CONCRETE CONSTRUCTION IN THE PHILIPPINE ISLANDS. 131 



Compression tests of coral rock concrete. 



In every instance the majority of the stones in the concrete were 

 broken or crashed. However, the harder coral rock concrete was stronger 

 at 7 days than the other at 29 days. 



Three sands and four stones were available for a certain concrete 

 structure. They were all sent to this laboratory for inspection and test- 

 ing. The report is interesting inasmuch as it illustrates the great 

 variability in the efficiency of different available materials and the ac- 

 curacy and value of preliminary inspection. 



Briefly summarized the report was as follows : 



Sand tests {preliminary report). 



Sand. 



Specific 

 grav- 

 ity. 



Voids, 

 dry. 



Description. 



Order 



of 

 merit. 



Beach 



No. 1 



No. 2 



2.60 



2.62 



2.74 



Per ct. 

 47.3 



45.0 

 41.7 



Very fine in grain; 10 per cent "dead sand;" poor granular- 

 metric composition. 

 Clean, calcareous, and of good granularmetric composition- 

 Similar to sand No. 1, but better in all respects. _ __ 



3 



2 

 1 







Mortar tests (final report). 



Sand. 



Tensile strength, in pounds, per square inch. 



Relative com- 

 pression strength 

 of mortar cylin- 

 ders (7 days in 



1:2 by volume. 



1:3 by volume. 



1:3 by weight. 



moist air; 21 

 days outside). 



7 days. 



28 days. 



7 days. 



28 days. 



7 days 



28 days. 



1:2 by 

 vol- 

 ume. 



1:3 by 

 volume. 



Beach 



285 

 306 



398 

 378 



183 

 170 

 135 



260 

 200 

 240 



162 

 128 

 188 

 308 



225 

 194 

 242 

 366 



1,788 

 2,790 

 2,910 



1,550 

 1,597 

 1,715 



No. 1 . 



No. 2 



Standard Ottawa 





















Sand No. 2 gives the best mortar results. 



