Strength is commonly used as a basis for acceptance of concrete. International standards explicitly indicate that during fresh concrete unloading many (cubic or cylindrical) samples must be taken and carefully cured in sheltered, humid condition; after 28 days these samples will be tested for compressive strength. The number and frequency of sampling usually depends on the total amount of the concrete batch and is fixed by national laws.
In case concrete specimens results not compliant with the required strength, some interventions like additional structural reinforcement may be necessary or, in worst cases, demolition of the unqualified concrete structure.
