1.0 Introduction
Clay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried or fired. Clay deposits are mostly composed of clay minerals (phyllosilicate minerals) and variable amounts of water trapped in the mineral structure by polar attraction. Organic materials which do not impact plasticity may also be a part of clay deposits. Clay is a widely distributed, abundant mineral resource of major industrial importance for an enormous variety of uses (Ampian, 1985). In both value and amount of annual production, it is one of the leading minerals worldwide. In common with many geological terms, the term “clay” is ambiguous and has multiple meanings: a group of fine-grained minerals which show plasticity through a variable range of water content, and which can be hardened when dried or fired i.e., the clay minerals; a particle size (smaller than silt); and a type of rock i.e., a sedimentary deposit of fine-grained material usually composed largely of clay minerals (Patterson & Murray, 1983; Bates & Jackson, 1987). Clays find wide range of applications, in various areas of science, due to their natural abundance and the propensity with which they can be chemically and physically modified to suit practical technological needs (Xi et al., 2005).
Clays are distinguished from other fine-grained soils by various differences in composition. Silts, which are fine grained soils which do not include clay minerals tend to have large particle sizes than clays but there is some overlap in both particle size and other physical properties, and there are many naturally occurring deposits which include both silts and clays. The distinction between silts and clay varies by discipline.Geologists and soil scientists usually consider the separation to occur at a particle size of 2µm (clays being finer than silts), sedimentologists often use 4-5µm, and colloid chemists use 1um. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, ISO 14688 grades; clay particles as being smaller than 0.063mm and silts one larger.
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Limitation of the study and Definition of technical terms.
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