PHYSICAL AND CHEMICAL PROPERTIES. PARTS IV, V. 173 
Tensile and compressive strengths in pounds per square inch. 
Percent of 
Age in days. Age in months. gain based on 
Ce- strength. 
ment. Description. 
7. 28. 3. 6. 12. | 24, 28. |7 days. | 28 days. 
L | Tensile strength of neat 
mortar in water --____- 2509 603 668 703 | 670) 690 666 |+ 30.8 +10.4 
CO) iN ees GOs sss anes Fr 653 107 718 664 | 641) 652 651 |— 0.3 | — 7.9 
L | Compressive strength of 
neat mortar in water-__| 4,620 | 6,100 | 6,820 | 7,930} | 11,010 |+-138.3 | +80.5 
Omi ease doy eee ee 7,050 | 8,250 | 7,550 | 8,150) xX x 9,890 |+ 40.3 | +19.8 
L Tensile strength of 1:3 
Ottawa sand mortar 
weathered outside_____ 239 393 375 455 | 514) 537 763 |-+219.0 | +94.2 
OF |= = i ee ee 339 476 380 350 | 389, 547 683 |--101.7 | +43.5 
L_ | Compressive strength of 
1:3 Ottawa sand mor- 
tar weathered outside _| 2, 180 | 3,180 | 2,820 | 4,100| x x 5, 260 |--147.0 | +68.1 
Oy) eee Cs fr Sale ey tage 2,620 | 3,680 | 3,780 | 4,040} x 4,930 |+ 88.2 | +35.8 
L | Tensile strength of 1:3 | 
Ottawa sand mortar 
iniwaters-=- <=) 55555 233 287 347 369 | 370] 348 345 |+ 48.1 |) +20.2 
(ois eee GW ccocaseceseezsssene 313 379 364 340 | 304] 269 278 |— 11.2 | —26.7 
L_ | Compressive strength of 
1:3 Ottawa sand mor- 
tar in water x | 2,080 | 2,340 | 2,930} x x 3, 280 x +61.6 
Osea ope seeee ae sees < | 2,565 | 2,660 | 3,950] x x 3, 537 x +37.9 
L | Tensile strength of 1:3 
quartz sand mortar in 
water 292-222 225202. 153 201 283 280 | 288] 265 255 |+ 66.7 | +26.8 
OW La=== GC) ee 227 297 291 269 | 234] 200 195 |— 14.1 | —34.4 
Compressive strength of 
L 1:3 quartz sand mortar 
in water _ 1,645 | 2,120 | 2,160 | 2,200] x x 2,921 | +77.6 | +37.7 
(8) |iceeeel (010) eens 2,187 | 2,873 | 3,051 | 2,727} x 3,073 | +40.8 |} + 6.9 
| 
® The value of each test represents the average of 10 determinations. 
Therefore, it is evident that greater constancy in volume and 
strength is obtained by reducing the quantity of free lime in 
hard-burned Portland cements regardless of whether this is 
accomplished by seasoning or by better burning. 
The same conclusions may be drawn from the data of others. 
For example, 7 brands of typical, American rotary cemerit, the physical 
properties of which showed that they were all hard-burned products, were 
examined at the St. Louis Testing Laboratories.” Twelve of the 70 
samples tested gave imperfect results when subjected to the steam test 
and, although the unsoundness was slight, the characteristic effect of the 
" Bull. U. S. Geol. Survey (1908), No. 331. 
