A case study on developing asphalt mix performance grading (Mix-PG) system in Ontario

Abstract Road infrastructure plays a crucial role in facilitating the movement of goods and people, promoting global economic growth, trade, and connectivity. Achieving sustainability and resiliency within road systems extends their lifespan, stabilizes economies, enhances climate adaptability, and reduces both maintenance costs and environmental impact. With the increasing use of recycled materials and chemical additives in asphalt mixes, relying only on asphalt binder Performance Grading (PG) is insufficient for predicting field performance of asphalt pavements and material resilience under various climatic projections and severe weather events. Therefore, this study introduces the concept of asphalt mixture PG system (Mix-PG system) for evaluating asphalt materials resilience. The proposed Mix-PG system is demonstrated using the following three laboratory tests: (1) the Disc-Shaped Compact Tension (DC(T)) test assessed low-temperature cracking resistance, establishing a minimum threshold for fracture energy to determine the continuous low-temperature PG, (2) the Hamburg Wheel Tracking (HWT) test measured rutting resistance, with a maximum threshold for creep slope defining the continuous high-temperature PG, and (3) the Illinois Flexibility Index Test (I-FIT) evaluated intermediate-temperature cracking resistance, ensuring mixes meet a minimum Flexibility Index (FI) threshold value. This research revealed that meeting a single threshold value of a laboratory test, at a single temperature, may not result in a comprehensive evaluation of mix performance and durability at various climatic projections and material resilience under severe weather events. However, a mix PG assessment diagram—integrating low- and high-temperature PGs and FI values—offers a comprehensive framework for assessing asphalt materials’ resilience for major decisions and high-profile projects based on expected climate performance and projections. The Mix-PG system is not intended for routine mix design or quality control/assurance. Instead, it is proposed for critical decision-making scenarios—such as evaluating alternative mix designs or incorporating innovative materials—particularly in high-profile projects like major highways, high-traffic intersections, or projects where climatic resilience is a key design objective. Additionally, the proposed framework may be applied at the network level to assess typical climatic resilience using common mixture types, thereby helping to identify potentially vulnerable areas under various climate change scenarios. Ultimately, this approach may be used in supporting the development of resilient and sustainable road infrastructure.