RECLAIMED (RECYCLED) ASPHALT PAVEMENT (RAP)
Asphalt pavements are 100% recyclable, and asphalt is American's No. 1 recycled material. For decades, agencies have allowed the use of RAP in new pavement construction with great success. A recent report by the Federal Highway Administration had this to say about RAP: " Recycling asphalt pavement creates a cycle of reusing materials that optimizes the use of natural resources. Reclaimed asphalt pavement (RAP) is a useful alternative to virgin materials because it reduces the need to use virgin aggregate, which is a scarce commodity in some areas of the United States. It also reduces the amount of costly new asphalt binder required in the production of asphalt paving mixtures."
The National Cooperative Highway Research Program (NCHRP) and the National Center for Asphalt Technology (NCAT) have conducted several research projects on the use of RAP in new pavement construction (NCHRP 9-12, NCAT 96-05, & NCAT 95-01). The Pacific Coast Conference on Asphalt Specifications (PCCAS) also has done extensive work on RAP standards and specifications.
The main concern identified with the use of RAP is with the effect of the RAP binder on the virgin binder. As a result with the NCHRP report, the Federal Highway Administration (FHWA) has developed guidelines for incorporating RAP in new pavement construction. The guidelines recommend changes to the virgin binder grade based on the percentage of RAP incorporated.
Caltrans has allowed the use of a maximum of 15 percent RAP on QC/QA projects. In Fall of 2006, Caltrans issued a Caltrans Policy Directive (CPD) that allows HMA producers to use a maximum of 15 percent RAP on all Caltrans projects. Many local agencies are allowing a higher percentage of RAP in their mixes.
Local agencies in southern California have used RAP since the early 70's. The predominant specification book for local agencies in Southern California, the "Greenbook," otherwise known as the "Standard Specifications for Public Works Construction," allows the use of RAP in HMA.
The FHWA defines a high-RAP policy as utilizing RAP at 25 percent or above. A survey of state transportation departments, sponsored by the American Association of State Highway and Transportation Officials (AASHTO) in 2009, found that 28 states had policies for high volume RAP in surface courses—all above California. Seven states allowed up to 100 percent RAP in HMA.
RAP stockpiles ready for reuse.
The Caltrans Construction Procedure Directive (CPD 13-5) on how to implement the contractor option for higher RAP, with various attachments, can be found HERE.
NAPA's national survey, published in 2013, of RAP, RAS and WMA usage is HERE.
An overview of asphalt recycling from the Asphalt Alliance. Click HERE.
A 2010 NAPA news announcement on the push to use more recycled asphalt can be found HERE.
Click HERE to download a presentation on RAP by CalAPA member Tom Carter delivered at the 2009 CalAPA "California Asphalt Pavement Forum."
Click HERE to download a presentation on RAP by Gerry Huber delivered at the 2010 CalAPA "Paving Green" Conference Oct. 28 in Sacramento.
April 2011 FHWA report on Recycled Asphalt Pavement use. Click HERE.
The special FHWA RAP website of resources can be found HERE.
The website of the FHWA's Recycling Asphalt Pavement Expert Task Group can be found HERE.