The Redwood gazette., 1935-08-29
new STABILIZED
GRAVEL SURFACE
TRIED in COUNTY
Redwood to North Redwood
Road Treated in New
Manner

Construction OF new type cal
cium chloride stabilized gravel
surface on the one and three-quar
ter miles of road north from Red
wood Falls to the river at North
Redwood was completed by the
county highway department last
week.
The road is the first in Redwood
county to be improved by the new
stabilization method recently de-
veloped through soil studies of the
United States Bureau of Roads.
Approximately $50 miles of roads
of this type were constructed in
the state last year.
Viewed by foremost engineers
as the greatest progress in recent
years in the science of building
durable roads from local soils, the
stabilization process is low in cost
and for that reason is considered
ideal for a program of widespread
improvement OF secondary high
ways. The decision to use this
type of construction on the North
Redwood road was made after
members of the county board had
visited other stabilized roads in
other sections of the state.
In building the stabilized sur
face, new principles of soil science
developed by the laboratory stud
les of soil engineers are applied.
Clay, gravel and soil fines, to
which calcium chloride is added
either in the mixture or as a sur
lace treatment, are used to pro-
duce the hard surface. These mat
erials are combined according to
definite formula, after the grada-
ton of the gravel has been care
fully determined and the sticki-
ness of the clay has been measur-
ed.
These measurements are used to
determine a mixture which will
produce the most densely compact
ed mat and the best all-weather
road.
After a study of the sand-clay
roads of the south and considera-
ton of the phenomenon at Day
tona Beach, Florida, where the
beach sands, when favorably
moist, compact into an ideal rae
ing course, the soils engineers de-
termine that it is the moisture
films surrounding the fine soil par
ticles that produce the cementing
effects in moist sand and wet clay.
By supplying enough fine soil to
produce the cementing effect, and
at the same time retaining enough
coarse gravel to furnish resis-
tance to the shearing action OF
traffic and to provide wet-weather
stability the stabilized mixture
was produced. introduced only a
few years ago, this type of con-
struction has now been successful
ly used on hundreds of miles Of
roads in eastern and midwestern
states.
The function of calcium chloride
in roads of this type is more than
that of dustlayer. The calcium
chloride, which is a Microscopic
compound attracting moisture
both from the air and from the
subsoil, supplies the moisture nee
essary to preserve the road in it's
firmly bonded condition. During
dry weather occasional light appli-
cations of the calcium chloride are
made to the surface to maintain
the moisture content. By this
means, the road surface is pre-
served as a dense mat, free from
dust and from loose float material.
In constructing the North Red
wood road, tests were first made
of the existing gravel to determine
its gradation. Clay, which had
been tested for its Elasticity or
sickness, was then supplied to
the road in the proper amount.
The clay was allowed to dry and
was then pulverized. 1t was then
mixed with the gravel by blading
back and forth across the road
way. The mixed material was
then windrowed to the side of the
road, and was brought into the
roadway in thin layers, sprinkled
and allowed to compact under
| traffic.