Warm-Mix Asphalt Use Reaches New Heights
The latest NAPA/FHWA survey of asphalt producers' use of recycled materials and warm-mix asphalt find that nearly a quarter of all asphalt produced during the 2012 construction season was produced using warm-mix asphalt technologies.
The survey, conducted by NAPA under contract to FHWA, found that about 86.7 million tons of WMA in 2012. This is a 26 percent increase since 2011 and a 416 percent increase in the use of warm mix since the survey was first conducted in 2009.
The survey also found that about 68.3 million tons of reclaimed asphalt pavement (RAP) and 1.86 million tons of reclaimed asphalt shingles (RAS) were used in new asphalt pavement mixes in the United States during in 2012. For the first time since the start of this survey in 2009, the amount of RAP and RAS used by producers exceeded the amount collected.
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 than 1 million tons of these materials in 2012.
The 1.86 million tons of RAS is a 56 percent increase over 2011, and a 165 percent increase since 2009. Since 2009, RAS usage has been reported in 37 states. RAP usage showed a modest increase from 2011 to 2012; however, the 68.3 million tons used in 2012 is a nearly 22 percent increase since 2009.
The survey was conducted in mid-2013. Results from 213 companies with 1,141 plants in 48 states and Puerto Rico, along with data from 36 State Asphalt Pavement Associations, were used to calculate industry estimates for total tonnage. A full copy of the survey, including state-by-state appendixes can be downloaded from www.AsphaltPavement.org/recycling.
Warm-Mix Asphalt Wins NOVA Award
The National Asphalt Pavement Association (NAPA) has received the prestigious 2013 NOVA Award from the Construction Innovation Forum (CIF) for its work to speed the deployment and uptake of warm-mix asphalt.
"NAPA is proud to accept this award on behalf of the asphalt pavement industry, warm-mix technology developers, and our partners at the Federal Highway Administration (FHWA) and state departments of transportation nationwide. The success of warm mix is due to cooperation and a willingness to innovate from road owners and builders alike," said NAPA President Mike Acott.
In selecting warm mix to win a 2013 NOVA Award, the investigators cited its ability to improve compaction, reduce fuel or energy use, improve worker comfort, lengthen the paving season, and reduce overall paving costs. Continued
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.