Destruction of Concrete by Alkali. 
BY 
WM. P. HEADDEN. 
Cement has been found so generally serviceable and beset with so few 
disadvantages that its use is generally recommended without any reserva¬ 
tion, and this confidence has been fully justified with but few exceptions so 
far as the limited literature at my disposal indicates. 
The principal condition under which good portland cement has failed 
to fulfill the requirements of the structure in which it was used, seems to 
have been where the structure was exposed to the action of sea water. 
Such exposure has not resulted uniformly in the destruction of the cement, 
so that even this condition, i.e., the exposure to sea water, a solution com¬ 
paratively rich in magnesic chlorid and sulphate, may not have been the de¬ 
termining factor in the trouble noted. 
The following case of deterioration may be of some interest as it pre¬ 
sents some new points. There were sent to me some months ago a number 
of fragments of tiling which had been laid but from eight to nine months. 
They had been disintegrated to such an extent that one of the samples was 
simply a white putty-like mass mixed with sand. There was nothing about 
this sample remotely suggestive of concrete. Another of the samples con¬ 
sisted of a fragment of the tile, the interior portions of which had been 
wholly decomposed, while there still remained an outer and inner portion in 
good condition, or comparatively so. Another sample had been attacked on 
the inner side leaving the mass of the tile outside of the zone of decomposi¬ 
tion apparently sound. The line of decomposition was sharply limited and 
showed distinctly, but even in this case there remained a thin layer of 
cement on the inside. 
I do not know whether the tile were running full of water or not, 
probably not, as the fragments seem to be parts of i6 or i8 inch tile. 
The importance of this point is simply this, that it would answer any ques¬ 
tion in regard to the separation of solid ‘'alkali” salts on that portion of the 
tile above the water line. That such a separation of these salts should take 
place does not seem very probable in this case. 
The point of attack so far as the samples at my disposal indicate, is 
either in the center of the cement mass or near the inner surface. In either 
case we are almost compelled to assume the action of the water, i. e., of the 
salts held in solution. At the sam;e time we see the resisting power of the 
outside and inside surfaces, which are evidently richer in cement than the 
inner portion of the mass of the tile. 
The sand used in making the tile was quite fine.* The proportion used 
was S:i. We can readily see that the individual masses of cement in the 
interior mass of the tile must be small and readily attacked by solutions of 
salts capable of reacting with the cement. 
It seems quite evident that the agents causing this disintegration of 
the cement must gain access to the interior portion of the mass of the tile 
*I do not know the character of the water used. 
