UME AND CEMENT INDUSTEIES 737 



Portland cements, be used, in addition to trials of the neat cement. 

 The qualities used in the mixture should be determined by weight. 



The tests should be applied to the cements as offered for sale. 

 If satisfactory results are obtained with a full dose of sand, the 

 trials need go no further. If not, the coarser particles should 

 first be excluded by using a no. 100 sieve in order to determine 

 approximately, the grade the cement would take if ground fine; 

 for fineness is always attainable, while inherent merit may not be. 



The following table, showing the average minimum and maxi- 

 mum tensile strength per square inch which good cements have 

 attained when tested under the conditions specified elsewhere in 

 the report, has been prepared by the committee. Within the 

 limits given in the following table the value of a cement varies 

 closely with the tensile strength when tested with the full dose 

 of sand. 



American natural cement, neat: 



One day; one hour, or until set, in air, the rest of the 24 hours 

 in water, from 40 to 80 pounds. 



One week; one day in air, six days in water, from 60 pounds 

 to 100. 



One month (28 days); one day in air, 27 days in water, from 

 100 pounds to 150 pounds. 



One year; one day in air, the remainder in water, from 300 

 pounds to 400 pounds. 



American and foreign Portland cements, neat: 



One day; one hour, or until set, in air, the rest of the 24 hours 

 in water, from 100 to 140 pounds. 



One week; one day in air, six days in water, from 250 to 550 

 pounds. 



One month (28 days); one day in air, 27 days in water, from 

 350 to 700 pounds. 



One year; one day in air, the remainder in water, from 450 

 to 800. 



American natural cements, one part of cement to one part of sand: 

 One week; one day in air, six days in water, from 30 pounds 



to 50. 



One month (28 days); one day in air, 27 days in water, from 



50 to 80 pounds. 



One year;, one day in air, the remainder in water, from 200 



to 300. 



