192 ANNUAL REPORT 
remarkable, and it might be well for manufacturers to take up this 
matter, as it might open a way for greatly improving their product. The | 
cost of adding dry slaked lime to the cement is insignificant compared 
with the results obtained, especially as, in addition, it causes the cement 
to work much smoother under the trowel. It might be suggested to add 
the lime when using the cement. ‘Though even this increases the result- 
ing strength, the results are much more striking when the lime is ground 
together with the cement. Messrs. H. B. Nichols and Ross E. Hamilton, 
students in the Department of Civil Engineering, Ohio State University, 
tested Louisville cement by making it up with varying amounts of fat 
slaked lime and sand in the proportion 1:2, as shown by the accompany- 
ing table: : 
Louisville cement. IRM Be, | Tensile strength 1:2 
per cent. after 26 weeks. Pounds per sq. in. 
me | . 292 
96 4 335 
92 8 325 
90 10 325 
ee 15 322 
atl 20 357 
75 25 304 
wv 30 335 
50 50 170 
These experimenters, when making up Several Portland cements with 
fat lime, found not only no increase, but at once a decrease in tensile 
strength with 1:3 mixtures, just as was to be expected, owing to the fact 
that Portland cement already has its quota of lime. 
Strength of Roman Cements.—In regard to the strength of Roman 
cements it should be said that in most cases they possess ample crushing 
strength for all practical purposes, but have two great drawbacks, viz: 
first, lack of uniformity; second, inconstancy in volume. The great- 
est difficulty in using Roman cements is their liability to increase in 
volume, which makes them unsuited for exact work like sidewalks and 
similar uses. For foundations, especially when used in very sandy 
mortars, the natural cements answer many purposes very well. At pres- 
ent, with the constantly lowering price of Portland cement, the natural 
cement industry has a difficult position, which can be improved only by 
bringing the quality of the rock cements up to the highest possible point. 
