This work shall consist of the construction
of portland cement concrete sidewalks on a gravel base course to the
dimensions shown in the details.
Concrete sidewalks shall not be constructed
after October 1 nor before April 15 unless methods of protection are
approved by the Engineer.
A. Excavation. Excavation, including removal of any existing
sidewalk, shall be made to the required depths below the finished
grade as shown on the plans or as directed. All soft and yielding
material shall be removed and replaced with suitable material.
B. Gravel base. The gravel base shall be placed in layers
not over six inches in depth and to such a depth that after compaction
it shall be at the specified depth below the finished grade of the
walk. The base shall be wetted and rolled or tamped after the spreading
of each layer.
C. Forms. Forms shall be of metal or wood, straight,
free from warp and of sufficient strength to resist springing from
the pressure of the concrete. If of wood, they shall be of two-inch
surfaced plank, except that at sharp curves thinner material may be
used. If of metal, they shall be of approved section and shall have
a flat surface on the top. Forms shall be of a depth equal to the
depth of the sidewalk. Forms shall be securely staked, braced and
held firmly to the required line and grade and shall be sufficiently
tight to prevent leakage of mortar. All forms shall be cleaned and
oiled or wetted before concrete is placed against them. Sheet metal
templates 1/8 inch in thickness, of the full depth and width of the
walk, shall be spaced at intervals of 12 feet or as directed. If the
concrete is placed in alternate sections, these templates shall remain
in place until concrete has been placed on both sides of the template.
As soon as the concrete has obtained its initial set, the templates
shall be removed.
D. Finishing. The surface of the concrete shall be finished
with a wood float or by other approved means. The outside edges of
the slab and all joints shall be edged with a one-fourth-inch-radius
edging tool. Each slab shall be divided into two or more sections
by forming dummy joints with a jointing tool as directed.
E. Curing.
(1)
Curing shall be done with a liquid membrane-forming
curing compound approved by the Engineer. The material shall be a
combination curer-hardener-sealer-type compound and shall be similar
or equal to Demicon Temp Color as manufactured by the McMillan Products
Division of the Hausman Steel Company of Detroit, Michigan. The rate
of application shall be in accordance with the manufacturer's instructions.
(2)
The curing compound shall be applied to all
exposed surfaces of the concrete immediately following the disappearance
of the water sheen following the final finishing and before any marked
dehydration of the concrete or surface checking occurs.
(3)
When the forms are removed before seven days
after the concrete has been placed, the exposed sides shall be covered
with the compound at the same rate as applied to the surface.
(4)
If the film is damaged by rain or in any other
way before drying, the curing compound shall be reapplied to the affected
areas.
F. Backfilling and removal of surplus material. The sides
of the sidewalk shall be backfilled with suitable material thoroughly
compacted and finished flush with the top of the sidewalk. All surplus
material shall be removed and the site left in a neat and presentable
condition to the satisfaction of the Engineer.