review of reinforcment standard AS/NZS4671  

At present AS/NZS4671 (Steel Reinforcing materials) and AS4672 (Prestressing steel materials) are being reviewed by a combined NZ and Australian Committee. I am the ConcreteNZ representative on the committee. The following is brief report from the kick off meeting and a request for feedback.  Please email me on any comments you may have at dene.cook@fb.co.nz

AS/NZS4671

The main emphasis for the review is to get greater clarity on the information that should be provided on material certificates by either producers (manufactures) of reinforcement, and those that process reinforcement (typically steel fabricators).

Clearly producers need to be able to demonstrate compliance with AS/NZS4671. If a processor simply takes straight bar and then fabricates into stirrups, standard bend etc, then a fabricator has not modified the input material properties of the reinforcement and so can rely on the producers material certificates.  However, if material is straightened from coil to effectively a straight bar, before converting to stirrups and standard bends, then the producer will need to demonstrate that the coil after it has been straightened is compliant with AS/NZS4671.  The issue is to get clarity of this using “Standards speak”.  When the draft comes out for public review I would appreciate feedback on how successful the committee has been at getting this point across.

Within the Standard 600, 650 and 750 Grades are proposed to be introduced. However this only applies to class N and L Grade.  Since NZS3101 mandates the use of class E, the change will have little impact in NZ.

One area I would request feedback is the idea of reducing the required uniform elongation for plain Grade 300 bars from 15% to 10%. Deformed Grade 300 bars would continue to be required to have a uniform elongation of 15%.  Plain (round) bars are typically only used for stirrups and as such the ductility demands are often only modest hence reducing the ductility targets should be acceptable.  However I would like feedback of situations where engineers may be using Grade 300E plain bars in which high ductility demand is required.  I cannot think of any situations but would like to canvas the industry to get other view points before submitting the proposal to the committee.  The reason for considering the modification is that obtaining 15% uniform elongation of coil straightened reinforcement can be technically demanding. . 

AS4672

The proposed changes to the prestressing standard are small (adding the properties of 15.7mm strand to a table). I had circulated these to the NZ industry before the meeting and all were comfortable.  The changes were approved at the meeting and a public comment draft will appear over the next few weeks.

The next committee meeting is the 28/29 June so it would be appreciated if feedback could be received before that date.

Dene Cook

dene.cook@fb.co.nz