4. Properties of clay materials, soils and mudrocks
The purpose of this chapter is to provide a background to the properties of natural clay materials used in the construction industry and other applications (see Table 4.1). There is a frequent need to evaluate clay materials for civil engineering projects, which has led to a bias in this chapter towards a consideration of their geotechnical properties. The intention is to present this information, and also some data applicable to other applications, in a manner suitable for scientists and engineers with an interest in clay materials. Both fundamental material behaviour and derived parameters are described.
This chapter considers the engineering behaviour of rock and soil materials that consist largely of clay mineral grains, together with minor amounts of other minerals. As discussed in Chapter 1, the term clay may mean a material made of clay-sized grains (smaller than 2 µm or 0.002 mm) or of grains consisting of clay minerals (see Chapter 2). Grains smaller than 2 µm may be clay minerals or other materials such as finely ground quartz or rock flour. Clay mineral grains may be larger than 2 µm and they are often bound into silt-sized (0.002-0.06 mm) aggregates. The Chapter concentrates on the properties of the material relevant to the exploitation and uses of excavated or extracted clays and mudrocks, rather than those of soil and rock masses in the ground, which are outside the scope of this report.
The behaviour of clays depends on their particle size distribution, mineralogy and moisture content. In terms of moisture content, it is convenient to identify three distinct ranges of liquid and plastic limits, as defined in Section 4.2.3:
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.