Evening star. [volume] (Washington, D.C.) 1854-1972, 1899-12-15
Wearing Surface.
The wearing surface was composed Of

Per cent.
Broken and rock dust ............. % to %
Paving ccmcnt-.-... OBSERVATION-DISCLOSURES. IL to 10
Hydraulic cement. Observation-Disclosures. 3
Slaked lime. Observation-Disclosures. Is
tSee report Of 1851, pp s3i s32 for specifications
The coSt of maintenance of coal tar
paveuents laid in 1887 was fG5 cents per
yard per year for a period of ten years, and
that laid in 1883; $50 cents per yard per
year for a period of nine years. OF these
pavements 1900 yards were found so bad
ly worn at the end of ten years that It was
deemed best to remove them entirely and
substitute standard asphalt. In future re-
pairs in these pavements in many cases it
will be necessary to treat them in this man.
ner. To resurface an asphalt pavement it
is only necessary to strip off the surface,
and the original grade and croSs-Sectfon of
the street are preserved. With the coal tar
or concrete pavements the base binder and
surface unite forming a solid mass. II
new surface is applied over the old pave
ment the cutters become almost obhter-
ated if the cutters are cut out and
lowered the crown of the street is increased
to a dangerous extent. 1t is especially diff
fiCult to reSurface a concrete roadway
along railroad track. and the only prac
teal way is to remove it entirely and sub
stitute standard asphalt. For this reason,
arart from the proved superiority OF stan
dard asphalt in other respects, it is not
probable that any more coal tar distillate
pavementS Will be laid.
In 1sss. among other forms of pavement,
WtldI was hIp" II DIS IleN CblIiDIiItit
phaIt pavement on hydraulic base" was
specified, and COrcoran street between 18th
and New Hampshire avenue was laid in
this manner. The restriction as to price
remaining, an attempt was made to keep
within the limit by specifying a base of
hydraulic cement concrete, four inches
thick. and instead of a wearing surface
two and one-half inches thick, including
cushion coat of one-half inch, a binder
course one and one-half inches thick was
introduced. This consisted of clean broken
stone not exceeding one and one-fourth
inches in largest dimension and No. coal
tar paving cement. The wearing surface
WAS composed of refined Trinidad asphalt.
heavy petroleum residuum, fine sand, fine
stone dust and fine powder of carbonate of
lime. This was essentially the same as the
pavement now in use but with four-inch
hydraulic base instead of six-inch. A four
inch base was considered sufficient for the
light travel many of the streets of
Washington, and the Introduction of the
binder course was believed and has since
proved TO improve the quality of the pave
mcnt.
Cutters Dcteriorate.
Early in the experience with asphalt and
coal tar pavements it was found that the
cutters deteriorated more rapidly than the
rest of the pavement. This was especially
true on streets having a light longitudinal
grade. and even on streets having good
fan it was found that the softening of the
payements allowed the hoofs of horses and
wheels of vehicles standing for any length
Of time to make indentations which the
light travel in these places never removed.
These formed hollows to hold the water
which rapidly rotted out the asphalt.
To ubviate this difficulty. granite blocks
We're introduced in 1880. and in 1888 vitrifed
brick, or block commenced to be- and are
now, used for the cutters OF asphalt street
pavements with satisfactory results. The
cutters for a width of two feet are paved
with vttrihed blocks laid on concrete.
In 1878 the test of asphalt block pave
ments was commenced, and since then the
use has been continued. At this date about
100000 square yards have been laid Most
of these pavements have been laid on a
! gravel base. With the exception of some
! OF the earlier pavementS, which were laid
with detective blocks, they have given ex-
ceilent satisfaction. About 5000 SQUARE
yards of these earlier pavements have been
surfaced with sheet asphalt and all are
row in good condition.
Several of the old macadam and cobbre
pavements in the city have been surfaced
Win sheet asphalt Some of them have
| been done ten years, and appear to VICAR
| as We'll as those laid on concrete base