8. Compositional and textural analysis of clay materials

Abstract

The composition and textural fabrics of clay materials control their applications for constructional and other purposes. Discussed below are the most commonly used techniques to characterize these aspects of clay materials. The analytical approaches, their advantages and their limitations are summarized without giving detailed discussions of each technique, but references to more detailed accounts are provided.The overall sampling and analytical approach, and how it will help define and/or solve potential problems, needs to be carefully planned. A preliminary reconnaissance sampling and analysis programme, taking into account desk studies (see Chapter 7) and any related available information needs to be made before embarking on full scale detailed and comprehensive analyses.Sampling and sample preservation methods are too often inadequately designed and this can limit or even negate the results from later sophisticated and costly analyses. Sampling needs to be planned to provide adequate representative samples taking into account the nature of the problem to be answered and the heterogeneity of the materials—clay materials are often very heterogeneous, even on a small scale. Once sampled, the material needs to be carefully preserved so as to minimize alteration of the sample from its original state prior to analysis. For example, drying of samples needs to be undertaken at temperatures which will not dehydrate minerals such as gypsum, i.e. at 40°C rather than the 105°C that is often required in standard procedures.Also the sampling and preservation procedures need to be designed in the context of the objectives of the investigation and