The temperature to be userd in accelerated tests for soundness is a point which has received much attention and is still under discussion. In 1890 M. Deval described a series of experiments he had made, in which he employed a temperature of 80° C. While this is much more severe than the temperature used by Mr. Faija, it is still mild in comparison to some temperatures that have been advocated.

125. Mr. W. W. Maclay, who was probably the first engineer in this country to introduce a hot test requirement in specifications, gave the results of his experiments in a paper presented to the American Society of Civil Engineers in 1892. The method used "consists in molding six pats of pure cement and water, about one-half inch thick and about three inches in diameter, on thin glass plates, and of the same consistency as for the briquets for tensile strength." The treatment to which these pats are submitted is as follows:

1 "Portland Cement Testing," by H. Faija, Trans. A. S. C. E., Vol. xvii, p. 222.

No. 1, in steam (vapor) bath, temperature 195° to 200° F., as soon as made. No. 2, in same vapor bath when set hard (bear 1/24 inch wire weighing one pound). No. 3, ditto, after twice the length of time in air allowed the second pat. No. 4, ditto, after 24 hours.

No. 5, in water of temperature about 60° F. when set hard.

No. 6, kept in moist air at temperature of about 60° F.

"The first four pats are each kept in the steam bath three hours, then immersed in water of a temperature of about 200° Fahr. for twenty-one hours each, when they are taken out and examined. To pass this test perfectly, all four pats, after being twenty-one hours in hot water, should, upon examination, show no swelling, cracks, nor distortions, and should adhere to the glass plates. The latter requirement, while it obtains with some cements nearly free from uncombined lime, is not insisted upon; the cracking, swelling and distortion of the pats being much the more important features of this test. The cracking or swelling of No. 1 pat alone can generally be disregarded".