ACI Concrete Field Testing Technician - Grade I Practice Exam

When the slump is greater than 3 inches, which method of consolidation is required?

1. Finishing

2. Rodding

3. Vibration

4. Tamping

The correct answer is: Rodding

When the slump exceeds 3 inches, the appropriate method of consolidation is vibration. This choice is based on the characteristics of the concrete mix and the intended application. A greater slump indicates a higher water-cement ratio, typically leading to a more fluid and workable mix. In such cases, vibration is effective in removing air pockets and ensuring uniformity in the concrete, allowing it to flow and fill the formwork adequately. Vibration helps in enhancing the density of the concrete and improving its overall strength by compacting it more thoroughly. This is particularly important in higher-slump mixes, as they can be susceptible to segregation and may not achieve the desired strength or durability if not consolidated properly. While other methods of consolidation, such as rodding and tamping, can be effective for lower slumps, they may not provide the necessary compaction for higher-slump mixes. Therefore, vibration is the recommended consolidation method in this scenario to ensure that the material sets evenly without entrapped air, ultimately leading to a more robust finished product.