Page 145 - Geotechnical Engineering Soil and Foundation Principles and Practice

Soil Minerals
140 Geotechnical Engineering
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Table 6.1 Mineral Structure Spacing, A Remarks
X-ray diffraction
Kaolinite group AB 7.14 Nonexpansive
spacings used in
Halloysite ABþH 10.0 Must keep wet
mineral identification
Mica clay ABA 10.0 Nonexpansive
minerals
Smectites ABAþnH 10þ, variable Expansive
Treated with 17.7 For identification
ethylene glycol
Air-dry, 15.4 Two water layers
Ca-saturated
Wet, 19.6 Three water layers
Ca-saturated
Air-dry, 12.2 One water layer
Na-saturated
Wet, Unlimited expansion under zero loading
Na-saturated
Vermiculite ABAþH 14.4 Nonexpansive
Chlorite ABAþB 14.4 Nonexpansive
Gypsum CaSO 4 (2H 2 O) 4.29 Sulphate mineral
Quartz 3D linked A 4.21, 3.26 Often dominant
Feldspars 3D linked A 3.2 Many varieties
Calcite CaCO 3 3.03 Calcium carbonate

Note: 1 A ˚ ¼ 10 8 cm = 0.1 nm (nanometer).

watching for a fizz. Portland cement concrete also reacts because hydrated cement
compounds gradually become carbonated by CO 2 from air.

6.6.6 Geoenvironmental Problems with Silt-Size Particles
Prolonged inhaling of any dust particles that are silt size and smaller can lead to
serious health problems.

Black lung disease that leads to early retirements of coal miners involves inhaling
large quantities of relatively inert carbon particles that plug lung passages.
Kaolinite dust from processing of china clay, metal dusts from grinding, and
organic dusts such as fungal spores (‘‘farmers’ lung’’) cause similar problems. An
air-borne fungus indigent to desert areas causes lung scarring and flu-like
symptoms referred to as ‘‘valley fever.’’

Dusty environments are common near unpaved roads and construction sites
unless there is active control, and dusts can become highly concentrated in
confined areas such as in tunnels and mines.

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