ACI Concrete Field Testing Technician - Grade I Practice Exam

When the slump is less than 1 inch, which method of consolidation should be used?

1. Vibration

2. Rodding

3. Finishing

4. Pouring

The correct answer is: Vibration

When the slump is less than 1 inch, the most appropriate method of consolidation is vibration. This technique is particularly effective for low-slump concrete because it helps ensure that air pockets within the mix are eliminated and that the concrete achieves a proper density. Vibration facilitates the flow of concrete into tight spaces and around reinforcement, allowing it to settle evenly. In cases of very stiff mixes, such as those with a slump of less than 1 inch, relying on methods like rodding might not effectively consolidate the concrete since they typically depend on the workability of the mix. Therefore, vibration is preferred because it applies continuous and uniform energy to the concrete, enhancing compaction without damaging the integrity of the material. Vibrating is essential for achieving a uniform distribution of aggregates and maintaining the intended strength and durability of the hardened concrete. This is why, in this scenario, utilizing vibration for consolidation proves to be the best choice.