While the end of winter brings warmer temperatures and green grass, it also heralds the beginning of one of the most difficult times of year for drivers: pothole season.
Manik Barman, an associate professor in the Swenson College of Science and Engineering at the University of Minnesota Duluth and a scholar with the Center for Transportation Studies, discusses what causes potholes, the work that goes into fixing them and how drivers can stay safe on uneven roads.
Q: What causes potholes?
Prof. Barman: Minnesota’s roads experience harsh weather conditions. Severely cold temperatures, heavy snowfall, freeze-thaw cycles and de-icing salt significantly influence the state of roads in our region. Potholes are generally a secondary distress symptom following other structural issues caused by traffic load, material wear and weather, which is the primary factor in play. When water infiltrates the pavement structure and transforms into ice during the colder months, it creates micro-cracks in the asphalt layer. As the ice thaws, those cracks spread and disintegrate the asphalt materials as vehicles pass over it, creating potholes.
Q: How are potholes patched?
Prof. Barman: Potholes need to be repaired quickly for the safety of road users. Different patching methods and materials are available, including conventional asphalt mixes, cold mixes and other proprietary materials. In the winter, potholes have typically been temporarily patched using a cold mix until more permanent patching methods could be applied. Since patching with hot mixes is usually performed in non-winter seasons, crews have historically had to visit and repair the same pothole multiple times.
Q: How have repair methods changed?
Prof. Barman: In recent years, innovations have been made in both methods and materials, and the University of Minnesota has been involved with many projects designed to help crews make Minnesota roads safer. Hot mixes are the best to repair potholes, and on-site equipment has advanced so they can be used during winter, too. By heating existing materials around the pothole, hot mixes enhance the bonding of the patch and lead to better long-term conditions. Among these new patching materials, the University of Minnesota Duluth’s taconite-based patching material is fast-setting, lasts significantly longer and can be applied more easily in winter.
Q: What should Minnesotans know about potholes?
Prof. Barman: Transportation agencies work hard to take the edge off frustrating and hazardous pothole-infested roads, including preventive maintenance and periodical repair projects. However, it is safe to assume our ever-present weather conditions — especially the freeze-thaw cycle — will keep creating potholes.
Here are some tips for handling potholes:
- Expect potholes and consider scheduling extra time to drive slowly and cautiously.
- Watch for vehicle damage after pothole encounters.
- Report pothole occurrences to transportation agencies in your city, county and/or MnDOT as soon as possible.
- Try to keep calm when dealing with pothole-related road difficulties — they are a reality of harsh Minnesota weather.
Q: How is the University of Minnesota advancing road maintenance techniques and technology?
Prof. Barman: “Better roads” is the theme of my research. I work on creating innovative and sustainable pavement materials and designs, rehabilitation and maintenance. MnDOT used the pothole patching guide and decision framework I developed to create easy-to-follow flashcards for maintenance crews to select the appropriate patching method based on the pothole features. I also determined the most cost-effective pavement crack sealing method for Minnesota roads so we can decrease moisture infiltration and stay ahead of the freeze-thaw cycles that create potholes. One of my recent projects focuses on mitigating the heaving of asphalt pavement cracks in frigid winter temperatures, which is also a significant factor for pothole formation.
Manik Barman, Ph.D., is an associate professor in the Swenson College of Science and Engineering at the University of Minnesota Duluth and a scholar with the Center for Transportation Studies. His scholarly focus is on pavement design, rehabilitation and maintenance. He is currently researching pavement rehabilitation and maintenance issues, fiber reinforced concretes for long-lasting pavement rehabilitation and asphalt mixtures for low-volume roads.
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About the Center for Transportation Studies
The Center for Transportation Studies at the University of Minnesota is a national leader in transportation research, engagement and education. CTS collaborates with public-sector, industry and academic partners to shape transportation systems that are sustainable, serve the needs of all users, support a strong economy and improve our collective quality of life. Learn more at cts.umn.edu.
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