ACI Concrete Field Testing Technician - Grade I Practice Exam

What is the maximum number of layers when using vibration as a method of consolidation?

1. 1

2. 2

3. 3

4. 4

The correct answer is: 2

The maximum number of layers when using vibration as a method of consolidation is two layers. This practice is recommended because it ensures that each layer can be adequately vibrated to eliminate air pockets and achieve proper density without over-vibrating, which can lead to segregation of the mix. When using vibration, it's important to control the placement of concrete to avoid issues such as excessive bleeding or segregation. In practical terms, consolidating concrete in two layers allows for better control of the consolidation process, helping to ensure a consistent, dense, and properly compacted final product. Each layer can be vibrated effectively to ensure that all voids are filled, leading to improved strength and durability of the concrete after curing. The option referring to a higher number of layers may lead to inadequate consolidation. If too many layers are attempted, it could become difficult to achieve full compaction of the concrete, resulting in potential weak spots within the structure.