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P.K.Mallick General Sponsor
Joined: 14 Dec 2008 Posts: 1098 Location: Kanpur. p.k.mallick1962@gmail.com

Posted: Thu Jan 29, 2009 2:35 am Post subject: CEMENT AND MIX DESIGN. 


IS:102621882 Reaffirmed 2004(Recommended Guidelines for Concrete Mix Design) shows a graph in form of Fig2 which gives corelation between watercement ratio, 28day concrete strength and 28day strength of cement tested according to IS:40311968.
Now, if a particular brand of 43Grade cement shows strength of 50N/sqmm,while using the aforesaid graph should we use strength of cement as 50N/sqmm or restrict it to 43N/sqmm as the grade of cement is 43Grade.


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mkalgal Silver Sponsor
Joined: 26 Jan 2003 Posts: 54

Posted: Thu Jan 29, 2009 10:16 am Post subject: 


Dear Mr.Mallick
The said curve refers to concrete strength and not cement strength.
Cement strength does not depend on cement strength alone!
regards
Dr. M. R. Kalgal


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mkalgal Silver Sponsor
Joined: 26 Jan 2003 Posts: 54

Posted: Thu Jan 29, 2009 10:18 am Post subject: 


Dear Mr. Mallick
I am sorry. I wanted to type "concrete strength does not depend on cement strength alone" and typed it wrongly. Realised it after submitting submit button!!
Dr. M. R. Kalgal


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P.K.Mallick General Sponsor
Joined: 14 Dec 2008 Posts: 1098 Location: Kanpur. p.k.mallick1962@gmail.com

Posted: Thu Jan 29, 2009 2:48 pm Post subject: 


Respected Dr. M. R. Kalgal
I am referring to fig2 of IS:102621982(Reaffirmed 2004),page8 under the heading "RELATION BETWEEN FREE WATERCEMENT RATIO AND CONCRETE STRENGTH FOR DIFFERENT CEMENT STRENGTHS.
Regards.


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Dr. N. Subramanian General Sponsor
Joined: 21 Feb 2008 Posts: 5327 Location: Gaithersburg, MD, U.S.A.

Posted: Thu Jan 29, 2009 4:18 pm Post subject: CEMENT AND MIX DESIGN. 


Dear Mr. Mallick,
I think you have to determine the cement strength as per IS 4031 : Part 6 : 1988Methods of physical tests for hydraulic cement: Part 6 Determination of compressive strength of hydraulic cement (other than masonry cement). As I do not have a copy of the same here, I am unable to comment. Please look into it for determining the correct cement strength.
In this connection I wish to inform you that my friend Mr. N. P. Rajamane, Head, Concrete Composites Lab., SERC has developed the following equation to represent the Mix design curves of SP 231981(see NBM &CW May05, pp.124127).
fc= 0.39* fcem*[(1/wc)0.50]
where
fc= 28 day comp. strength of cement concrete, MPa
fcem= 28 day comp. strength of cement as per IS 4031part6:1988, MPa
wc=Water cement ratio (by weight)
It was found that the above equation differs from BIS curves by a margin of +7.8 % to 2.8% and hence can be used to estimate the initial compressive strength of cement concrete before starting the trial mixes in the Lab.
Best wishes
Subramanian
Dr.N.Subramanian,Ph.D.,F.ASCE, M.ACI,
Consulting Structural Engineer
Maryland, USA
See my books at: www.multiscience.co.uk/subramanianbook.htm
www.oup.co.in/search_detail.php?id=144559
 On Thu, 1/29/09, P.K.Mallick <forum@sefindia.org> wrote:
Quote:  From: P.K.Mallick <forum@sefindia.org>
Subject: [SEFI] Re: CEMENT AND MIX DESIGN.
To: general@sefindia.org
Date: Thursday, January 29, 2009, 8:18 PM
Respected Dr. M. R. Kalgal
I am referring to fig2 of IS:102621982(Reaffirmed 2004),page8 under the heading "RELATION BETWEEN FREE WATERCEMENT RATIO AND CONCRETE STRENGTH FOR DIFFERENT CEMENT STRENGTHS.
Regards.

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P.K.Mallick General Sponsor
Joined: 14 Dec 2008 Posts: 1098 Location: Kanpur. p.k.mallick1962@gmail.com

Posted: Thu Jan 29, 2009 6:55 pm Post subject: Re: CEMENT AND MIX DESIGN. 


Respected Subramanian Sir,
Can I get a copy that article written by your friend?
My Email id: munamallick@yahoo.co.in
OR
mallick.pravatkumar@gmail.com
Warm Regards.
P.K.MALLICK


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mks ...
Joined: 27 Dec 2008 Posts: 82 Location: Patna: email mks.b08@gmail.com

Posted: Fri Jan 30, 2009 9:30 pm Post subject: Re: CEMENT AND MIX DESIGN. 


Dear Mallick Sir,
The graph in fig2 is generalized graph of water cement ratio Vs 28th day compressive strength of concrete for a particular grade of cement like A, B, C, D, E, F having compressive strength in respective range like 31.9  36.8 N/mm^2, 36.8  41.7 N/mm^2 ....... There fore in my opinion, we can use the graph depending upon the test results of cement falling under the range of respective grade.
I think this graph has been taken from German practice where also 6 Nos of grade of cement was in use. They were Grade 30, 35,40,45,50 & 55 having 28th day compressive strength 30, 35,40,45,50 & 55 N/ mm^2. Fig 2 of IS: 10262 is also having 6 Nos of curve similar to German Graph namely A, B, C, D, E & F.
Kindly see the attached article of Dr. S.C. Maiti , Mr. Raj K. Agrawal & Mr. Rajeeb Kumar from ICJ.
Regards.
Mithilesh.
P.K.Mallick wrote:  IS:102621882 Reaffirmed 2004(Recommended Guidelines for Concrete Mix Design) shows a graph in form of Fig2 which gives corelation between watercement ratio, 28day concrete strength and 28day strength of cement tested according to IS:40311968.
Now, if a particular brand of 43Grade cement shows strength of 50N/sqmm,while using the aforesaid graph should we use strength of cement as 50N/sqmm or restrict it to 43N/sqmm as the grade of cement is 43Grade. 
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P.K.Mallick General Sponsor
Joined: 14 Dec 2008 Posts: 1098 Location: Kanpur. p.k.mallick1962@gmail.com

Posted: Sat Jan 31, 2009 1:27 pm Post subject: Re: CEMENT AND MIX DESIGN. 


Respected Mithilesh Sir,
Thanks for your response.Let us look into Indian cement Market. OPC has almost vanished from the market. It is now PSC and PPC. The former is abundant in the Eastern Part of the country.
Now let us look into respective IS Codes for those cement.
IS 1489(Part1):1991(Reaffirmed 2000) PORTLANDPOZZOLANA CEMENTSPECIFICATION(FLY ASH BASED)
IS 1489(Part2):1991(Reaffirmed 2000) PORTLANDPOZZOLANA CEMENTSPECIFICATION(CALCINED CLAY BASED)
Clause 7.4.1 the average compressive strength at 672+=4h is 33 Mpa,Min
Hence strength wise it is equivalent to Grade33 OPC.
IS:455:1989(Reaffirmed 2005) PORTLAND SLAG CEMENTSPECIFICATION
Clause 6.4 the average compressive strength at 672+=4h is 33 Mpa,Min
Hence strength wise it is also equivalent to Grade33 OPC.
It is my observation of last six months that particular brand of PPC gives a compressive strength on an average 53 Mpa. Now the question comes while designing concrete mix should we take the observed compressive strength of 53 Mpa or 33 Mpa.
Again it is of my opinion (conservative of course) that while designing mix we should restrict to 33Mpa because fly ash used in PPC is obtained from the exhaust gases of coal fired power station and the quality of fly ash depends on the ash content of the coal used. See the variables associated Flyash. So depending upon type of Flyash used, the strength of PPC shall vary and we can not question the manufacturer as long as the minimum requirement of 33Mpa is satisfied. Hence is it not risky proposition to depend on undependable observed compressive strength? Of course the consolation is that cement manufactures usually get the fly ash from one source.
Same can be said about OPC43 grade which (sometimes) is actually rejected OPC53 Grade and even sometimes the OPC53 comes in the bag of OPC43 because it is not economically viable for a manufacturer to have different manufacturing facilities for different Grade of cement.
Hence let us use the designated compressive strength not the observed compressive strength while using the curves of Design Mix code.
_________________ P.K.Mallick
p.k.mallick1962@gmail.com


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ibarua General Sponsor
Joined: 26 Jan 2003 Posts: 1039

Posted: Sun Feb 01, 2009 7:00 am Post subject: CEMENT AND MIX DESIGN. 


1/2/2009
My thanks to Mr Mallick for pointing out the realities of the Indian cement scene, especially in the astern part of our country.
Indrajit Barua.
On Sat, 31 Jan 2009 P.K.Mallick wrote :
Quote:  Respected Mithilesh Sir,
Thanks for your response.Let us look into Indian cement Market. OPC has almost vanished from the market. It is now PSC and PPC. The former is abundant in the Eastern Part of the country. Now let us look into respective IS Codes for those cement. IS 1489(Part1):1991(Reaffirmed 2000) PORTLANDPOZZOLANA CEMENTSPECIFICATION(FLY ASH BASED)
IS 1489(Part2):1991(Reaffirmed 2000) PORTLANDPOZZOLANA CEMENTSPECIFICATION(CALCINED CLAY BASED)
Clause 7.4.1 the average compressive strength at 672+=4h is 33 Mpa,Min Hence strength wise it is equivalent to Grade33 OPC.
IS:455:1989(Reaffirmed 2005) PORTLAND SLAG CEMENTSPECIFICATION
Clause 6.4 the average compressive strength at 672+=4h is 33 Mpa,Min Hence strength wise it is also equivalent to Grade33 OPC.
It is my observation of last six months that particular brand of PPC gives a compressive strength on an average 53 Mpa. Now the question comes while designing concrete mix should we take the observed compressive strength of 53 Mpa or 33 Mpa. Again it is of my opinion (conservative of course) that while designing mix we should restrict to 33Mpa because fly ash used in PPC is obtained from the exhaust gases of coal fired power station and the quality of fly ash depends on the ash content of the coal used. See the variables associated Flyash. So depending upon type of Flyash used, the strength of PPC shall vary and we can not question the manufacturer as long as the minimum requirement of 33Mpa is satisfied. Hence is it not risky proposition to depend on undependable observed compressive strength? Of course the consolation is that cement manufactures usually get the fly ash from one source.
Same can be said about OPC43 grade which (sometimes) is actually rejected OPC53 Grade and even sometimes the OPC53 comes in the bag of OPC43 because it is not economically viable for a manufacturer to have different manufacturing facilities for different Grade of cement.
Hence let us use the designated compressive strength not the observed compressive strength while using the curves of Design Mix code.
 P.K.Mallick munamallick@yahoo.co.in mallick.pravatkumar@gmail.com

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mks ...
Joined: 27 Dec 2008 Posts: 82 Location: Patna: email mks.b08@gmail.com

Posted: Sun Feb 01, 2009 8:47 am Post subject: Re: CEMENT AND MIX DESIGN. 


Repected Mallick Sir and Experienced Sifians
Thank u Mallick Sir for your nice elaboration on the issue. I do agree 100% with your comment that, we shall use the designated compressive strength of the cement in general.
But on the other hand a lot of improvements has been done in the quality and strength of Indian cement since 1982 to 2003 (before reaffirmation of IS 10262). I think Kipping in view of these improvements, the graph in form of Fig02 has been included in IS: 10262 – 1982 (Reaffirmed 2004).
It is also the fact that the test results of different samples of cement taken from same batch of cement produced in the same manufacturing unit may varies within some range (minimum to maximum) In my opinion, to generalized the representation of the sample to the bulk quantity and to take the advantage of the improvement of the quality of the cement, the graph of Fig – 2 IS 10262 have 6 nos of curve namely A,B,C,D,E & F having range of 28 – Day strength of cement tested according to IS: 4031 1968 as 31.9 – 36.8 Mpa, 36.8 – 41.7 Mpa, 41.7  46.6 Mpa, 46.6 – 51.5 Mpa, 51.5 – 56.4 Mpa, 56.4 – 61.3 Mpa respectively instead of Grade of cement like 33, 43, 53 Grade of cement.
If interpretation of these curves is limited to minimum strength of designated grade of cement then we have only three grades of cement like 33,43,53 grade as per respective IS code. In this case the curve B, D and F has no use.
There fore I am in opinion to take the proper advantage of the strength of cement of concerned batch of supply while doing the Mix design based on test results as per relevant IS and this result should also be compared with the manufacturers test certificates for the concerned batch of cement.
comments from Seniors are highly appreciated
Regards
mithilesh
P.K.Mallick wrote:  Respected Mithilesh Sir,
Thanks for your response.Let us look into Indian cement Market. OPC has almost vanished from the market. It is now PSC and PPC. The former is abundant in the Eastern Part of the country.
Now let us look into respective IS Codes for those cement.
IS 1489(Part1):1991(Reaffirmed 2000) PORTLANDPOZZOLANA CEMENTSPECIFICATION(FLY ASH BASED)
IS 1489(Part2):1991(Reaffirmed 2000) PORTLANDPOZZOLANA CEMENTSPECIFICATION(CALCINED CLAY BASED)
Clause 7.4.1 the average compressive strength at 672+=4h is 33 Mpa,Min
Hence strength wise it is equivalent to Grade33 OPC.
IS:455:1989(Reaffirmed 2005) PORTLAND SLAG CEMENTSPECIFICATION
Clause 6.4 the average compressive strength at 672+=4h is 33 Mpa,Min
Hence strength wise it is also equivalent to Grade33 OPC.
It is my observation of last six months that particular brand of PPC gives a compressive strength on an average 53 Mpa. Now the question comes while designing concrete mix should we take the observed compressive strength of 53 Mpa or 33 Mpa.
Again it is of my opinion (conservative of course) that while designing mix we should restrict to 33Mpa because fly ash used in PPC is obtained from the exhaust gases of coal fired power station and the quality of fly ash depends on the ash content of the coal used. See the variables associated Flyash. So depending upon type of Flyash used, the strength of PPC shall vary and we can not question the manufacturer as long as the minimum requirement of 33Mpa is satisfied. Hence is it not risky proposition to depend on undependable observed compressive strength? Of course the consolation is that cement manufactures usually get the fly ash from one source.
Same can be said about OPC43 grade which (sometimes) is actually rejected OPC53 Grade and even sometimes the OPC53 comes in the bag of OPC43 because it is not economically viable for a manufacturer to have different manufacturing facilities for different Grade of cement.
Hence let us use the designated compressive strength not the observed compressive strength while using the curves of Design Mix code. 


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