FHWA Pavements program What s s Happening John D AngeloD Office of Pavement Technology 1
σ Loads and Layer Stiffness E * Mr M r Mechanistic Analysis Layered Elastic Analysis Strain Calculations at Critical Locations E = σ/ε 2
Current Status of MEPDG MEPDG Software Version 1.0 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 3
FHWA DGIT Workshops Upcoming Traffic 3 PMS Database Inputs - 1 Future Local Calibration Weighing Impacts of MEPD for Next Generation Traffic Data Past Workshops Introduction to the DG 8* Traffic 2 Materials 11* Climatic Inputs 12* *Webcast available Climatic Workshop Locations 4
FHWA Other Activities 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 5
Future FHWA Workshops National Highway Institute NHI Course #131109 Pilot: April 2007 Analysis 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 6
Future FHWA Workshops Local Calibration for M-E PDG models Awaiting deliverables from NCHRP 1-40 B Pilot planned for Fall 2007 Purpose: discuss Sensitivity of inputs & calibration, educate Pavt Designers & Pavement Managers 7
Asphalt 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. 8
Asphalt Mix Performance Tester Develop new pooled fund for purchase of the equipment. Establishment of a technician training school for operation of the equipment. Develop precision and bias for test procedure. 9
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Problem-High Temperature Binder Criteria Does G*/sinδ reflect rutting performance of modified binders. General anecdotal data says no. What are the alternatives? ZSV, LSV, Creep & Recovery testing 11
NCHRP 9-109 Rutting Test Repeated Creep Recovery Test Shear Stress, 68 1 Shear Stain, mm/mm 10 20 Accumulated Strain 1 10 20 12
New High Temp Criteria Jnr 30 25 Normalized Strain % 20 15 10 5 J nr = γ u / τ τ = stress applied during creep J nr = non-recoverable compliance γ u = Avg. un-recovered strain 0 0 20 40 60 80 100 Time s 13
As-Built Pavement Lanes R-AZ PG Air ---- 70-22 Blown 0-22Control SBS LG CR-TB TP PG 70-22 PG SBS Air + 70-2264-40 Blown Fibers SBS LG TP 1 2 3 4 5 6 7 8 9 10 11 14 12
Jnr ALF binder 64C 0.25 0.2 Jnr 0.15 0.1 64-40 64C AB 64C SBS LG control 64C Elvaloy 64C TBCR 64C 0.05 0 0 5000 10000 15000 20000 25000 30000 Stress Pa 15
1.0 0.9 0.8 0.7 HMA Layer Rutting for All Lanes L9S1(SBS 64-40 6") L9S2(SBS 64-40 6") L6S1(Terpolymer 4") L8S1(Control 6") HMA Layer Rutting, in. 0.6 0.5 0.4 0.3 0.2 0.1 0.0 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") 0 10,000 20,000 30,000 40,000 50,000 L5S1(TBCR 60,000 4") ALF Wheel Passes 16
12 10 8 y = -7.4519x + 10.956 R 2 = 0.1261 G*/sin d 64C 6 4 2 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 rutting inches 17
0.25 0.2 Relationship between Jnr and ALF rutting y = 0.4736x - 0.1167 R 2 = 0.8167 0.15 Jnr 0.1 0.05 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 ALF Rutting in 18
Hamburg Rut testing MINN Road mixes Jnr 12.8kPa 1.4000 1.2000 y = 0.0398x - 0.0289 R 2 = 0.9646 1.0000 0.8000 Jnr 0.6000 0.4000 0.2000 0.0000 0 5 10 15 20 25 30 35 19 rut mm
Miss I55 6yr rut Jnr 3.2 kpa 0.4 0.35 0.3 0.25 6 yr Jnr 3.2 kpa binder mod true grad rut mm 70C Ultrapave SBR 70-27 4.5 0.17 Styrelf SB 77-29 2 0.044 GTR 80 75-29 1.5 0.121 Sealoflex SBS 82-27 3 0.019 Multygrade 72-24 5 0.213 Cryo Rubber 75-28 7 0.162 Control 70-24 11 0.35 y = 0.031x R 2 = 0.7453 Jnr 0.2 0.15 0.1 0.05 0 0 2 4 6 8 10 12 rut mm 20
High Temperature Binder Criteria Non-recoverable compliance of the binder describes the stress dependency of the binder. Creep and recovery testing done at multiple stress levels on one sample can be run to describe the stress dependency of the binder. Creep and recovery non-recoverable compliance can be correlated to mix testing done at different stress conditions and related to performance. 21
Affect of Jnr on Rutting Reducing Jnr by half typically reduced rutting by half. This affect is seen on ALF sections and Hamburg Rut Testing But most importantly this is seen on the Mississippi I 55 sections. 22
Determination of a Specification criteria. The existing binder specification works very well for neat binders. The grading for neat binders should not change. Establish new Jnr criteria based on response of neat binders at their continuous grade temp. Evaluate the binders near the end of their linear range. Most neat binders remain 23
Sample ID ALF 6727 BBRS3 Evaluation of Straight run MN county rd 112 MN county rd 112 MN county rd 112 Minn Road Name binders Grade true grade Temp Jnr 3.2kPa Control 70-22 72.7-74.2 74.2 72.7 0.439122 straight 64-22 66.1-27.3 66.1 0.418449 neat Valero 58-28 60.8-33.4 60.8 0.368445 neat Citgo 58-28 59.5-29.8 59.5 0.529647 AshlandM 58-28 60.7-31.4 60.7 0.430165 straight 58-28 61.8-30.8 61.8 0.302951 Miss I-55I CSL 67-22 68.3-25.1 68.3 0.266912 Shandong BBRS3 BBRS3 MD project straight 64-22 64.4-23.5 64.4 0.444057 straight 70-22 71.4-24.8 71.4 0.480855 straight 58-28 61.3-30 30 61.3 0.400345 straight 64-28 64.8-29.6 64.8 0.459335 average 0.412753 24
Grade bumping recommendation All testing should be done at the environmental grade temp. The standard grade should be based on the Jnr value of existing neat binders 0.4. For high traffic the Jnr value should be reduced by half at the grade temp to 0.2. For standing traffic the Jnr value should be reduced by half again 0.1. 25
New high Temp Spec PG 64 (Standard, Heavy, Very heavy) based on traffic. PG 64S-XX J nr => 0.4 PG 64H-XX J nr => 0.2 PG 64V-XX J nr => 0.1 26
How do we identify Polymers? Use DSR Use DSR Approach Muti Stress Creep Recovery Test Two creep stress levels Ten cycles per stress level For Elastomeric modifiers Specify: % strain recovery 3200 Pa > 15% or 20% Overall change between stress levels 100-3200 Pa < 75% Run on the RTFOT Run on the same sample as RTFOT grading 27
What criteria? % recovered strain Creep 1st cycle 70C 1000 Pa 450 400 350 300 (Peak Strain - recovered Strain)/Peak Strain % strain 250 200 control Elvaloy Stylink AB 150 100 50 0 0 2 4 6 8 10 12 time 28
MSCR selection of stress levels 0.6 0.5 0.4 poor structure good structure Jnr 0.3 3200 Pa 0.2 0.1 0 10 100 1000 10000 100000 Stress Pa 29
General relationship between ER and MSCR 90.00 85.00 80.00 75.00 PG 64-28 PG 64-34 PG 70-28 PG 58-28 3200 Pa % Recovery 70.00 65.00 60.00 55.00 50.00 45.00 40.00 Special EVA Incompatible SBS 35.00 30.00 25.00 20.00 65.00 70.00 75.00 80.00 85.00 90.00 95.00 100.00 UDOT Elastic Recovery @ 25 C, % 30
Effect of X-linking X on ER 1.8 1.6 1.4 CI 05 ER 36.3 CI 05 04 ER 56.3 CI ER 32.5 1.2 Jnr 1 0.8 0.6 0.4 0.2 0 60 65 70 75 80 85 Temp C 31
BBRS Study 90 % recovery 3.2kPa 80 70 60 50 40 30 SBS Elva 70-28 Elvaloy 70-28 SBS 70-28 SBR 70-22 Ergon 76-22 Elvaloy 76-28 64V,70S 64V, 70H, 76S 64V, 70S 58V, 64H, 70S 70V, 76H, 82S 70V, 76H, 82S 20 10 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 32 Jnr
Warm Mix Task Group: Gaylon Baumgardner Gayle King Gerald Reinke Matt Corrigan Chris Abadie 33
Question: (RTFO, PAV or both?) Master Curve Development (DSR) PTSi SuperPave True Grade (Through DTT) PTSi Physical Hardening (30 days saturation at - 12 C) Bending Beam Rheometry (BBR) - PTSi Multi-Step Creep Recovery (MSCR) FHWA Glass Transition Tg (MDSC) WRI/MTE Atomic Force Microscopy (AFM) WRI 34
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Superpave Gyratory Compactor Calibration Making Superpave Mixtures Consistent 36
4.1 AASHTO Designation: T 312-03 Preparing... Specimens by SGC Superpave Gyratory Compactor an average internal angle of 1.16 + 0.02.. (only internal angle with simulated mix measurement) 37
Internal Angle Measurement with Hot Mix Asphalt DAV on Top to measure α T DAV on Bottom to measure α B 38
APAC External Calibrated to 1.25 degrees External 3.5 4.0 4.5 Air Voids (Va), % 39
APAC Internal Calibrated to 1.16 degrees Internal 3.5 4.0 4.5 Air Voids (Va), % 40
Asphalt Institute Calibrated Externally at 1.25 4.0 4.5 5.0 Air Voids (Va), % 41
Asphalt Institute Calibrated Internally at 1.16 4.0 4.5 5.0 Air Voids (Va), % 42
University of Arkansas Calibrated Externally at 1.25 4.0 4.5 5.0 Air Voids (Va), % 43
University of Arkansas Calibrated Internally at 1.16 4.0 4.5 5.0 Air Voids (Va), % 44
HMS & RAM 45
Specification Recommendations Drop procedures related to use of HMA drop reference in T312; eliminate TP48 Implement new TP for simulated loading add reference in T312 Precision: Troxler 4140 NOT INCLUDED Refer to manufacturers recommendations Applies to specific procedures for using various devices Applies to hot-versus versus-cold question(s). Inform users that RAM ~ DAV2/HMS Angle tolerance: move to +/- 0.03 deg 46
EFFECT OF DESIGN COMPACTION 47
Effect on VMA Change in VMA 3.0% 2.0% Aggregate Blend Constant 19 MM MIXTURES 1.0% 0.0% -60-40 -20 0 20 40 60-1.0% -2.0% Change In Gyrations 48
Effect of Design Gyrations Aggregate Properties Constant (gradation, CAA, FAA) LAB N design ROAD % Asphalt high low low high
Effect on Stiffness G*(0.1Hz), kpa 120,000 100,000 80,000 60,000 40,000 20,000 Volumetric Properties Constant - -60-40 -20 0 20 40 Change from Design Gyrations 60 50
Effect of Design Gyrations Volumetric Properties Constant (air voids, VMA, VFA) LAB N design ROAD Skeleton high strong low weak
What Should Design Gyrations Be? 20-30 gyrations changes VMA by 1% 0.4% asphalt content Mixture stiffness by 25 to 30% about one PG high temp grade difference SO.......
Design ESALs Millions Average Design High Air Temperature <39 C 39 40 C 41-42 C 41 44 C N ini N des N ma N ini N des N ma N ini N des N ma N ini N des N ma x x x 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 < 100 8 109 174 9 121 195 9 128 208 9 135 220 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 53
Estimated Design Traffic Level (Millions 1 Compaction Parameters ESALs) N init N des N max < 0.3 6 50 75 0.3 to < 3 7 75 115 3 to < 30 8 100 160 30 9 125 205 54
In Superpave (Marshall too) Air voids and VMA specified Controls asphalt content Gradation is not SO.... to change asphalt content, change VMA requirement
Effect of Design Gyrations Volumetric Properties Constant (air voids, VMA, VFA) LAB N design ROAD Skeleton high strong low weak
CONCLUSIONS Density at end of service life not appropriate to define N design N-design does not influence asphalt content N-design in Superpave is in the ball park 57
Recommended Ndesign Table 9-9 (1) Proposed Ndesign Levels 20-Year Design Traffic, ESALs 2-Year Design Traffic, ESALs Ndesign Unmodified < 300,000 < 30,000 50 300,000 to 3,000,000 3,000,000 to 10,000,000 10,000,000 to 30,000,000 30,000 to 230,000 230,000 to 925,000 925,000 to 2,500,000 65 80 80 Ndesign PG 76-22 NA 50 65 65 > 30,000,000 > 2,500,000 100 80 58
Fine Aggregate Specific Gravity Issues Task Group Objectives: Identify problems/issues with current standard AASHTO T 84 Evaluate alternate methods Make recommendations regarding changes and/or new methods Additional scope -- Mixture gravity determination issues T 209 59
Other NCHRP Projects 34: : Improved Conditioning Procedure for Moisture Susceptibility 9-34 9-38: Endurance Limit of HMA Mixtures to Prevent Fatigue Cracking 9-39: Determining Mixing and Compaction Temperatures of PG Binders in HMA 9-45 45: : Development of Specification Criteria for Mineral Fines Used in HMA 60
WARM MIX ASPHALT TECHNOLOGY 44 th Annual Idaho Asphalt Conference October 21, 2004 Moscow, Idaho 61
Thank You http://www.fhwa.dot.gov/pavements pavements 62