id 
STATE GEOLOGIST. 25 
was 308 pounds per square inch. The average of six cements, at another 
laboratory, tested at six months of age, was 404 pounds. ‘The average of 
14 American and German cements at one year old, in proportions of I 
cement and 3 sand, was 361 pounds. ‘The average of tests from ten dif- 
ferent cement testers upon Giant Portland cement mortar, I cement and 
3 sand, one year old, was 414 pounds; while 8 of the same testers gave 
results for 1 cement and 2 sand which averaged at one year old 492 pounds. 
Actual crushing tests upon 12 inch cubes of Giant cement concrete, 3 
months old, made in the proportions of I cement, 3 sand, and 5 broken 
stone, and tested at the government testing laboratory, gave. crushing 
strengths varying from 3,081 pounds to 4,451 pounds per square inch and 
averaging over 4,000 pounds per square inch. Such concrete would sup- 
port a column of its own material 3,600 feet high without crushing. 
Where thick or heavy masonry work is to be built, the interior mortar 
joints are more or less excluded from contact with air, and consequently 
from the carbonic acid contained in the air, hence it is safe to conclude 
that it will take long periods of time for the lime mortar to become per- 
fectly hardened. During this time the structure is liable to settlement 
and deformation, therefore the necessity of some more permanent and 
quickly hardening material for mortar. 
Baker says in a note on lime mortar, “Lime mortar taken from the 
walls of ancient buildings has been found to be only 50 to 8o per cent. sat- 
urated with carbonic acid after nearly 2,000 years of exposure.’ “Lime 
mortar 2,000 years old has been found in subterranean vaults, in exactly 
the condition, except for a thin crust on top, of freshly mixed mortar.” 
For the heavy structures of the present day it is quite apparent that 
such defects would be dangerous. 
The question of protection from the destructive action of the elements 
is often as important a factor of consideration with smaller structures as it 
is with the larger ones. The porosity of lime and mortar would allow 
moisture and temperature changes to affect the durability of such work. 
Cement mortar, upon the other hand, can be made impervious to water. 
It will set under water and without contact with air and will continue to 
gain strength for an unknown period of time. Cement mortar in the 
center of a thick wall will be practically as hard and durable as the ex- 
terior surface at the same age. 
Lime mortar is of no value in submarine work. Good, durable 
masonry can not be laid in water without cement mortar. The fine break- 
waters lately constructed by the United States Government at Buffalo and 
Cleveland, the concrete jetties at the mouth of the Mississippi river, the 
sea-walls around Galveston, Texas, and Havana, Cuba, all illustrate 
the value of cement in marine or hydraulic service. 
