Table 26. Cold And Hot Tests On Samples Of One Brand Of Portland Cement

Behavior Of Pats Made July 2, 1894

No. 1 in vapor, when held 1/4 # wire.

No. 2 in vapor, when held 1# wire both above immersed in water 80° C. after three hours in vapor.

No. 3 in tank, when held 1# wire.

No. 4 in tank ; two hours after held 1# wire.

Cement: A, No. 1 off glass in two days; No. 2 warped some in two days. " A, No. 3 O.K. after twenty-one days; off glass and warped in fifty-two days.

" A, No. 4 loose on glass in twenty-one days; off glass and warped in fifty-two days.

" B, No. 1 off glass and warped some in two days; No. 2 entirely disintegrated in two days; No. 3 loose on glass in twenty-one days; off glass and warped in fifty-two days; No. 4 loose on glass in twenty-one days; off glass and warped in fifty-two days.

134. In Table 26 are given the results of tests by the author, on samples of a single brand of Portland cement. The portion marked "A" had been spread out in open air for seventy-seven days in a thin layer. The portion marked "B" was taken directly from the barrel July 2d, and B' was taken from the same barrel April 16th. Samples B and B' are not identical, because the cement had undergone some change, though stored in the barrel. Each result is the mean of five briquets.

In the short time cold tests there was nothing to indicate that the cement directly from the barrel was not good, except the very small evidence in the fact that pat No. 3 was loose on glass plate after twenty-one days. In fact, the cold water briquet tests at seven and twenty-eight days unmistakably declare in favor of the sample B. On the other hand, how sharply did the hot tests bring out the defects, two days in hot water being sufficient to entirely disintegrate one of the pats. Although sample B' showed a considerable tensile strength at seven months with two parts sand, yet the pats of neat cement failed, even in cold water, after two months, altogether too late a date to be of any value in preventing the use of the cement.

135. In a paper read before the American Society for Testing Materials, July, 19031 Mr. W. P. Taylor of the City Testing Laboratory, Philadelphia, gives some very interesting data concerning the behavior of cements that failed to pass the boiling test. The method employed was to make cakes of cement in the form of a small egg, keep them in moist air for twenty-four hours, then place them in cold water which is gradually raised to the boiling point and maintained at that temperature for three hours. The results cited show that some unsound cemerits may be much improved by sifting out the coarse particles, and that a cement failing in the boiling test when fresh may pass it satisfactorily after four or five weeks.

1 Proceedings Amer. Soc. for Testing Materials, 1903.

Examination of the results showed that 96 per cent, of a large number of specimens which did not pass the hot water test failed within three hours, and 99 per cent, in four hours. This fixes a practical limit to the time necessary to continue the test. Some very valuable tests are cited to show the ultimate failure in cold water of samples that failed in the hot tests. Ten cements which passed the cold water pat test of twenty-eight days' duration, but which failed in the boiling test above described, gave normal results in one-to-three mortars at twenty-eight days, showing a tensile strength of 217 to 252 pounds per square inch, but gave only 47 to 147 lbs. per square inch at four months.

Another valuable comparison is given by Mr. Taylor: A compilation of data, covering over a thousand tests on many varieties of cements, showed that "of those samples that failed in the boiling test but remained sound at twenty-eight days (in cold water), 3 per cent, of the normal pats showed checking or abnormal curvature in two months; 7 per cent, in three months; 10 per cent, in four months; 26 per cent, in six months and 48 per cent, in one year; and of these same samples, 37 per cent, showed a falling off in tensile strength in two months; 39 per cent, in three months; 52 per cent, in four months; 63 per cent, in six months and 71 per cent, in one year".

136. It may be of interest to introduce here some of the opinions that have been expressed concerning hot tests. M. Candlot1 says that cements of normal composition, the burning of which has not been carried to the point of vitrification, would be condemned by the hot test of neat cement, although mortars made with them show no signs of alteration in sea water, and, when preserved in air, give entirely satisfactory results. Referring to the tests of one-to-three mortar briquets in water at 80° C, he considers that "cements containing free lime give in hot water, lower resistances than in cold water; cements of good quality give resistances at least equal and nearly always greater in hot water than in cold. Cements well proportioned and homogeneous, but not having obtained the maximum burning, give satisfactory results with this test".

1 "Ciments et Chaux Hydrauliques," par M. Candlot, pp. 144—145.

In using the slit cylinders mentioned in § 130, M. H. Le Chatelier found 1 that the addition of 5 per cent, of lime could be detected by cold tests in a few hours, while 5 per cent, of magnesia could not be detected in twenty-eight days. The cement containing 5 per cent, lime disintegrated almost at once in hot water, while the sample to which 5 per cent, of magnesia had been added, swelled considerably in one day.

Mr. A. Marichal2 found that "the percentage of water entered in combination, after ten days in hot water, was the same as for six months in cold water, and that the strength of the cement was increasing with the amount of water entered in combination. It was discovered incidentally, that cement containing over 5 per cent, of magnesia, or 3 per cent, of uncom-bined lime, would not stand the boiling test".