Formwork for Concrete Structures by R.L.Peurifoy and G.D- By EasyEngineering.net

72 Chapter Four
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Cold, dry, smooth side Cold, moist, smooth side
Thickness, in. Out, in. In, in. Out, in. In, in.
1
⁄8 9 7 6 4
3
⁄16 16 14 9 6
¼ 25 22 14 10
5
⁄16 35 30 20 16
Minimum Bending Radii for Tempered Hardboard around
Smooth Cylinders, in.
TABLE 4-21
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Fiber Form Tubes
Round fiber-tube forms are fabricated by several manufacturers.
These fiber forms are available in lengths up to 50 ft with inside diameters
ranging from 12 to 48 in., in increments of 6 in. Two types of
waterproof coatings are used. One is a plasticized treatment for use
where the forms are to be removed and a clean finish is specified, and
the other is a wax treatment for use where the forms will not be
removed or where the condition of the exposed surface of the concrete
is not important. The latter treatment is less expensive than the
former. These forms can be used only once.
The tubes are manufactured by wrapping successive layers of
fiber sheets spirally and gluing them together to produce the desired
wall thickness. When the forms are removed from the columns, they
will leave a spiral effect on the surface of the concrete. Seamless tubes,
which will not leave a spiral effect when they are removed, are also
available at slightly higher costs. These tubes may be purchased precut
to specified lengths at the mill, or they may be cut at the project.
Steel Forms
Steel forms are of two broad types: those that are prefabricated into
standard panel sizes and shapes and those that are fabricated for
special uses. For some projects either one or both types may be used.
Among their uses are the following:
1. Concrete walls
2. Concrete piers, columns, and related items
3. Combined decking and reinforcing for concrete slabs
4. Built-in-place concrete conduit
5. Concrete tunnel linings and concrete dams
6. Precast concrete members
7. Architectural concrete
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