SLAG BRICKS AND SLAG BLOCKS. G77 



in laying up, and are at least equal to clay bricks in crushing strength. 

 The product usually seems to find a ready market, though, of coi, 

 the low value of the material, relative to its bulk and weight, precludes 

 long railroad transportation. 



Methods at special plants. Slag bricks were manufactured at the 

 Cleveland Slag Works, Middlesborough, England; but the manufac- 

 ture has been discontinued for some years At this plant the wet granu- 

 lated slag was mixed with "selenitic lime" (see Ch. XV) instead of 

 with common lime. The selenitic lime was composed of 80 per cent 

 quicklime, 10 per cent gypsum, and 10 per cent iron oxide. About 

 670 Ibs. of this selenitic lime was sufficient for 1000 bricks. The mix- 

 ture of slag and lime was pressed to shape in a brick-press; and the 

 bricks were stacked in sheds for a week, to harden enough to handle 

 well. After this they were stacked in the open air for five or six weeks 

 more, when they were ready for use. The bricks were dull-gray in 

 color, and very hard and tough. Buildings onstructed of them over 

 twenty years ago are still in a good state of preservation. The manu- 

 facture of slag bricks at these works was given up for reasons not con- 

 nected with the technical value of the product, which seems to have 

 acquired an excellent local reputation. 



At Vitry, France, the manufacture * of slag bricks and pipes is 

 carried on in connection with the manufacture of slag cement. The 

 bricks are made by mixing 60 parts of slaked lime with from 250 to 

 300 parts of granulated slag. Sufficient water is added to this mix- 

 ture to make a firm paste, from which the bricks are molded in hand- 

 or steam-presses. These slags are found to be especially useful for 

 foundations or basement work, pavements, etc. " Facing brick" are 

 made from a similar mixture, with the addition of some fine sand. 

 Sewer pipes are made from a mixture consisting of 500 kgs. of 

 slag cement and 1 cu. m. of sand. This mixture is made into a 

 stiff mortar, and forced into steel molds by iron rammers. The molds 

 are removed as soon as the ramming has finished. The pipes are then 

 dried for three days, after which they are immersed in water for twenty- 

 four hours. They are then stacked in the factory ground for several 

 months, after which they are ready for market. 



Slag bricks are manufactured f on a large scale at Kralovedvoor, 

 near Prague, Bohemia. The slags normally used at this plant vary in 

 composition within the following limits; 



* Engineering News, Jan. 1, 1897. 



t Engineering and Mining Journal, April 16, 1898. 



