Essex County herald. [volume] (Guildhall, Vt.) 1873-1964, 1915-12-24
POPULARITY OF
CONCRETE ROADS
Rapid Increase Of Mileage In
Recent Years.
BOTH DURABLE and SMOOTH

Advantages and Disadvantages Con-
trasted In New Bulletin of the De-
partment of Agricuiture-Advice For
Construction of Concrete Highways.
The mileage of concrete pavement In
the United States has increased rapid
ty, and it is likely to continue to In
crease according to a new bulletin Of
the department of agriculture. This
bulletin gives the estimated amount of
concrete pavement in the United States
in 1914 as 100000 square yards. Ii
1909 it was only $4,000 square yards.
The principal advantages of concrets
pavements which have led to this in
crease in popularity are said to be:
Durability under ordinary traffic con,
ditiOns
A smooth, even surface, offering little
resistance
Absence of dust and ease with which
1t may be cleaned.
Comparatively small cost of Mainte,
nance until renewals are necessary.
Availability as a base for another
type of surface If desirable.
Attractive appearance.
The disadvantages of concrete as q
road surface are:
Its nOise under horse traffic.
The wearing of the necessary joints
IN hO fon1nnoH, fr
crack, with It's cOngequent rapid de
terioration.
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 a bitumi
nous wearing surface At the present
time the specialists in the department
hold that this cannot be economically
justified, although it is possible that
future investigation may change the
situation In this respect. In the pres
ent state Of road science, however, it
seems that where traffic conditions are
such that bituminOus surface on a con-
crete road is practicable a bituminous
surface macadam road would be equal
ly practicable and certainly cheaper
Who're traffic Is too heavy for macadam
road the bituminous surface is likely
to give way end the uneven manner In
which it fails tends to produce Excess
'ive wear on portions of the concrete.
For a successful concrete road, hard
ness, toughneSS and uniformity arc the
most essential qualities. These can be
secured to great extent by care in the
selection of the constituent materials
and the proportions in which they are
mixed. The cement. it is said, should
always conform to some standard spec
lticatiOns 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 8
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 OF
gravel. In either case it is very desira-
bic 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 one to five. and
the proportion Of sand : [coarse aggre
gate not less than one and one-half TO
three, nor greater than two to three.
A useful formula when gravel is used
SIS coarse aggregate is one part of ce-
ment to one and one-half parts Of sand
70 three parts of gravel. When crush
ID stone is used one and three-duar
Der parts Of sand may be substituted
t0 place of one and One-half parts.
In addition to discussing the engi.
neering details Of construction the bull
Ietin calls attention to the fact that
ordinarily from One-third to one-half of
the total cost Of constructing a con.
crete pavement is for labor after the
materials are delivered
The most economical method is TO
have the work of mixing and placing
the concrete as nearly continuous as
practicable. The work should be plan
ned with a primary view of keeping
the mixer going full time. The drain.
age structures, the grading and the
sub grade should, therefore, be com.
pleted well in advance of the mixer
and provision made for obtaining all
Of the necessary materials without de-
lay. A common error is the failure 70
make adequate provision for deliver
ing water on the work and the amount
which given stream is capable of SUD.