Something rotten in the state of concrete

Buried away in a story on substandard concrete being supplied to 70 sites in Auckland are a few clues that the building industry sector is heading for another disaster.

New Zealand’s largest publicly listed company Fletchers via their subsidiary Firth is being forced into cleaning up the mess caused by dodgy business practices or quality control failure.

In a story today titled Costly repairs for motorway – Remedial work on Waterview ramp to fix faulty concrete will start later this year.

Lets say that again slowly. Concrete supplied to 70 building sites was sub standard.


Investigations are being carried out into weak, substandard, faulty Firth concrete supplied to the $1.4 billion Waterview Connection.

The Well-Connected Alliance building Waterview and the NZ Transport Agency, which will own it, are involved in the work.

A spokeswoman yesterday said: “The NZ Transport Agency and the other organisations in the Well-Connected Alliance are still investigating what repairs will be needed, and how they will be carried out.”

The most interesting part of the story.

“A whistle-blowing contractor working on Waterview estimated it would take a month to demolish the work. The contractor said repairs probably would not hold up the huge tunnel and motorway interchange job.

“But I’m guessing it would take a month so it’s going to cost someone a lot of money,” he said, referring to Ramp 4 retaining walls, footpaths and crash barriers.

The worker said a concrete beam also contained weak concrete.

“It’s a very, very big structural beam across Ramp 4 and almost holding the whole bridge up. That has to be demolished.”

None of the companies involved in the issue front-footed it by revealing how Firth had made then sold the faulty concrete. The worker said the concrete was less than half the strength it should have been.

Questions were put to Fletcher Building, which owns Firth, about these claims, but they were not directly answered by the company.”

The italics are mine. The implication is that unless the whistle blower had mentioned it that the companies involved on billions of dollars worth of construction projects would have just kept quiet.

As I understand it what causes faulty concrete is “Not enough cement had been added to the mix so the concrete would never harden to the required strength” and “Tests were carried out on the big sites to ensure engineering standards were met.”

I’m not an expert on concrete at all, but surely it is much better to have quality tests when the concrete is actually being made and not a month or so after it has been delivered to building sites and used to build important stuctures?

If the concrete is tested AFTER being poured on site then it can only be remedied by demolition and rebuilding. It’s not like building a motorway is cheap.

The Waterview Connection project is $1.4b. The science building project at University of Auckland is $200m and there are all those other projects affected by this giant screw up.

It is good that faulty concrete has discovered but it does seem like finding out your concrete will never harden to the required standards weeks AFTER it has been used in a building project is just plain stupid.

In many (if not most) cases concrete is being used as a structural element in the building process. Everything that is built on those concrete foundations will need to be reworked in some way.

I wonder if new buildings in Christchurch and Wellington – especially are safe – given that the implication of this story is thanks to a whistle blower who called it when the management did not.

P.S I’m told that the (concrete) ingredients are measured at the mixing stage and there was a fault in measuring the cement levels at mix time. It would be good to know about in country that suffers from earthquakes and with hundreds of leaky buildings still out there. It’s not like public confidence in the building sector is solid at all.

Update: 12 May – I spoke with a civil engineer about this issue. He says he was surprised that the company fessed up. ( They didn’t – it was a whistle blower.  A bad sign in my view.) Also that large works tend to be over-engineered to provide a safety margin. Besides tests on concrete process at the plant there is a test at 7 days and then again at 28 days on site. He said that fixing any large works like the Waterview ramp would be a major undertaking. If concrete is at 50% or less of the required density then that is not a simple process error. Lets hope this is not a systemic hidden issue in the building sector.