Cement economic importance

Most abundant group of materials, composed of silicates of aluminium with sodium, potassium, calcium, and rarely barium. Most economically important mineral. Used for ceramics, glass, abrasive wheels, cements, insulation and fertilizer. 

The scales of carbonate redistribution, and thus reservoir quality enhancement, are difficult to constrain. Several workers have argued that the reservoir properties of sandstones are greatly enhanced due to large-scale carbonate dissolution (Lonoy et al., 1986 Schmidt McDonald, 1979). As the undersaturated waters have to circulate through large volumes of permeable sediment to cause economically important carbonate cement dissolution, it is expected that such secondary porosity develops in partially rather than pervasively cemented sand-... 

The strength of cementation is often an important characteristic in engineering terms. Well-cemented quartz sandstones can be very strong mechanically, whereas friable uncemented sandstones are relatively weak rocks. Siltstones, mudstones and shales are usually weak rocks because of the dominance of platey clay minerals that provide little frictional resistance. Moreover, conglomerates and sandstones exhibit relatively high volumes of void fraction (i.e., porosity) and are economically important as aquifers for water supply and reservoir rocks for gas and petroleum. 

There are a wide variety of cementitious materials. Among these, the one that is of most economic importance and is most widely used is Portland cement. Portland cement is manufactured in rotary kilns. Various raw materials are used in its making. The overall composition is made up of two phases tricalcium silicate (3Ca0Si02) and dicalcium silicate (2CaO Si02). Figure 11.24 shows the microstructure of a... 

The various fields of chemistry play an important role in the discovery and exploitation of oil and gas reserves. Improved drilling and well completion fluids, cement slurries, hydraulic fracturing and acidizing fluids to improve well productivity, various chemical additives to be used in these fluids, and chemicals for enhanced oil recovery are essential to the improvement of production economics and to an increase in recoverable hydrocarbon reserves. Chemistry will become increasingly important in future hydrocarbon production with the decreased likelihood of major onshore discoveries, increased discovery and production costs associated with deep offshore wells and Arctic frontier provinces, and the decline in drilling since early 1982. 

The most important industrial alkalis are the weak alkali ammonia (Section 9.3), caustic soda (sodium hydroxide), and lime (calcium oxide).1-6 For many industrial and agricultural purposes, the most economical source of alkali is lime, which is used in steelmaking and other metallurgical operations ( 45% of U.S. production of lime), in control of air pollution from smokestack gases (Chapter 8), in water and sewage treatment (Sections 9.6 and 14.5), in pulp and paper production (Section 10.4), in reduction of soil acidity, in cement and concrete manufacture (indirectly, as discussed later), and in many chemical processes such as paper making (Section 10.4). In short, lime is one of the most important of all chemical commodities. 

Prezbindowski D.R. (1985) Burial cementation-is it important A case study, Steward City trend, south central Texas. In Carbonate Cements (eds. N. Schneidermann and P.M. Harris), pp. 241-264. Society Economic Paleontologists and Mineralogists Special Publication 36, Tulsa, OK. 

Regeneration of S02 from gypsum has been done via the Krupp-OSW process, the most important facility formerly being the Fedmis plant in South Africa, which made about 300 tons per day H2S04 and a similar amount of cement. Apparently, because of the high cost of cement and sulfur in this remote location, the plant was not economically viable and shut... 

Although simulations happen to be the most economic and fastest way to carry out the evaluation ofthe Hj source term in various cement-based materials, it is advisable to perform periodical experiments, preferably following an important conceptual modification, in order to check certain predictions and also to fix certain parameters of the model. These experiments generally are related with the test-bars of cement material irradiated in closed vessel or the material poured within air-tight mini-containers (Fig. 8). 

Because of economic considerations, the tungsten in cemented carbide scrap is not the only value of interest. The value of the other constituents, such as Co and Ta, are also important. Both metals, at least at this time, are more expensive than tungsten. 

With respect to corrosion, the conventional classification of climates in marine, inland, industrial, etc. types is not sufficient. It should now be specified with respect to the actual chemical components in the atmosphere, as well as humidity and other factors. Recent research in this field has led to much more precise methods for estimating corrosion rates in polluted atmospheres (38). Economically, perhaps even more important problems are caused by the increased corrosion of water supply pipelines. Not only copper is dissolved, but also cadmium from soldered joints, and larger steel and cement pipelines may also be affected. 

In Poland the artificial pozzolana i.e. fly ash is the most important among the pozzolanic additions, application of which in cement production is rational both from the economic and ecological reasons. 

The PLACID process could be perfectly integrated if it were employed in parallel with a pyrometallurgical smelter. In this way, any lead fumes, drosses and slags from Ae pyrometal-lurgical line can be passed to the leaching bath of the PLACID line and the cements from the purification stqi could be fed into the furnace. Important gains would be obtained fix)m the oiviromnental, process efficiency, product quality and economical points of view. 

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