Role of Deicing Salt in Pavement Deterioration by Frost Action

Frost action is a major cause of pavement deterioration in cold climates. Thermal cracking, differential heaving, and loss of bearing capacity during spring thaw are often identified as the main mechanisms involved. Except for thermal cracking, frost-susceptible subgrade soils are generally considered to be the source of the problems. Field observations suggest that frost action within the pavement granular layers could also contribute to pavement deterioration. Differential freezing conditions associated with the contamination of the base material by deicing salt are believed to be the cause of this problem. Indeed, field observations of heaved pavement surfaces near discontinuities, such as cracks or pavement edges, suggest that an ice enrichment process is occurring in pavement granular layers during the freezing season. In a laboratory testing program, salt concentration gradients reproduced in freezing temperature create conditions favorable to an ice enrichment process and contribute to a substantial increase in the frost susceptibility of granular materials. Under steady isothermal cooling conditions, samples placed in layers of increasing salinity have exhibited heave at rates as high as 6 mm/day. Normal freezing tests on the same material free of salt have shown no significant segregation potential. Surface heave resulting from ice enrichment can be highly detrimental to pavement performance. Induced distortion contributes to rapid deterioration of the pavement surface. When occurring along transverse cracks, the phenomenon may seriously alter the ride quality of the pavement.