Start curing after 24 hrs of pouring
Stop : Every Batch of Mix 6 concrete cylinder will be taken to laboratory for Compression Test.
7 days, 14 days and 21 days
2cylinder, 2cylinder 2 cylinder
Suppose you pour concrete of 3000 psi to stop the curing you need to achieve 70% of the strength of the concrete.
First crush test after 7 days.. If you achieve the strength you can stop curing after 7 days. If first set of cylinder failed to achieved the test then
Second set of cylinders will be crushed on 14 days.. If the test failed
Then third set of concrete on 21st day will be crushed if the test passed then you can stop the curing.
But if 3rd set of concrete failed then Your poured concrete will be rejected..
7 days = 2 cylinder (70% of concrete strength 3000 psi (2100 psi)
14 days
21 days
I hope you got your answer..