The Dawson news. (Dawson, Ga.) 1889-current, 1914-08-21

these, though, probably are due TO
other causes than a defect in the
natural asphalt In some cases the
defects might have been in the ma
nipulation of the material. For in
stance, the foundation might not
have been thoroughly dry when the
binding course was put on, thus caus-
ing steam to form, which broke the
cohesion between the foundation and
the binding course and causing the
asphalt to be somewhat displaced un-
der traffic The top course might
not have been put on soon enough al
ter the binder was laid. The rolling
or compression might have been in
adequate. The edges of the cutters,
around the manholeS and along the
railing of the street car tracks might
not have been properly fixed. The
character and grade of sand used
might not have been suitable for the
particular pavement. For instance,
the sand might have been too course,
causing the pavement to be porous
and open. If there is not enough fine
sand of 100 and 80 mesh material
sufficient amount of filler cannot be
used. The fine PARTICLES of sand keep
the dust filler from segregating into
balls in hot mixture, thus causing
the mixture to be nOn-uniform. Also
the character of the grains might not
have suited; because asphalt will ad-
here to the grains of some sands bet
ter than it will to the grains of 9TH
ers. In some cases the filler might
have been deficient in quantity as
we'll as in quality. The heavier the
traffic the greater the quantity of
filler that is required. The percent
age runs from 10 to IS per cent.
Portland cement has been found to
give the best results as it helps to
make the asphalt impervious to wa
ter and increases the specific gravity
of the asphaltic surface.
Very probably the cause Of most
failures are due to the materials
used, that was obtained by distllla-
ton of petroleum or other oils. They
are asphalts in name only and not in
quality. A good many products of
petroleum and coal tar have been
showed on the market as asphalt and
naturally have been found wanting.
No one will say that any artificial
article, may it be ever SO scientltlcal-
ly manufactured, is as good as the
natural asphalt when it has taken
nature ages to produce it. Do not
wish to state that the scientists By
their chemical methods expect to out
do nature and produce a material
equal to that of nature in a few
days? The reconstructed ruby, made
from the chips of the precious stone
itself, does not compare with the
genuine gem, and is valued accord
ingly.
Mr.. Richardson says that he has
found by long experience and trial
that oil asphalts obtained from as
phaltic petroleum are not as satlstac-
tory as the natural asphalts OF Trim
idad and BermudeZ lakes. 1t is
considered almost impossible to iden-
tify mixtures of natural and oil as
phalts, especially when the mixture
is made into aspha1tic cement. The
cement is usually made by fuxing
the refined asphalt with maltha or
other petroleum residums. II the
chemist has no means Of detection
is it any wonder that the practice OF
substituting oil asphalts for natural
asphalts exists? The chemical knowl-
edge of asphalt seems to be very lin
tied, the chemical test used being
mostly arbitrary ones.
Very little is known of the chemical
composition of the bitumens contain
ed in asphalt. They are hydrO-car-
bons of complex structure, largely
cycle and bridge compounds together
with a small amount of sulphur and
nitrogen derivatives, and are closely
related to the hydrocarbons occur
ding in petroleum.. The difficulty in
distinguishing between the natural
and artificial asphalts is that the
process of converting the oil into as
phalt, which took ages in nature, is
used in the manufacture OF oil as
phalts and is accomplished in a few
days.
Mr.. Malencovic states that oil as
phalts and natural asphalts differ in
that the former do not react with
mercuric bromide solution, the lat
ter, however, owing to their sui
phuric contents give a precipitate.
The sulphur content in oil asphalts
and natural asphalts is, if the oil as
phalt is sulphonated, quite different.
Trinidad contains more than per
cent and that of California less than
| 2 per cent. But this test is not suffi-
cient alone, as the oil asphalt is so
easily sulphonated.
The acid number is of good value
for a preliminary test to determine
| whether we are dealing with natural
asphalts or oil asphalts. The results
given show clearly that the acid val
ues of natural asphalts are consider
ably higher than those of the oil as
| phalts.
Acid value, list dist. End dist.
Pure Trinidad 1872 p. ct. 8.4 pct.
Pure Bermudez 9.8 p. ct. 80 pct.
Pure. California 10 p. ct. .O4 p. ct.
MaItha Flux 49,. .12 pct. 20 p ct.
The second distillate in both Trim
| idad and BermudeZ asphalts show
some acid value, while in California
the second distillate is almost free
| from acids. Therefore, if the acid
value falls below /. We may safely say
that we are dealing with oil asphalts
or a mixture. If we deal with an