Form work

 Form work 

Form work is a temporary structure that hold the plastic concrete in its original position until it is sufficiently rigid. When the concrete is able to lift its own and overhead load, the form work is removed.

The form work should be sufficiently strong and firm to bear the weight of wet concrete, the impacts generated when compaction of concrete and the load of concreting workers, if the form work bends or shrinks at the time of concreting or during the hardening period of the concrete ,the final appearance of the concrete structure will be distorted, which is very difficult to fix later.if the concrete components are bent or bent slightly for some reason while moulded , then later ,like other construction materials, they cannot repaired.the deffective part has to be broken and re cast. 

Part of form work 

The complete form work is divided into two parts.

(1) Shuttering 

(2) Centering Or Staging 

1) Shuttering

The mold that is prepared to mold the concrete components into the desired shape is called shuttring in order to keep the mold in the desired position, 

Shuttering comes in direct contact with concrete.The inner surface of the shuttering should be clean,knotless, flat and smooth to get the best finish of the concrete component. In high quality concrete works.when the inner surface of the Shuttering is specially prepared,there is no need to separately plaster the concrete components. 

(2) Centering Or Staging 

the vertical and diagonal components given below it are called stagging or props.

Staging is not required when the concrete component is moulded on the ground floor or foundation.templates are used to mold precast units of concrete, which are mostly made of metal.

The staging should be firm enough so that the weight does not get stuck down, but there should not be any problem while removing it. 

Requirements of a good form work.

A good form work should have the following characteristics: 

(1) Concrete Perimeter 

Form work should be pure and accurate according to the measurements of concrete components. Concrete shrinks at the time of setting ,so this should be taken care in the inner measurement of the Shuttering. 

(2) Flat Surface 

The inner surface of the Shuttering should be clean, flat, knotless and seamless so that the results of concrete components are beautiful and smooth.The form should be inspected before pouring concrete.

(3) Persistence 

The form work should be strong and firm enough to bear the weight of the wet concrete and the load of compact of vibrators and workers working on it. The reinforced concrete is weighted 2500 kg/cum.

(4) Waterproofing

The Shuttering should be waterproof so that it does not absorb the concrete water. All the inner joints of the mould should be completely waterproof, while pouring the concrete, its slurry should not drip out of the joints of the form work.

(5) Low Load 

The form work load should be reduced,so that there is no difficulty while applying/ removing them.

(6) Ease of removal 

Staging or shuttering should be made and erected in such a way that it can be removed easily after construction.it should not stick to the concrete surface.

(7) Strength of props 

The strength of the props of should be strong and firm, beacuse when they are rolled, where the whole work is destroyed,the life of the workers working on it will also be in danger 

(8) Standard Section 

Section of form work should adopt standard dimensions so that they can be used repeatedly.

(9) Generally Security ...

There should not be any hindrance in other activities going on at the construction site due to the form work.

(10) Cost 

The cost of form work is about 20 to 35% of the cost of total concrete construction. Therefore ,it should be economical and it can be reused when needed.