Formwork is the term
given to either temporary or permanent moulds into which concrete or similar
materials are poured. In the context of concrete construction, the falsework
supports the shuttering moulds.
Formwork comes in several types:
Traditional timber formwork
The formwork is built on site out of
timber and plywood or moisture-resistant particleboard. It is easy to produce
but time-consuming for larger structures, and the plywood facing has a
relatively short lifespan. It is still used extensively where the labour costs
are lower than the costs for procuring re-usable formwork. It is also the most
flexible type of formwork, so even where other systems are in use, complicated
sections may use it.
Engineered Formwork System
This formwork is
built out of prefabricated modules with a metal frame (usually steel or
aluminium) and covered on the application (concrete) side with material having
the wanted surface structure (steel, aluminium, timber, etc.). The two major
advantages of formwork systems, compared to traditional timber formwork, are
speed of construction (modular systems pin, clip, or screw together quickly)
and lower life-cycle costs (barring major force, the frame is almost
indestructible, while the covering if made of wood; may have to be replaced
after a few - or a few dozen - uses, but if the covering is made with steel or
aluminium the form can achieve up to two thousand uses depending on care and
the applications).
Re-usable plastic formwork
These interlocking
and modular systems are used to build widely variable, but relatively simple,
concrete structures. The panels are lightweight and very robust. They are
especially suited for low-cost, mass housing schemes.
Permanent Insulated Formwork
This formwork is
assembled on site, usually out of insulating concrete forms (ICF). The formwork
stays in place after the concrete has cured, and may provide advantages in
terms of speed, strength, superior thermal and acoustic insulation, space to
run utilities within the EPS layer, and integrated furring strip for cladding
finishes.
Stay-In-Place structural
formwork systems
This formwork is assembled on site, usually out of
prefabricated fibre-reinforced plastic forms. These are in the shape of hollow
tubes, and are usually used for columns and piers. The formwork stays in place
after the concrete has cured and acts as axial and shear reinforcement, as well
as serving to confine the concrete and prevent against environmental effects,
such as corrosion and freeze-thaw cycles.
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