46 4 NNUAL REPORT 
The comparison bet\veen the mortar placed between the bricks in as 
nearly the same maniitr as a mason would lay brick masonry and the 
mortar molded ints briquettes is shown in table number It. 
A sunilar series of tests upon the same cements mixed with lime 
paste, the mortar being formed by using the materials in proportions by 
weight instead of volume, is now being carried on by students of the Ohio 
State University. So far as the tests have proceeded they seem to 
corroborate the tests given above. 
PLASTER. 
An important use for cement mortar is in the form of plastering or 
coating surfaces such as the impervious coatings for retaining water in 
cisterns, reservoirs and tanks, or the outer coating used to prevent water 
entering sub-surface areas as in basements, manholes and conduits. - It 
is also used upon the exterior surfaces to protect them from the destructive 
influences of the elements, and upon the inner walls and ceilings of houses 
to give a hard, smooth finish. Care should be exercised to proportion 
the sand and the cement so that the mortar shall be impervious by hav- 
ing all the voids filled. A Portland cement is best for this purpose. Its 
proportions should be about one part cement and one and three-quarters 
to two and one-half parts of clean sand, the proportion varying according 
to the voids contained in the sand. 
The Buckeye Portland Cement Company publish the following: 
“Wor water tight work, as cisterns, etc., in coats 3%, of an inch thick, the 
following proportions of Portland cement-lime-mortar can be used with safety 
and economy.” 
TABLE 12. 
Proportions in Portland Cement-Lime-Mortar. 
Portland Cement. Sand. Lime Paste. 
1 part | 2 parts 0.5 part 
1 66 | 3 66 IL 66 
ill a4 ’ | 5 ee ees) 66 
il 66 6 (14 3.0 66 
“Mortar made with five or six parts sand to one of Buckeye Portland 
cement is good enough as far as strength is concerned, but is then too ‘poor,’. 
‘short’ or ‘brash,’ and does not adhere sufficiently to the stone and brick. 
“The addition of slacked lime in small proportions makes the mortar ‘fat,’ 
‘rich’ and pleasant to work. 
“It greatly increases its adhesiveness and density, and, contrary to general 
belief, also adds to the strength of all such mixtures. 
“Any greater or any less proportion of lime to the mixture given will 
lessen the density, the tensile strength, the crushing strength and the adhe- 
siveness. This lime paste or slacked lime is more than half water. 
