194 
ANNUAL REPORT 
(5) All briquettes are to remain in the water until they are placed 
in the testing machine, except in the case of twenty-four-hour tests. 
(6) Neat twenty-four-hour tests shall not show less than 125 
pounds per square inch. Neat seven-day tests shall not show less 
than 400 pounds per square inch. Neat twenty-eight-day tests shall 
not show less than 500 pounds per square inch, and should show at 
least 10 per cent. increase above the seven-day test. 
J2. Sand Test.—Owing to insufficient data, the Committee is not 
prepared to specify a sand test. 
13. Specific Gravity.—The specific gravity, determined upon dried 
cement which has passed through a No. 100 sieve, shall not be less 
than 3.10 nor more than 3.30. The specific gravity can be conveniently 
and accurately determined by the use of Le Chatelier’s apparatus 
as recommended by the Committee on uniform tests of cements. 
14. Chemical. —Chemical analyses should show not more than 5 
per cent. of magnesia, nor more than 1.75 per cent. of sulphuric 
anhydride. 
15.  Uniformity.—lIf in the tests of any given brand of cement 
any sudden, irregular or wide variation from its normal action is 
found, it should be withheld from use until-more extended tests 
shall have demonstrated its reliability. 
NATURAL CEMENT. 
NOTE—Only those sections of the natural cement specifications 
which differ from those of the Portland cement are printed here. To make 
these specifications complete, supply the missing numbers from the preced- 
ing. 
1,  Definition,—Natural cement is a product formed of calcinated 
limestone containing clay and carbonate of magnesia reduced to a fine 
powcacer. 
3.  Weight.—One barrel shall contain not less than 300 pounds of 
cement. (West of the Allegheny Mountains this may be 265 pounds.) 
Three paper sacks or two jute sacks of cement shall be equivalent in 
weight to one barrel. 
8. Fineness—Not less than 80 per cent. of the cement tested 
shall pass through a No. 100 standard sieve. 
9. Set. .(1) Initial set shall not occur in less than twenty (20) 
minutes. 
(2) Final set shall not occur in less than forty-five (45) minutes 
nor more than four (4) hours. | 
(6) The amount of water required to make a paste of normal 
consistency varies with different cements, but will be found to 
be approximately 30 per cent. of the weight of the cement. It should 
have a temperature of 70 degrees Fahrenheit. 
JJ. Tensile Strength—(1) The briquette used in testing shall 
be formed in molds of the size and form now in customary use and 
recommended by the American Society of Engineers, the stress 
to be applied at a uniform rate of 400 pounds per minute until 
fractured. 
(6) Neat twenty-four-hour tests shall not show less than 60 
pounds per square inch. Neat seven-day tests shall not show less 
