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

312 Chapter Ten
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FIGURE 10-16 Placement of concrete in round fiber tube columns. (Source: Sonoco
Products Company)
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The forms are fabricated as one-piece units, so no assembly is
required. They can be cut or sawed on the job to fit beams and to
allow for utility outlets. Because of their exceptional light weight, the
forms are easily handled and provide a fast forming method. Placing,
bracing, pouring, and finishing require minimal time.
Fiber tube forms have a variety of special uses. Sections can be
used in forming pilasters, and half-round, quarter-round, and obround
columns. In forming such columns, the form section is used in connection
with the plywood or wooden form. The forms can also be used to
stub piers for elevated ramps, outdoor signs, pole and fence-pole bases,
flagstones, and round steps.
Various inside coatings of fiber tubes are available, which offer
different finishes after the tube is stripped from the column. The
coated tube produces a visible spiral seam on the stripped column. A
seamless tube with a specially finished inner ply is available which
minimizes, but does not completely eliminate, the spiral seam appearance
on the finished concrete column. A high-quality tube that is fitted
with a plastic liner is available, which imparts a smoother architectural
finish to round columns.
The forms should be stripped as soon as possible after concrete has
set. The recommended time is 24 to 48 hours and should not exceed
5 days. The forms can be stripped by setting a saw blade to the thickness
of the form and making two vertical cuts, then removing the form.
An alternate method is to slit the form 12 in. from the top with a sharp
knife, then use a broad-bladed tool and pry the form off the column.
Steel Forms for Round Columns
Steel forms, consisting of sheet steel attached to prefabricated steel shapes,
such as angles, are frequently used for round columns where the number
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