Glass mountain could improve concrete
James Cook University scientists have proposed a solution to Australia’s growing, unwanted stockpile of waste glass, as a ban on exporting the glass overseas looms.
The researchers have found the material can instead be used to improve the strength and durability of concrete.
Associate Professor Rabin Tuladhar from JCU’s College of Science and Engineering said Australia will start banning the export of waste glass for processing overseas by July this year.
“There has been pressure on developing countries to stop importing waste from the developed world. Australia’s government is considering a halt to all waste exports by 2022 and waste glass may be banned as early as July 2020,” said Dr Tuladhar.
He said Australia produces 1.5 million tonnes of waste glass annually, but only 40 percent of it is recycled.
“Recycling glass in Australia is very expensive. Many councils are currently crushing it and are storing it in warehouses without knowing what to do with it,” said Dr Tuladhar.
Working with Cairns Regional Council and Pioneer North Queensland Concrete, the scientists found that crushed glass can be used as a replacement for sand in concrete.
“The research showed that replacing up to 40% of natural sand with waste glass could improve the strength and durability of concrete,” said Dr Tuladhar.
He said one of the reasons glass was not used in concrete is the potential reaction between silica in glass and alkali in concrete, which makes concrete crack.
“Our research showed that when glass is crushed to the fineness of sand or cement it in fact reduces this reaction and further contributes to concrete strength.
“We also found if we pulverised waste glass to cement fineness, it develops binding properties and can be used to replace up to 10% of cement in concrete.”
He said the results show crushed glass can be a good substitute for natural sand and can be effectively used for producing non-structural concrete such as footpaths, bike ways and small precast elements like drainage pits and culverts.
Based on the research, Cairns Regional Council last year successfully trialled the use of crushed glass as sand replacement in the construction of a 100-metre footpath.
Dr Tuladhar said there were some hurdles to overcome before the waste stockpile found its way into construction products. He said the challenges mostly come from the contaminants in waste glass like paper and organic materials such as sugar. Modern glass crushing facilities such as those in the Townsville Material Recovery Facility have the capability to remove these contaminants to a certain extent.
“There was no sign of sugars in the crushed glass. We think this is because the glass waste we used from Cairns Regional Council was left outside in the rain and the sugars just washed away. This shows that simple washing of the glass can effectively remove any sugar content,” said Dr Tuladhar.
Dr Tuladhar said the team are working with Townsville City Council, the Waste Management company and local concrete companies to secure funding for a large scale trial using crushed waste glass in concrete in Townsville.
Video discussing the process: https://www.facebook.com/jcuconnect/videos/523277145202365/
Dr Rabin Tuladhar (Townsville)
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