1) Cement can be classified into three grades

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Last updated: April 2, 2019

1)     OrdinaryPortland Cement – OPC –         Ordinary Portland Cement(OPC) is the most important type of cement. –         Ordinary Portland Cementis manufactured by burning siliceous material like limestone at 1400ºC and thengrinding it with Gypsum.-         Before 1987, there wasonly one grade of Ordinary Portland Cement, which was governed by IS 269-1976.-         After 1987, highergrades of cement were introduced in India.

–         The Ordinary PortlandCement can be classified into three grades depending upon the strength of thecement at 28 days as per IS 4031- 1988.-         Grade-33-         Grade-43-         Grade-531(a)  Grade-33:             Ifthe strength of the cement tested at28 days is not less than 33N/ mm2,it is called 33 Grade Cement. 1-         Ordinary Portland CementGrade 33 is certified by IS 269:1989.2-         Ordinary Portland CementGrade 33 is rarely used by current industries as higher strength cement isbecoming popular.-         Ordinary Portland CementGrade 33 is more useful for–         Mass concreting-         Plain Cement Concreting-         Plastering (b)  Grade-43:             Ifthe strength of the cement tested at 28 days is not less than 43N/mm2,it is called 43 grade cement. 1 –         Ordinary Portland CementGrade-43 is certified by IS 8112:1989.2-         Ordinary Portland CementGrade-43 is in high demand in India.-         The production ofOrdinary Portland Cement Grade-43 consists of about 50% of the total cementproduction in India.

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–         It is most popularlyused cement in India.  ·        Ordinary PortlandCement Grade-43 is Used in the Following Applications:-         Precast items likeblocks, tiles, pipes, etc.-         General CivilEngineering Construction Works.-         Reinforced CementConcrete work.-         Non-structural workslike Plastering, Flooring, etc.-         In Asbestos productssuch as sheets and pipes.  (c)   Grade-53: –         If the strength of thecement tested at 28 days is not less than 53N/ mm2, it is called 53grade cement.

1 –         Ordinary Portland CementGrade- 53 is certified by IS 12269:1987.2-         Ordinary Portland CementGrade-53 is known for its rich quality and high durability.  ·        Ordinary PortlandCement Grade-53 is used in the Following Applications. –         Pre-stressed ConcreteComponents.

–         Runways, Concrete Roadsand Bridges.-         Precast concrete itemssuch as paving blocks, tiles, building blocks, etc.-         Reinforced cementconcrete work.             The manufacturing of Ordinary Portland Cement isdecreasing all over the world due to increasing popularity of blended cement onaccount of:-         Low energy consumption-         Environment pollution-         Economic and othertechnical reasons.1            Considering the Year 1998-99, the total cement productionin India was 79 million tonnes, out of which Ordinary Portland Cementproduction was 57 million tonnes i.e.

70 % of total cement production with thepassing years, the production of Ordinary Portland Cement may come down but itwill always remain an important type for general construction.1             It has become possible to upgrade the quality of cementby using; –         High quality limestone-         Modern equipment-         Closer online control ofconstituents-         Maintaining betterparticle size distribution-         Finer grinding-         Better packing1High gradecement makes stronger concrete. They are little costlier than low grade cement,yet they offer 10-20% savings in cement consumption besides other hiddenbenefits.1 2)     RapidHardening Cement (RHC): –         Rapid Hardening Cementis similar to Ordinary Portland Cement.-         It is certified with IS8041-1990.-         As the name suggestsRapid Hardening Cement develops higher rate of development of strength, i.e.the strength, which is developed by Rapid Hardening Cement at the age of 3days, the time taken for Ordinary Portland Cement to develop the same strengthis 7 days.

1 ·        The Raw MaterialsRequired for the Manufacturing of Rapid Hardening Cement are:-         Limestone-         Shale-         Gypsum-         Coke3 ·        The Process ofManufacturing of Rapid Hardening Cement is carried out as Follows:-         Limestone and shale areheated at extremely high temperature to produce cement clinker.-         Thereafter, Gypsum isadded in small quantity to the cement clinker and lastly finely ground toproduce Rapid Hardening Cement.1             ThusRapid Hardening Cement is produced by dry process technology. It must be storedin a dry place as its quality decreases gradually due to premature carbonationand hydration.1  ·        The Rapid Rate ofDevelopment of Strength of RHC is due to–         High C3S andlower C2S content.

–         High fitness of grindingof Rapid Hardening Cement. (Specific surface is not less than 3250 sq.cm pergram.)1  ·        Disadvantage ofRapid Hardening Cement: –         Higher fineness ofcement particles needs greater surface area for action of water. Also higherproportion of C3S causes quicker hydration.

            ThereforeRapid Hardening Cement gives out much greater heat of hydration during earlyperiod and thus Rapid Hardening Cement must not be used in mass concreteconstruction.1  ·        Advantages andUses of Rapid Hardening Cement:-         It is used where highearly strength is needed.3-         It is used forconstructing road, pavements, where it is essential to open the road to controltraffic quickly.

3-         It is used in industriesmanufacturing concrete products like slabs, electric poles, etc. because mouldscan be released quickly.3-         It is used for coldweather concreting, because rapid evolution of heat during hydration protectsthe concrete against freezing.3-         It is used inpre-fabricated concrete construction.1-         It is used framework isrequired to be removed for re-use elsewhere.1-         It is used in coldweather concrete where rapid rate of development of strength reduces thepossibility of concrete to the frost damage.

1  ·        CompaniesProducing Rapid Hardening Cement: –         ACC-         Gujarat Ambuja-         JK Cement-         Grasim Industries-         Indian Cement Ltd.3            TheIndian Cement Industry produces the highest Rapid Hardening Cement and alsoexports it to other countries.  3)     Extra RapidHardening Cement-         Extra rapid hardeningcement is prepared by adding calcium chloride to rapid hardening cement. Theaddition of calcium chloride should not be more than 2% by weight of the RapidHardening Cement.

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