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SUPERPAVE

SUPERPAVE. FHWA Condensed Superpave Asphalt Specifications Lecture Series. What is Superpave. Final product of the 1987-1993 FHWA Strategic Highway Research Program to investigate better pavement materials & design methods. Sup erior Per forming Asphalt Pave ments = Superpave

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SUPERPAVE

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  1. SUPERPAVE FHWA Condensed Superpave Asphalt Specifications Lecture Series

  2. What is Superpave • Final product of the 1987-1993 FHWA Strategic Highway Research Program to investigate better pavement materials & design methods. • Superior Performing Asphalt Pavements = Superpave • Produced new standards for aggregates and bituminous binders used in paving as well as mix design changes.

  3. Aggregates Usually refers to a soil that has in some way been processed or sorted.

  4. 100 100 90 72 65 48 36 22 15 9 4 100 99 89 72 65 48 36 22 15 9 4 Aggregate Size Definitions • Nominal Maximum Aggregate Size • one size larger than the first sieve to retain more than 10% • Maximum Aggregate Size • one size larger than nominal maximum size

  5. Percent Passing 100 max density line restricted zone control point nom max size max size 0 .075 .3 2.36 4.75 9.5 12.5 19.0 Sieve Size (mm) Raised to 0.45 Power

  6. Superpave Aggregate Gradation Percent Passing 100 Design Aggregate Structure 0 .075 .3 2.36 12.5 19.0 Sieve Size (mm) Raised to 0.45 Power

  7. Superpave Mix Size Designations Superpave Nom Max SizeMax Size Designation (mm) (mm) 37.5 mm 37.5 50 25 mm 25 37.5 19 mm 19 25 12.5 mm 12.5 19 9.5 mm 9.5 12.5

  8. - Larger max size Gradations * Considerations: - Max. size < 1/2 AC lift thickness + Increases strength + Improves skid resistance + Increases volume and surface area of agg which decreases required AC content + Improves rut resistance + Increases problem with segregation of particles - Smaller max size + Reduces segregation + Reduces road noise + Decreases tire wear

  9. Percent Crushed Fragments in Gravels • Quarried materials always 100% crushed • Minimum values depended upon traffic level and layer (lift) • Defined as % mass with one or more fractured faces

  10. Rounded Aggregates in Pavement • Crushed face aggregates help to reduce shear plane slides and mass deformation of the pavement structure.

  11. Percent Crushed Fragments in Gravels 0% Crushed 100% with 2 or More Crushed Faces

  12. Traffic Depth from Surface Millions of ESALs < 100 mm > 100 mm < 0.3 < 1 < 3 < 10 < 30 < 100 >100 --/-- --/-- 50/-- 60/-- 80/75 95/90 100/100 55/-- 65/-- 75/-- 85/80 95/90 100/100 100/100 Coarse Aggregate Angularity Criteria First number denotes % with one or more fractured faces Second number denotes % with two or more fractured faces

  13. Asphalt Cements Background History of Specifications

  14. Asphalt Soluble in petroleum products Generally a by-product of petroleum distillation process Can be naturally occurring Tar Resistant to petroleum products Generally by-product of coke (from coal) production Background

  15. Penetration in 0.1 mm 100 g After 5 seconds Initial Penetration Testing • Sewing machine needle • Specified load, time, temperature

  16. Penetration Specification • Five Grades • 40 - 50 • 60 - 70 • 85 - 100 • 120 - 150 • 200 - 300

  17. Ductility

  18. Typical Penetration Specifications Penetration 40 - 50 200 - 300 Flash Point, C 450+ 350+ Ductility, cm 100+ 100+ Solubility, % 99.0+ 99.0+ Retained Pen., % 55+ 37+ Ductility, cm NA 100+

  19. Viscosity Graded Specifications

  20. Types of Viscosity Tubes Zietfuchs Cross-Arm Tube Asphalt Institute Tube

  21. Table 1 Example AC 2.5 AC 40 Visc, 60C 250 + 50 4,000 + 800 Visc, 135C 80+ 300+ Penetration 200+ 20+ Visc, 60C <1,250 <20,000 Ductility 100+ 10+

  22. Penetration Grades AC 40 40 50 AC 20 60 70 AC 10 85 100 AC 5 120 150 AC 2.5 200 300 100 50 Viscosity, 60C (140F) 10 5

  23. Asphalt Cements New Superpave Performance Graded Specification

  24. PG Specifications • Fundamental properties related to pavement performance • Environmental factors • In-service & construction temperatures • Short and long term aging

  25. High Temperature Behavior • High in-service temperature • Desert climates • Summer temperatures • Sustained loads • Slow moving trucks • Intersections Viscous Liquid

  26. Pavement Behavior(Warm Temperatures) • Permanent deformation (rutting) • Mixture is plastic • Depends on asphalt source, additives, and aggregate properties

  27. Permanent Deformation Courtesy of FHWA Function of warm weather and traffic

  28. Low Temperature Behavior • Low Temperature • Cold climates • Winter • Rapid Loads • Fast moving trucks Elastic Solid

  29. Pavement Behavior(Low Temperatures) • Thermal cracks • Stress generated by contraction due to drop in temperature • Crack forms when thermal stresses exceed ability of material to relieve stress through deformation • Material is brittle • Depends on source of asphalt and aggregate properties

  30. Thermal Cracking Courtesy of FHWA

  31. Superpave Asphalt Binder Specification The grading system is based on Climate PG 64 - 22 Min pavement temperature Performance Grade Average 7-day max pavement temperature

  32. Pavement Temperatures are Calculated • Calculated by Superpave software • High temperature • 20 mm below the surface of mixture • Low temperature • at surface of mixture Pave temp = f (air temp, depth, latitude)

  33. Mi t Rq= 2 p Ri2 L W R g = Ro - Ri Concentric Cylinder Rheometers • Concentric Cylinder

  34. 2 M p R3 R Q h tR = gR = Dynamic Shear Rheometer (DSR) Shear flow varies with gap height and radius Non-homogeneous flow • Parallel Plate

  35. Short Term Binder Aging • Rolling Thin Film Oven • Simulates aging from hot mixing and construction

  36. Pressure Aging Vessel(Long Term Aging) • Simulates aging of an asphalt binder for 7 to 10 years • 50 gram sample is aged for 20 hours • Pressure of 2,070 kPa (300 psi) • At 90, 100 or 110 C

  37. Bending Beam Rheometer Computer Deflection Transducer Air Bearing Load Cell Fluid Bath

  38. Direct Tension Test Load Stress = s = P / A D L sf D Le ef Strain

  39. PAV Long Term Aging RTFO Short Term Aging No aging Summary Low Temp Cracking Fatigue Cracking Rutting Construction [DTT] [RV] [DSR] [BBR]

  40. Superpave Binder Purchase Specification

  41. Superpave Asphalt Binder Specification The grading system is based on Climate PG 64 - 22 Min pavement temperature Performance Grade Average 7-day max pavement temperature

  42. Performance Grades CEC Avg 7-day Max, oC PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG 82 1-day Min, oC -34 -40 -46 -10 -16 -22 -28 -34 -40 -46 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -10 -16 -22 -28 -34 ORIGINAL > 230 oC (Flash Point) FP <3Pa.s@135 oC (Rotational Viscosity) RV (Dynamic Shear Rheometer) DSR G*/sin  > 1.00 kPa 46 52 58 64 70 76 82 (ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 % (Dynamic Shear Rheometer) DSR G*/sin  > 2.20 kPa 46 52 58 64 70 76 82 (PRESSURE AGING VESSEL) PAV 20 Hours, 2.07 MPa 90 90 100 100 100 (110) 100 (110) 110 (110) (Dynamic Shear Rheometer) DSR G* sin  < 5000 kPa 28 10 7 4 25 22 19 16 13 10 7 25 22 19 16 13 31 28 25 22 19 16 34 31 28 25 22 19 37 34 31 28 25 40 37 34 31 ( Bending Beam Rheometer) BBR “S” Stiffness & “m”- value S < 300 MPa m > 0.300 -24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -18 -24 Report Value (Bending Beam Rheometer) BBR Physical Hardening > 1.00 % (Direct Tension) DT -24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -18 -24

  43. How the PG Spec Works 58 64 CEC Spec Requirement Remains Constant Avg 7-day Max, oC PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG 82 1-day Min, oC -34 -40 -46 -10 -16 -22 -28 -34 -40 -46 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -10 -16 -22 -28 -34 ORIGINAL > 230 oC (Flash Point) FP <3Pa.s@135 oC (Rotational Viscosity) RV (Dynamic Shear Rheometer) DSR G*/sin  > 1.00 kPa 46 52 58 64 70 76 82 (ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 % (Dynamic Shear Rheometer) DSR G*/sin  > 2.20 kPa 46 52 58 64 70 76 82 (PRESSURE AGING VESSEL) PAV 20 Hours, 2.07 MPa 90 90 100 100 100 (110) 100 (110) 110 (110) Test Temperature Changes (Dynamic Shear Rheometer) DSR G* sin  < 5000 kPa 28 10 7 4 25 22 19 16 13 10 7 25 22 19 16 13 31 28 25 22 19 16 34 31 28 25 22 19 37 34 31 28 25 40 37 34 31 ( Bending Beam Rheometer) BBR “S” Stiffness & “m”- value S < 300 MPa m > 0.300 -24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -18 -24 Report Value (Bending Beam Rheometer) BBR Physical Hardening > 1.00 % (Direct Tension) DT -24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -18 -24

  44. PG Binder Selection > Many agencies have established zones PG 52-28 PG 58-22 PG 58-16 PG 64-10

  45. Summary of How to Use PG Specification • Determine • 7-day max pavement temperatures • 1-day minimum pavement temperature • Use specification tables to select test temperatures • Determine asphalt cement properties and compare to specification limits

  46. Asphalt Concrete Mix Design History

  47. Hot Mix Asphalt Concrete (HMA)Mix Designs • Objective: • Develop an economical blend of aggregates and asphalt that meet design requirements • Historical mix design methods • Marshall • Hveem • New • Superpave gyratory

  48. Requirements in Common • Sufficient asphalt to ensure a durable pavement • Sufficient stability under traffic loads • Sufficient air voids • Upper limit to prevent excessive environmental damage • Lower limit to allow room for initial densification due to traffic • Sufficient workability

  49. MARSHALL MIX DESIGN

  50. Marshall Mix Design • Developed by Bruce Marshall for the Mississippi Highway Department in the late 30’s • WES began to study it in 1943 for WWII • Evaluated compaction effort • No. of blows, foot design, etc. • Decided on 10 lb.. Hammer, 50 blows/side • 4% voids after traffic • Initial criteria were established and upgraded for increased tire pressures and loads

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