SLAG CEMENT: LIME, MIXING AND GRINDING. 657 



Example. Assume that the two raw materials have the following 

 composition : 



Silica (Si0 2 ) S "" 



Alumina (A1 2 O 3 ) 12 . Q 12 



iron oxide (FeO, Fe 2 O 3 ) 0.6 0.4 



Lime (CaO) 48.1 94*0 



Magnesia (MgO) 2.3 1.2 



Operation 1. Slag. 



Silica X2. 8 = 32. 2X2. 8= 90.16 



Alumina X 1.1 =12.0X1.1 = 13.20 



Iron oxide X0.7= 0.6X0.7= 0.42 



103.78 



Lime Xl. 0=48. 1X1.0= 48.1 



Magnesia Xl.4= 2.3X1.4= 3.22 



103.78-51. 

 Operation 2. Lime. 



Silica X2.8= 1.8X2.8= 5.04 



Alumina Xl.l= 1.2X1.1= 1.32 

 Iron oxide X0.7= 0.4X0.7= 0.28 



6.64 



Lime XI. 0=94. 0X1 .0= 94.00 



Magnesia Xl.4= 1.2X1.4= 1.68 



95.68 

 95.68-6.64 = n = 89.04 



Operation 3. 



100 m 100X52,46 5246 f 34. 6 = parts unslaked quicklime for 

 I. In = 1.7X89.04 = 151.4 = \ 100 parts dry slag. 



Pulverizing and mixing. The greatest differences in practice exist 

 in the processes for grinding and mixing the slag and lime. The state- 

 ment has been made in several publications that the differences in 

 hardness between dry granulated slag and slaked lime is so great that 

 it is impracticable to pulverize them together in a continuously operated 

 mill. A number of plants, therefore, have installed small discontinuous 

 mills, each of which is charged, locked, operated for a sufficient time to 

 pulverize both constituents of the mixture, and discharged. The dis- 

 advantages of this intermittent system are obvious and it seems especially 

 unfitted for American conditions. The statement that no continu- 

 ously operated mill was able to handle the mixture seemed inherently 



