SPECIFICATIONS FOR PORTLAND CEMENT. 



13. Time of Setting. It shall not develop initial set in less than ten minutes; and shall not 

 develop hard set in less than thirty minutes, or in more than three hours. 



i j. Tensile Strength. The minimum requirements for tensile strength for briquettes one 

 s(|ti.tre inch in cross section shall be as follows, and the cement shall show no retrogression in 

 strength within the periods specified : 



Age. Neat Cement. Strength. 

 24 hours in moist air 75 lb. 



7 days (l day in moist air, 6 days in water) 150 " 



28 days ( I " ' 27 ) 250" 



One Part Cement, Three Parts Standard Ottawa Sand. 



7 days (i day in moist air, 6 days in water) 50 lb. 



28 days (i ' 27 ) 125" 



15. Constancy of Volume. Pats of neat cement about three inches in diameter, one- half 

 inch thick at center, tapering to a thin edge, shall be kept in moist air for a period of twenty-four 

 hours. 



(a) A pat is then kept in air at normal temperature. 



(b) Another is kept in water maintained as near 70 F. as practicable. 



16. These pats are observed at intervals for at least 28 days, and, to satisfactorily pass the 

 tests, shall remain firm and hard and show no signs of distortion, checking, cracking, or disinte- 

 grating. 



PORTLAND CEMENT. 



17. Definition. This term is applied to the finely pulverized product resulting from the 

 calcination to incipient fusion of an intimate mixture of properly proportioned argillaceous and 

 calcareous materials, and to which no addition greater than 3 per cent has been made subsequent 

 to calcination. 



18. Specific Gravity. The specific gravity of cement shall not be less than 3.10. Should the 

 test of cement as received fall betow this requirement, a second test may be made upon a sample 

 ignited at a low red heat. The loss in weight of the ignited cement shall not exceed 4 per cent. 



19. Fineness. It shall leave by weight a residue of not more than 8 per cent on the No. 100, 

 and not more than 25 per cent on the No. 200 sieve. 



20. Time of Setting. It shall not develop initial set in less than thirty minutes; and must 

 develop hard set in not less than one hour, nor more than ten hours. 



21. Tensile Strength. The minimum requirements for tensile strength for briquettes one 

 square inch in cross section shall be as follows, and the cement shall show no retrogression in 

 strength within the periods specified: 



Age. Neat Cement. Strength. 



24 hours in moist air 175 lb. 



7 days ( I day in moist air, 6 days in water) 500 " 



28 days (i 27 ) 600" 



One Part Cement, Three Parts Standard Ottawa Sand. 



7 days (i day in moist air, 6 days in water) 200 lb. 



28 days ( I 27 '" ) 275" 



22. Constancy of Volume. Pats of neat cement about three inches in diameter, one-half 

 inch thick at the center, and tapering to a thin edge, shall be kept in moist air for a period of twenty- 

 four hours. 



(a) A pat is then kept in air at normal temperature and observed at intervals for at least 28 

 days. 



(b) Another pat is kept in water maintained as near 70 F. as practicable, and observed at 

 intervals for at least 28 days. 



(c)^ A third pat is exposed in any convenient way in an atmosphere of steam, above boiling 

 water, in a loosely closed vessel for five hours. 



23. These pats, to satisfactorily pass the requirements, shall remain firm and hard, and show 

 no signs of distortion, checking, cracking, or disintegrating. 



24. Sulphuric Acid and Magnesia. The cement shall not contain more than 1.75 per cent 

 of anhydrous sulphuric acid (SOj), nor more than 4 per cent of magnesia (MgO). 



