Superpave Superpave TodayToday

Kenneth Ray Hobson, P.E. –Kenneth Ray Hobson, P.E. – Bituminous Bituminous EngineerEngineer

khobson@odot.orgkhobson@odot.org

City of TulsaMay 13, 2011

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

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

Automatic Marshall Automatic Marshall HammersHammers

Texas Gyratory Hveem Texas Gyratory Hveem CompactorCompactor

Superpave Gyratory Superpave Gyratory Compactor (SGC)Compactor (SGC)

Limitations of Limitations of Traditional Binder Traditional Binder

SpecificationsSpecifications• 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

Limitations of Limitations of Traditional Binder Traditional Binder

SpecificationsSpecifications• 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

Superpave Asphalt Superpave Asphalt Binder SpecificationBinder Specification

The grading system is based on Climate

PG 64 - 22

Performance Grade

Average 7-day max. pavement

temperature

Min. pavement

temperature

Performance Graded Performance Graded Binder SpecificationsBinder Specifications

• Based on Mechanical Properties(DSR, BBR)oModulusoDeflectionoLoad Response (Rate)

• Other Tests Remain UnchangedoMass Change, Flash Point, Elastic Recovery, etc. ER is known as PG+ Spec.• ODOT 2009 Std. Spec. 708.03 Table 708:2

Aggregate TestsAggregate Tests

• Superpave similar to Hveem with added tests: oFine Aggregate Angularity (FAA)oBulk Specific Gravity (used for

FAA and VMA computations)oMicro-Deval (30+ MESALs)

Mix Design Proof Mix Design Proof TestingTesting

• Marshall Cohesiometer• Hveem Stabilometer• Hamburg Rut Test

Design by Traffic Design by Traffic VolumeVolume

• Hveem – ADToLab Specimens (4” diameter)

Compacted the Same (275oF)oAir Void Limits Adjusted by Traffic

• Superpave –ESALs in 20 YearsoLab Specimens (6” diameter)

Compacted More with More Traffic (300oF)

oAir Void Limits Kept Constant

Mix Design NotesMix Design Notes

• Ndes – Number of SGC Gyrations at JMF Binder

• Nini – Number of SGC Gyrations backcalculated from Ndes SpecimensoDensity Similar to That Behind Paver

• Nmax – Number of SGC Gyrations at End of Pavement Life (mix design only)

Future Items of NoteFuture Items of Note

• WMA – The Future is here now!oProvides Many Benefits

• Tack Coats – 0.15 gal/SY Diluted 1:1oTrackless Tack Emulsion – Near

100% BondingoPave Sprayer Applied PMCRS-1S –

Near 100% Bonding

2009 Std. Spec. 4112009 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

Future Items of NoteFuture Items of Note

• Increased Binder Content by Special ProvisionoPossible Reduction in SGC

GyrationsoPossible VMA Increase by 0.5%

Links of NoteLinks of Note• Construction EngineeringoStandards, Specifications, Materials

and Testing• http://www.okladot.state.ok.us/cnstrctengr.htm

• Materials Division Contactso http://

www.okladot.state.ok.us/materials/index.htm

• Materials & Testing e-Guideo http://www.okladot.state.ok.us/materials/material

s.htm

Links of NoteLinks of Note• Guidelines (Binder Selection and Thickness by

Type)o http://

www.okladot.state.ok.us/materials/pdfs/GUIDE-01.pdf

• Approved Performance Graded Binders and Otherso http://

www.okladot.state.ok.us/materials/htm-smap/11062p-BIT.htm

• Approved Superpave Mix Designso http://www.okladot.state.ok.us/materials/acmixportal.htm

• 100 Years of Transportation 1911 – 2011o www.okladot.state.ok.us/odot100

Links of NoteLinks of Note• Approved List of Anti-Strip Additives and WMA

Technologieso http://www.okladot.state.ok.us/materials/htm-smap/

11062p-ASA.htm

• WMA Special Provisionso http://www.okladot.state.ok.us/c_manuals/

specprov2009/pdfs/xspn411-13.pdfo http://www.okladot.state.ok.us/c_manuals/

specprov2009/oe_sp_2009-708-22.pdf

• WMA – Information in Detailo http://warmmixasphalt.com/

SummarySummary• Asphalt Mix Design Methods

o Superpave Most Common in History• Laboratory Mixture Compactors

o New SGC Compacts 6” Diameter Specimens• Asphalt Binders

o Performance Graded Using Mechanical Properties

• Aggregate Testso Little Added

• Mix Design Proof Testingo Rut Testing Prevents Premature Failure

SummarySummary

• Design by Traffic VolumeoBased on ESALs for 20 Years

• Mix Design NotesoSGC Gyrations Critical for

Predictive Performance• Future Items of NoteoWMA – Adopted Nationwide Faster

than Superpave

SummarySummary

• 2009 Std. Spec. 411oPay Factors – Increased for

Density by 10% and Removed Gradation

• Links Of NoteoSources for Additional InformationoUpdated Daily as Applicable

Special ThanksSpecial Thanks

• Danny Gierhart, P.E. – Former Bituminous Engineer and Current Regional Asphalt Institute Engineer

• Reynolds H. Toney, P.E., Materials Division Engineer

• AudienceoEspecially Those with Questions

Questions?Questions?