EME2 specifications for QLD roads

Enrobé à module élevé (EME) has long been France’s heavy duty asphalt mix of choice.

The hot mix asphalt technology has been used extensively on the nation’s main routes and airports since its introduction in the 1990s. Thanks to its hard grade bitumen, applied at a higher binder content, EME is thinner than conventional asphalt and is ideal for roads designed for heavy traffic. The performance-based philosophy behind EME also separates it from the pack.

Part of the mix design process involves testing five specific areas to ensure EME’s success. These are workability, durability, rut resistance, stiffness and fatigue. Following this French design philosophy means EME can be designed to a proved methodology.

This performance-based criteria has made EME an attractive asset, one which road agencies and industry alike have been active in procuring for use here in Australia.

EME technology was introduced to the country following international study tours involving ARRB, Austroads and Australian Asphalt Pavement Association (AAPA) in 2012.

A long collaboration between ARRB, Austroads, AAPA, state road agencies and industry has brought the implementation of EME on Australian roads to fruition.

EME2 (EME class 2) was developed and demonstrated for the first time on the country’s roads in February last year. Eagle Farm in Brisbane was selected as the test site and Boral conducted the production and lay in collaboration with the Queensland Department of Transport and Main Roads and Brisbane City Council.

“The objective of the first EME2 demonstration was to assess whether or not we can produce the mix using existing Australian equipment,” explains Laszlo Petho, ARRB Principal Engineer Pavement Technology and Project Leader for the EME2 technology transfer.

The EME2 technology transfer was assessed based on three elements. The first was the question of whether or not Australian materials, including aggregate and binder, could be used to make EME2. The second tested the capabilities of Australian machinery to undertake the lay and compaction. The goal was to use everything already available. This is to avoid buying or bringing in new equipment as it pushes the costs to such a high level that no one would even start thinking about it. Third, EME2 was assessed on how it performed in the long-term. “Whether or not we can make it came down to compaction,” he adds.

One and a half years on and EME2 has ticked all the boxes.

“We can definitely use all Australian equipment. They performed exceptionally well on site,” says Dr. Petho.

In the initial demonstration, EME2 was laid alongside a control mix to compare the two and show the benefits of the performance-based methodology. The control mix – a normal, heavy duty dense-graded mix – was laid in two layers at 150 millimetres in total and EME was demonstrated at a depth of just 100 millimetres. “And we subjected both to the same traffic,” says Dr. Petho. “The control and EME2 performed similarly in terms of structural capacity.”

In short, EME2 performed just as well as the control mix but with a 30 per cent reduction in asphalt base layer thickness.

Dr. Petho says that a year and a half is a long enough indicator to ensure the effectiveness of the EME2 asphalt treatment. “If there were any issues or faults we would know by now,” he says.

“Some people obviously have concerns that you need to have a ten-year performance review to make sure. In France they have 30 years of validation – we follow the French approach exactly, therefore it should work.”

Following the demonstration, two specification documents have now been produced and made available: PSTS107 – High Modulus Asphalt (EME2) and Technical Note 142 – High Modulus Asphalt (EME2) Pavement Design. Both documents allow the immediate application of EME2 on Queensland’s roads. “It was the eventual goal to not just do research, but to have a practical outcome,” explains Dr. Petho.

He says EME2 has already garnered interest from the likes of Brisbane City Council and the Gold Coast City Council.

“It’s got a fairly big momentum. VicRoads also completed its EME2 demonstrations in the first week of June,” he says, referring to the EME2 demonstration undertaken in the state by Downer on the South Gippsland Highway.

“In Victoria we have similar obstacles, like whether or not we can actually produce it and pave it,” he says. Like the Queensland EME2 demonstration, the Victorian one includes a control mix element. “This is a heavy traffic route and in a year we can be confident about [the EME2] performance.”

A New South Wales EME2 demonstration is anticipated to take place later in the year and Dr. Petho says Main Roads Western Australia is looking into the technology too.

Dr. Petho says the success of EME2 so far is a precursor to introducing more asphalt technologies, particular performance-based ones, to the Australian market. He presented on the EME2 research and demonstrations at the AAPA International Flexible Pavements Conference 2015 at the Gold Coast in September.

“It’s really great progress. The Queensland specifications are a good starting point and proof that we can make it happen,” he says.