STATE GEOLOGIST. - 4] 
The results show a high content of magnesium and calcium sul- 
phates, both of which are injurious to concrete. 
Mr. Bleininger says that the water leaching through the concrete 
brings to the fine hair-cracks these soluble alkalies, calcium and mag- 
nesium sulphates, and they are deposited along the cracks upon evapora- 
tion, together with other chemicals which form insoluble compounds 
The leaching process opens the concrete for still further leaching and the 
concentration of the chemicals induces greater changes and thus the dam- 
age increases. 
Of course in winter the water, freezing in the cracks, expands them, 
and the stone having been weakened by the leaching chemicals is ready to 
go to pieces. The organic salts and sulphuric acid aid greatly the solu- 
bility of the mortar materials and these chemicals may be greatly aug- 
mented from the soil and particularly from the cinder foundations. 
Poorly tamped or porous concrete will also be more easily attacked in 
this manner. 
LIME IN CEMENT MORTAR. 
Lime is frequently used in cement mortar for various reasons. 
Masons claim that cement mortar works harsh and brittle, and that the 
addition of lime paste to the mortar “gives it body” and makes it “work 
smoothly” under the trowel. Lime paste is frequently added to cement 
mortar to cheapen it; the claim being made that lime paste up to 25 per 
cent. of the cementitious material used may be added without perceptibly 
weakening the mortar. General Gilmore says that lime paste equivalent 
to one-half or three-fourths of the volume of cement may be used without 
producing serious deterioration in the mortar. Lime paste is frequently 
added to cement mortar to make it impervious. Others have added 10 to 
20 per cent. of cement to lime mortar in order to strengthen it. 
In 1891, the writer carried on a series of tests to prove some of these 
claims for lime-cement mortars. The tests were carefully made in the 
laboratory of the University of Illinois and covered a period of five 
months. The mortar used was composed of one part cement to two 
parts of clean coarse sand of standard sized grains. The cement was 
composed of various parts of lime and a natural cement, ranging from all 
natural cement to all lime paste. A parallel set of tests was also conducted 
with Portland cement and lime. The tests were made to find the ad- 
hesive and cohesive strength of such mortars and compare them with the 
tensile strength ordinarily found by making the mortar into briquettes 
and breaking them. Bricks were laid crosswise to each other and cemented 
together with these mortars and their strength or resistance to breaking 
apart was obtained. Eight hundred of these adhesive tests and 160 of 
the ordinary tensile tests were made with each kind of cement. Table 
number 8 shows the proportions of lime, cement and sand used in parts 
by volume. 
