FEEBLY HYDRAULIC LIMES: SELENITIC LIMES. 



193 



The samples discussed in the above table were made up into 6-inch 

 cubes and kept in air one year before testing. The results in the table 

 have been reduced to pounds per square inch. 



300 Ibs. 



| 100 Ibs. 



I I I 



FIG. 32. Compressive strength of plain hydraulic and selenitic limes. 



The gain in strength due to this process of selenitizing is obvious^ 

 but it must be recollected that it gives satisfactory results only when- 

 employed on feebly hydraulic limes. With common non-hydraulic 

 limes, and with the better grades of hydraulic limes, the results are not 

 commensurate with the extra expense. For American use, therefore, 

 Scott's process has little to commend it, for our good natural cements, 

 would leave little field for such a product as selenitic lime^ 



