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Clays are an integral part of the environment and due to their unique properties such as their ability to adsorb water, hold vital nutrients and provide assistance for the propagation of life. In particular the effects on soil permeability through shrinking/swelling, dispersion/flocculation and attenuation characteristics make them important constituents of all soil systems. Consequently, the object of this web-site is to collect and amalgamate the body of literature regarding clay minerals into an easily digestible document. In doing this, provide a broad overview into the unique properties of clay minerals.

Clays are an interesting phenomenon and it seems that even with all the vast amount of literature, their significance in everyday life, and their possible influence on the beginnings of life, they still seem to remain an elusive subject. So, what is clay? The term ‘clay’ generally refers to particles less than 2 microns (µm) in diameter, which was the limits of microscopic resolution in the nineteenth century, the best available technology at the time (Velde, 1992, p.1). From a geologist’s perspective, clay minerals are the fine-grained layer or “sheet” silicates (Velde, 1992). However, in practice ‘clay’ is the fine-grained, colloidal fraction of earth material.

Fine-grained soils generally have a lower hydraulic conductivity than coarse grained soils; due to the greater surface area and hence the greater frictional resistance to the flow of the water. Added to this is the ‘affinity’ of clay for water, that is, water present in the soil matrix can electro statically attract and bond to clay particles contained within the soil matrix. This is interconnected to the clay inter-layers and edge-effects, which is discussed in more depth under properties. Ultimately, even with a high percentage of pore space many clay soils still show a low permeability (Watson and Burnett, 1993, p.48).

In summary, the aims of this web site are to:

  • Formulate an understanding regarding the basic properties and crystalline structures of the clay minerals;
  • Provide a readable review of the hydrological properties regarding the clay minerals;
  • Develop an extensive understanding about how the specific properties of clay minerals influence hydraulic conductivity in soil, in particular the differences between the swelling and non-swelling clays;
  • Use the theoretical background for the comprehension of the experimental investigation regarding the main properties of clays (i.e. swelling, dispersion, and flocculation).(top)

This web site was constructed by Benjamin.K. Galton-Fenzi. Last Updated: 21 Feb, 2004 10:16 AM
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