STATE GEOLOGIST, 29 
ment upon their hard smooth surfaces to give strength to the mortar. 
The increased strength of the standard quartz mortar is largely due to 
the irregular rough grain of the sand which allows the grains to interlock 
and which also gives rough adhesion surfaces for the mortar contact. 
THE EFFECT OF FINE SAND UPON THE STRENGTH OF MORTAR. 
During the last winter the writer carried on a few tests to determine 
the effect of fine sand upon cement mortar. Similar and more extensive 
tests have been carried on by others, and in the main all agree that fine 
sand weakens cement mortar. The tests made by the writer are here 
presented in tabular form: 
TABLE 5. 
Effect of Fine Sand Upon Cement Mortar. 
1 to 1 Mortar. ( 1 to 2 Mortar. 
Per cent. ; Per cent. 
Lake Sand. of 7 28 3 of "7 28 
Water. | Days. | Days. | Mos. | Water. | Days. | Days. 
Passing a 11 315 395 14 315 367 
No. 50 lls 426 578 668 
- Sieve 18 394 533 617 
Remaining on 1/ 
No. BO Shes 1246 51% 514 629 
Remaining on y ; ih 
Noamsosieve 1246 546 625 650 
Remaining on. ‘ 
ia, 0) Stiga 1246 495 599 6138 
Remaining on , 
Nie. 18 Shes 1216 460 521 557 
Standard 
Quartz 1216 53d 632 740 
Lake Sand j 
Uaetienad 14 500 581 12% 367 428 
The number of the sieve designates the number of meshes to the 
linear inch. The tests show a marked increase in strength in mortars from 
fine to coarse sand, up to the size of the standard sand grain; from that 
size up the strength seems to decrease. It may be noted that the lake 
sand between the 20-30 sieves gives results comparable with the standard 
quartz mortars. The general results of these tests agree quite well with 
the results of other testers. : 
This series of tests was limited, only about 150 briquettes being 
broken. But the tests were made with great care in all details and will 
give a general idea of the action of fine sand upon cement mortar. 
The unsieved lake sand occupies a place intermediate between the 
50 and the 30 sieve. The results with different proportions of sand would 
probably differ slightly, but the two sets of briquettes broken from the 1 
to 2 mortar indicate relatively similar results. 
