xni.A, 4 Witt and Reyes: Solubility of Portland Cement 161 



SUMMARY 



When cement is shaken with water in a closed vessel large 

 amounts of calcium with relatively small amounts of most of 

 the other elements present go into solution. 



The factors that effect the results have been found to be (a) 

 absence of carbon dioxide, (b) method of agitation, (c) fineness 

 of grain, (d) volume of water, and (e) time. Of these, volume 

 of water is the most important. The effect of temperature has 

 not been studied. 



As the volume of water is increased, the amount of calcium 

 going into solution in a given time increases rapidly. When 

 cement is treated with approximately eight thousand times its 

 weight of water, 90 per cent of the calcium present goes into 

 solution in twenty-four hours, with indications that still more 

 would dissolve in a greater volume. 



Though the work was not undertaken as a study of hydration, 

 the results obtained are closely related to the theories of hydra- 

 tion that have been formulated from time to time. 



Since all the important compounds in cement contain calcium, 

 and 90 per cent of all calcium present goes into solution, it may 

 be stated that under favorable conditions the hydration of all 

 important compounds results in the formation of calcium 

 hydroxide. 



It has not been found possible to obtain a saturated solution 

 of calcium hydroxide by shaking cement in water. This may 

 be due to the fact that presence of dissolved calcium hydroxide 

 inhibits further hydration, or it may be that when the concen- 

 tration of the calcium hydroxide solution reaches a certain value 

 a colloid is formed, according to Michaelis' theory. 



