An ACI Standard
Specication for Unbonded Single-Strand Tendon Materials Reported by Joint ACI-ASCE Committee 423
4 1 7 . 3 2 4 I C A
First Printing November 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. The technical committees responsible for ACI committee reports and standards strive to avoid ambiguities, omissions, and errors in these documents. In spite of these efforts, the users of ACI documents occasionally find information or requirements that may be subject to more than one interpretation or may be incomplete or incorrect. Users who have suggestions for the improvement of ACI documents are requested to contact ACI via the errata website at http://concrete.org/Publications/ DocumentErrata.aspx. Proper use of this document includes periodically checking for errata for the most up-to-date revisions. ACI committee documents are intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. Individuals who use this publication in any way assume all risk and accept total responsibility for the application and use of this information. All information in this publication is provided “as is” without warranty of any kind, either express or implied, including but not limited to, the implied warranties of merchantability, fitness for a particular purpose or non-infringement. ACI and its members disclaim liability for damages of any kind, including any special, indirect, incidental, or consequential damages, including without limitation, lost revenues or lost profits, which may result from the use of this publication. It is the responsibility of the user of this document to establish health and safety practices appropriate to the specific circumstances involved with its use. ACI does not make any representations with regard to health and safety issues and the use of this document. The user must determine the applicability of all regulatory limitations before applying the document and must comply with all applicable laws and regulations, including but not limited to, United States Occupational Safety and Health Administration (OSHA) health and safety standards. Participation by governmental representatives in the work of the American Concrete Institute and in the development of Institute standards does not constitute governmental endorsement of ACI or the standards that it develops. Order information: ACI documents are available in print, by download, on CD-ROM, through electronic subscription, or reprint and may be obtained by contacting ACI. Most ACI standards and committee reports are gathered together in the annually revised ACI Manual of Concrete Practice (MCP). American Concrete Institute 38800 Country Club Drive Farmington Hills, MI 48331 Phone: +1.248.848.3700 Fax: +1.248.848.3701 www.concrete.org
ACI 423.7-14 Specification for Unbonded Single-Strand Tendon Materials An ACI Standard
Reported by Joint ACI-ASCE Committee 423 Carin L. Roberts-Wollmann, Chair Theresa M. Ahlborn Robert W. Barnes Florian G. Barth Asit N. Baxi Roger J. Becker Kenneth B. Bondy Charles W. Dolan James P. Donnelly Pierre Esselinck Martin J. Fradua William L. Gamble Harry A. Gleich Shawn P. Gross
Amy M. Reineke Trygestad, Secretary
Pawan R. Gupta William M. Hale H. R. Trey Hamilton III Carol Hayek Mohammad Iqbal Donald P. Kline Larry B. Krauser Jason J. Krohn Mark E. Moore * Theodore L. Neff † Sami H. Rizkalla James Rogers Bruce W. Russell
David H. Sanders Thomas C. Schaeffer Morris Schupack * Richard W. Stone Miroslav F. Vejvoda Jeffrey S. Volz H. Carl Walker Zuming Xia Paul Zia Consulting Members Robert N. Bruce Jr. Ned H. Burns
Chunsheng ‘Steve’ Cai Steven R. Close Henry J. Cronin Jr. Ward N. Marianos Jr. Hani Melhem Antoine E. Naaman Thomas E. Nehil Andrea J. Schokker _________________ * Deceased † Chair of subcommittee responsible for preparation of specication.
5.5—Connecting components, p. 4 5.6—Tape, p. 4
This material specication provides materials criteria and fabrication requirements for unbonded single-strand tendons. Keywords: fabrication; post-tensioning; PT coating; te ndon; unbonded.
6—MANUFACTURE, p. 4 6.1—Minimum quantity of post-tensioning (PT) coating, p. 4 6.2—Manufacturing processes, p. 4 6.3—Sheathing coverage, p. 4 6.4—Nonencapsulated systems, p. 5 6.5—Encapsulated systems, p. 5
CONTENTS 1—SCOPE, p. 2 1.1, p. 2 1.2, p. 2 1.3, p. 2 1.4, p. 2
7—MECHANICAL PROPERTIES, p. 5 7.1—Prestressing steel, p. 5 7.2—Post-tensioning (PT) coating, p. 5
2—DEFINITIONS, p. 2 2.1, p. 2 3—REFERENCED STANDARDS, p. 3 3.1—American Concrete Institute, p. 3 3.2—ASTM International, p. 3 3.3—International Organization for Standardization, p. 3 3.4—Federal Test Method Standard, p. 3
8—DIMENSIONS, DENSITY, AND PERMISSIBLE VARIATIONS, p. 5 8.1—Prestressing steel, p. 5 8.2—Sheathing, p. 5 8.3—Anchorages, p. 5 8.4—Connecting components, p. 6
4—ORDERING INFORMATION, p. 3 4.1, p. 3
9—ANCHORAGE ASSEMBLY TESTING, p. 7
5—MATERIALS, p. 4 5.1—Prestressing steel, p. 4 5.2—Post-tensioning (PT) coating, p. 4 5.3—Sheathing, p. 4 5.4—Anchorages and couplers, p. 4
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 reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.
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SPECIFICATION FOR UNBONDED SINGLE-STRAND TENDON MATERIALS (ACI 423.7-14)
9.1—Validation, p. 7 9.2—Components, p. 7 9.3—Encapsulated systems, p. 7 9.4—Static test, p. 7 9.5—Fatigue test, p. 7 9.6—Hydrostatic test, p. 7
10—TESTING SERVICES, p. 7 10.1—Prestressing steel, p. 7 10.2—Anchorage assembly, p. 7 11—CERTIFICATION, p. 7 11.1, p. 7 12—PACKAGING AND IDENTIFICATION, p. 8 12.1—Bundling and banding, p. 8 12.2—Identication of components, p. 8 13—HANDLING, STORAGE, AND SHIPPING, p. 8 13.1—Handling, p. 8 13.2—Storage before shipping, p. 8 13.3—Shipping, p. 8 13.4—Protection from moisture, p. 8 14—INSTALLATION DRAWINGS, p. 8 1—SCOPE 1.1 This specication provides materials criteria and fabrication requirements for unbonded single-strand tendons. 1.2 This specication shall not apply to post-tensioned slabon-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. 1.3 The text of this standard references notes and footnotes that provide explanatory material. These notes and footnotes (excluding those in tables and gures) shall not be considered as requirements of the standard. 1.4 Values 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 2.1 The following denitions govern in this specication. See “ACI Concrete Terminology” for additional denitions. 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, architectural rm, or engineering rm developing Contract Documents or administering the Work under Contract Documents, 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, specications, 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 lled with posttensioning coating that provides a watertight connection to all anchorages protecting the wedges and the tendon tail from moisture inltration. The watertight connection shall include a mechanical interlock of a type that does not rely on friction alone to be held in place. f pu —specied tensile strength of prestressing steel, psi (MPa). fxed 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 specics of the post-tensioning system and tendon placement such as the number, size, length, marking, location, elongation, and tendon proles (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 immediately surrounding the anchorage device and any conning 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
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SPECIFICATION FOR UNBONDED SINGLE-STRAND TENDON MATERIALS (ACI 423.7-14)
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 serrations that bite into and grip the prestressing steel to transfer the prestressing force to the anchorage. wedge cavity —opening in anchorage designed to accommodate the prestressing steel passing through and housing the wedges. Work —the entire construction or separately identiable parts thereof required to be furnished under Contract Documents.
3—REFERENCED STANDARDS 3.1—American Concrete Institute ACI 318-11—Building Code Requirements for Structural Concrete ACI 350-06—Code Requirements for Environmental Engineering Concrete Structures 3.2—ASTM International ASTM A416/A416M-12—Standard Specication for Steel Strand, Uncoated Seven-Wire for Prestressed Concrete ASTM B117-11—Standard Practice for Operating Salt Spray (Fog) Apparatus ASTM C1077-14—Standard Practice for Laboratories 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 Petroleum 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 Evaluating Degree of Rusting on Painted Steel Surfaces ASTM D638-10—Standard Test Method for Tensile Properties of Plastics
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ASTM D792-13—Standard Test Methods for Density and Specic 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 Sulde Ion in Water ASTM D6184-98(2005)—Standard Test Method for Oil Separation from Lubricating Grease
3.3—International Organization for Standardization ISO/IEC Guide 65:1996—General requirements for Bodies Operating Product Certication Systems ISO/IEC 17065:2012—Conformity Assessment – Requirements for Bodies Certifying Products, Processes and Services 3.4—Federal Test Method Standard FTMS 791B Method 321.2 4—ORDERING INFORMATION 4.1 It 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 specication. 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 specically excluded by the purchaser. 4.1.1 Prestressing steel 4.1.1.1 Certied mill test reports and typical load-elongation curves for each coil or pack of strand used in fabrication of the tendons containing the following information: a) Heat number and identication b) Tensile strength c) Yield stress at 1 percent extension under load d) Elongation at failure e) Modulus of elasticity f) Diameter and net area of strand g) 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 verication 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 shipping c) Testing results for tests required under 7.1 of this specication, conformities (or nonconformities), and resultant actions d) Calibration records for all testing and control devices
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SPECIFICATION FOR UNBONDED SINGLE-STRAND TENDON MATERIALS (ACI 423.7-14)
e) Statistical records of quality performance evidencing the occasion, frequency, and percentage of accepted and rejected nal 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 certication — A copy of the tendon fabrication plant certication. If the certication is not from a nationally accredited organization, provide documentation demonstrating compliance with 11.1. 4.1.6 Stressing jack calibration — Calibration certicates for every jack and gauge set supplied to the project.
5—MATERIALS 5.1—Prestressing steel Prestressing steel used in unbonded single-strand posttensioning tendons shall conform to: a) ASTM A416/A416M b) Strand not specically covered in ASTM A416/A416M that conforms to minimum requirements of this specication and has properties meeting requirements of ASTM A416/ A416M. 5.2—Post-tensioning (PT) coating PT coating shall meet the criteria of 7.2 and demonstrate the following performance requirements: a) Provide lubrication between the strand and sheathing b) Resist ow caused by gravity within anticipated temperature range of exposure c) Provide continuous nonbrittle coating at lowest antici pated temperature of exposure d) Be chemically stable and nonreactive with prestressing steel, reinforcing steel, sheathing material, and concrete 5.3—Sheathing Tendon sheathing material shall be high-density polyethylene or polypropylene that meets the criteria of 8.2 and that demonstrates the following performance requirements: a) Sufcient 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 extractable from the sheathing material d) Nonreactive with concrete, prestressing steel, reinforcing steel, and PT coating
5.4—Anchorages and couplers Castings shall be nonporous and free of sand, blow holes, and voids. 5.5—Connecting components Any 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 9.3 b) 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—Tape Tape used as a component for enclosing couplers shall: a) Be self-adhesive and moisture-proof b) Be nonreactive with sheathing, PT coating, or prestressing steel c) Have elastic properties d) 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 ll the annular space between the strand and sheathing. The PT coating shall extend over the entire tendon length. 6.2—Manufacturing processes Sheathing shall be manufactured by an extrusion process that provides watertight encasement of the PT coating. 6.3—Sheathing coverage Sheathing 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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SPECIFICATION FOR UNBONDED SINGLE-STRAND TENDON MATERIALS (ACI 423.7-14)
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 xed 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 systems Unless otherwise specied, the use of nonencapsulated systems shall be permitted for applications not governed by ACI 318 or ACI 350. 6.5—Encapsulated systems 6.5.1 Encapsulation — For all tendons used in applications 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 lled with PT coating in conformance with 5.2. 7—MECHANICAL PROPERTIES 7.1—Prestressing steel 7.1.1 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, nished strand shall be tested during production for relaxation 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 requirements of ASTM A416/A416M and the requirements herein. The relaxation test shall be performed as a full 1000hour test at initial production and every third year thereafter. 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 satisfactory results.
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7.1.3 Premature failure —For tests required in this specication 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 ne 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) coating 7.2.1 Mechanical properties and acceptance —The PT coating shall be a compound that complies with the tests and associated acceptance criteria specied 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 steel All samples tested shall be checked to ensure that the strand meets the dimensional requirements listed in ASTM A416/A416M. 8.2—Sheathing 8.2.1 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 diameter 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—Anchorages 8.3.1 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 certied independent laboratory indicates anchorage performance equivalent or superior to anchorages satisfying the requirements of this section. a) At transfer load
f cp
= 0.75 f ci′
Ab′ Ab
(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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SPECIFICATION FOR UNBONDED SINGLE-STRAND TENDON MATERIALS (ACI 423.7-14)
Table 7.2.1—Testing of PT coating Test no.
Test description
Test method
Acceptance criteria
1
Dropping point
ASTM D566 or D2265
Minimum 300°F (149°C)
Oi l sepa rat ion 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)
Corrosion test (5 percent salt fog at 100°F [38°C], 0.005 in. [0.127 mm], minimum hours, Q Panel Type S)
ASTM B117
5
Rust Grade 7 or better after 1000 hours of exposure according to ASTM D610
6
Water-soluble ions:* a. Chlorides b. Nitrates c. Suldes
ASTM D512 ASTM D3867 ASTM D4658
10 ppm maximum 10 ppm maximum 10 ppm maximum
ASTM B117 (modied)
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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)
No emulsication of the coating after 720 hours of exposure.
ASTM D4289 (ASTM D792 for density)
Permissible change in hardness: 15 percent volume: 10 percent
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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 D638
Permissible change in tensile strength: 30 percent
2
*
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 c oated beaker is lled 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 t he 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 ash 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 li mited 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.
but not greater than 1.25 f ci′ b) At service load
f cp
= 0.6 f c′
Ab′ Ab
(8.3.1b)
but not greater than f c′ where f cp is the permissible concrete compressive stress; f c′ is the specied concrete compressive strength; f ci′ is the specied 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 function of transferring force to the concrete.
8.4—Connecting components 8.4.1 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).
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SPECIFICATION FOR UNBONDED SINGLE-STRAND TENDON MATERIALS (ACI 423.7-14)
9—ANCHORAGE ASSEMBLY TESTING 9.1—Validation The adequacy of a tendon system shall be conrmed 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—Components Component 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 systems The 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 byACI 350: 10 psi (68.8 kPa) 9.4—Static test 9.4.1 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 f pu 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 test 9.5.1 Fatigue tests shall be performed on tendon specimens with representative samples from production runs and with a minimum length of 3 ft (1 m) between anchorages. In the rst test, the tendon shall be subjected to 500,000 cycles between 60 and 66 percent f pu. In the second test, the tendon shall be subjected to 50 cycles between 40 and 85 percent f pu. One complete cycle involves change from the lower stress level to the upper stress level and back to the lower. 9.6—Hydrostatic test 9.6.1 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.
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9.6.1.1 Anchorages shall remain watertight when tested and subjected to a hydrostatic pressure of no less than that specied 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 xed 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 coating b) Use a colored dye in the water that will contrast with the white color of the post-tensioning coating c) After 24 hours, the encapsulation system shall be removed and the color of the coating shall be noted No colored dye staining inside the encapsulation system anywhere on the white PT coating is permissible.
10—TESTING SERVICES 10.1—Prestressing steel Mechanical property and dimensional tests may be performed in-house by the manufacturer. Relaxation tests shall be performed, or observed and conrmed, by an inde pendent laboratory accredited under ASTM C1077. Any testing facility used, whether in-house or other, shall be identied completely including physical address and contact information. 10.2—Anchorage assembly Static, 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 11.1 Unbonded single-strand tendons shall be fabricated in a plant audited and certied by an external program accredited by a national accreditation body such as the American National Standards Institute (ANSI), International Accreditation Service (IAS), American Association for Laboratory Accreditation (A2LA), or equivalent. Nonaccredited certication programs shall meet the essential requirements of ISO/IES Guide 65 or ISO/IEC 17065, including, at a minimum, the following: a) Have a documented structure which safeguards impartiality including provisions to ensure the impartiality of the operations of the certication body; this structure shall enable the participation of all parties concerned in the development of policies and principles regarding the content and functioning of the certication system b) Be free of commercial/nancial pressures that might inuence results and be independent from the entity they are certifying c) Have personnel that are competent and who meet dened minimum relevant criteria as dened by the certi fying agency
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SPECIFICATION FOR UNBONDED SINGLE-STRAND TENDON MATERIALS (ACI 423.7-14)
d) Have criteria outlined in specied standards e) Have a procedure for making rules and procedures available to the public
12—PACKAGING AND IDENTIFICATION 12.1—Bundling and banding Individual 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 materials using padding material between banding and tendons. 12.2—Identification of components 12.2.1 Wedges and anchorages — Wedges and anchorages shall be identied by individual concrete placement area, oor 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 identication 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 —Identication of all component parts of the encapsulation system and assembly instructions shall be provided to the eld. 13—HANDLING, STORAGE, AND SHIPPING 13.1—Handling 13.1.1 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 shipping 13.2.1 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—Shipping 13.3.1 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 encapsulation materials shall be protected from exposure to moisture, deicing salts, and other corrosive elements during transportation 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, transportation, and unloading. 13.4—Protection from moisture 13.4.1 Tendons shall be protected from exposure to moisture, deicing salts, and other corrosive elements. 14—INSTALLATION DRAWINGS 14.1 Nonprestressed reinforcement required for anchorages 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 specied 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. · Spring and fall conventions to facilitate the work of its committees. · Educational seminars that disseminate reliable information on concrete. · Certification programs for personnel employed within the concrete industry. · Student programs such as scholarships, internships, and competitions. · Sponsoring and co-sponsoring international conferences and symposia. · Formal coordination with several international concrete related societies. · Periodicals: the ACI Structural Journal, Materials Journal, and Concrete International. Benefits of membership include a subscription to Concrete International and to an ACI Journal. ACI members receive discounts of up to 40% on all ACI products and services, including documents, seminars and convention registration fees. 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.
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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 certications 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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