The herald. [microfilm reel] (Los Angeles [Calif.]) 1893-1900, 1896-05-17

mentitious nature, suitable in all re-
spects to make. upon proper admixture
with the refined liquid asphalt a dura-
bic and satisfactory cement.
The refined natural liquid asphalt
must be obtained by treating in suta-
BILE vessels, and at suitable tempera-
ture natural liquid asphalt, so as to
deprive it of all water. of all oils vapor-
liable under temperature of $50 de-
grees Fahrenheit, and of all other dele
ferrous substances; and the refining pro-
cess shall be conducted as in no wise to
impair the valuable qualities of the
liquid asphalt 1t shall be absolutely
Tree from admixture with any COM
pounds OF paraffine or Of coal tar, and
snail contain no less than 81 per cent OF
bitumen.
The resulting asphaltic cement must
be free from water, volatile oils and all
other deleterious substances, and it's
contained bitumen shall in all respects
be suitable to meet the requirements Of
an adhesive and lasting cement, and 1t
shall in all respects have the temper
ana other qualities so that the melting
point of the asphaltic cement shall b.
between 220 and $50 degrees Fahrenheit;
provided, however. that the variations
shall not exceed 10 degrees on any street
paved under one contract.
The sand and asphaltic cement must
be heated in separate vessels to about
800 degrees Fahrenheit, and in no case
must the temperature be permitted to
rach over $50 degrees Fahrenheit. After
this being suitably heated, the sand and
asphaltic cement in their proper pro-
portions shall be mixed together in
suitable power mixer, so that every par
ticle of sand shall be thoroughly coated
with thin layer of asphaltic cement
The sand must be clean, sharp. salt
cious sand of such size that none of it
and the whole of 1t must pass through a
l2-mesh screen, and shall be thoroughly
washed in sieve having not less than
twelve meshes to the inch. The sievs
is to be given a horizontal motion and
operated under water of a sufficient
depth and quantity to carry off all waste
material, such as loan. Quicksand or
other deleterious matter. The sand
which passes through the sieve is to be
thoroughly dried before weighing for
the purpose of prOpOrtioning the sand
and asphaltic cement
The proportion of asphaltic cement
and of sand must be such that, after the
asphaltic pavement-layer has received
its utmost compression, the voids be-
tween the sand particles shall be filled
up completely with asphalt; and no more
bitumen shall be present than may be
necessary to secure this result.
The mixture shall then be brought on
W TIE street III suitable carts, ana Snall
be spread at tempera ture of about 275
degrees Fahrenheit on the hydraulic ce-
ment concrete foundation, which has
been previously prepared and cleared
OF all rubbish, and which has thoroughly
set and dried. The asphaltc mixture
must be uniformly spread with hot iron
rakes to such depth that. after receiv-
ing its ultimate compression, the finish
ed asphaltic layer shall show a thick
ness of no less than two inches. After
being spread. the mixture shall be ironed
and compressed with hot iron rollers,
weighing at least $50 pounds to the foot
run. after which small amount of ny
draulic cement must be swept over 1t.
and the whole thoroughly compressed
by steam roller weighing not less than
250 pounds to the inch run, the rolling to
be continued for not less than five hours
for every 1000 square yards of surface.
The resulting pavement must show an
even and smooth surface, true to grade
and cross-section. and free from all hol-
lows and inequalities.
Bidders must submit samples fsX