Concrete Finishing

1. After the fresh concrete has been leveled (screeded) in the forms, let it set until the surface of the concrete looks shiny-or you note that the excess water is gone and the concrete can withstand foot pressure. The concrete should feel gritty under trowel pressure.
2. Float the surface. A wooden float is used for this. If the float has handle and is large, it is called a bullfloat. If the float looks like a finishing trowel, it is called a float. A float removes excess water from the surface of the concrete and knocks down the small ridges left by the screeding operation. Push and pull the bullfloat across the surface. Lift it after each stroke. On small jobs, use the hand float working it in a circular motion. Don't dig the edges into the concrete.
3. Edge the concrete with an edging tool. Edging provides a round smoothed edge to keep the slab from chipping. Run the edger back and forth, using the wood form as a guide for the tool.
4. Cut control joints- You can use the trowel or a grooving tool for this job. The groove should be 1/4 the thickness of the concrete slab. Use a straightedge for a guideline to run the trowel or grooving tool.
5. After floating, finish the concrete. You can do this with a steel concrete trowel. Move the trowel in a circular motion. Easier than a trowel is a broom finish. Brooming is done after edging and floating the slab. Simply run a push broom with stiff bristles evenly on the surface of the fresh concrete. Pull the broom toward you; lift it after each stroke. Light pressure is plenty good enough on the broom for depth of grooves.

Curved edge slab-
A curved edge is no more difficult to set than a straight one. A series of saw kerfs are cut into the form board every 1/4-in. to a depth of one half the board thickness. This makes the form f strong enough to withstand the thrust of the concrete mixture, which is plenty. Space the form stakes fairly close together; you want plenty of lateral support to hold the form boards stiff. If the design calls for wooden spacers, install these at the time the forms are set, but after the excavating and fill work has been done. Drive nails through the thickness of the spacers near the fill to help hold them tight.

Free-form slab-
A freeform slab can be laid with properly kerfed and braced form boards. Location of control joints is determined by a combination of known stress factors and aesthetic effect. If your project is a slab patio, and it measures more than 10 ft. in length or width, you need to cut equally-spaced control joints. The joints should never be more than 10 ft. apart; they may be closer than this if you want. Also, permanent forms do not require grooved control joints as long as the boards are spaced to these specs. The interior wood strips will serve as control joints. On large jobs such as slabs, it is suggested that you enlist the aid of several helpers to assist you.

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