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PROCEDURE FOR CONCRETE WORK
a) Lean Concrete
Lean Concrete shall not be placed prior to a recorded pre-placement inspection And authorization to proceed by Client Company Representative and Notification of minimum of 24 hours before beginning concreting operations.
b) Form work General
– Secure IFC drawing regarding the shape, size and dimension of the forms required.
– Fabricate the forms as per the requirement specified in the project specification, Concrete Construction and in accordance with ACI 34 7 and tolerance limit listed in ACI 301, using either 12mm or 18mm thick plywood and ribbed wit 2″x2″ or 2″x4″ timber. Form frame shall have longitudinal ribs, and ribs shall be free form deformities and defects to resist buckling effect when subjected to enormous dead load of concrete.
– Apply form-releasing agent approved prior to fixing of any formworks in use.
– 25mm plastic chamfer strips to exposed exterior comers of the concrete structure or as specified on general notes.
– Assemble and fix the forms to the conect position as marked by the Surveyor. Check the dimension to conform to the required size and shape of the concrete member, subject to the tolerances prescribed in the project specification.
– Secure the forms to its position properly by using tie rods. clamps, wood cleats or combination of which that is suitable depending on site condition . Forms must be watertight to prevent run-off of cement paste from the fresh concrete and to avoid Honeycombs.
Please read also: METHOD STATEMENT FOR WALL PRECAST CONCRETE OF MANHOLE-CIVIL
– Use approved waterproof through-tie system for underground structures, especially For pits.
– Wall forms shall be in layer of sectional units. The joints formed by the assembly of these sectional units must be fitted well, aligned and secured properly.
– In the case of overhead form works, make sure that the scaffolding and other part of the staging are properly fixed and have passed the safety requirements, if necessary.
– Provide bracings on sides of forms to prevent any movement or displacement of any part during the pouring or mechanical form jacks with ends anchored on solid and stable base. For overhead formwork, bracings can be anchored on patt of the scaffold found suitable.
– Check and correct any misalignment or displacement resulting during the fixing of braces and supports.
-Mark the top of concrete elevation by fixing nail on two opposite sides inside the form and on starter bars for wider areas of pouring.
– Clean the inside forms. For deep forms, provide an opening at the bottom of the fonnworks big enough for di1t, small wood pieces and other debris to pass through when air blown.
– Forms shall be free of noticeable wrinkles, warps, big patches, and other such defects. Contact surface of forms shall be clean, free of ruts and other roughness.
– Determine the wind velocity during installation of wide and big pre-fabricated form-works and stop when the wind speed dictates that it’s unsafe to do lifting works.
Removal of Forms
Fom, removal shall be in accordance with Client Company Standards.
– Forms for columns, walls, sides of beams and other placing, if the concrete has hardened Sufficiently as per Client Company Specification.
– Remove the bracings and supports carefully to avoid inflicting or causing damage to the concrete.
– Remove first all the side support and bracings followed by the clamps and tie rods.
– Using a crowbar, strip the forms carefully in a manner that will not cause damage to concrete surface.
– Clean the removed forms of any hardened concrete. Remove any protruding nails, wood and plywood spurs upon removing the formwork.
Coating Preparation:
– Where coatings are to be applied all nail and other protrusions are to be totally removed .
– Concrete is to be prepared as required by Client Company Specification.
c) Rebar work
– Rebar shall be handled and shipped carefully and properly covered. Proper tagging and marking system shall be implemented for easy identification.
– Rebar shall be stored above ground on wooden platform skid or other support approved by EPC Contractor and shall not be placed directly on the ground.
Fabrication
– Secure standard drawing regarding the shape, dimension and diameter of bars for the required reinforcement according to IFC drawing.
– Prepare the bar bending schedule in the widely used, each item shall indicate the diameter of bar, the shape to be fonned, the number of bars for each shape, the dimensions for each shape, length of each bar, the total number of each shape, the total length of shape, and the total weight for each item. Mark the correct length and cut the bars in-group of items having the same lengths and sizes.
– Secure the fabricated rebar in bundles properly marking them with non-metallic tags indicating the structure, the mark number, shape code, diameter of bar, length and bar quantity.
• Installation of re bar
– Clean the re bar of any soil, mud, oil or other materials that may adversely affect or reduce the bond between the bar and the concrete.
– Place the reinforcing bars to correct positions as marked on site and fix.
– Make sure that the placing, concrete cover thickness; lapping locations and lapping lengths are in accordance to the specified requirements. Fix the cover spacers firmly to prevent getting displaced during concrete pouring and to maintain the required concrete cover for the rebar. Proper and safe platforms with access ladders must be erected prior to installation of rebar in elevated areas.
– Use chairs to support top mats of slab rebar or any structure with top and bottom rebar. The chair shall be of diameter sufficient to prevent any sagging of top rebar.
– No welding allowed for purpose of rebar installation/splicing. Rebar shall be cut and bend, install where splicing is permitted as per standard rebar arrangements.
d) Concrete work
• Prior to concrete pouring of the unit/ area scheduled for pouring, Client Company Specification should be inspected by subcontractor Inspector Client Company PID Representative And shall be acceptable for Pouring. Inspections are to be in accordance with the Approved SA TIP/SAIC/SA TR, project specification and latest construction drawings.
-Make the necessary preparation for concrete pouring. Mason tools, concrete vibrators. hessians. polyethylene sheet, testing apparatus, and clean water for concrete curing must be provided at the site. The use of personal protection equipment’s shall also be imposed upon all the personnel.
• Proper access for concrete truck mixers and pump car location should be arranged on time. An advance notice must be given to every department about scheduled concrete pouring so that they can plan their work and give way for the pouring of concrete without disturbance. Quality test such as slump and temperature shall be carried out by 3rd party laboratory prior to the release of concrete for pouring. If the concrete meet all the required quality criteria as per Client Company Standards/Specification the pouring of concrete can be start.
• Pour the concrete directly to or close to where it is to be finally deposited, if possible. Use suitable chute when discharging directly from the truck mixer to prevent segregation of
aggregates from the cement paste. When discharging through pump, height of the pump hose from pouring layer not to exceed 1.0 meter as per SAES-Q-001 para 7. 7. Extra care should be observed in placing concrete especially in direct pouring, to avoid movement of structure being poured. Concrete shall be poured in courses or layers not exceeding 400mm thickness unless otherwise directed by EPC Contractor.
• All concrete shall be thoroughly consolidated by concrete vibrator during placement and thoroughly worked around the reinforcement, embedded fixtures and into corners of forms. Suitable vibrator shall be used not to damage the epoxy coated re-bars. Sufficient concreting personnel should be arranged, and have continuous activity even during break time.
• Vibrators to be inserted and withdrawn at points approximately 0.5m apart. For each insertion the duration should be sufficient to consolidate the concrete but not cause segregation, generally from 5 to 15 seconds. Spare vibrator should be kept ready in case of breakdown. Do not use vibrator for transfer and leveling of fresh concrete.
Immediately after completion of pouring, concrete is to be covered by polyethylene sheet to prevent premature drying, excessive hot/ cold temperature and mechanical disturbances.
when concrete is hard enough, cover it with saturated burlaps and covered with a plasticized sheet vapor barrier. The curing shall be continue until reached 70% but not less than 7days after placement.
Tag showing the casting date shall be placed on the foundation for easy identifying of curing duration.
• In some occasions wherein a curing compound is required to cure a concrete, material approval from Client Company PID Representative shall be obtained. Curing of concrete is carried out in accordance with SAES-Q-001.
• In concrete pouring, adequate arrangements shall be made to the following:
– To pour the concrete rapidly as possible to its final position without segregation and contamination.
– Prior to discharge, the truck mixer chute may be watered a bit just to have a smooth flow of concrete.
– The re-bars shall be protected from any possible damage to during the concrete pouring.
– Fresh concrete shall not be contact with aluminum surface.
– No segregation to the concrete shall be allowed during pouring. If the re-bar is dense, flexible drop chutes shall be employed.
– Stand-by equipment such as, but not limited to, concrete pump, vibrator to be available throughout concreting.
– No concreting during adverse climate conditions which deteriorate the quality of the product.
– Adequate arrangements to obtain the required concrete surface finish, especially on units with large surface area.
– Plan the pouring work to abide all safety regulations and requirements. Generally, Concreting work should be performed in normal working hours. Proper housekeeping shall be done during and after work.
TOOLS & EQUIPMENT
• Concrete Pump
• Concrete Transit Mixer
• Concrete Vibrator
• Air Compressor
• Water Tanker
• Rebar Cutting Tools
• Power Saw
• Shovel/Trowels
• Hammer
SAFETY CONTROL
1) EPC Contractor, Subcontractor Safety Personnel shall carry out the safety site inspections to ensure that safety requirements laid out in the Safety Management Plan are followed during the execution of the concrete works.
2) All person involved in concrete works must be provided with and use the necessary PPE and as a standard each person shall wear a Safety Helmet and Safety footwear, and etc. The Requirement for personal protection equipment shall be approved by Client Company.
All personnel will be issued with the following personal Protective equipment and must be worn at all times.
• Safety helmets
• Safety boots
• Safety Spectacles
• Hand Glove
• Dust Masks
• Ear Defenders
• Respirators as Required
• Wellington Boots
• Cotton overalls with full sleeves shall be worn on construction site
3) All personnel involved in the concrete works shall have to undergo Safety Training being conducted by EPC Contractor HSE Department.
4) Barricade
• Determine a warning or protective type.
• BatTicades are required around critical areas excavation, holes, or openings in floor, roofs, Elevated platforms. Barricades are also required to protect lifting operations, overhead Travelling material and other material stockpile for construction use at site.
Hole Protection
The following describes the minimal requirements for covering floor holes, floor openings and wall openings.
• All holes or openings through floors decking or walls must have properly identified hole covers or hard barricades installed immediately. Materials or equipment must never be stored on a hole-cover.
• Covers must be secured so they cannot slip, and extended adequately beyond the edge the hole.
Covers must be strong.
– Signs: Legible signs must be placed on barricade stands, posts, or other suitable stanchions before work starts, and removed promptly upon completion.
– Stairwells: Floor openings shall be guarded by a standard handrail and toe boards on all exposed sides except at the entrance to opening. The set-up will ensure that workers cannot walk directly into the opening.
– Any grating removal, alteration etc to grating will be controlled by a specific permit to work.
Tools and Equipment’s
• All of tools and equipment e.g. hand and power tools, slings etc. require special attention and protection for their use and guidelines for storage.
• All tools and equipment shall be inspected in accordance with EPC Contractor and PMT Procedures.
• All damaged, unsafe or defective tools will be marked, tagged as Unsafe or with a Red Paint and taken away from operation to assure that no one will use such tools on the job.
• Electrical tool and equipment shall be used in accordance with GFCI requirement.
Material Handling
• Based on material delivery and condition with the schedule, all material requires Special attention and protection for their usage and guidelines for storage.
• Hazardous substances likely to be used during civil work i.e. concrete, bitumen (paving work), black coal tar paint for concrete foundations, lubricants etc shall be used safely in accordance with the information from a Material Safety Data Sheet (MSDS).
• The relevant safety information including PPE, First aid, Fire prevention, Spillage control etc shall be extracted from the detailed MSDS and a brief MSDS made covering the key points.
• This informatation shall be communicated via tool box talks to all persons who are likely to be exposed to the substances and in addition a copy of the MSDS provided to the site nurse or nominated first aider.
• The brief MSDS shall be posted in the working area were the substance is in use for all persons to be reminded of the safe working requirements.
• Toxic and Combustibles will be stored separately.
• Sign of hazard contained by such materials will be posted.
• SUB-CONTRACTOR introduces a material onto the project shall provide:
• The following minimum information shall be available.
– Name and address of the supplier.
– Trade name or commonly known name.
– use and purpose.
– Fire extinguishing mediums.
– Waste management and disposal.
– Emergency actions.
– Personal protective clothing.
– First aid and medical treatment.
– Storage, package and labeling.
Entering Confined Spaces
• No one may enter any deep excavation or manhole without specific approval and a current work Permit. Prior to entering any deep excavation or deep manhole, gas test and instruments
are required.
• No new activity shall be introduced into a confined space without the permission and Signed approval of the permit to work issuing authority.
• Subcontractors shall not enter or commence work in any deep excavation, deep Manhole, pipe or chamber or other enclosed space, until a valid permit to work has been issued. Where Subcontractor operations may result in a dangerous atmosphere arising during the work activity the permit to work issuing authority shall be made aware of this before permit issue.
• Contractor shall check the atmosphere of the confine space prior to start work by gas Testing.
• Confined space training is conducted by EPC Contractor.
• Only CS trained personnel to work inside.
• Trained CS entry attendant to monitor the entry and egress of workers.
• Maintain the confined spaces well ventilated at all times, if required.