184 



CEMENTS, LIMES, AND PLASTERS. 



TABLE 79. 

 COMPRESSIVE STRENGTH OP TEIL HYDRAULIC-LIME MORTARS. 



pression, they are usually tested in tension. For this reason it is desir- 

 able to ascertain, as definitely as possible, the ratio which exists between 

 the compressive and the tensile strength of any type of lime or cement. 

 If this ratio be once determined, a tensile test can thereafter be used to 

 determine the compressive strength of the material. 



In the present case, the tensile and compressive tests given in 

 Tables 77, 78, and 79 have been compared. The results are sufficiently 

 close to indicate that the compressive strength of a hydraulic-lime 

 mortar mixed in the usual working proportions (1 lime to 2 or 3 sand) 

 will be from five to six times the tensile strength of the same mixture. 

 (The actual average value, given by eight tests, for this ratio was 5.38 

 to 1.) 



Proportions for mortars and concretes. The following proportions 

 for making mortars and concretes with hydraulic lime are recommended 

 by Beckwith: 



(a) Mortar for use in salt water: 10 U. S. bushels (590 Ibs.) of 

 Teil lime to 1 cubic yard of sand, equivalent to one scant 

 measure of lime to two full measures of sand. 



(6) Mortar for use in fresh water: 9 U. S. bushels (506 Ibs.) of Teil 

 lime to 1 cubic yard of sand, equivalent to 1| measures of 

 lime to 3 measures of sand. 



(c) Mortar for use in air: 1\ U. S. bushels (421 Ibs.) of Teil lime 



to 1 cubic yard of sand, equivalent to 1 measure of lime to 

 3 measures of sand. 



(d) For concretes the usual proportions are: 



(1) For use in salt water, 2 measures mortar to 3 measures of 



broken stone. 



(2) For use in fresh water, 1 measure mortar to 2 measures of 



broken stone. 



