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Cover of Use of Road-grade Recycled Plastics for Sustainable Asphalt Pavements: Final Performance and Environmental Assessment Part A
Use of Road-grade Recycled Plastics for Sustainable Asphalt Pavements: Final Performance and Environmental Assessment Part A
  • Publication no: AP-R669-22
  • ISBN: 978-1-922700-37-7
  • Published: 3 May 2022

This report is the third of a series of reports for project APT6305. The first report examined the use of road-grade recycled plastics in asphalt pavements and investigated the most suitable types of recycled plastics for incorporation into asphalt. The second report provided a comprehensive overview of the initial development of various testing frameworks for the characterisation of road-grade recycled plastic, the incorporation of recycled plastics in bitumen and asphalt via various methods, and the study of possible emissions and microplastics release.

This report details the full results obtained from the testing frameworks developed in the second report, including the physical, rheological and mechanical performance of recycled plastic-modified bitumen and asphalt, emissions and the release of microplastics. In addition, a testing framework has been developed for assessing the future recyclability of plastic-modified asphalt.

  • Summary
  • 1. Introduction
    • 1.1 Study Purpose
    • 1.2 Study Scope
    • 1.3 Methodology
  • 2. The Use of Recycled Plastic as a Bitumen Modifier (Wet Method)
    • 2.1 Recycled Plastic-Modified Bitumen (RPMB)
      • 2.1.1 Blending Procedure
      • 2.1.2 Testing Framework
    • 2.2 Sensitivity to Blending Time
    • 2.3 Sensitivity to the Bitumen Source
    • 2.4 Physical and Other Basic Properties of RPMBs
      • 2.4.1 Penetration
      • 2.4.2 Softening Point
      • 2.4.3 Torsional Recovery
      • 2.4.4 Elastic Recovery
      • 2.4.5 Dynamic Viscosity
      • 2.4.6 Storage Stability
      • 2.4.7 Summary of the Physical Properties
    • 2.5 Rheological Properties of RPMBs
      • 2.5.1 Stress Ratio Test
      • 2.5.2 Linear Amplitude Sweep Test
      • 2.5.3 Multiple Stress Creep and Recovery Test
      • 2.5.4 Consistency 6% at 60 C, DSR Test
      • 2.5.5 Summary of Rheological Properties
    • 2.6 Compatibilisers
    • 2.7 Performance-based Assessment Framework
  • 3. Recycled Plastics in Asphalt Through Binder Modification (Wet Method) and Aggregate Replacement (Dry Method)
    • 3.1 Recycled Plastic-Modified Asphalt
    • 3.2 Asphalt Mixing Procedure
    • 3.3 Mix Design
    • 3.4 Testing Framework
    • 3.5 Asphalt Compactability
      • 3.5.1 Wet Method
      • 3.5.2 Dry Method
      • 3.5.3 Comparisons and Discussion
    • 3.6 Stiffness and Asphalt Master Curves
      • 3.6.1 Wet Method
      • 3.6.2 Dry Method
      • 3.6.3 Comparisons and Discussion
    • 3.7 Cracking Resistance
      • 3.7.1 Fatigue Cracking – FPBB Test
      • 3.7.2 Cracking Tolerance – IDEAL CT Test
      • 3.7.3 Cracking Resistance – Comparisons and Discussion
    • 3.8 Rut Resistance – Hamburg Wheel-track Testing
      • 3.8.1 Wet Method
      • 3.8.2 Dry Method
      • 3.8.3 Comparison and Discussion
    • 3.9 Moisture Damage – Tensile Strength Ratio (TSR)
      • 3.9.1 Wet Method
      • 3.9.2 Dry Method
      • 3.9.3 Comparisons and Discussion
    • 3.10 Performance-based Assessment Framework
  • 4. Potential Emissions from Recycled Plastic-modified Binder and Asphalt Containing Recycled Plastics
    • 4.1 Development of Emissions Testing Framework
      • 4.1.1 Bitumen: Wet Method
      • 4.1.2 Asphalt: Dry and Wet Method
      • 4.1.3 Materials
      • 4.1.4 Testing Procedure and Sample Preparation
      • 4.1.5 Emission Measurement and Analytical Conditions
      • 4.1.6 Testing Variables
    • 4.2 Results and Discussion
      • 4.2.1 Method Validation and Sensitivity Analysis
      • 4.2.2 Bitumen: Wet Method Analysis
      • 4.2.3 Asphalt: Wet Method Analysis
      • 4.2.4 Asphalt: Dry Method Analysis
    • 4.3 Analysis of Specific Compounds
      • 4.3.1 Bitumen: Wet Method
      • 4.3.2 Asphalt: Wet Method
      • 4.3.3 Asphalt: Dry Method
    • 4.4 Effect of Plastics in Bitumen and Asphalt
      • 4.4.1 Solid Phase Microextraction of Recycled Plastics
      • 4.4.2 Thermogravimetric Analysis
      • 4.4.3 Sorption of PAHs and VOCs onto Plastics
    • 4.5 Summary of Experimental Results
    • 4.6 Emissions Testing Framework
      • 4.6.1 Summary of Objectives
      • 4.6.2 Optimised Parameters
      • 4.6.3 Conclusion
  • 5. Potential Release of Microplastics from Recycled Plastic-modified Asphalt
    • 5.1 Introduction
    • 5.2 Methodology
      • 5.2.1 Abrasion Procedure
      • 5.2.2 Extraction Procedure
      • 5.2.3 Procedure Validation
    • 5.3 Results and Discussion
      • 5.3.1 Wet Method (Plastic in Bitumen as a Modifier)
      • 5.3.2 Dry Method (Plastic as Aggregate Replacement) and Mixed Method (Plastic as Aggregate
      • 5.3.3 Optimised Testing Parameters
      • 5.3.4 Environmental Impact of Plastic-modified Asphalt
    • 5.4 Conclusions and Outlook
      • 5.4.1 Summary of Objectives
      • 5.4.2 Optimised Test Parameters
      • 5.4.3 Comparison of MPs Release – Key Findings
      • 5.4.4 Applicability of the Abrasion Test to Field Assessments
  • 6. Recyclability of Plastic-modified Asphalt
    • 6.1 Introduction
    • 6.2 Ageing of Asphalt Mixes: Field vs. Laboratory Ageing
    • 6.3 Methodology
      • 6.3.1 Production of P-RAP
      • 6.3.2 Validation
    • 6.4 Preliminary Results
  • 7. Overall Discussion, Conclusions and Future Developments
  • References
  • Appendix A Supplementary Figures
    • A.1 Emissions Analysis
      • A.1.1 Thermogravimetric Analysis (TGA) Results
      • A.1.2 Sorption Analysis
      • A.1.3 Analytes of Interest
    • A.2 Release of Microplastics
      • A.2.1 Abrasion Procedure Optimisation for Wet Method Specimens using 6 % RLDPE-modified Asphalt
      • A.2.2 Abrasion procedure optimisation for Dry Method Specimens using 0.5 % RABS-modified Asphalt
  • Appendix B Proposal for the Characterisation of Recycled Plastics to be Used in Bitumen and Asphalt Mixes
    • B.1 Plastic Selection Framework for Bitumen/asphalt Modification
  • Appendix C Proposal for the Performance-based Evaluation of Bitumen and Asphalt Incorporating Recycled Plastics
    • C.1 Microplastics Release Assessment
      • C.1.1 Recommendations on the Abrasion and Extraction Procedures
      • C.1.2 Benchmarking and Validation of New Plastic-modified Asphalt Products
    • C.2 Emissions Assessment
      • C.2.1 Recommendations on the Sampling and Extraction of Fumes
      • C.2.2 Benchmarking and Validation of New Recycled Plastic-modified Binder and Asphalt Products
    • C.3 Plastic-modified Asphalt Assessment
      • C.3.1 Assessment Framework for Moderate-to-heavily Trafficked Asphalt Pavements
      • C.3.2 Assessment Framework for Lightly Trafficked Asphalt Pavements and Local Roads
    • C.4 Plastic-modified Binder Assessment
      • C.4.1 New Zealand Scenario
      • C.4.2 Australian Scenario
      • C.4.3 Proposal for Performance-based Evaluation of Plastic-modified Binders
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