616 CEMENTS, LIMES, AND PIASTERS. 



then boiled for twenty-four hours, be kept for five days in water, and 

 show 350 Ibs. tensile strength. 



Department of Bridges, New York City, 1901. 



(106) That all cement used on this work must be the best quality 

 of imported or American Portland cement, manufactured by works 

 of established reputation for furnishing a high-grade and uniform product. 

 Cement must show a chemical analysis satisfactory to the engineer. 



(107) That briquettes of neat cement exposed to air for twenty- 

 Jour hours and then immersed in water for six days must have a tensile 

 strength of at least 400 Ibs. per square inch. 



(108) That briquettes of mortar mixed in proportion of one part 

 of cement to two and one half parts of dry sand, by weight, exposed 

 to the air for twenty-four hours and then immersed in water for six 

 days, must have a tensile strength of not less than 180 Ibs. per square 

 inch. 



(109) That cement mast be ground so fine that 90 per cent of it 

 will pass through a sieve of 10,000 meshes per square inch. 



(110) That pats of neat cement set in the air and then immersed 

 in boiling water for twenty-four hours must show no checks or cracks. 



(111) That cement must be sufficiently fresh to have lost no strength 

 from age, but it must not be so fresh as to be "hot" and quick-setting. 

 Neat cement at temperature of 70 F. must not take an initial set in 

 less than thirty minutes, nor its final set in less than one hour. 



(112) That the contractor must provide adequate storage and enough 

 cement ahead to enable seven-day tests to be made before cement has 

 to be used. 



(113) That the contractor must furnish every reasonable facility 

 to the inspectors for drawing samples of cement, and not less than ten 

 days (holidays and Sundays excluded) must elapse between time of 

 drawing the samples and using the cement. 



(114) That cement must at all times be protected from dampness, 

 air-currents, or other source of injury. 



(115) That the laboratory tests given above are not final. Should 

 the engineer at any time deem any lot of cement damaged or question- 

 able in any respect, the same shall be rejected, although it may pre- 

 viously have met other tests. 



(116) That cement must be delivered on the work in barrels of 

 375 Ibs. net weight, or in sacks of 94 Ibs. net weight. 



