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

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Properties of Form Material 73
For certain uses, forms made of steel have several advantages over
forms made of other materials. They can provide adequate rigidity
and strength. They can be erected, disassembled, moved, and reerected
rapidly, provided suitable handling equipment is available for
the large sections. They are economical if there are enough reuses. The
smooth concrete surface may be an advantage for some projects.
Forms made of steel have some disadvantages. Unless they are
reused many times, they are expensive. Also, unless special precautions
are taken, steel forms offer little or no insulation protection to
concrete placed during cold weather.
Corrugated metal sheets have been used extensively to form floor
and roof slabs of buildings. Patented pans and domes are often used
to form concrete decks of bridges and for structural floor slabs of
buildings.
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Aluminum Forms
Forms made from aluminum are in many respects similar to those
made of steel. However, because of their lower density, aluminum
forms are lighter than steel forms, and this is their primary advantage
when compared with steel. Because the strength of aluminum in handling,
tension, and compression is less than the strength of steel, it is
necessary to use larger sections when forms are made of aluminum.
Because wet concrete can chemically attack aluminum, it is desirable
to use aluminum alloys in resisting corrosion from the concrete.
Support trusses fabricated with aluminum alloys have been effectively
used for flying forms. These forms are lightweight and allow
large lengths of deck forms to be moved easily. Cast aluminum alloy
molds have also been used successfully to form ornamental concrete
products. Aluminum wall forms have also been used to produce textures
on the surfaces of concrete walls.
Plastic Forms
Fiberglass plastic forms can be used for unique shapes and patterns
in concrete. In addition to their ability to form unusual shapes, plastic
forms are lightweight, easy to handle and strip, and they eliminate
rust and corrosion problems.
The forms are constructed in much the same manner that is commonly
used in the hand forming of boats. Because of careful temperature
and humidity controls that must be exercised at all times during
the manufacture of plastic forms, fabrication of the forms is performed
under factory conditions.
There are several manufacturers of plastic forms. Most of these
forms are fiberglass reinforced for column forms and dome pan forms,
which are custom-made forms for special architectural effects.
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