420-1 DESCRIPTION
This section covers construction of all cast-in-place concrete elements of structures. See
Article 1000-4 of the Specifications for the Contractor's responsibility for concrete mix designs.
420-3 FALSEWORK AND FORMS
(A) GENERAL
Unless otherwise required in the plans or Special Provisions, the Contractor is not required to submit falsework and form plans for approval except for bridge superstructures. The plans and special provisions should be carefully checked to determine if falsework and form plans are required for structure elements other than superstructures. Generally, they are required for caps of “hammer head” bents, large box culverts, and arch culverts. Erection of falsework and forms for bridge superstructures is not to be started until plans have been submitted by the Contractor for review, comments, and acceptance by the
State Structures Engineer. In no case is concrete to be cast unless the falsework and forms are in accordance with the approved plans. The status of working drawing submittal reviews can be found at this link:
https://connect.ncdot.gov/resources/Structures/Pages/Drawing-Submittal-Status-and-Design-Notes.aspx?SortField=Letter_x0020_Sent_x0020_Date&SortDir=Asc
Approval of falsework and form plans does not relieve the Resident Engineer of responsibility of seeing that the falsework as actually installed is safe and does not relieve the Contractor of full responsibility for the work.
In grading forms and falsework, allowance must be made for settlement in the falsework due to compression of the joints and also the falsework and beam deflections.
Sufficient “telltales” should be provided to quickly and easily show any settlement of the forms when loaded. Required adjustments must be made while the concrete is still plastic. No adjustments shall be made after the concrete has taken its initial set.
(B) FALSEWORK
Falsework may be supported on sills, piles, or portions of the completed structure when permitted in writing by the Engineer. Sills should be used only when supported on firm material that can support the applied loads without appreciable settlement. When settlement is anticipated, the Engineer should require jacks or other means to afford adjustment.
Falsework piles are to be driven to an adequate bearing capacity with the tips well below any likelihood of scour.
Sufficient bracing of falsework is required to resist lateral forces from flowing water and unequal loading while the forms are being filled.
(C) FORMS
Forms shall be built to the contours required in the finished concrete. They shall be rigid enough to retain these contours under the weight of the concrete with no bulging or displacement.
With few exceptions, a rubbed surface finish is not required for structure concrete. Therefore, the form surface that will be in contact with exposed concrete should be smooth and uniform in texture. Use of forms that are dented, warped, split, or otherwise damaged should not be permitted.
(D) FORMS FOR CONCRETE BRIDGE DECKS
When allowed by the plans, the Contractor may elect to use a deck forming system other than the one shown on the plans. In these instances, the Contractor is responsible for the submittal. Once the submittal has been reviewed and approved, the Contractor will also be responsible for submitting plans for a plan revision. Three videos are available on the NCDOT YouTube channel regarding Bridge
Deck Buildups, SIP Decking, and Overhangs
(E) FALSEWORK AND FORMS OVER OR ADJACENT TO TRAFFIC
When forms and falsework present a potentially hazardous situation for traffic, the Contractor is required to make a submittal on the falsework or forming system to be used. The falsework or forms must be constructed in accordance with the approved system. Prior to casting concrete, the Contractor must provide a written certification that the system complies with the accepted drawings.
In addition, some projects contain a Special Provision, “MAINTENANCE AND PROTECTION OF TRAFFIC BENEATH PROPOSED STRUCTURES AT STA_____” . This Special Provision requires the Contractor to protect traffic and temporarily brace girders at prescribed locations along the project. This is to ensure the stability of the girders against temporary loads and wind until the entire framework is installed and is self-stabilizing, and to protect from any tools or materials which could be dropped into traffic. The Contractor should submit details and calculations for review and approval to the
Structures Management Unit.
The proposed traffic protection system must at least cover the area between beams over travel lanes. Also, the overhang falsework must be left in place over traffic until the barrier rails are cast.
The lateral stability for all girders over traffic must be reviewed and provided for. In some cases, such as for prestressed concrete girders, the Contractor may provide calculations to show the girders do not need temporary bracing. In other cases, such as large and/or curved plate girders, the girders will have to be erected in pairs or a temporary bracing system provided.
If this Special Provision is included in the contract, the Technician should have an approved copy before allowing the Contractor to erect the members. No separate payment is made for this work.
420-4 PLACING CONCRETE
Structure concrete is designed to carry predetermined stresses. The actual strength attained in the structure is not only dependent on proper proportioning and mixing but also on handling and placement in accordance with the Specifications.
Before allowing the Contractor to start casting concrete, the Resident Engineer or his Technician shall check the forms for stability, size, location, and cleanliness. The reinforcing steel shall be checked for size and position. The results of these checks should be recorded in the
Inspector's Daily Report. He shall make sure that the Contractor has adequate personnel and equipment at the site to cast the concrete.
Any concrete found to be honeycombed, cracked, or otherwise defective shall be called to the Area Construction Engineer's attention prior to repair.
Detailed requirements for the pumping of concrete are covered in
Article 420-5 of the Specifications. During placement of concrete, the following check list is suggested:
- Will the concrete be placed within the time limits stated in Subarticle 1000-4(E)?
- Is concrete temperature within the Specification limits?
- Does the method of placement prevent segregation and displacement of reinforcing steel?
- Does the concrete meet air and slump requirements?
- Is the concrete dropped less than
5 feet?
- Is the concrete deposited as near as possible to its final position?
- Is concrete being vibrated sufficiently for adequate consolidation?
- Is the concrete placed in continuous horizontal layers?
- Is maximum layer thickness
12 inches when there are horizontal layers of reinforcing steel?
When pouring fresh concrete against previously placed concrete it is vital that the existing concrete surface is clean and saturated for two hours before the pour in order for the old and new mix to bond together properly. Vertical surfaces (such as transverse deck joints, cloumn repairs, and phased cap joints) may be difficult to keep wet. Repeated application of water, wrapping or packing the area with wet burlap, or other wetting methods may be necessary.
When concrete arrives on the job with an air content below the specified level by more than the allowable tolerance, the supplier may use additional air entraining admixture if the following conditions are met:
- The admixture is the same brand and type as originally introduced at the plant unless otherwise permitted by the Engineer.
- The admixture, if liquid, is measured into a bucket containing 1 gallon of water. The admixture, if prepackaged powder, is added according to the manufacturer’s recommendation.
- The admixture, if liquid, is thoroughly mixed with the water and the mixture, is then directed to the front of the drum with the drum momentarily stopped.
- The maximum allowable water-cement material ratio of the concrete is not exceeded with the addition of water and admixture solution.
- The concrete is then mixed 30 revolutions at mixing speed.
- A record is kept by project personnel of the brand, type, and quantity of admixture and of water added clearly noted on the sample card and batch ticket.
This policy should apply only to trucks already on site and in route. However, air adjustments may be necessary on subsequent loads due to variations in raw materials at the plant.
420-5 PUMPING CONCRETE
Pumped concrete is defined as concrete that is conveyed by pressures through either rigid pipe or flexible hose and discharged directly into the desired location. Pressure is applied by piston pumps, compressed air, or squeeze pressure. Rigid pipes and flexible hoses are available in sizes from
3 to 8 inches in diameter with
4 inches being the most common size used.
The success of good pumped concrete is dependent upon several items. Therefore, in considering a request by a Contractor to pump concrete and before beginning any actual work, the following items must be considered and where appropriate complied with:
- There must be a steady supply of pumpable concrete. This will require that the concrete contain uniform aggregates that are properly graded, consistently batched materials, and the thorough mixing of the concrete.
- Frequent moisture tests of the aggregates will be required to ensure that a uniform slump is maintained.
- The concrete pump must be located as near the placing area as practical and the entire area around the pump must be of sufficient strength to support the concrete delivery trucks. Only in extreme situations will pumps be permitted on completed bridge decks. If such a request is made, it shall be referred to the
State Structures Engineer for review and approval.
- Lines from the pump to the placing area must be laid out with a minimum of bends so the line friction will be held to a minimum.
- There must be direct communications maintained between the pump operator and the placing crew.
- When pumping concrete for bridge decks and culvert slabs, the line shall be firmly supported above the reinforcing steel to prevent the transmission of vibrations through the reinforcing steel into the freshly placed concrete.
- The rate of placing must be estimated so the concrete can be ordered at an approximate delivery rate that will ensure a continuous operation.
- Prior to ordering concrete, the pump should be started and operated to ensure that it operates properly.
- If a grout mortar has been pumped into the line or a “slick pack” added to provide lubrication for the concrete, the mortar or concrete containing the “slick pack” shall not be incorporated into the structure.
- Usually when there is enough concrete in the line to complete the unit being cast, the pump is stopped and a “go devil” inserted in and forced through the line to clear it out. The remaining concrete shall be ejected in a manner that will prevent contamination of the concrete or separation of the materials.
- All samples of concrete that are used in the making of slump and air tests and test cylinders shall be taken from the discharge end of the pump line. The sample should be taken from unvibrated concrete already discharged onto the deck or directly from the stream of the pump as it is working. The pump should not be stopped or repositioned in order for the sample to be taken. Doing so can result in unrepresentative results on air tests. Any request to deviate from this requirement shall be referred to the State Construction Engineer.
Prior to the first concrete pumping operation on a project, the Resident Engineer shall meet with the Contractor to review his plan of pumping to ensure that the items listed above have been considered and adequate preparations made. The meeting should include the foreman in charge of the work, the pump operator, a representative of the concrete supplier, the appropriate project personnel, the Section Materials Specialist, and the Area Construction Engineer. After the first use of a concrete pump on a project, a subsequent meeting should be held if conditions encountered warrant.
When pumping is utilized in the placement of deck concrete, the following guidelines should be observed:
- A minimum of three technicians should be present on a pour in which a pump is used for placement. They should be used for the following:
- On the bridge deck to check placement, depths, finishing, straight edging, curing, etc.
- Documentation of batch tickets, frequency of tests, and assistance of testing.
- Testing including chase, pot, temperature, and slump as required at the pump and on the deck.
- On the first load, the Technician should run a chase, pot, and slump from the truck after the Contractor adjusts the water. At the pump discharge, before vibration, the Technician should run a pot and slump for correlation of losses. Inasmuch as losses are variable, the Technician should run additional correlation tests for the following: the beginning of the pour until some consistency is noted, when cylinders are required, when changing spans, or if a variation in slump or excessive boom angle is noticed.
- To account for pump losses, concrete should be placed into the pump with a maximum slump of
4 inches and 5.5 to 7.5% air. Concrete which falls within these limits may be accepted at the truck unless the correlation indicates that the discharged concrete will be outside the acceptable ranges. Rejection of concrete must be based from samples obtained from the pump discharge. As always, samples used for cylinders must be obtained from the pump discharge.
- The concrete company QC person may add an air entrainment agent to the trucks only until adjustment can be made at the plant.
- Wet epoxy coated steel is slick. To assist the Technicians in obtaining samples, the Contractor should provide a plank walkway from the pump discharge across the mat of steel.
In conclusion, it should be remembered that if you have not had experience in the pumping of concrete or if you have any questions concerning the pumping of concrete, you should contact the Area Construction Engineer for help.
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420-6 SLUMP TESTS
Comparative air content, slump, and compressive strength tests shall be performed on all
FHWA projects for Independent Assurance purposes. The Resident Engineer should communicate all concrete pours with the Section Materials Specialist.
The specifications state that if the results of the first slump test exceed the specified maximum, a check test should be made immediately from the same batch or truck load of concrete. If a passing result cannot be produced on the check test, the load will be rejected. Allowing the truck to sit for a period of time and rechecking the truck for slump is not an acceptable practice. If the slump is less than the specified minimum, the Contractor has the option to add water to the truck as long as they do not exceed the maximum allowable water per cubic yard of concrete. The amount of water added should be recorded by the inspector on the ticket. No water shall be added after the testing has been performed. If this occurs, the tests shall be re-run prior to allowing the mix to be placed.
420-7 PLACING CONCRETE IN COLD WEATHER
Concrete is not to be placed when the air temperature in the shade is
below35° F without special permission from the Resident Engineer. Extreme care shall be exercised in granting such permission especially when thin concrete sections such as slabs are involved. Special attention should be given to the mix to assure frozen materials (stone and sand) are not contained in the discharged mix.
When concrete is cast under the cold weather conditions set forth in the Specifications, strict adherence to the special batching and protection requirements is necessary.
It is very important that the temperature of the ingredients of the concrete mix be kept
below
150° F. If this temperature is exceeded, a flash set may occur before the concrete can be properly placed and finished.
The most common method of protecting concrete during cold weather is by use of insulation. The type of insulation materials used are identified in the comprehensive approved product listing and must be approved by the
Materials & Tests Unit for each project. Insulation on forms should be in place before concrete is deposited. Thin sections such as bridge deck overhangs must be insulated on the bottom forms as well as the top surface. When insulation is to be placed on top of the concrete surface such as for bridge decks and culvert slabs, it is extremely important that the insulation be placed as soon as the surface has set sufficiently to support the insulation without damaging the surface. This will retain most of the heat from initial hydration of the concrete.
Ice, snow, and frost must be removed from the forms, reinforcing steel, and any other surfaces that the concrete will come in contact with just before concrete is placed.
Concrete is not to be cast on frozen soil.
420-8 CONSTRUCTION JOINTS
Construction joint locations will be shown in the plans. Unless shown as a permitted construction joint, the elimination or addition of construction joints will not be allowed without written permission of the Area Construction Engineer.
Construction joints are provided to simplify forming requirements, prevent excessive side pressures on the form, and reduce shrinkage stresses.
Before placing fresh concrete, surfaces of construction joints shall be properly cleaned, prepared, and wetted in accordance with the Specifications.
420-10 EXPANSION JOINTS
Seal all expansion joints with a low modulus silicone sealant in accordance with
Article 1028-4. As an option, the Contractor may completely remove the filler material in lieu of sealing.
420-11 DRAINS IN WALLS AND CULVERTS
The location of drain holes in structure units is shown in the plans. Although the Resident Engineer has authority to deviate from the plan requirements for drains, adequate drainage is very important and should be carefully considered when changes are proposed. The Area Construction Engineer shall be consulted before making a change.
420-12 ANCHOR BOLTS AND BEARING AREAS
(A) ANCHOR BOLTS
Extreme care is required in setting anchor bolts to assure proper fit of the structural steel or bearing assemblies. To avoid errors, the bolts should be set by the Contractor's forces and then independently checked by Department personnel. When possible, locations should be checked by measuring from previously cast substructure units. Ideally, anchor bolts will be measured from previously cast bents with a steel tape. If this is not possible and an instrument is used, the instrument should be placed in line with the two bolts to be measured to reduce error.
(B) BEARING AREAS
Bearing areas should be finished as smooth and level as possible while the concrete is still plastic. However, additional finishing of these areas is usually required after the concrete has hardened and anchor bolt templates are removed to attain a suitable bearing surface. Grinding may be allowed, but adding material is never allowed without consulting the Area Construction Engineer.
Bridge seat elevations shall be rechecked immediately after casting of a cap is complete to assure form and falsework settlement has not occurred.
420-13 ADHESIVELY ANCHORED ANCHOR BOLTS OR DOWELS
Adhesive anchoring must utilize an approved system. The Contractor should supply manufacturer’s literature for the system being utilized. Unless otherwise stated in the plans, follow all of the manufacturer’s recommendations for the use of the system. Proper preparation and cleaning of the hole prior to setting the adhesive is critical to the performance of the system. The plans will specify whether to test the embedded bolt or dowel.
420-14 PLACING AND FINISHING BRIDGE DECKS
Other articles concerning structure concrete construction covers a variety of concrete structure work in addition to bridge floors. Since bridge floors require more durable concrete than other structure units, certain factors are treated in more detail in this article. A suggested procedure for grading overhang forms, headers, concrete buildups over beams, and screeds for continuous span bridges is included in the
Engineering Control Section of this Manual. Similar procedures are to be used for grading simple span bridges.
When casting deck concrete in Divisions 5, 7, 9-14, the class AA concrete must contain either fly ash or slag. This requirement is stated in a plan note on the general drawings. However, these pozollans are allowed and encouraged in any division as long as it is included in the approved mix design.
A pre deck pour meeting shall be held prior to the first deck pour on a project. The Contractor, Resident Engineering staff, Materials and Tests, Bridge Construction Engineer, concrete supplier, and the concrete pumping company should all be in attendance at this meeting. A recommended pre-pour agenda is included at the end of this section for concrete and latex modified concrete deck pours.
(A) PLACING CONCRETE
Before casting a floor slab, the size and placement of reinforcing steel and the line and grade of forms should be carefully checked. Prior to beginning the pour, the Contractor shall make a dry run of the screed over the deck in the presence of the Technician. A copy of this procedure is included at the end of this section as a part of the pre-pour agenda and in the Engineering Control section of this manual. Every twentieth, fortieth, or sixtieth point on the exterior girders shall be checked in accordance with the included procedures and recorded in the Technician’s workbook. After the exterior girders are checked and the screed rail adjusted as necessary, as a minimum, the deck thickness and cover over the steel shall also be checked and recorded on fifty percent of the remaining twentieth, fortieth, or sixtieth points of each lane, and at the centerline of the bridge. If problem areas are encountered the number of checks should increase.
During the pour, the Technician should again check and record deck thickness and concrete cover immediately behind the screed. The locations for these checks should be as near as possible to locations which were checked during the dry run. In order to perform these checks, the Technician will need a device which will measure both thickness and cover. The straight end is used to check deck thickness and the "T" end to check steel cover.
An example of such a device is shown.
Note: This device can be made from a piece of CHCM. Cut the CHCM to the desired length, straighten the end legs, and remove the other legs. An alternate method of construction would be to cut and tack weld two pieces of form tie.
Should the decks during the pour indicate variations from plan dimensions in excess of
1/2 inch, the Contractor shall be notified and shall take corrective actions. The Technician should document what corrective actions were taken.
The Resident Engineer should assure himself that all of the equipment to be used in placing the concrete is adequate and in good working order before permitting the Contractor to begin placing concrete.
Longitudinal screeds are rarely used today in bridge construction. The Engineering Control section of this manual contains guidance for these screeds for situations where they are encountered.
Uniform consistency of the concrete is necessary in order to get a good bridge floor. Variations in the amount of shrinkage can cause cracking and early deterioration of the floor.
(B) FINISHING
The most important piece of equipment used in building a good riding bridge is the screed used to finish the floor slab. Investing adequate time in the setup and dry run process pays huge dividends in reduced problems during the pour and improved finish and ride.
The number of passes made over the concrete with the screed should be kept to a minimum. No more than
3 passes should be needed. Immediately after the concrete is struck off by the screed, the surface must be checked by the Contractor with a
10 foot straightedge in strict conformity with Specification requirements. The procedures for using the straightedge are outlined in this
section of the Specifications.
Other very important pieces of equipment used in casting bridge decks are the work bridges that will provide adequate access to the work. The Contractor shall not be permitted to begin casting deck concrete until at least
2
work bridges are at the site and adjusted to fit the supports. The first one should be placed in operating position as soon as possible, and the second one as needed.
Certain combinations of temperature, wind, and humidity can cause severe shrinkage cracking in the concrete surface. The Contractor is required to have suitable water fogging equipment at the bridge site. The purpose of fogging is to lower the temperature and raise the relative humidity in the vicinity of the work. It shall not be used to add water to the concrete other than to replace moisture lost by evaporation. Adding water in this manner contributes to shrinkage cracking and weakens the top layer of the concrete. An orchard type sprayer is not considered an acceptable fogging device. It shall be the responsibility of the Contractor to determine when this equipment is to be used since he will be held responsible for plastic shrinkage cracks. A little fogging water is cheaper than patching or replacing a cracked deck.
Regardless of the weather predictions for rain, the Contractor must have available at the site sufficient coverings to protect the fresh concrete in case of an unexpected rain shower.
Before concrete becomes non-plastic, the surface of the floor shall be further finished by a burlap drag, fine bristle broom, belting, or other acceptable methods. The purpose of this procedure is to spread out any surface water that might be present and to obtain an approximately uniform texture. The burlap drag may be full width and attached to the work bridge when a transverse screed is used or may be a short width of burlap attached to the screed carriage.
Application of pre-wet burlap should follow closely behind the burlap drag finish. Concerns over marring the deck surface by placement of wet burlap should not outweigh the need for timely covering of the concrete for proper curing and prevention of plastic shrinkage cracks. Dry burlap should never be applied to the deck, as it will draw moisture from the concrete before it can be wet.
The Contractor is allowed to walk the screed over a previously cast deck; however the concrete deck must still be in a plastic state, or have a minimum compressive strength of
1500 psi.
As soon as practical after the required curing period, the deck surface shall be tested with the rolling straight edge for any variations in excess of the
1/8 inch in 10 feet Specification requirement.
A video is available at the NCDOT YouTube site regarding the
Rolling Straightedge. If there are any variations, the Resident Engineer shall consult with the Area Construction Engineer before advising the Contractor relative to areas to be corrected. The method for repair of low areas and sealing when grinding extends below the top layer of grout should be discussed with the Area Construction Engineer.
After all necessary corrective measures have been performed on the deck, the surface shall be grooved using a mechanical saw device. The resulting slurry must be removed from the bridge floor. If the slurry is not removed using a vacuum pickup, the Area Construction Engineer should be consulted as to an acceptable alternate method of removal.
420-15 CURING CONCRETE
This article covers in detail the
4 approved methods of curing concrete. The Resident Engineer should determine the method of curing before casting and see that sufficient material is at the site.
Rapid evaporation of surface moisture can and very often does cause shrinkage cracks in concrete. In most cases, the fogging equipment should be used until curing is started. The Contractor will be held responsible for all plastic shrinkage cracks. Should cracks occur, the method of repair shall be approved by the Area Construction Engineer.
Regardless of the type of curing used, the Specification requirements should be rigidly enforced. When liquid membrane curing compound is used on structures, it shall be of the wax free type and should be thoroughly mixed in the storage container just before use. The inspector should measure the volume of compound actually used to verify that the rate of 1 gal. per 150 square feet is satisfied. It should also be verified that the spray pattern is even, and that the resulting coverage is not "graffiti like" in appearance. Liquid membrane curing compound shall not be used where epoxy coating is required.
Attention is called to the fact that membrane curing compound shall not be used for curing bridge floors unless permitted by the State Construction Engineer and the water method of curing is required on bridge decks.
420-16 REMOVAL OF FALSEWORK AND FORMS
The rate of strength gain in concrete varies considerably depending upon the materials used in the mix and also temperature during curing. For this reason, the concrete strength in major structure units will determine when forms and falsework can be removed. Minimum strengths required shall be as shown in
Table 420-1 of the Specifications. The
2400 psi requirement for walls of box culverts only applies when the top slab and walls are cast monolithically or when the wall height
exceeds
10 feet. In other cases, the
12 hour requirement applies.
It is usually desirable to remove curb face forms as soon as the concrete set permits in order to work the surface with hand tools; however, in no case, should these forms be removed in less than 3 hours after the concrete is cast.
When forms are removed before the end of the required curing period, one of the curing methods required by the Specifications must be started immediately.
420-17 SURFACE FINISH
All required patching is to be performed immediately after form removal. When forms are removed before the end of the required curing period, the entire exposed concrete surface is to be kept damp until patching is completed and one of the permitted curing processes is started. Cement and sand for the patching grout must be from the same sources and in the same proportions as used in the concrete to assure even coloration of the finished surface. Curing requirements for grout patches are the same as for concrete. Improperly cured patches will shrink and crack.
420-18 EPOXY COATING
Apply epoxy coating only to the areas identified in this specification. Proper surface preparation is critical to the performance of the coating. The completed surface must be free of voids or defects. Curing compound shall not be used where epoxy coating is required.
420-19 PROTECTION OF SUBSTRUCTURE CONCRETE FROM RUST STAINS
Prior to setting unpainted structural steel, the Contractor should be encouraged to protect the substructure concrete from staining. It is easier to protect the concrete from stains than to allow the concrete to stain and attempt removal after staining occurs.
420-20 PLACING LOADS ON STRUCTURE MEMBERS
Judgment should be used before allowing the larger earthmoving equipment over box culverts. Contact the Area Construction Engineer if you have any doubts.
When the Contractor intends to operate or cross a bridge with heavy equipment, which is not legally allowed on a roadway, he is required to submit his plan for approval. Examples of equipment that fall under this requirement include, but are not limited to, crawler cranes, truck cranes and concrete pumping trucks operating with outriggers down, scrapers, off-road trucks, fine grading machines, concrete paving machines and any track mounted equipment.
Structures Management Unit will review the submittal for bridges being constructed under the contract and for bridges on or adjacent to the project that are open to public traffic. The Contractor’s Designer of Record will review the submittal for detour bridges that have been designed by the Contractor. The Designer of Record will review the submittal for new bridges that have been completed under the contract. In no case, should heavy equipment be allowed to operate on bridges without prior approval.
During and after the placement of barrier rail, no equipment or traffic other than that necessary to place additional rail will be allowed on the deck until the rail has obtained a compressive strength of
3000 psi. Any additional rail placement operations shall be conducted so as to minimize vibrations.
420-21 MEASUREMENT AND PAYMENT
Installing SIP metal decking, precast concrete deck panels, overhangs and reinforcing steel in a deck slab can be a time consuming task. During this time the contractor and subcontractors (some of which are small businesses) must wait for payment for their work until the deck slab is complete unless partial payment is allowed. The following guidelines are customary when paying partial amounts for the item of Reinforced Concrete Deck Slab:
- Metal decking
- 5% after decking installed
- 5% after overhang
- 30% after rebar tied
- Balance after deck cast
- P.C. Deck Panels
- 20% after panels installed
- 5% after overhang installed
- 15% after rebar tied
- Balance after deck cast
