Types Of Cement
Cements of unique characteristics
for desired performance in a given environment are being manufactured by changing the chemical
composition of OPC or by using additives, or by using different raw materials.
Some of the cements available in the market are as follows.
Rapid Hardening Portland Cement (IS: 8041) has high
lime content and can be obtained by increasing the C3S
content but is normally obtained from OPC clinker by finer grinding (450 m2/kg).
The basis of application of rapid hardening cement (RHC) is hardening
properties and heat emission rather than setting rate. This permits addition of
a little more gypsum during manufacture to control the rate of setting. RHC
attains same strength in one day which an ordinary cement may attain in 3 days.
However, it is subjected to large shrinkage and water requirement for
workability is more. The cost of rapid hardening cement is about 10 per cent
more than the ordinary cement. Concrete made with RHC can be safely exposed to
frost, since it matures more quickly.
Initial setting time 30 minutes (minimum)
setting time l0 hours (maximum)
day 16.0 N/mm2
day 27.5 N/mm2
Uses: It is suitable for repair of roads and bridges and when
load is applied in a short period of time.
High Alumina Cement (IS: 6452): This is
not a type of Portland cement and is manufactured by fusing 40 per cent
bauxite, 40 per cent lime, 15 per iron oxide with a little of ferric oxide and
silica, magnesia, etc. (Table 5.5) at a very high temperature. The alumina
content should not be less than 32%. The resultant product is ground finely.
The main cement ingredient is monocalcium aluminate CA which interacts with
water and forms dicalcium octahydrate hydroaluminate and aluminium oxide
2(CaO.AL2O3.10H2O) + H2O
= 2CaO.Al2O3.8H2O + 2Al(OH)2
The dicalcium hydroaluminate gel consolidates and
the hydration products crystallise. The rate of consolidation and
crystallisation is high leading to a rapid gain of strength. Since C3A
is not present, the cement has good sulphate resistance.
Composition of a Typical High Alumina Cement
FeO, Fe3O4 13.1
on ignition 0.2
Properties: It is not
quick setting: initial setting time (minimum) is 30 minutes, even up to 2
hours. The final setting time should not exceed 600 minutes. It attains
strength in 24 hours, high early strength, high heat of hydration and
resistance to chemical attack. Compressive strength after one day is 30.0 N/mm2
and after 3 days it is 35.0 N/mm2. After setting and hardening,
there is no free hydrated lime as in the case of ordinary Portland cement. The
fineness of the cement should not be less than 225 m2/kg. The cement
should not have expansion more than 5 mm.
Uses: It is
resistant to the action of fire, sea water, acidic water and sulphates and is
used as refractory concrete, in industries and is used widely for
precasting. It should not be used in places where temperature exceeds 18 o C.
Supersulphated Portland Cement
(IS: 6909) is manufactured by intergrinding or intimately
blending a mixture of granulated blast furnace slag not less than 70 per
cent, calcium sulphate and small quantity of 33 grade Portland cement. In this
cement tricalcium aluminate which is susceptible to sulphates is limited to
less than 3.5 per cent. Sulphate resisting cement may also be produced by the
addition of extra iron oxide before firing; this combines with alumina which
would otherwise form C3A, instead forming C4AF which is
not affected by sulphates. It is used only in places with temperature below
40 o C.
Water resistance of concretes
from supersulphate Portland cements is higher than that of common Portland
cements because of the absence of free calcium oxide hydrate. In supersulphate
Portland cements the latter is bound by slag into calcium hydroaluminates of
low solubility and calcium hydrosilicates of low basicity, whereas concretes
from Portland cement carry a large amount of free calcium oxide hydrate which
may wash out and thus weaken them. Supersulphate Portland cement has
satisfactory frost and air resistances, but it is less resistant than concrete
from Portland cement due to the fact that hydrosilicates of low basicity show
greater tendency to deformation from humidity fluctuations and resist the
combined action of water and frost less effectively.
has low heat of hydration and is resistant to chemical attacks and in
particular to sulphates. Compressive strength should be as follows:
72 ± 1 hour 15 N/mm2
168 ± 2 hours 22 N/mm2
672 ± 4 hours 30 N/mm2
It should have a fineness of 400
m2/kg. The expansion of cement is limited to 5 mm. The initial
setting time of the cement should not be less than 30 minutes, and the final
setting time should not be more than 600 minutes.
Portland cement is used for similar purpose as common Portland cement. But owing
to its higher water-resisting property, it should be preferred in hydraulic
engineering installations and also in constructions intended for service in
moist media. RCC pipes in ground water, concrete structures in sulphate bearing
soils, sewers carrying industrial effluents, concrete exposed to concentrated
sulphates of weak mineral acids are some of the examples of this cement. This
cement should not be used in constructions exposed to frequent
freezing-and-thawing or moistening-and-drying conditions.
Sulphate Resisting Portland
Cement (IS: 12330): In this cement the amount of tricalcium aluminate
is restricted to on acceptably low value(< 5). It should not be mistaken
for super-sulphated cement. It is manufactured by grinding and intimately
mixing together calcareous and argillaceous and/ or other silica, alumina and
iron oxide bearing materials. The Materials are burnt to clinkering
temperature. The resultant clinker is ground to produce the cement. No material
is added after burning except gypsum and not more than one per cent of
air-entraining agents are added.
The specific surface of the cement should not be less than 225 m2/kg.
The expansion of cement is limited to 10 mm and 0.8 per cent, when tested by
Le-chatelier method and autoclave test, respectively. The setting times are
same as that for ordinary Portland cement. The compressive strength of the
cubes should be as follows.
± 1 hour 10 N/mm2
± 2 hours 16 N/mm2
± 4 hours 33 N/mm2
It should have a fineness of 400
m2/kg. The expansion of cement is limited to 5 mm. The initial
setting line of the cement should not be less than 30 mm and the final setting
time should not be more than 600 mm.
This cement can be used as an alternative to order
Portland cement or Portland pozzolana cement or Portland slag cement under
normal conditions. Its use however is restricted where the prevailing
temperature is below 40 o C. Use of sulphate resisting cement is particularly
beneficial in conditions where the concrete is exposed to the risk of
deterioration due to sulphate attack; concrete in contact with soils or ground
waters containing excessive sulphate as well as concrete in sea water or
exposed directly to sea coast.
Portland slag Cement (IS: 455): It is
manufactured either by intimately intergrinding a mixture of Portland
cement clinker and granulated slag with addition of gypsum or calcium sulphate,
or by an intimate and uniform blending of Portland cement and finely ground
granulated slag. Slag is a non-metallic product consisting essentially of glass
containing silicates and alumino-silicates of lime and other bases, as in the
case of blast-furnace slag, which is developed simultaneously with iron in blast
furnace or electric pig iron furnace. Granulated slag is obtained by further
processing the molten slag by rapid chilling or quenching it with water or
steam and air. The slag constituent in the cement varies between 25 to 65 per
Properties: The chemical requirements
of Portland slag cement are same as that of 33 grade Portland cement.
The specific surface of slag cement should not be less than 225 m2/kg.
The expansion of the cement should not be more than 10 mm and 0.8 per cent when
tested be Le Chatelier method and autoclave test, respectively. The initial and
final setting times and compressive strength requirements are same as that for
33 grade ordinary Portland cement.
Uses: This cement can be used in all
places where OPC is used. However, because of its low heat of hydration
it can also be used for mass concreting, e.g., dams, foundations, etc.
Low Heat Portland Cement (IS:12600) To limit
the heat of hydration of low heat Portland cement (LHC), the tricalcium
aluminate component in cement is minimised and a high percentage of dicalcium
silicate and tetracalcium alumino ferrite is added. The heat of hydration
should not be more than 272 and 314 J/g at the end of 7 and 28 days
respectively. The rate of development of strength is slow but the ultimate
strength is same as that of OPC. To meet this requirement, specific surface of
cement is increased to about 3200 cm2/g.
Properties: Less heat is evolved
during setting low heat Portland cement. When tested by Le Chatelier method and
autoclave test the expansion should not be more than 10 mm and 0.8%,
respectively. The minimum initial setting time should not be less than 60
minutes, and the final setting should not be more than 600 minutes.
compressive strength should be as follows.
± 1 hour 10 N/mm2
± 2 hours 16 N/mm2
± 4 hours 35 N/mm2
Uses: It is most suitable for
large mass concrete works such as dams, large raft foundations, etc. Portland
Puzzolana Cement (IS: 1489 (Part I): It is manufactured by grinding
Portland cement clinker and puzzolana (usually fly ash 10-25% by mass of
PPC) or by intimately and uniformly blending Portland cement and fine
puzzolana. Puzzolana (burnt clay, shale, or fly ash) has no cementing value
itself but has the property of combining with lime to produce a stable
lime-puzzolana compound which has definite cementitious properties. Free lime
present in the cement is thus removed. Consequently, the resistance to chemical
attack increases making it suitable for marine works. The hardening of Portland
puzzolana cement consists in hydration of Portland cement clinker compounds and
then in interaction of the puzzolana with calcium hydroxide released during the
hardening of clinker. At the same time, calcium hydroxide is bound into a
water-soluble calcium hydrosilicate according to the reaction with the effect
that puzzolana Portland cement acquires greater water-resisting property than
ordinary Portland cement.
+ SiO2 + (n - 1) H2O = CaO.SiO2.nH2O
have lower rate of development of strength but ultimate strength is comparable
with ordinary Portland cement.
72 ± 1 hr 16.0
± 2 hrs 22.0 N/mm2
± 4 hrs 33.0 N/mm2
The initial and the final setting
times are 30 minutes (minimum) and 600 minutes (maximum), respectively. The
drying shrinkage should not be more than 0.15% and the fineness should not be
less than 300 m2/kg.
Uses: It has
low heat evolution and is used in the places of mass concrete such as dams and
in places of high temperature.
Quick Setting Portland Cement: The
quantity of gypsum is reduced and small percentage of aluminium sulphate
is added. It is ground much finer than ordinary Portland cement.
setting time = 5
setting time = 30
Use: It is used when concrete is to be laid under water or in
Cement (IS 3466): The Portland cement clinker is ground and mixed
intimately with pozzolanic material (flyash or calcined clay), or
non-pozzolanic (inert) materials (lime-stone, conglomrates, dolomite,
granulated slag) and waste materials (carbonated sludge, mine tailings) and
gypsum and air entraining plasticizer in suitable proportions. The physical
requirements of masonry cement are as follows.
1. Fineness: Residue on 45-micron IS Sieve,
Max, Percent (by wet sieving) 15
2. Setting Time (by Vicat Apparatus):
Min 90 min
Max 24 h
expansion, Max 10 mm
expansion, Max 1 %
Compressive Strength: Average strength of not less than 3
mortar cubes of 50 mm size, composed
of 1 part masonry
cement and 3 parts standard sand by
7 days 2.5 MPa
28 days 5 MPa
5. Air Content: Air content of mortar
composed of 1 part masonry cement 6 per
and 3 parts standard sand by volume,
6. Water Retention: Flow after suction of
mortar composed of 1 part 60 % of
masonry cement and 3 parts standard
sand by volume, Min original flow
White and Coloured Portland
Cement (IS: 8042): It is manufactured from pure white chalk and clay
free from iron oxide. Greyish colour of cement is due to iron oxide. So,
the iron oxide is reduced and limited below 1 per cent. Coloured cements are
made by adding 5 to 10 per cent colouring pigments before grinding. These
cements have same properties as that of ordinary Portland cement and are
non-staining because of low amount of soluble alkalis. Sodium alumino fluoride
is added during burning which acts as a catalyst in place of iron.
Properties: Loss on ignition of
white cement is nil. The compressive and transverse strength of this cement is
90 per cent of that of 33 grade ordinary Portland cement.
Uses: These cements are used for
making terrazzo flooring, face plaster of walls (stucco), ornamental works, and
Air Entraining Cement: Vinsol
resin or vegetable fats and oils and fatty acids are ground with ordinary
cement. These materials have the property to entrain air in the form of fine
tiny air bubbles in concrete.
Properties: Minute voids are
formed while setting of cement which increases resistance against freezing and
scaling action of salts. Air entrainment improves workability and water/cement
ratio can be reduced which in turn reduces shrinkage, etc.
Uses: Air entraining cements are used for the same purposes as
that of OPC.
Calcium Chloride Cement: It is
also known as extra rapid hardening cement and is made by adding 2 per
cent of calcium chloride. Since it is deliquescent, it is stored under dry
conditions and should be consumed within a month of its dispatch from the
Aggregates: These are obtained by crushing from quarries of
igneous, sedimentary or metamorphic rocks. Gravels and sand reduced to
their present size by the natural agencies also fall in this category. The most
widely used aggregate are from igneous origin. Aggregates obtained from pits or
dredged from river, creek or sea are most often not clean enough or well graded
to suit the quality requirement. They therefore require sieving and washing
before they can be used in concrete.
increase in the volume of a given mass of fine aggregate caused by the presence
of water is known as bulking. The water forms a film over the fine
aggregate particles, exerts force of surface tension and pushes them apart
increasing the volume. The extent of bulking depends upon the percentage of
moisture present in the sand and its fineness. With ordinary sand bulking
varies from 15-30 percent. It increases with moisture content up to a certain
point (4-6%), reaches maximum, the film of water on the sand surface breaks,
and then it starts decreasing. Figure 6.2 shows the bulking of sand with
moisture content. In preparing concrete mixes if sand is measured by volume and
no allowance is made for bulking, the moist sand will occupy considerably
larger volume than that prepared by the dry sand and consequently the mix will
be richer. This will cause, less quantity of concrete per bag of cement. For
example, if the bulking of sand is 10% and if mix ratio is 1:2:4, the actual
volume of sand used will be 1.1 × 2 =2.2 instead of 2 per unit volume of
cement. If this correction is not applied the actual dry sand in the concrete
will be , instead of 2 per unit volume of cement. The mix proportion then would
be 1:1.82:4 rather than 1: 2: 4. Which indicates lesser production of concrete.
Also, there will be chances of segregation, honeycombing and reduced yield of
of sand can be determined, in field, by filling a container of known volume (A)
with damp sand in the manner in which the mixer hopper will be filled. The
height of sand in the container is measured. The sand is then taken out of
container carefully, ensuring no sand is lost during this transaction. The sand
is then either dried and filled back into the gauge box, or the container is
filled with water and the damp sand is poured in to displace the water.
Whichever method is adopted, the new depth of aggregate in the container gives
the unbulked volume (B).
percentage bulking expressed as a percentage of the dry volume = A B
Note: The dry
and fully saturated (flooded) sand occupy almost same volume