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Precast Boundary Wall

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Method Statement for Pouring Precast Boundary Wall

Introduction:

This work procedure is prepared to describe the work procedure for the construction and erection of a precast boundary walls.

Scope:

Construction Methodology for Pre-cast Panels as per relevant specification(s) and approved drawings.

Construction Machinery:

#

DESCRIPTION

CAPACITY

NO.

STANDBY

Remarks

1

Batching Plant

60 cum/hr.

1

2

2

Transit Mixers

8 cum

3

2

3

Concrete Vibrators

3 HP

4

4

Construction Methodology:

  • Panel Casting

Panel Moulds:
10 Moulds for pre-cast panel casting shall be fabricated & erected as per drawing along with necessary supporting assembly for the casting of Panels. Similarly, adequate molds for the casting of columns should also be arranged as per the drawing followed. If required, depending upon the work progress and site requirement, further molds may be fabricated.

    • The sequence of Casting Panels:
      • Clean the bottom shutter of the mold and apply shutter release oil.
      • Place the reinforcement cage in position for the casting of the Panel.
      • Fix the four sides formwork of mold.
      • If the railing is to be provided, then fix the insert plate of size 150×150×10 mm for the railing as per the approved drawing.
      • Cast the Panel & column.
      • De-shutter the Panel by removing the four sides formwork of the panel.
      • Carry out the de-molding operation with the help of Hydra.
      • Curing the cast panel for a period of 07 days in the stacking yard. Process/steps will be repeated till the total required casting is completed.
    • Concreting:
      The concrete required (M-25/30) shall be produced as per the approved design mix at the centralized batching plat and transported by transit mixers to the pouring location. Before pouring, the concrete slump of 210+/-25mm shall be checked at the pouring location. Concrete placement will commence from one end to another in the same manner till completion. Concrete should be poured by the use of chute ensuring that the height of fall of Concrete is not more than 1.5 M. The concrete shall be vibrated using 45mm/25mm diameter needle vibrators. Concrete cubes shall be taken for testing of compressive strength at the pouring location. Proper care shall be taken to see that concrete temperature shall not exceed 32 degrees C.
    • De-shuttering:
      The de-shuttering shall be commenced after the concrete has attained 7.5 MPA crushing strength.
    • Lifting of Panels:
      The Precast Panels shall be lifted from 2 nos. Lifting hooks were provided for the purpose in the top surface of the panel using a suitable gantry crane and place in the stacking yard.
  • Column Casting
    Column Moulds:
    Adequate molds (Minimum 10) for pre-cast column casting shall be fabricated & erected as per drawing along with necessary supporting assembly for the casting of the column. If required, depending upon the work progress and site requirement, further molds may be fabricated

    • The sequence of casting column
      • Clean the bottom shutter of the mold and apply shutter release oil.
      • Place the reinforcement cage in position for the casting of the column.
      • Fix all sides formwork of mold.
      • Cast the column.
      • De-shutter the column by removing the two sides formwork of the column.
      • Carry out the de-molding operation.
      • Curing the cast panel for a period of 07 days in the stacking yard. Process/steps
      • will be repeated till the total required casting is completed.
    • Concreting:
      The concrete required (M-25/30) shall be produced as per the approved design mix at the centralized batching plat and transported by transit mixers to the pouring location. Before pouring, the concrete slump of 210+/-25mm shall be checked at the pouring location. Concrete placement will commence from one end to another in the same manner till completion. Concrete should be poured by the use of chute ensuring that the height of fall of Concrete is not more than 1.5 M. The concrete shall be vibrated using 45mm/25mm diameter needle vibrators. Concrete cubes shall be taken for testing of compressive strength at the pouring location. Proper care shall be taken to see that concrete temperature shall not exceed 32 degrees C.
    • De-shuttering:
      The de-shuttering shall be commenced after the concrete has attained 5.0 MPA compressive strength.
    • Lifting of Panels:
      The Precast Panels shall be lifted carefully by using the suitable device to avoid corner damage purpose in the top surface of the panel using suitable gantry crane and place in stacking yard.
  • Panel Erection:

Erection of pre-Cast Panel and columns shall involve the following steps:

    • Transportation
    • Pre-inspection
    • Lifting & fixing
    • Alignment
    • Reinforcement & shuttering
    • Concreting

      • Transportation of Panel:
        Loading of panels will be done by Hydra of suitable capacity in the casting yard. It will be tied with the trailer with the help of rope/slings properly. The panel will be shifted to the required location by trailer. Either Panel may be unloaded directly by hydra crane during lifting or unloaded at the site on the ground with the help of a suitable capacity hydra crane. Panels will be lifted directly from the trailer for launching. Care shall be taken to ensure that Panels will be unloaded on the ground exactly below the Lifting location.
      • Pre-inspection of Panel:
        Panels shall be checked against any damage during transportation. It should also be checked for the status of the reinforcement dowel.
        • Lifting of Panel:
          Lifting of panels will be done with the help of a hydra crane either from the ground or from the trailer. Crane will be positioned at a suitable location to access maximum length. Sling will be attached with a lifting hook for lifting. Panels lifted will be brought to a pre-determined location. Then it will be rest over the deck in the position required at the respective location followed by fixing the Panels with U-bar. Lifting & fixing of Panels will be repeated as above procedure.
        • Alignment:
          Panels alignment to be done by using suitable props. Then for final alignment, it shall be checked with respect to the centerline.
        • Reinforcement Fixing:
          For fixing of reinforcement for columns, the bar bending schedule shall be prepared as per the approved construction drawings. The re-bars should be rust-free, or if required, they may be cleaned with a wire brush. The Reinforcement shall be cut using cutting machines or manually as required and bent. The reinforcement shall be transported to a location in the trailer/truck to the location or manually depending upon the lead.
        • Fixing of reinforcement:
          The reinforcement shall be manually fixed into its position as shown in the construction drawing. A lap length of 50D should be provided. The reinforcement fixed shall be checked by the Engineer in charge or his representative.
        • Shuttering:
          Before placing the shuttering, shuttering oil shall be applied on the shutter face in contact with the concrete, to ensure easy removal of shuttering & proper concrete finish. For preventing leakages from joints, a rubber strip/foam strip shall be provided at the joints of shuttering plates.
        • Concreting:
          The required grade of concrete, as per approved drawings shall be produced as per the approved design mix at the centralized batching plant and transported by transit mixers to the pouring location. Before pouring concrete, slumps of 175mm to 200 mm shall be checked at the pouring location. The concrete shall be placed by Concrete Bucket. Concrete placing will commence from one end to another in cascading manner till completion. The concrete shall be vibrated using 25mm/45mm diameter needle vibrators. Concrete cubes shall be taken for testing of compressive strength as per IS: 456-2000 at pouring location. Proper care
        • Miscellaneous works:
          Special care shall be taken for curing the concrete for 07 Days.

Safety, Health & Environment:

For Panels casting to be carried out in a scheduled location, an approved barricade shall be provided. All site personnel shall wear Personal Protective Equipment. For other activities such as handling of reinforcement, electrically operated equipment, etc., safety devices/ precautions will be taken as per the approved safety plan. All precautions will be taken for carrying out the activity.

Precautions:

    • Caution boards indicating danger will be fixed at the proper place.
    • Safe access should be provided.
    • During night floodlight shall be used for lighting up the area.
    • All the workers and supervisory staff shall wear PPE s (Personal Protective
    • Equipment) during the execution.
    • The work methodology of the activity will be explained to all the key personnel
    • and workmen involved in that activity and standing instruction will be given.
    • Daily inspection checklist to be completed by site engineers and safety personnel
    • before starting the work.
    • The safety manager, through deputing safety personnel at the site, round the clock, will look after all safety aspects of the job.
    • Tool Box meeting to be conducted before starting the work.
    • All the workmen will follow the safety rules.
    • All plants and lifting equipment used in work shall be tested by a third party
    • competent person wherever required.

Quality Assurance and Quality Control

Quality control and assurance shall be strictly followed as per QAP approved by Engineer-in-charge.

Method Statement for Precast Boundary Wall Works

Title

Method Statement for Precast Boundary Wall Works

Purpose and scope

The aim of this method statement is to describe the process and sequence of erection of precast elements for the boundary wall in this project.

Work procedure

  1. General
    • The erection process shall conform to the requirements of project specification and or relevant standards.
    • The precast concrete elements will be transported to the site after approval by in-house QA/QC staff.
    • An on-site survey shall be carried out for all site dimensions, axes locations, and to meet project requirements.
  2. Preparation of Civil Works:
    • Earthwork shall be carried out as per the required level.
    • Compaction, testing, and blinding shall be done before starting erection.
    • The main grid line and benchmark will be marked by the surveyor.
    • The site access road for the movement and parking of mobile cranes and trailers will be ensured at the site before starting of erection.
    • Backfilling after completion of the erection of the boundary wall shall be made after the installation of precast elements.
        • Stage 1 – After erecting of footing and columns.
        • Stage 2 – After erecting the first boundary wall panel.
  3. Erection of Footing
    • Footings for columns shall be transported on the bed trailers where they are properly tied with chains and latches.
    • Lifting anchors and sleeves openings are provided in the footings in proper locations as per design requirements for safe and easy handling and erecting purposes.
    • Footing shall be received at the site painted with one primer coat of waterproofing bitumen followed by two finishing coats of waterproofing bitumen.
  4. Precast Footing
    • Footing shall either be installed in its location at the site using a mobile crane of adequate capacity.
    • Individual markings for footings shall be made by the surveyor.
    • Blinding shall be cleaned and the waterproofing bitumen shall be applied before erecting any precast footing.
    • Footing shall be leveled prior to receiving the column and four-line (axis of column) to be marked on the foundation to specify the locations of the column face.
    • Backfilling around the footing shall be done as per the approved method statement of backfilling works.
  5. Erection of Precast Column
    • Column shall be provided with 1 anchor on the hole on top for handling and for erection purposes Precast Column
    • Column shall be transported on flat-bed trailers secured to the trailer with the help of latching chains or belts.
    • Precast column shall be unloaded by mobile crane of adequate capacity.
    • Then column shall be tilted with a crane and lifted vertically in order to bring it to its exact location onto the footing.
    • Column shall be aligned at the tail end to match the axis.
    • Wooden wedges shall be fixed at the sides between the face of the neck column and the inner face of the footing to keep the column in place without tilting or displacing.
    • The verticality of the column shall be checked with the help of line and other instruments and any deviation shall be adjusted prior to grouting.
    • The bottom of the column shall be grouted in the footing with approved grouting material.
  6. Erection of Precast Wall
    • Precast walls shall be transported on special trailer see figure below
    • Precast wall shall be provided with lifting anchor or hook as per drawing for easy and safe handling and erecting purposes.
    • Precast wall is unloaded from the trailer by mobile crane of adequate capacity.
    • Precast wall then shall be placed on proper storage racks or taken directly for erection.
    • Precast shall be installed in its exact location between two columns and shall ensure the stability of the wall and prevent it from tilting or displacing.
    • Inspection Request would then be submitted for checking and approval of the Engineer.

Safety

  • All works shall comply with safety procedures or instructions set out in the project safety plan and Municipality rules and regulations.
  • Know the safe working load of the hoisting equipment and hardware before use. Never exceed the Safe Working Load (SWL).
  • Know the height and size of the precast element before rigging for lifting.
  • Always inspect the rigging element prior to every use.
  • Never wrap the hoist line around the load.
  • Always use taglines with the precast element while lifting to keep the load steady.
  • Always check the stability of the load before lifting.
  • Check for any overhead power lines.
  • Make sure that the rigging elements are correct and safe to use for the intended load.
  • Never use damaged slings, blocks, hooks for lifting, all damaged lifting gears are to be returned to the store for repair or replacement.
  • Basic PPE to be worn by all staff and laborers.
  • Trained operators and banks man will be engaged to control or operate heavy equipment machines.

Equipment’s and tools

  • Mobile crane
  • Flat trailers
  • Shovel and JCB for excavation
  • Plate compactors
  • Web-sling
  • Grinders and drill machines
  • Hammers
  • Plastic chemo for leveling
  • Total Station for survey

Materials and references

  • Grouting material
  • Approved drawing
  • Specification

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