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ACCEPTANCE CRITERIA OF CONCRETE
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P.K.Mallick
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PostPosted: Mon Apr 02, 2012 2:58 pm    Post subject: Re: ACCEPTANCE CRITERIA OF CONCRETE Reply with quote

In the earlier discussion I had written that :
"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.  

Let me explain what I wrote with help of few examples.Let me take test data sets of the article of ICJ first.

Grade of Concrete M-30
"ITR" criteria for acceptability-27Mpa.
"4 consecutive test results" criteria for acceptability-33Mpa
(AFTER RESULTS OF 30 SAMPLES,WHEN ACTUAL STANDARD DEVIATION IS ESTABLISHED ,DEPENDING UPON THE ESTABLISHED STANDARD DEVIATION THE VALUE OF ACCEPTABILITY FOR CONSECUTIVE TEST RESULTS CAN BE MORE THAN 33Mpa.But for illustration purpose let us assume ,we are at initial stage  of the project,30 samples are yet to be obtained,hence 33Mpa is the acceptance criteria.)

Test data set 1 (D of the article)
38,26,27,44 Mpa
Average=33.5>33Mpa.

Hence batch of concrete represented by result of 26Mpa is at risk.
Rest of the concrete is acceptable.

Test data set 2 (C of the article)  
35,25,41,34 Mpa.
Average=33.5>33Mpa.

Hence batch of concrete represented by result of 25Mpa is at risk.
Rest of the concrete is acceptable.

Test data set 3
30,32,33,34 Mpa.
Average 32.5<33Mpa
Concrete as whole represented by test data set-3 is at risk.
(I had come across similar situation in one of the construction site recently.)

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bijay sarkar
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PostPosted: Mon Apr 02, 2012 3:47 pm    Post subject: Reply with quote

Dear Sirs,

Whatever i have learnt from the above postings, all are tried to be incorporated in an excel file prepared by me today itself with 32 sample data i.e. 4 x 32 = 128 cube test data which are all arbitrarily choosen.  

I think, at the end of this discussion, i would be able to finalise the same particularly after decision taken on the queries made by Mr Mallick.

The file is attached herewith. Input data portion is editable to facilitate users to give input as per their requirement. If you want to unprotect the sheet and edit the equations in the output data, unprotect the sheet by clicking on tools.......unprotect sheet.......password is 123456789.

Regards,

Bijay Sarkar



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Acceptance Criteria.xls
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Acceptability of Concrete

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sspawar
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PostPosted: Mon Apr 02, 2012 9:18 pm    Post subject: Re: ACCEPTANCE CRITERIA OF CONCRETE Reply with quote

Dear Mr. Mallick,

Hope below explanation, could convince you that if out of 4 results one results goes below Fck-3, then whole sample will not be acceptable.

While sample selection code does not says that you have to choose sample only from 4 continuous batches.
These batches may be of any number like 10,15,25 or more. Out of that only 4 batches you can opt.
Code says frequency of 4 samples (mean rate of sampling) is 50cum or 60cum, also it will be less, depends on case to case .
Now what is a quantity of one batch. It depends upon Batching plant capacity. Normally CP 30 or CP45 will produce per batch concrete quantity is 1 cum to 3 cum.

Now my point of concern is if any one batch is giving result below Fck-3, then it is no guarantee, non-tested surrounding batches can not fall in this category.

Hence whole concrete with the definition of clause 16.3 will come under the purview of rejection.

The part of Clause 16.3 - "shall only be at risk "- means while investigation according to clause 17, you should not forget or to leave the part of structure affected by that particular batch.

while other 3 batches or 2 batches if not falling below fck-3, could not be tested, and in place of those, suspected surrounding part of affected area has to be chosen for sampling.

Regards

P.K.Mallick wrote:
In the earlier discussion I had written that :
"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.  

-----------
(I had come across similar situation in one of the construction site recently.)


Last edited by sspawar on Tue Apr 03, 2012 1:08 am; edited 1 time in total
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PostPosted: Mon Apr 02, 2012 9:38 pm    Post subject: Re: ACCEPTANCE CRITERIA OF CONCRETE Reply with quote

Thank you NP RAJMANE SAHEB,

You have looked back and accepted one of my doubt/comment as stated in your below reply.

But rest of 3 queries also of same nature and value are also at your end commendable.

Moreover I have also commented on conclusion part, giving a comparative statement of Fck-3 versus Fc at z=2.33.

Hope you might have gone through thoroughly.

Next, I am writing on this topic since a long back, but you could not recognized me. i am really surprised.

Regards

rajmane wrote:
v:
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:

----
(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


Last edited by sspawar on Tue Apr 03, 2012 9:23 am; edited 3 times in total
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PostPosted: Tue Apr 03, 2012 3:54 am    Post subject: Reply with quote

Dear Mr. SARKAR,
With given sets of data, parameters (values ) are as follows:

Total Data = 32 (35.67,36.33,37.33,37.67,36,33,
35.33,36.67,36.67,37,36,
37.67,36,31.67,36.33,35.67,36,36.67, 37.33,36,36.67,37.33,36.33,37,37.33,37, 37,36,37.33,36.67,36.33,36.33)

Mean         = 36.32281

SD             = 1.222
P'tion SD    = 1.203
Excel Result= 1.244

Thus TMS =  Fck+ (1.65*SD) = 30+(1.65*1.244)
                                             = 32.00

> of Fck+.825*SD or Fck+3 = 33.00

Regards

bijay sarkar wrote:
Dear Sirs,

Whatever i have learnt from the above postings, all are tried to be incorporated in an excel file prepared by me today itself with 32 sample data i.e. 4 x 32 = 128 cube test data which are all arbitrarily choosen.  

I think, at the end of this discussion, i would be able to finalise the same particularly after decision taken on the queries made by Mr Mallick.

The file is attached herewith. Input data portion is editable to facilitate users to give input as per their requirement. If you want to unprotect the sheet and edit the equations in the output data, unprotect the sheet by clicking on tools.......unprotect sheet.......password is 123456789.

Regards,

Bijay Sarkar



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copy_of_acceptance_criteria_144_corrected_896.xls
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PostPosted: Tue Apr 03, 2012 12:45 pm    Post subject: Reply with quote

Dear Mr Pawar,

Thank you for correcting the file.  Due to haste, I missed the square rooting of variance for calculation of SD and also last two rows of data (added later on) in mean.

Now some of the texts are revised and attached here without password.
regards,

bijay sarkar



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PostPosted: Wed Apr 04, 2012 12:34 am    Post subject: Reply with quote

Dear Mr. Sarkar and all,

Yes, In attached excel sheet because of little human error, values were different, but now it is alright.

The second important thing

This particular sets of samples are giving a unique result.
Here SD = 1.244 ~ 1.00 (as per code every fraction of 0.5 will be rounded off)
BY this TMS  = 30+(1.65*1) =31.65 =32.00
Minimum average of 4 samples while acceptance test of production as per clause  16 table 11 =  30+(0.825*1) or 30+3, which one is greater,
Thus this value is 33.00 > TMS (32.00)

Thus every sample if attained, TMS  value  while acceptance test, will  come under non acceptance.
Hence
This exercise says that Value of SD if coming lesser than 2.00,  
=>1.65*SD  >/=   3
=> SD = 3/1.65 = 1.81 ~ 2.00

will be invalid and that has to be considered as atleast = 2.00


And thus TMS  will be revised , in this case it will be = 30+1.65*2 = 33.3 ~ 33.00

thus  TMS SHOULD ALWAYS > OR = to the Fck +3
Or in other words SD will never be less then 2.00.


Before amen no 3 this av value was Fck + 4, now hence it is Fck +3 .

This point was raised by Mr Mallick earlier in this topic itself and was discussed.

Regards





sspawar wrote:
Dear Mr. SARKAR,
With given sets of data, parameters (values ) are as follows:

Total Data = 32 (35.67,36.33,37.33,37.67,36,33,
35.33,36.67,36.67,37,36,
37.67,36,31.67,36.33,35.67,36,36.67, 37.33,36,36.67,37.33,36.33,37,37.33,37, 37,36,37.33,36.67,36.33,36.33)

Mean         = 36.32281

SD             = 1.222
P'tion SD    = 1.203
Excel Result= 1.244

Thus TMS =  Fck+ (1.65*SD) = 30+(1.65*1.244)
                                             = 32.00

> of Fck+.825*SD or Fck+3 = 33.00

Regards

bijay sarkar wrote:
Dear Sirs,

Whatever i have learnt from the above postings, all are tried to be incorporated in an excel file prepared by me today itself with 32 sample data i.e. 4 x 32 = 128 cube test data which are all arbitrarily choosen.  

I think, at the end of this discussion, i would be able to finalise the same particularly after decision taken on the queries made by Mr Mallick.

The file is attached herewith. Input data portion is editable to facilitate users to give input as per their requirement. If you want to unprotect the sheet and edit the equations in the output data, unprotect the sheet by clicking on tools.......unprotect sheet.......password is 123456789.

Regards,

Bijay Sarkar
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P.K.Mallick
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PostPosted: Wed Apr 04, 2012 9:53 am    Post subject: Reply with quote

Let us relook into the clause-16.3 of the IS: 456-2000 once again. It says:
“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. When the mean rate of sampling is not

specified the maximum quantity of concrete that four consecutive test

results represent shall be limited to 60 cubic meter.”


Let us take the same example as given in the article of Indian Concrete
Journal.

Grade of Concrete M-30

Four consecutive test results are


35,25,41,34 Mpa.
As explained in my earlier post, this four consecutive test results satisfy

the criteria 16.1(a) of IS:456-2000.But from “ITR” point of view ,test

strength of 25 Mpa  is at risk and needs further investigation as per
clause 16.4 of IS:456-2000.

Let us further assume that exactly 60 cubic meters of concrete

represents those four consecutive test results and one batch of

concrete represent one cubic meter of concrete. Hence there are 60

batches of concrete.

The first paragraph of Clause 16.3 of IS: 456-2000 says:

“The quantity of concrete represented by a group of four consecutive

test results shall include the batches from which first and last samples

were taken together with all intervening batches.”


Well, this makes our job easy. When there are 60 batches of concrete

as per the above clause, the first sample is taken from first batch and

the last sample is taken from 60th batch.


Two more assumptions, the second sample is from 20th batch and the

third sample is from 40th batch.


Hence

Test result of 35Mpa is from first batch of concrete.

Test result of 25Mpa is from 20th batch of concrete.

Test result of 41Mpa is from 40th batch of concrete.

Test result of 34Mpa is from 60th batch of concrete.

Going strictly by second paragraph of clause 16.3, the 20th batch of

concrete representing test result of 25 Mpa shall be at risk.

Not logical enough? Certainly not? How a sample can represent a lone

20th batch of the population when the population can be 2nd batch to

39th batch (maximum) considering first sample as a discrete sample

(which is not a correct approach as first sample is always part of a

continuous sample but as a conservative approach let us assume it as

discrete) and the third sample has no spread to its left(which is again

not an correct approach as each intermediate sample will have 50% of

the spread to its right as well as to its left in a continuous  sampling

process ,but let us continue with our assumed approach being on

conservative side.)!


By principle of continuous sampling the population of second sample

shall be from 11th batch to 30th batch. Hence the concrete from 11th

batch to 30th batch shall be at risk (by conservative approach 2nd batch

to 39th batch).Rests of the concrete batches shall be acceptable as

clause 16.1(a) of IS: 456-2000 is satisfied.
<xml><o> </o>

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PostPosted: Wed Apr 04, 2012 12:55 pm    Post subject: Reply with quote

Dear Mallick,

If  I accept rejection of single sample only.

This logic will also allow that out of four because of any one sample average is not coming as fck +3 or fck+.825sd, while all are passing ITR criteria.

and hence only that individual batch will be at risk and will only be failure.

Whereas clause 16.1 and 16.2 and 16.4 are very clear that whole lot of from batch of sample one to last sample batch will not be acceptable.

Here code is using - concrete shall be deemed to-----.
Means not confirm but clause 16.4 will decide ultimately.

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PostPosted: Wed Apr 04, 2012 4:32 pm    Post subject: Reply with quote

sspawar wrote:
Dear Mallick,

If  I accept rejection of single sample only.

This logic will also allow that out of four because of any one sample average is not coming as fck +3 or fck+.825sd, while all are passing ITR criteria.

and hence only that individual batch will be at risk and will only be failure.

Whereas clause 16.1 and 16.2 and 16.4 are very clear that whole lot of from batch of sample one to last sample batch will not be acceptable.

Here code is using - concrete shall be deemed to-----.
Means not confirm but clause 16.4 will decide ultimately.

Regards


Respected Pawar Sir
I have gone beyond single sample.Please look into my post once again.
Going out of station .More when I come back on 12th April.
Warm regards.It has been a pleasure to interact with you through SEFI.

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