The City of Darebin’s transformation of a Victorian hockey field shows what can be achieved by using recycled material rather than conventional methods.
At the end of its useful life, the KP Hardiman Hockey Field in Kingsbury needed a total reconstruction.
Oliver Nellessen, City of Darebin Senior Project Manager, says the council considered a range of options for the project, and while it was initially designed using virgin materials, it was seen as an ideal opportunity to try sustainable methods.
“Council went a step further when they heard of grants being available for the use of recycled materials. We revisited and re-engineered the project following the tender conclusion and the awarding of the contract,” Oliver says.
He says revisiting the project design set in motion what would become a successful example of using recycled material as part of the field’s resurfacing and surrounding constructions.
“We asked ourselves, what’s possible?” Oliver says. “We have an approved design, we have a tendered design, now let’s see how we could maximise the use of recycled materials and still achieve what we set out to achieve. Which was to create a brand-new hockey field that holds up to scrutiny, meets the applicable technical standards and Australian standards for projects, and is also certified by the hockey federation (FIH).”
Traditionally, the council had relied on conventional products for projects, including virgin quarry materials.
For the hockey field project, the council decided to test what would be possible with a range of different components.
Recycled bricks and concrete were used in a layer of the field, recycled glass was bedded in trenches, soft plastics were included as aggregate in pathways around the field, while bench seating was made from recycled hard plastics.
Materials were sourced from local suppliers in the surrounding Melbourne suburbs.
“Everything that we used on the field came from Victoria. For example, the recycled glass was a supplier in the north of Melbourne,” Oliver says. “We also had a contractor source and supply the crumbed recycled rubber from car tyres.”
About 98 per cent of the material used to create the shock pad layer under the field was sourced from recycled rubber.
Oliver says the use of materials such as soft plastics was an important step for the council.
“We went out of our comfort zone with the use of soft plastics that would otherwise usually go to landfill,” he says. “This is where we had an interest and where we worked closely with the contractor and its supplier.
“Some supermarket chains collect most of their used plastic bags and other soft plastics. We of course needed huge quantities of soft plastics in the form of recycled pellets as part of this construction.”
More than one million plastic bags were used in the construction; just one aspect of the project which, Oliver says, “pushed the envelope” on what could be done with recycled materials.
The soft plastics were used as a concrete aggregate additive and incorporated into the concrete pour.
“Key to success was also identifying a batch plant that could deliver this special concrete in commercially viable quantities reliably,” says Oliver.
He says while presenting some challenges, the process ultimately delivered a desirable outcome.
“Overall, the feedback from the concreters on site was that the workability of the material was very good. It surprised them and us. So naturally this led to council questioning – if it worked in the hockey field application, why can’t we put these soft plastics into all footpaths overall? Why can’t we incorporate this into a park path?
“The material was very similar in the aspects of performance and workability to concrete with only conventional type aggregate, therefore there is no reason to avoid using these materials again.”
The materials were tested over a 56-day period. Results showed that the structure had the same level of strength as one produced with conventional concrete after 28 days and 56 days.
The City of Darebin is considering the wider use of recycled materials.
“A successful project like the hockey field renewal creates more momentum for recycled product use, it gives it more credibility,” Oliver says.
“The positive outcome will help a project which would similarly feature recycled materials gain approval.”
The council has been approached by neighbouring councils asking about the experience with using the recycled materials, and if they would recommend their use as an option for future projects.
“Of course, it is up to the individual councils to make the right selection on their own particular projects,” says Oliver.
“But at Darebin we have determined that the risk is manageable when using these materials for certain types of concrete paving.”