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.