PHYSICAL AND CHEMICAL PROPERTIES. PARTS IV, V. 157 
economic efficiency in modern concrete construction depends upon 
perfections in the manufacture of Portland cement. 
TABLE XLIV.— Time tests of the tensile strength of typical natural and 
Portland cements of good quality.” 
Tensile strength in pounds per square inch. 
Mortar. a a a a on n a a a ‘a 
n iy we uy I ua uy mw uw u ~ Cy 
ES 3 a a a a 3 a 3 @ a 3 
3 oo) o o ® ° o oO o oO BS, 
Gs) iS > BS > ES ES > > > > zB 
ist N Lon! Nn oO st 12 o é co for} cal 
“Giant’’ Portland cement (1894). 
Nea bee eatin See Sere. 547 | 699] 666} 645) 673} 678} 668) 642] 631] 659) 676) 689 
MiZisandvee st ooo 255 2 397 | 529 769} 755) 775 | 793 755 | 670} 677} 695] 669] 651 
“Union’’ natural cement (1894). 
245 | 460] 453] 443) 458) 465) 540] 493] 615 | 427 |_______ 
190} 526) 574| 599) 635) 677} 775 | 728) 744] 737) 837 
® These figures are reproduced from a report by R. W. Lesley, Amer. Soc. Test. Mat. (1905), 
ee of Cement Tests on the New Croten Dam Division of the New York Aqueduct 
Commission representing a record of nearly half a million barrels of “Union” natural and 
“Giant” Portland cements. 
Commercial Portland cement.—The character of the curves 
of tensile strength is influenced by the extent to which the 
cement has seasoned. The general effects of thorough aéra- 
tion on sound commercial Portland cements are recorded in 
Table XLV (see Table A, Appendix I, Parts I and II, for the 
chemical analyses). 
The cements described in Table XLV were all received in 
sound, paper-lined barrels and contained practically no cake. 
They had been sufficiently seasoned as they failed to show any 
tendency toward unsoundness when subjected to the accelerated 
tests. Therefore, the physical properties of these cements are 
characteristic of properly packed and stored, uninjured, sound 
products produced by the manufacturers. 
‘The data recorded in Table XLV make it apparent that the 
tensile strength, and even the character of the curve of strength, 
of any given cement may he affected to a considerable extent 
by the method of molding employed or the quantity of water and 
the quality of sand used. In spite of these variable factors 
certain characteristics of Portland cement influence the strength 
to such an extent as to be readily apparent. 
