PHYSICAL AND CHEMICAL PROPERTIES. PARTS Iv, Vv. 189 
CONCLUSIONS. 
(1) The qualities in Portland cement which we need are 
constancy in volume and setting properties, and reliability of 
strength, and it is of vital importance that this material both 
harden rapidly and maintain great strength. We believe that 
the enforcement of the following recommendations will increase 
the efficiency of the present standard cement specifications of 
the American Society for Testing Materials. 
A. Concerning the constancy of volume: 
(a) In order to secure the desired efficiency in Portland cement, 
the manufacturer must be induced to burn his materials 
so that no seasoning is required to produce a sound 
cement. 
(6) Failure to meet the requirements of the accelerated tests 
shall (in place of “need not” as now specified) be sufficient 
cause for rejection. 
B. Concerning the specific gravity: 
(a) In order to secure the best burning and proper storing, the 
specific gravity of the cement as received (i. e., dried but 
not ignited) shall not be less than 3.10 unless the loss by 
ignition is less than 2 per cent.* 
(6) The clause “Should the test of cement as received fall below 
this requirement a second test may be made upon a 
sample ignited at a low red heat” should be omitted. 
(c) The clause “A low specific gravity in conjunction with a high 
loss by ignition is positive proof of undesirable burning, 
adulteration, or seasoning” should be substituted for the 
present paragraphs concerning the significance of the 
specifie gravity. . 
C. Concerning the fineness: 
(a) As the specifications now stand, there is little incentive to 
induce the manufacturer to grind to the degree of pul- 
verization that modern improvements in grinding machin- 
ery has made practicable unless his cement is so poor 
that extreme fineness is necessary to enable it to pass the 
requirements for strength and soundness. Therefore: 
(6) That the cement shall leave a residue of not more than 5 
per cent by weight on the No. 100, and not more than 20 
per cent on the No. 200 sieve. 
The above recommendation provides for the possibility of a well-burned 
cement with a lower specific gravity provided the low gravity is not due to 
subsequent absorption of volatile constituents; but our experience does not 
include such a possibility. 
