255 SECTION 602
602.01 Description
This work consists of the construction of bridges, cast-in -place box culverts, and cast-in -place retaining walls.
602.02 Equipment
A.General. Do not use aluminum tremies, forms, hoppers, downspouts, or chutes. Use a batch plant and equipment as specified in Section 155, “Concrete Equipment”.
B.Deck Finishing Equipment. Use a deck finishing machine as specified in Section 155.07 C, “Bridge Deck Finishing Equipment ”.
C.Sandblasting Equipment. Use compressed air type sandblasting equipment to clean concrete surfaces.
D.Water -Washing Equipment. Use water washing equipment that meets the requirements of one of the following: − A water pressure washer with a minimum of 160°F water at 1,800 psi minimum nozzle pressure; − A hydroblast washer using water at 7,000 psi minimum nozzle pressure; or − A steam cleaning unit using a minimum of 320°F water at 305 psi minimum operating pressure.
E.Curing Concrete. Use a fogging machine as specified in Section 156.02, “Fogger” for exposed surfaces.
F.Shot Blasting Equipment. Use centrifugal or wheel type shot blasting equipment that is designed to clean concrete surfaces and leave no oil or other foreign material on concrete surfaces. Use a shot blaster capable of collecting blast media and dust.
602.03 Materials
A.General. Item Section Portland Cement Concrete 802 Epoxy Resin Adhesives 806.02 Burlap Cloth 810.01 A Penetrating Water Repellent 822 Preformed Expansion Joint Fillers 826.02 C , D, or F Sealant 826.02 B.1 256 B. Waterproof Membrane. Provide self-adhesive b lack polyethylene membrane that meets the following requirements: - Has sheeting with a minimum thickness of 0.004 inch; and - Has rubberized asphalt coating with a minimum thickness of 0.056 inch.
602.04 Construction Requirements
A.Falsework.
1.Design and Construction. Design, construct, and maintain structurally adequate falsework. Do not adjust falsework after the concrete reaches its initial set.
2.Removal of Falsework. Leave supporting wedges and falsework in place for 14 days or until the concrete has reached 70 percent of the design strength. Remove all falsework. Uniformly lower the falsework to avoid excessive stresses in any part of the structure. Backfill and com pact all open excavations resulting from the construction and removal of falsework as specified in Section 210, “Structural and Channel Excavation, Foundation Fill and Preparation” with approved material at no additional cost to the Department.
B.Forms.
1.Design and Construction. Design, construct, and maintain forms. Use forms that are clean and in good condition. Construct the forms to be mortar tight and to have a smooth surface. Use forms that are impervious to water when using tubes for column forms or to produce voids. Use deck forms that have adjustable positive risers. Perform initial adjustments to the d eck form risers after all beams are in place. Perform final adjustments to the deck form risers after placing reinforcement. Form a 3/4 inch chamfer at all permanently exposed corners of the structure. Before placing concrete, treat forms with a form release agent that will not adhere to or discolor the concrete. Do not allow the release agent to come in contact with the reinforcing steel. Use steel or fiberglass form ties. Only use steel ties that are entirely removable, or removable to a depth of at least one inch below the finished concrete surface. Fill marks caused by steel form ties with grout meeting the requirements of Section 806.01, “Rapi d- Hardening Cementitious Materials” . Grind all fiberglass breakoffs flush with the concrete surface. Do not use wire ties. 257 If the bottom of the forms are inaccessible, provide temporary openings for cleaning out all extraneous material before placing conc rete.
a.Wood Forms. For exposed surfaces construct forms using dressed lumber of uniform thickness lined with smooth sheathing. Plywood shall be of maximum sizes that can be cut from standard size sheets. The Engineer will allow use of undressed lumber forms for unexposed surfaces.
b.Steel Forms. Use steel forms that are free from rust, grease, and substances that may discolor the concrete.
2.Removal of Forms. Leave deck slab forms in place for a minimum of 14 days and a maximum of 28 days after concrete is placed. Leave forms other than deck slab forms in place until the 7 day or 10 day curing period is complete.
C.Placing Concrete.
1.Placement.
a.General. After all preparations are complete, notify the Engineer a minimum of 24 hours before placing concrete. Remove deleterious material inside the form area, before placing concrete. Do not place concrete on or against frozen ground. Remove struts, stays, and braces used to temporarily hold forms in correct shape and alignment when fresh concrete reaches the elevation that makes them unnecessary. Place and consolidate concrete without causing segregation of the aggregates. Place concrete in continuous horizontal layers. Place subsequent layers of concrete before the preceding layer attains initial set. Place concrete as close to the final position as possible. If the placement location or the dimensions of the forms prevent the use of chute s or tremies and concrete must be placed with a free fall greater than 5 feet, use placement methods that prevent segregation of the concrete. If necessary, extend open chutes down inside the forms or through holes left in the forms. Arrange chutes to avoid steep slopes. When steep slopes are necessary, terminate the chutes into a hopper with a vertical downspout or equip the chutes with baffle boards made in short lengths that alter the direction of movement of the concrete. Keep tremies full of concrete during placement. Keep the lower end of the tremie buried in the concrete throughout the pour. When placing concrete in caisson foundations, bury the lower end of the tremie at least 5 feet in the concrete throughout the pour. The Engineer will allow concrete to be pumped from the mixer or the truck to the point of deposit in the forms. When pumping deck concrete use a 90 degree elbow with a minimum of 10 feet of flexible conduit placed horizontally. Use one of the following configurations at the discharge end in other locations: − An S-shaped configuration or − A 90 degree elbow with a minimum of 10 feet of flexible conduit placed horizontally.
b.Foundations and Substructures.
1.General. Use a wooden template to strike off unformed upper surfaces. Force the coarse aggregate below the surface. Work the surface with a wooden or cork float to obtain a fine -grained, smooth texture. Do not use mortar topping.
2.Column or Wall Placement. Place concrete in one continuous operation. Allow the concrete to reach 70 percent of design strength, determined from cylinder breaks , before placing pier cap reinforcing and concrete.
3.Foundation Seal Concrete. The Engineer may allow placement of foundation seal concrete. Submit work drawings that include buoyancy calculations. The Engineer will determine if the designed piling can support the additional weight. If the placement of foundation seal concrete is allowed, place the concrete as follows : − In a manner so the water remains still during placement and curing; − With cement content 10 percent greater than normally required for the class of concrete specified; − With a method that prevents segregation; − Continuously from start to finish; − Keeping the surface of the concrete horizontal; and − Without manipulating the concrete during placement. Remove all concrete that interferes with clearance required for reinforcing steel placement for the permanent structure.
c.Deck Placement . Do not place deck concrete until all the previously placed substructure concrete is at least 14 days old or has reached 70 percent of the design strength based on cylinder breaks . Build the deck to the designated thickness. Make the required adjustments in deck elevation and riser dimensions to accommodate the variations in the camber of beams and girders. 259 Before concrete placement, move the finishing machine across the rails to check and adjust the screed to ensure proper cross slope, concrete deck thickness and cover over the reinforcing steel. If concrete placement is to occur after an interim or final completion date in the contract, consult with the Engineer and the Department’s Bridge Division to determine a course of action to complete the work. Do not start placing concrete if inclement weather is anticipated at any time during the concrete pour up until the time of initial set. Carry a uniform quantity of concrete in front of the screed for its entire length. Place deck concrete between designed construction joints in one continuous operation and at a minimum rate of 25 cubic yards per hour. Place concrete curbs and rails in one continuous operation. If an emergency occurs in which the concrete placement operations are stopped with the approval of the Engineer, install a keyed transverse construction joint at a location determined by the Engineer. Remove all concrete beyond the joint. If corrective measures are not feasible and the deck is not within the specified tolerances, remove the unacceptable work. Allow the concrete to cure for a minimum of 72 hours before continuing concrete placement.
2.Vibration. Consolidate the concrete using an internal or external vibrator. Ensure the vibration does not displace reinforcing steel or forms. Vibrate for a sufficient duration and intensity to thoroughly consolidate the concrete without causing segregation. Use vibrators capable of visibly affecting the concrete mixture a distance of at least 18 inches from the vibrator. Do not apply vi bration directly to reinforcement that extends into non-plastic sections or layers of concrete. Do not use vibrators for moving concrete in the forms.
3.Removal of Excess Mortar. Keep reinforcing steel and surfaces of forms free from accumulations of mor tar from previously placed concrete. Clean reinforcing steel without damaging or breaking the concrete-steel bond at and near the surface of the previously placed concrete. Keep surfaces of previously placed concrete clean.
4.Weather Limitations. Obtain the Engineer’s approval to place concrete if the air temperature is expected to fall below 40°F during the curing period specified in Section 602.04 F, “Curing Concrete” . Submit a written request that includes provisions for maintaining the required curing temperatures. The Engineer’s acceptance of the written request does not relieve the Contractor of the obligation to remove and replace concrete that is damaged due to not maintaining concrete tem perature within the required range during the curing period. 260 D. Deck and Bridge Approach Slab Finishing.
1.General. If approach slabs are constructed and no deck or deck overlay is constructed with the approach slabs, finish approach slabs as specified in Section 602.04 D.2 “Approach Slab Tining”. If either a deck or deck overlay is constructed along with approach slabs, finish the deck and approach slabs as specified in Grooving”.
2.Approach Slab Tining Run a clean metal tine longitudinally along the approach slab. Begin tining 6 inches from the beginning and ending of the approach slab. Stop tining 24 inches from the face of barrier and c urb. The tine may be hand-operated. Use a tine that provides grooves that are 1/8 inch in width (±1/64 inch) and 1/8 inch in depth (±1/64 inch) with a center to center spacing of 3/4 inch.
3.Deck and Approach Slab Grooving. After curing is complete and any c orrective action is taken for surface tolerance, perform grooving by cutting longitudinal grooves into the deck and approach slabs using a mechanical cutting device. Cut grooves that are 1/8 inch in width (±1/64 inch) and 1/8 inch in depth (±1/64 inch) wi th a center to center spacing of 3/4 inch. Begin grooving 6 inches from the beginning and ending of the deck, approach slabs, and expansion joints. Stop grooving 24 inches from the face of barrier and curb.
E.Surface Tolerances. After the concrete has cured, the Engineer will test the bridge dec k, approach slabs, and adjacent pavement, if applicable, for surface irregularities with a 10 foot straightedge. The Engineer will check the profile using a 10 foot straightedge oriented in the longitudinal direction and starting at one end of the deck, move the straightedge transversely across the deck to the other edge with constant contact with the deck. Repeat this process in 5 foot intervals from one end of the deck to the other. Check the cross slope using the 10 foot straightedge oriented in the tr ansverse direction and starting at one end of the deck, move the straightedge longitudinally from one end of the deck to the other end with constant contact with the deck. Repeat this process in 5 foot intervals from one side of the deck to the other. Grind areas with a deviation greater than 1/8 inch, but less than or equal to 1/2 inch, until the deviation is 1/8 inch or less. The Engineer will apply a contract price reduction as specified in Section 602.06 B, “S urface Tolerance” . The Engineer will make a serviceability determination as specified in Section 105.07, “Conform ance with the Contract Requirements ” for any deviations greater than 1/2 inch. 261 F. Curing Concrete.
1.General. Maintain the concrete surface temperature between 40°F and 90°F for the duration of the curing period. Use a curing period of at least seven days. Use a curing period of at least ten days if using pozzolans to replace greater than 10 percent of the cement used in the mix. Cure all surfaces not covered by forms with a double thickness of burlap. Keep the burlap continuously moist until the end of the curing period. Do not use a waterproof material to cover the wet burlap during the cur ing period. If the concrete is exposed to air temperatures lower than 40°F on any day, extend the curing period by the number of days the concrete is exposed to these low temperatures. If concrete is exposed to air temperatures below freezing during the curing period, the Engineer and Department’s Bridge Division will perform an evaluation of the in place concrete to determine serviceability. The results of the evaluation may require remedial action or removal of the affected material or structural element. If enclosures are used, heat the enclosure with an electric heater or properly vented combustible heater. Before removing the enclosure, decrease the concrete’s surface temperature to the air temperature at a rate not to exceed 15°F per hour.
2.Deck and Approach Slab Concrete. Cover deck concrete with a double thickness of burlap placed within 15 minutes of the passing of the finishing machine. Use a work bridge to place the burlap without marring the surface. Pre-wet burlap prior to placing on the deck or approach slab. A light fog spray may be used after finishing to moisten the concrete surface after finishing to prevent the surface from drying before placement of the wet cure. Keep the burlap continuously moist at all times. Do not perform work and do not allow vehicles and equipment on the deck or approach slabs during the curing process.
G.Barriers.
1.General. Perform corrective actions on any surface that deviates by 3/8 inches or more when measured with a 10 foot straightedge. Make corrections by grinding, filling with an approved epoxy mortar, or replacing. Except at expansion joints, construct V -grooves that are 3/4 inch wide and 3/4 i nch deep in all faces of the barriers at each pier and at equal spaces between piers and abutments at approximately 10 foot spacing. 262 2. Conventional Forming. Adequately tie forms to avoid any shifting during concrete placement. If concrete inserts in the deck slab are holding the barrier forms in place, remove the inserts. Clean and fill the cavities flush with the deck slab using an epoxy resin adhesive.
3.Slipforming. Conventional form a minimum distance of 4 feet on each side of expansion joints before slip forming. After the reinforcement is installed, check the clear distance between the reinforcement and the slipform for the entire length of the pour. The Engineer will allow slab overhang distance to be increased up to 1 inch provided the specified gutter line is maintained. The Engineer will allow a radius to be used instead of a bevel on all edges of the barrier.
H.Construction Joints. Clean the existing concrete surface and steel of all rust scale, oil, concrete lattice, dirt, and other deleterious material. Paint the existing concrete surface with a bonding grout that is equal parts cement and sand. Apply the bonding grout to a dry surface. Control placement of the grout so it does not dry before concrete placement.
I.Surface Finish.
1.Surface Finish A. Use surface finish A on formed concrete surfaces. Within 24 hours after form removal, remove all fins and irregular projections from surfaces that are to receive surface finish C or D or to be waterproofed. Remove form ties to a minimum depth of 1 inch. Repair sand pockets, honeycombed areas, cavities resulting from form ties, and other holes as follows: − Clean the repair area; − Saturate with water; − Fill with mortar that i s less than one hour old and made of one part cement and two parts fine sand; and − Compact the mortar to fill all voids.
2.Surface Fini sh B. Use surface finish B on all unformed upper surfaces at the time of concrete placement. Use a wooden template to strike off unformed upper surfaces not including floors, curbs, or sidewalks. Force the coarse aggregate below the surface. Work the surface with a wooden or cork float to obtain a fine- grained, smooth texture. Do not use mortar topping.
3.Surface Finish C. Use surface finish C on all surfaces of concrete visible to the public unless surface finish D is specified in the Plans . Produce a surface that is uniform in texture and appearance and fr ee of imperfections. After completion of surface finish A or B immediately : - Saturate the surface with water; - Using a small quantity of mortar, rub surfaces with a medium coarse silicon carbide stone or mechanical finisher. Mix the mortar using cement and fine sand and water mixed in the proportions used in the concrete being finished; - Rub until form marks and imperfections are removed and the surface is smooth - Do not expose the coarse aggregate; - Rub patches after they set without delaying the rubbing of the remainder of the surface; and - Spread or brush the paste produced by rubbing uniformly over the surface and allow it to set. Perform the final rubbing after the curing period has expired and after all concrete above the surface being finish ed has been cast. Produce the final surface finish by rubbing the concrete with water and a fine silicon carbide stone. Continue rubbing until the surface has a smooth texture and is uniform in color and appearance.
4.Surface Finish D. Use surface finish D on all surfaces designated in the Plans. After achieving surface finish A or B and after the curing period has ended, roughen the surface by sandblasting. Use a commercially packaged cement based masonry coating material. Place one or more coatings using the rates and application methods specified by the manufacturer. Finish the surface with a uniform texture, color, and appearance free from fins, projections, cavities, and porous spots.
J.Penetrating Water Repellent Treatment . Apply the penetrating water repellent after the following conditions are met: • The concrete bridge deck and approach slab have been in place for 21 days; • Grooving has been completed; • Bridge deck barriers and curbs are placed; • All surface finishes are complete; and • Silicone sealant is applied to the joint where the deck and barriers meet. Apply penetrating water repellent solution to the following surfaces: • Top of bridge deck; • Top of approach slabs; • Front face and top of medians; • Front face and top of curbs and walls ; • Front face and top of barriers ; and 264 • Top of abutment and pier cap bearing surfaces . Clean all surfaces receiving treatment using either sandblasting, shot blasting, or water - washing equipment. Remove dirt, dust, grease, oil, laitance, asphalt, or other materials that may inhibit the coverage and penetration of the solution. Use hand tools or solvents approved by the penetrating water repellent manufacturer to remove any bonded foreign materials. Do not remove or alter the existing surface finish or expose the coarse aggregate. Allow any wet concrete surfaces to dry a minimum of 48 hours or longer if required by the manufacturer. Apply the penetrating water repellent when the following conditions are met: • The air temperature is within the following: o 40 °F and rising; or o 95 °F and falling; • Wind is less than 25 mph; and • Rain is not expected within 4 hours. Use airless equipment that has a pressure range between 15 to 40 psi and apply the penetrating water repellent uniformly to the surface. Use the manufacturer’s recommended rate or 200 sf per gallon, whichever is less. Squeegee or broom excess material to avoid ponding.
K.Waterproof Membrane.
1.General. When shown in the plans, apply membrane and primer to surfaces that are dry, clean, free of sharp protrusions and when the air temperature is above 40°F.
2.Primer. Prime the surface according to the manufacturer’s recommendation and at the recommended rate.
3.Membrane Installation. Roll membrane on to surfaces within 36 hours of the surface being primed. Keep the membrane free of wrinkles and bubbles. Lap joints a minimum of 2.5 inches. Seal the joints and exposed edges with a joint seal ing mastic recommended by the manufacturer of the membrane.
L.Anchor Bolts. Place anchor bolts directly into plastic concrete or secure them in preformed or drilled holes using an epoxy resin adhesive.
M.Bearings Surfaces. Set bearings within 0.01 feet of the specified elevation. If necessary, finish bearing areas to a true plane and elevation by grinding. If bearing elevation is too low, contact the Engineer of Record for recommendations and approval. Perform bearing elevat ion adjustments at no additional cost to the Department. Clean and lubricate the sliding surfaces of expansion bearings.
N.Opening to Traffic. Do not operate construction equipment on the structure until the concrete has reached 70 percent of its design strength, based on concrete cylinder breaks. After the concrete has achieved 70 percent of its design strength and before it reaches full design strength, limit the weight of each piece of construction equipment to 14,000 pounds gross vehicle weight. Do not allow public traffic on the structure until the concrete has reached its full design strength.
602.05 Method of Measurement
The Engineer will measure, completed and in place as specified in Section 109.01, “Measurement of Quantities” and as follows: The plan quantity of concrete will be used for measurement and payment.
602.06 Basis of Payment
Pay Item Pay Unit Class ____ Concrete Cubic Yard Class ____ Box Culvert Cubic Yard Concrete Bridge Approach Slab Square Yard Jersey Barrier Formed or Slip Formed Linear Foot
A.General. Such payment is full compensation for furnishing all materials, equipment, labor, and incidentals to complete the work as specified.
B.Surface Tolerance. The Engineer will process a contract price adjustment for deck concrete based on the surface tolerance measurements determined in Section 602.04 E, “Surface Tolerances” . The amount of the contract price adjustment will be determined by multiplying the contract unit price for “Class AAE- 3 Concrete” by the total area that is ground to meet tolerance, measured in square yards, and the appropriate Contract Price Reduction Factor in Table 602 -01. Table 602 -01 Deviation Contract Price Reduction Factor > 1/8 inch and ≤ 1/4 inch 2.5% > 1/4 inch and ≤ 1/2 inch 7.5% Section 604 266 SECTION 604 PRESTRESSED CONCRETE BEAMS
604.01 Description
This work consists of furnishing required materials and fabricating, transporting, erecting, finishing, and prestressed concrete beams.
604.02 Equipment
Use a plant and equipment as specified in Section 155, “Concrete Equipment” . The Engineer may grant written permission to use other types of concrete mixers.
604.03 Materials
A.General. Item Section Portland Cement Concrete 802 Deformed Steel Bars for Concrete Reinforcement 836.02 A Steel Welded Wire Reinforcement , Plain , for Concrete 836.03 B Steel Strand, Uncoated Seven -Wire for Concrete Reinforcement 836.03 E Use the same brand and grade of cement and admixture for all beams in any one bridge structure.
B.Concrete Mix Design.
1.General. Develop a mix design that produces concrete that will achieve a minimum compressive strength of 5,000 psi within 28 days. Modify Section 802.01 H, “Air Content” will not apply. Obtain the Engineer’s approval for admixtures before developing the mix design. Include any admixtures in the mix design. Perform tests to determine the concrete’s compressive strength using 6 inch by 12 inch cylinders.
2.NDDOT Quality Assurance Procedures. If the beam fabrication plant meets the requirements of the Department’s Quality Assurance procedure, the following apply:
a.The Department will waive the sampling, testing, and inspection requirements specified in Sections 604.03 D, “Inspection” and 604.03 E, “Sampling and Testing During Manufacture of Beams ” and substitute the following: − Furnish a certificate of compliance that also includes the source of the materials used in manufacturing.
Source: North Dakota Standard Specifications for Road and Bridge Construction, 2022 Edition. Pages 290–300 of 550.