Asphalt Review

Harmonised asphalt specification demonstrated on Gateway Project

A harmonised asphalt specification is being used on Western Australia's Gateway Project

A harmonised asphalt specification is being used on Western Australia's Gateway ProjectWestern Australia’s Gateway Project is the largest road project ever to be undertaken in the region.

The $1 billion development includes constructing and upgrading five main interchanges, widening an area of Tonkin Highway to six lanes, and improving a section of Leach Highway to an expressway standard.

This project, along with the Perth Freight Link and NorthLink WA projects, form part of an upgraded freight connection from Muchea, through the Perth metropolitan area, to Fremantle Port. Construction began in early 2013, and completion is projected for mid-2016. The Gateway Project is a first for the region, while also forming an important part of the bigger picture for Australia’s asphalt industry.

In 2013, Main Roads, Western Australia’s state road authority, identified the need to use a new asphalt specification for the region’s latest road projects, including the Gateway Project. The problem was that the thinner asphalt mixes used in the region did not allow for asphalt to be laid during cold weather, imposing limitations and delays on construction crews. “This created the need to utilise full-depth asphalt,” says Jim Beesley, former Australian Asphalt Pavement Association (AAPA) Executive Officer for Western Australia. He notes that Main Roads hadn’t had extensive experience implementing thicker, full-depth asphalt.

AAPA contacted Main Roads and invited them to conduct a brief tour of Queensland and New South Wales to see what the respective state road authorities were doing with full-depth asphalt and how they were successful. “It was purely to do with the way Main Roads’ equivalents handle the new products and technologies that [AAPA] is bringing to the market,” he says. Representatives from Main Roads met with their NSW counterparts, Roads and Maritime Services, and senior management industry figures in QLD as part of the eastern tours. Both were in the process of harmonising their specifications. It was this harmonisation of a single asphalt specification that AAPA intended to extend out to WA.

A harmonised asphalt specification offers many advantages. A project manager can theoretically call in a construction crew from out of state to do a job. Although this specification has specific criteria, local materials from each respective region can be used in the recipe.

One of the key differences in this harmonised specification is the use of a nuclear density gauge, a non-destructive testing method, to ascertain the level of compaction and quality of the pavement. This testing method was implemented following exploration of the harmonised specification and a demonstration in WA. Previous testing methods often required drilling multiple holes in the asphalt’s layers, which potentially jeopardised the road’s strength. Nuclear density testing requires the use of a device which is placed on the surface to measure the compacted density of the work.

Following the tours of the eastern states, WA is onboard too. The state’s momentous WA Gateway Project has become the perfect project to implement the specifications.

In the past year, demonstrations have been undertaken on sections of the WA Gateway Project. Off the back of a regional AAPA meeting, Fulton Hogan volunteered to design a harmonised asphalt mix, while Boral agreed to implement it on the WA Gateway Project. This was in addition to trials already taking place on the project. Mr. Beesley says that the demonstrations marks a significant step in the right direction for the harmonisation of a national asphalt specification.

Boral conducted demonstrations of mixes based on this harmonised specification at the beginning of May. General Manager WA at Boral Asphalt Nathan Lammers says they will compare this full-depth asphalt laying process and its appearance to the asphalt mixes previously used on the Gateway Project. One demonstration is being undertaken on a section of the Tonkin Highway, which involves nearly 1500 tonnes of asphalt. Nuclear density testing hadn’t been used in WA and Boral went through the steps of implementing it in the region. Mr. Lammers says that this asphalt will be tested with a nuclear density gauge.

Pat Tinnelly, General Manager Industries at Fulton Hogan WA, says the mixes used and designed by Meda Sicoe, Technical and Quality Manager at FH Industries Western, are in line with the harmonised specification, and represent a way forward for the asphalt industry: “It’s about industry wanting to work with the road agencies to make sure we’re all getting value for money roads and getting a good value asphalt.”

He says a lot of the credit goes to AAPA Chief Executive Officer Michael Caltabiano and Managing Director Main Roads WA Stephen Troughton in making the harmonisation process between states happen. “This is probably about three years in the making,” he says. “The local AAPA branch definitely had the desire for change to happen.”

The overall goal for AAPA in harmonising this specification and its testing methodology is to achieve a national specification for full-depth asphalt. “It means that there’s full knowledge, nationally, of the asphalt requirements,” says Mr. Beesley. He adds that this is part of a bigger process that involves AAPA and research organisations Austroads and ARRB, noting that those bodies are interested in perpetual pavements. Mr. Beesley says that these perpetual pavements are ideal for Australia’s infrastructure. These full-depth asphalt pavements can be laid at an optimum thickness for heavy vehicle use. Maintenance only occurs every 20 years, and the top layer of asphalt can be removed, recycled and laid back down again.

Mr. Beesley says that the trialling of this harmonised specification on the Gateway Project couldn’t have happened without the co-operation of all the parties concerned, specifically that of the Materials Engineering Branch of Main Roads.

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