dad natural asphalt |1.40 | 7 | 56-57 | 100
Bermudez asphalt cement |1.04-1.06|Up to 135 | 95-97 |99.5 or more
-------------------------+---------+----------+----------+------------

-------------------------+---------+----------+----------+------------
(A) | (F) | (G) | (H) | (I)
-------------------------+---------+----------+----------+------------
Mexican oil asphalts | 70-80 | 13-16 | 200 deg.C. up| 60-100
California oil asphalts | 75-80 | 10-12 | 200 deg.C. up| 100+
Texas oil asphalts | 75-80 | 12-14 | 200 deg.C. up| 50-100
Bermudez natural asphalt| 68-70 | 13-14 | ... | ...
Trinidad natural asphalt | 64-65 | 10-11 | ... | ...
Bermudez asphalt cement | 77-80 | 11-12 | 175-200 | 25-50
-------------------------+---------+----------+----------+------------

=Specifications.=--Some properties of bituminous materials can be
varied in the process of manufacture, while others are inherent in the
material and cannot be changed in the process of manufacture.
Specifications must therefore be drawn with care to insure that the
requirements can be met by satisfactory materials. But certain
properties, such as specific gravity, may vary greatly among materials
equally satisfactory for construction purposes. One should not be
misled by apparent differences in the characteristics of materials,
because these may simply be natural peculiarities which have no
bearing on the usefulness of the material. There are given in Table 8
the properties of some of the commonly used bituminous materials and
the properties that can be varied in the process of manufacture are
indicated with an asterisk. A variation in these properties will
usually result in some change of other properties, but generally not a
great change.

SURFACES IN WHICH BITUMINOUS MATERIALS ARE UTILIZED

I. Surface Treatments

Attention has been directed to the rapid deterioration of water-bound
macadam when subjected to passenger automobile traffic.

In water-bound macadam the stones are held in place by a weak cement
composed of stone dust and water, and this cement is not sufficiently
strong to hold the stones in place when they are subjected to the
shear of automobile tires. In finishing the water-bound macadam
surface, the spaces between the stones are filled with screening and
in addition a layer about one-four