- 513 - SECTION 706 -- CONCR ETE BRIDGE FLOORS
706.01 Description
1.This work shall consist of providing all necessary materials and construction of concrete bridge floors in accordance with the contract and specifications.
706.02 Material Requirements
1.Reinforcement shall be furnished, handled, and placed in accordance with the requirements of Section 707.
2.White polyethylene film shall comply with the requirements of Section 1010.
3.Concrete retardants shall meet the requirements of Sections 1002 and 1007.
4.Concrete shall meet the requirements of Section 1002.
706.03 Construction Methods
1.Reinforcement Steel:
a.Before placing concrete for bridge floors, the placement of top reinforcing steel shall be checked for clear ance to the surface of the slab by measuring from the reinforcing steel to the strike-off screed.
b.Such checking shall be done by the Contractor in the presence of the Engineer and shall be repeated at a sufficient number of locations to demonstrate that concrete cover over the reinforcing steel as required in the contract will be obtained at all points on the slab.
c.Such checking does not preclude subsequent checks by the Engineer during and after concrete placement.
2.Environmental Conditions: a. The Contractor shall perfor m bridge floor construction in accordance with the requirements of Se ction 704. Bridge floor concrete shall not be placed when the anticipated wind velocity during the concrete placement period is expected to exceed the limitations shown in Table 706.01. Table 706.01 Temperature and Wind Velocity Limitations Air Temperature in the Shade Maximum Wind Velocity 90°F (32°C) 10 mph (16 kph) 77°F (25°C) 16 mph (25 kph) 68°F (20°C) 22 mph (35 kph) 59°F (15°C) 28 mph (45 kph) 50°F (10°C) 40 mph (65 kph)
b.Bridge floor concrete shall not be placed when the ambient air or concrete temperature is above 90°F (32°C).
706.03 Concrete Bridge Floors
- 514 - 3. Placement:
a.The Contractor's sequence of placing shall be as shown in the contract.
b.Placement of bridge floor co ncrete shall be continuous, and no delays are allowed between successive loads for any reason except at an expansion or construction joint.
c.Concrete slab bridge floors shall be placed and finished at a rate of at least 10 feet/hour (3 m/h).
d.Concrete bridge floors on steel girders, prestressed concrete girders, or prestressed double-tee beam s shall be placed and finished at a rate of at least 20 feet/hour (6 m/h).
4.Removal of Formwork: a. The Contractor shall notify the Engineer before releasing any temporary structural supports.
b.The Contractor shall remove falsework before placing concrete floors on steel spans.
c.The Contractor's floor and curb forms shall be supported entirely by the steel frame.
5.No work shall be performed on the bridge deck, including forming and placing reinforcement for concrete curbs or railing until the wet curing of the concrete deck is complete. Only equipment necessary for forming and pouring the bridge rail shall be allowed on the deck during the 7 days of white pigment curing.
6.Finishing: a. The Contractor shall fi nish concrete bridge decks and approach slabs with an approved mechanical, self-propelled finishing machine.
b.The finishing machine shall consist of one or more devices mounted on a rigid frame and be capable of striking off and finishing the surface either transversely or longitudin ally. Finishing machines shall be of sufficient size to finish the entire width of the bridge deck in one pass.
c.Finishing Machine: (1) The machine shall be supported on adjustable rails or tracks of sufficient strength to prev ent deflection between rail supports.
2.The rails should be installed outside the slab limits and shall be set and maintained true to the desired grade, line, and cross section during the entire finishing operation.
3.Rail supports shall be unyielding, and falsework or forms shall be strengthened as necessary to support the imposed load without deflection.
4.Rail supports located within the limits of the slab shall be constructed to allow their removal to at least 2 inches (50 mm) below the slab surface. The resulting holes in t he concrete slab shall be acceptably filled during the final finishing operation.
5.Supports shall not be welded to the girders. Concrete Bridge Floors 706.03 - 515 - d. The finishing machine shall make at least 2 passes over the bridge floor at such intervals as will give proper consolidation and produce the desired surface condition. The conc rete shall not be disturbed or worked further, except that any rema ining surface irregularities or mortar ridges shall be immediately removed by use of a long-handled float or straightedge.
e.The Engineer may require the Contractor to submit a complete description of the proposed method for handling, placing, and finishing the slab, including the equipment for trans porting and delivering the concrete, the finishing machine, and complete details of the supports for such equipment. Approval by the Engineer will not relieve the Contractor of the responsibility for the satisfactory performance of his/her methods and equipment.
7.Finishing Small Areas:
a.For finishing concrete slab widenings or other small or irregular deck areas, hand-finishing methods will be allowed.
b.After the concrete has been consolidated, as specified in Subsection 704.03, the surface shall be carefully struck-off with an approved screed to conform to the grade and cross section shown in the contract and to accurately match adjacent existing concrete surfaces.
c.The screed shall be advanced with a combined longitudinal and transverse shearing motion, moving always in the direction in which the work is progressing and manipulated so that neither end is raised from the side form or template during the process.
d.Excess concrete shall be maintained in front of the cutting edge to avoid creation of surface low spots.
e.The surface shall be floated using approved methods and equipment to remove all surface irregularities and to seal the surface. Special attention shall be given to areas adjacent to cons truction joints to achieve proper consolidation and surface finish.
f.Immediately after floating, the surface shall be tested with a 10 foot (3 m) straightedge. Any de pressions shall be filled with fresh concrete, struck off, consolidated, an d refinished. High areas shall be cut down and refinished. Special attention shall be given to areas adjacent to deck joints so that these surfaces are especially smooth.
8.Surface Texture: a. Immediately following the fi nishing machine, the Contractor shall give the bridge floor surfaces a drag finish with wet burlap, carpet, or a soft bristled broom. The drag finish shall create a uniform, fine-grained finish on the sealed concrete surface.
b.Grooving
1.When grooving is called for in the contract, transverse tining the plastic concrete of brid ge decks (and approac hes on new bridges and bridge deck replacements) will not be allowed.
2.The Contractor shall cut longitudinal grooves into hardened concrete surfaces using a mechanical cutting device. The Contractor shall perform longitudina l grooving after surface correction grinding.
706.03 Concrete Bridge Floors
- 516 - (3) The longitudinal grooves shall be:
i.1/8 inch ± 1/64 inch wide, (ii) 1/8 inch to 1/4 inch (3 mm to 6 mm) deep, and (iii) Uniformly spaced at 3/4 inch intervals measured center to center of groove.
4.Longitudinal grooving shall include both bridge and paving approaches. Grooving shall terminate approximately 6 inches (150 mm) from bridge expansion joints.
5.Longitudinal grooving on the bridge deck and approach sections shall be discontinued 3 feet from the bridge curb, rail, raised medians, or barriers unless otherwise indicated in the contract.
6.For phased bridge and bridge approach construction:
i.The Contractor may cut longitudinal grooves in the hardened concrete at the end of each phas e of construction or wait until all phases have been completed. If the Contractor elects to delay cutting of the longitudinal grooves until completion of all phases, the Contractor shall apply an interim broom finish on the concrete deck and bridge approach during placement for all phases opened to traffic. (ii) The Contractor shall finish all longitudinal grooving for all phases within 30 calendar days following completion of the last phase of the bridge. (iii) The interim broom finish will not be allowed as a surface texture when opened to traffi c over a winter season. If the interim broom texture is present a nd the Contractor is not in a position to finish all phases of the bridge, the Contractor shall cut longitudinal grooving into the hardened concrete in order to establis h an acceptable driving surface texture for the winter season.
7.Grooves shall be constructed using multi-blade saw cutting equipment, fitted with diamond-tipped circular saw blades.
i.Before grooving operations, two approved gauges to verify groove depth shall be supplied. The gauges shall be accompanied by the manufacturer’s instructions for their use. (ii) During grooving operations, the groove dimensions will be checked at random. If the minimum groove depth has not been achieved, grooving operations shall stop and the necessary adjustments shall be made.
8.Sidewalks and top of curbs shall not be grooved and shall receive a final finish with a fine – bristle broom.
c.Tining: (1) When grooving is not called for in the contract, bridge floors and approach slabs except those which are to receive a subsequent concrete overlay surface course shall also be tine textured. Tining shall consist of creating uniform, transverse gr ooves in the final concrete surface.
2.The grooves shall be appr oximately 1/8 inch (3 mm) wide by 1/8 inch (3 mm) deep, spaced 0.6 inch (15 mm) apart. Concrete Bridge Floors 706.03 - 517 - (3) Grooves shall be disconti nued at 2 feet (600 mm) from the bridge curb or rail.
4.A tining rake shall be used to texture the surface after the burlap or carpet drag finish. The use of a corrugated bull float or other device that creates a smooth finish between the grooves will not be permitted.
9.Curing a. For this Specification, the bridge deck is defined as the concrete deck and pavement cast between the bridge grade beams. Approaches outside the grade beams are excluded.
b.For complete deck replacements of girder and slab bridges: (1) The Contractor shall cure the concrete deck with wet burlap for at least 240 hours. Burlap with Polyethylene backing will not be allowed on decks unless allowed by the Engineer.
i.The Contractor shall place uniformly saturated wet burlap on the concrete no later than 20 minutes after the finishing machine passes. (ii) The burlap shall be thoroughly wetted prior to placing it on the concrete. The burlap shall be kept continuously wet by means of a sprinkling or wetting system for the 10 days. (iii) The wet burlap shall be secured or weighed down so that it remains in contact with the concrete surface. (iv) After 96 hours, t he Contractor may place white opaque polyethylene film over the wet bu rlap to reduce the amount of water needed.
2.After the 10 day wet cure, the Contractor shall apply an approved white pigment curing compound within 45 minutes of removing the wet burlap.
i.The total rate of combined applications shall be a minimum of 1 Gal/150 SF of surface area. (ii) The Contractor shall cure the deck with the white pigment curing membrane for an additional 7 days. The Contractor may work on the bridge concrete rail during the 7 days provided caution is used to limit damage to the membrane. (iii) Curing compound shall not be applied to construction joints or reinforcing steel.
c.For partial deck replacements and deck widenings; including approaches that are not part of a complete deck replacement:
1.The contractor shall place uniformly saturated wet burlap on the finished concrete within 20 minutes of finishing the concrete.
2.The contractor shall keep the burlap uniformly saturated for 96 hours.
3.After 96 hours, the Contractor may place white opaque polyethylene film over the wet burlap to reduce the amount of water needed.
706.03 Concrete Bridge Floors
- 518 - d. The Contractor must prov ide a list of equipment, equipment certification, and the number of personnel that will be dedicated to the curing operation at least 24 hours befo re the actual casting date.
e.The Contractor shall be respon sible for the repair of all visible cracks more than 3 inches (75 mm) in le ngth that develop on the bridge deck up to the time the project is accepted at no additional cost to the Department.
f.Cracks shall be repaired with a product from the Approved Product List for “Bridge Deck Crack Sealant”. The crack sealants shall be installed in accordance with the manufacturer’s recommendations.
g.Concrete Bridge curbs and rails shall be cured in accordance with Subsection 704.03.
10.Grinding a. The grinding and grooving shall not be done until after the 17 days of curing is complete.
b.Bridge decks shall be grou nd for smoothness in accordance with Section 733.
1.For bridge decks and approaches that are not covered by Section 733:
i.The Contractor shall test the cured concrete for surface irregularities with either a 10 foot straightedge placed or operated parallel to the centerline of the road way or some other device for measuring deviations from a plane. Variations gr eater than 1/8th inch shall be plainly marked for removal, except that for de cks which are to receive a subsequent overlay course greater than 1 inch thick, where 1/4 inch variations are allowed. (ii) The Contractor shall grind or cut irregularities that exceed the above limits. Bush hammeri ng or other impact methods are not allowed.
11.Retarders: a. Retarders may be used to aid concrete finishing. b. Retarders shall be used to establish a one hour delay in the concrete set time when the air temperature is 60ºF (15ºC) or higher.
1.Type B – Retarding Admixture or Type D – Water Reducing and Retarding Admixtures, as shown on the Department’s Approved Products List, shall be used.
2.Type A – Water Reducing Admixtures, as shown on the Department’s Approved Products Lis t, shall not be used as retarders.
c.Retarders are intended to keep the concrete from setting while construction loads are still at critical locations on the deck.
1.Dosage rates vary depending on the length of time the retardation needs to last and the air and concrete temperature.
2.Admixture suppliers shall supply recommendations for dosage rates for varying lengths of time and temperatures. Concrete Bridge Floors 706.04 - 519 - 12. Decks Overlays:
a.When the bridge floor is to receive a subsequent overlay course of high density, low slump conc rete, the Contractor shall form test wells into the concrete floor surface. Wells shall be 10 inches (250 mm) by 10 inches (250 mm) and set 1 1/2 inches (38 mm) below the floor surface.
b.The Contractor shall place te st wells at intervals not to exceed 50 feet (15 m), except at the point where placing starts. The first 3 wells will be placed at 5 foot (1.5 m) intervals.
13.Drainage: a. The Contractor shall furnis h and install deck drainage systems at the locations shown in the contract. This work includes drain boxes, pipes, anchors, supports, and connections.
b.Floor drains and appurten ances shall be fabricated from structural steel and/or ga lvanized standard steel pipe (schedule 40) meeting the requirements of ASTM A 36/A 36M or ASTM A 53 Grade B, respectively. After fabrication, floor drains and ap purtenances shall be galvanized in accordance with the applicable sections of ASTM A 123.
14.The Contractor shall paint a ll exposed metal, except weathering grade steel, as described in Section 709.
15.Time for Opening Bridge Floors to Public Traffic: a. The Contractor shall not op en the bridge floor to traffic until approval has been given by the Engineer. The Engineer may open the bridge when the concrete has reached a minimum age of 17 days and developed a minimum compressive strength of 3500 psi.
b.Construction equipment will not be allowed on the deck until after the 10 day wet curing period. Vehicles needed for construction activities and weighing less than 4.0 kips, and comparable materials and equipment loads, may be allowed on any span only after the last placed deck concrete has attained a compressive strength of at least 2.4 ksi. Loads in excess of the above shall not be carried on bridge decks until the deck concrete has reached 80% of the minimum compressive strength described in the contract and after the 10 days wet curing period.
706.04 Method of Measurement
1.a. The Department will pay contract quantity when items are constructed according to the contract geometrics.
b.The Contractor may request that the Departm ent recalculate the quantity for the concrete haunch, using the girder shim shots on a prestressed concrete girder bridge.
2.Drainage systems or floor drains will be measured as single units, complete and in place.
706.05 Concrete Bridge Floors
- 520 - 706.05 -- Basis of Payment
1.P a y I t e m P a y U n i t Concrete Class _____ for Bridges Cubic Yard (CY) [ C u b i c M e t e r ( m3)] Drainage System at Station ______ Each (ea) Floor Drains _____ Each (ea) Bridge Deck Grooving Square Yard (SY) [Square Meter (m 2)]
2.Finishing, curing, texturing, set retarders, and test wells are subsidiary to th e concrete floor.
3.Miscellaneous items that are list ed in the contract to be included in the complete structure, but for whic h separate items are not shown in the proposal and for which no direct payment has been provided, shall be incorporated in the structure and th e necessary work performed by the Contractor. Direct payment for such items will not be made, and they shall be considered as subsidiary to the relevant pay item.
4.If the recalculated concrete q uantity of the concrete haunch on a prestressed concrete girder bridge is greater than the contract quantity, the additional concrete quantity will be paid at 1.33 times the concrete invoice price. The Contractor shall furnish the Engineer signed invoices for the Concrete Class_____ for Bridges prior to the request for recalculating the concrete haunch quantity.
5.Payment is full compensation for all work described in this Section. - 521 - SECTION 707 -- REINFORCEMENT
707.01 Description
1.This work shall consist of furnishing and placing reinforcing steel as required by these Specifications and as shown in the contract.
707.02 Material Requirements
1.Reinforcing steel shall conform to the requirements as described in Sections 1020, 1021, 1023, and 1024.
2.Two samples of all reinforcing steel (coated and uncoated) shall be submitted to the Department's Materials and Research Division for testing. The length of each sample shall be 6 linear feet (1.8 m).
707.03 Construction Methods
1.Fabrication:
a.Reinforcing bars shall be shipped in standard bundles, tagged and marked in accordance with the Code of Standard Practice of the Concrete Reinforcing Stee l Institute. When reinforcing bars are not shipped from tested and approved stock, the identification of all reinforcing bars (manufacturer, heat number, and size) shall be maintained by the fabricator throughout the fabricatio n process to assure that the fabricated bars are identified with proper tags for final shipment to the job site.
b.The Contractor shall bend reinforcing bars without the use of heat to the dimensions and shapes shown in the contract, and bars having cracks or splits at the bends shall be rejected.
c.Epoxy Repairs: (1) The epoxy coated rebar shall be free of any cracking or debonding. The Contractor may repair epoxy coated reinforcing bars that show any visible evidence of cracking or disbonding of the coating in the bend area with approval of the Engineer.
2.Epoxy coatings cut, broken, or abraded shall be repaired before rusting of the bar occurs.
3.All patching shall be done as provided in Section 1021. d. All reinforcing steel sha ll be identified and tagged as required in Subsection 1021.03.
2.Protection of Material:
a.The Contractor shall protec t reinforcing steel from damage at all times. When placed in the work, the reinforcing steel shall be free from dirt, paint, grease, oil, rust, or other foreign substances. The Engineer shall be the final judge as to acceptability of the reinforcing material's condition.
b.Reinforcement with any appreciable reduction in section dimensions caused by corrosion will be rejected.
3.Placing and Fastening: a. The Contractor shall place all reinforcement in the position shown in the contract, and it shall be held securely in position.
Source: Nebraska Standard Specifications for Highway Construction, 2017 Edition. Pages 547–554 of 1,048.