SPECIFICATIONS FOR PORTLAND CEMENT. 625 



thin pats on glass plates shall not crack, scale, or warp under the fol- 

 lowing treatment: Three pats will be made and allowed to harden in 

 moist air at from 60 to 70 F. ; one of these will be placed in fresh water 

 for twenty-eight days, another will be placed in water which will be 

 raised to the boiling-point for six hours and then allowed to cool, and 

 the third is to be kept in the air of the prevailing outdoor temperature. 



British Standard Specifications.* 



Quality and preparation. (1) The cement is to be prepared by 

 intimately mixing together calcareous and argillaceous materials, burn- 

 ing them at a clinkering temperature and grinding the resulting clinker. 

 No addition of any material is to be made after burning, except when 

 desired by the manufacturer, and if not prohibited in writing by the 

 consumer, in which case calcium sulphate or water may be used. The 

 cement, if watered, shall contain not more than 2 per cent of water, 

 whether that water has been added or has been naturally absorbed from 

 the air. If calcium sulphate is used, not more than 2 per cent calcu- 

 lated as anhydrous calcium sulphate of the weight of the cement shall 

 be added. 



Sampling and preparation for testing and analysis. (2) As soon 

 as the cement has been bulked at the maker's works, f or on the works 

 in connection with which the material is to be used, at the consumer's 

 option, samples for testing are to be taken from each parcel, each sample 

 consisting of cement from at least twelve different positions in the same 

 heap, so distributed as to insure, as far as is practicable, a fair average 

 sample of the whole parcel, all to be mixed together and the sample 

 for testing to be taken therefrom. 



(3) Before gauging the tests, the sample so obtained is to be spread 

 out for a depth of 3 inches for twenty-four hours, in a temperature of 

 58 to 64 F. 



(4) In all cases where consignments are of 100 tons and upwards 

 samples selected as above from each consignment, either at the maker's 

 works or after delivery at the works where the cement is to be used, 

 are to be sent for expert testing and for chemical analysis. In no 

 case is cement so tested and analyzed to be accepted or used unless 



* British standard specifications for Portland cement. Engineering News, 

 vol. 53, pp. 227-228. March 2, 1905. 



t Should the consumer desire to stipulate for any special quantity, the size of the 

 heap should be stated. 



