EMINENTLY HYDRAULIC LIMES: GRAPPIER CEMENTS. 177 



TABLE 72. 



ANALYSES OF THE VARIOUS BEDS IN THE HYDRAULIC LIMESTONE QUARRIES AT 



MALAIN, FRANCE. 



Burning. Hydraulic lime is burned in continuous kilns, like common 

 lime. No difference, in fact, exists between the burning of common 

 and of hydraulic limes, so far as the practical operations involved are 

 concerned. The temperature attained in burning is, however, higher 

 in hydraulic lime-kilns than in those burning common lime, and the 

 fuel requirements are correspondingly increased. Beckwith states, 

 for example, that at Teil 100 tons of coal are required to burn stone 

 equivalent to 500 tons of screened lime. This corresponds to a fuel 

 consumption of 20 per cent by weight on the lime production. 



The temperature and thoroughness of the burning are directly related 

 to the Cementation Index of the lime. The higher the index the less 

 care will be necessary to avoid the presence of too much free lime. A 

 hydraulic lime of index 0.75, for example, would be much more difficult 

 to burn properly than one whose index ran as high as 0.85 or so. In 

 fact, as the index approaches 1.00, the difficulty is, not to avoid free 

 lime, but to keep enough free lime in the product to enable it to slake 

 properly. 



In Tables 73 and 74 are given the analyses of a number of hydraulic 

 limes, after being burned but before slaking. 



