The Use of Phosphoric Acid to Stiffen Hot Mix Asphalt Binders

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FOREWORD

The Use of Phosphoric Acid to Stiffen Hot Mix Asphalt Binders provides guidelines for the use of the different commercially available grades of phosphoric acid to enhance the high temperature performance grade of asphalt binders derived from different crude oil sources for use in hot mix paving applications. The expected effect on pavement life, in terms of oxidative aging, moisture resistance, fatigue, rutting, and use with different types of aggregates are presented. Analytical procedures for detecting the presence of phosphoric acid using X-ray fluorescence spectroscopy as well as a simple rapid test method are included. 

The guidelines presented in this report will be useful to producers of asphalt binders, hot mix paving contractors, State departments of transportation, and local highway agencies.

Jorge E. Pagán-Ortiz
Director, Office of Infrastructure
Research and Development

Technical Report Documentation Page

SI* (Modern Metric) Conversion Factors

TABLE OF CONTENTS

• CHAPTER 1. INTRODUCTION
  • BACKGROUND
  • SOME PHOSPHORIC ACID CHEMISTRY
  • HOW PHOSPHORIC ACID IS USED TO MODIFY ASPHALT BINDERS
  • RESEARCH PLAN
    • Analysis
    • Effect of Acid Grade and Binder Types
    • Aging.
    • Reaction With Lime and Limestone Aggregates
    • Moisture
• CHAPTER 2. ANALYTICAL METHODS
  • QUANTITATIVE ANALYSIS OF ASPHALT BINDERS FOR PHOSPHORIC ACID
  • A SIMPLE QUALITATIVE TEST TO DETECT THE PRESENCE OF
    PHOSPHORIC ACID IN ASPHALT BINDERS
    • Reagents
    • Procedure
  • SATURATE, AROMATIC, RESIN, AND ASPHALTENE ANALYSIS OF
    ASPHALT BINDERS MODIFIED WITH PHOSPHORIC ACID
    • Findings
  • HOW DOES THE PHOSPHORIC ACID REACT WITH THE BINDER?
  • MAJOR CONCLUSIONS FROM CHAPTER 2, ANALYTICAL METHODS
• CHAPTER 3. EFFECT OF ACID GRADE AND BINDER TYPE
  • EFFECT OF ASPHALT TYPE
  • EFFECT OF PHOSPHORIC ACID GRADE
  • EFFECT OF TANK AGING AT 165 °C
  • CONCLUSIONS
• CHAPTER 4. AGING
  • DOES PHOSPHORIC ACID CATALYZE ASPHALT OXIDATION IN HOT MIX
    ASPHALT BINDERS?
  • CONCLUSIONS
• CHAPTER 5. LIME AND LIMESTONE AGGREGATES
  • LIME
  • LIMESTONE
  • CONCLUSIONS
• CHAPTER 6. MOISTURE
  • EFFECT OF WATER ON ASPHALT MASTICS WITH AND WITHOUT
    PHOSPHORIC ACID
    • Conclusions
  • EFFECT OF WATER ON NEAT ASPHALT BINDERS
    • Conclusions
  • EFFECT OF PHOSPHORIC ACID MODIFICATION IN THE USE OF
    ANTISTRIP ADDITIVES
    • Conclusions
• CHAPTER 7. SUMMARY OF CONCLUSIONS
• APPENDIX
  • IATROSCAN® TEST METHOD FOR SARA ANALYSIS OF ASPHALT
    BINDERS
    • Apparatus
    • Asphaltene/Material Separation
    • Iatroscan® TH-10 Procedure
    • Report
  • EFFECT OF OVEN AGING 12 DAYS AT 165 °C ON ASPHALT STIFFNESS
  • DOES PHOSPHORIC ACID CAUSE OXIDATION IN ASPHALT BINDERS?
• REFERENCES
• ADDITIONAL READING

LIST OF FIGURES

• Figure 1. Photo. XRF cup (inverted) with plastic membrane.
• Figure 2. Photo. XRF cup (inverted) filled with asphalt.
• Figure 3. Photo. Steel XRF cup holder.
• Figure 4. Photo. Interior of XRF spectrometer.
• Figure 5. Chart. XRF spectrum of asphalt AAB-1 modified with 1 percent of 105-percent phosphoric acid.
• Figure 6. Chart. XRF spectrum of asphalt AAB-1.
• Figure 7. Chart. XRF Calibration chart for phosphoric acid.
• Figure 8. Chart. Plot of XRF signal of SHRP reference asphalts modified with superphosphoric acid content.
• Figure 9. Chart. X-ray fluorescence of SHRP reference asphalts modified with superphosphoric acid corrected for baseline fluorescence.
• Figure 10. Chart. Accuracy of PPA analysis using XRF.
• Figure 11. Photo. Phosphoric acid detected by the blue color developed in the Susan P. Needham test.
• Figure 12. Chart. Results of SARA fractionation of AAD-1 and AAD-1 modified with 1 percent of 105-percent phosphoric acid or 0.75-percent phosphorus pentoxide.
• Figure 13. Chart. Results of SARA fractionation of asphalt AAK-1 modified with 1 percent of 105‑percent phosphoric acid or 0.75-percent phosphorus pentoxide.
• Figure 14. Chart. Results of SARA fractionation of asphalt AAM-1 modified with 1 percent of 115‑percent phosphoric acid , 1 percent of 105-percent phosphoric acid, or 0.75-percent phosphorus pentoxide.
• Figure 15. Chart. Results of SARA fractionation of asphalt ABM-1 modified with 1 percent of 115‑percent phosphoric acid or 0.75-percent phosphorus pentoxide.
• Figure 16. Chart. Results of SARA separation of asphalt AAD-1 modified with 115-percent phosphoric acid.
• Figure 17. Chart. Results of SARA separation of asphalt AAK-1 modified with 115-percent phosphoric acid.
• Figure 18. Chart. Results SARA separation of asphalt AAM-1 modified with 115-percent phosphoric acid .
• Figure 19. Chart. Results of SARA separation of asphalt ABM-1 modified with 115-percent phosphoric acid.
• Figure 20. Chart. Results of SARA separation of B6317 Venezuelan asphalt modified with 115‑percent phosphoric acid.
• Figure 21. Chart. NMR spectrum of heptane-insoluble fraction of phosphoric acid-modified asphalt.
• Figure 22. Chart. NMR spectrum of heptane soluble fraction of phosphoric acid-modified asphalt.
• Figure 23. Chart. Initial stiffness of SHRP reference binders modified with 115-percent phosphoric acid.
• Figure 24. Chart. Effect of phosphoric acid grade on the stiffness of asphalt AAD-1.
• Figure 25. Chart. Effect of phosphoric acid grade on the stiffness of asphalt AAK-1.
• Figure 26. Chart. Effect of phosphoric acid grade on the stiffness of asphalt AAM-1.
• Figure 27. Chart. Effect of phosphoric acid grade on the stiffness of asphalt ABM-1.
• Figure 28. Chart. Simulated tank aging of binders modified with 1 percent of 105-percent phosphoric acid.
• Figure 29. Chart. PAV aging of asphalt AAD-1 modified with 1-percent phosphoric acid at 100 °C under air.
• Figure 30. Chart. PAV aging of asphalt AAK-1 modified with 1-percent phosphoric acid at 100 °C under air.
• Figure 31. Chart. PAV aging of asphalt AAM-1 modified with 1-percent phosphoric acid at 100 °C under air.
• Figure 32. Chart. PAV aging of asphalt ABM-1 modified with 1-percent phosphoric acid at 100 °C under air.
• Figure 33. Chart. PAV aging of asphalt AAD-1 modified with 1-percent phosphoric acid at 100 °C under nitrogen.
• Figure 34. Chart. PAV aging of asphalt AAK-1 modified with 1-percent phosphoric acid at 100 °C under nitrogen.
• Figure 35. Chart. PAV aging of asphalt AAM-1 modified with 1-percent phosphoric acid at 100 °C under nitrogen.
• Figure 36. Chart. PAV aging of asphalt ABM-1 modified with 1-percent phosphoric acid at 100 °C under nitrogen.
• Figure 37. Chart. Performance grades of binders after treatment with lime.
• Figure 38. Chart. Effect of lime content on asphalt stiffness.
• Figure 39. Chart. Flow number for the mixture modified with binder from Lion Oil.
• Figure 40. Chart. Flow number for the mixture modified with binder from HollyFrontier® asphalt.
• Figure 41. Chart. PGs of phosphoric acid-modified binders recovered from limestone mixes.
• Figure 42. Chart. Plot of moisture absorption of Citgo® 50-percent asphalt/sand mastic modified with 115-percent phosphoric acid.
• Figure 43. Chart. Plot of moisture absorption of Citgo® 50-percent asphalt/diabase mastic modified with 115-percent phosphoric acid.
• Figure 44. Chart. Moisture absorption of Venezuelan 50-percent asphalt/gravel mastic modified with 115-percent phosphoric acid.
• Figure 45. Chart. Moisture absorption of Citgo® 50-percent asphalt/montmorillonite mastic modified with 115-percent phosphoric acid.
• Figure 46. Chart. Fifty-percent montmorillonite asphalt binder mastic after water immersion for 105 days.
• Figure 47. Chart. Plot of water absorption of Venezuelan asphalt beams modified with 115‑percent phosphoric acid.
• Figure 48. Chart. Plot of stiffness of phosphoric acid modified Citgo® asphalt after 245 days of water immersion.
• Figure 49. Chart. Plot of phosphate extracted from Lion Oil binder diabase aggregate gyratory specimen.
• Figure 50. Chart. Plot of phosphate extracted from BP Whiting binder diabase aggregate gyratory specimen.
• Figure 51. Chart. Plot of phosphate extracted from Lion Oil binder granite aggregate gyratory specimen.
• Figure 52. Chart. Plot of phosphate extracted from BP Whiting binder granite aggregate gyratory specimen.
• Figure 53. Chart. Plot of phosphate extracted from Lion Oil binder diabase aggregate loose mix.
• Figure 54. Chart. Plot of phosphate extracted from BP Whiting binder diabase aggregate loose mix.
• Figure 55. Chart. Hamburg rut test of Citgo® asphalt sandstone aggregate.
• Figure 56. Chart. Hamburg rut test of Citgo® asphalt limestone aggregate.
• Figure 57. Chart. Hamburg rut test of Citgo® asphalt granite aggregate.
• Figure 58. Chart. Hamburg rut test of Citgo® asphalt lime-treated sandstone aggregate.
• Figure 59. Chart. Hamburg rut test of Citgo® asphalt lime-treated limestone aggregate.
• Figure 60. Chart. Hamburg rut test of Citgo® asphalt lime-treated granite aggregate.
• Figure 61. Chart. Hamburg rut test of Citgo® asphalt AD-HERE® LA-2 antistrip-treated sandstone aggregate.
• Figure 62. Chart. Hamburg rut test of Citgo® asphalt AD-HERE® LA-2 antistrip-treated limestone aggregate.
• Figure 63. Chart. Hamburg rut test of Citgo® asphalt AD-HERE® LA-2 antistrip-treated granite aggregate.
• Figure 64. Chart. Hamburg rut test of Citgo® asphalt AD-HERE® LOF 65-00 antistrip-treated sandstone aggregate.
• Figure 65. Chart. Hamburg rut test of Citgo® asphalt AD-HERE® LOF 65-00 antistrip-treated limestone aggregate.
• Figure 66. Chart. Hamburg rut test of Citgo® asphalt AD-HERE® LOF 65-00 antistrip-treated granite aggregate.
• Figure 67. Chart. Hamburg rut test of Citgo® asphalt Innovalt®-W antistrip-treated sandstone aggregate.
• Figure 68. Chart. Hamburg rut test of Citgo® asphalt Innovalt®-W antistrip-treated limestone aggregate.
• Figure 69. Chart. Hamburg rut test of Citgo® asphalt Innovalt®-W antistrip-treated granite aggregate.
• Figure 70. Equation. Calculation of maltene concentration
• Figure 71. Equation. Calculation of n-heptane filtrate

LIST OF TABLES

• Table 1. History of State regulations on the use of phosphoric acid to modify asphalt.
• Table 2. Materials used in the study.
• Table 3. Properties of the SHRP asphalt binders.
• Table 4. Commercial grades of phosphoric acid used.
• Table 5. Stiffness (|G*|/Sinδ) of simulated tank-aged binders modified with 105-percent phosphoric acid.
• Table 6. Stiffness sensitivity of reference binders to PPA modification.
• Table 7. Limestone mix designs.
• Table 8. Phosphorus in recovered asphalt binders.
• Table 9. High temperature PGs of phosphoric acid-modified binders recovered from limestone mixes.
• Table 10. Percentage of the added phosphoric acid extracted after 245 days of immersion in water.
• Table 11. Summary of Hamburg rut testing results with antistrip additives.
• Table 12. Change in stiffness of asphalt AAD-1 with phosphoric acid modification immediately after mixing and after 24 h at 165 °C.
• Table 13. Change in stiffness of asphalt AAM-1 with phosphoric acid modification immediately after mixing and after 24 h at 165 °C.
• Table 14. Change in stiffness of asphalt AAK-1 with phosphoric acid modification immediately after mixing and after 24 h at 165 °C.
• Table 15. Change in stiffness of asphalt ABM-1 with phosphoric acid modification immediately after mixing and after 24 hours at 165 °C.
• Table 16. Oven aging at 165 °C asphalt AAD-1 modified with 115-percent phosphoric acid .
• Table 17. Oven aging at 165 °C asphalt AAD-1 modified with 105-percent phosphoric acid.
• Table 18. Oven aging at 165 °C asphalt AAD-1 modified with 85-percent phosphoric acid.
• Table 19. Oven aging at 165 °C asphalt AAD-1 modified with 75-percent phosphoric acid.
• Table 20. Oven aging at 165 °C asphalt AAD-1 modified with 50-percent "green" phosphoric acid.
• Table 21. Oven aging at 165 °C asphalt AAK-1 modified with 115-percent phosphoric acid .
• Table 22. Oven aging at 165 °C asphalt AAK-1 modified with 105-percent phosphoric acid.
• Table 23. Oven aging at 165 °C asphalt AAK-1 modified with 85-percent phosphoric acid.
• Table 24. Oven aging at 165 °C asphalt AAK-1 modified with 75-percent phosphoric acid.
• Table 25. Oven aging at 165 °C asphalt AAK-1 modified with 50-percent "green" phosphoric acid.
• Table 26. Oven aging at 165 °C asphalt AAM-1 modified with 115-percent phosphoric acid
• Table 27. Oven aging at 165 °C asphalt AAM-1 modified with 105-percent phosphoric acid.
• Table 28. Oven aging at 165 °C asphalt AAM-1 modified with 85-percent phosphoric acid.
• Table 29. Oven aging at 165 °C asphalt AAM-1 modified with 75-percent phosphoric acid.
• Table 30. Oven aging at 165 °C asphalt AAM-1 modified with 50-percent "green" phosphoric acid.
• Table 31. Oven aging at 165 °C asphalt ABM-1 modified with 115-percent phosphoric acid
• Table 32. Oven aging at 165 °C asphalt ABM-1 modified with 105-percent phosphoric acid.
• Table 33. Oven aging at 165 °C asphalt ABM-1 modified with 85-percent phosphoric acid.
• Table 34. Oven aging at 165 °C asphalt ABM-1 modified with 75-percent phosphoric acid.
• Table 35. Oven aging at 165 °C asphalt ABM-1 modified with 50-percent "green" phosphoric acid.
• Table 36. PAV aging asphalt ABM-1 under air pressure at 100 °C.
• Table 37. PAV aging asphalt AAD-1 under air pressure at 100 °C.
• Table 38. PAV aging asphalt AAK-1 under air pressure at 100 °C.
• Table 39. PAV aging asphalt AAM-1 under air pressure at 100 °C.
• Table 40. PAV aging asphalt ABM-1 under nitrogen pressure at 100 °C.
• Table 41. PAV aging asphalt AAD-1 under nitrogen pressure at 100 °C.
• Table 42. PAV aging asphalt AAK-1 under nitrogen pressure at 100 °C.
• Table 43. PAV aging asphalt AAM-1 under nitrogen pressure at 100 °C.

LIST OF ACRONYMS AND ABBREVIATIONS