ACI Concrete Field Testing Technician - Grade I Practice Exam

Compressive strength tests should be performed on concrete samples at established curing ages, typically at 7 and 28 days. This is crucial because concrete continues to gain strength as it cures, and these specific time intervals are standard benchmarks that correspond to the majority of concrete's strength development. Testing at these ages provides a reliable measure of the concrete's performance for use in construction, ensuring that it meets the structural requirements for the project.

Waiting until the concrete has matured to these specified points allows for an accurate assessment of its compressive strength, which is essential for determining if the concrete mix design is adequate for the intended application. Testing immediately after casting would not provide a valid measure, as the concrete has not had enough time to cure and develop its strength. Testing only when visual defects are noted is reactive rather than proactive, potentially leading to issues if the concrete is found to be insufficient after it has already been used. Lastly, performing tests after the concrete has been used does not help in making informed decisions about its structural integrity during the construction phase.