Industry News, Latest News, Up front

Recycling waste products in roads gaining traction

Roads & Civil Works Magazine looks at how post-consumer products are being repurposed in Australia’s roads.

Roads & Civil Works Magazine looks at how post-consumer products are being repurposed in Australia’s roads.On 22 September 1999, lightning struck a waste pile containing nearly seven million discarded tyres in Westley, California.

The stockpiled tyres at the Oxford Tyre Recycling Facility ignited and burned for 34 days, requiring drastic and expensive measures to contain it.

The incident became a catalyst for action from the Californian Asphalt Pavement Association (CalAPA), which pushed for further change in the repurposing of stockpiled tyres in the state.

Scrap car tyres have been experimented with, tested and used in many of California’s roads since the 1960s. Concern over large stockpiles and their environmental dangers have helped push the idea behind using these waste products in the likes of Crumb Rubber Asphalt (CRA) – an asphalt mix made exactly out of what it says: crumbled rubber tyres. Parts of the American asphalt industry has undertaken extensive testing to confirm the superiority of CRA to the conventional asphalt mix in the United States. CalAPA reports that since 2004 the California State Government has awarded $34.5 million in grants to the state Department of Transport and counties for asphalt mixes containing crumb rubber.

The Australian asphalt industry has a strong focus on environmentally friendly methods and mixes. Luckily, it hasn’t taken a month-long tyre fire to realise the true potential of recyclable end-of-life items in the country’s roads.

Further exploration into using CRA in Australia has come off the back of the Australian Asphalt Pavement Association (AAPA) International Knowledge Transfer Study Tour to the US in 2014.

Travis Edmonds, former VicRoads Manager Pavement Technology, was one of the Australian delegates on the tour. He presented some of his findings regarding CRA at the AAPA National Workshop Series: Quality Roads, Fixed Budgets in June.

Mr. Edmonds explains that crumb rubber is used in Australian spray-seal specifications, however, only Victoria and New South Wales have specifications for CRA. He says CRA is seen as a ‘boutique’ product because it has a higher capital cost per tonne.

The thick film thickness of CRA gives better resistance to oxidisation. In addition, its resistance to reflective cracking is a major advantage of CRA compared with conventional dense graded asphalt. However, it is the cost, odour and potential fuming of CRA during paving that make it unpopular. “As an industry, there are some concerns in handling CRA,” says Mr. Edmonds.

Warm mix asphalt technology can reduce the fuming issue during paving. However, a polymer-modified bitumen can be used in place of crumb rubber with some similar performance characteristics, without the smell and at a lower cost.

But, as Mr. Edmonds emphasises, only 16 per cent of waste tyres in Australia are recycled. He says the use of CRA is about being able to offer asphalt in the most sustainable means possible. “If there are enough drivers that come into play, that’s where it will get some traction.”

Mr. Edmonds says that the next steps are to work further with AAPA on investigating the possibilities of maximising CRA use in Victoria. “It’s a long road ahead, but at least it’s a start.”

Like VicRoads, Downer is environmentally focused in its efforts to create renewable, low CO2 products, and it’s not just targeting old tyres for the cause. Printer cartridges, glass bottles and other post-consumer recyclables are given extra life in the company’s own asphalt specifications.

Downer Executive General Manager Road Services, Dante Cremasco, says that the current best practice for Australia is for asphalt to include 30 to 40 per cent renewable materials. He says that a 100 per cent renewable asphalt is very achievable and the whole industry is focused on reaching that milestone.

Working closely with asphalt plant supplier Ammann, Downer designed its Bayswater asphalt plant in Victoria so that it could incorporate a high level of diverse recycled materials into its mixes.

The result? A 99 per cent renewable asphalt – a world first.

“For us, it’s really an education to see if we have the right technology,” says Mr. Cremasco. “It was very much a test of our capabilities.”

An estimated 10,000 tonnes of 99 per cent recycled asphalt will see 24.7 kilometres of existing asphalt road re-used, 7.5 million glass bottles recycled, 1250 used car tyres diverted from landfill and 425,000 printer cartridges recycled.

The mix incorporates these normally stockpiled end-of-life items and has a large proportion of reclaimed asphalt pavement (RAP). RAP is the process of reusing an existing pavement in the asphalt mix.

This reduces the reliance upon raw or virgin resources such as those taken from original sources like quarries.

“The problem for local governments is the ever-increasing costs of raw materials as they’re becoming rarer commodities,” explains Mr. Cremasco.

“This is a way of extending those resources,” he says. “It keeps going around and around.”

The challenge for Downer was to produce a renewable asphalt with RAP that could match the strength and resilience of a pavement made from virgin materials.

Part of the Bayswater plant’s innovation is its ability to rejuvenate the RAP binder, and make it reminiscent of its original properties. “Pretty quickly we can make something as good as the original product without massive changes,” says Mr. Cremasco.

The mix boasts a 30 per cent improvement in deformation resistance and a 16 per cent improvement in stiffness, resulting in a thinner surface layer.

According to Downer, the mix can decrease equivalent carbon dioxide (CO2-e) emissions by 52 per cent when compared with conventional asphalt due to the higher recycled material content.

Mr. Cremasco says the 99 per cent renewable asphalt mix can be laid the same as any regular mix. This was shown earlier in the year.

Downer partnered with the City of Boroondara, Victoria, in June to demonstrate the 99 per cent renewable asphalt. The asphalt was laid on a section of internal access roads at McKay Park on 5 June, which also happened to be World Environment Day.

Mr. Cremasco says the demonstration was a great representation of the mix. However, he notes that it’s still early days. The 99 per cent renewable asphalt is a product requiring a large market if it’s going to work.

“We’re targeting a significant reduction in virgin materials and that is only capable with scale,” he says. “If this it taken up in large volumes then we’ll be able to target a 35 to 40 per cent reduction in asphalt production costs.”

Mr. Cremasco says that the next step is to prepare for higher volumes of work and establish regular procurement of the recyclable materials. He says a 200,000-tonne market would give Downer the confidence to take the product to the next level.

Stan Krpan, CEO of Sustainability Victoria (SV), says that there are some exciting developments in recycled asphalt happening not only in Victoria, but around the country too. “Boroondara was the pilot in this,” he says. “We’re also seeing some great projects in Stonnington and Moreland.”

SV is now working with Queensland through ARRB to explore the potential of sustainable methods, such as Downer’s 99 per cent renewable asphalt, in Victoria.

“Asphalt roads are a terrific destination for some of our waste products, and having recycled tyres in pavements is a great alternative for virgin product,” says Mr. Krpan.

With virgin resources becoming rarer commodities, he says that it’s exciting to see companies like Downer showing this kind of leadership in sustainability. “If you can demonstrate [recycled material content] at 99 per cent, there’s no reason that 50 or 75 per cent isn’t achievable more often.”

However, Mr. Krpan explains that it takes more than just one company alone to reach a high-level of recyclable asphalt. It requires collaboration across a number of areas.

Boroondara City Council has been interested in improving its sustainability for some time, he says. Victoria-based Close the Loop is also the company that licensed the printer toner component of the asphalt.

Having road agencies such as VicRoads involved in these exercises also means that the specification for any recycled content can be improved and updated over time.

He explains that suppliers and local city councillors are eager to use post-consumer materials in their asphalt, 10 million end-of-life tyres are produced annually in Victoria alone after all.

However, part of the problem is a gap in knowledge. Many companies are reluctant to invest in something they know little about.

SV has a strong focus on market development.

Mr. Krpan explains there are three important factors it is focusing on right now to improve this knowledge base.

The first is research and development, which is conducted in partnership with VicRoads, industry, Swinburne University of Technology and ARRB. The second is using the research outcomes to update VicRoads specifications to provide industry and councils the confidence of quality performance. Finally, the third focus is on supporting councils and government agencies to procure pavement construction products that contain recycled materials.

SV is beginning to act on these steps. Recently, the organisation collaborated with VicRoads and the Municipal Association of Victoria (MAV) to establish a business case to help councils to use local recycled materials in pavement construction. The business case is directed at marketing the use of recycled products in the region’s roads.

Mr. Krpan says that Australia will begin to see an increase in stringent specifications around the sustainability cycle and how these post-consumer products are procured. This is thanks, in part, to large clients pushing the boundaries around sustainability.

“We’re seeing more countries around the world working to specifications using recycled content in their roads and pavements,” he says. “The M25 in the United Kingdom has 50 per cent recyclable content – [Australia has] got a way to go.”

Mr. Krpan asserts that councils and companies alike need to start building their sustainability credentials. As recyclable methods become more popular, these credentials will be a major selling factor. “It is the way of the future and now is the time to start.”

Leave a Reply

Send this to a friend