By Steve Cook
DOZENS OF new structures could be under threat from a catastrophic form of â€˜concrete cancerâ€™ â€“ with industry insiders warning the problem could end up costing millions of dollars over time.
The company at the centre of the concrete cancer controversy is Drymix, who control about five-percent of the $400 million-a-year cement market.
The company also has exclusive contracts with the likes of Mitre 10.
In January, February and March this year, Drymix imported tens of thousands of tonnes of cement which, according to their own test samples, failed to meet recognised industry standards.
The suspect cement â€“ which has a higher than accepted alkali content – has since been used in potentially hundreds of building projects right across the country, including the $40.6 million Manukau District Court upgrade.
There are growing fears those structures could be vulnerable to deterioration caused by whatâ€™s commonly known as concrete cancer.- a reaction between the alkali and aggregate in the concrete.
Concrete cancer is caused by unusually high alkali levels in cement combined with moisture in the concrete and a reactive form of silica in the aggregate.
When this occurs it can end up causing serious expansion and cracking in concrete, resulting in major structural problems further down the track.
Overseas, especially in earthquake-prone areas, there have been cases where structures have been entirely demolished because of concrete cancer. Â Read more »