Los Angeles herald., 1910-01-23
Classification of Macadams

CtaSSiIlCdlIOn OF M aCdudfFlS
The actual work in the field which 1
have inspected during the past two
months is as follows:
First-Site for stone quarry at Pa
coima in the San Fernando valley.
Second-Site for stone quarry near
San Dimas.
Third-The El Monte road work.
notwithstanding of roads where this
is being carried on at the present time.
Fifth-The office work in progress at
the offices of the highway commission.
In addition to this 1 have given con-
siderable time to the matter of organ
ization for handling the work in the fu-
ture, which will also be discussed in
this report.
Inspection of Work
Since making further examinations
of the Ell Monte road, the subject of
macadam construction for Los Angeles
county has appeared to me more and
more important. While the work done
on this section of roadway has not yet
been sufficiently well tested to develop
many serious defects, as only portion
of it has been thrown open to public
use, and that for a very short time
only, yet I am able to judge it from an
engineers standpoint sufficiently to af-
firm what ! said in my previous report.
Also having received a number of in
quiries regarding the various kinds of
macadam in use for building roads and
requests for more detailed reasons why
any of these kinds of road construc-
tions are not equally suitable for this
vicinity. I have decided to give the
proper classifications and descriptions
of macadams in this report. Roadway
macadams are properly classified into
three different classes as follows:
First-Dry macadams
Second-Proteeted macadams.
Third-Bonded macadams.
The first of these is the original
macadam which has been used for a
very long time and is made by covering
filling its interstices with screenings
from the same material as the broken
stone This type of construction has
been found to be satisfactory for heavy,
slow moving traffic, particularly when
hard, firm and fine grained rock has
| been used for crushed rock and screen
! ings Various limestones. not so hard,
! have also been found satisfactory for
| traffic which Is neither heavy nor rapid
The dry macadams have, however
always given the best satisfaction il
humid climates where they are contin-
! ually kept in a moist condition. In
dry climates like that of Southern
California the absence of rainfall dur
/ Ing the summer season has rendered
the use of dry macadams quite unsat-
isfactory even for conditions similar to
| those under which it has proved ex-
tremely successful in places where the
rainfall is more abundant and evenly
distributed. The reasons for this are
quite obvious. since the drying out OF
the rock causes a readjustment of the
particles which are only bonded to-
gether mechanically, and such re-
adjustment causes the formation OF
chuckholes in the roadway. The ONLY
satisfactory remedy for this condition
is to sprinkle the roadway sufficiently
to keep it moist at all times, but this
is both expensive and difficult of exc.
cution.
However, since the general use o
automobiles, dry maeadams hav,
proved undesirable for other reasons
A rapidly moving vehicle, such as
motor car, canses disturbance of dr.,
! macadams, even when they are kept il