The Worthington advance. [volume] (Worthington, Minn.) 1874-1908, 1900-11-02
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ExDerinaent Statien
lAs gravel Is the material chiefly &
used for the improvement 81 country
roads, the following instructions
taken from 9 bulletin issued ~ the
Wisconsin experiment. statlon will be
OF interest 70 many Sof our readers:
i 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 good road gravel must !
possess: 55s' &.
1. There must be one prevailing
size Of pebble In sufficient quantity SO ;
that when thoroughly rolled they
press against one another. S.
2. There must be enough of the
LEer sizes q coarse sand and fine
gravel to all the yoids 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
g sufficient amount Of water to. bind
the sand grains together and prevent
their rolling.
The coarse and fine gravel and
the sand must be made up of more or II
less singular 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. Is
It is not possible to give specific,
concise directions for identifying q
good road gravel, but, a man who has
seen and worked with II readily rec
ognizes it. s.
It 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 lis useless to
try to make road with It. Such ma
terials can only be used to temper
road which is too clayey in its texture
by reducing its water capacity. g
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
the screen, or both together. It will
be at once, apparent thatzwhere 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 road of or
as q tempering material.
There are many deposits of gravity
clay which it might appear would
make q 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 Dor
tons Of the United tates and through
which roads are often cut. =. -; 80
In the construction of a gravel road.
as in that of 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
~ 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 m0istened or the work be
suspended to take advantage of the
rains. ,...-. -
To make, q good road there should
be not less than three three-inch Law.
ers, and usually four will be better.
OF course road six inches thick will
be great improvement, and often
where the travel is light and the
roadbed thoroughly made three inches
of good gravel, well placed, will make
great improvement in the road.
serving as wearing surface.
CHEAP PLANT BOXES. I