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

neer VIII then set the necessary grade
stakes, after which the contractor shall
dress down or fill up to the true surface
all Irregularities as indicated by~ said
grade stakes; the surface shall then be
again rolled until it shall be true,
smooth, compact, and to the proper
grade
Such portions of the street as cannot
be reached by the roller, and all places
excavated to a sub-grade and refilled,
and all pipe trenches and other places
that cannot be properly compacted by
the roller. shall be tamped solidly by
the contractor, and, in case OF wet
weather or soft or muddy ground, max
ing the use of the roller unsafe or i'm
practicable. the rolling shall not be UNI
dertaken until the ground has become
sufficiently dry.
Upon the roadbed prepared ana
brought to sub-grade as above de-
scribed there must be constructed a
concrete foundation prepared IN the
following manner, and composed or
bed of hydraulic cement concrete six
inches in thickness when completed, ana
composed of by measure. one part OF
Portland cement, three parts or SAND,
six parts of broken rock.
The cement must be the best Portland
cement; the sand must be clean, sharp,
salicious sand, free from loan, mica. clay
or any earthly Impurities; and the
broken rock must have sizes ranging
from the size of a pea minimum to that
which will pass through two-inch ring
maximum.
All wheelbarrows or vessels employed
in measuring the parts of the concrete
must be of uniform capacity and size.
The sand and cement shall be thorough
ly mixed while dry and until the mass
assumes an even color; and to this mix
ture will be added the water to give the
mortar proper consistency; the rock
will then be added in the proportion as
given above, after having first been
thoroughly sprinkled with water so that
1t may be freed from all earthly impuri-
ties. The entire mass shall be mixed in
a water-tight box or platform, the whole
being thoroughly stirred and mixed !;
and the concrete thus prepared will be
spread upon the sub-grade in one layer;
this layer after being spread shall be
rammed to a uniform surface and until
the free mortar appears upon the SUR
face, and so as to have a depth of six
inches in thickness, and the top thereof
shall be two inches below the finished
surface of the pavement. The surface
of the concrete must be thoroughly wa
tered and protected from the wind and
sun for at least three days, after which
sufficient time shall be allowed for the
surface to become thoroughly dry be-
fore receiving the asphalt layer Under
no circumstances shall any concrete be
put into the work after the initial set
has taken place. The time of initial set
ting is to be determined by the city en-
gineer by test as hereinafter provided.
Upon this substratum of concrete
there must be constructed and spread
an asphaltic layer that shall not be less
than two inches in thickness after ulti-
mate compression and must be com
posed of asphaltic cement, II to II per
cent by weight; sand, thoroughly dried.
SS to SO per cent by weight
The asphaltic cement must be COM
posed of natural solid asphalt mixed
with n refined natural liquid as
phalt; and 1T shall contain not less than
81 per cent of bitumen.
The natural solid asphalt must con-
tain at least go per cent of bitumen, and
shall be free from all deleterious sub
stances, such as non bituminous organ
ic matter. soluble salts and loan. It
shall be of even and uniform compost
ton and shall contain nothing that will
volatilize under temperature of 300 de-
grees Fahrenheit. Its contained BIZ
tumen shall be of a permanent and ce-