We talk with leading educators and researchers to learn more about the people and topics of asphalt technology.
Dr. Peter Sebaaly, Ph.D., P.E., is a professor at the University of Nevada Reno and director of the Western Regional Superpave Center.
What drew you to pavement engineering?
I took the pavement design course as an elective in my senior year at the State University of New York, Buffalo. Through this course, I learned that every pavement project is unique and requires its own design and analysis. Pavement engineers do not have the luxury of ordering materials that meet certain specifications. They must exercise their technical knowledge to design each project and develop practical solutions for each problem encountered over the service life of the pavement. The challenge of combining highly variable natural materials like aggregate and asphalt binders to meet the combined load and climatic impacts seemed very intriguing to me and convinced me to continue on for graduate studies in pavement engineering.
What developments are coming in sustainable asphalt pavements?
I feel that cold in-place recycling (CIR) is a very efficient rehabilitation method that should be given serious consideration when rehabilitating badly deteriorated asphalt pavements. Re-using 100 percent of the existing asphalt concrete in-place with-out transport or heat is a good strategy for sustainable asphalt pavements. The CIR process has suffered some setbacks due to the lack of proper field control and engineering characterization of the CIR mix. The coming developments are; a) implementation of an in-place density measurement method during the compaction process, and b) measuring the engineering properties and performance characteristics of the CIR layer in order to be properly modeled in the M-E pavement design. A properly designed and constructed CIR layer will provide good long-term resistance to several modes of distresses.
Which asphalt additives need more attention and trial projects?
There are two asphalt additives that have shown promising results; a) tire rubber and b) gilsonite. Both additives have shown positive impacts on the performance of the AC mix. Using tire rubber reduces tire waste while gilsonite is a natural product. Each additive has a unique contribution to the performance of the AC mix and can add to the toolbox of the design engineer. Each additive can be used in conjunction with other additives to develop high quality engineered asphalt binders for very common applications such as resistance to reflective cracking and shoving. As the asphalt industry has gained more experience in the applications of the Superpave Performance Grading system and performance testing of AC mixtures, these two additives should move forward for field trials and further validations.
How important is research for graduate students’ education and training?
I strongly believe that the most important role of a pavement engineering program is to train graduate students for successful careers in the private industry. This is the technology transfer part of an academic program. By making graduate students responsible for the management and conduct of their own research project, they become independent thinkers and learn how to operate under the daily pressure that they will face in the real world. No part of the research is too trivial for graduate students. They should personally conduct it all starting from sampling through processing, mixing and testing. The role of the faculty is to supervise and encourage independent performance while ensuring the high quality of the research to be delivered to the sponsor.
Where should today’s students focus their asphalt research?
My advice to students in pavement engineering is they should not focus on a single topic of research. This will limit their chances to succeed in the business world. I recommend that students should focus their main research on one of the current new topics such as new and innovative additives and rejuvenators, engineered asphalt binders, recycling techniques, etc. They also should be involved in a second topic such as pavement preservation and management, non-destructive testing, etc. Students should also strive to use the latest technologies in their research for testing and evaluations. Students should extend the results of their research topic to show the impact of their findings on the design and performance life of asphalt pavements in order to show the full picture of their contributions.