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Laura Valic


From the ashes

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You’ve heard of engineered stone and engineered timber, but have you heard of engineered rock? The scientifically tested material, developed in Australia by builder and architect Maroun Rahme, is decades in the making and a sustainable product that comes with a whole range of building benefits.
Engineered rock is an apt description for the masonry block produced by Nu-Rock Australia because, despite appearances, the product isn’t made from natural resources like some of its counterparts – brick and concrete. 

While others have tried to merge waste into building materials, it appears none have taken it quite so far as Maroun Rahme. The architect and second generation builder – who can also claim technologist and block manufacturer to his growing list of credentials – felt some sustainably marketed products, which claimed to incorporate around 30 per cent of waste in their makeup, fell short of their potential. 

Maroun’s passion for sustainability and innovation drove him towards a highly ambitious goal of creating a building product that didn’t require precious and finite resources to produce, and included up to 95 per cent waste material – three times as much as other alternatives. 

Mike Retter, Director at Nu-Rock Australia as well as a long-term friend for 45 years, has watched and been part of Maroun’s innovation journey. He says Nu-Rock is far from being an overnight success: ‘Maroun first conceived the idea of Nu-Rock technology while building large homes with sandstone blocks in Sydney. The development process was spread over many years, and was both exhaustive and academically robust’.

Nu-Rock is made from a by-product of power plant stations

To get to the composition that Maroun envisaged, a significant amount of research and development was necessary. In this he was assisted by a number of institutions, including the CSIRO and universities, such as UNSW. The end result? A lightweight masonry product (approximately 9kg) made from a by-product of power plant stations – coal ash – and chemical binding agents. It’s strong, durable and offers a range of benefits, including good thermal insulation.

‘The lighter weight is a real advantage for brick and block layers because you can increase your production and move onto another project,’ Mike explains. ‘Builders love the speed walls can be built, and the current price advantage offered by Nu-Rock provides them with a much needed profit margin. For homeowners, houses constructed with Nu-Rock are warm in winter and cool in summer, reducing the need to rely on heating and cooling systems.’ 

Along with a robust R&D process, Nu-Rock has also undergone rigorous testing, here and in the US, ranging from strength, leachability and water absorption to radiation and fire resistance. 

‘We had fire tests show that on the one side of the block 1000°C was recorded, but the other side was only 80°C. That’s still hot but not something that would burn down,’ he adds. ‘The exterior would turn black [in a fire], but to come back to a house that’s completely black that you can paint over is a much better outcome than coming back to a home where you’ve lost absolutely everything.’ 

The company even gave thought to what would happen to the product at the end of its life cycle. Nu-Rock Australia successfully performed tests to crush the blocks and make them into new products, which went into recent housing projects. In the future this means a building can be knocked down, the blocks crushed up and used again on the new project or repurposed for another function. 
Maroun Rahme
With Nu-Rock exemplifying the HIA GreenSmart principles of sustainability and resource management, it was awarded the national 2020 HIA Australian GreenSmart Product accolade. However, for a material which the judges acknowledged as ‘a smart product with widespread potential’, it took a long time for it to be commercially viable in Australia. Mike says part of the problem was that Maroun’s thinking was just ahead of his time. Waste producers were reluctant to expend any effort beyond stockpiling or allow Nu-Rock to set up plants onsite next to the waste stream.

‘There was no perceived value or environmental imperative to recycle on an industrial scale back in the 1990s,’ he says. ‘All of the environmental science language that is commonly used and understood today was alien to most people.’ 

Maroun had better success overseas and Nu-Rock’s first 250,000 tonne block plant was established in Newcastle, South Africa in 1999. But when he returned to Australia it took much of the last 20 years to establish commercial opportunities with coal-fire power and steel companies on home soil. 

‘The lighter weight is a real advantage for brick and block layers’

Today, Nu-Rock is currently manufactured in all shapes and sizes at a small plant on Mt. Piper Power Station in NSW, and produces enough product to fill orders coming from its building projects. However, Mike says the business is on the cusp of greater things.

‘Nu-Rock is set to construct manufacturing plants in several locations around Australia, which will recycle both ash and steel waste into building products. They will have capacity to produce over 30 million building blocks per annum. All Nu-Rock plants will be located on waste sites to reduce truck movements and emissions; they also won’t require high levels of energy to operate.’

But he says the company won’t stop there. With its refined manufacturing formulas and processes, it will be able to produce other building products, for example, pavers, pipes, roof tiles, bricks, sea wall interlocking blocks, and ready-mix concrete. 

‘The waste producers are now showing a level of enthusiasm which we can’t fault – they’re doing everything they can to lend us assistance,’ Mike says. ‘We have half a billion tonnes of ash sitting on the ground in NSW alone. It’s a waste stream no one has been able to really utilise until now and we think it would be better put into buildings or other infrastructure than just sitting on the dirt.’ 

For Maroun, after years of working hard to educate government, industry and waste producers towards more sustainable thinking, the coming decade will surely be one of validation and a long-held dream finally being realised.

As Mike points out: ‘Nu-Rock is poised to bring lasting change to the Australian building product market, with the potential to transform the way people build and how industry manages its waste streams. In parallel with the vision for our Australian business, Nu-Rock will also expand overseas where billions of tonnes of ash and other waste streams remain unutilised. 

‘We hope to create a truly global solution for waste producers and [usher in] an exciting new era for sustainable builders’.