- Making of shutter panels straight and right angles to each other using right angles as per approved formwork drawings.
- It is important that all the staging materials should be visually checked and confirmed its sturdiness before being used at site.
- Formwork shall be erected in such a way that, it should support safely the worst combination factors of all Loads within prescribed tolerance limits and not causing any bulging or Deflection over concrete.
- Always remember, that the staging should rest on solid ground or over ISMB sections anchored well to the Concrete structure (I strongly recommend PCC floor) below. Base plates should not be placed on bricks or solid blocks which are likely to get crushed when wet.
- Ply wood material used for shuttering, should be dimensionally accurate in length, width for slabs and in depth for beams and also give the desired finish to the contact surface. Always, it is advisable to go for waterproofing plywood boards.
- Staging shall be true, rigid and thoroughly braced, shuttered and propped.
- To achieve desired rigidity, adequate bracing is to be provided. In case of cup lock shuttering system, bracing is automatic.
- The purpose of application of formwork oil to the shuttering surfaces is to create a separate medium between concrete and shuttering. It also helps keep the formwork clean and gives extra life to the shuttering in terms of more repetitions. The formwork oil to be applied 48 hours prior to concrete in case of roof concreting, and 2 – 3 hours in case of columns and wall concreting by foam gently smeared in oil.
- It is recommended to use a Branded shuttering oil or mixture of Grease and Diesel. Burnt machine oil or used oil is strictly not to be used, which is unsuitable and not only spoils shuttering surface, also have effects on concrete surface against plastering.
- Camber : For all spans in excess of 5 meters for beams and slabs, it is highly advisable to give a camber of 2 mm per 1 meter. Similarly for Cantilever portions, a camber at the end of span of 4 mm per 1 meter is recommended.
- Always for safety point of view, at all surfaces including even and slope surface, the erection of casing and shifting of formwork shall be effectively carried out under the personnel supervision of experience shuttering foreman.
Striking time for de- shuttering works:
- As per IS 456:2000, the Striking time for formwork or de-shuttering works, under normal conditions is as follows.
|Walls, Columns, Starters etc.||12 hours|
|Slab (span < 5mtrs)||7 days|
|Beam (span < 5mtrs)||14 days|
|Slab beam (span > 6mtrs)||as per Consultant’s instruction|
|Props to cantilever||as per Consultant’s instruction|
- In case due to weather conditions if the concrete is taking extra time for its setting, the de –shuttering time to be extended after discussing with the project manager.
Caution: Before removal of formwork it is highly recommended to obtain the 7th day cube test results for slab, beams and staircase.
- Formwork is designed and constructed to the required dimensions, lines and shapes, shown on the drawings with the tolerances given below.
- Tolerance for cross-sectional dimensions of cast in-situ: +10 mm / -5 mm.
- For cast in-situ elements, the deviation of level of any point from the intended level: ± 10 mm.
- Tolerance for plumb: 3 mm / m, maximum 20 mm.
- Place the Shutter panel (fabricated with H-16 beams, Plywood’s and Steel Whalers) on all four sides for walls or columns and check the line and level.
- Continue the fixing of Shutter panels, with level and alignment checking till the end on one side of the wall.
- After one side of shutter fixing Fix cover blocks at 600 c/c on both sides.
- Similarly fix other side shutter panels and check the line &level, then place remaining shutter panels continuously.
- Place the alignment props at required places with head/foot adapter assembly.
- To maintain uniform wall thickness, fix the Timber spacers at regular intervals of every 1 m distance the top between the shutter panels.
- Use alignment struts for checking plumb for shutters and double check with plumb bobs.
- The alignment of shutters on both sides can be checked and fixed with the help of fixing line thread on top of the plywood boards.
- To checking inside corners of shuttering, Use inside right angle corners and tighten the supports to match the requirements on the outer side boards.
- Use separate and independent cup-lock scaffolding with platforms for concrete personnel.
- Concrete to be filled in layers of 300 mm height and up to 900 mm ht. per hour to restrict the designed concrete pressure.
- Caution: concrete pipe line should not be connected or supported to shutters. Always use independent vertical support staging system for pipe line.
Remove the wing nut first, then, Alignment Struts and Accessories. Tie rods used for shuttering, shall be sacrificed and cut 25 mm inside the surface.
Remove shutters one by one.
Construction Manager: should take responsible for all construction activities.
Site Engineer: should take responsibility for executing all work in safe manner as per drawings. He shall guide the foremen and work men in the execution of work.
Site Supervisor: Responsible for managing all plant and machinery and men including the safety of workers.
QA/QC In charge: Responsible for ensuring the quality of work as per the standards and specifications.
HSE Manager/Engineer: Maintaining safety standards at project site is paramount important, and it is the responsibility of HSE manager to giving proper instructions to all supervisors, engineers to ensure the safety of workers during the progress of work. Safety inductions of each staff including new comers and workers shall be done. Daily PPE checks to be done and tool box talk at the morning hours before the start of work.
Safety compliance required for the activity: to be enforce at site