511 Concrete for Structures


Mix Design

Materials (511.02)

Placing Concrete for Substructures (511.10)

Construction Joints (511.12)

Documentation Requirements – 511 Concrete for Structures



Concrete mix design, mixing equipment, and control is as set forth in Item 499.  Inspectors whose assignments involve concrete as applied to structures are to follow the procedures described here and should familiarize themselves with these instructions.


Mix Design

Concrete for structures will be Class C, S, HP, or as specified in the contract documents.  The mix design and control are as outlined in Item 499 except as modified for specific uses as hereinafter described.  If the concrete for structures is to be QC/QA, refer to SS 896.


Materials (511.02)

511.02 requires all concrete above the ground line in a given substructure unit or all concrete for any given superstructure to be made of aggregate of the same kind and color, except upon permission of the Engineer.

All superstructure concrete (deck concrete including safety curbs, sidewalks, and parapets) is to be made with natural sand, crushed stone, crushed air-cooled blast-furnace slag, or gravel.  The kind and color of aggregate are considered to be the same from any one source.

When a Contractor desires high-early-strength concrete he may use high-early-strength cement, additional cement, accepted water reducing, set-retarding admixture or a combination of these as specified in 511.07.  If the Contractor desires high early strength using additional cement and/or admixtures as a continuing practice, his method should be submitted to the Engineer for review.


All concrete used in structures must contain the amount of entrained air specified in 499 unless otherwise specified.  An air determination should be made for each part of the structure. This determination should be made as early as possible on the first load of concrete.  For substructure concrete, as many additional air tests as necessary should be made to assure required air content.  For superstructure concrete, an air test should be made for each load of concrete used.  Concrete containing less than the specified amount of air may have the air content increased by addition of an air entrained agent then, providing additional minimum of 30 revolutions, at mixing speed, as long as the time limitation for discharge is not exceeded. 


Concrete that is pumped can lose air as the concrete passes through the pump.  Therefore, it is important that air tests be made at the point of placement, after the concrete passes through the pump.

The slump of concrete for Class C and S concrete shall be maintained within the range specified in 499.03.  An occasional load exceeding the nominal slump (but within the maximum) may be used provided immediate steps are taken to adjust the slump of succeeding loads.  Before concrete exceeding the nominal slump range may be used, the Contractor or supplier must take positive action to reduce the slump of following loads. 

Accepted chemical admixtures may be incorporated into concrete to improve workability and extend the setting time.  Chemical admixtures must meet the requirement of 705.12 that specifies they meet the requirements of ASTM C 494 chemical admixtures.  These admixtures are as follows:

·         TYPE A - Water reducing

·         TYPE B - Retarding

·         TYPE C - Accelerating

·         TYPE D - Water reducing and retarding

·         TYPE E - Water reducing and accelerating

·         TYPE F - Water reducing, high range

·         TYPE G - Water reducing, high range, and retarding


The type of admixture is optional with the Contractor.  However, when the air temperature is 60°F  (16° C) or higher at the time of placement of superstructure concrete, and the span is over 20 feet (6.1 m), a Type B or D admixture is required for Class S concrete and Type A or D is required for Class HP concrete.


The results of the air tests together with yield tests are shown on the back of Form TE-45.  The Ready Mixed Concrete Plant Ticket must show the number of revolutions at mixing speed.  A mixer’s rated RPM for mixing speed and agitation speed will be listed with the operating data on the mixer.  The mixers must be checked to see that they are operating at the rated speeds.  The structure unit in which that load of concrete is placed should be noted on the ticket.  A full list  of the required data to appear on a batch ticket is listed in Table 499.08.

Advance Notice of Placing Concrete

The Contractor must notify the Engineer at least 24 hours in advance of placing concrete.  Review this provision with the Contractor near the start of work on a structure to ensure a clear understanding regarding the stage of completion of work necessary to permit inspection before approval to proceed.  The need for all or part of the 24 hours will depend on the amount of additional inspection required to insure that the reinforcing steel has been properly placed, and the forms are in the correct location.

Placing Concrete for Substructures (511.10)

Several methods may be used to convey the concrete to the forms.  Any method that assures placement of concrete of the proper consistency without segregation is satisfactory.  Usually ready-mix trucks with open chutes, buckets, drop chutes, and concrete pumps are used in placing substructure concrete.  Open chutes must be sloped sufficiently to allow concrete of the proper consistency to flow readily.  Drop chutes may be maneuvered to distribute the concrete but the delivery end must be kept vertical.  Concrete is deposited as near as possible to its final position with as short of a vertical drops as practical, but not over 5 feet (1.5 m).

Consolidation of concrete by the vibration method is required for structures.  Spud vibrators generally are used and should have a workman assigned exclusively to each vibrator.  The vibrator should be pushed into and pulled out of the freshly deposited concrete slowly and as nearly vertical as possible.  For narrow sections, the vibrator may be applied to the sides of the forms or a form vibrator may be used.  Establish a pattern of placing and vibrating that provides practically horizontal surfaces and uniform vibrator coverage.  Generally a vibrator can consolidate concrete in approximately a 4-inch to 8-inch radius depending on the type of concrete.  Class HP concrete and concrete with pozzolans often require more vibration than straight type 1 cement, even when there are high slumps.  Visual inspection of consolidation is a two-step process of one, seeing the surface of the concrete flatten out, and two, seeing air bubbles come to the surface within the vibration radius.  Therefore, a uniform coverage pattern must be used to assure uniform consolidation.


Where concrete will be placed to bedrock, the rock should be free of mud and cleared of all loose rock or other accumulations.  Soil serving as the footing bottom should be sufficiently dry and stable so that it will not be interspersed in the concrete.

Concrete may occasionally be placed in water.  However, with the exception of drilled shafts, concrete is not to be placed under water.  When concrete is placed in water, placement should begin in one corner of the forms and continue into that previously deposited until full height of footing is attained.  Full height should be carried forward, displacing the water ahead and out a small opening in the opposite corner of the forms.  Vibration of the concrete should be kept well back of the water.  Concrete must never be deposited in running water since it will cause separation of cement from the mixture. If pumping is controlling the water level, the pumping may be halted or reduced immediately after the concreting is complete, so that the water level rises slowly and inundates the footing to provide the cure.

When the plans require a concrete seal, or it becomes necessary for the Contractor to use a seal to stop the upward flow of water, the concrete must be deposited under water in a manner that minimizes separation of the cement.  This type of seal is sometimes referred to as a mud mat.  A concrete seal is deposited in a compact mass with a minimum of disturbance from the water it displaces.  When a tremie or concrete pump is used the end of the pump or tremie hose or tube must be plugged prior to lowering into the water and kept filled during placement.  Failure to keep the tremie or pump filled with concrete during placement could result in water entering into the tremie tube or pump hose.  This will result in the cement being washed from the aggregate.  The Contractor’s plans for the mix and placement should be reviewed prior to the pour.  Where the Contractor elects to use a seal, it is his responsibility to choose a thickness and methods that produce satisfactory results.

Piers and Abutments

Concrete for backwalls above the approach slab seat shall not be placed until the abutments have been backfilled to within 2 foot (610 mm) of the bridge seat elevation.  

When expansion joints are involved, the backwall should not be placed until after the superstructure concrete is placed.  As the superstructure concrete is placed, the beams will grow in length as the camber decreases.  If the backwall is placed prior to placing the superstructure concrete, the required opening in the end dam will be lost as the beams grow in length.

The tops of backwalls that become roadway surface require special methods for setting the grade.  Although the recommended methods have been used to set the end dams, the elevations can be slightly off grade. Therefore, the tops of the end dams should not be used alone to project the grade for the backwall.  The preferred method of obtaining the correct grade is to place a 10-foot (3.05 m) straightedge as a screed supported on the superstructure concrete and the end dam.   The backwall can be struck to the proper grade.  Grade strips tacked to the backwall form that have their elevations established in a manner described above may be used to establish the grade.  In the event that the grade for the surface of concrete is not flush with the end dam edge bar, it should be finished to the grade established above and edged to a radius equal to the offset where it abuts the edge bar.

After the forms have been stripped from backwalls and before the approach slabs are placed, the top surface of concrete is subject to damage by spalling of the sharp edge on the approach slab side.  Covering the surface with a plank or any other method that will afford equal protection should be provided.

Concrete should never be deposited through closely-spaced reinforcing steel where it may accumulate and take set prior to encasement or cause segregation of aggregate.  The bars, such as the top main bars in a pier cap, should be moved out of the path of the concrete or hopper temporarily until the concrete level has reached the vicinity of the bars, and then reset.  If the plans require bearings for which anchor bolt holes will be drilled later, the bars must be reset accurately and checked with a template.

Bearing Seats

Bearing areas on abutments and piers must be finished accurately to the plan elevations in order that the deck may be placed on profile grade.  The elevations should be checked accurately at the time of finishing to correct for possible errors and settlement of the forms containing the original marks.  Take elevations as soon as possible after completion of the substructure units and record them for future reference.

Bearing seats that are high or uneven must be leveled to the proper elevation by bush hammering or grinding, and then smoothed with a thin film of Portland cement paste to fill the pitted surface.  Bearing seats that are over 1/8 inch (3 mm) low are leveled as described above, if necessary, and raised to the proper elevation by steel shims placed under the masonry plates. If elastomeric bearings are specified, steel shims should not be placed under the bearing.  In this case, consult the Office of Structural Engineering pertaining to the acceptability of the Contractor’s proposed method of correcting the bearing seat.

Where it is necessary to cut down the bearing area, the lowering is extended approximately 1 inch (25 mm) around the area of the masonry plate and carried full width to the face of the abutment or pier cap for drainage.


Construction Joints (511.12)

The surface of construction joints should be even and have coarse texture such as produced by a wood float on fresh concrete.  Vibrated concrete with a closed level surface is satisfactory.  Where the construction joint terminates at an offset in the concrete surface, such as between the fascias of the deck slab and the sidewalk, the joint should be finished neatly at the corner with a wood float.

Transverse joints as permitted in 511.12, or longitudinal construction joints placed in deck slabs of steel beam or girder bridges, are constructed with keys located between the reinforcing mats and having a depth of 3/4 inch (19 mm).  If the Contractor desires a longitudinal construction joint due to an excessive slab width and not provided by the plans or specifications, the request must be submitted to the Office of Structural Engineering for review.

Pre-Pour Conference for Placing Concrete for Superstructures

Prior to the scheduled day for deck placement, preferably the day before, a conference should be held on the project to review the plans and preparations for the pour  (Forms CA-S-4 and CA-S-6).  The Contractor’s superintendent and key personnel, together with the Engineer and available inspectors who will be involved, should attend.  At this time the superintendent should state fully his plan of operation and agreement should be reached with the Engineer on all of the following:

1.        Provision for adequate concrete delivery to insure continuous placing and to provide sufficient length of workable concrete for proper straight edging.  This includes the number of trucks assigned and an access route where ingress and egress will be maintained at all times.

2.        Spacing of the trucks, especially at the start and end, so that no load will be delayed unduly in discharging or will placing be delayed for lack of concrete.

3.        A system of communicating with the concrete plant to permit ready adjustments in the mix or delivery

4.        Proper tools and equipment on hand have been checked and are in good working order.  A finishing bridge must be used when the deck cannot be reached for proper finishing.

5.        A competent and experienced bridge superintendent who will be in charge, and at least two experienced finishers

6.        Factors that might determine the need for chemical admixtures are explained

7.        Protection on hand in case of rain or low temperatures

8.        For decks with hinges, and where it is planned to terminate a pour at the expansion joint over the hinge, concrete placement should proceed in the direction that will load the longer part of the hinged span first.  This will minimize the effects of unequal span loading, unless otherwise specified in the plans.

9.        Properly curing the concrete and placing the wet burlap in a timely manner

Closure Pour

Many times a bridge deck will be constructed part width at a time to maintain traffic on a portion of the existing or completed structure. Also, at times, an existing structure will be widened by adding at least two beam lines.  A closure pour will be used to account for the differential deflection that will occur between the portion of the deck that has already been placed and has yet to be placed.  This closure pour is important and should be performed.  A closure pour involves a strip of concrete several feet (a meter) or more wide that is not placed until after the deck concrete is placed in both phases.  It is placed the entire length of the deck between the two portions of deck.

When a closure pour is specified, the forms on the second phase of the deck yet to be placed must not be supported by the first phase that has been previously placed.  Also, the reinforcing steel must not be spliced, and cross bracing shall not be placed between phases until the concrete in the second phase has been placed.

Immediately prior to placing the concrete in the closure pour it is important that the cross bracing between the first two phases be completely installed.  At this time it is also acceptable to support the forms for the closure pour from the two completed adjacent phases.

Setting the Grade for Finishing the Deck

When finishing a deck, setting the grade correctly is paramount for placing a deck on profile grade.  A table of screed rail elevations is shown on the plans for composite box beam bridges, rolled beam, girder, and concrete I beam bridges. 


The grade must be set by instrument using the elevations in the table.   Assuming that expansion joints and camber of beams, girders, or falsework are correct, and setting the grade the plan distance over the beams or plan thickness is not permitted.  Elevations must be taken on the end dams and at every point on the beams required for setting the grade of the screed rail, including points over the piers.  This is done so that deviations in the camber of the beams or girders can be adjusted when setting the forms, and not later when it would be more difficult.

Deviations in the camber of the beams or girder are corrected by varying the size of the haunch or fill over the beams.  The height of the haunch or fill is determined by subtracting the elevation of the top of the beams from the theoretical elevation of the bottom of the deck.  The theoretical elevation of the bottom of the deck is determined by subtracting the deck thickness from the screed rail elevations given in Table 511.A - Determining Haunch Height.  This is an acceptable method of recording this information.


Beam Row


Rear Abut

¼ Pt

½ Pt

¾ Pt

Pier 1


Deck Bot






Beam Top






Haunch Ht







Deck Bot






Beam Top






Haunch Ht







Deck Bot






Beam Top






Haunch Ht







Deck Bot






Beam Top






Haunch Ht







Deck Bot






Beam Top






Haunch Ht






Table 511.A - Determining Haunch Height


In the case where the beams or girders have excessive camber and it would cause the beam or girder to interfere with the deck thickness, the profile grade should be raised.  The new grade should parallel the plan profile as nearly as possible and provide the required deck thickness at points of maximum camber.  This will result in increasing the haunch height over the piers and abutments to an acceptable level.

Whenever the profile grade of the deck is adjusted, this must be considered when setting the grade for the approach slabs and pavement in order that a smooth transition will be provided.  Even though it has not been necessary to adjust the grade, the as-built grade of the deck should be used to establish the grade of the approach slabs, since the actual dead load deflections may vary from the calculated deflections shown on the plans.

When a closure pour is specified, the designer assumes that the finished elevation of the existing deck is correct.  However, due to either conditions beyond his control or conditions he has overlooked, the finished elevation of the deck may not be as he assumed.  If this condition exists, it should be detected prior to placing the widened or second portion of the deck.  Therefore, prior to placing the widened or second portion of the deck, the Contractor should check the finished elevation of the existing portion of the deck to assure that it is correct.  If it is determined that it is not correct, the Office of Structural Engineering should be contacted for additional instructions.  

Evaporation Rate

In an effort to reduce or eliminate drying shrinkage cracks in the superstructure concrete, the concrete should not be placed when the evaporation rate of water from the freshly placed concrete is too high.  Use the graph in section 511.10 of the CMS to check the evaporation rate.

The Contractor should check the evaporation rate immediately before the placement of superstructure concrete begins.  The evaporation rate should also be checked if there is a change in temperature, humidity, or wind speed during the placement of superstructure concrete.  The wind speed can have the greatest effect on the evaporation rate; therefore, changes in the wind speed should be more closely monitored.  Many times, during the summer months, it will be necessary to place superstructure concrete at night in order to comply with the evaporation rate. 

In addition to the evaporation rate, superstructure concrete is also not allowed to be placed when the ambient air temperature is 85° F (30° C) or higher or is predicted to go above 85° F (30° C) during placement.  The temperature of the concrete is also not allowed to exceed 90° F (32° C) during the mixing and placement.  Many times it is necessary for the Contractor to reduce the temperature of the mixing water and/or aggregates in order to control the temperature of the concrete.

Evaporation retardant is mostly water and its use is not permitted.  Be aware that evaporation retardants is also marketed as a finishing agents, but under either name their use is prohibited.

Machine Finishing

A machine finish is required except for small bridges, where the Engineer may waive the requirement.  Details of the method of supporting the machine on the deck and the complete procedure for placing the slab should be submitted to the Engineer for review.  Supports for the riding rails must be adequate for the weight of the machine to avoid failure or any vertical deflection.  The concrete handling, placing, and finishing procedure should be planned so that the concrete will be placed and struck off with a minimum of manipulation and at a sufficient rate to provide workable concrete in an area adequate for proper final hand finishing.  Success of the Contractor’s procedure on previous decks should be considered.


For transverse machines, the screed should be assembled or adjusted to the required crown established from a taut line while suspended in the same manner as it will be in operation.

Prior to ordering concrete and after the finishing machine has been made ready, make a dry run over the entire deck.  Check slab thickness and reinforcing steel cover along with crown conformance to both end dams and expansion joints.  If the rate of crown varies and the machine can be adjusted during operation, the required crown should be determined at regular intervals not exceeding 25 feet (7.62 m), the required increment of adjustment established and the location referenced on the side of the bridge.

Plan dimensions for deck thickness and reinforcing steel cover verified during the dry run and witnessing screed adjustments to the required crown must be recorded in the project records.  A last-minute check that form dimensions and reinforcement have been verified and documented should be made at this time on the inspectors Daily Report.

Although proper measurements made during the dry run should assure plan dimensions, check measurements after the concrete is struck to grade to verify that the machine is still in adjustment and reinforcing steel remains in place.  Slab thickness measurements can readily be obtained by probing with a 1/4 inch (6 mm) straight wire and the cover over re-steel with a 90° bent wire of the same size.  These measurements should be made soon after the start of the finishing operation and periodically thereafter or when an area appears questionable.  Wide flat sections such as super elevated slopes are questionable and must be checking.  The probing should be performed in plastic concrete where the void will be more easily closed.

Some cover checks are required.  However, they need not be as numerous as the depth checks that also reflect cover.  It is recommended that as many depth checks be made as available time permits.  A statement that check measurements have been made and conform to plan dimensions should be entered in the project records. If localized areas do not conform to plan dimensions these should be noted and any corrective action documented.

During operation, a uniform head of concrete should be maintained along the full length of the screed.  Screeds should be lifted from the surface when not in use.  During operation, only the operator is permitted on the machine.  The machine should be in operation as continually as practical, and the concrete placing procedure should not exceed the speed of the machine.

Tracking or walking in the screeded surface is not to be tolerated.

Final Finishing

It is imperative that final finishing follow immediately behind the finishing machine.  If this final finishing should fall behind, the rate of concrete placement should be reduced.


The construction joint surface under the sidewalk or the safety curb should not be used as a place for finishers to stand or as a passageway for workers.  Planks may be placed on the sidewalk reinforcement providing sufficient additional ties and braces are used if necessary to obtain a rigid framework that will not disturb the bond of the stirrups.

Minor surface irregularities left after screeding can be corrected with long handled floats.  This operation should be held to a minimum and any major irregularities encountered should be corrected by the use of a straightedge.  Use of water, evaporation retardants, or finishing agents on the surface of the concrete to facilitate finishing is not permitted.  If a Contractor is adding water by continuously “washing” his tools, require that they us a towel to dry the tools prior to reuse.


The deck surface must be textured (using a broom) to provide a surface satisfactory to the Engineer.  The broom must produce a uniform gritty texture in either the longitudinal or transverse direction.  The texturing should take place as the pour progresses after other finishing operations have been completed.  Note that if the concrete tears, or “mud balls” are produced on the surface, the Contractor needs to apply less pressure to the broom or wait a few minutes until the concrete has began to set.

After the water curing of the concrete is complete, transverse groves must be sawed into the surface of the deck. The grooves must be spaced at 3/8 to 1 3/4 inch (10 to 45 mm) with 50 percent of spacing being less than 1 inch (25 mm), and must be approximately 0.15 inch (4 mm) deep and 0.10 inch (3 mm) wide.  Groves must be within 9 to 12 inches from devices such as scuppers or expansion joints.  On skewed bridges, in order to accommodate the equipment used to saw the groves, the grooves must be sawed from 2 inches to 2 feet from the expansion joint.  This results in grooves with a staggered or stepped appearance.

Opening a structure to traffic prior to sawing rain grooves exposes the traveling public to a hazardous situation. Therefore, traffic must not be allowed on bridge decks until after the grooves have been sawed.


During the placing of a deck, unexpected difficulties may occur that halt further placing.  These may be a sudden shower, a breakdown in the concrete plant or the finishing machine, or other unforeseen interruptions.

When a shower occurs, no manipulation of concrete should be performed other than channeling the concrete that was last deposited so that water will not pond on the concrete and run back on the finished or partially finished surface.  The textured surface should be covered with the curing material as rapidly as possible.  Untextured surfaces should be covered with polyethylene sheeting.  After the shower, all ponded water should be removed from the concrete and out through the forms before resuming placing and finishing operations.  The last surface covered with the curing material should be inspected; if it has been marred, the texture should be restored.

Investigate breakdowns immediately.  If indications are that it will not allow resumption of concrete placing in sufficient time, a bulkhead must be placed immediately.  If practical, the location should not be over a pier.  The emergency bulkhead may consist of a wood strip laid across the top of the longitudinal reinforcing bars.  This strip should be as deep as the plan cover; usually  2 1/2 inches (64 mm).  Kickers can be used to secure the strip or shims inserted between the bars to obtain proper crown and grade.  The concrete below the wood strip should be compacted to about a 45-degree slope, and all excess removed as far from the joint as possible and disposed of before it hardens.  After the concrete has set but still fractures easily, the bottom edge should be broken to provide a vertical face below the bottom reinforcing steel.  This may be accomplished with a pry bar prying up from the forms, but exercise care to see that the surface of the forms is not damaged.  See Figure 511.A - Emergency Bulkhead.

Figure 511.A - Emergency Bulkhead

Curbs and Parapets

Forms for curbs and parapets should be observed carefully for condition of surface, flush fit of panel joints, proper installation of bevel strips, and visual and measured alignment and elevation.   Adequate form supports should be provided that insures proper position of concrete during and after placement.  Surface rubbing does not justify use of inferior forms or lack of adequate supports.

When expansion devices are used to allow for bridge deck expansion, slightly more open space for expansion must be provided in the curb and parapet than is required for expansion devices.  Where conduits cross this opening, give special attention to clearance for expansion fittings to assure free movement of the deck.

Transverse joints may be placed in the sidewalk or curb section near the center of any span.

Slipforming Parapets

In lieu of conventional forming, the Contractor may be permitted to slipform the parapets. This operation is accomplished with concrete that has a slump of around 1± inch.

Prior to placing the concrete, the Contractor must take additional measures to tie the reinforcing steel to prevent it from being dislocated during the slipforming operation. If these additional measures are not taken, the slipforming operation will cause the reinforcing move out of its proper location.

Due to the low slump, many times the Contractor will attempt to add water to the mix as it comes down the chute from the concrete truck and enters into the hopper of the slipforming machine.  This is not allowed since it will result in concrete of inferior quality.

During the slipforming operation, small amounts of concrete will drop from the edge of the deck and onto the surface below the bridge.  If the slipforming operation takes place directly over a traveled roadway, the Contractor should furnish all necessary platforms to protect the traffic from falling concrete.  These platforms will also allow access to complete the finishing operation and facilitate inspector access.

The Contractor should take steps to insure that the finished concrete meets the specified tolerances.  These steps should include items such as adequately tying the reinforcing steel, determining the proper slump, and properly setting up the slipforming machine.  Failure to meet the specified tolerances could result in the rejection of the parapet.

Any defects such as cracking, tearing, or honeycombing should be repaired immediately.  Occasionally, when repairing defects, the Contractor will not completely fill the defect with concrete but will only bridge over the defect by placing the concrete on the surface of the parapet.  This is not acceptable. The Contractor should take steps to insure that the defect is completely filled with concrete.

Normally, a small amount of hand finishing is required after the concrete has been formed.  Hand finishing can be difficult due to the low slump of the concrete.  To facilitate finishing the concrete, many times the Contractor will sprinkle water or evaporation retardant onto the surface of the concrete.  The use of these substances to aid in hand finishing is not allowed since it will only result in a surface that is subject to scaling in the future.

After the concrete has taken its initial set, it is important to saw the control joints to the plan depth into the parapet as soon as possible.  Any delay in performing this operation will result in additional shrinkage cracks in the parapet.

Curing (511.17)

Curing is governed by 511.17 that requires either Method (a) Water Curing or Method (b) Membrane Curing.  Curing time is seven days. No curing is required for surfaces covered by forms for the duration of the curing period.  Concrete that will be overlaid with concrete or sealed, and all superstructure concrete, must be cured in accordance with Method (a) Water Curing.  Concrete decks placed with Class HP concrete must be cured for 7 days in accordance to Method (a) and then cured within 12 hours in accordance with Method (B).

The curing material must be applied as soon as possible to avoid cracking of the concrete.  Application of the curing material should be applied immediately after the finishing operation has been completed.

When it is necessary to work on concrete during the curing period, such as placing deck concrete adjacent to a construction joint, only that area immediately adjacent to the joint should be exposed and the remaining area protected from damage by the workers.  Plywood sheets may be used for protection.  The exposed area should be kept moistened until adjacent work is completed, after that the cover should be restored and normal cure resumed.

Floor forms provide the cure for the underside of the slab and are not to be removed before the end of the curing period.

Method (a) Water Curing

When two thicknesses of burlap are used to water cure the concrete, they should be kept wet by the continuous application of water from soaker hoses or other sprinkling devices during the required period.  In lieu of continual sprinkling devices, white polyethylene sheeting or wet plastic coated blankets may be used to cover the concrete.

On bridge decks, a single layer of wet burlap is kept wet by a continuous application of water and covered by white polyethylene. The polyethylene should be placed transversely.  The edges should be lapped and held securely to maintain a moisture seal.  The curb area may be covered with a longitudinal strip that is held securely to the fascia form and laps the transverse strips.  A continuous batten may be used to seal the blanket to the form and reinforcing bars laid on the laps to make the seal.  Check areas suspected of having the seal broken during subsequent work or weather disturbances.  Then if it is found to be drying out, soak the burlap and reseal the white polyethylene.


Plastic-coated blankets must be inspected prior to use to assure that they are sound and will retain the moisture required to cure the concrete.  All holes and tears must be repaired so that they are watertight.  The material should be rejected if defects are numerous and repairs are questionable, or if the plastic coating has cracked from aging.

Burlap and plastic-coated blankets must be thoroughly soaked with water prior to placing on the surface of the concrete.  Dry material placed on the surface of the concrete will draw moisture out of the surface of the concrete; this will increase the chances of drying shrinkage cracks.  If new burlap is used, extra measures may be needed to insure that it is properly soaked since it doesn’t soak up water as well as used burlap.  If burlap to be soaked is delivered to the project in a tightly wrapped condition, it should be loosened to allow the penetration of water.

Method (b) Membrane Curing

The concrete curing membrane is white-pigmented material meeting specifications 705.07.  The material may be either Type 1 (clear or translucent without dye) or Type-D (clear or translucent with fugitive dye).

The membrane should be applied in one or more separate coats by spraying as a fine mist, at a uniform application rate of one gallon per 200 square feet (70.3 square meters) of surface.  The rate of application is controlled by laying out in advance, on the surface to be cured, an area that will be properly covered by the number of gallons of compound in the spray container.  The procedure helps insures that the membrane is applied at not less than the required rate.

Cold Weather Concreting

Heated concrete and protection must be provided whenever concrete is placed at an atmospheric temperature of 32° F (0° C) or lower, or whenever weather forecasts predict temperature below 32° F (0° C) within the curing period.  Concrete must not be placed in contact with material having a temperature of less than 32° F (0° C).

The official U.S. Weather Bureau forecast for any curing period generally can be obtained from the District Office.  This information also can be obtained from some local airports and radio stations.

When the five-day weather forecast does not predict 32° F (0° C) or lower temperatures at any time during the period, the Contractor should not be required to erect enclosures or use insulated forms.  However, during the fall, winter, and spring, adequate material and equipment should be on hand to provide for unpredicted temperatures below 32° F (0° C).

To assure freedom from freezing until protection can be established, the temperature of concrete as placed should not be less than the minimum of 50° F (10° C) specified, but should not exceed 90° F (32° C) maximum.  Concrete placed at low temperatures above freezing develops higher ultimate strength and greater durability than concrete placed at higher temperatures.  Higher temperatures require more mixing water, cause slump loss, possible quick setting, and increase thermal shrinkage.  Rapid moisture loss from hot exposed concrete surfaces may cause plastic shrinkage cracks.  It is recommended, therefore, that the temperatures of fresh concrete, as placed, be kept as close to the 50° F (10° C) minimum temperatures as practicable.  When the air temperature is 32° F (0° C) or lower, it is necessary to raise the temperature of the concrete by heating the mixing water or aggregate, or both.  The concrete must be protected from freezing and specified curing temperatures must be maintained by a heated enclosure, by insulated forms, or by either of these in combination with flooding.

Decks slabs less than 10 inches (254 mm) thick must be protected from freezing, and specified temperature maintained for the curing period, by a heated enclosure.

Arrangements for covering and insulating newly-placed concrete must be made in advance of placement and should be adequate to maintain the specification temperature in all parts of the concrete.

During the first few days requiring protection, most of the heat of hydration of the hardening cement is developed. As a result, if heat generated in the concrete is adequately conserved, outside heat generally is not required to maintain concrete at the correct temperature.  This heat may be conserved by using insulating blankets and by insulated forms where repeated reuse of forms makes this practical. Outside temperatures, at that concrete walls, piers, abutments, or slabs above ground may be protected with insulation under various conditions, are shown in the charts that follow.  On work where protection by insulation is permitted, project personnel should check the protection proposed by the Contractor and be reasonably sure that the proposed insulation is adequate for the expected exposure before concrete placement is permitted to begin.

The application of insulation should be as follows:

1.        Blanket insulation is applied tightly against wood forms with nailing flanges extending out from the blankets so they can be stapled or battened to the sides of the framing.  Seal the ends of the blankets by removing a portion of the mat and stapling or battening the blanket to headers so as to exclude air and moisture.  Corners and angles are most vulnerable.  Take extreme care to insure they are well insulated and the insulation held firmly in place.

2.        In case of steel forms, the insulation should be applied tightly against the form and held securely with the ends sealed to exclude air and moisture.

3.        Where practicable, the insulation or insulated form should overlay any cold concrete previously placed by at least one foot.

4.        Any tears in the liner are to be repaired immediately with accepted waterproof material.

5.        Where tie rods extend through an insulated form, a plywood washer, approximately 3/4 × 6 × 6 inches (19 x 150 x 150 mm), should be placed on top of the insulation blanket and secured in a satisfactory manner.

6.        The tops of all pours must be covered with insulating blankets, except for areas around protruding reinforcing bars that may be insulated with straw or wrapped with insulation blankets.  Waterproof covers should be used to cover the top of such pours as required by specifications.

7.        Protective enclosures may be constructed of canvas, plywood, polyethylene, plastic, etc. in such a manner that will maintain uniform temperatures and allow free circulation to the warmed air.

8.     For the underside of deck slabs, ¾ inch (19 mm) plywood forms have an equivalent thickness of 0.6 inch (16 mm) and will provide protection of 32° F (0° C) minimum air temperature.

9.        Close packed straw under canvas may be considered a loose fill type if wind is kept out of the straw.  The insulating value of a dead air space greater than about one-half inch (13 mm) thick, does not change greatly with increasing thickness.

Heated Enclosures

When salamanders or other heaters supply heat, local drying and burning of the forms may result and necessitate moving or adjustment of the setup.  Regular observance of the forms and burlap should be made to insure that the concrete is kept wet for the duration of the curing period, as required in 511.17.  Combustion type heating units shall be vented from the enclosure to preclude damaging fresh concrete. The enclosure should surround the top; sides, and bottom of the concrete to be placed during cold weather.

Temperature Control

Thermometers for use in enclosures should be the high-low recording type and be furnished by the Contractor.  If the enclosure is long or high, more than one thermometer may be required.  The readings in the morning and the afternoon normally represent the low and high temperature respectively; make careful selection of the time when the high-low recording thermometers are checked.

When insulated forms are used the thermometer must be furnished and installed by the Contractor.  They must be of such a type and so located that they will indicate surface temperature of the concrete.  In case of a tall section such as pier shafts or retaining walls, more than one thermometer will be required because of the temperature gradient.  Temperatures should be read twice daily for high and low readings.  When insulated forms are used, temperature of concrete will cause a lag in the change of temperature of the surrounding air.  Time of observance need not be as selective for representing the high and low, but is used to indicate a trend that may require venting of the forms or erecting an enclosure.  When venting of a vertical form is necessary it should be raised slightly at the bottom to create a chimney effect.

The temperature record must include the required temperature readings for the entire curing period.  Outside air temperatures may be local reported temperatures.

Temperature and control methods used as well as temperature readings must be recorded on the Inspector’s Daily Report.



Cold Weather Curing Time

To fulfill the curing requirements for concrete placed in cold weather, the surface temperature must be maintained as specified in 511.15 or be exposed to ambient air temperatures not less than 50° F (10° C) for 5 days.

In case any day’s temperature readings fall below the minimum specified, the duration of heating must be extended to provide the required number of days.  In case of loss or breakage of thermometers, replacements or other provisions must be made to provide a complete record.

Falsework and Form Removal

Falsework must not be removed until after the time-temperature requirements of 511.17 have been met or satisfactory beam tests have been attained.  During cold weather, forms are to be removed after the curing period in such a manner that the temperature of the concrete does not drop more than 20° F (7° C) in any 24-hour period.

Note 1 in Table 511.17-1 states that span is defined as the horizontal distance between faces of the supporting elements when measured parallel to the primary reinforcements.  For slab deck bridges the primary steel runs longitudinally down the deck.  For beam supported structures the primary steel runs transversely across the deck. 


As soon as possible after the removal of forms, all cavities produced by form ties and all other holes, honeycomb spots, broken corners or edges, and other defects (except air bubble holes that may be filled by grout cleaning) must be cleaned and after having been saturated with water shall be completely filled, pointed, and trued with a mortar of the same proportions as used in the concrete being finished.

On all exposed surfaces, all fins and irregular projections must be removed with a stone or power grinder, taking care to avoid contrasting surface textures.  Sufficient white cement must be substituted for the regular cement in the filling of holes and other corrective work to produce a finished surface of the same color as the surrounding concrete.

If shown on the plans, exposed surfaces having an appearance that is not satisfactory to the Engineer shall be grout cleaned in a manner satisfactory to the Engineer.

The Contractor should be advised that it will be necessary to use good formwork to obtain satisfactory surfaces.

Rubbed Finish (511.18)

When specified on the plans, rubbing shall be performed as outlined in 511.18.


Forms should be removed within 2 days after the concrete is placed.  Exceptions are the slab fascia form on which other fascia forms are set and wall forms that overlap a joint. If parapets are placed in cold weather, make provisions to remove forms and begin surface finishing on the day following placing, while maintaining a minimum temperature of 50° F (10° C), or postpone the placing of parapets until weather conditions are suitable for proper performance.

Grout Cleaning

Grout cleaning shall be performed as outlined in 511.18.

Float Finish

Concrete for sidewalks, safety curbs, and tops of substructure units are struck off with a template and finished with a float to produce a sandy texture.

Loading General

No traffic is to be permitted on a structure until the concrete has attained the age specified in 511.17.  For all spans this is 14 days without a beam test or 7 days with satisfactory beam test.

Loading of Completed Structure Units

No load is to be applied or work conducted that will damage new concrete.  This applies to loading or work on any part of the structure that will, in the opinion of the Engineer, cause damage.  Usually this criterion will permit work on a footing after 36 hours or sooner with a successful beam test, of normal curing where bending stresses will not occur.

Pay Quantity for Structure Concrete

The quantity of concrete for every reference number will be as determined from the plan dimensions, in place, complete and accepted with adjustments made for necessary changes or errors.  Plan dimensions shall be verified and recorded.

The final quantity for structure concrete is rounded off to the unit for the item that is listed in the proposal.  Where plan dimensions are in inches (mm), these should be converted to feet (m) and carried to a decimal place that will not affect the accuracy of the final unit.

Calculations made for necessary changes or plan errors are to be identified properly with the structure unit and reference number, and be validated by the signature or initials of the person who made the calculations and the date they were made.


Documentation Requirements - 511 Concrete for Structures

1.        Form dimensions and elevations field verified

2.        Forms clean and oiled

3.        Re-steel placed according to 509.04

4.        Concrete vibrated

5.        Record surface temperature inside of cold weather protection

6.        Forms and reinforcing steel heated to minimum 32° F (0° C) prior to placing concrete

7.        Amount of curing compound used and/or method of curing

8.        Placement and testing requirements documented on forms CA-C-1 and TE-45

a.        Place superstructure concrete when air temperature is 85° F (29° C) or less and not predicted to be above 85° F (29° C) during placement

b.        Evaporation rate as per 511.10

c.        On deck

d.        Document depth obtained on dry run

e.        Document depth obtained after final screed strike-off on day of pour

f.         Finish deck as per 511.19

g.        Smoothness requirements are outlined in 451.12.  A profilometer will be required to check smoothness

h.        Document saw grooves on surface as per 511.20.

9.        Loading as per 511.17

10.     Prepour meeting forms CA-S-4 and CA-S-6

11.     HP test slab acceptance

12.     If included results for HP Concrete Testing

a.        Rapid Chloride Permeability Test

b.        Drying Shrinkage Test

c.        Heat of Hydration Test