Evening star. [volume] (Washington, D.C.) 1854-1972, 1899-12-15
pavement was that it was very slippery. es-

peciafiy in wet weather.
Asphalt pavements laid according to speci-
fiCations of August, 1878, consisted of a base
OF hydraulic cement concrete six inches
thick and a wearing surface of asphalt
the basis of which. paving cement, was
refined asphaltum mixed with residuum of
petroleum. carbonate of lime and alumina.
The pavements for which bids were made
October 10. 1878, and awarded to ]. s. Bald
win. consisted of a base OF hydraulic ce-
ment concrete six inches thick and two and
a half inches of asphalt wearing surface.
The pavement Is known as "Grahamite."
invented by E. J. De Smedt. The constit-
uent parts, apart from concrete base, are
thus specified:
First, refined Trinidad asphalt; second
heavy pure petroleum OIL third, very fine
sand containing about IS per cent amor
phous carbonate of lime. or 10 per cent
pure hydrosilicate of aluminium. By mixing
petroleum oil and asphalt in the proportion
of four or five asphalt and one of OIL the
matriX of the pavement called asphaltic &C.
Hent is manufactured The aspha!tc CO.
ment is mixed with sand in the proportion
of fifteen to eighteen of cement to eighty
five or eighty-two of sand: the two ingre-
dien's are heated separately to about 300
degrees F. and the mixing performed in
twin pug mill.
The asphalt prepared in this manner is
brought to the ground in heated carts at
temperature of about go degrees. 1t is
spread in two coats. the first. aboosi one
half inch thick, called the protecting or
cushion coat. may be laid richer in asphalt
and is consolidated by rolling. The second
coat or wearing surface, exceeding by
about two-fifths the ultimate thickness re-
quired, is carefully spread with iron rakeS
and compacted by ramming or rolling. Hy
draulic cement is then spread or busted
over the surface, and rolled with a heavy
roller. This is essentially the specification
under which asphalt pavements have been
laid from 1877 to 1887. In 1887 and 1SSS a
departure was made from what may be
termed the standard asphalt pavement in
e +, oot
distillate, which was very similar to the old
Scharf and vulcanite pavements.
Comparative Durability.
In Captain Griffith's report for 1887 a
statement of the comparative durability
of asphalt and coal-tar pavements is given.
He says: "Of the Evans pavements 1924
square yards were resurfaced within two
years after laying. The mean average eX-
pense for maintenance of 745,3o5 square
yards is 5l2 cents per square yard for fif-
teen years That durable coal-tar pave
ment can be laid is proven by the fact
that the vulcanite pavements have only
averaged 80 cents pee square yard per an
mum for fourteen years maintenance. The
annual cost of maintenance of stj,!11 square
yards of asphalt and neuchatel paVemeuts
was 10 cents per square yard
While the superior durability of asphalt
pavements is shown, Captain Griffin says:
The return to the distillate pavement was
virtually forced upon the Commissioners
1SS6-'SI which provided that under this
appropriation no contract shall be made
for making or repairing concrete as
phalt pavements at a higher price than s.
per square yard of 4 quality equal to the
best laid in the District prior to July /,
1856, and with the same depth of base.
The lowest proposal received for stand
ard asphalt pavement was s2.25 per square
yard, the ruling price for the past few
years. This bid could not be considered,
and as smooth pavements had become a
necessary luxury in the city, the bids for
asphalt block and coal-tar distillate were
perforce accepted"
The amount of coal-tar distillate pave
ment laid was, in 1881 1921; square yards.
and in 1883, IS IA square yards. Total,
122.9S1 square yards These pavements
were composed and laid in the following
manner: They consisted of base and binder
IL inches in depth when compacted and
ness when compacted. The base was COM
posed of clean broken stone that would
pass through a 3-inch ring, well rammed
and rolled. to the depth of 1 inches, and
thoroughly coated with No. az coal-tar
paving cement in proportion of about 1 gal
Ion to the square yard of base.
The second or binder course was COM
posed of clean Broken stone. thoroughly
screened, not exceeding IL inches in larg
est dimensions, and No. i coal-tar paving
cement. The stone to be heated to a tenn
perature between go and 80 degrees F.
by passing through revolving heaters and
thoroughly mixed by machinery with the
paving cement in about the proportion of
gallon Of No tar to ! cubic foot of
stone; to be hauled upon the work, spread
upOn the base course at least inches
thick and Immediately rammed and rolled
with hand and steam roller while in hot,
plastic condition.