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Block 4 SP 14

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Block 4 SP 14

  1. 1. Senior/Graduate HMA Course Asphalt Binders Superpave Performance Graded Specification Asphalt Binders Superpave Binder Tests 1
  2. 2. 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 Asphalt Binders Superpave Binder Tests 2
  3. 3. Pavement Temperatures are Calculated • Calculated by Superpave software • High temperature – 20 mm (.8”) below the surface of mixture • Low temperature – at surface of mixture Pave temp = f (air temp, depth, latitude) www.tfhrc.gov/pavement/ltpp/ltppbind.htm Asphalt Binders Superpave Binder Tests 3
  4. 4. PG Specification Tests • Rheology – Fundamental properties related to HMA performance • Test parameters – Selected to represent in-service & construction temperatures • Asphalt binder conditioning – Environmental factors • Short and long term aging Asphalt Binders Superpave Binder Tests 4
  5. 5. Rheological Tests Selected • • • • Concentric Cylinders Dynamic shear rheometer Bending beam Direct tension Asphalt Binders Superpave Binder Tests 5
  6. 6. Tests Used in PG Specifications Construction RV Asphalt Binders DSR Superpave Binder Tests BBR 6
  7. 7. Construction Asphalt Binder Properties • Concentric cylinder rheometer – Used to insure a minimum workability (pumpability) at typical mixing temperature – Maximum viscosity 3kPa at 135oC (275 F) Asphalt Binders Superpave Binder Tests Construction [RV] 7
  8. 8. Rutting BBR RV DSR Asphalt Binders Superpave Binder Tests 8
  9. 9. Rutting • High in-service temperature – Desert climates – Summer temperatures • Sustained loads – Slow moving trucks – Intersections Asphalt Binders Superpave Binder Tests Viscous Liquid 9
  10. 10. Rutting • DSR testing – Minimum stiffness requirement • Original asphalt binder • Immediately after construction – Short term aging Rutting [DSR] Asphalt Binders Superpave Binder Tests 10
  11. 11. High In-Service Temperatures • Permanent deformation (rutting) • Mixture is plastic • Depends on asphalt binder source, additives, and aggregate properties Function of warm weather and traffic Asphalt Binders Superpave Binder Tests 11
  12. 12. Asphalt Binders Superpave Binder Tests 12
  13. 13. Short Term Aging • Simulates stiffening of asphalt binder during storage, mixing, and hauling • Function of: – Oxidation hardening • Asphalt binder reacts with oxygen • Volatilization of specific components • Simulated using rolling thin film oven Asphalt Binders Superpave Binder Tests 13
  14. 14. Short Term Aging • Rolling Thin Film Oven Test (RTFOT) – Simulates aging from hot mixing and construction Asphalt Binders Superpave Binder Tests 14
  15. 15. Mass Loss is Monitored • Calculate mass loss after RTFO Original mass - Aged mass Mass loss, % = Asphalt Binders x 100 Original mass Superpave Binder Tests 15
  16. 16. Rutting Superpave DSR test requirements: G*/sin δ on unaged (original) asphalt binder > 1.00 kPa G*/sin δ on RTFO aged asphalt binder > 2.20 kPa For the early part of the service life Asphalt Binders Superpave Binder Tests 16
  17. 17. Fatigue BBR RV DSR Asphalt Binders Superpave Binder Tests 17
  18. 18. Fatigue Cracking Function of repeated traffic loads over time (in wheel paths) Asphalt Binders Superpave Binder Tests 18
  19. 19. DSR Fatigue Cracking • Aged PG asphalt binder – Since long term performance problem, include: • Short term aging [DSR] • Long term aging • Determine DSR parameters using 8 mm plate and intermediate test temperature Asphalt Binders Superpave Binder Tests 19
  20. 20. Long Term Aging • Simulates aging of an PG asphalt binder for 7 to 10 years • Starts with RTFO aged PG asphalt binder – Additional aging with Pressure Aging Vessel (PAV) • 50 gram (1.75 oz) Asphalt Binders Superpave Binder Tests 20
  21. 21. PAV Components Bottom of pressure aging vessel Rack of individual pans (50g of asphalt / pan) Vessel Lid Components Asphalt Binders Superpave Binder Tests 21
  22. 22. PAV Testing • After RTFO aging – 50 gram sample/pan aged for 20 hours in PAV • Pressure of 2,070 kPa (300 psi) • Test temp 90, 100 or 110o C (194, 212,or 230 F) • The parameter addresses the later part of the fatigue life Asphalt Binders Superpave Binder Tests 22
  23. 23. Equipment Examples Asphalt Binders Superpave Binder Tests 23
  24. 24. Thermal Cracking RV Asphalt Binders DSR Superpave Binder Tests BBR 24
  25. 25. Low Temperature Behavior • Low Temperature – Cold climates – Winter • Rapid Loads – Fast moving trucks Elastic Solid Hooke’s Law σ=τE Asphalt Binders Superpave Binder Tests 25
  26. 26. Low Temperature • 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 Asphalt Binders Superpave Binder Tests 26
  27. 27. Thermal Cracking Asphalt Binders Superpave Binder Tests 27
  28. 28. Low Temperature • Two rheological tests – Bending beam • Stiffness – Direct tension • Strength Asphalt Binders Superpave Binder Tests Low Temp Cracking [DTT] [BBR] 28
  29. 29. Superpave Requirements • BBR Stiffness Properties – Max stiffness, S, at 60 seconds of 300 MPa – Min rate of change in stiffness • Min slope, m, of 0.300 MPa/sec • Strength – Currently being finalized Asphalt Binders Superpave Binder Tests 29
  30. 30. Summary Construction Rutting Fatigue Cracking Low Temp Cracking [DTT] [RV] No aging [DSR] [BBR] RTFO Short Term Aging PAV Long Term Aging Asphalt Binders Superpave Binder Tests 30
  31. 31. QUESTIONS ? Asphalt Binders Superpave Binder Tests 31

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