Requirements of a Good Formwork or Shuttering
Concrete being a plastic material it has to be keep enclosed until it will gain strength the temporary structure which are build for an concrete member called form work.It is use to give definite shape to the concrete formwork is also known as shuttering or casing.Timber is most common material used for the form work but in recent days steel plates are also used for their purpose formwork i.e.the sustained part in the cost of finish concrete in extreme case in about 60% to 70% of the over all cost of concrete normally formwork is design by the contractor & submit it to the consultant for approved following are the two components of form work.
1- Form Face:
It is the part of form work which is in contact with concrete & finishing of form face will decide 7 finishing of concrete it could be of hard board, timber, steel, plastic, fiber etc.
2- The Support:
These are the vertical member which transfer the weight of wet concrete from form face to ground these are called pups joints, runners etc.
Requirements of a Good Formwork:
1- Strength 7 stability
2- Smooth to give finish surface
3- Economy
4- Alignment
5- Rigidity
6- Toughness
7- Easily install & removed
8- Durability
Types of formwork:
1- Seasoned wood used for formwork
2- Hard wood is not used because of difficulty in work
3- Dry timber tends to swell in moisture
4- Green timber tends to dry & shrink in hot weather
5- Initial cost is very low as compare to concrete.
6- Difficult to assemble & removal
7- Wood surface is not smooth & plane
8- It can only be used for three to four times
Steel Timber:
1- Steel timber gives fine & smooth surface
2- It reduces cost because plaster is not necessary.
3- If it damaged then melt & reshaped
4- It can be used seven times commonly
5- It can carry very heavy loads
6- Easily install & removed by nuts & joints
7- Initial cost is very high
8- Available in standards size
