Making the case for foamed bitumen stabilisation

A recent project undertaken by WA Stabilising was an ideal proof of concept for foamed bitumen stabilisation in Western Australia, and it earned the company a top industry award.The Pilbara is an expansive region in Western Australia’s north, and covers more than half a million square kilometres.

Infrastructure in the region is vital in helping drive the economy in the west, especially given the area’s vast mineral deposits.

In 2015, WA Stabilising was contracted to deliver a vital project for Outback Travel Network close to Port Hedland in the Pilbara.

“The client came to us with a problem – they needed a pavement they could park heavy loads on for long periods of time,” explains Daniel Bayne, Operations Manager – Stabilising at WA Stabilising.

“The client originally wanted to use structural concrete, but we came up with an alternative solution – foamed bitumen,” he adds.

Since its establishment in 2004, WA Stabilising (part of the Global Civil Mining Group) has built a reputation as a high-quality service provider in Australia’s west.

The firm is well versed in the use of foamed bitumen stabilisation (FBS) having delivered in excess of 300,000 square metres of FBS work in Western Australia.

Given the client’s brief, the WA Stabilising team suggested using FBS.

The company has seen the cost savings and time efficiencies that come from using foamed bitumen, and deemed the Port Hedland project a suitable site for its application.

“It’s structurally sound and it’s a forgiving material to work with,” states Mr. Bayne. WA Stabilising’s FBS practices are informed by the research and information provided by Austroads and ARRB.

Construction commenced with earthworks – cut to fill. Soon after, when the subgrade was being prepared, Mother Nature bore down on site. “Probably one of the biggest challenges for the crew was a reasonable storm event,” says Mr. Bayne.

Torrential rain hammered the area for five days during production and, given the tight time constraints, the WA Stabilising team had to come up with a quick solution to keep work moving.

Rather than waiting for the rain to subside, the team added cement stabilisation to dry the subgrade, which also helped to create a stronger sub-base material.

Approximately 40 millimetres of sub-base material was imported, levelled and pre-compacted to 150 millimetres.

Foamed bitumen was stabilised to a depth of 180 millimetres in the basecourse, with the addition of 2.5 per cent C170 bitumen and 1.0 per cent cement.

The project was finished with 14/7 millimetres of polymer modified binder spray seal, with a 5-millimetre dry rack to cater for turning loaded road trains.

Although there were some obstacles to overcome in the logistics of getting suppliers to and from site, Mr. Bayne states the main hurdle was the weather. “The rain was certainly the biggest challenge, and some of the temperatures did get quite hot, but that’s all part of working in the Pilbara,” he adds.

In using FBS, WA Stabilising recorded a 30 per cent cost saving over the original proposed concrete pavement. Not only that, but the company’s efforts resulted in a significantly shorter construction time, while staged construction improved cash flow for the developer.

Deflections also indicated a robust pavement to support thin and stiff asphalt layers in the future.

The project demonstrated that heavy-duty pavements can be constructed in a short time frame. Moreover, stabilised pavements, especially those with a bitumen-stabilised basecourse, are a viable solution to provide cost-effective perpetual pavements.

“In this case, the client couldn’t be happier. They’ve said they’ll come to us with similar projects in the near future,” says Mr. Bayne.

Its impressive outcomes led to the project and the WA Stabilising team receiving the prestigious Innovation or Excellence in Sustainability in Pavement Stabilisation Award at the 2016 AustStab Awards of Excellence held in July.

“The award is recognition of what we’re trying to achieve as a business, and we’re certainly trying to be at the best in our area of expertise,” says Mr. Bayne.

He agrees that the Port Hedland project is an ideal proof-of-concept example for FBS use, particularly in Western Australia.

“It’s definitely not as widely utilised as in the likes of Queensland, New South Wales or Victoria, but it’s catching on over here,” he says. “People are starting to understand its capabilities.”

Even on the Port Hedland project, Mr. Bayne says one major obstacle at the beginning was convincing the client that FBS was the right application.

“FBS is something that we see as having a bit of a niche market. We see it as a good product and the industry is slowly catching up,” he says. “There’s still a lot of research and testing going on out there, and many of the results from those trials aren’t in yet.”

Main Roads Western Australia has seven regional offices strategically based throughout the state that independently manage the regional road networks. Mr. Bayne says the Wheatbelt branch is the only one utilising FBS consistently. “We have also done a FBS trial for Mid West Gascoyne Region,” he adds.

“It’s not the silver bullet – it’s an expensive product, but in the right site and in the right application it’s definitely worth a go.”

Even as a relatively new member of AustStab, Mr. Bayne says WA Stabilising is reaping the benefits of being a part of the association, particularly following the recognition the company has received through its recent award.

“AustStab are at the forefront and invest a fair bit in research and development, and trialling all kinds of stabilisation, not just foamed bitumen,” he says.

“We’ve only just become an official member, but we see them as a driving force for the stabilisation industry, and they’re getting out there in front of main roads departments and other government bodies.”

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