Just last year Downer Group, produced a 99 per cent renewable asphalt out of its Bayswater asphalt plant in Victoria, which incorporates such recyclables.
Thanks to these kinds of examples the effort to repurpose post-consumer material in pavement construction has garnered strong support within the roads and infrastructure sector. Thanks to some intelligent minds at Queensland’s James Cook University (JCU) and Queensland-based company Fibercon, concrete is getting a similar ‘green’ solution.
For three years JCU PhD student Shi Yin, his supervisor Rabin Tuladhar and the team from Fibercon have a ‘green’ concrete, which uses recycled polypropylene fibres taken from industrial plastic waste.
Now known by its commercial name Emesh, the technology serves as an alternative to using steel mesh in concrete footpaths.
Dr. Tuladhar says that steel mesh is often used in concrete footpaths to prevent shrinkage and cracking. In tropical climates such as that in North Queensland shrinkage cracks in concrete can be a common problem.
Plastic fibres have been used in lieu of steel mesh in concrete footpaths for nearly 15 years, however, utilising recycled industrial plastic rather than virgin plastic material has never been done before.
“With our improved melt spinning and hot drawing process we now have plastic fibres strong enough to replace steel mesh in concrete footpaths,” he says. The process developed by the JCU and Fibercon team sees the recycled polypropylene fibres drawn from the plastic waste and then cut into 50 to 60 millimetre strips. These can then be mixed with the material in a concrete truck on-site and ready to pour.
As no steel arrangement is required, less man-hours need be spent on construction and the use of recycled plastic waste makes the building product much more environmentally friendly, explains Dr. Tuladhar.
“Using recycled plastic, we are able to get more than a 90 per cent saving on CO2 emissions and fossil fuel usage compared to using the traditional steel mesh reinforcing,” says Dr. Tuladhar, referring to the environmental costs of manufacturing steel rather than recycling plastic. “The recycled plastic also has obvious environmental advantages over using virgin plastic fibres,” he adds.
Dr. Tuladhar says that in using recycled plastic there is a saving of nearly 50 per cent in CO2 emissions when compared to virgin plastic. Likewise, he asserts that recycled plastic in concrete has the same post cracking performance as concrete using virgin plastic material.
Overall, the ramifications of using this alternative and more environmentally friendly technology are significant. “We use a lot of concrete – it’s the most used construction material in the world,” he says. Concrete is also second only to water as the material most commonly used by humankind, with 24 billion tonnes poured globally every year. Using recycled industrial plastic will not only help reduce the stockpiling of said material, it will also help emphasise the value and benefits of using green-minded methods in concrete construction.
The genius of the technology was recognised most recently at The Australian Innovation Challenge awards in 2015. It won the Manufacturing, Construction and Innovation category at the prestigious awards ceremony.
Emesh has now been used on a number of footpaths at the JCU campus in North Queensland, including in the construction of a 100-metre-long concrete footpath and precast concrete drainage pits designed by Fibercon.
The technology is not suitable to replace steel in other concrete applications such as columns or beams, however the JCU and Fibercon team is exploring further applications. They are now talking to interested councils in Queensland about Emesh and are working with a precaster to trial the construction of concrete elements using the technology.
Dr. Tuladhar says the research is ongoing and the next phase will look at enhancing the mechanical and bond properties of the fibres using surface modification and looking into the broader applications of this simple, but genius innovation.
“It was a very small idea but the impact it can have is quite substantial. The plastic is already there, we’re just recycling it.”