Feasibility of Using Anti-stripping Additives as an Alternative to Hydrated Lime

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. This report can be downloaded from the Austroads web site at https://austroads.com.au/publications/pavement/ap-r708-24