Natural and Engineered Clay Barriers

Abstract

Key terms and concepts in clay science, which are used in this volume, are introduced in the present chapter with a focus on the microstructural and surface properties of clay minerals. For the sake of simplicity, this introduction focuses on the clay minerals that are most prevalent in engineered and natural clay barriers, such as smectite, particularly montmorillonite, illite, mixed-layers illite–smectite, and kaolinite. Important fundamental issues are highlighted that remain to be elucidated, and that could impede the interpretation of a number of macroscopic observations. In particular, the uncertainties related to the nature of the outer surface layers of clay mineral particles in natural samples, the detailed microstructure of clay media at in situ conditions (pressure, saturation), and the atomic-level structure of particle edges are discussed in details.