600 



CEMENTS, LIMES, AND PLASTERS. 



600 



500 



400 



6 8 10 



AGE IN MONTHS 



FIG. 155.* Effect of salt on Portland-cement mortar, 1 cement: 2 sand, made in 

 freezing weather. (Sabin.) 



AGE IN MONTH'S 



FIG. 156.f Effect of salt on tensile strength of mortars, 1 cement :1 sand and 1 

 cement: 4 sand. Those left in air remained frozen almost sixty days. Those 

 put in water were first frozen in air for three days. 



* From Johnson's " Materials of Construction ", p. 618. t Ibid., p. 619. 



