The Complete Handbook of Power Trowels

Chapter 1: Understanding Power Trowels

The Machine and Its Purpose

A power trowel, sometimes called a power float or a helicopter, is a self-propelled machine used to finish fresh concrete. It replaces the manual trowel, which is a hand tool with a flat blade that an operator pushes across the surface to smooth it. The mechanical version does this work much faster and with more consistent results. Instead of a single blade, a power trowel uses a set of 2 to 4 blades mounted on a rotating hub, driven by a gasoline or electric engine. As the hub spins, the blades are pitched at an angle so that they press down on the concrete, flattening the surface and working the paste to create a dense, smooth finish.

Understanding the trowel's purpose is about understanding the concrete itself. When a slab is poured, the mix contains water, cement, and aggregate. The aggregates settle, and water rises to the surface. This process is known as bleeding. The surface water must be allowed to evaporate or be worked back into the mix at the correct time. If you work the concrete too early, you can close the surface of the slab, trapping bleed water underneath, which weakens the slab's surface layer. If you work it too late, the concrete has stiffened to the point where it's impossible to manipulate. The power trowel is the tool used to work that surface at the precise moment when the concrete is in its plastic state—neither too