Performance Tests of Asphalt Mixtures Louay N. Mohammad, Ph.D. Department of Civil and Environmental Engineering LA Transportation Research Center Louisiana State University 42 nd Annual Rocky Mountain Asphalt Conference February 25 27, 2015 Denver, Colorado
My Story Baxkground Asphalt Mixture Design Review performance Tests High Temperature Intermediate Temperature Mixture Design Volumetric Mechanistic Summary
Background Asphalt cement Aggregate Coarse Fine Increased use of Reclaimed Materials RAP / RAS Waste tires Industrial waste
Background Practice of utilizing RAP and/or RAS in new asphalt mixtures has increased in recent years economic and environmental benefits RAP has most widely used materials Wearing Course: 15% Binder Course: 20% Base Course: 30% RAS has emerged as a material of interest to the paving community RAP and/or RAS valuable components in asphalt mixtures With increased demand and limited supply of aggregate and binder Potential benefits are high on use high percentages of RAP state agencies have not proceeded to use high percentages of RAP on their roadways non-uniformity of RAP materials agency s lack of confidence in the long term performance data and specifications. problem is further augmented when RAS is used in conjunction with RAP
Objectives of Mixture Design Perform permanent deformation fatigue cracking repeated load low temperature cracking moisture induced damage Safety Resist skid Constructable Workability
Typical Asphalt Mixture Design Volumetrics Voids in the Total Mix, VTM Voids in the Mineral Aggregate, VMA Voids Filled with Asphalt, VFA Densification Stages during lab compaction process VOLUME air asphalt MASS Total Volume aggregat e aggregate Total Mass
Current Volumetric mix design Ensure satisfactory performance strict material specifications requirement volumetric mix criteria No mechanical proof test Marshall mix design Limited Mechanical tests mix verification intermediate and high volume traffic Superpave Shear Tester (SST) Not widely used
Overall Relative Rut Susceptibility Ranking 3 Fair Relative Rut Susceptibility 2 1 Good Excellent 25 mm 19 mm 0 LA 4 BC LA 22 BC LA 22 WC LA 121 BC LA 121 WC LA 353 BC/WC
Laboratory Performance Assessments Mixture Design Binder Content Binder Quality Aggregates
Selection of Mechanical Tests Laboratory Tests Pavement Performance High Temperature Permanent deformation Intermediate Temperature Fracture/Fatigue Low Temperature Low temp cracking Features to be considered Measure/relate to fundamental properties Simple, repeatable, easily calibrated, quick, not requiring highly trained personnel, Can utilize low cost equipment. Sensitive to subtle changes in mixture properties
Laboratory Performance Tests
Louisiana Balanced Asphalt Mixture Design High temperature Performance Loaded Wheel Tracking Test Relation to F N Rutting Intermediate temperature Performance Semi Circular Bend Test Cracking Low temperature performance TSRST
SCB Test at Intermediate Temperature Fracture Mechanics Approach Analytical method to calculate the driving force on a crack characterize the material's resistance to fracture Cracks Initiates Small cracks Propagates Large crack Caused by tensile stresses analyzed by fracture mechanics models
Advantages of SCB Test Utilize laboratory SGC specimens or field cores multiple specimens can be obtained from one core reducing the error caused by heterogeneities among samples Test setup is simple Testing time is around 10 minutes per specimen Ease of sample preparation Stress field resembles pure tensile conditions
Draft Standard Test Method Developed Circulated
Test Equipment Development
LWT Test at High Temperature Test simplicity technician training requirements» Minimal» Several labs (state DOTs, Univ., testing labs) time for preparing samples» Compact, Cut, and preform volumetric measurements» 1 day for the set (4 specimens) testing specimens» 1 day for the set (2 samples = 4 specimens) analyzing data» Spreadsheet: 30 minutes
SCB test at Intermediate Temperature Test simplicity technician training requirements» Minimal» Several labs (state DOTs, Univ., testing labs) time for preparing samples» Compact, Cut, and Notch, preform volumetric measurements» 1 day for the set (12 test specimens) testing specimens» 1-2 hours for the set (12 test specimens) analyzing data» Spreadsheet with cut/paste: 15 minutes
Results
LWT Test Results 50 C, Wet SBS, CRM Rut Depth, 20K passes, mm 20 18 16 14 12 10 8 6 4 2 0 10.2 5.6 5.3 4.6 5.7 64CO 70CO M 76CO M 76CRM 76RAP15 Binder Type 2011 AAPT: Laboratory Evaluation of Asphalt Mixtures Containing Sustainable Technologies
Semi Circular Bend Test Results, 25 C SBS, CRM Jc, Kj/m2 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 64CO 70CO M 76CO M 76CRM Binder Type 2011 AAPT: Laboratory Evaluation of Asphalt Mixtures Containing Sustainable Technologies
LWT Test Results, 50 C, Wet Bio Binders 20 18 PG 64-22 PG 70-22 PG 76-22 Rut Depth @ 20,000 passes (mm) 16 14 12 10 8 6 4 2 0 6422CO 6422GR 7022CO 7016GR 7022GR 7622CO 7622GR Mixture ID 2013 TRB: Laboratory Evaluation of Asphalt Mixtures Containing Bio Binder Technologies
LWT Test Results, 50 C, Wet Bio Binders 20 18 PG 64-22 PG 70-22 PG 76-22 Rut Depth @ 20,000 passes (mm) 16 14 12 10 8 6 4 2 0 6422CO 6422GR 7022CO 7016GR 7022GR 7622CO 7622GR Mixture ID 2013 TRB: Laboratory Evaluation of Asphalt Mixtures Containing Bio Binder Technologies
Semi Circular Bend Test Results, 25 C Bio Binders PG 64-22 PG 70-22 PG 76-22 1 A Jc (Kj/m 2 ) 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 6422CO 6422GR 7022CO 7016GR 7022GR 7622CO 7622GR Mixture ID 2013 TRB: Laboratory Evaluation of Asphalt Mixtures Containing Bio Binder Technologies
Loaded Wheel Tracking Test Results, 50 C RAP and/or RAS 20.0 18.0 No Recycling Agents Recycling Agents Rut Depth, 20K Passes, mm 16.0 14.0 12.0 10.0 8.0 6.0 4.0 2.0 Mix 1 = 70CO Mix 2 = 70PG5P Mix 3 = 52PG5P RA 1 Mix 4 = 70PG5P RA 2 Mix 5 = 70PG5P RA 3 Mix 6 = 70PG5P15RAP RA 2 0.0 Mix 1 No RAP/RAS Mix 2 B 5RAS Mix 3 B 5RAS Mixture type Mix 4 B 5RAS Mix 5 B 5RAS Mix 6 B 15RAP+5RAS RA 1 RA 2 RA 3 RA 2
Semi Circular Bend Test Results, 25 C RAP and/or RAS 0.6 No Recycling Agents Recycling Agents 0.5 0.4 Mix 1 = 70CO Mix 2 = 70PG5P Mix 3 = 52PG5P RA 1 Mix 4 = 70PG5P RA 2 Mix 5 = 70PG5P RA 3 Mix 6 = 70PG5P15RAP RA 2 J c, KJ/m 2 0.3 0.2 0.1 0.0 RBR = 0 % Mix 1 No RAP/RAS RBR = 9.4 % Mix 2 B 5RAS RBR = 13.2 % Mix 3 B 5RAS Mixture type RBR = 26.4 % Mix 4 B 5RAS RBR = 22.6 % Mix 5 B 5RAS RBR = 41.5% Mix 6 B 15RAP+5RAS RA 1 RA 2 RA 3 RA 2
LWT Test Results, 50 C 90% Level 1 Level 2
Semi Circular Bend Test Results, 25 C
Louisiana Balanced Mixture Design Volumetric and Performance Mixture Testing Rutting LWT test (50 C, Wet) Cracking SCB test (25 C) Cracking Resistance 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0 5 10 15 20 Rutting Resistance High Temperature Performance Volumetric Parameters Cracking Performance
2013 Proposed Specification
2013 Proposed Specification Property 2006 Specifications 2013 Proposed Specifications Ndesign, 75 100 65 75 a Gyrations Minimum 10 13 10.5 13.0 VMA, % VFA, % 68 78 69 80 Air Voids, % 2.5 4.5 2.5 4.5 2014 TRB: Balanced Asphalt Mixture Design through Specification Modification: Louisiana s Experience
LWT Test Results, 50 C Rut Depth, mm 20 15 10 5 0 PG 64 22 PG 70 22M PG 76 22M PG 82 22CRM 0 5 10 15 20 25 30 35 40 45 50 55 Mixture Number
LWT Test Results, 50 C Rut Depth, mm 20 15 10 5 0 PG 64 22 PG 70 22M PG 76 22M PG 82 22CRM 0 5 10 15 20 25 30 35 40 45 50 55 Mixture Number
SCB test Results, 25 C PG 64 22 PG 70 22M PG 76 22M PG 82 22CRM 1.5 Jc, KJ/m 2 1 0.5 0 0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 Mixture Number
SCB test Results, 25 C PG 64 22 PG 70 22M PG 76 22M PG 82 22CRM 1.5 Jc, KJ/m 2 1 0.5 0 0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 Mixture Number
LWT Test Results, 50 C 20.0 Rut Depth, 20K passes, mm 16.0 12.0 8.0 4.0 0.0 PG 64 22 PG 70 22 M PG 76 22 M PG 82 22rm Binder Type 19 mm LS
Semi Circular Bend Test Results, 25 C 0.8 0.6 Jc, Kj/m2 0.4 0.2 0.0 PG 64 22 PG 70 22 M PG 76 22 M Binder Type 19 mm LS
Development Of Performance Based Specifications For Louisiana Asphalt Mixtures Laboratory and Field evaluation of 10 projects Projects in service for 3 10 years. Does SCB parameter translate to field performance? 105.00 100.00 LADOTD PMS Cracking Index 95.00 90.00 85.00 80.00 75.00 70.00 65.00 Y = 100 (0.969+0.036X) -170 ) r 2 : 0.73 60.00 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 Laboratory Measured Jc, kj/mm2
Selection of a Criteria 105.00 100.00 95.00 High Traffic PMS Trigger LADOTD PMS Cracking Index 90.00 85.00 80.00 75.00 70.00 Low Traffic PMS Trigger Y = 100 (0.969+0.036X) -170 ) r 2 : 0.73 65.00 60.00 0.30 0.40 0.50 0.60 0.70 0.80 Laboratory Measured Jc, kj/mm2 0.90 1.00
Implementation LADOTD SCB, min, Jc, kj/m 2 @ 25⁰ C, Aged All mix design level 1 must meet minimum 0.5 Jc, All mix design level 2 must meet minimum 0.6 Jc.
Summary Volumetric-based design Not sufficient Compliment Volumetric design Mechanistic tests Criteria Performance related Incremental/Evaluate Specifications Loaded Wheel Tester Test High Temperature Semi-Circular Bend Test Intermediate temperature Cracking performance Jc was sensitive to mixture parameters considered Further validation with more field and laboratory data
T H A N K Y O U