ACI Certification Practice Exam

When conducting slump tests, what is an important factor to remember?

1. The surface should be wet

2. The mold must be dry

3. The mold should be lightly tapped

4. Slump can be measured at any stage

The correct answer is: The mold should be lightly tapped

When conducting slump tests, it is crucial to ensure that the mold should be lightly tapped. This practice helps to eliminate any air voids that may be trapped in the concrete mix, ensuring that the concrete settles properly into the mold. The purpose of the slump test is to assess the workability and consistency of fresh concrete. If the mold is not tapped appropriately, the measurement of the slump could be skewed, leading to inaccurate results. Lightly tapping the mold helps to achieve a more homogeneous concrete column, which allows for a clearer and more precise slump measurement once the cone is lifted. In this context, while other factors associated with the slump test may be relevant, they do not carry the same significance regarding the accuracy and reliability of the test as the careful tapping of the mold does.