Roads that are more durable, last longer, are safer, cost less to maintain, and have lower carbon impacts are possible by using something that has long been considered a problematic waste stream in Aotearoa New Zealand.
In a recent webinar, Anna D’Angelo of the National Transport Research Organisation (NTRO) in Australia presented a compelling case for the use of crumb rubber in roading.
Crumb rubber from recycled tyres used as a bitumen modifier makes the road surface more elastic and resistant to cracking. It also enhances cohesion and aggregate retention, enhancing performance under stress.
Another benefit comes from the carbon black in tyres, which acts as a ‘sunscreen’ for the road. According to NTRO research, this reduces ultraviolet damage by as much as 42 per cent. This is especially relevant for residential roads, where failure isn’t normally caused by heavy traffic, but by oxidisation, which causes cracking and leads to further damage from water ingress.
There is an emission benefit, too. Research conducted by Tyre Stewardship Australia (TSA) shows a nine per cent reduction in greenhouse gas emissions from crumb rubber sprayed seal compared to other polymer-modified bitumen.
In terms of health and safety, monitoring and research conducted by NTRO has shown there are no harmful emissions above recommended limits. TSA research findings around leaching and water quality also didn’t raise any concerns because the rubber becomes part of the bitumen.
Last, but certainly not least, while the cost of using crumb rubber modified bitumen can be higher, NTRO research shows that this is more than offset by improved performance and life span. It’s also worth noting that the cost of the bitumen is only one small part of the overall cost of building a road.
Fulton Hogan recently re-sealed a road at its Roydon Quarry, near Christchurch, using crumb rubber modified bitumen. The Australian experience shows that crumb rubber can be used at rates of up to 15 per cent, improving road surfacing flexibility and durability.
Tyrewise, New Zealand’s regulated product stewardship scheme for end-of-life tyres, expects that these benefits, along with local research, trials and pilots, will drive an increase in demand. The scheme is working closely with onshore processors to ensure supply can meet that demand, and that the crumb rubber is processed to the correct specifications for roading applications.
More webinars on the topic are being planned. To stay up to date, subscribe to the Tyrewise newsletter at www.tyrewise.co.nz/contact. To learn more about crumb rubber in roading, visit www.tyrewise.co.nz/rubber-in-roading.