Centering And Shuttering

Centering and shuttering are two of the ways to prepare formwork in the construction area. Formwork refers to all the arrangements done to support the fresh concrete mix until the strength is sufficient to support its own weight. Formwork is also known as temporary work. Formwork significantly helps us to determine the geometry, size, and shape of the masonry area.

 Centering

 Centering is usually the formwork, made generally from plywood, which is used to support the masonry on an arch or barrel vault before the masonry is placed and before it gains enough strength so that it can support its own weight. Centering will firmly support the masonry and form the curvature or shape and size of the arch or the vault. Centering can be reused to build multiple arches, depending upon the structure.

 Centering supports the horizontal surfaces like slab, beam, chajja.

 Centering can also be done using mild steel centering plates but we generally use plywood.

 Equipment used for centering:

 • Wall form and accessories

 • Adjustable prop 

• Telescope span 

• Steel couplers 

• Tie rod 

• Wedge clip 

• Single clap

• Step centering 

• Centering plates 

• Cup lock system 

• Column farma 

• Bracing and tying-in 

• Tabular scaffolding 

• Scaffolding propex 

• Joint pin 

• Scaffolding plank 

• Fixed base plate 

• Sikanja clamp 

• Plane vibrator 

• Needle vibrator 

• Table vibrator 

• Screen board vibrator 

• Adjustable stirrup head 

How is centering done?

 For minor works, mud masonry is constructed for centering to match with the inner soffit of the arch or barrel vault, then plastered. Later, this masonry is dismantled when the arch is constructed and curved.

 We generally use timber wood or steel for centering since, it is simplest, cheapest, easy to dismantle, and can be used several times. A plank with the horizontal bottom is selected whose width is normally 10cm, then it is supported on vertical timber posts called props, with wooden edges to tighten or loosen the centering. Nails and anchors are used to support the ply with each other or to get attached to the beam.

 Shuttering

 Shuttering is also a part of a formwork that is used to support the wet concrete mix until it gains strength for self-support.

 Shuttering supports vertical structures like the wall, column, beam side, slab side, chajja side, etc.

 Equipment used for shuttering 

• Telescope span 

 • Wall form

 • Single clamp 

• Cup lock system

• Corner angle 

• Adjustable stirrup head 

• Shuttering couplers 

• Wedge clip 

• Column mould 

• Ms planks 

• Tie rod 

• C channels 

 How is shuttering done?

 Using plywood or steel, two sides or four sides of the column are secured in position by the use of clamps. For deep beams or RCC walls, it is mandatory to secure the shuttering at the central zone else the sides should get deformed on the outer side due to the pressure of concrete. This work is done by putting a tie bar through the beam. The tie beam consists of a mild steel rod with threading on both sides. The tie beam always remains in the RCC beam. The tie rod is inserted in a PVC pipe sleeve before putting in the beam if the bar is to be taken out. The tie rod remains in the concrete which can easily be taken out from the sleeve.

Differences between centering and shuttering

Centering	Shuttering
They are used to support the horizontal surface.	They are used to support the vertical surface.
They are generally done using plywood.	Then are done using steel or plywood.
They should be handled more carefully as vertical rods are throughout the structure to support large horizontal ply.	They are less risky as ply or steel is supported by rods or wood taking less space in the structure.
They are done while constructing surfaces like slab, chajja, beam, etc.	They are done for construction structures like column, wall, beam side, etc.