The Manufacture of Hydraulic Cements

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Geological Survey of Ohio, 1904 - Cement - 391 pages
 

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Page 370 - Significance. — It is generally accepted that the coarser particles in cement are practically inert, and it is only the extremely fine powder that possesses adhesive or cementing qualities. The more finely cement is pulverized, all other conditions being the same, the more sand it will carry and produce a mortar of a given strength.
Page 375 - The sand and cement should be thoroughly mixed dry. The mixing should be done on some non-absorbing surface, preferably plate glass. If the mixing must be done on an absorbing surface it should be thoroughly dampened prior to use.
Page 377 - Test pieces should be broken as soon as they are removed from the water. Care should be observed in centering the briquettes in the testing machine, as cross-strains, produced by improper centering, tend to lower the breaking strength. The load should not be applied too suddenly, as it may produce vibration, the shock from which often breaks the briquette before the ultimate strength is reached.
Page 131 - NH4OH boiled, and the second precipitate collected and washed on the same filter used in the first instance. The filter paper, with th.e precipitate, is then placed in a weighed platinum crucible, the paper burned off and the precipitate ignited and finally blasted...
Page 376 - A moist closet consists of a soapstone or slate box, or a metallined wooden box: the metal lining being covered with felt and this felt kept wet. The bottom of the box is so constructed as to hold water, and the sides are provided with cleats for holding glass shelves on which to place the briquettes. Care should be taken to keep the air in the c'.oset uniformly moist.
Page 374 - The determination of the time of setting is only approximate, being materially affected by the temperature of the mixing water, the temperature and humidity of the air during the test, the percentage of water used, and the amount of molding the paste receives.
Page 378 - ... tend to lower the breaking strength. The load should not be applied too suddenly, as it may produce vibration, the shock from which often breaks the briquette before the ultimate strength is reached. Care must be taken that the clips and the sides of the briquette be clean and free from grains of sand or dirt, which would prevent a good bearing. The load should be applied at the rate of 600 Ibs. per minute. The average of the briquettes of each sample tested should be taken as the test, excluding...
Page 369 - The specific gravity of cement is lowered by underburning. adulteration and hydration, but the adulteration must be in considerable quantity to affect the results appreciably. 9. Inasmuch as the differences in specific gravity are usually very small, great care must be exercised in making the determination. 10.
Page 370 - ... introduced, and the level of the liquid rises to some division of the graduated neck. This reading plus 20 cu. cm. is the volume displaced by 64 gr. of the powder.
Page xiii - THE SURVEY IN ITS RELATIONS TO' THE PUBLIC. The usefulness of the Survey is not limited to the preparation of formal reports on important topics. There is a constant and insistent desire on the part of the people to use it as a technical bureau for free advice in all matters affecting the geology or mineral industries of the State. A very considerable correspondence comes in, increasing rather than decreasing in amount, and asking specific and particular questions on points in local geology.

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