EXAMINATION OF BITUMINOUS ROAD MATERIALS, 3 



and possibly injured during process of manufacture, or prepared 

 from a solid native indurated bitumen, the determination of bitumen 

 insoluble in carbon tetrachloride may be made. The paraffin scale 

 determination is made on those materials which are to be identified as 

 being partly composed of heavy paraffin hydrocarbons. The residue 

 obtained from the volatilization test is usually subjected to either the 

 float or penetration test, and in addition it may be subjected to any 

 or all of the above-described tests as occasion may require. 

 Tar and tar products are subjected to the following tests: 



Specific gravity. 



Distillation. 



Bitumen soluble in carbon disulphide. 



Petroleum and asphalt emulsions are subjected to some of the 

 methods of examination applicable to fluid and viscous residual 

 petroleums and also to the following test3 : 



Determination of water. 

 Determination of ammonia. 

 Determination of fixed alkali. 

 Determination of fatty and resin acids. 



In addition, the viscosity test may be employed for fluid products 

 and it is highly desirable that the float test be made on all of the 

 viscous and semisolid tar products. The more cr less solid refined 

 tars or tar pitches are also subjected to the melting-point determina- 

 tion. Mixtures of tar and petroleum or asphalt products are in 

 addition subjected to the dimethyl sulphate test. 



Some exceptional materials can not be satisfactorily examined 

 according to any one predetermined scheme, and at the present time 

 this matter must be left to the judgment and experience of the analyst. 

 Practically all of the methods described in this bulletin are, however, 

 applicable to the more common materials, and for a given material 

 methods should be selected which will give the most information 

 concerning its character and suitability for the specific use for which 

 it is intended. 



Bituminous aggregates are first of all examined for the percentage 

 of bitumen soluble in carbon disulphide. If the amount is in excess 

 of 5 per cent, an extraction is then made on a large sample and the 

 recovered bitumen is examined according to one of the above-men- 

 tioned schemes if it run be identified, or, if not, it is subjected to 

 those tests which are of most yahie as suggested above. The ex- 

 ted mineral aggregate is usually quantitatively graded and, if it 

 is to be used o>- has been used as an integral pari of the road proper, 

 its percentage of voids is sometimes determined. 



Forms for reporting the results of examination of bituminous road 

 materia] according to the methods described in this bulletin are 

 given in i be appendix 



