Spray-on solution to earthquake strengthening
Spray-on "bendable" concrete sounds oxymoronic, but it's helping earthquake-strengthen the century-old toilets in Wellington's Courtenay Place as they are converted to a pizza bar.
The concrete, called Flexus, will also be used to shore up vulnerable older buildings in Christchurch.
Derek Lawley, general manager of Auckland firm Reid Construction Systems, said Flexus had polyvinyl alcohol synthetic fibres – sourced from Japan – bonded to the concrete to give it tensile strength.
"You can imagine the old brick buildings or blockwork buildings, under earthquake loads they're very brittle ... and they can end up as a pile of bricks.
"If we spray this material onto them, we can turn [them] into something that can bend and take the earthquake loads and keep the building together."
Strengthening unreinforced masonry buildings traditionally involved using reinforcing steel that was then covered with concrete about 10 centimetres thick, Lawley said. But a coat of Flexus could be just 1cm thick – meaning there was little change to the building – and it was often applied to the interior walls of historic buildings so their facades were not ruined.
Flexus was also used to make Sir Richard Taylor's Rugby World Cup sculpture in Wellington's Civic Square, create building facades, strengthen the iconic brick chimney at Auckland's Victoria Market, and would be applied to buildings in Christchurch, including ASB Bank in Rangiora and the historic pub Lyttelton Times Cafe, Lawley said.
The solution was relatively cost-effective, he said, costing roughly $50 a square metre for a 1cm coat.
The company began using Flexus, which is also being used on wharves and bridges, after developing it with researchers at Auckland University, and in Japan and the United States, and Lawley believed it was the first company in the world to commercialise its application.
Reid trains regional firms including Wellington company Aardvark Concrete Services to apply Flexus.
It is setting up a Christchurch reseller.
Before the Christchurch earthquakes in 2010 and 2011, councils had taken a relatively relaxed approach to earthquake strengthening. A lot more pressure was now being placed on building owners to ensure their properties were up to standard, Lawley said.
Reid had offices in Britain and Dubai, and was planning to take Flexus to those markets.
The conversion of the Courtenay Place toilets into a pizza, coffee and gelato bar is expected to be completed by the middle of the year.
- © Fairfax NZ News
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