A. 
General.
Mix concrete only in quantities for immediate use and discard any concrete that has set or is not completely discharged at the site within the maximum time allowed for placement. Retempering of any set concrete is strictly prohibited. When concrete arrived at the project with a slump below that specified, water may be added only if neither the maximum permissible water-cement ratio or the maximum slump is exceeded. The water shall be incorporated by additional mixing equal to at least half of the total mixing required.
B. 
Notification.
The placement of concrete without the prior approval of the Engineer or designated representative of the Engineer is strictly prohibited. The Contractor shall notify the Engineer or designated representative of the Engineer a minimum of twenty-four (24) hours before placing concrete.
C. 
Protection from Adverse Weather.
Unless adequate protection is provided, or approval is obtained, do not place concrete during rain, sleet, snow or freezing weather. Do not permit rainwater to increase the amount of mixing water or to damage the surface finish. If rainfall occurs after placing operations begin, provide adequate covering to protect the work from any adverse damage.
D. 
Placing Temperatures.
All concrete shall be placed in accordance with the following provisions:
1. 
Cold Weather Placement.
Unless special provisions are made for heating the concrete mix and the concrete in forms, do not place any concrete when the air temperature is below 40° F or is predicted to be below 40° F within forty-eight (48) hours of placement.
2. 
Hot Weather Placement.
When the air temperature is above 85°F, use an approved retarding agent in all concrete. Concrete temperature prior to placement shall not exceed 95° F.
E. 
Maximum Time to Placement.
Any concrete that has attained its initial set or has contained its mixing water or cement for more than forty-five (45) minutes shall not be placed in the work. The addition of an approved retarding agent may be proposed by the Contractor to increase the maximum time to placement. The increase of time to placement shall be proposed the Contractor and approved by the Engineer or designated representative of the Engineer when the design mix is submitted for approval.
(Ordinance 2007-106, App. B, adopted 3/20/07)
A. 
Placement of Concrete.
The placement of concrete shall be in accordance with the following procedures:
1. 
Normal Weight Structural Concrete.
Place concrete only upon a subgrade or surface approved by the Engineer or designated representative of the Engineer. All forms shall be clean of dirt, and other construction debris, and all water shall be removed or drained from the forms before concrete is placed. Concrete shall be handled from mixer to transport vehicle to final place of deposition in a continuous manner and as rapidly as possible without segregation or loss of ingredients until the approved unit of operation is completed. Placing will not be permitted when, in the opinion of the Engineer or designated representative of the Engineer, the sun, heat, wind, or limitations of facilities furnished by the Contractor prevent proper finishing and curing of the concrete. Forms or reinforcement shall not be splashed with concrete in advance of pouring. Concrete shall be deposited in uniform layers and as close as practicable to its final position. Immediately after placing, concrete shall be compacted and consolidated by vibration, spading, rodding, or forking such that the concrete is worked around reinforcement, embedded items and into the corners of the forms. The method used to consolidate and compact concrete shall meet with the approval of the Engineer or designated representative of the Engineer and shall be done so as not to cause segregation of the concrete. Special care shall be taken in placing and spading concrete against forms and all the joints to prevent the formation of voids and honeycombs. Tapping or other external vibration of forms will not be permitted. Vibrators shall not be used to move concrete in the forms. Concrete shall not be placed on concrete that is sufficiently hard to cause the formation of seams and planes of weakness within the section. Concrete shall not be allowed to drop freely more than five (5) feet in unexposed work nor more than three (3) feet in exposed work. Where greater drops are required, a tremie or other approved means shall be employed. The discharge of the tremies shall be controlled so that the concrete may be effectively compacted into horizontal layers not more that twelve (12) inches thick and the spacing of the tremies shall be such that cavities do not occur. Concrete to receive other construction shall be screeded to proper level to avoid excessive shimming or grouting.
2. 
Concrete Riprap.
Place concrete on the slopes and other areas to be protected as shown on the plan details and as approved by the Engineer or designated representative of the Engineer. All surfaces shall be moist when the concrete is placed. If the surfaces are dry and not consolidated properly, the Engineer or designated representative of the Engineer may require the entire area to be sprinkled or sprinkled and consolidated before the concrete is placed. After the concrete has been placed, compacted and shaped to conform to the dimensions shown on the plans and after it has set sufficiently to avoid slumping, the surface shall be finished with a wooden float to secure a reasonably smooth surface. Concrete riprap which is pneumatically placed shall conform to the requirements of subparagraph 3 “Pneumatically Placed Concrete.”
3. 
Pneumatically Placed Concrete.
The compressor or blower used to supply air for placing concrete shall be capable of delivering a sufficient volume at a pressure range of thirty (30) to sixty (60) pounds per square inch (psi) as required by the size of the nozzle being used. When a hose length of one-hundred (100) feet is used, the pneumatic pressure at the nozzle shall be forty-five (45) pounds per square inch (psi), or more, as necessary to efficiently prosecute the work. For lengths over one-hundred (100) feet, the pressure shall be increased five (5) pounds per square inch (psi) for each additional fifty (50) feet of hose required. Steady pressure must be maintained throughout the placing process. The water pump shall be of sufficient size and capacity to deliver the water to the nozzle at a pressure of not less than fifteen (15) pounds per square inch (psi) in excess of the required air pressure. Proper consistency of the concrete shall be controlled at the nozzle valve by the operator and a low water-cement ratio must be maintained. The mix shall be sufficiently wet to properly adhere and sufficiently dry so that it will not sag or fall from vertical or inclined surfaces or separate in horizontal work. In covering vertical or inclined surfaces, placing of the concrete shall begin at the bottom and be completed at the top. The nozzle shall be held at such distance (2 to 4 feet) and position that the stream of flowing concrete shall impinge as nearly as possible at right angles to the surface being covered. Any deposit of loose sand shall be removed prior to placing any original or succeeding layers of pneumatically placed concrete. Should any deposit of loose sand be covered with pneumatically placed concrete, the concrete shall be removed and replaced with a new coat of pneumatically placed concrete after the receiving surface has been properly cleaned. Before channel lining or riprap is placed, the slopes shall be thoroughly and uniformly consolidated and moistened. Sprinkling or sprinkling and consolidation may be required by the Engineer or designated representative of the Engineer before placement of concrete. The subgrade for lining shall be excavated and fine graded to the required section. The use of forms for lining will not be required. The surfaces of pneumatically placed concrete for both channel lining and riprap shall be accurately finished by hand floating methods before the concrete has attained its initial set. The original surface and each surface which is permitted to harden before applying succeeding layers shall be washed with water and blasted with air, or a stiff hose stream, and all loosened material removed. Sand which rebounds and does not fall clear of the work or which collects on horizontal surfaces shall be blown off from time to time to avoid leaving sand pockets. Rebound which is recovered and is clean and free of foreign matter may be reused as sand in a quantity not to exceed twenty (20) percent of the total sand requirement. Pneumatically placed concrete shall not be applied to a surface containing frost or ice. Where standing or running water is encountered, it shall be removed before pneumatically applying the concrete. Only experienced foremen, gunmen, nozzlemen, and rodmen shall be employed and satisfactory written evidence of such experience shall be furnished to the Engineer or designated representative of the Engineer upon request.
B. 
Surface Finish on Concrete.
1. 
Monolithic Slab Finishes.
a. 
Trowel Finish:
Apply a trowel finish to monolithic slab surfaces exposed to view and slab surfaces to be covered with resilient flooring, carpet, ceramic or quarry tile, paint, or another thin film-finish coating system.
b. 
Nonslip Broom Finish:
Apply a nonslip broom finish to exterior concrete sidewalks, platforms, steps, and elsewhere as indicated.
(1) 
Immediately after float finishing, slightly roughen concrete surface by brooming with fiber-bristle broom perpendicular to main traffic route. Coordinate required final finish with Engineer or designated representative of the Engineer before application.
2. 
Finishing Formed Surfaces.
a. 
Rough-Formed Finish:
Provide a rough-formed finish on formed concrete surfaces not exposed to view in the finished Work or concealed by other construction. This is the concrete surface having texture imparted by form-facing material used, with tie holes and defective areas repaired and patched, and fins and other projections exceeding 1/4 inch (6 mm) in height rubbed down or chipped off.
b. 
Smooth-Formed Finish:
Provide a smooth-formed finish on formed concrete surfaces exposed to view or to be covered with a coating material applied directly to concrete, or a covering material applied directly to concrete, such as waterproofing, dampproofing, veneer plaster, painting, or another similar system. This is an as-cast concrete surface obtained with selected form-facing material, arranged in an orderly and symmetrical manner with a minimum of seams. Repair and patch defective areas with fins and other projections completely removed and smoothed.
c. 
Smooth-Rubbed Finish:
Not later than one day after form removal, provide smooth-rubbed finish on concrete surfaces that have received smooth-formed surface but are not scheduled to be coated or covered.
(1) 
Moisten concrete surfaces and rub with carborundum brick or another abrasive until producing a uniform color and texture. Do not apply cement grout other than that created by the rubbing process.
C. 
Curing of Concrete.
1. 
Moist Curing.
All freshly placed concrete shall be cured by keeping the exposed surfaces, edges and corners continuously moist for a minimum duration of seven (7) days by spraying, ponding or covering with waterproof paper, polyethylene film or wet burlap. The temperature of the concrete shall maintained above 50° F for the seven (7) day curing period. All materials for protecting and curing the concrete shall be on hand and ready for use before concreting begins. Wood forms left in place will not be considered adequate for moist curing. Ceilings and inside walls may be cured by leaving the forms on for at least four (4) days.
2. 
Curing Compound.
In lieu of moist curing, a curing compound which is acceptable to the Engineer or designated representative of the Engineer as to color, quality, and moisture retention, may be used. Apply curing compound in accordance with manufacturer’s instructions.
(Ordinance 2007-106, App. B, adopted 3/20/07)
A. 
General.
The Owner shall obtain the services of an independent qualified testing laboratory to perform the required testing and inspection of the concrete. All construction materials necessary for tests shall be provided by the Contractor at no additional expense to the Owner or the testing laboratory.
B. 
Slump Test.
Contractor shall perform slump tests on each batch of concrete delivered to the job site. Slump tests shall be performed under the guidance and supervision of the testing laboratory representative and/or Engineer or designated representative of the Engineer. The maximum permissible slump for concrete prior to addition of water reducing agents shall be as follows:
Location of Concrete
Maximum Slump (in.)
Reinforced foundation walls and footings
5"
Plain footings and piers
5"
Slabs, beams and reinforced walls
5"
Pavements
4"
Water reducing admixtures (plasticizer) may be added as allowed by the concrete producer after the initial slump test. The maximum slump after adding water reducing admixtures shall be 8".
C. 
Field Test Cylinders.
The testing laboratory shall prepare one (1) set of concrete test cylinders, consisting of a minimum of three (3) cylinders, for each one-hundred (100) cubic yards (CY) of concrete pour or major fraction thereof. If the quantity of concrete poured in a day is less than one-hundred (100) cubic yards (CY), one (1) set of concrete tests cylinders is required. Each concrete test cylinder shall be made in accordance with the provisions outlined in ASTM C31. Test cylinders shall be cured under laboratory conditions except when, in the opinion of the Engineer or designated representative of the Engineer, prevailing job site conditions necessitate cylinders be cured under job conditions. Testing of concrete test cylinders shall be done by the testing laboratory in accordance with the provisions outlined in ASTM C39. One (1) cylinder shall be tested for compressive strength at the age of seven (7) days and a minimum of one (1) cylinder shall be tested for compressive strength at the age of twenty-eight (28) days. If any cylinder test is below the specified strength requirements, the Engineer or designated representative of the Engineer shall have the right to require changes in the mix design, require additional curing time, change the batching process, or take other necessary actions to insure that the concrete being placed in the work will meet the specified strength requirements.
(Ordinance 2007-106, App. B, adopted 3/20/07)
All tie holes and other surface defects shall be repaired immediately after form removal. Approved patching grout shall be used to fill the minor voids left by form ties and all protruding defects left by forms shall be removed with a rubbing stone.
(Ordinance 2007-106, App. B, adopted 3/20/07)