Page 65 - Masonry and Concrete

Concrete Construction Techniques
64 CHAPTER THREE

CONCRETE FINISHING TOOLS

A straight-edged board is used to strike off freshly poured concrete
level with the tops of the forms (Figure 3-23). A tamper or “jitterbug”
is used to consolidate stiff concrete mixes, settling the large aggregate
and bringing fine material to the surface for easier finishing. A bull
float is used to apply the first rough finish in large areas, or a darby in
small areas. A wood float smooths and works the surface, a steel finish-
ing trowel produces a final smooth finish, and an edging trowel gives a
rounded edge that will not break off easily. A jointer or groover with a
1
blade at least 1 in. deep or 4 the thickness of the slab is used to form
control joints. A stiff broom can be used to apply a nonslip finish, and
other tools and techniques can be used to create decorative finishes.

finish applied. As soon as the first few feet or the first section of con-
crete is poured, you should begin striking off or screeding the excess
concrete so that the surface is level with the top of the forms. Use a
length of 2 4 that is slightly wider than the forms. Keep both ends of
the strikeoff board pressed down on top of the forms and drag it along
to roughly level the surface of the concrete (Figure 3-24). Fill any hol-
low areas that are left with shovels of concrete mix, and then strike
them off. Wide elements like slabs and driveways next require a bull
float with a long handle to begin smoothing the screeded concrete (Fig-
ure 3-25). You can make a bull float with a 4-ft. long 1 12 with a 12-
ft. long 2 2 for a handle, or you can buy one. Place the float at the
opposite edge of the slab from where you are standing, and draw it
toward you. After you have finished a section, repeat the process from
the opposite side. For smaller elements like sidewalks, a wooden
darby can be used instead. Do not do any more finishing until the
water sheen is gone from the surface, and the concrete will hold your
1
weight without your foot sinking more than 4 in. The time that this
will take will vary depending on the temperature, wind and humidity,
and the type of cement used.
For sidewalks, driveways, and patios, begin the concrete finishing
operations by edging the slab. First, use the point of a small trowel to
cut the top inch or so of concrete away from the face of the form (Fig-
ure 3-26), then edge the slab with an edging trowel to form an attrac-

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