In our previous article on "The Basics of Power Troweling" we introduced the concept of preparing freshly poured concrete by floating and finishing, and considerations in choice of machine type for large and small surface areas.
In this article, we continue with our first part introducing the processes involved in troweling concrete.
WHEN TROWELS ARE USED
The best smooth, even surfaces on freshly poured concrete can be achieved by processing it before it dries. For small surface areas a hand trowel can be used, but for larger areas powered machines are often employed; these do the same task as hand trowels but with much more speed and efficiency.
Whether walk behind or the larger sit and ride machines, power trowels can be easy to use; but if you have never used one before then you may find the following tips particularly useful.
Timing is everything...
Make sure your pour is set for a rain free day. Once poured, the concrete mixture will start to dry. It is critical to wait for the right time to start your trowel. A useful guideline is when the operator can stand on the concrete surface and leave footprints of about 1/8”-1/4” depth. When you can walk on it firmly without the top layer sticking to your boots it is ready to power float.
Right away you will be able to tell if you are working the top 1/4" slurry or sinking in. Stop if you think it's too soft but watch it closely.
To move the trowel, lift the handle up a little go left, and push down to move right. The machine doesn't react immediately so watch that it doesn't swing too far in either direction.
Float First, Finish Second
The concrete surface should be floated prior to finishing. This means a power trowel has to be fitted with the correct tools for floating first; there are 3 options available.
- Combination blades are easy to use but more expensive than using a combination of floats and finish blades. You only have to bolt on one set of blades. You leave the combination blade flat for floating and then adjust the angle of the pitch for finishing. The front side of the combination blade is curved up and the back side is a flat edge.
- Clip-on float blades. Finish blades are kept bolted to the trowel; you simply slide the clip-on float blades over the finish blades to start. Once you have floated the concrete enough, just slide the float blades off and run your finish blades starting with a slight pitch. The benefit is you will be able to use both sides of the finish blades after rotating them 180 degrees.
- Panning. Once again finish blades are kept bolted to the trowel; you set the entire trowel down on to the pan and slide the blades in to the fixtures provided. The benefit of the pan is it has much more surface area to work more quickly. The negative is that panning requires much more effort for the operator to control the trowel. This is because of the additional surface area of the pan.
- Don't over work the concrete; try to make nice even overlapping passes.
- Run your machine at lower speed when floating and keep it moving.
- Don't sit in one spot or make abrupt changes in direction.