woman holding a book
Column formwork is a term used for structures used to support forms or molds for hollow concrete columns. It can be as simple as a reinforced cardboard tube for small cylindrical columns or very complex shapes built with many pieces of wood and metal. Shapes can be stapled together for flat sided columns or complex shapes. In some cases the formwork must be left in place after the concrete is poured, and in others it must be removed after the concrete has set.
The simplest and most basic type of column formwork is the cardboard tube. These tubes are not like the typical corrugated cardboard used for boxes, but are made by gluing together several layers of paper or cardboard and rolling them tightly into a cylindrical shape. The tubes have walls at least 1.25 cm thick, which are very dense, rigid and strong. These pipes are sometimes left in place after the concrete is poured and used as a base for additional decorative cladding. These types of column form tubes are limited by the size of the columns and are not available for very large or heavy columns.
Another common type of cylindrical column formwork is corrugated steel formwork which is usually left in place after pouring. These shapes are usually made from very thick galvanized steel, which is molded into the shape of tubes. They have wavy sides that resemble screw threads, but with rounded ends and grooves. These forms are often inserted into the earth and then filled in, increasing the strength of the spine.
Like paper and metal tubes, there are column forms made of heavily fiberglass-reinforced plastic. They are used for applications where additional protection for the concrete is needed, such as columns or other applications where the column will be exposed to the elements. These shapes are usually left in place after the column is poured.
Concrete columns with non-cylindrical shapes require more complex shapes. These forms are constructed from an intricate assembly of wood, metal, or metal-reinforced wood panels, beams, and spacers held together with staples. Almost any column format can be built this way. Once the concrete has been poured and allowed to cure long enough to hold its shape on its own, the column formwork is removed.
Some column shapes, for both cylindrical and flat columns, are built by assembling a series of interlocking metal plates to build a mold, which is removed once the column has been secured. Other types of column formwork are also possible. Any structure or form for pouring concrete into columns can be considered column formwork, and builders and homeowners can find many ways to improvise or invent other methods.