SLAG CEMENTS: COMPOSITION AND PROPERTIES. 669 



some purposes, as in dams, a heavy material is preferable; for others, 

 as in floors, the lighter cement would be better. 



Color of slag cements. Slag cements can usually be distinguished 

 from Portlands by being much lighter in color and slightly different 



600 



140 210 



AGE IN DAYS 



FIG. 164.* Effect on tensile strength of slag cements of hardening in air or in 



water. (Tetmajer.) 



4000 



3000 



2000 



COMPR 



230 



70 140 210 



AGE IN DAYS 



FIG. 165.* Effect on compressive strength of slag cement of hardening in air or in 



water. (Tetmajer.) 



in tint, while from most natural cements they differ markedly in tint. 

 They are commonly bluish-white to lilac, the exact color of any speci- 

 men depending partly on the respective colors of the lime and the 

 slag which have been used in its manufacture, but more largely on 



* From Johnson's " Materials of Construction ", p. 576. 



