VAA Spring/Summer 2020

VAASPHALT.ORG 25 SUSTAINABLE... RESILIENT... ASPHALT extensive patching and grinding to maintain a minimum level of serviceability. New pavement designs using conventional materials were initially selected to increase traffic capacity and replace the existing pavement. However, an alternative pavement design using sustainable materials was proposed and selected. This pavement design grew from the lessons learned from the 2011 rehabilitation of I-81 and the 2012 NCAT Test Track sections. The cradle for the alternative pavement design incorporated recycled asphalt pavement (RAP), recycled concrete pavement, sub-base reclamation, and asphalt mixes containing RAP produced with warm mix asphalt technologies. In an analysis performed by Dr. Brian Diefender- fer, P.E., Principal Scientist at the Virginia Transportation Research Council, the alternative pavement sections on I-64 contained up to 80% recycled materials. This is a vast departure from the traditional approaches to designing and constructing pavements. During the “use” phase of a highway, the 2014 TechBrief pointed out the pavement characteristics of roughness, stiffness/ rigidity, and macrotexture. To varying degrees, these characteristics impact the consumption of fuel and resulting vehicle emissions. In a 2006 report prepared by James Gillespie and Kevin McGhee of Virginia Transportation Research Council 2 , the potential cost savings and fuel savings through smooth pavements are docu- mented. Virginia has employed an Interna- tional Roughness Index based ride spec since the late 1990s, and today the average IRI on Virginia’s interstate system is 73 inches per mile 3 . While most of the interstate does have an asphalt surface, some districts do maintain a concrete surface. Figure 16 of the same report shows the increased roughness experienced on concrete surfaces. The last stage in the pavement life cycle is End of Life. The 2014 TechBrief defines this stage as “the final deposition and subsequent reuse, processing or recycling of any portion of the pavement system that has reached the end of its performance life.” For I-64, the End of Life involved the removal of concrete slabs, crushing the material and reuse as a stabilized sub-base. For most of the asphalt pavements in Virginia, the End of Life has not been reached. Even for interstate sections constructed over 50 years ago, most mileage still has the original asphalt base and intermediate layers. Where asphalt layers have been removed, the material has been recycled into new asphalt mixes. Asphalt – The Resilient Choice Today, highways are the lifeline for the economy—locally, nationally, and interna- tionally. When these lifelines get impacted or severed by disasters (natural or man- made), economies suffer. Recent examples of large-scale disasters are Hurricane Maria (2017), Puerto Rico Earthquake (2019), Hurricane Michael (2018), and the Alaska Earthquake (2019). Within the state of Virginia, historic flooding has been wide- spread in 2018 and 2019. These floods have wiped out sections of roads and entire bridges, as well as leading to numerous landslides. When the pavement is gone, it’s imperative to replace the pavement quickly. Multiple emergency projects in 2018 and 2019 involved the placing of an aggregate fill material and base layer, then overlaid with continues on page 26 △ CCPR Plant For I-64 Project