Research findings could support more sustainable asphalt

Two highway workers are using shovels to distribute asphalt along a pothole in the road on a sunny day.

Rubber modified asphalt could significantly reduce the amount of tires in landfills and incinerators. 

By Peter Murphy

Published February 1, 2023

Engineers at the University at Buffalo are examining the potential benefits and drawbacks of using rubber modified asphalt (RMA) instead of traditional asphalt to build roadways. 

Investigation underway to quantify the environmental implications of rubber modified asphalt

“If our results support use of RMA, this project could remove a large amount of waste tires from landfill or incineration streams. ”
James Lang, MS student
Department of Civil, Structural and Environmental Engineering

RMA is not widely used in the United States, and not at all in New York. According to James Lang, an MS student in structural and earthquake engineering, if the results of these findings support using RMA, this project could have widespread benefits.

“Understanding [RMA’s] environmental impact will inform decisions more fully, justifying its use or disuse. If our results support use of RMA, this project could remove a large amount of waste tires from landfill or incineration streams,” Lang says. “For context, if rubber modified asphalt was used for all asphalt paving today, there would not be enough waste tires to satisfy demand.”

Researchers are quantifying the chemical leaching behavior and life cycle environmental impacts of RMA to inform their decisions. 

Chemical leaching refers to the chemicals released from a solid surface when that material is in contact with water. The amount and type of chemicals released when RMA touches water is just one of the many environmental impacts the team is investigating to determine the feasibility of using RMA.

James Lang, a male student wearing a dress shirt, smiles straight ahead in front of a painting of vines.

James Lang, MS structural and earthquake engineering student

According to the U.S. Environmental Protection Agency, every year in the United States, 280 million scrap tires are generated, and 60% of those scrap tires are being landfilled or combusted. The team, including John D. Atkinson, Scott and Coleen Stevens Chair in Engineering Sustainability and associate environmental engineering professor, will investigate whether RMA could be a proposed solution to this waste source.

“RMA is conventional asphalt modified with a small fraction of finely ground tire rubber in the mix. This application has the potential to consume up to 2,000 tires per vehicle lane mile of RMA roadway, dramatically reducing waste generation in favor of recycling,” Lang says. “While civil engineering work has shown the pavement to be quieter and potentially longer lasting, there is a gap in knowledge relating to the environmental and economic impacts of RMA. As a result, many states are hesitant to apply the materials in paving projects.”

The project was initially funded by a $55,000 seed grant from UB’s Stephen Still Institute of Sustainable Transportation and Logistics (Stephen Still ISTL), and after preliminary results, the team secured $100,000 from the U.S. Tire Manufactures Association to investigate chemical leaching, specifically. The additional funding allows the team to expand the project’s scope and use the Federal Highway Administration’s life-cycle assessment (LCA) tool to consider the environmental benefits of removing tires from landfills and incinerators for this specific purpose, one of the first projects to do so.

“Landfilling is poor for the environment in pretty much every aspect – greenhouse gas emissions, habitat destruction, wasted natural resources – and is not a long-term solution,” Atkinson says. “Incinerating tires releases greenhouse gases and while energy is recovered, the value of the material is largely wasted. Recycling tires for rubber reuse extends the life of the high-value material.”

John D. Atkinson 2021.

John D. Atkinson, Scott and Coleen Stevens Chair in Engineering Sustainability

This work coincides with the objectives of the Stephen Still ISTL, considering not only waste tires generated by the transportation industry – like passenger vehicles – but also transportation infrastructure applications for recycled materials. The investigative team consists of several faculty members in the Stephen Still ISTL, UB’s Department of Civil, Structural and Environmental Engineering, and the Research and Education in Energy, Environment and Water (RENEW) Institute. In addition to Lang and Atkinson, the research team consists of Ravi Ranade, associate professor in civil engineering, Aditya Vedantam, assistant professor in UB’s School of Management, and Michael Shelly, an environmental economist in UB’s RENEW Institute. The team is also collaborating with UB’s Department of Chemistry on some aspects of this project, including chemical leaching.

Lang presented this project, as well as the methodology behind the chemical leaching study and life cycle assessment during the Stephen Still ISTL’s reception at the Transportation Research Board’s 102nd annual meeting in Washington, D.C. featuring several transportation administrators, practitioners, policy makers, and researchers. The research team is also preparing two publications, one describing LCA and economic impacts of RMA, and one describing chemical leaching.