EXAMINATION OP BITUMINOUS ROAD MATERIALS. 



DISPLACEMENT METHOD (USED FOR HARD SOLID BITUMENS). 

 EQUIPMENT. 



1 chemical thermometer reading from —10° C. to 110° 0. 



1 analytical balance, capacity 100 grams, sensitive to 0.1 milligram. 



1 Wood or metal platform. 



1 150 cubic centimeter low-form glass beaker. 



1 piece of fine silk thread. 



METHOD. 



For materials which are hard enough to be broken and handled 

 in fragments at room temperature, the following method will prove 

 convenient. A small fragment of the bitumen (about 1 cc.) is sus- 

 pended by means of a silk thread from the hook on one of the pan 

 supports, about 1^ inches above the pan, and weighed. This weight 

 is called a a." It is then weighed immersed in water at 25° C, 

 as shown in figure 3, 

 and this weight is call- 

 ed a b." The specific 

 gravity may then be 

 calculated by means 

 of the following for- 

 mula: 



Specific gravity = — — v 



USE OF SPECIFIC GRAVITY 

 DETERMINATION. 



The specific gravity 

 determination is made 

 on all bitumens con- 

 taining less than 50 

 per cent mineral matter, and also on bitumens recovered from 

 bituminous aggregates. The specific gravity is usually reported 

 to the third decimal place. 



SPECIFIC VISCOSITY DETERMINATION. 



EQUIPMENT. 



[meter complete with thermometers, burner, and rubber tubing. 

 ] 100 cubic centimeter cylindrical glass graduate, 

 p watch. 



METHOD. 



r l be of fluid bituminous road materials may be determined 



at any suil ble temperature by means of the Engler viscosimeter. 

 This apparatus is shown in figure, 4, and may be described as follows: 

 a is a brass vessel for holding the material to be tested, and may bo 



Fig. 3.— Displacement method of determining specific gravity. 



