Minnesota Research Projects

Missouri Research Projects

Transportation Pooled Fund Program 

The increased interest in using recycled asphalt shingles (RAS) in varying hot mix asphalt (HMA) has spurred demand for research in state highway agencies. A partnership known as the Transportation Pooled Fund (TPF) Program TPF-5(213) was formed to meet these needs. The group consisted of the Federal Highway Administration and state department of transportation from Missouri (lead agency), California, Colorado, Illinois, Indiana, Iowa, Minnesota, and Wisconsin. Each state, except California, performed their own demonstration project that investigated the use of recycled asphalt shingles (RAS) in varying hot mix asphalt (HMA) applications. Laboratory performance tests were conducted on field and laboratory mixes, and field surveys were conducted after placement. The goals and results of each state’s research project are laid out in the report and are summarized below.

Missouri

The Missouri DOT demonstration project evaluated a 5% replacement of recycled asphalt pavement (RAP) with fine and coarse RAS. Fine RAS was defined as 100% passing the 3/8” sieve and coarse RAS was defined as 100% passing the 1/2” sieve. Three mixes were evaluated: a control mix with 15% RAP and no RAS, a mixture that replaced 5% of the RAP with fine RAS, and a mixture that replaced 5% of the RAP with coarse RAS.

• Missouri DOT reported that the fine RAS mixture created a more visually homogenous mixture than the coarse RAS mixture.

• Flow number and dynamic modulus test results showed an improved rutting resistance meaning there was less of a measurable amount of wheel path deformation in the pavements as RAS increased.
• The fine RAS mixture was shown to have lower strain accumulation and higher dynamic modulus than the coarse RAS mixture, giving it objectively better performance.
• Four-point bending beam test results showed the control mix having a higher fatigue resistance at high strain when compared to the RAS mixes.
• The estimated fatigue endurance limit improved with the addition of RAS with fine RAS having the highest and most desirable endurance limit.
• Semi-circular bending (SCB) test results showed no statistically significant change in the low temperature fracture energy between the mixtures meaning all have similar low temperature fracture properties.
• Field surveys were conducted one and two years after placement. RAS pavement had a higher amount of transverse cracking than the control, but the control pavement had a higher proportion of moderate or greater severity transverse cracking. The fine RAS mixture had the lowest proportion of moderate or greater severity cracking.
• The Missouri DOT demonstration produced a RAS mix that met the state’s quality assurance specifications and demonstrated the use of RAS for the Transportation Pooled Fund project.

Colorado

The CDOT demonstration project evaluated a replacement of RAP with RAS in a typical CDOT mix. Two mixes were evaluated: a control mix with 20% RAP and no RAS and a mix with 15% RAP and 3% post-manufactured RAS.

• CDOT reported that the RAS mixture with 1/2” minus grind size of the RAS resulted in individual tabs being visible on the pavement surface during night paving.
• Flow number and dynamic modulus test results showed no statistically significant difference in rutting resistance between mixtures.
• The estimated fatigue endurance limit improved with the addition of RAS.
• SCB test results showed no statistically significant change in the low temperature fracture energy between the mixtures meaning both mixes have similar low temperature fracture properties.
• Field surveys were conducted one winter season after placement. Low severity transverse cracking were observable in both mixes; the RAS mix had a greater amount.
• The CDOT demonstration produced a RAS mix that met the state’s quality assurance specifications and demonstrated the use of RAS for the Transportation Pooled Fund project.

Illinois

The IDOT demonstration project evaluated a replacement fibers and virgin asphalt with RAS in stone mastic asphalt (SMA). Varying mixes were evaluated with combinations of 5% RAS, 11% RAP, 70-28 Binder PG, and 58-28 Binder PG with 12% ground tire rubber. All mixes contained 5% post-consumer RAS.

• Flow number test results “displayed excellent rutting resistance” among mixtures with varying binder. 
• Dynamic modulus test results were higher for mixtures with RAP vs no RAP. Some plant produced mixes yielded lower fatigue lives than lab produced mixes when conducting the four-point bending test.
• SCB test results showed no statistically significant change in the low temperature fracture energy between the mixtures with varying binders, RAP use, and production, meaning all mixes had similar low temperature fracture properties.
• Field surveys were conducted one winter season after placement. No pavement distress was observed.
• The IDOT demonstration produced a RAS mix that met the state’s quality assurance specifications and demonstrated the use of RAS for the Transportation Pooled Fund project.

Indiana

The Indiana DOT demonstration project evaluated the use of RAS with or without foaming warm mix technology. Three mixes were evaluated: a mix with 15% RAP and no RAS, a mixture with 3% RAS, and a mixture with 3% RAS produced with foaming warm mix asphalt (WMA) technology. Both RAS mixture contained no RAP.

• Dynamic modulus test results were similar across all mixes.
• Flow number test results showed an increased rutting resistance for mixtures with RAS vs. the RAP mixture and use of foaming WMA technology did not affect rutting resistance.
• SCB test results showed no statistically significant change in the low temperature fracture energy between the mixes, meaning all mixes had similar low temperature fracture properties.
• Field surveys were conducted one, two, and three years after placement. The RAS mixtures showed a greater amount of transverse cracking than the RAP mixture, however, the RAP mixture had a greater proportion of moderate or greater severity level cracking than the RAS mixes. The RAS mix using foaming WMA technology had the least proportion of moderate or greater severity level cracking.
• The Indiana DOT demonstration produced a RAS mix that met the state’s quality assurance specifications and demonstrated the use of RAS for the Transportation Pooled Fund project.

Iowa

The Iowa DOT demonstration project evaluated “the effects of adding different percentages of post-consumer RAS in HMA.” Four mixes were evaluated: a mix with 0% RAS, a mix with 4% RAS, a mix with 5% RAS, and a mix with 6% RAS.

• Dynamic modulus values increased at high temperatures with RAS use thereby improving the rutting resistance. Values increased at intermediate temperatures and 4% RAS use but decreased at intermediate temperatures and 5% and 6% RAS use.
• Flow number test results showed an increase in flow number with an increase in RAS use thereby giving the mixture more resistance to permanent deformation as RAS use increased.
• SCB test results showed that the RAS use either decreased or had no detrimental effect on cracking performance at low temperatures.
• Field surveys were conducted one and two years after placement. Results showed that after two years, mixes without RAS had the highest amount of transverse cracking while mixes with 4% had the least amount. The 5% had the second greatest amount and the 6% mix had the third greatest amount.
• The Iowa DOT demonstration produced a RAS mix that met the state’s quality assurance specifications and demonstrated the use of RAS for the Transportation Pooled Fund project. 

Minnesota

The MnDOT demonstration project evaluated “the effects of post-consumer RAS and post-manufactured RAS in HMA.” Three mixes were evaluated: a 30% RAP mix, a 5% post-consumer RAS mix, and a 5% post-manufacture RAS mix. Both RAS mixture contained no RAP.

• The difference in dynamic modulus values between the mixes was not statistically significant.
• Flow number test results showed an increase in flow number with an increase in RAS use thereby giving the mixture more resistance to permanent deformation as RAS use increased. The post-consumer mix had a higher flow number than the post-manufacturer mix, however, this difference could be attributed to the difference in fine (post-manufacturer) and coarse (post-consumer) gradation of shingles between the mixes.
• SCB test results showed no statistically significant change in the low temperature fracture energy between the mixes, meaning all mixes had similar low temperature fracture properties.
• Field surveys were conducted two, three, and four years after placement. Results showed all mixes having some amount of transverse cracking. The post-consumer RAS mix exhibited slightly less transverse cracking than the post-manufactured RAS mix.
• The MnDOT demonstration produced a RAS mix that met the state’s quality assurance specifications and demonstrated the use of RAS for the Transportation Pooled Fund project

Wisconsin

The WisDOT demonstration project evaluated “the effects of adding Evotherm® warm mix asphalt technology as a compaction aid in HMA containing post-consumer RAS.” The project evaluated one mix with Evotherm® and one mix without Evotherm®. “Both mixtures contained 3% post-consumer RAS and 13% fractionated recycled asphalt pavement.”

• The difference in dynamic modulus and flow number values between the mix with Evotherm® and the mix without was not statistically significant.
• SCB test results showed no statistically significant change in the low temperature fracture energy between the mixes, meaning all mixes had similar low temperature fracture properties.
• Results from the four-point bending beam test and the dynamic modulus at intermediate temperatures showed improved fatigue properties for mixtures with Evotherm® than mixtures without.
• Field surveys were conducted one winter season after placement, and showed no change in distress in the pavement.
• The WisDOT demonstration produced a RAS mix that met the state’s quality assurance specifications and demonstrated the use of RAS for the Transportation Pooled Fund project

References

[1] Iowa State University Institute for Transportation, “Performance of Recycled Asphalt in Hot Mix Asphalt: Final Report September 2013,” 2013.