The future of flexible pavements

India Murphy, Journalist, Infrastructure Magazine

Carlos Rial, APPA CEO

Carlos Rial,
APPA CEO

The constant changing demands of society and transportation technology has created the need for the Australian flexible road, asphalt and pavement industry to be, well, flexible. And nobody knows this better than the CEO of the Australian Asphalt and Pavement Association (AAPA), Carlos Rial, who has more than 20 years of industry experience. Infrastructure spoke to Mr Rial about the biggest industry trends, current challenges, and what the future holds for flexible pavements.

The AAPA prides itself on leading the way in technology, research, training and innovation within the industry. As a peak body representing the industry, it is critical that the AAPA keeps ahead of the curve on current trends, technological advances and vision for the future.

What’s trending in flexible pavements?

According to Mr Rial, the two biggest trends in flexible pavements are circular economy policies and the shift to performance-based specifications.

The introduction of the Chinese National Sword regulation, which restricts the importation of solid wastes, has escalated Australia’s need to accelerate strong circular economy policies and practices across the nation, including the roads sector.  

In a circular economy, materials keep circulating within the economy at their highest value for as long as possible. This is through upcycling, reuse, recycling and remanufacturing.

Flexible bituminous pavements (such as asphalt) are one of the most recyclable products on the planet, with the product able to incorporate certain waste while maintaining strong engineering performance.   

Because of the ripple effect of the regulation, the AAPA is currently working with its members nationally across industry and government to see the increased use of crumb rubber (addressing waste tyres), glass and recycled asphalt.  

The AAPA is also supporting increased research into the future responsible use of plastics as a polymer to modify bitumen in Australia, without harmful environmental impacts.

“This is an exciting time for Australia as this work is driving improved sustainability practices across our sector,”
Mr Rial said.

The second biggest trend is the shift of road owners wanting to align with international best practices by using performance-based specifications and moving away from unnecessarily prescriptive engineering specifications.

“This approach allows clients to take advantage of the intelligent contractors we have in our country.  

“Specifying the operational requirements of the product through performance-based specifications fosters an innovation environment that allows contractors to showcase their smart technologies and practices.

“This is a shift nationally that AAPA supports and is working with members through the transition,” Mr Rial said.

Exciting innovative technologies

According to Mr Rial, there is a variety of advanced materials, processes and technologies currently being implemented in the construction of roads and pavements, but EME2 is the standout technology.

Introduced in recent years, EME2 asphalt is a new high modulus asphalt technology. EME2 asphalt has the potential to reduce base course layer thickness of heavily trafficked road by up to 30 per cent and be stronger and longer lasting than traditional asphaltic pavements.

The AAPA is working with its members and key stakeholders such as the ARRB Group and Austroads to ensure it is progressively being adopted nationally.  

Perpetual Pavements are also revolutionising flexible pavement design through the introduction of the perpetual pavement design method.  

The AAPA supported the introduction of “perpetual pavement” design concepts which both reduce the cost of the pavement and simplify the maintenance obligations to just surface wearing course upgrades.  

On many of the pavements, investing in the base course strength shifts the pavement from a structural failure in 20 years, to almost no need to replace the pavement structure.

“The long-term benefits to Australia, and potential savings over time through reduced rehabilitation and reconstruction costs are significant with the introduction of this new concept,” Mr Rial said.

The financial challenges facing the industry

Mr Rial said funding essential infrastructure is a significant challenge that the road and pavement sector is currently facing.

“One of our most renowned economists, Mr Bernard Salt, noted that the current and future challenge for government to fund Australia’s essential infrastructure (such as roads), given our tax base, is an increasing challenge.”

“This is reflected in the accumulated backlogs in road network maintenance across Australia — up to four times the annual maintenance budget in some states.

“Government is looking more and more to industry to support this growing challenge,” Mr Rial said.

The government and the private sector are currently working in partnership, shifting away from the traditional “master-servant” relationship to help solve the funding challenge.

Through long-term partnerships, which manage, build and maintain the roads, the industry will foster new financing and innovation opportunities.  

“We need to shift away from the short-term boom/bust funding cycles and adopt more sustainable longer-term funding arrangements over multiple years,” Mr Rial said.

“These increased funding arrangements will also drive efficiencies in the planning and delivery of works on our roads.”

Mr Rial said that the industry is prepared to do its part through innovation and construction reliability, however the delivery environment in Australia needs to continually mature to allow our smartest and best performing contractors to showcase this innovation.

“The industry does struggle in each jurisdiction with the boom/bust funding cycles in our sector. This is a challenge for not just industry, but also government and their associated departments to reliably deliver access for all our road users.  

“I have not yet met a road owner that had more funding than its needs.

“It is only by working in partnership that industry and government can establish alternative more sustainable delivery and funding models.”

The effects of the Circular Economy

The global economy is currently transforming, evolving towards a more circular model. Australia is also transitioning towards this and moving away from a predominantly linear approach, where products are typically made using virgin raw materials, used and then thrown away.

“The shift to a circular economy approach for bituminous products in the flexible pavements industry has been seen as a part of good business practice,” Mr Rial said.

Pavement products which are upcycled (old granular basecourses improved with foamed bitumen) and waste, such as old tyres, that is ground up and added to bitumen, outperform and are of lower cost.

Recycled asphalt pavements (RAP, one of the most recyclable products on the planet) reuse the aggregates, extending the lives of quarries and reusing the available bitumen as well.  

Mr Rial said while this is a good news story for Australia, more is still needed.

“International best practice shows we can do more in the roads sector to drive sustainable circular economy outcomes for Australia.

“Through improved engineering practice in our bituminous roads and surfacings, we can right now use more crumb rubber and percentages of RAP on our highways (lowering project costs) and incorporate higher percentages of glass.

“Road owners have to understand their responsibility in moving to the circular economy.”

This responsibility includes promoting innovation and generating the market demand for this sustainable practice.   

“I am currently seeing this increased focus across all road stewards nationally, which is great to see,” he said.

It is also important to understand that at present, market drivers may not support the policy objectives of a circular economy. For example, it is cheaper to import crumb rubber from overseas than use local supplied product, and it is cheaper to import glass than recycle it in Australia.   

The AAPA has supported the “perpetual pavement” design concept and also supports circular economy practice. Increasing the durability of the asset is more easily justified in circular economy thinking.

Accommodating the reuse of products in the waste stream is a key driver. But, taking glass and plastics out of the industrial and domestic waste stream requires research, changes to specifications and investment by industry to incorporate them.  

This requires coordination and collaboration which the AAPA is fostering amongst its members who include the state road authorities, local government and the providers of bitumen, asphalt and spayed sealing in Australia.   

The future implications of EVs

According to Mr Rial, the effect on road infrastructure from the implementation of electric and autonomous vehicles remains somewhat uncertain at present, especially as the needs may differ between urban and rural environments.  

“In urban environments the evolution of autonomous connected vehicles should allow greater vehicle capacity on our existing road network, as vehicles will commute closer to each other safely. This may result in delaying the need to upgrade certain roads for a time.”

Some predict that with tighter controls of vehicle travel paths, there will be a need for stronger pavements due to wheels having less lane wander and loading in one path. There are current engineering solutions which could solve this issue, should this come to play.

“One thing is for certain, as the degree of autonomy of vehicles progressively increases, the need for reliable well-maintained road infrastructure is essential as vehicles will not just be communicating with each other, they will be sensing and communicating with our road infrastructure.

“Internationally there is significant research on how infrastructure will communicate with the vehicles and adapt to the new expectations of users.  

“This includes self-healing roads through nanotechnology, solar roads, pavements that charge vehicles as they drive, and so on. It is an exciting future,” Mr Rial said.

The introduction of electric vehicles also poses a significant funding challenge for government.  As the demand for fuel reduces so does the fuel tax applied to each litre of fuel.

This links to the funding challenge mentioned earlier and further highlights the need for government to establish new transport infrastructure charging mechanisms.

“What reduced fuel usage means for bitumen volumes remains uncertain.”

The road ahead

Mr Rial sees the future of Australia’s road and pavement sector facing significant developments in their current practices and approaches to industry issues.

Infrastructure will be required to be more resilient when faced with the predicted climate change implications such as natural disasters, sea level rise and increased global temperatures.

Mr Rial said Australia will adopt sustainable circular economy practices, driving a new generation of flexible pavements through greater use of renewable materials.

Given the tax base of Australia and the backlog of infrastructure needs, Mr Rial sees a continued progression towards innovative private sector investment and partnerships to deliver and maintain roads.

“With the current trend towards increased use of electric cars and governments reduced tax from fuel excise, new charging models for road use will be needed. These funds will in part be dedicated back to roads.

“Significant investment into transport infrastructure over the next 20 years will support an efficient economy and also the continual transition towards fully autonomous vehicles.”

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