S02. Stressing Tendons Revised 23 Jul 2025.pdf

Columbus VAMC Specification

VA Project 757-24-204 100% Bid Documents Submission

Columbus OH Parking Garage Tendon Repair Design 18 Jul 2025

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SECTION 03 23 00

STRESSING TENDONS

PART 1 - GENERAL

1.1 DESCRIPTION

A. This section specifies furnishing, installing, grouting, and stressing tendons in post-tensioned building framing members as shown on the drawings and described herein.

1.2 RELATED WORK

A. Section 01 45 29, TESTING LABORATORY SERVICES: Materials Testing and inspection during construction.

B. Section 01 81 13, SUSTAINABLE CONSTRUCTION REQUIREMENTS

C. Section 03 30 00, CAST-IN-PLACE CONCRETE: Concrete.

1.3 QUALITY ASSURANCE

A. Codes and Standards: Comply with requirements of the Post-Tensioning

Manual, except where more stringent requirements are specified or shown on the drawings. Maintain two copies at job site.

B. Bearing Stresses: Comply with requirements of Post-Tensioning Manual, Chapter 3, Paragraph 3.1.7, and ACI 318, Chapter 18.

C. Source Quality Control:

1. Tests for Unbonded Single Strand Tendons or Bonded Tendons must comply with requirements of the Post-Tensioning Manual, Chapter 3, Paragraph 3.1.8.

2. Certified data from prior tests may be submitted.

D. Supplier Qualifications:

1. Use a fabricating plant certified by PTI.

2. Successfully provided all materials for at least 5 post-tensioning repair projects in parking structures in the United States with a structural system similar to Project within the previous 5 years.

Provide all information requested on the form at the end of this section.

E. Installer Qualifications:

1. Certified by PTI.

2. Successfully performed at least 5 post-tensioning repair projects in parking structures in the United States with a structural system

03 23 00 - 2 similar to Project within the previous 5 years. Provide all information requested on the form at the end of this section.

3. Use a full-time Project superintendent that has supervised at least

5 projects of a similar magnitude.

4. Use PTI Level 2 Certified Field Installers to install and stress post-tensioning system.

F. Prior to bid, Engineer/Architect will accept, tentatively accept, or reject Supplier or Installer based on compliance with criteria referenced in this section. Engineer/Architect's decision is final.

Engineer/Architect may issue an addendum indicating accepted and tentatively accepted Suppliers prior to bid date. Engage only accepted or tentatively accepted Suppliers. Following a qualifications check, tentatively accepted Suppliers will be notified of acceptance or rejection at or before shop drawing stage. Contractor is responsible for delays due to such rejection.

G. Suppliers, who do not meet the qualification requirements above, shall be rejected:

H. Comply with requirements in ACI 301, Section “Post-Tensioned Concrete.”

I. Perform all post-tensioning Work under the supervision of a Project

Superintendent who is present during all operations including installation, concrete placement, stressing and finishing.

1.4 ADMINISTRATIVE REQUIREMENTS

A. Sequencing:

1. Deviations in the construction and stressing sequence shown on the

Drawings are not permitted without written acceptance from

Engineer/Architect.

B. Submittals and Resubmittals:

1. Engineer will review each submittal the initial time and, should resubmittal be required, one additional time to verify that reasons for resubmittal have been addressed by Contractor and corrections made.

2. Circle resubmittal changes/revisions/corrections. Engineer will review only circled items and will not be responsible for non-circled changes, revisions, corrections, or additions.

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3. Should additional resubmittals be required, reimburse Owner for all costs incurred, including the cost of Engineer’s services made necessary to review such additional resubmittals..

C. Requests For Information

1. Engineer reserves the right to reject, unprocessed, any Request for

Information (RFI) that the Engineer, at its sole discretion, deems frivolous.

2. Engineer reserves the right to reject, unprocessed, any RFI that the

Engineer, at its sole discretion, deems already answered in the

Contract Documents.

3. Do not use the RFI process to request substitutions. Procedures for substitutions are clearly specified elsewhere in the contract documents.

1.5 SUBMITTALS

A. Submit in accordance with Section 01 33 23, SHOP DRAWINGS, PRODUCT

DATA, AND SAMPLES.

B. Shop Drawings:

1. Submit fabrication and placement details to the Contracting

Officer’s Representative (COR) for review and approval. Show complete details of tendon layout, tendon sizes, type of post-tensioning enclosure, end anchorage and coupler details, and stressing equipment. Submit the type and chemical analysis of grease, and type, material, and thickness of post-tensioning repair tape. Give details of jacking operation, including all calculations.

2. Locate and dimension penetrations in post-tensioned slabs.

3. Detail horizontal and vertical curvature of tendons at blockouts and anchorage.

4. Describe tensioning sequence, type of jack and pressure-monitoring devices, anchorage set, tendon elongation and tendon cutoff procedures, grouping, spacing, placing sequence, supports and locations, and tendon supports.

5. Number, arrangement and designation of tendons.

6. Tendon profile and method of tendon support. Show tendon profiles at sufficient scale to clearly indicate tendon high and low points.

7. Tendon anchorage details including bundled tendon flaring.

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C. Product Data: For each product as indicated.

1. Corrosion Inhibiting Coating: Type and chemical analysis.

2. Sheathing: Type, material, density, and thickness.

3. Anchorage Device: Type, material, and size.

4. Coupler Device: Type, material, and size.

5. Intermediate Stressing Coupler Device: Type, material, and size.

6. Pocket Former: Type, material, and size.

7. Sheathing Repair Tape: Type, material, and width.

8. Encapsulation System: Type and materials.

D. Calculations: Submit sealed detailed calculations prepared by a qualified professional structural engineer registered in the state where the project is located to substantiate stressing procedures. All losses shall be accounted for in the calculations. Submit the following:

1. Calculations shall be prepared under the supervision of a qualified registered professional structural engineer, of losses due to anchorage seating, elastic shortening, creep, shrinkage, relaxation, friction, and wobble, used to determine tendon sizes and number.

2. Calculations of test results of adequacy of anchorage.

3. Statistical and field proof of stressing and fixed end seating losses.

4. Calculations for final required jacking elongation corresponding to final jacking force of tendons.

E. Mill Test Reports:

1. Furnish certified Mill Test Reports for each coil or pack of strand, containing as a minimum the following test information:

a. Heat number and identification.

b. Minimum breaking strength.

c. Standard chemical analysis for heat of steel.

d. Ultimate tensile strength.

e. Yield strength at 1 percent extension under load.

f. Elongation at failure.

g. Modulus of elasticity.

h. Diameter and net area of strand.

i. Type of material (stress-relieved or low relaxation).

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2. Base relaxation losses for low relaxation type material on relaxation tests of representative samples for a period of 1000 hours, when tested at 21 degrees C (70 degrees F) and stressed initially to not less than 70 percent of minimum guaranteed breaking strength of strand.

3. Tests in accordance with ASTM A416, and ASTM E328.

F. Calibration Tests: Stressing rams and gauges shall individually be identified and calibrated against known standards at intervals not exceeding six months. Submit calibration certificates for each jack used to the COR for review and approval.

G. Records: Keep post-tensioning records and submit to the COR. Record on each report items listed in PART 3—EXECUTION.

H. Qualification Data: For Supplier and Installer at least 14 days prior to bid date using the forms at the end of this section.

I. Test and Evaluation Reports: Indicating compliance with the following requirements:

1. Tests required by ACI 301, Section “Post-Tensioned Concrete.”

2. Relaxation loss tests required by ACI 423.7 for low relaxation prestressing steel.

J. Field Quality-Control Reports: Within 72 hours of inspection.

K. Warranty: Proposed warranty prior to the start of construction.

1.6 APPLICABLE PUBLICATIONS

A. Publications listed below form a part of this specification to extent referenced. Publications are referenced in text by basic designation only.

B. American Concrete Institute (ACI):

318/318r-19.............Building code requirements for Structural

Concrete and Commentary.

ACI 301.................Specification for Structural Concrete.

ACI 347.................Recommended Practice for Concrete Formwork.

ACI 362.1R-97...........Guide for the Design of Durable Parking

Structures.

ACI 423.3R..............Recommendations for Concrete Members

Prestressed with Unbonded Tendons.

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ACI 423.7...............Specification for Unbonded Single-Strand Tendon

Materials and Commentary.

C. ASTM International (ASTM):

A416/A416M-18...........Standard Specification for Low-relation, Seven-

Wire Steel Strand for Prestressed Concrete

B117-19.................Standard Practice for Operating Salt Spray

(fog) Apparatus

D92-18..................Standard Test Method for Flash and Fire Points by Cleveland Open Cup Tester

D95-13(2018)............Standard Test Method for Water in Petroleum

Products and Bituminous Materials by

Distillation

D512-12.................Standard Test Methods for Chloride Ion in Water

D566-20.................Standard Test Method for Dropping Point of

Lubricating Grease

D2265-20................Standard Test Method for Dropping Point of

Lubricating Grease Over Wide Temperature Range

D3867-16................Standard Test Methods for Nitrite-Nitrate in

Water

E328-13.................Standard Test Methods for Stress-Relaxation

Tests for Materials and Structures

D. Post-Tensioning Institute, 1717 W. Northern Avenue, Suite 114, Phoenix, AZ 85021; 602/870-7540:

Post-Tensioning Manual, Fifth Edition

PTI, "Guide Specifications for Post-Tensioning Materials."

PTI, "Performance Specification for Corrosion Preventive Coating."

PTI, "Specification for Unbonded Single Strand Tendons."

PTI, "Field Procedures Manual for Unbonded Single Strand Tendons."

PTI, “Guide for evaluation and Repair of Unbonded Post-Tensioned

Concrete Structures.”

E. Concrete Reinforcing Steel Institute (CRSI):

CRSI MSP-2, "Manual of Standard Practice."

F. International Code Conference (ICC):

ICC, "International Existing Building Code."

ICC, "International Existing Building Code Standards."

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1.7 DELIVERY, STORAGE AND HANDLING

A. Assign all tendons in same member the same heat number and identify accordingly.

B. Package each tendon bundle at source to prevent physical damage to tendon during transportation and storage, and to protect strand from moisture. Use heavy padding; cardboard is not permitted. Do not use wire binding or other materials that could cut the sheathing or tendon.

C. Deliver, store, and handle post-tensioning materials according to ACI

423.7.

D. Immediately remove damaged components from Project site and replace at no cost to Owner.

E. Do not remove sheathing on stressing end until the day of stressing.

1.8 WARRANTY

1. The Contractor shall guarantee against any and all defects in workmanship and materials for newly installed tendon strands, splices, anchorages, and anchoring hardware for a period of 5 years.

2. The Manufacturer shall guarantee against any and all defects in materials for newly installed tendon strands, splices, anchorages, and anchoring hardware for a period of 5 years.

3. Written warranty, signed by Contractor/Manufacturer, including:

a. Repair or replacement of post-tensioning tendon repairs installed by Contractor:

1) That does not comply with requirements.

2) With corroded or fractured prestressing steel or corroded post-tensioning accessories in the repair area.

3) With corroded or fractured prestressing steel or corroded post-tensioning accessories in areas away from repair, which are directly due to post-tensioning repairs installed by

Contractor.

b. Removal and patching of concrete is necessary to remedy distress of post-tensioning repairs covered by warranty.

c. Repair or replacement, to satisfaction of Owner, of other work or items which may have been displaced or damaged as consequence of defective work.

d. Make immediate emergency repairs within 24 hours of notice of defective post-tensioning repairs.

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e. Owner will reimburse Contractor for reasonable costs if post-tensioning distress is not due to Work performed by Contractor.

f. Warranty Period: 5 years after Substantial Completion date.

PART 2 - PRODUCTS

2.1 MATERIALS

A. Post-Tensioning Steel:

1. Conform to ASTM A416, Grade (270K), uncoated, seven-wire, Low

Relaxation strand, with anchorages developing at least 95 percent of the minimum specified ultimate strength of the prestressing steel.

a. Manufactured by a single source.

b. Strands manufactured outside United States subject to

Engineer/Architect’s approval based on evidence of satisfactory performance in the United States during the previous 5 years.

c. Use of high stress bar system instead of strand system is not permitted unless accepted in writing by the Engineer.

d. Conform to ACI 423.7 for relaxation loss requirements.

2. Provide low relaxation strand with a mill applied continuous permanent physical marking to permit field identification.

3. Package material at the source in a manner that prevents physical damage to strand during transportation and protects material from deleterious corrosion during transit and storage.

B. Post-tensioning materials comply with Post-Tensioning Manual Guide

Specifications and perform satisfactorily in ACI 362.1R-97 zone III environment without long-term corrosion or other distress.

1. PT repairs are to be based on the following: Do not exceed the maximum tensile stress in the tendon during the stressing operation.

The maximum tensile stress is 74 percent of the specified tensile strength of the tendon.

2. Do not exceed 64 percent of the specified tensile strength after the anchors are seated.

C. Anchorages and Couplings:

1. Design tendon anchorages and coupling to develop static and dynamic strength requirements of Section 3.1.6(a) and Section 3.1.8 (1) and

(2) of Post-Tensioning Manual Guide Specifications for Post-

Tensioning Materials. Castings shall be nonporous and free of sand, 03 23 00 - 9 blowholes, voids, and other defects meeting the testing and material requirements of ACI 423.7. Tendon anchors shall be/include:

a. Plastic coated bearing plates sized in accordance with ACI 423.7, unless certified test reports substantiate comparable or superior performance, for transfer at minimum stressing concrete strength.

b. Capable of complying with PTI Guide Specification requirements for aggressive environments.

c. Capable of developing at least 95% of the actual ultimate strength of tendon.

2. Average compressive concrete bearing stress of anchorages shall not exceed limits set forth in Section 3.1.7 of Post-Tensioning Manual

Guide Specifications for Post-Tensioning Materials.

3. For wedge type anchorages, design wedge grippers to preclude premature failure of prestressing steel due to notch or pinching effects under static and/or dynamic test load conditions stipulated under Paragraph 1 for both stress relieved and low relaxation prestressing steel materials. Wedge requirements include:

a. Minimum wedge cavity opening of at least 0.19 inches larger than tendon diameter. Reaming of anchor wedge cavity is not permitted.

b. Wedges capable of precluding failure of tendon due to notching or pinching effects during static and fatigue load tests stipulated in ACI 423.7.

4. Use couplings only at locations specifically indicated on contract documents or as approved. Coupler assemblies shall be an assembly of strands and wedges meeting the testing and material requirements of

ACI 301, this includes:

a. Capable of complying with PTI Guide Specification requirements for aggressive environments.

b. Capable of developing at least 95 percent of the ultimate strength of tendon.

c. Wedges capable of precluding failure of tendon due to notching or pinching effects during static and fatigue load tests stipulated in ACI 423.7.

5. Coat couplings with the same corrosion preventive coating used on strand and enclose in sleeves.

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6. Anchorages shall include design features permitting a watertight connection of sheathing to anchorage, and watertight closing of wedge cavity, for stressing and nonstressing (fixed) anchorages.

Design intermediate stressing anchorages to permit complete watertight encapsulation of prestressing tendons. Watertight connection requirements include:

a. Provisions for a plastic cap which fits tightly and seals barrel end on stressing side of anchor.

b. Provisions for a plastic sleeve which prevent moisture infiltration into anchor casting or tendon sheathing on bearing side of anchor.

D. Corrosion Preventive Coating of Unbonded Tendons:

1. Corrosion preventive coating material shall have the following properties:

a. Provide corrosion protection to prestressing steel.

b. Provide lubrication between strand and sheathing.

c. Resist flow from sheathing within anticipated temperature range of exposure.

d. Provide a continuous nonbrittle film at the lowest anticipated temperature of exposure.

e. Be chemically stable and nonreactive with prestressing steel, sheathing material, and concrete.

2. Film shall be an organic coating with appropriate polar, moisture displacing, and corrosion preventive additives.

3. Minimum weight of coating material on prestressing strand shall be not less than 1.1 kg (2.5 pounds) of coating material per 30 m (100 feet) of 13 mm (0.5 inch) diameter strand, and 1.3 kg (3.0 pounds) of coating material per 30 m (100 feet) of 15 mm (0.6 inch) diameter strand. The amount of coating material used shall be sufficient to ensure complete filling of annular space between strand and sheathing. Extend coating over the entire tendon length.

4. Provide test results in accordance with Table I for corrosion preventative coating material.

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TABLE I

PERFORMANCE SPECIFICATIONS FOR CORROSION

PREVENTATIVE COATING

Test Test Method Acceptance Criteria

Dropping Point, degrees F ASTM D566 or

ASTM D2265

Minimum 300

Oil separation at 160 degrees F;

percent by weight

FIMS 791B

Method 321.2

Maximum 0.5

Water, percent maximum ASTM D95 0.1

Flash point, degrees F, (degrees

Celsius) (Refers to oil component)

ASTM D92 Minimum 300

Corrosion test, 5 percent salt fog at 100 degrees F (37.8 degrees

Celsius) 5 mils, minimum hours (Q

Panel Type S)

ASTM B117 Rust Grade 7 or better after 1000 hours of exposure, test according to

ASTM D610 (Note 1)

Water soluble ions (Note 2)

Chlorides, ppm maximum

Nitrates, ppm maximum

Sulfides, ppm maximum

ASTM D512

ASTM D3867

APHA 4270

(15th Edition)

Soak Test

5 percent salt fog at 100 degrees F

(38.8 degrees Celsius) 5 mils coating, Q panels, Type S. Immerse panes 50 percent in a 5 percent salt solution and expose to salt fog.

ASTM B117

(Modified)

No emulsification of the coating after

7200 hours of exposure

Notes To Table I:

Note 1: Extension of exposure time to 1000 hours for greases used in corrosive environments requires use of more or better corrosion inhibiting additives.

Note 2: Procedure: The inside (bottom and sides) of a 1l Pyrex beaker

(approximate outside diameter 105 mm, height 145 mm) is thoroughly coated with 100 + 10 grams of corrosion preventive coating material.

The coated beaker is filled with approximately 900 cc of distilled water and heated in an oven at a controlled temperature of + 38 degrees C (+ 100 degrees F) for 4 hours. The water extraction is tested by the noted test procedures as ppm in the extract water.

E. Sheathing For Unbonded Single Strand Tendons:

1. Tendon sheathing for unbonded single strand tendons shall be made of seamless and extruded high density polypropylene or seamless and

03 23 00 - 12 extruded high density polyethylene with a specific gravity greater than 0.95 conforming to ACI 423.7 material with following properties:

a. Sufficient strength to withstand irreparable damage during fabrication, transport, installation, concrete placement, and tensioning.

b. Watertightness over entire sheathing length including all connections and components.

c. Chemical stability, without embrittlement or softening over anticipated exposure temperature range and service life of structure.

d. Nonreactive with concrete, steel, and tendon corrosion preventive coating. Minimum thickness of sheathing is 1 mm (0.040 inch) for medium or high-density polyethylene or polypropylene.

e. Minimum inside diameter of sheathing at least 0.8 mm (0.030 inch) greater than maximum diameter of strand.

f. Contrasting color of corrosion inhibiting coating to enhance visibility of damage. Black/dark colored sheathing is not acceptable.

g. Annular space between sheathing and strand completely filled with corrosion inhibiting coating.

2. Connect sheathing to stressing end, intermediate and fixed end anchorages in a watertight fashion, thus providing a complete encapsulation of prestressing steel.

F. Encapsulation System for New Prestressing Steel: Watertight encapsulation along the entire length of new tendon, including new anchorages and new couplers, when subjected to hydrostatic testing required in ACI 423.7 for aggressive environments.

1. Sleeve: Translucent plastic with a positive mechanical connection to anchorages capable of resisting 100 lbs. pulling force. Minimum 10 inches long and 4 inches overlap with sheathing, completely filled with corrosion inhibiting coating.

2. Anchor Cap: Translucent plastic with a positive mechanical connection to anchorages capable of resisting 100 lbs. pulling force. At intermediate anchorages, open to allow passage of strand.

3. Subject to the requirements provide one of the following systems:

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a. “Zero Void,” General Technologies, Inc.

b. “Hayes Posi-Lock Plus,” Hayes Industries, Ltd.

c. Accepted equivalent.

2.2 ACCESSORIES

A. Pocket Formers: Capable of completely sealing wedge cavity from intrusion of concrete or cement slurry; sized to provide at least a 2-inch recess and allow access for cutting strand tail.

1. If Zero Void encapsulation system in used, the “Zero Void Nail-Less

Pocket Former” is required.

B. Anchorage Fasteners: Stainless-steel ring nails. Subject to the requirements use one of the following:

1. Clendenin Brothers, Baltimore, MD.

2. Swan Secure Products, Baltimore, MD.

3. R.J. Leahy Co., San Francisco, CA.

C. Sheathing for Repair at Existing Prestressing Steel:

1. Watertight, chemically stable, and non-reactive with prestressing steel, corrosion inhibiting PT coating, and reinforcing steel.

2. Color shall contrast with PT coating so that sheathing tears will be readily visible.

3. Polypropylene or polyethylene tubing:

a. Minimum thickness of 0.050 inches.

b. Inside diameter is at least 0.030 inches greater than prestressing steel diameter.

c. Slit tubing longitudinally for sheathing repairs at continuous prestressing steel.

D. Sheathing at New Intermediate Anchorage and Couplers:

1. Heat-shrink tubing to encapsulate couplers and splicing hardware at intermediate stressing locations.

2. Heat shrink tubing shall be watertight, chemically stable, and non-reactive with prestressing steel, corrosion-inhibiting PT coating, and reinforcing steel.

3. Use one of following or approved equal:

E. Protection at New End and Intermediate Anchorages:

1. Epoxy coating field-applied to all surfaces of wires, plates, anchor washers, etc. at locations of end and intermediate anchorages and center stressing splices.

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F. Sheathing Repair Tape: Elastic, self-adhesive, moisture-proof tape with a minimum width of 2 inches in contrasting color to tendon sheathing, and that is non-reactive with sheathing, corrosion inhibiting coating, or tendon. Subject to the requirements use one of the following:

1. “3M Tape No. 226,” 3M, St. Paul, MN.

2. “Polyken 826,” Berry Plastics Corp, Evansville, IN

3. “Tyco Adhesives No. 398,” Tyco Adhesives, Franklin, MA

G. Sheathing Repair Material: For nicks and cuts less than 0.25 inches use one of the following:

1. “Scotch-Weld DP-8005,” by 3M.

H. Corrosion inhibiting coating: Capable of meeting the requirements of

ACI 423.7. Subject to the requirements, use one of the following.

1. "Greasrex K-218," ExxonMobil Oil Corp., Irving, TX.

2. “Red-i PT Coating Grease,” Lubricating Specialties Co., Pico Rivera, CA

3. “Renolit PTG,” Fuch’s Lubricant Co., Harvey, IL

4. “Royal PT-1 and PT-2 Corrosion Inhibiting Grease,” Troco Oil Co., Tulsa, OK

5. “Strand Shield,” Martin Specialty Lubricants, North Kansas City, MO

I. Tendon supports: Bolsters, chairs, spacers, and other devices for spacing, supporting, and fastening tendons in place. Use tendon supports capable of meeting the requirements in CRSI’s “Manual of

Standard Practice” and as follows:

1. Clearly marked to differentiate by height.

2. Capable of resisting overturning during construction operations.

3. Minimal contact with forms where concrete is exposed to view.

4. Do not cause voids or damage to surrounding concrete.

5. All-plastic supports conforming to CRSI Class 1 protection requirements and with a compressive strength higher than concrete.

6. Acceptable manufacturers:

a. Aztec Concrete Accessories, Inc.

b. General Technologies, Inc.

c. Accepted equivalent.

2.3 GROUT MATERIALS

A. Premixed, nonmetallic, noncorrosive, non-staining grout product containing selected silica sands, Portland cement, shrinkage

03 23 00 - 15 compensating agents, plasticizing and water reducing agents, complying with ASTM C 1107, Grade B, with fluid consistency and a 30-minute working time.

B. Non-reactive with prestressing strand, anchorage materials, or concrete and without chlorides or other chemicals known to be deleterious to prestressing strand.

C. Subject to compliance with requirements, provide one of the following:

1. Sure Grip Grout, Dayton Superior.

2. Euco N.S., Euclid Chemical Co.

3. Masterflow 928/SikaGrout®-928, Master Build Solutions/Sika.

2.4 EQUIPMENT

A. Stressing Equipment: Hydraulic jacks with calibrated pressure gauges, capable of gripping prestressing steel and stressing prestressing steel to specified levels. Maintain equipment in safe, working condition.

1. Provide certified pressure gauges with means to cross check accuracy constantly. Second gauges are recommended for larger projects.

2. Provide at Site current, not to exceed 6 months, calibration chart for each jack relating gauge pressure to jacking force.

3. Exercise care in handling of stressing equipment.

B. Necessary equipment to detension, cut, and splice prestressing strands.

C. Calibration of hydraulic equipment and gauges.

D. The Contractor shall provide the equipment and use appropriate methods to expose the embedded post-tensioning sheathing. The demolition to expose embedded post-tensioning sheathing shall not compromise the structural integrity of the slab and shall minimize damage to the tendon sheathing. The following equipment, or an approved equal, may be used on this project.

1. Chipping hammers of nominal 15-lb. class or less for removal of concrete to expose tendon sheathing.

2. Compressed air equipment capable of removing dust and dirt from concrete repair areas.

E. All equipment is to be operated and maintained according to the manufacturer's recommendations or the approved testing procedures.

F. Operation of stressing equipment shall be performed by tradesman experienced in this work with a PTI level 2 Unbonded – Field

Installation certification.

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PART 3 - EXECUTION

3.1 PRECAUTIONS

A. Prestressing steel under stress has significant stored energy. Exercise

1 care in detensioning and stressing.

1. Erect and maintain work platforms in safe condition, in conformance with Government regulations.

2. Protect areas around, adjacent to, and below work area, including vehicular traffic, from damage.

3. Protect construction personnel and passersby from injury.

a. Do not allow anyone to stand in front of, behind, over, or beneath hydraulic jack, or anywhere along the tendon during stressing or prestressing steel to be detensioned.

b. After stressing, when releasing jack pressure to transfer force to wedges, laborers’ fingers shall be kept clear of assembly.

B. Close off area around, adjacent to, and below work area or use canopies and barriers as necessary to protect public.

C. Detensioning shall be performed by cutting, preferably while tendon is still embedded in concrete, by use of specialty detensioning equipment, or by other approved means.

3.2 PREPARATION

A. Prior to concrete removal, locate prestressing steel using non-destructive testing (NDT) methods at locations along the length of each tendon in each bay, or by other approved means.

B. Identify and clearly mark fractured, corroded, or otherwise damaged sections of prestressing steel. Create exploratory openings in concrete as necessary to locate fractured or corroded sections. Engineer will inspect tendon and determine appropriate repair method before replacement. Tendons with fractured or severely corroded wires shall be replaced for their entire length or repaired by splicing in sections of new tendons similar in kind and size and restressing of tendons.

C. Where significant concrete removal is required or a significant number of tendons require spliced repair and restressing, install shoring and/or sequence repairs as directed by Engineer. This shoring must be designed by an Engineer competent in shoring design.

03 23 00 - 17

D. Remove unsound concrete as specified in Division 03, Section “Cast-in-

Place Concrete,” and as approved by Engineer. Exercise care to avoid damaging prestressing steel, sheathings, anchorages, and remaining sound concrete. Do not remove concrete at post-tensioning anchorages unless directed to do so by Engineer.

E. Maintain tendon profile. Use grout or other means as necessary to securely maintain tendon position during Work.

F. Identify damaged sheathing and document locations.

3.3 INSTALLATION

A. Where splicing of prestressing steel is required, the following requirements must be met.

1. Scope:

a. Repair tendons with broken or severely corroded wires at the locations determined by the Engineer by splicing in sections of new strands/tendons similar in kind, tensile strength, and size.

b. Restress the spliced tendons to obtain their design long-term effective post-tensioning force, 0.64 Pu (or other force determined by the Engineer after seating losses. Typically, to obtain 64% of specified tensile strength in tendon after the anchors are seated, the jacking force should not exceed 74% of the specified tensile strength of the strand.)

2. Detension prestressing steel as necessary by cutting, preferably while still embedded in concrete, or by the use of specialty detensioning equipment or by other approved means. Where detensioning of only a portion of the tendon length is desired, install lock-off anchor at location determined by Engineer.

3. Remove concrete as required to expose sufficient length of prestressing steel that is not deteriorated, on both sides of deteriorated strand section, and to permit installation of splice hardware allowing adequate room for movement of the splice during elongation of the prestressing steel. Exercise care to avoid damaging remaining sound concrete and sheathing.

4. If prestressing steel drapes into or across the area of concrete removal, discuss method of removing prestressing steel with

Engineer. Maintain the design tendon profile.

5. Remove the deteriorated section of prestressing steel.

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6. Discuss splicing procedure with Engineer to ensure that remaining concrete is not overstressed during stressing. (It is important to ensure that the prestressing force gets into the concrete. As a result, it is desirable to limit the size of the tendon repair openings so that a significant portion of the member cross-section remains available to resist the prestressing force as it is restored to the structure. This is particularly critical at anchorage zones of repaired end anchors, but the extent of concrete removal should be considered at all cross-sections along a member being repaired.)

7. Form as necessary and cast concrete repairs that are necessary for stressing prestressing steel. (This will include the anchorage zone in front of new tendon end anchors and may include other locations along the tendon length as appropriate for restoring the member cross-section prior to stressing. Note that prestressing steel will elongate, so repair openings must not be recast prior to stressing in a manner that would inhibit movement of the tendon and its couplers and central stressing splices. A common technique is to leave “boxouts” of sufficient size around couplers and central stressing splices to allow them to move during stressing.) Do not stress prestressing steel until repair concrete has achieved at least 3,000 psi. Concrete repair areas shall be prepared per provided details, the exposed prestressing steel addressed per

Paragraph I below, and the repair opening formed and cast per

Division 03, Section “Cast-In-Place Concrete.”

8. Install splice materials.

a. Pull ends of existing prestressing steel (strand/wires/tendon) taut.

b. Install couplers, new end anchors, and central stressing 1 splices with new section of prestressing strand.

c. New sheathing may need to be placed on the tendon during splicing operations.

9. Prepare existing prestressing steel.

a. Coat exposed existing prestressing steel with corrosion-inhibiting PT coating.

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b. Install slit-tube sheathing (or wrapped sheathing for button-head wire tendons) over existing prestressing steel and wrap with specialty waterproof tape as described above in Section 3.3.

10. At locations of couplers (and center stressing splices for 7-wire strand tendons) (and sections of new tendon wires for button-head wire tendons), use heat shrink tubing to make sheathing continuous across repair opening. Install per Paragraph above.

11. Stress PT tendon per below.

12. When stressing operation has been completed and following tendon force verification, prepare repair openings, and form and cast repair openings with concrete.

a. Inspect anchors for correct installation.

b. Inspect sheathing for damage and for continuous seal between sheathing and anchor.

1) Repair sheathing damage to watertight condition and correct anchor deficiencies.

2) Do not leave tendons and repair areas exposed to weather without protection prior to concrete placement. The Contractor shall propose to the Engineer the plan to guarantee a full protection of the PT system to weather aggression.

c. Apply PT coating to exposed prestressing tendons/strands/wires, including strand tails at anchorages, and restore sheathing per

Paragraph 3.3.

d. Shrink heat-reactive tubing into position to encapsulate prestressing steel. Seal ends of new sheathing with specialty moisture-proof sheathing tape.

e. Sandblast clean the exposed concrete and steel surfaces. Protect tendons from damage.

f. Coat other exposed steel, epoxy, galvanized coating, or approved method.

g. Install dowels into sides of full-depth repair openings as required, anchoring with epoxy.

h. Add supplemental reinforcing as directed by Engineer.

i. Install encapsulation caps over strand tails and secure. Fill stressing anchorage pockets with grout. When grout will be visible, trowel smooth and rub to match adjoining surface.

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B. Where extracting and threading new post-tensioning strands/wires:

a. Provide access to tendon to be removed at appropriate locations.

(Excavate access openings at high and low points and/or and end anchors: Remove external cover; etc.)

b. Detension post-tensioning strand/wires as necessary by saw cutting, preferably while still embedded in concrete, or specialty detensioning equipment. Provide protection at the end anchorages to prevent anchorage, wedges, or tendon from rebounding during detensioning and causing damage to property or passerby.

c. Extract existing strand and thread new strand through existing sheathing. If the existing strand is wet when exposed, dry sheathing. At the Engineer discretion, clean sheathing with clean rags until two clean passes are achieved. Rags may be saturated with an approved cleaning solvent prior to use. Fill sheathing with new corrosion inhibiting grease. Thread new strand through existing sheathing.

d. Install new end anchorages and repair concrete. Provide new wedges and hardware compatible with new end anchor.

e. Stress new strand per Paragraph 3.4.

f. Restore access openings at the completion of re-stressing.

C. Do not expose tendons to excessive temperatures, welding sparks or electric ground currents.

D. Install stressing anchorages perpendicular to tendon axis. Curvature in tendon profile shall preferably not be closer than 900 mm (3 feet) from stressing anchorage.

E. Sheathing Inspection:

1. After installing the tendons in forms and prior to concrete casting, inspect sheathing for damage.

2. At locations of damaged sheathing, remove concrete to expose sheathing at least 4 inches beyond damaged portion and to create space between the sheathing and the concrete. Exercise care to avoid further damage to sheathing. Concrete removal beneath a stressed tendon shall be minimized where the profile of the tendon may be affected.

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a. At small, localized areas of sheathing damage, as determined by

Engineer(Note: Items 1 through 4 below are the repair procedure for isolated punctures, holes, and slits where sheathing is mostly intact with minimal damage):

1) Remove rough portions of existing sheathing at damaged area.

2) Fill sheathing with corrosion-inhibiting PT coating.

3) Clean and prepare surface of existing sheathing per tape manufacturer’s recommendations. Outer surface of sheathing shall be dry and free of corrosion-inhibiting PT coating.

4) Tape damaged area of sheathing. Wrap tape spirally around sheathing to provide at least layers of tape at all locations.

Extend tape at least 2 inches beyond damaged area.

b. Remove damaged portion of sheathing.

c. Lightly sandblast exposed prestressing steel to remove rust.

Protect existing sheathing from damage (at least a minimum of 4

in. of existing sheathing should be protected at each end of the exposed portion of the sheathing within a repair opening).

d. Coat exposed prestressing steel or pressure-inject with corrosion-inhibiting PT coating. PT coating must extend to, but not cover, 4 in. of intact existing sheathing at ends of the exposed portion of sheathing.

e. Clean and prepare the existing sheathing per tape manufacturer’s recommendations. At a minimum, the surface of the sheathing shall be dry, clean, and free of corrosion-inhibiting PT coating.

f. Install new slit tube sheathing (For sheathing repairs where slit tube sheathing does not completely cover the stand, use waterproof tape in place of split sheathing).

1) Place slit tubing around prestressing strand. Position slit on side of prestressing steel, with shingle overlap (i.e., with upper portion overlapping lower portion).

2) Extend new sheathing at least 2 inches over existing sheathing.

3) Tape new sheathing. Wrap tape spirally around sheathing to provide at least 2 layers of tape. Extend tape at least 2 inches onto existing sheathing.

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g. Install new wrapped sheathing (For sheathing repairs where slit tube sheathing of sufficient width to be placed around the entire circumference of the prestressing strand/wires is not available).

1) Wrap polyethylene sheeting around prestressing strand/wires, continuing around the prestressing steel at least three times to provide 3 layers of sheeting at all locations.

2) Position edge of sheeting on side of prestressing steel, with shingle overlapping (i.e., with upper portion overlapping lower portion).

3) Extend new sheeting at least 2 inches over existing sheathing.

4) Wrap specialty sheathing tape spirally around sheathing to provide at least 2 layers of tape at all locations. Extend tape at least 2 inches onto existing sheathing.

h. Sheathing at couplers, central stressing splices (for 7-wire strand tendons), shall consist of heat shrink tubing. Place heat-shrink tubing over coupler, central stressing splice, or tendon during assembly of spliced tendon repair. Do not heat shrink tubing into final position until stressing is completed. Shrink tubing using a heat gun as approved by the Engineer, open flames shall not be permitted. Provide 2 in. minimum overlap with sheathing for adjacent section of tendon.

i. Protection of Anchorages (and Center Stressing Splices)

1) All new end anchor castings shall be supplied fully encased in

1 protective plastic cover, with plastic trumpet and plastic-covered encapsulation cap, to provide for full encapsulation of the new anchor.

j. Sheathing repairs shall be watertight.

3.4 STRESSING

A. Unless otherwise indicated, do not start stressing until concrete has attained a compressive strength of no less than 75 percent of its 28-day strength as confirmed by field cured test cylinders. Additionally, before stressing, verify that prestressing steel is free moving along its length. Orient anchorage wedges in the cavity perpendicular to the jack position during stressing.

A. After tests indicate that concrete has reached sufficient strength, stress tendons by means of hydraulic jacks equipped with calibrated

03 23 00 - 23 pressure gauges with an accuracy of 1 percent of scale range to permit the stress in tendons to be computed at any time. Equip hydraulic stressing rams used to stress unbonded single strand tendons with stressing grippers that will not notch strand more severely than normal anchoring wedges. Notify the COR 48 hours before any stressing operation that takes place.

1. Conduct stressing operation as recommended by manufacturer of stressing tendons and in conformance with approved shop drawings.

Stressing operations shall be performed by personnel experienced in this Work with a minimum of PTI level 2, or under direct supervision of stressing equipment supplier’s representative with a minimum of

PTI level 2. Exercise care in handling stressing equipment to maintain accuracy of calibration.

a. Stress tendon to provide a final tensile force after seating loss of 0.64 Pu. Typically, to obtain 64% of specified tensile strength in tendon after the anchors are seated, the jacking force should not exceed 74% of the specified tensile strength of the strand.

1) Calculate elongation for specified tensile stress for each tendon.

2) Sequence stressing as necessary.

3) Monitor hydraulic pressure and convert to jacking force with jack calibration curve.

4) Measure prestressing steel elongation and compare with calculated elongation. If the difference is more than 7 percent notify the Engineer for direction. When specified tensile stress has been attained, anchor prestressing steel with wedges).

5) If required, perform lift-off test in presence of Engineer after stressing and seating of wedges (for 7-wire strand tendons). As an example, Liftoff testing may be required if the elongations do not meet the 7% as shown above.

6) Maintain stressing records during stressing operations.

b. If turnbuckle-type cable splice is used, stress tendon per the manufacturer’s recommendations.

1) Calculate elongation for specified tensile stress for each tendon.

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2) Restress tendon using calibrated torque wrench. Stress to designated tensile force using calculated correlation between applied torque and tensile force.

3) Measure prestressing steel elongation at various levels of stressing force and compare with calculated elongation.

4) If measured and calculated elongations differ by more than 7 percent, cease stressing operations until cause of deviation is found and corrected.

5) Record applied torque, determine calculated tensile force, and submit to Engineer for review and approval.

2. Keep records of elongation and of tension applied to each tendon and submit four copies to the COR promptly upon the completion of post-tensioning of each member. Make elongation measurements at each stressing location to verify that effective force has been properly achieved. Measured elongations shall agree with calculated elongations within + 10 percent. Resolve discrepancies exceeding +

10 percent with the COR. At time of stressing first member of each type, check stresses in individual tendons to establish a post-tensioning procedure producing uniform results.

3. Complete stressing records during the tensioning operation, with following data recorded as a minimum:

a. Tendon mark or identification.

b. Required elongation.

c. Gauge pressure to achieve required elongation.

d. Actual elongation achieved.

e. Actual gauge pressure.

f. Date of stressing operation.

g. Signature of stressing operator or inspector.

h. Serial or identification number of jacking equipment. Stressing records shall then be turned over to the Government and professional engineer of record for verification and approval.

4. Obtain written permission of the COR before cutting tendons or capping post-tensioned anchorages.

B. Anchor prestressing tendons at an initial or "Transfer Stress" that will result in retention of working forces or stresses of not less than those shown on the drawings as the final prestress force after all

03 23 00 - 25 losses. In no case shall tendons be anchored at stresses above 74 percent of specified tensile strength of tendon.

C. Do not do any welding around tendons.

D. Take reasonable care to prevent damage to tendons. In the event that a single wire in multiple wire strands is broken, replacement will not be required providing total loss caused by broken strand is less than 2 percent of total prestress in the member. Contractor shall replace tendon at no additional cost to the Government in the event prestress loss through breakage is greater than 2 percent.

3.5 FINISHING

A. Trimming of excess tendon length: As soon as possible after tendon tensioning and satisfactory check of elongation and the accepting of stressing records by the COR, cut excess tendon length and prepare repair openings for concrete placement per 3.3.12. Tendon length protruding beyond wedges after cutting shall have at least 1-3/4 inches of concrete cover.

B. Tendons may be cut by means of oxyacetylene cutting, abrasive wheel, or hydraulic shears. In case of oxyacetylene cutting of tendons, take care to avoid directing flame toward wedges.

1. Do not damage prestressing steel, anchorage, or concrete. Leave prestressing steel end clean and free of burs.

2. Do not cut strands less than ½ inch from wedges.

C. Clean prestressing steel, anchorages, and concrete pockets of corrosion-inhibiting grease. Use non-corrosive solvent.

D. Fill stressing pockets with non-shrink mortar as soon as practical after tendon stressing and cutting. Under no circumstances shall grout or mortar used for pocket filling contain chlorides or other chemicals known to be deleterious to prestressing steel.

E. Coat exposed strand and wedge areas with tendon coating material comparable to that used over length of the tendon and a watertight cap shall be applied over the coated area. Prior to installing pocket mortar, coat or spray inside concrete surfaces of pocket with a resin bonding agent.

1. Install protective cap on cut ends where possible to prevent moisture infiltration.

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2. Prestressing steel ends shall be accessible for inspection prior to and during cutting, and prior to placement of protective caps and grout.

1.2 FIELD QUALITY CONTROL

A. Stressing records shall be filled out during retensioning operations and then be submitted to the Engineer for review and verification, per

PTI M-10. The following data shall be recorded as a minimum:

1. Name of the project

2. Tendon number correlated to a plan view identifying tendon locations.

3. Gauge pressure to achieve required force as per supplied calibration chart.

4. Calculated elongation, and allowable range of elongations, at design tensile force.

5. Actual elongation achieved.

6. Actual gauge pressure at end of stressing.

7. Date of stressing operation.

8. Name and signature of the stressing operator or inspector.

9. Serial or identification number of jacking equipment.

10. Date of approved shop drawings used for installation and stressing.

B. Maintain drying records documenting changes in moisture content during drying operations and submit to Engineer.

C. Contractor shall inspect tendons after installation. Reject, repair, or replace nonconforming work.

D. Inspect sheathing for unrepaired damage, for watertight seal between sheathing and anchor, and for correct installation of anchors, before concrete is placed around tendons.

E. Engineer or testing agency retained by Contractor will inspect installed Work prior to concrete placement. Contractor shall submit a minimum of three (3) independent contractors that test tendons for review/selection by the Owner. Contractor shall provide the results of the testing to the Owner prior to concrete placement.

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POST-TENSIONING SUPPLIER QUALIFICATION FORM

GENERAL INFORMATION:

Project: City:

Supplier:

General Contractor:

SAMPLE PROJECT #1 Date Completed:

Project Name: $ Value of PT Sub-contract:

City and State: Tonnage of PT tendons:

Engineer of Record General Contractor

Name: Project Manager:

Firm: Firm:

Phone Number: Phone Number:

Email: Email:

SAMPLE PROJECT #2 Date Completed:

City and State: Tonnage of PT tendons:

Engineer of Record General Contractor

Name: Project Manager:

Firm: Firm:

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SAMPLE PROJECT #3 Date Completed:

City and State: Tonnage of PT tendons:

Engineer of Record General Contractor

Name: Project Manager:

Firm: Firm:

SAMPLE PROJECT #4 Date Completed:

City and State: Tonnage of PT tendons:

Engineer of Record General Contractor

Name: Project Manager:

Firm: Firm:

03 23 00 - 29

SAMPLE PROJECT #5 Date Completed:

City and State: Tonnage of PT tendons:

Engineer of Record General Contractor

Name: Project Manager:

Firm: Firm:

REQUIRED ATTACHMENTS

Quality plan for…