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KANSAS ACADEMY OP SCIENCE. 



adds to it. There seems to be no important difference between the 

 effect of clay and that of loam. It is also apparent from the diagrams 

 that short-time tests of this nature are not of much value. 



Table 3 gives the amounts of water absorbed by the briquettes 

 in twenty-four hours, stated as percentages of the dry weights. These 

 results, while not conclusive, point to the inference that one-to-three 

 mortars made with sand containing up to five or six per cent, of clay 

 or loam are at least as dense as those made with clean sand. With 

 leaner mortars — that is, those with a smaller proportion of cement — 

 the greater density of the dirty mortars would doubtless be more ap- 

 parent. It will be noted that the effect of clay in increasing the 

 density of mortar is noticeably greater than that of loam. This is 

 doubtless due to the exceedingly small size of the clay grains, engibling 

 them to fill the interstitial spaces of the cement. 



Table 3. — Showing absorption of mortars 

 with clay and loam added. 



Some other experimental evidence bearing out the conclusions just 

 stated may be briefly noted. 



A number of years ago, Mr. E. 0. Clark, of Boston, concluded, from 

 tests* made with Rosendale cement, that an admixture of a small 

 amount of loam or clay did not weaken mortar after six months or a 

 year. His experiments were continued in part over two and one- 

 half years. 



About two years ago a series of tests was carried out at the Ohio 

 State University t along the same line. These tests were quite 

 similar in their nature to those just described, but were much more 

 extended. Two Portland cements and three kinds of sand were ex- 

 perimented with, and the tests covered the period of a year. The re- 

 sults of these tests pointed strongly to the conclusion that the effect 



* Trans. Am. Soc. of Civil Engineers, vol. 14, p. 163. 

 t Engineering News, vol. 50, p. 443. 



