107 



BACTERIA AND THE DISINTEGRATION OF CEMENT. 



By R. Greig Smith, M.vSc, Macleay Bacteriologist 

 ' TO THE Society. 



Occasionally the cement work of water canals and reservoirs 

 disintegrates below the water level, and instead of showing a 

 smooth and apparently hard face, the surface is seen to be more 

 or less eroded. When struck with a pick, the cement easily 

 comes away, and a porous internal structure is revealed. The 

 cement matrix has disappeared, and the sand, grit and stones are 

 practically all that remain. Above the water line the cement 

 remains quite hard, and shows no sign of disintegration. 



Stutzer and Hartleb* investigated such a case, and as a result 

 of their work, they considered that the nitrous organisms — that 

 is. bacteria which convert ammonia into nitrous acid — might 

 assist in the decomposition of the cement, through the production 

 of nitrous acid, which dissolves the lime forming the soluble 

 calcium nitrite. They worked upon a sample of brownish coloured 

 mud taken from the bottom of the Bonn water reservoir. Chemi- 

 cally it proved to be disintegrated cement, and bacteriological ly 

 it was found capable of causing the nitrification of a solution of 

 ammonium sulphate. 



Barth,t in publishing his experience with h3''draulic cements, 

 said that a destruction of the cement might take place in so 

 relatively short a time as three years. In the case which came 

 under his notice, the water did not contain an excess of free 



* Stutzer and Hartleb, Zeit. fur angew. Chemie, 1899 (17) 402; Abstract 

 in Jour. Soc. Chem. Industry, xviii. 495. 



t Barth, ibid., 1899 (21) 489; Abstract, ihid., xviii. 686. 



