622 CEMENTS, LIMES, AND PLASTERS. 



half as much water as is used for neat briquettes. Six briquettes will 

 be made from each sample. 



15. Tensile strength. The neat briquettes prepared as specified 

 above shall stand a minimum tensile strain per square inch as follows : 



For one day in air and six days in water 450 Ibs. 



For one day in air and twenty-seven days in water. . . 550 ' ' 



The sand-mortar briquettes, prepared as specified above, shall stand 

 a minimum tensile strain per square inch as follows: 



After one day in air and six days in water 175 Ibs. 



After one day in air and twenty-seven days in water. . 225 " 



16. Requirements. The above are to be considered the minimum 

 requirements. The neat tests are to be considered of less value than 

 those of sand and cement. The twenty-eight-day tests must always 

 be higher than the seven-day tests. A cement may be rejected which 

 fails to meet any of the above requirements. 



Canadian Society of Civil Engineers.* 



The whole of the cement is to be well-burned pure Portland cement, 

 of the best quality, free from free lime, slag dust, or other foreign mate- 

 rial. 



(1) Fineness. The cement shall be ground so fine that the residue 

 on a sieve of 10,000 meshes to the square inch shall not exceed 10 per 

 cent of the whole by weight, and the whole of the cement shall pass 

 a sieve of 2500 meshes to the square inch. 



(2) Specific gravity. The specific gravity of the cement shall be 

 at least 3.09, and shall not exceed 3.25 for fresh cement, the term 

 "fresh" being understood to apply to such cements as are not more 

 than two months old. 



(3) Tests. The cement shall be subjected to the following tests: 

 (a) Blowing test. Mortar pats of neat cement thoroughly worked 



shall be troweled upon carefully cleaned 5-inch by 2^-inch ground- 

 glass plates. The pats shall be about \ inch thick in the center and 

 worked off to the sharp edges at the four sides. They shall be covered 

 with a damp cloth and allowed to remain in the air until set, after which 

 they shall be placed in vapor in a tank in which the water is heated 

 to a temperature of 130 F. After remaining in the vapor six hours, 



* Proposed Canadian standard specifications for Portland cement. Cement, 

 vol. 4, pp. 98-99. May, 1903. 



