620 



CEMENTS, LIMES, AND PLASTERS. 



U. S. Reclamation Service, 1904. 



1. Definition. The cement shall be high-grade Portland cement. 

 By the term Portland cement is to be understood the material obtained 

 by finely pulverized clinker produced by burning to semi-fusion an inti- 

 mate mixture of finely ground calcareous and argillaceous materials. 



2. Composition. It must be of normal composition, in which the 

 proportion of the sum of calcium oxide and alkalies to the sum of the 

 silica, alumina, and ferric oxide must not be less than 1.7 to 1 nor more 

 than 2.2 to 1. It shall not contain over 3 per cent of magnesia nor 2 

 per cent of sulphate of lime. But in certain cases where such amounts 

 of these substances are objectionable the engineer in charge may specify 

 lower percentages. Its freedom from uncombined lime shall be deter- 

 mined as in article 12. The question of adulteration may be determined 

 either by chemical analyses or by inspection of the process at the factory. 



3. Bids. Bids will be received only from manufacturers or their 

 authorized agents, and the name of the brand offered shall in all cases 

 be stated. 



4. Weight per barrel or sack. The average weight per barrel shall 

 not be less than 375 Ibs. net. Four sacks shall contain 1 barrel of cement. 

 If the weight as determined by test weighings is found to be below 

 375 pounds per barrel, the contractor may be required to supply, free 

 of cost to the United States, an additional amount of cement equal 

 to the shortage. 



5. Barrels; damaged cement. If the cement is delivered in barrels, 

 the barrels shall be strong and lined with paper, and the cement shall 

 be free from lumps. Any package that is broken or that contains dam- 

 aged cement may be rejected by the United States agent in local charge. 



6. Sampling. Samples of cement are to be taken from the barrels 

 or sacks with a sampling-tube in such manner as to secure fair average 

 of the packages. They are to be taken from every tenth barrel or for- 

 tieth sack and numbered, and the packages from which they are taken 

 to be sealed and corresponding numbers attached for future identifi- 

 cation. The quantities taken are to be kept separate and tested 

 separately. Where the results of tests indicate variation in the quality 

 of the cement, additional barrels or sacks will be sampled and tested. 



7. Aeration and testing. No cement shall be shipped until at least 

 sixty days after its manufacture, except that in case of an emergency, 

 and with the approval of the engineer in charge, a shorter time may 

 be allowed, but if the cement shows indications of unsoundness, a longer 



