ACI Certification Practice Exam

Should strength samples be taken before 10% or after 90% of the batch has been discharged in a revolving drum truck?

1. True

2. False

3. Either option is acceptable

4. Only before 10%

The correct answer is: False

In the context of concrete sampling, the correct approach involves understanding when to take strength samples to ensure they are representative of the entire batch. Strength samples should actually be taken after 90% of the batch has been discharged from the revolving drum truck. This practice allows for a more accurate reflection of the final mix characteristics and reduces the risk of including any improperly mixed materials that may be present in the initial portion of the batch. When samples are taken too early, before a significant portion of the concrete is discharged, there is an increased likelihood of obtaining samples that do not accurately represent the entire batch's composition. Taking samples after most of the batch has been dispensed ensures that the sampling is more representative of the concrete that will be used, leading to more reliable strength test results. Thus, the methodology of taking samples after 90% of the discharge is supported by industry standards and best practices.