266 SECTION 604
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. 267 − Furnish the required certificate for the wire, strand, and reinforcing steel. Furnish a certificate analysis of the aggregates and stating that the aggregates have been tested and approved. − At the time of stress transfer, test two concrete test cylinders for a single beam pour, and three concrete test cylinders for a continuous pour representing the beams as provided for in Section 604.03 E.1 “Concrete” .
b.The Department will waive the requirements of Section 604.03 B.3, “Trial Mix” .
3.Trial Mix. Produce a trial mix using the mix design in the presence of the Engineer. Cast, cure, and test a minimum of ten cylinders under the observation of the Engineer. Produce the cylinders as specified in ND T 23. Test four cylinders at 14 days and the remaining six at 28 days. Test the cylinders as specified in AASHTO T 22. Submit the test results with the mix design to the Engineer for approval at least 14 days before casting the beams.
4.Mix Design Revisions. If any material or material source changes, develop and submit a revised mix design as specified in Section 604.03 B, “Concrete Mix Design” .
C.Wire, Strand, and Bars Assign lot numbers to all wire, strands, and bars and tag them for identification.
D.Inspection. Notify the Engineer a minimum of two weeks before manufacturing the beams. Allow the Engineer free entry to all parts of the work involving the manufacture of the beams.
E.Sampling and Testing During Manufacturing the Beams.
1.Concrete. Cast cylinders as specified in ND T 23. Cast cylinders in a sequence so all concrete used in the beams is represented by tests. If casting a single beam, cast and test a minimum of five cylinders. Test 2 cylinders to determine concrete compressive strength at the time of stress transfer. Test 3 cylinders on or before the 28 day test period to determine the compressive strength for delivery and the Engineer’s acceptance. If casting two or more beams during one continuous operation, cast and test a minimum of six test cylinders: − 3 cylinders per bed, to be tested at the time of stress transfer, that include: • 1 cylinder representing the first beam cast; • 1 cylinder representing a beam near the center of the bed; and • 1 cylinder from the last beam cast. 268 − 3 cylinders for determining compressive stren gth to make delivery and obtaining acceptance by the Engineer on or before the standard 28 day test period.
2.Wire, Strand, and Bars. Submit a certified mill test report and a certificate of compliance for reinforcing installed in beams. Include the diameters, elongation at rupture, and ultimate tensile strengths in the mill report.
F.Acceptance. Deliver the beams after the design compressive strength requirements are obtained. The Engineer will reject beams not meeting the design compressive strength requirements at 28 days. Furnish a certified statement showing the number of beams cast in each continuous operation and the number of each beam. − If the fabrication plant meets the requirements of the Department’s Quality Assurance procedure, the manufacturer’s representative shall sign the statement. − If the plant does not meet the requirements of the Department’s Quality Assurance procedure, the Department’s representative at the plant shall sign the statement.
604.04 Construction Requirements
A.General. Determine the prestress force applied to the strands by strand elongation and check the force applied using hydraulic jacks. Furnish a statement of curve showing the load elongation relationship at 75 percent (low elongation strand) of ultimate stress for the prestress steel that will be used and a certified calibration curve for each hydraulic jack that is used. Submit these items with the certificate of compliance specified in Bars” .
B.Work Drawings. Provide work drawings that include: - Beam dimensions; - Size and location of all reinforcing and prestressing steel including; o Strand layout; o Pull down locations; o Tensioning forces; o Elongation; and o Proposed changes in the reinforcing s teel; - Initial prestress forces; - Location of handling hooks or devices; and - Losses in the prestress due to: o Elastic shortening; o Shrinking or creeping of concrete; and o Relaxation of steel stress as determined by the Contractor method of stressing. 269 Submit calculations and work drawings that are signed, sealed, and dated by a Professional Engineer registered in the State of North Dakota as set forth in NDCC Title 43.
C.Placing and Fastening Steel. Place steel as specified in Section 612.04, “Construction Requirements” and as follows: Maintain distances between the forms and steel reinforcing using stays, ties, hangers, or other approved supports. Ensure metal bar chairs and bolsters in contact with the forms are galvanized or noncorrosive metal. Do not leave wooden blocks in the concrete. Straighten prestressing elements by applying low initial tension to insure proper positioning. Include this initial tension in the total tension applied. If requir ed, provide suitable horizontal and vertical spacers to hold elements in true position.
D.Placing Concrete. Place concrete in forms made entirely of steel. Vibrate concrete for the beams. Vibrate without displacement of reinforcing, conduits, voids, or wire. Vibrate for a sufficient duration and intensity to thoroughly consolidate the concrete without causing segregation. Rough float and transversely broom the top of the beams.
E.Curing Concrete. Steam or water cure members until the concrete has reached the compressive strength required for stress transfer. Protect members from rain, cold weather, and moisture loss between placement of the concrete and the beginning of the steam or water cure. Cover all exposed surfaces with two layers of burlap as soon the covering is able to be placed without damaging the concrete. Maintain a uniform curing temperature.
1.Steam Cure. Cover steam cured members with a suitable covering to contain the live steam. Distribute the steam uniformly throughout the enclosure and do not jet the steam directly on the beam. Maintain the temperature of the enclosure below 90°F until the beam has cured for a minimum of three hours. After this period the Engineer will allow the temperature within the beam enclosure to be raised to a maximum of 160°F in increments less than 40°F per hour.
2.Water Cure. Apply water to the burlap cover so that the concrete surfaces are kept continuously wet.
F.Pretensioned Beams. Debond strands, if needed, using a rigid poly mer sheathing with no split seam. Accurately hold prestressing tendons in position and stress the tendons with jacks. Submit a record of the jacking force and the elongation produced. 270 Do not allow bond stress to be transferred to the concrete and do not release end anchorages until the concrete has reached the compressive strength required for stress transfer. Cut tendons only after heating them to relieve the stress. Cut tendons so the lateral eccentricity of prestress force is minimized.
G.Transportation and Storage. Transport precast beams in an upright position, and ensure the points of support and directions of the reactions with respect to the beam are approximately the same during transportation and storage as when the beam is in its final position.
H.Beam Placement. Do not place beams on structure until previously placed concrete is at least 14 days old or has reached 70 percent design strength.
604.05 Method of Measurement
The Engineer will measure as specified in Section 109.01, “Measurement of Quantities”.
604.06 Basis of Payment
Pay Item Pay Unit Prestressed Beams Linear Foot Such payment is full compensation for furnishing all materials, equipment, labor, and incidentals to complete the work as specified. Section 606 271 SECTION 606 PRECAST REINFORCED CONCRETE BOX (PRCB) CULVERTS
606.01 Description
This work consists of furnishing required materials as well as fabricating, transporting, and installing Precast Reinforced Concrete Box Culverts (PRCB).
606.02 Equipment
Reserved.
606.03 Materials
A.General. Item Section Steel Strand, Uncoated Seven -Wire for Concrete Reinforcement 836.03 E Geosynthetic 858
B.Waterproof Membrane. Provide self- adhesive black 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.
606.04 Construction Requirements
A.Design and Manufacture. Design and manufacture the PRCB as specified in the applicable portions of AASHTO LRFD Bridge Design Specifications, Section 12, and AASHTO Materials Specification M 259. Use an ACPA or NPCA certified plant in the construction.
B.Concrete. Use concrete that will achieve a minimum compressive strength of 3,000 psi after 28 days. Use a mix design having a minimum cement content of six sacks per cubic yard.
C.Barrels. Use barrel sections that are a minimum of 4 feet long measured along the shortest side. Construct the sections with a minimum concrete thickness of 8 inches. Do not allow any haunch or fillet at the inside corners of the barrel to exceed a triangular shape with 12 inch horizontal and 12 inch vertical legs. Use tongue and groove section joints in which the tongue is a mi nimum of 4 inches long and 3.5 inches thick at the end of the tongue.
D.Work Drawings. Submit work drawings containing the following information: − Layout showing PRCB placement; − Type and strength of concrete and reinforcing steel; − All concrete and reinforcing dimensions; − Reinforcing steel clearances; − Method of tying sections together;
Source: North Dakota Standard Specifications for Road and Bridge Construction, 2022 Edition. Pages 301–305 of 550.