PHYSICAL PROPERTIES OF PORTLAND CEMENT. 



599 



tradictory, but it seems probable that any addition of salt will decrease 

 the ultimate tensile and compressive strength of the mortar in which 



20 40 



X PERCENT SOLUTION 



FIG. 153.* Effect on the freezing-point of cement of various proportions of 

 glycerine, alcohol, and salt. (Tetmajer.) 



5 10 15 20 



PERCENTAGE OF SALT 



FIG. 154. f Effect of salt on mortar, 1 cement: 2 sand, made in freezing weather. 



(Sabin.) 



it is used, but that for the lower percentages of salt this injurious effect 

 may be slight enough to be safely disregarded. 



*From Johnson's " Materials of Construction", p. 615. 

 f Ibid., p. 617. 



