Concrete formwork is a temporary mould into which concrete is poured. It is a technical word and is used mostly in construction, material and mechanical studies such as engineering, architecture and design among others. There are formworks of several types and these are –
- Traditional timber formwork – The formwork is built usually on the place where construction is to take place. The material used is timber and plywood. Although as compared to larger structures, this kind of formwork is easy to make it is tedious for larger structures and plywood ones have a shorter life span than other types of traditional timber formworks. This type of formwork has the advantage when used in a location where labour is cheaper to construct than buying better raw material and construction equipment. It is the most agile type of formwork too, so it can be used in combination with other types of formworks wherein complicated sections are used
- Re-usable plastic formwork – These interlocking and modular plastic formworks are used to build a variety of widely variable but relatively simple concrete structures. The panels are lightweight, durable and definitely robust. They are especially suited for similar structure multiple projects and low cost mass housing schemes.
- Engineering Formwork System – This kind of formwork is built on prefabricated modules with a metal frame which is usually metal or aluminium and covered on the concrete pouring side with material having the wanted surface structure (steel, aluminium etc. ) Some of the key advantages of this type of formwork as compared to other formwork designs are speed of construction (it is much lower in this) and lower life-cycle costs (if the covering is made of wood it lasts upto 25 uses, if it is made of aluminium then it lasts forever, it is practically indestructible
- Permanent insulated formwork – This kind of formwork is usually assembled on site and on demand, it is made of a material called 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 among other many unique features.
- Stay-In-Place structural formwork systems – This type of formwork is assembled using 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 like the previous type except here it acts as an axial and shear reinforcement, it confines the concrete and prevents against environmental effects.
Usage of Formwork
For removable formworks it is approximated that 24 hours to 7 days are required to ensure that concrete has formed well and that removing the formwork will be safe, prudent and successful. This time period is called setting of concrete or curing of concrete. Post curing the formwork is struck or stripped – which means removed to expose the settled concrete. For example the California Department of Transportation requires the forms to be in place for 1 to 7 days after pouring. Each organisation or regulating body has set its own guidelines and central principles.