Downer’s pavement stabilisation and rehabilitation business unit has provided high-quality outcomes on some of the nation’s largest infrastructure assets, while using Wirtgen Group machinery.
With 44,000 people across 300 sites, mainly in Australia and New Zealand, Downer’s commitment to the infrastructure sector has resulted in the development of efficient and high-quality projects.
The company’s history dates back more than 150 years. Since that time, Downer has cemented its place as one of the leading infrastructure construction companies across Australia and New Zealand.
But how do you build trust and deliver promises consistently to clients, for more than a century?
Matt Billings, Downer’s National Operations Manager Stabilisation, says innovation is key. Not only in relation to new materials equipment and machinery, but also sustainability and safety.
“Downer is the first Australian infrastructure company to register a binding, science-based, net-zero emissions target with the United Nations,” he says.
“We’re at the forefront of reducing emissions and deployment of recycling alternatives to supplant virgin material extraction with similar or better product performance characteristics. Downer’s stabilisation business is just one example where this commitment to drive sustainability can be seen in action.”
Sustainable stabilisation
Downer’s pavement stabilisation and rehabilitation service enables existing pavements to be recycled, and when compared to conventional rehabilitation techniques, can provide cost and environmental benefits.
The process consists of reviewing the initial client design, sampling, laboratory testing and then an infield trial section completed with the specified stabilisation treatment. Testing on the trial section of works ensures the stabilisation treatment has met the design performance criteria and the stabilisation treatment is ratified based on this evaluation. In construction, the lime or cement-based binders are then spread at a specified rate by the spreader truck, before a stabiliser mixes the binder into the pavement while also injecting water directly into the mixing chamber achieving a homogeneously mixed layer of pavement.
The stabilised pavement construction is then completed through the final stages: compaction, grading and further conditioning through the addition of water by a water cart help achieve a tight bound pavement that is suitable for the next layer of pavement.
As Billings explains, this process reduces the need for virgin materials to be imported, as well as excavation for the disposal of materials on-site.
“Since the recycling of existing pavements using in situ stabilisation is quick, involves no excavation and requires either no or minimal removal of materials off site, the environmental benefits of using these techniques in comparison to using other rehabilitation techniques are quite substantial,” he says.
“The purpose of stabilisation is to recycle or rehabilitate the existing material in situ, thereby upgrading the engineering and economic values of the existing pavement or ground conditions.”
By using pavement stabilisation, Downer is able to re-engineer unsuitable material into a product with improved performance properties.
Reducing the required trucking to deliver virgin materials not only decreases greenhouse gas emissions, but also provides construction materials for sites in regional areas, where a local quarry may not be available. Communities can also benefit from reduced traffic on local roads.
“In situ stabilisation is usually much quicker than other rehabilitation methods, with effectively no excavation and minimal materials both taken away from site and consequently brought onto site,” Billings says. “With the materials being recycled on-site, there’s far less exposure to the risks of poor weather causing extended delays as well.”
Lime, fly-ash and slag are all binders that can be used within each of these mixes, with each presenting their own benefits. A slag-lime mix is able to reduce the potential for future cracking, decreasing maintenance costs over time.
Stabilisation in practice
Downer has deployed a portion of its pavement stabilisation team on the Inland Rail project. The $5 billion Inland Rail endeavour will see the construction of a 1700-kilometre rail line, connecting Melbourne and Brisbane via regional Victoria, New South Wales and Queensland.
Mark Jekki, New South Wales Operations Manager, says Downer are undertaking the stabilisation of cut and fill materials in two 400mm layers in the rail corridor, culvert crossings and sidings as part of the project.
He says the aim of the works will be to
raise the rail line and minimise the impact
of flooding.
“We collaborated extensively prior to tender, to identify the best equipment available to support the delivery of the project,” he says.
Banking on a professional relationship – lasting more than 20 years – Downer engaged Wirtgen Group to learn more about the company’s machinery and equipment offerings.
Billings says this also presented an opportunity for Downer to participate in what is still an Australian first.
“It was a very proud moment. The Inland Rail project gave us the opportunity to purchase two WR250 Stabilisers, the first two in Australia to be commissioned for stabilisation. We strongly believe that these are the some of the world’s best stabilisers in terms of design and productivity,” he says.
“We recognised an opportunity to provide the project with a unique solution and this was supported by our partners Wirtgen and our client who were excited to bring world class technology and performance to such an iconic project.”
Downer’s Inland Rail project team was able to utilise its experience with the WR250’s little brother, the WR240. Jekki says that upgrading to the WR250 has enabled his team to increase their productivity daily.
“The difference with the WR 250 is that it’s close to 200 more horsepower. It’s also got a different milling drum unit, with roughly 30 per cent more teeth on it. We’re achieving effectively 30 per cent more mixing in each pass,” he says.
And when Downer required support, Wirtgen Group were there every step of
the way.
“It’s a professional relationship, which is making us more productive, especially when you combine the expertise and skills of our operators in conjunction with the reliability of the machines we purchased from Wirtgen,” Jekki says.
“Wirtgen have been there to support, train and develop our people to get the absolute best out of these machines.”
Downer’s progress on the Inland Rail project is on-going, with expectations that the works will be successfully completed in September this year.
This article was originally published in the August edition of our magazine. To read the magazine, click here.
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