NON-COMPLIANT CONCRETE REINFORCEMENT
From recent news reports you will be aware that MBIE are investigating non-compliant concrete reinforcement (bars and mesh) in the New Zealand market. This involves imported reinforcing steel and more surprisingly New Zealand sourced steel.
There are two ways reinforcing steel may be non-compliant:
- It is not manufactured to meet the NZ Standards (or equivalent)
- It may be manufactured to Standards but is not appropriately tested for conformance to the NZ Standards
Both of these are undesirable and both provide an undetermined level of conformance. This is normally overcome by requiring some level of verification based on testing of conformance with the Standards. In New Zealand and Australia these Standards for steel reinforcing or steel prestressing are:
- AS/NZS 4671:2001 Steel Reinforcing Materials, or
- AS/NZS 4672.1:2007 Steel Prestressing Materials - General Requirements, and
- AS/NZS 4672.2:2007 Steel Prestressing Materials - Testing Requirements
The problem is that AS/NZS 4671 (Appendix A) offers a number of ways of verifying conformance, some being better than others. However Product Certification seems the most robust way as it is an independent assurance and verification scheme. This involves independent sampling and testing and subsequent verification, along with requiring the manufacturer to maintain production quality control.
Credible Certification would be preferably provided from an independent New Zealand or Australian TELARC/NATA laboratory, testing chemical composition and physical properties of all reinforcing steel. There may be other acceptable testing laboratories, but these would need to be assessed very carefully. All testing will be in compliance with Clause B7 of AS/NZS 4671 or Clause 12 of AS/NZS 4672.2, including frequency of sampling and testing.
Australia has been trying to grapple with the presence of some substandard imported reinforcing steel in their market for some time. To counter the non-conformance the Australian Certification Authority for Reinforcing Steels (ACRS) created an independent certification scheme for reinforcing steel and structural steel by product and manufacturer/processor. This certifies compliance with Australia/New Zealand Standards. This scheme uniquely makes compliant manufacturers (from all over the world including New Zealand) who have joined the scheme visible to everybody on the ACRS website. So you can quickly find compliant manufacturers and compliant products. ACRS seems to be a robust scheme, however it is possible for other independent testers to provide compliance information which may be acceptable as an alternative, but consider them carefully.
There is no easy answer to this issue. The designer needs to know that the reinforcing complies with the Standards and for that the designer needs to have confirmation and verification. Masterspec have updated and modified the concrete sections and related sections involving reinforcement, with stronger clauses addressing both compliance and confirmation. These clauses will still need to be modified to suit specific project needs.
Masterspec will investigate the need to further tighten up the compliance requirements of structural steel. More on this next month.
ACRS Web site: www.steelcertification.com
MBIE media released: MBIE not concerned product a safety risk for houses
Building Controls Update 178: Conformance of reinforcing steel mesh (MBIE)
Building Officials Institute article: Inquiry under way into steel mesh testing (BOINZ)