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Grade of cement vs Grade of concrete

 
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pggopal_85
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PostPosted: Tue May 29, 2012 11:47 am    Post subject: Grade of cement vs Grade of concrete Reply with quote

Dear all,
What is the role of grade of cement over the grade of concrete?  Is there any role of cement grade in the concrete mix design?

Regards,
Gopal
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subingeorge43
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PostPosted: Tue May 29, 2012 12:05 pm    Post subject: Frp Reply with quote

How to plot stress strain interpolation diagram for frp wrapped short column
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Dr. N. Subramanian
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PostPosted: Tue May 29, 2012 3:27 pm    Post subject: Re: Grade of cement vs Grade of concrete Reply with quote

Dear Er Gopal,

It is a good question. Previously Grade 33, 43, and 53 cements were available in the market. The numbers 33, 43 and 53 indicate the compressive strength of cement after 28 days when tested as per IS: 4031-1988, eg, 33 Grade means that 28 days of compressive strength is not less than 33 N/mm2 (MPa) . Similarly for 43 grade and 53 grade the 28 days compressive strength should not be less than 43 and 53 MPa respectively.

The common man's perception is that 53 grade is the best cement- it is not only due to the aggressive marketing strategies of the cement manufacturers but also on the presumption that the heat generated during hardening of concrete is an index of its quality.  Note that 43 and 53 attain strength quickly and hence the heat generated during hydration process is very high and require careful curing. (3day strengths of these cements are 16, 23 and 27 MPa and 7 day strengths are 22, 33 and 37 MPa resply). In fact for normal applications involving M 20 to M25 grade 33 cement is sufficient and will not result in early age cracking, provided there is sufficient curing. Higher grades are to be used with HSC.

43 and 53 grades are also being introduced in PPC and PSC shortly by the Bureau of Indian Standards (BIS)!

Best wishes
NS
pggopal_85 wrote:
Dear all,
What is the role of grade of cement over the grade of concrete?  Is there any role of cement grade in the concrete mix design?

Regards,
Gopal
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pggopal_85
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PostPosted: Thu May 31, 2012 1:09 pm    Post subject: Reply with quote

Thanks for reply .

One more query regarding the subject

Does the higher grade of cement results in the lesser quantity of cement consumption for the preparation same grade of concrete?

Regards,
Gopal
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P.K.Mallick
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PostPosted: Thu May 31, 2012 2:12 pm    Post subject: Reply with quote

pggopal_85 wrote:
Thanks for reply .

One more query regarding the subject

Does the higher grade of cement results in the lesser quantity of cement consumption for the preparation same grade of concrete?

Regards,
Gopal


Yes,higher grade of cement will result in the lesser quantity of cement as long as the minimum quantity of cement from durability point of view is maintained.

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Dr. N. Subramanian
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PostPosted: Thu May 31, 2012 2:57 pm    Post subject: Reply with quote

Dear Er Gopal,

Again a good question. It is better to use PPC cement or blended cement which replaces cement with fly ash or other similar material than to use high grade cement.

Use of higher grade cement will not result in lesser cement consumption. Note we need to have minimum quantity of cement for a particular w/c ratio, as per IS 456 also. Cement is binding the other constituents of concrete and hence min. quantity is needed to coat other constituents, so that they are bound properly.

See also the following article written by Associated Cement Companies: http://www.hindu.com/pp/2006/07/15/stories/2006071500970400.htm

Can one save on quantity of cement by using high-grade cement?

This is a misconception. Even if you were to use less cement, you would need to add the same quantity of water to prepare a concrete mix. This would increase the water cement ratio, as the cement quantity has been reduced. But it is common knowledge that when the water-cement ratio is increased, the resultant concrete tends to suffer from reduced strength and durability. This will certainly compromise the long-term strength of your construction.

Does high grade of cement ensure better results?

The grade of cement only indicates its compressive strength at 28 days. But cement continues to increase in strength beyond that period of time with not much of difference in the long-term strength.

You would not want your dream home to be tested after a mere 28 days. While almost all cements provide some basic initial strength, what you should look for is its long-term strength. It has been proved that blended or composite cements render higher strengths for a long duration.

Should we use cement that sets quickly?

Quick setting of the mix depends not only on the quality of cement but also on the quantity of water used in preparing the mix. If you consider that you are constructing your dream house after years of waiting and planning, you know you can easily afford to wait for the essential few additional hours needed for cement to set slowly and attain its strength.

Similarly, concrete also needs adequate time to set properly and attain its fullest strength. If your mason complains about the quality of cement saying `it sets slowly', ask him to be patient. Wait a little while longer before you begin to worry. Setting is an essential property of cement. Slow setting of cement is healthy and does not necessarily mean that the cement cannot provide long-term strength.

Can you judge the quality of cement from its colour?

The colour of the cement has absolutely no relationship or bearing on its quality. The colour of cement is determined by the colour and quantity of the raw materials that are used to manufacture it.

Best wishes
NS
pggopal_85 wrote:
Thanks for reply .

One more query regarding the subject

Does the higher grade of cement results in the lesser quantity of cement consumption for the preparation same grade of concrete?

Regards,
Gopal
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