METHODO STATEMENT FOR FORMWORK, REINFORCEMENT & CONCRETING IN STRUCTURAL WORK

 

METHODO STATEMENT FOR FORMWORK,
REINFORCEMENT & CONCRETING IN STRUCTURAL
WORK

1. Scope:

 · Form work: This work shall consists of furnishing and fixing of form work (shuttering) of approved quality for cast- in- situ / pre-cast/ pre-stressed plain or reinforced concrete with necessary props, staging, centering, scaffolding and any temporary construction required for their support.

·    Reinforcement: This work shall consist of furnishing and placing of high yield strength deformed bars of the shape and dimensions as shown in approved drawings.

·    Concrete: This work shall consist of furnishing and placing of plain or reinforced concrete of all grades with 40 or 20mm down graded aggregates as defined in technical specifications of contract, machine mixed and mechanically vibrated to the required level, slope, etc. as per approved drawings.

2. References:

  MORT&H specifications clause No: 1000, 1500, 1600, 1700 and technical specification of contract.

3. Materials:

~ The source of materials (for cement, coarse aggregate, fine aggregate, water, admixture, reinforcement steel) shall be identified as per specification.

      Cement: The cement to be used in the works shall be Ordinary Portland Cement of 43/53 grade confirming to IS 8112/ IS 12269. The manufacturer test certificate shall be furnished, and cement shall be stored as per IS 4082.

     Water: The water to be used shall be as per clause 1010 of MoRT&H specification.

      Coarse aggregate: Coarse aggregate shall confirm to IS 383, when tested in accordance to IS 2386 parts 1 to 8. The grading of coarse aggregate shall confirm to table 1000-1 of MOST specification.

      Fine aggregate: Fine aggregate shall consist of clean, hard, strong, dense, and durable pieces of crushed stone or natural sand or a combination of both. All fine aggregates shall confirm to IS 383, when tested in accordance to IS 2386 parts 1 to 8. The grading shall confirm to table 1000-2 of MOST specificati

     Admixtures: Admixtures shall be high water reducing agents, retarders, super-plasticizers, air entrainers or a combination confirming to the requirements of IS 9103. The manufacturer test certificate shall be obtained and submitted to Concessionaire. The appropriate dosage of admixture shall be determined at the mix design stage. The admixture-cement compatibility shall be tested for every type, grade or source of cement.

 Reinforcement: For plain or reinforced cement concrete the reinforcement shall be of grade S415/500 confirming to IS 1786- HYSD bars. The steel supplied with test certificate shall be assembled in accordance with approved drawings and shall ensure storing to avoid deterioration and corrosion.

4. Equipment:

  Batching plant, Wheel loader, Boom placer, Static concrete pump, Crane, crane bucket, transit mixers, trailors, Bar bending and shearing machine ,Auto level with staff etc.

5. Tools:

   Measuring tape, plumb bob, Line rope etc…

6. Procedure:

a) FORM WORK:

  The formwork shall provide a smooth finish of uniform texture and appearance.

    Ensuring necessary care will be taken, the formwork in true to line, levels, plumb, etc., rigid, adequately braced both horizontally and vertically. Form joints shall be minimized as much shall be tight and shall not permit any leakage of slurry from concrete.

    Required formwork shall be made out off plywood/ steel shutters to suit the site

    Conditions. Formwork materials shall be rigid, even surface, and sufficiently strong to prevent deformation during concrete. Releasing agents such as diesel mixed with grease, shuttering oil, etc. shall be applied before fixing formwork, and shall not allowed to come into contact with any reinforcement or prestressing tendons and anchorages. The formwork shall be cleaned carefully, dried and releasing agents shall be applied before re-use.The formwork shall be so removed as not to cause any damage to the concrete.

   Formwork shall be gradually and uniformly lowered so as the concrete to take stresses due to its own weight uniformly and gradually to avoid any shock or vibration.

   Before re-use all components of formwork shall be examined for damage and damage pieces shall be rectified. Before re-use all components shall be cleaned of deposits of soils, concrete or other unwanted materials. Threaded parts shall be oiled after cleaning.

b) REINFORCEMENT STEEL:

~ Bar bending schedule shall be strictly as per approved drawings, and reinforcement steel shall be cut and bent as per approved bar bending schedule. Bars shall be bent cold to the specified shape and dimensions, using a proper bar bender, operated by hand or power to obtain correct radius of bends and shape.

    Reinforcement bars shall be placed accurately in position as shown in the drawings.

    The bars, crossing one another shall be tied together at every intersection with binding wire (dia of binding wire shall not be less than 1mm) where the spacing is more than150mm and at alternate intersection where the spacing of bars is less than 150mm,to make the skeleton of reinforcement rigid such that it does not get displaced during placing.

    Spacer bars at approx. 2m intervals shall separate layers of reinforcement. Cover blocks of thickness equal to the specified cover shall be placed between formwork and bars made of concrete/ cement mortar of specified grade of concrete/ strength as those of the member.

    Necessary stays, blocks, chairs, spacers, hangers, etc. or other subsidiary reinforcement shall be provided to fix the reinforcement firmly in its correct position.

~ Laps shall be staggered.

c) CONCRETE:

   The grades of concrete shall be as specified in the drawings/ contract. Necessary mix designs shall be submitted to Concessionaire . The mix design of concrete shall be as per clause 1700 of MoRT&H specifications / IS456:2000 / IS10262 / IS SP23. the workability of concrete when determined by slump cone test shall be 75-125mm.

d) Mixing:

   The mixing of concrete shall be done in batch type concrete mixer or by concrete batching and mixing plant. All measuring devices shall be maintained in a clean and serviceable condition. Its accuracy shall be checked periodically.

Mixing of concrete shall be continued till the individual particle of coarse aggregate shows complete coating of mortar containing its proportionate amount of cement.

Corrections in water and aggregate with respect to moisture present in the aggregates shall be done on day-to-day basis.

 The mixing shall also be done in 10/7 mixers at site and weigh batchers shall be used for the weighment of CA and FA.

e) Transportation and placing:

~ Concrete shall be transported and placed as near as practicable to its final position, so that no contamination, segregation or loss of its constituent materials takes place. Concrete from batching plants shall be transported by scoop tippers or transit mixers.

Concrete shall be placed in horizontal layers to a compacted layer not exceeding 450mm. Concrete when deposited shall have a temperature neither less than 5*C nor more than 40*C.

f) Compaction:

  The concrete shall be compacted within 30minutes of its discharge from the mixer.

     To maintain required slump, it is necessary to add retarding/ plasticising admixtures.

~ This shall be controlled by taking slump at batching plant and site.

~ Concrete shall be thoroughly compacted with vibrators or other means

~ Where immersion vibrators are used contact with reinforcement and all inserts shall be avoided. Standby vibrators in serviceable conditions shall be kept at site so that they can be used in the event of breakdowns.

g) Construction joints:

Construction joints shall be minimised as far as possible. The old surface shall be thoroughly cleaned and soaked with water. Standing water shall be removed and surface shall be wetted with neat cement slurry shortly before placing of fresh concrete and shall be thoroughly compacted.

For a vertical construction joint, a supporting board shall be fixed at predetermined position and shall be properly stayed to prevent displacement or bulging when concrete is compacted against it. Concreting shall be continued right up to the board.

h) Curing:

Exposed surfaces of concrete shall be kept continuously in a damp or wet condition by ponding or by covering with a layer of sacks, canvas, Hessian or by similar materials and shall be kept constantly wet at least for a period of 7-14 days. Curing compounds can also be used.

i) Finishing:

 Immediately after removal of forms, exposed tie rods or bolts, if any, as far as possible shall be removed, or if necessary, shall be cut inside the concrete member to a depth at least 50mm below surface of concrete and the resulting hole shall be filled by fresh cement mortar.

7. Safety requirements:

~ All dumpers, rollers, tankers shall be provided with reverse horn & light.

~ Wherever required, Flagman shall be provided
~ The speed of vehicles plying in stretch shall be restricted to 30kmph. ~ Levelling staff shall be fibre or Wooden.
~ Any labour, if being used in the job for surveying shall be screened and trained.
~ All workmen at work area shall wear PPE^·s and reflective jackets.

~ During night work sufficient lighting shall be provided.
~ It shall be ensured that the safety belts were wore, tied and anchored properly while Working at heights.
~ All working platforms shall be tied at the both ends firmly.
~ The working condition of the reinforcement cutting and bar bending machines limit Switch shall be ensured before starting the day^·s work.
~ Hand gloves shall be used for cutting, bending and shifting of reinforcement rods.

 ~  The electrical connections for vibrators / lighting shall be given by qualified /Experienced P&M personnel and through ELCB only.

   ~Ensure that all moving parts of vibrator / compressor ifany, shall be provided with guards.

 ~ If concrete is being done by crane, the capacity of crane and its reach shall be Reviewed.