“EXAMINATION OF BITUMINOUS ROAD MATERIALS, il 
The float test is a most convenient one for roughly checking the 
uniformity of different shipments of bituminous material furnished 
under specifications. 
PENETRATION TEST. 
EQUIPMENT. 
I penetrometer complete, with a seconds pendulum or metronome. (Figs. 6 and 7.) 
1 tin box approximately 5 centimeters in diameter by 3.5 centimeters in height. 
Llarge metal kitchen spoon. 
1 steel spatula or kitchen knife. 
1 glass penetration dish approximately 10 centimeters in diameter by 6 centimeters 
high. 
1 enamel-ware dish approximately 3 inches deep and 9 inches in diameter. 
1 chemical thermometer reading from —10° C. to 110° C. 
METHOD. 
The object of the penetration test is to ascertain the consistency 
of the material under examination by determining the distance a 
weignted needle will penetrate into it at a given temperature. A 
standard needle is employed for this. purpose and this needle is 
usually weighted with 100 grams. The depth of penetration is de- 
termined upon the bitumen maintained at 25° C., while the load is 
applied for five seconds. 
The standard needle is made from round, polished, panealederecl 
drill rod having a diameter of from 0.0405 to 0.0410 inches. The 
rod is tapered to a sharp point at one end, with the taper extending 
back one-fourth inch. It is then highly polished, tempered, and 
agai polished with jewelers’ rouge. ‘The finished needle is from 1? 
to 2 mches in leneth and exactly 0.040 inch in diameter. This 
needle, as made in the laboratory of the office, gives the same results 
as the old standard No. 2 cambric needle, and possesses the advantage 
that it ean be exactly duplicated and accurately described. 
The penetration apparatus shown in figure 6 consists of a standard 
needle a, inserted in a short brass rod, which is held in the alummum 
rod b by a binding screw. The aluminum rod is secured m a frame- 
work so weighted and balanced that, when it is supported on the point 
of the needle, the framework and rod will stand in an upright posi- 
tion, janet the needle to penetrate perpendicularly without the 
aid A a support. 
The frame, aluminum rod, and needle weigh 100 grams with the 
weight ¢ on the bottom of the frame, while without the weight they 
weigh 50 grams. Figure 6 shows the needle and weighted frame, 
together with side and front views of the entire apparatus, put 
together and ready for making a penetration. The shelf for the 
sample is marked d; e is the clamp to hold the aluminum rod until 
it is desired to make a test; and fis a button which, when pressed, 
