18, 2 King: Philippine Concrete and its Aggregates 209 
OCCIDENTAL NEGROS 
Results obtained from concrete specimens coming from Occi- 
dental Negros and marked 1 :2:4,1:2.5:5,and1:3:6are 
so much alike that one is almost forced to conclude that the 
entire series of test pieces was made from mixtures of more or 
less the same proportions. Specimens made of 1 : 2 : 4 concrete 
and aged 28 to 33 days gave an average compressive strength 
of 681 pounds per square inch; 1 :2.5:5 specimens aged 30 
to 34 days average 601 pounds; and the 1 : 8 : 6 test pieces 
ranging in age from 27 to 42 days average 722 pounds per square 
inch. With one exception, increasing age brought about in- 
creasing compressive strength in the series of test pieces made 
of 1:2:4 concrete; those aged 38 to 42 days average 859 
pounds per square inch, those aged 48 to 55 days average 1,044, 
and those aged 64 to 67 days average 1,279. The oldest speci- 
mens in this series however, those 85 and 93 days old, respec- 
tively, show less strength, and give the mean value of 1,038 
pounds per square inch. Test pieces made of 1 : 2.5 : 5 con- 
crete aged 37 to 41 days average 554 pounds per square inch, 
whereas those aged 56 to 63 days average 836 pounds per square 
inch. Values obtained from the 1 : 2 : 4 specimens are low 
and indicate a very poor grade of concrete. Fair strengths were 
given by the other mixtures. Only one sand coming from 
Occidental Negros was tested, and the results obtained are 
very satisfactory, though from field data it seems that this 
sand was never used in actual construction. 
ORIENTAL NEGROS 
Results shown by field specimens from Oriental Negros are 
good, though most of them were obtained from cubes consid- 
erably older than those made in the laboratory, so that compari- 
son of the two is unsatisfactory. Laboratory-made concrete 
proportioned 1 : 2:4 at 28 days gives an average compressive 
strength of 2,258 pounds per square inch. Only two field-made 
test pieces made of 1:2:4 were tested, and these at an age 
of 43 days average 1,964 pounds per square inch. The values 
given by the field specimens made of 1 : 3 : 6 concrete compare 
favorably with those obtained from laboratory-made cubes. 
The latter at 28 days average 1,128 pounds per square inch, 
and a single test piece of the former at 31 days gives 705 pounds. 
At ages ranging between 42 and 44 days, field specimens of 
1:3:6 concrete give a mean compressive strength of 1,202 
pounds per square inch. Only one sand from Oriental Negros 
