Evening star., 1936-10-03

Not unlike our nealIu Vi Slccp'
We are conscious of it when 1t Is gone
or waning.
Currently, the roads of Maryland
are becoming topic Of conversation
because of their condition and anti
uuated designs, and because project
is under consideration to raise $780,
600 900 in order to restore Marylands S
reputation as a progressive State IN
the important matter of roads.
To the average person. requirements
for a good highway are, roughly, a
smooth-running surface, wide enough
TO allow ample space for cars to pass
with properly calculated grades on
curves to take care e the centrifugal
force. drainage and elear-cut mark
ines. At least, this is what the aver
age person should look for In good
road. Actually, we look for very 1T
tie and generally content ourselves
with an sppraising glance at 'ne
smoothness of the surface ahead
When sloo,0Oo,ooo is being con-
templated to be sunk in roadways
in order to give them the present-day
status as such, 1t should be OF IN
terest to investigate just what ooes
constitute a good road, how 1t comes
about and how chance Is being over
come. in order to insure future serv-
ice with the minimum of upkeep cost
America has been the pioneer coun-
trv in the perfection of roads, we nave
had no opportunity to study other
countries experiences for our oenent
hut on 'the contrary, we are lookeo
upon from the outside as leaders IN
thi, important field. Especially in the
Far East and in South America, hard
surfaced roads have been introduced
nv American experts, American
trained engineers or American super
vision. Our engineering and technl-
cal colleges always have had group
of foreign students, especially inter
ested to learn the secrets OF good-roao
construction.
EIRST. a visit to a well-eQulpped
laboratory in which material for
road building is tested and then an
inspection tour over any road under
construction. in the company OF roao
engineer. will tell us with magic speed
that roads do not just happen to be
good.
For an asphaltic road, which un-
doubtedly Is the most interesting,
since more derivations of this type
are to be found throughout the coun-
try. asphalt, crushed stone, sand and
dust are used as basis. With the
choosing of these materials, the actual
work of the technician begins. He
must determine just what type OF
asphalt shall be used, what sort OF
crushed stone or rock, what sand and
dust.
The answer to these questions de-
pends largely on the locality in which
the road will be built-the type OF
sub-soil to be encountered there. the
climate characteristics of the country,
the present base. If any, and many
less important factors, too long to
enumerate.
As working basis in reaching a
decision on these questions, actual
samples of material-soil. sub-soil,
stone, etc. from the existing road
bed and adjacent territory are sent
to the construction company's labora-
tory. The proper inspection of these
samples will decide whether or not
the material will be useful for the
construction.
Since today the use of natural
asphalt, that is, the residue of evapor-
ated petroleum found extensively in
the Dead Sea and in Trinidad, South
America, has practically been discard
ed in the United States in favor Of
artificial asphalt, obtained as a resi-
due Of petroleum and some types Of
tar, the latter only shall come to
our consideration. A 10 or IL ounce
can of asphalt which is likely to
fill the requirements, several pounds
of stone, sand and dust are shipped
to the laboratory, together with an
extensive report from the field en-
Rineer, giving his impressions Of the
characteristics of the land, its climate,
conditions Of the sub-soil, and the
base. Of utmost importance, also, is
the attached report approximating
the amount of trafic the road has
been subjected to: the probable in
crease when resurfaced, and the type
of traffic, whether passenger cars,
freight or other commercial vehicles.
IT is too long and too technical
process to follow in detail the
chemical tests to which the asphalt
IL submitted in the laboratory while
evaluating its fitness to the require
ments, but some of the other tests
are equally important and present
Interesting points.
Having in mind the temperature
variations throughout the year. in the
place where the asphalt Is to be used,
q test of its hardness Is made. The
specifications of the field engineer
contained the minimum and maximum
hardness the material should have
In this experiment We check with a
penetration machine This machine
is composed Of needle loaded with a
five-gram weight, which Is released
for five seconds on the surface of the
asphalt being tested. The depth Of
penetration of the needle is measured,
care having been taken to have the
temperature of the asphalt sample
q uniform n degrees Fahrenheit
throughout the operation. BY this
first test the sample is classified as q
hard, soft or medium type.
In order to ascertain the fiexibility
of the asphalt and its expansion
capacity. q ductiity test is effected,
during which the sample is some
times expanded to an incredible
length.
For the proper consistency of the
mixture, very much care is
exercised in the grading of the size
of stone or gravel to be used. Labor
atory screen tests of interminable
length are made in order to find the
proper size and quantity of stone,
from 1880 Of an inch up to perhaps
az inches. The same Is done with
dust. which passes through very fine