142 REIBLING AND REYES. 
value in a month or a year. Cements unsound in hot water 
and sound in cold disintegrated if boiled after six months in 
cold water.” The failure of the lime to slake in six months 
can be attributed to the impermeability of the hardened neat 
cement to cold water. The instances given in Table XXXVII 
show that a cement which contains slow-slaking lime not only 
may remain sound in boiling water, but also that ordinary 
boiling with water may fail to slake all of the free lime in a 
hardened cement. 
TABLE XXXVII.—The effect of the condition of the free lime upon the 
soundness. 
Fineness. Soundness. 
Microscopic free lime 
200 | 100 eeSr 5-hour 28-day 
mesh. | mesh. steam test. water test. 
Source of the cement. 
P. ct. | P. ct. 
Ground, well-burn- | 93.6 | 100 Some anhydrous sin- | Not warped. Not | Sound. 
ed, nonseasoned tered lime. eracked. Hard. 
clinker. 
Ground, under-| 176.1] 94.0 | Considerable sinter- | Completely disinte- | Completely 
burned, nonsea- ed, nonsintered, grated and badly disinte 
soned clinker. and some slaked swollen. grated. 
lime. 
The same aérated 8/ 7.61} 94.0 | No active free lime-___| Sound ----_--_----- Sound. 
days. 
The same (aérated | 94.0] 1.00 | Sintered, nonsinter- | Slightly disinte- Do. 
8 days) and re- ed, and slaked lime. grated and rather 
ground. soft. 
Commercial cement | 76.4} 95.6 | Some sintered, non- | Sound ---_--------__ Do. 
“N’’ as received. sintered, and_slak- 
ed lime. 
Same reground --_-__ 99.0 | 100 Same, but greater in | Disintegrated --.-_- Do. 
amount. 
The failure of boiling water to attack the free lime in the 
aérated cement until regrinding had been resorted to, can be 
attributed to the impermeability of coatings of slag or calcium 
carbonate surrounding microscopical particles of free lime. 
(Table VI in Part I.) Therefore, we can extend McCready’s 
conclusions and state that even sound cements may contain free 
lime the destructive force of which may not develop in a month 
or a year. 
Obviously the force which operates to cause cements and 
mortars to disintegrate will not become apparent to the eye until 
it has overcome the strength of cohesion developed by other con- 
stituents in the cement, but it can not operate at all without 
weakening the force which binds the particles together. Conse- 
