Construction of RCC Formwork is a critical activity in construction of RCC members in any type of civil construction. Typically this activity includes following steps :
- Propping and centering.
- Shuttering.
- Provision of camber.
- Cleaning & surface treatment.
Propping and Centering
The props used for centering may be of steel, timber post or ballies. Pillars made up of brick masonry in mud mortar are also sometimes used as props.
Shuttering
can be made up of timber planks or it may be in the form of panel unit made either by fixing ply wood to timber frames or by welding steel plates to angle framing.
Provision of camber
Certain amount of deflection in structure is unavoidable. It is therefore desirable to give an upward camber in the horizontal member of concrete structure to counteract the effect of deflection.
Surface Treatment
Before laying concrete, the formwork should be cleaned of all rubbish particularly the sawdust savings & chippings etc.
Before laying concrete, the face of formwork in contact with concrete shall be cleaned & treated with release agent like raw linseed oil or soft soap solution as to prevent the concrete getting struck to the formwork.
Order and method of removing formwork
Shuttering forming vertical faces of walls, beams & column sides should be removed first. Shuttering forming sofit to slab should be removed next. Shuttering forming soffit to beams, girders or other heavily loaded member should be removed in the end.
Duration taken for removal of formwork
- Walls, Columns and Vertical Sides pf beams : 1 to 2 days.
- Slabs : 3 Days.
- Beam Soffit : 7 Days.
- Removal of props to Slabs.
- Slabs spanning upto 4.5 meters : 7 Days.
- Slabs spanning over 4.5 meters : 14 Days.
- Removal of props to beams and arches.
- Spanning upto 6 meters : 14 Days.
- Spanning upto 6 meters : 21 Days.