Mechanistic Studies of Asphalt Aging Aimed at the Discovery of Anti-aging Additives

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Asphalt pavements constructed for municipal, provincial and national agencies today rarely last as long as they did 25 years ago. Some regions have seen lifespans shrink by as much as 50-60% (Annual Report, Auditor General of Ontario, 2016), largely due to poor practices and materials. The decline is due to heavier traffic, anomalous weather (extreme summer/winter temperatures), lack of knowledge among agency staff leading to the use of inadequate specifications, and the “greening” of our roads through the incorrect and/or irresponsible use of certain recycled materials. Across Canada, ~$120 billion-worth of roads are in fair, poor or very poor state (Canadian Infrastructure Report Card, 2016).******Since 2004, my group has developed rigorous specification standards and implemented them to great effect in numerous user agencies in Ontario and abroad. We now need to investigate how to mitigate aging with effective additives to further reduce cracking.******Our short-term objective is to understand how to better assess thermoreversible aging by monitoring the precipitation of waxes, resins and asphaltenes in asphalt at ambient and cold temperatures. In a first for this sector, we will use innovative infrared spectroscopy methods developed to monitor wax and asphaltene precipitation in crude oils to measure wax and asphaltene precipitation in asphalt. ******We will study gel formation by measuring properties for asphalt that has been chemically aged to varying degrees with sophisticated rheological methods. Factors defining the onset of gelation will provide a more accurate measure of when asphalt becomes prone to cracking than those currently used for specification grading.******We will also study irreversible aging to add evidence to longstanding disputes in the literature on how asphalts react with oxygen and harden over time. We will use oxygen-17 nuclear magnetic resonance spectroscopy, again for the first time in this sector, together with more conventional proton, carbon-13 and silicon-29 spectroscopy, in both one and two dimensions. We will use isotope enriched protective groups where feasible. ******As a long-term goal, we will evaluate the use of wax inhibitors, dispersants, antioxidants and unconventional base asphalts to mitigate aging, and use the spectroscopic, thermal and rheological analysis techniques to assess the effectiveness of our innovative anti-aging additives.******This research program will reduce cracking distress in pavements and provide a more sustainable, durable road infrastructure. Federal, provincial and municipal governments, as well as the general public in Canada and abroad, will achieve enormous savings on future infrastructure expenditures, reduce travel delays and improve road safety. The embedded training program will give students a highly desirable set of transferable skills and sought-after knowledge that will give them a competitive edge in the work force.**