A performance-based solution

Having been involved in the introduction and first demonstration of Enrobés à module élevé (EME) on Australian roads, Boral is looking for more applications and opportunities for the asphalt technology around the country.In February 2014, a collaborative effort between Australia Asphalt Pavement Association (AAPA), ARRB, state road authorities and industry helped bring the nation’s first demonstration of EME to fruition.

EME2 (EME class 2) was developed and demonstrated for the first time on the country’s roads at Eagle Farm in Brisbane in 2014. This 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 hot mix asphalt technology had been on the Australian pavement sector’s radar since an AAPA international study tour to South Africa in 2012. Boral wanted to be a part of the process bringing it to Australian shores.

In the first year of the project to introduce EME2 to Australia, an Australian specification framework for EME2 mixes was developed and the requirements for manufacturing, paving and compliance were provided.

“As EME2 was new to Australia, Boral took the additional step of sending ingredients to France to compare performance against the world’s best practice and develop correlation to local Australian tests,” explains Ryan Jansz, Boral’s National Pavement Manager – Asphalt. “We shared this information with ARRB through AAPA so that the benefits could be shared across the whole industry for the betterment of the community.”

Mr. Jansz explains that EME2 piqued the company’s interest particularly because of the benefits it can have on Queensland roads. “One of the main reasons EME2 came to the forefront for us was because traffic loads are growing and, particularly in Queensland with its warmer weather, this requires quite deep asphalt pavements,” he says.

However, he explains that EME2 has relevance all over Australia, not just in warmer climates. “There is a preconceived notion that the benefits of EME2 can only be realised in warmer climates like Queensland due to temperature-dependent characteristics, but this is at odds with its origins in France, which would generally have a cooler climate than that of any Australian capital city.”

Thanks to its hard grade bitumen, applied at a higher binder content, EME2 is thinner than conventional asphalt (up to 30 per cent in some instances) and is ideal for roads designed for heavy traffic.

Part of the mix design process involves testing five specific areas to ensure EME2’s success. These are workability, durability, rut resistance, stiffness and fatigue. Following this design philosophy means EME2 can be designed to a proved methodology.

This performance-based criteria has made EME2 an attractive asset, one which road agencies and industry alike have been active in procuring for use here in Australia.

“EME2 also leads into other discussions around philosophies in asphalt technology, such as the perpetual pavement concept,” says Mr. Jansz. “Now that the industry has the equivalent Australian specification for tests, it makes sense to rely on local testing so that EME2 mixes can be developed more expediently and without further duplication of effort.”

Following the demonstration, two specification documents were 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.

The positive flow-on effects of the demonstration are evident, with a number of other similar events taking place in the likes of Victoria and New South Wales involving other road contractors.

“The introduction of EME2 has been systematic under the guidance of AAPA,” states Mr. Jansz. “While only demonstration projects have been implemented across Australia so far, there is expected to be significant uptake of the technology in major projects and in road maintenance treatments in the near future. EME2 can reduce road pavement thickness, construction costs, excavation depth and waste, while preserving natural resources.”

Since completing the initial demonstration, Boral has continued to develop its working processes with EME2 and is finding new ways to expand its use here in Australia.

The company also found a suitable application for the technology at one of its major quarry sites in Victoria.

“Our Deer Park quarry is undergoing a major upgrade so that it continues as one of the major sources of quarry material in the greater Melbourne area for many decades to comes,” explains Mr. Jansz. “We chose EME2 because it will carry the heavy forces from loaded trucks leaving the site, while allowing a thinner pavement to be constructed.” He says the project was also an opportunity to demonstrate the versatility of the quarry in supplying a different combination of materials for EME2 asphalt mixes, and help reduce the amount of waste material extracted from the site. EME2 can use a range of different aggregate sizes, thereby improving quarry utilisation.

The results of the demonstration have been positive, with the application of the asphalt mix showing that the Austroads EME2 specification has been met and the required field compaction achieved.

Boral is now looking at exploring the different ways EME2 can be used in Australia, including in a maintenance capacity and in large-scale projects.

Mr. Jansz says the development of EME2 is predominantly driven by industry, but while the specification and knowledge is there, more confidence needs to be built around the testing methodologies, especially as each state or territory will have different specification requirements in this space.

“When EME2 binder becomes widely available, it can be used to assist in maintenance patching where thin patches with low life expectancy are often used due to budget constraints. By using EME2, the same patch thickness might deliver more optimal life expectancy,” he says.

“Boral continues to explore every opportunity for EME2 so the best technology can be employed on Australian roads while preserving scarce quarry resources for future generations.

“Pavement design consultants and state road authorities are being made aware of the benefits of EME2 through technology transfer sessions and during bid enquiries throughout Australia.

“Once the benefits of EME2 are realised and it becomes an accepted product by state road authorities, the benefits will be widespread. Our hopes are that it will become a staple asphalt product for most major projects around the country.”

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