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.
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.