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
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