The Bossier banner. [volume] (Bellevue, Bossier Parish, La.) 1859-1952, 1912-08-01

successive cultivation of the soil. and
If this soil is used in the construction
of road it is known as top soil road.
There are many varieties of clay and
consequently wide variation in the
characteristics of a sand-clay road
The quality of the sand is variable
factor, as it may range all the way
from fine, dust-Iike particles to coarse
grains and gravel and may be perfect
ly clean or mixed with loan and other
material In consequence of these wide
differences in the materials constitut
Ing sand-clay roads it is impossible to
maintain a uniform standard as to
quality of the road or methods of con
structiOn.
Not all but most sand consists of
tiny grains of quartz. While quartz
is one of the hardest minerals known.
it possesses practically no binding or
cementing power. The grains Of sand.
instead of cohering in a tough mass
under the impact of traffic and the ar-
ton of water, remain loose and shift
ing. Fine sand when dry is easily
displaced by the wind, which pro
duces in this way the ever shifting
sand hills. No road is so difficult to
travel as one through fine sand
If clay has been carried in small
quantities by running water and de
posted as sediment it is known eas
"sedimentary clay" If the feldspathi''
rock has been disintegrated in place by
water the clay is known as residual
clay" The sedimentary clay. having
been carried in the form Of fine par
ticles, is finer grained than the residual
clay and Is more sticky and plastic
In contrast with sand which possesses
| no binding power, but is very hard.
clay is a powerful binder but does not
| possess the quality Of hardness. 1t IS
evident that in the construction of a
| sand-clay road the important property
In the clay is its Elasticity or tendency
to become sticky and elastic when
mixed with water. The clays which
are most plastic are called ball
clays' Another important property
which is possessed by clays in widely
4 varying degrees is the porosity or ca
racity for rapid absorption of water
Clays which possess this quality in
| the highest degree fall to pieces unde!
the action of water. These clay>
are called shaking clays." 1t will read
ily be seen that the plastic or ball c!ays
will form better and more powerful
binder for sand-clay roads than will
the shaking clays; but, on the othe1
hand, they will be much more difficult
| to mix, as they disintegrate with fa'
less rapidity.
The shrinkage Of clay IS an impor
tant characteristic in connection witt
the building of roads. When water i
mixed with clay expansion results. anf
when the water evaporates the clay
contracts. This characteristic OF ex
pansion is much more pronounced IL
some clays than in others. and It mus
be apparent that the clays which ex
pand the least are preferable for rOat
building.
The theory of the sand-cfay road i
very similar to the theory Of the mae
adam road. In the latter rock dus
and screenings fill the voids betweel
the angular fragments of stone ant
when wet serve as cement or binder
The grains of sand may be li'Eened t
the angular fragments of stone AM
clay to the rock dust binder. In tn
most successful sand-clay road just
sufficient amount Of clay is used 10 fl
the yoids between the grains of sane
In this way the sand sustains th
wear, while the clay serves as