172 REIBLING AND REYES. 
developed by an indurated Portland cement should be the more 
reliable the less free lime it contains. The results obtained by 
testing two hard-burned cements, one of which contained more 
nonslaked free lime than the other, are recorded in Table LII. 
TABLE LII.—Physical properties of hard-burned commercial cements, brands 
L and O. 
Total in- 
crease in 
) the length 
. As received. 4 Reground.* “| of neat ex- 
eo} pansion 
5 bars kept 
in in water. 
[a3] 
‘ Per cent. 
L A little slaked lime and a little hard- | A slight increase in the amount of 
burned, nonslaked lime. slaked and nonslaked free lime. 
than brand L. of slaked and nonslaked free lime. 
(dried at 1109). || 0 | 3.08 
|=! 
81.2 per cent through the 200-mesh sieve. 
97.3 per cent through the 100-mesh sieve. 
O | 77.4 per cent through the 200-mesh sieve. 
95.2 per cent through the 100-mesh sieve. 
| Specific gravity |{ L | 3.11 
| Fineness --_--_-- 
0. 044 
oO More slaked and nonslaked lime | A considerable increase in the amount ‘a 
8 Lime determined microscopically by the phenolate test. 
The 7- and 28-day results show that cement O had much 
greater early strength, due in all probability, since L was ground 
the finer, to its larger content of quick-hardening calcium sili- 
cates and aluminates. However, the strength of cement O im- 
proved very little with age, showing in many instances even a 
marked ultimate decrease. 
On the other hand, cement L, which contained less free lime 
and possessed greater constancy in volume, improved consider- 
ably with age, the 28-month report showing in all instances, 
whether constantly submerged in water or weathered outside 
in the sun and rain, a decidedly greater strength than at seven 
and twenty-eight days. In spite of its comparatively low early 
strength, cement L showed the greater efficiency at the end of 
twenty-eight months. 
