SPECIFICATIONS FOR BITUMINOUS ROAD MATERIALS. 3 
The specifications appearing in the following pages are grouped 
according to type of material, as shown in the detailed table of con- 
tents. A special index, however, is given for the convenience of 
engineers interested in materials suitable for particular methods of 
use or types of construction. Following each specification is a 
brief paragraph stating the purpose for which the material is in- 
tended, its method of use, the type of road, and general conditions 
for which it is suited, and the results which may be expected if it 
is properly used. 
This information is necessarily general in character and should not 
be interpreted too rigidly. Varying combinations of climate, traffic, 
and character of the nonbituminous portion of the road which can 
not be discussed in a single paragraph will often influence the selec- 
tion of the bituminous material and its method of use. More de- 
tailed information and advice relating to their use in maintenance 
and construction may be obtained upon application to the office. 
It is realized that all classes and types of bituminous materials 
have not been covered and it is intended to add to the number of these 
specifications from time to time as additional information is ob- 
tained. In the meantime they are offered more as a guide and help 
to those engineers who are not thoroughly familiar with the charac- 
teristics of bituminous materials rather than as a substitute for 
specifications now in use which have already demonstrated their value 
in securing the material which is desired. It is realized that the same 
material is often described by two entirely different sets of tests and 
test limits, so that the same ultimate result may be obtained by two 
different specifications. Unfortunately different methods of specify- 
ing bituminous materials are followed by various highway engineers 
and commissions, and it would appear highly desirable that uniform 
practice in this matter be generally adopted. It is hoped that the 
typical specifications here given may further such practice, in the 
interests of both consumer and producer. 
For the convenience of engineers and in order to make this bul- 
letin complete in itself the methods of test to which reference is made 
in the specifications, and directions for sampling are included in 
this bulletin. 
