Aug. 13, 191 7 



Toughness of Bituminous Aggregates 



327 



Table IX. — Petrographic analyses of crystalline rocks used in toughness cylinders (second 



series) 



o Not analyzed. 



On realizing that changes in the size of particles in the aggregate 

 might have resulted from the efifects of compressing the cylinders, the 

 bitumen was extracted from the aggregates after the tests had been 

 made, and the rock particles were graded again by sieve analysis. The 

 results so obtained are given in Table X. Interesting changes were 

 noted in the proportioning of the aggregate and, whereas none of the 

 cylinders originally contained any particles passing a 50-mesh screen, 

 one of them. No. 8989, now contained 37.65 per cent passing this screen. 

 The relative proportion of all the sizes of particles have been changed 

 materially, but a careful study of the results fails to reveal any explana- 

 tion of the problem under discussion. 



Table X. — Grading of aggregate from cylinders after compression xvith percentage of 

 voids in compressed cylinders 



No. 



Sand. 



lOIOI. 



9093 • • 

 10108. 



9445 • • 

 9095.. 



9094. • 

 8136.. 

 8992 . . 

 9321.. 

 8993 . . 



9281. 



Sieve analysis. 



Retained on- 



lo-mesh. 20-inesh. 50-mesh 



20. 65 

 19.65 

 13.90 

 17. 00 



14. 00 

 13.90 

 14- 25 



15. 10 

 16.05 

 14. 80 

 15.40 

 II. 10 

 17. 00 



24. 90 

 32-30 



28.75 

 28. 60 



30- 55 

 28. 40 



30-65 

 26. 50 



27- 75 

 30.75 

 28. 65 

 25-05 

 26. 50 



41. 80 



35-75 

 36.50 

 33-90 

 35-95 

 35-90 

 40- 73 

 28. 90 

 37-70 

 33-25 

 41-05 

 26. 20 

 31-75 



Passing 

 so-mesh. 



12.65 

 12. 30 

 20.85 

 20.30 

 19- 50 

 21. 80 



14-35 

 29- 50 

 18.50 

 21. 20 

 14.90 

 37-65 

 24-75 



Unfilled 

 voids in 

 cylinders. 



23-9 

 26.8 

 26. I 

 25-4 

 23- 2 

 26. 2 

 25.8 

 26. 4 



25-5 

 24. 2 

 27.7 

 24. 2 

 21. o 



