T1L1ZAT10N OF IRON AND STEEL SLAGS. 
By Edwin C. Eckel. 
INTRODUCTION. 
Iii recent years the attention of many technologists has been directed 
to the problem, of slag utilization. Certain slags may, of course, be 
considered as low-grade iron ores, and have been used as such for 
many years. By far the greater portion of the slag annually j)ro- 
duced by iron and steel works is not available for this use, however, 
and it is only in comparatively recent years that uses have been found 
for many of these slags. At present, slag is utilized extensively in 
cement and slag-brick manufacture, as a fertilizer, and in the form of 
mineral wool; to a less extent in the manufacture of alum, paint, and 
glass; and a considerable quantity is disposed of less profitably for 
use as road metal, railroad ballast, and in land reclamation. These 
uses will be discussed in order. 
SLAG CEMENT. 
Slag cement, properly so called, is the product obtained by pulver- 
izing, without calcination, a mixture of granulated basic blast-furnace 
slag and slaked lime. This product, though in reality a member of 
the class of pozzuolanic cements, is usually marketed as "Portland 
cement," in spite of the fact that it differs from a true Portland 
cement in method of manufacture, ultimate and rational composition, 
and properties. Eight plants are at present engaged in the manu- 
facture of this material in the United States, the production for 1901 
being about 400,000 barrels, while that for 1902 was in the neighbor- 
hood of 800,000 barrels. The writer has discussed the manufacture 
of slag cement in detail in a recent publication." A brief resume of 
the technology of the material in question is here given. 
As to composition, the material used in the manufacture of slag 
cement must be basic blast-furnace slag. Tetmajer stated that the 
ratio should never be less than unity, and that the best results 
2 Al O 
were obtained when the ratio -^~~ gave a value of 0.45 to 0.50. 
Si() 2 
Prost and Mahon later obtained good results from slags in which the 
"Mineral Industry, Vol. X, pp. 84-95. See also Mineral Resources IT. S. 1SXX), p. 747, where a 
description of two Alabama slag-cement plants is given. 
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