Judith Gap journal. [volume] (Judith Gap, Mont.) 1908-19??, 1912-05-24

successive cultivation Of the soil. and
x this soil IL used in the construction
AZ a road it Is known as top soil road"
There are many varieties Of clay and
consequently a wide variation in the
characteristics of 4 sand-clay road.
THE quality Of the sand is a variable
1ActOr. as 1t may range all the way
from fine. dust-like particles to coarse
grains aud gravel and may be perfect
u 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 q uniform standard as to
guilty Of the road or methods of con.
aEructiOn.
Not all bat most sand consists OF
t1ny grains Of quartz While quartz
= one Of the hardest minerals known.
@ possesses practically no binding or
cumenttng power. Tho grains Of sand.
INSTEAD Of cohering In a tough mass
under the impact Of traffic and the &C.
don Of water. remain loose and shift
ing. Fine sand when dry Is easily
displaced by the wind, which pro-
0uces In this way the ever shifting
aand hills. No road Is so difficult to
travel as one through nne sand.
IL clay has been carried in small
4hantiues By running water and de-
0Dsited as sediment it Is known as
'11edimentary clay" II the feldspathic
nsck has been disintegrated In place by
water the clay is known as residual
el1y." The sedimentary clay. having
teen carried in the form Of fine par
t1cles. is finer grained than the residual
ebay and Is more sticky and plastic
- contrast with sand. which possesses
- binding power, but is very hard.
a1ay Is a powerful binder. but does not
POSSESS the quality Of hardness. 1t Is
evident that in the construction Of
aRnd-clay road the important property
= the clay is its Elasticity or tendency
d become sticky and elastic when
Wtxed with water. The clays which
90 most plastic are called "ball
days" Another important property
which Is possessed by clays in widely
VnRying degrees IS the porosity or ca
Unefty for rapid absorption of water.
Gays which possess this quality in
0e highest degree fall to pieces under
TIA action of water. These clays
axa called shaking clays." 1t will read
II be. seen that the plastic or ball clays
W1l form better and more powerful
1Rder for sand-clay roads than will
~ shaking clays; but. on the other
hand, they will be much more difficult
q mix. as they disintegrate with far
Ina rapidity.
The shrinkage of clay is an impor-
lint characteristic in connection with
ne building of roads When water is
mixed with clay expansion results, and
When the water evaporates the clay
contracts. This characteristic OF ex-
UnnsiOn is much more pronounced In
some clays than In others. and it must
apparent that the clays which ex-
Uand the least are preferable for road
butding.
The theory Of the sand-clay road ia
wUy similar to the theory Of the mac
adlam road. In the latter rock dust
ma screenings fiji the voids between
the angular fragments Of stone and
when wet serve as a cement or binder.
The grains Of sand may be likened to
Ne angular fragments of stone and
cay to the rock dust binder. In the
ust successful sand-clay road Just
0dicient amount Of clay is used to fill
the voids between the grains Of sand.
u this way the sand sustains the
wear, while the clay serves as 4