This method statement covers the scope of work including the placement of formwork, reinforcement bars and ready mixed concrete.
Arrange following equipment before start of the work:
- Batching Plants 1-2
- Mobile Concrete Pumps 1-4
- Truck-mixers 1-8
- Air Compressor 1-3
- Mobile Water Tank 1
- Diesel Generator 1
Risk: Falling from height
Action: Personnel to be 100% tied-off when working outside of handrails or on incomplete scaffolding or walkways while participating in their erection. Handrails to be fitted to walkways and stairways
Risk: Vehicles and mobile plant and equipment driving or working too close to work area or Striking of equipments
Action: Banksman to be employed for equipment traffic.
Risk: Working with Concrete; and Contact with concrete, burns to the skin
Action: Necessary PPE must be worn and provided at all times when working with additive (gloves, safety glasses, face mask etc.)
Risk: Access between areas can be poor
Action: Access equipment and structures should be assembled, which makes access easier.
Formwork system which gives an advantage of combining speed and quality of construction will be used.
The vertical load carrying members will be made of steel whereas the horizontal members will be of plywood inserted two wooden beams thereby forming a web flange.
All the formwork and support systems will be designed for the loads coming during the actual execution stage.
All the members in the formwork and the support system will be designed as per the relevant codes and standards.
In case of a wall formwork system the H-Beams along with steel components are assembled to form a very convenient and safe formwork system up to the sub structure levels.
The wall formwork facilitates fixing of working platforms for access, checking of reinforcement, concreting etc.
The formwork panel along with the working platform and alignment systems can be lifted as a single unit using a crane thus the labor involved in each operation of erection and de-shuttering is reduced to a minimum.
Formworks shall have adequate bracing and support to carry the concrete load and other loads foreseen prior to and during concreting.
Proper access (scaffolding, ladders, etc.) and working platforms will be provided for elevated formworks.
The wall formwork system can handle very large pressures generated due to pumping of concrete. The interiors of the forms shall be clean and smooth.
All embedded items shall be supported against displacement; reinforcement shall be secured with adequate number and type of spacing.
Columns, Beams, Concrete Walls, Footings and Foundations
Scaffolding system (including wooden shuttering beams, shuttering boards -plywood- and supporting systems) which shall be erected for foundations, columns, beams and concrete walls. For footings and grade beams a simpler system shall be used which consist of shuttering boards and supporting systems.
Foundations shall be placed on lean concrete and sub-grade compaction and strength results shall be obtained prior to lean concrete. Concrete shall be placed in formwork; casting against soil is not permitted.
Concrete shall not be placed directly in standing water.
Following the concreting of footings/foundations, place formwork and reinforcing bars for the column and finish concreting for the columns. Waterproofing will be done as per the specification.
After the columns are cast, formwork will be placed for the suspended slabs and the beams, reinforcement will be tied and the concreting will be done.
H-Type scaffolding system shall be used in slabs. It shall be erected near one of the walls as a single row. The forkheads shall be placed on the top of H-Type System.
Then the shuttering beams into the forkheads and, the shuttering boards by plywood shall be erected above them.
Erection of Formwork and Support System
The Table formwork shall be erected using the Crane. All alignments & levels shall be checked & The formwork shall be erected using the mobile crane.
All alignments & levels shall be checked & verified from established datum on the project site. Concrete edges shall be chamfered.
Dismantling of Formwork and Support System
Once the concrete achieves the required strength, the formwork shall be dismantled. The minimum duration for dismantling of formwork shall be in accordance with the standards and civil works specification.
The Dismantling shall be done in a pre planned manner leaving the required number of props in position till the concrete attains its required strength.
Formwork material shall be handled by mobile crane, where access is available.
Concrete repairs shall be done immediately after the removal of formwork. For underground bituminous coating shall be carried out prior to commencement of backfilling and after minor repairs are done. Concrete repair method shall be submitted with separate work method statement.
Reinforcing Rebar Works
The reinforcing bars in conformity with the valid drawings shall be used in the construction. Steel workers shall bend all rebar under supervision of the foremen.
These foremen have to organize bending works according to the valid revision of related project. After that steel fixers shall install all reinforcing steel.
Erection of rebar shall take place in layers from bottom to top, and the embedded items (if exist) shall be installed at the required level.
Installation of Embedded Items
All box-outs shall be wooden elements, and shall be fixed to the rebar temporarily. The installation of bowouts shall be done in accordance with the drawings during the rebar production by the supervision of site manager.
All plates and other embedded items shall be installed and fixed on the surface of the reinforcement under supervision of survey group.
Ready mix concrete supplied by the ready mix concrete supplier will be used for concreting. The design mix and materials for the grade of concrete specified will be prepared by the ready-mix concrete supplier’s laboratory and will be approved by clients.
Admixtures as specified in accordance with the Technical specifications will be added to the concrete during mixing. The concrete will be transported by transit mixer and pumped to the locations.
Maximum allowable transport duration for ready mix concrete shall be in accordance with related standards and technical specifications.
The operation of placing and vibrating are interdependent and will be carried out almost simultaneously. They are most important for the purpose of ensuring the requirements of strength, impermeability, and durability of the hardened concrete in the structure.
Care will be taken to place the concrete as close as possible to its final position (max free fall ≤ 1.5 m) so that segregation is avoided and the concrete can be fully compacted.
Wherever required for foundation or deep concreting, necessary precautions will be taken as will be defined in the specific work method statements, so that the concrete can be placed without segregation.
For concrete to be placed above ground, concrete pump with pipe line of required capacity & height will be used.
Concrete will be discharged in pour point in uniform layers and vibrated by adequate type of vibrators as will be defined in the specific work method statements.
The process of compacting concrete by vibration consists essentially of the elimination of entrapped air and forcing the particles into a closer configuration.
Concrete finish shall be done in accordance with approved IFC drawings submitted by contractor.
Method of “Concrete works in cold weather” shall be submitted with a separate work method statement.
Concrete Curing Plan
In order to obtain good quality concrete, the placing of an appropriate mix will be followed by curing in a suitable environment.
Curing shall be done using potable water complying with applicable standards.
All freshly placed concrete surfaces will be protected from damages and from harmful effects of weather including rain, sun & Wind. Concrete surfaces will be covered or protected for curing using hessian or PE sheet.
Horizontal surfaces shall be covered with PE sheeting or hessian, which shall be in contact with concrete surface, with the edges lapped or tied down to exclude air circulation.
Generally curing will be done up to period as per the relevant code to achieve the required strength. Curing shall commence immediately after finishing and shall be done as per standards.
Construction joint will be provided as required during construction in accordance with standards and technical specifications shown as per the RFC drawings.
Construction joint will be prepared to achieve good bonding between old and new concrete by removing laitance and to expose top surface or aggregate without damaging / dislodging of aggregate.
For all works, excavation (for ground works), lean concrete (if needed), earthing (if needed), embedded parts (anchors and plinths) and shutter checks shall be done before concreting by Survey team. Embedded parts (anchors and plinths) check shall be done after concreting by Survey Team. (survey check)
Abrams cone test and temperature monitoring shall be done to fresh concrete by concrete producers technicians under control of QC Team on the site.
Enough concrete samples shall be taken by concrete producer’s laboratory under control of QC Team according to TS 206-1. Concrete pouring records including information about fresh concrete shall be prepared by QC team. (QC check)
Concrete Strength Test for 7 days and 28 days shall be done by concrete producers’ officially accredited laboratory for compressive strength. (QC check)
Concrete strength test for 24 hr or 3 days shall be done for the planning of formwork stripping.
If required, QC team shall control the temperature of the hardened concrete for required period.(QC check)