VAA Virginia Asphalt Spring/Summer 2021

22 SPRING/SUMMER 2021 The 20Year Fallacy Trenton M. Clark, P.E., Virginia Asphalt Association 2021 marks the 28 th year since I graduated from Virginia Tech. Except for a week or two in Dr. Martin's Transportation Engineering class, I never took a pavement class while in college. After graduat- ing from Tech, I landed with a pavement specialty firm—PCS/ LAW, located in Maryland. Over the next three decades, I worked for PCS/LAW, VDOT, and now Virginia Asphalt Association (VAA). During that time, I have seen a lot of asphalt and learned to question some common assumptions. I performed pavement designs, analyzed existing pavements, and conducted “failure” investigations. I designed new interstate pavements, and I designed subdivision pavements. I have analyzed airport pavements in the Middle East and shipping ports in the Bahamas. Within the Commonwealth of Virginia, I have had the pleasure of conducting pavement investigations on nearly every type of facility maintained by VDOT. I do not share my background to boast but lend credence to what I'm about to relay in this article. My first job after college was as a staff pavement engineer. I was asked to crunch numbers, conduct visual condition surveys and occasionally design a pavement. With no formal education in pavement design, I decided to read the 1993 AASHTO Guide for the Design of Pavement Structures (1993 AASHTO) from cover to cover. While not classic literature, it gave me a background on pavement structures. Also, I was blessed to have numerous leaders in the pavements field in our office, including Dr. Matt Witczak, Dr. Chuck Schwartz, Dr. Gonzalo Rada, Pete Stephanos, and John Miller. Each came with different strengths in the area of pavements. I recall Dr. Witczak saying one day, “Pavements are the only civil engineering structure we design to fail.” While it may only be a pothole, a pavement at some point will fail. Repeated loads, aging, environmental conditions, and other factors will lead to failure. The key is balancing the road’s needs and the funds available to provide a pavement structure for a specified length of time. As my career progressed, I moved from office work with limited field visits to spending more time on projects. I got to see several of my designs constructed and investigated pavements in apparent need of reconstruction or major rehabilitation. Early on in my career, I was under the impression that pavements lasted a specified number of years (or ESALs) and that asphalt pavements fail from I-81 Roanoke County