SPECIFICATIONS FOR PORTLAND CEMENT. 615 



cement-testing office in Albany, and will be subjected to the following 

 tests, and any cement failing on either of them will be rejected, though 

 the further right is reserved to reject any and all cements the qualities 

 of which have not become well known through prior use in State work 

 or elsewhere. 



Portland cement must be of the best quality and of such fineness 

 that 95 per cent of the cement will pass through a sieve of 2500 meshes 

 to the square inch, and 90 per cent through a sieve of 10,000 meshes 

 per square inch. Portland cement when mixed neat and exposed one 

 day in air and six days in water shall withstand a tensile strain of 

 not less than 400 Ibs. to the square inch, and when mixed in the ratio of 

 3 Ibs. clean, sharp sand to 1 Ib. of cement and exposed one day in air 

 and six days in water, it shall withstand a tensile strain of not less than* 

 125 Ibs. per square inch. 



Rapid-transit Subway, New York City, 1900-1901. 



Fineness. Ninety-eight per cent shall pass a No. 50 sieve and 90 

 per cent a No. 100 sieve. 



Tensile strength. At the end of one day in water after hard set, 

 150 Ibs. neat; at the end of seven days, one day in air, six days in 

 water, 400 Ibs. neat; at the end of twenty-eight days, one day in air, 

 twenty-seven days in water, 500 Ibs. neat. When mixed 2 to 1 with 

 quartz sand : At the end of seven days, one day in air, six days in water, 

 200 Ibs. ; at the end of twenty-eight days, one day in air, twenty-seven 

 days in water, 300 Ibs. 



Chemical analyses. Chemical analyses will be made from time 

 to time, and cement furnished must show a reasonably uniform com- 

 position. 



Soundness. Tests for checking and cracking and for color will be 

 made by molding, on plates of glass, cakes of neat cement about 3 inches 

 in diameter, inch thick in the center, and with very thin edges. One 

 of these cakes when set per ectly hard shall be put in water and examined 

 for distortion or cracks, and one shall be kept in air and examined for 

 color, distortion, and cracks. Another cake shall be allowed to set 

 in steam for twenty-four hours and then put in boiling water for 

 twenty-four hours. Another cake shall be allowed to set hard in dry 

 air for twenty-four hours and then put in boiling water for twenty-four 

 hours. Such cakes should at the end of the tests still adhere to the 

 glass and show neither cracks nor distortion. A briquette, in like man- 

 ner, should be allowed to set hard in dry air for twenty-four hours, 



