ACI Certification Practice Exam

What is the number of stroke rods required per layer to consolidate the sample?

1. 10

2. 15

3. 20

4. 25

The correct answer is: 25

The correct choice indicates that 25 stroke rods are required per layer to adequately consolidate the sample. In the context of concrete testing, particularly in methods like the slump test or compacting concrete in molds, proper consolidation is crucial for eliminating air bubbles and ensuring uniform density throughout the sample. The specific number—25 stroke rods—has been established through standardized testing procedures which dictate that this amount is sufficient to achieve the desired density and eliminate voids within the sample. Each stroke rod applies force to the material, ensuring that it fills the mold appropriately and reduces segregation or layering. While the other options suggest fewer stroke rods, they would likely lead to insufficient consolidation. This could result in a sample that does not accurately represent the material's properties or strength because it may contain trapped air or inconsistent density. Thus, using 25 stroke rods ensures that the sample is properly compacted and ready for reliable testing outcomes.