MATERIALS FOR FORMWORK
Following are the materials which are used for formwork:
This is by far the most common material used for the facing panel. It is easily cut to shape on site, and if handled and stored carefully, it can be used many times.
Note the different thickness: A standard plywood thickness on site is 18mm. this is usually sufficient for most pours. However, if the formwork is curved, a thinner plywood is used to facilitate bending. Thicker plywood may be used when the weight of concrete causes a standard thickness plywood to bow out, distorting the concrete face.
This is the most common material used for bracing members to the form face. Like plywood, it can be easily cut to size on site. Formwork made from timber is called traditional formwork. The construction methods using timer formwork have been used on site for years, and all well understood by trained operators.
Steel is also used in pre-fabricated formwork. Purpose made steel forms are fabricated when dimensional tolerances are critical, or when the forms are planned to be re-used. Steel forms become cost-efficient after about a dozen uses, although they can be used upto 100 pours if they are carefully cleaned and stored.
Often used in pre-fabricated formwork, that is put together on site. Aluminium is strong and light, and consequently fewer supports and ties are required. The lighter sections will deflect more, but this can be avoided by simply following the manufacturers recommendations.
Glass reinforced plastics (GRP) and vacuum formed plastics are used when complicated concrete shapes are required (e.g. waffle floors). Although vacuum formed plastics will always need support, GRP can be fabricated with integral bearers making it self supporting. Like steel, plastic formwork can be re-used many times, as long as care is taken not to scour the surface whilst vibrating the concrete.