Reinforcement or Steel Reinforcement

Reinforcement or Steel Reinforcement

Material and size of Bar

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Reinforcement for concrete shall conform to the respective Pakistan, British, ASTM, or other standard as specified in the drawing, plan or in the contract document. Unless otherwise specified all plain reinforcing bar shall comply with the requirement of B.S 4449 for the plain mild steel bars and shall have a minimum characteristics strength of 250 Mpa. Unless other otherwise specified all deformed bars shall comply with the requirement of B.S 4461 for deformed cold worked new stock billet steel bars and shall have a minimum characteristics  strength of 460 mpa.

Reinforcement of all types is to be stored on site in an approved manner so as to avoid damage.If the reinforcement is supplied by the employer then the contractor should inform the employer of his requirement much before it's use in construction.

What is Pakistan, British and ASTM Standard

Pakistan Standards

• P.S 241 Tensile testing of the steel
• P.S 244 Bend test for steel
• P.S 380 Rolled deformed steel bars for the concrete reinforcement.(intermediate grade)
• P.S 605 Rolled deformed steel bars for the concrete reinforcement.(hard grade)
• P.S 606 Rolled deformed steel bars for the concrete reinforcement.(structural grade)
• P.S 607 General Technical delivery requirement for steel.

British Standards

• B.S 633 General requirement for oxy- acetylene welding of mild steel.
• B.S 783 Hot rolled bars and hard drawn wire for the reinforcement of concrete.
• B.S 1856 General requirement for the metal arc welding if mild steel.
• B.S 4419 Hot rolled steel bars for reinforcement of concrete.
• B.S 4461 Cold worked steel bars for reinforcement of concrete.
• B.S 4468 Bending dimensions and scheduling of bars for the reinforcement of concrete.

ASTM Standard

• A 305 Minimum requirement for the deformations of deformed steel bars for concrete reinforcement.
• A 615 Deformed billet steel bars for the reinforcement concrete.

Delivery and Storage

Delivery

Steel reinforcement bars shall be kept in bundles firmly secured and tagged, each bar or bundle of bars shall be identified by marks stamped on hot ot cold or painted on or by another means. The identifying marks shall contain the following information.

• None of the procedure or his trade
• Standard to which the bars have been manufactured
• The class types and strength
• The diameters
• The number of the test certificate

Storage

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The method of storage shall be approved by the engineer and reinforcing bars shall be stored in racks or platforms above the surface of ground and shall be protected free form scaling, rusting, oiling, coating, damage, contamination and structural defects prior to placement in works. Bars of different diameter and grades of steel reinforcement shall be kept separately.

Bar Bending Schedule

The contractor shall prepare bar bending schedule of all the reinforcing steel bars and these bar bending schedules shall submitted to the engineer for the approval. The contractor shall obtain approval of the bar bending schedule before starting actual bar bending works.

Bending, Fabricating and Placing

All metal for reinforcement shall be free form loose mill scale, loose rust, mud, oil, grease or other harmful matter immediately before the concrete is placed. Reinforcement is to be accurately placed according to the plain or drawing and secured against displacement by using the 16 gauge wire ties or suitable  slips at intersections and supported from the form work by using concrete, petal or plastic chairs and spacers or hanger of an approved pattern. Where concrete blocks are used for ensuring the cover, they shall be made of mortar not leaner than 1 part of cement to 2 parts of sand. Where the concrete surface will be exposed to the weather in the finished structure, the portion of all accessories in contact with the form work shall be galvanized or shall be made of plastic.

      Bars shall be placed to the following tolerance.

• Concrete cover to formed surfaces   = +5 mm
• Minimum spacing between bars       = -5 mm 
• Top bars in beam and slabs

1.             Members 200 mm deep or less    = +5 mm
2.             Member more than 200 mm but not over 600 mm deep = 10 mm
3.             Member more than 600 mm deep = + 25 mm

• Crosswise member = space evenly within 50 mm
• Lengthwise members  = 50 mm

                             Bar may be moved as necessary to avoid interference with other reinforcing steel, conduits or embedded items. If bars are moved more than one bar diameters or enough to exceed the above tolerance the resulting arrangement of bar. Vertical bars in column shall be off set at least one bar diameter at lapped splices to ensure proper placement, templates shall be  furnished for all dowels.

                            No splice of reinforcement shall be made except as shown in the working plan or drawing.No concrete is to be carried out until the reinforcement has been checked and approved by the engineer.