Characterizing the Effect of Freeze-Thaw Cycling on Pore Structure of Asphalt Concrete Mixtures Using X-ray CT Scanning.

Freeze-thaw (F-T) cycling presents a challenge when building durable pavement structures in cold regions. Understanding the changes within the microstructure of asphalt concrete (AC) due to F-T conditions is crucial for developing a resilient pavement design. This study investigates the impact of F-T cycles on five AC mixtures using X-ray computed tomography (CT) scanning. Image analysis was completed to evaluate the changes in the microstructure of the AC samples before and after exposure to 30, 60, and 90 F-T cycles. The changes/degradation in the microstructure were evaluated based on analyzing the distribution and properties of air voids within the AC samples. The results showed that an X-ray CT scan can successfully capture the impact of F-T cycles on the structure of air voids in different AC mixtures. The findings of this research provide guidelines for understanding the mechanism of F-T damage within AC, which can assist in optimizing the performance of AC in cold regions.