The Washburn leader., 1916-05-12

dreds Of practical road builders from
all parts Of the country have inspected
it from time to time and have mar
veled at the excellence of the work. ;,
Manufacturers who have supplied
bituminouS materials for the treat
ment Of the road have detached their
special experts for this service, and
the traffic over the road has demon
strated under carefully observed con-
ditions the relative value of the several
types Of road making up this great
highway. f f#s
The Chevy Chase road is experiment.
al. 1t consists Of different types Of
Observation-Disclosures macadam laid
by the penetration method, surface
treatments of waterbound macadam.
asphaltic surfaces ON concrete fOunda-
tions, bituminous surfaced concrete,
plain and oil cement concrete aud Wit
rified brick, all of which are under
daily observation by expert road build.
ers to ascertain which Of the types is
best suited to the traffic and which is
condemned by practical test under the
same conditions Of climate, soil, rain
fall, heat and cold and like traffic re-
quirements. 1t would be just the. same
to the Office Of public roads which has
written this open book in concrete,
brick and stone whether any part Of
It or all parts of 1t should foil; tail
in materials used. in CONSTRUCTION ,sin
durability. in cost. in maintennncetS. !
Road building is science now. and
efficiency is the only test of quality.
In the stones used in the construction
of the Chevy Chase road, their specific
gravity, their weight per cubic foot,
their water absorption. their percent
age of wear, their hardness and tough
ness are all determined by the most
careful scientific tests. Patrolmen are
constantly employed on this road to
keep account Of whatever defects in
materials and construction may devel-
op and exact data as to the cost Of
maintenance.
In one Of the experiments covering
1851 square yards the cost per square
yard for two and one-half inch btu
minous wearing surface was 46.18
cents. This experiment was made In
1911. For the maintenance Of surface
there was no expense in the following
two years. but in 1914 this expense
was $79.7O.
On another section Of the road the
cost per square yard for two and one
half-inch bitumin0us wearing surface
was 64.42 cents and for supplementary
construction 1920 cents. This expert
ment covered an, area of 7O5 square
yards, and in the three years from 1912
TO 1914 inclusive there was no expense !,
for maintenance. n
All surfaces on this road. were built
Of a uniform thickness OF eight inches
and Of total width Of nineteen feet.
The base course was Of stone ranging
In size from one to three inches, spread
to depth Of five inches, the voids he,
ing filed with screenings. The wear
ing course consisted Of stone ranging
from one to two inches generally, and
upon this course the bitumen was ap. 4
Piled in two applications Of approxi-5
mately one and one-half to one-half
gallon respectively. The cost of the
stone used in the foundation and Wear-
Ing courses varied according to tke *
pense Of quarrying and delivery, !, % Il
would vary at all other points. and OF "
all the materials Of construction and Il
charges for maintenance exact account
has been kept. ,s3 S2