Strong salt expansion and frost heave are induced to make the infrastructure in the salted region damaged with water or salt phase change at low temperature. Laboratory test based on differential scanning calorimetry is used to investigate salt and water phase transformation and their crystallization mechanism in sodium sulfate soils and solutions. During the experimental process, crystallization heat release, crystallization period and supercooling are measured. According to the conservation principle of mass and heat, salt and ice crystallization are separated, and unfrozen water content is calculated at different temperatures. Moreover, variations of unfrozen water content, as well as the supercooling degree of sodium sulfate soils with different size are compared and analyzed based on heterogeneous nucleation theory. The results demonstarte occurance of the ice crystallization before salt crystallization in minor soil samples; however, salt crystallization appears first in pure solution at high concentration. The interval at which the ice and salt crystallization begin decreases as the salt content increases, and the supercooling decreases as the salt content or sample size increases. Additionally, water freezing in small soil samples is more difficult than that in larger soil samples, and the unfrozen water content increases as the salt content or sample size decreases.

强烈的盐分膨胀和霜冻起伏使盐分区域中的基础设施受到低温水或盐分相变的损害。基于差示扫描量热法的实验室测试用于研究盐和水在硫酸钠土壤和溶液中的相变及其结晶机理。在实验过程中，测量了结晶放热，结晶时间和过冷度。根据质量和热量的守恒原理，将盐和冰的结晶分离，并在不同温度下计算未冻结的水含量。此外，基于非均相成核理论，对不同尺寸的硫酸钠土壤的未冻水含量变化以及过冷度进行了比较和分析。结果表明，在少量土壤样品中，在盐结晶之前，冰结晶发生了。然而，盐的结晶首先出现在高浓度的纯溶液中。冰和盐结晶开始的间隔随着盐含量的增加而减小，过冷度随着盐含量或样品量的增加而减小。另外，小土壤样品中的水冷冻比大土壤样品中的水难得多，并且未冷冻的水含量随着盐含量或样品尺寸的减少而增加。随着盐含量或样本量的增加，过冷度降低。另外，小土壤样品中的水冷冻比大土壤样品中的水难得多，并且未冷冻的水含量随着盐含量或样品尺寸的减少而增加。随着盐含量或样本量的增加，过冷度降低。另外，小土壤样品中的水冷冻比大土壤样品中的水难得多，并且未冷冻的水含量随着盐含量或样品尺寸的减少而增加。