ACI Concrete Field Testing Technician - Grade I Practice Exam

During concrete sampling from a revolving drum truck mixer, what is the minimum number of sampling intervals required?

1. 1

2. 2

3. 3

4. 4

The correct answer is: 2

When sampling concrete from a revolving drum truck mixer, it is crucial to obtain a representative sample that accurately reflects the entire load of concrete. The minimum number of sampling intervals required is two. This is because taking just one sample would not provide sufficient assurance that the sample accurately represents the variability of the concrete mix throughout the entire batch. By taking samples at two different intervals during the discharge process (and ideally at evenly spaced intervals), you can better ensure that the properties of the concrete, such as consistency and aggregate distribution, are adequately represented. This practice helps account for any potential inconsistencies in the mix that may arise due to segregation or varied mixing. Sampling too infrequently can lead to a misrepresentation of the concrete's quality and performance characteristics, which is why two intervals are considered the minimum standard in the industry.