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Performance Issues of RAS Mixtures in Missouri

With Solutions. 6 th Asphalt Shingle Recycling Forum Denver, CO. Performance Issues of RAS Mixtures in Missouri . As seen on shinglerecycling.org. Steve Jackson, PE Technical Manager NB West Contracting. Joe Schroer, PE Field Materials Engineer Missouri Department of Transportation.

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Performance Issues of RAS Mixtures in Missouri

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  1. With Solutions 6th Asphalt Shingle Recycling ForumDenver, CO Performance Issues of RAS Mixtures in Missouri As seen on shinglerecycling.org Steve Jackson, PE Technical Manager NB West Contracting

  2. Joe Schroer, PE Field Materials Engineer Missouri Department of Transportation Missouri’s Use of Reclaimed Materials in Asphalt Pavements2012 - MO AGC/MoDOT Conference Steve Jackson, PE Excellence Engineer NB West Contracting

  3. Steve Jackson • B.S. of Civil Engineering • B.S. of Economics • University of Missouri- Rolla • Professional Engineer • 23 years in construction • 15 years in asphalt

  4. History • First shingle research in 2003 • 2.5%, 5%, 7.5%, 10%, 15% • First shingle project 2004 • First MoDOT shingle project 2005 • First MoDOT shingle – WMA project 2009

  5. MoDOT RAS Mix Designs • Most contractors were using RAP & RAS concurrently (2006-2010) • 18% RAP and 2% RAS • 17% RAP and 3% RAS • Due to the Smooth Road Initiative most work was being done on interstates • Superpave mixes • Percent Within Limits (Pay Factors)

  6. Tonnage

  7. Industry Questions • Can we eliminate the fibers in SMA (Stone Matrix Asphalt) and replace them with shingles? • Can we use shingles and PG 64-22 asphalt cement in lieu of polymer modified asphalt?

  8. Dynamic Modulus (E*)SMA

  9. SMA with RAS PG 64-22 PG 76-22

  10. RAS Pooled Fund Study • Iowa State, Dr. Chris Williams, P.I. • Missouri Lead State • FHWA, MN, IA, IN, CA, CO, IL, WI (IL Tollway) • Binder & Mixture Properties • QC/QA • Grind Size • RAP & FRAP • Preconsumer vs. Postconsumer • Demonstration Projects

  11. Ground Shingles Coarse Fine

  12. Thank You

  13. Ground Shingles - Roadway Coarse Fine

  14. Fatigue Life (139) (145) (159)

  15. Low Temperature Testing _ _ _ _ _

  16. Pavement Evaluation

  17. Pavement Cracking • At the same time we introduced shingles we also made other changes: • Warm Mix Asphalt to eliminate joint bumps • Added an elastic recovery specification for asphalt binder • AASHTO Mechanistic – Empirical Design • AMPT/SPT – Mixture evaluation led to thinner pavements • 9.5 mm Superpave mixture laid 1 ¼” thick

  18. Lessons Learned • Shingle size is key to success • Overheating shingle mixes to “melt” the shingles (370° - 390° F) • Variability in RAS asphalt content • Real and perceived • Inflated specific gravities impact mixes*

  19. SRI – Phase Two • Emphasis shifted from Primary Routes to Secondary Routes • Bituminous Pavements (MoDOT Section 401) in lieu of Superpave (MoDOT Section 403) • Less advanced quality control testing • Gradation, deleterious, asphalt content and density • No Percent Within Limits

  20. Work Availability and Recycle • Contractor Perspective • Asphalt Cement prices are high • Supply of shingles is high • Less “Mill & Fill” projects • Less RAP from projects • Large amounts of RAP stockpiled • Fiercely competitive market • Longer haul distances

  21. Longer Hauls – low volume roads

  22. 2011 MoDOT Specifications • 401.4.4.1 Base, BP-1 and BP-2 mixtures shall have the following properties, when tested in accordance with AASHTO T 245. The number of blows with the compaction hammer shall be 35 or the number of gyrations shall be 50 with the gyratory compactor. Air Voids Stability lb(N) VMA 3.5-4.5 750 (3350) 13.0

  23. MoDOT Bituminous Pavements

  24. MoDOT Bituminous Pavements

  25. MoDOT RAS Specification 2011 • 403.2.6.2 Reclaimed Asphalt Shingles. Reclaimed Asphalt Shingles (RAS) may be used in any mixture specified to use PG 64-22 in accordance with AASHTO PP 53 except as follows: When the ratio of virgin effective binder to total binder in the mixture is between 60 and 70 percent, the grade of the virgin binder shall be PG 52-28 or PG 58-28. • Shingles shall be ground to 3/8-inch minus.

  26. Mix Designs and the Market • Higher percentages of recycled materials • Less virgin binder in the mixes • Dryer looking mixes • Rut resistant roadways • Fatigue cracks earlier? • Is there a limit on recycled materials? • Contractors attempted to run up to 12% RAS • Not the mix Ron Sines spoke about yesterday

  27. 2012 MoDOT 401 Specifications • Changed design air voids to 3.5% • Increased VMA requirements: • Bit Base 13.0% • BP-1 13.5% • BP-2 14.0% (Surface Leveling) • 50 gyration mix design was eliminated and replaced with a 35 gyration mix design • Requires a higher asphalt content

  28. What happened? • Corelok specific gravities were used in lieu of traditional AASHTO T 84/T 85 • Gse values were variable • 2.450 to 2.800 • Could be impacted by reported asphalt content • No significant change in virgin binder content in some areas, but some higher quality aggregates were used

  29. Gse Calculation • Pb = Percent binder in the shingles • Gmm = Rice value of the shingles • Gb = Specific gravity of the shingle binder • Gse is used as the Gsb during mix design

  30. Gse Calculation • Higher RAS asphalt content the higher the specific gravity • Higher specific gravity makes it easier to meet the VMA requirements however it allows for lower asphalt content

  31. Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates NassimSabahferMustaqueHossain, Ph.D.,P.E. Department of Civil EngineeringKansas State University

  32. VMA Obtained Using Gsb from Different Methods (Shilling RAP)

  33. Effective Binder 403.2.6.2 Reclaimed Asphalt Shingles. Reclaimed Asphalt Shingles (RAS) may be used in any mixture specified to use PG 64-22 in accordance with AASHTO PP 53 except as follows: When the ratio of virgin effective binder to total binder in the mixture is between 60 and 70 percent, the grade of the virgin binder shall be PG 52-28 or PG 58-28.

  34. Gse Calculation • Lower RAS asphalt content the lower the effective binder replacement • Allows more shingles to be used in the mix

  35. Effective Binder calculation 71%

  36. Effective Binder calculation 58%

  37. Problems with RAS Mixtures • Sporadic Mixing Problems • Confined to Plants not Mixture • Harder to Place in Cool Weather • Low Voids on Long Haul • Tenderness • Asphalt Foamers Run at HMA Temps. • Shingle Pancakes – Clumps, Wads, Clinkers

  38. Not Acceptable

  39. Not Acceptable

  40. MoDOT Response • No shingles were permitted to be used in the surface leveling mixtures for the May and June contracts. • Not very many contracts - 2 • Did not impact Superpave or other low volume route mix designs

  41. Industry Action • Contractors got together in a morning session, worked together to provide recommended specification changes. • Met with MoDOT representatives after lunch and discussed the recommendations. • Adopted as a job special provision for the next bid letting.

  42. 2013 Job Special Provision - SL • Set Gsb of RAS at 2.600 • Changed the gradation of the Surface Leveling mix design: 90-100% passing the 3/8” sieve. • Set Gsb of RAP at the Gsb of the virgin aggregates* • VMA minimum: 14.5%

  43. Effective Binder • Mixtures containing a combination of RAS and RAP may have a 30 to 40 percent effective virgin replacement under the following conditions: (1) with a virgin binder grade change from a PG64-22 to a PG 58-28 or (2) with a combination of a PG64-22 binder and a rejuvenator provided testing demonstrates that a PG58-28 , meeting the requirements of AASHTO M320, is achieved.

  44. How NB West is Successful

  45. Coffee Grounds not Corn Flakes

  46. Education

  47. Warm Mix Asphalt • Compaction Aid • Surfactant • Anti-Strip

  48. Metallica

  49. 56th ANNUAL ASPHALT CONFERENCE December 3-4, 2013 HavenerCenter, Campus of Missouri S&T Rolla, MO asphalt.mst.edu

  50. Questions? Steve Jackson sjackson@nbwest.com www.nbwest.com @sjackson_nbwest

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