SAMPLING AND TESTING HIGHWAY MATERIALS. 
11 
through the neck; (4) remove the thermometer and add sufficient kerosene to fill 
exactly to the mark on the neck, drawing off any excess with the burette; (5) run into 
the flask about one-half of the kerosene in the bulb to remove air bubbles and then 
run in more kerosene, removing any material adhering to the neck of the flask, until 
the kerosene is just below the ground glass; (6) place the hollow ground -glass stopper 
in position and turn it to fit tightly and then 
run in kerosene exactly to the 200 c. c. (6.76 
ounces) graduation on the neck, care being- 
taken to remove all air bubbles in the flask; 
(7) read the specific gravity from the gradua- 
tion on the burette, and the temperature of 
the oil in the flask, noting the difference be- 
tween the temperature of the oil in the bulb 
before the determination and that of the oil in 
the flask after the determination; (8) make a 
temperature correction to the reading of the 
specific gravity in accordance with the table 
furnished by the manufacturer of the apparatus, 
adding the correction if the temperature of the 
kerosene has increased and subtracting it if the 
temperature of the kerosene has decreased. 
7. WEIGHT PER CUBIC FOOT AND VOID 
TESTS ON COARSE AGGREGATE. 
(1) The weight per cubic foot of coarse aggre- 
gate shall be determined as follows: A cylin- 
drical measure of at least one-fourth cubic foot 
capacity, with inside diameter approximately 
equal to inside height, or a box approximately 
cubical in shape and of not less than one-half 
cubic foot capacity shall be used. Ordinarily, 
the determination should be made on aggregate 
in air-dry condition. When the aggregate con- 
tains an appreciable amount of moisture, the 
percentage of water by weight shall be deter- 
mined and recorded. 
(2) About one-fourth of the total amount of 
aggregate necessary to fill the measure shall 
first be introduced in such manner as to avoid 
separation of sizes. This material shall then be 
shaken down by rocking the measure from side 
to side until no further settlement takes place. 
The process shall be repeated until the measure 
has been filled to overflowing, after which it shall be struck off level with the top 
with a straightedge and weighed. 
The percentage of voids in the aggregate may be determined from the weight per 
cubic foot and specific gravity in the usual manner. 
8. WEIGHT PER CUBIC FOOT TEST FOR FINE AGGREGATE. 
(1) For determining weight per cubic foot of fine aggregate use a cylindrical metal 
measure having an inside diameter equal to the inside depth. A measure of capacity 
of one-fifth to one-half cubic foot is suggested, but a measure as small as one-twentieth 
cubic foot capacity may be used. Ordinarily the weight per cubic foot should be 
Fig. 9. — Jackson specific-gravity apparatus. 
