FORMWORK

Form-work is required to support the concrete until it attains sufficient strength to support itself.

A good form-work should have the following properties.

• It should be strong enough to resist the pressure or the weight of the fresh concrete and superimposed loads, if any.
• It should be rigid enough to retain the shape without excessive deformation.
• It should be economical in total cost.
• It must be easily removable.

Materials for Formwork

The main items which affect the cost of formwork are materials and labour in fabricating, erecting and removing the formwork. Materials used for formworks are decided by economy, requirement or a combination of both. most commonly employed materials are timber, plywood, Steel and Aluminium (nails, bolts and form connectors, etc). If the materials can be used more than one time, the cost per use may be relatively low.

Removal of Formwork 

The formwork may be removed after the expiry of following periods under normal conditions when ordinary Portland cement has been used when rapid hardening cement is used, the above period is greatly reduced.

Formwork for Columns

 Column form work may be out of timber, steel or fiber-board. The four sides of the Box are held in position by the use of wooden Blocks, bolts and yokes. A wash of water should be given to the inside of the formwork just before starting the placing of concrete.

The beam formwork

Consists of a three-side box which is supported by column forms or cross members called head trees.

Wall Formwork

The wall formwork consists of timber sheeting supported by vertical post and horizontal Wales. Small pieces of timber known as spacers may be used and they are to be removed as the concrete 

Formwork for Staircase

It consists of stringers, sheets, joists, bearers and vertical posts. Stair is designed to be self supporting longitudinally from floor to landing or across wall to wall. The sloping slab is supported by planking which is further supported on battens and posts. To give shape to the stringers, inclined planks are fixed.