FORM WORKS - METHODOLOGY

Ø         Formwork is temporary support given to concrete until it gains strength to withstand its self-weight.

Ø         Formwork shall be so designed to support safely the worst combined effects of all loads within acceptable dimensional tolerance and without causing bulging or deflection. Formwork should be:

• Strong enough to bear the self-weight of formwork, wet concrete, reinforcement, and dynamic effects of placing and compacting, construction traffic and wind load.
• Water tight to avoid grout loss
• Easily removable without any damage and should be re-usable

Ø         It should be dimensionally accurate and give the desired finish to the contact surface.

Ø         Always use staging of MS tubes with timber runners. The staging should be placed on hard even surface. If placed on ground compact it and use planks under the base plate to distribute load. Base plates should not be placed on concrete blocks or bricks, which are likely to get crushed when wet. 

Ø         Staging shall be true, rigid and thoroughly braced, shuttered and propped.

Ø         To achieve desired rigidity ample studs, braces, bolts, spacer blocks and stay wire to be given to avoid distortion.

Ø         Check the shuttering work for vertical and horizontal alignment, level, surface cleanliness, water tightness, and ability to withstand loads without distortion.

Ø         Scaffolding:  At the ground level, walk round the perimeter of the scaffold and check for 

• Subsidence of the ground
• Cavities underneath sole plates
• Dislocation of base plates

Rectify with adjustable base plates or fill with concrete

Do not use Casarino poles/ Bamboo as struts or supports.

Ø         Guardrails and toe boards

Both guardrails and toe boards should be fixed to the inside of the outer standards and remain in position before decking is removed. Guardrails should be fitted at not less than 0.9m and not more than 1.15m above the decking. Toe boards should be at least 150m high above the decking and the clear spacing between the guardrails and the boards should not exceed 0.75m.

Ø         Formwork oil

• The formwork oil basically serves the purpose of a separation medium. It acts as an intermediary that avoids any damage to the concrete.  It also helps keep the formwork clean and ensures easy maintenance. The application of oil should be done with the help of foam or a similar soft medium and should be applied within 48 hours prior to concreting.

• Machine oil or used oil is totally unsuitable and is unacceptable at any cost due to the chemical reaction this type of oil has on concrete. Clefts created will have a telling effect on the external and internal plastering, with the plastering tending to peel off. 

• It is recommended to use formwork oil of a reliable manufacturer. There are also alternative sources available that serve the purpose, which maybe an expensive proposition e.g., Natural oils such as Rapeseed oil, Sunflower oil, etc.  

Ø         All spans in excess of 5 metres for beams and slabs should be kept within a pre camber of 2mm per 1 metre. For cantilever, give a camber at the end of span of 4mm per 1 metre.

Ø         The quality of finished concrete is dependent on the quality of formwork.

Ø         Erection casing and shifting of formwork shall be done under the personnel supervision of a competent foreman.

Ø         Striking time for formwork is as follows under normal conditions.

Walls, Columns, Starters etc – 24 hours

Slab (span<6mts) – 7 days

Beam (span < 6mts) – 14 days

Slab beam (span > 6mts) – 21 days

Props to cantilever – 28 days

Ø         For balcony and other rib beams, duct beams support should be continuous for at least 3 floors.

Ø         Due to weather conditions if the concrete is not sufficiently hardened, the striking time to be extended after discussing with the project in charge.

Ø         Obtain the 7th day cube test result before the removal of formwork.

INSPECTION METHODOLOGY FOR QUALITY ASSURANCE

• Check the shuttering work for surface cleanliness, water tightness, and ability to withstand loads without distortion. Stability, safety, dimensional correctness, levels and alignment are the key factors.
• Check for plumb and parallelity using 1m/ 2m spirit level to the formwork at various points.
• All formwork in the periphery of the building to be plumb.
• For all required cut outs and shaft openings:  - Are as per drawings    - Inner right angles at all 4 corners checked using right angle template    - Check of diagonals using a measuring tape   - Curved Cornices – checked visually and using a compass spirit level

• In case of slab formwork, supports to be perfect. The formwork should be supported by wooden wedges and not fixed by nails (because the wedges are movable and provide maneuverability) 

• All supports to plinth beams should be provided with a runner, as load distribution is uniform.
•  All window bands to be cast using plaster hooks