The Hattiesburg news., 1912-05-28

! "Sumrall."
will form a better and more powerful
binder for sand-clay roads than will
the shaking clays; but, on the other
hand. they will be much more difficult
to mix. as they disintegrate with far
less rapidity.
The shrinkage of clay Is an impor-
tant characteristic In connection with
the building of roads. When water
is mixed with clay expansion results.
! and when the water evaporates the
clay contracts The characteristic Of
expansion is much more pronounced
in some clays than in others, and 1t
must be apparent that the clays which
expand the least are preferable for
road building.
The theory of the sand-clay road Ia
very similar to the theory Of the mac
adam road. In the latter rock dust
and screenings fill the voids between
the angular fragments Of stone and
when wet serve as q cement or binder.
The grains Of sand may be likened to
the angular fragments OF stone and
clay to the rock dust binder. In the
most successful sand-clay road just q
sufficient amount of clay is used to
fill the voids between the grains Of
sand. In this way the sand sustains
the wear, while the clay serves as a
binder If too much sand is used the
result will be loose sand on the sur
face; If too much clay is used the
surface of the road will become sticky
after rains.
The best mixture of sand and clay
can be made when the materials are
wet, and particularly is this true of
the plastic or ball clays.
If the clay Is a plastic or ball clay
much greater effort will be necessary
to obtain complete mixture; If 1t is
shaking clay the mixture will be much
more readily obtained. This kind of
clay is not as satisfactory, however,
as the ball clay, as its binding powers
are much less. In selecting clay for
road purposes it is always best to Sc
lect the stickiest clay available. A
common test is to wet the thumb and
place it againt piece of clay. If the
clay will not stick to the thumb it Is
safe to assume that 1t will be poor
binder in a sand-clay soil.
AS the desirable proportions of sand
and clay are such that the particles of
clay barely fill the voids between the
grains of sand, 1t is well in determin-
ing the quantity of clay to be applied
TO a sand road or sand to be applied to
clay road to know approximately
low much is needed. A simple meth
cd for determining the relative guam
tity is to take two glasses of the same
size AMI fill one with dry sand which
it is proposed to use and the other
with water.
The water should then be poured
carefully in the glass Of sand and al
lowed to trickle down through the
sand until it reaches the bottom of the
class. When the water has been
poured into the glass of sand to the
point of overflowing we may assume
that the voids between the grains OF
zand have been filled, and consequent
~ the amount of water taken from the
full glass would represent the volume
of clay needed to fill the voids in a
volume of sand equal to that In the
other glass. 1t is better to use little
less clay than would appear to be
necessary, as the tendency is to over
estimate the amount needed.
Good drainage is the most essential
feature of the sand-clay road just as 1t
is of all other types of road. A sandy
or gravelly soil affords better natural
drainage, and II the sand is present to
an exceptional extent the only pro-
vision necessary for drainage will be
to crown the surface of the road in the
same manner as prescribed for earth,
gravel or macadam roads. II the road
is located through land that is 80 low
as to be continually wet it will be nee
essary in addition to crowning the
road to provide wide bitches on each
side and to raise the roadbed little
higher than the surrounding country.
After proper drainage has been Sc
cured the roadbed should be crowned.
beginning near the sources of supply
of the clay or sand. The clay should
then be spread to q depth Of from ak