STATE GEOLOGIST. 35 
mixing the mortar, the water varied according to the loam used, but the 
mortar was kept as nearly as possible at the same consistency. 
To obtain the effect of weathering, 10 briquettes were made at one 
time and alternate briquettes were selected and subjected to the outdoor 
conditions. All the briquettes were kept in moist air for 48 hours and 
then the outdoor set of 5 briquettes was put in an exposed place with 
about one or two inches of loose earth thrown over them, while the indoor 
set was placed in pans of water. They were allowed thus to remain until 
broken, the outside set being exposed to all kinds of weather. The tests 
were carried on over a period of 8 months. 
The following conclusions were reached: 
I. The curves from the plotted results plainly show that conclu- 
sions drawn from tests three months of age would not always safely hold 
for longer period tests. 
2. [he mortars containing the highest percentages of loam weath- 
ered better than the clean sand mortar and the mortars containing the 
lower percentages of loam. The curves, for similar mortars which were 
kept outside and inside, did not harmonize at all for the lower percentages 
of loam used, but for the higher percentages of loam, the curves paral- 
leled each other, the outside stored mortars being slightly lower in strength 
up to the 8 month period, but gradually approaching each other as their 
age increased. 
The deduction was, that the higher density of the mortars with 
larger percentages of loam prevented the rapid absorption of water and 
the consequent damage to the briquettes by freezing and thawing. 
3. A cement mortar containing large percentages of loam will 
not reach its ultimate strength as quickly as one containing little or no 
loam. 
The rate of increase in strength, however, becomes greater for large 
percentages of loam, over low percentages, as the age increases, at least 
up to the 8 months limit. 
| If a mortar is to be used in a structure which is to be immediately 
subjected to great stress, a sand should be used which does not contain 
more than 10 per cent. of loam. As ordinary bank sand does not contain 
more than 7 or 8 per cent. of loam it is quite safe to use bank sand for 
such buildings. 
4. If the mortar is to be used under water, clean sand should be 
used. 
5. Mortars exposed to the weather gain strength slower than those 
placed under water, but ultimately they attain equal strength. 
The deduction was made, that mortar placed outside was frozen part 
of thé time and was dependent upon the thawing and rains for the neces- 
sary amount of additional water for hardening which the briquettes on the 
inside could get at once. 
