Formwork - Definition, Types, Uses etc

 Definition of formwork

Form work

Formwork is a mould or open box, like container into which fresh concrete is poured and compacted. When concrete is set, the formwork is removed and solid mass is produced in the shape of the inner face of the framework. The top of the formwork is normally left open.

Requirement properties for Formwork

1. Strong and enough to resist the pressure the pressure for or the weight of concrete.

2. Rigid enough to retain the shape without undue deformation.

3. Economical in terms of the total cost of the forms

4. Sufficiently watertight to avoid leakage of joints

Types of Formwork

Depending of the materials 

A.    Timber Formwork

B. Metal Formwork

C. Plastic Formwork

Form work for column

A.     Timber formwork 

There are two types of timber formwork, they are 

(i) Lumber Formwork

It is commonly available material and has excellent strength and cost factor.

(ii) Plywood Formwork

The use of plywood in concrete forming has improved quantity if finished concrete.

B.      Metal formwork

Metal Formwork

The initial cost of metal formwork is more than timber formwork but the number of reuse of metal formwork is higher than that of timber. In long run metal form work is more economical. Steel or aluminum or magnesium is the most widely used metals.

C.     Plastic formwork

They have impervious surface that usually create a smooth finish to the concrete. Plastic formwork could be reinforced or un- reinforced. Plastic Formwork is lighter but less durable than metal formworks.

Depending Upon Shape

a.       Column Formwork

b.      Beam Formwork

c.       Slab Formwork

d.      Wall  Formwork

a.       Column Formwork

Column formwork is made usually either of timber or metals panels. The box is held in positions by steel columns clamps or bolted yokes and support by the timber props.

b.       Beam formwork

Formwork for beam

Beam formwork consist of open through the section and because it is not closed at the top requires more supporting formwork to restrain the sides. The supports need to be maintained to the soffit and also provide lateral support to the sides. Generally metal and timber formwork is used.

c.       Slab Formwork

Floors are required a larger area of formwork to be provided usually from beam to beam. Timber and metals props can be used for vertical support.

d.      Wall Formworks

Wall formworks is a simpler than other concrete unit as the actual forces against it are less. The panels at the both sides are held in position by ties. Ties are also used as spacer. Wall support system are usually sloping props at satisfactory intervals.

Forming Ties

When the concrete is placed in wall formwork, the pressure exerted by the fresh concrete tends to force the opposite sides of the formwork apart. Economical solutions of this problems to use of soldiers on either side of the formwork. Because soldiers are prevent form moving apart by use of steel rods passing through the concrete to connect the two soldiers together.