An Australian-first specification is set to inform the use of crumb rubber in asphalt applications on low-traffic roads.
For the past six months, Liam O’Keefe, Senior Strategy Manager at Tyre Stewardship Australia (TSA), has been travelling from state to state on an education mission.
Going beyond platitudes about the circular economy, Mr. O’Keefe has been focused on supporting the product pull-through of tyre-derived product in roads. It’s a simple strategy – change the specifications, demonstrate benefit, create demand and subsequently enable supply.
From last year’s Australian Asphalt Pavement Association (AAPA) followed by the Institute of Public Works Engineering Australasia (IPWEA) Conference, Mr. O’Keefe has been a busy man. He’s since presented at the Major Roads Project Victoria Forum, the Australian Local Government Association Roads Congress in SA, the Local Government Association of Queensland Waste Forum and an AAPA Breakfast in Perth.
Around three months ago, when trawling through his notes at the Australian Local Government Association conference for yet another presentation, the dot points evoked a simple yet impactful message.
“The reality is that the best proponents of councils to build roads with tyre-derived product are councils who have built roads,” he recalls.
“The message has much more resonance when it comes from fellow practitioners than people like myself.”
While crumb in spray sealing is well known and used across Australia, notably in Victoria, it’s tyre-derived product asphalt applications that are once again back on the agenda.
“When Russell King from the City of Mitcham gets up and says ‘I’ve done it, I’ve built it!’, it just cuts through. So what we want to do is create an army of council proponents, advocates or representatives who have done it themselves on their own roads,” Mr. O’Keefe says.
In looking at Queensland, Mr. O’Keefe is talking real numbers and tangible outcomes.
“What we’ve seen in Queensland is we have reports of significant declines in polymer modified binder usage of around 30 to 40 per cent in some regions,” he says.
With that in mind, the “we’re doing it!” battle cry of crumb rubber asphalt in roads has taken more than five years to hold such significance – but a distinct shift is evident.
TSA worked collaboratively with major road authorities to change the specifications. These were predominately around open and gap graded asphalt, including the Victorian Department of Transport, Main Roads WA and Department of Transport and Main Roads Queensland.
Over that time, TSA accelerated uptake in the market in 2018 when it shifted focus for its market development fund from research and development to demonstration and infrastructure. However, a clear piece of feedback was that councils have their own nuances, and so a customised set of specifications was needed.
“What we’ve found is the local government sector has different requirements for the way in which they manage their assets to road authorities,” Mr. O’ Keefe says.
He says that part of the reason TSA has traditionally focused on the road authorities is that councils defer to the road authority specifications.
“It’s kind of like a default to manage risk, but in reality, the specifications and the recipes for building roads for road authorities are somewhat different to local government,” Mr. O’Keefe explains.
“So now we’re really focusing on giving local government what they need to build rubberised roads – that’s the priority.”
In November, the Department of Transport in Victoria released the light traffic crumb rubber asphalt specification. The specifications are a collaborative effort between Sustainability Victoria – which co-funded their development – the Department, AAPA, the Australian Road Research Board and IPWEA Victoria.
Arthur Apostolopoulos, Manager Pavement Technology at the Department of Transport, says the key driver of the specifications was to increase the use of crumb rubber in asphalt.
“While there are specifications out there for the use of crumb rubber, it was usually focused on heavy traffic roads, which makes [crumb rubber] asphalt expensive,” Mr. Apostolopoulos says.
He says that with an appetite from the local government sector for greener infrastructure, the Department saw an opportunity to increase crumb rubber uptake in a low-traffic landscape not competing with polymer modified binders.
A submission was put to Sustainability Victoria at the start of 2019 to develop a specification. From there, the Australian Road Research Board conducted laboratory tests to ensure the crumb rubber asphalt was comparable to conventional light traffic asphalt mixes. The results went out to industry for public comment in the middle of the year, and a formal specification was published by the end of last year.
Mr. Apostolopoulos says that because the specification is currently limited to low-traffic roads, the Department is confident it can go straight to implementation.
AAPA Executive Director Norbert Michel says that local governments typically refer to the Department for guidance on pavement treatments. For this reason, he says, having a document published by the Department and endorsed by AAPA members will likely lead to an increase in the uptake of sustainable pavement treatment alternatives.
He says that greater uptake of crumb rubber solutions is likely to drive down the price of production. This will ultimately make the selection of such a treatment cost competitive to a standard treatment, with the improved performance characteristics compared to a conventional treatment.
“This value proposition is an easy sell for a local government to its community, especially when they can state that they are assisting with the sustainability of the environment through reduced stockpiling of a waste product,” Mr. Michel says.
Mr. Michel says that ultimately, having a harmonised set of specifications across Australia will yield significant benefits through increased efficiency and reduced costs. He says the AAPA will continue to work with its members and other road agencies in the states and territories to encourage the uptake of sustainable resources that have been tried and tested.
Mr. O’Keefe says the specification is a game-changer. As a first in Australia, the goal now will be to raise awareness so that every council can consider how crumb could be applied to local government-managed low-traffic asphalt roads.
The document explains light traffic crumb rubber asphalt is an asphalt which contains crumb rubber, obtained from waste tyres, to be used as surfacing on low-traffic roads. The section is a supplement to Standard Section 407 – Hot Mix Asphalt and provides the requirements for light traffic crumb rubber asphalt that can complement, or override, the requirements of Section 407.
The specifications cover compliance with Australian Standards AS2008, Austroads Documents AGPT/T190 and VicRoads Codes of Practice RC 500.01 and RC 500.16.
Crumb rubber must comply with the requirements of AGPT/T190, and the use of uncured or devulcanised rubber is not permitted. Crumb rubber must be processed from waste tyres generated in Australia and processed by a TSA-accredited supplier. Additionally, the specification indicates they must be a uniform material consisting of synthetic or natural rubber from car or truck tyres or a mixture of both and free of deleterious materials.
Other applications and the relevant standards are also noted, such as undertaking a dry or wet mixing process, aggregates, filler, a binder or reclaimed asphalt pavement.
In terms of next steps, Mr. O’Keefe says the plan is to test the specifications across a range of different Victorian road conditions, with expressions of interest to be released for up to 10 participating councils. This could include a mix of urbanised, coastal, desert and mountainous environments.
“We want case studies that demonstrate the utility of crumb rubber mixes to help councils create a better road network for their community,” he says.
He says, for example, the western suburbs, which has expansive clay surfaces, could benefit from crumb rubber, which could offer resistance to reflective cracking.
“In Victoria, we’ve got really varied landscapes and road circumstances; for example, the Alps,” Mr. O’Keefe says.
David Hallett, IPWEA Victoria CEO, says that the light traffic crumb rubber asphalt is a positive step forward for IPWEA members looking for confidence in specifying crumb rubber asphalt.
“Local government is typically risk-averse given its responsibility to be prudent with ratepayer money and to use products that will last,” Mr. Hallett says.
“Council engineers are also very visible to the communities they serve – especially in regional areas – so there is a personal dimension to the introduction of any new material or process.”
IPWEA’s role will be to support the local government sector’s appetite for increased sustainability outcomes.
“The challenge is the gap in the middle, which is really a risk gap to ensure all products are suitable for the long-term,” Mr. Hallett says.
“So we’ve been very keen to support whatever proving can be done to give everyone the comfort they need so that they can be informed buyers.”
He says that by demonstrating the product in different environments and monitoring it over time, IPWEA believes the mixes can be demonstrated and validated Victoria-wide.
Mr. Hallett says that while road performance is best measured in decades, the practicality of testing the product’s effectiveness will be continual.
“I think we’ll be looking to measure it after six months, 12 months, two years and beyond. It will be an ongoing process, but we’ll be hoping we can report back success of the product in all of these different environments over an extended period.”
Mr. Hallett points out that tyre-derived products are also suited to bike paths, car parks and other council road applications.
Mr. O’Keefe says that he hopes the model can be used in other states and territories.
In addition, this year, he says TSA is also looking at national binder specifications for crumb rubber with Austroads. Over in Queensland, TSA is working on a regional strategy to inform council-specific specifications for the South East Queensland region with Brisbane City Council and the Australian Road Research Board.
To that end, Mr. O’Keefe hopes contractors will continue to invest in crumb-rubber-specific equipment, including mobile and regional plants.
“There are hundreds of thousands of tonnes of asphalt laid every year. One of the benefits of crumb rubber is that it always costs a similar amount for companies and government procurers – the price doesn’t fluctuate as it does with commodity prices for waste sent offshore,” Mr. O’Keefe.
He says that of the thousands of tonnes of asphalt laid each year, he could confidently estimate TSA is looking at accelerating around 3000 to 6000 tonnes of crumb rubber within the sector annually.
“This is a tangible example of where real impact is being realised. In this case, the circular economy isn’t so hollow,” he jokes.
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