Superpave Future Directions 2/21/01
John D'Angelo 1
The Superpave System –Filling the gaps.
John A. D’AngeloFederal Highway Administration
FHWA Binder labContinuous support to the States:
Training / Ruggedness / Development / Validation
Trouble shooting of binder problems.
Superpave Future Directions 2/21/01
John D'Angelo 2
New Low Temp. SpecificationCombines the results of the BBR and DT.
Thermal stress compared to strength.
Superpave Future Directions 2/21/01
John D'Angelo 3
Specification Comparison
-40
-34
-28
-22
-16
-40 -34 -28 -22 -16
Current Spec
Prop
osed
Spe
c
AAA-1 AAB-1 AAD-1 AAF-1 AAM-1Lamont #1 Lamont #3 Lamont #6 Lamont #7
Proposed MP1a Spec.
Binder Tcr Current Spec Tcr Proposed Spec
70-22 Air Blown -24.5 -22.570-22 Conventional -25.1 -22.570-22 SBS Modified -26.0 -30.5Chemically Modified 64-28 A -29.0 -28.0Chemically Modified 64-28 B -27.5 -27.0Chemically Modified 64-28 K1 -29.5 -27.5Chemically Modified 58-28 M1 -27.3 -27.0Elvaloy Modified 64-34 DP -34.7 -36.0
Superpave Future Directions 2/21/01
John D'Angelo 4
Binder High Temp PropertiesStudy same mix different binders.
PG 64-22 mod. no rutting PG 64-22 unmod. 15mm rutting
Binder High Temp PropertiesNew test procedure to evaluate binders.
0.0
0.2
0.4
0.6
0.8
1.0
0 2.5 5 7.5 10
time, s
Nor
mal
ized
Stra
in
BM (PMA)
HSK(Conventional)
εac c HSK
εac c BM
Superpave Future Directions 2/21/01
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DSR Creep TestingTesting 3 different PG 82's
02468
101214
0 200 400 600 800 1000 1200
Time
Accu
mul
ated
Str
ain
SBRPEOxd
Comparison of Specification Values for Binders with a Value of G*/sin d = 1KPa as a Function of the
Phase Angle
0
1
2
3
4
5
55 60 65 70 75 80 85 90
Delta
G*(f(
d)
1/sin dAroon's f(d)
M&R's f(d)
Superpave Future Directions 2/21/01
John D'Angelo 6
Binder Fatigue Test:Time Sweep in the DSR
StressStress
StrainStrain
ττττττττmaxmax
γγγγγγγγmaxmax
Binder Fatigue PropertiesFa tigue o f Asp hal t B in der s
0 .00 E+ 00
2 .00 E+ 04
4 .00 E+ 04
6 .00 E+ 04
8 .00 E+ 04
1 .00 E+ 05
1 .20 E+ 05
0 .00 E+ 00 2 .00 E+ 04 4 .00 E+ 04 6 .00 E+ 04 8 .00 E+ 04 1 .00 E+ 05 1 .20 E+ 05 1 .40 E+ 05 1 .60 E+ 05
Number of c ycles
Dis
sip
ated
En
erg
y R
taio
W i = 1 0 00 P a
W i = 5 0 00 P a
W i = 1 0 00 0 P a
Superpave Future Directions 2/21/01
John D'Angelo 7
Binder Characterization
Strain Sweeps @ G*= 5000kPa
35
40
45
50
55
60
65
70
0 5 10 15 20 25 30
strain
pha
se a
ngle
Flux
BaseUnMod 70 -28
Air-BlownElvalo y
SBS-Linear Graft edSBS-Linear SBS-Radial Graft ed
EVAEVA- Gr afted
N/A
Fine aggregate specific gravity test
Measure Temp & Moist. in
Measure Temp & Moist. out
Test controls FAA and VMA
Current procedure highly variable
New test will reduce variability by taking out operator error.
Superpave Future Directions 2/21/01
John D'Angelo 8
New Specific Gravity Equipment
90-05 Agg. Gravity ProcedureProduction version under development.
Superpave Future Directions 2/21/01
John D'Angelo 9
90-05 Agg. Gravity ProcedureProduction version under development.
Gyratory Comparisons
Superpave Future Directions 2/21/01
John D'Angelo 10
Analysis of 30 Production MixesF test & Student “ t ” test
3.142 < 2.0421.30 < 2.07Design
Critical“ t ” value
Calculated“ t ” value
CriticalF value
CalculatedF value
Gyrations
There is a measurable bias between the two compactors. On average the one unit’s Gmb is 0.005 higher. However, this is well within T 166’s precision (0.02).
Standard Deviation Average (Mean)
KeyUniform procedures between the two mobile laboratories
AASHTO PP XX-01, “Standard Practice for the Evaluation of Different SGC’s used in the Design and the Field Management of Superpave Mixes”
Routine maintenance and calibrationwas performed
Superpave Future Directions 2/21/01
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Not Every Day is a Good Day!Not Every Day is a Good Day!Not Every Day is a Good Day!
We are seeing measurabledifferences in the field.
State DOT expressed concern regarding measured differences in specimens compacted in SGC’s between the Stateand several local Contractors
Differences as high as1.5 % air voids !
Superpave Future Directions 2/21/01
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Angle DefinitionsHow parallel?How perpendicular?
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Gyratory Internal Measuring Device
Superpave Future Directions 2/21/01
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State DOT vs ContractorBased on the data, how would you expect the compactors to compare?
0.951.001.051.101.151.201.251.30
STATE CONTRACTOR
FindingsBased on the limited testing, the Contractors SGC appears not to be maintaining the internal angle of gyration dynamically.
Also, the DOT’s SGC appears to be operating on the high side if the specification.
Superpave Future Directions 2/21/01
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The Kit Only in the Mold
1.27
1.33
1.381.42
1.48
y = 1.02 x
R2 = 0.995
1.20
1.25
1.30
1.35
1.40
1.45
1.50
1.55
1.60
1.20 1.25 1.30 1.35 1.40 1.45 1.50
External Angle Setting, degrees
Kit
Angl
e
HMA and the Kit in the Mold
1.16
1.20
1.25
1.30
1.36
y = 1.02 x - 0.12R2 = 0.997
1.10
1.15
1.20
1.25
1.30
1.35
1.40
1.45
1.50
1.20 1.25 1.30 1.35 1.40 1.45 1.50
External Angle Setting, degrees
Kir
Ang
le
Superpave Future Directions 2/21/01
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Vision
“Future validation will be based upon an angle of gyration, measured dynamically, under load of a specimen.”
What Do We Do Now
Interim Step – is to use a procedure to compare compactors and determine an offset between them.
Superpave Future Directions 2/21/01
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Gyratory Internal Measuring Device
FHWA Mobile Asphalt Lab
Superpave Future Directions 2/21/01
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Mobile Asphalt Labs Provide “Hands-on” of Superpave System
Volumetric Mix DesignField QC/QA Procedures, NCHRP 9-7Simple Performance Test Device, NCHRP 9-19Performance Related Specifications 9-22
4 to 6 week visitsData used to support ETG’s
Superpave SpecificationsRoadway Densities
Specifications the same, mixes different.
Superpave Future Directions 2/21/01
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Superpave Specifications
Contrasting Stone Skeletons
Superpave SpecificationsRoadway Densities.
Lift thickness does effect compaction.Recommended lifts should be 3 to 4 times nominal maximum size or 2 1/2 to 3 times max size.
Superpave Future Directions 2/21/01
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Superpave Compaction
X-ray Tomography System
X-Ray Source
Detector
Specimen
Collimator(window)
Superpave Future Directions 2/21/01
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Image Processing-Air Voids
Air Void
Asphalt Binder
Aggregate
Vertical distribution of Air Voids in Gyratory Specimens and Field Cores
0
10
20
30
40
50
0 4 8 12 16 20 24
Air Voids (%)
Dep
th (
mm
) FC-1 -13FC-1 -19FC-2 -18FC-2 -9FC-3 -12FC-3 -25
Fie ld Core s
020406080
100120140
0 4 8 12 16 20 24Air Voids (%)
Dep
th (m
m) LHCC
LLCCHHCCLHHC
Gyratory Spec ime n
Superpave Future Directions 2/21/01
John D'Angelo 21
90-03 Mix TendernessStudy variables
Determine effect of moisture on mix properties.• Procedure developed to produce mix with 2%
mois ture in agg.
Measure moisture in plant mix.• Develop procedure to determine actual measure in
plant mix.
Superpave CompactionMix Tenderness
Study underway with the Asphalt Institute.Major cause of tenderness is moisture Minor affect gradation
Superpave Future Directions 2/21/01
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90-03 Mix TendernessProducing Mix With High
Moisture
90-03 Mix TendernessMoisture Effects mix
Superpave Future Directions 2/21/01
John D'Angelo 23
SUPERPAVE PERFORMANCE
MODELS
Proposed Changes to the Long-Range Plan for 2005
Superpave Performance Models and Test Methods
1999 - 2002: NCHRP Project 9-19, Superpave Support and Performance Models Management
Complete all tasks begun in FHWA project.
1998 - 2001: NCHRP Project 1-37A, Development of the 2002 Guide for the Design of New and Rehabilitated Pavement Structures
Mechanistic-empirical HMA performance models.
Superpave Future Directions 2/21/01
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Original 1999 PlanProject 9-19: Materials characterization model and test.Future Projects: Mechanistic models for non-linear, viscoelastic HMA behavior based on 3-D finite element analysis and similar advanced computing techniques. Realistic completion date: 2007 or 2008.Estimated future funding: $7.65 million.
Revision of the Long-Range Plan for 2005
NCHRP Project Panels 9-19 and1-37ATRB Superpave CommitteeAASHTO Standing Committee on Research
Superpave Future Directions 2/21/01
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Revised PlanUse HMA performance models and integrated climatic model from the 2002 Design Guide (Project 1-37A) for Superpave mix analysis and, possibly, HMA PRS (Project 9-22). Realistic completion date: 2004 or 2005.Estimated future funding: $1 -2 million.
Revised PlanSuperpave effort finished on schedule.Common tools for HMA mix design, structural design, and PRS.Common materials characterization test; reduced need for new equipment; simplified technician training.Next generation of multi-use, mechanistic HMA performance models developed with minimal duplication of effort.
Superpave Future Directions 2/21/01
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NCHRP 9-19 s imple performance test. Preliminary evaluation currently underway.
The Superpave SystemSuperpave is in place and it does work.There is a great deal of work needed to fill gaps in the system.Work is continuing to fill the gaps.A plan is in place to complete the system by 2005.
Superpave Future Directions 2/21/01
John D'Angelo 27
Thank You