AFK10

April 21, 2005

Structural StudyStructural Studyat the NCAT Test Trackat the NCAT Test Track

R. Buzz PowellDr. David Timm

STRUCTURAL EXPERIMENTSTRUCTURAL EXPERIMENT

5” 9” 7”

ObservationsObservations

• 5 inch layers failed about as predicted5 inch layers failed about as predicted

• Some cracking in 7 inch layersSome cracking in 7 inch layers

• Modified sections failed first but not by Modified sections failed first but not by muchmuch

• Less rutting in modified sectionsLess rutting in modified sections

Based on Test Track Work Based on Test Track Work the Following has been Adoptedthe Following has been Adopted

• AL, FL, and NC use more fine-graded mixesAL, FL, and NC use more fine-graded mixes

• FL uses more modified bindersFL uses more modified binders

• AL, OK, and TN have begun to use SMAAL, OK, and TN have begun to use SMA

• OK has more confidence in APAOK has more confidence in APA

• AL, GA and TN have increased AC contentsAL, GA and TN have increased AC contents

Automated QC TestingAutomated QC Testing

Utilization of Automation and Real-Time Testing to Improve QC/QA Procedures

For Hot Mix Asphalt

Dr. Randy West

QC/QA State of PracticeQC/QA State of Practice• Most HMA requirements for QC are quite Most HMA requirements for QC are quite complexcomplex..• QC focus has shifted to the end product and QC focus has shifted to the end product and away away

from controlling the processfrom controlling the process..• Due to the time lag between production and Due to the time lag between production and

results, hundreds of tons are likely to have been results, hundreds of tons are likely to have been produced, creating a produced, creating a high riskhigh risk if mix is out of if mix is out of tolerance.tolerance.

Automated Asphalt Content Automated Asphalt Content Using a Plant’s ControlsUsing a Plant’s Controls

Use binder flow rate (gal./min. → tons/hr) with a flow meter or non-powered, positive-displacement pump.

And feed rates of aggregates and RAP (tons/hr) with belt scales, tachometers and a computer integrator.

AC Content ComparisonsAC Content Comparisons

Permeable HMA BasePlant Reading 2.1% AC

HMA Binder MixPlant Reading 3.9% AC

Comparison of Binder Comparison of Binder Viscosity MeasurementsViscosity Measurements

PG 67-22

Why Warm Asphalt?Why Warm Asphalt?

Research by Stroup-Gardiner and Lange at AUIndicates increased emissions with increased temp.

We Can Reduce Temperatures We Can Reduce Temperatures Today with No AdditivesToday with No Additives

• Pre-Superpave – typical compaction Pre-Superpave – typical compaction temperature 275 temperature 275 FF

• Place Thicker Lifts – NCHRP 9-27Place Thicker Lifts – NCHRP 9-27– 3 x NMAS for fine graded3 x NMAS for fine graded– 4 x NMAS for coarse graded4 x NMAS for coarse graded

• Tarp TrucksTarp Trucks

• Drier Aggregate – pave under stockpilesDrier Aggregate – pave under stockpiles

Time Available for Compaction

0

5

10

15

20

25

30

35

40

45

50

240 260 280 300 320 340

Delivery Temperature, F

Tim

e, m

inut

es

1.5 in2.0 in2.5 in

Based on MultiCool

What are Warm Asphalt What are Warm Asphalt Mixes?Mixes?

Several process have been developed to Several process have been developed to improve mixture workability allowing improve mixture workability allowing lower production and laydown lower production and laydown temperaturestemperatures– WAM Foam – Shell/Kolo VeidekkeWAM Foam – Shell/Kolo Veidekke– Zeolite – Eurovia/Hubbard ConstructionZeolite – Eurovia/Hubbard Construction– Sasobit – Sasol Int./Moore and MungerSasobit – Sasol Int./Moore and Munger– New processesNew processes

AIRFIELD ASPHALT AIRFIELD ASPHALT PAVEMENT TEST PROGRAMPAVEMENT TEST PROGRAM

(AAPTP)(AAPTP)

PROCESSPROCESS

• FAA Funded in July 2004FAA Funded in July 2004

• Contractor is Auburn UniversityContractor is Auburn University

• AAPTP Director reports to the College AAPTP Director reports to the College of Engineering not to the Director of of Engineering not to the Director of NCATNCAT

• Program size $1.6 million per yearProgram size $1.6 million per year

• WEB Site: WEB Site: www.AAPTP.uswww.AAPTP.us

Process Continued Process Continued

• Program Coordinating GroupProgram Coordinating Group– 14 Members – 14 Members – – Met in October 2004Met in October 2004– Provides overall direction to programProvides overall direction to program– Identifies the projectsIdentifies the projects

• Project Development PanelProject Development Panel– Project DirectorProject Director– Representative of FAARepresentative of FAA– Representative of DODRepresentative of DOD– Two subject area expertsTwo subject area experts

Initial ProjectsInitial Projects

• Adjusting PG Binder Grade Selection Adjusting PG Binder Grade Selection ProceduresProcedures

• Development of Guidelines for Development of Guidelines for RubblizationRubblization

• Guidance on the Use of Superpave Mix Guidance on the Use of Superpave Mix Design Procedures for Airfield Design Procedures for Airfield PavementsPavements

• Evaluation of SMA for AirfieldsEvaluation of SMA for Airfields

Initial Projects (Cont.)Initial Projects (Cont.)

• Longitudinal Joint ConstructionLongitudinal Joint Construction

• Improved OGFCImproved OGFC

• Evaluate Need and Develop Plan for Evaluate Need and Develop Plan for National Certification of Airport HMA National Certification of Airport HMA TechniciansTechnicians

Endurance Limit of Hot Mix Endurance Limit of Hot Mix Asphalt Mixtures to Prevent Asphalt Mixtures to Prevent Fatigue Cracking in Flexible Fatigue Cracking in Flexible

PavementsPavements

Ray BrownRay BrownBrian ProwellBrian Prowell

NCHRP 9-38

Flexible (Asphalt) Pavement FatigueFlexible (Asphalt) Pavement Fatigue

SurfaceSurface

BaseBase

BaseBase

BaseBase

Sub-baseSub-base Sub-baseSub-base

SubgradeSubgrade

12” ?12” ?

Bottom Up FatigueBottom Up Fatigue

SurfaceSurface

Top Down FatigueTop Down Fatigue

SurfaceSurface

Long LifePavement

Idealized Endurance Limit

1

10

100

1000

1 10 1001,000

10,000

100,000

1,000,000

10,000,000

100,000,000

1,000,000,000

10,000,000,000

Number of Cycles to 50% Stiffness

Tar

get m

icro

Str

ain

Endurance Limit

Tire/Pavement Noise

Pavements testedPavements tested

• LocationsLocations– NCAT test track, Michigan, Alabama, NCAT test track, Michigan, Alabama,

New Jersey, Maryland, Colorado, New Jersey, Maryland, Colorado, Nevada, California, Arizona, Texas, Nevada, California, Arizona, Texas, Florida, Virginia, Minnesota and ColoradoFlorida, Virginia, Minnesota and Colorado

• Numbers of surfaces testedNumbers of surfaces tested– Total – 244 surfacesTotal – 244 surfaces– HMA – 201 surfacesHMA – 201 surfaces– PCCP – 43 surfacesPCCP – 43 surfaces

Average ResultsAverage Results• Hot Mix AsphaltHot Mix Asphalt

– Dense Graded HMA – 97 dB(A)Dense Graded HMA – 97 dB(A)– Stone Matrix Asphalt – 97 dB(A)Stone Matrix Asphalt – 97 dB(A)– New Generation Open Graded Friction CoursesNew Generation Open Graded Friction Courses

• Fine Graded – 92 dB(A)Fine Graded – 92 dB(A)• Coarse Graded – 95 dB(A)Coarse Graded – 95 dB(A)

• Portland Cement Concrete PavementPortland Cement Concrete Pavement– Transverse Tined –104 dB(A)Transverse Tined –104 dB(A)– Diamond ground – 99 dB(A)Diamond ground – 99 dB(A)– Longitudinally Tined – 100 dB(A)Longitudinally Tined – 100 dB(A)

Bomag’s Asphalt Manager Bomag’s Asphalt Manager – A First Look– A First Look

Brian D. ProwellBrian D. Prowell

U. S. DemonstrationU. S. Demonstration

• Intelligent compaction forum, sponsored by Intelligent compaction forum, sponsored by FHWA, in Auburn, AL December 2004FHWA, in Auburn, AL December 2004

• Testing conducted on BOMAG Asphalt Testing conducted on BOMAG Asphalt Manager in conjunction with NCHRP 10-65Manager in conjunction with NCHRP 10-65– Nuclear gage and PQI readings taken after each Nuclear gage and PQI readings taken after each

roller passroller pass– Roller placed in finish position to evaluate use as Roller placed in finish position to evaluate use as

“testing device”“testing device”

Example Growth CurveExample Growth Curve

Location 3

130

135

140

145

150

155

160

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Roller Passes

Den

sity

, lb/

ft^3

0

50

100

150

200

250

300

Density Site 6 Density Site 7 Evib Site 6 Evib Site 7

Evaluation of NEvaluation of NDesignDesign for Superpave Mixesfor Superpave Mixes

ObjectivesObjectives• Evaluate performance of Superpave mixesEvaluate performance of Superpave mixes

• Compare to performance of Marshall mixes Compare to performance of Marshall mixes

• Find same materials/traffic conditionsFind same materials/traffic conditions– PG Binders and same aggregatesPG Binders and same aggregates– Similar traffic/ESAL loadingSimilar traffic/ESAL loading

• Optimize the Superpave NOptimize the Superpave NDesignDesign levels levels

Project ComparisonsProject Comparisons

• AgeAge– Marshall - 5.0 yearsMarshall - 5.0 years– Superpave - 4.9 yearsSuperpave - 4.9 years

• AADTAADT– Marshall - 13,220Marshall - 13,220– Superpave - 13,971Superpave - 13,971

Rutting Comparison

0.000.050.100.150.200.250.300.350.400.45

1 6 11 16 21 26 31 36 41

Projects

Ru

t D

ep

th (

in)

MarshallSuperpave

Avg.Marshall 0.06Superpave 0.07

Intensity of Cracking

02468

101214161820

1 6 11 16 21 26 31 36 41

Projects

% C

rac

kin

g,

lf/s

f

MarshallSuperpave

Avg.Marshall 3.5Superpave 2.4

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

1 6 11 16 21 26 31 36 41

A.C. Comparison

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

1 6 11 16 21 26 31 36 41

Project

A.C

. (%

)

MarshallSuperpave

Avg.Marshall 5.5Superpave 5.1

Superpave Roadway Air Voids

0.01.02.03.04.05.06.07.08.09.0

10.011.012.013.0

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Projects

Va (

%)

Avg. WP = 5.9

Avg. BWP = 7.7

0.010.020.030.040.050.060.070.080.090.0

100.0

No

. o

f G

yra

tio

ns

1 2 3 4 5 6 7 8

Project

Locking Point Comparison

LP-1LP-2LP-3

Avg. Std.LP-1 52 8.7LP-2 58 9.4LP-3 82 10.3

0.010.020.030.040.050.060.070.080.090.0

100.0

No

. o

f G

yra

tio

ns

1 2 3 4 5 6 7 8

Project

Locking Point Comparison

LP-1LP-2LP-3

Avg. Std.LP-1 52 8.7LP-2 58 9.4LP-3 82 10.3

Compaction Level vs Rutting(without Outlier)

R2 = 0.427

R2 = 0.1533

R2 = 0.0059

0

5

10

15

20

40 50 60 70 80 90 100 110

Compaction Level

Ru

t D

ep

th (

mm

)

MarshallSuperpaveLocking Point

Thanks