34 ANNUAL REPORT 
the sand being clay or loam. Each thesis included three series of tests, 
one with standard quartz sand, one with lake sand, and one with equal 
proportions of the two mixed. In each series, separate tests were made 
with clay and with loam, used in the following proportions by weight of 
the sand, namely, 2, 4, 6, 8, 10, 12 and 15 per cent. A total of about ten 
thousand briquettes were broken. The same conclusions were reached 
in each of the four theses written, namely, that either clay or loam added 
to sand up to the limit of 15 per cent. by weight, did not have any injuri- 
ous effect upon Portland cement mortar after the first two weeks and up 
to the limit of time which the tests covered, namely, 12 weeks. 
On the contrary the clay and loam added considerably to the strength 
of the mortar. The results differed with different cements, and with the 
different sands. Their conclusions were that the chemical composition of 
the cement influenced the results to some degree. In some cases IO per 
cent. seemed to give maximum results, but the majority of the tests 
showed that 15 per cent. of clay or loam gave the greatest strength. Clay 
uniformly gave higher results than loam. One detrimental result was 
definitely established, that mortars made from sand carrying clay or loam 
could not be placed under water safely, in less than 48 hours after mixing, 
because the loam softened and warped under the influence of water. 
Thus, for subaqueous masonry it would be unsafe to use sand con- 
taining clay or loam in mortar. There is one plausible explanation for 
the increased strength obtained and that is in the addition of smaller par- 
ticles of material which aid in filling up the voids in the sand. If Io or 
I5 per cent. of fine sand was added to the ordinary standard quartz ‘it 
would undoubtedly give stronger results than with the clear crushed quartz. 
Before finally accepting these tests as conclusive, it would seem best 
to submit a series of briquettes to a long time test of at ‘least two years, 
allowing them to weather and freeze under conditions similar to those ‘to 
which actual structures would be submitted. 
Work of Chubb and Chaffin.—Since writing the foregoing para- 
graphs upon the effects of loam and clay upon cement mortars, Messrs. 
J. H. Chubb and W. W. Chaffin, civil engineering students in the class of 
1904, of the Ohio State University, have carried on another extensive 
set of tests under the writer’s direction, upon loam in cement mortars, 
noting particularly the effect of weathering and temperature upon such 
mortars. They also carried the percentages of loam used up to 27 per 
cent. of the weight of the sand. The percentages of loam used were 10, 
I5, 18, 21, 24 and 27 per cent. by weight of the sand used in the mortar. 
The cements used were Giant and Atlas. The sands used were 
standard, lake and bank sand. The loam used was the ordinary clay 
field loam from the university campus, dried and sifted through a number 
40 sieve. The mortars were all made of I part of cement to 3 parts of 
sand by weight, the loam being a percentage of the 3 parts of sand. In 
