Omaha daily bee. (Omaha [Neb.]) 187?-1922, 1905-08-27

/ by providing for the minimum OF bitumen
in the mixtures subject to the boiling
naptha test. which determines the malthene
or pertolene components which constitute
the cementing quality of asphaltic bitumen.
Eject of water on Asphalt.
Another feature OF considerable comment
upon which opinions are as varied as there
are interests is the claim OF susceptibility
of certain asphalts TO the effects Of moist
ure, and which, for that apparent reason,
are used as a basis TO exclude such as
phalts and thereby favor certain con-
tractors and punish others. From practical
contact with the varied features of this
question l am led to regard specifications
provisions placing power in boards or off,
GERS OF boards TO discriminate on grounds
OF the above nature as far more dangerous
to the honest public service than any pos
sible shortcoming affecting longevity OF
pavements from such alleged defects. The
asphalt pavement does not exist which can
withstand continued exposure under water
without deterioration. Asphalt pavements
when under water a length Of time be-
come soft and the great deterioration re-
sulting from water upon asphalt pave
ments is the action Of wheels and horses
hoofs upon the softened surface. Sand
stones, when wetted and exposed to abra-
sive forces, act like grindstones, wearing
away rapidly as the grinding goes on
whilst being subjected to moisture. This
is equally the case with the bituminous
sandstone. Chief Inspector Dow Of Wash
ington, who is perhaps, the ablect ex-
ponent and originator OF the provision to
! the dangerous clause giving preference to
asphalts not readily affected by water, in
| formed the author of this article last sum
meF, when extending him many courtesies
on an inspection tour Of Washington pave
ments, that for the last seven years all
/ cutters on asphalt paved streets In the
Capital city had been paved with vitrihed
| brick Mr.. Dow must have concluded that
ali asphalts deteriorated more rapidly
! when subjected 20 water influences ana
had little faith in the theory that GER
tain asphalts were not readily affected by
water. or he would not have urged the
! exclusion from use Of asphalts alleged TO
be affected and then studiously avoided
using those OF preferred merit from gut
ters. where they would be exposed to
| moisture influence.
Quality OF Sand.
Having disposed OF the asphaltlc fea-
lures OF the mixture. the equally and pos
! slbly more important mixture factor is
| the sand. which comprises approximately,
/ 90 per cent of the asphalt covering. To
bring forcibly 10 mind the sand factor l
need but cite you to a discussion at the
recent International Congress OF Engi-
neers Of the relative value Of stones for
macadam. One OF the speakers, referring
/ to sand stones, said that II should not be
i forgotten that there are extreme differ
| ences in the quality Of sand stones. No
/ one who has observed sand stones from
various quarrles and localities can fan
I to be impressed with the truth OF this
! statement. Yet few stop 20 think that
! sand stones are cOmponents Of grains Of
! various grades OF sands. That being the
case, is II not evident that an asphalt
paved surface, an artificial sand stone
monolith covering, ls as apt to vary IN its
I qualities owing 10 different gradings Of
| sand, as the natural sand stone itself?
Extended observations on this subject have
/ clearly shown that to produce the best
wearing mixtures sand OF certain various
graded grains gives better results than
other sands.
The problem of how to determine and
secure the sand that will grade best and
at the same time prove the toughest and
| most adaptable TO resist wear like the
natural sand stone Of the best quality, is
still only partially solved. Independent OF
the sand and asphalt, have already out
npSd ths need Of ; suitable alisE Ny In