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Advanced Asphalt Mix Design Methods and Superpave Technology Overview

Learn about Superpave asphalt mix design methods, laboratory compactors, performance graded binders, and future innovations in asphalt technology.

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Advanced Asphalt Mix Design Methods and Superpave Technology Overview

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  1. Superpave Today Kenneth Ray Hobson, P.E. – Bituminous Engineer khobson@odot.org City of Tulsa May 13, 2011

  2. Overview • Asphalt Mix Design Methods • Laboratory Mixture Compactors • Asphalt Binders • Aggregate Tests • Mix Design Proof Testing • Design by Traffic Volume

  3. Overview • Mix Design Notes • Future Items of Note • 2009 Std. Spec. 411 • Links Of Note

  4. Automatic Marshall Hammers

  5. Texas Gyratory Hveem Compactor

  6. Superpave Gyratory Compactor (SGC)

  7. Limitations of Traditional Binder Specifications • Penetration & ductility tests are purely empirical • Tests are conducted at one standard temp (i.e.. Pen @ 77ºF,Vis @ 140ºF), despite different climatic conditions • Entire range of pavement temperatures (esp. low temp’s) not considered

  8. Limitations of Traditional Binder Specifications • Asphalt cements can have different temperature and performance characteristics within same grade (Pen or Vis) • Not applicable to modified binders (more use in recent years) • E.g. Grades AC-20, PMAC-1C

  9. Superpave Asphalt Binder Specification The grading system is based on Climate PG 64 - 22 Min. pavement temperature Performance Grade Average 7-day max. pavement temperature

  10. Performance Graded Binder Specifications • Based on Mechanical Properties (DSR, BBR) • Modulus • Deflection • Load Response (Rate) • Other Tests Remain Unchanged • Mass Change, Flash Point, Elastic Recovery, etc. ER is known as PG+ Spec. • ODOT 2009 Std. Spec. 708.03 Table 708:2

  11. Aggregate Tests • Superpave similar to Hveemwith added tests: • Fine Aggregate Angularity (FAA) • Bulk Specific Gravity (used for FAA and VMA computations) • Micro-Deval (30+ MESALs)

  12. Mix Design Proof Testing • Marshall Cohesiometer • Hveem Stabilometer • Hamburg Rut Test

  13. Design by Traffic Volume • Hveem – ADT • Lab Specimens (4” diameter) Compacted the Same (275oF) • Air Void Limits Adjusted by Traffic • Superpave –ESALs in 20 Years • Lab Specimens (6” diameter) Compacted More with More Traffic (300oF) • Air Void Limits Kept Constant

  14. Mix Design Notes • Ndes – Number of SGC Gyrations at JMF Binder • Nini – Number of SGC Gyrations backcalculated from Ndes Specimens • Density Similar to That Behind Paver • Nmax – Number of SGC Gyrations at End of Pavement Life (mix design only)

  15. Future Items of Note • WMA – The Future is here now! • Provides Many Benefits • Tack Coats – 0.15 gal/SY Diluted 1:1 • Trackless Tack Emulsion – Near 100% Bonding • Pave Sprayer Applied PMCRS-1S – Near 100% Bonding

  16. 2009 Std. Spec. 411 • Table 411:2 – Calculate Density (RD) Based on Latest Gse at JMF Binder Content for Pay Factor • Table 411:4 – Binder Content (Pb) and Air Voids (AV) for Pay Factors • CPF = (4 x RD + (3 x AV) + (3 x Pb)) / 10

  17. Future Items of Note • Increased Binder Content by Special Provision • Possible Reduction in SGC Gyrations • Possible VMA Increase by 0.5%

  18. Links of Note • Construction Engineering • Standards, Specifications, Materials and Testing • http://www.okladot.state.ok.us/cnstrctengr.htm • Materials Division Contacts • http://www.okladot.state.ok.us/materials/index.htm • Materials & Testing e-Guide • http://www.okladot.state.ok.us/materials/materials.htm

  19. Links of Note • Guidelines (Binder Selection and Thickness by Type) • http://www.okladot.state.ok.us/materials/pdfs/GUIDE-01.pdf • Approved Performance Graded Binders and Others • http://www.okladot.state.ok.us/materials/htm-smap/11062p-BIT.htm • Approved Superpave Mix Designs • http://www.okladot.state.ok.us/materials/acmixportal.htm • 100 Years of Transportation 1911 – 2011 • www.okladot.state.ok.us/odot100

  20. Links of Note • Approved List of Anti-Strip Additives and WMA Technologies • http://www.okladot.state.ok.us/materials/htm-smap/11062p-ASA.htm • WMA Special Provisions • http://www.okladot.state.ok.us/c_manuals/specprov2009/pdfs/xspn411-13.pdf • http://www.okladot.state.ok.us/c_manuals/specprov2009/oe_sp_2009-708-22.pdf • WMA – Information in Detail • http://warmmixasphalt.com/

  21. Summary • Asphalt Mix Design Methods • Superpave Most Common in History • Laboratory Mixture Compactors • New SGC Compacts 6” Diameter Specimens • Asphalt Binders • Performance Graded Using Mechanical Properties • Aggregate Tests • Little Added • Mix Design Proof Testing • Rut Testing Prevents Premature Failure

  22. Summary • Design by Traffic Volume • Based on ESALs for 20 Years • Mix Design Notes • SGC Gyrations Critical for Predictive Performance • Future Items of Note • WMA – Adopted Nationwide Faster than Superpave

  23. Summary • 2009 Std. Spec. 411 • Pay Factors – Increased for Density by 10% and Removed Gradation • Links Of Note • Sources for Additional Information • Updated Daily as Applicable

  24. Special Thanks • Danny Gierhart, P.E. – Former Bituminous Engineer and Current Regional Asphalt Institute Engineer • Reynolds H. Toney, P.E., Materials Division Engineer • Audience • Especially Those with Questions

  25. Questions?

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