A power trowel (also known as a "power float", "helicopter" or "trowel machine" or "whirlybird") is a piece of light construction equipment used by construction companies and contractors, to apply a smooth finish to concrete slabs.
Types
Power trowels differ in the way they are controlled:
A hand tool for the same task is called a concrete float.
References
Power trowel Wikipedia(Text) CC BY-SA