11
FHWA Pavements programFHWA Pavements programWhatWhat’’s Happenings Happening
John DJohn D’’AngeloAngeloOffice of Pavement TechnologyOffice of Pavement Technology
22
Loads and Layer Stiffness
Mechanistic AnalysisLayered Elastic Analysis
E*
Mr
Mr
σ
Strain Calculations at Critical Locations
E = σ/ε
33
• Downloadable, must be connected to Internet to use• Updated on NCHRP website: www.trb.org/mepdg• Voted on by the SOM and SOD • Next step AASHTO SCOH • AASHTO to develop actual design software in 2010
MEPDG Software Version 1.0
Current Status of MEPDGCurrent Status of MEPDG
44
*Webcast available
Climatic Workshop LocationsWorkshop Locations
UpcomingUpcomingTraffic Traffic –– 33PMS Database Inputs PMS Database Inputs -- 11
FutureFutureLocal Calibration Local Calibration Weighing Impacts of MEPD for Next Weighing Impacts of MEPD for Next Generation Traffic DataGeneration Traffic Data
Past WorkshopsPast WorkshopsIntroduction to the DG Introduction to the DG –– 8*8*Traffic Traffic –– 22Materials Materials –– 11*11*Climatic Inputs Climatic Inputs –– 12*12*
FHWA DGIT WorkshopsFHWA DGIT Workshops
55
DGIT & Office of Freight Management / Operations
Contract with Auburn University• Models in M-E PD that deal with truck size & weight • Assessing impacts of raising weight limits
FHWA cross-disciplinary cooperation team• Identify methods to assign cost to infrastructure damaged by increased highway load limits• Strive for official FHWA position on this topic
FHWA Other Activities
66
National Highway Institute NHI Course #131109
Pilot: April 2007Analysis of New and Rehabilitated Pavement Performance
with Mechanistic-Empirical Pavement Design Software
• Hands-on format with computers loaded with software
• Focus on user, not theory
• Objective is for audience to be capable of performing flexible, rigid, rehab designs
Future FHWA WorkshopsFuture FHWA Workshops
77
Local Calibration for M-E PDG modelsAwaiting deliverables from NCHRP 1-40 B
Pilot planned for Fall 2007
Purpose: discuss Sensitivity of inputs & calibration,
educate Pavt Designers & Pavement Managers
Future FHWA WorkshopsFuture FHWA Workshops
88
Asphalt Mix Performance TesterAsphalt Mix Performance Tester
The test can evaluate the rutting and fatigue response of the mix.
The equipment is relatively inexpensive and easy to use.
Provides input data for MEPDG
Can be used for Construction acceptance.
99
Asphalt Mix Performance TesterAsphalt Mix Performance Tester
•• Develop new pooled fund for purchase of Develop new pooled fund for purchase of the equipment.the equipment.
•• Establishment of a technician training Establishment of a technician training school for operation of the equipment.school for operation of the equipment.
•• Develop precision and bias for test Develop precision and bias for test procedure.procedure.
1010
1111
ProblemProblem--High Temperature Binder High Temperature Binder CriteriaCriteria
•• Does G*/sinDoes G*/sinδδ reflect rutting performance of reflect rutting performance of modified binders.modified binders.–– General anecdotal data says no.General anecdotal data says no.
•• What are the alternatives?What are the alternatives?–– ZSV, LSV, Creep & Recovery testingZSV, LSV, Creep & Recovery testing
1212
NCHRP 9NCHRP 9--10 Rutting Test 10 Rutting Test Repeated Creep Recovery TestRepeated Creep Recovery Test
1
68
Shear Stress,
10 20
1
Shear Stain, mm/mm
10 20
Accumulated Strain
1313
0
5
10
15
20
25
30
0 20 40 60 80 100
Time s
Nor
mal
ized
Stra
in %
γu = Avg. un-recovered strain
Jnr = γu / τ
τ = stress applied during creep
Jnr = non-recoverable compliance
0
5
10
15
20
25
30
0 20 40 60 80 100
Time s
Nor
mal
ized
Stra
in %
γu = Avg. un-recovered strain
Jnr = γu / τ
τ = stress applied during creep
Jnr = non-recoverable compliance
New High Temp Criteria New High Temp Criteria JnrJnr
1414
AsAs--Built Pavement Lanes Built Pavement Lanes
CR-AZ----70-22
1
PG70-22Control
2
AirBlown
3
SBSLG
4
CR-TB
5
TP
6
PG70-22
+Fibers
7
PG70-22
8
SBS64-40
9
AirBlown
10
SBSLG
11
TP
12
1515
Jnr ALF binder 64C
0
0.05
0.1
0.15
0.2
0.25
0 5000 10000 15000 20000 25000 30000
Stress Pa
Jnr
64-40 64CAB 64CSBS LGcontrol 64CElvaloy 64CTBCR 64C
1616
HMA Layer Rutting for All Lanes
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 10,000 20,000 30,000 40,000 50,000 60,000
ALF Wheel Passes
HMA
Laye
r Rut
ting,
in.
L9S1(SBS 64-40 6")
L9S2(SBS 64-40 6")
L6S1(Terpolymer 4")
L8S1(Control 6")
L10S1(Air Blown 6")
L11S1(SBS-lg 6")
L3S1(Air Blown 4")
L2S1(Control 4")
L1S1(CR AZ 4")
L4S1(SBS-lg 4")
L12S1(Terpolymer 6")
L7S1(Fibers 4")
L5S1(TBCR 4")
1717
y = -7.4519x + 10.956R2 = 0.1261
0
2
4
6
8
10
12
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8rutting inches
G*/s
in d
64C
1818
Relationship between Relationship between JnrJnr and ALF and ALF ruttingrutting
y = 0.4736x - 0.1167R2 = 0.8167
0
0.05
0.1
0.15
0.2
0.25
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
ALF Rutting in
Jnr
1919
Hamburg Rut testing MINN Road mixesHamburg Rut testing MINN Road mixesJnr 12.8kPa
y = 0.0398x - 0.0289R2 = 0.9646
0.0000
0.2000
0.4000
0.6000
0.8000
1.0000
1.2000
1.4000
0 5 10 15 20 25 30 35rut mm
Jnr
2020
Miss I55 6yr rut Miss I55 6yr rut JnrJnr 3.2 3.2 kPakPay = 0.031x
R2 = 0.7453
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 2 4 6 8 10 12rut mm
Jnr
6 yr Jnr 3.2 kPabinder mod true grad rut mm 70C
Ultrapave SBR 70-27 4.5 0.17Styrelf SB 77-29 2 0.044GTR 80 75-29 1.5 0.121Sealoflex SBS 82-27 3 0.019Multygrade 72-24 5 0.213Cryo Rubber 75-28 7 0.162Control 70-24 11 0.35
2121
High Temperature Binder Criteria High Temperature Binder Criteria
–– NonNon--recoverable compliance of the binder recoverable compliance of the binder describes the stress dependency of the binder.describes the stress dependency of the binder.
–– Creep and recovery testing done at multiple stress Creep and recovery testing done at multiple stress levels on one sample can be run to describe the levels on one sample can be run to describe the stress dependency of the binder.stress dependency of the binder.
–– Creep and recovery nonCreep and recovery non--recoverable compliance recoverable compliance can be correlated to mix testing done at different can be correlated to mix testing done at different stress conditions and related to performance. stress conditions and related to performance.
2222
Affect of Affect of JnrJnr on Ruttingon Rutting
•• Reducing Reducing JnrJnr by half typically reduced by half typically reduced rutting by half.rutting by half.
•• This affect is seen on ALF sections and This affect is seen on ALF sections and Hamburg Rut TestingHamburg Rut Testing
•• But most importantly this is seen on the But most importantly this is seen on the Mississippi I 55 sections.Mississippi I 55 sections.
2323
Determination of a Specification Determination of a Specification criteria.criteria.
•• The existing binder specification works The existing binder specification works very well for neat binders.very well for neat binders.
•• The grading for neat binders should not The grading for neat binders should not change.change.
•• Establish new Establish new JnrJnr criteria based on criteria based on response of neat binders at their response of neat binders at their continuous grade temp.continuous grade temp.
•• Evaluate the binders near the end of their Evaluate the binders near the end of their linear range. Most neat binders remain linear range. Most neat binders remain
2424
Evaluation of Straight run Evaluation of Straight run bindersbindersSample IDSample ID NameName GradeGrade true gradetrue grade TempTemp JnrJnr 3.2kPa3.2kPa
ALF 6727ALF 6727 ControlControl 7070--2222 72.772.7--74.274.2 72.772.7 0.4391220.439122
BBRS3BBRS3 straightstraight 6464--2222 66.166.1--27.327.3 66.166.1 0.4184490.418449
MN county rd 112MN county rd 112 neat Valeroneat Valero 5858--2828 60.860.8--33.433.4 60.860.8 0.3684450.368445
MN county rd 112MN county rd 112 neat neat CitgoCitgo 5858--2828 59.559.5--29.829.8 59.559.5 0.5296470.529647
MN county rd 112MN county rd 112 AshlandMAshlandM 5858--2828 60.760.7--31.431.4 60.760.7 0.4301650.430165
MinnMinn RoadRoad straightstraight 5858--2828 61.861.8--30.830.8 61.861.8 0.3029510.302951
Miss IMiss I--5555 CSLCSL 6767--2222 68.368.3--25.125.1 68.368.3 0.2669120.266912
ShandongShandong straightstraight 6464--2222 64.464.4--23.523.5 64.464.4 0.4440570.444057
BBRS3BBRS3 straightstraight 7070--2222 71.471.4--24.824.8 71.471.4 0.4808550.480855
BBRS3BBRS3 straightstraight 5858--2828 61.361.3--3030 61.361.3 0.4003450.400345
MD projectMD project straightstraight 6464--2828 64.864.8--29.629.6 64.864.8 0.4593350.459335
averageaverage 0.4127530.412753
2525
Grade bumping Grade bumping recommendationrecommendation
•• All testing should be done at the All testing should be done at the environmental grade temp.environmental grade temp.
•• The standard grade should be based on The standard grade should be based on the the JnrJnr value of existing neat binders 0.4 .value of existing neat binders 0.4 .
•• For high traffic the For high traffic the JnrJnr value should be value should be reduced by half at the grade temp to 0.2 reduced by half at the grade temp to 0.2 ..
•• For standing traffic the For standing traffic the JnrJnr value should value should be reduced by half again 0.1 .be reduced by half again 0.1 .
2626
New high Temp SpecNew high Temp Spec
•• PG 64 (Standard, Heavy, Very heavy) PG 64 (Standard, Heavy, Very heavy) based on traffic.based on traffic.–– PG 64SPG 64S--XX XX JJnrnr => 0.4=> 0.4–– PG 64HPG 64H--XX XX JJnrnr => 0.2=> 0.2–– PG 64VPG 64V--XX XX JJnrnr => 0.1=> 0.1
2727
How do we identify Polymers?How do we identify Polymers?Use DSR ApproachUse DSR Approach
•• Use DSR Use DSR –– MutiMuti Stress Creep Recovery TestStress Creep Recovery Test
•• Two creep stress levelsTwo creep stress levels•• Ten cycles per stress levelTen cycles per stress level•• For For ElastomericElastomeric modifiers Specify: modifiers Specify:
–– % strain recovery 3200 Pa > 15% or 20%% strain recovery 3200 Pa > 15% or 20%–– Overall change between stress levels 100Overall change between stress levels 100--3200 Pa < 3200 Pa <
75%75%
•• Run on the RTFOTRun on the RTFOT•• Run on the same sample as RTFOT grading Run on the same sample as RTFOT grading
2828
C reep 1st cycle 70C 1000 Pa
0
50
100
150
200
250
300
350
400
450
0 2 4 6 8 10 12
tim e
% s
trai
n
controlE lvaloyStylinkAB
What criteria? % recovered strainWhat criteria? % recovered strain
(Peak Strain - recovered Strain)/Peak Strain
2929
0
0.1
0.2
0.3
0.4
0.5
0.6
10 100 1000 10000 100000
Stress Pa
Jnr
poor structuregood structure
3200 Pa
MSCR selection of stress levelsMSCR selection of stress levels
3030
General relationship between ER General relationship between ER and MSCR and MSCR
Special EVA Incompatible SBS
20.0025.0030.0035.0040.0045.0050.0055.0060.0065.0070.0075.0080.0085.0090.00
65.00 70.00 75.00 80.00 85.00 90.00 95.00 100.00UDOT Elastic Recovery @ 25°C, %
3200
Pa
% R
ecov
ery
PG 64-28PG 64-34PG 70-28PG 58-28
3131
Effect of XEffect of X--linking on ERlinking on ER
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
60 65 70 75 80 85Temp C
Jnr
CI 05 ER 36.3CI 05 04 ER 56.3CI ER 32.5
3232
BBRS StudyBBRS Study
0
10
20
30
40
50
60
70
80
90
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8Jnr
% re
cove
ry 3
.2kP
a
SBS Elva 70-28Elvaloy 70-28SBS 70-28SBR 70-22Ergon 76-22Elvaloy 76-28
64V,70S64V, 70H, 76S64V, 70S58V, 64H, 70S70V, 76H, 82S70V, 76H, 82S
3333
Warm Mix Task Group:Warm Mix Task Group:GaylonGaylon BaumgardnerBaumgardner
Gayle KingGayle KingGerald Gerald ReinkeReinkeMatt CorriganMatt CorriganChris Chris AbadieAbadie
3434
–– Question: (RTFO , PAV or both?)Question: (RTFO , PAV or both?)
•• Master Curve Development (DSR) Master Curve Development (DSR) –– PTSiPTSi•• SuperPaveSuperPave™™ True Grade (Through DTT) True Grade (Through DTT) ––
PTSiPTSi•• Physical Hardening (30 days saturation at Physical Hardening (30 days saturation at --
1212°°C) Bending Beam C) Bending Beam RheometryRheometry (BBR) (BBR) -- PTSiPTSi•• MultiMulti--Step Creep Recovery (MSCR) Step Creep Recovery (MSCR) –– FHWAFHWA•• Glass Transition Glass Transition TgTg (MDSC) (MDSC) –– WRI/MTEWRI/MTE•• Atomic Force Microscopy (AFM) Atomic Force Microscopy (AFM) ––WRIWRI
3535
3636
Superpave Gyratory Superpave Gyratory Compactor CalibrationCompactor Calibration
Making Superpave MixturesMaking Superpave MixturesConsistentConsistent
3737
AASHTO Designation: T 312AASHTO Designation: T 312--0303Preparing ... Specimens by Preparing ... Specimens by …… SGCSGC
Superpave Gyratory CompactorSuperpave Gyratory Compactor –– …… an an average internal angle of 1.16average internal angle of 1.16°°++ 0.020.02°°……....
(only internal angle with simulated mix (only internal angle with simulated mix measurement) measurement)
4.1
3838
Internal Angle MeasurementInternal Angle Measurementwith Hot Mix Asphaltwith Hot Mix Asphalt
DAV on Bottomto measure αB
DAV on Topto measure αT
3939
APACAPACCalibrated to 1.25 degrees Calibrated to 1.25 degrees ExternalExternal
4.0 4.53.5Air Voids (Va), %
4040
APACAPACCalibrated to 1.16 degrees Calibrated to 1.16 degrees InternalInternal
4.03.5 4.5Air Voids (Va), %
4141
Asphalt InstituteAsphalt InstituteCalibrated Externally at 1.25Calibrated Externally at 1.25°°
4.5 5.04.0Air Voids (Va), %
4242
Asphalt InstituteAsphalt InstituteCalibrated Internally at 1.16Calibrated Internally at 1.16°°
4.54.0 5.0
Air Voids (Va), %
4343
University of ArkansasUniversity of ArkansasCalibrated Externally at 1.25Calibrated Externally at 1.25°°
4.5 5.04.0Air Voids (Va), %
4444
University of ArkansasUniversity of ArkansasCalibrated Internally at 1.16Calibrated Internally at 1.16°°
4.54.0 5.0Air Voids (Va), %
4545
HMS & RAMHMS & RAM
4646
Specification RecommendationsSpecification Recommendations•• Drop procedures related to use of HMADrop procedures related to use of HMA
–– drop reference in T312; eliminate TP48drop reference in T312; eliminate TP48
•• Implement new TP for simulated loadingImplement new TP for simulated loading–– add reference in T312add reference in T312–– Precision: Precision: TroxlerTroxler 4140 NOT INCLUDED4140 NOT INCLUDED–– Refer to Refer to ““manufacturersmanufacturers’’ recommendationsrecommendations””
•• Applies to specific procedures for using various devicesApplies to specific procedures for using various devices•• Applies to hotApplies to hot--versusversus--cold cold question(squestion(s).).
–– Inform users that RAM Inform users that RAM ~~ DAV2/HMSDAV2/HMS
•• Angle tolerance: move to +/Angle tolerance: move to +/-- 0.03 deg0.03 deg
4747
EFFECT OF EFFECT OF DESIGN COMPACTION DESIGN COMPACTION
4848
19 MM MIXTURES
-2.0%
-1.0%
0.0%
1.0%
2.0%
3.0%
-60 -40 -20 0 20 40 60
Change In Gyrations
Cha
nge
in V
MA
Effect on VMAEffect on VMAAggregate Blend Constant
Effect of Design GyrationsEffect of Design Gyrations
N designN design
highhigh
lowlow
Aggregate Properties Constant (gradation, CAA, FAA)Aggregate Properties Constant (gradation, CAA, FAA)
% Asphalt% Asphalt
lowlow
highhigh
LABLAB ROADROAD
5050
Effect on StiffnessEffect on Stiffness
-
20,000
40,000
60,000
80,000
100,000
120,000
-60 -40 -20 0 20 40Change from Design Gyrations
60
G*(
0.1H
z), k
Pa
Volumetric Properties Constant
Effect of Design GyrationsEffect of Design Gyrations
N designN design
highhigh
lowlow
Volumetric Properties Constant (air voids, VMA, VFA)Volumetric Properties Constant (air voids, VMA, VFA)
SkeletonSkeleton
strongstrong
weakweak
LABLAB ROADROAD
What Should Design Gyrations What Should Design Gyrations Be?Be?
•• 2020--30 gyrations changes30 gyrations changes–– VMA by 1%VMA by 1%
0.4% asphalt content0.4% asphalt content
–– Mixture stiffness by 25 to 30%Mixture stiffness by 25 to 30%about one PG high temp grade differenceabout one PG high temp grade difference
–– SO . . . . . . .SO . . . . . . .
5353
Average Design High Air Temperature
<39 C
39 – 40 C
41 - 42 C
41 – 44 C
Design
ESALs
Millions Nini
Ndes
Nma
x
Nini
Ndes
Nma
x
Nini
Ndes
Nma
x
Nini
Ndes
Nma
x
< 0.3
7 68
104
7
74
114
7
78
121
7
82
127
< 1
7
76
117
7
83
129
7
88
138
8
93
146
< 3
7
86
134
8
95
150
8
100
158
8
105
167
< 10
8
96
152
8
106
169
8
113
181
9
119
192
< 30 8
109
174
9
121
195
9
128
208
9
135
220
< 100 9
126
204
9
139
228
9
146
240
10
153
253
> 100
9
142
233
10
158
262
10
165
275
10
172
288
5454
CompactionParameters
EstimatedDesign Traffic
Level(Millions1
ESALs) Ninit Ndes Nmax
< 0.3 6 50 75
0.3 to < 3 7 75 115
3 to < 30 8 100 160
≥ 30 9 125 205
In Superpave (Marshall too)In Superpave (Marshall too)
•• Air voids and VMA specifiedAir voids and VMA specified–– Controls asphalt contentControls asphalt content
•• Gradation is notGradation is not
–– SO . . . . to change asphalt content, change VMA SO . . . . to change asphalt content, change VMA requirementrequirement
Effect of Design GyrationsEffect of Design Gyrations
N designN design
highhigh
lowlow
Volumetric Properties Constant (air voids, VMA, VFA)Volumetric Properties Constant (air voids, VMA, VFA)
SkeletonSkeleton
strongstrong
weakweak
LABLAB ROADROAD
5757
CONCLUSIONSCONCLUSIONS
•• Density at end of service life not Density at end of service life not appropriate to define N designappropriate to define N design
•• NN--design does not influence asphalt design does not influence asphalt contentcontent
•• NN--design in Superpave is design in Superpave is ““in the ball parkin the ball park””
5858
9-9 (1) Proposed Ndesign Levels
2020--Year Design Year Design Traffic, ESALsTraffic, ESALs
22--Year Design Year Design Traffic, ESALsTraffic, ESALs
Ndesign Ndesign UnmodifiedUnmodified
Ndesign PG Ndesign PG 7676--2222
< 300,000< 300,000 < 30,000< 30,000 50506565
8080
8080
100100
NANA300,000 to 300,000 to 3,000,0003,000,000
30,000 to 30,000 to 230,000230,000
5050
3,000,000 to 3,000,000 to 10,000,00010,000,000
230,000 to 230,000 to 925,000925,000
6565
10,000,000 to 10,000,000 to 30,000,00030,000,000
925,000 to 925,000 to 2,500,0002,500,000
6565
> 30,000,000> 30,000,000 > 2,500,000> 2,500,000 8080
Recommended Ndesign TableRecommended Ndesign Table
5959
Fine Aggregate Specific Gravity IssuesFine Aggregate Specific Gravity Issues
•• Identify problems/issues with current Identify problems/issues with current standard AASHTO T 84 standard AASHTO T 84
•• Evaluate alternate methodsEvaluate alternate methods•• Make recommendations regarding Make recommendations regarding
changes and/or new methodschanges and/or new methods•• Additional scope Additional scope ---- Mixture gravity Mixture gravity
determination issues T 209determination issues T 209
Task Group Objectives:Task Group Objectives:
6060
Other NCHRP ProjectsOther NCHRP Projects
99--3434: Improved Conditioning Procedure for : Improved Conditioning Procedure for Moisture SusceptibilityMoisture Susceptibility9-38: Endurance Limit of HMA Mixtures to Prevent Fatigue Cracking99--3939: : Determining Mixing and Compaction Temperatures of PG Binders in HMA99--4545: Development of Specification Criteria for : Development of Specification Criteria for Mineral Fines Used in HMAMineral Fines Used in HMA
6161
WARM MIX ASPHALTWARM MIX ASPHALTTECHNOLOGYTECHNOLOGY
44th Annual Idaho Asphalt Conference
October 21, 2004
Moscow, Idaho
6262
Thank YouThank You………………
http://www.fhwa.dot.gov/http://www.fhwa.dot.gov/pavementspavements