boiler-plant cinders, ... inches[80] in thickness shall be laid. Broken
stone for this purpose may be of any durable stone crushed to such size
that all will pass through a screen with two inch openings. Crusher-run
material may be used unless it contains an excessive quantity of fine
material. Gravel for the purpose may be any sound durable gravel all of
which will pass through a two inch screen and be retained upon a
one-fourth (¼) inch screen. If cinders are used they must be good
boiler-plant cinders from which the ashes have been screened out. The
cinders must be thoroughly drenched with water at least one week before
they are placed in the sidewalk.[81]
=143.= This drainage material shall be placed on the sub-grade and
properly graded. After grading it shall be thoroughly compacted by
ramming or rolling, and its surface shall be brought to a plane parallel
to and ... inches below the designed surface of the sidewalk, after
which the surface inequalities may be leveled up with screenings or
small gravel.
The bottom of the drainage course shall be connected with the street
drains or sewer inlets by three-inch hard drain pipe at such points, not
more than three hundred feet apart, as will drain all standing water out
of the drainage course.
=144. Concrete, Bottom Course.=—The bottom course of concrete ...[82]
inches in depth, shall be constructed and placed in accordance with
Sections 28, 29, 30, 31, 32, 33, 34, 35 and 36 of these general
specifications, except that the maximum size of the crushed stone shall
not exceed one-half the thickness of the bottom course of concrete and
the concrete shall be uniformly composed of one part Portland cement,
three parts sand and six parts of crushed stone. Its upper surface shall
be brought to a plane parallel to and one inch below the designed
sidewalk surface.
=145. Surface or Finishing Course.=—The surface or finishing course
shall be of concrete, one inch thick, composed of one part Portland
cement, one and one-half parts sand and two and one-half parts of hard,
durable stone, crushed to such sizes that all will pass through a screen
having openings one-half (½) inch square and none will pass through a
screen having openings one-eighth (⅛) inch square.[83] This concrete
shall be made as specified in Sections 28, 29, 30, 31, 32, 33, 34, 35
and 36 except in the particulars named in the preceding paragraph. Care
must be taken to make the mixing very thorough. The quantity of water
used in this concrete shall be just sufficient to make a moderately wet
mixture, and care shall be taken to make the different batches as nearly
as practicable of the same consistency.
The surface concrete shall be spread over the bottom-course concrete
before the latter has begun to set,[84] properly graded, well compacted
by ramming, and its upper surface brought to the true designed plane and
surface of the sidewalk by the use of straight-edges and troweling,[85]
after which the surface shall be lightly gone over with a wire broom or
brush to slightly roughen the surface. The finished plane of the
sidewalk shall have a transverse downward slope toward the street of
one-fourth (¼) inch to one foot of horizontal width. At no place shall
the thickness of the surface-course be less than three-fourths of one
inch. The outer top corners of the sidewalk shall be rounded off with a
suitable tool to a radius of three-fourths (¾) inch.
=146. Forms.=—Substantial and suitable forms of wood or iron shall be
furnished and used by the contractor to support the concrete until it is
hard set, when they shall be removed at his expense.
=147. Expansion Joints.=—After the laying of both courses of concrete is
completed expansion joints at right angles to the sidewalk, and not more
than four (4) feet apart shall be constructed in the sidewalk in the
following manner: the joint will be located by a line on the surface of
the sidewalk and a straight-edged cutting tool one-fourth (¼) inch thick
will be used to cut entirely through both courses of concrete,
accurately along the line marked out, entirely across the sidewalk,
after which a T-shaped trowel or tool shall be used to smooth and
compact the cut surfaces for a depth of one inch, and to round off the
corners of the sidewalk blocks to a radius of one-fourth (¼) inch.[86]
Where the ends of the sidewalk abut against the curbing a clear
expansion joint one and one-fourth (1¼) inches wide shall be left
between the sidewalk and the curb.
=148.= After the concrete laying is completed it shall be protected from
use or injury until the concrete is set hard enough to withstand travel,
and it shall be kept continuously damp for at least five days after the
concrete is laid.
=149. Weather.=—Concrete in sidewalks shall not be laid in freezing
weather nor shall frozen materials be used in the work. Completed work
must be securely protected from frost for at least seven days after the
concrete is laid. Any concrete sidewalk that shall become frozen within
that period of time shall be wholly taken up and replaced with new work,
at the expense of the contractor.
=150. Regrading.=—Directly after the concrete is completed, the forms
removed, and the work inspected by the engineer, the space between the
outer edge of the sidewalk and the street curb shall be excavated or
filled up and dressed to a plane one inch below the top of the sidewalk
and the top of the street curb; and the space on the inner side of the
sidewalk shall be graded to a plane one inch below and parallel to the
surface of the sidewalk for a distance of two feet back from the edge of
the sidewalk and completed with a slope of one and one-half to one to
the natural surface of the ground. Where this regrading requires filling
up the filling material, for a depth of four inches from the surface,
shall be good, rich surface soil.
=151.= Should any defects due to faulty material or workmanship develop
in the sidewalk within one year after the completion of the same the
contractor shall repair or reconstruct all such defective places at his
expense, doing the work in accordance with these specifications.
=152. Measurement and Payment.=—Concrete sidewalk will be measured and
paid for by the square foot of completed sidewalk surface, and the unit
price per square foot shall cover the entire cost of the work, including
grading, drainage work, all material and labor, forms, and the regrading
or dressing up after the completion of the concrete work; except that
the drain pipe used will be paid for per linear foot at the price named
in the contract which price shall cover the cost of furnishing and
putting the pipe in place complete.