Essex County herald. [volume] (Guildhall, Vt.) 1873-1964, 1915-09-24
Concrete Roads.
GROWTH IN POPULARITY INDICATED
BY RAPID INCREASE IN MILEAGE IN
RECENT YEARS.

continue to increase, according to a
new bulletin of the department.
This bulletin gives the estimated
amount of concrete pavement in the
United States in 1914 as 10, 100000
square yards; in 1909 it was only
1854, 900 square yards.
The principal advantages of con-
crete paVements which have led to
this increase in popularity are said
to be:
ID Durability under ordinary
traffic conditions.
~ A smooth, even surface of
fering little resistance.
90 Absence of dust and ease
with which it may be cleaned.
(4) Comparatively small cost of
maintenance until renewals are nec-
cessary.
(5) Availability as a base for
another type of surface if desirable.
CO Attractive appearance.
in commenting upon these ad-
vantages the bulletin states that the
durability of concrete roads has
not yet been proved by actual prac-
tice, because there are no very old
pavements as yet in existence, but
from the condition of those which
have undergone several years
service it seems probable that they
will be found to wear we'll.
The disadvantages of concrete as
a road surface are:
(l) It's noise under horse traf-
fic.
w The wearing of the neces-
, sary joints in the pavement, and
the tendency to crack, with it's con-
sequent rapid deterioration.
(3) The difficulty of repairs
when these become necessary.
In the past efforts have frequent
ly been made to overcome these OBJ
jections to certain degree by COW
ering the concrete pavement with a
bituminous wearing surface. At
the present time, the specialists in
the department hold that this can
not be economically justified,
although it is possible that future
investigation may change the situ-
alton in this respect. In the pres
ent state of road science, however,
it seems that where traffic conditions
are such that a bituminous surface
Oh concrete road is practicable a
bituminous-surface macadam road
would be equally practicable and
certainly cheaper. Where traffic is
too heavy for macadam road the bit
luminous surface is likely to give
way and the uneven manner in
which it fails tends to produce ex-
cessive wear on portions of the con-
crete.
For a successful concrete road,
hardness, toughness, and uniformity
are the most essential qualities
; These can be secured to a great ex.
tent by care in the selection of the
constituent materials and the pro.
portions in which they are mixed
Sample specifications are included
in the bulletin, No. 249, Portland
; Cement Concrete Pavements fol
: Country Roads. These specifca
tons are believed to typify the best
, engineering practice as it has beer
developed up to this time. They
cover such points as materials
grading, subgrade, and construc
ton.
The cement, it is said, should al
ways conform to some standard
specifications for Portland cement
such as those issued by the United
States Bureau of Standards or thu
American Society for Testing Ma
terials. The sand should not con
, tain more than per cent of for
eign materials, and sand with NOR,
coarse than fine grains is to be pre-
ferred. The coarse aggregate ma!
. consist of either crushed stone o.
: gravel. In either case it is very de
9 sirable that the coarse aggregat,
n be we'll graded in size between prop
: er limits.
! The proportion of cement to tn
9 sand and coarse aggregate com
bined should not be less than abou
| to 5, and the proportion of san,
to coarse aggregate not less thai
4 d to 3, nor greater than 2 to
] A useful formula when gravel i
y used as coarse aggregate is | par