Sustainable pavements: ARRB

Margaret Brownjohn from the Australian Road Research Board takes a look at lifecycle assessment and promoting the uptake of innovative recycling materials in roads. 

Sustainable development spans economic, social, environmental and governance aspects. Sustainability is no longer a “nice to have”.

The infrastructure industry in Australia is now driving outcomes that help reduce its ecological footprints. Many state and territory governments are also doing their bit to promote sustainability.

They have policy targets that govern procurement decision making. This includes reducing their annual greenhouse gas emissions, local jobs creation and diverting waste away from landfill.

Many states and territories are also requiring that major infrastructure projects undergo an Infrastructure Sustainability Council of Australia rating. This is an independent assessment process to assess innovation, sustainability and continuous improvement and compared to business-as-usual.

ASSESSING SUSTAINABILITY

A challenge in promoting the uptake of more sustainable pavement technologies is communicating its whole-of-lifecycle sustainability and lifecycle asset performance to transport practitioners. Often there are win-win commercial and sustainability outcomes from the use of innovative pavement technologies.

As part of the National Asset Centre of Excellence (NACoE) partnership between Transport and Main Roads in Queensland and the Australian Road Research Board (ARRB), a number of innovative pavement technologies have been developed, tested and trialled for application on Australian roads.

ARRB conducted a study where the lifecycle sustainability costs and benefits of different pavement technologies were assessed. This included quantification of greenhouse gas reductions over the pavement lifecycle.

These included the following technologies:

EME 2

Reclaimed asphalt pavement (RAP)

Crumbed rubber in binders

Foam bitumen stabilised (FBS) Bases

Local marginal materials.

EME 2 is a high-strength asphalt used in high-traffic urban arterials and motorways. It often reduces the base layer thickness by up to 30 per cent, which means lower use of virgin materials. It also means fewer lifecycle emissions due to less use of materials, haulage and construction emission. Approximately three per cent of lifecycle emissions and lifecycle cost savings are achievable with the use of EME 2 in an urban context.

RAP is a reprocessed pavement containing reused asphalt. This means less use of virgin materials and less clearing of trees for quarries. There may also be fewer emissions from haulage. 5.1 per cent lower emissions and lifecycle cost savings are also achievable. This is particularly notable where landfill levies and fees are applicable in regions like Queensland, which has an escalating levy each year.

The use of crumbed rubber in binders promotes local and circular economies, which both create jobs. Crumbed rubber also reduces the imports of materials like polymer modified binders. It may be hauled large distances and still achieve lifecycle greenhouse gas reductions.

FBS is a processed pavement base with increased strength and resilience to flood events. This reduces the risk of rehabilitation required after a flood. Because of its stiffer and thinner base, it also has lifecycle emissions reductions.

Marginal materials are locally sourced materials. They are beneficial where higher performing virgin materials are expensive and required to be hauled long distances. Due to reduced haulage, up to 22 per cent reduction in lifecycle emissions are achievable. It also promotes local industries in rural areas.

All technologies achieved lifecycle greenhouse gas reductions and commercial savings in the right context. General findings included that high durability and resilient pavements have good whole-of-lifecycle sustainability performance.

The largest emissions reductions are also achievable through vehicle technologies, such as electric vehicles. But every year of delay adds to cumulative emissions in the atmosphere and over the pavement lifecycle.

Future work will include quantifying the benefits of additional sustainable materials, including, but not limited to, the use of recycled glass and warm asphalt. The tool provides a framework in which pavement options may be assessed on a project-by-project basis for smarter procurement decision making.

If you are interested in finding out more about this work and its potential application, or customisation to your needs, contact ARRB at sustainability@arrb.com.au

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ARRB awarded Sustainability Victoria grant

The Australian Road Research Board (ARRB) has been awarded a $200,000 Sustainability Victoria grant to trial recycled crushed glass asphalt on local roads.

The grant was issued to ARRB in collaboration with Vic Roads and Brimbank City Council in Melbourne’s west.

According to ARRB project lead Doctor James Grenfell, over 250,000 tonnes of glass is recovered in Victoria every year.

“Using finely crushed glass in road pavement materials has the potential to create viable markets for the vast amounts of glass collected in Victoria, especially that which is low-value and not easily recycled back into other glass products,” Dr Grenfell said.

“ARRB has done significant research in this space – much of which was showcased at its recent Smart Pavements Now masterclass event in Melbourne.”

Dr Grenfell said the trial will specifically look at repurposing low-value glass that is not easily recycled back into other glass products.

“The potential for use of recycled glass in asphalt offers great opportunities for councils, especially in helping deal with Australia’s current recycling issue,” Dr Grenfell said.

“The other exciting aspect is the engagement with a local city council, and to have the ability to monitor a field trial for an extended period of time.”

The ARRB grant is one of nine issued under Sustainability Victoria’s research, development and demonstration grants program.

Sustainability Victoria interim CEO Carl Muller said the grants are designed to support Victoria’s growing circular economy.

“We need proven recycled content products and markets for those products to make recycling viable,” Mr Muller said.

“This will build confidence and market demand.”

The grant proposal was developed by Dr Grenfell and ARRB colleagues Melissa Lyons and Lydia Thomas.

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TSA and ARRB trial crumb rubber asphalt

A crumb rubber asphalt trial will soon begin in Melbourne, with funding from Tyre Stewardship Australia (TSA) and the Australian Road Research Board (ARRB).

According to TSA CEO Lina Goodman, while crumb rubber is routinely used in rural road surfacing in Victoria, more testing is needed on highly trafficked roads.

“The aim of this project is to increase the opportunity to use crumb rubber in metropolitan roads,” Ms Goodman said.

“This trial is a landmark opportunity in the development of the circular economy in Australia.”

ARRB will trial a range of asphalt mixes and monitor performance over time.

ARRB Senior Professional Leader Melissa Lyons said the trial is a first of its kind in regard to scale and number of testing mixes.

“ARRB is proud to be a supporting partner of this project, which is about finding sustainable solutions to Australia’s tyre problem,” Ms Lyons said.

The crumb rubber asphalt will be laid on a 1.5 kilometre southbound East Boundary Road carriageway, between Centre Road and South Road in Bentleigh East.

Lab and field testing will be conducted at regular intervals, with a final report due by mid 2022.

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ARRB reviews the use of vehicle tyres in bitumen

The Australian Road Research Board (ARRB) is recommending further research into the use of passenger vehicle tyres in bitumen production.

ARRB Senior Professional Leader Guy Hand said Victoria’s Transport Department, formerly VicRoads, engaged ARRB to undertake a literature review on the subject.

“Using more end-of-life tyres in road construction is a known way to curb significant environmental challenge for Australia. The question is, how do we make that happen?,” Mr Hand said.

“One possibility is to engage the use of end-of-life car tyres.”

Most crumb rubber repurposed into Australian road construction currently comes from end-of-life truck tyres.

According to Mr Hand, truck tyres are predominantly composed of natural rubber, whereas car tyres contain a high proportion of synthetic rubber, as well as a nylon component.

“It is not well understood whether synthetic rubber will behave in bitumen in the same nature that natural rubber does,” Mr Hand said.

“No data from an Australian context is available to establish the compatibility and performance of synthetic rubber in bitumen.”

Mr Hand said the key objective of the review is to understand the current specifications of crumb rubber sourced by other road agencies, and the market availability and processing requirements of passenger vehicle tyres.

ARRB were additionally asked to identify the benefits and limitations of using passenger vehicle tyre crumb rubber as a road material in asphalt and sprayed seals.

“There are also barriers for recycling car tyres to be considered, such as economic, environmental and processing challenges,” Mr Hand said.

“With the Victorian Government’s focus on increasing the use of recycled materials in road construction, this literature review will help inform all stakeholders on the issues associated with the use of passenger vehicle tyres in bitumen.”

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Deputy PM opens ARRB’s new HQ

Deputy Prime Minister, Michael McCormack, has officially opened the National Transport Research Centre – the Australian Road Research Board’s (ARRB) new national headquarters – in front of more than 250 guests at Port Melbourne.

McCormack, who is also the Federal Minister for Infrastructure and Transport, paid tribute to ARRB’s work as the National Transport Research Organisation, which will be furthered by the state-of-the-art research facility.

“Our transport future is on us now,” said McCormack.

“The George Jetson philosophy and visions of the future are happening right before us, and you at ARRB are front and centre of that.

“This facility is going to be front and centre of everything our nation is relying on (in roads and transport) with your world-class facilities,” he said.

ARRB Chief Executive Officer, Michael Caltabiano, has earmarked the Fishermans Bend precinct, where the new facility is situated, as a possible new test-bed for driverless vehicles.

“We need an urban test platform, and that is Fishermans Bend,” he said.

While it will need government commitment to make that happen, ARRB’s new multi-million dollar home offers the potential to be home base for a driverless vehicle test-bed to benefit all Australians and help shape Australia’s connected mobility future.

Created in partnership with workplace consulting specialists, Amicus, the National Transport Research Centre features world-class research labs and more than 100 staff working on everything from driverless vehicles and road safety to new smart pavements and what smart cities of the future should look like.

The opening day’s activities included displays of autonomous and electric vehicles from Holden, Tesla, Volvo, Jaguar and Mercedes, a hydrogen-powered Toyota, plus a look at one of ARRB’s current projects – a road safety drone.

The drone is engineered to deliver emergency equipment through traffic to accident victims who need it.

Millions of tyres could soon be used in Australia’s roads

New national specifications for Crumbed Rubber Modified (CRM) asphalt could see millions of waste tyres being used in Australia’s road infrastructure.

The Australian Asphalt Pavement Association (AAPA), Tyre Stewardship Australia (TSA), Main Roads Queensland, Main Roads WA, Sustainability Victoria and the Australian Road Research Board have worked together to develop and analyse research and development data to achieve cohesive national standards.

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The new national specifications could see nearly 10 per cent of the accessible feedstock for Australian tyre-derived crumb rubber used in domestic road manufacturing, which adds up to almost 4 million end-of-life tyres every year.

The document was published by the AAPA national technology and leadership committee to facilitate the construction of demonstration trials of CRM gap graded asphalt (GGA), and to promote the use of CRM open graded asphalt in Australia.

The crumb rubber binder technology is based on the technology used in the US, with the first demonstration section of CRM GGA in the Gold Coast placed in late June.

CRM Asphalt can offer better drainage, reduced noise, improved rut and crack resistance and reduced maintenance cycles.

Engineers and road contractors are now able to work within parameters of the new national specifications to take advantage of CRM asphalt and spray seal.

TSA Market Development Manager Liam O’Keefe said reaching a national standard has been a critical part of increasing the potential market for crumb rubber use in Australian roads.

“To fully realise this potential for that use we must continue to work with industry partners to ensure the delivery of better roads and better environmental outcomes for all,” Mr O’Keefe said.

“The important next phase of the task is ensuring that the new specifications are used. As utilisation of the new specifications grows, so too will the benefits to the end- of-life tyre industry.”

AAPA Director of Technology and Leadership Erik Denneman said this is a great outcome that has come from the close collaboration between industry and road agencies in Australia.

“For AAPA this initiative fits our objective of encouraging the efficient use of available resources and promoting the use of sustainable products,” Mr Denneman said.

The new national specifications can be found here.

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