Researchers at Queensland’s James Cook University (JCU) have helped develop a concrete reinforced with recycled plastic, greatly reducing carbon dioxide emissions from the production of concrete.
The project was a collaboration between JCU PhD student Shi Yin and Queensland company Fibercon, with the aim of reducing some of the environmental costs of concrete by focusing on the material used to reinforce the concrete. At the 2015 Australian Innovation Challenge, this project took out the Manufacturing, Construction and Innovation category.
Concrete is a mixture of Portland cement, supplementary fly ash or furnace slag, aggregates, and water. It is the most widely used synthetic material in the world, but it is also one of the most environmentally unfriendly.
Its production involves mining and transporting the raw materials, heating them in a kiln to over 1400°C, and chemically turning limestone into clinker. These processes release huge amounts of carbon dioxide — so much so that the International Energy Agency estimates each kilogram of cement produced releases the same amount of carbon dioxide into the atmosphere. Concrete manufacturing is responsible for around five percent of global carbon dioxide emissions.
Yet, with the construction boom in Australia and in other countries, the use of concrete is set to increase, leading to industry interest in developing more environmentally friendly variants.
Much of the concrete used in construction today is reinforced with steel. However, steel itself can be very energy-intensive to manufacture and shape.
Dr Rabin Tuladhar, senior lecturer at James Cook University’s College of Science, Technology and Engineering, who supervised the research, says using plastic to reinforce concrete instead of steel can reduce carbon dioxide production by about 50%.
“However, with recycled plastic, you can save 50% more carbon dioxide than you could with virgin plastic,” Dr Tuladhar explained, “Because you are using plastic that has already been made and repurposing it.”
The researchers sourced recycled polypropylene fibres from industrial plastic wastes, then refined a melt spinning and hot drawing process to create plastic fibres that are strong enough to replace steel mesh in concrete footpaths.
The production of these plastics produces 90% less carbon dioxide compared to the equivalent steel.
As a proof of concept, JCU had a 100 m long footpath at its Science Place site constructed using the plastic-reinforced concrete. Additionally, Fibercon is using the material in its pre-cast concrete drainage pits.
Dr Tuladhar said the next phase of the research will examine enhancing the mechanical and bond properties of fibres using surface modification and looking into broader applications of recycled plastic fibres in other pre-cast concrete elements.