PARTS IV, V. 
159 
TABLE XLVII.—Showing the effects of thorough, prolonged aération on 
finely ground Portland cement. 
PHYSICAL AND CHEMICAL PROPERTIES. 
% Tensile strength in pounds per square inch. 
2 Neat mortar. 1:3 Ottawa sand mortar. 
Cement. 5 : 
2 a | a 
2 n we} f n > 0 
= Fay See eet Nay Selgin lbienl eet oa) Nias 
EB pW seeeh PTET Joby egy I Mek FST 
is2) 1) - a ) al é a Cr) a 
H Aigireceivied® sis. tue usb ule ee 2.97 460 | 477 | 498] 503] 205} 301) 350) 290 
H Thoroughly aérated 4 months _.; 2.742 0; 820] 297) 320 0} 148; 284] 289 
N Asreceived, theresidueremain- 
ing on a 200-mesh sieve being 
ejected te tem asa reese 8.091 | 550} 564] 582] 570} 317) 412) 447) 425 
eee Thoroughly aérated 100 days, 
the residue remaining on a 
200-mesh sieve being rejected_| 2.807 0) 820] 365 | >395 Of eae 280 | 6335 
« Less than. 
b One year and four months. 
Owing to the protective coating of carbonate which surrounds 
the particles of aérated cement, the rate at which the inner 
active constituents become indurated depends on the per- 
meability and exposure of the mortar. A good example of this 
is the 28-day values of the aérated cement H. As recorded in 
Table XLVII, the sand mortar developed a strength of 143 
pounds while the neat remained almost too weak to support the 
weight of the clips. As is shown in Tables XLVIII and XLIX, 
it was found that larger specimens, especially those which were 
not submerged in water, hardened so slowly that the time tests 
of aérated and nonaérated cement showed a greater difference 
than the briquettes. 
TABLE XLVIII.— One-year tensile and compressive strengths of aérated and 
Average compressive 
nonaérated cement H in pounds per square inch. 
Average tensile strength 
0: 
strength of 3’ x 4’ 
cylinders of 1:3 sand 
Specific f 1:3 sand mortar 3 
Cement H. gravity.| briquettes which were mortar which were 
ReaPonineaten stored 7 days in moist 
; air and then weathered 
outside. 
As received -____------1--- 2.97 | 274 (efficiency = 100) -____ 8,696 (efficiency = 100). 
Aérated 90 days__---.----- 
2.83 
222 (efficiency = 81)______ 
2, 280 (efficiency = 61.7). 
