STATE GEOLOGIST. 61 
trated several meters, but when the sand was compact there was no result. 
In the mid-stream piers, sheet piling was first driven for the coffer-dams 
and then grout was injected into the gravel surrounding the sheeting, 
resulting in a perfectly water tight coffer-dam. The interior of one of 
the coffer-dams was also treated in this manner and it was found upon 
excavation that wherever the sand was not in compact beds, hard, well 
bonded beds of concrete existed so that only part of the interior had to 
be excavated. 
The same method was successfully employed upon two other bridges 
in Bavaria in 1898 and Igoo. 7 
THE EFFECTS OF FREEZING UPON MORTAR. 
Experimental work * carried on in 1895 by students of the Ohio 
State University, indicated that in natural cement mortars, frost affected 
them in about the ratio that they contained magnesium oxide, but this did 
not prove to be the case with Portland cements. In natural cement 
mortars freezing disintegrated the exterior to a greater or less depth, 
materially weakening the mortar, while in Portland cement mortars dis- 
integration did not appear and the loss of strength was very much less. 
Baker and Symonds, of Thayer School of Civil Engineering, Dart- 
mouth College, came to the following conclusions after having made 7,150 
tests, that freezing does not disintegrate Portland cement mortar but does 
disintegrate Rosendale cement mortars; that while it seriously damages the 
natural cement mortars, Portland cement mortars lose from 2 to 40 per 
cent. of their strength. 
Tests in the Royal laboratory of Berlin in 1886, showed from 2 per 
cent. to 33 per cent. loss in different cements under different conditions 
when subjected to freezing. 
W. W. McClay, M. Am. Soc. C. E., showed that the attempt to 
prevent the injurious effect of frost by heating the material and then using 
it in freezing temperatures was more hurtful than using the ingredients 
cold. In two sets of briquettes made of cement paste, one made at 45 
degrees F. and the other at 100 degrees F., and treated exactly alike until 
broken, the strength of the heated mortar was found to be only 7 to 20 
per cent. of that of the cold mixture. In case of a mortar of 1 cement ‘and 
2 of sand the strength of the heated mixture was only 30 per cent. of that 
of the cold mixture. This set of experiments, however, was upon one 
brand of cement only. 
The Austrian Society of Engineers and Architects made some prac- 
tical tests in the winter of 1892-93. They constructed 14 brick and stone 
walls, 3 feet, 4 inches long, 6 feet, 8 inches high, and 10 inches | 
thick, using the following mortars: (1) common fat lime mortar. (2) 
*Thesis of Frank Haas and John A. McGraw, on “Effect of Magnesia on the Strength of 
Cements when Subjected to Freezing.” 
