American Cements

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Rogers & Manson, 1898 - 299 páginas
 

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Página 104 - One of these cakes, when hard enough, should be put in water and examined from day to day to see if it becomes contorted or if cracks show themselves at the edges, such contortions or cracks indicating that the cement is unfit for use at that time. In some cases the tendency to crack, if caused by the presence of too much unslaked lime, will disappear with age.
Página 40 - Now, all the pottery belonging to the mound-builders, age, which I have seen, is composed of alluvial clay and sand or a mixture of the former with pulverized fresh-water shells. A paste made of such a mixture...
Página 105 - If satisfactory results are obtained with a full dose of sand, the trials need go ' no further. If not, the coarser particles should first be excluded by using a No. 100 sieve, in order to determine approximately the grade the cement would take if ground fine; for fineness is always attainable, while inherent merit may not be.
Página 105 - ... off level; the molds in each instance, while being charged and manipulated, to be laid directly on glass, slate or some other non-absorbent material. The molding must be completed before incipient setting begins. As soon as the briquettes are hard enough to bear it, they should be taken from the molds and be kept covered with a damp cloth until they are immersed.
Página 10 - ... go to pieces, and those exposed to air and weather only are comparatively of inferior strength. By this memorable discovery Smeaton overset the prejudices of more than . two thousand years, adopted by all former writers, from Vitruvius in ancient Rome to Belidor in France and Semple in this country, who agreed in maintaining that the superiority of lime consisted in the hardness and whiteness of the stone, the former of which may or may not be accompanied by water-setting or powerful cementing...
Página 103 - The first tests of inexperienced, though intelligent and careful, persons, are usually very contradictory and inaccurate, and no amount of experience can eliminate the variations introduced by the personal equations of the most conscientious observers. Many things, apparently of minor importance, exert such a marked influence upon the results, that it is only by the greatest care in every particular, aided by experience and intelligence, that trustworthy tests can be made.
Página 100 - The cake used for setting test will be preserved, and when examined from day to day must be of uniform color, exhibiting no blotches or discolorations. 30. Fineness. — The cement must be evenly ground, and when tested with the following standard sieves, must pass at least the following percentages. No. 50 sieve, having 50 meshes per lineal inch, 98 per cent; No. 74 sieve, having 74 meshes per lineal inch, 94 per cent; No. 100 sieve, having 100 meshes...
Página 108 - ... every barrel delivered. Usually, where cement has a good reputation, and is used in large masses, such as concrete in heavy foundations or in the backing or hearting of thick walls, the testing of every fifth barrel seems to be sufficient; but in very important work, where the strength of each barrel may in a great measure determine the strength of that portion of the work where it is used, or in the thin walls of sewers, etc., etc., every barrel should be tested, one briquette being made from...
Página 109 - The material that seems likely to give the best results is the crushed quartz used in the manufacture of sand-paper. It is a commercial product, made in large quantities and of standard grades, and can be furnished of a fairly uniform quality. It is clean and sharp, and although the present price is somewhat excessive (3 cents per pound), it is believed that it can be furnished in quantity for about $5.00 per barrel of 300 Ibs.
Página 103 - It cannot be said that a new and untried cement will by the same tests be proved to be satisfactory; only a series of tests for a considerable period, and with a full dose of sand, will show the full value of any cement; and it would be safer to use a trustworthy brand without applying any tests whatever than to accept a new article which had been tested only as neat cement and for but one day only. The test for compressive strength is a very valuable one in point of fact, but the appliances for...

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