PHYSICAL AND CHEMICAL PROPERTIES. PARTS Iv, v. 179 
(b) The effect of free lime upon the soundness is influenced by 
the cohesive properties of the cement, the “speed of 
slaking,”’ the fineness, the temperature, the amount of 
water used in gauging, and the effect of impurities and 
retarders. 
(c) The test for soundness as an indication of the presence of 
free lime is relatively crude compared with the micro- 
scopic study of calcium hydroxide-phenol crystals. 
(d) Slaked lime does not cause failure in soundness tests. 
(e) Nonsintered lime must be present in quantity to cause un- 
soundness, in which case the disruption is likely to occur 
in water or air, as well as in steamed pats. 
(f) Fused sintered lime is liable to cause unsoundness in the 
accelerated tests. 
(g) The agreement between the microscopic evidence of free lime 
and the result of tests for soundness was very close. 
PART Il. THE SEASONING OF PORTLAND CEMENT. 
(3) The absorption of both gaseous substances by both clinkers 
and pulverized cement verified the microscopic tests and demon- 
strated the following: 
(a) The penetration of air into a mass of undisturbed cement is less 
than 13 millimeters. Water absorbed from the atmosphere 
may slowly penetrate farther. 
(6) Cements stored in air-tight receptacles show a slow decrease in the 
percentage of moisture, due, as evinced by the microscopic 
evidence, to the slaking of free lime. 
(c) The rate of absorption decreases very rapidly as the reaction 
proceeds, and the fine particles absorb proportionally more than 
coarser ones. ° 
(d) Under the same atmospheric conditions the amount and rapidity 
of absorption depends largely upon the quality and quantity 
of free lime. 
(e) Perfectly sintered clinker is practically inert to water and atmos- 
pheric influence and consequently the free lime embedded in 
this hard, dense, inert magma is more thoroughly protected than 
the free lime in underburned clinker, and hard-burned clinker 
may season less efficiently than soft-burned clinker. 
(4) A study of manufacturing practises and the strength 
developed by hard-burned and underburned cements led to the 
following conclusions: 
(a) Aération is the least efficient practical method of seasoning 
Portland cement. 
(6) A high loss by ignition and a corresponding low specific gravity 
are not characteristic of commercial cements made from well-: 
burned clinker. 
