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33,43 & 53 GRADE OPC CEMENT.
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P.K.Mallick
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PostPosted: Sat Feb 21, 2009 7:04 pm    Post subject: Reply with quote

I think it is now time for Respected  N P Rajamane Sir to conclude.
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ibarua
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PostPosted: Mon Feb 23, 2009 1:01 pm    Post subject: 33,43 & 53 GRADE OPC CEMENT. Reply with quote

23rd Feb 2009

What does Neville in 'Properties of Concrete' say? I'll check up after my return to my hq. on the 1st March.

Indrajit Barua.

On Tue, 17 Feb 2009 drnsmani wrote :
Quote:
Dear Mr. Mallick,

I am not a scientist on cement. Hope my friend Mr.
Rajamane of SERC can throw some light on the question
raised by you.

Anyway, the enclosed paper may be of interest to you.

Best Wishes
Subramanian





From: P.K.Mallick <forum@sefindia.org>
To: general@sefindia.org
Sent: Monday, February 16, 2009 11:38:36 AM
Subject: [SEFI] 33,43 & 53 GRADE OPC CEMENT.

     What factors contribute towards higher compressive
strength as we move from 33 grade OPC. to 53 grade OPC
? Is the fineness of cement is the only factor or some
other factors contribute towards higher compressive
strength for higher Grade of OPC ?
     


P.K.Mallick
munamallick@yahoo.co.in (munamallick@yahoo.co.in)
mallick.pravatkumar@gmail.com
(mallick.pravatkumar@gmail.com)
http://360.yahoo.com/munamallick
(http://360.yahoo.com/munamallick)






Attachments:
http://www.sefindia.org/forum/files/ChemicalandPhysical_-
175.pdf



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ibarua
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PostPosted: Mon Feb 23, 2009 1:29 pm    Post subject: 33,43 & 53 GRADE OPC CEMENT. Reply with quote

23rd Feb 2009

In the works designed by us, we do not allow gr.53 cement except in PSC members. I was advised thus by a very senior engineer, who based his opinion on some unpleasant experience with gr. 53 cement many years ago in a project undertaken by BARC /Atomic Energy.

Dr Rajamane may perhaps clarify.

Indrajit Barua.

On Tue, 17 Feb 2009 rajmane wrote :
Quote:
17th Feb 2009 10 pm
This is a very vast, important, but very delicate
topic/subject. Many points are involved. I would like
to write my response after we listen to different views
on this. I hope my good friend Dr NS would agree to
wait for my view. The idea is to receive the maximum
number of views/queries/issues and then make up a
detailed technical write up.

N P Rajamane, SERC


drnsmani wrote:
Quote:
          Dear Mr. Mallick,

I am not a scientist on cement. Hope my friend Mr.
Rajamane of SERC can throw some light on the question
raised by you.

Anyway, the enclosed paper may be of interest to you.

Best Wishes
Subramanian





From: P.K.Mallick
To: general@sefindia.org (general@sefindia.org)
Sent: Monday, February 16, 2009 11:38:36 AM
Subject: [SEFI] 33,43 & 53 GRADE OPC CEMENT.

     What factors contribute towards higher compressive
strength as we move from 33 grade OPC. to 53 grade OPC
? Is the fineness of cement is the only factor or some
other factors contribute towards higher compressive
strength for higher Grade of OPC ?
     


P.K.Mallick
munamallick@yahoo.co.in (munamallick@yahoo.co.in)
(munamallick@yahoo.co.in (munamallick@yahoo.co.in))
mallick.pravatkumar@gmail.com
(mallick.pravatkumar@gmail.com)
(mallick.pravatkumar@gmail.com
(mallick.pravatkumar@gmail.com))
http://360.yahoo.com/munamallick
(http://360.yahoo.com/munamallick)
     



     
Download Attachments:
ChemicalandPhysical.pdf (http://www.sefindia.org/forum/f-
iles/ChemicalandPhysical_175.pdf)








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mkalgal
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PostPosted: Mon Feb 23, 2009 2:06 pm    Post subject: Reply with quote

Dear Mr. Mallick

Sorry for the delayed response.

In a cement factory there is need to chemically and physically engineer cements for specific markets and specific seasons of the year.
The actual components of Portland Cements are often complex chemical crystalline and amorphous structures, denoted by cement chemists as "elite" (C3S), "belite" (C2S), and various forms of aluminates. The behavior of each type of cement depends on the content of these components. Characterization of these compounds, their hydration, and their influence on the behavior of cements are presented in full detail in many texts.

In terms of cement composition, the C3S and C2S will have the primary influence on long term development of structure, although aluminates may contribute to formation of compounds such as ettringite (sulfoaluminate hydrate), which can cause expansive disruption of concrete.

One very important point to remember is not to confuse oneself between High Early Strength Gain vs   High Strength. We are looking at cement strength at 28 days- period.

Cements high in C3S (especially those that are finely ground) will hydrate more rapidly and lead to higher early strength. However, the hydration products formed will, in effect, make it more difficult for hydration to proceed at later ages, leading to an ultimate strength lower than desired in some cases. Cements high in C2S will hydrate much more slowly, leading to a denser ultimate structure and a higher long-term strength.
But with a given limestone source (with more or less fixed lime content) you cannot do much about C3S and C2S content. One would then try to get higher cement strength with higher grinding only, although it is energy intensive.

It is possible to increase the strength by the addition of some polymers, but the cost of cement goes up substantially. I do not know if any cement manufacturer has taken this route.

Over to Mr. Rajamane!

regards

Dr. M. R. Kalgal
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PostPosted: Tue Feb 24, 2009 5:38 am    Post subject: 33,43 & 53 GRADE OPC CEMENT. Reply with quote

Dear Mr. Mallick/ Dr Kalgal /SEFIANS
I agree with most of the observations of Dr Kalgal. I am using the text of Prof Kalgal to express myself!

The cement factory has to chemically and physically engineer cements as most of raw materials for cement making are from natural resources and hence they can vary in properties from point to point.

The reactivity of Portland Cements is often easily understood by knowing its composition by Bogue’s compounds, C3S, C2S, C3A, C4AF. The behavior of each cement depends on the content of these components. Characterization of these compounds, their hydration, and their influence on the behavior of cements are discussed in many texts, such as Chemistry of Cement And Concrete by Lea, Cement Chemistry by HFW Taylor, Chemistry of Portland Cement by Bogue, etc.

The C3S contribute to early age strengths; but, C3S and C2S would reach the same strength level in the long run.

When looking at cement strength at 28 days period, C3S content is very important. As Prof Kalgal writes, cements high in C3S (especially those that are finely ground) will hydrate more rapidly and lead to higher early strength.

Higher cement strength are also obtained with proper distribution of particle sizes of cement besides overall fineness.

It is possible to increase the cement/concrete strength by the addition of suitable accelerators and adopting rational curing regime.

Rajamane N P
SERC, CSIR (24-2-2009)


mkalgal wrote:
[quote]          Dear Mr. Mallick

Sorry for the delayed response.

In a cement factory there is need to chemically and physically engineer cements for specific markets and specific seasons of the year.
The actual components of Portland Cements are often complex chemical crystalline and amorphous structures, denoted by cement chemists as "elite" (C3S), "belite" (C2S), and various forms of aluminates. The behavior of each type of cement depends on the content of these components. Characterization of these compounds, their hydration, and their influence on the behavior of cements are presented in full detail in many texts.

In terms of cement composition, the C3S and C2S will have the primary influence on long term development of structure, although aluminates may contribute to formation of compounds such as ettringite (sulfoaluminate hydrate), which can cause expansive disruption of concrete.

One very important point to remember is not to confuse oneself between High Early Strength Gain vs High Strength. We are looking at cement strength at 28 days- period.

Cements high in C3S (especially those that are finely ground) will hydrate more rapidly and lead to higher early strength. However, the hydration products formed will, in effect, make it more difficult for hydration to proceed at later ages, leading to an ultimate strength lower than desired in some cases. Cements high in C2S will hydrate much more slowly, leading to a denser ultimate structure and a higher long-term strength.
But with a given limestone source (with more or less fixed lime content) you cannot do much about C3S and C2S content. One would then try to get higher cement strength with higher grinding only, although it is energy intensive.

It is possible to increase the strength by the addition of some polymers, but the cost of cement goes up substantially. I do not know if any cement manufacturer has taken this route.

Over to Mr. Rajamane!

regards

Dr. M. R. Kalgal

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Dr. N. Subramanian
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PostPosted: Tue Feb 24, 2009 3:11 pm    Post subject: Re: 33,43 & 53 GRADE OPC CEMENT. Reply with quote

Dear Dr. Kalgal and Dr Rajamane,

Thanks for explaining about the constituents of cements and how they gain strength depending upon the percentage of C3S or C2S. But in one of the earlier posts Mr. Mallick had raised a question: If we use a particular type of cement, say Grade 44 and if the 28-day cube strength of this cement (not concrete) has an average strength greater than 44 MPa, can we take that strength or it has to be restricted to 44 MPa only?.

First of all do we have to do determine cube strength of cement in order to establish the 28-day strength of concrete? Normally we test only concrete cubes, of course the cement strength is taken as given by the manufacturer. Is there any acceptability criteria for factory made cement, whose strength should not vary much? Mr. Mallick says he has looked into the standard issued by BIS but could not find any. As one of you worked in a cement company and another doing research on concrete, you should be able to give correct perspective on this issue.

Regards
Subramanian


[quote="rajmane"]Dear Mr. Mallick/ Dr Kalgal /SEFIANS
I agree with most of the observations of Dr Kalgal. I am using the text of Prof Kalgal to express myself!

The cement factory has to chemically and physically engineer cements as most of raw materials for cement making are from natural resources and hence they can vary in properties from point to point.

The reactivity of Portland Cements is often easily understood by knowing its composition by Bogue’s compounds, C3S, C2S, C3A, C4AF. The behavior of each cement depends on the content of these components. Characterization of these compounds, their hydration, and their influence on the behavior of cements are discussed in many texts, such as Chemistry of Cement And Concrete by Lea, Cement Chemistry by HFW Taylor, Chemistry of Portland Cement by Bogue, etc.

The C3S contribute to early age strengths; but, C3S and C2S would reach the same strength level in the long run.

When looking at cement strength at 28 days period, C3S content is very important. As Prof Kalgal writes, cements high in C3S (especially those that are finely ground) will hydrate more rapidly and lead to higher early strength.

Higher cement strength are also obtained with proper distribution of particle sizes of cement besides overall fineness.

It is possible to increase the cement/concrete strength by the addition of suitable accelerators and adopting rational curing regime.

Rajamane N P
SERC, CSIR (24-2-2009)
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PostPosted: Wed Feb 25, 2009 4:57 am    Post subject: 33,43 & 53 GRADE OPC CEMENT. Reply with quote

Dear Mr. Mallick,

Have you seen any difference in the constituents? I am surprised to note that all grades have the same fineness.The particle size of Grade 55 should be less than Grade 44 and 33.

Regards
Subramanian

Dr.N.Subramanian,Ph.D.,F.ASCE, M.ACI,

Consulting Structural Engineer
Maryland, USA

See my books at: www.multi-science.co.uk/subramanian-book.htm
www.oup.co.in/search_detail.php?id=144559





--- On Fri, 2/20/09, P.K.Mallick <forum@sefindia.org> wrote:
Quote:
From: P.K.Mallick <forum@sefindia.org>
Subject: [SEFI] Re: 33,43 & 53 GRADE OPC CEMENT.
To: general@sefindia.org
Date: Friday, February 20, 2009, 10:31 PM

IS:12269(SPECIFICATION FOR 53 GRADE OPC CEMENT)
IS:8112(SPECIFICATION FOR 43 GRADE OPC CEMENT)
IS:269(SPECIFICATION FOR 33 GRADE OPC CEMENT)
All these codes specify that the specific surface of cement shall not be less than 225 sqm/kg.
Hence codal provisions do not differentiate 33,43 & 53 grade cement by fineness.
Which factor(s) is(are) then responsible for higher strength as we move from 33 Grade OPC to 53 Grade OPC?
     


P.K.Mallick
munamallick@yahoo.co.in (munamallick@yahoo.co.in)
mallick.pravatkumar@gmail.com (mallick.pravatkumar@gmail.com)
http://360.yahoo.com/munamallick
     



     


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PostPosted: Wed Feb 25, 2009 7:52 am    Post subject: 33,43 & 53 GRADE OPC CEMENT. Reply with quote

25 Feb 2009
Dear Dr N Subramanian and SEFIANs

Regarding Mr. Mallick’s question, We can see the following :

1. There is only 43 Grade cement (not Grade 44). Grade indicates the minimum 28 day cube strength of cement mortar when cast and tested as per IS:4031. There is no upper limit and hence a cement of strength 71 MPa can be considered as belonging to all the 33, 43, and 53 Grades as per BIS Codes on Portland cement.

2. We must determine the cube strength of cement mortar (as per IS : 4031, using standard sand) in order to characterize the cement for concrete mix design purpose and if that strength does not occur in cement on site, concretes mix design/proportions may have to be changed suitably.

3. Normally we test only the concrete cubes on site for characterizing the concrete. The cement strength is to be found out during mix design stage and also verified frequently on site, but not depend only upon the value given by the manufacturer.

4. The acceptability criteria for factory made cement is as per BIS Codes where generally only a threshold value of strength is given. Hence, cements of any particular grade can have a very wide range of strength level, but always more than the minimum specified! Only European codes are able to specify both upper and lower limits for the cements.

5. Earlier, Mr Mallick wrote that

“ The strength of cement to be used in mix design computations is not mean strength fm of certain number of test results (say n), but should be the characteristic strength fck give by equation: fck=fm-ks where "k" is probability factor, a statistical parameter for not more than 5 percent test results to fall below the characteristic strength fck and "s" is the standard deviation.”

The above is equation is for concrete mix design only and not for cement. BIS codes on mention the average cement strength, not characteristic cement strength


Regards

Rajamane N P
Deputy Director & Head, Concrete Composites Lab, Structural Engineering Research Centre, CSIR, Taramani, Chennai 600113 India (Secretary, Indian Concrete Institute (ICI), Tamil Nadu Centre) Email : rajmane@sercm.org,rajmane@sercm.csir.res.in,rajamanenp@yahoo.co.uk (rajmane@sercm.org,rajmane@sercm.csir.res.in,rajamanenp@yahoo.co.uk)
(25-2-2009)



drnsmani wrote:
[quote]          Dear Dr. Kalgal and Dr Rajamane,

Thanks for explaining about the constituents of cements and how they gain strength depending upon the percentage of C3S or C2S. But in one of the earlier posts Mr. Mallick had raised a question: If we use a particular type of cement, say Grade 44 and if the 28-day cube strength of this cement (not concrete) has an average strength greater than 44 MPa, can we take that strength or it has to be restricted to 44 MPa only?.

First of all do we have to do determine cube strength of cement in order to establish the 28-day strength of concrete? Normally we test only concrete cubes, of course the cement strength is taken as given by the manufacturer. Is there any acceptability criteria for factory made cement, whose strength should not vary much? Mr. Mallick says he has looked into the standard issued by BIS but could not find any. As one of you worked in a cement company and another doing research on concrete, you should be able to give correct perspective on this issue.

Regards
Subramanian


[quote="rajmane"]Dear Mr. Mallick/ Dr Kalgal /SEFIANS
I agree with most of the observations of Dr Kalgal. I am using the text of Prof Kalgal to express myself!

The cement factory has to chemically and physically engineer cements as most of raw materials for cement making are from natural resources and hence they can vary in properties from point to point.

The reactivity of Portland Cements is often easily understood by knowing its composition by Bogue’s compounds, C3S, C2S, C3A, C4AF. The behavior of each cement depends on the content of these components. Characterization of these compounds, their hydration, and their influence on the behavior of cements are discussed in many texts, such as Chemistry of Cement And Concrete by Lea, Cement Chemistry by HFW Taylor, Chemistry of Portland Cement by Bogue, etc.

The C3S contribute to early age strengths; but, C3S and C2S would reach the same strength level in the long run.

When looking at cement strength at 28 days period, C3S content is very important. As Prof Kalgal writes, cements high in C3S (especially those that are finely ground) will hydrate more rapidly and lead to higher early strength.

Higher cement strength are also obtained with proper distribution of particle sizes of cement besides overall fineness.

It is possible to increase the cement/concrete strength by the addition of suitable accelerators and adopting rational curing regime.

Rajamane N P
SERC, CSIR (24-2-2009)

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PostPosted: Wed Feb 25, 2009 9:28 am    Post subject: 33,43 & 53 GRADE OPC CEMENT. Reply with quote

25-2-2009
Dear Dr N Subramanian and SEFIANs

All grades have the same fineness only in specifications of BIS as they give lower limit only; but in practice a higher strength cement (grade is different from strength) would tend to have higher fineness. Besides the particle sizes, other influencing strength factors are particle size distribution, C3S content, w/c ratio, temperature, etc.

Regards

Rajamane N P
Deputy Director & Head, Concrete Composites Lab, Structural Engineering Research Centre, CSIR, Taramani, Chennai 600113 India (Secretary, Indian Concrete Institute (ICI), Tamil Nadu Centre) Email : rajmane@sercm.org,rajmane@sercm.csir.res.in,rajamanenp@yahoo.co.uk (rajmane@sercm.org,rajmane@sercm.csir.res.in,rajamanenp@yahoo.co.uk)
(25-2-2009)


drnsmani wrote:
[quote]          Dear Mr. Mallick,

Have you seen any difference in the constituents? I am surprised to note that all grades have the same fineness.The particle size of Grade 55 should be less than Grade 44 and 33.

Regards
Subramanian

Dr.N.Subramanian,Ph.D.,F.ASCE, M.ACI,

Consulting Structural Engineer
Maryland, USA

See my books at: www.multi-science.co.uk/subramanian-book.htm
www.oup.co.in/search_detail.php?id=144559





--- On Fri, 2/20/09, P.K.Mallick  wrote:
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PostPosted: Fri Feb 27, 2009 4:59 am    Post subject: 33,43 & 53 GRADE OPC CEMENT. Reply with quote

Dear Barua sir,

I have also heard from Senior Professors of IIT to discourage the usage of 53 grade cement. In this regard, late Prof.Sai of IIT, Kanpur answered the question of a Senior BARC officer in 1996 in the STP programme on "Developments in Concrete Construction". He explained that the use of 53 grade cement produces surface cracks unless some special care is taken. This is because of its faster rate of hydration and high heat of hydration.

Jagannadha Rao

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