Clearwater Republican. [volume] (Orofino, Idaho) 1912-1922, 1916-06-16
POPULARITY OF
CONCRETE ROADS
Rapid Increase Of Mileage In
Recent Years.
BOTH DURABLE AND SMOOTH

Advantages and Disadvantages Con-
trasted In a New Bulletin of the De.
partment of AgrcuIture-Advice For
Construction of Concrete Highways.
The mileage of concrete pavement in
the United States has increased rapid.
ly. and ii is likely to continue to in
crease. according to new bulletin Of
the department of agriculture. This
bulletin gives the estimated amount OF
concrete pavement in the United States
in 1914 as 19,2OO,00O square yards. In
1909 1t was only 36I 900 square yards.
The principal advantages of concrete
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 base for another
type of surface If desirable.
Attractive appearance.
The disadvantages Of concrete as
road surface are:
Its noise under horse traffic.
The wearing of the necessary joints
In the pavement and the tendency to
crack, with its consequent rapid de-
terioration.
The difficulty Of repairs when these
become necessary.
In the past efforts have frequently
been made to overcome these objec-
lions to certain degree by covering
the concrete pavement with bitumi-
nous wearing surface. At the present
time the specialists in the department
hold that this cannot be economically
Justified, although 1t Is possible that
future investigation may change the
situation In this respect. In the pres
ent state of road science. however. II
seems that where traffic conditions are
such that bituminous surface on a con.
crete road is practicable bituminous
surface macadam road would be equal
ly practicable and certainly cheaper.
Where traffic is too heavy for macadam
road the bituminous surface is likely
TO give way and the uneven manner in
which 1t fails tends TO produce eyces-
sive wear on portions of the concrete.
For successful concrete road. hard
ness. toughness and uniformity are the
most essential qualities. These can be
secured to a great extent by care In the
selection of the constituent materials
ana the proportions in which they are
mixed. The cement, 1t Is said. should
always conform to some standard spec
ihcations 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 it is very desira.
Die That the coarse aggregate he well
graded In size between proper limits.
The proportion of cement to the sand
aud coarse aggregate combined sbould
not be less than about one to five. and
the proportion of sand to coarse aggre
gate not less than one and one-half to
three. nor greater than two to three
useful formula when gravel Is used
rs coarse aggregate is one part of &c.
Inenf to one and one-half parts OF sand
70 three parts of gravel. When crush.
81 stone Is used one and three-uuar-
Ter parts OF Sand may be substituted
q place of one and one-half parts.
IN addition to discussing the enyi |
teering details of construction the bull
etin calls attention to the fact that
ordinarily from one-third to one-half of
he total cost of constructing con.
'rete Pavement is for labor after the
narerials are delivered.
The most economical method IL to /
ave the work of mixing and placing
&c concrete aS nearly continuous us
acticdb bic. The work should be plan.
I'd with primary view of keeping
he mixer soins full time. The drain.
se structures. the grading and the
nb grade should. therefore, be com.
ieted well in advance of the mixer
al provision made for obtaining all
I tue necessary materials without de
~ common error is the failure to
aake adequate provision for deliver
lg water on the work and the amount
hicn given stream is capable of sup
wing Is frequently overestimated