Improving the structural strength of asphalt

When Main Roads Western Australia wanted to implement EME2 bitumen on the Kwinana Freeway extension, they enlisted the help of SAMI Bitumen Technologies and its new blowing column.

Over the years Main Roads Western Australia (MRWA) has identified a need to use improved asphalt performance specifications and pavement design in the state’s heavy-duty road projects.

When they recently earmarked a section of the Kwinana Freeway extension for 10,000 tonnes of EME2 asphalt, they recruited the help of regular collaborators SAMI Bitumen Technologies.

According to MRWA, growth in traffic volumes over recent years has resulted in congestion and flow breakdown on Kwinana Freeway northbound — south of Roe Highway. In response, the state and federal governments have committed $49 million to widen the freeway northbound. Upon completion, the project will reduce travel times and address congestion for road users in Perth’s southern suburbs.

SAMI General Manager, Sebastien Chatard, says a special hard-grade binder will be used for the project, with SAMI designing the asphalt mix and producing it in a new blowing column at its bitumen import terminal in Kwinana.

According to Mr. Chatard, the newly commissioned blowing column will help facilitate the commercial scale manufacture of EME2 bitumen required for the MRWA project, while simultaneously enabling the company to produce at that level in the long-term.

“The new blowing column will assist SAMI to produce multigrade and EME2 bitumens, which can be used to improve the structural strength of asphalt — thereby extending the life of pavements under heavy traffic loading.

“This development paves the way for road asset owners to access a new range of high-performance bitumen grades not previously produced in Western Australia,” Mr. Chatard says.

EME2 technology was first introduced into Australia — following its inception in France in the 1980s — in 2014 after multiple international study tours involving the Australian Road Research Board, Austroads and Australian Asphalt Pavement Association.

Part of the EME2 mix design process involves testing five specific areas to ensure its success, workability, durability, rut resistance, stiffness and fatigue. EME2 mixes are produced using a hard-paving grade bitumen applied at a higher binder content than conventional asphalt bases.

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

“EME2 asphalt has become very popular. For example, since its introduction in Australia, Queensland Transport and Main Roads have started using it extensively on its major highways. The same goes to Main Roads Western Australia,” Mr. Chatard says.

In a report published earlier this year, ARRB characterised EME2 by its high stiffness and durability — arguing the mix provided superior resistance to permanent deformation, and better fatigue resistance than traditional bitumens.

“The key here is obviously stability, when you combine the EME2 mix with our new blowing column you’re producing a high-quality product,” Mr. Chatard says.

“SAMI’s news blowing column will therefore help support the infrastructure industry as it continues to expand under the main roads pipeline.”

Mr. Chatard says the blowing column is part of SAMI’s ongoing investment in its innovative bitumen import terminal in Kwinana, the design of which is based on a similar column that has been in operation at SAMI’s Brisbane facility since 2012.

“The new bitumen terminal is a big investment for SAMI and its shareholders, but we are confident that the new blowing technology will open up opportunities to improve pavement performance for the local and national construction industry,” Mr. Chatard says.

Using the blowing column, the base bitumen properties are enhanced through air rectified to produce a binder that is less susceptible to low-temperature cracking and high-temperature rutting under traffic.

According to Mr. Chatard, the new column will also allow pavement design engineers to reduce the thickness of the structural asphalt layer, thereby saving the client more money when delivering new road and port projects.

“The prime benefit of EME2 and the new blowing column is that it can potentially reduce the layer thickness of the base course for a heavily trafficked pavement by up to 30 per cent, depending on climatic and traffic conditions,” Mr. Chatard says.

“Alternatively, it can be used to design and build stronger and longer lasting pavements. Either way, this has major cost benefits to road, airport and container terminal asset owners.”

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