ACI Concrete Field Testing Technician - Grade I Practice Exam

When sampling from a stationary mixer, how often must the batch be sampled during discharge?

1. At least 1 interval

2. At least 2 intervals

3. At least 3 intervals

4. At least 4 intervals

The correct answer is: At least 2 intervals

When sampling from a stationary mixer, it is required to take samples during the discharge process. The practice of sampling at least two intervals ensures a more representative sample of the batch. This is important because, during the mixing and discharging process, the consistency of the concrete can vary due to factors such as material segregation or variations in the mix. By taking samples at multiple intervals, you can assess the uniformity of the mix and identify any discrepancies that may occur throughout the discharge. This helps in ensuring that the concrete being tested truly reflects the properties and performance of the entire batch, leading to more accurate and reliable testing results. Sampling at just one interval could give a skewed representation, and more than two intervals might not be necessary for maintaining efficiency while still achieving a representative sample. Thus, sampling at two intervals strikes a balance between representativeness and practicality during the testing process.