These specifications for concrete sidewalks
are designed for and intended to cover the construction of sidewalks:
A.
By property owners in the street in front of their
own premises where construction is carried on either by a sidewalk
contractor employed by the property owner or by the property owner's
own labor.
B.
By the City of Ithaca constructing sidewalks either
by contract or force account at property of the City of Ithaca, at
premises where sidewalks have been ordered built but property owners
have failed to construct and at premises where the City has agreed
to construct or oversee the construction of sidewalks upon the petition
of abutting property owners.
As used in this article, the following terms
shall have the meanings indicated:
The City Engineer or other person appointed by the Board
of Public Works to oversee sidewalk construction.
The party or parties contracting to do any work described
herein or authorized representatives of such party or parties or property
owners constructing sidewalks at their own premises.
Before delivery on the job and at such other
times as the Engineer deems necessary, the contractor shall furnish
any required samples of the materials hereafter mentioned. Materials
shall pass the following requirements.
A.
Cement. Cement shall meet the requirements of the
current Standard Specifications for Air Entraining Cement of the American
Society for Testing and Materials. A sack containing 94 pounds of
cement will be considered one cubic foot.
B.
Fine aggregate.
(1)
Fine aggregate shall consist of natural sand having
clean, hard, strong, durable, uncoated grains free from organic materials.
Not more than 25% shall pass a 50-mesh screen. It shall be well-graded
from coarse to fine and shall contain not more than 3% by weight of
clay, loam or silt.
(2)
Fine aggregate shall be of such quality that mortar
composed of portland cement and fine aggregate shall show tensile
and comprehensive strength at seven and 28 equal to or higher than
mortar composed of portland cement and standard Ottawa sand.
C.
Coarse aggregate.
(1)
Coarse aggregate shall consist of crushed rock or
gravel. The particles of coarse aggregate shall consist of clean,
hard, tough and durable material, free from vegetable or other deleterious
substance and free from soft, thin, elongated or laminated pieces.
D.
Water. Water shall be clean and free from alkali,
oils or acid.
E.
Joint filler. Joint filler shall be premolded strips
of asphalt or pitch and fiber or mineral aggregate passing an 80-mesh
screen, 1/2 inch thick, as wide as the thickness of the concrete slab
and at least two feet long. It shall have such a consistency that
it will not run in summer or chip out in winter.
F.
Forms.
(1)
Forms shall be of lumber two inches thick or of steel
of equal strength, except on curves, where flexible strips may be
used.
(2)
They shall be held rigidly in place by stakes or braces
with top edges at true line and grade given by the Engineer. Ends
of adjoining forms shall be flush. Forms shall be set so as to give
the walk a slope towards the curb of 1/4 inch per foot of width.
H.
Subgrade.
(1)
That portion of the ground surface directly beneath
the slab shall be called the "subgrade."
(2)
All soft and spongy material in the subgrade shall
be removed and replaced with suitable material. Fills shall be compacted
in layers not exceeding six inches in thickness. Spots previously
compacted by traffic shall be loosened to a depth of six inches. The
whole subgrade shall be thoroughly and uniformly compacted to a firm
surface having as nearly as possible a uniform bearing power.
(3)
A template, resting upon the side forms and having
its lower edge at the exact elevation of the subgrade, shall be drawn
along the forms before any concrete is laid. Any high places in the
subgrade shall be removed so that the template will pass over without
being raised off the side forms or being tipped at an angle to the
sidewalk surface.
(4)
The subgrade shall be damp but not muddy when concrete
is placed upon it.
I.
Drains. Where, in the opinion of the Engineer, it
is considered necessary to save the walk from damage by frost action,
drains of three-inch farm tile or such other type of drainage pipe
as may be required shall be laid on the lines and grades given by
the Engineer.
J.
Subbase. When drains are impracticable and the soil
is poorly drained or colloidal clay, a five-inch subbase shall be
constructed of cinders, gravel or other porous material approved by
the Engineer. The subbase shall be thoroughly tamped until the surface
is firm and shall be drained into the street gutter in a manner approved
by the Engineer.
K.
Thickness and proportions.
(1)
Concrete shall be mixed in the proportion of one part
portland cement, two parts of fine aggregate and 3 1/2 parts
of coarse aggregate.
(2)
The concrete sidewalk shall be of one course at least
four inches in thickness; and at points where driveways are to be
provided, the concrete shall be six inches in thickness.
L.
Mixing.
(1)
The use of transit-mix concrete supplied by local,
well-established and acceptable suppliers is recommended but not required.
Mechanical batch-mixing on the job will be allowed, provided that
the following requirements are met. Hand-mixing on the job will not
be permitted, except for patchwork requiring less than 1/2 cubic yard
of concrete.
(2)
Where concrete is to be batch-mixed on the job, the
coarse and the fine aggregate shall be delivered separately to the
work site and then mixed in the required proportions.
(3)
The ingredients of the concrete shall be thoroughly
mixed until each particle of fine aggregate is coated with cement
and each particle of coarse aggregate is coated with mortar.
(4)
When a mechanical mixer is used, it shall be of an
approved batch type. Each batch shall be mixed at least one minute
from the time all the materials, including water, are in the drum
until the beginning of the discharge.
(5)
The consistency of the mixed concrete shall be such
that no separation of the ingredients takes place and some tamping
is necessary to bring the mortar to the surface.
M.
Placing and finishing.
(1)
The freshly mixed concrete shall be placed immediately
on the prepared subgrade. It shall then be struck off and tamped with
a straightedge resting upon the side forms and advanced with a crosswise
sawing motion. It shall then be floated with a wooden float until
the surface has a true contour and the concrete is thoroughly compacted.
It shall be troweled with a magnesium trowel after the water sheen
has disappeared. It shall then be broomed to give a nonskid finish.
(2)
The placing of concrete shall not be suspended for
45 minutes or longer, except at the end of a slab.
(3)
No concrete shall be placed on a frozen subgrade or
when the temperature is or is liable to be, within 24 hours, below
40° F., except with the written permission of the Engineer.
N.
Jointing.
(1)
The walk shall be marked into separate rectangular
slabs. No plain concrete slab shall be longer than six feet on any
one side.
(2)
Where division plates have been used, they shall be
removed after the concrete has hardened sufficiently to avoid breaking
the edges of corners of the slabs.
(3)
The surface edges of each slab shall be rounded to
a radius of about 1/4 inch. Markings shall be exactly at cuts between
slabs.
O.
Expansion joints. Expansion joints shall extend from
the surface to the subgrade, be truly at right angles to the sidewalk
surface and be made by putting the specified joint filler in place
before placing the concrete. They shall be placed as follows:
(1)
At or near all places where the sidewalk line intersects
a curbline or other sidewalk, a one-inch expansion joint shall be
made at right angles to the center line of the walk.
(2)
When the sidewalk fills the space between the curb
and the building line, a one-half-inch expansion joint shall be placed
between the curb and the sidewalk and between the sidewalk and the
building.
(3)
A one-half-inch expansion joint shall be made across
the walk at approximately fifty-foot intervals.
P.
Curing.
(1)
As soon as the concrete has set sufficiently, it shall
be sprinkled and kept moist until covered. As soon as it can be done
without damage to the walk, the concrete shall be covered with four
thicknesses of burlap, tarpaulin or other approved covering. The walk
shall then be cleaned and opened to traffic, and all tools, leftover
supplies and rubbish must be removed from the street.
(2)
The contractor shall protect the concrete from damage
by rain, pedestrians and animals with suitable covers and barricades
and by red lights at night.
