Cement

BHAGWAN MAHAVIR COLLEGE OF ARCHITECTURE
SUBJECT- BUILDING MATERIAL GUIDENCE BY:-NIRAV SIR
AND CONSTRUCTION -ABHISHEK SIR

 INTRODUCTION
 HISTORY
 RAW MATERIALS AND COMPOSITION OF CEMENT
 COMPOSTION OF CEMENT
 MANUFACTURE OF CEMENT
 PROPERTIES OF BOGUE’S COMPOUNDS
 HYDRATION OF CEMENT
 HEAT OF HYDRATION
 SETTING AND HARDENING OF CEMENT
 FALSE SET
 TYPES OF CEMENT
 TEST FOR CEMENT
 STORAGE OF CEMENT
OUT LINES


INTRODUCTION
 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).
 It was first made by Joseph Aspdin in 1824 in
England


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 (around1800).


RAW MATERIALS FOR CEMENT
Cement
Argillaceous
Material
Clay, Shale
Calcareous
Material
Lime stone,
chalk


COMPOSTION OF CEMENT
Lime Calcium
Oxide (CaO)
60 – 65% (63%)
Silica (SiO2) 20 – 25% (22%)
Aluminium Oxide 4 - 8% (6%)
Iron Oxide 2 – 4 % (3%)
Magnesium Oxide 1 – 3 %
Gypsum 1 to 4%
C3S-
Tricalcium
silicate
3.Cao .SiO2 25-
50%
C2S – Dicalcium
silicate
2.CaO.SiO2 20-
45%
C3A-Tricalcium
Aluminate
3.CaO.Al2
O3
8-
12%
C4AF-Tetra
Calcium
Alumino Ferrite
4.CaO. Al2
O3, Fe2O3
8-
12%


MANUFACTURING OF
CEMENT
CRUSHING
• This is the first step in the manufacture of Portland Cement.
• 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 ¾of an inch.
• It is than send for either Wet process or Dry process. Wet process is
universally employed.


MANUFACTURING OF
CEMENT
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.


MANUFACTURING OF
CEMENT
MIXING PROCESS
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.


MANUFACTURING OF
CEMENT
STORAGE OF GROUND MATERIALS
• The ground materials containing 30 – 40% of water is stored in separate tanks
equipped with agitators.


MANUFACTURING OF
CEMENT
BURNING
• Slurry is burnt in rotary kiln where actual chemical changes takes place.
• Kiln 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 kiln from the upper end as the kiln rotates
material passes slowly towards the lower end.
• Kiln is heated by burning pulverised coal or oil and temperature is maintained
at about 1400-1500°C. At clinkering temperature actual chemical reactions
takes place.


MANUFACTURING OF
CEMENT
GRINDING
Clinkers are finally grinned 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 naphthalene or sulphonic acid are
added to prevent the formation of lumps and cakes in the cement.
Water proofing agents are also added.

C3S-
• Its responsible for early strength.
• First 7 days strength is due to C3S.
• Its produces more heat of hydration.
• A cement with more C3S content is better for cold weather concreting.
C2S-
• The hydration of C2S starts after 7 days. Its gives strength after 7 days.
• C2S hydration and hardness slowly and provides much of the ultimate strength.
• It is responsible for the later strength of concrete.
• Its produce less heat of hydration.
C3A-
• The reaction of C3A with water is very fast and may lead to an immediate
stiffening of paste, and this process is termed as flash set.
• To prevent this flash set, 2 to 3% gypsum is added at the time of grinding
the cement clinkers. The hydrated C3A don’t contribute strength of concrete
PROPERTIES OF BOGUE’S
COMPOUNDS


C4AF-
• C4AF hydrates rapidly.
• Its does not contribute to the strength of concrete.
• The hydrates of C4AF shows a comparatively higher resistance
to the sulphate attacks than the hydrates of C3A
PROPERTIES OF BOGUE’S
COMPOUNDS


• When water is added to cement, ingredients of cement react
chemically with water and form various complicated chemical
compounds. The chemical reaction that take place between cement and
water is referred as HYDRATION OF CEMENT
• The largest crystals of C3S or C2S are about 40μ size.
• An average size of cement crystal would be 15-20 μ.
• It has been observed that after 28days of curing, cement grains have
been found to have hydrated to a depth of only 2μ.
• It has also been observed that complete hydration under normal
condition is possible for cement partials smaller then 50μ.
• The process of hydration takes 1 year.
HYDRATION OF CEMENT

 This % amount of water shown in the
table, chemically combined with
cement. And therefore it is known as
BOUND WATER.
 15% of water is imbibed within gel-
pores, this water is known as GEL
WATER.
 Thus, 38% (23+15) water is required
for complete hydration.
 If less than 38% of water is used then
complete hydration is not possible.
Hence, strength of the concrete will
be reduced.
 If more than 38% of water is used,
than the access water will cause
undesirable capillary cavities and
concrete becomes porous.
WATER REQUIREMENTS
FOR HYDRATION
Major
compound
% water by weight
of cement
C3S 24
C2S 21
C3A 40
C4AF 37


HEAT OF HYDRATION
 The quality of heat per gram of
unhydrated cement , evolved upon
complete hydration at a given
temperature is defined as HEAT OF
HYDRATION.
 For Heat of hydration, mass concrete
works like concrete gravity dam,
retaining wall etc. are important.
 It has been observed that the
temperature in the interior of large
mass concrete is 50°C above the
original temperature of the concrete
mass at the time of placing. Hence,
high temperature causes cracks in
concrete.
 C3S and C3A produce more heat than
C2S.
 During hydration cement produce 120
celery/gram heat of 1 gram cement.


SETTING AND HARDENING
OF CEMENT
Setting of cement Hardening of cement
• Setting is the term used to describe
the stiffening of the cement paste.
• Hardening refers to gain of strength
of a set cement paste.
• It refers to a change form a fluid to a
rigid state.
• It refers to formation of solid mass
possessing good compressive
strength.
• The setting of cement starts after 30
minutes from the instant when
water is added to cement and
completed within 10 hours.
• The process of hardening of cement
continues for a period more than 1
year.
• To know the setting of cement,
initial setting time test and final
setting time test are conducted.
• To know the hardening of cement,
compressive strength test is
conducted.


FALSE SET
• A phenomenon of abnormal premature stiffening (hardening) of cement within
a few minutes of mixing with water, is termed as false set, it differs from flash
set in that no appreciable heat is evolved, and remixing the cement paste
without addition of water restores plasticity of the paste until it sets in the
normal manner and without a loss of strength.
• Some of the causes of false set are to be found in the dehydration of gypsum
when inter ground with too hot a clinker; hemihydrate or anhydrite are
formed, and when the cement is mixed with the water these hydrate to form
gypsum thus ‘plaster set’ takes place with a resulting stiffening of the paste.
• False set can be due to the activation of C3S by aeration at moderately high
humidities water is adsorbed on the grain of cement and these freshly activated
surfaces can combine very rapidly with more water during mixing, this rapid
hydration would produce false set.
• Another cause of false set may be associated with the alkalis in the cement.
During storage they may carbonate, and alkali carbonates react with Ca (OH)2
liberated by the hydrolysis of C3S to form CaCO3. This precipitates and
includes a rigidity of the paste.


TYPES OF CEMENT
Ordinary Portland Cement
• This is by far the most common cement in use : about 70 percent of all cement
of all cement used in India if of the ordinary type .
• Prior to 1987, there was only one grade of OPC governed by IS 269 : 1976. After
1987 higher grade cement were introduced in India. The OPC was classified
into three grades as under:
Grade Minimum compressive strength at
28 days as per IS 4031-1988
33 Grade 33 N/mm2
43 Grade 43 N/mm2
53 grade 53 N/mm2
• In the modern construction activities, higher grade moments have become so
popular that 33 grade cement is almost out of the market. Although they are little
costlier then low grade cement; they offer many benefits like 10-20% saving in
cement consumption, faster rate of development of strength and higher strength.
[ For general concrete construction when there is no exposure to sulphates in the soil ]


TYPES OF CEMENT
Rapid Hardening Cement
• As the name implies , it develops strength rapidly and therefore can be called as high
early strength cement. The rate of setting is same as that of ordinary portland cement.
• The strength of RHC ate age of 3 days is equal to to the 7 days strength of OPC with
the same w/c ratio.The increased rate of gain of strength of RHC is achieved by
higher C3S content and by finer grinding of clinker.
• the rapid gain of strength is accompanied by a high rate of heat development and
hence it should not be used in mass concrete construction like concrete gravity dam,
concrete retaining wall etc.
USES
1. In pre-casted fabricated concrete construction
2. For road repair
3. Where form-work is required to be removed early for re-use elsewhere.
4. In clod weather concreting
5. wall sealing etc.


TYPES OF CEMENT
Extra Rapid Hardening Cement
• This cement is obtained by intergrading calcium chloride with RHC. The
Quantity of calcium chloride should not exceed 2 percent. it is necessary that
the concrete made by using extra rapid hardening cement should be
transported, placed, compacted, and finished within 20 minutes. This cement
must be stored under dry condition and should generally be used within one
month of despatch from the factory.
• A large quantity of heat is evolved in a very short time after placing. A small
amount of initial corrosion of reinforcement ha also been reported. This cement
is not recommended for use in prestress concrete construction.
• The strength of extra rapid hardening cement is bout 25% higher then rapid
hardening cement at 1 r 2 days and 10% to 20% higher at 7 days. however at 90
days the strength of extra Rapid hardening cement and RHC is nearly the
same.
• It is suitable for cold weather concreting. It is suitable where a very high early
strength is required.


TYPES OF CEMENT
Quick Setting Cement
• This cement sets very early but dose not gain strength early. The early setting
property. Sometimes aluminium sulphate is added to accelerate the setting
process. It contains higher percentage of C3A. It is required to be mixed, placed
and compacted very early.
USES
1. Underwater construction
2. Grouting operation


TYPES OF CEMENT
Low Heat Cement
• The reaction of cement with water is exothermic and produces a considerable
quantity of heat.
• The rise in temperature in the interior of a large concrete mass due to the heat
of hydration can lead to serious cracking.
• As per IS specification the heat of hydration of low heat cement shall be as
follow:
7 days - not more then 65 calories/gram
28 days - not more then 75 calories/gram
• a low heat evaluation is achieved by reducing the contents of C3S and C3A
which are the compounds evolving the maximum heat of hydration are
increasing C2S.
USES
1. Mass concrete construction
2. Where it is necessary to produce resistance to sulphate attack.
3. Hot weather concreting


TYPES OF CEMENT
Sulphate Resisting Cement
• Ordinary portland cement is susceptible to the attack of sulphates, in particular
to the action of magnesium sulphate (gypsum) and with hydrate of calcium
aluminate to form calcium sulphoaluminate, the volume of which is about
227% of the volume of the original aluminates.
• Their expansion within the framework of hardened cement paste results in
cracks and subsequent disruption. This phenomenon is known as sulphate
attack.
USES
1. Concrete to be used in marine conditions
2. Concrete to be used in the construction of sewage treatment plants.
3. Concrete used for fabrication of RCC pipes which are likely to be buried in
marshy region
4. Concrete to be used in foundation and basement where soil is infested with
sulphates.
5. Concrete to be used in the construction of chemical factory.


TYPES OF CEMENT
Super Sulphate Cement
• This cement is manufacturing from well-granulated slag (80 to 85 %) and hard
burnt gypsum (calcium sulphate) (10 to 15 %) together with 1 to 2 % of
Portland cement.
• This mixture is ground finer then that of portland cement.
• It specific surface is between 2-1/2to 4 hours and final setting time between 4-
1/2 to 7 hours.
• It’s total heat of hydration is very very low, about 38 calories/gm at 7 days and
42 calories/gm at 28 days.
• Its setting action is different from other cements and admixtures should not be
used with it.
USES
1. In foundation, where chemically aggressive conditions exist.
2. in marine work.
3. RCC pipes likely to be used in sulphate bearing soil.
4. Mass concreting.


TYPES OF CEMENT
Portland Pozzolana Cement
• Portland Pozzolana cement is manufactured by the integrating of OPC clinker
with 15 to 35 of pozzolanic material.The pozzolanic materials generally used
for manufacture of portland pozzolana cement are flash and calcined clay.
• The pozzolanic material are essentially a siliceous or aluminous material which
itself possessing no cementitious properties, which will, in finely divided form
and in the presence of water, react with calcium hydroxide
• It is important to note that the addition of pozzolana dose not contribute to the
strength at early ages, but gives later strengths similar to those of OPC.
• It is economical, as costly clinker is replaced by cheaper pozzolanic material.
USES
1. For Hydraulic structures.
2. For marine structure
3. For mass concrete structures like dam, bridges piers and raft foundation


TYPES OF CEMENT
Portland Slag Cement
• This type of cement is made by grinding portland cement clinker , gypsum and
granulated blast furnace slag.
• The quantity of blast furnace slag mixed with portland clinker will range from 25
to 65%.
• Blast-Furnace slag is a waste produce consisting of a mixture of lime, silica and
alumina obtained in the manufacture of pig iron.
• The slag can also be used together with lime stone as a row material for the
inventional manufacture of portland cement resulting in clinker which when
ground gives Portland slag cement.
• It has been pointed out that glassy granulated slag could be used for the
manufacture of slag cement.
• The portland slag cement should not be used in clod weather as the low heat of
hydration coupled with moderately low rate of strength development, can lead to
frost damage.
USES
1. For mass construction work
2. For marine works


TYPES OF CEMENT
Coloured cement(white cement)
• The greys colour of Portland cement is due to the presence of iron oxide.
• The process of Manufacturing of white cement is the same as that of Portland
cement but the amount of iron oxide is limited to less then 1 percent. The kind of
limestone required for manufacturing white cement is only available near Jodhpur
in Rajasthan.
• The row material used are high purity lime stone (96% CaCO3 and less then 0.07%
iron oxide)
• For manufacturing various coloured cements either grey portland cement or white
cement is used as a base. With the use of grey cement only red or brown cement
can be produced.
• The use of white cement as a base is costly. Coloured cement consist of Portland
cement with 5-10% of pigment. For proper mixing of pigment, it is usual to grind
pigment and cement clinker together.
USES
1. To fill joints of glazed tiles in W/C, bathroom, kitchen etc.
2. To fill the joints in flooring


TYPES OF CEMENT
Hydrophobic Cement
• Hydrophobic cement is obtained by adding water repellent file forming substance
such as oleic acid, stearic acid and boric acid to OPC clinker at the time of grinding.
The water-repellants film formed around each grain of cement, prevents the entry
of atmospheric moisture and reduces the rate of deterioration of the cement during
long storage, transport or under unfavourable condition.
• The film is broker out where the cement and aggregate are mixed together at the
mixer exposing the cement particles for normal hydration.
• The film forming water-replacement substance will entrain certain amount of air in
the body of concrete which will improve the workability of concrete.


TYPES OF CEMENT
Air Entraining Cement
• Air entraining cement is made by mixing a small amount of an air-entraining agent
with OPC clinker at the time of grinding.
• The main air-entraining agents used are
1. Alkali salts of wood resins.
2. Calcium salts of glues and other proteins obtained in the treatment of animal
hides
3. Calcium lignosulphate derived from the sulphite process in paper making
4. Synthetic detergents of the alkyl aryl sulphonate type.
5. Animal and vegetable fats, oils etc.
6. Bleaching powder.
7. Hydrogen peroxide, Aluminium powder
• The air-entraining agents may be used in powder or in liquid forms to the extent
of 0.025 1.0 percent. Air-entraining agents will produce at the time of mixing.
• tiny discrete non coalescing air bubbles in the mass of concrete which will modify
the properties of plastic concrete with respect to workability, segregation and
bleeding.


TYPES OF CEMENT
Masonry Cement
• ordinary cement, when used in masonry, gives a harsh mortar and because of the
sucking water by masonry, often results in poor bond.
• To avoid this, masonry cement is now used which is made of Portland cement
clinker, limestone, gypsum and air-entraining agent.
• The masonry cement should possess fattiness, be workable, adhere to the surfaces,
should have a low volume change, possess plasticity and cohesiveness.
• The air-entraining agent helps the grinding and the plasticity, workability and the
water retentive property. It shrinkage too.


 Following four field tests may be carried out to
ascertain roughly of carried cement:
• (1) Colour
• (2) Physical properties
• (3) Presence of lumps
• (4) Strength.
FILD TEST OF CEMENT


FILD TEST OF CEMENT
(1) Colour:
• The colour of cement should be uniform.
• It should typical cement colour i e grey colour with a light greenish shade.
• This is not always a reliable test.
• But it gives an indication of excess lime or clay and the degree of burning.
(2) Physical properties:
• The cement should feel smooth when touched or rubbed in between fingers.
• If it is felt rough, it indicates adulteration with sand. hand is inserted in a bag or
heap of cement, it should feel cool and not warm. If a small quantity of cement is
thrown in a bucket of water, It should sink and should not float surface.
• A thin paste of cement with water should feel sticky between the fingers If the
cement contains too much of pounded clay and silt as an adulterant, the paste will
give an earthy smell.


LABORATORY TESTS FOR
CEMENT
TYPES OF SLUMP
PROCESS OF SLUMP TEST
(3) presence of
lumps:
• The cement should
be free from any
hard lumps.
• Such lumps are
formed by the
absorption of
moisture from the
atmosphere.
• Any bag of cement
containing such
lumps should be
rejected.


FILD TEST OF CEMENT
(4) Strength
• (i) The briquettes with a lean or weak mortar are made. The hre of briquette may
be about 75 mm x 25 mm x 12 mm. portion of cement and sand 116. The briquettes
are in water for a period of 3 days. If cement is of sound quality, such briquettes will
not be broken easily and it will be difficult to convert them into powder form.
• (ii) A block of cement 25 mm x 25 mm and 200 mm long is prepared and it is
immersed for 7 days in water. It is then placed on supports 150 mm apart and it is
loaded with a weight of 340 N. The block should not show signs of failure.
• (iii) A thick paste of cement with water is made on a piece of thick glass and it is
kept under water for 24 hours. It should set and not crack.


1. Finesse
2. Standard consistency
3. Initial and final
setting time
1. Compressive strength
2. Soundness
CEMENT

1. FINENESS TEST:-
• Weight correctly 100 grams of cement
and transfer it on a standard IS sieve
No.9 (90 microns sieve).
• Break down the air lumps in the sample
with fingers.
• Sieve the sample giving circular and
vertical motion continuously 15
minutes. (Mechanically sieve shaker may
be used).
CEMENT
No. Type of
cement
% wt. of
residue
on
90micron
sieve
Specific
surface
area
(Cm2/gm
)(min.)
1 Ordinary
Portland
cement
10 2250
2 Rapid
hardening
cement
5 3250

CONSISTENCY TEST-
The purpose of this test is to determine the
percentage of water required for preparing
cement pastes for other tests. Following
procedure is adopted:
• Take 300 gm of cement and add 30 per
cent by weight or 90 gm of water to it.
• Mix water and cement on a non-porous
surface. The mixing should be done
thoroughly.
• Fill the mould of Vicat apparatus. The
interval between the addition of water
to the commencement of filling the
mould is known as the time of gauging
and it should be 33/4 to 41/4 minutes.
CEMENT

• It consists of a frame to which is attached a movable rod weighing 300 gm and
having diameter and length as 10 mm and 50 mm respectively. An indicator is
attached to the movable rod. This indicator moves on a vertical scale and it gives the
penetration. The Vicat mould is in
• The form of a cylinder and it can be split into two halves. The vicat mould is placed
on a non-porous plate. There are three attachments square needle, plunger and
needle with annular collar. The square needle is used for initial setting time test, the
plunger is used for consistency test and the needle with annular collar is used for
final setting time test.
• The plunger is attached to the movable rod of Vicat apparatus. The plunger is gently
lowered on the paste in the mould.
• The settlement of plunger is noted. If the penetration is between 5 mm to 7 mm from
the bottom of mould, the water added is correct. If penetration is not proper, the
process is repeated with different percentages of water till the desired penetration is
obtained.
CEMENT

INITIAL SETTING TIME:-
• The cement weighing 300 gm is taken and it is mixed with percentage of water as
determined in consistency test.
• The cement paste is filled in the Vicat mould.
• The square needle of cross-section 1 mm x 1 mm is attached to the moving rod of
the Vicat apparatus.
• The needle is quickly released and it is allowed to penetrate the cement paste. In the
beginning, the needle penetrates completely. It is then taken out and dropped at a
fresh place. The procedure is repeated at regular intervals till the needle does not
penetrate completely. The needle should penetrate upto about 5 mm measured
from bottom.
• The initial setting time is the 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.
CEMENT

FINAL SETTING TIME:-
• The cement paste is prepared as above and it is filled in the Vicat mould.
• The needle with annular collar is attached to the moving rod of the Vicat
apparatus. This needle has a sharp point projecting in the centre with annular
collar.
• The needle is gently released. The time at which the needle makes an impression
on test block and the collar fails to do so is noted.
• The final setting time is the difference between the time at which water was added
to cement and time as recorded in(3).
• This time should be about 10 hours for ordinary cement.
CEMENT

SOUNDNESS
TEST:-
CEMENT
Undesirable expansion of some constituents of cement after setting is know as
unsoundness. It is create cracks in concrete.


• The distance between the points of indicator is noted. The mould is again
placed in water and heat is applied in such a way that boiling point of
water is reached in about 30 minutes. The boiling of water is continued
for one hour
• The mould is removed from water and it is allowed to cool down
• Distance between the points or indicator is again measured the
difference between the two readings indicates the expansion of cement
and it should not exceed 10 mm.
CEMENT
• PROCEDURE:-
• The cement paste is prepared. The percentage of
water is taken as determined in the consistency test.
• The mould is placed on a glass plate and it is filled
by cement paste.
• It is covered at top by another glass plate. A small
weight is placed at top and the whole assembly is
submerged in water for 24 hours. The temperature
of water should be between 24 c to 35 c.

COMPRESSIVE STRENGTH TEST:-
(1)Equipment and materials:
• Metal cube mould of size 7.06 cm x 7.06 cm x7.06cm
• Compression testing machine.
• Non-porous enamel tray, trowel.
• Measuring cylinder.
• Ordinary Portland cement( O.P.C)
• Standard sand (IS 650:1991)
(2)Procedure-
• The mortar of cement and sand is prepared. The proportion is 1:3 which gm of
cement is mixed with 3x gm of sand.
• The water is added to the mortar. The water cement ratio is kept as 0.4 which
means that 0.4 r gm of water is added to dry mortar.
CEMENT

• The mortar is placed in moulds. The test specimens are in the form of cubes with
side as 70.6 mm or 76 mm. The moulds are of metal and they are constructed in
such a way that the specimens can be easily taken out without being damaged. For
70.6 mm and 76 mm cubes, the cement required is 185 gm and 235 gm respectively.
• The mortar, after being placed in the moulds, is compacted in vibrating machine
for 2 minutes.
• The moulds are placed in a damp cabin for 24 hours
• The specimens are removed from the moulds and they are submerged in clean
water for curing.
• The cubes are then tested in compression testing machine at the end of 3 days and
7 days. The testing of cubes is carried out on their three sides without packing.
Thus three cubes are tested each time to find out the compressive strength a the
end of 3 days and 7 days. The average value is then worked out. During the test the
load is to be applied uniformly at the rate of 350 kg/cm2 or 35 N/mm2
• The compressive strength at the end of 3 days should not be less than 115 kg/cm or
11.50 N/mm2 and that at the end o 7 days should not be less than 1 kg/cm2 or
17.50 NImm2
CEMENT

The cement exposed to air absorbs moisture slowly, and gets deteriorated. An
absorption of 1 to 2 % of water has no appreciable effect, but a future amount of
absorption retards the hardening of cement and reduce its strength
.
 The following points should be observed while storing of cement.
• Bagged cement should be stored in waterproof shed with nonporous walls and
floor.
• The plinth level should be well above ground level.
• Numbers of opening like doors, windows and ventilators
should be minimum kept tightly shut.
• Drainage should be provided if necessary to prevent
accumulation of water in the vicinity shut.
• Cement bag should be kept 30 cm away from walls.
STORAGE OF CEMENT

• Not more than 14 bags should be kept one above
other.
• To reduce air circulation no gap is desirable between
rows of cement bags.
• In moist area cement bags should be placed on
wooden planks kept above floor.
• Old bags should be used first, for beams and slab
casting use fresh bags.
• Once the cement has been properly stored it should
not be disturbed unit it is to be used.
• The practice of moving and restacking the bags,
exposes fresh cement to air.
STORAGE OF CEMENT

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