Investigating the Freeze-Thaw Damage in Asphalt Concrete Using Imaging Techniques

In cold regions, asphalt concrete (AC) pavements experience freeze-thaw (F-T) cycles. F-T cycles can cause damage and disintegration of AC mixtures, which cause significant operational problems and a reduction in the service life of AC pavements. The evolution of the internal structure of an AC mix due to exposure to F-T cycles should be explored to have a better understanding of the mechanism of F-T damage in the mix. In this study, different AC specimens were evaluated before and after F-T cycles using two techniques: indirect tension test (IDT) to evaluate strength deterioration of specimens, and imaging techniques to capture changes in the internal structure of specimens. Three imaging techniques were used in this project: digital camera, stereomicroscope, and X-ray computer tomography (CT) scan system. Each technique has its potentials to show the internal damage details. AC specimens have been assessed at different levels of F-T cycles. 2D and 3D images for the internal structure of the specimens were collected and analyzed at 0, 15, 30 and 45 F-T cycles. The captured images will be analyzed to quantify the F-T damage according to adhesion failure (%), cohesion failure (%), broken aggregate (%), and the total length of microcracks (mm). The results from image analysis will be correlated to IDT results.