Oklahoma’s Test Section at NCAT Track AMAP 12 th Annual Conference Western Crown Center Hotel

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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2

4

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8

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25 50 75 100 125 150 175

Tra

nsv

erse

Off

set

(fee

t)

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

0

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400

600

800

1000

1200

1400

0 20 40 60 80 100 120 140

Mid-Depth Temperature, F

Te

nsi

le M

icro

stra

in

N8 N9

More Distress at 3.4 MESALs

0

2

4

6

8

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25 50 75 100 125 150 175

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Longitudinal Distance from Far Transverse Joint (feet)

June 16, 2010 Repair

Terminal Distress at 3.8 MESALs

0

2

4

6

8

10

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25 50 75 100 125 150 175

Tra

nsv

erse

Off

set

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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

0

2

4

6

8

10

12

25 50 75 100 125 150 175

Tra

nsv

erse

Off

set

(fee

t)

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

• [email protected]

• 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?