Better Roads Staff
The Tech Brief contains the latest responses to a biannual survey on RAP use conducted by the RAP ETG. With the assistance of AASHTO, the survey was conducted in 2007, 2009 and 2011. “In 2007, the typical hot-mix asphalt mixture contained about 12-percent RAP,” the document states. “From 2007 to 2009, about 27 states increased the amount of RAP permitted in asphalt mixtures, and, as of 2009, 23 states have experience with high-RAP mixtures. As of 2011, the majority of state highway agencies (more than 40) allow more than 30-percent RAP; however, only 11 report actually using 25-percent RAP or more.”
The RAP ETG Tech Brief also lists recent documents that articulate new technical information on higher RAP contents. Download it by searching for “FHWA-HRT-11-057.”
Earlier in 2011, the FHWA rolled out a definitive document that maintains that, based on an evaluation of pavements containing 30-percent RAP through the LTPP program, performance of pavements containing up to 30-percent RAP is similar to that of pavements constructed from virgin materials with no RAP.
The April 2011 report, Reclaimed Asphalt Pavement in Asphalt Mixtures: State of the Practice (Publication No. FHWA-HRT-11-021), provides new guidance on best practices when using RAP, and documented information about long-term performance of high-RAP pavements.
The state of the practice for RAP use across the United States, as well as common challenges for increasing the use of RAP, are identified. Authored by FHWA’s Audrey Copeland, best practices for the use of RAP are presented for developing specs, and for sourcing, processing, stockpiling, testing, designing, evaluating, producing and placing high-RAP mixtures. Ways to attain best performance for high-RAP mixtures are presented. Download the report by searching for “FHWA-HRT-11-021.”
When Politics Drives RAP Use
While other states adopt a tiered approach to higher percentages of RAP, California is using legislation to aggressively adopt higher RAP in HMA specifications.
The California Asphalt Pavement Association (CalAPA) reported in October 2011 that Caltrans’ acting director Malcolm Dougherty says the state transportation department is “moving aggressively” to adopt new standards to permit more RAP usage on state highway jobs.
The pledge comes as assembly speaker pro tem Fiona Ma is pressing Caltrans in legislation to allow up to 50-percent RAP in mixes. In an August 10, 2011 letter to Dougherty, Ma said she was “disappointed” by an earlier letter to her office from Caltrans indicating a lengthy process involved in evaluating a move to a higher RAP standard.
In his official response dated September 5, Dougherty said his department “recognizes the benefits of using a higher percentage of [RAP]. Caltrans is moving aggressively to introduce specifications and guidelines that will incorporate a higher percentage into our projects, while ensuring long-term performance of our paving materials.”
Dougherty announced that the department has accelerated an internal deadline, from June 2012 to November 2011, to develop a specification for 25-percent RAP, which will be incorporated into pilot projects in 2012 and evaluated. Current Caltrans specifications limit RAP to 15 percent of mixes.
“Industry’s reaction to the news was mixed,” CalAPA reports. “On the one hand, industry representatives were glad that Caltrans was recognizing the need to increase RAP limits, but the incremental approach and relatively slow pace of the changes bred frustration.”
CalAPA reported Bill Williams of Bo Dean & Co., an asphalt producer in Santa Rosa, as having said, “There is no known reason why Caltrans should limit high percentage RAP to 25 percent. I believe that 25 percent is achievable without fractionalization, especially when incorporated with warm-mix asphalt technology. Caltrans should not limit our ability to move toward a greener asphalt that creates better roads.”