Using Concrete Test Cylinders For f'c in Design

[RFreund]

If you have the concrete test breaks can you increase f'c using ACI 5.6.3.3 ? Assuming that is the only information you have. If not what information would you need.
If the above is incorrect - say you were to take an in-place field sample for testing what process is used to determine f'c?
I could have sworn this has been discussed on here before.



EIT

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[JAE]

Is this a new structure under construction or an existing structure?

If existing - look at 20.2.3 and its commentary.

If new - then you can theoretically use the acceptance criteria found in 5.6.3.3 to upgrade the value of f'c (i.e. back calculate an f'c that would meet the two criteria) but I would do that with some caution because of the limited "knowledge" you have with limited tests.

It also depends a bit on what elements are involved in this re-establishment of f'c. Shear capacity is very sensitive to f'c while flexure is not.



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[RFreund]

Thanks JAE.

In this case I'm not sure if the concrete would be considered new or existing. It has been poured and has cured for 28 days. There was an additional hole unaccounted for and an analysis requires a higher f'c for flexure (5,500 vs 4,000 in this case) The test results were near 10,000psi. Small area though only 3 test cylinders.

EIT

http://www.HowToEngineer.com

 

[JAE]

I suppose you could take some additional cores out of the concrete to bracket the area involved.


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[hokie66]

Very unusual to require 5500 psi concrete for flexure. What sort of special case do you have?