- 561 - SECTION 711 -- CONCRETE BRI DGE DECK REPAIR AND OVERLAY
711.01 Description
1.This work shall consist of the removal of the existing deck surfacing, resurfacing with class 47B-O L concrete, and other incidental work as shown in the contract.
2.A pre-placement conference at a time mutually agreed upon shall be held before the initial placement of Class 47B-OL concrete. Representatives of the admixture manu facturers, the concrete producer, the Contractor, and Materials and Research shall meet with the Engineer to discuss the following:
a.Mix proportions. b. Batching sequence. c. Batch size.
d.Work schedule.
e.Applicable specif ications and special notes.
f.All equipment that will be used. g. Delivery details. h. Special training for finishers. i. Duties of all personnel.
j.Overlay construction details.
k.Testing requirements. l. Acceptance criteria. m. Contingency plans. n. Methods of measurements. o. Basis of payment.
711.02 Material Requirements
1.Materials shall conform to the requirements in Table 711.01. Table 711.01 Material Requirements Applicable Materials Section Portland Cement Concrete ..................... 1002 Curing Material s ...................................... 1010, 1011 Sand and Gravel Aggregate .................. 1033 Ledge Rock Aggr egate ........................... 1033 Water for Concrete .................................. 1005
2.Ledge Rock aggregate for use in Class 47B-OL concrete shall be uniformly saturated with water before it is used. The wetting shall begin 24 hours before concrete mixing to allow complete saturation.
711.03 Equipment
1.Machines with oil leaks or drips shall not be used on the prepared deck surface.
711.03 Concrete Bridge Deck Repair and Overlay
- 562 - 2. Surface preparation equipment shall be of the following types:
a.Concrete saws capable of sawing to a specified depth.
b.Scarifying equipment capabl e of uniformly cutting the existing concrete surface to the depths required.
c.Sandblasting equipment able to remove rust and concrete from exposed reinforcing bars. The equipment shall also be able to remove loose and fractured particles from the prepared concrete surface.
d.Power-driven hand tools will be allowed with the following restrictions:
1.Jackhammers greater than the nominal 60 pound (27 kg) class shall not be used.
2.Jackhammers or chipping tools shall not be operated at an angle greater than 45 degrees measured from the deck surface.
3.Chipping hammers great er than the 30 pound (13.5 kg) class shall not be used to remove concrete from beneath reinforcing bars in Class II repair.
3.The placing and finishing equipment shall include adequate hand tools for distributing the plastic mix an d working it down to approximately the correct level for striking off with the screed. Approved hand-operated vibrators may be used in small, otherwise inaccessible areas.
4.Finishing Machine: a. An approved finishing machine shall be used. It shall comply with the requirements of Section 603 and the following additional requirements.
1.The finishing machine shall consist of 1 or more devices mounted on a rigid frame, capable of striking off and finishing the surface either transversely or longitudinally. Finishing machines shall be of sufficient size to finish the entire width of the bridge deck in 1 pass.
2.The finishing machine shall be equipped to travel on rails. (i) The machine shall be supported on adjustable rails or tracks of sufficient strength to prev ent deflection between rail supports. (ii) 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. (iii) Rail supports shall be unyielding, and falsework or forms shall be strengthened as necessary to support the imposed load without deflection. (iv) Rail supports located within the limits of the slab shall be constructed to allow their removal to at least 2 inches below the slab surface. The resulting holes in the concrete slab shall be acceptably filled during the final finishing operation.
v.Supports shall not be welded to the girders. (vi) Rails shall be securely anchored to provide stability in all directions. The method of anchor ing shall not damage the concrete Concrete Bridge Deck Repair and Overlay 711.04 - 563 - overlay. Supports for rails shall be fully adjustable (not shimmed) to obtain the correct profile.
b.The finishing machine shall be self-propelled, capable of forward and reverse movement under positive control, and shall have provision for raising the screeds to clear the work when traveling in reverse.
c.When placing concrete in a lane abutting a previously completed lane, that side of the finisher adjacent to the completed lane shall be equipped to travel on the completed lane.
d.Design of the finishing machine and associated equipment shall be such that positive machine finishing of the plastic concrete will be obtained as near the face of existing cu rbs as is possible. The length of the finishing shall be sufficient to extend at least 6 inches beyond the line where a saw cut is intended to form the edge of a subsequent placement and shall overlap the sawed edge of a previously placed lane at least 1 inch.
e.Design of the finishing machine and associated equipment shall be such that positive machine finishing of the plastic concrete will be obtained within 6 inches of the face of existing curbs.
f.The machine shall be inspected and approved in advance of the start of concrete placement.
711.04 Construction Methods
1.Concrete Removal Requirements:
a.The Contractor shall remove, scarify, or chip the old concrete deck to the depths indicated in the cont ract and until all unsound concrete is removed. Where scarifying equipment cannot be used, hand chipping will be required.
b.At points where removal of unsound concrete is adjacent to reinforcing bars or the removal of unso und concrete leaves over two-thirds of the bar diameter exposed, the remova l shall be continued to at least 3/4 inch below the bar that will allow new concrete to bond to the entire periphery of the exposed bar.
1.Care shall be exercised to prevent cutting or otherwise damaging any exposed reinforcing bars. Repairs to damaged reinforcing steel shall be performed at no expense to the Department. Additional concrete removal and replacement necessary to repair damaged bars shall be at no expense to the Department.
2.Any damaged epoxy coating of existing reinforcing steel shall be repaired according to Subsection 1021.03.
c.Any removals shall be carefully done to prevent damage to the bottom of the adjacent slab and to leave removal boundaries which will allow complete filling with plastic concrete.
d.The Contractor shall take al l necessary precautions to prevent damage to persons or property beneat h the structure from falling rubble.
e.Removal work is divided into 3 classes according to the depth of material removed:
1.Class I Repair - covers concrete remova l from the deck surface to a depth shown in the contract (varies with each project).
711.04 Concrete Bridge Deck Repair and Overlay
- 564 - (2) Class II Repair - covers concrete removal from the lower limit shown in the contract for Class I Repair to the mid-depth of the deck.
3.Class III Repair - covers c oncrete removal depths from the mid depth of the slab throug h the entire remaining deck.
f.Where machine scarifying is employed to remove concrete, extreme care shall be used to avoid cutting reinforcing bars. An occasional bar may be cut to as much as 25% of its diameter without impairing the structure; but if a substantial num ber of bars are damaged, machine scarifying will be prohibited and other methods required. Any damage caused by the Contractor shall be repair ed by the Contractor as directed by the Engineer at no additional cost to the Department.
g.Class III Repair:
1.Wherever removal of unsound concrete extends to a depth exceeding 50% of the original de ck thickness, the remaining thickness shall be removed to the full depth of the slab; and such areas of removal shall be classified as "Class III Repair".
2.When concrete removal is at approximately mid-depth of the slab, the Engineer shall determine if, in his/her judgment, the concrete quality and structural integr ity of the remaining thickness requires full depth removal.
h.Any concrete removal which is necessary to allow striking the full required overlay thickness down to meet roadway joints, floor drains, or other fixtures will be considered to be "Class II Repair".
2.Preparation of the Surface:
a.The Contractor shall sandblast and clean all exposed reinforcing bars, all prepared concrete surfaces, the portion of the bridge curb and all surfaces of steel roadway joints which will be in contact with the overlay concrete, and all edges of previ ously placed lanes not more than 24 hours before concrete placement.
b.Partial placements shall be given a 72-hour wet-burlap cure and shall be sandblasted and cleaned before proceeding with the general concrete overlay.
c.In cases where the placem ent of the overlay concrete is delayed beyond 24 hours after the sand blasting has been completed, the formation of incidental rust on the rebars due to humidity or rain shall not be cause for re-sand blasting.
d.All debris and rubble resulting from deck removal shall be thoroughly swept up and disposed.
e.Any areas of the prepared deck surface contaminated by oil leaks or substances detrimental to a good bond shall be thoroughly cleaned by an approved detergent method or s hall be removed to such a depth as may be necessary.
f.All reinforcing steel which does not have sufficient clearance shall be depressed and fastened down. If necessary, concrete shall be removed beneath reinforcing bars to allow depressing the bars. Concrete so removed shall be classified as Class II Repair. If the areas where reinforcing bars lack sufficient clearance are extensive, the Engineer may modify the Concrete Bridge Deck Repair and Overlay 711.04 - 565 - profile grade to obtain the desired clearance without depressing the reinforcing bars.
g.No loads other than construction equipment shall be allowed on any portion of the concrete de ck which has undergone preparation and removal of the old concrete surface. No construction load will be allowed which exceeds either an 8,000 pound wheel load or a 16,000 pound axle load. Any combination of axles closer than 4 feet center-t o-center will be considered to be one axle.
3.Forming:
a.Forms shall be provided in areas of Class III Repair requiring full depth slab replacement. Forms for small areas (1 square yard or less) may be wired to the reinforcing bars for support. Forms for larger areas shall be supported by blocking from the beams.
b.Construction Joints: (1) Longitudinal construction joints shall be provided as shown in the contract. If not shown, locations will be subject to the Engineer's approval. Longitudinal joints shall not be located in the traffic wheel paths if avoidable.
2.A transverse construction joint shall be constructed in case of a delay in the placement operations exceeding 30 minutes.
i.Transverse construction joints shall be minimized. (ii) These joints shall be made against a bulkhead. (iii) These joints must be sawed back as described in this Subsection.
3.At transverse and longitudinal construction joints, the edge of the previously placed concrete s hall be sawed back to a straight and vertical edge before all abutting concrete is placed. Slurry from wet sawing shall be thoroughly removed from the prepared deck surface.
4.Bulkheads or steel dam plates to be used at roadway joints shall be installed to accurate grade and crown.
4.Proportioning and Mixing: a. Portland cement concrete shall be supplied by certified Ready Mix Plants that are in compliance with the requirements in the Quality Control Manual, Section 3, -- Certif ication of Ready Mixed Concrete Production Facilities published by the National Ready Mixed Concrete Association. Refer to the Department’s Material Sampling Guide for the policy on stationary and portable plants.
b.The high range water reducer (Type F) may be added on the project site. The admixture shall be spread over the entire concrete surface inside the mixing truck and then mixed.
c.The testing for slump shall commence after the concrete is discharged and shall be performed as frequently as necessary to maintain control. The maximum allowable slump shall be 7 inches. There shall not be more than 2 inches of slump difference between any of the loads of concrete placed. The slump shall be increased by the addition of Type F, high range water reducer.
711.04 Concrete Bridge Deck Repair and Overlay
- 566 - d. Water shall not be added at the project site. Only enough water to rinse the charging hopper and fins after the addition of the admixture is allowed. This water must be estimated and recorded on the batch ticket.
5.Placing Concrete:
a.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.
b.Individual areas of Class III removal re quiring full depth slab placement shall be poured on forms. Any such areas exceeding 1 square yard (square meter) will require two-stage concrete placement. The first stage shall be poured up to the lower limit of Class I removal area or to match adjacent areas of Class II removal. This partial placement shall be made with Class 47B-OL concrete with a compressive strength of 4000 psi.
c.The Contractor shall thoroughl y clean the deck, then saturate it with water 2 hours before concrete placement. Immediately before placing 47B-OL concrete, the deck shall be in a damp condition. Any excess water shall be removed.
d.The delivery truck may be positioned on the prepared deck to discharge the concrete directly in front of the finishing machine or may be located off the bridge deck and the concrete transported to the finisher by means of an approved system. In eit her case, equipment and operations shall be closely observed to ensure that no foreign materials are brought onto the prepared and cleaned deck surface.
e.Concrete placement shall be continuous. The forward speed of the finishing machine shall be adjust ed to the average progress of the concrete production in order that t he strike-off operations shall be as continuous and uninterrupted as possibl e. Hand finishing with a wood float may be required to produce a tight uniform surface.
f.The elapsed time between depositing the concrete on the deck and screeding shall not exceed ten minutes.
g.During delays of 30 minutes or less, the concrete that is placed in front of the paver sha ll be protected from drying by fogging, wet burlap or others means approved by the engineer . Concrete that has been discharged in front of the paver more than 30 mi nutes shall be removed. The concrete overlay may be resumed only after 72 hours of cure has elapsed. This restriction does not prohibit continuat ion of the concrete placement provided a gap is left in the overlay. This gap shall be sufficient in length to allow the finishing machine to clear the previously placed concrete.
h.The Contractor shall proportion , mix, place, and finish at least 2 1/2 CY/hr.
i.The finishing machine shall be operated so that the time between the screeding of the concrete on the deck and finishing shall not exceed 10 minutes. Concrete Bridge Deck Repair and Overlay 711.04 - 567 - 6. Consolidation Requirements:
a.All fresh concrete shall be internally vibrated in addition to surface screeding.
7.Finishing Requirements: a. The Contractor shall finish concrete bridge decks with an approved mechanical, self-propelled finishing machine.
1.Rails for the finishing machine shall be set to the grade established by the Engineer to achi eve the desired profile and to produce the minimum required overlay thickness over all points on the prepared deck surface. Before beginning concrete placement, a block with a thickness equal to the minimum overlay thickness shall be attached to the finishing machine screed and the machine oper ated over the prepared deck. All concrete failing to clear the block shall be removed.
2.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 concrete shall not be disturbed or worked further, except that any remaining surface irregularities or mortar ridges shall be immediately removed by use of a long-handled float or straightedge.
b.The addition of water directly to the surface during the finishing operations will not be allowed, but the use of an admixture finishing aid is allowed.
8.Smoothness:
a.The floor surface shall be tested for smoothness with a 10 foot straightedge while the concrete is still plastic.
b.The 10 foot straightedge sha ll be held in successive positions parallel to the road centerline and in contact with the surface.
c.The whole area shall be tested from one side of the floor to the other as necessary. The 10 foot straig htedge shall be advanced along the deck in successive stages of not more than one half its length.
d.Any depressions found shall be immediately filled with freshly mixed concrete, struck off, and refinish ed. High areas shall be cut down and refinished.
e.The straightedge testing and refloating shall continue until the entire surface has no deviations from the 10 foot strai ghtedge that are greater than 1/8 inch and the floor has the required grade and contour.
f.When the surface area is so small it will not allow use of a 10 foot straightedge, special tools shall be employed to ensure that there are no deviations in the required longitudinal gr ade or contour lines in excess of 1/8 inch in 10 feet.
9.Surface Texture: a. 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.
b.The texturing requires 1/8 inch deep transverse grooves approximately 1/8 inch wide and spac ed at 1/2 to 3/4 inch on center.
711.04 Concrete Bridge Deck Repair and Overlay
- 568 - c. This operation shall be done at such time and in such manner that the desired texture is achieved with a minimum displacement of coarse aggregate particles.
d.The textured surface shal l be discontinued 2 feet from the bridge curb.
e.As soon as finishing has been completed, all vertical joints with adjacent concrete shall be sealed by painting with thinned grout. Before sealing, the adjacent surface shall be sandblasted or water-blasted to remove all dirt, curing compound residue, laitance, and any other foreign material.
10.Curing: a. The Contractor shall incr ementally apply white-pigmented curing compound within 30 minutes afte r the finish machine passes over the concrete. The application rate shall be a minimum a 1 Gal/100 SF of surface area for tined surfaces or 1 Gal/150 SF of surface for all other finishes.
b.The surface shall be covered with wet burlap as soon as it will support a single layer of wet burlap without deformation. Care shall be exercised to ensure that the burlap is well drained and that the surface is not damaged.
c.The Contractor shall cure t he concrete with wet burlap for at least 168 hours. The burlap shall be ke pt continuously wet by means of a sprinkling or wetting system. However, after 72 hours, the Contractor may cover the wet burlap with a layer of 4 mils polyethylene film for a minimum of 96 hours in lieu of continuing the sprinkling or wetting system. The polyethylene film shall be fastened down along all edges throughout the curing period to prevent drying. Polyethylene film shall meet the requirements of Section 1010.
d.The 168 hours of curing ti me shall be counted when the overlay in place temperature is 40° F or greater. Hours during which the concrete temperature is below 40°F will not be counted as acceptable curing hours.
e.Adequate precautions shall be taken to protect freshly placed concrete from sudden or unexpected rain. The Engineer may order removal of any concrete damaged by rain.
11.Environmental Conditions: a. Evaporation Rates: (1) Class 47B-OL concrete for bridge deck overlays shall be placed when the rate of evaporation will not exceed 0.15 lb/SF/h.
2.The initial rate of evaporation will be obtained by measuring the relative humidity near the deck, the wind velocity, the air temperature, and the deck concrete temperature.
3.The fresh concrete temperature will be used in place of the deck temperature once placement has begun for calculating the evaporation rate.
4.After the concrete paving operation has begun, if the rate of evaporation exceeds 0.15 lb/SF/h, white-pigmented curing compound shall be applied immediately behind the finishing operation. Concrete Bridge Deck Repair and Overlay 711.04 - 569 - (5) The Contractor must notify the Engineer regarding additional actions that will be taken to prevent plastic shrinkage cracking.
6.The rate of evaporation shall be obtained by using the nomograph shown in Figures 711.01.
b.Temperature:
1.Class 47B-OL concrete for bridge deck overlays shall not be placed when the ambient air temperature is above 77°F.
2.Unsuitable climatic conditions may require that the concrete be placed at night.
3.The Contractor shall provide adequate lighting for any night work.
12.The Contractor shall paint a ll exposed metal, except weathering grade steel, as described in Section 709.
13.Time for Opening Bridge to Traffic: a. The Contractor shall not open the bridge deck to traffic until approval has been given by the Engineer. The Engineer may open the bridge deck when the concrete has reached a minimum of 7 days and has developed a compressive strength of 4000 psi.
b.Construction equipment m eeting legal load limits will be allowed on the deck for bridge work after the 7 day wet curing period provided the deck has achieved a minimum 3500 psi compressive strength.
14.Acceptance: a. Compressive strength tests shall be made in accordance with ASTM C 39. The 28-day compressive strength shall be 4,000 psi.
b.Before opening for traffic, the new overlay will be examined by the Engineer using visual and soundi ng techniques. All areas that are not bonded to the underlying deck will be removed to sound concrete and repaired at no additional cost to the Department.
c.The Contractor shall be responsible for repair of all visible cracks more than 3 inches in length t hat develop on the bridge deck up to the time the project is accepted at no additional cost to the Department.
d.Cracks shall be repaired wi th an approved bridge deck crack sealant (methacrylate). Crack sealants shall be installed in accordance with the manufacturer’s recommendations.
e.The Contractor shall take every reasonable precaution to produce a smooth-riding concrete surface.
1.Immediately after the curi ng period is completed, the deck surface shall be tested for surface irregularities with a 10 foot straightedge or other device for measuring deviations fr om a plane. High spots in excess of 1/8 inch in 10 feet shall be plainly marked. The Contractor shall eliminate such high spots by the use of grinding equipment in accordance with Section 733.05, Paragraph 2.
2.The surfaces adjacent to longitudinal construction joints shall also match within 1/8 inch. Irregul arities greater than 1/8 inch shall be removed by grinding to provide a smooth transition over the joint.
711.04 Concrete Bridge Deck Repair and Overlay
- 570 - (3) Surface defects shall be co rrected by the Contractor at no additional cost to the Department.
711.05 Method of Measurement
1."Class I Repair", "Class II Repa ir", and "Class III Repair" will be measured for payment by the square yards of deck area repaired in accordance with each classification, as determined by field measurements.
2."Placing, Finishing, and Curing Concrete Overlay – 47B-OL" will be measured for payment by the square yards of deck surface overlayed as determined by field measurement.
3."Concrete for Overlay – 47B-OL" shall be measured for payment by the cubic yards of concrete placed in the structure (based on truck load tickets). Unacceptable concrete and an y waste shall be deducted from the volume for which payment is made.
4.The plan quantity for “Concr ete for Overlays - 47B-OL” is determined by the area of the deck time s the depth of class 47B-OL overlay. Additional quantities of class 47B-OL concrete may be required to complete any Class II repairs. Additional quantities of class 47B-OL concrete may also be required to complete any Class III repairs that are under one square yard. The pay quantity of class 47B-OL will be based on the actual amount measured in the field. Concrete Bridge Deck Repair and Overlay 711.05 - 571 - EVAPORATION NOMOGRAPH TO USE THIS CHART:
1.Enter with air temperature, move up to relative humidity.
2.Move right to concrete temperature.
3.Move down to wind velocity.
4.Move left: read appr ox. rate of evaporation. IF THE EVAPORATION RATE EXCEEDS 0.15 lb/sf/h, THEN THE CONTRACTOR SHALL TAKE ACTIONS TO PREVENT PLASTIC SHRINKAGE CRACKING. Figure 711.01
711.06 Concrete Bridge Deck Repair and Overlay
- 572 - 711.06 -- Basis of Payment
1.P a y I t e m P a y U n i t Concrete for Overlay – 47B-OL Cubic Yard (CY) [ C u b i c M e t e r ( m3)] Placing, Finishing, and Curing Square Yard (CY) Concrete Overlay – 47B-OL [Square Meter (m 2)] Class I Repair Square Yard (CY) [Square Meter (m2)] Class II Repair Square Yard (CY) [Square Meter (m2)] Class III Repair Square Yard (CY) [Square Meter (m2)]
2.Payment is full compensation for all work described in this Section. - 573 - SECTION 712 -- FIXED BEARINGS AND EXPANSION BEARINGS, PTFE TYPE
712.01 Description
1.The Contractor shall furnis h and install fixed bearings and polytetrafluoroethylene (PTFE) type expansion bearings at the locations shown in the contract.
2.The fixed bearings and expansion bearings, PTFE type, shall consist of the upper and lower assemblies shown in the contract. Prior to fabrication, the Contractor shall submit shop drawings to the Engineer for review.
712.02 Material Requirements
1.Fixed Bearings:
a.Upper Assembly: (1) The upper assembly shall consist of a sole plate conforming to the requirements of ASTM A709/A709M grade 50W (345W ) weathering steel. All flame cut edges of the sole plate shall be ground to reduce hardness. All corners of the so le plate shall be rounded to a 1/16 inch (1.5 mm) radius.
2.As an alternate, the sole plate may be ASTM A36/A36M grade 36 (250) steel, metallized. If the ASTM A36/A36M grade 36 (250) alternate is used, all flame cut edges of the sole plate shall be ground to reduce hardness and facilitate blast cleaning. All corners of the sole plate shall be rounded to a 1/16 inch (1.5 mm) radius. All exposed surfaces shall be blast cleaned to a near white finish and zinc metallized with a minimum thickness of 8 mils (200 mm). Zinc metallizing must be performed in accordance with American Welding Society Specification AWS C2.2.
b.The lower assembly shall consist of a cotton duck reinforced elastomeric pad (CDP) conforming to the requirements of the current AASHTO LRFD Specifications for Highway Bridges and the Department of Defense Specificat ion MIL-C-882.
2.Expansion Bearings, PTFE Type:
a.Upper Assembly:
1.The upper assembly shall consist of a sole plate conforming to the requirements of ASTM A709/A709M grade 50W (345W) weathering steel with an ASTM A240/A240M Type 304 stainless steel plate (at least 16 gauge when the maximum dimension of the surface is less than or equal to 12.0 in. and at least 13 gauge when the maximum dimension of the surface is larger than 12.0 in.) atta ched to the lower surface. All flame cut edges of the sole plate shall be ground to reduce hardness. All corners of the sole plate shall be rounded to a 1/16 inch (1.5 m) radius.
2.As an alternate, the sole plate may be ASTM A36/A36M grade 36 (250) steel, metallized. If the ASTM A36/A36M grade 36 (250) alternate is used, all flame cut edges of the sole plate shall be ground to reduce hardness and facilitate blast cleaning. All corners of the sole plate shall be rounded to a 1/16 inch (1.5 m) radius. All exposed surfaces shall be blast cleaned to a near white finish and zinc metallized with a minimum thickness of 8 mils (200 mm). Zinc metallizing must be performed in accordance with American Welding Society Specification AWS C2.2.
Source: Nebraska Standard Specifications for Highway Construction, 2017 Edition. Pages 595–606 of 1,048.