618 CEMENTS, LIMES, AND PLASTERS. 



(6) Tests may be made of the fineness, specific gravity, soundness, 

 time of setting, and tensile strength of the cement. 



(7) Fineness. Ninety-two per cent of the cement must pass through 

 a sieve made of No. 40 wire, Stubbs gauge, having 10,000 openings 

 per square inch. 



(8) Specific gravity. The specific gravity of the cement, as deter- 

 mined from a sample which has been carefully dried, shall be between 

 3.10 and 3.25. 



(9) Soundness. To test the soundness of the cement, at least two 

 pats of neat cement mixed for five minutes with 20 per cent of water 

 by weight shall be made on glass, each pat about 3 inches in diameter 

 and inch thick at the center, tapering thence to a thin edge. The 

 pats are to be kept under a wet cloth until finally set, when one is to 

 be placed in fresh water for twenty-eight days. The second pat will 

 be placed in water which will be raised to the boiling-point for six hours, 

 then allowed to cool. Neither should show distortion or cracks. The 

 boiling test may or may not reject at the option of the engineer officer 

 in charge. 



(10) Time of setting. The cement shall not acquire its initial set 

 in less than forty-five minutes and must have acquired its final set in 

 ten hours. 



(The following paragraph will be substituted for the above in case 

 a quick-setting cement is desired: 



The cement shall not acquire its initial set in less than twenty nor 

 more than thirty minutes, and must have acquired its final set in not 

 less than forty-five minutes nor in more than two and one-half 

 hours.) 



The pats made to test the soundness may be used in determining 

 the time of setting. The cement is considered to have acquired its 

 initial set when the pat will bear, without being appreciably indented, 

 a wire T V inch in diameter loaded to weigh \ Ib. The final set has been 

 acquired when the pat will bear, without being appreciably indented, 

 a wire -^ inch in diameter loaded to weigh 1 Ib. 



(11) Tensile strength. Briquettes made of neat cement, after being 

 kept in air for twenty-four hours under a wet cloth and the balance 

 of the time in water, shall develop tensile strength per square inch as 

 follows : 



After seven days, 450 Ibs.; after twenty-eight days, 540 Ibs. 

 Briquettes made of 1 part cement and 3 parts standard sand, by 

 weight, shall develop tensile strength per square inch as follows: 

 After seven days, 140 Ibs.; after twenty-eight days, 220 Ibs. 



