An experimental study on the influence of cooling rates on salt expansion in sodium sulfate soils

This experimental study examined salt expansion in sodium sulfate soils. The results indicated that salt expansion was caused by the crystallization of sodium sulfate decahydrate when the supersaturation ratio of the sodium sulfate solution in the soil reached a maximum value. The maximum supersaturation ratio of the sodium sulfate solution decreased as the sodium sulfate content increased, and the supersaturation ratio decreased as crystals continued to precipitate. The total amount of crystal generation was related to the crystal growth rate. The rate of crystal growth decreased exponentially as temperature decreased. The formation of crystals was influenced by the rate of cooling. When mirabilite began to precipitate, the supersaturation rate was reduced versus the rate of cooling, whereas the salt expansion rate of the soil increased. When the salt content of sodium sulfate was less than 1.5%, salt crystals began to form after the phase change of the solution from water to ice, but salt expansion did not occur. When salt content of sodium sulfate was less than 0.7%, the precipitation of salt crystals was minimal or did not occur. (C) 2016 Elsevier B.V. All rights reserved.