Engineers have struck upon a new resting place for Victoria’s vast and ever-growing stockpile of waste glass, and it’s right under our feet.
About 250,000 tonnes of non-recyclable glass ends up in state landfill each year. In a plan to stem this tide, Swinburne University of Technology’s Centre for Sustainable Infrastructure is fine-tuning ways to use crushed glass in constructing roads, footpaths and bike-paths.
A road trial is under way at Laverton, under the direction of senior research fellow Binh Vuong, where engineers are testing nine 80-metre sections of road, each made of a different blend of crushed glass, recycled concrete, crushed rock and traditional quarry materials.
With the trial due to end next May, the research backers are keenly awaiting the results. They include VicRoads, which builds highways and freeways, the Municipal Association of Victoria, which represents councils that look after local roads, footpaths and bike paths, Alex Fraser Recycling Industries, which supplies recycled materials for road construction, and the ARRB Group (formerly Australian Road Research Board), where Associate Professor Vuong is a principal engineer.
What does crushed glass look like?
People tend to think of broken glass as being very sharp and shiny. But actually, with the crushing and sorting processes, manufacturers can crush the glass very, very finely for construction applications. It looks like fine sand.
Roads are traditionally made of quarry rock, right?
Yes. In Victoria, we are lucky that we have all the good quarry materials for making roads. For many years, VicRoads has been developing specifications for using such materials. In the past VicRoads hasn’t encouraged the use of non-homogeneous materials in roads because in the construction stage it can lead to problems — caused by different material densities, for example, which can lead to problems of material segregation and variable road compaction.
Where does glass come into it?
Recently we found new improved manufacturing and construction processes — with more control in construction using non-homogeneous materials, and with an improved compaction standard — to allow the use of more crushed glass.
What’s happening in the road trial?
I am overseeing the test program — from the design of the road sections, to the materials we use, to how the materials are handled and compacted. The purpose of that activity is to identify any issues during construction, because we need the material to be “at ease” in terms of workability, for use by various sizes of road constructors, from small to very large.
So you need the right blend?
Yes. Or there might be problems later on — for example, non-uniform pavements. Roads have to meet the requirements of the state. If you construct a one-kilometre road, even if you have one small section that ends up potholed, then we have to declare that whole kilometre of road sub-standard. So workability is very important. Also, we need roads to withstand at least 20 years of heavy traffic. So long-term performance and durability is critical too.
What will you do with your results?
Based on those observations, I will identify issues that might lead to changes in VicRoads specifications for road construction. Currently, VicRoads only allows up to 5 per cent crushed glass in road construction. But with all the trials at the moment and in future, we hope that we can increase that to 30 per cent in various applications. In addition, the finding from this research has contributed to other projects nationally.
What types of projects?
For the past two or three years, I and other researchers at Swinburne and ARRB Group have been working with local councils in various states on how to use recycled glass in footpaths. We have developed a new specification for footpaths for the MAV: for a low-traffic pavement like a footpath, the percentage of crushed recycled glass can increase substantially. We are also helping the Australian Food and Grocery Council to develop a national specification for recycled glass for use as engineering materials. So, a fair bit of work to do!
