Pavement
- Publication no: AP-R708-24
- ISBN: 978-1-922994-27-1
- Published: 3 April 2024
- PDF (free) Download
Hydrated lime is widely used in Australia to reduce the moisture susceptibility of asphalt mixes in service. However, the local asphalt industry is concerned about the sustainability of the continued use of hydrated lime in asphalt.
This report presents the findings of a desktop review of the potential use of alternative liquid anti‑stripping agents. A literature review was undertaken to understand the key factors affecting the moisture susceptibility of asphalt mixes, identify commonly used moisture susceptibility test methods and document advantages and disadvantages of using hydrated lime and liquid anti‑stripping agents. The literature review found that both hydrated lime and liquid anti-stripping agents can be effective in reducing the risk of asphalt stripping; however, the effectiveness of these additives depends on the specific aggregate–binder combination being considered. There are several test methods available to assess the moisture susceptibility of asphalt mixes containing anti-stripping additives. It is, however, evident though in the literature reviewed that all these tests have limitations and there is not currently consensus regarding the most appropriate test method to use. Therefore, an interim moisture susceptibility testing protocol comprising of multiple tests has been developed to assess the effectiveness of different anti-stripping additives in the laboratory.
Stakeholder engagement was also undertaken to determine current practices in Australia and New Zealand for managing the risk of moisture damage in asphalt pavements.
- Summary
- 1. Introduction
- 1.1 Purpose
- 1.2 Scope
- 1.3 Methodology
- 2. Moisture Damage in Asphalt Layers
- 2.1 Background
- 2.2 Failure Mechanism
- 2.3 Factors Affecting Asphalt Stripping
- 2.3.1 Pavement Design and Road Drainage
- 2.3.2 Asphalt Mix Properties
- 2.3.3 Asphalt Manufacturing and Construction
- 2.3.4 Environmental and Traffic Conditions
- 2.4 Summary of Findings
- 3. Moisture Susceptibility Test Methods
- 3.1 Assessment of Loose Asphalt Samples
- 3.2 Assessment of Compacted Asphalt Specimens
- 3.2.1 Specimen Conditioning
- 3.2.2 Indirect Tensile Strength Tests
- 3.2.3 Compression Tests
- 3.2.4 Wheel Tracking Tests
- 3.3 Other Moisture Susceptibility Assessment Methods
- 3.4 Critical Review of Moisture Susceptibility Test Methods
- 3.4.1 Specimen Conditioning Procedures
- 3.4.2 Aggregate–Binder Adhesion Tests
- 3.4.3 Asphalt Stripping Tests
- 3.5 Summary of Findings
- 4. Asphalt Anti-stripping Additives
- 4.1 Background
- 4.2 Hydrated Lime
- 4.2.1 Effectiveness of Hydrated Lime to Reduce the Moisture Susceptibility of Asphalt
- 4.2.2 Secondary Effects of Hydrated Lime in Asphalt
- 4.2.3 Safety, Environmental and Construction Considerations when Using Hydrated Lime
- 4.2.4 Current Usage of Hydrated Lime as an Anti-stripping Additive in Asphalt
- 4.3 Liquid Anti-stripping Agents
- 4.3.1 Effectiveness of LAAs to Reduce the Moisture Susceptibility of Asphalt
- 4.3.2 Secondary Effects of LAAs in Asphalt
- 4.3.3 Safety, Environmental and Construction Considerations when Using LAAs
- 4.3.4 Current Usage of LAAs in Asphalt
- 4.4 Other Anti-stripping Additives in Asphalt
- 4.5 Summary of Findings
- 5. Stakeholder Engagement
- 5.1 Survey Responses
- 5.2 Summary of Stakeholder Engagement Findings
- 6. Interim Laboratory Assessment Protocol
- 6.1 Available Assessment Protocols
- 6.1.1 Australia and New Zealand
- 6.1.2 International
- 6.2 Interim Assessment Protocol
- 6.2.1 Standard Material and Asphalt Mix Characterisation Testing
- 6.2.2 Asphalt Performance Testing
- 6.2.3 Laboratory Assessment Protocol
- 6.1 Available Assessment Protocols
- 7. Conclusions and Recommendations
- 7.1 Conclusions
- 7.2 Recommendations
- References
- Appendix A Stakeholder Questionnaire