Using a power trowel to finish concrete
I learned to finish concrete in about 1974, using hand trowels. That I understood. Now that I am being forced to be my own concrete subcontractor, I am trying to learn how to use a power trowel. What I am unsure about is timing: When do I start troweling? Soft, hard,slow, fast???
How many times??
what the heck
was I thinking?
Heck, I am absolutely positively certain that this is not a learn as you go thing.
You need to get a lesson or two, or at least do your experimenting on someone else's slab.
Joe, I learn everything the hard way.I am hoping to get a lesson or two right here from some experienced samaritan.My own slabs can be so-so, it's my clients slabs that I want to be perfect.
Cheers, Jameswhat the heck was I thinking?
If you have floated and troweled before than the timing is about the same. I bull float (actually I use a darby) with the pour and fill in screeds as normal. Float again if necessary. You know how concrete is so don't leave. When you can walk on it firmly without the top layer sticking to your boots it is ready to power float. Right away you can tell if your are working that top 1/4" slurry or sinking in. Stop if you think it's too soft. Don't over work, try to make nice even overlapping passes. Run full power, keep it moving and don't sit in one spot or make abrupt movements. You lift up a little on the handle to go left and down for right. It does not react immediately so watch out it doesn't go overboard. The floats run flatter than the trowels and the angle is controlled by the large knob in the center of the handle. When you take off the float pads give the knob a half turn clockwise so the trowel doesn't cut in when you start the machine. Just like hand troweling you don't want to be right up on the edge or too flat. One time with the floats and two with the trowels should be all you need. Make sure the trucks will come back to back, sometimes the little guy gets left waiting.
I've never run a power trowel but I've been around them a lot over the years. From my observations, the slab can be pretty hard before you have to get back on it. In fact, this summer I had a finisher place and finish my 24x40 shop slab. He requested 1% calcium/accelrator. The day started out cloudy and humid even threatening rain. About the time the slab kicked and was ready to shine, the sun came out and a light breeze picked up. This guy was hustlin' to say the least. But even with the accelerator, sun and breeze, he could bring the top cream back enough to get a really hard, slick finish.
Two coats of cure & seal, the second after a two day cure time, and I've got a really fantastic slab. No trowel marks whatsoever. I think in order to avoid killing yourself in front of others, though, you might want to 'practice' on a sheet of plywood or your garage slab at low throttle until you get the feel of how the machine handles.
Dennis in Bellevue WA
Hammer gave you the basics. The only items I would add are to have help to handle the troweling machine on and off the slab, and hang a small buucket of water on the handle.
The helper is a necessity to lift the machine on and off the slab and keep it flat. I have tried it by myself and always dig a divot in the finish.
This time of year the bucket of water may not be needed, but I keep one handy anyway for the occassional hot spots. Summer time on a large pour it is given that you will get one or more spots that just won't work up enough fines without a few sprinkles of the water.
Thanks to all, am taking a break after pouring a 28' x 32' radiant floor for a log cabin.Still WAY too wet to get on, looks like I may be on it late tonight in the headlights, then need to cover,will get down to low 20's, about 50 now and cloudy.The rental trowel I use has no float paddles, sometimes I get out on the knee boards to float, won't do that today, floor will eventually get covered everywhere.Thanks again.
jwwhat the heck was I thinking?
"dig a divot in the finish."
slide a 18 inch square piece of 20mil or 32 mil T3 or T6 temper aluminum sheet under the paddle that would divot - worked for me...