VAA Virginia Asphalt Fall/Winter 2021

DEFINING ASPHALT’S FUTURE withstand disruptions without knowing the environmen- tal or safety risks may enhance resilience, but that doesn’t mean it’s sustainable. What you will notice, however, is that most resilient options are also sustainable options, such as using warm mix asphalt to both lower emissions (sustainable) and to increase haul distances if a local asphalt plant is taken offline due to disruption and the roadway needs rapid repair (resilient). Resilient to What? The National Oceanic and Atmospheric Administra- tion (NOAA) tracks annual “Billion-Dollar Weather and Climate Disasters.” As of October 8, the year 2021 has had 18 different billion-dollar weather/climate disasters such as hurricanes, wildfires, drought and flooding, to name a few. The year 2020 had the most billion-dollar climate disasters ever at 22 (NOAA 2021). As hurricanes inundate our coastal roadways, floods from rapid snowmelt drown midwestern highways, drought followed by heavy precip- itation causes highway failures over expansive clays from Texas through Alabama and beyond, we have found our- selves with a unique challenge. Drawing on ASCE’s 2021 Infrastructure Report Card, the roads in the U.S. were given a grade of “D” (ASCE 2021). The report card cites a $435 billion backlog of repair needs to existing roadways. How will we revitalize our pavements while making them more resilient to these disruptions? We Have a Full Toolbox The good news is we already have many tools in our toolbox, and many live in the part of the Venn diagram that overlaps sustainable and resilient. An inherent attribute of asphalt pavements is that they can be rapidly constructed. If an earthquake occurs—like the one that struck Anchorage, Alaska in 2018, causing slope stability FALL/WINTER 2021 12 failures that lead to pavement failure—asphalt pave- ments can be rapidly reconstructed in days or as little as hours to get the roadway operational again (Bowers and Gu 2021). Asphalt is also designed to be climate adapt- able, like the Binder Performance Grading system, along with the ability to use polymers, fibers and other addi- tives. Mixes can be designed to withstand extremely high and low temperatures and even temperature swings. As previously mentioned, warm mix additives can increase haul distances when local asphalt plants have been compromised. Porous asphalt is specifically designed to manage stormwater, making it a tool that can be used to handle heavy precipitation. Pavements can also be designed to be perpetual or long- life, as was done in Iowa after the 2018 floods destroyed sections of the interstate (Bowers and Gu, 2021). When flooding occurs, it can cause a lowering in base stiffness, leading to premature failure or triggering undermining of the roadway. In either case, using a perpetual pave- ment can help mitigate these issues. These are just a few of the tools the asphalt industry already has that can be used to increase the resilience of pavements. Where Do We Go From Here? I believe that we need to find ways to adapt our infra- structure that make it both more resilient and more sustainable. Take, for example, techniques like full-depth reclamation (FDR). If a coastal highway is undergoing regular flooding and loss of base stiffness, FDR can be used to stabilize 14+ inches of the existing pavement and base, 100% recycling what’s in place with minimal hauling. An asphalt overlay can then be placed on top to add structure and serve as the wearing surface. If cor- rectly designed, a perpetual pavement structure can be △ continued from page 11 Figure 1 Venn Diagram of Sustainable, Resilient and Resilient + Sustainable Practices and Attributes for Asphalt Pavements (Courtesy of the National Asphalt Pavement Association [Bowers and Gu 2021]). Sustainable + Resilient Practices or Attributes Sustainable Practices or Attributes · Use of recycled materials · Cold Recycled Asphalt · Asphalt mix and plant optimization Sustainable + Resilient Practices or Attributes · Warm Mix Asphalt (low emissions + increase in haul distance) · Porous pavement systems (stormwater management + nuisance flooding) · Perpetual Pavement Design · Deep reconstruction of pavement (increase deep layer moduli) · Rapid construction · Ability to adjust pavement design to climate/climatic events to extend pavement life Resilient Practices or Attributes That Are Not Sustainable · Use of novel materials with unknown environmental or safety risks · Use of climate adaptable materials when the social and environmental benefits do not outweigh the costs (e.g., use of polymer modified binders for low-volume roads) · Over-designing for low-risk catastrophic events Sustainable Practices or Attributes Resilient Practices or Attributes