Congressional Serial Set, Ausgabe 4690

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U.S. Government Printing Office, 1904
Reports, Documents, and Journals of the U.S. Senate and House of Representatives.
 

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Seite 22 - By a Portland cement is meant the product obtained from the heating or calcining up to incipient fusion of intimate mixtures, either natural or artificial, of argillaceous with calcareous substances, the calcined product to contain at least 1.7 times as much of lime, by weight, as of the materials which give the lime its hydraulic properties, and to be finely pulverized after said calcination, and thereafter additions or substitutions for the purpose only of regulating certain properties of technical...
Seite 39 - ... 10 to 25 per cent, of the amount quarried is salable as slate. The remaining 75 to 90 per cent, is of no service to the slate miner. It is sent to the dump heap and is a continual source of trouble and expense.
Seite 332 - ... (2) Natural cements, after burning and grinding, are usually yellow to brown in color and light in weight, their specific gravity being about...
Seite 52 - rock emery" type, and reduced the clay to a fine powder, in which condition it was fed, after being weighed, to the mixer. The marl was weighed and sent directly to the mixer, no preliminary treatment being necessary. The average charge was about 25 per cent, clay and about 75 per cent. marl. The mixing was carried on in a mixing pan 12 feet in diameter, in which two large rolls, each about 5 feet in diameter, and i6-inch face, ground and mixed the materials thoroughly.
Seite 56 - A mixture which will give a cement carrying 59 per cent. of lime, for example, will require much less thorough burning than would a mixture designed to give a cement with 64 per cent. of lime. With equal lime percentages, the cement carrying high silica and low alumina and iron will require a higher temperature than if it were lower in silica and higher in alumina and iron. But, on the other hand, if the alumina and iron are carried too high, the clinker will ball up in the kiln, forming sticky and...
Seite 361 - it is attackable by weak acids and also by alkalies. It combines particularly with hydrated lime in setting, and gives rise to silicates and aluminates of lime identical with those which are formed, by entirely different reactions, during the setting of Portland cement. It is upon this property that the manufacture of slag cements, which assumes daily greater importance, is based.
Seite 44 - The hygroscopic or mechanically held water of clays can be driven off at a temperature of 212° F., while the chemically combined water is lost only at a low red heat. The total water, therefore, to be driven off from clays may range from 6 to 42 per cent., depending on the weather, the drainage of the clay pit, and the care taken in preventing unnecessary exposure to moisture of the excavated clay. The average total amount of moisture will probably be about 15 per cent. In dealing with shales...
Seite 56 - Portland cement mixtures are very slight if compared, for example, to the differences between various natural cement rocks. But even such slight differences as do exist exercise a very appreciable effect on the burning of the mixture. Other things being equal, any increase in the percentage of lime in the mixture will necessitate a higher temperature in order to- get an equally sound cement. A mixture which will give a cement carrying 59 per cent. of lime, for example, will require much less thorough...
Seite 55 - In dealing with a wet mixture, which may carry anywhere from 30 to 70 per cent of water, the results are more variable, though always worse than with dry materials. In working a 60-foot kiln on a wet material, the...
Seite 33 - This reestablishment in favor of the hard limestones is doubtless due, in great part, to recent improvements in grinding machinery, for the purer limestones are usually much harder than argillaceous limestones like the Lehigh district "cement rock," and it was very difficult to pulverize them finely and cheaply with the crushing appliances in use when the Portland cement industry was first started in America. A series of analyses of representative pure hard limestones, together with analyses of the...

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