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The materials used in roads can change the sound, efficiency and carbon effects for years to come. Research on the use of scrap tires in asphalt shows it to be cost-effective, safer, quieter and environmentally-friendly.

The Ray, U.S. Tire Manufacturers Association (USTMA) and Missouri Center for Transportation Innovation recently presented a webinar on the subject. The event resurfaced issues that are important, as the U.S. creates legislation and funding to improve infrastructure while aiming for decarbonisation.

RMA – Where the Rubber Is Part of the Road

Allie Kelly, Executive Director of The Ray, introduced Dr Bill Buttlar, Director of the Missouri Center for Transportation Innovation. He oversees the Mizzou Asphalt Pavement and Innovation Lab (MAPIL).

Kelly says: “RMA will make our roads more productive, safer and cleaner for us to drive.”

Buttlar walked hundreds of participants through the key findings and beneficial aspects of RMA that appears in his report, ‘The State of Knowledge Report on Rubber Modified Asphalt’.

Buttlar says, early in his career, he learned about recycling polymer into asphalt. There was a lot of use of polymer modified asphalt and new polymers going into asphalt to extend the life.

“It wasn’t until maybe 5 or 6 years later that I learned about the ground tire rubber research. That was when I was a professor at the University of Illinois for 20 years before joining Mizzou,” explains Buttlar.

The report was commissioned to bring together all the research, identify gaps and advance the circular economy for scrap tires. It also provides research that shows that RMA is a sustainable infrastructure solution. Buttlar says he is “super passionate about the findings.”

“There are 260 million scrap tires generated in the U.S. annually. There is no substitute for rubber. However, rubber is an incredibly tough and durable material and poses considerable end of life challenges.”

Rubber modified asphalt uses ground tire rubber (GTR) that is mixed with asphalt by a wet or dry process.

The report focuses on three aspects of RMA: environment and sustainability; performance and safety; and economics. The report was peer-reviewed by a panel of experts from academia, industry and state federal agents. 

Environmental And Sustainable Benefits of Rubber Modified Asphalt

For environment and sustainability, RMA provides a huge environmental impact. It reduces CO2 emissions by -34%, ozone depletion by -38% and water depletion by -30%.

RMA also has low permeability and the potential to reduce leaching by 85%. RMA reduces tire tread emissions by 30 to 50% and reduces tire wear.

Smoother RMA roads reduce noise up to 12 decibels, decreasing the need for sound walls that can cost up to $1 Million a mile to construct. RMA roads create rolling resistance which will incur fuel savings, says Buttlar.


How Does RMA Improve Performance And Safety?

Rubber modified asphalt helps with many issues. With twice the life extension on roads, fewer people get hurt while working on the road. Cracking and rutting are reduced by RMA.

RMA improves tire grip. Skid resistance improves 25%. The improved pavement smoothness makes roads safer.

Buttlar says, for rainy soaked areas, water goes through the RMA.

“You not only get the water benefit – you get the surface that you want.”


How Much Money Does RMA Save?

The cost savings of RMA are significant. The dry process is less expensive than traditional polymer modified asphalt with comparable performance. Plus, thinner designs provide comparable performance to traditional asphalt at a lower cost, he says.

Over life, there is a 43% saving in cost and a 40% savings in maintenance costs, reports Buttlar.

Why Aren’t All The Roads in The US Made of RMA?

Some states do not have contractors who can do this kind of road surfacing. However, when contractors find out that RMA road surfacing is less expensive, they can do more competitive bids. Then, they are more likely to use it, he explains.

He concluded the webinar by stating, rubber modified asphalt is a proven ready technology for over 40 years with attractive environmental performance and economic benefits.


Where Can RMA Be Seen in Use?

One place to see a clear demonstration of RMA works is The Ray. On I-85 in Georgia, 42,240 pounds of scrap tire were used with the RMA dry process. It resulted in extended pavement life with crack resistance added wet weather safety and noise reduction, says Kelly.

Kelly asked Buttlar what is needed next in the current climate where there is planned federal support for infrastructure improvements.

Buttlar says a coordinated effort is critically needed to bridge knowledge gaps to get the information out about best practices to demonstrate performance and also to share data and specifications to increase RMA usage. He also suggested incentives and funding for support.

“I think we should share the data and the experience and also incentivize RMA. Funding could be used to create a clearinghouse of information. There needs to be an establishment of a centre for the information,” advises Buttlar.

The report calls for the establishment of a National Center of Excellence for Rubber-Modified Asphalt. It would facilitate research and could assist in the dissemination of research being carried out at other institutions nationwide and across the world.

To learn more, Buttlar urges the download of the PDF of the report that shows the most recent research.

He says: “There’s always work to be done to make it more sustainable and economical.”

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