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Moisture Related Problems in Stabilized Materials
Published in A. Gomes Correia, Fernando E.F. Branco, Bearing Capacity of Roads, Railways and Airfields, 2020
The Pharr caliche material stabilized with varying cement contents met the 7-day unconfined compressive strength requirement of ACI. However, only the Pharr caliche stabilized with 1.5 percent cement met the TxDOT strength requirements. The other two mixture combinations exceeded the 7-day unconfined compressive strength requirement of TxDOT. Compressive strength decreased after the TST for the Pharr caliche stabilized with 1.5 percent cement, whereas, strength increased for the Pharr caliche stabilized with 3.0 and 4.5 percent cement.
Weathering and Soils
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Soil color is one of the easiest ways to tell soils apart and is also the easiest way to see soil horizons (Fig. 11.44). Although color is not a good indicator of all soil attributes, it does provide information about soil composition and moisture content, and about the nature of the parent material. Usually, soil color reflects the presence of different iron oxides, carbonates or other salts, or eluviated humus. Figure 11.44 shows some examples of different colored soils. Highly leached soils, like the North Carolina soil, may have a very red color due to concentration of iron oxides, especially hematite, and absence of other mineral matter. The South Dakota soil is dark colored due to high organic content. The Texas soil contains nodules of caliche (white calcium carbonate). The Rhode Island soil is yellowish due to high goethite (an iron hydroxide) content.
Superficial deposits
Published in A.C. McLean, C. D. Gribble, Geology for Civil Engineers, 2017
In arid regions where soils are enriched in lime, a layer of caliche may be formed. Such a deposit is formed on a peneplain in a climate that leads to sharply defined alternations of saturation and desiccation. Caliche is a ‘hard cap’ deposit produced by upward capillary migration of ground waters during the arid period. Depending upon the composition of the underlying rock, and therefore the composition of these migrating solutions, precipitates of carbonate (calerete), siliceous (silcrete) or ferruginous (ferricrete) materials may be deposited. The position of deposition of different chemical layers depends upon the solubility of the constituents of the migrating solutions, the most soluble salts being deposited nearest the surface (although rainwater action may produce a reversed sequence just below the surface).
The use of seawater in mining
Published in Mineral Processing and Extractive Metallurgy Review, 2018
Luis A. Cisternas, Edelmira D. Gálvez
The natural deposits of nitrates or saltpeter are called caliche (Wisniak and Garces, 2001). This mineral is a conglomerate of various mineralogical species that in a high proportion are soluble in water at room temperature, being the most abundant: polyhalite, glauberite, bloedite, gypsum, and anhydrite (sulfates), halite (chloride) and nitratine, humberstonite and darapskita (nitrates). On the other hand, there are lautarita and hectorfloresite (iodates) and some chromates and perchlorates, which are in small proportions. The insoluble species (approximately 60% to 70%) that the caliche also contains are mainly quartz and other silicates (Valencia et al., 2008). The Caliche exploitation is concentrated in Northern Chile, in the Atacama Desert, and produces mainly natural sodium nitrate (a fraction then is converted into potassium nitrate) and iodine (approximately 22,000 t/year).