All reinforcement for use in the permanent works shall be specified on the drawings and shall comply with the Standards specified below. Deformed bars shall have Type 2 bond classification. BS or American Standards are applicable as mentioned but not limited to the following.
- BS 4449: Carbon Steel Bars for Reinforcement of Concrete
- BS 8666-2000, BS EN ISO 4066: Bending Dimensions and Scheduling of Bars for the Reinforcement of Concrete
- BS 4483: Steel Fabric for the Reinforcement of Concrete
- BS 4482: Cold reduced steel wire
- BS 8110 Part 2: Code of Practice for Special Circumstances
- BS 8110 Part 3: Design Charts for Singly Reinforced Beams, Doubly Reinforced Beams and Rectangular Columns
Shop drawings are prepared and submitted for approval including placing of reinforcement in accordance with applicable procedures. Indicate on shop drawings, bar bending details, lists quantities of reinforcement, sizes, spacing, locations of reinforcement and mechanical splices, with identifying code marks to permit correct placement without reference to structural drawings.
Indicate sizes, spacing and locations of chairs, spacers and hangers. Prepare reinforcement drawings in accordance with the consultant instructions. Detail lap lengths and bar development lengths. Provide tension lap splices where indicated.
Reinforcement Bar Schedules
The Contractor shall schedule the reinforcement in accordance with BS 8110 and BS 4466, the information on the Drawings, this Specification, and subsequent instructions.
The Contractor shall include for all necessary chairs and spacers, and his price and rates for steel thus shown shall include for these.
The Contractor shall prepare reinforcement detail drawings and other relevant shop drawings on reproducible negatives to the following scales:
Walls and slabs 1:50
Beam and column elevations 1:20
Beam and column sections 1:20 or 1:10
Sketches will not be acceptable. These drawings shall show all openings for services, and up-stands or plinths for equipment and cast-in items.
Bending schedules and reinforcement detail drawings shall be submitted for approval. The Contractor shall correct these schedules and resubmit as reasonably required to ensure a high standard of work. He shall program his work and submit schedules for approval allowing time for such verification, rectification and re-submission as necessary. Such approval shall not relieve the Contractor of his responsibility for the accuracy of such schedules.
No concreting shall be allowed to proceed until such time that the drawings and bending schedules for that particular section of works are approved. Any delay incurred in obtaining approval shall be the Contractor’s responsibility.
Reinforcement Technical Submittals
The Contractor shall submit full details of reinforcement that he proposes to use for making concrete. Approved materials shall not thereafter be altered or replaced by other materials without the consent of the consultant.
All reinforcement shall comply with the appropriate British Standards, which include the following:
BS 4449:1997 Specification for carbon steel bars for the reinforcement of concrete
BS 4482:1985 Specification for cold reduced steel wire for the reinforcement of concrete
BS 4483:1998 Steel fabric for the reinforcement of concrete
BS ISO 14654:1999 Epoxy-coated steel for the reinforcement of concrete
All reinforcement for use in the Works shall be tested for compliance with the appropriate British Standard in a laboratory acceptable to the consultant and two copies of each test certificate shall be supplied to the consultant. The frequency of testing shall be as set out in the British Standard.
In addition to the testing requirements described above, the Contractor shall carry out additional tests as instructed by the consultant.
Any reinforcement that does not comply with the Specification shall be removed from Site
Where reinforcement couplers are specified or are permitted by the consultant they shall be used in accordance with the manufacturers recommendations.
The tensile strength and the fatigue performance of coupled sections of bar should comply with the relevant British Standard for the type of bar.
Tying Wire: tying wire shall be 1.6mm diameter black annealed mild steel wire. The use of any other type requires the approval of the consultant. The ends of the wire shall be bent back away from the surface of the member to avoid rust staining.
Spacers: the type of spacer requires the approval of the consultant. They shall be of durable material and shall be designed to avoid corrosion of reinforcement and spalling of concrete.
Concrete spacer blocks shall be made from cement, sand and small size coarse aggregate. The mix proportions shall match those of the surrounding concrete and the blocks shall be comparable to the surrounding concrete in strength, durability and appearance.
The spacer blocks, their positioning and fixing shall be in accordance with good practice as recommended by the Concrete Society in their publication “Spacers for Reinforced Concrete”
Reinforcement Storage and Handling
Reinforcement shall be stored on Site either in racks or on a hard impermeable base so that it remains straight and free from contamination.
Any reinforcement that is likely to remain in storage for a long period shall be protected from the weather so as to avoid corrosion and pitting. All reinforcement that has become corroded or pitted to an extent that will affect its properties shall be removed from Site.
Epoxy coated reinforcement shall be stored and handled on Site in strict accordance with the requirements of BS ISO 14654:1999 [Epoxy-coated steel for the reinforcement of concrete].
All stored reinforcement shall be protected from wind blown sand and the salt laden atmosphere.
Reinforcement Bars Cutting and bending
All necessary bar bending schedules shall be prepared by the Contractor and submitted for approval. The Contractor shall cut reinforcement to length and bend it to the shape shown on the schedules within the dimensional tolerances given in BS 8666:2000 [Specification for scheduling, dimensioning, bending and cutting of steel reinforcement for concrete]. Bars shall be bent cold by the application of slow steady pressure. Hooks or right angle bends shall be formed where called for by the schedules and to the dimensions and tolerances specified in BS 8666:2000 [Specification for scheduling, dimensioning, bending and cutting of steel reinforcement for concrete].
Bar bending machines shall be equipped with suitable rollers such that epoxy coating is not damaged during bending. All cut ends of coated bars shall be made good in accordance with the manufacturer’s instructions with epoxy supplied by the manufacturers. Coated bars shall not be bent by hand.
After bending, bars shall be securely tied together in bundles or groups and legibly labelled as set out in BS 8666:2000 [Specification for scheduling, dimensioning, bending and cutting of steel reinforcement for concrete].
Usage of Spacers
Spacers or chairs shall be used for ensuring that the correct cover is maintained on the reinforcement. Spacers shall be as small as practicable and of a shape agreed by the consultant. The prime requirement of a spacer or chair is that during casting, it holds the reinforcement in the correct position within the concrete and does not significantly reduce the durability of the structure.
Spacers are divided into two main groups:
Clip-on where the clip action is an integral part of the design of the spacer. These are generally of plastic.
Wire-on where the spacers are attached to the bar by the use of tying wire. These are generally cementitious. The mix used for cementitious spacers should have minimum cube strength of 50 N/mm2, and the largest size of aggregate shall not exceed 10mm. BS 8110 states that concrete spacers made on the construction site must not be used.
Wires cast into the block for tying into the reinforcement shall be 1.6mm diameter coated soft annealed iron.
The spacer or chair must not cause any harm to the reinforcement or the concrete, that is to say it must not allow the free passage of water to the reinforcement and it must not cause spalling of the finished face.
When steel chairs are required to support reinforcement off an exposed face, the ends of each chair leg must be encased in a protective tip, such as a coated plastic sleeve, for a distance of at least 40mm.
Generally, spacer blocks for use in building work shall not exceed 50mm2 in cross sectional area. In building works, spacer blocks shall not be used without the approval where the concrete face will be visible in the finished face.
Spacers, chairs etc for epoxy coated bars shall comply with the requirements of BS ISO 14654:1999 [Epoxy-coated steel for the reinforcement of concrete].
Reinforcement shall be securely fixed in position within a dimensional tolerance of 20mm in any direction parallel to a concrete face and within a tolerance of 5mm at right angles to a
face, provided that the cover is not thereby decreased below the minimum specified in Clause 3.4.
Unless otherwise agreed by the consultant, all intersecting bars shall be tied together with 1.6mm diameter coated soft annealed iron wire and the ends of the wire turned into the body of the concrete, or shall be secured with a wire clip of a type agreed by the consultant. Plastic coated wire shall be used for binding epoxy coated bar.
Reinforcement shall be rigidly fixed so that no movement can occur during concrete placing. Any fixings made to the formwork shall not be within the space to be occupied by the concrete being currently placed.
No splices shall be made in the reinforcement except where shown on the Drawings or agreed by the consultant. Splice lengths shall be as shown on the Drawings.
Reinforcement shall not be welded except where required by the Contract or agreed by the consultant. If welding is employed, the procedures shall be as set out in BS EN 1011-1:1998 [Welding. Recommendations for welding of metallic materials. General guidance for arc welding] and BS EN 1011-2:2001 [Welding. Recommendations for welding of metallic materials. Arc welding of ferritic steels]. Full strength butt welds shall only be used for steel complying with BS 4449:1997 [Specification for carbon steel bars for the reinforcement of concrete], and if used on high yield deformed bars complying with BS 4449:1997 [Specification for carbon steel bars for the reinforcement of concrete] the permissible stresses in the vicinity of the weld shall be reduced to those applicable to plain bars complying with that specification.
Fabric reinforcement shall be used in standard sheets where possible. Adjoining sheets shall overlap by at least one rectangle or 60 diameters of the bar at the lap whichever is the greater.
Mechanical splices shall not be used unless the consultant agrees otherwise. Where used with epoxy coated bars, the mechanical splices shall have a compatible protection system to be agreed with the consultant. This may take the form of a proprietary heat shrunk sleeve.
The Contractor shall ensure that reinforcement left exposed in the Works shall not suffer distortion, displacement or other damage. When it is necessary to temporarily bend aside protruding mild steel reinforcement, the radius of the bend shall not be less than four times the bar diameter for plain bars or six times the bar diameter for high yield bars. Such bends shall be carefully straightened before concrete placing continues, without leaving residual kinks or damaging the concrete round them.
Bars complying with BS 4449:1997 [Specification for carbon steel bars for the reinforcement of concrete] or other high tensile bars shall not be bent after placing in the Works.
Coated Grade 250 bars may be bent to radii not less than BS 8666:2000 [Specification for scheduling, dimensioning, bending and cutting of steel reinforcement for concrete]. Coated Grade 460 bars must not be bent or straightened without the approval of the consultant.
Before concrete is placed in any section of the Permanent Works which includes reinforcement, the reinforcement shall be completely clean and free from all contamination including concrete which may have been deposited on it from previous operations. Reinforcement shall be thoroughly cleaned and all dirt, loose rust, scale, oil and other contaminants removed before it is placed in the Works. Reinforcement contaminated by blown sand, salts, chemicals or other materials after being fixed shall be cleaned to the satisfaction of the consultant.
Scaffold boards shall be provided to ensure that the reinforcement is not walked upon during concreting or other operations. During concreting operations, a competent steel fixer shall be in attendance to ensure that reinforcement is maintained in position as pouring and compaction proceeds.
Coated reinforcement shall be inspected for damage to the coating both during and upon completion of fixing. Bars with cumulative damage exceeding 1% of the surface area shall be replaced. All visible damage shall be patched with a special epoxy formulation for patching supplied by an approved supplier. Patching shall be carried out strictly in accordance with the instructions of the epoxy manufacturer.
Cover to reinforcement
The concrete cover to reinforcement shall be a minimum of 75mm unless otherwise stated in the general notes accompanying the Drawings, or indicated on the Drawings, with a tolerance of ±5mm.
Cover to reinforcement in concrete members in building works shall be:
Internal members 40mm Except Slabs for which is 25mm
External members 40mm or 50mm where no moisture protection measures are applied
Members in contact with the ground 75mm
When welded splices are specified on the Engineering drawings, the welding shall conform to AWS D1.4. Each rebar to be welded must be physically tested to AWS D1.4 and the weld procedure must be reviewed and approved. Splices in welded wire fabric shall be made by lapping a minimum of one mesh plus 50 mm but not less than 300 mm.
No splices shall be made in the reinforcement except where shown on the Drawings or agreed by the consultant. Splice lengths shall be as shown on the Drawings or as otherwise directed by the consultant. Mechanical splices shall not be used unless the consultant agrees otherwise in writing.
Sheets of steel mesh fabric reinforcement shall overlap each other by at least twice the wire spacing in the direction of the lap or as shown on the Drawings and shall be securely fastened at the ends or edges.
Starter bars shall be protected from wind-blown dust, sand and sea salts by wrapping with polythene sheet or other approved means.
All embedded items shown on the drawings shall be fixed in the positions shown within the specified tolerances. Where this necessitates the modification or displacement of the reinforcement the Contractor’s proposals for such work shall be approved by the consultant. Embedded items shall not be supported by welding to reinforcement.
Unless specified otherwise, dowel bars shall be straight round smooth mild steel bars complying with BS 4449. The free end shall be sawn and free from burrs or other irregularities.
Where shown on the Drawings, dowel bars shall be debonded with an approved debonding compound or proprietary dowel bar sleeve. The consultant may require the Contractor to demonstrate the efficiency of the method of debonding by carrying out the test described below.
The average bond stress on debonded bars cast into concrete specimen and subjected to pull out tests at 7 days shall not exceed 1.4MN/sq.m and the total movement of the dowel bar relative to the concrete shall be not less than 0.25mm at the stress. The concrete specimens shall be 150mm x 150mm in section and 450 mm long and made with the same mix proportions as used in the Works. The number of tests will be at the consultant discretion.
Compressible Caps: Caps shall be securely fixed and shall permit free movement of one end of the bar.
Dowel bars shall be rigidly supported so that they are correctly aligned.
Steel Reinforcement Testing
The Contractor shall be responsible for all testing. Testing laboratories require the consultant approval. Consultant shall be permitted access to the laboratories to witness any tests and he may request further test if necessary. Two copies of all test results shall be submitted to the consultant within 48 hours.
The Contractor shall demonstrate to the consultant satisfaction that the production of concrete cubes and the measurement of slump are being carried out only be persons competent in the required techniques.
|ITEMS TO BE TESTED||RELEVANT BRITISH STANDARD||NUMBER OF TESTS||NOTES|
|Minimum number of tests for certification purposes to be 10 initially prior to 1st steel fixing then testing as required by the consultant but not less than 2 samples from each bar dia. per delivery to site.
(Tests shall include tensile, bend, rebend and chemical analysis)
|1. Contractor to submit manufacturer’s and/or supplier’s certificates as proof that material meets BS requirements and is representative of materials used on site.
2. The acceptance criteria for the reinforcement testing is to be in accordance with the relevant British Standards for the tests being undertaken.
All reinforcement shall be cleaned to ensure it is free of all oil, dust and deleterious material. Concrete shall be subsequently placed within 24 hours. Cleaning shall be by wire brushing or grit or sand blasting to the consultant satisfaction. If blasting is required the blasting medium shall be clean and salt free. If at any time the consultant is not satisfied with the result of mechanical cleaning he may require the contractor to adopt an alternative method.
Water cleaning of reinforcement to remove chloride contamination shall be carried out at the consultant discretion prior to pouring of concrete.