Clause 17.2 Material and Construction Requirements for Reinforcing Steel

Section 17 replaces Section 19 in the previous edition of AS3600.

17.2.1 Materials
17.2.1.1 Reinforcement

Reinforcement shall be deformed Ductility Class N bars, or Ductility Class L or Ductility Class N welded wire mesh (plain or deformed), except that fitments may be manufactured from Ductility Class L wire or bar, or plain Ductility Class N bar.

All reinforcement shall comply with AS/NZS 4671.

Dowel bars for pavements are not specifically mentioned in AS3600-2009. They are generally cut from Grade R250N plain round bars.

Designs using fibre reinforcement, either steel or plastic, are not covered by AS3600-2009.

17.2.1.2 Protective Coatings

A protective coating may be applied to reinforcement provided that such coating does not reduce the properties of the reinforcement below those assumed in the design.

17.2.2 Fabrication

(a) Reinforcement shall be fabricated to the shape and dimensions shown in the drawings and within the following tolerances-

(i) On any overall dimension for bars and mesh except where used as a fitment.

(a) For lengths up to 600 mm............................................................–25, +0 mm
(b) For lengths over 600 mm.............................................................–40, +0 mm

(ii) On any overall dimension of bars or mesh used as a fitment.

(a) For deformed bars and mesh......................................................–15, +0 mm
(b) For plain round bars and wire......................................................–10, +0 mm

(iii) On the overall offset dimension of a cranked column bar..... –0, +10 mm

(iv) For the sawn or machined end of a straight bar intended for use as an end-bearing splice, the angular deviation from square, measured in relation to the end 300 mm, shall be within.......................................................................................................2º

(b) Bending of reinforcement shall comply with Clause 17.2.3.

(c) Welding if required shall comply with AS 1554.3. Tack welding not complying with that Standard shall not be used.

17.2.3 Bending
17.2.3.1 General

Reinforcement may be bent either:

(a) Cold, by the application of a force around a pin of diameter complying with Clause 17.2.3.2, so as to avoid impact loading of the bar and mechanical damage to the surface of the bar; or

(b) Hot, provided that:

(i) The steel must be heated uniformly through and beyond the portion of the bend;
(ii) The temperature of the steel must not be allowed to exceed 600º C,
(iii) The bar must not be cooled by quenching, and
(iv) If during heating the temperature of the bar exceeds 450º C, the design yield strength of the steel after bending shall be taken as 250 MPa.

Designs using fibre reinforcement, either steel or plastic, is not covered by AS3600-2009.

The temperature can be controlled by thermal crayons, etc. Quenching would totally alter the crystal structure.

Reinforcement which has been bent and subsequently straightened or bent in the reverse direction shall not be bent again within 20 bar diameters of the previous bend.

This distance is intended to keep cold working from the original bending zone separated from additional bending.

Reinforcement partially embedded in concrete may be field bent (ie, in situ) provided that the bending complies with items (a) or (b) above, and the bond of the embedded portion is not impaired thereby.

The greatest need encountered with this bending is to control the bend curvature without notching the bar, and to prevent spalling of the concrete, particularly in thin members. It is very rare for a site bent bar to be bent correctly, with bars often being pulled out against the edge of the concrete or bent with a pipe. These methods of bending severely notch the bar and can cause bar breakage.

17.2.3.2 Internal Diameter of Bends or Hooks

The nominal internal diameter of a reinforcement bend or hook shall be taken as the external diameter of the pin around which the reinforcement is bent. The diameter of the pin shall be not less than the value determined from the following as appropriate:

(A) For fitments of -

(i)  500L  bars.............................................................................3d_b;
(ii) R250N bars..........................................................................3d_b; and
(iii) D500N bars.........................................................................4d_b

Clause 8.2.12.4 requires a 4 db pin be used for all beam ligatures

(b) For reinforcement, other than specified in Items (c) and (d) below, of any grade.....................................................................................................5d_b

(c) For reinforcement, in which the bend is intended to be subsequently straightened or rebent, of

(i) 16 mm diameter or less......................................................4d_b;
(ii) 20 mm diameter or 24 mm...............................................5d_b; and
(iii) 28 mm diameter or greater..............................................6d_b

Any such straightening or rebending shall be clearly specified or shown in the drawings.

(d) For reinforcement that is epoxy-coated or galvanized, either before or after bending, of

(i)  16 mm diameter or less...............................................................5d_b;
(ii) 20 mm diameter or greater.........................................................8d_b

17.2.4 Surface Condition

At the time concrete is placed, the surface condition of reinforcement shall be such as not to impair its bond to the concrete or it’s performance in the member. The presence of millscale or surface rust shall not be cause for rejection of reinforcement under this clause.

Rust and millscale, of themselves, do not adversely affect bond. Dirt and oil are much worse.