Sustainable Asphalt Mixes with High RAP Contents and Rejuvenating Agents: Laboratory Evaluation and Plant Validation

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Asphalt concrete is used in about 90 percent of the paved roads and highways in Canada. Materials costs are the most expensive part of asphalt mix production, comprising about 70 percent of the cost to produce Hot Mix Asphalt (HMA). A flexible pavement can be reclaimed at the end of its service life to reuse some of its valuable ingredients such as asphalt cement (AC) and mineral aggregates. Reclaimed Asphalt Pavement (RAP) is now one of the most recycled materials in the world. Therefore, reusing the aged asphalt cement (AC) in RAP can lower the need for virgin AC and also help with the economy of construction projects.In spite of the several environmental and economic benefits of re-using RAP in a new mix production, the nature of its oxidized AC limits its usage. Currently, use of RAP in surface mixes merely reaches 20 percent of the total mix. Maximizing the RAP usage requires further investigations to ensure that RAP incorporated mixes perform better than, or at least the same as, the conventional asphalt mix. To this end, rejuvenating the aged asphalt binder is a promising approach to restore the properties of an aged binder to a condition that resembles that of virgin binders. In this project, Imperial Oil is coming together with the University of Waterloo to produce sustainable asphalt concrete mixes by replacing up to 70% of their virgin ingredients with RAP. For this purpose, two rejuvenating oils will be identified that would be compatible with the domestic materials in Canada, ensuring that the new asphalt concrete mixes withstand the extreme climatic conditions and growing traffic loading in Canada. The outcome of this project will be a synthesis document that provides practical recommendations to the professionals of the Canadian asphalt industry for a better use of RAP to produce more economic, sustainable and environmentally friendly asphalt mixes. The increase of recycling rate by even 5% would lead to a reduction of the use of virgin aggregates by more than 600,000 tons annually. Therefore, the success of this research program would have a real significant positive impact on the economy and the environment of our country.