New research reduces footpath footprint

Melbourne’s newly laid footpaths will leave much smaller carbon footprints than their predecessors, thanks to new research from Swinburne University’s Centre for Sustainable Infrastructure.

The research, undertaken in conjunction with the Municipal Association of Victoria (MAV), has found that the amount of recycled material in footpaths can be significantly increased, without adversely affecting path strength.

Currently footpaths and bike paths are primarily made up of crushed rock. But, in light of Swinburne’s research, the MAV has released changes to specifications that will allow councils to include up to 50% crushed brick and 30% crushed glass in their footpaths and shared paths.

This is a significant change, as previously specifications have only allowed footpaths and shared paths to include a total of 3% foreign content, such as glass, brick or metal.

According to lead researcher Dr Arul Arulrajah, the change in specifications will go a long way to reducing brick and glass stockpiles.

“As a community we recycle a lot of glass, but unfortunately not all of it is actually re-usable,” he said. “In Victoria alone, about 1.4 million tonnes of crushed brick and 250,000 tonnes of non-recyclable glass end up in landfill every year.

“By introducing crushed brick or crushed glass into footpaths and shared paths we’ll be making use of materials that would otherwise be dumped.”

Arulrajah said that the new specifications will also reduce our reliance on virgin quarried material.

“Traditional footpath and bike path-building materials are becoming scarce in some regions. The use of these materials is becoming unsustainable from both an environmental and cost perspective.”

Comprehensive tests were undertaken at the Centre for Sustainable Infrastructure Geotechnical Laboratory before the researchers recommended the changes to the MAV.

“We introduced different percentages of crushed brick and crushed glass into crushed concrete and rock,” Arulrajah said. “We then assessed the mechanical properties of each blend, including the particle density, particle size, plasticity, permeability and load-bearing capacity.

“We found that all blends with up to 50% brick and 30% glass matched or exceeded footpath and shared path strength and workability requirements. The crushed glass content may even be increased up to 50%, depending on the outcomes of future field trials.”

The Swinburne research project was funded by the Municipal Association of Victoria.

Earlier this week, a trial footpath that meets the newly adopted specifications was launched at Andersons Creek Road in Doncaster East.

This trial footpath saved approximately 12.6 tonnes of glass from entering landfill.