ACI 423.4R-98

Corrosion and Repair of Unbonded Single Strand Tendons

Reported by ACIIASCE Committee 423

Charles W. Dolan Chairman

Kenneth B. Bondyt Catherine W. French

Robert N. Bruce Jr. Clifford Freyermuth

Dale C. Buckner William L. Gamble

Ned H. urns st Hans R. Ganz

Gregory P. ~hacos ' Mohammad Iqbal

Jack Christiansen Francis J. Jaques

Todd Christopherson Daniel P. Jenny

Steven R. Close L.S. Paul Johal

Thomas E. Cousins Susan N. Lane

Apostolos Fafitis Ward N. Marianos Jr.

Mark W. Fantozzi Leslie D. Martin

Martin J. ~ r a d u a t Alan H. Mattock

'Co-chairmen of subcommittee responsible for preparation of report ?Member of subcomm~ktee responsible for preparation of report.

This report gives general information regarding the evaluation of corrosion damage in structures reinforced with unbonded single strandpost-tension- ing tendons. Historical development of those parts of the building code dealing with durability and coi.rosion protection is explained. Evolution of the types and components of unbonded tendons is described. Specific aspects of corrosion in unbonded single strand tendons are described, and common problems in structures reinforced with these tendons are discussed. Methods are presented for I-epairing, replacing, andsupplementing tendons.

Keywords: allowable stresses; anchorage; carbonation; concrete con- struction; corrosion; corrosion protection; cover; durability; embrittle- ment; external post-tensioning; grease; inspection; post-tensioned concrete; pre-stressed concrete; repair; sheathing; single strand tendons; surveys; tendons; tests; unbonded post-tensioning.

ACI Committee Reports, Guides, Standard Practices, and Commentaries are intended for guidance in planning, design- ing, executing, and inspecting construction. This document is 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. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom.

Reference to this document shall not be made in contract documents. If items found in this document are desired by the ArchitectEngineer to be a part of the contract docu- ments, they shall be restated in mandatory language for in- corporation by the ArchitectIEngineer.

Henry J. Cronin Jr. Secretary

Gerard J. ~ c G u i r e t David H. Sanders

Mark Mooret Thomas C. Schaeffer

Antoine E. Naaman Morris Schupack+

Kenneth Napior Kenneth Shushkewich

Thomas E. Nehil* Khaled S. Soubra

Mrutyunjaya Pani Patrick J. Sullivan

Kent H. Preston Luc R. Taenve

Denis C. Pu Carl H. Walker

Julio A. Ramirez Jim J. Zhao

Ken B. Rear Paul Zia

David M. Rogowsky

Bruce W. Russel

CONTENTS Chapter l-lnlro-sducti:%i&rrt, p, 423.4R-2

1 . 1 4 e n e r a l 1.2-Background 1.3-Scope 1 .&Limitations

Chapter 2-Review of code requirerne~ts and changes, p. 423.4R-3

2.1--General 2.2--Cover requirements for unbonded tendons 2.3-Allowable tensile stresses in concrete 2.4-Protection of unbonded tendons

Chapter 3-Unbonded tendons, p. 423.4R-5 3.1-Evolution of unbonded tendons 3.2-Sheathing problems 3.3-Detailing practices 3 .+Storage, handling, and construction problems 3.5-Deterioration mechanisms 3.6-Performance record

ACI 423.4R-98 became effective February 23, 1998. Copyright O 1998, 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 ret~ieval system or device, unless permission in writing is obtained from the copyright proprietors.

MANUAL OF CONCRETE PRACTICE

Fig 3. I-(a) Live end anchorage assembly for button-headed wir~epost-tensioning system; (b) intermediate anchorage assenzbly with threaded coupler I,O& and (c) dead end anchor- age assembly; dimensions "A" and "B" were usually 4 and 6 in. (100 and 150 nznz), respectively, for a typical 7-wire slab tendon (reprinted front Reference I).

Initially, there were no corrosion protection standards for the grease (except in the nuclear industry, refer to ACI 359- 74, "Code for Concrete Reactor Vessels and Containments"), so the tendon manufacturers used the grease of their choice. Corrosion-resisting properties of the grease were not speci- fied, nor were there standards for the uniformity and amount

Coated Strand P a p e r - w r a p p e d 1 9 5 5 - 1 975+

This ~ a r f i o n of sfrand usualiy unsheathed. Lenglh varies.

P l a s t i c S h e a t h 1 9 6 0 - P r e s e n t

coated Strand plbstic Shenth

Pioslic tube with wotertighl

ose Fitting

1 9 8 5 PTI R e c o m m e n d e d /

S y s t e m L 7 - w i r e strand with Plclsiic Coo corrasron preventive cooling completely filling annular spoce ~~~h~~~~~

Plostic. qrease filled tube wit6 watertight connection at anchorage. Plastic Cop

\ , filled with

E l e c t r i c a l l y grease

Isolated T e n d o n

Piostic coated completely filling onnulor space anchorage

Entire Tendon Assembly covered with electrically isolating rnaleriol.

Fig. 3.2-Evolution of corrosion protection for unbonded sin- gle strand tendons for buildings (reprintedfrom Reference 2).

of grease to be applied to the prestressing steel. Deterioration of the grease was not expected, but as problems became known they were addressed by the PTI in their recommended specifications.

3.2-Sheathing problems The push-through system required that the sheathing be

sufficiently oversized to allow the greased strand to be in- serted without too much difficulty. This resulted in a tendon with many air voids inside the sheathing and allowed infil- tration of water during storage, shipping, and installation, and in service.

With the heat-sealed system, the sheathing was provided in rolls of flat plastic tape that was usually 20 to 40 mils (0.5 to 1.0 mm) thick. During tendon fabrication, the strand would be taken from the pack and passed through a grease extrusion head. The tape was then folded over the greased strand and the lapped seam welded shut with a flame. This method also formed a slightly oversized sheathing that could have air voids. The seam weld was interrupted every time there was a pause in the process, and sometimes the sealed seam pulled apart during handling or installation. This sys- tem is frequently found to have gaps from one cause or an- other that expose the greased strand to contact with the concrete.

Seamless extruded sheathing first appeared in the early 1970s.~ The extruded sheathing minimized the problems ex- perienced with the push-through and heat-sealed systems by providing a snug, seamless sheathing around the greased strand.

3.3-Detailing practices Certain details that were initially considered acceptable

are insufficient to provide the degree of durability required

SINGLE STRAND TENDONS 423.4R-7

PUSH-THROUGH the unsheathed strand and the hardened concrete is disturbed at the stressing end during this elongation, thus providing a

PREFORMED TUBE path for water to find its way to the strand and into the

STRAND PUSHED THROUGH sheathing.2

AS GREASE IS APPLIED. Since the dead end anchor did not have to move during

HEAT-SEALED FORMED FROM FLAT STRIP AS GREASE IS APPLIED.

EXTRUDED FORMED BY EXTRUDING OVER

STRAND AS GREASE IS APPLIED.

Fig 3.3-Plastic sheathing types (reprintedfuonz Reference 2)

by recent versions of ACI 3 18. It is now recognized that con- crete cannot provide reliable protection to the strand, even if the strand is greased.

It was common practice in both detailing and installation to allow the sheathing to stop short of the anchorages, as shown by Fig. 3.4 (the grease can get wiped away from these sections of strand during the installation of anchorages at s.h-essing and nonstressing ends). During stressing opera- tions, the strand at the stressing end moves about 8 in. per 100 ft (200 mm per 30 m) of length. Direct contact between

stressing, it was considered acceptable for the strand near the dead end to be exposed to the concrete. However, this also allowed the end of the tendon to be exposed to dirt and water during storage, handling, and placement, prior to placing the protective concrete. The end of the sheathing was, for prac- tical purposes, open, and the voids inside the tendon sheath- ing provided a means for any available water to gain access to the tendon. Even if the storage time at the site was relative- ly brief (which was not always the case), there was ample op- portunity for water to get into the tendons due to any snow and rain that might occur while the tendons were stored on the ground or on the formwork. For those portions of the strand not adequately protected by grease, water and oxygen could cause corrosion and then could be further exacerbated by the presence of chloride-ions. Some typical defects con- tributing to corrosion in the end anchor region are shown in Fig. 3.4.

The stressing side of the live-end anchorage was protected by filling the stressing pocket in which the anchorage was re- cessed with a protective cementitious grout (Fig. 3.4). The casting, wedges, and strand tail were not coated. Often, shrinkage of the grout plug in the stressing pocket caused a space between the side of the stressing pocket and the grout that allowed water to gain access to the tendon anchorage. Corrosion of the bearing plate casting is often found but has not been known to cause failures. On tendons with barrel and wedges sitting on bearing plates, heat-treated barrels

-. . ." '4 Chloride ion penetration

Cernentitious grout plug at anchorage pocket shrinks and becomes loose. Poor bond andlor poor quality mortar permits aggressive materials access to anchorage and prestressing steel.

Shallow cover to pre- stressing steel allows corrosion to start or chloride ion penetrates and starts stub corrosion.

Portlon of strand covered wlth grease exposed to concrete because no physical connectton IS made between sheath and anchorage. At stressing end, this portion of tendon IS

pulled through intlmate concrete enclosure when stressed and tends to disrupt grease protect~on.

Fig 3.4-Potential defects in con"osion protection at unbonded single strand tendon live end anchorage.

SINGLE STRAND TENDONS 423.4R-9

Fig. 3.6-Photonticrograph showing irvegula~ transgranu- lar c~*ackpath characteristic of stress-corrosion cracking (hydiaogen-induced cracking) in cold-drawn, high-strength wiipe.

Fig. 3.5-Scanning electi*on n1ic7,ogi*aph showing fracture surface exhibited by one wire in a failedstrand. Fracture surface is brittle and irregular as is cha~#acteristic of stress- corrosion cracking.

the possibility that grease will be discontinuous, so corro- sion can begin if water and oxygen are available. Corrosion can be accelerated if chlorides are present in the water. As the wire(s) corrodes and the cross-sectional area decreases, the stress in the remaining section rises past its ultimate ten- sile strength, and the wire(s) fails. Failure by embrittlement of the strand wires can also occur if other aggressive materi- als, such as nitrates and sulfides, are pre~ent.~.',~ Embrittle- ment failures can occur without significant loss of cross- section in the strand. It is not uncommon for the failure sur- faces of one or two wires at a strand break to be jagged, typ- ical of embrittlement failures, while the remaining wires have cup-cone configurations that are typical of ductile fail- ures. It is not necessary, or liltely, that all of the wires at a given cross section will be similarly affected at the same time (Fig. 3.5, 3.6, and 3.7).

A strand can burst from the concrete when it fails if the cover is small, usually less than about 3/4 in. (20 mrn) (Fig. 4.1 and 4.2). Whether this happens depends on the drape of the tendon, the type of sheathing, and the presence of per- pendicular reinforcement between the brolten tendon and the surface of the concrete. Occasionally the strand will be re- leased by the anchor and project past the edge of the struc- t~re.~a'O

Tendons can be subjected to vehicular damage if the con- crete cover spalls off or is abraded away. This most com- monly happens where the concrete cover is less than 3/4 in.

Fig. 3.7-brittle fractures in failed strand. Note mixtui-e of watel; grease and corrosion by-product on wires of strand Ji-eshly extractedfrom structure.

(20 rnrn) and can be the result of misplacement of the tendon or poor screeding and finishing of the concrete. The sheath- ing is not intended to resist direct contact of in-service traffic and is easily breached under these circumstances. Thereafter, the grease quicltly disappears and contaminated water is free to enter the sheathing and cause corrosion.

3.6-Performance record In general, tendons with extruded type plastic sheathing

provide superior corrosion protection when compared with tendons from other unbonded systems and with other types of sheathing. The improvement in performance, however, may also be due to improvements in the quality and applica- tion methods of the grease that occurred at about the same time that most fabricators changed to the extruded plastic sheathing system. The extruded type sheath now predomi- nates in the industry, probably as a result of the 1985 PTI "Specification for Unbonded Single Strand Tendons." From random corrosion incidents, it is clear that care must be taken to ensure that no aggressive materials, including water, enter through the sheath or anchorage.

ACI 423.6-011423.6R-01

Specification for Unbonded Single-Strand Tendons and Commentary

Reported by ACI Committee 423 Ward N. Marianos Shawn P. Gross

Chairman Secretary

Sarah L. Billington Pawan R. Gupta Julio A. Ramirez

Kenneth B. ~ o n d ~ * J. Weston Hall David M. Rogowsky

Ned H. ~ u m s ~ Mohammad Iqbal Bruce W. Russell

Gregory P. Chacos Francis J. Jacques David H. Sanders

Todd J. Christopherson L. S. Paul Johal Thomas C. Schaeffer

Steven R. closet Susan N. Lane Andrea J. Schokker

Henry J. Cronin, Jr. Leslie D. Martin Morris schupackt

Charles W. Dolan Gerard J. ~ c ~ u i r e ~ Kenneth W. Shushkewich

Apostolos Fafitis Mark Edward Moore Richard W. Stone

Martin J. Fradua Antoine E. Naaman H. Carl walkert

Catherine E. French Thomas E. Nehil .Paul ~ i a t

William L. Gamble Denis Chuen Pu

'chair of subcommittee that prepared this specification. t ~ e m b e r of subcommittee that prepared this specification.

This specification provides specific pe~formance criteria for materials for unbonded single st1,and tendons and detailed recommendations for fabrica- tion and installation of unbonded single strand tendons. Specifications are presented for tendons in non-aggressive environments and for tendons in aggressive environments. The more restrictive material, fabrication, and construction requirements for tendons used in aggressive environments are essential to the long-telm durability of tendons used in such circumstances.

Notes to Specifier: This specification is incor-porated by reference in the project specifications using the wording in P4 of the preface and including the information from the mandatory, optional, and submittal checklists following the specification.

ACI Specification 423.6-01 and Commentary 423.6R-01 are pre- sented in a side-by-side column,format, with specifjcation textplaced in the leji-hand column and the corresponding commentaly text aligned in the right column. Commentary section numbers are preceded by the let- ter "R. " The Commentaly is not apart of this specification.

ACI Committee Reports, Guides, Standard Practices, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. The Commentary is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept re- sponsibility for the application of the material it contains. The American Concrete Institute disclaims any and all re- sponsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom.

Reference to the Commentary shall not be made in con- tract documents. If items found in this document are de- sired by the ArchitecdEngineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the ArchitecdEngineer.

Keywords: anchorage; construction joint; contractor; coupler; deicer; post- tensioning; prestress; prestressing steel; sheathing; specification; strand; unbonded tendon.

CONTENTS Preface, p. 423.61423.6R-2

1.3-Referenced standards 1.4-System description 1.5-Submittals

1.5.1-Prestressing steel 1 S.2-Anchorages and couplers 1 S.3-Sheathing 1 S.4-Post-tensioning coating 1 S.5-Fabrication plant 1.5.6-Stressing jack calibration 1.5.7-Stressing records

1.6-Fabrication 1.6.1-General 1.6.2-Handling, storage, and shipping

1.6.2.1-Handling 1.6.2.2-Storage before shipping 1.6.2.3-Shipping

1.7-Delivery, handling, and storage

ACI 423.6-011423.6R-01 became effective October 31,2001. Copyright O 2001, 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 elechonic 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.

423.61423.6R-4 ACI STANDARD AND COMMENTARY

SPECIFICATION 1.2 - Definitions

Aggressive environment - An environment in which structures are exposed to direct or indirect appli- cations of deicing chemicals, seawater, brackish water, or spray from these water sources; and salt-laden air as occurs in the vicinity of seacoasts. Aggressive envi- ronments also include structures where stressing pockets are wetted or are directly in contact with soils.

Anchorage - A mechanical device comprising all components required to anchor the prestressing steel and permanently transmit prestressing force to concrete.

Concrete contractor - Contracting entity respon- sible for placing, finishing, and curing the post-tensioned concrete.

Coupler - A device designed to connect ends of two strands together, thereby transferring the pre- stressing force from end to end of the tendon.

Encapsulated tendon - A tendon that is com- pletely enclosed in a watertight covering from end to end, including a protective cap over the tendon tail at each end.

Engineer - Design professional responsible for the structural design of the post-tensioned concrete members on the project.

Non-aggressive environment - All environments not specifically defined herein as aggressive, including enclosed buildings.

Prestressing steel - High-strength steel used to prestress concrete, most commonly 7-wire strand. It is the element of a post-tensioning tendon that is elon- gated and anchored to provide the necessary design prestressing force.

Post-tensioning coating - Material used to protect against corrosion and reduce friction between pre- stressing steel and sheathing.

Post-tensioning installer - Contracting entity respon- sible for unloading the post-tensioning materials, storing and protecting them on the job site at all stages of handling, storage, placement, tendon installation, stressing, and tendon finishing in accordance with the contract documents and this specification.

COMMENTARY

Post-tensioning supplier - Contracting entity responsible for providing all components of the post- tensioning system including the tendons, anchorages, couplers, field placement drawings, and stressing equipment, and delivering them to the job site.

ACI 423.7-07

Specification for Unbonded Single-Strand Tendon Materials (ACI 423.7-07) and Commentary

An ACI Standard

Reported by Joint ACI-ASCE Committee 423

Theresa M. Ahlborn

Robert W. Barnes

Florian G. Barth

Sarah L. Billington

Kenneth B. Bondy

Ned H. Burns

Gregory P. Chacos

Steven R. Close

Bruce W. Russell Chair

Henry J. Cronin, Jr.

Charles W. Dolan

Martin J. Fradua

William L. Gamble

Pawan R. Gupta

H. R. Trey Hamilton I11

Mohammad Iqbal

L. S. Paul Johal

ACI Specification 423.7-07 and Commentary are presented in a two-column format, with Specification text in the left column, and corresponding Commentary text in the right column. To distinguish the Specification from the Commentary, the Specifi- cation is printed in Helvetica, which is the typeface for this paragraph.

the typeface for this paragraph. Commentary section numbers are preceded by the letter "R" to distinguish them fiom Specification section numbers. The Commentary is not a part of ACI Specification 423.7-07.

Shawn P. Gross Secretary

Donald P. Kline

Ward N. Marianos, Jr.

Mark E. Moore

Antoine E. Naaman

Theodore L. Neff

Thomas E. Nehil (

Sami H. Rizkalla

David H. Sanders

Thomas C. Schaeffer

Andrea J. Schokker

Morris Schupack

Richard W. Stone

H. Carl Walker

Jarin L. Roberts-Wollmann

Paul Zia

NOTES TO SPECIFIER This Specification is incorporated by reference in the

Project Specifications using the wording in P3 of the Preface and including the information from the mandatory and optional checklists following this specification.

PREFACE PI. ACI Specification 423.7 is intended to be used by

reference or incorporation in its entirety in the Project Spec- ification. Do not copy individual Parts, Sections, Articles, or Paragraphs into the Project Specification, because taking them out of context may change their meaning.

P2. If Sections or Parts of ACI Specification 423.7 are copied into the Project Specification or any other document, do not refer to them as an ACI Specification, because the specification has been altered.

ACI Committee Reports, Guides, Manuals, Standard Practices, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This document is 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. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom.

Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architecfingineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the ArchitectIEngineer.

P3. A statement such as the following will serve to make ACI Specification 423.7 a part of the Project Specification:

"Work on (Project Title) shall conform to all requirements of ACI 423.7-07 published by the American Concrete Insti- tute, Farmington Hills, Michigan, except as modified by these Contract Documents."

P4. Each technical Section of ACI Specification 423.7 is written in the two-part Section format of the Construction

ACI 423.7-07 supersedes the material-related specification information contained in ACI 423.6-01, became effective October 2007, and was published January 2008.

Copyright 0 2007, 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.

ACl STANDARD

SPECIFICATION COMMENTARY The average bearing stress PIAb 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.

2.4.2 - Castings

Castings shall be nonporous and free of sand, blow holes, voids, and other defects.

2.5 - Tendons in aggressive environments

2.5.1 - Encapsulation

Protect all encapsulated anchorage assemblies, including the anchorage, wedges, and prestressing steel, against corrosion by a watertight connection to the sheathing and a watertight closure of the wedge cavity. Encapsulation systems that employ the use of bare metallic anchorages produced from a material that is subject to corrosion are unacceptable.

2.5.2 - Anchorage or coupler-to-sheathing connection

2.5.2.1 - Sleeves to anchorages

Sleeves used to connect the sheathing to the anchorage of encapsulated systems shall:

a) Meet or exceed the same requirements as the sheathing for durability during fabrication, transpor- tation, handling, storage, and installation;

b) Have 0.050 in. (1.27 mm) minimum thickness;

c) Have a positive mechanical connection to the anchorage at all stressing, intermediate, and fixed ends;

d) 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;

For a rectangular anchorage, Al, can be determined by extending the diagonals of the anchorage rectangle to form progressively larger rectangles concentric with the anchorage until one diagonal reaches an edge of the concrete bearing surface (either vertical or horizontal). The gross area of the resultant larger rectangle is Al, . For other anchorage shapes, Al, is determined in a similar manner.

R2.4.2 - Castings

Important considerations in the design of castings are: raw material grade, surface roughness, surface hardness, flatness of conical angle, and compatibility and tolerance of wedge cavity angle geometry in combination with wedges and strand geometry (Sc::tion 2.6.3). For information on standard surface conditions of castings, see Society of Automotive Engineers (1963).

R2.5 - Tendons in aggressive environments

R2.5.1- Encapsulation

Corrosion protection of the anchorage may be obtained by various means, including epoxy coating or plastic encapsu- lation. Special inspection is required to identify damage that can occur to the epoxy or plastic coating systems during transportation, handling, and installation. Damaging the coating would breach the encapsulation and make the system unacceptable.

R2.5.2.l(e) -The requirement that prohibits voids may be satisfied by filling the sleeves with post-tensioning coating. Transition components, such as sleeves, at anchorages and couplers should be designed to be void-free. Some small bubbles and air spaces are normal and unavoidable in the fabrication and assembly process and should not normally be considered as "voids" in the context of this section.

e) Be translucent or have another method of veri- fying that the post-tensioning coating material is free of voids;

ACl STANDARD

SPECIFICATION

2.6.8 - Hydrostatic tests

Representative couplers and anchorages shall be tested to ensure a watertight encapsulation of prestressing steel and all connections in conformance with Sections 2.6.8.1 through 2.6.8.3. Three tests are required for each assembly with all three passing for the system to pass.

Encapsulation systems using tape as a component are acceptable provided they pass all requirements of the hydrostatic water test and the requirements of Section 2.5.2.3.

2.6.8.1 - Anchorages shall remain watertight when arranged in a horizontal position and subject to a uniform hydrostatic pressure of no less than 1.25 psi (8.6 kPa) for a period of 24 hours.

2.6.8.2 - Representative samples from production runs, selected and assembled by the manufacturer shall be used in testing. Stressing, intermediate, and fixed-end assemblies shall each be tested.

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

1) Add white pigment to the post-tensioning coating;

2) Use a colored dye in the water that will contrast with the white color of the post-tensioning coating; and

3) After 24 hours, the encapsulation system shall be removed and the color of the coating shall be noted.

COMMENTARY

R2.6.8.1 - When testing an encapsulated assembly for watertightness, the specimen should be arranged in a horizontal position to ensure equal minimum hydrostatic pressure of 1.25 psi (8.6 kPa) over the entire specimen length. The hydrostatic pressure of 1.25 psi (8.6 kPa) approximates 3 ft (1 m) of hydrostatic head. This pressure is considered to be a worst-case situation for normal beam and slab applications. For structures where the hydrostatic head may exceed 3 ft (1 m) (for example, swimming pools, tanks, beams, or slabs below grade), the project specification should require a more stringent test performance. ACI 350-01 (ACI Committee 350 2001) provides more stringent requirements for environmental structures where greater hydrostatic heads would be anticipated.

No colored dye staining inside the encapsulation system anywhere on the white post-tensioning coating is permissible.