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

• Effect of maximumsupersaturation ratio on ten water sodium sulfate crystals to precipitate is studied.
• The relationship between the speed of crystal growth and the temperature is presented.
• The effect of the rate of temperature fall on the formation of crystal is investigated.
• The initial salt crystallization and value of salt expansion ratio are influenced by cooling rate.
• The condition of salt expansion and salt crystal is studied.

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.