EXAMINATION OF BITUMINOUS ROAD MATERIALS, 3 
and possibly injured durmg 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 materiais which are to be identified as 
being partly composed of heavy paraffin hydrocarbons. The residue 
obtained from the volatilization test 1s 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 tests: 
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-pomt determina- 
tion. Mixtures of tar and petroleum or asphalt preducts 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 
those 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 m carbon disuiphide. Hf 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 can be identified, or, if not, it is subjected to 
those tests which are of most value as suggested above. The ex-. 
tracted mineral aggregate is usually quantitatively graded and, if it 
is to be used or has been used as an mtegral part of the road proper, 
its percentage of voids is sometimes determmed. 
Forms for reporting the results of examination of bitummous road 
materials accordmg to the methods described in this bulletin are 
given in the appendix 
