Work procedure of Formwork shuttering

Srinivasan

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Sep 7, 2017
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Work procedure of Formwork shuttering

SCOPE/PURPOSE
This procedure covers erection and checking and removal of formwork.

CODES/SPECIFICATION
Project specification.
IS-456.

RESPONSIBILITY
Responsibilities of all concerned is clearly mentioned with respect to overall administration and implementation in the approved Organogram.

MATERIALS TO BE USED
Plywood, Ballies, Acrow span, Pipe scaffolds,Steel plates,Wooden battens etc

SAETY REQUIRMENT
As per the requirement and the direction of HSE Officer.

DEPLOYMENT OF EQUIPMENT
As per the requirement and the direction of Project Manager.

DEPLOYMENT OF LABOUR
As per the requirement and the direction of Project Manager.

IMPLEMENTATION
Pre-checks:

Check for Cleaning of materials, Damaged timbers/ shutters, All the steel components are in good working order, Inspection & test plan for new wooden materials
Plywood
Rate of sampling
Physical Check: permissible tolerances.
Manufacturers test certificates shall be obtained for other test

Timber:
Rate of Sampling
Physical tests: permissible tolerances in measurements,Inspect timber for splits , cracks, twist, cry rots, wet rots & Knots


FORMWORK SCHEME
Scheme for formwork and its supports shall be prepared based on the design to withstand the worst combination of self weight, reinforcement, wet concrete weight, concrete pressure, construction load, wind load and rate of pour etc.
Formwork scheme showing sketches shall be prepared considering unusual condition like cantilever slab, large opening.
Formwork scheme shall clearly indicate the pour sequence, construction joints, rate of pour/ rize, sequence and minimum period of removal of formwork based on time/ concrete strength.

FORMWORK MAKING
Formwork shall be made of exact dimensions within the permissible tolerances.
Required thickness and quality of plywood shall be used to meet requirements of design/ formwork
scheme and of surface finish.
For beam bottom & sides, proper size of timber at required spacing shall be provided to take the design
load/ pressure considering sleeves, conduits, anchors and inserts.

For columns and wall panels the following shall be used considering sleeves, conduits, Anchors, inserts
&reinforcement dowel bars.
a) Proper size of H- beam with required spacing to the requirement of design pressures.
b) Wallers shall be provided at required spacing in proper locations.
c) Lifting hooks shall be fixed in proper place.
d) Clean-out openings shall be provided wherever required.
For climbing formwork, location of anchor cone shall be fixed accurately in the shutter.

FORMWORK ERECTION
Erect staging/ shuttering as per scheme drawings /sketches in such a way that deshuttering can be done easily including provision for re-propping.
Always use wire rope sling and D- shackle with crane for lifting/lowering the formwork material with guide ropes to avoid accidents during handling.
Suitable size and thickness of sills shall be provided whenever the staging rests on ground/ thin floor concrete with full contact between the base plate & sill to keep the bearing pressure within the permissible limits.
Check the location, line level, plumb and dimension of the formwork to ensure that the deviations are within permissible limits.
Erect & check verticality of the towers by always using spindles at foot and by fixing bracings.
Provide bracing at proper places & intervals as specified by the manufacturer or as per formwork scheme to take care of formwork loads.
Erect and check the size, number ,spacing of H-beam/timber as per scheme design requirements.
Apply form oil / other coatings as release agents before reinforcement steel is placed.
Check all shutters are properly aligned and fixed firmly with required lateral supports and ties.
Check all the spanning members have proper bearing at the supports.
Wedges and jacks shall be secured in position after the final check of alignment.
Forms shall be thoroughly cleaned of all dirts, mortars and other matters such as metals, blocks ,saw dust, and foreign materials before concreting, if required through clean out Openings.
Check all the inserts / embedments and openings are exactly placed as per the drawings.
Check all gaps / openings are properly closed to avoid leakage of cement slurry of concrete mix.

Inspection of forms during and after concreting
Formwork shall be continuously monitored during the entire concrete pouring and also after concreting until concrete has been screeded by an responsible person.
In case of leakages, bulging and sagging immediate action shall be taken by tightening wedges or adjusting by jacks which must be done before the concrete takes its initial set

FORMWORK REMOVAL
All forms shall be removed after the minimum period stipulated below without damage to the concrete including removal without shock
Minimum period before removal of formwork

Walls, columns and vertical faces of all structural members = 24 to 48 hours
Slabs (props left under)* = 3 days
Beam soffits (props left under) = 7 days
Removal of props under slabs
Spanning upto 4.5 m = 7 days
Spanning over 4.5 m = 14 days
Removal of props under beams beams
Spanning upto 6 m = 14 days
Spanning above 6 m = 21 days

The number, size and position of props left under shall be such as to be able to safely carry the dead load of the slab, beam or arch together with any live load likely to occur during curing on further construction Where PPC Cement or retardation super plasticizers are used, the removal time shall be adjusted
accordingly, taking into account the rate of hardening of the mix.

1) If form removal is based on strength of concrete , it shall be ensured from tests on cubes before formwork is struck.
2) Sequence of deshuttering shall be done in such a way that there is no overstressing of formwork and permanent structure.
3) Formwork components shall not be dropped but shall be lowered without damage to the components and structures.
4) All the removed formwork material shall be cleaned immediately and staked properly for reuse
5) All the shutter panels shall be kept vertically on the floor after shifting.

TOLERANCES ON CONSTRUCT
The following are the permissible tolerances.
Columns &walls:
Variation from plumb ± 6 mm up to 3 meter height, ± 12 mm up to 6 meter height .
Straightness for walls ± 6mm up to 3 meter, ± 12 mm up to 12 meter

Work procedure of Formwork shuttering is attached below.
 

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