Which statement describes the function of vibrators during placement?

• A. To color the concrete
• B. To consolidate concrete, eliminate air pockets, and improve uniform distribution while avoiding over-vibration that causes segregation
• C. To cure the concrete faster by heat generation
• D. To remove excess water from the surface

Answer: (B)

Vibrators during placement are used to consolidate fresh concrete, push it into contact with all surfaces and around reinforcement, and expel entrapped air. This creates a denser, more uniform mix with fewer voids, improving strength and durability. It’s crucial to avoid over-vibration because it can cause segregation of aggregates and fines and push too much water to the surface, undermining uniformity. This combination—consolidating the concrete, eliminating air pockets, and promoting uniform distribution while avoiding over-vibration that leads to segregation—best describes the function of vibrators. Coloring, curing, or surface water removal are not accomplished by vibration.