2404Concrete Wearing Course for Bridges

2404.1DESCRIPTION

The Work consists of constructing a Portland cement concrete wearing course on a B ridge Structural Slab or approach panel.

2404.2MATERIALS

Provide a wearing course made of low slump concrete placed at least 2 inches deep in accordance with the following: A Low Slump Concrete Provide low slump concrete in accordance with 2461, “Structural Concrete,” and as modified by the following: A.1 Mix Requirements Provide 3U17A concrete in accordance with Table 2404.2-1 and the requirements of 2461, “Structural Concrete.” Use a Department approved Type A Water-reducing Admixture at the manufacturer’s recommended dosage rate to achieve the specified slump . Table 2404.2-1 Concrete Mix Design Requirements for 3U17A Mix Number Maximum W/C Ratio Water Content (pounds) Cement Content (pounds) Fine Aggregate Content (pounds) Coarse Aggregate Content (No. Pit Number/pounds)† percent Air Content Slump Range (inch) Minimum 28 Calendar Day Compressive Strength (psi) 3U17A* 0.32 270 836 1415 ǁ No. 06002-1369 No. 17001-1374 No. 52003-1364 No. 73006-1411 No. 87002-1385 No. 94009-1540 No. 94035-1530 6.5 1/2-1 5600 * Do not provide 3U17A containing fly ash or slag cement. ǁ Includes assumed 3 percent moisture. † Meeting CA-70 gradation as shown in Table 3137.2-4 and Class A coarse Aggregate meeting the requirements of 3137.2D.2, “Coarse Aggregate for Bridge Superstructure.”

B Bonding Grout Provide grout consisting of Portland cement mixed with water to form a slurry with the consistency of paint to bond the new concrete to the Bridge Structural Slab. Coat the in-place concrete, including vertical joints, immediately before placing the concrete wearing course.

2404.3CONSTRUCTION REQUIREMENTS

A General Provide Equipment to proportion, mix, place, and finish the concrete as approved by the Engineer. Place the concrete wearing course on the Bridge Structural Slab after the slab has cured for at least 7 Calendar Days unless the Contract requires a longer curing period for the Bridge Structural Slab. Place the concrete wearing course on the approach panels after the panels have cured for at least 72 hours. Mix concrete in accordance with the Concrete Manual requirements for the Equipment used. Mix the concrete until uniform in composition and consistency. Provide concrete at a rate allowing the finishing operations to proceed at a steady pace and completion of the final finishing in accordance with 2404.3D, “Concrete Placement and Texturing.” Provide placing and finishing Equipment, including adequate hand tools, to place and Work the concrete to the correct level for strike-off. B Finishing Machine Use a power-operated finishing machine approved by the Engineer and meeting the following requirements:

depositing the concrete on the Bridge deck and the final screeding no greater than 15 minutes

subsequently placed section and capable of overlapping the edge of a previously placed section at least 6 inches

reverse Demonstrate the capability of the finishing machine to produce results in accordance with 2404.3D, “Concrete Placement and Texturing,” under the Project conditions, unless otherwise directed by the Engineer. Place rails on the outside of the wearing course area to support the traveling finishing machine . Provide rail anchorages for horizontal and vertical stability . Do not ballistically shoot rail anchorages into concrete that will not be overlaid. After setting the rails to the grade and elevation shown on the Plans and before placing the concrete, check the clear distance from the bottom of the screed to the top of the prepared concrete surface in the presence of the Inspector. Attach a fill strip or other approved device to the bottom of the screed during this check to detect areas encroaching on the wearing course thickness shown on the P lans. Set sufficient screed rails to perform the clearance check in one continuous run over a distance equal to one complete day’s placement. Make corrections as directed by the Engineer to obtain the thickness shown on the Plans. When necessary, place longitudinal joints at the edge of Traffic Lanes as approved by the Engineer.

C Deck Preparation Within 48 hours before placing the concrete wearing course, clean the slab surface and shotblast the entire Bridge surface and approaches to be overlaid. Shotblast to remove surface film, laitance, fractured concrete particles, and other Materials that may impede the bond of the concrete wearing course. Remove the steel shot before placing the concrete wearing course. Control and abate the dust generated by the blasting operation meeting the requirements of MPCA Rule 7011.0150. Submit the proposed Plan for dust abatement to the Engineer at least 14 Calendar Days before starting the Work. Power sweep the Bridge and approach slabs before blasting. Use the least amount of water necessary to minimize the dust from the sweeping operation. Provide housing for the blast wheel or blasting nozzles meeting the following requirements and characteristics:

into a filtered collection system

within the housing by the blasting Equipment

the deck surface during blasting operations Clean the filter collection system to ensure proper filtration. Provide a housing and filter collection system constructed, maintained, and operated to eliminate avoidable dust emissions. After blasting, hand sweep or use a “pickup” type power sweeper equipped with adequate dust storage capacity to sweep the prepared surface. Remove minor debris remaining after the sweeping operation by air blasting. Provide an air supply system with an oil trap placed in the air supply line between the storage tank and the nozzle. Shotblast, sweep, and clean the Bridge Structural Slab before placing the concrete wearing course. Allow time for the Engineer to inspect the surface during daylight hours. After shotblasting the surface, the Engineer will perform a visual inspection of the B ridge deck, and locate cracks appearing on the top surface. Furnish only one of the Materials listed on the APL, Bridge, “Bridge surface and crack sealers.” Fill located cracks with an approved crack sealer following the manufacturer's recommendations, and as otherwise directed by the Engineer . Ensure the sealer is cured prior to preceding pre-wetting of the deck, as required for placement of a low slump concrete wearing course. Control the application of the crack sealer such that the maximum width of crack sealant does not exceed 3/4 inch. If exceeding the permitted width of 3/4 inch, remove excess by means of surface grinding to prevent debonding of concrete wearing course. Furnishing and placing the sealer on new structural slabs as specified above is included in the cost of the concrete wearing course. Payment for sealing cracks in existing Bridge Deck Slabs getting a new low slump wearing course as provided for in the Special Provisions. Within 12 hours of placing the concrete wearing course, use potable water to pre-wet the deck surface to a saturated surface dry condition (not absorbing water from or contributing water to the concrete mixture). Maintain the saturated surface dry condition for at least 6 hours. Do not allow free water on the surface when placing the bonding agent as stated in 2404.2B, “Bonding Grout.”

D Concrete Placement and Texturing Place and finish concrete at a linear rate, measured parallel to the centerline of the Bridge, of at least 40 feet per hour under normal working conditions. Do not place concrete wearing course placement widths greater than 28 feet. Place joints in the concrete wearing course directly above the original joints constructed in the Bridge Structural Slab and in accordance with 2401.3E, “Joint Construction.” Make saw cuts as soon as the concrete can be cut without raveling the surface and expeditiously to minimize the exposure of the uncured concrete to surface drying. Seal saw cuts with joint sealer in accordance with 3723, “Hot-Poured, Elastic Type Joint and Crack Sealer,” or 3725, “Hot-Poured, Extra-Low Modulus, Elastic Type Joint and Crack Sealer.” After consolidating, screeding, and floating the concrete, draw a carpet drag longitudinally along the pavement before the concrete attains its initial set. Adjust the carpet drag to produce a texture as approved by the Engineer. Use artificial grass type carpet drag meeting the following characteristics and requirements: mounted on a Work Bridge, a longitudinal length of 3 feet, width equal to the concrete placed, artificial grass type, molded polyethylene pile face, blade length of from 5/8 inch to 1 inch, total weight of at least 70 ounces per square yard. In lieu of the carpet drag texturing, the Contractor may use coarse broom texturing as approved by the Engineer. Immediately following the carpet drag, texture the Bridge Deck Slab surface with a metal-tine pattern. Install the transverse texturing (tining) on a slight diagonal, at an angle of approximately 10 degrees to a line perpendicular to the Roadway centerline, produced by using a device meeting the following characteristics and requirements:

thick

The Contractor may use other texturing Equipment that will produce an equivalent texture as approved by the Engineer. Do not texture within 1 foot of curbs or gutterlines. Do not extend tining into areas within 1 foot of a curb or gutterline. Ensure the final surface does not vary by greater than 1/8 inch within a 10 foot straightedge laid longitudinally on the final surface. This surface tolerance includes areas near expansion devices and other breaks in the continuity of the wearing course. Remove and replace the surface areas not meeting the tolerances specified above. Alternatively, grind the high spots on the surface areas not meeting the tolerances specified above as directed by the Engineer. The Department defines uncorrected nonconforming areas as unacceptable W ork in accordance with 1512, “Unacceptable and Unauthorized Work.” Place joint sealer Material of the type as shown on the Plans or Special Provisions in accordance with 2301.3N.3, “Joint Sealing.” If the National Weather Service predicts a daytime temperature of at least 80 °F for a scheduled concrete placement, reschedule the placement or begin the concrete placement between midnight and 5:00 a.m. Terminate placements at 5:00 a.m. that are started after midnight, but not completed by 5:00 a.m. if the ambient air temperature is at or above 80°F. If the air temperature is below 80°F at 5:00 a.m.,

the placement may continue until such time as the temperature reaches 80°F. Do not place concrete wearing course if the air temperature falls below 40°F or if the slab surface shows signs of frosting. Notify the Engineer at least 24 hours in advance of scheduling a night operation. Provide an area with a minimum of 50 foot candles of light to ensure quality workmanship and adequate inspection. Confirm the adequacy of lighting with a light meter. Except if heating and housing the concrete, do not place concrete for wearing courses in accordance with any of the following requirements:

The Contractor may place concrete for wearing course before April 15 or after September 15 or October 1 as specified above, if heating and housing the deck and performing the following:

maintenance of acceptable curing temperatures to the Engineer. Do not begin Work until the Engineer approves the cold weather protection Plan and all Materials identified in the Plan are on site

air circulation above the surface and protecting the concrete against freezing, rain, or snow

Provide insulation blankets or heating facilities to maintain the curing temperatures in item (4) below

or higher for the first 4 Calendar Days after concrete placement. Do not expose the concrete to temperatures lower than 40°F until at least 26 Calendar Days after the initial 4 Calendar Day period

as approved by the Engineer E Low Slump Concrete E.1 Mixer Requirements Provide mixing Equipment in accordance with 2461, “Structural Concrete,” except use a continuous mixer with metered proportioning capability. Complete the following:

is present during the test

on the job

E.2 Finishing Machine Requirements Provide a finishing machine meeting the following requirements and characteristics:

Install identical vibrators or pillow blocks with eccentric cams to provide at least one vibrator or source of vibration for each 5 feet of screed length. If only vibrating one screed, vibrate the front screed. Ensure the bottom face of the screed is at least 5 inches wide and contains a turned-up or rounded leading edge to minimize surface tearing. Ensure each screed produces a pressure of at least 75 pounds per square foot of screed area on the bottom face. Provide each screed with positive control of the vertical position, angle of tilt, and shape of the crown. Equip the finishing machine with an adjustable power-operated paddle or auger to strike off concrete in front of the first screed. E.3 Concrete Placement Scrub the bonding grout into the deck surface and adjacent contact points at a controlled rate (based on field conditions) to prevent drying before covering with the concrete wearing course. Mechanically strike off the concrete slightly above final grade before consolidating and screeding to final grade. Saw the wearing course at transverse and longitudinal joints to a straight, vertical edge . Remove trimmings before placing the adjacent wearing course. Do not operate impact Equipment in the adjacent lane during the first 72 hours after placing the concrete unless otherwise approved in writing by the Engineer. Use thinned bonding grout to seal vertical joints with adjacent in-place concrete surfaces after finishing and texturing to assure the vertical joint is sealed. E.4 Curing Requirements Coat the concrete with membrane curing compound in accordance with 3754, “Poly-Alpha Methyl Styrene (AMS) Membrane Curing Compound,” within 30 minutes after placing the concrete. Use an airless spraying machine containing the following:

Before application, agitate the curing compound in the shipping containers to obtain a homogeneous mixture. Apply the compound to provide a uniform, solid white, opaque coverage equal to a white sheet of paper on exposed concrete surfaces. Respray areas that appear to have a coating that is less than a white sheet of paper. Respray membrane film damaged before the placement of the wet cure. Apply the membrane curing within 45 minutes after depositing concrete if revibrating the concrete as directed by the Engineer. If the Contractor fails to apply membrane curing in the required time after depositing concrete, the Department will consider this as unacceptable W ork in accordance with 1512, “Unacceptable and Unauthorized Work.” Remove and replace concrete in areas not coated with membrane curing compound within the required time at no additional cost to the Department. As soon as the concrete can be walked on without damage, place wet burlap or curing blankets in accordance with 2401.3G, “Concrete Curing and Protection,” for a minimum of 4 Calendar Days. Maintain burlap in a wet condition for the entire curing period. After completion of the wearing course curing period and prior to opening to public, clean and evaluate cracking in accordance with2433.3C.2, “Deck Cleaning and Mapping Cracks.” Seal cracks in accordance with 2433.3C.1, “Bridge Deck Crack Sealing Process.”

The measurement will not be made for any of the following:

When 2433.3C.1 requires use of 2433.3C.5, “Methyl Methacrylate (MMA) Flood Seal,” the Department will share in the cost of MMA flood seal application by executing a Change Order compensation rate equal to $0.85 per square foot of concrete wearing course area sealed by MMA Flood Seal (methyl methacrylate). The compensation rate is compensation in full for all costs of furnishing and applying the sealer including surface preparation, traffic control, and all incidentals thereto. Do not allow vehicular traffic on the concrete wearing course during the 4 Calendar Day curing period. If the daily mean temperatures during the 4 Calendar Day curing period fall below 60°F, provide additional curing time before allowing traffic on the surface as required by the Engineer.

2404.4METHOD OF MEASUREMENT

The Engineer will measure the Concrete wearing course by surface area based on the dimensions shown on the Plans. The Engineer will not deduct the surface area of expansion devices or other miscellaneous appurtenances.

2404.5BASIS OF PAYMENT

The Department will pay for Concrete wearing course for Bridges on the basis of the following schedule: Item No. Item Unit

2404.518 Concrete Wearing Course (Mix Design) square foot