For concrete to be deemed satisfactory, what is required of the last three consecutive tests?

In assessing the quality of concrete, it is crucial that the last three consecutive tests demonstrate an average strength that exceeds the required specified compressive strength, denoted as F'c. This requirement ensures that the concrete mix is performing adequately to support the structural loads it will encounter throughout its service life.

Meeting or exceeding the required F'c is a critical determinant of the concrete's long-term durability and safety. If the three consecutive test results consistently indicate an average strength above the required F'c, it provides a strong assurance that the concrete will perform reliably under the expected conditions.

Consistently achieving results above the threshold also serves as a buffer, accommodating potential fluctuations in strength due to variations in material properties, mixing, or placement conditions. This approach emphasizes quality control and assurance in concrete construction, which is essential for maintaining structural integrity and safety standards in engineering projects.