The Pacific commercial advertiser., 1910-12-25

OF FORT STREET PAVED WITH B]
much chance for Improvement, COM
mnced to experiment along lines of his
own, aiming to produce pavement
that would have greater durability than
asphalt, provide a foothold for horses
equal TO macadam, and at the same time
ness of an asphalt pavement and over
come the necessity of muddy or dusty
condition of macadam and provide a
pavement that, while having the density
of solid stone, would at the same time
have great elasticity.
Previous to this time, all tar maca-
, dam surfaces were formed of successive
layers of stone, graded from coarse
layer at the bottom to a finer layer
at the surface With this stone was
mixed.s either before or after laying,
greater sor less. proportion of some
form of tar binder, the tar being used
to bind together the stone and fine
mineral grains, which in themselves
had no frmness to sustain traffic.
Mr.. Warren believed that the mineral
aggregate should have a stability of its
own, regardless of the binder used, and
that the only function of the binder
/ should be the filing of voids in order
to exclude moisture. and to cement the
particles of aggregate. After nine
months of laboratory work he intro
{ duced to the world an entirely new
form of pavement construction, founded
on prime iples so simple that no one had
ever beferes thought of applying them
! to the building Of pavements. The new
pavement was patented and given the
name 'Bitulithie,' coined from the
Latin word ''Bitunlen'' (bitumen) and
''Lithos' (stone), the pavement being
made. of a combination of bitumen and
stones andFsa company for its manufac
ture was formed with Fred J. Warren
as president. -
Validity of the Warren Patents
1t was natural to expect that the
new company would be obliged to fight
! hard in order to defend the validity
, of it's patents and such has proven to
be the case.
The Barber Asphalt Paving Company
| of New York City in several instances
submitted bids in competition with the
! Warren Brothers Company, offering to
construct a pavement similar to btu
lithlc at a lower cost. Municipalities
which contracted for such work with
the asphalt concern were promptly sued
/ by the Warren Brothers Company for
infringement of the bituIthic patents,
! the New York Company in each case
| guaranteeing to stand the expense of
defending any suit which might be
! brought as result of its receiving a
! contract.
! The final disposal of the eases was
made in May, 1909. The city of Owos-
| so. Michigan, one of the cities in which
The Barber Asphalt Paving Company
constructed pavement and against
which suit was brought by Warren
| Brothers Company, applied to the Uni
! ted States Supreme Court for a writ
OF certiorari This was refused on May
| 81. 1909, which had the effect OF con
| frming the decision of the United
States Circuit of Appeals of the Sixth
District in favor of Warren Brothers
| Company BY this decision three of
the bituIithic patent claims in dispute
were affirmed and this ends the litiga-
tion in regard to these patents.
Methods of Construction.
! The method of construction of the
pavement was shown in the past two
weeks when an expert of the Warren
people laid the first bitulithic material.
| Tho tnuni1 riNn soil rolled hv
steam roller and over this was laid
! LAYER of heavy broken rock and again
rolled and then smeared over with boil
| ing bitumen.
| After the base has been prepared it
is covered by the wearing surface
which consists of a two-inch layer of
the best stone that can be obtained,
properly graded in size from two and
a half inches in diameter down to an
impalpable powder
The material is heated and dried in
rotary drums and then screened in
six or more sizes. Careful laboratory
tests are made to determine Just what
proportions of the different sizes will
give the densest mixture with the small
est percentage of voids.
These proportions are mixed together
mechanically at a temperature of abont
250' F, giving combination having
about ten per cent. voids. While the
stone is in the mixer sufficient quan-
titv of heated bituminous cement il
added to coat all of the stone particles,
I'll the voids and leave small surplus.
After the stone and cement have be-