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Regarding Concrete acceptance criteria

 
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piyush.civilengg
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PostPosted: Thu Aug 09, 2018 3:07 am    Post subject: Regarding Concrete acceptance criteria Reply with quote

Dear All,

     Suppose Grade of Concrete is M30,By chance the cube result become fail,so directly go with Core the measure the actual strength of the concrete member now, my question is which strength i have to considered for acceptance.

   As per IS 456 Table 11 Characteristic comprehensive strength Compliance requirement ( Page No. 44)

For M30 grade       

1. Fck+0.825 x standard deviation
2. Fck + 4

Which ever is greater with condition individual test results is greater than or equal to Fck


As per IS 456 above clause for M30 grade of concrete it's
interpretation for




Strength of Concrete member is greater than or equal to 34 N/mm2 and individual test results is greater than or equal to 30 N/mm2.



Please give your expert opinion on the above subject.




Regards,
Piyush Parmar
940 949 2827
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HITESHRPATEL_1989
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PostPosted: Thu Aug 09, 2018 9:30 am    Post subject: Regarding Concrete acceptance criteria Reply with quote

Hi,  Here is Mr. Hitesh Patel,
Firstly if I am not wrong, correct Fck+4 with Fck+3 for mean of group of four non-consecutive and Fck-3 for individual test result  for M20 and more as per riv-4,  amendment-2.
To accept M30 grade concrete, mean cube strength must be 33 and more with individual test result not less than 27.
To accept M30 grade concrete, mean core strength must be more than 0.85x30 with individual test result more than 0.75x30.


Hitesh r. Patel.



On Thu, Aug 9, 2018 at 8:37 AM, piyush.civilengg <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear All,

     Suppose Grade of Concrete is M30,By chance the cube result become fail,so directly go with Core the measure the actual strength of the concrete member now, my question is which strength i have to considered for acceptance.

As per IS 456 Table 11 Characteristic comprehensive strength Compliance requirement ( Page No. 44)

For M30 grade      

1. Fck+0.825 x standard deviation
2. Fck + 4

Which ever is greater with condition individual test results is greater than or equal to Fck


As per IS 456 above clause for M30 grade of concrete it's
interpretation for




Strength of Concrete member is greater than or equal to 34 N/mm2 and individual test results is greater than or equal to 30 N/mm2.


Please give your expert opinion on the above subject.




Regards,
Piyush Parmar
940 949 2827
     



     


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suraj
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PostPosted: Sun Sep 16, 2018 7:06 am    Post subject: Evaluation of Hardened Concrete Strength Reply with quote

Evaluation of Hardened Concrete Strength
Refer to ACI 318 Code relevant Chapter
That is descriptive in this instance
But, compliance to core cutting & sampling is a must, which is not incuded probably in ACI
Core capping compound & core length over core dia ratio is too significant

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kunalkansara
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PostPosted: Wed Sep 19, 2018 4:25 pm    Post subject: Reply with quote

Dear Er Piyush

I suppose you are mixing up two things.

If you are using the cube strengths as a means for checking the quality compliance, you should use what Table 11 suggests. However, if the cube tests are inconclusive or non-dependable, and if the Engineer-in-charge approves the use of core sampling as a legitimate and representative approach for quality compliance, you will have to use clause 17.4.

Clause 17.4 suggests that the average compressive strength of cores should not be less than 85% of the specified compressive cube strength of the concrete, and any individual core sample's compressive strength should not be less than 75% of the specified cube compressive strength.

With M30 being your specified cube compressive strength, the average compressive strength based on core testing should be more than (0.85x30 =) 25.5 MPa and none of the core samples should have a compressive strength less than (0.75x30=) 22.5 MPa.

Hope this helps.

Kind regards
Kunal
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Dr. N. Subramanian
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PostPosted: Wed Sep 19, 2018 8:28 pm    Post subject: Reply with quote

kunalkansara wrote:
Dear Er Piyush

I suppose you are mixing up two things.

If you are using the cube strengths as a means for checking the quality compliance, you should use what Table 11 suggests. However, if the cube tests are inconclusive or non-dependable, and if the Engineer-in-charge approves the use of core sampling as a legitimate and representative approach for quality compliance, you will have to use clause 17.4.

Clause 17.4 suggests that the average compressive strength of cores should not be less than 85% of the specified compressive cube strength of the concrete, and any individual core sample's compressive strength should not be less than 75% of the specified cube compressive strength.

With M30 being your specified cube compressive strength, the average compressive strength based on core testing should be more than (0.85x30 =) 25.5 MPa and none of the core samples should have a compressive strength less than (0.75x30=) 22.5 MPa.

Hope this helps.

Kind regards
Kunal
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