Transcript File

CEMENT
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Prepared by
M Sohail saleh
M Anees
M Zahid Ali
Sajjad Shukar
Abbas Shukar
INTRODUCTION
The term "cement" originates from the Latin word
"Caementum", which signifies chopped stone.
Definition: “Cement is a crystalline compound of
calcium silicates and other calcium compounds
having hydraulic properties” .
History
Lime and clay have been used as
cementing material on constructions
through many centuries.
Romans are commonly given the credit
for the development of hydraulic
cement,
the
most
significant
incorporation of the Roman’s was the
use of pozzolan-lime cement by mixing
volcanic ash with lime.
In 1824 Joseph Aspdin from England
invented the Portland cement
WHAT IS CEMENT????
Binding
material.
Composite material.
Material with adhesive and cohesive
properties.
Hydraulic properties.
Chemical composition
Tricalcium Silicate (50%)
Dicalcium Silicate (25%)
Tricalcium Aluminate (10%)
Tetracalcium Aluminoferrite (10%)
Gypsum (5%)
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RAW MATERIALS
• Main constituents of cement include:
• Lime
• Alumina
• Iron
• Laterite
• These constituents are obtained
• from following raw materials:
• Lime stone
• Clay
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• Shale
• Gypsum
• iron ore
• Slag / Fire Clay
DO YOU KNOW ?
1 ton of Portland
cement required 1,6
tons of raw
materials
Types of Cement
 2 types of cement normally used in
building industry are as follows:
a) Hydraulic Cement
b) Nonhydraulic Cement
Hydraulic Cement
Cements
are
considered
hydraulic because of their ability to
set and harden under or with
excess water through the hydration
of
the
cement’s
chemical
compounds or minerals
Non-hydraulic Cement
It cannot harden while in contact with
water, as opposed to hydraulic cement.
It is created using materials such as nonhydraulic lime and gypsum plasters etc.
which has liquid properties. After nonhydraulic cement is utilized in construction,
it must be kept dry in order to gain strength
and hold the structure.
Commonly used Types of cement
• 1 Ordinary Portland Cement (OPC)
• 2 Sulphate Resisting portland
Cement (SRPC)
• 3 Rapid hardening cement
• 4 White Cement etc.
Ordinary Portland Cement
Artificial cement Made by the mixing
clinker with gypsum in a 95:5 ratio.
Additional, specific properties can be
enhanced by altering the cement-making
process or the size of the particles and so
producing different cements.
White cement
• specially selected raw materials, usually
pure chalk and white clay containing very
small quantities of iron oxides and
manganese oxides.
• White cement is frequently chosen by
architects for use in coloured concretes that
will be exposed, inside or outside buildings,
to the public's gaze.
Rapid Hardening Portland
Cements
• The average particle size is smaller
• they gain strength more quickly than do
opc.
• They generate more heat in the early stages
and can be useful in cold weather
concreting.
Uses of R.H.C.
• In pre-fabricated concrete construction.
• Where formwork is required to be removed
early for reuse.
• Road repair works.
• In cold weather concrete where the rapid
rate of development of strength reduces the
vulnerability of concrete to the frost
damage.
Sulfate-Resisting Cements
• SRPC contain’s a high content of iron oxide
in order to limit the amount of the mineral
phase (C3A)
• increase its sulfate resistance.
• SRPC is normally a low alkali cement
which benefits concrete in resisting the
alkali silica reaction (ASR)
Uses of S.R.C.
• Concrete to be used in marine condition;
• Concrete to be used in foundation and
basement, where soil is infested with
sulphates;
• Concrete used for fabrication of pipes
which are likely to be buried in marshy
region or sulphate bearing soils;
• Concrete to be used in the construction of
sewage treatment works.
Production of Cement
Consumption of OPC
Physical Properties of Portland
Cements
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Fineness,
Soundness
Consistency
Setting time
Strength
Heat of hydration
Fineness of Cement
Rate of hydration increases with fineness,
leads to high strengths and heat generation.
• . Finer particles will be more completely
hydrated.
• Increasing fineness decreases the amount of
bleeding but also requires more water for
workability which can result in an increase
in dry shrinkage.
Soundness
• Soundness is the ability of a hardened paste to
retain its volume after setting.
• A cement is said to be unsound if it is subjected to
delayed destructive expansion.
• Unsoundness of cement is due to presence of
excessive amount of hard-burned free lime or
magnesia
consistency
• It refers to the relative mobility of a freshly
mixed cement paste
• For normal consistency of cement the
maimum amount of water to be added is
30%
• The plunger of vicatt’s appratus(10mm
diameter) shuold penetrate 10mm
Setting, and Hardening
- When cement is mixed with sufficient water, it loses
its plasticity and slowly forms into a hard rock-type
material; this whole process is called setting.
- Gypsum retards the setting process
- Hot water and calcium chloride used to accelerate
the setting process.
Initial setting
• Time taken by the paste to stiffen to such an
extent the vicatt’s needle not penetrate
through the paste 25 mm
• Measured by Vicatt’s apparatust
Final setting
• Time after which the vicatt’s needle doesn’t
sink visibly nad leave impression on paste
• Measured by Vicatt’s apparatus
Heat of Hydration
• Cement + H2O = Calcium Silicate Hydrate
(C-S-H) +Ca (OH)2 +H2O
• Early age cracking, due to thermal and
shrinkage stress.
• This is a concern about high performance
concrete subjected to higher temperatures
• Most concrete is made with a water to
cement mass ratio ranging from 0.45 to 0.65
Water Cement Ratio
 Water demand can decrease with increasing
limestone content.
 Increase with fineness of cement.
 The proportions of gypsum, anhydrite.
 Dependent on the temperature.
 Soluble sulphate and C3A reactivity changes.
Disadvantages
• Limits on flexibility
• deficiency of
natural resources
• Production of CO2
• Increasing
temperature of
earth
CO2 emission in cement
production
• Calcination
• Burning
• Power
Total
540kg
55%
340kg
35%
90kg
10%
970kg CO2 / ton OPC
For simplicity 1 ton cement 1 ton CO2
emission
360
350
340
330
320
Atmospheric CO2 Concentration
370
380
Time Series Plot for Monthly CO2
in the Atmosphere 1965-2004
0
100
200
300
Month
400
Uses Of Portland Cement
• Main use is in the fabrication of concrete and mortars
• Modern uses
Building (floors, beams, columns, roofing, piles,
bricks, mortar, panels, plaster)
Transport (roads, pathways, crossings, bridges,
viaducts, tunnels, parking, etc.)
Water (pipes, drains, canals, dams, tanks, pools.)
Civil (piers, docks, retaining walls, silos,
warehousing, poles, pylons, fencing)
Agriculture (processing, housing, irrigation)
fire-proof material
Storage
• 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 dray.
• At the time of use cement should be freeflowing and free of lumps.
THANK YOU