304 



CEMENTS, LIMES, AND PLASTERS. 



TABLE 145. 

 PRODUCTION OF PORTLAND CEMENT FROM VARIOUS MATERIALS. 



* Including also the product from alkali waste and clay 

 t Including also the product from slag and limestone. 



from 1898, when they produced less than one tenth of the total output, 

 to 1903, when they produced almost three tenths. The soft chalky 

 limestones show little increase and are still unimportant producers, 

 though the writer believes that they offer brilliant possibilities. 



Valuation of Deposits of Cement Materials. 



Determining the possible value for Portland-cement manufacture 

 of a deposit of raw material is a complex problem, depending upon a 

 number of distinct factors, all of which must be given due consideration. 

 The more important of these factors are: 



1. Chemical composition of the material. 



2. Physical character of the material. 



3. Amount of material available. 



4. Location of the deposit with respect to transportation routes. 



5. Location of the deposit with respect to fuel supplies. 



6. Location of the deposit with respect to markets. 

 Ignorance of the respective importance of these factors frequently 



leads to an overestimate of the value of a deposit of raw material. Their 

 effects may be briefly stated as follows: 



1. Chemical composition. The raw material must be of correct 

 chemical composition for use as a cement material. This implies that 

 the material, if a limestone, must contain as small a percentage as possi- 

 ble of magnesium carbonate. Under present conditions 5 or 6 per cent 

 is the maximum permissible. Free silica in the form of chert, flint 



