ACI 423.7-14: Specification for Unbonded Single-Strand ...

AC

I 423

.7-1

4Specification for Unbonded Single-Strand Tendon Materials

Reported by Joint ACI-ASCE Committee 423

An ACI Standard

Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=University of Texas Revised Sub Account/5620001114, User=erur, ert

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First PrintingNovember 2014

ISBN: 978-0-87031-961-7

Specification for Unbonded Single-Strand Tendon Materials

Copyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This material may not be reproduced or copied, in whole or part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of ACI.

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This material specification provides materials criteria and fabrica-tion requirements for unbonded single-strand tendons.

Keywords: fabrication; post-tensioning; PT coating; tendon; unbonded.

CONTENTS

1—SCOPE, p. 21.1, p. 21.2, p. 21.3, p. 21.4, p. 2

2—DEFINITIONS, p. 22.1, p. 2

3—REFERENCED STANDARDS, p. 33.1—American Concrete Institute, p. 33.2—ASTM International, p. 33.3—International Organization for Standardization, p. 33.4—Federal Test Method Standard, p. 3

4—ORDERING INFORMATION, p. 34.1, p. 3

5—MATERIALS, p. 45.1—Prestressing steel, p. 45.2—Post-tensioning (PT) coating, p. 45.3—Sheathing, p. 45.4—Anchorages and couplers, p. 4

5.5—Connecting components, p. 45.6—Tape, p. 4

6—MANUFACTURE, p. 46.1—Minimum quantity of post-tensioning (PT) coating,

p. 46.2—Manufacturing processes, p. 46.3—Sheathing coverage, p. 46.4—Nonencapsulated systems, p. 56.5—Encapsulated systems, p. 5

7—MECHANICAL PROPERTIES, p. 57.1—Prestressing steel, p. 57.2—Post-tensioning (PT) coating, p. 5

8—DIMENSIONS, DENSITY, AND PERMISSIBLE VARIATIONS, p. 5

8.1—Prestressing steel, p. 58.2—Sheathing, p. 58.3—Anchorages, p. 58.4—Connecting components, p. 6

9—ANCHORAGE ASSEMBLY TESTING, p. 7

Carin L. Roberts-Wollmann, Chair Amy M. Reineke Trygestad, Secretary

ACI 423.7-14

Specification for Unbonded Single-Strand Tendon Materials

An ACI Standard

Reported by Joint ACI-ASCE Committee 423

Theresa M. AhlbornRobert W. BarnesFlorian G. Barth

Asit N. BaxiRoger J. Becker

Kenneth B. BondyCharles W. DolanJames P. DonnellyPierre EsselinckMartin J. Fradua

William L. GambleHarry A. GleichShawn P. Gross

Pawan R. GuptaWilliam M. Hale

H. R. Trey Hamilton IIICarol Hayek

Mohammad IqbalDonald P. KlineLarry B. KrauserJason J. Krohn

Mark E. Moore*

Theodore L. Neff †Sami H. Rizkalla

James RogersBruce W. Russell

David H. SandersThomas C. Schaeffer

Morris Schupack*

Richard W. StoneMiroslav F. Vejvoda

Jeffrey S. VolzH. Carl Walker

Zuming XiaPaul Zia

Consulting MembersRobert N. Bruce Jr.

Ned H. Burns

Chunsheng ‘Steve’ CaiSteven R. Close

Henry J. Cronin Jr.Ward N. Marianos Jr.

Hani MelhemAntoine E. Naaman

Thomas E. NehilAndrea J. Schokker

_________________*Deceased†Chair of subcommittee responsible for preparation of specification.

ACI 423.7-14 supersedes ACI 423.7-07, became effective October 22, 2014, and was adopted and published November 2014.

Copyright © 2014, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by any

means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or oral, or recording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.

1Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=University of Texas Revised Sub Account/5620001114, User=erur, ert


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9.1—Validation, p. 79.2—Components, p. 79.3—Encapsulated systems, p. 79.4—Static test, p. 79.5—Fatigue test, p. 79.6—Hydrostatic test, p. 7

10—TESTING SERVICES, p. 710.1—Prestressing steel, p. 710.2—Anchorage assembly, p. 7

11—CERTIFICATION, p. 711.1, p. 7

12—PACKAGING AND IDENTIFICATION, p. 812.1—Bundling and banding, p. 812.2—Identification of components, p. 8

13—HANDLING, STORAGE, AND SHIPPING, p. 813.1—Handling, p. 813.2—Storage before shipping, p. 813.3—Shipping, p. 813.4—Protection from moisture, p. 8

14—INSTALLATION DRAWINGS, p. 8

1—SCOPE

1.1This specification provides materials criteria and fabrica-

tion requirements for unbonded single-strand tendons.

1.2This specification shall not apply to post-tensioned slab-

on-ground, mat, or raft foundations on expansive soils.NOTE 1—For membrane-type structures primarily under

tensile forces resulting from temperature effects and concrete shrinkage, the provisions apply where deemed appropriate by Architect/Engineer.

1.3The text of this standard references notes and footnotes

that provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be consid-ered as requirements of the standard.

1.4Values stated in inch-pound units are to be regarded as

standard. Values given in parentheses are mathematical conversion to SI Units that are provided for information only, and are not considered standard.

2—DEFINITIONS

2.1The following definitions govern in this specification.

See “ACI Concrete Terminology” for additional definitions. http://www.concrete.org/Tools/ConcreteTerminology.aspx

anchorage—a device used to maintain elongation in prestressing strand by transferring compression force to concrete.

Architect/Engineer—the architect, engineer, architec-tural firm, or engineering firm developing Contract Docu-ments or administering the Work under Contract Docu-ments, or both.

Contract Documents—a set of documents supplied by Owner to Contractor as the basis for construction; these documents contain contract forms, contract conditions, specifications, drawings, addenda, and contract changes.

coupler—a mechanical device that connects ends of two strands together, thereby creating a continuous tendon by transferring the post-tensioning force from one strand to the other strand.

encapsulated tendon—a tendon that is completely enclosed in a watertight covering from end to end, including anchorages, sheathing, post-tensioning coating, sleeves, and an encapsulation cap over the strand tail at each end.

encapsulation cap—plastic cap filled with post-tensioning coating that provides a watertight connection to all anchorages protecting the wedges and the tendon tail from moisture infiltration. The watertight connection shall include a mechanical interlock of a type that does not rely on friction alone to be held in place.

fpu—specified tensile strength of prestressing steel, psi (MPa).

fixed anchorage—anchorage located at end of tendon where stressing of tendon is not required (also known as dead-end anchorage).

installation drawings—drawings showing information about the specifics of the post-tensioning system and tendon placement such as the number, size, length, marking, loca-tion, elongation, and tendon profiles (also referred to as shop drawings).

intermediate anchorage—anchorage located between the ends of the tendon for application of post-tensioning force.

local zone—rectangular prism (or equivalent rectangular prism for circular or oval anchorages) of concrete immedi-ately surrounding the anchorage device and any confining reinforcement.

non-encapsulated tendon—a tendon that has bare metallic anchorages, and sheathing that is continuous between anchorages but not connected to the anchorages.

post-tensioning—method of prestressing in which prestressing steel is tensioned after concrete has hardened.

post-tensioning coating—material used to protect the prestressing steel against corrosion and reduce friction between prestressing steel and sheathing.

prestressed concrete—structural concrete in which internal stresses are introduced to reduce potential concrete tensile stresses resulting from loads.

prestressing steel—high-strength steel, most commonly a seven-wire strand, used to impart prestress forces to concrete.

sheathing—an extruded high-density polyethylene or polypropylene covering that encases prestressing steel to

American Concrete Institute – Copyrighted © Material – www.concrete.org

2 SPECIFICATION FOR UNBONDED SINGLE-STRAND TENDON MATERIALS (ACI 423.7-14)



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prevent bonding of the prestressing steel with the surrounding concrete, to provide corrosion protection, and to contain the post-tensioning coating.

sleeve—device for connecting sheathing to anchorage.strand tail—protruding length of strand outside of the

wedges that remains in place after the tendon tail has been cut off.

stressing anchorage—anchorage at one end or both ends of tendon where stressing of tendon is required (also known as live-end anchorage)

tendon—in post-tensioned applications, the tendon is a complete assembly consisting of anchorages, prestressing steel, post-tensioning coating, and sheathing.

tendon tail—protruding length of strand outside of the stressing anchorage needed temporarily for stressing of the tendons.

unbonded tendon—tendon in which prestressing steel is prevented from bonding to concrete, and is free to move relative to concrete. The longitudinal prestressing force is permanently transferred to concrete by the anchorages only.

wedges—pieces of tapered high-strength steel with serra-tions that bite into and grip the prestressing steel to transfer the prestressing force to the anchorage.

wedge cavity—opening in anchorage designed to accom-modate the prestressing steel passing through and housing the wedges.

Work—the entire construction or separately identifi-able parts thereof required to be furnished under Contract Documents.

3—REFERENCED STANDARDS

3.1—American Concrete InstituteACI 318-11—Building Code Requirements for Structural

ConcreteACI 350-06—Code Requirements for Environmental

Engineering Concrete Structures

3.2—ASTM InternationalASTM A416/A416M-12—Standard Specification for

Steel Strand, Uncoated Seven-Wire for Prestressed ConcreteASTM B117-11—Standard Practice for Operating Salt

Spray (Fog) ApparatusASTM C1077-14—Standard Practice for Laborato-

ries Testing Concrete and Concrete Aggregates for Use in Construction and Criteria for Laboratory Evaluation

ASTM D92-12—Standard Test Method for Flash and Fire Points by Cleveland Open Cup Tester

ASTM D95-13—Standard Test Method for Water in Petro-leum Products and Bituminous Materials by Distillation

ASTM D512-12—Standard Test Methods for Chloride Ion in Water

ASTM D566-02(2009)—Standard Test Method for Drop-ping Point of Lubricating Grease

ASTM D610-08(2012)—Standard Test Method for Eval-uating Degree of Rusting on Painted Steel Surfaces

ASTM D638-10—Standard Test Method for Tensile Prop-erties of Plastics

ASTM D792-13—Standard Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement

ASTM D2265-06—Standard Test Method for Dropping Point of Lubricating Grease Over Wide Temperature Range

ASTM D3867-09—Standard Test Methods for Nitrite-Nitrate in Water

ASTM D4289-13—Standard Test Method for Elastomer Compatibility of Lubricating Greases and Fluids

ASTM D4658-09—Standard Test Method for Sulfide Ion in Water

ASTM D6184-98(2005)—Standard Test Method for Oil Separation from Lubricating Grease

3.3—International Organization for StandardizationISO/IEC Guide 65:1996—General requirements for

Bodies Operating Product Certification SystemsISO/IEC 17065:2012—Conformity Assessment –

Requirements for Bodies Certifying Products, Processes and Services

3.4—Federal Test Method StandardFTMS 791B Method 321.2

4—ORDERING INFORMATION

4.1It shall be the responsibility of the purchaser to specify

all requirements that are necessary for the manufacture and delivery of the unbonded single-strand tendon under this specification. Such requirements to be considered include, but are not limited to, the submittal items in 4.1.1 through 4.1.6. Submittal item 4.1.1.1 shall be required unless specifi-cally excluded by the purchaser.

4.1.1 Prestressing steel4.1.1.1 Certified mill test reports and typical load-elonga-

tion curves for each coil or pack of strand used in fabrication of the tendons containing the following information:

a) Heat number and identificationb) Tensile strengthc) Yield stress at 1 percent extension under loadd) Elongation at failuree) Modulus of elasticityf) Diameter and net area of strandg) Type of material (normal or low-relaxation)4.1.1.2 Relaxation test results.4.1.1.3 Samples from each heat (or manufacturer’s length,

in the case of strands), properly marked, for verification of prestressing steel properties.

4.1.1.4 Strand records related to material production containing the following information:

a) Purchasing records showing the purchase of appropriate base materials used in production

b) Product traceability through production and shippingc) Testing results for tests required under 7.1 of this speci-

fication, conformities (or nonconformities), and resultant actions

d) Calibration records for all testing and control devices


SPECIFICATION FOR UNBONDED SINGLE-STRAND TENDON MATERIALS (ACI 423.7-14) 3



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e) Statistical records of quality performance evidencing the occasion, frequency, and percentage of accepted and rejected final product; records shall include internal and external occurrences such as on-site lab results and customer responses

f) Suitability and testing of raw materials, including quality reports from wire or rod suppliers

g) Procedure for the quarantine and disposal of noncom-pliant product and records of same

Strand records shall be maintained for a minimum period of 5 years.

4.1.2 Post-tensioning (PT) coating—Test results on PT coating, tested in accordance with 7.2.1.

4.1.3 Sheathing—A sheathing material report containing type, thickness, and density of material; information about added ultraviolet light stabilizers (if used); and supporting test data demonstrating compliance with all requirements of 5.3.

4.1.4 Anchorages and couplers—Static and fatigue test reports of representative assemblies for each different assembly to be used on the project.

4.1.5 Fabrication plant certification—A copy of the tendon fabrication plant certification. If the certification is not from a nationally accredited organization, provide docu-mentation demonstrating compliance with 11.1.

4.1.6 Stressing jack calibration—Calibration certificates for every jack and gauge set supplied to the project.

5—MATERIALS

5.1—Prestressing steelPrestressing steel used in unbonded single-strand post-

tensioning tendons shall conform to:a) ASTM A416/A416Mb) Strand not specifically covered in ASTM A416/A416M

that conforms to minimum requirements of this specification and has properties meeting requirements of ASTM A416/A416M.

5.2—Post-tensioning (PT) coatingPT coating shall meet the criteria of 7.2 and demonstrate

the following performance requirements:a) Provide lubrication between the strand and sheathingb) Resist flow caused by gravity within anticipated

temperature range of exposurec) Provide continuous nonbrittle coating at lowest antici-

pated temperature of exposured) Be chemically stable and nonreactive with prestressing

steel, reinforcing steel, sheathing material, and concrete

5.3—SheathingTendon sheathing material shall be high-density polyeth-

ylene or polypropylene that meets the criteria of 8.2 and that demonstrates the following performance requirements:

a) Sufficient strength and durability to withstand damage during fabrication, handling, transport, installation, concrete placement, and stressing

b) Watertight and impermeable to water vapor over entire sheathing length

c) Chemically stable, without embrittlement or softening over the anticipated exposure temperature range and service life of the structure; free chloride ions shall not be extract-able from the sheathing material

d) Nonreactive with concrete, prestressing steel, rein-forcing steel, and PT coating

5.4—Anchorages and couplersCastings shall be nonporous and free of sand, blow holes,

and voids.

5.5—Connecting componentsAny component used to connect the sheathing to any

anchorage or coupler enclosure in encapsulated systems shall conform to the following:

a) Be watertight in conformance with 9.3b) Meet or exceed the same requirements as the sheathing

for durability during fabrication, transportation, handling, storage, and installation

c) Be translucent or have another method of verifying compliance with 5.5(a) and 6.5.2(c)

d) Be translucent or have other method of verifying overlap with sheathing

5.6—TapeTape used as a component for enclosing couplers shall:a) Be self-adhesive and moisture-proofb) Be nonreactive with sheathing, PT coating, or

prestressing steelc) Have elastic propertiesd) Have a minimum width of 2 in. (50 mm)e) Have a contrasting color to the tendon sheathing

6—MANUFACTURE

6.1—Minimum quantity of post-tensioning (PT) coating

The minimum amount of PT coating on the prestressing strand shall be at least 2.5 lb (1.14 kg) of PT coating per 100 ft (30.5 m) for 0.5 in. (12.7 mm) diameter strand, and 3.0 lb (1.36 kg) of PT coating per 100 ft (30.5 m) for 0.6 in. (15.3 mm) diameter strand. The minimum quantity of PT coating for other strand sizes can be determined by linear extrapolation.

The PT coating shall completely fill the annular space between the strand and sheathing. The PT coating shall extend over the entire tendon length.

6.2—Manufacturing processesSheathing shall be manufactured by an extrusion process

that provides watertight encasement of the PT coating.

6.3—Sheathing coverageSheathing shall be continuous between anchorages and

shall prevent intrusion of cement paste or loss of coating materials. For nonencapsulated applications, a maximum





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of 1 in. (25 mm) of unsheathed strand shall be permitted at stressing anchorages, and up to 12 in. (400 mm) shall be permitted at fixed anchorages. Coupler components shall be protected with the same PT coating used on the strand, and shall be enclosed in sleeving with adequate length to permit necessary movements during stressing.

6.4—Nonencapsulated systemsUnless otherwise specified, the use of nonencapsulated

systems shall be permitted for applications not governed by ACI 318 or ACI 350.

6.5—Encapsulated systems6.5.1 Encapsulation—For all tendons used in applica-

tions governed by either ACI 318 or ACI 350, protect all anchorage assemblies by encapsulation, including the anchorage, wedges, and prestressing steel, against corrosion. The encapsulation shall include a watertight connection of the sheathing to the anchorage, and a watertight closure of the wedge cavity and prestressing steel.

Encapsulation systems shall employ plastic coating to protect the metallic components from corrosion. The use of bare metallic anchorages produced from a material that is subject to corrosion shall not be permitted.

6.5.2 Connection component—Any component used to connect the sheathing to any anchorage or coupler enclosure shall conform to the following:

a) Have a watertight, mechanical connection to the anchorage protection or coupler enclosure and a watertight connection at the tendon sheathing

b) Have a minimum 4 in. (100 mm) overlap between the end of the extruded sheathing covering the prestressing steel and the end of the sleeve

c) Within the connecting component or enclosure, either the prestressing steel shall be covered by sheathing for its full length, or the annular space between the sleeve and the strand shall be filled with PT coating in conformance with 5.2.

7—MECHANICAL PROPERTIES

7.1—Prestressing steel7.1.1 Mechanical properties—Tests shall be performed in

accordance with the methods and frequency prescribed in ASTM A416/A416M.

7.1.2 Relaxation properties—For low-relaxation strand, finished strand shall be tested during production for relax-ation at least annually, but also on any occasion of change in the type of raw material or manufacturing process. The relaxation test shall be performed according to the require-ments of ASTM A416/A416M and the requirements herein.

The relaxation test shall be performed as a full 1000-hour test at initial production and every third year there-after. Interim annual relaxation tests may be performed as 200-hour tests with results extrapolated to 1000 hours, provided that the previous full 1000-hour test exhibits satis-factory results.

7.1.3 Premature failure—For tests required in this specifi-cation for both normal and low-relaxation prestressing steel, failure of prestressing steel due to notch or pinching effects from wedges is not acceptable.

7.1.4 Acceptance criteria for surface condition—Strand used for tendon manufacture shall be dry. Surface rust, if any is present, shall be removable with a fine steel wool pad or by vigorous rubbing with a cloth. Pits on steel surface shall not exceed 0.002 in. (0.05 mm) in diameter or length.

NOTE 2—Guidance for evaluating the degree of rusting on strand is presented in Sason (1992).*

7.2—Post-tensioning (PT) coating7.2.1 Mechanical properties and acceptance—The PT

coating shall be a compound that complies with the tests and associated acceptance criteria specified in Table 7.2.1. PT coating shall be tested whenever any change is made to its chemical composition and at least once every 5 years.

8—DIMENSIONS, DENSITY, AND PERMISSIBLE VARIATIONS

8.1—Prestressing steelAll samples tested shall be checked to ensure that the

strand meets the dimensional requirements listed in ASTM A416/A416M.

8.2—Sheathing8.2.1 Thickness—Minimum thickness of sheathing shall

be 0.050 in. (1.27 mm). Variations in sheathing thickness of up to 10 percent shall be acceptable, provided an average of four equidistant readings along the circumference equals or exceeds the required thickness.

8.2.1 Density—Minimum density of sheathing shall be 0.034 lb/in.3 (941 kg/m3).

8.2.2 Diameter—Sheathing shall have an inside diameter at least 0.030 in. (0.76 mm) greater than the maximum diam-eter of the strand.

8.2.3 Surface—Sheathing shall provide a smooth circular outside surface and shall not visibly reveal lay of the strand.

8.3—Anchorages8.3.1 Bearing stresses—Anchorage dimensions shall

be such that average bearing stresses on concrete created by an anchorage shall not exceed values computed by the following equations unless testing by a certified independent laboratory indicates anchorage performance equivalent or superior to anchorages satisfying the requirements of this section.

a) At transfer load

0.75 b

cp cib

Af f

A′

= ′ (8.3.1a)

* Sason, A. S., 1992, “Evaluation of Degree of Rusting on Prestressed Concrete Strand,” PCI Journal, V. 37, No. 3, May-June, pp. 25-30.





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but not greater than 1.25fci′b) At service load

0.6 bcp c

b

Af f

A′

′= (8.3.1b)

but not greater than fc′where fcp is the permissible concrete compressive stress; fc′ is the specified concrete compressive strength; fci′ is the specified concrete compressive strength at time of initial prestress; Ab′ is the maximum area of the portion of the concrete anchorage surface that is geometrically similar to

and concentric with the area of the anchorage; and Ab is the net bearing area of anchorage.

The average bearing stress P/Ab in the concrete shall be computed by dividing the force P of the prestressing steel by the net bearing area Ab between concrete and bearing plate or other structural element of the anchorage that has the func-tion of transferring force to the concrete.

8.4—Connecting components8.4.1 Any component used to connect the sheathing to

any anchorage or coupler enclosure in encapsulated systems shall have 0.050 in. (1.27 mm) minimum thickness.

8.4.2 Tape used as a component for enclosing couplers shall have a minimum width of 2 in. (50 mm).

Table 7.2.1—Testing of PT coatingTest no. Test description Test method Acceptance criteria

1 Dropping point ASTM D566 or D2265 Minimum 300°F (149°C)

2 Oil separation at 160°F (71°C) FTMS 791B Method 321.2 (ASTM D6184)

0.5 percent maximum by mass

3 Water content ASTM D95 0.1 percent maximum

4 Flash point (refers to oil component) ASTM D92 Minimum 300°F (149°C)

5Corrosion test (5 percent salt fog at 100°F

[38°C], 0.005 in. [0.127 mm], minimum hours, Q Panel Type S)

ASTM B117 Rust Grade 7 or better after 1000 hours of expo-sure according to ASTM D610

6

Water-soluble ions:*

a. Chloridesb. Nitratesc. Sulfides

ASTM D512ASTM D3867ASTM D4658

10 ppm maximum10 ppm maximum10 ppm maximum

7

Soak test (5 percent salt fog at 100°F [38°C], 0.005 in. [0.127 mm] coating, Q Panel Type S) Immerse panels 50 percent in a 5 percent salt

solution and expose to salt fog)

ASTM B117 (modified) No emulsification of the coating after 720 hours of exposure.

8

Compatibility with sheathing:a. Hardness and volume change of polymer

after exposure to grease, 40 days at 150°F (66°C)

b. Tensile strength change of polymer after exposure to grease, 40 days at 150°F

(66°C)

ASTM D4289(ASTM D792 for density)

ASTM D638

Permissible change in hardness: 15 percentvolume: 10 percent

Permissible change in tensile strength: 30 percent

*Procedure for Test 6: The inside (bottom and sides) of a 1.06 quart (1 L) glass beaker (approximate outside diameter 4.13 in. [105 mm], height 5.71 in. [145 mm]) is thoroughly coated with 3.53 ± 0.35 oz (100 ± 10 g) of corrosion-inhibiting coating material. The coated beaker is filled with approximately 30 oz (900 cc) of distilled water and heated in an oven at a controlled temperature of 100°F ± 2°F (37.8°C ± 1.1°C) for 4 hours. The water extraction is tested by the noted test procedures for the appropriate water-soluble ions. Results are reported as ppm in the extracted water.

Notes:Tests 1 and 2—Limiting the dropping point to 300°F (149°C) minimum is intended to ensure product stability under the elevated temperatures that are possible during tendon fabrication and installation. Together, Tests 1 and 2 minimize bleeding of the lighter components from the coating.Test 3—Water content is limited to exclude the presence of free water in the coating material.Test 4—This test refers to the oil component in the coating material. Too low a flash point indicates higher content of volatile derivatives, which affect the long-term stability and consistency of the coating material.Test 5—This test provides a method to determine the effectiveness of the corrosion-inhibiting properties of the coating. The method is a standard test used for corrosion-inhibiting coatings such as paints. The acceptance criterion of Grade 7 or better (according to ASTM D610) after 1000 hours of exposure requires that only 0.3 percent of the area exposed can have indications of corrosion. The test is conducted on a 3 x 6 in. (76 x 152 mm) steel panel with a coating thickness of 0.005 in. (0.127 mm). When determining the percent of area corroded, only the area inside 1/4 in. (6 mm) from the edges of the panel is evaluated.Test 6—Water-soluble ions known to cause corrosion are limited by this requirement.Test 7—The soak test is designed to determine the ability of the coating to provide corrosion protection after having been exposed to standing water for a period of time. Certain coatings will absorb water to the extent that they will emulsify and thus not be an effective barrier against moisture reaching the steel. This test will guard against use of such coatings.Test 8—Certain petroleum derivatives react with polyethylene or polypropylene, changing their physical properties to the point where they are no longer usable as sheathing materials. This test is required to preclude the use of coatings with such derivatives.





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9—ANCHORAGE ASSEMBLY TESTING

9.1—ValidationThe adequacy of a tendon system shall be confirmed by

static and fatigue conformance tests in accordance with the minimum requirements outlined in 9.4 and 9.5. Separate specimens shall be used for static and fatigue tests. Retesting is required whenever a component of an assembly changes.

9.2—ComponentsComponent parts from different manufacturers shall not

be used in an anchorage assembly unless the combination has been tested in accordance with 9.1.

9.3—Encapsulated systemsThe encapsulation assembly shall remain watertight when

tested and subjected to a uniform hydrostatic pressure for a period of 24 hours in accordance with 9.6. The following minimum uniform hydrostatic pressure shall be used in the test:

a) For applications governed by ACI 318: 1.25 psi (8.6 kPa)b) For applications governed by ACI 350: 10 psi (68.8 kPa)

9.4—Static test9.4.1 Static tensile tests of tendons shall be performed.

The test assembly, consisting of standard production quality components and tendons, shall be at least 3.5 ft (1.1 m) long between anchorages. The test shall provide determination of the yield stress, tensile strength, and percent elongation of the complete tendon.

9.4.1.1 Strength test criteria—Anchorages and couplers of unbonded tendons shall develop at least 95 percent fpu when tested in accordance with 9.4.

9.4.1.2 Ductility criteria—Total elongation under breaking load when tested in accordance with 9.4.1 shall not be less than 2 percent. Elongation shall be measured in a minimum gauge length of 3 ft (915 mm) between two points at least 3 in. (75 mm) from each anchorage. Tendon couplers shall not reduce elongation at rupture below that required for anchorages.

9.5—Fatigue test9.5.1 Fatigue tests shall be performed on tendon speci-

mens with representative samples from production runs and with a minimum length of 3 ft (1 m) between anchorages. In the first test, the tendon shall be subjected to 500,000 cycles between 60 and 66 percent fpu. In the second test, the tendon shall be subjected to 50 cycles between 40 and 85 percent fpu. One complete cycle involves change from the lower stress level to the upper stress level and back to the lower.

9.6—Hydrostatic test9.6.1 Representative couplers and anchorages shall be

tested to verify a watertight encapsulation of prestressing steel and all connections in conformance with 9.6.1.1 through 9.6.1.3. Three tests are required for each assembly with all three passing for the system to pass.

9.6.1.1 Anchorages shall remain watertight when tested and subjected to a hydrostatic pressure of no less than that specified in 9.3 for a period of 24 hours.

9.6.1.2 Representative samples from production runs, selected and assembled by the manufacturer, shall be used in testing. Stressing, intermediate, and fixed anchorage assem-blies shall each be tested.

9.6.1.3 During the testing procedure, the following steps are required to detect the presence of moisture:

a) Add white pigment to the post-tensioning coatingb) Use a colored dye in the water that will contrast with

the white color of the post-tensioning coatingc) After 24 hours, the encapsulation system shall be

removed and the color of the coating shall be notedNo colored dye staining inside the encapsulation system

anywhere on the white PT coating is permissible.

10—TESTING SERVICES

10.1—Prestressing steelMechanical property and dimensional tests may be

performed in-house by the manufacturer. Relaxation tests shall be performed, or observed and confirmed, by an inde-pendent laboratory accredited under ASTM C1077. Any testing facility used, whether in-house or other, shall be identified completely including physical address and contact information.

10.2—Anchorage assemblyStatic, fatigue, and hydrostatic tests shall be performed

by an independent testing laboratory selected by the system manufacturer. The independent testing laboratory shall be accredited under ASTM C1077.

11—CERTIFICATION

11.1Unbonded single-strand tendons shall be fabricated in a

plant audited and certified by an external program accred-ited by a national accreditation body such as the American National Standards Institute (ANSI), International Accredi-tation Service (IAS), American Association for Laboratory Accreditation (A2LA), or equivalent.

Nonaccredited certification programs shall meet the essen-tial requirements of ISO/IES Guide 65 or ISO/IEC 17065, including, at a minimum, the following:

a) Have a documented structure which safeguards impar-tiality including provisions to ensure the impartiality of the operations of the certification body; this structure shall enable the participation of all parties concerned in the devel-opment of policies and principles regarding the content and functioning of the certification system

b) Be free of commercial/financial pressures that might influence results and be independent from the entity they are certifying

c) Have personnel that are competent and who meet defined minimum relevant criteria as defined by the certi-fying agency





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d) Have criteria outlined in specified standardse) Have a procedure for making rules and procedures

available to the public

12—PACKAGING AND IDENTIFICATION

12.1—Bundling and bandingIndividual tendons shall be secured in bundles using a

tying process that does not damage the sheathing. The tendon sheathing shall be protected from damage by banding mate-rials using padding material between banding and tendons.

12.2—Identification of components12.2.1 Wedges and anchorages—Wedges and anchorages

shall be identified by individual concrete placement area, floor sequence, or both. In the event that materials intended for one concrete placement area are exchanged into another concrete placement area, the transaction shall be noted for traceability purposes.

12.2.2 Prestressing steel—The strand manufacturing process shall be controlled and documented in a manner providing identification and traceability with regard to coil(s) of strand, wire rod heat number, and wire coil(s) used to produce the strand.

12.2.3 Encapsulated systems—Identification of all component parts of the encapsulation system and assembly instructions shall be provided to the field.

13—HANDLING, STORAGE, AND SHIPPING

13.1—Handling13.1.1 Tendons shall not be damaged during handling,

loading, moving, or unloading.13.1.2 Smooth forklift booms or padded forks shall be

used to handle tendons.13.1.3 Slings used to lift tendons shall be nonmetallic

and not choked when handling tendon coils. Metal chokers, chains, or hooks shall not be used to lift tendons or tendon bundles.

13.2—Storage before shipping13.2.1 Fabricated tendons shall be stored on a paved

surface with proper drainage away from tendons or on proper dunnage.

13.2.2 Tendons that are exposed to sunlight (with possible ultraviolet ray degradation) longer than 2 weeks (or 1 month maximum when ultraviolet light stabilizers are added to the sheathing per manufacturer’s recommendations) shall be protected by tenting or tarping with adequate ventilation.

13.3—Shipping13.3.1 Nonmetallic tie-downs shall be used to secure

tendon bundles to bed of the transport vehicle. Metal strap-ping or chains shall not be used.

13.3.2 Protection shall be provided between bed of the transport vehicle and bundles to prevent damage to the sheathing during shipping.

13.3.3 Tendons, accessories, equipment, and encapsula-tion materials shall be protected from exposure to moisture, deicing salts, and other corrosive elements during transporta-tion by shipping inside of enclosed trailers, by covering with tarps, by shrink-wrapping the tendon bundles, or by other methods accepted by the Architect/Engineer. Sheathing and anchorages shall not be damaged during loading, transporta-tion, and unloading.

13.4—Protection from moisture13.4.1 Tendons shall be protected from exposure to mois-

ture, deicing salts, and other corrosive elements.

14—INSTALLATION DRAWINGS14.1 Nonprestressed reinforcement required for anchor-

ages in the local zone shall be indicated on installation drawings.

14.2 Couplers shall be used only at locations approved by the Architect/Engineer. The location of the couplers shall be specified to maintain proper concrete cover and to allow longitudinal displacement of the couplers during stressing. Couplers shall not be used at points where tendon radius of curvature is less than 480 strand diameters.





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As ACI begins its second century of advancing concrete knowledge, its original chartered purpose remains “to provide a comradeship in finding the best ways to do concrete work of all kinds and in spreading knowledge.” In keeping with this purpose, ACI supports the following activities:

· Technical committees that produce consensus reports, guides, specifications, and codes.

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As a member of ACI, you join thousands of practitioners and professionals worldwide who share a commitment to maintain the highest industry standards for concrete technology, construction, and practices. In addition, ACI chapters provide opportunities for interaction of professionals and practitioners at a local level.

American Concrete Institute38800 Country Club DriveFarmington Hills, MI 48331Phone: +1.248.848.3700Fax: +1.248.848.3701

www.concrete.org



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38800 Country Club Drive

Farmington Hills, MI 48331 USA

+1.248.848.3700

www.concrete.org

The American Concrete Institute (ACI) is a leading authority and resource

worldwide for the development and distribution of consensus-based

standards and technical resources, educational programs, and certifications

for individuals and organizations involved in concrete design, construction,

and materials, who share a commitment to pursuing the best use of concrete.

Individuals interested in the activities of ACI are encouraged to explore the

ACI website for membership opportunities, committee activities, and a wide

variety of concrete resources. As a volunteer member-driven organization,

ACI invites partnerships and welcomes all concrete professionals who wish to

be part of a respected, connected, social group that provides an opportunity

for professional growth, networking and enjoyment.

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ACI 423.7-14: Specification for Unbonded Single-Strand ...

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