PHYSICS, CHEMISTRY AND ENGINEERING 



161 



Tests of specimens gaged with varying amounts of water 

 (see Fig. 4) show that for cases in which strength is impor- 

 tant a high strength can be reached by using a small amount 

 of water. Results shown here are not for materials selected 

 as the best, but for a good grade of second settle calcined gyp- 

 sum and are shown in order to give an idea of the great in- 

 crease in strength going along with a decrease in the percentage 

 of water. 



2600 



200 



30 35 <40 <45 



SO 



55 eo 



Percentage of W&fer 



r&** 



Tests made to determine the effect of water on the strength 

 of specimens previously dried show that the absorption of a 

 small amount of moisture by a thoroughly dry specimen re- 

 duced its strength materially. No further loss of strength 

 seemed to be caused, however, by further exposure indefi- 

 nitely to a very moist air. Immersing in water caused the 

 strength to fall off rapidly to about 50 per cent of the strength 



