Microstructural analysis of pore characteristics of natural structured clay.

Distributed widely in structured marine clay, intra- and inter-particle pores significantly influence the physical properties, hydraulic conductivity, and mechanical behavior of such soil. However, the distribution and morphology characteristics of these pores cannot be quantified through particular single method, and instead, a combination of techniques with different measuring ranges is required. This paper focuses on natural marine clay retrieved from Zhanjiang, China (ZJ clay), this being a typically structured clay with cementation bonding. In this study, the methods of scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and nitrogen gas adsorption (NGA) were applied in combination to (i) analyze the microscopic characteristics of the pores in natural ZJ clay and the factors influencing the evolution of those pores and (ii) establish the relationship between the microstructural characteristics and macroscopic performance (including both physical and mechanical behaviors) of ZJ clay. The test results show that natural ZJ clay is featured by a randomly oriented open-flocculated structure with cementation bonding and the particles within this clay are interconnected by edge-to-face or edge-to-edge contacts, which contributed to the high structural strength and stability. The hysteresis loops in both the extrusion curves from the MIP tests and the desorption isotherms from the NGA tests indicate the existence of ink-bottle pores in ZJ clay. Through the test results of SEM, MIP, and NGA, further qualitative and quantitative analyses of the complete pore size distribution characteristics of marine clay were allowed. This study enhances the comprehension of pore characteristics of natural structured clays from a microscopic perspective. [ABSTRACT FROM AUTHOR]