How to Use a Concrete Vibrator, Bull Float & Darby
Pouring concrete is backbreaking work but the tools you choose can make the job easier. When you're working on a flat pour, such as a driveway or a patio, arrange to have a concrete vibrator, a bull float and a darby on hand to settle the concrete and to help smooth the surface.
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Things You'll Need
- Concrete vibrator
- Bull float
- Darby
- Prepared concrete forms
- Concrete
- Protective clothing
Instructions
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As soon as the wet concrete is roughly leveled in the forms, it's time to begin the screeding process. A concrete vibrator, attached to a 2" X 4" dimensional board, approximately 2 ft. longer than the width of your pour is needed for the initial screeding.
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Place one worker on either side of the pour at the highest elevation. Each worker will hold and control one end of the screed board to which the vibrator is attached. Another worker will turn the vibrator on and off, using a switch attached to the vibrator with a long cord.
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Turn the concrete vibrator on while the workers on each side slowly pull the screed board along the top edge of the form. The vibration makes it easier to pull the board and it encourages larger bits of gravel to sink while bringing moisture to the surface of the wet concrete. Work very quickly. Concrete can set up within a matter of minutes, especially on a hot day.
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Float the surface of the screeded concrete with a bull float. This is a one-man tool with a long pole and a flat rectangular plate. By pushing the float from the near side to the far side and then pulling it back again, the large plate smooths the surface, leaving the concrete shiny and wet.
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Repeat the floating process one or more times while the concrete is wet enough to draw water to the surface with each pass. Take care not to touch the bull float plate to dirt or sand to avoid picking up gravel that can mar the surface of the new pour.
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Use a darby after the concrete begins to set. A darby is a two-handed, long trowel that finishes the texture on the surface of the pour. Since patterns on the concrete may remain after it dries, use uniform round or semi-round strokes with the darby. This tool is handy around the edges of a pour but it isn't feasible for troweling the center section of a wide pour. For that, a power-trowel is necessary.
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Tips & Warnings
Wear long sleeves, long pants and protective eyewear when pouring concrete. Wet concrete quickly leaches moisture from the skin, leaving it dry, irritated and prone to cracking.
Arrange for more workers than you think you'll need and go over everyone's job before you begin. Once the concrete truck arrives, everyone will be working frantically to finish the pour before the concrete sets and there will be no time for training.
Use all tools with caution and under the supervision of a knowledgeable construction professional.
Don't swing a bull float around, the pole is so long, anyone standing within 10 ft. may be injured.
Resources
- Photo Credit Image, courtesy of Stock.xchng
