The Pensacola journal. (Pensacola, Fla.) 1898-1985, 1907-02-02

and Utah; and bituminous limestone
OF France, Germany, Utah and other
; Western States.
Liquid asphalt, when it passes
| through clay, carries clay in suspen-
sion, and we have impure asphalt in
greater or less deposits of which Trim
idad Lake is the most remarkable in
size"
The Uncertainties of Asphalt.
| l will take an extract from a set of
| specifications before me to point out
some of the uncertainties of an as
I phalt pavement even beyond the COM
position of the asphalt itself.
Wearing surface-The wearing
! surface shall be compounded Of
! Asphalt cement (pure carbon) 9 to
I II per cent
Sand (pure silica) IS to 70 per cent.
! Pulverized carbonate of lime to
10 per cent.
I'm order to make the pavement
! homogeneous, the proportion of as
! phaltic cement must be varied &C
cording to quality and character of
sand. The carbonate of lime may be
/ reduced or omitted entirely when suit
! able sand can be obtained. The sand
and asphaltic cement will be heated
! separately to about three hundred
degrees Fair. The pulverized car
Donate of lime shall be mixed with
hot sand in the required proportions
and then mixed with the asphaltic ce-
ment at the required temperature, and
/ in proper proportions, in a suitable
, apparatus which will effect a thorough
mixture. The above mixture must be
| brought to the street to be paved at
a temperature of two hundred and
I fifty degrees Fair"
! You can see uncertainty through
out the entire labor of manufacturing
asphalt pavement; first, a selection of
proper asphalt, then proper selection
and proportion of fiux; then the Sc
! lection of proper sand; on the selec-
ton of the sand to depend whether or
not carbonate of lime or Portland &C.
ment shall be used or not, and if
used, in what proportion
Then special care must be given to
| properly heating the mixture; not
only the asphalt cement must not be
made too hot, but equal care to see
/ that the sand is not made too hot, for
sand. too, will also burn the asphalt
cement and make it worthless.
Not only must the mixture be prop
erly heated in its preparation, but it
must reach the street on which it is
/ to be placed at the proper tempera-
! ture-not less than two hundred and
| fifty degrees Fair
In repairs not only are the above
lchances of failure, but even more
| the tamping and smoothing tools must
not be too hot. They, too, will burn
/ and kill the asphalt.
| Several patches on Peachtree, re-
Gently put down by the city forces,
/ show the injurious effect of hot irons
! Care must be taken to give time
/ for all moisture in the concrete foun-
datiOn to dry out, in order that said
moisture may not be converted into
steam when the hot asphaltic mixture is
, placed thereon, which would permeate
/ such mixture and, with Trinidad. or
any other asphalts affected by water,
would cause disintegratiOn
For this reason asphalt repairing.
! or new asphalt paving. should ,rrt be
done in wet weather-in fact, sheet
! pavementS, requiring the mixtures to
possess high degree of heat. should
| only be put down in clear and warm
weather The effect of repairing on
damp foundations can be seen also in
several patches recently put down by
the city's repair force.
The effect is very apparent-the
! patch remains damp long after ada
cent paving has dried-sOon it is
completely disintegrated and the
wheels grind it into dust.
The oils of asphalt are more or
less volatile and will gradually evap-
crate. When poor in oil, or
snort IN dUctility, the pavement will
crack under sudden changes of tenn
perature-a drop down toward the ze-
no point, contraction takes place and
the pavement does not possess enough
Vlscoslty. or life, or elasticity to with
stand contraction and a rent occurs.
frequently extending entirely across
the street Several very decided ex-
amples are to be seen Of this on
Washington, Peachtree and Peters
streets, though the last named nave
ment has been down less than three
years The asphalt must have been
snort when pavement was put down
The same contraction in freezing
weather is what makes it impossible
10 efectually patch asphalt pavements.
The seam between the old paving and
the new patch is the weakest part and
naturally contraction causes a rent
between the old and new. into which
water percolates, freezes, lifts up the
edges which passing wheels grind on
and make the holes larger and larger
daily.
Into contraction cracks water per-
colates and soon disintegration begins
on the under side of the wearing sur
race, which shows itself in waves, or
saucer Roles. and soon commence TO
crumble and is ground into dust.
Even though street car rails are per-
fectly rigid as to foundation-heat
and cold will cause expansion and
contraction; which crawling will
break the bond between the pave
ment and the rail. into which water
VIII percolate and thus cause disin-
Iteration to set in against the rail.
which soon shows itself in deep ruts
adjacent &c the rails. This can be
49,