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What Is Formwork?

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  • Written By: Mary Lougee
  • Edited By: C. Wilborn
  • Last Modified Date: 06 July 2014
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    2003-2014
    Conjecture Corporation
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Formwork is the addition of base materials and concrete contained within retaining walls to use as a slab for construction of homes, businesses, and other buildings. The importance of the formwork for concrete is based on strength and durability. These items are necessary to support the weight of the building or structure that is built on top of it.

Concrete is extremely heavy, at about 150 pounds per cubic foot (2,400 kg per m3). This weight is held in place by a structure of wood or metal assembled on the exterior of the form first to contain the concrete. The concrete is then poured by a concrete truck, cement mixer, or by a concrete pump to fill the form to the required level.

The thickness of formwork is determined by the height and weight of the structure that will be built on it or how it will be used. Roads, sidewalks, and patios also use a formwork design to enclose the concrete until it cures. This type of construction formwork may range from 3 inches (7.62 cm) to 1 foot (0.3 m) in thickness. Large structures may use forms up to 20 feet (6.09 m) thick for support.

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Insulated formwork includes the use of insulated concrete forms (ICFs). These make use of Styrofoam™ blocks, in most cases, that are placed on the outer edge of the form before the walls are filled with concrete. This type of concrete formwork is usually viewed as more energy efficient, holding the heat from the ground inside the home or building and thereby can lower heating costs. The reverse is true in the summer, so that the coolness of the ground can help to lower cooling costs.

Formwork jobs include building the exterior of wood or steel for retaining walls and their removal when necessary after the concrete is dry and cured. Concrete truck drivers generally direct the flow of concrete into the form by using the truck chute, and concrete pumps also require workers for placement of concrete. After the concrete is placed, it is smoothed either by hand with specialized rakes or with a concrete leveler which operates much as a zero-turn riding lawnmower.

Level formworks should have equal strength throughout their entirety. This should help prevent cracks in the foundation at a future date, which is sometimes caused by water retention under the formwork. Construction formwork that cracks may lead to expensive repairs in order to raise and re-level the surface.

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Discuss this Article

abdulsalam
Post 3

I want to know what fastening materials are used, so pleas help me.

widget2010
Post 2

I used to work in a theatre scene shop where we used spray-foam and spray-on "concrete" several times. While you don't really need to make forms for those types of products the same way as for poured concrete, we had to make sure we layered it evenly and usually needed a really specific shape to mold it around, often made out of chicken wire or foam. It also required ventilation to use; the fumes of pretty much any spray-on product can be very harmful.

stolaf23
Post 1

For a time my dad was pursuing amateur concrete form work. He made a few birdbaths and other yard ornaments, and I think he made his molds primarily with scraps of wood that he measures and cut in the workshop. It was actually a really simple process, but I imagine working on industrial amounts of concrete would be far more complicated.

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