Internal vibrators

Concrete Construction, May, 2002

Internal vibrators consolidate freshly placed concrete by helping entrapped air to escape. Most of the internal vibrators used today can be classified as either flexible-shaft, motor-in-head, or pneumatic. The primary difference is in how the power gets to the vibrator head. Flexible-shaft vibrators have an external power source (gas engine or electric motor) that spins a flexible shaft enclosed in a flexible housing to power the vibrator.

Motor-in-head units have a small electric motor inside the vibrator head. Pneumatic vibrators have a spinning rotor inside the vibrator head powered by compressed air. Choosing a vibrator includes selecting the right head size, frequency, and amplitude for the job. A general rule of thumb is: the lower the concrete slump, the higher the frequency of vibrator needed. Here are several currently on the market.