

I B] l.U 

 European cements 



BllAND 



. 



i 



... 

 



* RIl.il 



Boulogne ! 



Si". 





41,0, 



6.91 



7 





.'3 



If .4 



C* ' 



»1 41 



84.69 



KgO 



1.44 



i 84 

 1.01 



1 .04 



so, 



1 89 



1.47 

 1.07 



1 -7 

 1 56 



.7 

 .75 



AUTHORITY 



B. G. B. 



Curullot 



Manufacture of Portland cement 

 Xh, usually 1'.. Unwed are preparation of the raw mate- 



rials, mixing, burning, grinding and boltii 



In Portland cement manufacture there are two general meth- 

 preparation, the aim of each being to mix thoroughly the 

 raw materials. These methods are known as wet and dry nieth- 

 In the wet method proper the materials are mixed by 

 bem into a thin paste with water, after which they are 

 dried before burning. In the dry method only enough water is 

 used to permit forming the materials into bricks, so that they 

 can be charged into the kiln. A modification of the dry method 

 consists in grinding the material dry and charging it in this man- 

 ner into the rotary furnace, or mixing only enough water to 

 make it ball. 



Wet process. The raw materials best adapted to this method 

 are soft chalk and plastic clay, which on account of their condi- 

 tion can be easily mixed with water. The material has sometimes 

 to be reduced to a powder by means of crushers, but this is not 

 ah'. . and the mixing is done in water. It is the 



custom at some works to give the material a preliminary mixing 

 by spreading it in alternating layers of chalk and clay on the 

 floor, and, when it is removed to the washing mill, digging into 

 it vertically. 



ash mills in which the mixing is done consist of several 

 different forms, but they are essentially cylindrie tanks, some- 



