Construction material cement

Construction Material
CEMENT
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THE CEMENT
Cement is most important material in building
construction . The name “cement” refer to the
material manufacture from lime stone and clay and
made available in powder form, which mixed with
water can set to hard durable mass even under
water.
FUNCTION OF CEMENT :
to bind the sand and coarse aggregate together to fill
voids in between sand and coarse aggregate particle to
form a compact mass

Classification of Cement
OPC
Ordinary Portland Cement
PPC :
Portland Pozzolzna Cement
Grade 33 –IS 269-1989 designated as C-33
SRPC : Sulpahte Resisting
portland cement
IS 1489 (Part 1)1991 flyash based
IS 1489 (Part 2) 1991 calcined clay-based
BFSC : Portland blast
furnace slag cement
IS 12330-1988
Hydrophobic Cement
IS 455-1989 (PSC)
Blended Cement
IS 8043-1991
RHPC : Rapid hardening
portland cement
IS 8041-1990

OPC: Ordinary Portland cement
Chemical composition of Portland Cement:
a) C3S: Tricalcium Silicate = 3CaO.SiO2 (50%)
b) C2S :Dicalcium Silicate = 2CaO.SiO2 ( (25%)
c) C3A :Tricalcium Aluminate = 3CaO.Al2O (10%)
d) C4AF :Tetracalcium Aluminoferrite = 4CaO. Al2O3.Fe2O3 (10%)
e) Gypsum (5%)

 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.
C3S: Tricalcium Silicate

C2S : Dicalcium Silicate
 Hydrates and hardens slowly.
 Contributes largely to strength increase at
ages beyond one week.
 Responsible for long term strength

Alite (C3S) and Belite (C2S)

C3A :Tricalcium Aluminate
 Liberates a large amount of heat during the first
few days of hydration and hardening.
 Also contributes slightly to early strength
development.
 Gypsum added to the cement slows down the
hydration rate of C3A.
 Cements with low percentages of C3A are
especially resistant to soils and waters
containing sulfates.

C4AF :Tetracalcium Aluminoferrite
 Assist in the manufacture of Portland Cement
by allowing lower clinkering temperature.
 Also act as a filler
 Contributes very little strength of concrete
eventhough it hydrates very rapidly.
 Also responsible for grey colour of Ordinary
Portland Cement

Hydration of Cement
 In the presence of water the cement compounds
chemically combined with water (hydrate) to form
new compounds that are the infrastructure of the
hardened cement paste in concrete.
 Both C3S and C2S hydrate to form calcium
hydroxide and calcium silicate hydrate (CSH).
Hydrated cement paste contains 15% to 25%
Calcium hydroxide and about 50% calcium
silicate hydrate by mass. The strength and other
properties of hydrated cement are due primarily
to calcium silicate hydrate.

 C3A reacts with water and calcium hydroxide
to form tetracalcium aluminate hydrate.
 C4AF reacts with water and calcium
hydroxide to form calcium aluminoferrite
hydrate.
Hydration of Cement

Hydration Reactions

Relative Reactivity of Cement
compounds

Relative volume of major compounds in
hydrated cement paste

CEMENT -MANUFACTURE

THE CEMENT MANUFACTURING
PROCESS
1. BLASTING : The raw materials that are used
to manufacture cement (mainly limestone and
clay) are blasted from the quarry.
Quarry face
3. CRUSHING AND TRANSPORTATION : The raw materials, after crushing, are transported to the plant by conveyor. The plant stores
the materials before they are homogenized.
2. TRANSPORT : The raw materials are loaded
into a dumper.
crushing
conveyor
dumper
storage at
the plant
loader

PROCESS
4. RAW GRINDING : The raw materials are very finely ground in order to produce the raw mix.
5. BURNING : The raw mix is preheated before it goes into the kiln, which is heated by a flame that can be as hot as 2000 °C. The raw
mix burns at 1500 °C producing clinker which, when it leaves the kiln, is rapidly cooled with air fans. So, the raw mix is burnt to
produce clinker : the basic material needed to make cement.
conveyor
Raw mix
kiln
cooling
preheating
clinker
storage at
the plant
Raw mill

PROCESS
6.GRINDING : The clinker and the gypsum are very finely ground giving a “pure cement”. Other
secondary additives and cementitious materials can also be added to make a blended cement.
7. STORAGE, PACKING, DISPATCH :The cement is stored in silos before being dispatched either in bulk or in bags to
its final destination.
clinker
storage
Gypsum and the secondary additives are added
to the clinker.
silos
dispatch
bags
Finish grinding

CEMENT - MANUFACTURE

Portland Pozzolana Cement (PPC)
 This type of cement is most common type
available now in market.
 This is made by blending 10-25% reactive
pozzolana like flyash or calcined clay with
OPC
 Addition of pozzolana makes cement
sensitive to curing and it requires longer
curing than OPC.

SULPHATE RESISTANT
PORTLAND CEMENT
 Sulphate-resisting Portland cement (SRPC) is a
special purpose cement used where sulfates are
present in concentrations that would damage
Normal Portland cement concrete or mortar.
 Sulfate resistance is achieved by adjustments to
chemical composition to limit the level of
tricalcium aluminate (C3A) in the SRPC

SRPC : PROPERTIES
 Applied at place where there is exposure to
sulphate such as used in concrete below
ground
 Higher content of Tetracalcium Aluminoferrite
& reducing the Tricalcium aluminate to
aluminium
 Has darker color than OPC

 SRPC is made by fusing together a precisely
controlled blend of very finely ground
limestone, shale and iron oxide at high
temperatures to form cement clinker.
 A small quantity of gypsum is added to this
clinker before grinding to produce the final
fine powder - Sulfate-resisting Portland
cement.
 SRPC is manufactured in a modern dry
process works at Castlemungret, Co.
 Limerick and is supplied either in bulk or in
bags.
SRPC : PROPERTIES

SRPC : ADVANTAGES
 Long Term Strength Development
 High Strength Concrete
 Heat of Hydration
 Pure Water and Acid Attack
 Sulphate Attack
 Alkali Aggregate Reactivity

Long Term Strength Development
 A significant characteristic of SRPC is the
ability to continue significant strength
development beyond the normal 28 day
period.
 The benefits of this are obvious, considering
that 28 days is a very short period in the life
of most concrete structures

High Strength Concrete
 Studies have shown amazing benefits of the
use of SRPC in high performance concrete.
 The lower reactivity of the slag makes it
easier to control slump in the first two hours
that follow mixing,
 as well as to reduce the amount of heat
developed during hydration at higher cement
contents.

Heat OF Hydration
 Sulphate Resistant Portland Cement have a
much lower heat of hydration than other
cements, making them ideal for mass
concrete work.
 The lower heat of hydration results in smaller
temperature gradients within mass concrete
structures, thereby minimising thermal
cracking.

Pure Water and Acid Attack
 The use of SRPC is recommended in
applications where concrete is exposed to
pure water and/or acidic conditions.
 Examples are water pipes and reservoirs, soft
drink factories and sewage works.

Sulphate Attack
 SRPC provides higher resistance to sulphate
attack for applications specifically requiring
sulphate resistance.
 Applications include sewage works and
coastal environments.

Alkali Aggregate Reactivity
 SRPC has been shown to reduce the risk of
alkali aggregate reaction in concretes
containing reactive aggregates.

BFSC Portland blast furnace slag
cement
 This type of cement constitutes about 10% of
cement produced in India.
 The slag forms 25-60% of the cement.
 Every ton of cast iron produce 0.3 tons of
furnace slag which can be used in cement
industry.
 During its setting the Ca(OH)2 liberated by
OPC hydration acts as an activator for the
slag.

BFSC Portland blast furnace slag
cement
 Even though it is equated with OPC it
behaves more like PPC and has lower heat of
hydration and better sulphate resistance.
 At present BFSC produced in India is only
Grade-33 and there are proposals to make
Grade-43 cements with 45-70% slag content.
 BFSC with more than 50% slag has good
sulphates resistance

Hydrophobic cement
 In places of high rainfall and humidity normal
cement tends to set when stored, due to
mositure present in the atmosphere.
 By grinding the cement clinker with water
repellent film forming substance like oleic acid,
a water repellent film is formed around cement
particle during manufacturing itself. This
prevent setting of cement during storage.
 During mixing with aggregates this film is
broken and cement behave as ordinary
cement

Blended cement
 For economy a mixture of portland cement,
blast furnace slag and flyash is allowed to be
used in some countries. This is known as
blended cement.
 In India this type of cement is not produced.

Rapid Hardening Portland cement
(RHPC)
 Rapid Hardening Portland cement (RHPC) is
a special purpose cement used in concrete to
ensure a higher rate of early age strength
development than that typically achieved
using Normal Portland cement (NPC).
 The improved early age strength performance
of RHPC is principally achieved through
increased product fineness.

RHPC : PROPERTIES
 Similar chemical composition as OPC but
different proportion
 Causes to the increased rate of early
hardening
 Concrete made with RHPC develops in 7
days the same strengths
 High early strength is achieved by increasing
the CS & CA content

RHPC : ADVANTAGES
 More finely grounded than OPC
 Allows formwork to be struck earlier
 Providing savings either the quantity of
formwork required in time
 Produce heat earlier than OPC, so it can be
used in cold weather

RHPC :Qualities
 RHPC is produced using carefully selected
raw materials.
 Strict quality control throughout each stage
of the manufacturing process ensures that a
consistent final product is achieved.

RHPC : Strength
 Rapid Hardening Portland cement achieves
higher earlier strengths than OPC because it
is more finely ground.
 Rapid Hardening Portland cement is
chemically similar to OPC and as such
concrete mixes should be designed with this
in mind.
 In particular, optimum ultimate strength of
concrete using RHPC will depend, like OPC,
on careful attention to the water/cement ratio,
consistent with ensuring satisfactory placing
and compaction.

PHYSICAL TESTS OF CEMENT
Fineness
Consistency
Soundness
Setting Time
Compressive Strength
Heat of Hydration

FINENESS OF CEMENT
Fineness of cement is a measure of size of
particle of cement. It is expressed as specific
surface of cement (in sq. cm /gm).
FINENESS OF
CEMENT
SIZE OF
PARTICLE
SPECIFIC
SURFACE OF
CEMENT
IS MEASURE OF
IS EXPRESSED AS

PHYSICAL TESTS OF CEMENT
IS 4031 (PART-1 to 11) & I. S. 269 1978.
Test for Fineness
The first requirement is that 90% of cement
should pass IS 90 mircons. Indian standard
also specifies fineness test by blaine’s air
permeability method as described in IS 4031-
1968
 95% of cement particles are smaller than 45
micrometer, with the average particle around
15 micrometer.
 Fineness of cement affects heat released and
the rate of hydration.

TESTS FOR FINENESS
(IS 4031 & I. S. 269 1978. )
The principle is based
on relation between
the rate of flow of air
through a cement bed
and surface area of
particles comprising
the cement bed of
given porosity
It should be at least 225
m2
/kg
BLAINE AIR PERMEABILTY
APPARATUS

TESTS FOR FINENESS
(I. S. 269 1978. )
BLAINE AIR
PERMEABILTY
APPARATUS

TESTS FOR FINENESS
STEP WISE PROCEDURE
1. Calculate the bulk volume of compacted bed of standard cement
V = (WA-WB) / D Where
WA= gms of, mercury required to fill the permeability cell
WB= gms of mercury required to fill the portion of the cell not
occupied by the bed of cement formed by 2.8 gms of standard
cement sample .
D= Density of mercury at temperature of test.
2. Determine the weight of the standard sample ( W) required to
produce a bed having porosity
of 0.500 ± 0.005 (e) as follows:
W = 3.15V(1-e)
Where V = Bulk volume of compacted cement powder
And e = Desired porosity of bed of cement (0.500 ± 0.005)

TESTS FOR FINENESS
STEP WISE PROCEDURE
3. Determine the time taken by the manometer liquid to fall from
second mark from the top to the third mark on the, manometer
when air is allowed to permeate through the compacted cement
4. Calculate the constant of the apparatus (k) by using the following
formula
Ss = k √ Ts where k = Ss/ √ Ts
Where Ss is the fineness of standard portland cement in Sq.
cm/gm.
5. Using the same quantity (w) of the cement sample find the time
(Ts) in seconds required for the manometer liquid fall from
second mark to third mark
6. Calculate the specific surface of cement in Sq. cm/gm using the
form
S= k √ Ts

BIS REQUIREMENT FOR
FINENESS
1. As per I. S. 269 the residue of cement sampled on the sieve 90 micron
after sieving should not exceed .following % by weight for different
types of cements.
Ordinary Portland cement 10%
Rapid hardening cement 5%
Low heat cement 5%
2. As per I. S. 269 the specific surface area of cement sample should not
exceed following for different types of cement.
Ordinary Portland cement 2250 sq. cm per gm
Rapid hardening cement 3050 sq. cm per gm
Low heat cement 3250 sq. cm per gm

TESTS FOR FINENESS
(IS 4031 )
 More is the fineness
of cement more will
be the rate of
hydration.
 Thus the fineness
accelerates strength
development
principally during the
first seven days
Very large picture of cement

Test of Normal or standard
Consistency (IS 4031)
 Consistency refers to the relative mobility of a freshly
mixed cement paste or mortar or its ability to flow.
Normal / standard consistency
Permit vicat’s plunger to penetrate
5 to 7 mm from bottom
Amount of water as % by weight of
dry cement

Test of Normal or standard
Consistency ( IS 4031)
It is the consistency at which
the vicat plunger G of
10mm diameter and
50mm length will
penetrate 33-35 mm
within 3 to 5 minutes of
mixing .
The test procedure is to
carry at least three trial
experiment by mixing the
cement with distilled water
varying from about 24 to
27 % of weight of cement . VICAT APPARATUS

Test of Normal or standard Consistency
STEPWISE PROCEDURE: (as per I.S.4031-1988)
1. Weigh about 400 gm of cement accurately and placed it in
enamel trough .
2. To start with add about 25% of potable water and mix it by
means of spatula. Care should be taken that the gauging time is
not less than three minutes and not more than 5 minutes.
3. Apply thin layer of oil to inner surface of mould. Fill the Vicat's
mould with this paste in the mould resting on non- porous plate.
4. Make the surface of cement paste in level with the top of mould
with the trowel. The mould should be slightly shaken to the expel
air.
5. Place the mould together with the non-porous plate under the
rod bearing the plunger so that it touches the surface of the test
block.

Test of Normal or standard Consistency
STEPWISE PROCEDURE: (as per I.S.4031-1988)
6. Release quickly the plunger allowing it to sink in the cement
paste in the mould. Note down the penetration of the plunger in the
paste ,when the penetration of plunger becomes stable in the
mould.
7. If the penetration of plunger in the paste is less than the 33 to 35
mm from the top of the mould, prepare the trial paste with
increasing percentage of water and repeat the above mentioned
procedure until the plunger penetrate to a depth of 33 to 35 mm
from the top or 5 to 7 mm from the bottom of mould.
8. Expressed this amount of water as a percentage by weight of
dry cement.

Test for Soundness (IS 4031)
 Soundness is the ability of a hardened paste to
retain its volume after setting.
 The cement is said to be sound when the
percentage of free lime and magnesia is with in
specified limits .
 A cement is said to be unsound (i.e. having lack
of soundness) if it is subjected to delayed
destructive expansion.
 These materials expand in the structure and
thus the concrete or mortar also expand,
causing unequal expansion of paste

Test for Soundness (IS 4031)
The Soundness test is an indication of excess of
lime caused by inadequate burning of cement or
excess of magnesia or sulphates .
1. Le chatelier’s Test
2. Autocalve test

Le Chatelier Test
STEP WISE PROCEDURE ( AS PER IS : 4031):
1. Prepare a cement paste formed by gauging cement with 0.78 times
water required to give a paste of standard consistency. The
gauging time should not be less than 3 minutes nor greater than 5
minutes.

Le Chatelier Test
STEPWISE PROCEDURE ( AS PER IS : 4031):
2. Oil the inner surface of the mould. Place the mould on a glass sheet
and fill it with cement paste, taking care to keep the edges of the
mould gently together. Cover the mould with another piece of glass
sheet and peace a small weight on this covering glass sheet and
immediately submerge the whole assembly in water at a
temperature of 27°Cand keep it for 24 hours.
3. Take out the assembly from water after 24 hrs. Measure the
distance between the indicator points and record it (D1)
4. Submerge the mould again in water and bring the water to boiling in
25 to 30 minutes and keep it boiling for three hours.
5. Remove the mould from the water. Allow it to cool and measure the
distance between the indicator points and record it ( D2 ).
6. Three samples should be tested and average of the results should
be reported.

Le Chatelier Test
This test shows unsoundness due to lime only.
Unaerated cement paste at normal consistency
is first tested for expansion. If the test results
does not satisfy requirement of 10mm
expansion .
Another test shall be made after aeration of
cement by spreading of sample to a depth of
75mm at relative humidity of 50% to 80% for 7
days the expansion in this aerated cement test
should not be more then 5 mm

Autoclave Test
Autocalve Test is used for both lime and
magnesia excess indication .
All the cement having a magnesia content more
then 3 % is to be tested for soundness by this
test with unaerated cement .
The test consist of heating bar made of cement
paste with water of normal consistency and
measuring its expansion

Test for Setting Time
The Setting Time is also determined by vicat’s
needle on cement paste of normal
consistency . For this test , we use 1mm
square needle , this time to penetrate 33-
35mm is taken as initial setting time.
For final setting time we use special needle (5mm
dia) and time at which this needle will not
penetrate more then 0.5mm is taken as final
set.

Compressive Strength
This is most important test. The compressive
strength of cement is determine from cube of
face 50cm2
in area made of cement mortar with
one part cement and three part of standard
sand (conforming to IS 650-1966) by weight
and water corresponding to 25% normal
consistency plus three percent of combined
weight of cement and sand .

Heat of Hydration (IS 4031-1968)
Hydration of cement is chemical reaction and it
produce heat . In very massive construction this
effect can rise the temperature of concrete as
much as 50°C . In such cases , we should use
low heat cements or adopt cooling method.
The test is carried out by calorimeter. Low heat
cement should satisfy following criteria
1. In 7 days, heat generated should not be more
than 65 calories/gm of cement.
2. In 28 days, heat generated should not be more
than 75 calories/gm of cement.

Cont. on Heat of Hydration
 Cements do not
generate heat at
constant rate as
illustrated in
Figure for a typical
Portland cement

Storage of Cement
 Cement is moisture-sensitive material; if kept
dry it will retain its quality indefinitely.
 When exposed to moisture, cement will set
more slowly and will have less strength
compared to cement that kept dry.
 At the time of use cement should be free-
flowing and free of lumps.

Storage of Cement

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