Two New Reclaimed Asphalt Pavement Publications
Best Practices for RAP and RAS Management (Quality Improvement Publication 129) by Randy C. West, Ph.D., P.E., covers pavement milling, inventory management, processing, sampling, and testing of RAP and recycled asphalt shingles (RAS), as well as a discussion of production concerns.
High RAP Asphalt Pavements: Japan Practice — Lessons Learned (Information Series 139) by Randy C. West, Ph.D., P.E., and Audrey Copeland, Ph.D., P.E., reports out the findings of a 2014 industry scanning tour of Japan to study that country’s use of high levels of RAP in its pavements. Information about Japanese innovations for porous asphalt pavements are also included.
Both publications were produced under NAPA’s cooperative agreement with the Federal Highway Administration (FHWA) and are available as free, high-quality PDF electronic documents through the NAPA Online Store, http://store.asphaltpavement.org.
Steady Increase in Asphalt Sustainability
The latest NAPA/FHWA survey of asphalt producers' use of recycled materials and warm-mix asphalt finds that almost a third of all asphalt produced during the 2014 construction season was produced using warm-mix asphalt technologies.
The survey, conducted by NAPA under contract to FHWA, found that 114 million tons of WMA was produced in 2014. This is a 7 percent increase from 2013 and greater than 577 percent increase in the use of warm mix since the survey was first conducted in 2009. In the 2009 survey less than 5 percent of asphalt pavement mix tonnage was produced using warm-mix technologies; in 2014, it was more than 32.3 percent.
The survey also found that about 71.9 million tons of reclaimed asphalt pavement (RAP) and 1.96 million tons of reclaimed asphalt shingles (RAS) were used in new asphalt pavement mixes in the United States during in 2014. Reclaiming and reusing the asphalt cement in RAP and RAS saved about $2.8 billion in 2013 compared to the use of virgin materials.
Producers were also asked about ground tire rubber, steel and blast furnace slag, and other waste material repurposed into pavements. Although national estimates of usage were not calculated, survey respondents reported using more 1.2 million tons of these materials in 2014 to produce more than 8 million tons of asphalt pavement mixes.
The survey was conducted in mid-2014. Results from 228 companies with 1,185 plants in all 50 states, along with data from State Asphalt Pavement Associations for 35 states, were used to compile the report. A full copy of the survey, including state-by-state appendixes can be downloaded from www.AsphaltPavement.org/recycling.
Research Finds Unintended Consequences of Reflective Pavements
Addressing the urban heat island effect (UHI) is a growing concern for many municipalities, but a new report from Arizona State University (ASU), "Unintended Consequences: A Research Synthesis Examining the Use of Reflective Pavements to Mitigate the Urban Heat Island Effect," calls into question many common assumptions about the ability of reflective pavements to mitigate UHI.
Reflective surfaces redirect solar energy and for this reason high-albedo, reflective, or "cool" roofs have been suggested as an important tool for UHI mitigation. However, efforts to apply the same principle to pavements overlook the complexities of urban geography and how ground-level reflections interact with pedestrians, vehicles, and the built environment.
"We cannot assume that reflective pavements will behave the same as reflective roofs. When energy is reflected from a ground surface, it doesn't return directly to the sky. It reflects back at buildings and pedestrians. Heat concentration in urban areas is a multifaceted problem; it requires a solution that looks at more than just one mitigation strategy," said Heather Dylla, Ph.D., Director of Sustainable Engineering for the National Asphalt Association (NAPA).
A copy of the report can be downloaded from the ASU National Center for SMART Innovations website at http://ncesmart.asu.edu/news/unintended-consequences.