Crumb rubber asphalt: putting theory into practice

By the end of September 2017, the City of Casey in Victoria laid 8500 tonnes of crumb rubber asphalt (CRA) across a variety of road surfaces. The material – produced from shredding and granulating end-of-life tyres – was used for applications including roundabouts, heavy-vehicle driveways and patching.

In total, the City of Casey’s administration of CRA used 13,600 end-of-life tyres – tyres that may have gone to less productive outcomes such as landfill or burning instead, and are just a small portion of the 56 million tyres generated in 2017, according to Tyre Stewardship Australia (TSA).

City of Casey is one of many local government authorities embracing CRA in the construction and maintenance of its road assets. Its push to introduce the sustainable construction material was fuelled by its significant environmental benefits.

“The main reason we started using CRA is that it’s very environmentally friendly. But, the driving factor was that we could get rid of the tyres,” explains City of Casey Team Leader Civil Construction Michael Apps.

“Like all councils, we have an enormous number of tyres that need to be dealt with every year,” Mr. Apps says, adding that utilising the material also produced other added bonuses.

“Soon after we laid it, we started to see how good it is. We’re finding it impervious to water and it’s stronger, wearing better than normal asphalt,” he says. “Normal asphalt ruts to 8 millimetres. However, CRA only ruts to 2 millimetres, so it’s stronger. There is also a noticeable reduction in road noise – anyone with a four-wheel drive will notice a big difference.”

Not only has City of Casey realised the benefits of CRA but so too have other local government authorities. “Quite a few other councils have contacted me regarding this product. It’s certainly got people’s attention and I know of at least two councils that will soon be using the product for large projects,” Mr. Apps adds.

The inherent benefits of CRA is being increasingly realised upon application by local government authorities, such as City of Casey, which Liam O’Keefe, Market Development Manager at TSA, says has made headway for the uptake of different types of tyre-derived products in Australia.

“The interesting thing about City of Casey is that it’s produced one of the larger applications of CRA in Victoria, otherwise the major utilisation of crumb rubber products for roads in Victoria, New South Wales and increasingly in Queensland is spray seal,” he says.

Tyre Stewardship Australia plays a prominent role in assisting the development of national domestic markets for tyre-derived products, and has seen first hand some of the developments happening in the uptake of crumb rubber products.

“Councils are able to be a bit more particular on the application of crumb rubber products in road construction. Most councils work to road authority specifications, but if they find a product and it is applicable to their government area, they are capable of independently using it. What bodies like City of Casey is doing is diversifying the product’s use.”

Road authorities are taking proactive steps in this area too, with VicRoads recently outlining some significant targets in its recent report Country Roads: Your insights, our actions. “Each year in Victoria almost 14 million tyres reach their end of life. If they are not reused, they are dumped or stockpiled. Across country Victoria over the next five years, our goal is to reuse one million tyres in road works annually and invest $1 million towards research to identify new opportunities to use recycled product,” the report reads.

“We will be much more sensitive to the environmental impacts of our projects, and have set a bold target to double the amount of tyre rubber we recycle in roads for a start.”

Given the fact crumb rubber has been used in asphalt and spray seal to some degree in Australia since the 1970s, Mr. O’Keefe says the scope to increase the use of tyre-derived products has been slow, but it’s reaching a critical juncture where the industry and TSA need to take the next step. “There has been increase in demand for crumb rubber products in pavement construction and maintenance in Victoria, New South Wales and increasingly Queensland, but it’s still something that’s underutilised in certain areas. South Australia and Western Australia are areas of increased focus to enhance the application of crumb rubber products being used moving forward too,” he says. “Crumb rubber in spray seals started in Victoria and has become kind of a legacy because it works so well, but the problem is that people still question it.”

While TSA has traditionally leaned towards research and design-orientated outcomes, with CRA and other crumb rubber products increasingly recognised for their environmental and practical benefits, the organisation is shifting its focus towards more practical and direct outcomes.

TSA’s central investment mechanism to support the market is its Tyre Stewardship Research Fund. The fund was developed primarily to support collaborative research and growth of the end-of-life tyre product market in Australia, but Mr. O’Keefe says TSA is now looking at how it can be used on a greater scale, including on large infrastructure projects.

“Initially, the focus was more on the research and development side because we didn’t want to be too overt and influence the market unduly, particularly as a new organisation. But, now we are more familiar with the markets – we know the road and rail sectors better, so we feel we’re better able to work with the appropriate bodies to deliver better outcomes with less risk to existing businesses and markets,” he explains. “We’ve got a great relationship with the likes of Australian Asphalt Pavement Association (AAPA) and Australian Road Research Board (ARRB), who we’re working with along with Queensland Department of Transport and Main Roads to further the scope for crumb rubber spray seal use in Queensland.”

Likewise, TSA is working closely with Main Roads Western Australia to further implementation and uptake in the west.

“What we’re trying to do is move to a more active approach in collaborating with state authorities and organisations, but that really relies on the states coming on board,” Mr. O’Keefe says. “AAPA are a great conduit to engage with industry and government across the supply chain, especially as we are a smaller organisation and don’t have the reach to the councils to the extent we would like. So, we are looking to be more active in the practical space for a number of reasons. Within the organisation, for instance, we need to be more active in councils signing up to be TSA-accredited, use tyre-derived products and use accredited recyclers.”

TSA is also already developing a training course for road engineers around the utilisation of crumb rubber binder in spray seal and asphalt applications with AAPA.

Mr. O’Keefe says TSA plans to interact with more decision makers and the practitioners who specify and build the roads, in an effort to produce more practical outcomes.

“In last three to five years I think a lot of people in the industry have become more accepting of crumb rubber. We are seeing increasing demand in different applications and that’s because we have had a coordinated approach and are seeing the outcomes in the industry as a result,” he says.

The increasing acceptance is also seeing tyre-derived products explored in other infrastructure applications, including in rail track ballasts and prefabricated materials for construction purposes.

“AAPA, ARRB, state road authorities – they’re all important to this conversation. When the experts are talking to each other that’s when people listen. The important thing we’d like to see with research organisations is these great ideas for reusing end-of-life tyres have real-world impacts,” Mr. O’Keefe says. “Different markets are at different stages and we need to be able to facilitate growth and provide support where we can.”