200 DETAILED REPORT ON ALABAMA CLAYS. 



Analysis of Clay, W. J. BecJewith, Colbert Co. (No. X S.) 



Silica (total) 58.20 



Alumina 29.86 



Water 9 12 



Magnesia tr. 



Lime 20 



Ferric oxide 2 22 



Alkalies .....' tr! 



Moisture 1.18 



100.78 



Free silica 22.59 



Total fluxes 2.44 



Specific gravity 2.18 



THE UTILIZATION OF CLAY FOR PORTLAND 

 CEMENT. 



Aside from being used for the manufacture of clay pro- 

 ducts, there remains the possibility of using some of the 

 Alabama clays for the manufacture of Portland cement. 

 The three essential elements of this material are lime, 

 silica and alumina. The first of these is supplied by 

 limestone, marl or chalk, while the other two are contain- 

 ed in clay. 



In the manufacture of Portland cement the two mate- 

 rials are ground and intimantely mixed after which they 

 are burned to vitrification. During the burning certain 

 compounds are formed, especially calcic aluminates and 

 silicates, whose union with water and subesquent crystal- 

 lization causes the cement to set. The mixture of clay 

 and limestone is manipulated so that in the finished 

 product, the per centage of lime shall be equal to 2.8 

 times the silica plus 1.1 times the alumina and to main- 

 tain this constancy requires that the composition of the 

 materials used must be constantly watched. 



While it is possible to get a proper cement mixture 

 from materials showing an appreciable range in composi- 

 tion, at the same time care must be exercised. Highly 



