Judith Gap journal. [volume] (Judith Gap, Mont.) 1908-19??, 1912-10-18

produced BY the front wheels and that
practically the entire disturbance OF
the road is produced by the rear or
driving wheels. II the effect were pro.
duced BY suction or vacuum the action
Of both front and rear wheels should
be somewhat similar at least. 1t seems
apparent to the. writer. therefore, that
the road best adapted to motor traffic
Is the road which will best resist this
powerful tractlve shear. 1t has already
been demonstrated that no plain mac
adam road IL capable Of resisting this
force.
The efforts of progressive highway
engineers are thus directed primari.
" toward the preservation Of our stone
surfaced roads and the construction of
dustless roads by the use of binder
more powerful than stone dust and.
secondly. to, minimizing or mitigating
the dust nuisance.
For the purpose of discussing intelli-
gently the experiments thus far con-
Quoted with special binders the term
dust preventives" has been applied
to all Of the various binders having for
their main object either suppression or
the prevention Of dust. These may be
divided Into two classes. temporary
and permanent. The temporary binders
serve merely as palliatives and require
frequentrenewai. The permanent bind
ers. so called. enter into the structure
OF the road as a constituent element
and IRE either Incorporated with the
other materials at the time of the con.
struction or applied later by surface
treatment.
In the class Of temporary binders
may he included water. salt solutions.
light oils and tars and oil and tar
emulsions. waste sulphite liquors. etc.
while the permanent binders include
the heavy petroleums and tars. pitches
and numerous oil. tar and asphalt prep.
arations. The value of salt solutions.
which have been used to some extent.
lies In the Microscopic character of the
dissolved salt. which. having consider
able affinity for water. keeps the road
surface in a moist condition long after
q surface treated with water alone
would have become dry through evapo-
ration.
The light oils and tars as we'll as the
oil and tar emulsions depend for their
eject upon comparatively small
amount Of true binding base left upon
the road surface after the volatile
products have evaporated. These ma
terials prove effective only so long as
they retain their binding power. When
the binding power is destroyed it is
necessary to apply more material.
The heavy oils aud tars differ from
the lighter products In that they con-
tain q much greater amount of true
binding base. The results are. there
fore. of more lasting character and
hence the name permanent binders"
The semisolid and solid preparations
usually contain a still greater amount
Of binder. With some few exceptions
all Of the true binders are bitumens.
The usual method Of applying these
materials to the road surface Is by
sprinkling. The temporary binders can
usually be applied cold. but the perma-
nent binders because OF their much
greater viscosity must be heated until
sufficiently duid. In England and
France the use of coal tar is practiced
to lurge extent. and their methods Of
application have been highly developed.
Machines are in general use which are
self propelling and in which the tar Is
heated and applied to the road surface
as a spray under high pressure. These
SO called "tar sprayers" are not only
very economical in the use Of tar. but
insure more even distribution aud
better penetration Of the road surface
than II Is possible to obtain In almost
any other way.
In the construction Of dustless roads
the crucial question is that of cost. The
effort must be to develop form OF
construction which will withstand fast
automobile traffic and ut the same time
be within the financial resources Of the
community. This is largely being done
at present by the use of Il bituminous
binder instead of rock dust. The two
methods generally employed are known
as the penetration and the mixing
methods. In the former the hot liquid
binder is sprinkled or sprayed over the
stone and allowed to penetrate through