Focused Form-work

RCC involves the study of concrete ,reinforcements and form work.
This article brings you details of the form work in a simple language.

Overview:
Form work is the temporary arrangement for giving support to the concrete till it gains the strength.
All horizontal faces are supported by centering whereas the vertical faces get supported by shuttering.
Entire arrangement is such that it is temporary and is in position only till the concrete attains 

strength.
Therefore it is essential that the erection and dismantling of formwork must be easy and safe.
Further, if the strike-off is not done smoothly,  it may damage the edges of concrete due to jerks & twists.
Form work in place for a water tank
Form work in place for a water tank


Centering
:
Centering is used to support slab & beam bottom , water tank ,chajjah &  lintel bottom .
It can be done either in mild steel centering plates or plywood.
The  form work gets used number of rimes for different buildings and therefore the regular maintenance is essential.

Centering in position & being made ready to receive the concrete.
Centering in position & being made ready to receive the concrete.
Shuttering:

For shuttering sides are prepared in steel plates or plywood  and it called making.

Shuttering on the Inner face of the Lift well secured in position.
Shuttering on the Inner face of the Lift well secured in position.

Securing the shuttering :

The two sides of beam or the four sides of column are secured  in position by use of clamps                        ( Hindi: Shikanja )
In case of deep beams or RCC walls, it is necessary to secure the shuttering at the central zone else the sides shall get deformed on the outer side due to pressure of concrete. This is done by putting a tie bar through the beam .The tie beam is a mild steel rod with threading on both sides. After inserting from the shuttering nuts are tightened on both ends.These nuts are opened for removing the shuttering.
The tie rod remains in the RCC beam. If the bar is to be taken out , then the tie rod is inserted in a PVC pipe sleeve before putting it in the beam. the tie rod can be taken out easily from the sleeve which remains in the concrete.
Staging:
The method by which both centering and shuttering are supported is known as the staging.
staging can be done in wooden ballies or Mild steel pipes ( props ) or H frames or Space frames.
SINGLE STAGING
SINGLE STAGING

Single Staging & Double Staging :

For roof slabs or beams at a height up to 10′ to 12′, it is possible to use Pipes of 10′ to 12′ in single lengths.This is called single staging.However, for further heights, it is not safe to only join ballies or pipes together .In such cases, a platform is first made at 10′ height > ballies and pipes are further erected on top of this platform .This is called double staging.

IMG_20130605_105137_0

Scaffolding:
The platform made for workers and engineers to safely stand or sit or walk for working or for inspection purpose is called scaffolding .
It can be either single ( wall supported ) or double ( self standing or independent scaffolding ).
SCAFFOLDING IN WOODEN BALLIES ERECTED FOR DOING PLASTERING WORK
SCAFFOLDING IN WOODEN BALLIES ERECTED FOR DOING PLASTERING WORK
Strike off:

The removal of centering & shuttering after certain specified days is called as strike-off or De-shuttering .The period after which it is removed is called de-shuttering.

Safety tips:

While striking off it is a general tendency to throw the plates or other material to the ground floor which is a safety hazard and also damages the material .It must be strictly  discouraged.

Some more terms:
Form finished concrete:
Sometimes for aesthetic reasons it may be decided to keep the concrete as it is without doing any plastering.In such cases the centering is done with new plywood sheets so that the concrete surface is neat & clean without any blemishes.Such concrete is known as form finished concrete .

Conclusion :

Form work gives shape and stability to the fresh concrete till it becomes strong.
The precautions taken during Form work ensure that the geometry ,line ,level and finish of the concrete are exactly as specified. A negligence in proper checking of form work means extra costs spent on breaking the extra edges, swollen surfaces and leads to added finishing cost.
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