Book excerpt: Concluding the trilogy on geological materials in construction, this authoritative volume reviews many uses of clays, ranging from simple fills to sophisticated products. Comprehensive and international coverage is achieved by an expert team, including geologists, engineers and architects. 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, plus the geological formation of clay deposits and their fundamental materials properties. World and British clay deposits are reviewed and explained. New compositional data are provided for clay formations throughout the stratigraphic column. Investigative techniques and interpretation are considered, ranging from site exploration to laboratory assessment 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.