Development of Climate Adaptation and Asphalt Selection Tool (CAAST)

ABSTRACT
This paper introduces the Climate Adaptation and Asphalt Selection Tool (CAAST), which is a new computer software used to select climate resilient Performance Grade (PG) of asphalt binder for Superior Performing Asphalt Pavements (Superpave) based on extreme high and low pavement temperatures. Developed by National Research Council Canada (NRC), CAAST uses projected climate change temperature data provided by Environment and Climate Change Canada (ECCC) for Canadian cities, obtained from the Canadian Regional Climate Model (CanRCM), version 4, from 1950 to 2100. The CAAST software analyzes the projected temperature data file within a certain time period (i.e.: road design life) to extract and calculate environmental parameters that will be used to assess the impact of climate change and to select the climate resilient asphalt binder performance grade (PG). CAAST incorporated the shortcomings of the existing Long-Term Pavement Performance Bind Online (LTPPBind) such as standing traffic speed, besides slow and fast traffic speed and annual temperature variations in terms of Degree Days (change within a year not only during 6 months).

The paper compares and analyzes Superpave PG results obtained from ECCC's projected temperature data via CAAST against the existing method (LTPPBind) based on Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) temperature data. The study shows that the indices such as Mean Annual Lowest Air Temperature (MALAT) and Mean Annual Degree Days (MADD) for cities in Atlantic, Central, Prairies, Western and Northern Canada are significantly higher when using the new proposed method compared to MERRA-2. The analysis also suggests that climate change can induce higher upgrades in high and low PG grades over the next 25 years than those predicted by MERRA-2 via LTPPBind. Consequently, the use of CAAST with embedded projected air temperature data can provide an effective solution for selecting resilient PG binder types in response to climate change, which is an improvement over traditional approaches that rely on historical climate. Overall, this study highlights the importance of considering climate change projections in pavement design and emphasizes the need for tools like CAAST to ensure pavement performance under changing environmental conditions.