The Missouri Department of Transportation (MoDOT) is the lead state for TPF- 5(213) and came to the study with over six years of experience in researching and using post-consumer recycled asphalt shingles (RAS) in hot-mix asphalt (HMA) applications. Today, MoDOT is a national leader in the use of RAS and has diverted over 140,000 tons from the Missouri landfills.
MoDOT started their research with RAS in 2003 completing a series of demonstration projects and laboratory testing covering several years. A draft specification allowing up to 5% RAS with 100% passing the 1/2-inch sieve and not more than 1.5 percent wood by weight or more than 3.0 percent total deleterious content by weight was created in 2005. The allowable percentage of RAS allowed was increased to 7% in February of 2008, however, softer virgin binder grades were required for mixes with virgin binder contents between 60-70% . In 2009, MoDOT began to look at using a finer grind size due to issues with tabs in the surface matt and mixing concerns at the plant expressed by asphalt producers. In July 2010, MoDOT released a new supplemental specification requiring the RAS grind size to include 100 percent passing the 3/8-inch sieve.
MoDOT completed their TPF-5(213) demonstration project in May and June of 2010 on US Route 65 south of Springfield, Missouri. The project goal was to compare the use of a coarse grind RAS mix versus a fine grind RAS mix and document the potential economic and performance benefits that may be present when using a finer RAS grind size. The demonstration project included two test sections with mixes using 5% RAS and 15% recycled asphalt pavement (RAP) with one section using a coarse RAS (100% passing 1/2 inch minus) and one section using a fine RAS (100% passing 3/8 inch minus). The control section included 15% RAP only.
MoDOT's 2011 Specification allows RAS to be used in any mixture specified to use PG 64-22 with 100 percent passing the 3/8-inch sieve; mixes with a ratio of virgin effective binder to total binder between 60 and 70 percent are required to use a PG 52-28 or PG 58-28; post-consumer RAS shall not contain more than 1.5 percent wood by weight or a deleterious content of more than 3.0 percent by weight.
MoDOT is also working closely with Iowa State University to look at the effective binder available from RAS used in asphalt applications, along with researching other mix properties to determine reasonable limits.
Missouri DOT Partner:
Joe Schroer, P.E.
Field Materials Engineer
Phone: (573) 526-4353
Missouri Demonstration Project
May 16, 2012
The Missouri Demonstration Project was completed in June 2009. Three Distress Surveys were conducted, one in December 2010, one in May 2011 and the last one in March 2012. The following presentation summaries the project and surveys.