48 BULLETIN 949, U. S. DEPARTMENT OF AGEICULTUEE. 



all adhering bitumen. The reported penetration shall be the average of at least 

 three tests whose values shall not differ more than four points between maximum and 

 minimum. 



{b) When desirable to vary the temperature, time, and weight, and in order to 

 provide for a uniform method of reporting results when variations are made, the 

 samples shall be melted and cooled in air as above directed. They shall then be 

 immersed in water or brine, as the case may require, for one hour at the temperature 

 desired. The following combinations are suggested: 



At 0° 0. (32° F.), 200-gram weight, 60 seconds. 



At 46.1° C. (115° F.), 50-gram weight, 5 seconds. 



30. DETERMINATION OF DUCTILITY OF BITUMINOUS MATERIALS. 



(Method described in Trans. A. S. C. E., vol. 82, 1918, p. 1460.) 



A briquette of the material to be tested shall be formed by pouring the molten 

 material into a briquette mold. The dimensions of the briquette shall be 1 cm. 

 (0.394 inch) in thickness throughout its entire length; distance between the clips or 

 end pieces, 3 cm. (1.181 inches); width of asphalt cement section at mouth of clips, 

 2 cm. (0.787 inch); width at minimum cross section, half way between clips, 1 cm. 

 (0.394 inch). The centerpieces are removable, the briquette mold being held together 

 during molding with a clamp or wire. 



The molding of the briquette shall be done as follows: The two center sections shall 

 be well amalgamated to prevent the asphalt cement from adhering to them, and the 

 briquette mold shall then be placed on a freshly amalgamated brass plate. The 

 asphalt cement to be tested shall be poured into the mold while in a molten state, 

 a slight excess being added to allow for shrinkage on cooling. When the asphalt 

 cement in the mold is nearly cool, the briquette shall be cut off level, with a warm 

 knife or spatula. When it is thoroughly cooled to the temperature at which it is 

 desired to make the test, the clamp and the two sidepieces are removed, leaving the 

 briquette of asphalt cement held at each end by the ends of the mold, which now 

 play the part of clips. The briquette shall be kept in water for 30 minutes at 4° C. 

 (39° F.) or 25° C. (77° F.) before testing, dependent on the temperature at which the 

 ductility is desired. The briquette with the clips attached shall then be placed in 

 a "ductility test machine " (fig. 26) filled with water at one of the above temperatures 

 to a sufficient height to cover the briquette not less than 50 mm. (1.969 inches). This 

 machine consists of a rectangular water-tight box, having a movable block working 

 on a worm gear from left to right. The left clip is held rigid by placing its ring over a 

 short metal peg provided for this purpose; the right clip is placed over a similar rigid 

 peg on the movable block. The movable block is provided with a pointer which 

 moves along a centimeter scale. Before starting the test, the centimeter scale is ad- 

 justed to the pointer at zero. Power is then applied by the worm-gear pulling from 

 left to right at the uniform rate of 5 cm. (1.969 inches) per minute. 



The distance, in centimeters, registered by the pointer on the scale at the time of 

 rupture of the thread of asphalt cement shall be taken as the ductility of the asphalt 



31. STANDARD METHOD FOR THE DISTILLATION OF TAR AND TAR 



PRODUCTS. 



(A. S. T. M. Standard Method, Serial Designation: D 20-18.) 



(1) The sample as received shall be thoroughly stirred and agitated, warming, if 

 necessary, to insure a complete mixture before the portion for analysis is removed. 



(2) If the presence of water is suspected or known the material shall be dehydrated 

 before distillation. About 500 c. c. of the material are placed in an 800-c. c. copper 

 still provided with a distilling head connected with a water-cooled condenser (see 



