Uncovered: More faults in steel testing

7:13 pm on 23 March 2016

More evidence of faults in the quality control regime for construction steel has been uncovered by RNZ News.

A worker spreads ready-mix concrete over steel mesh (file)

A worker spreads ready-mix concrete over steel mesh (file) Photo: 123RF

A certificate for an initial test of Steel & Tube seismic mesh has revealed it does not meet a key measure of strength.

The test numbers were well below the standard for ductility - or stretchability - demanded since the Christchurch earthquakes, so that slab floors of multistorey buildings and all houses can resist cracking in a quake.

The test was done by New Zealand and internationally-accredited laboratory SGS.

The test was of a single sheet of mesh, testing its ductility at four different spots. A pass meant it could be used in building work.

The test results were 6.8, 6.4, 4.9 and 3.6 percent.

The minimum required standard is 10 percent.

This sheet was from a batch of mesh that had already been passed by Steel & Tube's own in-house testing, with scores of 10.5, 10.5, 12 and 12.5 percent. It had been sold for construction use.

The independent lab report for ductility listed the single sheet as "DNC" or "does not comply".

That was a fail against the Australian New Zealand Standard 4671, that all steel reinforcing products must comply with.

However, this standard - which demands one test per batch of mesh, just like the SGS test - also provided for a second lot of more testing if the mesh failed. If it passed the second round, it could be used. If it failed again, it was to be scrapped.

This single sheet of mesh has not been tested a second time.

It is understood that SGS uses the same test that the Commerce Commission uses on mesh, and that this test was tougher than the one some steel processors use, which might include Steel & Tube.

Steel & Tube, asked about the poor SGS test results, said it was uncomfortable commenting based on third-hand information and a report it hadn't seen.

RNZ News has chosen not to provide a copy of the test certificate, redacted or otherwise, to Steel & Tube but had offered to talk the company through all the numbers on it.

The Ministry of Business, Innovation and Employment said, generally, if a first test fails, then more tests needed to be done to conclusively determine whether a product complied or not.

It said it would wait for other testing being carried out on mesh by the Commerce Commission, which it expected would include Steel & Tube.

People in the industry said a test like this on a single sheet was not definitive, and there could be variability with steel, though not usually this much.

However, they said for low numbers like this to come back was worrying and they thought it would be cause to order immediate further testing.

The Commerce Commission has ordered testing of seismic mesh from several companies. It could be a week before those results would be known.

The commission put a hold on the seismic mesh of two importers early this month, when it failed the ductility test, and those companies were still barred from the market.

Meanwhile, International Accreditation New Zealand said all 20 steel certificates it had investigated over 12 months after complaints triggered by the Christchurch rebuild had fallen short.

It found certificates falsely purporting to be from top testing labs and others with fabricated or incorrect results.

IANZ'S head Llew Richards issued a warning today prompted by RNZ's own case of dealing with steel bars imported from China by Steel & Tube that were below strength (See a correction here).

"I suspect Steel & Tube thought they were doing the right thing by getting a test certificate but it's not one that we would recognise at all.

"It is possible that the product could be fine, the thing is that you don't know. And when we've looked at the test reports we've often found that the claims have not been reliable at all."

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  • Steel and Tube says it has no lab for testing mesh
  • Legal action looms over steel mesh testing
  • Questions over quake mesh certification