Formwork: An Essential Element of Construction

Posted by Armstrong Louis on September 21st, 2018

Formwork is a mould including all supporting structures used to shape concrete until it becomes strong enough to carry its own weight. It should be able to carry all imposed weights apart from its own. Formwork has been used since the beginnings of concrete construction. New materials like steel, plastic and fibreglass are now used in formwork. Formwork is now receiving greater attention from formwork suppliers and manufacturers in terms of design, fabrication, erection and dismantling. (Information Credit – http://southendscaffolding.co.za/product-category/scaffolding-shop/form-work)

Formwork must meet some requirements in order to successfully carry out its functions. These are as follows:

• Containment: Formwork must be able to shape and support the fluid concrete until it cures.
• Strength:  Formwork must be able to withstand the dead weight of the fluid concrete, labour weight, equipment weight and any other environmental loads without distortion or danger of caving in.
• Resistance to leakage:  All joints in formwork must be close fitting or covered with form tape. If grout leaks occur, the concrete will leak at those points. Leakages cause honeycombing of the surface, which is not desired.
• Accuracy: Formwork must be accurately set up so that the resulting concrete product is of the correct shape and measurements.
• Ease of Handling: Panels and units of the formwork must be designed in a way that can be handled manually or mechanically.
• Finish and reuse potential: The material of the form face must be selected so that it can impart the required concrete finish. It should, at the same time, be able to be reused the required number of times.
• Access for Concrete: A good formwork arrangement must provide the ease of access required for placing the concrete.
• Economy:  Formwork comprises the major chunk of investment in construction. The manufacturer must consider the number of times it can be reused, and must also design it in a way that will minimise erection time.

There are different types of formwork available for different purposes. Formwork for vertical concreting are called wall forms in general, and those for horizontal concreting are called floor or slab forms.

Constructing and Using Traditional formwork

• This consists of standard framed panels tied together, called waling.
• The waling has the basic function resisting the horizontal force of wet concrete.
• One side of the wall formwork is assembled while first ensuring that it is correctly aligned, plumbed and strutted.
• The steel reinforcement cage is then positioned before the other side of the formwork is erected and fixed.
• A sheet of plywood in combination with timber is commonly used for wall formwork.
• Wall forms are usually made with framed panels with the plywood sheet screwed on with studs on a timber frame. This allows the plywood to be easily removed, reversed and reused.
• Wall forms are susceptible to edge and corner damaged and must therefore be carefully handled.
• Corners and attached piers must be given special attention as the increased pressure of wet concrete could make the abutments open up, leading to grout leakage and a subsequent poor finish.