Below is a general method statement for illustrative purpose, there shall be different values for different parameters depending upon the type of project and climatic situations, which should be followed all the time.
EQUIPMENT’S & TOOLS REQUIRED
- Hand saw, wire cutter, brush, Shovel
- Steel Brush
- Air compressor
- Plumb bob
- Line dory
- Concrete Pump
- Vibrator
- Trowel
- Spirit Level
SAFETY & HEALTH REQUIREMENTS
Safety of the personnel and properties is to be given prime importance and all the works to be carried out without causing any accidents or property damages. Concrete works involves the following activities.
Shuttering and de-shuttering
Fabricating and fixing reinforcement steel.
Transportation of concrete.
Placing concrete at site
Adequate access and egress should be provided to the site for work.
All the personnel should wear basic personnel protective equipment’s.
Equipment, tools and tackles being used for the work should be in good working condition and maintained.
Operatives will be provided with toolbox talk on the procedures to execute the work safely.
Sequence of RCC Columns and Shear Wall Construction
Prior to start any activity on site, the consulting engineer must be notified.
Ensure that all workers are aware of the evacuation plan.
Cordon off the work area to prevent unauthorized entry.
Discuss the method of working with all supervision staff.
All the related documents such as shop drawings, method statements, material approvals, subcontractor’s approvals, test certificates etc. must be approved and available upon request.
Ensure the source of supply of ready mix and grade of concrete.
Arrange initial trial mix and conduct specified tests.
Submit mix design and trial mix test result for Client/Engineer approval.
Site lab with cube mould, Thermometer, Slump cone etc. shall be arranged prior to the concreting operation.
Spacer block shall be provided with the same grade of concrete.
Arrange the concrete testing area with proper shading/and lighting.
Polythene sheets, hessian cloths sweet water etc. shall be arranged for the proper concrete curing.
Ensure the position and alignment of starter bars of columns and walls.
Clean the starter bar from cement paste or grout.
Kicker shall be provided as per the requirements.
Access scaffoldings, ladder etc. will be erected to allow reinforcement to be fixed.
Reinforcement Placement
The rebar diameter, number and shape are to be as per the approved drawing and bar bending schedule.
Rebar spacing and lap length should be as per the approved drawing.
Adequate concrete cover to be maintained on all rebars.
Links shall be provided as per the space provided in the drawings.
Joints shall be staggered to minimize congestion.
The line and level of rebar is to be checked prior to casting.
The rebar will be fixed in such a manner that its stability is assured in all respect.
Rebar and existing concrete will be presented for inspection before placing shutters.
Prior to erecting the shutters, box out and cast in items will be installed. These will be fixed securely to ensure that they do not move during casting operation.
The area will be cleaned thoroughly by handpicking debris, blowing out sand if any with a compressed hose.
Form works
- All materials used for temporary form works should be clean strong and clear from any deflection.
- Shutter will be treated with approved shutter releasing agent to enable easier stripping.
- Install formwork to its dimensions correctly and ensure that lines and levels are within the tolerances.
- The shutters will be braced and anchorages properly as per the drawings to maintain the proper alignment and plumpness of the forms.
- Line and level of the shuttering will be set out by the surveyor. Shutters must be checked for correctness in their final position.
- Tie rods shall be used for proper alignment.
- Tie roads are to be correctly tightened and rechecked prior to casting.
- Gaps in the shutter must be plugged out to minimize the possibility of grout loss during the casting operation.
Concrete Placing, Compaction & Finishing
Concrete placement shall not start until all other trades have completed / installed their embedment. Once all embedment are completed CLIENT approval shall be obtained.
Preparation for Placing
All surfaces shall be cleared thoroughly, remove any water. De-shuttering oil shall be placed on the formwork.
Concrete Pouring Steps
- Appropriate arrangement and approval for conveying concrete (Chutes, pump, manual) shall be obtained from client.
- Cranes, concrete bucket, Pumps, chute, Shovel and manual methods will be used as per the elevation’ quantity of concrete and to suit the site condition towards conveying & spreading concrete.
- Concrete shall be delivered to site within 75 minutes after the introduction of the water to the cement, and shall be placed and compacted within 45 minutes of arrival. The concrete shall be compacted and in its finial position within 120 minutes of the introduction of the cement to the aggregate. Elapsed time between batching and placing of concrete using combination of GGBS and OPC of 180minutes can be accepted.
- Target slump will be 160mm to the mix with a tolerance +40mm as per approved mix design.
- Concrete, during and immediately after depositing, shall be thoroughly compacted. The compacting shall be done by mechanical vibrator.
- The vibration shall be of sufficient duration and intensity to compact the concrete thoroughly but shall not be continued so as to cause segregation.
- Pouring height should not exceed more than 1.5m to prevent segregation.
- Each layer shall be compacted so as to avoid the formation of construction joint with the previous layer which has not taken initial settlement.
- Concrete cover to be maintained as per drawings during casting operation.
- Concrete temperature shall be maintained below 30o C at the time of pour.
- Adequate illumination shall be provided during night concreting.
- Concrete temperature shall not exceed 30°C at the time of placing and during hot weather the forms shall be shaded and sprayed with water. To prevent the premature drying of concrete it shall be covered with polythene and reflective sheets
- During hot weather pouring will be carried out in such a way that there will be no formation of cold joint. If concreting activities are carried out during night time adequate illumination shall be provided. Concrete shall be placed in shallow layers enough to assure vibration well into the layers below and the elapsed time between the layers be minimized to avoid cold joints.
Concrete Finishing and Curing
Finish concrete surface as specified in the approved construction drawing and specifications.
Curing shall be started immediately after initial set of concrete and finishing as free water has disappeared from the surface of concrete.
The curing shall be continued for minimum of 7 days.
Form Removal
Forms and shoring in the formwork used to support the weight of concrete in beams, slabs and other structural members shall remain in place until concrete has reached a minimum of 70% of the specified 28 day strength i.e. 45 N/mm2. In absence of concrete cube results periods specified in specifications shall apply to the removal of formwork.
Concrete shall be thoroughly wetted as soon as the forms are first loosened and shall be kept wet during the removal operation and until the curing media is applied.
Great care shall be exercised during the removal of forms to avoid shocks or reversal of stresses in the concrete.
Surface defects if any corrected as per the engineer instruction.