CONCRETE CONSTRUCTION IN THE PHILIPPINE ISLANDS. 123 



Compression strength of concrete obtained with Pasig sand and gravel. 

 SAND NOT SCREENED. 



Proportion by 

 volume. 



■ 



Relative volume, in cubic 

 inches. 



Total strength 



of 6-inch cubes, 



in pounds. 



Compression 

 strength, in 

 pounds, per 

 square inch. 



Age, in 

 days. 



Ce- 

 ment. 



Sand. 



Gravel. 



Water. 



At first 

 crack. 



Ulti- 

 mate 

 strength 



At first 

 crack. 



Ulti- 

 mate 

 strength 



In 



moist 



air. 



In 

 open 

 air. 



1:2:4 



1:2:5 



1:2:6 



1:2:6" 



1 : 2 : 6« 



54 

 43 

 36 

 36 

 36 



108 

 86 

 72 

 72 

 72 



216 

 216 

 216 

 216 

 216 



50.0 

 41.3 

 32.9 

 35.3 

 40.2 



44, 280 

 46, 770 

 44, 490 

 32, 000 

 34, 740 



53, 200 

 52, 450 

 53, 440 

 42,870 

 39, 000 



1,230 

 1,300 

 1,236 



889 

 965 



1,480 

 1,457 

 1,484 

 1,191 

 1,083 



7 



7 

 7 

 7 

 7 



22 

 22 

 - 22 

 22 

 22 



SAND SCREENED THROUGH 10-MESH SIEVE. 



1:2:4 



1:2:5. 



1:2:6. 



54 

 43 

 36 



108 

 86 



216 

 216 

 216 



54.3 

 52.4 



34, 500 

 22, 210 

 22, 080 



39, 200 

 33, 230 

 26, 600 



960 

 617 

 613 



1,090 

 923 

 739 



22 

 22 



22 



a The effect of gauging with an excess of water is shown in these two results, 

 should be exercised not to overdo the "puddling" method. 



Care 1 



When these cubes were crushed, about 40 per cent of gravel broke ; 1:2:4,: 

 1:2:5, and 1:2:6 mixtures gave almost the same crushing strength, indicating that 

 the ultimate strength was due to the mortar which was much stronger than thei 

 gravel. The contract specified a 1:2:4 mixture. The voids in the gravel werei 

 only .37 per cent, and a 1:2:5 mixture gave a better concrete both in theory and! 

 in practice. 



The sarid contained 20.6 per cent of fine gravel remaining on the 10-mesh 

 sieve, 40 per cent of which was fine gravel retained by the 4-mesh. Accordingly 

 a 1 : 2 mixture produced a stronger mortar than it would if the sand had contained 

 no gravel. As this mortar was sufficient to fill the voids in the gravel, which 

 were lowered by the fine gravel from the sand, a stronger concrete resulted. 



It will be difficult to find a substitute for Pasig gravel because of 

 its cheapness. However, gravel has been dredged from the Mariquina 

 Eiver which enters the Pasig at a point about 10 miles from its mouth 

 and about 8 miles above Manila, which has proved far superior to the 

 usual Pasig aggregate since concrete made with it withstood a pressure 

 of over 2,000 pounds per square inch and yet showed few broken stones. 



The crushed stone at present used by the city for macadamizing; 

 streets is- not satisfactory for concrete construction, because of its frac- 

 ture and texture and the considerable amount of quarry dirt which it ! 

 contains. However, it seems very possible that crushed stone from the| 



