There Are Different Types of Cement As Classified By The Bureau of Indian Standards (BIS):
- Ordinary Portland Cement (OPC)
(a) 33 grade- IS: 269-1989
(b) 43 grade – IS: 8112-1989
(c) 53 grade – IS: 12269-1987 - Rapid Hardening Cement –IS: 8041-1990
- Extra Rapid Hardening Cement
- Low Heat Portland Cement –IS: 12600-1989
- Portland Slag Cement –IS: 455-1989
- Portland Pozzolana Cement –IS: 1489-1991(Part 1 and 2)
- Sulphate Resisting Portland Cement –IS: 12330-1988
- White Portland Cement – IS: 8042-1989
- Coloured Portland Cement –IS: 8042-1989
- Hydrophobic Cement – IS: 8043-1991
- High Alumina Cement –IS: 6452-1989
- Super Sulphated Cement –IS: 6909-1990
- Special types of cement
(a) Masonry Cement
(b) Air Entraining Cement
(c) Expansive Cement
(d) Oil Well Cement
Ordinary Portland Cement (OPC)
It is obtained by Pulverizing argillaceous and calcareous material in correct proportion.
Portland cement is the most common variety of artificial cement and is most commonly known as O.P.C. (Ordinary Portland Cement).
It is available in 3 grades:
(a) OPC-33 grade (IS: 269-989)
(b) OPC-43 grade (IS: 8112-1989)
(c) OPC-53 grade (IS: 12269-1987
The number 33, 43, and 53 corresponds to 28 days of characteristic compressive strength of cement as obtained from a standard test on cement sand mortar (1:3) specimens.
The OPC 33 is recommended for concrete mix having strength up to 20 N/mmi.e. M20.
These are most commonly used in general concrete construction, where there is no exposure to sulphates.
Due to high fineness, the workability of concrete increases for a given water-cement ratio. IS10262 has classified the OPC grade-wise from “A to F” based on 28 days of compressive strength as follows:
It is presently available in three different grades viz. OPC 33, OPC 43 and OPC 53. The numbers 33, 43 and 53 correspond to the 28 days (characteristic) compressive strength of cement as obtained from standard tests on cement-sand mortar specimens.
It is used in general concrete construction where there is no exposure to sulphates in the soil or in groundwater.
Rapid Hardening Cement (RHC)
It is finer than ordinary Portland cement.
It contains more C3S and less C2S than the OPC.
The 1-day strength of this cement is equal to the 3 days strength of OPC with the same water-cement ratio.
The main advantage of rapid hardening cement is that shuttering may be removed much earlier, thus saving considerable time and expenses.
Rapid hardening cement is also used for road work where it is imperative to open the road traffic with minimum delay.
The cost of Rapid hardening cement is nearly 10-15% more than OPC.
It can be safely exposed to frost as it matures more quickly.
Extra Rapid Hardening Cement (ERHC)
It is obtained by mixing calcium chloride (not exceeding 2% by weight of the rapid hardening cement) with rapid hardening cement.
The addition of CaCl2 imparts quick setting properties in extra rapid hardening cement.
The acceleration of setting, hardening and evolution of heat in the early period of hydration makes this cement very suitable for concreting in cold weather.
The 1 or 2-day strength of extra rapid hardening cement is 25% more than that of rapid hardening cement.
The gain of strength disappears with age and after 90 days strength of extra rapid hardening cement and rapid hardening cement are nearly the same.
The use of extra rapid hardening cement is prohibited in prestressed concrete construction.
The maximum time of using this cement is 20 minutes for mixing, transporting, placing and compaction.
Low Heat Cement (LHC)
It is a Portland cement that is obtained by reducing the more rapidly hydrating compounds, C3S and C3A and increasing C2S.
As per the Indian Standard specifications, the heat of hydration of low-heat cement shall be as
follows:
7 days – not more than 65 calories per gm
28 days – not more than 75 calories per gm
Since the rate of gain of strength of this cement is slow, hence adequate precaution should be taken in its use such as with regard to removal of formwork, etc.
LHC is used in massive construction works like abutments, retaining walls, dams, etc. where the rate at which the heat can be lost at the surface is lower than at which the heat is initially generated.
It has a low rate of gain of strength, but the ultimate strength is practically the same as that of OPC.
Portland Blast Furnace Slag Cement
This cement is made by intergrinding Portland cement clinker and granulated blast furnace slag.
The proportion of the slag is not less than 25% or more than 65% by weight of cement.
The slag should be granulated blast furnace slag of high lime content, which is produced by rapid quenching of molten slag obtained during the manufacture of pig iron in a blast furnace.
In general blast furnace slag cement is found to gain strength more slowly than the ordinary portland cement
The heat of hydration of Portland blast furnace slag cement is lower than that of OPC. So this cement can be used for mass concreting but is unsuitable for cold weather.
It has fairly high sulphate resistance, rendering it suitable for use in environments exposed to sulphates in the soil or in groundwater).
It is used for all-purpose for which ordinary Portland cement is used.
Because of its low heat evolution, it can be used in mass concrete structures such as dams, foundations and bridge abutments.
Portland Pozzolana Cement (PPC)
It can be produced either by grinding together Portland cement clinker and pozzolana with the addition of gypsum or by blending uniformly Portland cement and fine pozzolana.
As per the latest amendment, the proportion of pozzolana may vary from 15 to 35% by the weight of cement clinker. Earlier, it was 10 to 25%.
A pozzolanic material is essentially a siliccious or aluminous material that itself possesses no cementitious properties, which in finely divided form and in the presence of water reacts with calcium hydroxide, liberated in the hydration process at ordinary temperature to produce compounds possessing cementitious properties. This is known as pozzolanic action i.e.
Ca(OH)2 + Pozzolana + Water -> C-S-H(gel)
The pozzolanic materials generally used for the manufacture of Portland pozzolana cement are calcined clay (IS: 1489 part 2 of 1991) or fly ash (IS: 1489 part 1 of 1991).
Fly ash is a waste material generated in a thermal power station when powdered coal is used as a fuel.
PPC produces less heat of hydration and offers great resistance to the attack of impurities in water than OPC.
PPC is particularly useful in marine and hydraulic constructions, and other mass concrete structures
The disadvantage of using PPC is that the reduction in alkalinity reduces the resistance to corrosion of steel reinforcement. But considering the fact that PPC significantly improves the permeability of concrete, thereby increases the resistance to corrosion of reinforcement.
This cement has a higher resistance to chemical agencies and to seawater because of the absence of lime.
It evolves less heat and its initial strength is less but its final strength (28 days onward) is equal to ОРС.
It has a lower rate of development of strength than OPC.
The average compressive strength of cement mortar (1:3) at
(i) at 1 day 1 hr 16 MPa (Minimum)
(ii) at 7 day + 2 hr 22 MPa (Minimum)
(ii) at 28 day – 4 hr 33 MPa (Minimum)
Acid Resistant Cement (ARC)
An acid-resistant cement is composed of the following:
(i) Acid-resistant aggregates such as quartz, quartzites, etc.
(ii) Additive such as Na SiF (This accelerates hardening).
(iii) Solution of sodium silicate or soluble glass (sodium silicate is a binding material).
The addition of 0.5% of linseed oil or 2% of cerussite increases resistance to water also.
Sulphate Resisting Cement (SRC)
The Portland cement with low C3A and C4AF and ground finer than OPC is known as sulphate resisting cement and generally, C3S and C2S are kept at about 45 % each.
This cement is sulphate-resistant because the disintegration of hardened concrete is caused by the chemical reaction of C3A with soluble sulphate lime MgSO3. Caso4 and Na2so3 are inhibited.
The setting time is the same as that of OPC.
The compressive strength of the cubes should be as follows:
3 Day + 1 hr = 10 N/mm2
7 Day + 2 hr = 16 N/mm2
28 Day +4 hr = 33 N/mm2
This cement is “sulphate resistant” because the disintegration of concrete caused by the reaction of C3A in hardened cement with sulphate salt from outside is inhibited.
It is used in marine structures, sewage treatment works, and in foundations and basements where the soil is infested with sulphates.
However, recent research indicates that the use of sulphate resisting cement is not beneficial in environments where chlorides are present.
Coloured Cement (White Cement)
The process of manufacturing white cement is the same but the amount of iron oxide which is responsible for the greyish colour is limited to less than 1 per cent.
Sodium Alumino Ferrite (Cryolite) Na, AIF, is added to act as a flux in the absence of iron oxide.
The properties of white cement are nearly the same as OPC.
The whiteness of white cement is measured by the ISI scale or Hunter’s scale.
The whiteness should not be less than 70% on the ISI scale and on Hunter’s scale, it is generally 90%.
The strength of white cement is much higher than what is stated in IS: 8042-1989, the code for white cement.
The Grey colour of OPC is due to the presence of iron oxide. Hence in white cement, Fe,0, is limited to 1%. Sodium Alumino Ferrite (Cryolite) Na AIF is added to act as a flux in the absence of iron oxide.
High Alumina Cement (HAC)
It is very different in composition from Portland cement.
In this cement, the CSA content is very low due to which it is resistant to sulphur attacks and chemical attacks.
Its sets quickly and attains higher ultimate strength in a short period. Its strength after 1 day is about 40 N/mm2 and that after 3 days is about 50 N/mm2.
It is characterized by its dark colour, high early strength, and high heat of hydration.
The raw materials used for its manufacture consist of limestone (or chalk) and bauxite which is a special clay with high alumina content.
Bauxite is an aluminium ore. It is specified that total alumina content should not be less than 32 per cent and the ratio by weight of alumina to the lime should be between 0.85 and 1.30.
It is resistant to freezing and thawing.
It has an initial setting time of 3.5 hours and a final setting time of about 5 hours.
High alumina cement is very expensive to manufacture.
It is used where early removal of the formwork is required.
Its rapid hardening properties arise from the presence of calcium aluminate, chiefly monocalcium aluminate (Al2O3. Cao), as the predominant compound in place of calcium silicates of Portland cement and for setting and hardening, there is no free hydrated lime as in the case of Portland cement.
It must not be mixed with any other type of cement
Quick Setting Portland Cement
In the manufacture of this cement, gypsum content is reduced to get the quick setting property. Also, a small amount of aluminium sulphate is added.
It is ground much finer than OPC.
It sets quickly but does not harden quickly.
Initial setting time = 5 minutes, Final setting time = 30 minutes.
It is used when concrete is to be laid underwater.
Masonry Cement (IS: 3466)
Masonry cement consists of a mixture of Portland cement or blended hydraulic cement and plasticizing materials (such as limestone or hydrated or hydraulic lime) together with other materials introduces to enhance one or more properties such as setting time, and workability, water retention, and durability.
The addition of these materials gives good workability and reduces shrinkage and water retentively.
This cement is used for masonry works, plasterwork etc.
This cement must not be used for concrete work but used far Masonry construction.
Masonry cement when used for making mortar, incorporates all the good properties of lime mortar and discards all the non-ideal properties of cement mortar.
Super Sulphated Cement (SSC)
It is made from well-granulated blast furnace slag (80-85%), calcium sulphate (10-15%) and Portland cement (1-2%) and is ground finer than the Portland cement.
In this cement CA, which is susceptible to sulphates is limited to less than 3.5%.
Sulphate resisting cement can also be produced by the addition of extra iron oxide before firing this combines with alumina which would otherwise form C3A instead of forming C4AF which is not affected by sulphates.
It should be used in places with temperatures below 40°C.
Compressive strength should be as follows:
3 Day 1 hr = 15 N/mm2
7 Day + 2 hr = 22 N/mm2
28 Day + 4 hr = 30 N/mm?
It has a low heat of hydration.
It is used for the construction of dams and other mass concreting works.
Concrete made from super sulphated cement may expand if cured in water and may shrink if the
concrete is cured in air.
It has high resistance to chemical attacks.
Air Entraining Cement (AEC)
This cement is made by mixing a small amount of an air-entraining agent with OPC clinker at the time of grinding
It is manufactured by mixing a small amount of air-entraining agent i.e. 0.1% to 0.3% with OPC clinker at the time of grinding.
It offers good workability due to which it is having higher initial setting time than OPC.
It is having lesser final setting time as compared to OPC, due to which it offers resistance to freezing and thawing.
Air entrainment improves workability and the w/c ratio can be reduced which in turn reduces shrinkage etc.
It is yet not been covered by Indian Standard so far.
Some of the air-entraining agents are:
(i) Alkali salts of wood resins.
(ii) Synthetic detergents of the alkyl-aryl sulphonate type.
(ii) Calcium lignosulphate.
It produces tough, tiny, discrete, non-coalescing air bubbles at the time of mixing in the body of concrete which will modify the properties of plastic concrete with respect to workability, segregation and bleeding
Hydrophobic Cement
It is obtained by intergrinding OPC with 0.1-0.4 per cent of water-repellant film-forming substance such as oleic acid or stearic acid
The water repellant film formed around each grain of cement reduces the rate of deterioration of the cement during long storage, transportation, or under unfavourable conditions.
The properties of hydrophobic cement are nearly the same as that of OPC.
The cost of this cement is nominally higher than OPC.
Hydrophobic cement also features greater water resistance and impermeability
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| Que. Which one of the following cement is best for marine works? (a) Blast surface slag cement (b) High alumina cement (c) Low heat Portland cement (d) Rapid hardening cement Solution: (a) Que. For road pavements, the cement generally used is Que. The major compounds in Ordinary Portland Cement responsible for its |