Little Falls weekly transcript. (Little Falls, Morrison Co., Minn.) 1894-19??, 1898-02-25
CLAY AS ROAr METAL
NOT DESIRABLE EXCEPT IN SMALL
QUANTITIES.

y
QUANTITIES.
Acts 10 o Cement to Knit tho Stone To-
sether When Properly Used-Action OF
\ II water on tile Rondbed - Prevents Dust
a and Wenr-Trees aud Hedges.
The Fart played by water on crushed
stone " bile undergoing rolling is sew
/ nal fold. In practice broken stone COM
pletely wet down is thoroughly rolled
With roller weighing ten or more
IONS. The wet surface Of the angular
/, rock fragments permits more thorough
eompacting, as the water acts as lu-
I bricant, allowing the stones to slip by
one another with greater freedom than
would be the case were the fragments
dry. At the same time the water re-
tains the powdered rock resulting from
abrasion Of the PARTICLES and holds It
between the fragments. .
This process is reactionary and cumu-
lative, for the presence Of the powder
Of attrition acts through capillarity to
take up and retaih still greater guam
titles Of water until the spaces between
the pieces of broken stone composing
the upper part Of the road become COM
pletely filled with powdered rock. Not
. little Of the cementing or bonding of
road during rolling is in reality the
tGect of capillarity existing between the
grains of powdered rock and the adj
Joining walls.
This principle may DO observed ON
our seashores and sand roads. While
wet, the beach or road may be firm and
upyielding, allowing heavily loaded
teams to pass over them, but when dry
6hch places are impossible for heavy
teams aud difficult of passage for all
kinds Of vehicles. In this case cement
ing. as ordinarily understood, plays no
part in producing adhesion between
6be grains Upon drying, the grains are
Entirely free to move over one another.
having lost the water which served to
bind them together
When NJ acadam road is thoroughly
oompacted, careful inspection will
show that the fragments of broken stone
are closely packed together and the
spaces betwe cen ure filled with fine
powdered rock, which, if derived from
8 suitable road material, carries small
percentage of clay. Any Of our COM
monty used road stones contains an ,ap-
preciable quantity Of clay disseminated
IN little particles in the feldspar whence
Il has been derived by the weathering
u the rock prior to it's removal from
the quarry.
The microscope shows that the field
dpar CT Our traps ana GRANTEES aud other
road stoues ia never entirely free from
Z considerable amount of kaolinization
d alteration to clay. This change has
taken place in the crust Of the earth to
1 great depth. and 10 road material can
{pntain teldspars free from more or less
4 this mineral, depending upon the
Character Of the rock and the amount
u weathering to which it has been sub
iected. BY the gradual wearing Of the
4eldspar, by the abrasive action Of the
nDller, the wheels Of carriages, aud the
feet of animals, a small but important
Quantity Of clay is liberated, and this
h combination with any clayey ma
uerial that may have been added to the
xpad serves to furnish the necessary
quantity Of cement to knit the broken
Acne firmly together. It 10 not to be
1pderstood that an appreciable quantity
Z clay acts otherwise than objection
jbly when used in roadbuilding. As .
lille nothing is more undesirable than
I be clay element in highway construc.
Ion, yet little mixed with some Of
@br southern limestones serves to in.
cease their cementing and enduring
Qualities. Upon drying, the powdered
4bCk sets much after the manner of
ndy clay AID serves not only to bind
DE piec.s vi rock together, thus giving
6eidity 10 Tue way, but to retard the
wear due tc any differential motion of
9be fragments over one another while
Che load is passing along the road. A
Netting of the superficial portion Of
Roadway during rains tends by the ex'
passion Of the cement to knit the sur
face together aud make it impermeable
% the passage of water.
= ACAI q uASOASGASAA 6VA0ukO1AO -
would seem probable that certain con-
6tion Of mt IRE instead Of being OBJ.
fctionable ~ roadway undergoing
CONSTANT use is rather desirable than
4herwise A condition Of moistness
dervcs to prevent less Of material worn
6Le ly the pbrusive action of the wind,
Gld the presence Of thin film of wet
3nst acts as cushion to protect the
fragments Of rock from tie rude touch
SID impact Of passing traffic, thus less
ching the wear and tear of the surface.
III the same manner the moist cement
ofe1ates to distribute the bearing sur.
faces Of the broken stone and to reduce
tbe local intensity Of the friction be-
tween one rock and another, although
CEMENT in this condition will tend to
GLOW a greater freedom Of movement
among the broken stones, and hence in
ibis way make the surface more yield
Ing. Assuming that tho loss through
Increased abrasion Of material resulting
'&pm moist cement between the rock
fragments il equal to the saving due to
De cushioning effect Of a small quanti-
x of moistu-e on the surface, there still
4mains Z saving to the road BY the
1Eotection afforded by preventing ex.