section 4-2 reinforcement

4-1 / 1 Technical Specifications

4-2: Reinforcement

SECTION 4 - 2 : REINFORCEMENT

PART I: DESCRIPTION

1.1 Scope

This work shall consist of furnishing and placing reinforcement bars of the grade, type and size stated shown in accordance with these Specifications, and in conformity with the requirements shown on the Drawings.

1.1.1 The materials and workmanship to be employed for the reinforcing steel works of concrete shall comply with the Building Code Requirements for Reinforced Concrete ACI 318-02, and these Specifications. In the event of conflict between ACI Standard and these Specifications, the latter shall be prevailed.

1.1.2 This section specifies the furnishing and placing of reinforcement bars of the grade, type, and size shown in accordance with these Specifications, and in conformity with the requirements shown on the Drawings.

1.1.3 Bending schedules shown on the Drawings are for guidance only and shall be checked by the Contractor according to ACl315-99 or latest edition.

1.2 Tolerances

Reinforcement shall be placed and maintained in the position shown on the Drawings to the following tolerances:

Concrete cover +6 mm / -3 mm

Longitudinal location of bends and ends of bars ±25 mm except that the specified cover at

ends of members should not be reduced by more

than 3 mm.

1.3 Storage and Handling

1.3.1 Reinforcement for structures shall be handled and stored in a manner that will prevent bending out of the desired shape and the unnecessary accumulation of dirt, oil, and paint. As recommendation, Reinforcement shall be stored on above ground concrete slab under cover, shaded and racked as necessary.

1.3.2 When placed in the work reinforcement shall be free from dirt, oil, grease, paint, mill-scale and loose or thick rust.

1.4 Shop Drawings

Shop drawings are specified in the GENERAL SPECIFICATIONS.

4-2 /8 Technical Specifications4-2: Reinforcement

PART ll:PRODUCTS

2.1 Materials

2.1.1 General

All mild steel bars shall be plain round bars and shall conform to the following specifications and have a yield stress not less than 235 N/ m m 2 mm2 . (The yield stress is defined as the stress below which not more than 5% of the test results fail.) Steel Grade SR 24 shall conform to the latest edition of TIS 20 or ASTM A615.

All high yield steel bars shall be deformed bars and shall conform to the following specifications and have a characteristic yield stress not less than 390 N/mm2 or 490 N/mm2 for SD40 and SD50 respectively. Steel Grade SD 40 and SD 50 shall conform to the latest edition of TIS 24 or AASHTO M31.

Where welding to reinforcement bar is required steel bars shall be weldable grade conforming to the requirements of ISO 6935-2 or ASTM A706M, carbon content of 0.24, with maximum carbon equivalent not more than 0.52 percent by mass.

Where the yield strength (fy) of vertical reinforcing bar in existing columns or piers, exposed in accordance with Section 4-15, is higher than 60,000 psi or 420 MPa, additional vertical bars of grade SD-40 shall be installed via bonding in predrilled holes in concrete of the proposed structure in the rate of 1.2 times of the required quantity. The additional bars shall be arranged to each face of member in the former installing proportion. The additional bars so arranged shall be glued by approved epoxy resin and bonded to predrilled concrete hole in such a way that the bars are yielded by in-place pull- out test prior to the bond being failed. The Contractor shall propose the method of construction for the approval of the Engineer before the commencement of work.

2.1.2 Bar Reinforcement

Bar reinforcement for concrete shall conform to the requirement of Thai Industrial Standard (TIS) for Steel Bars for Reinforced Concrete:

Deformed Bars. Bars to quality level 2 and 3 shall be used in the works. Quality level 2 bars, identified by the symbol SD 40 shall be rolled deformed bar with longitudinal and transverse ribs, characteristic yield stress not less 390 N/ m m 2 mm2, and shall generally be used throughout the Project.

When quality level 3 bars, as identified by symbol SD 50 are used, they shall be deformed bars as above but of higher characteristic yield stress not less 490 N/ m m 2 mm2.

Deformed bars with diameter 32 mm and greater shall be steel Grade SD 50 while the other sizes of deformed bars shall be steel Grade SD 40.

The use of cold twisted bars and rail steel bars shall not be permitted. Steel for all bars shall be produced by open hearth, basic oxygen or electric arc furnace methods, unless otherwise specified in the Drawings or in the Special Provision.


2.1.3 Wire and Wire Mesh

Wire shall conform to the requirements of AASHTO Standard Specification M32 – Cold Drawn Steel Wire for Concrete Reinforcement.

Wire mesh shall conform to the requirements of AASHTO Standard Specification M55 - Welded Steel Wire Fabric for Concrete Reinforcement.

2.1.4 Bar Mat Reinforcement

Bar mat reinforcement for concrete shall conform to the requirements of AASHTO Standard Specification M54 -– Fabricated Steel Bar or Rod Mats for Concrete Reinforcement.

2.1.5 Binding Wire

Reinforcement binding wire shall be best black annealed milUd steel wire, approximately

1.625 mm in diameter minimum according to TIS 138 1. 38.

Unless otherwise permitted by the Engineer, all intersecting bars shall be tied together and the ends of the tying wire turned into the main body of the concrete.

2.1.6 Cover Blocks

Cover blocks shall be as small as possible consistent with their purpose, designed not to overturn or deform when the concrete is placed, and of a shape acceptable to the Engineer. If made of concrete they shall have 1O mm aggregate size and the same mix proportions so as to produce the same strength as the adjacent concrete. Wire shall be cast in the block for the purpose of tying it to the reinforcement.

2.1.7 Epoxy-Coated Rebars

Deformed and plain steel reinforcing bars at link slab or closure strip details shown on the Drawing shall be received epoxy-coated by electrostatic spray method, conformed to the requirements of ASTM A 775 M. The coating thickness after curing shall not be less than 300µm.

2.2 Ordering Material

The name of the proposed supplier (or suppliers) of the reinforcement shall be submitted as soon as possible to the Engineer for his approval. The Contractor shall submit necessary information concerning the supplier as requested by the Engineer. Copies of orders placed shall be submitted to the Engineer.

The Contractor shall furnish the Engineer with copies of the manufacturer's certificates of tests for the steel reinforcement to be used in the Works. These certificates shall include all relevant data on the steel, i.e. breaking strength, yield strength, characteristics on elongation, chemical composition etc. for approval by the Engineer. No steel shall be delivered without certificate guaranteeing the yield stress.


2.3 Conformity Tests

All reinforcement shall be bundled by size with separation of casts and bundle shall be identified by durable tags bearing the manufacturer's name or mark, the reinforcement size or designation and the cast mark as appropriate. Upon delivery to the Site, the Engineer may require the Contractor to carry out conformity tests on further samples at a laboratory nominated by the Engineer.

Approximately one sample shall be tested from each 50 tons of reinforcement delivered to the Site. Any steel which as a result of the conformity tests, does not comply with the foregoing specification, will be rejected and shall be removed from the Site without delay.

PART Ill: EXECUTION

3.1 Cutting and Bending

3.1.1 Bars shall be cut and bent cold, unless otherwise permitted by the Engineer, to dimensions and shapes as shown on the Drawings. Bars partially embedded in concrete shall not be site bent except as shown on the Drawings or with the approval of the Engineer.

3.1.2 Stirrups and tie bars in Grade SR 24 shall be bent around a pin having a diameter not less than four times the minimum bar diameter.

3.1.3 Bends for other bars shall be made around a pin having a diameter not less than 12 times the minimum bar diameter except for bars larger than 30 mm in which case the bends shall be made around a pin of eight bar diameters.

3.1.4 Hooks shall conform to American Concrete Institute Standard Building Code

Requirements for reinforced concrete ACI 318, or as shown on the Drawings.

3.1.5 High tensile steel reinforcement bar must not be re-bent or straightened on site.

3.2 Placing, Supporting and Fastening

3.2.1 All bar reinforcement shall be placed, supported, and secured before the beginning of concreting operations. The reinforcement shall be checked and approved by the Engineer before placement of concrete begins. The relation between the minimum spacing of bars and the maximum size of aggregate shall be as follows unless otherwise stated by the Engineer. The minimum clear distance between two bars in a beam or column shall not be less than the diameter of the bar or 25 mm or the largest size of aggregate plus 1O mm whichever is the greatest. Laying or driving bars into the concrete after placement shall not be permitted.


3.2.2 All horizontal reinforcement shall be supported on metal supports or mortar blocks of approved shape with the wires embedded in them. Supports, which are in contact with the external face of the concrete will all be mortar blocks. The use of small stones or wood blocks shall not be permitted.

3.2.3 The reinforcement shall be held securely in place at the exact position and at the exact spacing as indicated on the Drawings by the use of wire ties at bar intersections, supports and spacer blocks. Wire ties shall be securely tied and folded so that they do not project beyond the planes formed by the reinforcing bars. The adequacy of the supports and ties to secure the reinforcement properly shall be subjected to the approval of the Engineer.

3.2.4 The number, size, form and position of all steel reinforcing bars, ties, links, stirrups and other parts of the reinforcement shall be in exact accordance with the Drawings. They shall be kept in the correct position and with the required cover without displacement during the process of compacting the concrete in place in a manner approved by the Engineer. The Contractor shall provide all necessary distance pieces and spacer bars to maintain the reinforcement in the correct position. The type of distance pieces shall be subject to the approval of the Engineer.

3.2.5 Any tie, link or stirrup connecting the bars shall be taut so that the bars are properly braced and the inside of hooks and bends shall be in actual contact with the bars around which they are intended to fit.

3.3 Splicing

3.3.1 No splicing shall be made in reinforcement except where shown on the Drawings and/or shop drawings approved by the Engineer. Splicing of steel bar reinforcement shall be made in accordance with ACI 315.

3.3.2 Reinforcement shall be furnished in the lengths indicated on the Drawings. Lap splicing except where shown on the Drawings shall not be permitted without written approval from the Engineer. If additional lap splices are used the additional weight occasioned by such lap splices shall not be included in the measurement of reinforcement for payment.

3.3.3 All splices for high yield steel bars shall have a lap length of not less than 40 diameters of the smaller bar or as shown on the Drawings. All splices for mild steel bars shall have a lap length of not less than 40 diameters of the bars when hook is used and 50 diameters for bars without hook or as shown on the Drawings. Lap splices shall generally be located at points of minimum tensile strength. Except where otherwise shown on the Drawings lap splices shall be made with the bars placed in contact and wired securely together.

3.3.4 Welding of reinforcing steel may be done only if approved in writing by the Engineer.


Before the Engineer approves of welding, the Contractor shall submit such samples as the Engineer may require for testing and make allowance for the time elapsing before test results are available. Welding of high yield bars in places of variable tension shall not be permitted. Welding shall be done only on the weldable reinforcing steel only.

3.3.5 Welding of reinforcement steel and steel parts shall conform to the Structural Welding Code AWS 01.4 of the American Welding Society and applicable special provisions and shall only be done where shown, specified, or permitted by the Engineer. Every welder shall posses a welding certificate issued by recognized institutionsapproved institute. The certificate must be available for inspection by the Engineer.

3.3.6 Mechanical couplers may only be used with prior written approval of the Engineer and shall in general comply with ACl-318 M-08 Article 12.14.3 and the requirements below.

All couplers shall be of a type which are simple to be installed and can be confirmed by quick visual inspection. Couplers shall be correctly installed and achieve the required full strength connections. Couplers for tension joint shall develop full tensile strength of the bar away from the joint. Threaded system shall have prallel metric threads to facilitate fixing with no reduction in cross-section area at the joint location. Tapered thread system are not permitted.

All couplers shall be cleanly stamped with the batch or heat number. This number shall be traceable to the origin cast. The relevant material mill certificates for couplers are to be submitted with each delivery. The certificates shall show the salient material properties of the couplers.

For threaded systems every prepared bar end shall undergo a load test prior to leaving the supplier's workshop. Minimum test loading shall be to 75% of the characteristic strength and maximum 100% of the characteristic strength. A positive indication shall be stamped on the rebar to indicate that this operation has been carried out.

Any special tools and equipment required for use with the couplers shall be as recommended by Manufacturer for the accepted couplers. Such tools and equipment shall be serviced and calibrated at intervals recommended by the Manufacturer. The Contractor shall retain documentation in respect of servicing and calibration for inspection by the Engineer.

Each couplers shall be visually examined prior to use to ensure the absence of rust and of any foreign material on the inside surface. All completed couplers shall be inspected and verified in accordance with the Contractor's accepted method statement. Couplers that do not meet the acceptance standards shall be completely removed and the bars re- connected as required.

The Contractor shall submit to the Engineer for his acceptance particularly the proposed materials and methods of mechanical couplers installation including the manufacturer's literature.

3.4 Substitution

3.4.1 Substitution of different size bars shall be permitted only with specific authorization by the Engineer. If steel is substituted, it shall have a cross-sectional area equivalent to the design area,


or larger. The additional weight occasioned by such substitution shall not be included in the measurement of reinforcement for payment.

3.4.2 The Contractor shall provide, in the case of substitutions, at his own expense and to the approval of the Engineer working drawings of all reinforcement accompanied by bending schedules and copies of orders placed for bars.

3.5 Bundled Bars

Where bundled bars are specified on the Drawings, they shall be placed in the closet possible contact to act as a unit and shall be tightly bound by binding wire, at centers of not more than 24 diameters of the smallest bar in the bundle.

3.6 Projecting Reinforcement

Where shown on the Drawings, steel reinforcement shall be left projecting for the purpose of bonding or splicing on subsequent work. Care shall be taken to avoid damage to the bars after they have been set and any damage to the bars or their setting shall be repaired by the Contractor at his own expense.

Projecting reinforcement which, in the opinion of the Engineer, requires protection from corrosion shall be coated with cement slurry or other materials as directed by the Engineer.

Where shown on the Drawings, dowels shall be wrapped with bituminous felt or other approved material to prevent bond.

Projecting vertical bars which might be hazardous to human health shall be adequately shielded.

3.7 Cleaning and Inspection

Immediately before concreting, the reinforcement shall be examined for accuracy of placing and cleanliness and corrected if necessary.

No concreting shall take place before inspection and approval of the reinforcement by the Engineer.

3.8 Cover to Reinforcement

Unless otherwise indicated on the drawings or approved by the Engineer, the concrete cover to the reinforcement nearest the surface shall not be less than:

top bars in slabs = 50 mm

bottom bars in slabs = 38 mm


main bars inall other structures = 50 mm

stirrups, links and ties in all other structures = 38 mm

END OF SECTION

section 4-2 reinforcement

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