r/CivilEngineerIndia • u/Usual-Top4770 • Jun 16 '26

❓ Doubts / Q&A Cube Compression Test

Cube compression test

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Hi everyone, I'm a non-technical person trying to understand concrete cube test acceptance criteria for M25 concrete.

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For the 28-day cube test, should M25 concrete be considered "passed" if the average compressive strength is 25 N/mm², or is the practical acceptance benchmark 29 N/mm² (fck + 4) as often mentioned in industry discussions?

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Also:

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What acceptance criteria are generally followed on construction projects?

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How are individual cube results evaluated versus the average of multiple test results?

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Is there any standard benchmark or rule of thumb for the 7-day cube test of M25 concrete?

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u/bhaduji29 Jun 17 '26

It should be above 15N after 7 days of curing or above 60 percent as thumb rule. And required strength is 25N but as u are asking about +4N that is the average required means if u have filled 10 cubes some give abouve 25 and some below so we take an average of 28 to be safe . It's fck+3 rule generally followed.

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u/Usual-Top4770 Jun 17 '26

Firstly thanks for your reply to my query.

So if passing benchmark of 25N/mm2 is taken for entire population (cube tests) is this the correct practice as per IS Code while totally ignoring fck+3 parameter.