Team installing sensors during construction of trial site

Researchers from VU’s College of Engineering and Science are continuing world-first research exploring the use of recycled materials as backfill in utilities trenches metres below busy city roads.

The current practice is to use precious natural aggregates for backfill that needs to be excavated, crushed and often trucked in from great distances.

Dr Ehsan Yaghoubi, Professor Sam Fragomeni and Associate Professor Maurice Guerrieri have received a Sustainability Victoria grant to look at using an alternative of crushed recycled concrete aggregates from demolished structures, such as buildings and bridges, that normally go to landfill.

This project follows the team’s successful delivery in 2020 of another Sustainability Victoria-funded project at a demonstration site in Wyndham. It showed that a blend of recycled plastic, glass and tyres with self-compacting properties could serve as backfill in ‘non-trafficked’ trenches.

“In the new project, we are looking at stronger materials that can perform well when roads with moving vehicles are built on top of the trenches,” said Dr Yabhoubi.

These world-first solutions could keep tonnes of demolition rubble, as well as waste plastic, glass and tyres, out of landfills. It is estimated about 7000 tonnes of waste that would otherwise go to landfills could be used for every kilometre of pipeline.

Recycling Victoria has a target to divert 80% of wastes from landfills by 2030.

“The latest project is important as rapid urbanisation is creating more roads and the percentage of sewer pipelines constructed beneath areas with traffic is increasing,” Dr Yaghoubi said.

This project is currently at the laboratory investigation stage before the researchers design, construct and develop instrumentation for a full-scale trial site in a possible future project.

VU committed to the circular economy

Both projects are conducted through a collaboration between VU and the University of Melbourne, together with Greater Western Water and Ground Science as industry partners.

VU’s geotechnical and pavement laboratories at its Footscray Park Campus were refurbished for the projects, including new state-of-the-art facilities for performance-testing of the recycled blends proposed in the new project.

Dr Yagyoubi said the project demonstrates VU’s commitment to the circular economy by proving the suitability of recycled materials to build the infrastructure for essential services.

The team’s latest project was awarded VU’s Vice-Chancellor’s Award for innovation in 2021.

This grant for the project is supported by the Recycling Victoria Research and Development Fund – Materials.