SAMPLING AND TESTING HIGHWAY MATERIALS. 67 
Suggested Method fob Examination of Bituminous Mobtabs. 
Bituminous mortars may be extruded by the use of bronze Bitammom 
tubes which are capable of being whirled in the type of centrifuge mor tars. 
similar to the Babcock milk tests. This method is based on de- 
cantation of the supernatant solvent. The difference between the 
amount of final aggregate and the original amount taken gives the 
amount of bitumen extracted, which is subject to correction by 
deducting the amount of ash determined from the washings. The 
ash correction to be made as given under A. 
MECHANICAL ANALYSIS OF EXTRACTED AGGREGATES. 
(A. S. T. M. standard method, serial designation I> 19-16, slightly 
modified.) 
The mineral aggregate left after extraction of the bituminous 
material shall be dried at not over 11<> : C. (230° F.) to a constant 
weight. It shall be separated by the use of a screen having open 
ings one-quarter inch in diameter. The portion retained on the 
screen shall be examined in accordance with the method for me- 
chanical analysis of broken stone, etc. The portion passing this 
screen shall be examined in accordance with the method for the 
mechanical analysis of sand or other fine aggregate, except that 
the percentage of 200-mesh material shall be determined as fol- 
lows : A 10-mesh sieve shall be superimposed on a 200-mesh sieve 
and the aggregate placed on the 10-mesh sieve. The material is 
then immersed and gently oscillated in a bath of gasoline until all 
fine material has been washed off. The washed material is then 
dried and weighed. The weight of material passing the 2< h >-mesli 
sieve may be obtained as follows : 
Weight of total mineral aggregate (including weight of mineral 
material recovered from extract) minus weight of material re- 
tained on sieve gives weight of mineral matter passing 200-mesh 
sieve. 
The mechanical analysis shall be recorded in the following 
manner : 
Per cent. 
Passing 200-mesh sieve 
Passing 80-mesh sieve and retained on a 
200-mesh sieve 
Passing 40-mesh sieve and retained on a 
80-mesh sieve 
Passing 10-mesh sieve and retained on a 
40-mesh sieve 
Passing one-quarter-incb screen and re- 
tained on a 10-mesh sieve 
Passing one-half -inch screen and retained 
on a one-quarter-inch screen 
Passing three-quarter-inch screen and re- 
tained on a one-half-inch screen 
100. On 
In the sieve analysis of the sand fraction, the following sizes 
of sieves shall be used: 10-mesh. 40-mesh. 80-mesh, and 200-mesh. 
MECHANICAL ANALYSIS OF BROKEN STONE OR BROKEN 
SLAG, EXCEPT AGGREGATES USED IN CEMENT CON- 
CRETE. 
(A. S. T. M. standard method, serial designation D 18-16. slightly 
modified. ) 
The method shall consist of (1) drying at not over 110" < \ 
(230° F.) to constant weight a sample weighing in pounds six 
times the diameter in inches of the largest holes required ; (2) 
