The Bolivar bulletin. (Bolivar, Tenn.) 1888-1946, 1900-11-02
THE USE OF GRAVEL.
Road Building Instructions PrOmU1-
gated by the Wisconsin, sta4a
Experiment station

Experiment Station.
As gravel is the material chiefly
used for the improvement OF country
roads, the following instructions
taken from a bulletin issued by the
Wisconsin experiment station will be
of interest to many of our readers:
1t occasionally happens that nat
ural gravel beds are found which pos
sess the right characteristics for maxi
ing roads, and when the gravel is just
right excellent roads may be made
from it.
There are several important feat
ures which a good road gravel must
possess:
l. There must be one prevailing
size of pebble in sufficient quantity so
that when thoroughly rolled they
press against one another.
2. There must be enough of the
Liner sizes of coarse sand and fine
gravel to fill the voids between the
coarser gravel.
3. There must be enough of fine
loan to fill the voids between the
| coarse sand and fine gravel and retain
sufficient amount of water to bind
the sand grains together and prevent
their rolling.
4. The coarse and fine gravel and
the sand must be made up of more or
less angular fragments in order that
fiat faces of rock may set together
and thus lessen the danger of rolling
and of crushing under the weight of
the load.
1t is not possible to give specific,
concise directions for identifying a
good road gravel, but a man who has
seen and worked with it readily rec
ognizes it.
1t will be apparent at once that the
several characteristics which have
been pointed out are not likely often
to occur together in just the right
| ratios; and so there will be all pos
sible gradations from the ideal gravels
to those which will not answer at all.
Indeed it must be said that most
gravel beds have had the finer mate
rails so completely washed out that
only clean sand and gravel remain;
and when this is true it is useless to
try to make road with it. Such ma
terials can only be used to temper a
road which is too clayey in its texture
by reducing its water capacity.
1t happens in the majority of cases
that much of the gravel is too large
and too rounded to permit close pack
ing and fast binding. When this is
true much better qualities may be
| secured by using either the crusher or
he xx-i1I
be at once apparent that where much
OF the gravel is too coarse, to run it
through the crusher so as to reduce
the material to a more uniform size
| and at the same time to increase the
angularity of the fragments will make
a much better road material to use
either by itself, to build a road of or
as a tempering material.
There are many deposits of gravity
clay which it might appear would
make a good road material but the
principle must be kept always in mind
that too much of a too fine material
will take in and retain so much water
that the binding quality OF the water
is lost. 4nese gravelly clays occur in
many of the hills of the glaciated por-
tiOns of the United Atates and through
which roads are often cut.
In the construction of a gravel road,
as in that of a stone road. it is of
prime Importance to secure first of
all properly shaped and thoroughly
rolled and firmed roadbed before any
gravel is laid on. When this has been
done, and suitable gravel has been
found, the next step is to spread even
ly over the surface and thoroughly
roll layer which, when finished, will
measure three inches thick.
In the rolling it will be important
to firm the outer edges of the gravel
first in order that the rolling may not
force it outward and destroy the slope.
Should the gravel be too dry to pack
it must be moistened or the work be
suspended to take advantage of the
rains.
To make a good road there should
be not less than three three-inch lay
ers, and usually four will be better.
OF course a road six inches thick will
be a great improvement, and often
where the travel is light and the
roadbed thoroughly made three inches
of good gravel, well placed, will make
a great improvement in the road,
serving as a wearing surface.