10 ANNALS NEW YORK ACADEMY OF SCIENCES 



shown (4). This may perhaps be due to an increase of coagulation of 

 the colloidal constituents, by reason of the presence of salts of greater 

 ionization than are generally present. On the basis of the crystallization 

 theory, this phenomenon is rather difficult to interpret. 



QUALITY OF WATER THAT MAY SUBSEQUENTLY COME IXTO CONTACT 

 WITH THE SYSTEM 



Having material in solution. A large number of failures in concrete 

 structures have been attributed to the disintegrating action thereon of 

 water impregnated with various salts. Inasmuch as all ground water is 

 charged to some degree with salts which it has accumulated in its passage 

 through the soil and rocks, this problem is worthy of the most careful 

 attention. For our purpose, such mineral-laden waters may be divided 

 into 



1. Sea water 



2. Alkali water (from western alkali soils) 



3. Deep rock waters. 



The mineral constituents are common in all these cases, and vary only 

 in the prominence of one or more of them. Thus in sea water the chlo- 

 rides of sodium and magnesium, in alkali water the alkaline carbonates, 

 and in deep rock water the chlorides of calcium and magnesium and the 

 sulphate of magnesium are the distinctive constituents. Whether the 

 effect of these electrolytes is cumulative, so that the continued action of 

 solutions of low concentrations will work harm, or if not, what are the 

 limiting concentrations to assure safety to the structure, has not been 

 worked out. Obviously, it is not a laboratory problem, since the factors 

 which obtain in nature are impossible to duplicate on a small scale. The 

 solution lies in careful inquiry into the mechanism of the action and in 

 observation of the instances of failure in construction work, with a study 

 of its causes. 



Sea water. The effects of sea water upon set cement have been sum- 

 marized in the statement by Feret, "Xo cement has yet been found which 

 presents absolute security against the decomposing action of sea water" 

 (97). Le Chatelier, after a series of experiments extending over ten 

 years, confirms this conclusion (53). Poulsen concludes, however, that 

 the chemical action of salt water is not alone sufficient to cause Portland 

 cement mortars to deteriorate (76). 



The diversity of results reported in the observation of the action of 

 sea water upon cement indicates that there are varying factors at work 

 that so far have not been clearly recognized. Whether the precise nature 



