PROPERTIES OF PORTLAND CEMENT. PART III. 239 



200 





r 





^2S 



1 1 1 r 



1 1 1" 



3/8 3 /■* 3/0 3.06 3 02 2.98 



SPEC/F/C GRAy/Ty. 



2.94 



2.90 



Fig. 21. 



The figures recorded in Table XXXI prove that the behavior of these 

 mixtures vrhen subjected to thorough aeration vs^as exactly as had been 

 anticipated. They shovf conclusively that the manufacturer before pack- 

 ing his cement can readily ascertain the nature and extent of changes 

 in set which future seasoning may induce. 



However, air only penetrates slightly beyond the exposed surfaces of 

 packed cement, water absorbed from the atmosphere readily enters far- 

 ther. The free lime will gradually unite with the water which may be 

 present as moisture in Portland cement, if no other soi;rce of water is 

 available. Consequently, it is the effect of the hydration of the lime, 

 and not its conversion into calcium carbonate to which the manufacturer 



