PUZZOLANIC MATERIALS IN GENERAL. 



Artificial Puzzolanic Materials. 



Blast-furnace slag is by far the most prominent of the artificial poz- 

 zuolanic materials. Other artificial materials have, however, been used 

 for this purpose, burnt clay being one of the better known of these minor 

 products. 



Burnt clay. The following recent note * is of interest in the present 

 connection. 



"Mortar composed of lime and burnt clay was used extensively in 

 constructing the Asyut Barrage completed in 1902, across the Nile, 

 and described in detail in a paper by Mr. George Henry Stephens, M. 

 Inst. C. E., to the institution of Civil Engineers on March 15, 1904. 

 After being burnt the clay was ground and passed through a 100-mesh 

 sieve. The best results were had with a clay burnt to a light terra-cotta 

 color as compared with clay burned brick-red and clay burned dark 

 red to purple. The ground clay was mixed with slaked lime and sand 

 was added to form a mortar. The following are the results of long- 

 time tensile tests made with various mixtures moulded into standard 

 briquettes kept in water after 12 hours in air": 



TABLE 242. 

 STRENGTH OF LIME BURNT-CLAY MORTARS. 



Blast-furnace slags. Slags, according to the general use of that 

 term, are the fusible silicates formed during metallurgical operations 

 by the combination of the fluxing materials with the gangue of the ore. 

 The composition of the slag, therefore, depends upon the character 

 and relative proportions of the gangue and the fluxes. The slag will, 

 in general, contain only those elements present in either gangue or 

 flux; though it may contain also a percentage, usually small, of the 

 metal which is being reduced, and its composition may, in some processes, 



* Engineering News, vol. 53, p. 177. Feb. 16, 1905. 



