The Monmouth inquirer. [volume] (Freehold, N.J.) 1865-1933, 1924-06-12
5o1s1 ia 1se4risy Indicated ~
Rapid increase in Mileage In "A
Recent Years.

J The mileage Of concrete pavementS
In the United States has been in-
creased rapidly, ard it is likely to cons
tinue to increase, according to new
bulletin Of the United States depart-
nient Of agriculture.
The principal advantages Of con-
crete pavements which have led to
this increase in popularity are said to-
be: I
% Durability under ordinary traffic
conditions.
~ A smooth, even surface Offer
ing little resistance.
(3) Absence of dust and ease with
which it may be cleaned.
"a Comparatively small cost OF
maintenance until renewals are neces-
sary.
81 Availability as a base for anoth-
er type of surface if desirable.
go Attractive appearance.
In commenting upon these advan-
tages, the bulletin states that the dur
ability Of concrete roads has not vet
been proved by actual pactice, be
Gauss there are no very old pave
ments as yet in existence, but from
the condition Of those which have I'M
dergone several years service, It
seems probable that viii be found to
wear well
The disadvantages Of concrete as a
road surface are:
~ It's noise under horse traffic
~ The wearing of the necessary
joints in the pavement; and the ten
deney to crack, with its consequent
deterioration.
go The difficulty of repairs when
these become necessary.
In the past efforts have frequently
been made to overcome these objec-
tons to a certain degree by covering
the concrete pavement with bitunl-
nous wearing surface. At the present
time, the specialists in the depart
ment Of agriculture hold that this
can not be economically justified al
though it is possible that future In
Yestigation may change the situation
IL this respect. In the present state
of road science, however, it seems
that where traffic conditions are such
that a bituminous surface on con-
crete road is practicable bituminous
surf1ee macadam road would be
eqaaliy practicable and certainly
cheaper Where traffic is too heavy
for mscadam road, the bituminous
surface is likely to give way and the
uneven manner in which It fails tends
to produce excessive wear on portions
OF the concrete.
For a successful concrete road, hard
ness, tonghness, and uniformity are
the most essential qualities. These
can be secured to a great extent by
care in the selection of the constitu-
ent materials and the proportions in
which they are mixed. Sample speci-
flcations are included in the bulletin.
No. 249, "Potland Cement Concrete
Pavements for Country Roads" These
specifications are believed to typify,
the best engineering practice as it
has been developed up to this time.
They cover such points as materials.
grading, sub-grade, and construction.
The cement, 1t is said, should al
ways conform to some standard spec
ifcations for Portland cement, such
as those issued by the United States
Bureau of Standards or the American
Society for Testing Materials The
sand should not contain more than 3
per cent of foreign material, and sand
with more coarse than fine grains is
to be preferred. The coarse aggregate
may consist of either crushed stone
or gravel In either case 1t is very de-
sirable that the coarse aggregate be
well graded in size between proper
limits.
The proportion of cement to the
sand and coarse aggregate combined
should not be less than about to S,
and the proportion of sand to coarse
aggregate not less than 1 1-s to 8. nor
greater than to 3. A useful forrnu-
Ia when gravel is used as coarse ag-
gregate is part of cement to 8 parts
of gravel. When crushed stone is
used. 1 "a parts of sand may be sub
stituted in place Of IL parts.
u QAcG0SS4tS LA4C CA6A-
neering details of construction, the
bulletin already mentioned calls at
tention to the fact that ordinarily
from 1-3 to IL Of the total cost OF
constructing a concrete pavement is
for labor after the materials are de-
livered. This emphasizes the inn
portance of efficient organization and
proper equipment. Failure to take
these factors into consideration fire.
quently results, it is said, in adding
from 10 to 20 per cent to the cost f.
of a concrete pavement.
The most economical method is to
have the work of mixing and placing
the concrete as nearly continuous as
practicable. The work should be
planned with a primary view Of keep
ing the mixer going full time. The
drainage structures, the grading, and
the sub-grade should, therefore, be
cor,Dla4aS we'll in advance 0f the mix