Cement production applications

Wood is one of the oldest constructional materials. Historically it was important in world exploration and trade, and the defence of that trade, in the provision of merchant ships and navies. It was also important in the early days of railway engineering and in building construction. Although in many applications wood has been replaced by other materials, this renewable resource now supports the growing industries of manufactured wood products. Prominent amongst these are the panel materials chipboard, flake-board, strandboard, plywood and blockboard, hardboard and softboard, wood-cement products and the products of the very large pulp and paper industries. 

Non-destructive analysis is especially valuable in an on line situation. X-ray fluorescence has above all become of major importance for the analysis of inorganic process streams. Cement production is an example of the successful application of this technique. The X-ray analyser can be used for the simultaneous assay of the various feedstocks (iron ore, clay and limestone) for Fe203, A1203, Si02 and CaO. In turn the signals from the analyser are used to control the feedstock supplies to the blending mill and to maintain an optimum product composition. 

METLCAP is a chemical cement that encapsulates, stabilizes, and solidifies hazardous heavy metals in solid form, in slurry form, or in solution. The cement is composed of magnesium oxychloride, which forms when magnesium chloride and magnesium oxide, with water, are mixed together with the metals. The hardened cement product is insoluble and itself becomes a usable resource as cement or as fill material. The METLCAP technology is applicable as an in sitn or ex situ treatment or for high-pressure injection grouting and construction of slnrry walls. Currently, the process is patented and commercially available from Stark Encapsulation, Inc. 

Overall, these characteristics demonstrate that ammonium dihydrogen phosphate makes excellent rapid-setting grouts for outdoor applications such as road-repair materials in winter time in cold countries, because cold weather retards the initial setting, release of ammonia does not affect the workers and users in an open atmosphere, and the high strength makes these cements superior to conventional Portland cement. Products based on this material have been marketed commercially. 

Hydrogen fluoride is produced worldwide in 10 ta by reaction of fluorspar with sulfuric acid (equation 1). The reaction is endothermic (AF/298 = 59kJmol ) and is carried out in rotary furnaces that produce up to 45td . The crude HF is scrubbed by H2SO4 and purified further by distillation as required. Silicon tetrafiuoride is a by-product from silicate impurities (equation 2) and is recovered as H2SiFe (equations). Another by-product, CaS04, is used in cement production and other applications. ... 

Acrylic latices have been used successfully for more than 35 years to modify portland cement composites. The use of solid grade acrylic cement modifiers has become common during the past few years. Both of these types will be discussed later in this section. The level of polymer modification is measured as a ratio of polymer solids by weight of cement. A 15%-20% modification represents the range for optimum performance lower modification levels may prove acceptable for certain product applications (Rohm Haas, 1989). 

Considerable effort has been devoted to finding alternative fibers or minerals to replace asbestos fibers in their applications. Such efforts have been motivated by various reasons, typically, availability and cost, and more recently, health concerns. During World War I, some countries lost access to asbestos fiber supplies and had to develop substitute materials. Also, in the production of fiber reinforced cement products, many developing countries focused on alternatives to asbestos fibers, in particular on cellulose fibers readily available locally at minimal cost. Since the 1980s however, systematic research has been pursued in several industrialized countries to replace asbestos fibers in all of their current applications because of perceived health risks. 

It is not possible to make a global risk assessment of the ecotoxicological importance of these emissions, mainly because very few investigations and observations have been carried out. The phytoavailability of thallium from contaminated soils decreased rapidly after application (Martin and Kaplan 1998). More detailed results have been reported on the thallium flow in cement production, whereupon thallium is introduced into the process via the stone (limestone, clay) and ore raw materials. 

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 lijima Refinery is the only refinery in the world which applies the hematite process for iron removal. This process is excellent for recovering Au, Ag, Cu, Pb and rare metals, and for the precipitation of iron oxide usable in cement production, because of its high iron content. Furthermore, we are trying to develop a new process to recover more rare metals and to purify the iron oxide to broaden its application base. 

As we look to the future, we see an increasing application of electronic controls in clinker and cement production, expensive automated systems that, theo retically, eventually provide a higher-quality product at a reasonable price. The essential value and use of microscopy in the cement industry, however, have not changed. The light microscope remains an economical, practical, easily applied means of material quality control from the quarry to the construction. It should be a complementary tool amidst other equally valued instruments of analysis. But, as in mastery of the piano, the virtuoso must practice, practice, practice. One can always make better observations, tighter correlations, and more explanatory interpretations. 

The Ca-Fe-0 system is of central importance for steelmaking. During the reduction of iron oxides in the blast furnace the reactions with CaO (lime), one of the most important additives, is of particular interest. The resulting calcium ferrites are consequentially important slag forming phases. The second industrial field of application of the calcium ferrites is the cement production. 

Carbon fiber has made significant advances in replacing asbestos in asbestos cement products in two basic applications—structural covering and flues [215]. 

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