Source: TOOLS OF THE TRADE Magazine
Publication date: May 18, 2004
By Bob Simonelli, El Nuevo Constructor
Finishing concrete has always been about good timing: being in the right place at the right time with the right tool. Now, with the widespread acceptance of the F-number system that rates flatness, proper power troweling techniques are essential since floor flatness (FF value) depends directly on a finisher's ability to run trowel machines.
The Right Tool and Time
Power floating embeds the large aggregate just beneath the surface of the mortar, removes surface irregularities, and compacts the concrete while it consolidates mortar at the surface in preparation for other finishing operations. The timing of when you should power float a floor is critical. The rule of thumb on when a slab is ready for the power float is that your footprint should only be 1/4-inch deep or less, with little or no bleed- water present. Most floors that do not end up being very flat (resulting in low F-numbers) are the direct result of finishers getting on to a floor too early with power trowels and creating lumps and bumps. Remember, at this point the concrete is in its most plastic state that the floor will be in during a power floating sequence. Timing is everything-poor timing causes finishing problems. Also remember that any finishing operation done while there is excess moisture or bleed-water on the surface can cause dusting or scaling after the concrete cures.
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