The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1901-08-08

thickness, with a wearing surface OF
asphalt mixture two and a half inches
in thickness when compressed. But ex-
perience and tests have shown that on
light traffic streets foundation and
wearing surface can be made of less
thickness. It was also found that the
asphalt wearing surface could be LAID
on foundation of ole stone blocks. OF
brick or macadam which had been con-
solidated and wei packed by years OF
use. Thus in New York over a million
and a quarter yards of asphalt pave
ment We're laid on old stone block pave
ment, and in Chicago several lne as
phalt pavements are laid on old ma
caCsm foundations.
But in general a street is graded from
the ground up for asphalt pavement
The preliminary work begins on the
sub-grade Of the street, which is care
fLIIy graded to within eight ana nan
inches of the finished surface All
spongy or soft places in the suDgIaoe
are dug out and fresh earth Is nlled III:
remmed down and well packed, anu
then a tWelve-ton steam roller makes
the entire roadbed compact and Solo.
A bed of hydraulic cement concrete
made of hydraulic cement, clean, sharp
sand and broken stone Is lald' SIX
inches thick, upon the earJn Ioulod-
ton, and here is where good WoTk Se rs
L the concrete bed is not well laid the
wearing surface of the asphalt road
way s0en viii betray the dlshonest
character of the foundation, for poor
work. like murder, VIII out.
The asphalt blanket is laid on TINS
concrete foundation in two courses
the cushion" or binder" and the
surface" coat The street mixture is
brought to the work in carts and has a
temperature of about 800 degrees The
binder" is from One-half to an inch
thick and the surface coat varies from
an inch and a half to two inches in
thickness.
The workmen handle the hot street
mixture with hot tools, for the rakes,
iron hampers, smOOthers and other tools
are always heated before they are
brought into use. Broad iron sOles are
strapped to the shoes of the wOrkmen
and the mixture is spread from curb
u curb and tempered and smOOthed
to the proper thickness. A hand roller
is first run over the mixture, then
five-ton roller and finally a ten or
twelve-tOn steam roller is brought into
play to pack the asphalt and make II
even and springy.
Before the heavy rollers are passed
over the surface hydraulic cement is
swept over the top coat and the rollers
press it into the mixture The street
mixture is composed of from Is to 20
to SIS per cent of sand and from 5 to Is
per cent Of pulVerized carbonate of
lime
Where an asphalt pavement is left
undisturbed little or no repairs are
made on il for years. But in large
cities where wires, gas and water pipes
and sewers require the opening up Of
streets the asphalt pavements frequent
" are torn up. In former years this
proved to be a great objection to as
phaIt paving. The pipe layers or sewer
builders cut out patches Of the asphalt
coating with axes. and when they were
through the trenches were filed up and
a new coat of asphalt was laid on. The
most careful work failed TO restore the
pavement to its original hOmOgenity
and smoothness. So it was that as
phalt streets were covered with IN
slightly scars and soft spots
But bright man invented the sur
face heater" and now inv.s be patches
are put on asphalt streets as well as on
shoes. The surface heater is a hori-
zontaI gasoline tank On low iron wheels.
A hood projects from this tank, and
under the hood are rows of burners.
A hand pump for COMPRISING air is
attached to the machine, and the COM
pressed air forces the gasoline to the
burners. The heater. which weighs
about 700 pounds, is pushed to the spot
where the patch is to be put on. The
heat from the gasoline flames soon
sOftens the asphalt, which is removed
Fresh asphalt mixture IS laid on, and
the new and old mixtures are intimate
" and thoroughly Incorporated. The
patch is raked, tamped and rolled I'M
til it IS level with the general surface
and in a few DAYS the patch has dis
appeared and the pavement shows no
signs Of having been opened.
In large cities asphalt road builders
have large mixing plants in which is
installed heavy and expensive machin-
cry for preparing the ssphaItum for
street paving purposes. But in smaller
towns and cities the amount of pavine,
to be done would not justify large ex-
penditureS for permanent plants. The
large asphalt companies meet this con-
dition with their railroad plants"
which consist of cars fitted up with
the machinery required. A boarding
car for the workmen is attached to
the travelling plant and the whole af-
fair is run on to a side track in the
little town which has grown ambitious
enough to want asphalt streets, and
kept there until the contract is COM
pieted. This travelling plant is re-
garded as the solution Of the paving
problem for smaller cities.
The Pan-AmeriCan exposition in Buff
falO, with the city. form an interesting
exhibit of the use of asphalt for paving
purposes. All the walks and roadways
IN the fair grounds. the broad espIan-
ade and the by-paths are of asphalt.
and the city Of Buffalo itself has over
225 miles of fine asphalt streets. more
than any other city in the world
MALCOLM MCDOWELL.
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THE WORM 1FTTR RTEn