MATERIALS FOR CONCRETE CONSTRUCTION IN MANILA. 477 



the smallest sieve. In this diagram the analj'sis follows very closely the 

 even grade line. The percentage of voids in a sample of washed Sisiman 

 rock was found to be 43.4. 



90 

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K Q 50 

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CENTIMETERS ^",wi^---^ ^ ^ .. 

 INCHES 10 IS 20 30 .45 .6 7 lOO /.SO 2 2S 



DIAMETER OF PARTICLES IN CENTIMETERS AND INCHES 



Pig. 16. — Gkanulakmeteic Analysis of Sisiman Cedshed Stone, Fines Excluded. 



E^jflciency. — ISTo tests have been made to show the strength which may 

 be obtained in concrete using the Sisiman stone. It appears to be very 

 satisfactory when used as crusher run. It may, however, prove to show 

 a higher percentage of efSciency when selected sizes are used. The fines 

 from the rock if replotted as sand, show 23 per cent passing a 100-mesh 

 sieve. This is really a rock flour, and as has already been suggested above, 

 should be excluded from concrete work by washing the stone. 



The crushing strength of Sisiman stone was determined by dressing a 

 block to true edges and crushing it in a compression strength machine. 

 It broke under a pressure of 1,115 tons to the square foot (1088. kilo- 

 grams per square centimeter). 



At the writer's suggestion, the United States Army engineers opened 

 a quarry on Corregidor. The stone is a white dacite, very much sheared 

 and jointed so that it requires but little breaking up for feeding to a 

 crusher. A block of this stone dressed to true edges crushed under a 

 pressure of 1,009 tons to the square foot (985. kilograms per square 

 centimeter) . 



A stone from the site of the new city quarry near Angono crushed 

 under a pressure of 1,584. tons to the square foot (1547. kilograms per 

 square centimeter). 



It is piroposed to make further tests of the crushed stone available for 

 use in Manila and include in this work all the quarries wdiich have been 

 mentioned above. 



