<P> Concrete exerts less pressure against the forms as it hardens, so forms are usually designed to withstand a number of feet per hour of pour rate to give the concrete at the bottom time to firm up . For example, wall or column forms are commonly designed for a pour rate between 4--8 ft / hr . The hardening is an asymptotic process, meaning that most of the final strength will be achieved after a short time, though some further hardening can occur depending on the cement type and admixtures . </P> <P> Wet concrete also applies hydrostatic pressure to formwork . The pressure at the bottom of the form is therefore greater than at the top . In the illustration of the column formwork to the right, the' column clamps' are closer together at the bottom . Note that the column is braced with steel adjustable' formwork props' and uses 20 mm' through bolts' to further support the long side of the column . </P> <Ul> <Li> <P> Plastic concrete formwork for cross wall . </P> </Li> <Li> <P> Coal tunnel constructed using handset aluminum concrete forms . </P> </Li> <Li> <P> Concrete pool construction using aluminum concrete forms . </P> </Li> <Li> <P> Soffit formwork to a flight of concrete stairs . </P> </Li> <Li> <P> Stair formwork showing the use of strongbacks to support the riser shutters . </P> </Li> <Li> <P> Sketch showing the use timber props for beam forms . </P> </Li> <Li> <P> Coal silo construction using radius concrete formwork . </P> </Li> <Li> <P> Detail of an alternative to column clamps for larger columns . Twin steel walers and tie bolts, as used in wall forms . </P> </Li> <Li> <P> An example of permanent formwork . A column using spiral ducting . </P> </Li> <Li> <P> An example of permanent formwork, a suspended house slab on roll formed galvanized steel . The formwork in this case is also structural, being bonded to the slab . </P> </Li> <Li> <P> Concrete fence construction using ashlar stone aluminum concrete forms . </P> </Li> <Li> <P> Concrete housing construction in Venezuela using aluminum concrete formwork . </P> </Li> <Li> <P> Concrete construction in Brazil using handset aluminum concrete formwork . </P> </Li> <Li> <P> Concrete construction in Moscow metro using special aluminum concrete formwork </P> </Li> <Li> <P> Engineered Formwork System in Moscow metro </P> </Li> <Li> <P> Engineered Formwork System in Moscow metro </P> </Li> </Ul> <Li> <P> Plastic concrete formwork for cross wall . </P> </Li>

Method of construction for a typical column formwork