Portland cement processing

Portland cement process. Sand is mixed with pordand cement (10% of sand weight) and water (5% of sand weight). Molds are air dried for 24h and may then be dried out more rapidly. 

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. 

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. 

Hydraulic cements. These cements are formed from two constituents one of which is water. Setting comprises a hydration and precipitation process. Into this category fall Portland cement and plaster of Paris. 

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. 

V. R. Negomedzyanov, V. P. Bortsov, V. S. Denisov, V. V. Slepov, and S. S. Volkova. Plugging composition for use in oil and gas extraction industry—contains Portland cement and aluminium-containing additive in form of slag dust waste from aluminium production process. Patent RU 2029067-C, 1995. 

Improved Materials Processing and Recycling Techniques that Reduce Energy Consumption and GHG Production (e.g., reduction of Portland cement use by substitution of industrial waste products such as fly ash, which has several side-benefits). 

Calcium cyanamid process, for ammonia synthesis, 11 114, 115 Calcium cyanide, 8 194-197 Calcium cyanide diammoniate, 8 195 Calcium dichromate, molecular formula, properties, and uses, 6 561t 5-Calcium disilicate monosulfate, phase in Portland cement clinker, 5 472t 5-Calcium disilicate monocarbonate, phase in Portland cement clinker, 5 472t Calcium disilicide, 4 530 8-Calcium disodium trialuminate, phase in Portland cement clinker, 5 472t Calcium doping, 23 842-844 Calcium P-alumina, 2 406t Calcium ethylenediaminetetraacetate, 7 596t... 

See also Iron entries hydration, 5 477-478 in Portland cement, 5 467 in Portland cement clinker, 5 473t classification of, 11 55-58 crystal chemistry of, 11 59-71 defined, 11 55 energy losses in, 11 64-66 physical properties of, 11 59-71 processing of, 11 71-75 properties of spinel and M-type,... 

Gypsum, 4 582-601 5 467, 785t 23 576 forms and composition, 4 583t hardness in various scales, 7 3t in Portland cement, 5 467 in Portland cement hydration, 5 477t thermal reduction of, 23 577 thermodynamics and kinetics of formation- decomposition, 4 586-588 Gypsum board, 4 600-601 Gypsum processes, obtaining sulfur from, 23 576-577... 

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... 

More than 2 billion tires are disposed of annually in the USA. Before being recycled and/or reused, scrap tires or crumb rubber are first processed to remove any loose steel and fibers and then finely ground. Research has been conducted on the use of crumb rubber in highway construction such as in lightweight fill, subgrade insulation, and channel slope protection, as well as an additive to Portland cement concrete pavement [66,67,259,260]. 

Chemical hxation is another possible process to handle drilling fluids. A typical process uses a mixture of potassium or sodium silicate with portland cement to turn a drilling fluid into a soil-like solid that may be left in place, used as a landhll, or even used as a construction material [13]. 

The replacement of Portland cement by fly ash class F (ASTM C 618) has been found to reduce the rate of slump loss in a prolonged mixed concrete, and the extent of the reduction is greater with increased cement replacement (Fig. 7.37). Fly ash also was found to be beneficial in reducing slump loss in concretes with conventional water-reducing and retarding admixtures [95], The effect of fly ash on reducing slump loss can be attributed to chemical and physical factors. It was found that the surface of fly ash particles may be partly covered with a vapor-deposited alkali sulfate that is readily soluble [103, 104], Thus the early hydration process of Portland cement is effected because sulfate ions have a retarding effect on the formation of the aluminates. Indeed, fly ash was found to be a more effective retarder than an... 

The air-bubble generating and stabilizing process requires a minimum paste consistency. Silica fume particles are smaller than those of Portland cement and addition of silica fume therefore increases the fine fraction of the particles. The higher fraction of smaller particles then increases the surface area causing a greater binding of the water in the mix. This removes the water required for the bubble-generating process. 

The HAZCON solidification process is an ex situ technology for the immobilization of metals and inorganic hazardous wastes in wet or dry soil and sludges. The technology is a cement-based process in which the contaminated material is mixed with pozzolanic materials such as Portland cement, a patented additive called Chloranan, and water. The process is capable of treating solids, sludges, semisolids, or liquids. The mixture hardens into a cohesive mass that immobilizes heavy metals. 

Ash from pulverized coal combustion is a strategic material that has many critical applications from a source of aggregate to the most important source of pozzolan for addition to Portland cement concrete. Environmental control measures on the emissions of coal combustion have resulted in a loss of quality for these materials. In response we have seen the advent of beneficiation processes applying both proven and new technologies to produce high-quality consistent products from these materials. Currently we estimate that about one-fifth of all ash products marketed are processed through some form of beneficiation method. We expect that the demand for quality and consistency will continue and the relative amount of process ash products will increase in the future. 

Upon addition of water, the hydration reactions initiate, and the hydraulic cement begins to gain strength. This process is very complex, but the strengthening effect is due basically to the formation of three types of hydration products colloidal products such as C2S xH20, which have a size of less than 0.1 p.m submicrocrystalline products such as Ca(OH)2, Al +, Fe +, and S04 phases with sizes from 0.1 to 1 tim and microcrystalline products, primarily of Ca(OH)2, with particle sizes greater than 1 p,m. The most common type of hydraulic cement, Portland cement, usually contains mostly colloidal products. 

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