124 



KEIBLING. 



quarry at Sisiman, near Mariveles across Manila Bay, or from the old 

 Spanish quarries near Angono on Bay Lake, and more especially the 

 materials located by George I. Adams, of the division of mines, Bureau 

 of Science, just north of Angono (which is the best rock for road material 

 thus far found near Manila) may be found so efficient as to prove the 

 most economical material in the end. The stone frpm Sisiman with- 

 stands a pressure of 1,115 tons per square foot. By using leaner mix- 

 tures of properly crushed and graded stone or less massive concrete, it 

 may be able to compete in cost with reliable concrete made with Pasig 

 gravel. Then, too, important work often demands the best concrete 

 obtainable, regardless of expense. 



Sisiman rock unfortunately has a very undesirable, splintery or spally 

 fracture which reduces its concrete efficiency. However, if uniformly 

 graded it produces a good aggregate for concrete as the following test 



will show: 



Sisiman rock concrete.* 



Dimensions, in 

 inches. 



Propor- 

 tions, by 

 volume. 



Age. 



Total strength, 

 in pounds. 



Strength, in 

 pounds, per 

 square inch. 



Mark on cubes. 



In 



moist 



air. 



In 

 air. 



First 

 crack. 



Ulti- 

 mate. 



First 

 crack. 



Ulti- 

 mate. 



6 X 6 X 6 



1:2:4 



Days. 



7 



Days. 

 21 



47, 745 



75, 770 



1,326 



2, 105 





"Beach sand was used. The stone was all broken to pass 1.5 inch circular- openings 

 and the fine material passing J inch mesh sieve was removed. 



Comparative tests between 1:2:5 mixtures of good Mariquina gravel 



and of broken basaltic rock, used with the same cement and sand, showed 



that the rock, despite its larger percentage of voids, gave the more efficient 



aggregate. 



Mariquina gravel versus basaltic rock concrete. 



Dimensions of 

 cubes, in inches. 



Propor- 

 tions, by 

 volume. 



Age. 



Total strength, 

 in pounds. 



Strength, in 

 pounds, per 

 square inch. 



Mark on cubes. 



In 



moist 



air. 



In 

 air. 



First 

 crack. 



Ulti- 

 mate. 



First 

 crack. 



Ulti- 

 mate. 



6 X 6 X 6 



6 X 5 X 6 



1 1 : 2 : 5 



Weeks. 

 3 



Weeks. 

 9 





I 



-1,550 

 -2, 124 



2,026 

 2,380 



Mariquina gravel. 

 Basaltic stone. 





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