SLAG BRICKS AND SLAG BLOCKS. 



683 



with coarser particles, and in the latter case it would be like a fine even- 

 grained sand without any really fine dust. 



"The slag used for brickmaking should preferably be new; but it 

 has been found that a slag which had been exposed for twenty years 

 still possessed setting properties when acted upon by steam. One of 

 the bricks exhibited was made in the summer of 1901 from slag which 

 had been exposed to the atmosphere for over twenty years. 



"In the case of a slag which disintegrates on exposure to the atmos- 

 phere, it would not be wise to use it directly after it has cooled unless 

 the ground-moistened slag is permitted to stand until the free lime is 

 thoroughly hydrated. This could be effected in silos erected directly 

 over the brickmaking machine; and twenty-four hours in this condi- 

 tion would be sufficient. In general the better plan would be to allow 

 the slag to stand for about ten days before being used, as in such cases 

 the grinding would be facilitated by the disintegrating. 



" The slag for brickmaking should preferably be cast in thin layers 

 capable of being easily broken up in sizes suitable for being passed into 

 the grinding-mill, rendering a stone-breaker unnecessary. 



''The bricks are almost perfect in form, there being no twisting or 

 distortion produced by the induration, and in strength and other 

 qualities they will compare with the best qualities of clay bricks. 



TABLE 252. 

 CRUSHING STRENGTH OF INDURATED SLAG BRICKS. 



" Objections have been raised against granulated slag bricks on account 

 of their porosity, which ranges in some cases as high as 15 per cent. No 

 objections of this kind can be raised against these indurated slag bricks, 

 the absorption being remarkably low, as shown in Table 253. 



" The bricks before testing were thoroughly dried at 212 and then 

 immersed for twenty-four hours. 



TABLE 253. 

 POROSITY OF SLAG BRICKS. 



