1. Optimal Timing of Preventive Maintenance for Addressing Environmental Aging in Hot-Mix Asphalt Pavement Pooled Fund Study TPF5-153 MnROAD 27 May 2010

2. Research Team Asphalt Institute –Mike Anderson, PI –Phil Blankenship, Senior Research Engineer AMEC –Doug Hanson, Researcher Consultant –Gayle King, Researcher

3. Research Objectives Primary Objective –to develop and validate technology that can be used by the Minnesota DOT (Mn/DOT) and other highway agencies to determine the proper timing of preventive maintenance in order to mitigate damage caused by asphalt aging. Help highway agencies to define a pavement preservation strategy which optimizes life-cycle cost while maintaining safety and serviceability for the driving public, with primary emphasis on countering the deleterious effects of asphalt aging

4. Expected Deliverables Expected deliverables: –Identification of an asphalt binder or mixture parameter related to durability as a result of environmental aging that can be determined from testing of pavement cores. –Specification limits (Warning and Action limits) for the durability parameter that indicate the need for preventive maintenance. –Guidelines for monitoring the durability parameter during the life of an asphalt pavement. –Economic evaluation of the cost effectiveness of applying surface treatments at various times in the life of an asphalt pavement. –Final Report describing the results of the research.

5. Research Tasks Tasks –Task 1 Information Gathering –Task 2 Selection of Pavement Test Sections –Task 3 Status Meeting –Task 4 Lab and Field Evaluation of MnROAD –Task 5 Field Evaluation –Task 6 Economic Evaluation –Task 7 Final Report

6. Proposed Project Timeline

7. Task 1 Information Review –Review mechanisms for environmental aging –Review binder properties that are affected by aging –Review test methods used to evaluate binder properties –Review modes of pavement distress caused by aging and surface treatments used to mitigate these distresses. –Review pavement preservation techniques US and international Determine current best-practice with regard to the timing of surface treatments Assess new technologies that could deserve accelerated deployment

8. Task 2 Selection of Pavement Test Sections –MnROAD Determine which sections have received surface treatments Determine what tests have already been performed Determine what retained materials are available for testing –Other pavement test sections

9. Task 3 Status Meeting –After completion of Tasks 1 and 2 –Draft interim report Findings to date

10. Task 4 Laboratory and Field Evaluation of MnROAD and Other Test Sections –Objective identify test methods that correctly rank distress determine critical binder or mixture failure limits that might be used as objective triggers for the various preservation strategies

11. Task 4 Laboratory and Field Evaluation of MnROAD and Other Test Sections Critical fracture parameters monitored throughout the life of the pavement –Appropriate remedial action can be taken as the critical limit is approached Simple tests to be used for field monitoring purposes –physical properties from simple tests correlated to crack predictions from DC(t) or other more sophisticated fracture tests.

12. AAPTP 06-01 Question As the Airport Manager… –What test do I run or what calculation can I do that will tell me when the pavement is expected to begin showing significant non- load related distress?

13. Concept 0246 Year Durability Parameter Critical Range Cracking Non-Cracking

14. Concept for Non-Load Related Distress Options –Use conventional construction data (e.g. binder properties, density, etc.) with climatic data together in an aging/cracking model to project time to remediation –Run mix test on cores at construction to get cracking property and fit data within aging/cracking model to project time to remediation

15. Concept for Non-Load Related Distress Options –Run binder test on sample recovered from cores at construction to get cracking property and fit data within aging/cracking model to project time to remediation –Run binder and/or mix test at construction to get cracking property and continue to pull cores from pavement at periodic intervals to check progression of cracking property

16. Task 4 Selected Test Sections –Inspected on a yearly basis for age-related damage MnROAD performance measures will be supplemented with careful monitoring to classify the types and origins of visible cracks –Cores 10 Between wheel path, closely spaced longitudinally

17. Task 4 Cores Gmm Recovered Binder Testing Mixture BBR Testing Mixture DC(t) Testing Extra

18. Task 4 Cores: Binder, Mix BBR Testing Layer A Layer B Layer C Layer D 50 mm

19. Task 4 Cores: Binder Testing Layer A –Extraction/Recovery Centrifuge extraction using toluene/ethanol Recovery using Rotavapor and AASHTO T319 –Lower temperature, higher vacuum –2 Cores (150-mm diameter x 12.5-mm thickness) ~50 grams asphalt –assuming Gmb=2.300 and asphalt content = 5.0%

20. Task 4 Cores: Binder Testing Layer A –DSR Frequency Sweep Three temperatures (5, 15, 25°C) using 8-mm plates –Possible different temperatures? Rheological mastercurves for modulus (G*) and phase angle ( δ ) –DSR at 45°C, 10 rad/s G′/(η′/G′)

21. Task 4 Cores: Binder Testing Layer A –BBR 2-3 temperatures Tc determined to the nearest 0.1°C for S(60) and m(60) Difference in Tc

22. Task 4 Cores: Binder Testing Layer A –DENT Double-edge notched tension Conducted at intermediate temperatures using modified ductility molds Proposed by Professor Simon Hesp Intended to examine ductile failure and provide an indication of the crack tip opening displacement and essential work of fracture

23. Task 4 Cores: Binder Testing Layer A –Linear Amplitude Sweep Conducted at intermediate temperatures using DSR Strain increases linearly until failure Proposed by Dr. Hussain Bahia Continuum damage approach to calculate fatigue resistance

24. Task 4 Cores: Mixture Testing Layer A –Mixture BBR Testing Conducted at 2 temperatures using BBR –Low binder grade temperature +10°C –Low binder grade temperature +22°C Work by Dr. Mihai Marasteanu

25. Task 4 Cores: Mixture Testing Top 50-mm of Core –Mixture DC(t) Testing Disk-shaped compact tension test Conducted at low binder grade temperature +10°C Work by Dr. Bill Buttlar Fracture energy –May be related to top-down cracking

26. Task 5 Field Evaluation –Evaluation of test sections in July each year –Cores obtained Tested using best procedure identified in Task 4 Time dependence of durability parameter

27. Task 6 Economic Evaluation –Time dependence of durability parameter –Recommended practice to evaluate durability –Recommended limits for preventative and corrective action

28. Task 7 Final Report –Report –Executive Summary (1-2 pages) –Technical Brief (4 pages) describe the durability parameter explain testing procedures needed to determine the durability parameter provide suggested specification limits indicating when pavement remediation is impending provide suggested monitoring guidelines for asphalt pavements to effectively capture the durability reduction as a function of time

29. Task 7 Final Report –Workshop Understand what the durability parameter is, how it is obtained, what the numbers mean, and how to know when to take action 4-8 hours Conducted as a webinar or on-demand video presentations?

30. Recent Research Findings AAPTP 06-01: Techniques for Prevention and Remediation of Non-Load Related Distresses on HMA Airport Pavements (Phase II) –Asphalt Binder Testing establish correlations between fracture and rheological properties as asphalt binders age in a mix or in the PAV

31. Recent Research Findings: AAPTP 06-01 Asphalt Binders –West Texas Sour (PG 64-16) –Gulf-Southeast (PG 64-22) –Western Canadian (PG 64-25)

32. Relationship between Ductility and DSR Parameter (Glover et.al., 2005)

33. DSR Fatigue Parameter (derived from Mastercurve)

34. Relationship between DSR Fatigue Parameter and Ductility

36. Mastercurve Procedure

37. Standard DSR

38. Gulf-Southeast: BBR

39. Effect of PAV Aging Time on  T c

40. Relationship between  T c and Ductility

41. Relationship between G′/(  ′/G′) and  T c

43. Black Space Diagram: Western Canadian Asphalt Binder

45. Rheological Index – R

46. Rheological Index SHRP Report A-369 –Rheological Index, R, is the difference between the glassy modulus and the complex shear modulus at the crossover frequency (where tan δ = 1).

47. Rheological Index SHRP Report A-369 –“…[R] is directly proportional to the width of the relaxation spectrum and indicates rheologic type. R is not a measure of temperature, but reflects the change in modulus with frequency or leading time and therefore is a measure of the shear rate dependency of asphalt cement. R is asphalt specific.”

48. Calculating R

49. Determination of R at Same Conditions as G′/(η′/G′)

50. Relationship between G′/(η′/G′) and R (15°C, 0.005 rad/s)

51. Field Core Data

52. Relationship between G′/(  ′/G′) and Δ T c (with Field Cores)

53. Witczak and Mirza: Global Aging Model (1995)

54. DC(t)

55. DC(t) Specimen (after testing)

56. DC(t) Data Output

57. DC(t) Fracture Energy

58. DC(t) Results

59. DC(t) What is It? –Fracture energy test for asphalt mixtures modeled after a fracture toughness test for metals Developed by researchers at the University of Illinois to evaluate the cracking performance of field cores and laboratory-compacted HMA samples. What Type of Specimen is Tested? –Cylindrical specimen with a single-edge notch –Usually 50-mm thick –Can be lab-produced or field core

60. DC(t) How Does the Test Work? –Specimen loaded on its side –A gauge is placed at the notch and the opening of the “crack mouth” is recorded as the specimen is loaded in tension. –The fracture energy is calculated using specimen dimensions and the area under the load-displacement curve. –Generally valid at temperatures of ~10° C (50° F) and lower.

61. DC(t) Why Use this Test? –Fracture test –Successfully used on several projects to describe the cracking resistance of asphalt concrete. –Believed to discriminate between polymer- modified asphalt mixtures more broadly than the indirect tensile strength test

62. Thanks!