Superpave
Today
City of Tulsa
May 13, 2011
Kenneth Ray Hobson, P.E. –
Bituminous Engineer
khobson@odot.org
Overview
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Asphalt Mix Design Methods
Laboratory Mixture Compactors
Asphalt Binders
Aggregate Tests
Mix Design Proof Testing
Design by Traffic Volume
Overview
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Mix Design Notes
Future Items of Note
2009 Std. Spec. 411
Links Of Note
Automatic Marshall
Hammers
Texas Gyratory Hveem
Compactor
Superpave Gyratory
Compactor (SGC)
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
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
Superpave Asphalt Binder
Specification
The grading system is based on Climate
PG 64 - 22
Performance Grade
Min. pavement
temperature
Average 7-day
max. pavement
temperature
Performance Graded
Binder Specifications
• Based on Mechanical Properties
(DSR, BBR)
o Modulus
o Deflection
o Load Response (Rate)
• Other Tests Remain Unchanged
o Mass Change, Flash Point, Elastic
Recovery, etc. ER is known as PG+ Spec.
• ODOT 2009 Std. Spec. 708.03 Table 708:2
Aggregate Tests
• Superpave similar to Hveem with
added tests:
o Fine Aggregate Angularity (FAA)
o Bulk Specific Gravity (used for FAA and
VMA computations)
o Micro-Deval (30+ MESALs)
Mix Design Proof Testing
• Marshall Cohesiometer
• Hveem Stabilometer
• Hamburg Rut Test
Design by Traffic Volume
• Hveem – ADT
o Lab Specimens (4” diameter) Compacted
the Same (275oF)
o Air Void Limits Adjusted by Traffic
• Superpave –ESALs in 20 Years
o Lab Specimens (6” diameter) Compacted
More with More Traffic (300oF)
o Air Void Limits Kept Constant
Mix Design Notes
• Ndes – Number of SGC Gyrations at
JMF Binder
• Nini – Number of SGC Gyrations
backcalculated from Ndes Specimens
o Density Similar to That Behind Paver
• Nmax – Number of SGC Gyrations at
End of Pavement Life (mix design
only)
Future Items of Note
• WMA – The Future is here now!
o Provides Many Benefits
• Tack Coats – 0.15 gal/SY Diluted 1:1
o Trackless Tack Emulsion – Near 100%
Bonding
o Pave Sprayer Applied PMCRS-1S – Near
100% Bonding
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
Future Items of Note
• Increased Binder Content by Special
Provision
o Possible Reduction in SGC Gyrations
o Possible VMA Increase by 0.5%
Links of Note
• Construction Engineering
o Standards, Specifications, Materials and
Testing
• http://www.okladot.state.ok.us/cnstrctengr.htm
• Materials Division Contacts
o http://www.okladot.state.ok.us/materials/index.htm
• Materials & Testing e-Guide
o http://www.okladot.state.ok.us/materials/materials.htm
Links 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 Others
o http://www.okladot.state.ok.us/materials/htm-smap/11062pBIT.htm
• Approved Superpave Mix Designs
o http://www.okladot.state.ok.us/materials/acmixportal.htm
• 100 Years of Transportation 1911 – 2011
o www.okladot.state.ok.us/odot100
Links of Note
• Approved List of Anti-Strip Additives and WMA
Technologies
o http://www.okladot.state.ok.us/materials/htm-smap/11062pASA.htm
• WMA Special Provisions
o http://www.okladot.state.ok.us/c_manuals/specprov2009/pdfs/
xspn411-13.pdf
o http://www.okladot.state.ok.us/c_manuals/specprov2009/oe_s
p_2009-708-22.pdf
• WMA – Information in Detail
o http://warmmixasphalt.com/
Summary
• 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 Tests
o Little Added
• Mix Design Proof Testing
o Rut Testing Prevents Premature Failure
Summary
• Design by Traffic Volume
o Based on ESALs for 20 Years
• Mix Design Notes
o SGC Gyrations Critical for Predictive
Performance
• Future Items of Note
o WMA – Adopted Nationwide Faster
than Superpave
Summary
• 2009 Std. Spec. 411
o Pay Factors – Increased for Density by
10% and Removed Gradation
• Links Of Note
o Sources for Additional Information
o Updated Daily as Applicable
Special Thanks
• Danny Gierhart, P.E. – Former
Bituminous Engineer and Current
Regional Asphalt Institute Engineer
• Reynolds H. Toney, P.E., Materials
Division Engineer
• Audience
o Especially Those with Questions
Questions?