Freeze-thaw Performance of Phase Change Material (PCM) Incorporated Canal Foundation Expansive Soil

Abstract

Drought and water shortages severely restrict the development of agriculture in China. The complex process of freezing and thawing experienced by the canal foundation soil in cold regions will cause leakage and loss of canal water. It is a common measure to improve the foundation soil of canals in cold regions. Phase change material (PCM) store or release heat in the form of latent heat during the phase change process, which is a new type of temperature control material. In this study, PCM-modified soil was used as the research object. Volume deformation measurement, unconfined compressive strength test, differential scanning calorimetry, and scanning electron microscopy tests were carried out on modified soil samples with different PCM content after freeze-thaw (F-T) cycles. The influence of the number of F-T cycles and the content of PCM on the expansion-shrinkage deformation and mechanical properties of the modified soil was revealed. The results show that: the greater the PCM content, the smaller the volume change, but there will be an optimal mixing ratio. The stress-strain curve characteristics, the failure strain with the number of F-T cycles and the PCM content have a great relationship. The effects of F-T cycles have a greater impact on the mechanical properties of PCM-modified soil. Among them, the first cycle is the most obvious, and it stabilizes after the third cycle. PCM can inhibit the attenuation of soil strength, and the greater the amount, the better the effect. The freezing time of PCM-modified soil has been increased, the supercooling phenomenon is no longer obvious, and the thermal stability has been improved. PCM reduces the connectivity of pores, and macroscopically suppresses the expansion and shrinkage characteristics and strength attenuation of expansive soil. The studies have shown that 8% PCM-modified soil has obvious advantages in resisting the harsh weather in cold regions, which can provide a reference for actual engineering design.