THE PHILIPPINE 
JOURNAL OF SCIENCE 
A. CHEMICAL AND GEOLOGICAL SCIENCES 
AND THE INDUSTRIES 
VoL. VII JUNE, 1912 No. 3 
PHYSICAL AND CHEMICAL PROPERTIES OF PORTLAND 
CEMENT. PARTS IV AND V. 
By W. C. REIBLING AND F. D. REYEs. 
(From the Laboratory of General, Inorganic and Physical Chemistry, 
Bureau of Science, Manila, P. I.) 
PART IV.—THE STRENGTH OF PORTLAND CEMENT. 
INTRODUCTION. 
The most important as well as the most elusive and subtle 
problem met with in the consideration of the hardening of Port- 
land cement is in respect to the development and permanency of 
its strength. 
Normal cement burned in the old dome and ring kilns seldom 
attained great early strength. The later, rapid development 
of the rotary-kiln process in the United States soon uniformly 
produced a Porland cement which hardened very rapidly. As 
such cement aided rapid construction work, consumers were 
eager to secure it. They even went so far as to offer a bonus 
for sound cement which would give exceedingly high 7-day tests. 
However, it soon became known that this sound, high testing, 
rotary cement usually developed an abnormal decrease in strength 
which was not characteristic of the sound, slower hardening, 
set-kiln products. 
At first this retrograde movement was thought to be character- 
istic of only the neat tensile strength determinations, but now it is 
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