SLAG BRICKS AND SLAG BLOCKS. 685 



SUMMARY OF COST OP PRODUCTION PER 1000 BRICKS. 



8. d. 



Cost of labor , 4 Q 



Slag at 6d. per ton (4 tons) 2 



Wear and tear 1 Q 



Power and steam 3 Q 



Depreciation 1 6 



Oils, sundries, etc 6 



Total cost of production 13 



" The above calculation is based on only producing 10,000 bricks 

 per day. The plant would 'be capable of making up to 12,000 per day; 

 so that by only calculating on this reduced output sufficient allow- 

 ance is made for unforeseen losses. If a larger plant were installed the 

 cost could be very considerably reduced; on a plant producing, say, 

 20,000 bricks per day, the cost per 1000 should not be more than 10s. 

 to 11s. 



"This refers more particularly to limy slags; but in the case of slags 

 not so rich in lime, hydrated lime can be added to the ground slag and 

 the hardening effected in the same way, but in such cases the cost of 

 production is increased by the cost of this added lime. 



" As before pointed out, most limy slags have setting properties with- 

 out being steamed; and with slags containing from 40 to 48 per cent 

 of lime, bricks may be made by merely grinding and pressing the mate- 

 rial and permitting the bricks to stand out in the open air, the same 

 conditions being observed as in making granulated slag bricks, but 

 this method is not so satisfactory as the hardening by steam. In many 

 slags there is a proportion of soluble salts which tend to spoil the bricks 

 when allowed to harden naturally by appearing as efflorescence. This in 

 some cases is so violent that the outer crust will be forced away from 

 the brick; but the same effect does not happen when they are steamed, 

 the steaming either turning the salts into a stable compound or driving 

 them off. 



" These bricks will withstand the weather equally with a high-class 

 clay brick. Bricks have been exposed to the weather the whole winter 

 and no effect whatever is noticeable upon them. They have been soaked, 

 then frozen, and afterwards put into hot water without deterioration." 



Slag Blocks. 



Under this heading will be considered all these products ("slag 

 blocks", "slag tiles", etc.) made by running molten slag, direct from 

 the furnaces, into molds of proper shape. The term slag block will 

 be employed as a general but distinctive name for this class of products 



