ABSTRACT
Smectite clay is widely used for waste isolation, particularly in top and bottom liners of waste landfills. This is primarily because of its excellent sealing ability. The hydraulic conductivity and self-healing capability of the clay are its most valuable properties. Since the cost of high-quality clay is high, mixtures of smectite clay and inexpensive suitably graded soil are often used – as are thin woven mats containing smectite clay of high quality. In recent years smectite clay has become an important engineered barrier material for use in the deep disposal of radioactive waste. This subject will form the focus of this and subsequent chapters. As in the case of natural sedimented deposits of smectites, the macroscopic (bulk) physical properties of artificially prepared smectite clay depend very much on the resultant microstructure obtained in the preparation process. This can be considerably more complex than natural clay sediment deposits.
