204 
The Philippine Journal of Science 
1921 
strength with advancing age. Cognizance by those in charge of 
construction was apparently taken of the poor results given by 
the 1 : 2 : 4 mixture, and an effort was made to increase the 
ultimate compressive strength of the concrete by increasing the 
quantity of cement some 15 per cent. The average result ob- 
tained from the 1.2 : 2 : 4 specimens at 29 to 31 days is 1,512 
pounds per square inch, and that of older specimens in this 
series, aged 35 to 48 days, is anomalously lower, being 1,225 
pounds per square inch. Mixtures proportioned 1.15 : 2 : 4 and 
aged 29 to 34 days gave better results, showing a mean value 
of 1,841 pounds per square inch. Increase in the quantity of 
cement gave higher results at the end of 28 to 31 days than did 
the 1:2:4 mixture ; but at later periods the results given by 
richer mixtures are practically the same as, or less than, those 
obtained from the leaner mixtures. Comparatively few tests 
were made of 1:2:5 and 1 : 2.5 : 5 mixtures. Results ob- 
tained from test pieces made of 1 : 2 : 5 concrete aged 29 to 35 
days average 821 pounds per square inch, and those given by 
1 : 2.5 : 5 specimens aged 28 to 33 days average 1,296, which is 
much higher than the results given by 1:2:4 specimens of 
similar ages. Increasing the percentage of cement in this series 
to yield the mixtures 1.12 : 2.5 : 5 and 1.2 : 2.5 : 5 gives such 
anomalous results as to lead one seriously to question the methods 
of proportioning employed. Increased cement content should in- 
crease the compressive strength of the concrete, but the re- 
sults actually obtained are lower. The 1.2 : 2.5 : 5 specimens 
aged 28 to 33 days average 810 pounds per square inch, and the 
1.12 : 2.5 : 5 test pieces aged 28 to 35 days average 666. 
A consideration of the values secured from the 1:3:6 speci- 
mens discloses some of the lowest compressive strengths recorded 
in this paper, the lowest result, 97 pounds per square inch, being 
obtained from 1:3:6 concrete made in Capiz. Concrete from 
Barugo School averages 130 and 251 pounds per square inch; 
that from Tabontabon School, 154 pounds; three specimens from 
Ormoc Market, 118 pounds; and some test specimens made of 
concrete used in Hilongos Market gave a mean compressive 
strength of 295 pounds. These results are rather disquieting; if 
the concrete in the test specimens is representative of that 
actually used in the respective structures, failures may be ex- 
pected. The grand average of 444 pounds per square inch is ob- 
tained from the values given by the 1 : 3 : 6 specimens aged 27 
to 31 days ; with aging there is a substantial increase of strength, 
specimens of this mixture aged 37 to 47 days showing an aver- 
age of 926 pounds per square inch. An increase in cement con- 
