128 



KEIBLING. 



Plate I is a photograph of the second to the last cube recorded in the 

 above table. Each arrow points to the center of the exposed surfaces of 

 crashed or cracked stones. As can be observed, the mortar between these 

 stones is almost perfectly sound. 



A more specific description of the stones designated by the arrows is 

 as follows : 



Arrow No. 



Dimensions 



of exposed 



surface, in 



inches. 



Remarks. 



1 „ 



1. 5 x 0. 6 



1.5 Xl.5 



1. 25 X 0. 6 

 l.OX 0.75 

 1.5X1.0 

 3.0X1.0 

 1. 2X0.5 

 2 X 1. 25 

 1. 3 X 0. 6 



1.25X1 



Large piece of wood charred on the outside. 

 Large round stone of soft, yellow substance which is about 

 as durable as dry clay. Stone was completely crushed. 



Do. 



Do. 



Do. 



Do. 

 Harder than above. One end cracked off as illustrated. 

 Large stone, cracked in two places. 

 Large stone, split through the center. 



Do. 

 Small cracked and crushed stones. 



2 



3 



4 



7 



8 



9 



11. __ 



13 



17 



5, 6, 10, 12, 14, 15, 16, 18_ 







The floor concrete from the Naga Kiver Bridge also contained poor 

 gravel, and again showed poor strength despite good mortar and proper 

 proportioning. 



Concrete cubes from Naga River Bridge. Province of Ccbn.& 



Dimensions, in inches. 



Propor- 

 tions, by 

 volume. 



Age. 



Total strength, 

 in pounds. 



Total strength, 



in pounds, per 



square inch. 



Mark on cubes. 



First 

 crack. 



Ulti- 

 mate. 



First 

 crack. 



Ulti- 

 mate. 



6X 6X6 



1:2:4 



Days. 

 30 

 30 

 30 

 30 

 29 

 29 



12, 255 

 11, 750 

 20, 105 

 14, 055 

 16, 685 

 8,460 



21, 285 

 20, 820 

 28, 000 

 25, 940 

 18, 525 

 11, 260 



340 

 326 

 558 

 390 

 463 

 235 



591 

 578 

 778 

 720 

 515 

 213 



P-1. Floor. 

 P-2. Floor. 

 P-3. Floor. 

 P-4. Floor. 

 P-5. Floor. 

 P-6. Floor. 





a The mixture is good and the mortar hard, but the gravel is fine and of poor quality. 

 Much of it broke through weathered material. 



At other times good enough gravel has been used ; but poor sand, weak 

 mortar or improper proportioning has caused poor concrete. A few 

 examples will serve to illustrate this. 



