Tensas gazette. [volume] (St. Joseph, La.) 1886-current, 1917-10-05
GRAVELROADTYPES
Constitute About 0ne-Third OF
Surfaced Roads in the
United States.
BEST SELECTION OF GRAVEL
Quality Of Material Is Next In lmpor-
lance to Proper Drainage-ciay Is
Poorest cementing Material
We Have.

FOOTSoI SStuSuliuS "asS'o
We Have.
prepared by the United States Depart
ment of Agriculture.1
Roads that are artificially surfaced
with gravel, OF with earthly material
In the composition of which gravel pre-
dominates, are called gravel roads.
This designation covers variation in
type which ranges from roads sur
faced with natural sand-clay mixture
containing q considerable percentage
of gravel to those having so-called
"gravel macadam" surfaces, composed
almost wholly of pebbles and con-
structed in practically the same man.
ner as first-class macadam roads. Grav'
ell roads constitute about one-third the
total mileage Of surfaced roads in the
United States and are confined to no
especial section of the country.
In the following discussion Of gravel
roads it is convenient to consider the
subject under the two general heads,
Selection Of Gravel" and "Construc-
ton Methods"
Selection Of Gravel.
Ordinarily the selection Of gravel for
use in road surfacing must be confined
to local materials which are or can
be made suitable for that purpose.
Because Of high freight costs it seldom
happens that road gravel Of even the
very best quality is transported by rail
a greater distance than about 100
miles from the source Of supply, and
in the vast majority Of cases it Is
hauled directly from pit to road in
wagons. Since the quality of gravel
varies to a considerable extent, some
times in different parts Of the same
pit. II is essential that local road Off
Gals, who frequently are charged with
the selection Of such material, should
have some knowledge of the relation
between the physical characteristics of
gravel and its wearing qualities when
placed in a road surface. While such
knowledge can best be gained by &C
tual experience with different kinds OF
gravel, there are certain general re-
ourements which may be stated fol-
the guidance Of the inexperienced
For example, the following excerpt
from Bulletin No. 2 Of the Michigan
state highway department presents In
very concise form the characteristics
which gravel for road surfacing should
possess, in the judgment Of the state
highway commissioner, In order II
meet the Michigan conditions.
Next to proper drainage, the mos
important thing in building grave
roads is to secure good quality o
gravel. Authorities have differed al
to the requirements of suitable roat
gravels, most of them, In my opinion
placing too much stress on the imme
date packing qualities. Indeed, tn
average township commissioner AM
farmers generally have become so i'm
bued with the idea that it is necessar
to use a gravel that will pack quick.
that they have almost lost sight o
the fact that the only thing whic
makes a gravel road better than al
earth road Is the pebbles, real stones
that It contains and is dependent w
on to bear up traffic and resist wear.
| Gravels that come from the pit wit
the pebbles cemented together, eve
though they contain no clay, will n
cement in the road and become harde
than they were in the pit. Tests @
specimens Of this kind always shO'
that there is much lime present an
usually some iron, both of which al
excellent cementing materials. Brie
ly, the experience Of the state higl
4 way department warrants the stat
ment that there are few, If any, ban
/ gravels in Michigan that do not col
! tain enough limestone and other so
pebbles which grind up under trail
TO furnish sufficient binder to caus
them to consolidate in a few month
time, If separated from the surpll
sand and earth, and properly treate
! after applying to the road.
In accordance with these sugge
lions, grsvels are considered valuab
= for road purposes in the followir
, order:
1. Almost in direct proportion to Il
percentage Of pebbles constituting Il
mass.
2. In direct proportion to the vail
as road metal Of the rock fragmen
constituting the pebbles.
3. In direct proportion to the val
as a ce,nenting material under all co
ditiuna of weather, of the finer pa
ticles of earthly matter constitute
the filler or binder.
In general, the physical character
tics Of gravel which determine
suitability for use In surfacing a 70
are:
CD The durability of the pebbles
rock fragments, (2) the quality of
binder, (3) the grading of the pebbl
and (4) the proportion in which
binder material is present. While
influence each of these factors shot
exert in fixing the selection of graz
4 for particular road depends upon
cal conditions and necessarily is
question for individual judgment
4 decide, nevertheless a few points
4 connection with each factor that m
q aid materially in reaching decis
8 will be summarized in the follow
D. paragraphs.
Il Durability Of Pebbles.
The principal qualities which DIET
IS mine the durability of pebbles