1.SCOPE
The scope of this method of statement is to cover concrete works activity which includes (Formwork installation, rebars supply and installation, concrete supply and placement, water proofing, etc.) d supply for cast in situ Concrete in the project. In accordance with contract requirements and approved project specification, project safety procedure and approved issued for construction drawings.
Download link given in the bottom
2. PURPOSE
The method statement shall address the precedence of physical operations applicable for the supply and placing Structural / nonstructural Concrete on the project.
This Method Statement is to ensure that concrete works activity will be expedite in an efficient and safe manner in accordance with all relevant contract documents, (Specification and Drawing) and international accepted methods, utilizing proven methods and procedures, as detailed herein and was implemented on previous projects.
This Method Statement is for submittal to Consultant / Employer for their concurrence.
This Method Statement will, if deemed necessary, be revised as and when required to accommodate circumstantial requirements that cannot be foreseen at this page.
3. REFERENCES
- Project Standard Specification for CONCRETE WORK.
- 25457 – 0000 – 3PS – DB00 – 0001 Rev. 001 for Concrete Work
- 25457 –0000 – 3PS - DB01 – 0001 Furnishing and Delivering Ready- Mix Concrete
- 25457 - 0000 - 3PS – DG01 – 0001 Reinforced steel, Embedded items and Miscellaneous Concrete Accessories.
- EN 206-1 Concrete specification, performance, production and conformity.
- EN 12620 –Aggregates for Concrete.
- ENV 13670 Execution of Concrete Structures
- ACI 347 Guide to Formwork for Concrete
- ACI 305.1 Specification for Hot Weather Concreting
4. RESPONSIBILITIES:
- Project Director / Project Manager have the responsibilities for overall the project activities including safety measures.
4.1. Project Engineer / Construction Manager (Civil)
In charge shall be responsible for coordination and supervision of construction works (activities) and construction groups, ensuring that works is done as per project specification and approved drawings, and all safety measures are implemented, of site construction and report to construction manager civil.
4.2. Site Engineer / Site General Foreman
General Foreman Shall be supervising closely that activities designated to them ensuring that all instruction are followed are strictly adhered to, (this may involve providing alternative access routes for moving Traffic with Traffic Signs if necessary are in place prior to commencing the work, safety procedures of the project are strictly followed.The SE shall be responsible for the following:- To ensure construction is carried out to the required Project Specifications and drawing as well as in accordance with the approved ITP’s and QCP’s and to this method statement.
- To ensure that the surveyor has completed setting out with reference points complying with the approved for construction drawings.
- Ensure that all parties who are required to make any kind of test / inspection are suitably informed as to the overall program of the works and daily inspection testing requirements.
- Ensure checking and performing the concreting as per the Specification.
- The QC Engineer or his designee (QCI) shall be responsible for the following:
- Review all relevant documentation and test reports issued by parties involved (SE, Lab Tech (ITL Laboratory), Surveyor and QC Inspectors) and submit records to consultant.
- Ensure that all discipline activities that require to be inspected in the concreting operation has been inspected and approved.
- Organized and allocate inspection works to the Quality Control Inspectors (Civil).
- To issue NCR’s / DR’s, when and where required and to check that the construction department provides timely appropriate corrective and preventive action.
- The QCI shall be responsible for:
- Sign off and obtain signatures from the Consultant on the forms and verifying documents as required.
- Accompany the Consultant Supervision representative if required, to carry out inspections and release of hold points
- Identifying and reporting to the QA/QC Mgr. any non-conformances
- Keeping a daily log of all the inspection Request submitted by the SE.
- Carry out statistical analysis of the inspection and test result to improve quality control operation on site, to verify testing compliance and to advise the SE of the results.
- Filling and compiling controlled copies of all test reports under the supervision and instructions of the QC Engineer.
- The Lab Tech shall be responsible for:
- Sampling and conducting field testing according to the instruction of the consultant and QC Manager and in accordance with the Specifications.
- The ITL (Independent Testing Laboratory) to ensure that the required numbers of samples are taken from concrete works for the evaluation of quality and Durability of Concrete works.
- The Laboratory technician / Engineer shall be responsible to test all concrete aggregates constituent for quality ensuring it complies with specifications requirements and abide with the frequency stipulated in the specification.
- Ensure that all tests required specified for fresh concrete Production is completed.
- Issuing, reviewing / interpreting all laboratory test result report in timely manner, submitting it to QC department keeping records in laboratory for consultant Reference.
- Compilation and filling all laboratory Test Forms / RFI for Certification submitting all records to QC department.
- Scaffolding Supervisor: To ensure that all scaffolding system has been erected accordingly to safety and requirements.
- Safety Inspector: To ensure all safety precautions has been taken into consideration before commencing the concrete works.
- All equipment should be inspected by Bechtel inspector and should have entry pass before working on site.
- All heavy equipment operators such as excavator’s cranes, forklift, etc, should have third party license.
5. EQUIPMENTS:
- Concrete Mixing and Transport equipment
- Ready Mix Concrete Batching Plant
- Transport Mixer
- Concrete Pump
- Hoses / Concrete shoots
- Concrete buckets
- Air Compressor
- Survey Equipment
- Level
- Total Station (Surveying instrument for checking the levels & distances)
- Masonry Accessories
- Wheel Barrows
- Concrete Vibrators
6. MATERIAL:
- Form Plywood
- Timber
- Scaffolding
7. SHOP DRAWINGS.
Approved / Issued for Construction Drawings
8. PROCEDURE
8.1. Excavation and Backfilling
- All the areas where excavation is required, the surveyor will give the information to the excavation foreman to start the excavation to the levels indicated in the IFC drawings.
- After the excavation is completed, the surveyor will check the final grade of the excavation and the grade will be adjusted accordingly.
- Compaction shall be completed and shall be tested by an inspection company (Independent third Party laboratory).
- Slight trimming will be carried out when & where required before the placing of polyethylene plastic sheet.
- Concrete blinding will be carried out where indicated in IFC Drawings.
- Polyethylene plastic thickness to comply with the project specifications.
- Cast in situ elements shall be constructed in accordance with IFC drawings and line with project specification.
- MEP and Civil insert will be in place.
- Surveyor shall mark the location of structural member (foundation, wall, Column, etc.) as per approved drawings.
- Excavation shall be carried out up to bottom level of blinding, leveled, sprayed with water, compacted and tested as per relevant specification and approved drawings.
- Erect formwork for blinding with concrete mix class C12/15.
- Allow the concrete blinding to be hardened and cured as per relevant specification.
- Apply approved protective coating / Damp proofing or water proofing membrane on top of blinding as per specification and approved drawings.
- In specific condition and coordination with consultant when concrete workability is not meeting prevailing placement condition, re tempering of concrete with admixture shall be carried out.
- On specific areas where rate of concrete placement is to be very slow Dry mix concrete will be delivered to site. Water and Concrete admixture meeting concrete mix design requirements will be mixed on small batches using small site Mixers, the same site mixers will be used for Cement plaster.
- Where construction joints detailed on the drawing, width of concrete element warrant establishment of construction / expansion joints, or concrete placement to be stopped due to an avoidable circumstance on site, Construction joints shall be made, Concrete surfaces will be roughened cleaned to establish a good joint between old and new fresh concrete, QC inspection, Consultant approval is required before concrete placement continue in concrete member.
- On water retaining Concrete Structure and detailed on issued for Construction Drawings, approved water stops will be used as required by the project specifications.
- On concrete slabs and where detailed on drawing, Expansion / Construction joints will be established, the joint will be sealed with approved flexible materials.
- Cleaning of Starter Bars shall be carried out following concrete placement completed in preparation for the next concrete pouring.
8.2. Formwork
- Concrete placement will not commence before Engineer Approval of Formwork and Rebar Installation.
- The design and construction of formwork shall take account of safety and of the surface finish required. The formwork will be sufficiently rigid and tight to prevent loss of grout or mortar from the fresh concrete and stand concrete Vibration (Excreted Hydro static Pressure) without Movements. Form work and its supports to maintain the correct position and to maintain correct shape and profile.
- The formwork for foundation, beam connection, column neck and manholes etc. will be made of either traditional formwork (plywood and timber and supported by tie rod and steel support) or DOKA system which a combination of DOKA wooden beams, plywood and DOKA steel supports system with tie rod.
- Molds and formwork shall be prepared according to the IFC drawing.
- Formwork will be placed and aligned fixed to the required dimensions as detailed in issued for construction drawings by the carpentry crew.
- Formwork shall be rigid / sturdy and fixed in such a way to retain the structure member’s dimensions.
- QC Inspector will check the formwork installation and safety officer to ensure safety of the work.
- Before placing the steel reinforcement, an approved form release agent will be applied to the internal face of the formwork.
- For columns, walls shutter will not be closed before QC and consultant releases.
8.3. Steel Reinforcement:
- Grade of Steel will be as follows:
- B500B for 20mm and larger diameter
- B500C for 16mm and smaller diameter
- Based on the issued bar bending schedule, steel cutting and bending will be carried out either in site fabrication shop / supplier fabrication work shop delivered to site and assembled on site as per approved IFC drawings.
- Reinforcement will be placed above ground not in touch of soil, either using wooden blanks or concrete base to comply with project specification and international accepted procedures.
- Upon the arrival of steel rebar to site fabrication shop, the rebar fabrication crew will cut and bend rebar in accordance with project specification and IFC drawings.
- The rebar will be transferred to site by pick up or trailer and tagged.
- Before placing the fabricated rebar inside the formwork or mold, the formwork shall be clean, blown out by air with air compressor and coated with approved releasing agent.
- Rebar will be placed according to the project specifications and IFC drawings.
- Rebar will be assembled either inside or outside the concrete member, outside assembly steel will be placed by a crane to avoid any disturbance to the water proofing materials / or polyethylene plastic sheet. Additionally, when leveling concrete is provided, rebar mats can be assembled in the place.
- Reinforcement support shall be properly assembled at site: non metallic or plastic concrete spacer shall be used to maintain the cover as required by the specifications.
8.4. Embedded Metals, Anchor bolts:
- All embedded materials items for civil. Mechanical or electrical activities shall be placed / inspected by QC inspectors ensuring materials comply with specifications.
- All embedded items shall be unpainted unless noted otherwise, and free of deleterious materials, such as dirt, grease, and heavy scale.
- Anchor bolts and other embedded items shall be positioned and secured within the tolerances shown on the drawings, in accordance with ENV 13670 and as required by this specification.
- All embedded elements to comply with the project specification and fabricated in accordance with IFC drawings.
- The embedded metals and anchor bolts will be installed in accordance with IFC drawings.
- The QC inspector shall check formwork, rebar steel, embedded metal and anchor bolts prior to concrete placement.
- Section / Site Engineer will submit Request for inspection to QC inspector prior to start site delivery of concrete.
- After the concrete has hardened sufficiently, the exposed portion of anchor bolt shall be cleaned of all concrete and the threads chased. Threads shall then be carefully coated with grease and the washers and nuts installed.
8.5. Concrete Placement:
Stage 1:
- Project Engineer / Section Engineer shall ensure Concrete Grade / Class is approved by consultant / clients, the following concrete grades shall be used:
- All cast in place concrete ------------C30/37
- Precast Members----------------------C40/50
- Blinding concrete-----------------------C12/15
- Misc. Concrete--------------------------C20/25
- The QC inspector ensures that mix Design Proportions / Batch weight available in batching plant.
- Ready mix concrete supplier is aware of project specification requirements for concrete temperature and slump.
- Formwork installed to true lines and levels.
- Reinforcement as per approved drawings and bar bending.
- Embedded elements, inserts, box outs chases, champers, water bars etc. as per approved drawings.
- Surveyor marks the concrete top level on the shutter as per approved drawings.
- Formworks is clean from inside using compressor and magnetic bars used to remove pieces of binding wires.
- Sub- Contractors QC (civil) and company / contractor QCI (civil) shall inspect each member prior to pouring of concrete.
- Structural member is released by QC and consultant.
- Concrete pouring schedule submitted to batching plant.
8.6. Concrete Placement:
Stage 2:
- Concrete shall be placed at each individual pour location dependent on access and pour configuration either by;
- Direct discharge
- Crane and skip
- Concrete pump
- Chute
- The exact method / procedure for placing concrete shall be decided depending accessibility of structural member on site.
- All necessary laboratory tools for fresh concrete quality testing shall be available on site prior to pouring of concrete (cube moulds / cylinder mould, slump cone, thermometer etc.) And third party laboratory technician is available at site or Concrete site station (checking temperature, slump air content and fresh concrete density and samples taken as per specifications). Then transit Mixer released to specified Concrete location.
- Place the approved mix concrete into layers 450 mm per layer maximum using one of the above methods.
- Preparation forms, reinforcement, joints and mixing conveying.
- Concrete shall not be dropped from a height exceeding 1.8 meters.
- Expansion / Contraction joints shall be provided as per IFC drawings.
- If the air temperature is less than 30 deg C concrete shall be placed within 90 minutes of the introduction of the mixing water to the cement and aggregates, or cement to aggregates. If the air temperature is greater than 30 deg C mixing time shall be reduced and concrete placed within 60 minutes except when a suitable set retarding mixture is used and slump requirements can be met. The maximum time between batching and placing shall not be exceed 120 minutes in all cases.
- Specific measures taken for minimum dimension of any casting is .80 meters or more.
- Where Kicker is used it shall be at least 70 mm high and carefully constructed.
- Concrete in high temperature (ACI standard 305.1 for hot weather concrete shall be complied with.
- The minimum concrete cover maintained as detailed in specification.
- 75mm for all concrete poured against soil.
- 50mm for all foundation concrete poured against forms.
- 40mm for all other concrete exposed to soil but poured against forms.
- 40mm for all exterior concrete.
- 40mm to principle reinforcement of interior beams and columns.
- 35mm for interior slabs and walls.
- 50mm for columns, beams and walls & other exposed member of Maritime Structures.
8.7. Concrete Compaction:
Stage 3:
- Full compaction of the concrete shall be achieved throughout the entire depth of the layer using mechanical vibrators.
- Vibration of concrete shall be thoroughly worked against the formwork and around the reinforcement: successive layers shall be thoroughly bonded together during vibration.
- Ensure Reinforcement or form is not disturbed.
- Compaction of concrete shall be carried out by mechanical or electrical vibrators to expel all air bubbles formed during the mixing and casting.
- Immersion vibrators shall be withdrawn slowly to prevent the formation of voids.
- Care shall be taken to avoid over vibration which could cause segregation, surface laitance or leakage through formwork.
8.8. Concrete of Curing
Curing is the process of maintenance satisfactory moisture content or humid condition in concrete for certain period. Curing is done to complete the hydration reaction, so may continue until the desire properties are developed to a sufficient strength.
8.8.1. Spraying Water & Curing Compound
- Concrete must cure after concrete casting and finishing in early period of hydration. Water is sprayed on the concrete through a hose or by spray pump of several times during each day to maintain sufficiently moisture for at least 4 days.
- For vertical walls, columns, beams and shear walls, sprinkle water at least times a day for 4 day. This required at least 3 cycles for per day with interval of 4 hours.
- If shortage of water supply, curing compound to be applied on concrete surface using brush or roller as soon as possible after final troweling, it’s to prevent premature water loss due to evaporation. For vertical surfaces, apply immediately after removal of formwork.
8.8.2. Wet Gunny Bags
- For slab structures, wet gunny bags coverings method of curing is applied. This method can be achieved by applying coverings that are saturated with water.
- Care should be taken to cover the entire surface with wet fabric, including the edge of slabs. The covering should be kept continuously moist so that a film of water remains on the concrete surface throughout the curing period.
- Best way is to keep the concrete under wet gunny bags for 4 days and then commence water by way of ponding or spray
8.9. Concrete Repair
8.9.1. General
All concrete repair is a HOLD POINT in the ITP and only proprietary factory made materials approved by the Company shall be used for the repair.
The surface preparation of the concrete to be repaired & the mixing, application & curing of the (proprietary) repair mortars/(micro) concrete shall be as per manufacturers requirements/ recommendations and /or the specifications applicable for concrete shall be followed if specific requirements are not given by the manufacturer (e.g. curing).
All repair areas shall be covered from direct sunlight.
The repair shall only be carried out after the curing has been completed.
8.9.2. Repair of Cracks.
All cracks with a crack width greater than 0.3mm
Note: Cracks with a width exceeding 0.3mm are not confirming to the specification & a Non Conformance Report (NCR) shall be raised.
Open the crack, by chiseling a V –cut, to a depth where the crack visually seems to stop; however the maximum depth for chiseling is 20mm. The crack shall be cleaned with compressed air. Fill the crack up with water and observe whether or not the crack continues by looking for air bubbles in the water due to air escaping out of the crack.
If air bubbles are observed, an approved low viscosity resin shall be poured into the crack as per manufactures recommendation until the crack is fully saturated with the resin.
Repair / seal the V-cut of the crack, after injection, with an approved shrinkage controlled structural grade cementitious repair mortar system.
If no air bubbles are observed, the V-cut shall only be repaired/sealed as per above. Where detection of a possible continuation of the crack with water filling is not possible (on vertical faces) the crack repair shall be discussed between Company and Contractor, looking for similarities with horizontal cracks in the same area.
Where similarities are not found and/or agreed the crack shall be deemed to be deep and injected with epoxy and the V-cut further repaired/sealed as per above. All cracks with a crack width between 0.1 and 0.3mm (Only for Non Coated Areas) If the crack is reaching anchor bolts or box-outs, apply the same repair method as for cracks with a crack width of greater than 0.3mm.
8.9.3. Repair of Minor Surface Deficiencies in The Concrete (Air Voids, Etc.)
Surface defects that can be enclosed by a 50mm circle and in which circle the concrete cover is not reduced by more than 10mm are defined as minor surface deficiencies (refer to section 3.24 of T-13.376.358). These minor voids shall be filled with fine mortar incorporating polyvinyl acetate (approved is Renderoc RF, for a maximum thickness of 5mm).
8.9.4. Repair of Major Surface Deficiencies in The Concrete
Note: Major surface deficiencies are not confirming to the specification and a Non Conformance Report (NCR) shall be raised. Major surfaces deficiencies are deficiencies that cannot be enclosed by a circle of
50mm and/or where the concrete cover has been reduced by more than 10mm and up to the rebar zone (no rebar exposed). Defective concrete shall be removed up to sound concrete. These major deficiencies shall be repaired by an approved shrinkage controlled structural grade cementitious mortar system (approved is Renderoc Sxtra).
8.9.5. Major Concrete Repair
Note: Major concrete repairs are not confirming to the specification and a Non Conformance Report (NCR) shall be raised.
Areas where after removal of the defective concrete the rebar becomes exposed and/or where the extend of the repair is such that formwork has to be used are defined as Major Concrete Repairs. The defective concrete shall be removed up to sound concrete.
If the defective concrete extends to the rebar a clear gap of at least 20mm shall be created behind the rear face of the rebar, such that a gloved hand can comfortably reach behind the main bars.
All exposed rebar shall be carefully cleaned by wire brushing before the repair & the concrete faces to be scabbed & wetted as per requirement/recommendation of the manufacturer of the repair micro concrete.
8.10. Curing Compounds
This is the best method of curing. It is suitable for curing horizontal surfaces such as floors, roof slabs, road and air field pavements. The horizontal top surfaces of beams can also be ponded. After placing the concrete, its exposed surface is first covered with moist hessian or canvas. After 24 hours, these covers are removed and small ponds of clay or sand are built across and along the pavements. The area is thus divided into a number of rectangles. The water is filled between the ponds. The filling of water in these ponds is done twice or thrice a day, depending upon the atmospheric conditions. Though this method is very efficient, the water requirement is very heavy. Ponds easily break and water flows out. After curing it is difficult to clean the clay.
9. QUALITY CONTROL
The work ability of the concrete will be continuously monitored at delivery place before casting. Samples for conducting tests for determining the compressive strength on concrete will be taken according to the specifications.
Concreting will be carried out using the approved design mixes and that specified for the structure. The concrete from approved sources only will be used for all concreting works.
All rebar and forms will be cleaned of debris and foreign materials before pouring.
It will be ensured that the temperature of concrete at the time of placing does not exceed more than 30° C.
The concrete pouring will be done within the initial setting time of the cement. For the purpose of this, the time of batching as marked on the delivery sheet will be considered.
During hot weather, reinforcement temperature will be reduced by shading, water pray before pouring as well as additional crew wiII be engaged to expedite the finishing etc. However preference for night pouring of concrete will be given.
The concrete will then be poured into the mold I form after ensuring that it is free of all foreign materials or debris; the inserts are in place; the re-bars are as per the drawings and all other QC requirements are complied with.
The concrete surfaces will be rendered appropriate finish to eliminate all voids and pits unless specified otherwise in the drawings.
The concrete will be laid in layers not exceeding 300mm in thickness; each layer compacted separately before the next is laid.
At least two vibrators of needle type will be made available at the site, where one of them acts as a stand-by.
In case of mass pouring, the concreting will be done uninterrupted so that cold joints can be avoided. However, in case of slabs/ paving appropriate pre-approved construction joints will be provided.
For the mass concrete pouring, specific method statement will be submitted. Concrete surface will be finished as per specifications within the initial setting time of concrete. Immediately after finishing surface shall be covered with white polyethylene sheeting which shall be in contact with concrete surfaces to avoid evaporation of moisture content from fresh concrete. Control joints, if any, will be cut within 12 hours after placing of concrete.
10. SAFETY PLAN:
Safety of men and materials is a high priority for Client. All safety measures will be observed during the entire works. Detailed safety measures for every works will be elaborated in the concerned JSA being submitted by electrical safety department to PMT HSE department, however basic account of the safety strategy is given under:
- All the activities will be envisaged a week in advance and job safety requirements will be worked out by analyzing the likely hazards and resorting to preventive.
- Proper housekeeping at the end of the day is a part of the mandatory tasks assigned to workers to avoid accidents due to littered tools and materials.
- Flagmen will be engaged to control the movement of trailers, cranes, pumps and other mobile equipment’s.
- Weekly tool box talk will be conducted and brief safety measures required for the ensuing days will be discussed.
- First aid facility will be available entire the period in the work site.
- The JSA will be submitted separately by the HSSE department.
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CONCRETE REPAIR LOG
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AREA
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GRID
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CRACKS
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REPAIRED
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Signature
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A
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B
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1
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2
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3
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4
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5
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6
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7
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8
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9
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