We talk with leading educators and researchers to learn more about the people and topics of asphalt technology.
Dr. Isaac L. Howard is the Director of Mississippi State University’s Richard A. Rula School of Civil and Environmental Engineering.
What drew you to transportation engineering?
I grew up in a farming community in eastern Arkansas. I was accustomed to heavy equipment, soil and working outside. I also liked math and science, so civil engineering was a good fit for me. When I got to graduate school, my thesis and dissertation topics were a bridge and a road, respectively, but in both cases, the materials used to build these items were of primary interest. I became increasingly interested in asphalt paving over time as I realized all the opportunities that exist to make meaningful contributions to the profession.
How can long-term aging experiments increase the quality of asphalt pavements?
Long-term aging experiments are the truth in my view. They are also very credible and give decision-makers peace of mind that they are moving in a reasonable direction. I have arrived at the perspective over time that the combined environmental effects asphalt experiences over time are important to capture in our laboratory conditioning protocols that we use to simulate field aging. In my view, long-term aging experiments that are used to develop laboratory conditioning protocols are beneficial steps toward higher-quality asphalt pavements. The biggest challenge of these experiments is they require lots of support, diligence, patience, and commitment. It can be challenging to spend resources on an aging experiment and then wait for years before fruitful results are produced.
How is stone mastic asphalt being used in Mississippi?
Over the past few years, the Mississippi DOT has used a fair amount of stone mastic asphalt (SMA) on higher-volume routes, especially interstates. To my understanding, MDOT has been pleased with the use of SMA. In many cases, MDOT has placed SMA underneath an open-graded friction course to improve safety for the traveling public. Research-wise, work is ongoing in Mississippi to evaluate allowable mixing temperatures for SMA. This research includes longer-term field-aged mixes, fieldwork on active construction projects and laboratory evaluations.
What are some responsible ways to add more RAP to asphalt mixes?
Over the past ten to fifteen years, RAP has been proven in the sense that it can be used responsibly in asphalt mixes. Over ten years ago, I was fortunate enough to work on some research to increase RAP usage, and we focused on fundamental principles to view RAP as it is, not through some wishful lens. My opinion is that recycling anything, RAP or other, should be approached realistically; not everything about recycled material is positive. In RAP’s case, considering a portion of the total bitumen as inert, stockpile control, reduced reliance on VMA as RAP content increases, rejuvenators, early entry plants and covered stockpiles are examples that can be a part of responsible RAP usage.
Where should today’s students focus their asphalt pavement research?
In my opinion, students should find a topic they have a genuine interest in studying and focus their minds on making a positive difference in that arena. There are so many topics that can be studied to improve pavements; some examples: responsible recycling of plastic, mixture testing during production, balanced mix design, quantification of asphalt’s sustainability, additives, improved durability at competitive economics and implementable laboratory conditioning protocols to simulate field aging. I believe that to make a difference to a level that can stand the test of time that the individual, student or otherwise, needs to be committed mentally to the area and needs to be willing to work in the space for an extended period of time.