Concrete develops strength with continued hydration. Rate of gain of strength is faster to start with and rate get reduced with age. It is customary to assume the 28 days strength as full strength of concrete. But actually, concrete develops strength beyond 28 days also.
Percentage strength of concrete at various ages
The strength of concrete increases with age. Table shows the strength of concrete different ages in comparison with the strength at 28 days.
Age Strength per cent
1 day 16%
3 days 40%
7 days 65%
14 days 90%
28 days 99%
Concrete mix design is required to achieve target strength in structures.