SECTION 03300 – CAST-IN-PLACE CONCRETE
PART 1 - GENERAL
1.01
SCOPE OF WORK
A.
B.
1.02
Concrete Slabs
Concrete Walls and Footings
QUALITY ASSURANCE
Reference Specifications: The work under this division of the Specifications shall
conform generally to the requirements of Item 314 - "Concrete Pavement", Item 406 "Concrete for Structures", and Item 410 – "Concrete Structures" of the City of Fort
Worth's Standard Specifications for Street and Storm Drain Construction.
PART 2 - MATERIALS
2.01
FORMS
Forms shall be of ample strength, adequately braced, joined neatly and tightly and set
exactly to established line and grade.
2.02
REINFORCING MATERIALS
Reinforcing Bars: Reinforcing bars shall be round deformed bars meeting the
requirements of the current standard Specifications for Intermediate Grade Billet Steel
Concrete Reinforcing Bars of the A.S.T.M. Designation A-615. Reinforcing bars at the
time the concrete is placed shall be free from rust, scale or other coatings that will destroy
or reduce the bond. General reinforcing bars shall be number three bars spaced 18 inches
on center in walks and 12 inches in slabs as shown on Plans.
2.03
CONCRETE MATERIALS
A.
Cement: Portland cement shall meet the requirements of A.S.T.M. Specifications
Designation C-150 and shall be Type 1.
B.
Aggregates: Concrete aggregates shall consist of gravel or crushed stone and
shall be free from any excess amount of salt, alkali, vegetative matter or other
objectionable materials. The aggregate shall be well graded from fine to course
and the maximum size shall be one inch . Fine aggregate shall consist of sand
C.
Water: Water used in mixing concrete shall be clean and free from deleterious
amounts of acids, alkalies, vegetative matter or organic material. The concrete
shall be mixed in an approved batch mixer. The mixing time shall not be less
than one minute after all the batch materials are in the mixer. Cement content
shall be not less than five sacks per cubic yard of concrete and shall have a
minimum 28 day compressive strength of 3,000 psi.
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D.
2.04
2.05
Mixing: Transit mixed concrete shall meet all the requirements for concrete as
specified above. Sufficient transit mix equipment shall be assigned exclusively to
the project as required for continuous pours at regular intervals without stopping
or interrupting. Concrete shall not be placed on the job after a period of 1 1/2
hours after the cement has been placed in the mixer.
RELATED MATERIAL
A.
Expansion Joint Filler: Expansion joint material shall be one inch clear heart
redwood with cap and paved cross section as shown on the plans
B.
Dowels: Dowels for expansion joints shall be number four smooth round steel
bars with expansion tubes as shown on Plans. Dowels shall be placed eighteen
inches on center or as shown on Plans.
C.
Curing Compound: The membranous curing compound shall comply with the
requirements of A.S.T.M., Designation C-309, Type 2, white pigmented.
D.
PVC Sleeves: The Contractor shall furnish and install four inch class 200 PVC
pipe sleeves under concrete walk as shown on plans and details.
E.
Caulking and Sealants – See Section 07920
CONCRETE MIX DESIGN AND CONTROL
A.
Mix Design: The concrete shall contain not less than five sacks of cement per
cubic yard. Total water shall not exceed seven gallons per sack of cement. The
mix shall be uniform and workable. The amount of course aggregate (dry-loose
volume) shall not be more than 85 percent per cubic yard of concrete.
The net amount of water will be the amount added at the mixer plus the free water
in the aggregate or minus the amount of water needed to compensate for
absorption by the aggregates. Free water or absorption determinations will be
based on the condition of the aggregates at the time used. The absorption test will
be based on a thirty minute absorption period. No water allowance will be made
for evaporation after batching.
B.
Slump: When gauged by the standard slump test, the settlement of the concrete
shall not be less than 3 inches nor more than 5 inches, unless otherwise indicated.
C.
Quality: The concrete shall be designed for a minimum compressive strength of
3,000 pounds per square inch at the age of twenty-eight days using a 5 sack mix.
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D.
Control-Submittal: Within a period of not less than ten days prior to the start of
concrete operations, the Contractor shall submit to the Engineer a design of the
concrete mix proposed to be used together with samples of all materials to be
incorporated into the mix and a full description of the source of supply of each
material component. The design of the concrete mix shall conform with the
provisions and limitation requirements of these specifications. All material
samples submitted to the Engineer shall be sufficiently large to permit laboratory
batching for the construction of test beams to check the adequacy of the design.
When the design mix has been approved by the Engineer, there shall be no change
or deviation from the proportions thereof or sources of supply except as
hereinafter provided. No concrete may be placed on the job site until the mix
design has been approved by the Engineer in writing to the Contractor.
PART 3 - EXECUTION
3.01
REINFORCING
Metal reinforcing shall be accurately placed in accordance with the Plans and shall be
adequately secured in position by concrete, metal, or plastic chairs and spacers. Bar
splices shall overlap at least twelve inches. The re-bars shall be bent cold.
3.02
JOINTS
3.03
A.
Expansion Joints: Expansion joint materials shall be installed perpendicular to
the surface. The bottom edge of the material shall extend to or slightly below the
bottom edge of the slab and the top edge shall be held approximately 1/2 inch
below the surface of the slab. The edge of joints shall be tooled with an edging
tool having a 1/2 inch radius.
B.
Contraction Joints: Contraction joints shall be 1/4 inch wide by 3/4 inch deep,
tooled joints placed on six foot centers, unless otherwise indicated. Contraction
joints will not be required to be sealed. Sawed joints may be allowed only if
specifically approved by the Engineer. Joints will be sawed as soon as sawing
can be performed without stripping aggregate from the concrete, generally within
twelve to twenty-four hours after placement, and they shall be completed before
uncontrolled cracking of the pavement takes place.
C.
Construction Joints: Construction joints shall be installed in all concrete work at
the locations shown on the Plans. Construction joints formed at the close of each
day's work shall be located at any of the control joints designated on the Plans.
Joints may be constructed by use of wood or preformed metal bulkheads set true
to the section of the finished concrete and cleaned and oiled. Surplus concrete on
the subgrade shall be removed before resuming concreting operations.
PLACING CONCRETE
Placement of Concrete: The concrete shall be rapidly deposited on the subgrade
immediately after mixing is completed. Subgrade and forms shall be dampened prior to
placement of the concrete. The concrete shall be transported, placed and spread in such a
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manner as to prevent segregation of the aggregate or an excess amount of water and fine
materials to be brought to the surface. No concrete shall be placed when the air
temperature is less than forty degrees Fahrenheit nor when the temperature of the
concrete is eighty-five degrees Fahrenheit or higher, without approval of Construction
Inspector.
Placement shall be carried on at such a rate that the concrete is at all times plastic and
flows readily into the space between the bars. No concrete that has partially hardened or
that has been contaminated by foreign material shall be deposited in the work nor shall
retempered concrete be used. Each section of pavement between expansion and
construction joints shall be placed monolithically.
All concrete shall be thoroughly compacted by suitable means during the operation of
placing and shall be thoroughly worked around reinforcement and embedded fixtures and
into the corners of the forms. Special care shall be taken to prevent voids and
honeycombing. The concrete shall then be struck off and bull-floated to the grade shown
on the Plans before bleed water has an opportunity to collect on the surface.
3.04
FINISHING
All concrete shall be finished by experienced, qualified concrete finishers. All concrete
shall have a neat, rounded edge. Edging and jointing (radius described on Plans) shall be
accomplished with care so as not to leave deep impressions in the concrete surface
adjacent to edges and joints. After the concrete has been floated and has set sufficiently
to support the weight of cement finishers, a smooth steel trowel will be used to produce
hard surface. The entire surface will then be brushed with a stiff bristle broom to produce
a uniform textured finish. All edges and sides of concrete exposed to view shall be free
of warp and blemishes with a uniform texture and smoothness as described in Plans.
3.05
CURING
Curing Compound: Immediately after the finishing operations, the concrete shall be
completely covered with a curing compound. The concrete surface shall be kept moist
between finishing operations and the application of the curing compound. The curing
compound shall be applied under pressure by means of a spray nozzle at a rate not to
exceed 200 square feet per gallon. A minimum of 72 hours curing time will be required.
3.06
CONCRETE WALLS
A.
Placing Concrete
1.
Where tremies are used, or where the free drop is 5'-O" or more, and
through reinforcement, use a dumping box or board, moving the concrete
therefrom by shovels or hoes.
2.
Deposit concrete so that the surface is kept level throughout, a minimum
being permitted to flow from one position to another, and place as rapidly
as practicable after mixing.
3.
Do not use in this Work any concrete not placed within 30 minutes after
leaving the mixer.
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4.
5.
6.
7.
B.
3.07
Thoroughly work concrete around reinforcement and embedded fixtures,
and into corners of forms, during placing operations.
Completely compact with tamping poles and by tapping forms until the
concrete is thoroughly compact and without voids. Determine the number
of tampers needed by the amount and method of placing concrete.
Exercise care to tamp concrete vigorously and thoroughly to obtain
maximum density.
Use manual tampers as well as mechanical vibrators.
a.
Exercise care to direct the quick handling of vibrators from one
position to another.
b.
Do not over-vibrate concrete.
c.
Do not move concrete by use of vibrator.
Finishing
1.
All formed surfaces exposed to view shall have a smooth form finish.
2.
After concrete has been properly placed and cured, sandblast finish if
indicated on the plans and per specification Section 03350.
PROTECTION
After concrete is placed, finished and cured as required, permit no traffic thereon for
three days thereafter and further protect the surface from damage due to other causes.
END OF SECTION
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