Clay Mineralogy and Soil Structure

Clay Mineralogy and Soil Structure

Copyright: © 2015 |Pages: 75
DOI: 10.4018/978-1-4666-6505-7.ch002


Most civil engineering projects are built on soil or rock and are constructed solely or partly of these materials. This chapter provides engineers with a good knowledge of the type and characteristics of the terrain on which such projects are to be constructed in order to achieve optimum safety and economic performance. The earth's crust, which is of interest to geotechnical engineers, is made up of rocks and the so-called unconsolidated sediments composed chiefly of solid mineral particles derived primarily from the physical and chemical weathering of rocks. The concepts of plate tectonics and geologic and soil structures are used to explain the geological processes in the earth. Mineralogy is the primary factor controlling the size, shape, and properties of soil particles. It also determines the possible ranges of physical and chemical properties of any given soil; therefore, a priori knowledge of what minerals are in a soil provides intuitive insight as to its behavior.
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2.1 Elements And Compounds

All matter is made up of elements and compounds. Compounds consist of two or more elements and may be broken down into simpler substances, or formed from simpler compounds or elements by chemical reaction. The smallest subdivision of a compound which still retains its properties is the molecule which is a group of two or more atoms tightly held together. An atom is the smallest particle of an element which is capable of entering into a chemical reaction.

A chemical element is a pure chemical substance made up only of atoms with the same atomic number. Atomic number is the number of protons in the atom’s nucleus. Examples of elements include gold, iron, copper, carbon, silicon, mercury, sodium, calcium, hydrogen, nitrogen, chlorine, and neon. There are 118 known elements as of year 2010. The latest known element is ununseptium (Oganessian et al., 2010).

The Periodic Table is a summary of the properties of chemical elements. It arranges the elements in order of atomic number, usually in rows, so that elements with similar atomic structure (and hence similar chemical properties) appear in the vertical columns. Dmitri Mendeleev, a Russian chemist, invented the table in 1869, Dyar and Gunter (2008).

Hydrogen and Helium are the two most abundant elements in the universe. On Earth, element abundance is related to the different “spheres”: In the Atmosphere: Nitrogen (80% & Oxygen (19%) while in the Lithosphere, the continental Crust is the most abundant. The Continental Crust is composed as shown in Table 1.

Table 1.
Composition of continental crust
ElementSymbolWt %SizePacking
SiliconSi280.4A4 fold
AluminumAl80.5A4, 6 fold
IronFe50.72A6 fold
CalciumCa41.0A8 fold
SodiumNa31.0A8 fold
PotassiumK2.51.4A8 fold
MagnesiumMg2.10.65A6 fold

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