ACI Concrete Field Testing Technician - Grade I Practice Exam

What is the minimum size sample required for making strength test specimens in concrete testing?

1. 14 L (0.5 ft^3)

2. 28 L (1 ft^3)

3. 21 L (0.75 ft^3)

4. 35 L (1.25 ft^3)

The correct answer is: 28 L (1 ft^3)

The minimum size sample required for making strength test specimens in concrete testing is 28 liters (1 cubic foot). This requirement ensures that there is enough concrete material to produce the necessary test specimens while also accommodating variations that may arise during mixing. Having 28 liters allows for creating multiple test cylinders or beams, which can then be subjected to compressive strength testing. This volume helps to achieve accurate and reliable test results, as it guarantees that the samples are representative of the larger batch of concrete being tested. The choice of 28 liters is in line with various industry standards and practices that emphasize the importance of sample size in achieving consistency and accuracy in strength testing. A smaller sample might not provide the necessary volume to compensate for any non-homogeneity that could exist within the batch, potentially leading to misleading results. Thus, 28 liters represents the standard for ensuring sufficient material for comprehensive testing and promoting quality control in concrete production.