ACI Concrete Field Testing Technician - Grade I Practice Exam

How many different portions of the batch must a composite sample for a paving mixer represent?

1. 3

2. 5

3. 7

4. 10

The correct answer is: 5

A composite sample for a paving mixer must represent five different portions of the batch to ensure that the sample accurately reflects the properties of the entire batch of concrete. This sampling approach is critical because it helps to account for variability within the batch, including differences that may occur at different stages of the mixing process. In practice, this means obtaining portions of the concrete from different trucks or times during the mixing cycle, thus capturing a wide representation of the materials being mixed. By incorporating five portions, the technician can better ensure that any tests performed will yield reliable, consistent results that accurately reflect the quality and characteristics of the final product. Sampling fewer portions may introduce biases and inaccuracies, making it less representative of the whole batch.