Attachment_2_Supplemental_Spec_553.pdf

Section 553 – PRESTRESSED CONCRETE

Materials

553.02 Conform to the following Section and Subsections:

Add the following materials and paragraph:

High strength non-shrink grout 725.22 (c) Structural steel 555

Use Class P concrete in prestressed members unless otherwise SHOWN ON THE DRAWINGS.

Design the concrete mix in accordance with Subsection 552.03 with a 28-day design compressive strength as SHOWN ON THE DRAWINGS. Do not permit lightweight concrete unless otherwise SHOWN ON THE DRAWINGS.

Construction Requirements

553.03 Method Approval.

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Notify the CO a minimum of 10 days prior to fabrication of any prestressed members.

Inspect all prestressed concrete members by one of the following methods, unless otherwise SHOWN ON THE DRAWINGS or in the SUPPLEMENTAL SPECIFICATIONS:

• Use the quality control engineer of a plant certified by the Prestressed Concrete Institute (PCI). Submit a copy of the transmittal letter of the latest PCI inspection with the shop drawings. Furnish a copy of all testing and inspection reports to the CO upon delivery of the members to the jobsite.

• Use an independent licensed professional engineer experienced in prestressed concrete girder inspection to certify that the prestressed members were built in accordance with the drawings and specifications. Furnish, along with the certification, a copy of all testing and inspection reports to the CO upon delivery of the members to the jobsite.

Ensure that the prestressed members conform to the dimensional tolerances as given in Table 553-1.

Perform prestressing by pretensioning methods. Submit four copies of shop drawings for prestressed members and one copy of reproducible detailed drawings of the method, material, and equipment proposed for approval at least 21 days before starting prestressing.

Show the following:

(a) Method and sequence of stressing.

(b) Complete specifications, details, and test results for the prestressing steel and anchoring devices.

(c) Anchoring stresses.

(d) Arrangement of the prestressing steel in the members to include the strand pattern at midspan and at center span of bearing; and the location of total strand center of gravity at midspan, at hold-down points, at quarter points, and at centerline of bearing.

(e) Tendon elongation calculations for jacking procedures to be used, to include the calibration curve for the gauge and jacking system, the stress-strain curve for the prestressed strands, and the pressure gauge readings.

(f) Number, spacing, and method of draping pretensioned strands.

(g) The prestressing bed layout and overall length between grips at fixed and jacking ends, and the type of equipment to be used.

(h) Other substantiating calculations for the prestressing method.

(i) Certification of wire or strand taken in accordance with Subsection 709.03.

(j) Concrete mix design.

Provide the signature and seal of a licensed professional engineer on all shop drawings and calculations prepared for fabrication of prestressed members.

The CO will review mix designs and approve shop drawings prior to fabrication of prestressed members.

553.05 Concrete.

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As a minimum, use Class P(AE) (air-entrained) concrete according to Section 552 for the top 2 inches of the precast member.

553.07 Pretensioned Members.

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Cast pretensioned members in commercial prestressing plants that are PCI-Certified Plants in Product Group B—Bridges, category B3 (Prestressed Straight Strand Bridge Members) or category B4 (Prestressed Draped Strand Bridge Members), as applicable to the members to be manufactured.

553.08 Storing, Transporting, and Erecting.

Add the following paragraphs to the end of the section:

Advise the CO a minimum of 48 hours before prestressed girders for multibeam bridges are to be field welded, and before any field grout or mortar is to be placed.

Adjust, if necessary, multibeam girders by using galvanized steel shims the same length and width as the bearing pad or plate. Allow no more than 1/4 inch vertical difference between top of adjacent beam edges at each end of the span. When an asphalt wearing surface or cast-in-place deck is to be placed on top of the prestressed beams, allow a vertical tolerance of only 1/2 inch. Do not load beams to make them assume the same camber as an adjacent beam.

Perform abrasive blasting on the keyway surfaces of all multibeam prestressed concrete members to provide a new and clean concrete surface that is free of carbonated concrete and other contaminants, and to expose parts of the large aggregate beneath the concrete paste.

Use high-pressure water blasting (3,000 psi or more) to remove all debris and loosened paste in the keyways immediately prior to placing high-strength non-shrink grout (grout). Remove all freestanding water and allow keyways to completely surface dry. Test for the presence of carbonated concrete when directed by the CO or called for by the SUPPLEMENTAL SPECIFICATIONS. Repeat abrasive blasting and water washing as needed if tests indicate the presence of carbonated concrete.

Use grout in keyways between multibeam members and to patch defects, blockouts, or other areas on the concrete roadway portion of the structure 1 inch or more in depth and over 1 inch in width. Patch smaller areas on the concrete roadway with grout.

Maintain air and concrete keyway temperatures between 45°F and 85 °F before placing grout.

Maintain the temperature within these limits until grout placement and application of curing method is completed.

Use grout on all anchor bolts and dowels to make all repairs.

Strike off exposed grout surfaces flush with the same surface texture finish as the surrounding concrete as soon as the grout has set sufficiently. Cure the exposed surface as specified in Subsection 552.15. When artificial means are used to control the curing temperature of the grout, as during hot or cold weather, the CO will approve the method in advance. Use combustion heaters only if fully vented outside their enclosure. Store all dry grout materials and mixing and placing equipment such that their temperature is above freezing. Warm mixing water to provide grout at desired temperature, but ensure that it is at 85 °F or less when mixed with the dry materials. Use ice as part of the mixing water provided it is completely melted prior to the introduction of the water to the dry materials.

Ensure that patching grout is the same color as the parent concrete.

Ensure that all field welding meets the requirements specified in Section 555. When welding or burning on precast members, attach the ground lead directly to the base metal; reject any precast prestressed member used as a conductor for the ground, and replace the member without compensation.