Cement is a powdery material that binds other materials together when mixed with water. It is made through a process of crushing raw materials like limestone, mixing them into a slurry or powder, burning the mixture in a kiln, and finely grinding the resulting clinker. The most common type is Portland cement, which is a finely ground powder that sets and hardens through chemical reactions with water. Cement is widely used in construction for buildings, infrastructure, and other applications due to its ability to form strong structures and conform to various shapes.
2. CONTENTS
Introduction
Definition
History
Classification
Grades
Manufacture
Characteristics
Common applications
Advantages and disadvantages
Conclusion
3. INTRODUCTION
The word "cement" traces to the Romans, who
used the term opus caementicium to
describe masonry resembling modern concrete
that was made from crushed rock with burnt lime
as binder. The volcanic ash and
pulverized brick additives that were added to the
burnt lime to obtain a hydraulic binder were later
referred to
as cementum, cimentum, cäment, and cement.
4. DEFINITION
Cements are materials that
exhibit characteristic properties of setting
and hardening when mixed to a paste
with water. This makes them join rigid
masses into coherent structures. It is
powdery bonding material having
adhesive and cohesive properties.
Chemically it is a finely ground
mixture of calcium silicates and
aluminates which set to a hard mass
when treated with water. These are called
as Hydraulic Cements (Portland Cement)
and those setting in air are Non Hydraulic
cements (Ordinary Lime).
5. HISTORY
It is uncertain where it was first discovered that a
combination of hydrated non-hydraulic lime and
a pozzolan produces a hydraulic mixture, but
concrete made from such mixtures was first used
by the Ancient Macedonians and three centuries
later on a large scale by Roman engineers. They
used both natural pozzolans (trass or pumice) and
artificial pozzolans (ground brick or pottery) in
these concretes. Many excellent examples of
structures made from these concretes are still
standing, notably the huge dome of
the Pantheon in Rome and the massive Baths of
Caracalla. The vast system of Roman
aqueducts also made extensive use of hydraulic
cement.
The technical knowledge of making hydraulic
cement was later formalized by French and British
engineers in the 18th century.
Modern hydraulic cements began to be developed
from the start of the Industrial Revolution (around
1800).
Cement was first made by Joseph Aspdin in 1824
in England.
6. CLASSIFICATION OF CEMENT
•Natural Cement: Obtained by
calcinating and pulverizing natural
cement rock of argillaceous and clay
with limestone. It does not have
sufficient strength and is cheap and
quick setting & have hydraulic
properties.
•Pozzolana Cement: Volcanic ash
containing silicates of calcium, iron and
aluminum when mixed with lime and
heated produces this cement.
•Slag Cement: Mixture of blast furnace
slag (Ca and Al Silicates) and hydrated
lime. Sometimes accelerators like
clay, salt, caustic soda are added to
hasten hardening process.
•Portland Cement: It consists of
compounds of lime, silica, alumina and
iron. When mixed with water it forms a
paste which binds the rock, sand and
gravel to form concrete.
7. GRADES OF PORTLAND
CEMENT
33 grade –General Construction
like plastering, finishing
works etc, where strenth is not required.
43 grade –Useful for structural
works, precast items etc, Strength development is
faster than 33 grade.
53 grade–Used for multi-storey buildings, precast
pre-stressed items, bridges, tall structures,etc.
Develops very fast strength and speeds up
construction.
8. MANUFACTURE OF PORTLAND CEMENT
•Crushing
•Mixing (Wet Process)
•Mixing (Dry Process)
•Grinding (Ball Mill and Tube Mill)
•Storage of Ground Materials
•Burning
–Drying Zone
–Calcination Zone
–Clinkering Zone
•Grinding
–Retarder
–Dispersing Agent
–Water Proofing
•Packaging
9. CRUSHING
This is the first step in the manufacture of
Portland Cement.
Jaw crushers of various sizes are
employed for the crushing purpose.
Raw materials are crushed by crushers till
the size of the raw material reduces to ¾
of an inch.
It is than send for either Wet process or
Dry process. Wet process is universally
employed.
10. MIXING PROCESS
Wet process
Calcareous materials are crushed, powdered and stored in bins.
Argillaceous materials is mixed with water and washed. This removes
any adhering organic impurities.
Powdered Calcareous and Washed Argillaceous materials are mixed in
proper proportions to get a slurry.
Chemical composition is analyzed and corrected if necessary by addition
of the deficient materials.
This slurry is then fed into the rotary klin.
Dry process
Hard raw materials like cement rock or blast furnace slag are first crushed
to 50mm pieces in ball mill, then dried and stored.
Crushing is done by gyratory crushers and drying is done by rotary driers.
Separate powdered ingredients are mixed in required proportions to get
the raw mix which is then fed to rotary klins.
11. STORAGE OF
GROUND MATERIALS
The ground materials containing 30 – 40% of water is stored
in separate tanks equipped with agitators.
This step is followed by process of burning.
12. BURNING
Slurry is burnt in rotary klin where actual chemical changes takes place.
Klin is long steel cylinder 30-40 meter in length, 2-4 meter in
diameter, lined by refractory bricks. It is inclined at gradient of 0.5-0.75
inch and can be rotated at the desired speed.
The material is introduced in the klin from the upper end as the klin
rotates material passes slowly towards the lower end.
Klin is heated by burning pulverized coal or oil and temperature is
maintained at about 1400-1500°C. At clinkering temperature actual
chemical reactions takes place.
13. GRINDING
Grinding can be done in two stages
•Ball Mill
–Consists of cast iron drum containing iron and
steel balls of different sizes. The principle used in
ball mill s impact and shear produced by large
no. of tumbling and rolling balls.
•Tube Mill
–Ball mill grinding is followed by tube mill
grinding. Tube mill is conical at the discharge end
with separate inlet and outlet.
–Slower is the feeding speed finer is the product
coming out of the tube mill.
14. GRINDING
Clinkers are finally grinded in ball mill and tube
mill to a fine powder. Additives added are as follows.
Retarder:
Gypsum or Plaster of Paris acts as retarder to
prevent quick setting. After initial setting gypsum retards
the dissolution of tricalcium aluminate by forming
tricalcium sulphoaluminate.
Dispersing Agent:
Sodium salts and polymers of condensed
napthlene or sulphonic acid are added to prevent the
formation of lumps and cakes in the cement.
Water proofing agents are also added.
15. PACKAGING
The ground powder is
packed by automatic
machines in a bag.
This is then dispatched to
the markets where it is
sold.
16. CHARACTERISTICS OF
CEMENT
When water is added to initiate dry mixtures of
cement and sand, hydration of cement starts and it
will binds sand particles as well as the surrounding
surfaces of masonry and concrete.
The proportion of cement and sand will decide the
strength of mortar.
A richer mix than 1:3 proportion is prone to
shrinkage.
Solid surface are provided by well proportioned
mortar.
A leaner mix is not able of closing the voids in sand.
17. COMMON APPLICATIONS
OF CEMENT
Building
(floors, beams, columns, roofing, piles, bricks,
mortar, panels, plaster).
Transport
(roads, pathways, crossings, bridges, sleepers,
viaducts, tunnels, stabilization, runways, parkin
g).
Water
(pipes, culverts, kerbing, drains, canals, weirs, d
ams, tanks, pools).
Civil (piers, docks, retaining
walls, silos, warehousing, poles, pylons, fencing)
.
18.
19. ADVANTAGES AND
DISADVANTAGES
Advantages:
Cement is very strong.
It can create large structures quickly.
It conforms to different shapes (arcs and circles, etc).
It has high thermal mass (moderates temperature).
Disadvantages:
Cement is subjected to cracking.
It is very difficult to provide idoneous curing conditions.
It is not ideal for situation when settlement is expected.
20. CONCLUSION
Cement is a binder, a substance that sets and hardens
independently, and can bind other materials together.
It was first made by Joseph Aspdin in 1824 in England.
It is Classified as Natural Cement, Pozzolana Cement, Slag
Cement, Portland Cement.
Portland cement is most commonly used.
Its manufacturing process consists of Crushing, Mixing (Wet
Process), Mixing (Dry Process), Grinding (Ball Mill and Tube
Mill), Storage of Ground Materials, Burning, Packaging and
finally transporting to sell.
It is most commonly used in building construction, civil, water
carrying and storage, transportation and agriculture.