Novel Asphalt Cement Test Methods and Compositions for Improved Flexible Pavement Performance

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A primary research objective will be to develop simplified performance grading tests and acceptance criteria for asphalt allowing user agencies to better control pavement cracking. A secondary objective is to use these tests and criteria to design better modified asphalt for Canadian industry. Our work will focus on ways to shorten the time it takes to obtain data on how asphalt cements gradually harden during cold conditioning, addressing a concern that current tests take too long. Empirical and fundamental models will be used to predict long-term properties from short-term tests. A secondary objective will be to investigate improved asphalt compositions. The use of polymers to increase the temperature range over which an asphalt cement meets minimum performance requirements is well established. The most commonly used are block copolymers made with styrene and butadiene. However, polymers that contain a diene functional group in their backbone suffer from rapid oxidative degradation in service and a consequent loss in desirable properties. Hence, we will investigate how polymers with less diene functionality (high vinyl grades) or no diene (styrene-butyl acrylate copolymers) can be utilized. It is hypothesized that such materials outperform those currently available in the industry because of their significantly higher resistance to polymer chain cleavage. Finally, we will investigate how the base asphalt's oxidative stability can be improved. It is expected that oil sand bitumen can provide significantly enhanced starting materials for asphalt formulation. Oil sand bitumen derived asphalt cements are relatively low in readily oxidized, polar molecules, and hence should suffer little from gradual, reversible hardening at cold temperatures, or irreversible hardening through reaction with oxygen. However, there are currently no publications on this topic. Improved specification tests and asphalt compositions will be developed through both basic and applied interdisciplinary research. Both undergraduate and graduate students will be trained in important areas including rheology, failure mechanics, materials science and engineering, polymers, thermal analysis, etc. The research will lead to significant benefits for Canada's roads and knowledge base.