Power concrete screed
Power concrete screeds can be used in place of a man powered screed bar to strike off excess concrete. Concrete is poured from a wet mix of cement, sand, aggregate and water. Prior to the mix drying, the concrete should be smoothed out on the desired surface.
A power screed assists in the smoothing out process by leveling out and/or vibrating the wet mixture. There are friction screeds or "roller" screeds that level the concrete - such as the Lura enterprises Lightning Strike which is gas or electric, or the Bunyan striker which is a large heavy steel tube driven by hydraulics. Other power screeds rely on small gas powered engines or small electric motors such as a cordless drill for vibration which can in fact shake the heavier aggregate to the bottom of your pour.