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ACCEPTANCE CRITERIA OF CONCRETE
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sspawar
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PostPosted: Mon Mar 26, 2012 10:59 am    Post subject: Re: ACCEPTANCE CRITERIA OF CONCRETE Reply with quote

Dear Rajmane saab,

Since this topic is very old.
And I have gone through various views and comments. I would like to say that people answers in many ways.

The best one is which is rightly pin pointed.
What is concept of Fck , TMS,  SD and value K, is very much discussed earlier also.

Your elaboration on this subject is only because of few disagreement or because of your own views.

And Your disagreement from your reply is as follows:


  • I do not wish to state/agree here that 'target mean strength' is only for mix design stage and not for achievable on the site. -

You have presumed this view by mistake, I never said like this.
Definitely concrete poured at site is the same as been designed.
And concrete cube test filled and prepared at site should give the similar result as fit to as mentioned in  Table 11 of IS 456-2000. It is not exactly TMS.


  • Now I come to your second point, In which you again presumed my explanation that 1.65*SD  is quality lack.

This Normal distribution (Bell Curve) concept was in IS 456 1978.
The same concept again followed in IS456 2000. Before 3rd Amendment.
After amendment that concept was the same.
As

Fck - only 5 % results will fall below the standardized value.
TMS will be derived as Fck+k*SD , where for above Fck  = value of K is 1.65.
How 1.65 arrived you can refer SP23 figure 38.

But in above 3 cases, Acceptance Criteria is different , by Clause 16 (for 1978 it is clause 15)


  1. In IS of 1978 in clause 15.1 a it is clearly given if all sample results come above Fck or equal of Fck then concrete batch will be accepted.
  2. Where in IS of 2000 with amm 3,  in clause 16 table 11, this is shown for M20 and above, as greater of Fck+3, and Fck+.825*SD.

Now observe these  2, statements, if I say threshold value has been shifted towards TMS ( Fck+ KSD), then what is wrong, in this.


Now little bit concentrate on this point:
In IS 456, Clause 17.4.3, what it is accepting from the placed , hardened concrete.
It is accepting the concrete strength  as = Fck-0.15Fck, I ask you why?

Why the TMS  = Fck+1.65*SD value has gone to the Fck - 0.15Fck.

As per your view code should not accept this value.

Why cube results are accepted at TMS while designing and greater of Fck+3 or Fck+.845*SD just before of pouring, Where placed hardened concrete is being accepted at Fck-0.15Fck?

Because Cube filling and testing done in a controlled manner as per IS 516 as at laboratory level.
While pouring of concrete at actual place deals with various aspects which leads its quality low.

Next time I will elaborate it more, if not clear.

Regards






bsec wrote:
Dear All,

Sincere thanks to Mr Rajmane, who has explained in great detail the genesis of the IS:456 codal provision on acceptance criteria for concrete cubes, which in fact is the universal statistical procedure for acceptance, applicable for many cases.  

Difference between mean strength and characteristic strength has to be well understood by the Engineers involved in day to day construction works. Without this understanding there is always a scope for mis-interpretation of code.

Best Wishes

Alok Bhowmick  




From: rajmane [mailto:forum@sefindia.org]
Sent: Monday, March 26, 2012 9:14 AM
To: general@sefindia.org
Subject: [SEFI] Re: ACCEPTANCE CRITERIA OF CONCRETE



24 March 2012

Dear Mr. Mallick and Mr Pawar, and others



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PostPosted: Thu Mar 29, 2012 5:31 pm    Post subject: Re: ACCEPTANCE CRITERIA OF CONCRETE Reply with quote

Dear Er Mallick,

You may be interested in reading the recent paper published by Rajamane et al in the Apr. 2012 issue of ICJ.

Regards
NS



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PostPosted: Fri Mar 30, 2012 7:52 pm    Post subject: Re: ACCEPTANCE CRITERIA OF CONCRETE Reply with quote

Dear Dr. NS, and Sefian,

I am sorry that I want to say something about this article, before Mr Mallick could react over.

I could not dare to object on article of such a recognized number of fellows.
But my comments can be considered at a level of doubt and then could be scrutinized by themselves and by other fellows who suppose themselves as a competent in maths and relevant subject.
I would be happy if could be convinced.


  • On p 27 (p2) of article - formula for Z is mashed up with formula for Fm/Fck. Normal distribution curve is in turn used as normal standard table. The difference in this 2 curves is that first one have no negative side at any axes. Where 2nd one (SNT) have negative and positive value called Z at x axis. It is just shifted to left of normal distribution curve. maximum pick value of Y of NDC is Fm comes  from Fck+z*SD, to 0,0 called xbar in SNT.
  • On p 35 (6) , point 11-viii, value of Z is assumed in formula is 1.65, then it is recalculated with above frame of formulas using the value 1.65 and again z = 1.65 is proved. it is because formulas are wrongly mashing up.
  • On p 30 (5) , point no 11 ii and all - value of fm is considered Fck =30. thats why wrong conclusion comes out that lower value going up to 18 or so. on the same page if you look at figure 2 value of Fmean =38.5 is given. In fact here in place of 30 higher value will come like 42.
  • IN conclusion point number 2 and 4 are contradictory with point no 6.
Regards

Dr N. Subramanian wrote:
Dear Er Mallick,

You may be interested in reading the recent paper published by Rajamane et al in the Apr. 2012 issue of ICJ.

Regards
NS


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PostPosted: Fri Mar 30, 2012 7:59 pm    Post subject: Reply with quote

Dear Mr. Mallick, and Rajmane saab,

Attached are few papers from ACI, shows acceptance criteria and why for Hardened (In place) concrete.

Regards



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PostPosted: Sat Mar 31, 2012 3:51 am    Post subject: Reply with quote

Dear Rajmane Saab,And Dr. NS, and MR. Mallick and all,

I have made here a comparative statement of ITR of IS 456-2000-am 3 with 1 in 100 probability against most practical SDs in construction field.

Hope this will be able to reveal the adequacy of IS 456 over proposal of adapting 1in 100 probability.

Next suggestion given by authors for ITR is  Fm-2.65SD or Fck -SD, in my opinion is quite mathematical /statistical approach, away from practical results.

Regardless of some mathematical concepts overall article content is presented beautifully to reflect ITR criterion and its impact on quality and cost of production of batches.

Regards






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PostPosted: Sun Apr 01, 2012 11:39 am    Post subject: Reply with quote

Dear Sefian,

Since this discussion was restarted by Mr. Mallick with a question that
: Is BIS have forgotten to revise clause 17 along with clause 16 in year of 2000.

This question was related to fresh concrete strength versus in place (Hardened) concrete.

I have given my reply that it is not because of any thing forgetting.

I given the reason that in earlier code (of 1978) acceptance criterion limit for green (fresh) concrete was giving hardened concrete results below of condition mentioned in clause 17. And hence Acceptance criterion limit was revised with an increasing value to match with the clause 17.


Meanwhile Rajmane Sahab have posed a long draft regarding statistical concept (a tool) of  Design Mix and Acceptance Criterion.

Which is not a direct answer of main question, but it is a part of discussion, which deals with the evaluation of designed proportionate of concrete constituents and for acceptability of the same.

It is a very good part of discussion that we have got a chance to go through the Article on ITR criterion.

While going through this Article I came across 2 questions in my mind:

  • What is range of heterogeneity of concrete. By mathematical concept NDC is based on 8 sigma units. If I put SD is 5, then according to this principle samples will roll between +/- (4*5) =+/-20, ofcourse with different probabilities. But it makes us to think over how it is relevant with the practical samplings.
    In IS 456 there is an answer over range of Heterogeneity of concrete mix.It is from Clause 15, 15% plus /minus. Readers may understand that it will not for different samples.  
    As per IS 456 , sampling shall be done according to IS 1199. Looking to this process all samples of one batch will also not vary more than +/- 15%. But it will not valid for different batches.
    So where is answer, 2nd answer is within , exercise of  calculation of SD by number of data of samples (minimum required 30).
    This sample will tell you what is your concrete mix heterogeneity range, along with SD value and shape of NDC.
    so you can assess that probability of ITR will fall within this range, and it is not exactly the standardized (as mentioned in IS 456 =Fck-3 or any lowest value like of Z=2.33) value. So percentage probability of rejection of concrete batch because of this certain condition is not a matter of worries.
  • Second question is since every thing is depend on practical data and results.
    Mathematical concepts and principles are supports or tools to obtain the required outputs.
    So I want to put a poll survey among all 12000 engineers. Questions may be like that,

    1. Range of SD in the field of production of Concrete is in between 2 to 5. yes or no or no comments
    2. Lowest ITR value will depend 99% on history of data on which SD is fixed for MIX DESIGN. YES , NO , No Comments.

I also want attention of recognized experts to put there views and comments
Thanks and

Regards


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PostPosted: Mon Apr 02, 2012 2:32 am    Post subject: Re: ACCEPTANCE CRITERIA OF CONCRETE Reply with quote

What I am to going to discuss is very basic.Let us look into page 29 of the article(page-29 of ICJ to be precise.)

Test data set C.
(I) 35,(II) 25,(III) 41,(IV) 34 MPa.
The article says "Three of the above test results are more than 27Mpa,but one test result is less than 27Mpa. Hence this concrete is not acceptable from "ITR" criterion.Hence ,the concrete test data need not be scrutinized against other criteria of the code and we can now declare that the concrete as unacceptable as a whole."

Test data set D.
38 26 27 44 MPa.

The article says "Among the above four consecutive test results,two are more than 27mpa ,and one test result is equal to 27mpa.But there is a test value of 26mpa,which is 1mpa less than 27mpa.Hence,the concrete represented by the above four samples test value is not acceptable from "ITR" criterion.Therefore the concrete test data need not be scrutinized against other criteria of the code and it is possible to decide about unacceptability of concrete itself,immediately after checking against the ITR criterion".

Now let us look into clause 16.3 of IS:456-2000(Quantity of Concrete represented by Strength Test Results.)
The quantity of concrete represented by a group of four consecutive test results shall include the batches from which the first and samples were taken together with all intervening batches.
For the individual test result requirements given in col 3 of Table 11 or in item (b) of 16.2 only the particular batch from which the sample was taken shall be at risk.

Hence it is incorrect to reject the concrete represented by test data set C and test data set D as a whole BEFORE SCRUTINIZING AGAINST OTHER CRITERIA OF THE CODE. If the concrete fails to satisfy the other criteria ,then the only concrete can be rejected as a whole.
Hence "ITR"criteria only decides the fate of a concrete of a batch only   Where as the other criteria of the code decides about all batches of concrete as whole representing a group of four consecutive test results.

Hence it is incorrect to reject the entire concrete as a whole represented by  group of four consecutive test results based on "ITR" criteria only as done in the article in illustration "Test data set C" and "Test data set D".

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PostPosted: Mon Apr 02, 2012 4:44 am    Post subject: ACCEPTANCE CRITERIA OF CONCRETE Reply with quote

Normal 0     false false false  EN-US X-NONE X-NONE              MicrosoftInternetExplorer4              <![endif]-->                                                                                                                                             <![endif]-->    /* Style Definitions */ table.MsoNormalTable      {mso-style-name:"Table Normal";      mso-tstyle-rowband-size:0;      mso-tstyle-colband-size:0;      mso-style-noshow:yes;      mso-style-priority:99;      mso-style-qformat:yes;      mso-style-parent:"";      mso-padding-alt:0in 5.4pt 0in 5.4pt;      mso-para-margin:0in;      mso-para-margin-bottom:.0001pt;      mso-pagination:widow-orphan;      font-size:10.0pt;      font-family:"Times New Roman","serif";}  <![endif]-->  <![endif]-->   <![endif]-->
Dear Shri Mallick

Thank you for your interesting and highly useful observation. There is a need for  good discussion on this aspect. Clause 16.1 of IS:456-2000 given below makes it clear that both the conditions (mean strength of four consecutive test results and individual test result) have to be met.

“16.1 Compressive Strength

The concrete shall be deemed to comply with the strength requirements when both the following condition are met:

a) The mean strength determined from any group of four consecutive test results compiles with the appropriate limits in co1 2 of Table 11.

b) Any individual test result complies with the appropriate limits in co1 3 of Table 11.”


But, the Clause 16.3 has the following point:  

“For the individual test result requirements given in co1 2 of Table 11 or in item (b) of 16.2, only the particular batch from which the sample was taken shall be at risk.”  

Does it mean that when one of four ITR  values is not satisfied, still we can take this rejected sample for calculating the average of 4 samples? If the four average criterion is satisfied, then, can we accept the concrete as a whole, but, still allowing the risky concrete represented by the unacceptable ITR?

If we have, out of four, three ITR values are unacceptable   and the fourth ITR has so high value that the average of 4 samples criterion is satisfied, then, can we still accept the concrete ? Then, out of four samples, the concrete with reference to three becomes risky i.e., 75%, (and hence not acceptable) and only the  concrete represented by fourth i.e., 25%, is not risky and acceptable. Then how to consider issues such as the sanctity of ITR and scope of four samples, etc?

N P Rajamane (Ex-SERC)
Head, CACR, SRM University  

On Mon, 2/4/12, P.K.Mallick <forum@sefindia.org> wrote:
Quote:

From: P.K.Mallick <forum@sefindia.org>
Subject: [SEFI] Re: ACCEPTANCE CRITERIA OF CONCRETE
To: general@sefindia.org
Date: Monday, 2 April, 2012, 8:02 AM

     What I am to going to discuss is very basic.Let us look into page 29 of the article(page-29 of ICJ to be precise.)

Test data set C.
(I) 35,(II) 25,(III) 41,(IV) 34 MPa.
The article says "Three of the above test results are more than 27Mpa,but one test result is less than 27Mpa. Hence this concrete is not acceptable from "ITR" criterion.Hence ,the concrete test data need not be scrutinized against other criteria of the code and we can now declare that the concrete as unacceptable as a whole.[/color:286cf86d8a]"

Test data set D.
38 26 27 44 MPa.

The article says "Among the above four consecutive test results,two are more than 27mpa ,and one test result is equal to 27mpa.But there is a test value of 26mpa,which is 1mpa less than 27mpa.Hence,the concrete represented by the above four samples test value is not acceptable from "ITR" criterion.[/color:286cf86d8a]Therefore the concrete test data need not be scrutinized against other criteria of the code and it is possible to decide about unacceptability of concrete itself,immediately after checking against the ITR criterion".

Now let us look into clause 16.3 of IS:456-2000(Quantity of Concrete represented by Strength Test Results.)
The quantity of concrete represented by a group of four consecutive test results shall include the batches from which the first and samples were taken together with all intervening batches.
For the individual test result requirements given in col 3 of Table 11 or in item (b) of 16.2 only the particular batch from which the sample was taken shall be at risk. [/color:286cf86d8a]

Hence it is incorrect to reject the concrete represented by test data set C and test data set D as a whole BEFORE SCRUTINIZING AGAINST OTHER CRITERIA OF THE CODE. If the concrete fails to satisfy the other criteria ,then the only concrete can be rejected as a whole.
Hence "ITR"criteria only decides the fate of a concrete of a batch only [/color:286cf86d8a] Where as the other criteria of the code decides about all batches of concrete as whole representing a group of four consecutive test results.

Hence it is incorrect to reject the entire concrete as a whole represented by group of four consecutive test results based on "ITR" criteria only[/color:286cf86d8a] as done in the article in illustration "Test data set C" and "Test data set D".
     


P.K.Mallick
p.k.mallick1962@gmail.com

     



     



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PostPosted: Mon Apr 02, 2012 7:34 am    Post subject: Re: ACCEPTANCE CRITERIA OF CONCRETE Reply with quote

Dear Mr. Mallick and all,
What is pointed out , initially it is agreeable view.
At the same time below 2 clauses along with Amendment no 1.should be viewed.

16 ACCEPTANCE CRITERIA

16.1 Compressive Strength
The concrete shall be deemed to comply with the
strength requirements when both the following
condition are met:
a) The mean strength determined from any group
of four consecutive test results compiles with
the appropriate limits in co1 2 of Table 11.
b) Any individual test result complies with the
appropriate limits in co1 3 of Table 11.

16.4 If the concrete is deemed not to comply pursuant
to 16.3, the structural adequacy of the parts affected
shall be investigated (see 17) and any consequential
action as needed shall be taken.

Amendment no1-(Page 29, clause 16.4, line 2)
Substitute
16.1 or 16.2
as the case may be for 16.3.

It means for ITR and for set of 4 test results  
- condition of rejection will be applicable same.

Real scenario during execution is that these
results only comes out after 7/28 days and
till that structure had been got a very advanced
shape.

Here rejection of samples/ concrete will be on
record and after investigation will be taken place.

More over authors using  the term "whole concrete "
where Code using "Concrete " (in clause 16)
meaning is same as (as per clause 16.3 1st few lines)
"The quantity of concrete represented by
a group of four consecutive test-results
shall include the batches from which the
first and last samples were taken together
with all intervening batches"
and will come in purview of clause 16.1/16.2 and 16.4.

Whereas clause 16.3, is specifying
For the individual test result requirements given in
co1 3 of Table 11 or in item (b) of 16.2, only the
particular batch from which the sample was taken shall
be at risk.
It is to identify the concrete of that particular batch,
so that can be tested as per clause 17.
It is my personal views.
Regards
P.K.Mallick wrote:
What I am to going to discuss is very basic.Let us look into page 29 of the article(page-29 of ICJ to be precise.)

Test data set C.
--------

Hence it is incorrect to reject the entire concrete as a whole represented by  group of four consecutive test results based on "ITR" criteria only as done in the article in illustration "Test data set C" and "Test data set D".


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PostPosted: Mon Apr 02, 2012 8:23 am    Post subject: ACCEPTANCE CRITERIA OF CONCRETE Reply with quote

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2nd Apr 2012

Dear SEFIans

I noticed and also as pointed by some friends that the following corrections are to be used while reading the write-up:

(1) Page 28, Para “Concrete properties….”

Replace  

· Standard deviation of 28 day compressive strengths of concrete = 4 MPa.  

with

· Standard deviation of 28 day compressive strengths of concrete = 5 MPa.  

· Target mean compressive strengths of concrete at 28 day  

= fm
= fck + 1.65 * SD
= 30 + 1.65 * 5 = 38.25 MPa
= Population mean strength of the concrete mix
=µ  

(2) Page 30, Equation below the Sl No 8.

Replace  

<![endif]-->

with


<![endif]-->

(Note σ should be outside the square root)


(3) Page 30, Sl No (ii)

Replace  

(30-4) and (30+4) i.e., 26 and 34.

with

(38.25-5) and (38.25+5) i.e., 33.25 and 43.25.

(4) Page 30, Sl No (iii)

Replace  

(30-2*4) and (30+2*4) i.e., 22 and 38.

with

(38.25-2*5) and (38.25+2*5) i.e., 28.25 and 48.25.

(5) Page 30, Sl No (iv)

Replace  


(30-3*4) and (30+3*4) i.e., 18 and 42.

with

(38.25-3*5) and (38.25+3*5) i.e., 23.25 and 53.25.


Thanking you all, sorry for the inconvenience due to errors in the paper.

Yours sincerely

N P Rajamane (Ex-SERC)
Head, CACR, SRM University  

On Mon, 2/4/12, rajmane <forum@sefindia.org> wrote:
[quote]
From: rajmane <forum@sefindia.org>
Subject: [SEFI] Re: ACCEPTANCE CRITERIA OF CONCRETE
To: general@sefindia.org
Date: Monday, 2 April, 2012, 11:00 AM

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Dear Shri Mallick

Thank you for your interesting and highly useful observation. There is a need for good discussion on this aspect. Clause 16.1 of IS:456-2000 given below makes it clear that both the conditions (mean strength of four consecutive test results and individual test result) have to be met.

“16.1 Compressive Strength

The concrete shall be deemed to comply with the strength requirements when both the following condition are met:

a) The mean strength determined from any group of four consecutive test results compiles with the appropriate limits in co1 2 of Table 11.

b) Any individual test result complies with the appropriate limits in co1 3 of Table 11.”


But, the Clause 16.3 has the following point:

“For the individual test result requirements given in co1 2 of Table 11 or in item (b) of 16.2, only the particular batch from which the sample was taken shall be at risk.”

Does it mean that when one of four ITR values is not satisfied, still we can take this rejected sample for calculating the average of 4 samples? If the four average criterion is satisfied, then, can we accept the concrete as a whole, but, still allowing the risky concrete represented by the unacceptable ITR?

If we have, out of four, three ITR values are unacceptable and the fourth ITR has so high value that the average of 4 samples criterion is satisfied, then, can we still accept the concrete ? Then, out of four samples, the concrete with reference to three becomes risky i.e., 75%, (and hence not acceptable) and only the concrete represented by fourth i.e., 25%, is not risky and acceptable. Then how to consider issues such as the sanctity of ITR and scope of four samples, etc?

N P Rajamane (Ex-SERC)
Head, CACR, SRM University

On Mon, 2/4/12, P.K.Mallick  wrote:
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