Solid–liquid interface disjoining pressure of frozen clay and its effect on water transport

• Published in: Journal of crystal growth Vol. 614; p. 127218
• Main Authors: Cheng, Hua, Liu, Xiaoyan, Chen, Hanqing, Wang, Xuesong, Guo, Longhui, Wang, Xiaoyun
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.07.2023
• Subjects: A1. Frozen clay; A2. Disjoining pressure; B1. Water transfer; B2. Surface free energy; B3. Unfrozen water film; A1. Frozen clay; B1. Water transfer; A2. Disjoining pressure; B2. Surface free energy; B3. Unfrozen water film
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2023.127218

•A theoretical model of disjoining pressure at solid–liquid interface is established by considering the charge effect on clay surface, and the implicit equation of unfrozen water film is given.•An implicit equation for the thickness of the unfrozen water film was given and veried.•The distribution characteristics of solid–liquid interface disjoining pressure in unfrozen water film and its contribution to water migration are expounded. To account for the influence mechanism of solid–liquid interface disjoining pressure on water migration during clay freezing, this study first provides a theoretical calculation model of solid–liquid interface disjoining pressure by combining the thermodynamic equilibrium relation of solid–liquid interface with the parallel plate capacitor model. This is done at the molecular level. An implicit equation for calculating the film thickness d of unfrozen water is also given and the accuracy of the model verified. Secondly, considering that unfrozen water film is anisotropic, the concept of tensor is introduced to show the distribution characteristics and functions of solid–liquid interface disjoining pressure in unfrozen water film. Finally, the effects of solution concentration and undercooling degree on film thickness d of unfrozen water are discussed. The results show that solid–liquid interface disjoining pressure can be expressed by the excess free energy on the surface of charged media, and it is a single-valued function of unfrozen water film thickness. Solid–liquid interface disjoining pressure not only provides an effective driving force for water migration, but also provides growth space for ice lenses; the thickness of unfrozen water film d is negatively correlated with solution concentration and undercooling degree. The research results can provide a theoretical reference for the study of frost heave mechanism in clay soils.