In a significant stride towards sustainable construction materials, researchers have uncovered a method to enhance the performance and stability of rubber-modified asphalt, offering promising implications for the energy and construction sectors. The study, led by Danni Li from the Department of Civil and Environmental Engineering at the University of Tennessee, Knoxville, explores the effects of devulcanizing ground tire rubber (GTR) on its compatibility with asphalt, potentially revolutionizing pavement engineering.
The research, published in *Cleaner Materials* (which translates to *Cleaner Engineering Materials* in English), addresses a longstanding challenge in the industry: the poor storage stability of rubber-modified asphalt due to the separation of rubber and asphalt. “This separation issue has been a significant hurdle in fully realizing the benefits of recycling waste rubber in asphalt,” Li explains. “Our study demonstrates that devulcanization can markedly improve the compatibility between GTR and asphalt, paving the way for more efficient and sustainable pavement materials.”
The team employed a thermal–mechanical process using a twin-screw extruder to partially devulcanize GTR at varying temperatures (240°C, 260°C, and 280°C). This process partially alters the chemical structure of the rubber, enhancing its integration with asphalt. The researchers then evaluated the performance of the modified asphalt through a series of tests, including separation tests, rotational viscosity measurements, dynamic shear rheology, and bending beam rheometer tests.
The results were promising. The storage stability of the modified asphalt improved significantly, with the Separation Index dropping from over 40% for untreated rubber to below 10% for rubber devulcanized at 260–280°C. This enhancement in stability suggests that the modified asphalt can be stored and transported more efficiently, reducing waste and improving workflow in construction projects.
Moreover, the viscosity of the asphalt at 165°C decreased by up to 50%, making it easier to work with during application. “Lower viscosity means better workability, which can lead to more efficient construction processes and potentially lower costs,” Li notes. However, the study also revealed a trade-off: the rutting factor, which indicates high-temperature resistance, decreased from 25.7 kPa for untreated rubber to 3.7 kPa for rubber devulcanized at 280°C. This reduction in high-temperature performance highlights the need for careful optimization of devulcanization temperatures and rubber content to balance stability and performance.
The findings suggest that while devulcanization simplifies the mixing and application process, it can compromise the asphalt’s ability to resist deformation under high temperatures. “Optimizing the devulcanization process is crucial,” Li emphasizes. “We need to find the right balance between improving storage stability and maintaining the necessary performance characteristics of the asphalt binder.”
This research not only provides valuable insights into the GTR devulcanization process but also supports the development of cleaner and more efficient production techniques for rubber-modified asphalt. As the construction industry increasingly seeks sustainable and high-performance materials, these findings could shape future developments in pavement engineering, offering a more environmentally friendly alternative to traditional asphalt.
The study’s implications extend beyond the construction sector, touching on the broader energy sector as well. By improving the efficiency and sustainability of rubber-modified asphalt, this research could contribute to reducing the environmental impact of construction projects and promoting the circular economy. As Li and her team continue to explore the potential of devulcanized GTR, the construction and energy industries watch closely, anticipating innovations that could redefine the future of sustainable infrastructure.