Portland cement raw materials

Pyroprocessing, of Portland cement raw material, 5 488—489 Pyroredox process, 19 678 Pyrosulfuryl chloride, 23 641, 645, 647, 649 Pyrosultones, decomposition of, 23 527 Pyrotechnics... 

Portland cement raw materials contain small proportions of MgO as noted in Section 1.1.2, these must be limited to avoid formation of more than a minor amount of periclase. The iron in Portland cement clinkers is normally present almost entirely as Fe, but calcium aluminate cements may contain both Fe " and Fe . ... 

Chromy, S., "Process of Portland Clinker Formation, Reactivity, and Burnability of Cement Raw Materials Part I Mechanism of Portland Clinker Formation," Zement-Kalk-Gips, Vol. 35, No. 4, 1982, pp. 204-210. 

Portland Cement Manufacture. The second greatest use of limestone is as raw material in the manufacture of Pordand cement (10). The average limestone factor per ton of Pordand cement is 1.0—1.1 t of pulverized limestone. The limestone, calcined to lime in the cement rotary kiln, combines with siUca and alumina to form tricalcium siUcate and tricalcium aluminate and other lesser cementing compounds (see Cement). Most cement companies operate captive limestone quarries. 

Portland cement is manufactured by two basic processes, the wet process and the dry process. The dry process uses approximately 25% less energy per ton of Portland cement and is used to produce about 68% of the U.S. Portland cement. Both processes start by mixing selected raw materials, cmshed and/or milled to approximately s in. (1.9 cm) diameter, in the correct ratios to give the final desired chemical composition. 

Other Types of Portland Cements. White Portland cementis standard Type I or III Pordand cement with raw materials selected and controUed to have negligible amounts of Hon and manganese oxides, which impart the gray color. The white Pordand cement is used in decorative and architectural appHcations like precast curtain waUs, terra22o surfaces, stucco, tile grout, and decorative concrete. 

Special purpose and blended Portland cements are manufactured essentially by the same processes as ordinary Portland cements but have specific compositional and process differences. White cements are made from raw materials of very low iron content. This type is often difficult to bum because almost the entire Hquid phase must be furnished by calcium aluminates. As a consequence of the generally lower total Hquid-phase content, high burning-zone temperatures may be necessary. Past cooling and occasionally oil sprays are needed to maintain both quaHty and color. 

In the manufacture of Portland cement, many otherwise-waste materials can be used either as a substitute for the traditional raw material, or as a secondary fuel (e.g., used tires) [334,1577]. In particular, drilling wastes can be introduced in the clinker burning process [878]. For both waste disposal and cement manufacturers, a mutual benefit will emerge. The cement manufacturing companies reduce their demand for traditional raw materials and save the limited capacity of landfills and other waste-treatment industries. 

There are three fundamental stages in the process of manufacture of Portland cement, namely. (I) preparation of the raw mixture. (2) production of the clinker. (3) preparation of Ihe cement. Whether the process used is wet or dry. the raw materials are selected, analyzed, and mixed so dial, alter ireatmeni, Ihe product, or clinker, has a desired, narrowly specified composition A factory analysis of slurry, where the wet process is in use. is as follows calcium oxide 44%. aluminum oxide 3.5%. silicon oxide... 

In order to obtain the desired selling qualities in Ihc finished cement, there is added to the clinker about 2% of gypsum (calcium sulfate. CaSOj 2H2O), and ihe mixture is pulverized very finely. For every ton of Portland cement shipped, over two and one-half tons of raw materials and cement clinker must be ground very finely. See Table I. 

In the portland cement manufacturing process, three steps occur. First, raw materials are crushed and mixed. The raw materials are powdered limestone, alumina, iron, and silica. Second, the raw materials are fed to an inclined rotary kiln in which they are heated to at least 2700 F. A rock-like substance called clinker is formed, which exits the kiln and is cooled. Third, the cooled clinker is finely crushed, and about 5 percent gypsum is added to produce finished cement. Details of the process are explained below. 

Type III High-early-strength (HES) cements are made from raw materials with a lime-to-silica ratio higher than that of Type I cement and are ground finer than Type I cements. They contain a higher proportion of calcium silicate than regular portland cements. 

Two types of materials are necessary for the production of portland cement one rich in calcium (calcareous), such as limestone or chalk, and one rich in silica (argillaceous) such as clay. These raw materials are finely ground, mixed, and heated (burned) in a rotary kiln to form cement clinker. 

Lignosulfonates 400-550 Evaporation, precipitation, ultrafiltration, electrodialysis, ion exclusion Additive (oil well drilling muds, Portland cement concrete), dispersing agent and binder (textiles, products of printing industry, mineral slurries), raw material (vanillin, dimethyl sulfoxide, etc.)... 

Because of the large supply of sulfur, there is increased interest in its possible use in the construction industry (7-13). This chapter reviews research at The University of Calgary concerned with sulfur in civil engineering applications. Large volumes of materials are required for construction. The amount of sulfur which is available may be compared with the consumption of some of the principal construction materials (Table I). In Canada the annual production of sulfur is already a sizeable fraction of the yearly consumption of some of these materials. For example the annual sulfur production is about half that of raw steel and about three quarters that of portland cement. Elsewhere sulfur production is much smaller than that of presently used construction materials, but there are indications that sulfur production will be increasingly important. 

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