Oklahoma’s Test Section at NCAT Track

AMAP 12th Annual ConferenceWestern Crown Center Hotel

Kansas City, MOFebruary 16, 2011

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

Topics

• Test Sections – N8 and N9

• History of Performance

• N8 Repairs

• Success vs. Failures

• Use of Knowledge

OK Sections

OK Sections

2006 N8 and N9 History Perpetual Pavement Design

• N8 and N9 on Soft Clay Subgrade‒ N8: 10" HMA‒ N9 : 14" HMA

• RBL Bottom Lift for Both

• N9 - Successful

• N8 - Cracked

• N9: Continue Traffic

• N8: Mill and Replace Top Two Lifts

• N8: Retard Cracking by Two Fabrics

2009 N8 and N9 History Retard Cracking

N8 Reflective Cracking to RetardN8 Reflective Cracking to Retard

N8 Cracking at 2.7 MESALs

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Longitudinal Distance from Far Transverse Joint (feet)

Microstrain Comparison

N8 Strain = 21.487e0.0335*Temperature

R2 = 0.96

N9 Strain = 11.496e0.0298*Temperature

R2 = 0.9217

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Mid-Depth Temperature, F

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N8 N9

More Distress at 3.4 MESALs

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Longitudinal Distance from Far Transverse Joint (feet)

June 16, 2010 Repair

Terminal Distress at 3.8 MESALs

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25 50 75 100 125 150 175

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Longitudinal Distance from Far Transverse Joint (feet)

Observed Shear

End of Section

Shear Plane

End of Section

Reflective Crack

Preliminary Forensic Results

Additional Forensic Results

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25 50 75 100 125 150 175

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Longitudinal Distance from Far Transverse Joint (feet)

Final Forensic Results

N8 Repair Two• Forensics Showed Extensive Subgrade

Deformation

• Significant Repair Needed

• Use Design Similar to N7 (7.5% SBS)

• Make Sublot 3 Similar to Sublot 1‒ 9.5 mm NMS and Add Binder

−Similar to RBL Concept

2009 Group Experiment (+)

N8 Repair Two Details

• NTSS-1HM Tack Coats 0.07 gal/SY

• Average Mill Depth of 5.8"

• Bottom Two Lift Total Thickness 4.7"‒ N8-1 Like N7-1, 1.2" Thick‒ N8-3 Like N8-1 Except 0.2% Binder Added

• N8-2 Like N7-2, 19 mm NMS

N8 Repair Two Details

• N8-1 3.2% Air Voids, 91.4% Density

• N8-2 4.9% Air Voids, 94.2% Density

• N8-3 2.1% Air Voids, 94.3% Density

Matt After Rain

Matt on 1/21/2011

Improved IRI and MTD

Use of Knowledge

• Use Repair Concept on Interstate‒ NTSS-1HM Tack Coats 0.07 gal/SY‒ Use PG88-22 Binder for Top 3 Lifts‒ Top and Bottom Lifts (1 and 3)

-Use Superpave 9.5 mm NMS‒ Lift below Top Lift: Superpave 25 mm NMS‒ Use 50 SGC Gyrations for 9.5 mm NMS ‒ 2.0% Air Voids for Lift 3 (RBL Concept)

Spring 2012 Repair SiteI-40 Mile Posts 102-104

Acknowledgements

• Dr. R. Buzz Powell, P.E.

• Kraton Polymers LLC

• Jeff Dean, Pavement Engineer ODOT

• AMAP

• khobson@odot.org

• http://pavetrack.com

• Subscribe Dixie Contractor‒ Fournier, Paul. Failed Test Track

Section Repaired. Dixie Contractor. Vol. 84 Number 12, Dec. 2010

• ODOT 2009 Standard Specifications

Questions?