Investigation of asphalt concrete damage under the combined action of freeze-thaw and load using DIC-CT method

Freeze-thaw (F-T) and vehicle load are the main external forces acting on asphalt pavement in cold regions. Their concurrent action inflicts severe pavement damage, yet existing research has largely overlooked their combined impact, hampering a comprehensive understanding of asphalt concrete's damage characteristics under combined F-T and load (F-T-L) conditions. Therefore, this study employed a custom-designed F-T-L testing device to simulate asphalt pavement damage scenarios. Coupling the digital image correlation method (DIC) with computed tomography technology (CT), we meticulously tracked the strain evolution within cross-sectional images of asphalt concrete samples. By comparing the strain distribution and development under F-T-L and F-T cycles, the influence of load on the deterioration of asphalt concrete under F-T cycles was clarified. The strain images of the sectional image of the specimen intuitively show that the area rich in void and the mortar interface were vulnerable areas, and with the continuous application of external forces, the strain level increased and the damage progressed unevenly. The differences in strain distribution under F-T-L and F-T underscore that F-T action primarily drives expansive deformation in asphalt concrete, while load intensifies the deformation, introducing damage gradients, and augmenting damage non-uniformity, especially under high load levels. Our study not only uncovers the intricate interplay between F-T and load but also provides critical insights for enhancing pavement durability in frigid climates.