Analysis of moisture migration patterns in pavement concrete induced by the pot cover effect

Freeze-thaw (FT) damage to airport pavement in cold regions closely correlates with the evolution of internal moisture conditions, porosity, and strength. Most studies have examined top-down water infiltration and bottom-soak water migration, but less attention has been paid to the mechanism of moisture vapor migration driven by the pot cover effect (PCE). To address this gap, in this paper, an indoor experimental setup was designed to simulate this process, complemented by field monitoring to analyze its role in FT damage development. Results showed that the degree of saturation and moisture content of the specimens increased to 98.5% and 5.6%, respectively, after 33 effective days, which exceeded the critical value of FT damage (86%) and satisfied the Powers’ failure theory (91.7%). During initial testing, the vapor was mainly driven by temperature gradients, leading to condensation and adsorption at the specimen bases. Later, the liquid water migration rate was positively correlated with the matrix suction gradients. Both degree of saturation and moisture content increased with time at the same depth but decreased from bottom to top along the depth direction. Field monitoring revealed that moisture accumulation caused by the PCE in autumn serves as the primary source of frozen water in winter. FT cycles occur most frequently in early spring and late autumn, with higher frequencies in shallow layers. Based on these findings, recommendations are provided for preventing and controlling pavement distresses in cold-region airports and highways.