Specification and Installation of Galvanized Reinforcement

 

Reinforcing bar such as that manufactured under the ACRS certification scheme meets the requirements of Australian Standard AS/NZS4671, Grade 500N. These properties are retained after galvanizing and are altered only marginally on bars bent prior to galvanizing.

 

Properties of galvanized Grade 500N bar

Tensile properties:         No change from ungalvanized condition

Bending properties:       No change from ungalvanized condition

Toughness:                   Similar to ungalvanized

 

Galvanizing pre-bent Grade 500N bar

Grade 500N reinforcing bar bent prior to galvanizing remains ductile, allowing straightening and re-bending. The following minimum diameters (for 90° bends) are recommended in AS3600 if subsequent straightening* of the bar is required. 

Up to 16 mm dia:                      5d

Greater than 20 mm dia:           8d

*Re-bending from these bend diameters may cause cracking of the galvanized coating.

Grade 500N bar that has been bent, galvanized and straightened in accordance with the above practices retains the full yield and tensile strength of the original bar. Tensile elongation may be slightly reduced, but still easily meets the requirements of AS/NZS 4671

 

Do not use heat for bending or re-bending

The use of heat for bending or re-bending galvanized Grade 500N or any other reinforcing bar should be avoided due to the possibility of the zinc coating causing liquid metal embrittlement. Similarly, should welding of galvanized bar be required, the galvanized coating should first be removed by pickling, grinding or grit blasting.

Where possible, bend after galvanizing

The galvanizing of straight bars is easier and more economical. Transport costs are lower, and special bend configurations cannot be lost or misplaced during handling and storage.

 

Bending, re-bending after galvanizing

Although the bendability of galvanized Grade 500N bar is only marginally altered from that of uncoated bar, to minimize cracking of the galvanized coating the following minimum bend diameters (for 90° bends) are recommended in AS 3600. 

Up to 16 mm dia:                       5d

Greater than 16 mm dia:            8d

 

Effect of bending on the coating

Some cracking or flaking of the galvanized coating may occur at bends using smaller diameters than those recommended above.  Any damage to the galvanized coating should be repaired using a suitable zinc-rich paint in accordance with AS/NZS 4680.  Cut ends of galvanized bars should also be repaired.

 

Specifying galvanized reinforcement

Reinforcing steel should be specified to comply with Australian Standard AS/NZS 4671 “Steel Reinforcing Materials” and galvanized in accordance with AS/NZS 4680 ‘Hot-dip galvanized (zinc) coatings on fabricated ferrous articles’, and GAA’s standard specification for hot-dip galvanized steel.