8. Compositional and textural analysis of clay materials
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 the planned analytical programme. The flow diagram in Figure 8.1 indicates generally the manner in which different sample preparation procedures are needed for the different types of analyses described below.
Figures & Tables
Concluding the trilogy on geological materials in construction by specially convened Geological Society working parties, this authoritative volume reviews many uses of clays, ranginf from simple fills to manufactured products. Comprehensive and international coverage is achieved by an expert team, including geologists, engineers and architects, who met over six years to produce the book. Packed with information prepared for a wide readership, this unique handbook is also copiously illustrated. The volume is dedicated to the memory of Professor Sir Alec Skempton.
Various definitions of ‘clay’ are explored. Clay mineralogy is described, plust the geological formation of clay deposits and their fundamental materials properties. World and British clay deposits are reviewed. New compositional data are provided for clay informations throughout the British stratigraphic column. Investigate techniques and interpretation are considered, ranging from site exploration to laboratory asessment of composition and engineering performance.
Major civil engineering applications are addressed, including earthworks, earthmoving and specialized roles utilizing clays. Traditional earthen building is included and shown to dominate construction in places. Clay-based construction materials are detailed, including bricks, ceramics and cements. The volume also includes a comprehensive glossary.