North Carolina Building Contractor License Practice Exam

What is the main purpose of using a vibrator in concrete work?

1. To compact the concrete

2. To mix the concrete

3. To create air bubbles

4. To enhance coloration

The correct answer is: To compact the concrete

The primary purpose of using a vibrator in concrete work is to compact the concrete. When concrete is poured, air bubbles can become trapped within the mixture, leading to a porous structure that can weaken the finished product. A vibrator uses vibration to agitate the concrete, causing the air bubbles to rise to the surface and allowing the concrete to flow and settle more densely. This process enhances the concrete’s density and strength, reducing the potential for voids and improving overall structural integrity. Proper compaction is crucial for ensuring that the concrete achieves its desired durability and performance characteristics, as well as for achieving a smooth finish. The other options do not align with the primary function of the vibrator in concrete applications. Mixing concrete is typically done with other equipment before it reaches the site. Creating air bubbles is contrary to the intended use of a vibrator, as it aims to eliminate air pockets rather than create them. Enhancing coloration does not relate directly to the compaction process, as coloration is usually controlled through the selection of materials and additives rather than through the mechanical action of a vibrator.