CHAPTER 5. 



ECONOMIC CONSIDERATIONS AND METHODS OF 

 MANUFACTURE. 



Determining the possible value for Portland cement manu- 

 facture of a. deposit of raw material is a complex problem, de- 

 pending upon ai number of distinct factors, all of which must 

 be given due consideration. The more important of these fac- 

 tors are : 



(i.) Chemical composition od: the material. 



(2.) Physical character of the material. 



(3.) Amount oi 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. 

 The natural raw materials used at present in Portland cement 



manufacture are obtained by one of three methods, (a) quar- 

 rying; (b) mining, and (c) dredging. When the cement 

 manufacturer is given an opportunity to choose between these 

 different methods of excavation, his choice will depend partly 

 on the physical character of the material to be excavated and 

 partly oin the topographical and geological conditions. Usually, 

 however, there is no opportunity for a choice of methods, for 

 in any given- case one of the methods will be so evidently the 

 only possible mode of handling the material a,s to leave no room 

 for other considerations. 



The three different methods of excavation will first be briefly 

 considered, after which the cost of raw materials at the mill will 

 be discussed. 



Quarrying. In the following pages the term "quarrying" 

 will be used to cotver all methods of obtaining raw materials 

 from open excavations, quarries, cuts or pits whether the 

 material excavated be a limestone, a shale or a clay. Quarry- 

 ing is the most natural and common method of excavating the 



