Portland manufacture

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. 

The manufacture of Portland cement is very energy intensive. It has been identified by the Department of Commerce as one of the six most energy... 

Calcium Silicates. Cements aie hydiated at elevated tempeiatuies foi the commercial manufacture of concrete products. Using low pressure steam curing or hydrothermal treatment above 100°C at pressures above atmospheric, the products formed from calcium siUcates are often the same as the hydrates formed from their oxide constituents. Hence lime and siUca ate ftequendy used in various proportions with or without Portland cement in the manufacture of calcium siUcate hydrate products. Some of these compounds are Hsted in Table 6. 

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. 

ASTM C845 Type E-I (K) expansive cement manufactured ia the United States usually depends on aluminate and sulfate phases that result ia more ettriagite formation duriag hydration than ia normal Portland cements. Type K contains an anhydrous calcium sulfoaluminate, C A SI. This cement can be made either by iategraHy burning to produce the desired phase composition, or by intergrinding a special component with ordinary Portland cement clinkers and calcium sulfate. 

Oil well cements are manufactured similarly to ordinary Portland cements except that the goal is usually sluggish reactivity. Eor this reason, levels of C A, C S, and alkafl sulfates are kept low. Hydration-retarding additives are also employed. 

Portland cements are manufactured to comply with specifications estabUshed in each country (70). In the United States, several different specifications are used, including those of the American Society for Testing and Materials and American Association of State Highway and Transportation Officials (AASHTO). The ASTM aimuaHy pubhshes test methods and standards (24), which are estabhshed on a consensus basis by its members which include consumers and producers. 

Cement. Portland cement, a mixture of calcium siUcate and calcium aluminate minerals, is produduced by the calcination of argillaceous limestone or mixtures of limestone and clay (see Cement). Although other clays can be used, ka olin is preferred because of its alumina and siUca content and low level of impurities. It is especially desirable in the manufacture of white cement and other types requiring careful control of chemical composition. Air-floated ka olin, because of its low cost, is usually used. 

Ail Pollution Emission Factois for Portland Cement Manufacturing without Controls... 

Poljmrethane Foam Association (PFA), 272 Poljnjretliane Manufacturers Association (PMA), 272 POPCORN , sulfur, 108 Portland cement, 108 Portland stone, 109... 

The ASTM specifications provide for five types of Portland cements Types I, II, III, IV and V they are manufactured for use at atmospheric conditions [165]. The API Classes A, B and C correspond to ASTM Types I, II and III, respectively. The API Classes D, E, F, G, H and J are cements manufactured for use in deep wells and to be subject to a wide range of pressures and temperatures. These classes have no corresponding ASTM types. 

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. 

Figure 1.1 Methods of manufacturing plastic materials. After Titzschkau [9]. Reproduced by permission of Intertech Corporation, Portland, MN...

Spent foundry sand can be used as a good source of silica in manufacturing portland cement. Also, the clay fraction of foundry sand is an additional source of iron and aluminum oxides. According to the portland cement industry, spent foundry sand can be beneficially used in the manufacture of Portland cement, as sand possesses the following characteristics ... 

Surface bonding mortar or cement is mentioned in some building codes as an approved dampproofing treatment, but not as a waterproofing treatment. A number of manufacturers produce cements and mortars impregnated with fibrous glass or other fibers. Some of these may be chemically unstable in the alkaline environment of Portland cement. 

Uses. Manufacture of quicklime, Portland cement, and paints. United States Pharmacopeia (USP) grades are used in dentifrices, cosmetics, food, and pharmaceuticals such as antacids. 

Uses. The insoluble anhydrite is used in cement formulations and as a paper filler the soluble anhydrite is used as a drying agent the hemihydrate is used for wall plaster and wall-board gypsum is used in manufacture of plaster of paris and portland cement. 

The manufacture of Portland concrete consists of three basic steps—crushing, burning, and finish grinding. As noted earlier, Portland cement contains about 60% lime, 25% silicates, and 5% alumina with the remainder being iron oxides and gypsum. Most cement plants are located near limestone (CaCOs) quarries since this is the major source of lime. Lime may also come from oyster shells, chalk, and a type of clay called marl. The silicates and alumina are derived from clay, silicon sand, shale, and blast-furnace slag. 

Some of the most common stabilizing agents used in hazardous waste disposal are Portland cement, lime, fly ash, and cement kiln dust. Small quantities of hazardous wastes are disposed of by incineration, energy conversion, manufacture of fuels, or other practical applications. 

Hansen, W.C. (1956). The Role of Calcium Sulfate in the Manufacture of Portland Cement,... 

Another example of an important construction material in the Middle East is portland cement. For example, all-purpose Type I and sulfate-resisting Type V portland cements are manufactured in Saudi Arabia in three plants at Hofuf, Jeddah, and Riyadh. The cement production from the three plants totaled 1,790,000 tons in 1978 which is about a 38.5 percent rise over 1977. Portland cement is a basic construction material, and is primarily consumed by the construction industry. In Saudi Arabia cement does not seem to be encountering competition from any other building materials which are capable of endangering its present level of demand. 

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