The purpose of this study was to examine the relation of frost heave to pore-size distribution of compacted silty soils, and to propose that frost-susceptibility criteria based upon the distribution of porosity are more logical and versatile than those based upon texture and grain size.Rapid freezing laboratory tests were conducted to evaluate the heaving rate. The soils were compacted at different energy levels and water contents, and consisted of three different combinations of silt and kaolin.Mercury intrusion tests were performed to obtain the pore-size distributions of the compacted soils. Since this procedure requires the soil to be free of moisture, the soil samples were freeze-dried. This type of drying minimized the volume change and consequent structural modification expected from air or oven drying.The relation of frost heave to pore size was obtained using the method of linear regression. For a given soil, it is the quantity of interaggregate pores that controls the frost heave. These pores ar...