Investigation of Low and High Temperature Properties of Plant Produced Rap Mixtures

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FOREWORD

As asphalt prices fluctuate, reclaimed asphalt pavement (RAP) use mitigates variability in material costs, making RAP a valuable commodity for use in asphalt pavements. Understanding the performance of pavements containing high amounts of RAP (greater than 25 percent) is important to State highway agencies across the United States. The addition of high RAP typically stiffens an asphalt mixture, making fatigue and low-temperature performance properties a concern. This report documents a two-phase study that evaluated performance properties of high RAP mixtures. This study is unique because it evaluates plant-produced mixtures with high RAP contents (25 and 40 percent) and different binders (performance grade (PG) 64-22 and a softer PG58-28 binder). A control mixture with no RAP was also evaluated. Mixture volumetrics, binder performance grade, and performance tests, such as dynamic modulus, indirect tensile test, and fatigue, were performed to evaluate the behavior of different mixtures. In addition to insight on the performance of high RAP and plant-produced mixtures, this study provides information regarding RAP content limits, blending of virgin and RAP binders, and the extraction and recovery process. This report will be of interest to those involved in asphalt pavement mix design, as well as the design and construction of asphalt pavements.

Technical Report Documentation Page

SI* (Modern Metric) Conversion Factors

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380.
(Revised March 2003)

TABLE OF CONTENTS

INTRODUCTION

OBJECTIVES

BACKGROUND

• RATIONALE BEHIND CURRENT SPECIFICATIONS
• CURRENT ISSUES

RESEARCH APPROACH

• MIX DESIGN, PRODUCTION, AND SAMPLING
• LABORATORY TESTING PLAN, TEST PROCEDURES, AND DATA ANALYSIS
• COLLABORATIONS

TEST RESULTS AND DISCUSSION

• SUMMARY OF PHASE I RESULTS
• MIXTURE VOLUMETRICS
• BINDER TEST RESULTS
• |E*| TEST RESULTS
• Statistical Analysis
• Estimation of Blending
• IDT TEST RESULTS
• COMPARISON OF BINDER EXTRACTION/RECOVERY TECHNIQUES
• FHWA FATIGUE TESTING AND DATA ANALYSIS

OVERALL OBSERVATIONS AND CONCLUSIONS

APPENDIX A

• CONTRACTOR MIX DESIGNS AND/OR QC DATA

APPENDIX B

• BINDER CRITICAL TEMPERATURES

APPENDIX C

• ANALYSIS OF BLENDING

ACKNOWLEDGEMENTS

REFERENCES

LIST OF FIGURES

Figure 1. Graph. Number of gyrations to achieve 7 percent AV
Figure 2. Graph. Example master curves
Figure 3. Graph. Comparison of high critical temperatures (T_{c, DSR}) for binders recovered from plant mixtures
Figure 4. Graph. Comparison of low critical temperatures (T_{c, BBR}) for binders recovered from plant-produced mixtures (based on BBR m-value = 0.300)
Figure 5. Graph. Mix modulus of PG64-22 mixes from contractor 1
Figure 6. Graph. Mix modulus of control and PG58-28 mixes from contractor 1
Figure 7. Graph. Comparison of mix moduli of PG64-22 and PG58-28 from contractor 1
Figure 8. Graph. Mix modulus of PG64-22 mixes from contractor 2
Figure 9. Graph. Mix modulus of control and PG58-28 mixes from contractor 2
Figure 10. Graph. Comparison of mix moduli of PG64-22 and PG58-28 from contractor 2
Figure 11. Graph. Mix modulus of PG64-22 mixes from contractor 3
Figure 12. Graph. Mix modulus of control and PG58-28 mixes from contractor 3
Figure 13. Graph. Comparison of mix moduli of PG64-22 and PG58-28 from contractor 3
Figure 14. Graph. Mix modulus of PG64-22 mixes from contractor 4
Figure 15. Graph. Mix modulus of control and PG58-28 mixes from contractor 4
Figure 16. Graph. Comparison of mix moduli of PG64-22 and PG58-28 from contractor 4
Figure 17. Graph. Mix modulus of PG64-22 mixes from contractor 5
Figure 18. Graph. Mix modulus of control and PG58-28 mixes from contractor 5
Figure 19. Graph. Comparison of mix moduli of PG64-22 and PG58-28 from contractor 5
Figure 20. Graph. Example of thorough blending (mix 5B)
Figure 21. Graph. Example of poor blending (mix 4D)
Figure 22. Graph. IDT stiffness and pavement cracking temperature for contractor 1
Figure 23. Graph. IDT strength and pavement cracking temperature for contractor 1
Figure 24. Graph. IDT stiffness and pavement cracking temperature for contractor 2
Figure 25. Graph. IDT strength and pavement cracking temperature for contractor 2
Figure 26. Graph. IDT stiffness and pavement cracking temperature for contractor 3
Figure 27. Graph. IDT strength and pavement cracking temperature for contractor 3
Figure 28. Graph. IDT stiffness and pavement cracking temperature for contractor 4
Figure 29. Graph. IDT strength and pavement cracking temperature for contractor 4
Figure 30. Graph. IDT stiffness and pavement cracking temperature for contractor 5
Figure 31. Graph. IDT strength and pavement cracking temperature for contractor 5
Figure 32. Graph. Comparison of binder recovered using different solvents for mix A
Figure 33. Graph. Comparison of binder recovered using different solvents for mix B
Figure 34. Graph. Comparison of binder recovered using different solvents for mix C
Figure 35. Graph. Comparison of binder recovered using different solvents for mix D
Figure 36. Graph. Comparison of binder recovered using different solvents for mix E
Figure 37. Graph. Comparison of binder recovered using different solvents for mix F
Figure 38. Graph. Comparison of binders recovered using different procedures and same solvent for mix A
Figure 39. Graph. Comparison of binders recovered using different procedures and same solvent for mix B
Figure 40. Graph. Comparison of binders recovered using different procedures and same solvent for mix C
Figure 41. Graph. Comparison of binders recovered using different procedures and same solvent for mix D
Figure 42. Graph. Comparison of binders recovered using different procedures and same solvent for mix E
Figure 43. Graph. Comparison of binders recovered using different procedures and same solvent for mix F
Figure 44. Graph. Fatigue life for mixtures at 69.8 ºF (21 ºC) and 400µε
Figure 45. Graph. DSR critical temperatures—mixes with PG64-22 binder
Figure 46. Graph. DSR critical temperatures—mixes with PG58-28 binder
Figure 47. Graph. DSR critical temperatures—mixes with 25 and 40 percent RAP
Figure 48. Graph. BBR critical temperatures—mixes with PG64-22 binder
Figure 49. Graph. BBR critical temperatures—mixes with PG58-28 binder
Figure 50. Graph. BBR critical temperature—mixes with 25 and 40 percent RAP
Figure 51. Graph. TSAR™ critical temperature—mixes with PG64-22 binder
Figure 52. Graph. TSAR™ critical temperature—mixes with PG58-28 binder
Figure 53. Graph. TSAR™ critical temperature—mixes with 25 and 40 percent RAP
Figure 54. Graph. Contractor 2 evaluation of blending from master curves: mix A
Figure 55. Graph. Contractor 2 evaluation of blending from master curves: mix B
Figure 56. Graph. Contractor 2 evaluation of blending from master curves: mix C
Figure 57. Graph. Contractor 2 evaluation of blending from master curves: mix D
Figure 58. Graph. Contractor 2 evaluation of blending from master curves: mix E
Figure 59. Graph. Contractor 2 evaluation of blending from master curves: mix F
Figure 60. Graph. Contractor 3 evaluation of blending from master curves: mix A
Figure 61. Graph. Contractor 3 evaluation of blending from master curves: mix B
Figure 62. Graph. Contractor 3 evaluation of blending from master curves: mix C
Figure 63. Graph. Contractor 3 evaluation of blending from master curves: mix D
Figure 64. Graph. Contractor 3 evaluation of blending from master curves: mix E
Figure 65. Graph. Contractor 3 evaluation of blending from master curves: mix F
Figure 66. Graph. Contractor 4 evaluation of blending from master curves: mix A
Figure 67. Graph. Contractor 4 evaluation of blending from master curves: mix B
Figure 68. Graph. Contractor 4 evaluation of blending from master curves: mix C
Figure 69. Graph. Contractor 4 evaluation of blending from master curves: mix D
Figure 70. Graph. Contractor 4 evaluation of blending from master curves: mix E
Figure 71. Graph. Contractor 4 evaluation of blending from master curves: mix F
Figure 72. Graph. Contractor 5 evaluation of blending from master curves: mix A
Figure 73. Graph. Contractor 5 evaluation of blending from master curves: mix B
Figure 74. Graph. Contractor 5 evaluation of blending from master curves: mix C
Figure 75. Graph. Contractor 5 evaluation of blending from master curves: mix D
Figure 76. Graph. Contractor 5 evaluation of blending from master curves: mix E
Figure 77. Graph. Contractor 5 evaluation of blending from master curves: mix F

LIST OF TABLES

Table 1. Experimental design for each plant showing mix designations
Table 2. Participating contractors and plant details
Table 3. Mixture volumetrics for contractor 2
Table 4. Mixture volumetrics for contractor 3
Table 5. Mixture volumetrics for contractor 4
Table 6. Mixture volumetrics for contractor 5
Table 7. Comparison of measured and design binder contents
Table 8. Virgin and recovered binder properties for contractor 2
Table 9. Virgin and recovered binder properties for contractor 3
Table 10. Virgin and recovered binder properties for contractor 4
Table 11. Virgin and recovered binder properties for contractor 5
Table 11. Table 12. Statistical analysis of moduli at 25 Hz from contractor 1
Table 12. Table 13. Statistical analysis of moduli at 25 Hz from contractor 2
Table 13. Table 14. Statistical analysis of moduli at 25 Hz from contractor 4
Table 14. Table 15. Statistical analysis of moduli at 25 Hz from contractor 5
Table 15. Table 16. IDT results for contractor 1
Table 16. Table 17. IDT results for contractor 2
Table 17. Table 18. IDT results for contractor 3
Table 18. Table 19. IDT results for contractor 4
Table 19. Table 20. IDT results for contractor 5
Table 20. Table 21. Change in T_crit (ºC) with the addition of RAP
Table 21. Table 22. |E*| and phase angle data for PG 58-28 mixtures
Table 22. Table 23. |E*| and phase angle data for PG64-22 mixtures
Table 23. Table 24. Overall summary of fatigue life
Table 24. Table 25. Contractor 1 mix designs
Table 25. Table 26. Contractor 2 job mix formula (JMF) and QC test results
Table 26. Table 27. Contractor 3 QC test results
Table 27. Table 28. Contractor 4 mix designs
Table 28. Table 29. Contractors mix designs and QC results

AMENDED 1/10/2012

INTRODUCTION

Asphalt prices, supply issues, and growing interest in sustainable construction practices are leading to increased use of reclaimed asphalt pavement (RAP) in greater amounts and in more types of mixes. However, when using more than 15–20 percent RAP under most current specifications (State and national), contractors must change the virgin binder grade added to the mix. This frequently means using a less commonly available binder, which may be more expensive.

This report provides an analysis of the results of testing plant-produced hot mix asphalt (HMA) containing various levels of RAP and different grades of virgin binder. The study was initially undertaken to examine the effects of RAP on low-temperature properties of mixtures. In phase I of the study, mixes produced by one contractor in 2006 were tested. The results suggested that the addition of RAP stiffened the mix, but not to the extent expected based on linear blending.⁽¹⁾ There is evidence from other research that suggests that there are cases where linear blending does not apply.⁽²⁾ Consequently, in phase II of the project, four more contractors replicated the experiment in hot mix plants.⁽³⁾ The objectives of the current study were expanded to include an evaluation of the extent of blending of the RAP and virgin binders in plant-produced mixtures.

OBJECTIVES

The goal of this project was to improve the understanding of the performance characteristics of HMA mixtures with RAP at high, intermediate, and low temperatures and to provide knowledge regarding plant-produced HMA mixtures with RAP.

The specific objectives of this project were as follows:

• Validate the results from phase I of this project.
• Assess the current guidelines for RAP usage by determining the low- and high-temperature properties of plant-produced HMA with varying RAP contents and virgin binder grades.
• Further investigate the amount of blending that occurs between the RAP binder and virgin binder during plant production.