SPECIFICATIONS FOR NATURAL CEMENTS. 281 



ders will deliver a sample barrel for test before the opening of the bids. 

 Any cement showing by sample higher tests than those given must 

 maintain the average so shown in subsequent deliveries. 



(14) A cement may be rejected which fails to meet any of the above 

 requirements. An agent of the contractor may be present at the making 

 of the tests, or, in case of the failure of any of them, they may be 

 repeated in his presence. If the contractor so desires, the engineer 

 officer may, if he deems it to the interest of the United States, have 

 any or all of the tests made or repeated at some recognized standard 

 testing laboratory in the manner above specified. All expenses of 

 such tests shall be paid by the contractor, and all such tests shall be 

 made on samples furnished by the engineer officer from cement actu- 

 ally delivered to him. 



American Society for Testing Materials. 1904. 



11. Definition. This term shall be applied to the finely pulverized 

 product resulting from the calcination of an argillaceous limestone at 

 a temperature only sufficient to drive off the carbonic-acid gas. 



12. Specific gravity. The specific gravity of the cement thoroughly 

 dried at 100 C. shall be not less than 2.8. 



13. Fineness. It shall leave by weight a residue of not more than 

 10 per cent on the No. 100 and 30 per cent on the No. 200 sieve. 



14. Time of setting. It shall develop initial set in not less than 

 ten minutes, and hard set in not less than thirty minutes, nor more 

 than three hours. 



15. Tensile strength. The minimum requirements for tensile 

 strength for briquettes 1 inch square in cross-section shall be within 

 the following limits, and shall show no retrogression in strength within 

 the periods specified. 



NEAT CEMENT. 



Age. Strength. 



24 hours in moist air 50-100 Ibs. 



7 days (1 day in moist air, 6 days in water) . . 100-200 ' 

 28 days (1 day in moist air, 27 days in water) . 200-300 " 



1 PART CEMENT, 3 PARTS STANDARD SAND. 



7 days (1 day in moist air, 6 days in water) . . 25- 75 tc 

 28 days (1 day in moist air, 27 days in water) . 75-150 " 



16. Constancy of volume. Pats of neat cement about 3 inches in 

 diameter, \ inch thick at center, tapering to a thin edge, shall be kept 

 in moist air for a period of twenty-four hours. 



