176 



CEMENTS, LIMES, AND PLASTERS. 



These constituents act as fluxes, facilitating the combination of the 

 silica and lime. They also combine themselves with lime to form 

 aluminates and ferrites of lime. These latter salts do not increase 

 the hydraulic value of the product, for they become hydrated and inert 

 during the process of slaking, but their formation disposes of some of 

 the excess of free lime. 



The effect of these modifications is shown clearly when the Cementa- 

 tion Indexes of the ideal and the various commercial products are com- 

 puted and compared. Le Chatelier's ideal lime has a Cementation 

 Index of 0.75, while the actual limes whose analyses are given later 

 will average about 0.85. 



Analyses of a number of commercial hydraulic limes are given in 

 Table 74, page 179. 



Raw materials: hydraulic limestones. The limestones actually 

 used in the manufacture of hydraulic limes will carry from 70 to 80 

 per cent of lime carbonate. In hydraulic limestones of the best types, 

 such as are used at Teil, France, the silica will vary between 13 and 17 

 per cent, while the alumina and iron together rarely exceed 3 per cent. 

 Several analyses of hydraulic limestones are given in Tables 70 and 71. 



TABLE 70. 

 ANALYSES OF HYDRAULIC LIMESTONES, TEIL, FRANCE. 



1. Alignole quarry; average of six analyses by Rivqt. 



2. Gaillant quarry; average of three analyses by Rivot. 



3. Tinlifere quarry; analysis by Rivot. 



4. Lafarge quarry; average of nine analyses by Rivot. 



TABLE 71. 

 ANALYSES OF HYDRAULIC-LIME ROCKS, FRANCE AND GERMANY. 



1. Senonches, France. Descotils, analyst. 



2. Metz, Germany. Berthier, analyst. 



3. Hausbergen, Germany. Muspratt, analyst. 



4. Plassac, France. Vicat, analyst. 



Quoted by Zwick, "Hydraulischer Kalk und 

 Portland-Cement", pp. 66, 67. 



