What is formwork in construction?

Formwork means the surface of the form and framing used to contain and shape wet concrete until it is self-supporting.

Formwork includes the forms on or within which the concrete is poured and the frames and bracing which provide stability. Although commonly referred to as part of the formwork assembly, the joists, bearers, bracing, foundations, and footings are technically referred to as falsework.

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Formwork comes in several types:

What are 2 types of formwork?`

Basically, we can categorize formwork in two types as below;

Traditional formwork systems are typically constructed on-site from timber or plywood and supporting elements like scaffolding.
Modular formwork systems are specially designed and manufactured off-site. Modular systems usually have proprietary formwork components and rated load calculations set out by the manufacturer and are often made from hardboard, plastics, steel and aluminium products. Most formwork systems use two or more materials, for example plywood facing to steel frames for wall panels.

Furthermore, we can be divided formwork based on its material, durability, and ability of reusable, etc.

Traditional timber formwork.
Engineered Formwork System.
Re-usable plastic formwork.
Permanent Insulated Formwork.
Stay-In-Place structural formwork systems.
Flexible formwork.

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 labor costs are lower than the costs for procuring reusable formwork. It is also the most flexible type of formwork, so even where other systems are in use, complicated sections may use it.

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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, aluminum, 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). Metal formwork systems are better protected against rot and fire than traditional timber formwork.

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 similar structure projects and low-cost, mass housing schemes. To get an added layer of protection against destructive weather, galvanized roofs will help by eliminating the risk of corrosion and rust. These types of modular enclosures can have load-bearing roofs to maximize space by stacking on top of one another. They can either be mounted on an existing roof, or constructed without a floor and lifted onto existing enclosures using a crane.[citation needed]

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 fiber-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 environmental effects, such as corrosion and freeze-thaw cycles.

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Flexible formwork.

In contrast to the rigid moulds described above, flexible formwork is a system that uses lightweight, high strength sheets of fabric to take advantage of the fluidity of concrete and create highly optimised, architecturally interesting, building forms. Using flexible formwork it is possible to cast optimised structures that use significantly less concrete than an equivalent strength prismatic section, thereby offering the potential for significant embodied energy savings in new concrete structures.

Source; https://en.wikipedia.org/wiki/Formwork