7/25/2010
CONTENT SCHEDULE – 1st Meeting
Civil Engineering Materials
SAB 2112
Introduction to Cement
Dr Mohamad Syazli Fathi
1. Introduction, cement manufacturing process, types of
cement, chemical composition of OPC
2. Hydration of cement, testing of cement, types of
aggregates,
gg g
physical
p y
and mechanical characteristics
of aggregates
3. Size distribution and testing of aggregates, water in
concrete, types of chemical admixtures
Department of Civil Engineering
RAZAK School of Engineering & Advanced Technology
UTM International Campus
July 25, 2010
Objectives of the lecture
• The main objective of this lecture is to explain to students
that:
• How cement is manufactured, its principal constituents, the
types of cement, cement standards and the application of
different types of cement
Leonard P. Zakim Bunker Hill Bridge in
Boston. (Image courtesy of the Federal Highway
Administration.)
Definition
• In BS EN 197-1, ‘cement’ is defined as:
“ … A hydraulic binder, i.e. a finely ground inorganic
material which, when mixed with water, forms a paste
which sets and hardens by means of hydraulic reactions
and processes and which, after hardening, retains its
strength and stability even under water.”
• Factory produced EN 197 cements are given the
designation ‘CEM’
• In British Standards, mixer combinations are given the
designation ‘C’ not CEM
• Cement is a mixture of limestone, clay, silica and
gypsum.
• It is a fine powder which when mixed with water sets to
a hard mass as a result of hydration of the constituent
compounds.
• It is the most commonly used construction material 4
History of Cement
• In 1824, Joseph Aspdin, a British
(Leeds) stone mason, obtained a
patent for a cement he produced in
hi kitchen.
his
kit h
• The inventor heated a mixture of
finely ground limestone and clay in
his kitchen stove and ground the
mixture into a powder create a
hydraulic cement-one that hardens
with the addition of water.
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History of Cement
Basic Composition
• Aspdin named the product Portland
cement because it resembled a stone
quarried on the Isle of Portland off
th British
the
B iti h Coast.
C t
• With this invention, Aspdin laid the
foundation for today's Portland
cement industry.
The raw materials required to produce Portland
cement are found and exploited in nearly all parts of
the world, which is a significant reason for its
universal importance as a building material
material..
Table 1 indicates the standard mineralogical
composition of Portland cement and Table 2 indicates
its standard chemical composition.
composition.
Cement is so fine that one kg of cement contains more than 300
billion grains
Basic Composition
Basic Composition
Table 1 Mineralogical Composition of Portland Cements
(Brandt, 1995)
Gypsum
(3.5%)
Chemical Name
Common
Name
Chemical Notation
tricalcium silicate
alite
3CaO.SiO2
C 3S
38
38--60
dicalcium silicate
belite
2CaO.SiO2
C 2S
15
15--38
belite
3CaO.Al2O3
C3A
7-15
celite
4CaO.Al2O3.Fe2O3
C4AF
1010-18
celite
5CaO.3Al2O3
C4AF
1 -2
gypsum
CaSO4.2H2O
CSH2
2 -5
tricalcium
aluminate
tetracalcium
aluminoferite
pentacalcium
trialuminate
calcium sulphate
dihydrate
Abbreviated Mass Contents
Notation
(%)
Other
(1.5%)
Tetracalcium Aluminoferrite
(8%)
Tricalcium Aluminate
(12%)
Tricalcium Silicate
(50%)
Dicalcium Silicate
(25%)
Manufacturing of Cement
Basic Composition
Table 2 Chemical Composition of Portland Cements (Brandt, 1995)
Chemical
Name
Common Name
Chemical
Notation
Abbreviated
Notation
Mass
Contents(%)
calcium oxide
lime
CaO
C
58
58--66
silicon
ili
dioxide
di id
silica
ili
SiO2
S
18--26
18
aluminium
oxide
alumina
Al2O3
A
4-12
ferric oxides
iron
Fe2O3 + FeO
F
1 -6
magnesium
oxide
magnesia
MgO
M
1 -3
sulphur
trioxide
sulphuric
anhydrite
SO3
S
0.5
0.5--2.5
alkaline oxides
alkalis
K2O and NaO2
K+N
<1
• Producing a cement that meets specific chemical and
physical specifications requires careful control of the
manufacturing process.
• The first step in the Portland cement manufacturing
process is obtaining raw materials.
• Generally,
G
ll raw materials
t i l consisting
i ti off combinations
bi ti
off
limestone, shells or chalk, and shale, clay, sand, or
iron ore are mined from a quarry near the plant. At
the quarry, the raw materials are reduced by primary
and secondary crushers.
• Stone is first reduced to 5-inch size (125-mm), then to
3/4-inch(19 mm). Once the raw materials arrive at the
cement plant, the materials are proportioned to create
a cement with a specific chemical composition.
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Manufacturing of Cement
Type of Manufacturing
• Wet Process
• Dry Process - 74% of cement produced
• Preheater/Precalciner Process
Manufacturing of Cement
Manufacturing of Cement – Dry Process
Dry Process
• In the dry process, dry raw
materials are proportioned, ground
to a powder, blended together and
fed to the kiln in a dry state.
• In the wet process, a slurry is
formed by adding water to the
properly
l
proportioned
ti d
raw
materials. The grinding and
blending operations are then
completed with the materials in
slurry form. After blending, the
mixture of raw materials is fed
into the upper end of a tilted
rotating, cylindrical kiln.
In cement plant, to produce cement need seven steps
1.Crushing and Preblending
• In cement production process, most of the material need to be
broken, such as limestone, clay, iron ore and coal, etc. Limestone is
the largest amount of raw material in cement production, after
mining the size of limestone is large, with high hardness, so the
limestone crushing plays a more important role in cement plant.
2. raw material preparation
• In cement production process, producing each 1 ton of Portland
cement need grinding at least 3 tons of materials (including raw
materials, fuel, clinker, mixed materials, gypsum). Grinding
operation consumes power about 60% of total power in cement
plants, raw material grinding takes more than 30%, while coal mill
used in cement palnt consumes 3%, cement grinding about 40%. So
choosing the right grinding mills in cement plant is very important.
3. raw materials homogenization
• Adopting the technology of homogenization could rationally get the
best homo-effect and afford an eligible production to the demand
4. preheating and precalcing
• Preheater and calciner is key equipment for precalcing production
technique.
Source: http://www.crushersmill.com/production-line/cement-plant.html
Image from : http://www.adelaidebrighton.com.au/Images/cement%20manufacturing%20process%20low-res.jpg
Manufacturing of Cement – Dry Process
5.burning cement clinker in a rotary kiln.
• The calcination of Rotary Kiln is a key step of cement production , it makes
directly influence on the quality of cement clinker.
6. cement grinding
• Cement grinding is used for grinding cement clinker (and gelling agent,
performance tuning materials, etc.) to the appropriate size (in fineness, specific
surface area, said), optimizing cement grain grading, increasing the hydration area,
accelerating the hydration rate to meet the requirements of cement paste setting,
hardening.
7. cement packing
Source: http://www.tradekorea.com/products/heater.html?nationCd=CN&linkFlag=
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Manufacturing of Cement – Dry Process
• In the dry process, dry raw materials are
proportioned, ground to a powder, blended
together and fed to the kiln in a dry state.
• In the wet process, a slurry is formed by adding
water to the properly proportioned raw materials.
• The
Th grinding
i di and
d blending
bl di operations
i
are then
h
completed with the materials in slurry form.
• After blending, the mixture of raw materials is
fed into the upper end of a tilted rotating,
cylindrical kiln.
• The mixture passes through the kiln at a rate
controlled by the slope and rotational speed of
the kiln.
Summary of Kin Reactions
Manufacturing of Cement – Dry Process
• Burning fuel consisting of powdered coal or natural gas is forced
into the lower end of the kiln.
• Inside the kiln, raw materials reach temperatures of 1430oC to
1650oC. At 1480oC, a series of chemical reactions cause the
materials to fuse and create cement clinker-grayish-black pellets,
often the size of marbles.
• Clinker is discharged red-hot from the lower end of the kiln and
transferred to various types of coolers to lower the clinker to
handling temperatures.
Clinker
Source: http://www.aboutcivil.com/engineering-materials/cement-composition-types-and-manufacture.pdf
Manufacturing of Cement – Dry Process
• Cooled clinker is combined with
gypsum and ground into a fine
ggrayy ppowder. The clinker is
ground so fine that nearly all of
it passes through a No. 200 mesh
(75 micron) sieve.
• This fine gray powder is
Portland cement.
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Manufacturing of Cement – Wet Process
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Cement Standards
• BS EN 197-1:2000 (Inc. Amendment No.1:2004)
– Composition, specifications and conformity criteria for common
cements
• BS EN 197-4:2004
– Composition, specifications and conformity criteria for low early
strength blast furnace cements
• BS EN 196-series
– Methods of testing cement
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Cement Standards
• Cements are factory produced materials primarily conforming to
BS EN 197-1 or BS EN 197-4
• Some cements, such as Sulphate-resisting Portland cement
(SRPC) are however, still covered by residual British Standards
g of cements ranging
g g from simple
p Portland
• There is a wide range
cement to Composite cements containing up to three major
constituents
• Cements may be produced by inter-grinding or blending the
constituents at the cement works
• Cements can be CE marked against BS EN 197 standards using
BS EN 197-2 Conformity evaluation
Types of BS EN 1971Portland Cement
Portland Cement
Types of Portland Cement
• Different types of Portland cement are manufactured to meet
various physical and chemical requirements.
• The American Society for Testing and Materials (ASTM)
Specification C
C-150
150 provides for eight types of Portland cement.
cement
• BS EN 197-1 specified Five main classes of Portland cement
• However, Both BS EN and ASTM specified some other types of
cements for special functions.
How are Cements Designated
Cement strength Classes (I)
Portland cement is CEM I
NOT
Ordinary Portland cement
cement, OPC or PC
Note: Use of comma
rather than decimal
point
i t
BUT
CEM I
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Cement strength Classes (II)
Cement strength Classes (II)
These classes apply to all CEM cements
Low Heat Cement
Minor Additional Constituents (I)
• BS EN 197-1 allows for the inclusion of up to 5% by mass of a
minor additional constituent (or ‘mac’) in all types of cement
• A ‘mac’ is defined as: “specially selected inorganic natural
mineral materials, inorganic mineral materials derived from the
clinker production process or [specified cement] constituents
unless they are [already] included as main constituents in the
cement”
• Materials typically used as a ‘mac’ include:
Example: CEM III/B 32,5N - LH
Minor Additional Constituents (II)
A CEM I Portland cement with 5% mac is still a
Portland cement and will perform in the same way as
a similar cement without a mac !
– Finely ground limestone
– Fly Ash
– Cement kiln dust (CKD)
Other Cements
These standards will eventually be replaced by new
European Standards, but progress on a standard for
‘sulfate-resisting cement’ is slow
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CHEMICAL COMPOSITION OF
PORTLAND CEMENT
Compound
Chemical
Formula
Common
Formula*
Usual
Range,
weight (%)
Tricalcium silicate
3CaO SiO2
C3S
45 – 60
Dicalcium silicate
2CaO SiO2
C2S
15 – 30
Tricalcium aluminate
3CaO Al2O3
C 3A
6 – 12
Tetracalcium
aluminoferrite
4CaO Al2O3
Fe2O3
C4AF
6–8
•
HYDRATION PROCESS OF CEMENT
™ Cement + H2O C-S-H gel + Ca(OH)2
™ Chemical reaction between cement particles &
water.
™ It is an exothermic process where heat is liberated.
™ The silicates, C3S and C2S, are the most important
compounds, which are responsible for the strength
of hydrated cement paste.
™ C3S provides the early strength and liberated
higher heat of hydration.
*The cement industry commonly uses shorthand notation for chemical formulas:
C = calcium oxide. S = silicon dioxide, A = aluminium oxide and F = iron oxide.
(Michael S. Mamlouk & John P. Zaniewski, 1999)
49
50
Hydration Reaction 3 & 4
Hydration Reaction 1 & 2
Tricalcium Aluminate (C3A)
Tricalcium Silicate
2C3S + 6H
C3S2H3 + 3CH
water
Dicalcium Silicate
2C2S + 4H
C3A + 6H
C-S-H
calcium hydroxide
cement gel
C3A + 3CASH2 +26H
2C3A + C6ASH2 + 4H
C3S2H3 + CH
C3AH6
calcium aluminate hydrate
C6ASH32
ettringite
3C4ASH12
monosulphaluminate
+ new sulphate ions = ettringite
Tetracalcium Aluminoferrite (C4AF)
1/3 to 1/2
1/4 vol
Similar to C3A
51
Development of structure in the cement paste
The C-S-H phase is initially formed. C3 A
forms a gel fastest.
++
(a)
Development of structure in the cement paste
The volume of cement grain decreases as
a gel forms at the surface. Cement grains
are still able to move independently, but as
hydration grows
grows, weak interlocking begins
begins.
Part fo the cement is in a thixotropic state;
vibration can break the weak bonds.
++
Water
+ +
+ +
C3 S
++
C2 S
++
C3 A
+
+
C4 AF
52
+
(b)
53
54
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Development of structure in the cement paste
The initial set occurs with the development
of a weak skeleton in which cement grains
are held in place.
Development of structure in the cement paste
Final set occurs as the skeleton becomes
rigid, cement particles are locked in place,
and spacing between cement grains
increases due to the volume reduction of
the grains.
(c)
(d)
55
56
Clinker Microstructure
Development of structure in the cement paste
Speaces between the cement grains are
filled with hydration products as cement
paste develops strength and durability.
(e)
57
Source: http://www.aboutcivil.com/engineering-materials/cement-composition-types-and-manufacture.pdf
Grinding Mill
Cement hydration
Cement hydration is affected by:1.
2.
3.
4.
time,
temperature,
water:cement ratio, and
cement fineness and composition.
Source: http://www.aboutcivil.com/engineering-materials/cement-composition-types-and-manufacture.pdf
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Rates of Hydration of Cement
Compounds in OPC Paste
Typical results for heat evolution at 20°C of different
Portland cements:
(A) low heat, (B) ordinary & (C) rapid hardening
600
100
500
Heat of hydratio
on (J/g)
C
%
B
400
80
60
A
300
40
200
C3 S
C4AF
C2 S
20
100
0
1 day
C3 A
3 days 7 days
28 days
90 days
1 yr
0
5 yrs
20
Age (log scale)
61
Compressive Strength Development
in OPC Paste
40
60
Time (days)
80
100
62
Significant of Fineness
70
60
% 50
C3 S
40
30
20
C2 S
C3 A
10
C4AF
0
20
40
60
Time (days)
80
100
63
HYDRATION PROCESS OF
CEMENT
HYDRATION PROCESS OF CEMENT
¾ C2S reacts slowly, provide later strength, highly
chemical resistance (sulphate & chloride).
¾ C3A is undesirable, it contributes little or nothing to
the strength of cement except at early ages
ages, and
when hardened, cement paste is attacked by
sulphates, the formation of sulphoaluminate
(ettringite) may cause disruption.
¾ However, C3A is beneficial in the manufacture of
cement in that it facilitates the combination of lime
& silica.
65
¾ C4AF does not affect the behaviour of cement
hydration significantly.
¾ However, it reacts with gypsum to form calcium
sulphoferrite and its presence may accelerate the
hydration of silicates.
66
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Hydration of Cement
Hydration of Cement
• When Portland cement is mixed with water its chemical compound
constituents undergo a series of chemical reactions that cause it to
harden (or set).
• These chemical reactions all involve the addition of water to the
basic chemical compounds.
compounds This chemical reaction with water is
called "hydration". Each one of these reactions occurs at a
different time and rate. Together, the results of these reactions
determine how Portland cement hardens and gains strength.
• Tricalcium silicate (C3S). Hydrates and hardens rapidly and is
largely responsible for initial set and early strength. Portland
cements with higher percentages of C3S will exhibit higher early
strength.
• Dicalcium silicate (C2S). Hydrates and hardens slowly and is
largely responsible for strength increases beyond one week.
Hydrates and hardens
• Tricalcium aluminate (C3A).
quickest. Liberates a large amount of heat almost immediately and
contributes somewhat to early strength.
strength Gypsum is added to
Portland cement to retard C3A hydration. Without gypsum, C3A
hydration would cause Portland cement to set almost immediately
after adding water.
• Tetracalcium aluminoferrite (C4AF).
Hydrates rapidly but
contributes very little to strength. Its use allows lower kiln
temperatures in Portland cement manufacturing. Most Portland
cement colour effects are due to C4AF.
TESTING OF CEMENT
Hydration of Cement
• The result of the two silicate hydrations is the formation of
a calcium silicate hydrate (often written C-S-H because of
is variable stoichiometry).
• C-S-H
C S H makes up about 1/2 - 2/3 the volume of the
hydrated paste (water + cement) and therefore dominates
its behavior (Mindess and Young, 1981).
Why do we have to conduct the tests?
•To ensure the quality of cement.
•To determine the properties of cement.
What are the properties of cement?
•Chemical properties
•Physical properties
70
TESTING OF CEMENT
TESTING OF CEMENT
Tests should be conducted according to the relevant standard:
1.
2.
3.
MS 522 Part 1, 2, 3 – OPC
BS 12: 1978 – OPC and RHPC
BS 4550: Part 1: 1978 – Methods of testing cement.
New Standards
1.
2.
3.
BS EN 197-1:2000 (Inc. Amendment No.1:2004)
– Composition, specifications and conformity criteria for common cements
BS EN 197-4:2004
– Composition, specifications and conformity criteria for low early strength
blast furnace cements
BS EN 196-series
– Methods of testing cement
71
Testing of cement includes:
• Chemical composition
• Fineness of cement
• Setting
S i time
i
• Soundness
• Strength
72
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Chemical Composition
Physical Properties of Cement
• To determine the amount of C3S, C2S, C3A and
C4AF.
• Portland cements are commonly characterized by their
physical properties for quality control purposes.
• Their physical properties can be used to classify and
compare Portland cements.
• The challenge in physical property characterization is
to develop physical tests that can satisfactorily
characterize key parameters.
• Test
T being
b i conducted
d
d at the
h cement factory.
f
• For research, test has to be conducted in the lab.
73
Physical Properties of Cement
• Keep in mind that these tests are, in general, performed on "neat"
cement pastes - that is, they only include Portland cement and
water.
• Neat cement pastes are typically difficult to handle and test and
thus they introduce more variability into the results.
results
• Cements may also perform differently when used in a "mortar"
(cement + water + sand).
• Over time, mortar tests have been found to provide a better
indication of cement quality and thus, tests on neat cement pastes
are typically used only for research purposes (Mindess and Young,
1981).
• However, if the sand is not carefully specified in a mortar test, the
results may not be transferable.
Fineness Test
Physical Properties of Cement
Fineness
• Fineness, or particle size of Portland cement affects hydration rate and thus the
rate of strength gain. The smaller the particle size, the greater the surface area-tovolume ratio, and thus, the more area available for water-cement interaction per
unit volume. The effects of greater fineness on strength are generally seen during
the first seven days (PCA, 1988).
Fineness can be measured by several methods:
– AASHTO T 98 and ASTM C 115: Fineness of Portland Cement by the
Turbidimeter.
– AASHTO T 128 and ASTM C 184: Fineness of Hydraulic Cement by the 150mm (No. 100) and 75-mm (No. 200) Sieves
– AASHTO T 153 and ASTM C 204: Fineness of Hydraulic Cement by Air
Permeability Apparatus
– AASHTO T 192 and ASTM C 430: Fineness of Hydraulic Cement by the 45-mm
(No. 325) Sieve
Air Permeability Lea & Nurse
• Rate of hydration depends on the fineness of cement.
• Fineness is a vital property of cement; both BS and
ASTM require the determination of the specific
surface
f
((m2/kg).
g)
• The specific surface can be determined by the
following apparatus:
• Air Permeability Lea & Nurse:
• Blaine test:
77
By the Air Permeability Lea & Nurse:
• Measure the pressure drop when dry air flows at a
constant velocity through a bed of cement of known
pporosity
y and thickness.
• From this the surface area per unit mass of the bed
can be related to the permeability of the bed.
• BS 4550: Part 3: Section 3.3: 1978.
78
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7/25/2010
Fineness Test
Blaine test
Blaine test:
• A modification of the above method.
• ASTM C240-84.
• The air does not ppass through
g the bed at a constant
rate, but a known volume of air passes at a
prescribed average pressure.
• The rate of flowing diminishing steadily.
• The time of flow to take place is measured
• For a given apparatus and standard porosity, the
specific surface can be calculated.
Fineness
Fineness
Fineness
Fineness
Fineness
Strength ???
Workability ???
Bleeding ???
Heat of hydration ???
Cost of production ???
79
Physical Properties of Cement - Soundness
Soundness
• When referring to Portland cement, "soundness" refers to the
ability of a hardened cement paste to retain its volume after
setting without delayed destructive expansion (PCA,
1988). This destructive expansion is caused by excessive
amounts of free lime (CaO) or magnesia (MgO). Most Portland
cement
specifications
limit
magnesia
content
and
expansion. The typical expansion test places a small sample of
cementt paste
t into
i t an autoclave
t l
( high
(a
hi h pressure steam
t
vessel).
l)
• The autoclave is slowly brought to 2.03 MPa (295 psi) then kept
at that pressure for 3 hours. The autoclave is then slowly
brought back to room temperature and atmospheric
pressure. The change in specimen length due to its time in the
autoclave is measured and reported as a percentage. ASTM C
150, Standard Specification for Portland Cement specifies a
maximum autoclave expansion of 0.80 percent for all Portland
cement types.
80
Soundness
• It is essential that the cement paste after setting
does not undergo a large change in volume i.e.
expansion.
• Expansion may occur due to reactions of free
lime, magnesia and calcium sulphate.
• Free lime – hydrates very slowly occupying a
large volume than the original free lime oxide.
– The standard autoclave expansion test is: AASHTO T 107 and ASTM C
151: Autoclave Expansion of Portland Cement
Soundness
82
Soundness
Magnesia – reacts with water in a manner similar to
CaO, but only the crystalline form is deleteriously
reactive so that unsoundness occurs.
Calcium sulphate – cause expansion through the
formation of calcium sulphoaluminate (ettringgite)
from excess gypsum (not used up by C3A during
setting).
83
• Cements exhibiting this type of expansions are classified
as unsound.
• Le Chattelier’s accelerated test is prescribed by BS 4550:
g unsoundness due to
Part 3: Section 3.7: 1978 for detecting
free lime only. For OPC, expansion not more than 10 mm.
• In practice, unsoundness due to free lime is very rare.
• Autoclave test – ASTM C 151-84 – for testing
unsoundness due to magnesia.
• Calcium sulphate – no specific test is available.
84
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Physical Properties of Cement – Setting time
Setting Time
• Cement paste setting time is affected by a number of items
including: cement fineness, water-cement ratio, chemical
content (especially gypsum content) and admixtures.
• Setting
g tests are used to characterize how a p
particular cement
paste sets. For construction purposes, the initial set must not
be too soon and the final set must not be too late.
• Additionally, setting times can give some indication of whether
or not a cement is undergoing normal hydration (PCA, 1988).
• Normally, two setting times are defined (Mindess and Young,
1981):
Setting Time
• Term to described the stiffening of cement paste or
the change from fluid to a rigid state.
• Cement paste = Cement + Water
• Setting mainly caused by a selective hydration of
C3A & C3S and is accompanied by the temperature
rises in the cement paste.
– Initial set. Occurs when the paste begins to stiffen considerably.
– Final set. Occurs when the cement has hardened to the point at which
it can sustain some load.
86
Setting Time
Setting Time
• Initial set – corresponds to a rapid rise of
temperature.
• Final set – corresponds to the peak temperature
temperature.
• False set – different from initial and final set.
Sometimes occurs within a few minutes of mixing
with water. No heat is evolved in a false set and
the concrete can be remixed without adding water.
• Flash set – caused by the rapid reaction between C3A with
water and liberate heat. Prevented by the addition of
gypsum
• Test can be conducted using Vicat apparatus.
• For OPC
O C and
d RHPC:
C
• Initial set time – not less than 45 minutes.
• Final setting time – not more than 600 minutes.
• Final time = 90 + (1.2 × Initial time)
• Final time is affected by:
• Temperature 20 ± 2°C
• Relative humidity 65% − 90%.
87
Physical Properties of Cement – Vicat &
Gillmore
88
Physical Properties of Cement – Vicat
& Gillmore
Test Method
• These particular times are just arbitrary points used to
characterize cement, they do not have any fundamental
chemical significance.
• Both common setting time tests,
tests the Vicat needle and the
Gillmore needle, define initial set and final set based on the
time at which a needle of particular size and weight either
penetrates a cement paste sample to a given depth or fails to
penetrate a cement paste sample.
• The Vicat needle test is more common and tends to give shorter
times than the Gillmore needle test. Table 3.14 shows ASTM C
150 specified set times.
Vicat
Gillmore
Set Type
Time Specification
Initial
≥ 45 minutes
Final
≤ 375 minutes
Initial
≥ 60 minutes
Final
≤ 600 minutes
The standard setting time tests are:
¾ AASHTO T 131 and ASTM C 191: Time of Setting of
Hydraulic Cement by Vicat Needle
¾ AASHTO T 154: Time of Setting of Hydraulic Cement by
Gillmore Needles
¾ ASTM C 266: Time of Setting of Hydraulic-Cement Paste
by Gillmore Needles
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Physical Properties of Cement
Strength
• Cement paste strength is typically defined in three ways:
compressive, tensile and flexural.
• These strengths can be affected by a number of items including:
water-cement ratio,, cement-fine aggregate
gg g ratio,, type
yp and g
gradingg
of fine aggregate, manner of mixing and molding specimens,
curing conditions, size and shape of specimen, moisture content at
time of test, loading conditions and age (Mindess and Young,
1981).
• Since cement gains strength over time, the time at which a
strength test is to be conducted must be specified. Typically times
are 1 day (for high early strength cement), 3 days, 7 days, 28
days and 90 days (for low heat of hydration cement).
Mortar Test
Two methods:
T
h d
• Mortar test
• Concrete test – BS 4550: Part 3
92
Cement : Sand = 1 : 3
Mass of water = 10% of the mass of dry materials
Sand – standard sand, one size and spherical shape
Cube size of 71 mm
Materials being mixed and compacted using
vibrating table.
• After 24 hours, demould the mortar cubes and cure in
water until they are tested in a wet-surface condition.
• Get the average strength for three cubes.
• According to MS 522: Part 1:
1. OPC –
• 23 MPa at 3 days
• 41 MPa at 28 days
2. RHPC –
• 29 MPa at 3 days
• 46 MPa at 28 days
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94
Concrete Cube Test
•
•
•
•
•
• Strength tests are not made on neat cement paste −
difficult to obtain good specimen.
Mortar Test
Mortar = Cement + Sand + Water
•
•
•
•
•
Strength
Physical Properties of Cement
Cement : Aggregate = 1 : 6
Water cement ratio: 0.6, 0.55, 0.45
Materials must be mixed uniformly in the mixer
Cube size of 100 mm
P
Preparation
ti procedures
d
are the
th same as mortar
t test
t t
1. OPC –
• 11.5 MPa at 3 days
• 26 MPa at 28 days
2. RHPC –
• 18 MPa at 3 days
• 33 MPa at 28 days
When considering cement paste strength tests, there are two items to
consider:
1. Cement mortar strength is not directly related to concrete
strength. Cement paste strength is typically used as a quality
control measure.
measure
2. Strength tests are done on cement mortars (cement + water +
sand) and not on cement pastes.
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Physical Properties of Cement
Compressive Strength
• The most common strength test, compressive strength, is carried out on a 50
mm (2-inch) cement mortar test specimen. The test specimen is subjected to a
compressive load (usually from a hydraulic machine) until failure. This loading
sequence mustt take
t k no less
l
th
than
20 seconds
d and
d no more than
th
80
seconds. Following Table shows
ASTM C 150 compressive strength
specifications.
The standard cement mortar compressive strength test is:
– AASHTO T 106 and ASTM C 109: Compressive Strength of Hydraulic Cement
Mortars (Using 50-mm or 2-in. Cube Specimens)
– ASTM C 349: Compressive Strength of Hydraulic Cement Mortars (Using
Portions of Prisms Broken in Flexure)
Physical Properties of Cement
Tensile Strength
• Although still specified by ASTM, the direct tension test does not
provide any useful insight into the concrete-making properties of
cements It persists as a specified test because in the early years
cements.
of cement manufacture, it used to be the most common test since
it was difficult to find machines that could compress a cement
sample to failure.
Physical Properties of Cement
Heat of Hydration
• The heat of hydration is the heat generated when water and Portland cement
react. Heat of hydration is most influenced by the proportion of C3S and C3A
in the cement, but is also influenced by water-cement ratio, fineness and
curing temperature. As each one of these factors is increased, heat of
hydration increases.
• In large mass concrete structures such as gravity dams, hydration heat is
produced significantly faster than it can be dissipated (especially in the center
of large concrete masses), which can create high temperatures in the center
of these large concrete masses that, in turn, may cause undesirable stresses as
the concrete cools to ambient temperature. Conversely, the heat of hydration
can help maintain favorable curing temperatures during winter (PCA, 1988).
The standard heat of hydration test is:
– ASTM C 186: Heat of Hydration of Hydraulic Cement
Physical Properties of Cement
Curing
Time
I
IA
1 day
-
-
12.4
(1800)
19.3
(2800)
10.0
(1450)
15.5
(2250)
Portland Cement Type
IIA
III
IIIA
10.0
12.4
((1800)) ((1450))
10.3
8.3
24.1
19.3
(1500) (1200) (3500) (2800)
17.2
13.8
-(2500) (2000)
II
IV
V
-
-
8.3
3 days
(1200)
15.2
6.9
7 days
(1000) (2200)
20.7
17.2
28 days
(2500) (3000)
Note: Type II and IIA requirements can be lowered if either an optional heat of
hydration or chemical limit on the sum of C3S and C3A is specified
Physical Properties of Cement
Flexural Strength
• Flexural strength (actually a measure of tensile strength in bending) is
carried out on a 40 x 40 x 160 mm (1.57-inch x 1.57-inch x 6.30-inch) cement
mortar beam. The beam is then loaded at its center point until failure.
The standard cement mortar flexural strength test is:
– ASTM C 348: Flexural Strength of Hydraulic Cement Mortars
Specific Gravity Test
• Specific gravity is normally used in mixture proportioning calculations. The
specific gravity of Portland cement is generally around 3.15 while the specific
gravity of Portland-blast-furnace-slag and Portland-pozzolan cements may
have specific gravities near 2.90 (PCA, 1988).
The standard specific gravity test is:
– AASHTO T 133 and ASTM C 188: Density of Hydraulic Cement
Physical Properties of Cement
Loss on Ignition
• Loss on ignition is calculated by heating up a cement sample to
900 - 1000°C (1650 - 1830°F) until a constant weight is
obtained.
• The weight loss of the sample due to heating is then
determined. A high loss on ignition can indicate pre-hydration
and carbonation, which may be caused by improper and
prolonged storage or adulteration during transport or transfer
(PCA, 1988).
The standard loss on ignition test is contained in:
– AASHTO T 105 and ASTM C 114: Chemical Analysis of Hydraulic
Cement
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Application of Different Types of
Cement
Portland Cement CEM I
• CEM I is the cement that has been
commonly used throughout the world in
engineering and building works.
• Concretes and mortars made using CEM
versatile, durable and forgiving of
construction practice.
Applications of Type - CEM I
most
civil
I are
poor
Application of Different Types of
Cement
Applications of Type - CEM II
Sulphate-Resisting Cements
• SRPC is normally a low alkali cement which benefits concrete
in resisting the alkali silica reaction (ASR). However, it is not
the only sulphate-resisting cement available. Various factorymade composite cements are also sulphate-resisting including
the generally available CEM II/B-V type of Portland-fly ash
cement containing at least 25% of fly ash. Such CEM II/B-V
cements are permitted for use in the same wide-range of
sulphate exposure conditions as is SRPC and are also low in
reactive alkalis. Moreover, SRPC is a type of CEM I cement
with a high clinker content, it is no longer manufactured in the
UK and is becoming more difficult to source. Consequently,
greener sulphate-resisting composite cements will continue to
grow in importance.
Application of Different Types of
Cement
•
Sulphate Resistant Porland Cement (SPRC)
SRPC is used where precaution against moderate sulphate
attack is important, as in drainage structures where sulphate
concentrations in groundwater are higher than normal but not
y severe ((Table).
)
unusually
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Application of Different Types of
Cement
Rapid Hardening Portland Cements
Rapid Hardening Portland Cements
• Rapid hardening versions of CEM I cements are
available. The average particle size is smaller in these
cements and they gain strength more quickly than do
ordinary CEM I types.
• They generate more heat in the early stages and can be
useful in cold weather concreting.
• However, their principal use is in manufacturing precast
concrete units where the high early strength of the
concrete permits quick re-use of moulds and formwork.
Application of Different Types of Cement
White Cement
White Cement
• White cement is a Portland cement CEM I
made from specially selected raw materials,
usually
ll pure chalk
h lk andd white
hi clay
l
(k li )
(kaolin)
containing very small quantities of iron oxides
and manganese oxides.
• White cement is frequently chosen by
architects for use in white, off-white or
coloured concretes that will be exposed, inside
or outside buildings, to the public's gaze.
Admixtures
Summary
Material which is added to concrete during mixing in
order to modify particular properties of concrete
1.
2.
3.
4.
5.
Accelerators (CaCl)
CaCl) NaCl,
NaCl, formate triethenolamine
Retarders Gypsum, sugars, lignosulphates
Air entrainers Wood resins/soaps, fats and oils
Water reducers (plasticisers) Others
eg Corrosion Inhibiting Admixtures
• Portland cement, the major ingredient in concrete, is the most
widely used building material in the world.
• In the presence of water, the chemical compounds within
Portland cement hydrate causing hardening and strength gain.
• Portland cement can be specified based on its chemical
composition and other various physical characteristics that
affect its behavior.
• Tests to characterize Portland cement, such as fineness,
soundness, setting time and strength are useful in quality control
and specifications but should not be substituted for tests on PCC.
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