Method Statement for Preparation and Construction Of Cast In Place Concrete Works for Substructures

The purpose of this civil work method statement is to define the procedure for the preparation and construction of Cast in Place Concrete Works for substructures in accordance with the requirements specified in the relevant specifications, procedures and drawings, considering safety and quality of the work activities.

Click Here to download Full Civil Method Statement Package

This method statement covers:

• Concrete works for pile cap
• Concrete works for footings/tie beams
• Concrete works for ground floor slab

Concrete Pile Cap

All relevant activities should be carried out in accordance to the approved shop drawings and project specifications.

Previous work activities completed prior to construct the pile cap.

The contractor responsible for any removal of unsuitable materials found on site and replaced with suitable materials in accordance with the project specification. Please refer to the submitted method statement for earthworks for sub-structures.

The Surveyor establishes the location, axis and elevation of blinding concrete. Inspection sign-off and approved by Contractor and Consultant prior to proceed for the next activities.

The termite control for blinding to be completed and approved, please refer to the approved method statement and approved material for termite control.

Make sure the pouring of Concrete Blinding as per approved concrete mix design and casted according to approved drawings and specifications. Curing for Blinding to be done in accordance to specifications.

The water proofing and protection board to be completed above the blinding and carried out in accordance to manufacturer recommendation and approved material submittal with method statement. Refer to approved material submittal and method statement for waterproofing materials for pile cap and tie beams.

Complete the pile head treatment carried out in accordance to the approved materials submittal and manufacturer recommendation. Please refer to approved material submittal and manufacturer recommendation for pile head treatment.

Preparation works prior to cast the concrete pile cap

Setting out: The Surveyor to start markings and lay-out the pile cap location. Check the level, axis/grid lines, and dimensions and ensure that works are carried out in accordance to approved shop drawings.

Reinforcing Steel Bars: The contractor shall provide reinforcing steel with high grade deformed type with minimum yield strength of 460N/mm² and the testing requirement for each diameter of rebar’s shall include tensile, bend, rebend and chemical analysis.

The Contractor and Consultant shall witness the testing to ensure that the required test are carried out as per project specs. The result will be submitted and approved by the Consultant prior to installation of the rebar.

The Contractor ensures that materials submittal for rebar is approved by the Consultant prior to deliver the rebar on site.

For every delivery of rebar’s make sure that the mill certificates are submitted to contractor together with the invoice of the materials.

Inspection request for steel delivery shall be submitted to the consultant at least 24hrs prior the delivery time.

The Contractor ensures that all rebar’s are passed on the required test. The Contractor shall check the shop drawings for bar bending schedule approved by the Consultant prior to start the fabrication on site.

Fixing of Steel Rebar: Fix the pile cap reinforcement and column starter bars in accordance to the approved shop drawings and project specifications. Verify the quantity, bar splices, spacing, rebar sizes and bending. Make sure that all rebar are fixed properly in the proper location. Side form spacers used in pile cap shall be concrete block spacers and sizes vary as per concrete covering of steel. Tie manually the rebar’s using tie wires and not allowed for any welding of the reinforcement.

Formworks: The contractor can use either vacuum cleaner /manual/ air compressor to clean the area and remove the waste materials prior to fix the side formworks.

Use the Poly release WB mould/shutter release agent for formworks. Formworks materials are assorted wood and form plywood with minimum thickness of 18mm (Phenolic Board).

Formworks materials may be reused during progress of the works provided they are completely cleaned, reconditioned and capable to withstand pressure of the newly placed concrete considering the quality of concrete finished works.

Install/erect the formworks as per approved shop drawings and project specifications. Before placing of concrete, the contractor ensures that the embedments, reinforcements, formworks are rigid and safe, and other installed materials are based on the project specs, approved shop drawings and approved by the consultant.

The contractor shall be responsible to conduct the trial mix when the design mix is approved by consultant. The contractor and consultant representatives shall be present in the trial mix to ensure that mixing is carried out in accordance with project specifications and approved design mix. The Contractor ensures that the trial mix official reports are submitted and approved prior to use the concrete on site.

Pouring of Concrete to Pile Cap

Responsible parties including contractor shall check on site slump test, design mix and temperature of the concrete prior to proceeding on site works. The technicians are responsible for the preparation and providing materials cube samples with label, and testing as per project specifications.

Pouring/ depositing of concrete on the pile cap shall be done by contractor’s competent site personnel and workers in accordance to the approved shop drawings and project specifications.

Do not deposit any concrete in the work which has partly hardened or which has been contaminated with foreign objects.

Cast the pile cap concrete using concrete pump in one operation with their full design depth and dimensions.

Do not exceed 1.5m for vertical drop of concrete to prevent segregation of concrete.

Apply vibrators systematically, sufficient duration and intensity to compact the concrete thoroughly.

Avoid over vibrate to prevent the concrete segregation. Maintain / provide one spare vibrators for every three vibrators used for in case of breakdown. Use ready mix concrete through-out and as per approved supplier and mixed design by the consultant.

For Hot Weather Concreting

Pouring of concrete shall not be allowed when the ambient air temperature exceeds 38 degrees centigrade.

Take suitable precautions to ensure that the temperature of fresh concrete as placed does not exceed to 32 degrees centigrade.

Transporting, placing and finishing of concrete shall be done as quickly as practicable.

Elapsed time between batching and placing of concrete using OPC shall be 45minutes unless approved by the consultant.

The accepted elapsed time between batching and placing of concrete using combination of GGBS and OPC is 75 minutes.

Curing of Concrete

Curing and protection of concrete pile cap shall comply with the guidelines given in ACI 305R-91 and project specifications.

Protect and cure concrete in such a manner as to prevent the evaporation of moisture from the concrete and injury of the surface.

Immediately after finishing of concrete surfaces, Curing shall commence in the form of a complete covering of polyethylene sheets. As soon as the concrete has stiffened sufficiently after not more than 24hrs, the polyethylene sheet shall be removed and the surface covered by absorptive mats of fabric and keeps continuously wet.

Water used to keep the mats moist shall meet the requirements of BS 3148. Any curing compound materials used for concrete curing is subject for approval of the consultant

Removal of Formworks

Removal of forms shall comply with the project specifications. Striking/Removal of forms shall be carried out carefully by contractor’s competent carpenters, helpers and avoid to damage the concrete surface.

The concrete shall be thoroughly wetted as soon as the forms are first loosened and shall kept wet during the removal operation.

Potable water supply with hoses shall be available at each removal location.

Concrete Repair Works

After concreting works, for concrete works that is out of tolerances specified in the project specifications and for the concrete with major unacceptable quality of works, the Contractor shall responsible to repair the concrete defects immediately using the approved materials for concrete repairs.

Waterproofing works and protection board

Waterproofing works shall be started after the concrete works are completed and sufficient to receive the waterproofing materials. Refer to approved material submittal with method statement and manufacturer recommendations.

Backfilling

Compaction works shall be started after the waterproofing works and protection board are ready to receive the backfilling materials and approved by the Consultant. All backfilling / compaction works are carried out in accordance to project specifications.

Concrete Tie Beams / Footings

All relevant activities shall be carried out in accordance to the approved shop drawings and project specifications.

Previous work activities completed prior to construct Tie Beams / Footings

The contractor is responsible for removal of unsuitable materials found on site and replace it with suitable materials in accordance with the project specifications.

The Surveyor establishes the location, axis and elevation of blinding concrete. Inspection request is signed off and approved by contractor and consultant prior to proceeding for the next activities.

The termite control for blinding to be completed and approved.

Pouring of Concrete Blinding to be carried out as per approved concrete mix design and casted according to approved shop drawings and specifications. Curing for blinding to be completed in accordance to specifications, approved and sign-off by the Contractor and Consultant.

The water proofing and protection board to be completed above the blinding and carried out in accordance to manufacturer recommendation and approved material submittal with method statement.

Pouring of Concrete to tie beams / footings

The third party shall ensure on site slump test, design mix and temperature of the fresh concrete prior to proceed on site works. The technicians are responsible for the preparation and providing materials cube samples with label, and testing as per project specs.

Pouring/ Depositing of concrete on the tie beams / footings shall be done by Contractor competent Site Personnel and Workers in accordance to the approved shop drawings and project specifications.

Do not deposit any concrete in the work which has partly hardened or which has been contaminated with foreign objects. Pouring of concrete in the tie beams / footings using concrete pump. Do not exceed 1.5m for vertical drop of concrete to prevent segregation of concrete.

Apply vibrators systematically, sufficient duration and intensity to compact the concrete thoroughly. Avoid over vibrate to prevent the concrete segregation. Maintain / provide one spare vibrators for every three vibrators used for in case of breakdown. Use ready mix concrete through-out and as per approved supplier and mixed design by the Consultant.

Hot Weather Concreting: Pouring of concrete shall not be allowed when the ambient air temperature exceeds 38 degrees centigrade. Take suitable precautions to ensure that the temperature of fresh concrete as placed does not exceed 32 degrees centigrade.

Transporting, placing and finishing of concrete shall be done as quickly as practicable. Elapsed time between batching and placing of concrete using OPC shall be 45 minutes unless approved by the consultant. The accepted elapsed time between batching and placing of concrete using combination of GGBS and OPC is 75 minutes.

Curing of Concrete Tie Beams

Curing and protection of concrete tie beams / footings shall comply with the guidelines given in ACI 305R-91 and project specs. Protect and cure concrete in such a manner as to prevent the evaporation of moisture from the concrete and injury of the surface.

Immediately after finishing of concrete surfaces, Curing shall commence in the form of a complete covering of polyethylene sheets. As soon as the concrete has stiffened sufficiently after not more than 24hrs, the polyethylene sheet shall be removed and the surface covered by absorptive mats of fabric and keeps continuously wet.

Water used to keep the mats moist shall meet the requirements of BS 3148. Any curing compound materials used for concrete curing is subject for approval of the consultant.