Effects of Salt Concentration Changes During Freezing on the Unfrozen Water Content of Porous Materials

Abstract

By combining equations for salt concentration by water removal from porous bodies with those for freezing point depression in normal solutions, equations are developed for calculating freezing point depression shifts due to the gradual removal of water upon freezing in porous bodies. The same equations can be used for the calculation of shifts in the osmotic potential of the water in drying porous bodies by using a simple conversion factor. Graphs relating the remaining water content to the freezing point shift for various initial soluble salt contents are given. Good agreement is found between the measured freezing point depression shifts for a silty clay soil treated with three concentrations of sodium chloride and with dimethyl sulfoxide at various contents of unfrozen water and the calculated values. The order of magnitude of the shifts expected in various natural conditions is discussed.