

EXAMINATION OF BITUMINOUS ROAD MATERIALS. H 



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. 



1 penetrometer complete, with, a seconds pendulum or metronome. (Figs. 6 and 7.) 



1 tin bos approximately 5 centimeters in diameter by 3.5 centimeters in height. 



1 large 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. 



The object of the penetration test is to ascertain the consistency 

 of the material under examination by determining the distance a 

 weighted 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, annealed- steel 

 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 

 again polished with jewelers' rouge. The finished needle is from If 

 to 2 inches in length 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 can 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 aluminum 

 rod b by a binding screw. The aluminum rod is secured in 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, allowing the needle to penetrate perpendicularly without the 

 aid of a support. 



The, frame, aluminum rod, and needle weigh 100 grams with the 



■it <■ on the bottom of the frame, while without the weight they 



'i 60 grams. Figure 6 shows the needle and weighted frame, 



her with side and front views of the entire apparatus, put 



fcher and ready for making a penetration. The shelf for the 



sample is marked d; e is the clamp to hold the aluminum rod until 



jt. i desired fco make a test; and/is a button which, when pressed, 



