The performance of pavements in cold climates greatly depends on the frost susceptibility of the base and subgrade layers. Frost heave caused by ice lensing within the pavement structure can create distresses in the surface that lead to cracking and poor ride quality. Furthermore, thawing during a warm period can cause a supersaturated condition in the roadbed that dramatically reduces soil strength and increases vulnerability to damage under trafficking. A laboratory study was performed at the Texas Transportation Institute to assess the long-duration frost heave behavior of a limestone aggregate base material. The computer program ICE2, which tracks heat, water, and solute flow during the freezing process, demonstrates the important role of salt content in the ice lensing mechanism. The program successfully models a two-stage frost heave behavior observed in the laboratory and affords an explanation of the frost heave events in a step-by-step fashion. Accurate frost heave modeling must account for changes in solute concentrations during the freezing process.