By ANNUAL REPORT 
The mortar collars were kept in moist air for twenty-four hours and 
then stored in water for twenty-seven days before Denieuested=amesac 
water pressure in testing varied from 25 to 65 pounds per square inch. 
It was found that discs which did not leak in twenty-four hours would 
never leak. To be considered permeable, it was decided that drops of 
water must collect upon the outer surface of the mortar disc. Where 
discs became damp, but sufficient moisture did not come through to collect 
into drops, they were considered to be porous, but not permeable. 
aco 
Section é en pai on Concrete Dise 
Figure 2, 
The conclusions which they reached were: 
First—In plain mortars, permeability depends upon the voids in the 
sand. A mortar not poorer than I cement to 2 sand will not leak, no 
matter what kind of sand is used. Mortars of I cement to 4 sand will be 
impermeable if made of a normal mixture of sand, that is, a sand having 
the normal variation in size of grains. Any mortar will become imperme- 
able if the water acting against its face contains suspended matter. 
Second.—Cement Coatings.—One quarter inch coating of neat ce- 
ment will make mortar impermeable. 
permeable mortars do not justify the expense. It is better to procure sand 
with less voids, or use a richer mortar. Soap and alum used in the mortar 
do not make it impermeable, at least from the beginning. 
Work of Kettler and Sherman.—In 1901, Mr. F. C. Kettler and J. K. 
Sherman, students of the Ohio State University, continued the investiga- 
tions upon the permeability of cement mortars, using varying percentages 
of water in mixing the mortars, and using loam in the sand. They also 
used grout washes on the surface to prevent permeability. The thickness 
of the mortar tested was 1% inches. Their method of ramming and test- 
ing was the same as in the previous tests. ‘Their experiments with loam 
did not show any definite results effected. Loam with standard sand was 
very permeable, less so with lake sand. 
In the use of a varying quantity of water used in mixing the mortar, 
it was found that mortar of standard sand was quite permeable, the 
permeability decreasing as the percentage of water in the mortar increased 
from 8 to 14 per cent. The permeability of the lake sand mortar was 
