Selecting the Correct PG Asphalt for Your Airport Project

1. Selecting the Correct PG Asphalt for Your Airport Project A Driving Force In Asphalt 29th Annual FAA Airports Conference Hershey, PA March 2, 2006 Ronald Corun CITGO Asphalt Technical Support Manager CITGO Petroleum Corporation

2. What is SUPERPAVE? • New Asphalt Binder specification • New Mix Design procedure using a new laboratory compaction device

3. We Have Three Asphalt Binders • Q. How do we determine which asphalt binder is best for our project? • A. The asphalt binder that gives the best performance A B C

4. Performance ? • Q. What areas of poor performance do we want to avoid ? • Or, in other words, how do our asphalt pavements fail ?

5. How do asphalt pavements fail ?

9. How Did We Measure Asphalt Properties Before the PG Grading System? • Penetration Grading • Viscosity Grading

10. Viscosity Penetration vacuum 0 sec 5 sec penetration 100 g 100 g 25° C 25° C 60° C

11. Problem with one temperature grading

12. Problem with one temperature grading • According to the Penetration system: • According to theViscosity System:

13. Asphalt binders • Q. Are the properties of asphalt binders constant over a pavements performance life? • A. NO! An asphalt binder’s response to loading is a function of three factors. . . • Age • Temperature • Rate of Loading

14. Asphalt binder’s response to loading is a function of. . . 1. age

15. Aging • Asphalt binders undergo aging through the loss of volatiles (a.k.a. loss of light ends) and oxidation. • From the standpoint of determining an asphalt binder's performance there are three key ages we need to address.

16. Key Aging • New material - no aging • During construction • Aging in the plant • Aging during placement • Late in the pavement's life • 7 - 10 years of service

17. Aging - How ? • Early: To simulate the aging that occurs due to construction and initial service, we are going to employ the Rolling Thin-Film Oven (RTFO). This is a standard AASHTO test method, T 240. • Spec.: 85 minutes, 163°C,400 ml of air per minute, 15 rpm

18. 163°C controls fan airjet bottle carriage Rolling Thin Film Oven

20. Rolling Thin Film OvenSample Bottles Clean Bottle Before Loading After Loading Coated Bottle After Testing

21. Aging - How ? • Long term: To simulate the aging that occurs due to oxidation over a pavement's life, we are going to subject the RTFO residue to time, temperature, and pressure. For this we are going to develop a pressure aging vessel, (PAV).

22. Aging - How ? • Long term, Spec.: AASHTO PP1. • According to PP1, our RTFO residue is subjected to: • Temperature: 90 to 110°C • Time: 20 hours • Pressure: 2.1 kPa

23. air pressure temperature probe asphalt pressure vessel sample rack sample pan Pressure Aging Vessel

25. Asphalt binder’s response to loading is a function of. . . 1. age 2. temperature

26. - 20 20 60 135 Pavement Temperature, C

27. Temperatures • Q. What temperatures do we need to address ? • 1. Rutting occurs at. . . • 2. Fatigue Cracking occurs at. . . • 3. Low Temperature Cracking occurs at. . .

28. Temperatures • 1. Rutting occurs at high pavement temperatures, T(high) • 2. Fatigue Cracking occurs at intermediate pavement temperatures, T(inter), and • 3. Low Temperature Cracking occurs at low pavement temperatures, T(low).

29. Performance Grade Increments

30. Superpave Asphalt Binder Specification • Grading System Based on Climate PG 64-22 Performance Grade Average 7-day max pavement design temp Min pavement design temp

31. RTFO - aging No aging PAV - aging Low Temp Cracking Fatigue Cracking Rutting Construction [DTT] [RV] [DSR] [BBR] Pavement Age

32. Dynamic Shear Rheometer, DSR • Apply a oscillating shear stress • Measure strain • A materials modulus is • Modulus = Stress / Strain • A measure of material stiffness

33. Dynamic Shear Rheometer, DSR

34. Dynamic Shear Rheometer, DSR

40. DSR provides G* and  • G*, Complex Shear Modulus •  , Phase Angle • G* / sin  • Correlates to rutting resistance. • G* sin  • Correlates to fatigue resistance.

41. Rutting Specification - Minimum Stiffness @ T(high) • G* / sin  > 1.00 kPa on unaged binder • G* / sin  > 2.20 kPa on RTFO aged binder

42. RTFO - aging No aging PAV - aging Low Temp Cracking Fatigue Cracking Rutting Construction [DTT] [RV] [DSR] [BBR] Pavement Age

43. Fatigue Cracking Specification - Maximum Stiffness @ T(inter) • G* sin  < 5000 kPa on PAV aged binder

44. RTFO - aging No aging PAV - aging Low Temp Cracking Fatigue Cracking Rutting Construction [DTT] [RV] [DSR] [BBR] Pavement Age

45. Superpave Binder SpecificationLow Temperature Characterization • The Bending Beam Rheometer (BBR) determines the Creep Stiffness (S) of an asphalt binder at low temperatures. • If a binder is too stiff at service temperatures, you can expect low temperature cracking.

46. Bending Beam Rheometer, BBR Deflection Transducer Air Bearing Fluid Bath Control and Data Acquisition Load Cell Asphalt Beam Loading Frame Supports Thermometer

48. Bending Beam Rheometer, BBR binder specimen in mold aluminum mold rubber O-rings 12.7 mm acetate strips 125 mm 6.35 mm