In late 2018, the University of Melbourne contacted Hanson and suggested a pilot program of using waste materials in concrete, specifically waste glass. 18 months later, Hanson recently completed their first pour using recycled glass in concrete.
Traditionally, concrete is made from a combination of cement, sand and aggregate. To improve sustainability outcomes and increase the use of recycled materials Hanson incorporated Alex Fraser’s Recycled Glass Sand into the mix.
Manufactured from recycled glass material recovered from kerbside collections, the recycled sand is apt for a range of applications and is already widely utilised as the ideal alternative for quarried sand in asphalt, roadbase and bedding.
Funded by Sustainability Victoria and collaborating with North West Program Alliance and VicRoads, the trial is an important step forward for the state towards more sustainable infrastructure. Metropolitan sand quarries are fast depleting, making recycled construction materials essential to meet the demands of Victoria’s infrastructure works.
In a cubic metre of concrete, there is usually a little less than a tonne of sand. By replacing this with recycled glass sand, the scarce natural resources can be preserved.
VicRoads specifications for concrete are aimed at structural components, such as support beams and uprights. This trial aimed to achieve improvements to a stretch of pavement in a recently completed level crossing removal project.
Hanson’s Business Development Manager Bruce Ryan joined them in early 2019. He said that there was a great deal of preparation by all parties to get this trial off the ground.
“The University of Melbourne managed the early testing process; testing on five per cent recycled glass sand, washed and unwashed; and 10 per cent recycled glass sand, washed and unwashed. We’ve used the 10 per cent mix for this trial.”
The concrete was poured as part of the High Street, Reservoir Level Crossing Removal Project on March 18, and is sectioned to include a stretch of concrete incorporating 10 per cent unwashed glass sand, 10 per cent washed glass sand, and a control.
On the day of the pour it was determined that a little more water needed to be added to the mix. Bruce said there are some unknowns regarding the impact sugars or salt residue in the recycled glass may have on the pavement performance.
“Sugar is a natural retardant for cement. Starting with a limit of 10% recycled glass sand, we were confident that the concrete would successfully set. We’re now look forward to getting back there in six months to see how it has held up, and if there is any impact.”
Hanson also completed lab tests on the trials, testing alkali-silica reactions as this can cause concrete to lose strength over time.
Bruce said that even though there could be some sugar and salt residue in the concrete, there was no odour.
“There’s definitely no smell in the concrete pour. Some people say that recycled materials can emit an odour, but this definitely doesn’t,” he said.
Hanson is confident that this is the start of many future projects incorporating recycled glass sand into concrete, especially since the release of Victoria’s Recycled First initiative encouraging the increased use of recycled materials in major transport projects.