and level the surface of mould
with spatula
5. Fix the plunger of 10mm dia x 50mm long to the plunger holder
of the apparatus. Gently lower the plunger to touch the top surface
of the paste and leve it quickly. Due to the weight of header and
holder the plunger penetrates in to the cement paste
Normal Consistency Test of Cement (contd)

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6. Note the plunger’ penetration reading on the scale of
apparatus. The recorded penetration value is reckoned from
the bottom of mould
7. Remove the plunger and cement paste from the mould
8. Take sample of cement and repeat the entire process with
27% of water and note down the plunger penetration

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9. Repeat the above process with varying % of water and
note the penetration of plunger till the penetration value is
5 to 7 mm measured from the bottom of the mould to the tip
of the plunger
Note :The standard consistency of ordinary Portland
cement is 30 to 35% by weight of cement

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Calculation Procedure
Weight of cement taken = g
Percentage of water added = %
Initial reading on vicat scale in mm =
Final reading on vicat scale in mm =
Penetration of plunger measured from
bottom of mould in mm =

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Result
The standard consistency of mould = _____ %

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Initial and Final setting time of cement

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When water is added to cement, the paste starts stiffening
and gaining strength, simultaneously loosing its plasticity.
Two stiffening states identified are initial and final setting
times respectively
• Initial setting time is the time interval between the
addition of water to cement and the stage when
needle ceases to penetrate completely
• This time should be about 30 minutes for ordinary
cement
Initial Setting Time of Cement

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Procedure
(A) Preparation of test block (paste in the mould)
1. Prepare a neat cement paste by mixing the cement with
0.85 times the water required to give a paste of standard
consistency
2. Start stop watch at the instant when water is added to
cement. Thoroughly mix cement and water using gauging
trowels till required uniformity is attained in mixing
Test for Initial Setting Time of Cement (contd)

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3. Fill the mould completely and smoothen the surface
of the paste by making it level with the top of the
mould. The cement paste thus prepared in the mould
is the test block
Note :
• Clean appliance shall be used for mixing
• All apparatus shall be free from vibration
during the test
• Care shall be taken to keep the needle
straight

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(B) Initial Setting Time
1. Place the test block with porous plate at bottom, under the
rod, bearing the needle (C) as shown in the fig of Vicat
Apparatus
2. Lower the needle gently until it comes in contact with the
surface of test block and quickly release, allowing it to
penetrate into test block

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Vicat Apparatus
1

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3. Repeat this procedure at regular intervals of time until the
needle, when brought in contact with the test block and
released as above fails to pierce the block for 5 to 7 mm
measured from the bottom of the mould
4. The period elapsed between the time when water is added to
the cement and the time at which the needle fails to pierce
the test block to a point 5 to 7 mm measured from the
bottom of the mould shall be reported as initial setting time
Note :The initial setting time of ordinary Portland
cement is 30 minutes

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(C) Final Setting Time
1. Replace the needle ‘C’ with needle ‘F’ of the vicat apparatus
attachment
2. Prepare the test block according to the procedure given above
3. The cement shall be considered as finally set when, upon
applying the needle gently to the surface of the test block, the
needle makes an impression there while the attachment fails
to do so
Test for Final Setting Time of Cement (contd)

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4. The period elapsing between the time when water is
added to the cement and the time at which the needle
makes an impression on the surface of the test block
while the attachment fails to do so shall be the final
setting time
Note :The final setting time of ordinary Portland
cement is 600 minutes
Test for Final Setting Time of Cement (contd)

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Sample : Sample of OPC
Water required to prepare a cement paste of
standard consistency = p
Weight of cement required for 1 mould = 300 g
Weight of water added to cement =(0.85p x 300g ml)
100
Specimen Calculation for Initial Setting
Time of Cement

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( A) Initial setting time
Time elapsed since the water is added to cement = min
Initial reading on vicat apparatus in min (a) =
Final reading on vicat apparatus in mm (b) =
Penetration of vicat needle measured from
The bottom of mould in mm (b-a) =
Specimen Calculation for Initial Setting
Time of Cement (contd)

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Result
a) Initial setting time for the given cement
sample = __________ min
b) Final setting time for the given cement
sample = __________ min
Note
The result of initial and final setting times shall be reported to
nearest ‘five minutes’
Specimen Calculation for Initial Setting Time
of Cement (contd)

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4
Equipment for Soundness test

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1. The apparatus (shown in previous fig) consists of a small split
cylinder of spring brass or other suitable metal
2. It is 30mm in dia and 30mm high
3. On either side of the split are attached two indicator arms 165
mm long with pointed ends
Soundness test (contd)

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4. Cement Is gauged with 0.78 times the water required
for standard consistency (0.78p) in a standard manner
and filled into the mould and kept on a glass plate
5. The mould is covered on the top with another glass plate
6. The whole assembly is immersed in water at a
temperature of 270C - 320C and kept there for 24 hrs

94
7. The distance between the indicator points is measured
8. The mould is submerged again in water and the water is
heated to boiling point in about 25-30 minutes and boiling is
continued for 3hours
9. The mould is removed from the water, allowed to cool and
the distance between the indicator points is measured

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10.The difference between these two measurements
represents the expansion of cement. This must not
exceed 10mm for ordinary, rapid hardening and low
heat Portland cements
11.If in case, the expansion is more than 10mm as tested
above, the cement is said to be unsound ( not suitable )

GRADES OF CEMENT AND
THEIR COMPRESSIVE
STRENGTH
96

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Ordinary Portland Cement (OPC )
• It is a common variety of cement
• It is suitable for the building all civil engineering works except
under water constructions
• Cement occupied the place of lime because of its greater
strength
• The OPC is classified into three grades, namely 33 grade, 43
grade, 53 grade depending upon the strength of the cement (
in N/mm2 ) at 28 days when tested as per IS 4031 – 1988

98
Properties
1. Fineness : Residue shall not be less than 10% on
sieve No. 9 (90µ) when sieved
2. Soundness : Expansion of the cement should not be
more than 10 mm
3. Setting time : Initial setting time should be less than 30
minutes and final setting time not more
than 600 minutes
4. Compressive strength: Compressive strength values are
shown in the table

99
• If the 28 days strength is not less than 33 N / mm2, it is called
33 grade cement
43 grade cement
53 grade cement
Ordinary Portland Cement (O P C )

100
Designation of Grade of Cement
Grade
of Cement
Strength at 28
Days
33
33
N / mm2
43
43
N / mm2
53
53
N / mm2

102
Blended Cement
• Cement mixture containing Ordinary Portland Cement and at
least one supplementary cementitious materials (SCMs) or
puzzolanas is called blended cement
• Blended cements interground or blended at cement plants
are generally more uniform and produce better results than
blended concrete mixtures combined at the concrete mixer

103
• The blended cement will produce stronger and more
durable concrete than OPC concrete
• Blended cement will reduce the overall cost of the
concrete since the blends are by products available in
abundance and are cheaper
Blended Cement (contd)

104
sand
pc
pcpc
pc
pc
pc
pc
pc
scm
Portland cement
Supplementary Cementations
Material or puzzolana
Blended cement
Note -1: When OPC hydrates a glue like calcium silicate
hydrate is formed, this holds concrete together.
However, gaps in calcium silicate hydrate produce pathways
for moisture to penetrate and reduce strength

105
Note - 2
When supplementary cementitious materials (scms) or
puzzolanas are added, particles pack more tightly within the
voids and additional glue forms from the SCM hydration
process. With fewer voids, the concrete is less permeable and
stronger

106
Portland Pozzolana Cement
• Pozzolana is derived from Puzzouli, a town in Italy where the
sand available when mixed with lime was found to possess
hydraulic properties. It is volcanic dust
• Portland puzzolana cement is manufactured by grinding
Portland cement clinker and puzzolana, or by intimately and
uniformly blending Portland cement and fine puzzolana

107
Portland Pozzolana Cement (contd)
• Burnt clay, Shale, or Fly Ash are such other materials which
have no cementing value but have the property of combining
with lime to produce a stable lime - puzzolana compound
which has definite cementations properties

108
• The percentage of puzzolana should be between 10 to 30%
• It possesses almost the same properties of OPC
• Free lime present in the cement is thus removed hence the
resistance to chemical attack increases making it suitable for
marine works

109
Uses
• It can resist action of sulphate
• It improves workability
• It imparts high degree of water, lightness, fire
resistance
• It offers great resistance to expansion
• It is cheaper

110
Improved workability
• The spherical shape of fly ash particles and the glassy nature
of slag particles reduce the amount of water needed to
produce workable concrete
• Blended cements tend to have slower set times than OPC,
which can be a benefit during the warmer months
Curing
• As with all concretes, proper curing is essential to achieve
best performance

111
Enhanced strength
• Blends can improve long-term strength development,
depending on the proportions and materials used
• By reducing the amount of water required, blends produce
stronger concrete

112
Resistance to sulphate attack
• Blends can offer superior resistance to these attacks because
they contain fewer compounds that react with sulphates and
due to their low permeability which keeps out sulphates-
bearing moisture

Cement

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