Manufacturing of cement There are 3 steps of manufacturing of cement2) Mixing of raw materials3) Burning4) Grinding1) Mixing of raw Material :- clay and limestone are taken in appropriate proportion and mixed in dry and wet condition.2) Burning:- mixed material is heated about 1400 – 1600 Degree celcius and cooled by passing through coolers.3) Grinding:- so material obtained (clinker) is ground in mill and 2 % to 4 % gypsum is added to control the setting time of cement
T ype o C e nt sf me1)Ordinary Portland cement2)Portland Pozzolana Cement3)Sulphate Resisting Cement4)Coloured Cement5)Rediset Cement6)Very high strength cement7)Rapid Hardening Cement8) Portland Slag Cement9)Masonry Cement10)Oil Well Cement
Ordinary Portland Cement (is 269:1989) Although there are many types of Cement , about 80 -90% of total production is of Ordinary Portland Cement (OPC) only. OPC is classified in three types of grades depending upon strength of cement as 1)33 Grade 2)43 Grade 3)53 Grade Faster rate of development of strength Offers 10-20 % savings in cement consumption 33 grade cement is almost out of the market The manufacture of OPC is decreasing in view of popularity of blended cement on account of lower energy consumption, environmental pollution.
Portland Pozzolana Cement It is manufactured by intergrinding of OPC clinker with 10-25% of pozzolanic material PPC produces heat of hydration and offer greater resistance to the attack of aggressive water than OPC. PPC can generally be used where OPC is usable rate of development of strength unto 7 daysSuitability It is economical It offers durability charecteristics in marine & hydraulic structures Strength of PPC is higher than OPC
Coloured cement (is 8042-1989) For manufacturing of this cement ,white or grey portland cement is used as base Use of white cement is costly while using grey portland cement only red & brown cement can be produced Consists of PPC with 5-10% of pigment For manufacture of white portland cement required limestone is only available around Jodhpur(Rajasthan) White cement is ground finer than grey cement
Rapid Hardening Cement (is 8041-1990) This cement develops higher rate of development of strength Suitability -Road repair works -In pre-fabricated concrete construction -In cold weather concrete
Storage of cement Water proof mesonry walls should be provided. Leak proof roof with water proof cover should be provided. Ground should be drained away to prevent from rain water
Storage of cement bags Bags should not be allowed to directly rest on the walls. Not more than 15 bags be piled over the other. If cement is to be stored in mansoon or for long period piles should be covered by polythene sheet.
Field Tests for cement Cement should be of uniform color. When small sample of cement is rubbed between fingers ,it should feel smooth and cool. There should no lumps in the cement.
Laboratory tests of cement1)Fineness :- This test is varified by using I.S. sieve No.9. -now gentle sieving is done for fifteen minutes. -The residue left is measured this should not be exceed 10 % by weight of the sample of the cement.2)Consistency:- This is a test sonducted to estimate quantity of water to be mixed with cement.3) Soundness of cement ;- Due to excess of lime in the cement expansion of cement occurs, that should be minimized.
4)Setting time :- The object of this test is to make distinction between normal setting time and final setting time. This test can be conducted by using Vicat apparatus.
References S.Ramamrutham ,Basics of civil Engineering,Dhanpat rai publishing company,New Delhi. www.cemex.com