Errata

Date: October 22, 2013

Issuing Office: Federal Highway Administration—Office of Research, 

Development, and Technology: Infrastructure Research and 

Development

Address: Turner-Fairbank Highway Research Center, 6300 Georgetown 

Pike, McLean, VA 22101

Name of Document: Guidelines for Sampling, Assessing, and Restoring Defective 

Grout in Prestressed Concrete Bridge Post-Tensioning Ducts

FHWA Publication No.: FHWA-HRT-13-028

The following changes were made to the document after publication: 

Location Incorrect Values Corrected Values

Table 32 on page 90 CD3 0.08 < Cl− ≤ 0.20b CD3 0.2 < Cl− ≤ 0.50b

Table 33 on page 91 CD3 0.02 < Cl− ≤ 0.50 CD3 0.2 < Cl− ≤ 0.50
Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

Guidelines for Sampling, Assessing, and

Restoring Defective Grout in Prestressed

Concrete Bridge Post-Tensioning Ducts

Publication No. FHWA-HRT-13-028 october 2013
FOREWORD

Post-tensioned (PT) tendons have been widely utilized in concrete bridges in the United States. 

The advantages of PT bridges compared to bridges constructed using conventional reinforcement 

include greater span length, structural efficiency, reduced materials, and a more streamlined 

appearance. However, PT tendons can be susceptible to corrosion and ultimately failure if 

physical deficiencies (PDs) or chemical deficiencies (CDs) are present. Examples of PDs include 

separation, segregation, presence of soft material, and free water, while an example of a CD

includes concentrations of chloride that exceed the allowable limit as specified by the American 

Association of State Highway and Transportation Officials and other specifications. The failure 

of a few tendons can compromise overall structural integrity. 

Inspections of bridge PT tendons have revealed both PDs and CDs as well as strand tendon 

failures caused by corrosion have been reported. This study was performed to provide bridge 

owners with a practical protocol for inspecting, sampling, analyzing, evaluating, and responding 

to bridge grout concerns. 

Jorge E. Pagán-Ortiz 

Director, Office of Infrastructure

Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation 

in the interest of information exchange. The U.S. Government assumes no liability for the use of 

the information contained in this document. This report does not constitute a standard, 

specification, or regulation. 

The U.S. Government does not endorse products or manufacturers. Trademarks or 

manufacturers’ names appear in this report only because they are considered essential to the 

objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve 

Government, industry, and the public in a manner that promotes public understanding. Standards 

and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its 

information. FHWA periodically reviews quality issues and adjusts its programs and processes to 

ensure continuous quality improvement.
TECHNICAL REPORT DOCUMENTATION PAGE

1. Report No.

FHWA-HRT-13-028

2. Government Accession No. 3. Recipient’s Catalog No.

4. Title and Subtitle

Guidelines for Sampling, Assessing, and Restoring Defective Grout 

in Prestressed Concrete Bridge Post-Tensioning Ducts 

5. Report Date

October 2013

6. Performing Organization Code

7. Author(s)

Teddy S. Theryo, William H. Hartt, and Piotr Paczkowski

8. Performing Organization Report No. 

9. Performing Organization Name and Address

Parsons Brinckerhoff, Inc. 

2202 North West Shore Blvd. Suite 300 

Tampa, FL 33607 

William H. Hartt, PhD, PE, F-NACE

Consulting Engineer

20914 Morada Court

Boca Raton, FL 33433

10. Work Unit No.

11. Contract or Grant No.

12. Sponsoring Agency Name and Address

Office of Infrastructure Research and Development

Federal Highway Administration

6300 Georgetown Pike

McLean, VA 22101-2296

13. Type of Report and Period Covered

Final Report

14. Sponsoring Agency Code

15. Supplementary Notes

The Contracting Officer’s Technical Representatives (COTRs) were Y.P. Virmani and H. Ghasemi, HRDI-60. An 

expert task group comprised of members from industry, academia, State transportation departments, and the posttensioning industry provided valuable technical input and guidance. This study was part of the Long-Term Bridge 

Performance Program.

16. Abstract

A significant proportion of the U.S. bridge inventory is based on bonded post-tensioned (PT) concrete construction. An 

important aspect of maintaining corrosion protection of these PT systems is assuring that tendon ducts are properly grouted 

with an acceptable material. Grout is a cementitious material typically used to provide corrosion protection to the strands 

used in PT concrete bridges. However, inspections have revealed fractured strands and, in some cases, failed tendons as a 

consequence of corrosion, even with the newer prepackaged, preapproved thixotropic grouts. Studies to-date have attributed 

this corrosion to physical or chemical grout deficiencies (or both), the former consisting of air voids, free water, and 

unhardened, segregated, or separated grout and the latter of chloride concentration in excess of what is specified by the 

American Association of State Highway and Transportation Officials and other specifications. Based on collected 

information and data analysis, State transportation departments can evaluate if grout deficiencies are present in the tendons

of their PT bridges and determine the significance of any deficiencies. Durability concerns associated with PT tendons 

were raised as early as 1999 when tendon failures were seen in some PT bridges as a result of strand corrosion due to the 

collection of bleed water in grout voids at tendon profile locations like anchorages and crest areas. While the development 

of prepackaged thixotropic grout was thought to provide a solution to the bleed water problem, corrosion-caused tendon 

failures on relatively new PT bridges have occurred, and forensic studies have revealed separation and segregation of grout 

materials as well as the presence of soft material, free water, and high chloride and sulfate content.

(1–3) Consequently, it 

has become important to examine the overall quality of materials and construction for some in-place grouts in existing PT 

bridges. The purpose of this study is to provide State transportation departments with guidance regarding tendon inspection, 

grout sampling, data analysis, and interpretation. 

17. Key Words

Post-tensioned tendons, Bridges, Corrosion, Grout, 

Chlorides, Grout defects, Inspection, Sampling

18. Distribution Statement

No restrictions. This document is available to the public through the 

National Technical Information Service, Springfield, VA 22161.

19. Security Classif. (of this report)

Unclassified 

20. Security Classif. (of this page)

Unclassified

21. No of Pages

130

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized
ii
iii

TABLE OF CONTENTS

CHAPTER 1. BACKGROUND ................................................................................................... 1

CHAPTER 2. OBJECTIVES OF INSPECTION ...................................................................... 3

CHAPTER 3. PT SYSTEMS ....................................................................................................... 5

BACKGROUND ..................................................................................................................... 5

PT TENDON TYPES ............................................................................................................. 7

PT BRIDGE TYPES ............................................................................................................... 8

Cast-in-Place (CIP) PT Box Girder Bridges on False Works ............................................. 8

CIP PT Concrete Slab and T-Girder Bridges .................................................................... 10

CIP Segmental Balanced Cantilever Bridge ..................................................................... 11

Precast Spliced I-Girder Bridge ........................................................................................ 14

Precast Spliced U-Girder Bridge ...................................................................................... 15

Precast Segmental Balanced Cantilever Bridge ................................................................ 17

Precast Segmental Span-by-Span Bridge.......................................................................... 18

Concrete Cable-Supported Bridge .................................................................................... 21

Special PT Concrete Substructures ................................................................................... 22

CHAPTER 4. GROUT DEFICIENCIES ................................................................................. 25

BACKGROUND ................................................................................................................... 25

Cl− Threshold .................................................................................................................... 25

Previous Investigations ..................................................................................................... 27

Deficiencies....................................................................................................................... 32

CHAPTER 5. MINIMUM NUMBER OF TEST SAMPLES ................................................. 33

GENERAL ............................................................................................................................. 33

INSPECTION OPTIONS ..................................................................................................... 34

INSPECTING CL− CONTENT (OPTION 1) .................................................................... 34

Project with Complete Grouting Records ......................................................................... 34

Project with Incomplete or No Grouting Records ............................................................ 35

INSPECTING ALL GROUT DEFICIENCIES (OPTION 2) .......................................... 35

Probability of Defect Indicator ......................................................................................... 37

Consequence of Failure Indicator ..................................................................................... 39

Risk Level ......................................................................................................................... 41

Acceptable Fraction of Tendons with Undetected Deficient Grout .................................. 41

Minimum Number of Inspected Tendons ......................................................................... 41

Sampling Procedure Summary ......................................................................................... 46

EXAMPLES .......................................................................................................................... 47

Typical Balanced Cantilever Bridge ................................................................................. 47

Typical Spliced Girder Bridge .......................................................................................... 53

Typical Span-by-Span Segmental Bridge ......................................................................... 56

Typical PT Bridge with Draped Tendons ......................................................................... 58
iv

CHAPTER 6. GROUT SAMPLING AND TEST METHODS .............................................. 61

GENERAL CONSIDERATIONS ....................................................................................... 61

Sample Size ....................................................................................................................... 66

Analyses ............................................................................................................................ 66

Tools, Equipment, and Instrumentation ............................................................................ 68

Reporting........................................................................................................................... 69

CHAPTER 7. STRATEGIC SAMPLING LOCATIONS ....................................................... 73

BACKGROUND ................................................................................................................... 73

BALANCED CANTILEVER BRIDGE .............................................................................. 75

Continuity Tendon (Internal Tendon in the Bottom Flange) ............................................ 75

Cantilever Tendon (Internal) ............................................................................................. 77

PRECAST SEGMENTAL SPAN-BY-SPAN BRIDGE .................................................... 77

CIP PT BRIDGE ................................................................................................................... 78

SPLICED GIRDER BRIDGE ............................................................................................. 78

CHAPTER 8. RESTORATION METHODS ........................................................................... 81

GENERAL ............................................................................................................................. 81

TEMPORARY RESTORATION ........................................................................................ 82

External Tendon ................................................................................................................ 82

Internal Tendon ................................................................................................................. 83

PERMANENT RESTORATION ........................................................................................ 83

External Tendon ................................................................................................................ 83

Internal Tendon ................................................................................................................. 84

Grout Cap .......................................................................................................................... 85

RESTORATION MATERIAL ............................................................................................ 87

CHAPTER 9. INTERPRETATION OF RESULTS AND COURSES OF ACTION ........... 89

BACKGROUND ................................................................................................................... 89

Evaluation Approach and Interpretation ........................................................................... 89

Examples ........................................................................................................................... 92

Reinspections, Non-Destructive Testing (NDT), and Monitoring.................................... 94

APPENDIX A. TYPICAL BALANCED CANTILEVER BRIDGE PLANS ........................ 97

APPENDIX B. TYPICAL SPLICED GIRDER BRIDGE PLANS ...................................... 109

REFERENCES .......................................................................................................................... 119
v 

LIST OF FIGURES

Figure 1. Illustration. Basic PT anchorage system ......................................................................... 5

Figure 2. Photo. Old generation of PT anchorage system .............................................................. 6

Figure 3. Photo. New generation of PT anchorage system ............................................................. 6

Figure 4. Illustration. Internal tendon ............................................................................................. 7

Figure 5. Illustration. External tendon ............................................................................................ 7

Figure 6. Photo. External tendons at deviator ................................................................................. 8

Figure 7. Photo. CIP concrete box girder bridge on false works .................................................... 9

Figure 8. Illustration. CIP bridge typical tendon layout ................................................................. 9

Figure 9. Photo. Blister at the top flange ...................................................................................... 10

Figure 10. Illustration. Transverse internal tendon in the diaphragm ........................................... 10

Figure 11. Photo. CIP PT concrete slab bridge ............................................................................. 11

Figure 12. Illustration. PT slab bridge typical tendon layout ....................................................... 11

Figure 13. Photo. CIP segmental balanced cantilever bridge ....................................................... 12

Figure 14. Photo. CIP balanced cantilever bridge during construction using form traveler ........ 13

Figure 15. Photo. Typical bottom flange blister ........................................................................... 13

Figure 16. Illustration. Typical vertical tendon in the web ........................................................... 14

Figure 17. Illustration. Typical vertical tendon in the diaphragm ................................................ 14

Figure 18. Photo. Precast spliced girder bridge ............................................................................ 15

Figure 19. Photo. Precast spliced girder bridge during erection ................................................... 15

Figure 20. Photo. Precast spliced U-girder bridge during erection ............................................... 16

Figure 21. Photo. Precast U-girder supported on temporary false work ...................................... 17

Figure 22. Photo. Precast segmental balanced cantilever bridge erection using a segment 

lifter ............................................................................................................................................... 18

Figure 23. Photo. Precast segmental span-by-span erection using an overhead gantry ............... 19

Figure 24. Illustration. Typical precast segmental span-by-span external PT tendon layout ....... 20

Figure 25. Photo. Precast segmental cable stayed bridge ............................................................. 22

Figure 26. Illustration. Cross section of precast segmental columns ............................................ 23

Figure 27. Photo. PT straddle bent during construction ............................................................... 23

Figure 28. Photo. Failed tendon cross section .............................................................................. 27

Figure 29. Photo. Longitudinal section of a tendon section with types 1–3 grout identified ....... 28

Figure 30. Photo. Opened tendon end showing predominantly type 3 grout and strand 

corrosion products ......................................................................................................................... 29

Figure 31. Photo. Opened tendon end showing types 3 and 1 grout and strand corrosion 

products ......................................................................................................................................... 29

Figure 32. Photo. Opened tendon end revealing type 4 grout (bottom half), type 1 grout 

(center region), and strand corrosion products (upper region) ..................................................... 30

Figure 33. Photo. Opened anchorage on the Carbon Plant Road bridge over IH-37 .................... 30

Figure 34. Equation. Reaction of the ferrous ion with water and sulfate ion to yield 

ferrous hydroxide and sulfuric acid .............................................................................................. 31

Figure 35. Flowchart. Inspection options ..................................................................................... 34

Figure 36. Flowchart. Grout inspection processes ........................................................................ 36

Figure 37. Graph. Risk matrix ...................................................................................................... 37

Figure 38. Equation. Overall probability of defect indicator ........................................................ 39

Figure 39. Equation. Overall consequence of failure indicator .................................................... 40
vi 

Figure 40. Equation. Risk ............................................................................................................. 41

Figure 41. Equation. Probability mass function for hypergeometric distribution ........................ 42

Figure 42. Graph. Example of PMF for hypergeometric distribution .......................................... 42

Figure 43. Equation. CDF ............................................................................................................. 42

Figure 44. Graph. Example of CDF for a hypergeometric distribution ........................................ 43

Figure 45. Graph. Minimum number of tendons required to detect at least one tendon with 

deficient grout assuming 5 percent of the samples are defective.................................................. 44

Figure 46. Graph. Minimum number of tendons required to detect at least one tendon with 

deficient grout assuming 10 percent of the samples are defective................................................ 45

Figure 47. Graph. Minimum number of tendons required to detect at least one tendon with 

deficient grout assuming 20 percent of the samples are defective................................................ 45

Figure 48. Graph. Minimum number of tendons required to detect at least one tendon with 

deficient grout assuming 30 percent of the samples are defective................................................ 46

Figure 49. Graph. Balanced cantilever bridge—tendon risk categories ....................................... 48

Figure 50. Graph. Spliced girder bridge—tendon risk categories ................................................ 54

Figure 51. Graph. Span-by-span segmental bridge—tendon risk categories................................ 58

Figure 52. Graph. PT bridge—tendon risk categories .................................................................. 60

Figure 53. Photo. Dial gauge used to determine the depth of a grout air void ............................. 61

Figure 54. Photo. Grout sample acquisition at an opened internal tendon end cap by light 

chipping......................................................................................................................................... 62

Figure 55. Photo. Concrete excavation to expose an internal tendon ........................................... 63

Figure 56. Photo. Internal tendon access at an intermediate location by drilling ......................... 64

Figure 57. Photo. Access hole in an internal tendon at an intermediate location revealing 

strand and grout............................................................................................................................. 64

Figure 58. Photo. View of a duct interior revealing a channel air void ........................................ 65

Figure 59. Illustration. Bridge representation used to identify grout sampling locations............. 69

Figure 60. Illustration. Chart used to record the location and information for individual 

grout samples ................................................................................................................................ 70

Figure 61. Illustration. Chart used to record and present analysis results for individual 

grout samples ................................................................................................................................ 71

Figure 62. Photo. Removing a permanent grout cap .................................................................... 73

Figure 63. Photo. Exposed anchor head after grout sampling ...................................................... 74

Figure 64. Photo. Locating internal tendons in the web wall using GPR ..................................... 75

Figure 65. Photo. Partial removal of a grout cap .......................................................................... 76

Figure 66. Illustration. Typical cantilever tendon inspection point locations............................... 76

Figure 67. Illustration. Typical continuity tendon inspection point locations .............................. 77

Figure 68. Illustration. Typical span-by-span bridge external tendon inspection point 

locations ........................................................................................................................................ 78

Figure 69. Illustration. CIP PT bridge inspection point locations ................................................ 78

Figure 70. Illustration. Spliced bulb-tee girder bridge inspection point locations........................ 79

Figure 71. Photo. Spliced bulb-tee girder bridge CIP joint detail ................................................ 79

Figure 72. Illustration. Spliced U-girder bridge inspection locations ........................................... 80

Figure 73. Photo. Temporary restoration of an external tendon ................................................... 82

Figure 74. Photo. Permanent restoration of an external tendon using heat shrink sleeve ............ 83

Figure 75. Illustration. Permanent restoration of an internal tendon duct .................................... 84

Figure 76. Photo. Completed restoration of a partially cut grout cap prior to coating ................. 85
vii 

Figure 77. Photo. Applying elastomeric coating over a grout cap ................................................ 86

Figure 78. Photo. Completed permanent restoration of a grout cap ............................................. 86

Figure 79. Flowchart. Inspection, sampling, evaluation, and actions for levels 1 and 2 

inspections for option 1 ................................................................................................................. 92

Figure 80. Flowchart. Inspection, sampling, evaluation, and actions for levels 1 and 2 

inspections for option 2 ................................................................................................................. 92

Figure 81. Illustration. Segment layout—part 1 ........................................................................... 97

Figure 82. Illustration. Segment layout—part 2 ........................................................................... 98

Figure 83. Illustration. Bulkhead details ....................................................................................... 99

Figure 84. Illustration. Longitudinal PT layout—part 1 ............................................................. 100

Figure 85. Illustration. Longitudinal PT layout—part 2 ............................................................. 101

Figure 86. Illustration. Longitudinal PT layout—part 3 ............................................................. 102

Figure 87. Illustration. Longitudinal PT layout—part 4 ............................................................. 103

Figure 88. Illustration. Longitudinal PT layout—part 5 ............................................................. 104

Figure 89. Illustration. Longitudinal PT layout—part 6 ............................................................. 105

Figure 90. Illustration. Longitudinal PT layout—part 7 ............................................................. 106

Figure 91. Illustration. Longitudinal PT layout—part 8 ............................................................. 107

Figure 92. Illustration. Plan and elevation—main channel unit ................................................. 109

Figure 93. Illustration. Bridge section ........................................................................................ 110

Figure 94. Illustration. Pier cap PT details ................................................................................. 111

Figure 95. Illustration. Tendon profile—main channel unit ....................................................... 112

Figure 96. Illustration. Modified Florida bulb-T78 beam end segment ..................................... 113

Figure 97. Illustration. Modified Florida bulb-T78 beam haunch segment ................................ 114

Figure 98. Illustration. Modified Florida bulb-T78 beam drop-in segment ............................... 115

Figure 99. Illustration. Modified Florida bulb-T78 beam end block detail ................................ 116

Figure 100. Illustration. Typical sections—haunch segment ...................................................... 117
viii

LIST OF TABLES

Table 1. Bridge condition—probability of defect indicator.......................................................... 37

Table 2. Construction and inspection records—probability of defect indicator ........................... 37

Table 3. Visual evaluation—probability of defect indicators ....................................................... 38

Table 4. Tendon geometry and length—probability of defect indicators ..................................... 38

Table 5. Weight factors for probability of defect indicator .......................................................... 39

Table 6. Consequence of failure indicator versus cost of repair or tendon replacement .............. 39

Table 7. Consequence of failure indicator versus element/tendon redundancy ............................ 40

Table 8. Consequence of failure indicator versus bridge importance ........................................... 40

Table 9. Weight factors for consequence of failure indicator ....................................................... 41

Table 10. Acceptable fractions of undetected tendons with deficient grout ................................. 41

Table 11. Minimum number of tendons required to detect at least one tendon with 

deficient grout (75 percent confidence) ........................................................................................ 44

Table 12. Minimum number of tendons required to detect at least one tendon with 

deficient grout (95 percent confidence) ........................................................................................ 44

Table 13. Balanced cantilever bridge—probability of defect indicator ........................................ 48

Table 14. Balanced cantilever bridge—consequence of failure indicator .................................... 48

Table 15. Balanced cantilever bridge—minimum recommended number of tendons for 

inspection ...................................................................................................................................... 49

Table 16. List of continuity tendons ............................................................................................. 50

Table 17. List of external draped tendons ..................................................................................... 51

Table 18. List of selected transverse tendons ............................................................................... 51

Table 19. List of cantilever tendons .............................................................................................. 52

Table 20. Spliced girder bridge—probability of defect indicator ................................................. 54

Table 21. Spliced girder bridge—consequence of failure indicator ............................................. 54

Table 22. Spliced girder bridge—minimum recommended number of tendons for inspection ... 55

Table 23. List of longitudinal draped tendons .............................................................................. 55

Table 24. List of diaphragm tendons ............................................................................................ 56

Table 25. List of pier cap tendons ................................................................................................. 56

Table 26. Span-by-span segmental bridge—probability of defect indicator ................................ 57

Table 27. Span-by-span segmental bridge—consequence of failure indicator............................. 57

Table 28. Span-by-span segmental bridge—minimum recommended number of tendons 

for inspection ................................................................................................................................ 58

Table 29. PT bridge—probability of defect indicator ................................................................... 59

Table 30. PT bridge—consequence of failure indicator ............................................................... 59

Table 31. PT bridge—minimum recommended number of tendons for inspection ..................... 60

Table 32. CD classifications as determined by grout Cl− levels from an option 1 inspection 

and resultant recommended actions .............................................................................................. 90

Table 33. CD and PD classifications as determined by grout Cl− levels and in-place grout 

structure by an option 2 inspection and resultant recommended actions ...................................... 91
1 

CHAPTER 1. BACKGROUND

The purpose of this report is to provide guidance for grout sampling, testing, analysis, and 

interpretation of test results. The following topics are presented and discussed: (1) post-tensioned 

(PT) bridge types, (2) types of grout deficiencies, (3) statistical approach to grout sampling, 

(4) grout sampling protocol and test methods, (5) locations for sampling, and (6) interpretation of 

results and determination of courses of action. Consideration is given to the possibility that 

extraction of a statistically significant number of samples from PT structures may pose a 

significant challenge for State transportation departments because of the possibility that invasive 

inspection and sample acquisition methods might compromise long-term bridge durability and 

structural integrity.

Durability issues for PT tendons in the United States came to the forefront in 1999 when bridge 

engineers became aware of failures that resulted from grout voids, associated bleed water, and 

tendon strand corrosion at higher elevations, such as at anchorages and crest areas. To date, 

10 States have reported tendon problems that stem from grout deficiencies or excessive 

chlorides (Cl–

). (See references 1–4.) Most grouts used for PT bridge construction prior to 

2001 consisted of a mixture of cement, water, and added admixtures and were typically mixed 

at the project site.

To improve grout performance as a corrosion protection method for tendons, the PostTensioning Institute (PTI) and some State transportation departments revised their grout 

specifications between 2001 and 2002. This resulted in the formulation of prepackaged, 

preapproved thixotropic grouts to eliminate bleed water and thus improve the level of 

protection provided to PT tendons. Prepackaged grout is a proprietary product that has 

been widely used in PT bridges since 2001. 

While the development of prepackaged thixotropic grouts was thought to provide a solution to 

the bleed water problem, corrosion-caused tendon failures on relatively new PT bridges have 

continued to occur. Limited forensic studies involving these newer grouts have revealed the

presence of grout segregation, soft grout, bleed water, and high Cl–

 and sulfate contents. 

However, not all prepackaged grouts exhibited the above deficiencies. Consequently, it is 

important to investigative these newer grouts to examine the overall quality of in-place grouts 

in existing PT bridges. This report is intended as a guide for State transportation departments 

in this regard. 

3 

CHAPTER 2. OBJECTIVES OF INSPECTION

The overall objective of this study was to develop a general guide for State transportation 

departments for sampling grouts from external and internal tendons in existing PT bridges. 

To accomplish this, protocols for sampling grouts with both physical deficiencies (PDs) and 

chemical deficiencies (CDs) were developed. This report provides a rational approach to extract 

statistically significant numbers of grout samples for proper interpretation of the corrosion 

susceptibility to the enclosed strands. At the same time, the sampling approach is such that there 

is minimal negative impact on the future durability considering both grout sampling location 

and number. 

Specific issues addressed in this report include the following: 

• The types of tendons from which grout samples should be obtained. 

• The number of extracted grout samples required from each tendon type on a 

statistical basis. 

• An explanation of proposed methods for retrieving grout samples from tendons, including 

anchorages, such that any impact on future durability is not compromised. 

• Recommendations regarding the amount of grout and the tests required for 

property characterization.

• Recommendation of a systematic procedure for recording and reporting grout 

composition in order to define its quality and project its future performance. 

• Recommended repair/rehabilitation procedures for tendons in order to minimize the

impact on future durability caused by sampling. 

• Presentation of a decision path guideline based upon the grout analysis results that 

recommends future tendon inspection and, if necessary, grout sampling intervals. 

5 

CHAPTER 3. PT SYSTEMS

BACKGROUND

Anchorage systems in PT bridges are a proprietary system. Systems created by VSL

International, Dywidag-Systems International, Freyssinet International, BBR VT International 

Ltd. (BBR), and Schwager Davis Inc. can be found in PT bridges in the United States. PT 

anchorage systems differ in shape, size, and material depending on use. In general, a basic PT

anchorage system is comprised of a bearing plate, trumpet, wedge plate (anchor head), grout cap, 

and grout ports (see figure 1). Prior to drilling a hole through the grout port for internal trumpet 

inspection, it is necessary to determine the PT system used since each system has different grout 

port orientation and geometry to access the trumpet interior. The simplest way to identify the PT 

system and its detail is to locate the PT shop drawings for the project, if available. 

©VSL International

Figure 1. Illustration. Basic PT anchorage system. 

In 2003, the Florida Department of Transportation (FDOT) required an additional vertical grout 

port/vent located above the trumpet to facilitate post-grouting inspection and permanent grout 

cap in its PT specifications. The differences between the older and newer generations of PT 

anchorages systems are shown in figure 2 and figure 3. Many other State transportation 

departments have adopted PT anchorages with requirements similar to the FDOT requirements. 

For the new anchorages, the inspection access into the trumpet interior is much simpler through 

the vertical grout port. 
6 

©Dywidag-Systems International

Figure 2. Photo. Old generation of PT anchorage system. 

©Dywidag-Systems International

Figure 3. Photo. New generation of PT anchorage system. 
7 

PT TENDON TYPES

In general, PT bridges built in the United States consist of grouted internal tendons, grouted 

external tendons, or a combination of the two. A small number of bridges may also have greased 

unbonded tendons. This report only focuses on cement grouted tendons, which may be internal 

or external. 

Internal tendons are located inside the structural concrete section, are housed in corrugated 

metal ducts or corrugated plastic ducts, and are bonded to the structural concrete by means of 

cementitious grout (see figure 4). The plastic corrugated ducts are made from high-density 

polyethylene (HDPE) or polypropylene material. The high-strength steel tendon can be strands, 

wires, or bars.

Source: Parsons Brinckerhoff

Figure 4. Illustration. Internal tendon. 

External tendons are typically located outside the perimeter of a concrete section, are housed in 

HDPE smooth duct, and are filled with cementitious grout. External tendons are not bonded with 

the concrete structural section (see figure 5 and figure 6).

Source: Parsons Brinckerhoff

Figure 5. Illustration. External tendon. 
8 

Source: Parsons Brinckerhoff

Figure 6. Photo. External tendons at deviator. 

PT BRIDGE TYPES

PT bridges can be grouped into several categories based on the design and construction methods. 

Typical possible tendon types used for each bridge group are discussed in the following sections. 

Cast-in-Place (CIP) PT Box Girder Bridges on False Works 

CIP concrete box girder bridges built on false works consist of single- to multi-cell box girders, 

as shown in figure 7. Typically, these types of bridges have an internally draped tendon in the 

webs. In a continuous multispan structure, the PT anchors are anchored in the end diaphragms, 

and some tendons may be anchored in the intermediate diaphragms. For long-span bridges, 

additional internal tendons are also provided in the top and bottom flanges and anchored in 

blisters (see figure 8 and figure 9). The top deck could be either transversely PT or reinforced 

concrete using mild reinforcement.

PT tendon types include the following: 

• Draped longitudinal internal tendons in the webs. 

• Continuity internal tendons in the bottom flanges. 

• Internal longitudinal tendons in the top flange over the piers. 

Deviator

Typical External Tendon
9 

• Transverse internal tendons in the deck. 

• Transverse internal tendons in the diaphragm (see figure 10). 

• Vertical internal tendons in the diaphragm. 

Source: Parsons Brinckerhoff

Figure 7. Photo. CIP concrete box girder bridge on false works. 

Figure 8. Illustration. CIP bridge typical tendon layout. 
10 

 Source: Parsons Brinckerhoff

Figure 9. Photo. Blister at the top flange. 

Source: Parsons Brinckerhoff

Figure 10. Illustration. Transverse internal tendon in the diaphragm. 

CIP PT Concrete Slab and T-Girder Bridges

CIP concrete slab bridges (see figure 11) are very popular for short-span bridges. The CIP PT 

slab and T-girder bridges are also constructed on false works. Typically, this type of structure 

has shallow draped longitudinal internal tendons in the deck (see figure 12). In most cases, 

transverse internal tendons in the deck are also provided. The superstructure may be a singlespan or multispan continuous structure from abutment to abutment. 
11 

PT tendon types include the following: 

• Draped longitudinal internal tendons. 

• Transverse internal tendons in deck slab. 

Source: Parsons Brinckerhoff

Figure 11. Photo. CIP PT concrete slab bridge. 

Figure 12. Illustration. PT slab bridge typical tendon layout. 

CIP Segmental Balanced Cantilever Bridge

CIP segmental box girder bridges (see figure 13) are popular for long-span bridges. They are 

constructed using the balanced cantilever method with a set of form travelers (see figure 14). The 

segment is cast against the previous PT segment, which is about 15 ft long. This type of structure 

utilizes internal cantilever tendons in the top flange over the webs in combination with continuity 

internal tendons in the bottom flange anchored at blisters (see figure 15). Additional externally 

draped tendons may also supplement the internal tendons. The top deck is typically transversely 

PT with tendons encased in flat ducts. For long span bridges, it is also common to use vertical PT 

bars in the webs of segments close to the pier segment. 

PT tendon types include the following: 

• Top longitudinal internal cantilever tendons. 
12 

• Continuity top and bottom flange internal tendons. 

• Longitudinal external draped tendons. 

• Transverse internal tendons in the top flange. 

• Vertical internal tendons in the webs (see figure 16). 

• Vertical internal tendons in diaphragms (see figure 17). 

• Transverse internal tendons in diaphragms. 

Source: Parsons Brinckerhoff

Figure 13. Photo. CIP segmental balanced cantilever bridge. 
13 

Source: Parsons Brinckerhoff

Figure 14. Photo. CIP balanced cantilever bridge during construction using form traveler. 

Source: Parsons Brinckerhoff

Figure 15. Photo. Typical bottom flange blister. 
14 

Source: Parsons Brinckerhoff

Figure 16. Illustration. Typical vertical tendon in the web. 

Figure 17. Illustration. Typical vertical tendon in the diaphragm. 

Precast Spliced I-Girder Bridge

Precast spliced girder bridges have been gaining popularity within the last decade for mediumspan bridges (see figure 18 and figure 19). Several long pieces of pretensioned American 

Association of State Highway and Transportation Officials (AASHTO) I-girders or bulb-tee 

girders are PT using draped internal tendons in the web to form a continuous multispan girder 

from end to end. The joints between the girders are CIP concrete. The diaphragms are typically 

cast at the splice locations and are reinforced concrete or PT transversely. A temporary support is 

provided at the CIP joint locations to stabilize the structure until the girders are made continuous. 

The deck slab is CIP after the first PT stage is applied. The final PT is applied after the CIP deck 

slab reaches minimum concrete strength.

PT tendon types include the following: 

• Draped longitudinal internal tendon. 

• Transverse internal tendons in the diaphragm at CIP joints. 
15 

Source: Parsons Brinckerhoff

Figure 18. Photo. Precast spliced girder bridge. 

Source: Parsons Brinckerhoff

Figure 19. Photo. Precast spliced girder bridge during erection. 

Precast Spliced U-Girder Bridge

Similar to precast AASHTO I-girder bridges, precast spliced U-girder bridges have also been 

gaining popularity recently for medium-span bridges, especially horizontally curved bridges 
16 

(see figure 20 and figure 21). Several long segments of pretensioned or PT U-girders are PT

using draped internal tendons in the web to form a continuous multispan girder from end to end. 

The joints between the girders are CIP concrete. The diaphragms are typically cast at the splice 

locations and are reinforced concrete or PT transversely. A temporary support is provided at the 

CIP joint locations to stabilize the structure until the girders are made continuous. The CIP deck 

slab is placed after the first stage PT is applied and the rest of the PTs are stressed after the CIP 

deck is hardened.

PT tendon types include the following: 

• Draped longitudinal internal tendon. 

• Transverse internal tendons in the diaphragm at CIP joints. 

Source: Summit Engineering Group

Figure 20. Photo. Precast spliced U-girder bridge during erection. 
17 

Source: Summit Engineering Group

Figure 21. Photo. Precast U-girder supported on temporary false work. 

Precast Segmental Balanced Cantilever Bridge

Precast segmental balanced cantilever bridges are erected using the balanced cantilever method 

either with an overhead gantry, a beam and winch, a segment transporter/lifter, or a groundbased crane (see figure 22). The segments are precast using match cast in short-line or long-line 

casting yard that is about 10 to 12 ft long. During segment erection, epoxy is applied at the match

cast joints and stressed by internal cantilever tendons in the top flange. 

PT tendon types include the following: 

• Longitudinal cantilever internal tendons. 

• Continuity top and bottom flange internal tendons. 

• Longitudinal externally draped tendons. 

• Transverse internal tendons in the top deck. 

• Vertical internal tendons in the webs. 

• Vertical internal tendon in the diaphragms. 

• Transverse internal tendon in the diaphragms. 
18 

Source: Parsons Brinckerhoff

Figure 22. Photo. Precast segmental balanced cantilever bridge erection using a 

segment lifter. 

Precast Segmental Span-by-Span Bridge

Precast span-by-span bridges consist of precast match cast segments that are 10 to 12 ft long and 

erected using an under-slung gantry or an overhead gantry as shown in figure 23. The entire span 

is temporarily supported by overhead or under-slung gantry stressed together using PT bars after 

epoxy is applied on the match cast joint. The CIP joints are cast between precast segments and 

the diaphragm segments. Permanent longitudinal external tendons are PT from both diaphragms 

to complete the span construction. The process is repeated at the next adjacent span.

PT tendon types include the following: 

• Longitudinal external tendons (see figure 24). 

• Continuity bottom internal tendons (optional). 

• Transverse internal tendons in the top flange. 

• Vertical internal tendons in the diaphragms. 

• Transverse internal tendons in the diaphragms. 
19 

Source: Parsons Brinckerhoff

Figure 23. Photo. Precast segmental span-by-span erection using an overhead gantry. 
20 

Source: Parsons Brinckerhoff

Figure 24. Illustration. Typical precast segmental span-by-span external PT tendon layout. 
21 

Concrete Cable-Supported Bridge

There are three types of concrete cable-supported bridges in the United States as follows: 

• CIP cable-stayed bridge. 

• Precast segmental cable-stayed bridge (see figure 25). 

• Extradosed segmental bridge. 

The superstructure of concrete cable-supported bridges can be precast box girder or CIP deck 

consisting of two edge girders and transverse floor beams. 

The CIP cable-stayed bridge concrete deck construction typically utilizes a set form traveler and 

is constructed with a balanced cantilever construction method. The previously cast segments are 

supported by stay cables until the CIP deck reaches the mid-span. Next, a closure segment is 

placed between the two tips of cantilevers. The CIP deck is typically designed in the form of 

PT transverse floor beams supported on reinforced concrete edge girders where the stay cable 

anchorages are located. The pylons and pier columns can be CIP or precast elements with 

vertical PT. 

The precast segmental cable-stayed bridge deck consists of precast box girders. The construction 

method of the precast deck is very similar to a precast segmental balanced cantilever bridge, 

except the previously erected segments are supported by stay cables. The segments are PT

longitudinally with internal grouted tendons, external tendons, and internal transverse tendons, 

including diaphragm tendons. The pylons and pier columns can be CIP or precast elements with 

vertical PT. 

An extradosed segmental bridge is a hybrid between a balanced cantilever bridge and a cable 

stayed bridge and has a very low tower height-to-span ratio. The superstructure of an extradosed 

bridge is very similar to CIP or precast segmental cable stayed bridges. 

The pylon cross beams that support the superstructure of the three types of cable-stayed bridges 

are normally PT with internal tendons. 

PT tendon types include the following: 

• Longitudinal cantilever internal tendons (box girder). 

• Longitudinal draped external tendons (box girder). 

• Continuity bottom internal tendons (optional). 

• Transverse internal tendons in the top flange (box girder). 

• Transverse internal tendons in the floor beam. 

• Transverse internal tendons in the pylon cross beam. 
22 

• Vertical internal tendons in the diaphragms. 

• Transverse internal tendons in the diaphragms. 

Source: Parsons Brinckerhoff

Figure 25. Photo. Precast segmental cable stayed bridge. 

Special PT Concrete Substructures

Aside from the previously listed superstructure bridge types, PT substructures such as PT

segmental precast piers (see figure 26), pylon or CIP PT straddle bents (see figure 27), C-bents, 

pier caps, and pile caps are also common. Most of these structures utilize internal tendons except 

segmental precast piers—internal, external vertical PT, or combined. 

PT tendon types include the following: 

• Horizontal/longitudinal internal tendons. 

• Vertical internal or external tendons or a combination of both. 
23 

Source: Parsons Brinckerhoff

Figure 26. Illustration. Cross section of precast segmental columns. 

Source: Parsons Brinckerhoff

Figure 27. Photo. PT straddle bent during construction.

Typical 

Vertical 

Tendon

PT Anchorages

25 

CHAPTER 4. GROUT DEFICIENCIES 

BACKGROUND

The first line of corrosion protection of grouted PT tendon relies on adequate sealing of 

ducts from external sources of corrodants (i.e., water, air, Cl–, and carbon dioxide), while the 

second line of corrosion protection relies on encasement and direct contact of strands with a 

cementitious grout for which a high pH (> 13) is maintained. Thus, if strands are inadequately 

grout coated, protection may still be feasible if the duct is adequately sealed and there are no 

internal sources of corrodants. Alternatively, even if the first protection (by duct) is lacking, the 

grout acts as a secondary protection to the PT tendon. A necessary but not sufficient condition 

for strand protection is that Cl–, either as a background grout contaminant or from an external 

source, is maintained below a critical concentration. 

PTI, the American Concrete Institute (ACI), and AASHTO all list 0.08 weight (wt) percent 

cement as an upper acid soluble Cl− limit for PT grout or prestressed concrete. (See 

references 5–8.) The applicable European standard lists this upper limit as 0.10 wt percent

cement.(9) In sufficient concentration, Cl– facilitates corrosion of conventional reinforcement 

and PT strand by transitioning steel from a passive state for which corrosion rate is negligible 

to an active one where corrosion rate may be unacceptably high and reducing grout electrical 

resistivity, thus minimizing macrocell activity and a higher corrosion rate than would otherwise 

develop. The disclosure that grout may have Cl− concentrations greater than the above limit 

(0.08 wt percent cement) and that approximately 100 PT bridge projects may have utilized this 

material has prompted immediate concerns regarding the long-term integrity of these bridges and 

a need for reactive strategies and actions. In the limited PT tendon grout sampling that has been 

performed to-date on a bridge that utilized this Cl− contaminated grout, Cl−

 concentrations as 

high as 5.27 wt percent grout1 were reported.(1) However, Cl− concentration of this grout may 

have varied with production variables such that this contaminant was in an acceptable range for 

some lots but not others. The purpose of this section of this report is to define the deficiencies 

that are thought to have occurred with the contaminated grout and other PT grouts with emphasis 

placed on the consequences of Cl−

 concentration possibly being in excess of the above specified 

limit of 0.08 wt percent cement. 

Cl− Threshold

The corrosion process in cementitious materials such as PT grout involves two phases: 

(1) a time to corrosion initiation, Ti, during which the steel is passive and (2) a period of 

corrosion propagation, Tp, to the point where repair, rehabilitation, or replacement becomes 

necessary. PT strands in grout that have a Cl− concentration below the threshold for active 

corrosion initiation are normally passive and exhibit a negligible corrosion rate. However, if 

Cl– is present above a limiting value, passivity is compromised, and active corrosion may occur

at an unacceptable rate, provided oxygen and moisture are present. Oxygen and moisture are 

invariably present in grout pores of atmospherically exposed tendons, although water content 

may be minimal under extremely dry conditions, and oxygen concentration may be negligible if 

the grout is water saturated. From the standpoint of strand corrosion, a worst-case scenario arises 

 

1

Approximately two-thirds of grout is typically composed of cementitious material.
26 

in situations where the grout is subjected to repetitive wetting (presumably from periodic water 

infiltration from a source external to the duct) and drying. Such cycling may also be facilitated 

by temperature variations. Strand corrosion is particularly severe at an air-water interface. Both 

Ti and Tp are a function of a number of material and exposure variables, which are described in 

this chapter in conjunction with a discussion of the Cl− concentration threshold. 

The Cl‒ threshold itself, CT (i.e., the concentration of this species required to initiate active 

corrosion) is understood to be greater than 0.08 wt percent cement for good quality, high 

alkalinity in-place grout, although a definitive concentration has not been defined. This is 

because CT is known to conform to a distribution rather than being a distinct value, and there 

are a number of variables of influence. For example, air voids greater in diameter than about 

0.1 inches that intersect the reinforcement facilitate local premature corrosion initiation. (See 

references 10–17.) Such occurrences, either involving air voids or relatively large air pockets, 

result from air entrapment because of inadequate duct venting, incomplete duct filling, strands 

pressing against the duct interior surface, strand congestion, subsidence, or poor consistency with 

segregation (or a combination of these). These occurrences have been reported within PT ducts 

irrespective of the advent during the past decade of thixotropic grouts. (See references 10 and 

18–20.) Also, steel corrosion at air-grout interfaces, which can occur in conjunction with the 

previously listed causes, has been reported even with Cl− concentrations below the prescribed 

upper limit of 0.08 wt percent.

(21,22)

 However, the presence of Cl− should enhance this attack 

because of steel depassivation or reduced grout resistivity (or both). 

Other variables that have been reported to influence CT include mix proportions, cement type, 

tricalcium aluminate content, concentration of blended materials, water/cementitious materials 

ratio, temperature, relative humidity, and steel surface condition. However, it can be reasoned 

that CT depends on cement content alone irrespective of whether or not grout, mortar, or concrete 

is an issue since Cl− predominantly resides in the cement phase.

(23) As a result, CT is normally 

expressed on a cement wt percent basis. Also, it is the cementitious phase that is predominantly 

contiguous with conventional reinforcement or bonded PT strand. Thus, for conventional 

reinforcement, ACI reports CT as 0.2 wt percent cement for concrete, whereas Alonso et al.

determined CT to be in the range of 0.39 to 1.16 wt percent cement (also for mortar).

(24–26) Mean 

and standard deviations for CT in concrete have been reported as 0.896 and 0.260 wt percent

cement, respectively.(27,28) While this seems high compared to the other CT values listed, the 

preceding values are not mean values but concentrations at which initial corrosion onset 

occurred. Thus, if two standard deviations are subtracted (0.260 × 2 = 0.520) from the listed

mean (0.896) and if it is assumed that the data are normally distributed, then the result 

(0.376 wt percent cement) indicates that 2.5 percent of embedded steel should be active at this 

value. This concentration is in the same range as the other results. However, all the CT

determinations listed previously are for conventional reinforcing steel embedded in sound 

cementitious material. Conversely, if steel is exposed in air and if free water is present, then CT is 

essentially 0 wt percent. Because the corrosion rate of active carbon steel in aqueous solutions 

and in cementitious materials is normally controlled by oxygen availability, variations in alloy 

composition or microstructure (or both) generally have little influence. Consequently, corrosion 

behavior of PT strand is expected to be generally similar to that for conventional reinforcement. 
27 

Previous Investigations 

Previous forensic investigations of existing bridge tendons with prepackaged thixotropic grouts 

have reported the following four distinct grout textures/appearances: 

• Type 1: Segregated wet plastic (soft) grout with a clay-like consistency. 

• Type 2: Segregated grout with black striated layers. 

• Type 3: Segregated dry grout with a chalky white consistency. 

• Type 4: Hardened, gray, dry grout.

Only type 4 has the requisite properties to render it a desired in-place grout. In some instances, 

all four grout types have been reported in the same general vicinity along tendons. Where 

multiple grout consistencies occurred, type 4 was typically found along the lower portion of 

ducts, while types 1 and 2 were found at the highest elevations, indicating that gravimetric forces 

played a role in the segregation. Regions where grout was segregated often exhibited an air void 

or pocket along the top of the duct interior. Figure 28 shows a cross section of a tendon 

subsequent to its failure 8 years after construction.2

Figure 28. Photo. Failed tendon cross section.

(22)

In figure 28, the strands contact the duct inner surface at the upper-right portion of the tendon, 

and type 4 grout is apparent in the lower region. Type 3 grout, either outlined or delineated by a 

somewhat broad white line (labeled “C”), is also apparent at intermediate elevations, and soft, 

wet grout is seen near the top. As such, in this case, the segregated white grout tended to separate 

the gray grout from segregated soft, wet grout or air space, which is apparent near the top 

(labeled “A”). Thus, segregated white grout occurred either as a volume of material embedded in 

the grout or as an approximately 0.04-inch-thick layer at the top of the gray grout. The type 2 

grout (not apparent in figure 28) has been identified as either unmixed or segregated silica fume. 

Because segregation involved gravimetric causes, the three undesired grout forms have been 

most pronounced at elevated horizontal locations, near the top of inclines, and at anchorages. 

 

2 Cl− concentration of the grout from this bridge was below the specified 0.08 wt percent cement upper limit. 
28 

Although not necessarily identifiable in figure 28, corrosion products are contiguous to the upper 

strands. Figure 29 shows a longitudinal overhead view of the strands and grout in figure 28 with 

the duct top half removed and all three segregated grout types identified. Section A shows type 1 

segregated wet, soft grout, B shows type 2 black segregated grout, and C shows type 3 

segregated chalky white grout.

A

B

C

Figure 29. Photo. Longitudinal section of a tendon section with 

types 1–3 grout identified.

(22)

Figure 30 and figure 31 show opened tendon anchorages. In these cases, there was no grout 

contamination by Cl−

, and grout filling of the duct was complete. However, regions of varied 

grout quality and strand corrosion products are apparent. For example, the grout in figure 30

consists predominantly of type 3 grout with an interconnecting network of cracking. Corrosion 

products at some of the strand ends are also visible. Figure 31 illustrates much the same but with 

type 1 grout in the central region. Figure 32 is similar to figure 31 but with type 4 grout in the 

bottom region. Thus, poor grout quality for these ducts is pervasive.

Figure 33 shows an opened anchorage on the Carbon Plant Road bridge over IH-37 in Texas as 

reported by the Texas Department of Transportation (TxDOT).(1) Type 1 grout is seen in the 

upper region, while the lower portion consists of type 4 gray grout. Free water flowed from the 

anchorage upon opening, and corrosion of strands in the type 1 grout and air space was apparent.
29 

Source: Parsons Brinckerhoff

Figure 30. Photo. Opened tendon end showing predominantly type 3 grout and strand 

corrosion products.

Source: Parsons Brinckerhoff

Figure 31. Photo. Opened tendon end showing types 3 and 1 grout and strand corrosion 

products.

 
30 

Source: Parsons Brinckerhoff

Figure 32. Photo. Opened tendon end revealing type 4 grout (bottom half), type 1 grout 

(center region), and strand corrosion products (upper region).

Figure 33. Photo. Opened anchorage on the Carbon Plant Road bridge over IH-37.(11)

Bertolini and Carsana reported forensic analysis results for a PT bridge for which a tendon 

failure was disclosed less than 2 years after construction.3(21) The cementitious grout was not 

identified by the manufacturer or as being thixotropic; however, a water/cement ratio of 0.32 was 

 

3 The location of this bridge was not provided, but it is assumed to be in Italy.

Type 1 Grout

Type 4 Grout
31 

specified along with a commercial unidentified admixture specific for PT grouts. While most 

tendons examined were characterized as consisting of type 4 grout, some, including the 

anchorage area of the failed tendon, had a whitish unhardened plastic paste, which could be a 

combination of types 1 and 3. Such regions contained small hardened black spots, which could 

be type 2 grout. Heavy strand corrosion occurred in areas of the whitish grout. 

The limited findings suggest the possibility that segregation and as many as four different 

textures/consistencies can result for in-place grouts with active strand corrosion occurring for 

segregated grout types 1–3.(1,21,22) These studies identified air voids/pockets as a major problem 

and indicated that upward water migration through the grout occurred during setting. The 

TxDOT study identified Cl−, sulfide (S2-), sodium (Na+), and potassium (K+) in type 1 grout, 

and FDOT found higher levels of Cl− and calcium (Ca2+) in type 1 in comparison to the 

other types.

(1,22)

 

Using an ex-situ leaching method, FDOT measured higher Cl− concentrations at upper compared 

to lower elevations within a given duct cross section, suggesting that upward migration of this 

species occurred during grout setting.(22) The concentrations measured at elevated positions were

relatively low (maximum ~0.04 wt percent), which was consistent with this grout not necessarily 

being from Cl− contaminated batches. Also, any partitioning trend for sulfates (SO4

2-) between 

grout types was less distinct than for Cl− and Ca2+; however, SO4

2- concentrations as high as 

0.9 wt percent were found in the type 1 grout free water. Sulfates are invariably present in 

cement pore water, and several authors have associated this species with steel depassivation or 

passive current densities being an order of magnitude or more higher than for SO4

2- free 

simulated pore water solutions as well as passivity breakdown events. (See references 29–31 and 

22.) Based on anodic polarization and immersion experiments in saturated calcium hydroxide 

solutions, Gouda reported the critical SO4

2- concentration for initiation of active steel corrosion 

as 0.2 percent.(30) One recommendation has been that the grout maximum cement S2- content be 

limited to 0.01 percent.(19) Schokker and Musselman reported advanced strand corrosion after 

relatively brief exposure periods in test assemblies that employed a standard commercial gypsum 

(hydrated calcium sulfate) grout and contiguous air space but no free water for the purpose of 

simulating a tendon failure in the Varina-Enon bridge in Virginia.

(31) Bertolini and Carsana 

measured elevated SO4

2-, Na+

, and K+ in the tendon grouts they examined and attributed strand 

corrosion and resultant fracture to the elevated pH range where the soluble hydrous iron oxide 

(HFeO2

-

) corrosion product has been reported and low water resistivity was observed 

(1.64 ohm-ft).(21,31) Although thermodynamically feasible, such a role of HFeO2

-

 has not been 

previously reported. It is projected that sulfates were responsible. The European standard lists an 

upper limit of 4.5 wt percent cement for sulfates and 0.01 wt percent cement for sulfides.

(9)

In addition, sulfates may cause electrolyte acidification within occluded regions (crevices), such 

as the lines of contact between adjacent wires or strands where the solution becomes deaerated. 

The process is normally described in standard corrosion texts as involving Cl− rather than SO4

2-, 

since the former is generally more pervasive; however, any hydrolysable ions, including sulfates, 

can have the same effect.(33) Thus, the reaction at issue is as follows: 

Fe2+ + 2H2O + SO4

2- → Fe(OH)2 + H2SO4

Figure 34. Equation. Reaction of the ferrous ion with water and sulfate ion to yield ferrous 

hydroxide and sulfuric acid.
32 

Where sulfuric acid is a product. Because of the resultant drop in pH, corrosion rate in such 

circumstances is expected to be much greater than if the solution were near neutral or alkaline.

Deficiencies

Based on the findings discussed in this chapter, the following grout deficiencies are of concern:

• Grout subsidence such that strands become exposed in resultant air space. 

• Grout segregation resulting in grouts (some unhardened) and free water with high 

concentrations of corrosive ions (Cl− and SO4

2-) in the upper vicinity of tendons and at 

high tendon elevations that facilitate corrosion. 

• Cl−

 concentrations in excess of the upper 0.08 wt percent cement limit specified by PTI, 

AASHTO, and ACI. (See references 5–8.) 

The finding that corrosion-induced tendon failures have occurred relatively soon after 

construction compared to the intended service life, even in situations where Cl− concentrations 

were relatively low and within the prescribed 0.08 wt percent cement limit, strongly indicates 

that segregation, subsidence, and incomplete duct filling are major issues.(1,21,22) Corrosion that 

occurs in such situations is likely to be enhanced by elevated Cl− but will still initiate and 

propagate even if Cl− concentrations are below the 0.08 wt percent limit. 
33 

CHAPTER 5. MINIMUM NUMBER OF TEST SAMPLES

GENERAL

The determination of the number of tendons to be inspected for grout sampling is an important 

part of this guideline. If not enough samples are collected, the inspection may not provide a good 

assessment of the actual condition in the bridge. However, if too many samples are removed, it 

may be too costly and, without proper restoration, may result in future durability issues. It is 

critical to select a reasonable number of tendons for each tendon type based on practical and 

logical considerations such as tendon redundancy, function, workmanship, complexity, detailing, 

etc. For instance, the recommended number of samples for a relatively straight short horizontal 

tendon will be different than for a long-draped tendon or a cantilever tendon. This chapter

provides guidance on the determination of a reasonable number of sampling locations for each 

type of tendon by utilizing a statistical risk-based approach to categorize and rank the elements 

of the PT system. The recommended numbers can be adjusted on a case-by-case basis.

As previously stated in chapter 4, there are two main sources of grout deficiencies as follows: 

• Grout material/constituent CDs (e.g., elevated Cl−

, sulfate, or other). 

• Grout PDs (e.g., grout void, segregated, and soft grout). 

A single lot of grout typically varies in size from about 40,000 to 250,000 lb. Each lot consists 

of a series of batches about 1,100 lb each. It is expected that for the contaminated grout, the 

Cl− content will be uniform within each batch, but the Cl− content may differ slightly between 

batches in a single lot.(34,35) Depending on the size and length of a certain tendon, it is likely that 

the grout of each tendon originated from several batches. 

Assuming that deficiencies stem from only grout material contamination, relatively few samples 

may be required for tendons grouted with the material from a single lot, provided the tendon 

grouting log information is available. In cases where tendons are grouted with multiple grout 

lots, a greater number of grout samples will be required in order to best assure that as many 

lots are included in the sampling as possible. However, the grout log information may not be 

available for every bridge. Therefore, the statistical grout sampling method is a reasonable 

approach as it is implemented in other fields in the industry by ASTM E141-10, “Standard 

Practice for Acceptance of Evidence Based on the Results of Probability Sampling.”(36)

Deficiencies caused by poor workmanship may require more samples because the variation 

in workmanship is likely to be more random in nature, and there may not be any correlation 

between different grouting locations. The two main sources of deficiencies can occur 

independently or concurrently at the same location. The combined effects of deficiencies 

and the uncertain nature of any poor workmanship complicate the formulation of the 

quantitative basis for an optimal and cost effective grout sampling/inspection program. 
34 

INSPECTION OPTIONS

In some cases, bridge owners may be concerned with the Cl−

 contamination only. Therefore, 

the inspection guidelines provided in this chapter contain the following two options with 

two different inspection plans, as shown in figure 35: 

• Option 1: Inspection for Cl−

 concentration in the tendon grout. 

• Option 2: Inspection for all grout deficiencies, including the determination of 

Cl− concentration. 

In both options, the inspection is performed in two levels. Recognizing that invasive testing 

may create paths that allow corrodants access to strands and cause corrosion if the tendon is 

not properly restored/repaired, level 1 is intended to provide an initial indication of the grout 

condition in terms of preliminary screening tests, while level 2 provides a more comprehensive 

and higher confidence result. Bridge owners have the flexibility to select the inspection strategy 

and level of confidence and modify the inspection plans/procedures as appropriate for their 

bridge inventory and local conditions. 

For owners who are only concerned with the grout Cl−

 contamination, the sampling procedure 

for option 1 should be followed. Otherwise, the sampling procedure for option 2 is followed, as 

shown in figure 35. 

Grout Sampling 

Inspection

Option 1

Testing for Chloride 

Concentration Only

Level 1 Level 2

Option 2 

Testing for All Grout 

Deficiencies

Level 1

75% Confidence

Level 2

95% Confidence

Figure 35. Flowchart. Inspection options. 

Option 2 adopts 75 and 95 percent confidence levels for levels 1 and 2, respectively. The 

75 percent confidence approach requires fewer samples than the 95 percent confidence, but it

should still provide reasonable findings. 

INSPECTING CL− CONTENT (OPTION 1)

Option 1 assumes no grout PDs, voids, or strand corrosion. If grout PDs are found during 

sampling, it is recommended to perform an option 2 inspection. 

Project with Complete Grouting Records

Level 1

Under this approach, either a minimum of three random samples is taken for each lot from the 

primary tendon types, or, alternatively, one sample is taken randomly from 50 percent of all 

batches (one sample per batch) depending on whichever of the two is larger (see chapter 7 for 
35 

recommended locations of grout sampling). If the test results show that one or more samples has 

a Cl−

 content higher than the threshold limit (0.08 wt percent cement), then a level 2 inspection is 

required. If all analysis results are below this limit, then no further sampling is required.

Level 2

Under this approach, a minimum of one random grout sample for each batch from the primary 

tendon types should be obtained (see chapter 9 for the interpretation of the test results for any 

further actions). 

Project with Incomplete or No Grouting Records

Grout sampling for this type of project should follow the procedures based on statistical methods 

of sampling for all grout deficiencies (option 2).

INSPECTING ALL GROUT DEFICIENCIES (OPTION 2)

In general, the inspection process is performed in four steps (see figure 36). In the first step, an 

engineer should review the as-built plans, PT shop drawings, specifications, and construction 

records. Then, the engineer should conduct a walk-through visual inspection for the length of 

the bridge. The main objective of the walk-through inspection is to evaluate the overall condition 

of the structural system and identify possible defects and signs of deterioration. The visual 

inspection does not require any specialized equipment. The third step is to obtain grout samples 

and visually assess and document the grout condition and any signs of tendon defects. 

Depending on the type of structure/tendon, some specialized equipment/tools might be 

necessary. At this point, the possibility of causing a “weak spot” or distress in the element 

(e.g., tendon damage during drilling) and rendering it prone to corrosion in the future if not 

properly repaired becomes an important factor in selecting the number of tendons for sampling. 

Therefore, it is important to minimize the number of sampled tendons while still providing an 

acceptable level of accuracy in representation of the grout chemical composition and condition. 

Chapter 7 of this report discusses the strategy that should be used to identify and preselect test 

locations within a tendon that are most likely to have deficient grout. 
36 

Pre-Inspection Activities

Review As-built Plans

Review Construction 

Records

Review Inspection 

Documents

Review Load Rating 

Visual Inspection 

and

NDT

Walk Through 

Duct Sounding

(External Tendon)

Cracked Concrete

Signs of Water 

Leakage

Corrosion Protection 

System

Signs of Corrosion

Grout Sampling

Inspection

Presence of Voids

Grout Segregation

Grout Consistency

Grout Discoloration

Presence of Corrosion

Borescope Inspection

Grout Sample 

Collection

Grout Sample 

Evaluation

Grout Petrographic

Evaluation

Corrodant

Concentration

Moisture Content

Figure 36. Flowchart. Grout inspection processes. 

Since there is no quantitative methodology for ranking and identifying deficient areas, the 

elements of the PT system should be categorized based on the qualitative opinion of experts. The 

risk-based inspection methodology was adopted, and tendons are prioritized in terms of the risk 

associated with the potential failure.

(38)

 All tendons in the bridge are assigned to one of the 

following groups: 

• Low risk. 

• Medium risk. 

• High risk. 

The risk is expressed as a product of a probability of defect indicator and a consequence of 

failure indicator, as shown in figure 37. The critical factors influencing risk are defined in terms 

of a series of tables with designated categories. Numerical values from 1 to 5 are assigned to 

each category, with 1 being the least probable or lowest consequence, 3 being intermediate, and 

5 being most probable with very high catastrophic consequence.
37 

1 2 3 4 5

1

2

5

3

4

Probability of Defect Indicator

Consequence of Failure Indicator

Figure 37. Graph. Risk matrix. 

Probability of Defect Indicator 

Bridge Condition/Service Performance 

The overall condition and previous service performance history of a bridge is an important factor 

affecting the likelihood of an ongoing corrosion process. Existing serviceability issues such as

visible cracks, discoloration of concrete, or poor overall workmanship (or a combination of 

these) should be considered in assigning this factor. Table 1 lists the probability of defect 

indicators for the bridge condition categories considered. 

Table 1. Bridge condition—probability of defect indicator. 

Bridge 

Condition Description Value

Poor Very high degradation probability 5

Moderate High degradation probability 4

Good Average degradation probability 3

Very Good Low degradation probability 2

Excellent Very low degradation probability 1

Construction Records

An important factor affecting the risk associated with the potential tendon failure is the 

availability of the construction records and previous inspection records. Recommended 

probability of defect indicators are listed in table 2. 

Table 2. Construction and inspection records—probability of defect indicator. 

Construction and Inspection Records Value

No construction and inspection records exist 5

Limited construction and inspection records exist 4

Some construction and inspection records exist 3

Comprehensive construction and inspection records exist 2

Very comprehensive construction and inspection records exist 1
38 

Visual Condition Evaluation

The visual evaluation serves as an important first tool in selecting any problem areas and 

estimating the likelihood of more serious structural defects. The probability of defect indictors 

for the visual inspection categories are listed in table 3. The maximum value of the defect 

indicator should be selected from the list of assigned probability of defect indicators in 

this category. 

Table 3. Visual evaluation—probability of defect indicators. 

Visual Inspection Category

Major

Defect

Moderate

Defect

Small

Defect

Very Small

Defect

No

Defect

Signs of grout leakage 5 4 3 2 1

Workmanship 5 4 3 2 1

Cracked concrete 5 4 3 2 1

Duct condition (external PT) 5 4 3 2 1

Voids (external PT) 5 4 3 2 1

Signs of water leakage 5 4 3 2 1

Corrosion protection 5 4 3 2 1

Tendon Geometry and Length 

It was observed from prior investigation experiences that it is unlikely to have defective grout in 

short straight tendons or tendons with small curvature changes. The likelihood of a defect is 

higher for multispan long tendons with large curvature changes and large distances between 

lowest and highest points, particularly tall vertical tendons. The probability of defect indicators 

for the tendon shape categories are listed in table 4. 

Table 4. Tendon geometry and length—probability of defect indicators. 

Tendon Geometry and Length Value

Long multispan tendons with large curvature changes/large distance 

between lowest and highest points; tall vertical tendons

5

Short single-span tendons with large curvature changes/large 

distance between lowest and highest points; short vertical tendons

4

Long tendons with small curvature changes 3

Long straight tendons or short tendons with small curvature changes 2

Short straight/horizontal tendons 1
39 

Overall Probability of Defect Indicator

The overall probability of defect indicator, P, is determined as a weighted sum of the 

contributing factors as follows: 

=∑ WPP ii

Figure 38. Equation. Overall probability of defect indicator.

Where: 

Pi = Partial probability of defect indicator. 

Wi = Appropriate weight factor, as shown in table 5.

 

Table 5. Weight factors for probability of defect indicator. 

Probability of Defect Indicator Weight

Overall bridge condition 0.15

Construction and inspection records 0.15

Visual evaluations 0.30

Tendon geometry and length 0.40

Consequence of Failure Indicator

The consequence of failure indicator is intended to categorize the tendons in terms of the 

effect that eventual failure due to corrosion resulting from an undetected defect will have on 

the structure. 

Cost of Repair or Tendon Replacement 

The relative cost of repair/replacement accounts for the funding that would be needed to restore 

the full functionality of the structure after the elements have become damaged or failed. Table 6 

presents the consequence of failure indicators in this category.

Table 6. Consequence of failure indicator versus cost of repair or tendon replacement. 

Rank

Cost of Repair or 

Tendon Replacement

Very high 5

High 4

Moderate 3

Low 2

Very low 1

Element/Tendon Redundancy

Redundancy is generally defined as the extra capacity of a structural system to carry loads 

after partial damage or failure of its elements. For example, cantilever tendons have higher 

redundancy than bottom continuity tendons since a portion of the cantilever tendons is required 

to support the dead loads and erection equipment during free cantilever construction. After the 
40 

cantilever tips from two adjacent piers are connected, the negative moments demand will be 

reduced. However, the extra tendons are typically left in place. Diaphragm tendons are also 

considered to have high redundancy due to the presence of a large amount of ordinary 

reinforcement. The consequence of failure indicators associated with the element/tendon 

redundancy are listed in table 7. 

Table 7. Consequence of failure indicator versus element/tendon redundancy. 

Element/Tendon Redundancy Value

Loss of some tendons will cause a catastrophic failure 5

Loss of some tendons will cause severe distress to the 

structure—repairable

4

Loss of some tendons will decrease the capacity of the 

structural system—possible need for posting, no 

structural distress

3

Sufficient safety reserve exists. Loss of a small number 

of tendons will slightly impact the capacity, but the 

system can remain in service without posting

2

Tendon does not contribute to the resistance of the 

structural system

1

Bridge Importance 

The criticality of the bridge as an element of the transportation system is considered in 

this category. Major bridges carrying large volumes of traffic should be assigned to a high 

consequence category, while bridges in a rural area with low traffic volumes should be assigned 

a low number. Recommended consequence of failure indicators for this category are listed in 

table 8. 

Table 8. Consequence of failure indicator versus bridge importance. 

Bridge Importance Value

Critical bridges 5

Non-critical bridges 3

Less important bridges 1

Overall Consequence of Failure Indicator

The overall consequence of failure indicator, C, is determined as a weighted sum of the 

contributing factors as follows: 

= ∑ WCC ii

Figure 39. Equation. Overall consequence of failure indicator.

Where: 

Ci = Partial probability of defect indicator. 

Wi = Appropriate weight factor, as shown in table 9.
41 

Table 9. Weight factors for consequence of failure indicator. 

Consequence of Failure Indicator Weight

Cost for repair/tendon replacement 0.4

Element redundancy 0.4

Criticality of the bridge 0.2

Risk Level

Figure 37 is used to determine risk level and prioritize/categorize the tendons according to the 

relationship, as shown in figure 40. 

×= CPRISK

Figure 40. Equation. Risk.

Where: 

P = Overall probability of defect indicator. 

C = Consequence of failure indicator. 

Acceptable Fraction of Tendons with Undetected Deficient Grout 

The recommended minimum number of sampled tendons depends on element risk and the 

possibility of creating distress for the structure through intrusive inspection. The acceptable 

number of tendons with undetected deficient grout is lower for elements with high risk. Within a 

risk category, the acceptable number of tendons with undetected deficient grout decreases as the 

likelihood of structural distress associated with intrusive sampling increases. Table 10 presents 

recommendations regarding the acceptable number of tendons with undetected deficient grout to 

categories of element risk and inspection costs. 

Table 10. Acceptable fractions of undetected tendons with deficient grout

Element

Risk

Structural Impact Caused by Sampling

High Medium Low

High 20 percent deficient 10 percent deficient 10 percent deficient

Medium 30 percent deficient 20 percent deficient 10 percent deficient

Low 30 percent deficient 30 percent deficient 20 percent deficient

Minimum Number of Inspected Tendons 

To determine the minimum number of inspected tendons, tendons identified for testing are 

arranged in groups within which every tendon has approximately the same likelihood of having 

defective grout; each group is considered as a separate population. Depending on the total 

number of tendons in one group, N, as compared to the number of tendons in that group selected 

for inspection, n, selecting the sample n tendons from population N might significantly change 

the remainder of the population regardless of how many tendons with defective grout are in the 

sample. Therefore, it is assumed that the distribution of the number of tendons with defective 

grout in a random sample of n tendons is an approximately hypergeometric distribution with 

parameters m, k, and N, where m is the actual number of tendons with defective grout and k is the 
42 

number of times when the selected tendon is with defective grout. The probability mass function 

(PMF) of this distribution is expressed as follows:

( )

































−

−

















==

n

N

kn

mN

k

m

kXP

Figure 41. Equation. Probability mass function for hypergeometric distribution.

Where P(k) is the probability of observing k number of deficiencies when selecting without 

replacement n samples from the population of size N.

(39) Figure 42 presents an example of PMF

of the fraction of samples with defective grout calculated for N = 100, m = 25, n = 45, and 

k = 1...20. Each bar represents the probability that when 45 tendons are randomly inspected from 

a total population of 100 tendons, k tendons will have a defect. Since in this example 25 percent

of tendons have defective grout, the expected and most probable number of successes (detection 

of tendon with defect) is 25 percent of 45, or 11 tendons. 

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Probability P(X = k)

Number of Deficient Grout Samples

Probability Mass Function

Figure 42. Graph. Example of PMF for hypergeometric distribution. 

The cumulative distribution function (CDF) of the hypergeometric distribution is defined 

as follows: 

Figure 43. Equation. CDF. 
43 

Figure 44 shows CDF for PMF for the example PMF presented in figure 42. Based on the 

properties of CDF, it can be determined that there is (1 – Pd) = 10 percent probability of 

discovering not more than eight defective tendons and a Pd = 90 percent chance of discovering 

eight or more defective tendons where Pd is defined as the probability of detecting more than 

i number of defective tendons in the population of N with m tendons being defective.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Cumulative Probability

Number of Deficient Grout Samples

Cumulative Distribution Function

Figure 44. Graph. Example of CDF for a hypergeometric distribution. 

Calculations were performed to determine the minimum number of samples required to detect 

at least one tendon with defective grout, assuming different fractions of tendons with defective 

grout in the total population. For all considered cases, the probability of detection (confidence of 

detecting at least one) is set equal to 75 percent (level 1 inspection) and 95 percent (level 2 

inspection). The results are presented in the table 11 and table 12. Based on the results in 

table 12, if 100 tendons are identified in one risk group and eight are initially tested with no 

defects, then there is a 95 percent probability that the fraction of tendons with defects in the 

selected population is less than 30 percent. By testing an additional five tendons, it can be 

assured that there is 95 percent probability that the fraction of tendons with defects in the 

selected population is less than 20 percent. 

In some cases, it might be necessary to relax the assumptions by decreasing the probability of 

detecting at least one defective to minimize the number of tendons required to detect at least 

one tendon with defective grout. Figure 45 to figure 48 present the minimum required number of 

sampled tendons for confidence levels equal to 95, 85, and 75 percent assuming 5, 10, 20, and 

30 percent of the tendons have defective grout. The figures are intended to assist in making 

informed decisions regarding the sample size to minimize the sampling effort.
44 

Table 11. Minimum number of tendons required to detect at least one tendon with deficient 

grout (75 percent confidence). 

Number of 

Identified Tendons

Percent of Tendons with Deficient Grout

10 Percent 20 Percent 30 Percent

10 8 5 3

20 10 5 4

50 12 6 4

100 12 6 4

150 13 6 4

200 13 6 4

500 13 6 4

> 1,000 13 6 4

Table 12. Minimum number of tendons required to detect at least one tendon with deficient 

grout (95 percent confidence). 

Number of 

Identified Tendons

Percent of Tendons with Deficient Grout

10 Percent 20 Percent 30 Percent

10 10 7 6

20 15 10 6

50 22 12 7

100 25 13 8

150 26 13 8

200 26 13 8

500 27 13 8

> 1,000 28 13 8

0

10

20

30

40

50

60

0 100 200 300 400 500 600 700 800 900 1000

Required Sample Size

Total Number of Tendons

95% Confidence, 5% Defective

85% Confidence, 5% Defective

75% Confidence, 5% Defective

Figure 45. Graph. Minimum number of tendons required to detect at least one tendon with 

deficient grout assuming 5 percent of the samples are defective. 
45 

0

5

10

15

20

25

30

0 100 200 300 400 500 600 700 800 900 1000

Required Sample Size

Total Number of Tendons

95% Confidence, 10% Defective

85% Confidence, 10% Defective

75% Confidence, 10% Defective

Figure 46. Graph. Minimum number of tendons required to detect at least one tendon with 

deficient grout assuming 10 percent of the samples are defective. 

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

0 100 200 300 400 500 600 700 800 900 1000

Required Sample Size

Total Number of Tendons

95% Confidence, 20% Defective

85% Confidence, 20% Defective

75% Confidence, 20% Defective

Figure 47. Graph. Minimum number of tendons required to detect at least one tendon with 

deficient grout assuming 20 percent of the samples are defective. 
46 

0

1

2

3

4

5

6

7

8

9

10

0 100 200 300 400 500 600 700 800 900 1000

Required Sample Size

Total Number of Tendons

95% Confidence, 30% Defective

85% Confidence, 30% Defective

75% Confidence, 30% Defective

Figure 48. Graph. Minimum number of tendons required to detect at least one tendon with 

deficient grout assuming 30 percent of the samples are defective. 

Sampling Procedure Summary

The procedure to determine the recommended minimum number of sampled tendons to be tested 

consists of the following steps: 

1. Estimate the total number of tendons for each considered tendon type. Review the as-built 

plans, PT shop drawings, specifications, and construction records and identify all tendon 

types. Determine the number of tendons for each considered tendon type. 

2. Prioritize the tendons by assigning them to one of three risk categories (high, medium, 

or low). 

3. Determine the probability of defect indicator (see table 1 through table 5) for each considered 

tendon group. 

4. Determine the consequence of failure indicator (see table 6 through table 9) for each 

considered tendon group. 

5. Assign the group to one of the three risk categories as shown in figure 37. 

6. Based on the structural impact/distress caused by sampling tendons from each group, use 

table 10 to determine an acceptable fraction of tendons with undetected deficient grout. 

7. Determine the minimum number of sampled tendons. Use table 11 for level 1 inspection 

(75 percent confidence) and table 12 for level 2 inspection (95 percent confidence).

After the minimum number of sampled tendons to be tested is determined, it is necessary to 

locate the strategic inspection points for each tendon type (see chapter 7). 
47 

The selection of a random sample from the list of identified inspection locations involves the 

following steps: 

1. Assign a random number to each tendon. 

2. Sort each tendon according to the order it is numbered. 

Note that a predetermined number (percentage) of tendons should be selected starting from the 

top or bottom of the list of tendon numbers. 

EXAMPLES

Typical Balanced Cantilever Bridge

The procedure for option 2 inspection is presented in this section as an example using an existing 

precast segmental bridge. The plans for the considered bridge can be found in appendix A. The 

bridge consists of 10 spans with the total length of 2,256.33 ft. The following four distinct types 

of tendons are utilized in this bridge:

• Cantilever tendons: Internal longitudinal tendons (12 tendons with 0.6-inch diameter) in 

the top flange over the piers. The tendons are straight and vary from short to long with 

small curvature changes.

• Continuity top and bottom flange internal tendons: Internal longitudinal tendons 

(12 tendons with 0.6-inch diameter). The tendons are straight and vary from short to long 

with small curvature changes.

• Longitudinal external draped tendons: Short single-span tendons (12 tendons with 

0.6-inch diameter) with large curvature changes/long distance between lowest and 

highest points. 

• Transverse internal tendons in the top flange: Short internal tendons (four tendons 

with 0.6-inch diameter and nine tendons with 0.6-inch diameter) with small 

curvature changes.

Overall, the bridge is in good condition and has excellent workmanship. It is assumed that

construction records are not available or are incomplete. The sampling procedure used in this 

example is as follows:

1. Estimate the number of the tendons for each tendon type. 

• Total number of cantilever tendons = 242. 

• Total number of continuity top and bottom tendons = 112. 

• Total number of draped tendons = 40. 

• Total number of transverse tendons = 694. 
48 

2. Prioritize the tendons by assigning them to one of three risk categories. 

3. Determine the probability of defect indicator (see table 13).

Table 13. Balanced cantilever bridge—probability of defect indicator. 

Category

Weight

(table 5)

Tendon Type

Transverse Cantilever Continuity External

Bridge condition (table 1) 0.15 2 2 2 2

Construction and inspection 

records (table 2) 0.15 5 5 5 5

Visual inspection (table 3) 0.30 1 1 1 1

Tendon shape and length 

(table 4) 0.40 1 2 2 4

Probability of defect indicator 2 2 2 3

4. Determine consequence of failure indicator (see table 14). 

Table 14. Balanced cantilever bridge—consequence of failure indicator

Category

Weight

(table 9)

Tendon Type

Transverse Cantilever Continuity External

Cost of repair or 

replacement (table 6)

0.40 3 5 4 2

Element/tendon redundancy 

(table 7)

0.40 2 2 4 2

Bridge importance (table 8) 0.20 5 5 5 5

Consequence of failure indicator 3 4 4 3

5. Assign tendon groups to appropriate risk categories (see figure 49).

External 

Draped 

Tendons

Transverse

Tendons

Cantilever 

& 

Continuity 

Tendons

1 2 3 4 5

1

2

5

3

4

Probability of Defect Indicator

Consequence of Failure Indicator

Figure 49. Graph. Balanced cantilever bridge—tendon risk categories. 
49 

6. For each identified group, select an acceptable fraction of tendons with undetected deficient 

grout and determine the minimum number of sampled tendons (see table 15). 

Table 15. Balanced cantilever bridge—minimum recommended number of tendons for 

inspection. 

Type of Tendon

Total 

Number of 

Tendons Risk

Structural 

Impact 

Caused by 

Inspection

Acceptable 

Fraction Of 

Undetected 

Defective

Minimum 

Number of 

Tendons for 

Inspection

Level 1 Level 2

Transverse tendon 694 Medium High 30 percent 4 8

Cantilever tendon 242 Medium High 30 percent 4 8

Continuity tendon 112 Medium Medium 20 percent 6 13

External tendon 40 Medium Low 10 percent 12 22

7. Randomly select the required number of tendons for each tendon type. 

Table 16 through table 19 present the summary of all tendons. Each tendon is identified by its 

label. The first letter and number denotes the span number “S.” The second letter denotes the 

tendon name as shown in the as-built plans. The last number helps identify the tendon in case 

there are two or more tendons with the same profile at one location. All of the data in tables are 

sorted with respect to the random number assigned to each tendon. Bold text indicates level 1 

inspections, and bold italics indicates level 2 inspections. 
50 

Table 16. List of continuity tendons. 

#

Random

#

Tendon 

ID #

Random

#

Tendon 

ID #

Random

#

Tendon 

ID #

Random

#

Tendon 

ID

1 0.022 S7-C4-1 29 0.237 S1-C5-2 57 0.461 S1-C3-1 85 0.783 S8-C1-2

2 0.028 S5-T20-2 30 0.254 S4-T21-2 58 0.462 S2-C3-1 86 0.788 S4-C2-2

3 0.055 S7-C5-1 31 0.258 S4-T20-2 59 0.467 S4-C3-1 87 0.802 S2-C1-1

4 0.055 S7-T20-1 32 0.270 S8-C2-1 60 0.476 S2-T20-2 88 0.806 S5-C4-1

5 0.056 S9-T21-2 33 0.274 S10-C1-2 61 0.504 S3-C2-2 89 0.812 S2-C4-1

6 0.063 S9-C2-1 34 0.282 S2-C2-2 62 0.504 S1-T20-2 90 0.813 S1-C4-1

7 0.078 S5-T20-1 35 0.287 S9-C3-1 63 0.509 S8-C4-2 91 0.818 S6-C2-1

8 0.088 S3-C2-1 36 0.298 S9-C2-2 64 0.521 S7-T20-2 92 0.818 S3-T20-2

9 0.092 S6-C3-1 37 0.328 S7-C2-1 65 0.527 S5-C2-1 93 0.833 S3-C1-1

10 0.098 S5-C3-1 38 0.359 S6-C5-2 66 0.569 S4-C2-1 94 0.835 S3-C6-1

11 0.112 S2-C2-1 39 0.363 S10-C2-1 67 0.573 S1-C2-1 95 0.843 S1-C2-2

12 0.112 S6-C3-2 40 0.364 S6-T20-1 68 0.578 S7-C1-1 96 0.850 S3-C6-2

13 0.114 S5-C5-1 41 0.372 S7-C3-2 69 0.593 S7-C4-2 97 0.855 S6-C1-1

14 0.134 S5-C4-2 42 0.383 S6-T20-2 70 0.605 S1-C4-2 98 0.861 S5-C1-2

15 0.134 S8-C5-2 43 0.389 S7-C1-2 71 0.609 S3-C1-2 99 0.892 S8-C2-2

16 0.147 S7-C3-1 44 0.399 S6-C2-2 72 0.620 S2-C4-2 100 0.895 S10-C2-2

17 0.161 S8-T20-2 45 0.407 S8-C1-1 73 0.640 S1-C5-1 101 0.907 S4-T20-1

18 0.162 S7-C2-2 46 0.414 S5-C3-2 74 0.646 S2-C1-2 102 0.918 S3-T20-1

19 0.176 S4-C1-1 47 0.416 S1-T20-1 75 0.666 S9-C3-2 103 0.920 S4-C3-2

20 0.184 S4-C4-2 48 0.419 S2-T20-1 76 0.692 S8-C3-1 104 0.931 S10-T20-2

21 0.194 S8-C3-2 49 0.424 S1-C3-2 77 0.704 S5-C1-1 105 0.939 S3-C5-2

22 0.195 S3-C3-1 50 0.428 S9-T20-1 78 0.707 S7-C5-2 106 0.942 S1-C1-1

23 0.199 S9-C1-1 51 0.432 S3-C4-1 79 0.707 S5-C2-2 107 0.943 S3-C4-2

24 0.207 S10-C1-1 52 0.441 S6-C4-2 80 0.714 S3-C3-2 108 0.968 S1-C1-2

25 0.219 S9-C1-2 53 0.450 S8-C5-1 81 0.718 S2-C3-2 109 0.970 S8-C4-1

26 0.230 S10-T20-1 54 0.456 S6-C4-1 82 0.737 S4-T21-1 110 0.976 S6-C5-1

27 0.235 S4-C4-1 55 0.459 S4-C1-2 83 0.752 S9-T20-2 111 0.989 S9-T21-1

28 0.236 S6-C1-2 56 0.460 S5-C5-2 84 0.783 S8-T20-1 112 0.998 S3-C5-1
51 

Table 17. List of external draped tendons. 

#

Random

#

Tendon 

ID #

Random

#

Tendon 

ID

1 0.001 S10-E1-1 21 0.416 S9-E1-2

2 0.040 S7-E2-1 22 0.453 S4-E1-2

3 0.062 S4-E1-1 23 0.457 S4-E2-2

4 0.064 S10-E2-1 24 0.493 S3-E1-1

5 0.074 S7-E1-1 25 0.600 S4-E2-1

6 0.080 S10-E2-2 26 0.631 S5-E2-1

7 0.090 S9-E2-2 27 0.642 S3-E2-1

8 0.116 S9-E1-1 28 0.645 S8-E2-1

9 0.118 S3-E1-2 29 0.685 S1-E1-1

10 0.119 S8-E2-2 30 0.693 S8-E1-1

11 0.129 S7-E2-2 31 0.783 S1-E2-2

12 0.148 S2-E1-1 32 0.792 S5-E2-2

13 0.161 S3-E2-2 33 0.794 S2-E2-1

14 0.201 S1-E1-2 34 0.894 S10-E1-2

15 0.234 S2-E2-2 35 0.897 S7-E1-2

16 0.243 S5-E1-2 36 0.906 S5-E1-1

17 0.274 S2-E1-2 37 0.909 S9-E2-1

18 0.360 S6-E2-2 38 0.932 S1-E2-1

19 0.362 S6-E1-2 39 0.943 S8-E1-2

20 0.372 S6-E1-1 40 0.974 S6-E2-1

Table 18. List of selected transverse tendons. 

#

Random

#

Tendon 

ID

1 0.001 249

2 0.001 255

3 0.004 103

4 0.005 388

5 0.006 694

6 0.009 426

7 0.015 456

8 0.020 638
52 

Table 19. List of cantilever tendons. 

#

Random

#

Tendon 

ID #

Random

#

Tendon 

ID #

Random

#

Tendon 

ID #

Random

#

Tendon 

ID

1 0.016 P3-T11-2 62 0.285 P4-T1-2 123 0.503 P4-T2-2 184 0.741 P5-T3-1

2 0.016 P10-T2-1 63 0.288 P7-T10-1 124 0.504 P4-T2-1 185 0.744 P6-T1-1

3 0.020 P8-T5-2 64 0.291 P9-T3-1 125 0.504 P5-T9-2 186 0.746 P8-T14-2

4 0.022 P7-T9-1 65 0.304 P2-T3-2 126 0.509 P5-T3-2 187 0.759 P5-T7-1

5 0.027 P2-T10-1 66 0.306 P4-T8-2 127 0.511 P8-T10-1 188 0.760 P3-T1-1

6 0.032 P3-T7-1 67 0.307 P2-T8-2 128 0.522 P4-T5-2 189 0.762 P5-T6-2

7 0.038 P6-T2-1 68 0.309 P7-T5-1 129 0.525 P7-T7-2 190 0.763 P10-T4-2

8 0.038 P3-T4-2 69 0.309 P4-T10-1 130 0.528 P8-T10-2 191 0.782 P8-T4-1

9 0.046 P6-T4-2 70 0.309 P3-T8-2 131 0.529 P8-T13-1 192 0.782 P7-T6-2

10 0.049 P3-T5-2 71 0.322 P8-T2-1 132 0.531 P6-T14-2 193 0.789 P10-T2-2

11 0.050 P4-T10-2 72 0.328 P6-T5-1 133 0.533 P4-T16-2 194 0.798 P9-T9-1

12 0.053 P2-T8-1 73 0.343 P8-T7-1 134 0.536 P6-T9-2 195 0.807 P9-T4-1

13 0.055 P10-T1-1 74 0.350 P6-T4-1 135 0.538 P9-T6-2 196 0.808 P6-T8-1

14 0.058 P7-T4-2 75 0.351 P9-T1-1 136 0.540 P6-T13-1 197 0.810 P6-T9-1

15 0.058 P10-T5-1 76 0.353 P10-T6-2 137 0.548 P9-T1-2 198 0.815 P9-T7-2

16 0.059 P2-T5-1 77 0.359 P8-T9-1 138 0.549 P4-T11-2 199 0.836 P3-T10-2

17 0.061 P6-T13-2 78 0.369 P5-T11-2 139 0.552 P5-T10-2 200 0.838 P8-T9-2

18 0.070 P3-T14-1 79 0.377 P3-T10-1 140 0.560 P9-T12-1 201 0.838 P2-T7-2

19 0.074 P6-T8-2 80 0.377 P6-T11-2 141 0.568 P9-T14-1 202 0.844 P7-T13-1

20 0.084 P6-T7-1 81 0.380 P5-T1-1 142 0.568 P8-T3-2 203 0.847 P4-T4-1

21 0.085 P8-T12-2 82 0.380 P8-T14-1 143 0.569 P8-T7-2 204 0.853 P5-T7-2

22 0.089 P4-T7-1 83 0.381 P8-T5-1 144 0.572 P5-T10-1 205 0.858 P7-T13-2

23 0.097 P3-T1-2 84 0.381 P9-T16-2 145 0.578 P9-T5-2 206 0.860 P7-T10-2

24 0.100 P3-T6-1 85 0.389 P9-T8-2 146 0.581 P10-T7-2 207 0.862 P7-T4-1

25 0.104 P9-T5-1 86 0.396 P4-T9-2 147 0.582 P3-T14-2 208 0.865 P6-T5-2

26 0.105 P6-T1-2 87 0.398 P4-T4-2 148 0.586 P10-T3-2 209 0.872 P3-T2-2

27 0.107 P2-T1-2 88 0.398 P5-T4-1 149 0.590 P3-T15-1 210 0.876 P6-T14-1

28 0.109 P9-T12-2 89 0.399 P7-T11-1 150 0.608 P5-T1-2 211 0.878 P3-T15-2

29 0.112 P7-T8-1 90 0.399 P3-T5-1 151 0.609 P3-T9-2 212 0.886 P5-T13-2

30 0.120 P4-T7-2 91 0.400 P2-T5-2 152 0.618 P4-T6-1 213 0.888 P3-T12-2

31 0.134 P10-T4-1 92 0.403 P2-T9-2 153 0.626 P7-T12-2 214 0.889 P5-T11-1

32 0.136 P9-T7-1 93 0.404 P8-T3-1 154 0.627 P6-T7-2 215 0.891 P9-T15-2

33 0.138 P7-T8-2 94 0.405 P9-T15-1 155 0.629 P6-T12-1 216 0.892 P3-T4-1

34 0.146 P2-T6-1 95 0.405 P8-T8-1 156 0.630 P9-T11-2 217 0.894 P9-T10-1

35 0.153 P9-T16-1 96 0.410 P4-T13-1 157 0.630 P7-T2-2 218 0.895 P4-T6-2

36 0.159 P4-T8-1 97 0.412 P10-T1-2 158 0.630 P4-T14-2 219 0.907 P6-T3-1

37 0.162 P7-T9-2 98 0.413 P6-T3-2 159 0.633 P6-T12-2 220 0.925 P3-T13-2

38 0.163 P4-T9-1 99 0.415 P9-T6-1 160 0.633 P9-T13-1 221 0.933 P4-T11-1

39 0.165 P3-T13-1 100 0.416 P6-T6-1 161 0.636 P4-T12-1 222 0.937 P2-T7-1

40 0.165 P3-T16-1 101 0.418 P4-T16-2 162 0.640 P8-T6-1 223 0.940 P9-T13-2

41 0.165 P7-T14-1 102 0.420 P3-T2-1 163 0.644 P8-T11-1 224 0.940 P6-T6-2

42 0.169 P3-T16-2 103 0.435 P10-T6-1 164 0.652 P6-T10-2 225 0.952 P7-T14-2

43 0.182 P6-T10-1 104 0.435 P3-T11-1 165 0.654 P2-T10-2 226 0.962 P8-T1-2

44 0.185 P7-T3-2 105 0.437 P7-T1-1 166 0.659 P2-T1-1 227 0.964 P9-T3-2

45 0.186 P4-T15-2 106 0.441 P7-T2-1 167 0.660 P9-T10-2 228 0.965 P5-T5-2

46 0.189 P5-T4-2 107 0.446 P9-T2-1 168 0.664 P7-T12-1 229 0.967 P4-T3-1

47 0.194 P10-T8-2 108 0.447 P4-T3-2 169 0.668 P6-T2-2 230 0.968 P7-T5-2

48 0.207 P3-T3-2 109 0.449 P2-T2-1 170 0.669 P9-T9-2 231 0.969 P8-T4-2
53 

49 0.210 P8-T8-2 110 0.452 P8-T1-1 171 0.669 P10-T8-1 232 0.971 P2-T2-2

50 0.221 P3-T8-1 111 0.466 P3-T3-1 172 0.671 P5-T12-1 233 0.971 P6-T11-1

51 0.228 P9-T11-1 112 0.471 P4-T5-1 173 0.671 P2-T6-2 234 0.974 P5-T5-1

52 0.234 P4-T13-2 113 0.472 P7-T7-1 174 0.677 P5-T2-2 235 0.975 P4-T15-2

53 0.250 P10-T5-2 114 0.479 P3-T7-2 175 0.699 P3-T12-1 236 0.976 P9-T14-2

54 0.252 P5-T9-1 115 0.480 P4-T1-1 176 0.708 P2-T3-1 237 0.979 P8-T13-2

55 0.254 P7-T3-1 116 0.482 P4-T14-2 177 0.713 P8-T12-1 238 0.979 P3-T9-1

56 0.256 P7-T11-2 117 0.487 P5-T12-2 178 0.720 P7-T1-2 239 0.982 P10-T3-1

57 0.258 P5-T6-1 118 0.488 P5-T13-1 179 0.726 P9-T2-2 240 0.984 P8-T2-2

58 0.261 P8-T6-2 119 0.489 P2-T9-1 180 0.727 P2-T4-1 241 0.990 P4-T12-2

59 0.262 P5-T2-1 120 0.493 P9-T4-2 181 0.728 P3-T6-2 242 0.992 P5-T8-2

60 0.265 P10-T7-1 121 0.495 P8-T11-2 182 0.729 P9-T8-1 235 0.975 P4-T15-2

61 0.277 P5-T8-1 122 0.500 P7-T6-1 183 0.737 P2-T4-2

Typical Spliced Girder Bridge

In a second example, a typical existing spliced girder bridge was used with a 3-span 

configuration (main channel unit) as part of a 24-span bridge for a total length of 3,585 ft. The 

approaches were constructed with eight lines of Florida bulb-T78 precast prestressed concrete 

girders. The main channel unit is continuous over three spans that are 196.6 × 250 × 196.6 ft. It 

was constructed with eight lines of modified Florida bulb-T78 girders. Each girder line consists 

of two haunched pier segments, a main span drop-in segment, and two side span drop-in 

segments. Each segment is an individually precast pretensioned girder that supports its own 

weight and handling loads. All segments in one line of girder are continuously PT with 

four 15-internal draped tendons with 0.6-inch diameter from end to end. The haunch segment 

diaphragms are transversely PT with three tendons at each diaphragm. The plans can be 

viewed in appendix B.

The bridge is in good condition but has less than desirable workmanship based on visual 

inspection. The complete construction and inspection records are not available. The considered 

structure is a typical highway bridge carrying medium traffic volumes. It is assumed that the 

owner performed an option 2 inspection. The sampling procedure used in this example is 

as follows: 

1. Estimate the number of the tendons for each tendon type. 

• Total number of longitudinal draped tendons = 32. 

• Total number of pier cap transverse PT = 16. 

• Total number of diaphragm transverse PT = 6. 

2. Prioritize the tendons by assigning them to one of three risk categories. 

3. Determine the probability of defect indicator (see table 20). 
54 

Table 20. Spliced girder bridge—probability of defect indicator. 

Category

Weight 

(table 5)

Tendon Type

Longitudinal 

Draped 

Pier Cap

Transverse 

Diaphragm 

Transverse 

Bridge condition (table 1) 0.15 3 3 3

Construction and inspection 

records (table 2)

0.15 4 4 4

Visual inspection (table 3) 0.30 1 1 1

Tendon shape and length (table 4) 0.40 5 2 1

Probability of defect indicator 3 2 2

4. Determine the consequence of failure indicator (see table 21). 

Table 21. Spliced girder bridge—consequence of failure indicator. 

Category

Weight 

(table 9)

Tendon Type

Longitudinal 

Draped 

Pier Cap

Transverse 

Diaphragm 

Transverse

Cost of repair or replacement 

(table 6)

0.40 5 4 3

Element/tendon redundancy

(table 7)

0.40 3 2 2

Bridge importance (table 8) 0.20 3 3 3

Consequence of failure indicator 4 3 3

5. Assign tendon groups to appropriate risk categories (see figure 50).

Longit. 

Draped PT

Pier Cap & 

Diaphragm 

Trans. PT

1 2 3 4 5

1

2

5

3

4

Probability of Defect Indicator

Consequence of Failure Indicator

Figure 50. Graph. Spliced girder bridge—tendon risk categories. 
55 

6. For each identified group, select an acceptable fraction of undetected deficient grout 

locations and determine the minimum number of sampled tendons (see table 22). 

Table 22. Spliced girder bridge—minimum recommended number of tendons 

for inspection. 

Type of Tendon

Total 

Number of 

Tendons Risk

Structural 

Impact 

Caused by 

Inspection

Acceptable 

Fraction Of 

Undetected 

Defective

Minimum 

Number of 

Tendons for 

Inspection

Level 1 Level 2

Longitudinal draped 32 Medium High 30 percent 4 7

Pier cap transverse 16 Medium High 30 percent 4 6

Diaphragm transverse 6 Medium Medium 20 percent 5 6

7. Randomly select the required number of tendons for each tendon type. 

Table 23 through table 25 present the summary of all tendons. Each tendon is identified by its 

label. The first letters and number denote the girder number “G,” pier number “P,” and pier 

diaphragm number “DP.” The second letter denotes the tendon name “T” as shown in the as-built 

plans. All of the data are sorted with respect to the random number assigned to each tendon. The 

required number of tendons is selected from the top of the tendon list and is bold for the level 1 

inspections and bold italic for the level 2 inspections. 

Table 23. List of longitudinal draped tendons. 

#

Random

#

Tendon 

ID #

Random

#

Tendon 

ID

1 0.494 G1-T4 17 0.954 G8-T2

2 0.876 G6-T2 18 0.843 G4-T2

3 0.387 G4-T1 19 0.883 G3-T4

4 0.725 G3-T3 20 0.817 G5-T2

5 0.396 G6-T1 21 0.283 G2-T3

6 0.931 G7-T4 22 0.930 G8-T1

7 0.809 G1-T1 23 0.196 G2-T1

8 0.582 G7-T1 24 0.071 G8-T3

9 0.409 G5-T1 25 0.866 G2-T2

10 0.487 G4-T4 26 0.269 G2-T4

11 0.847 G4-T3 27 0.287 G1-T2

12 0.587 G7-T3 28 0.284 G3-T1

13 0.966 G6-T3 29 0.467 G3-T2

14 0.913 G5-T4 30 0.126 G1-T3

15 0.540 G7-T2 31 0.095 G5-T3

16 0.459 G6-T4 32 0.226 G8-T4
56 

Table 24. List of diaphragm tendons. 

#

Random

#

Tendon 

ID

1 0.068 DP11-T1

2 0.098 DP10-T2

3 0.414 DP10-T1

4 0.431 DP11-T2

5 0.699 DP10-T3

6 0.884 DP11-T3

Table 25. List of pier cap tendons. 

#

Random

#

Tendon 

ID

1 0.049 P10-T4

2 0.120 P10-T2

3 0.261 P12-T3

4 0.321 P11-T4

5 0.440 P11-T3

6 0.465 P9-T3

7 0.554 P11-T2

8 0.618 P9-T1

9 0.620 P11-T1

10 0.725 P12-T2

11 0.794 P9-T4

12 0.812 P12-T1

13 0.945 P10-T3

14 0.946 P10-T1

15 0.977 P9-T2

16 0.997 P12-T4

Typical Span-by-Span Segmental Bridge

In the third example, a typical eight-span precast segmental span-by-span bridge construction 

with a span configuration of 8 × 130 ft is examined. The superstructure consists of a single-cell 

box girder with 40-ft-wide top deck that is 8 ft deep. There are two types of PT tendons on this 

bridge as follows: 

• Transverse internal PT: Four 0.6-inch-diameter strands of transverse tendon at 

3-ft spacing.

• Longitudinal external PT: 19 0.6-inch-diameter multistrands with 3 pairs of draped 

tendons per span. 
57 

The bridge is in moderate condition and has bad workmanship based on visual inspection. 

Complete construction and inspection records are available. The bridge carries large volumes of 

heavy traffic. Option 2 was selected. The sampling procedure used in this example is as follows:

1. Estimate the number of the tendons for each tendon type. 

• Total number of transverse tendons = 347. 

• Total number of external tendons = 48. 

2. Prioritize the tendons by assigning them to one of three risk categories. 

3. Determine the probability of defect indicator (see table 26).

Table 26. Span-by-span segmental bridge—probability of defect indicator. 

Category

Weight 

(table 5)

Tendon Type

Transverse External

Bridge condition (table 1) 0.15 4 4

Construction and inspection records 

(table 2)

0.15 1 1

Visual inspection (table 3) 0.30 5 5

Tendon shape and length (table 4) 0.40 1 4

Probability of defect indicator 3 4

4. Determine the consequence of failure indicator (see table 27). 

Table 27. Span-by-span segmental bridge—consequence of failure indicator. 

Category

Weight 

(table 9)

Tendon Type

Transverse External

Cost of repair or replacement (table 6) 0.40 2 3

Element/tendon redundancy (table 7) 0.40 2 4

Bridge importance (table 8) 0.20 5 5

Consequence of failure indicator 3 4

5. Assign tendon groups to appropriate risk categories (see figure 51).
58 

External

Trans.

1 2 3 4 5

1

2

5

3

4

Probability of Defect Indicator

Consequence of Failure Indicator

Figure 51. Graph. Span-by-span segmental bridge—tendon risk categories. 

6. For each identified group, select an acceptable fraction of undetected deficient grout 

locations and determine the minimum number of tendons to be sampled (see table 28).

Table 28. Span-by-span segmental bridge—minimum recommended number of tendons 

for inspection. 

Type of 

Tendon

Total 

Number of 

Tendons Risk

Structural 

Impact 

Caused by 

Inspection

Acceptable 

Fraction 

Defective

Minimum 

Number of 

Tendons for 

Inspection

Level 1 Level 2

Transverse 347 Medium High 30 percent 4 8

External 48 High Low 10 percent 12 22

7. Randomly select the required number of tendons for each tendon type. 

Typical PT Bridge with Draped Tendons 

A five-span continuous bridge with a three-cell box girder superstructure was constructed on a 

160-ft-long false-work per span. The bridge was PT with 4 19-strand draped internal tendons 

with 0.6-inch diameter per web from abutment to abutment. In addition, at each pier the box 

girder was also PT with top internal tendons and anchored at blisters located at the intersection of 

web and top deck. The top longitudinal tendons over the exterior web are 3 19-strand tendons 

with 0.6-inch diameter and 6 19-strand tendons with 0.6-inch diameter over the internal web. 

The top deck is transversely PT with four 0.6-inch internal tendons at 3-ft spacing. The 

diaphragm is transverse PT with six 31-strand tendons with 0.6-inch diameter. The diaphragm 

has ample redundancy due to the large amount of ordinary reinforcing bars. Each diaphragm also 

has 12 vertical internal PT bars with 13

/8-inch diameter. The box girder is 7 ft deep. The bridge is 

in good condition and, it has no defects and average workmanship based on visual inspection. No
59 

construction and inspection records are available. The structure carries large traffic volumes. The 

procedure is as follows: 

1. Estimate the number of the tendons for each tendon type. 

• Total number of top transverse tendons = 267.

• Total number of top longitudinal tendons = 72. 

• Total number of web longitudinal draped tendons = 16. 

• Total number of transverse diaphragm tendons = 36. 

• Total number of vertical diaphragm PT bars = 72. 

2. Prioritize the tendons by assigning them to one of three risk categories. 

3. Determine the probability of defect indicator (see table 29). 

Table 29. PT bridge—probability of defect indicator. 

Category

Tendon Type

Weight

(table 5) Transverse Top Longitudinal

Transverse 

Diaphragm

PT 

Bars

Bridge condition (table 1) 0.15 3 3 3 3 3

Construction and 

inspection records (table 2)

0.15 5 5 5 5 5

Visual inspection (table 3) 0.30 3 3 3 3 3

Tendon shape and length 

(table 4)

0.40 1 1 5 3 1

Probability of defect indicator 3 3 4 3 3

4. Determine the consequence of failure indicator (see table 30). 

Table 30. PT bridge—consequence of failure indicator. 

Category

Tendon Type

Weight

(table 9) Transverse Top Longitudinal

Transverse 

Diaphragm

PT 

Bars

Cost of repair or 

replacement (table 6) 

0.40 2 2 4 1 1

Element/tendon redundancy

(table 7)

0.40 2 2 5 1 1

Bridge importance (table 8) 0.20 3 3 3 3 3

Consequence of failure indicator 2 2 4 1 1

5. Assign tendon groups to appropriate risk categories (see figure 52).
60 

Long.

Tr. Diaph

&

PT Bars

Trans.

&

Top

1 2 3 4 5

1

2

5

3

4

Probability of Defect Indicator

Consequence of Failure Indicator

Figure 52. Graph. PT bridge—tendon risk categories. 

6. For each identified group, select an acceptable fraction of undetected deficient grout 

locations and determine the minimum number of tendons to be sampled (see table 31). 

Table 31. PT bridge—minimum recommended number of tendons for inspection. 

Type of Tendon

Total 

Number

of Tendons Risk

Structural 

Impact 

Caused by 

Inspection

Acceptable

Fraction

Defective

Minimum 

Number of 

Tendons for 

Inspection

Level 1 Level 2

Transverse tendon 267 Medium High 30 percent 4 8

Top tendon 72 Medium High 30 percent 4 8

Longitudinal tendon 16 High High 20 percent 5 8

Transverse 

diaphragm tendon

36 Low High 30 percent 4 7

Vertical diaphragm 

PT bar

72 Low High 30 percent 4 8

7. Randomly select the required number of tendons for each tendon type. 
61 

CHAPTER 6. GROUT SAMPLING AND TEST METHODS

GENERAL CONSIDERATIONS

Material (grout in the present case) characterization requires that both composition and structure 

(macro and micro) be determined. Composition is determined by wet chemistry and analytical 

techniques such as ion chromatography, X-ray florescence, and energy dispersive spectroscopy 

(EDS), while structure is determined by petrographic methodologies, electron microscopy, and 

X-ray diffraction. 

As an initial step in the case of external tendons, the general appearance of the tendon should be 

documented. The duct should be inspected for any cracks or connections that could serve as 

conduits for corrosives from an external source. Access to grout and strands can be accomplished 

either by end cap removal or by sectioning away duct at an intermediate location along the 

tendon. In the latter case, duct wall thickness is determined from construction documents, and 

duct sectioning can be performed using either a plastic cutting wheel or a depth guard that limits 

grinding depth to that of the duct wall thickness. Caution should be used in duct sectioning so 

that strands are not impacted. It is important to recognize that these strands may press against 

the interior duct wall at some circumferential orientation. Upon exposing the grout, its visual 

appearance and presence of any strand corrosion (or lack thereof) should be documented. Direct 

access to strands may require removal of some grout cover, which is described later in this 

chapter. Alternatively, potential measurements can be made to assess the corrosion state of 

embedded strand. Figure 53 shows a dial depth gauge being used to measure the size of a grout 

air void at the top of a tendon at a location where access to the underlying grout was made on an 

external tendon. 

Source: Concorr Florida 

Figure 53. Photo. Dial gauge used to determine the depth of a grout air void. 
62 

Internal tendons represent special challenges because intermediate locations along the length 

require concrete excavation, and there is greater potential that damage to the tendon may occur 

compared to external tendons. Similar to external tendons, the investigation should document the 

initial general appearance of internal tendon end caps. An appropriate number of these end caps 

(see chapter 5) should be opened, and their condition should be assessed. Figure 54 shows a 

grout sample being taken at an opened internal tendon end by chipping after the cap was 

removed. Note the plastic sheet beneath the anchorage to ensure no sample contamination. If the 

grout condition within these is good and grout Cl− analysis results determine that concentration 

of this species is within acceptable limits, then no further sampling at intermediate locations 

should be required. However, if the grout appearance is problematic (i.e., undesirable grout types 

are encountered, see chapter 4), Cl−

 contaminated, or otherwise defective, then consideration 

must be given to inspect and sample additional end caps, intermediate locations, or both. This 

access should be performed by standard concrete excavation methods but with due diligence 

being taken to ensure that reinforcement is not cut or otherwise compromised and the tendon 

itself is not damaged. Figure 55 shows concrete excavation to access an internal tendon 

subsequent to its being located using ground penetrating radar (GPR). Once the tendon is 

exposed, then inspection and analysis can be performed the same as for external tendons. 

Source: Parsons Brinckerhoff 

Figure 54. Photo. Grout sample acquisition at an opened internal tendon end cap by light 

chipping. 
63 

Source: Concorr Florida

Figure 55. Photo. Concrete excavation to expose an internal tendon. 

If a grout sample has been acquired from an end cap, then it is probably not necessary to acquire 

additional samples from the same tendon. However, it may be appropriate to determine the grout 

quality at intermediate locations, particularly the presence of any air pockets at high points. This 

can be done for internal tendons with minimal concrete and tendon disruption by drilling with a 

1-inch-diameter bit, as shown in figure 56. There are noticeable changes in the drill noise and 

vibration when a tendon is contacted, which helps ensure that there is no strand damage. If an air 

pocket is disclosed, it can be inspected using a borescope.
64 

Source: Parsons Brinckerhoff

Figure 56. Photo. Internal tendon access at an intermediate location by drilling. 

If it is necessary to acquire grout samples at intermediate locations on internal tendons, 

relatively small excavations can be used, as shown in figure 57. In the figure, an approximately 

6-inch-diameter access was created to reveal the exposed strand and grout. 

Source: Parsons Brinckerhoff

Figure 57. Photo. Access hole in an internal tendon at an intermediate location revealing 

strand and grout. 
65 

Prior to opening a tendon end cap or duct at an intermediate location (external or internal), 

preparations should be made to capture a sample of any free water that might be present and 

otherwise lost. This involves placing an opened bag or sealable plastic container beneath the 

location(s) of anticipated runout. 

Particular attention should be given to the following: 

• Presence of any air pocket or void space along the top of the duct. Figure 58 shows an 

interior tendon void space. If defects are present, then components in the air space (the 

duct internal surface if access is at an intermediate location along the tendon or anchorage 

end plate and strand ends) should be inspected to determine if grout residue is present. 

Absence of residue is an indication of incomplete grout filling at the time of construction, 

while presence of residue may indicate grout subsidence. 

• Presence of free water.

• Presence and extent of any corrosion on strands and anchorage. 

• Differences in grout color, consistency, or segregation (or a combination of these). 

• Presence of voids in the grout (this should be documented for each type of 

grout appearance). 

Source: Parsons Brinckerhoff 

Figure 58. Photo. View of a duct interior revealing a channel air void. 
66 

The following should be collected and deposited in a clean freezer bag using a clean tool such as 

a flat blade screw driver, chisel, or chipping or a light duty power tool: 

• Water sample (if present). 

• Corrosion products (if present and accessible). 

• Samples of each grout type that is present. 

• Any other material that may prove to be of interest.

Samples should be collected as soon as practical after exposing the tendon interior since air 

exposure may alter composition and structure of the grout and of any corrosion products and free 

water that may be present. Individuals performing this work should wear clean plastic or rubber 

gloves to prevent contamination. In cases where the duct opening is at an intermediate position 

along a tendon and strands are found to have pressed against the duct interior surface, grout 

sample acquisition should be at the diametrical orientation where strands should have greatest 

cover. If corroding strands are present in void space, they should be examined using a borescope, 

either behind the anchor plate if access is at a tendon end or further along the tendon beyond the 

length where duct was removed at an intermediate location. 

Sample Size

A minimum of 75 g of solid sample (this may consist of more than one piece) of each grout type 

should be obtained and designated by number/letter according to location. While powder can be 

used for chemical analyses, a solid sample is required for petrography. If soft, wet grout is found, 

then at least one sample should be placed in a bag and sealed in such a manner that as much air 

as possible is expelled and that enough pressure is exerted on the grout such that free water is 

separated. The grout itself should then be removed and placed in a separate bag, and the free 

water should be retained in the original bag for compositional analysis. Also, as noted in chapter 

4, soluble ions have been reported to migrate upward through the grout as it hardens.(1,22)

Consequently, concentration of these may be greater in the upper regions of the grout. This 

possibility should be taken into account when acquiring samples. 

Analyses 

The following techniques are available for compositional determinations:

• X-ray florescence (solid or powdered samples only).

• EDS (solid or powdered samples only).

• Ion chromatography (solution only).

• Wet chemistry analysis for total Cl−

.

(40)

 

• Wet chemistry analysis for soluble Cl−.

(40)

 
67 

Standard analysis methods to determine both acid and water soluble Cl− are available. The 

former (acid soluble) represents the concentration that dissolves in nitric acid and is sometimes 

referred to as the “total” concentration of Cl− considering that virtually all Cl− is soluble. The 

latter (water soluble) is the Cl− concentration that is dissolvable in water, which is invariably less 

than for acid soluble, reflecting the fact that some Cl− is chemically bound by or absorbed on the 

cement calcium silicate hydrates. An upper limit of 0.08 wt percent cement acid soluble Cl− has 

been defined for PT grout by multiple specifications and guides; however, several publications 

also list an upper limit for water soluble Cl−

 as 0.06 wt percent cement. (See references 5–8.) It is 

recommended to determine the acid soluble Cl− concentration since the possibility exists that Cl−

that is bound at one time may later become free and facilitate corrosion. 

As a minimum, X-ray fluorescence and wet chemistry analysis should be performed. 

Components for which determinations should be made are Cl−

, SO4

2-, K+

, and Na+, Cl−, and 

SO4

2 are determinants of loss of passivity and onset of active corrosion, and K+

 and Na+ are

determinants of cement alkalinity. Any free water samples should be analyzed by ion 

chromatography. Estimating grout Cl− concentrations on site in real time can be accomplished 

using the Germann Instruments (GI) Rapid Chloride Test (RCT) test kit for acid soluble Cl−. The 

procedure requires a 5-g powdered sample and takes about 10–15 min to perform. A test kit for 

determining water soluble Cl− concentration (GI RCT water) is also available; however, the test 

for acid soluble Cl− is recommended. 

Petrographic analysis should be performed in accordance with the applicable ASTM standard.(41)

Researchers should also include an analysis and explanation of any grout color and consistency 

distinctions and lack of set. All analyses should be performed by the resident State transportation 

department or by a transportation department certified laboratory.

Additionally, an option is available to assess corrosion state and rate for strands embedded in 

grout. Corrosion state is determined by measuring potential. The methodology and data 

interpretation are described for conventional reinforcing steel in concrete in “Standard Practice 

for Calculation of Corrosion Rate and Related Information from Electrochemical 

Measurements.”

(42)

 Corrosion rate is determined by measuring polarization resistance from 

which corrosion rate can be calculated.(43,44) Both techniques require a standard reference 

electrode, a high impedance voltmeter, access to grout in the vicinity where the strands of 

interest are embedded, and an electrical connection to one or more strands. In addition, 

polarization resistance measurements require an external (counter) electrode in contact with the 

grout and a means for imposing small potential changes on the strands via the counter electrode. 

Because surface area of the strands is likely not known, corrosion rate determinations are 

qualitative in nature. Lau et al. reported results using both measurement procedures on opened 

PT tendons.(22) The procedures should only be employed by people familiar with the 

technologies, equipment, and methods. 
68 

Tools, Equipment, and Instrumentation

The following lists contain needed information, equipment, and instrumentation for the 

respective categories.

Background information (as available) includes the following: 

• As-built plans. 

• Construction documents. 

• Previous inspection reports. 

• PT shop drawings. 

• Grouting plan and log. 

Equipment for concrete excavation and strand/grout access includes the following: 

• Generator with power cord(s).

• Ventilation fan(s).

• Lighting. 

• Standard tool box. 

• Rotary hammer. 

• Electric drill. 

• Small grinder. 

• Steel core drill for end cap removal. 

Items for sample acquisition include the following: 

• Plastic bags. 

• Sealable plastic containers. 

• High-performance waterproof tape. 

• Lightweight power and manual chipping tools and hammer. 

• Clean rubber gloves. 

• GI RCT test kit if onsite Cl−

 is intended. 
69 

Items for tendon inspection include the following: 

• Digital camera. 

• GPR. 

• Borescope.

Instrumentation for strand corrosion assessment includes the following: 

• Reference electrode with Cl− free soap solution, sponge, and lead wires. 

• High-impedance multimeter. 

• Polarization resistance instrumentation.

Reporting

It is recommended that a common data collection and reporting format be employed by the 

transportation departments conducting grout sampling programs. Figure 59 shows a simplified 

bridge schematic where three horizontal PT tendons are in place on each side of the box 

segments. This allows for the identification and representation of grout sampling locations. 

Likewise, figure 60 provides a format for documenting individual grout samples, and figure 61

illustrates a tabular form for presenting data and analysis results.

Span No. 1 Span No. 2 Span No. 3 Span No. 4 Span No. n

W or S Bound

Plan

Elevation

North or East 

Bound

South or West

Bound

Figure 59. Illustration. Bridge representation used to identify grout sampling locations.
Girder Span Location on Tendon Notes Grout Lot 

No.

Grout 

Batch

Bridge Designation:

Sample 

No.

Tendon 

Designation

Tendon 

Type

Tendon/Sample Location Grouting 

Date

Figure 60. Illustration. Chart used to record the location and information for individual grout samples. 

70
Cl- SO4

2- K+ Na+ Cl- SO4

2- K+ Na+

1

2

3

4

Air Pocket

*Type 1. Segregated wet, plastic (soft) grout with a clay-like consistency.

 Type 2.

 Type 3.

 Type 4.

General Description/Remarks of Opened End Cap/Duct

Segregated grout with black, striated layers.

Bridge Designation:

Tendon 

Designation

-

Segregated grout with a chalky, white consistency.

Hardened, gray in appearance grout.

Petrographic Analysis 

Summary

Sample 

Number

Grout 

Type*

Grout Analysis Results, wt% grout Free Water Analysis Results, wt% sample

Figure 61. Illustration. Chart used to record and present analysis results for individual grout samples.

71

73 

CHAPTER 7. STRATEGIC SAMPLING LOCATIONS

BACKGROUND

After the number of sampled tendons are determined based on the methodology presented in 

chapter 5, it is important to strategically locate the sampling areas in a certain type of tendon 

after the target tendons are selected. The target tendons should be randomly selected from the 

bridge being inspected. It is not always possible to remove grout samples from a cut window in 

the duct away from the anchorages of an internal tendon due to the strand configuration in the 

duct. If the tendon has a permanent grout cap over the anchor head, the simplest way to collect 

grout samples is from the cap internal area as shown in figure 62 and figure 63. Extracting grout 

samples from the grout cap should be used as the first option. 

Source: Parsons Brinckerhoff

Figure 62. Photo. Removing a permanent grout cap. 
74 

Source: Parsons Brinckerhoff 

Figure 63. Photo. Exposed anchor head after grout sampling. 

Grout voids are typically formed by bleed water or trapped air during pumping of the grout. 

Bleed water tends to move upward in a tendon while transporting chemical compounds such as 

Cl−, which is a similar trend with trapped air. However, trapped air can be anywhere along the 

tendon. Therefore, typical grout CDs and PDs can be found at the high elevation of the tendon. 

This chapter provides a guideline on locating the strategic locations along each type of tendon, 

also known as the inspection point. In terms of internal tendons, prior to opening a hole in the 

tendon, the tendon should be located using GPR as shown in figure 64. It is not recommended 

to use as-built plans to locate internal tendons because tendon locations might change 

during construction. 

For both options 1 and 2 inspections, at least one grout sample per tendon should be selected 

from the preselected tendons determined in chapter 5. 
75 

Source: Parsons Brinckerhoff

Figure 64. Photo. Locating internal tendons in the web wall using GPR. 

BALANCED CANTILEVER BRIDGE 

Continuity Tendon (Internal Tendon in the Bottom Flange) 

If a permanent grout cap is accessible or exists, the cap should be removed from the blister (see 

figure 62 and figure 63). Alternatively, the cap can be partially removed using a core drill about 

3–4 inches in diameter toward the upper location, as shown in figure 65. The cored section

should be saved for later for grout cap repair. The grout sample should be removed as required in 

chapter 6 for further testing, and its physical condition should be inspected, including the 

exposed strands in the anchor head and the presence of voids. If the grout cap is not available/

accessible or if a void is present in the grout cap, the trumpet interior should be inspected by 

drilling through a grout port over the trumpet area. This drilling has to be done with extreme care 

to avoid damage to any strand in the trumpet. If a void is present, a videoscope should be used to 

inspect the condition of the internal void area. For each continuity tendon selected randomly, 

both ends of the anchorage should be inspected as shown in figure 66 and figure 67. If severe 

corrosion is discovered, the entire grout cap and grout over the anchor head should be removed 

for further investigation. 
76 

Source: Parsons Brinckerhoff 

Figure 65. Photo. Partial removal of a grout cap. 

Source: Parsons Brinckerhoff

Figure 66. Illustration. Typical cantilever tendon inspection point locations. 
77 

Source: Parsons Brinckerhoff

Figure 67. Illustration. Typical continuity tendon inspection point locations. 

After grout sampling and inspection are complete, the grout cap should be restored according to 

the procedure provided in chapter 8. 

In some bridges, no permanent grout cap was installed, and the anchor heads are protected by 

concrete pour-back. As a result, grout samples cannot be obtained from the anchor head areas. It 

is recommended to remove grout samples from internal ducts at the end of the blister by chipping 

concrete over the duct. If grout cap inspection cannot be done, workers should drill through the 

trumpet and check the condition of the grout in the anchorage. 

Cantilever Tendon (Internal) 

The simplest way to access the cantilever tendon is from the top deck. Because maintenance of 

traffic is required, it is recommended to access this tendon at night. After the tendon is identified, 

a chipping gun should be used to remove concrete in the PT block-out a minimum 1 × 2 ft in 

plan view or larger if necessary. If permanent grout cap is present, a core drill should be used to 

remove about 3- to 4-inch-diameter specimen of grout cap front face toward an upper location. 

For a cantilever tendon, at least two inspection points are required, as shown in figure 66 and 

figure 67. 

PRECAST SEGMENTAL SPAN-BY-SPAN BRIDGE 

The majority of span-by-span segmental bridge construction consists of external tendons as 

shown in figure 68. The typical external tendon profile is designed as inclined tendon anchored 

at both diaphragms of a particular span and draped down at one or two deviators in the bottom 

flange. For each tendon, a minimum of three inspection points are recommended for grout 

sampling and investigation. The first point is at the grout cap at the diaphragm, the second point 

is at the top duct coupler adjacent to the diaphragm, and the third point is at the lower duct 

coupler close to a deviator. 
78 

Source: Parsons Brinckerhoff

Figure 68. Illustration. Typical span-by-span bridge external tendon inspection point 

locations. 

CIP PT BRIDGE 

The CIP box girder bridge typically has draped internal tendons in the webs (see figure 69). It is 

not always possible to access the end anchorages in the end diaphragms. However, it is feasible 

to probe the tendon from inside the box girder close to the anchorages. For a typical two-span 

continuous bridge, at least three inspection points should be selected—the first point adjacent to 

the anchorages, the second point at a high point, and the third point at the lowest point of the 

tendon. For multiple continuous span bridges with more than two spans, additional inspection 

points may be required. 

Figure 69. Illustration. CIP PT bridge inspection point locations. 

SPLICED GIRDER BRIDGE

A PT spliced girder bridge typically has three to four internal tendons from end to end of a 

multispan continuous unit as shown in figure 70, figure 71 for bulb-tee girders, and figure 72 for 

a U-girder bridge. Similar to a CIP PT bridge, it is almost impossible to access the anchorage 

area due to a lack of sufficient clearance at the bridge ends. For a three-span continuous bridge, 

it is recommended to have a minimum of three inspection points—the first adjacent to the 

anchorages, the second at the CIP closure joint near the pier, and the third at the highest area 

over the pier (see figure 70 and figure 72).
79 

Source: Parsons Brinckerhoff

Figure 70. Illustration. Spliced bulb-tee girder bridge inspection point locations. 

Source: Parsons Brinckerhoff

Figure 71. Photo. Spliced bulb-tee girder bridge CIP joint detail. 
80 

Source: Summit Engineering Group

Figure 72. Illustration. Spliced U-girder bridge inspection locations. 
81 

CHAPTER 8. RESTORATION METHODS

GENERAL

Restoration of the tendon damage as a result of inspection and grout sample collection is one of 

the most important activities in grout sampling. Improper repair/restoration will provide a future 

path for corrosive agents to the PT system and can compromise long-term durability. Two types 

of restorations can be performed after inspection and grout sample collection are completed: 

temporary restoration and permanent restoration. 

Temporary restoration should be performed for the following reasons: 

• The ambient temperature is too cold. 

• There is insufficient restoration material or lack of proper equipment to perform 

permanent restoration. 

• There are unexpected findings that require further investigation (i.e., severe strand 

corrosion, soft grout, etc.). 

• There is a large void in the duct or trumpet finding that requires vacuum grouting for 

permanent restoration. 

Temporary restoration should be able to protect the tendon systems from future corrosive agent 

intrusion for a maximum of 3 to 6 months before permanent restoration can be conducted. For 

bridges located in corrosive environments, permanent repair should be done as soon as possible. 

This requirement on how soon the permanent repair should be done can be adjusted by the local 

authority based on the conditions and requirements for each project. 

An exposed open tendon should not be left for more than 4 h without proper temporary 

protection. Each day before leaving the project site, all areas of exposed tendons should receive 

a temporary protection prior to applying temporary restoration or permanent restoration. At 

minimum, waterproof tapes and plastic covers should be applied. If possible, permanent 

restoration of the corrosion protection should be performed on the same day as the inspection. 

The inspection team should provide a consistent and visible color marking at the inspection 

points based on the approved work plan (prior to the inspection) so that the client/owner of the 

bridge can keep track of what has been done for future maintenance activities. The industry 

repair standard practice should be adopted with owners’ approval, including the material 

ingredients, mixture proportions, mixing, placing, and curing method. The restoration material 

and methods should be included in the work plan and approved by the owners prior to onsite 

construction restoration. 
82 

TEMPORARY RESTORATION

External Tendon

The procedure for temporary restoration of external tendons is as follows: 

1. Properly clean any dust and soft material in the restoration area using vacuum cleaner or 

dry air blower. 

2. Apply an approved hydraulic cement grout mortar over any exposed strands. 

3. Reattach the original two half pieces of polyethylene (PE) ducts (two half duct). 

4. Seal the cut lines with sealant.

5. Wrap the restoration area with a minimum 4 inches of high-performance waterproof tapes at 

each end (see figure 73).

Source: Concorr Florida

Figure 73. Photo. Temporary restoration of an external tendon. 
83 

Internal Tendon

The procedure for temporary restoration of internal tendons is as follows: 

1. Properly clean any dust and soft material in the restoration area using a vacuum cleaner. 

2. Apply an approved hydraulic cement grout mortar over any exposed strands. 

3. For a metal duct, bend the duct back covering the mortar.

4. Apply hydraulic cement mortar over the duct/magnesium ammonium phosphate concrete 

(MAPC) to the concrete surface.

PERMANENT RESTORATION

External Tendon

The procedure for permanent restoration of external tendons is as follows: 

1. Properly clean any dust and soft material in the restoration area by vacuum cleaner or 

dry air blower. 

2. Apply an approved hydraulic cement grout mortar over any exposed strands. 

3. Reattach the original two half pieces of PE ducts.

4. Seal the cut lines with sealant.

5. Wrap the restoration area with a minimum of 4 inches of heat shrink wrap at each end 

(see figure 74).

Source: Concorr Florida

Figure 74. Photo. Permanent restoration of an external tendon using heat shrink sleeve. 
84 

Internal Tendon

The procedure for permanent restoration of internal tendons is as follows: 

1. Properly clean any dust and soft material in the restoration area using a vacuum cleaner.

2. Remove part of metal or plastic ducts.

3. Apply an approved hydraulic cement grout mortar over any exposed strands. 

4. For plastic duct, cover the grout mortar with a piece of new plastic duct of the same 

dimensions with the opening. Weld the new plastic section with the existing duct around the 

cut perimeter and apply epoxy over the perimeter of the cut (see figure 75).

5. Patch hydraulic cement mortar/MAPC over the restored duct to the concrete surface.

Note that it is not necessary to remove concrete all around the duct since this will cause more 

damage to the structure and will be more difficult to restore.

Figure 75. Illustration. Permanent restoration of an internal tendon duct. 
85 

Grout Cap 

The procedure for permanent restoration of grout caps is as follows: 

1. For an existing bridge with no grout cap or if the grout cap has been damaged during 

removal, install a new grout cap for permanent restoration. 

2. If a grout sample is removed from the anchor head, patch the area of the missing grout with 

an approved hydraulic cement grout mortar prior to reinstalling the grout cap. In cases where 

the whole grout is removed, regrout the cap cavity by gravity feed after the cap is installed.

3. For a partially cored grout cap, patch the area of the grout taken for a sample with grout 

mortar and the original cored piece reinstalled. Seal the perimeter of the piece with epoxy 

(see figure 76).

4. Reapply the elastomeric coating over the cap.

5. For cantilever or other tendons with a pour-back present, restore the pour-back with 

epoxy concrete.

Figure 76 through figure 78 show the permanent restoration process of a grout cap, including 

elastomeric coat application.

Source: Parsons Brinckerhoff 

Figure 76. Photo. Completed restoration of a partially cut grout cap prior to coating. 
86 

Source: Parsons Brinckerhoff 

Figure 77. Photo. Applying elastomeric coating over a grout cap. 

Source: Parsons Brinckerhoff 

Figure 78. Photo. Completed permanent restoration of a grout cap. 
87 

RESTORATION MATERIAL

It is recommended that approved material from the bridge owners be used in the restoration of 

tendons after invasive testing. For grout restoration, after the existing grout is removed for a test 

sample, the grout should be patched with an approved prepackaged grout mortar/hydraulic 

cement grout mortar applied to both internal and external tendons. 

Basic materials used for external tendon restoration include the following: 

• Approved prepackaged grout/hydraulic cement grout mortar. 

• High-performance waterproof tape. 

• Epoxy. 

• Heat shrink sleeve. 

• Elastomeric coat. 

Basic materials used for internal tendon restoration include the following: 

• Approved prepackaged grout/hydraulic cement grout mortar. 

• MAPC. 

• Hydraulic cement mortar. 

• High-performance waterproof tape. 

• Epoxy. 

• Elastomeric coating. 

89 

CHAPTER 9. INTERPRETATION OF RESULTS AND COURSES OF ACTION

BACKGROUND

Grout issues fall into the following categories:

• Cl−

 concentration in excess of the 0.08 wt percent cement limit. 

• Air pocket in the duct interior and exposed strand as a consequence of incomplete grout 

filling or grout subsidence (or both). 

• Presence of grout types 1–3 (see chapter 4).

Compounding factors that contribute to determining response actions are presence of free water, 

the extent of any strand corrosion, and occurrence of strand fractures. This chapter presents a 

generalized course-of-action decision guide based on a categorization of Cl− and extent of strand 

corrosion and fractures considering the grout issues and compounding factors. It is recognized 

that “no one size fits all” and that this guide may be modified, supplemented, or even supplanted 

by an alternative approach. Specifically, sound engineering judgment must be employed. 

Ongoing research under FHWA sponsorship is investigating implications of Cl− contaminated 

PT grout on strand performance.(43)

 Once available, results from this research could modify 

recommendations made in this report. 

Evaluation Approach and Interpretation 

Table 32 lists CD classifications and recommended actions, respectively, for option 1 inspections 

according to the determined condition of individual tendons. This considers that strands are 

embedded in sound grout and only CDs, as expressed in terms of four Cl−, are at issue. 

Conversely, option 2 inspections consider that the same CD classifications for option 1 are 

an issue as well as PDs (grout structure and presence of any air voids, strand corrosion, or 

strand fractures), as listed in table 33. Based on findings for either inspection option, individual 

tendons are assigned a grade from 1 to 10—the higher the grade, the more problematic the 

tendon condition. 

For option 2, assigning a tendon grade based on the determined CDs and PDs and projecting any 

resultant action requires multiple considerations. For example, if it is determined that Cl− is less 

than or equal to 0.08 wt percent cement (CD1) and a grout air pocket is noted (PD1), then a 

grade of 2 is assigned, and no action (A1) is recommended (see table 33). If the air pocket is long 

and larger than 0.5 inches, action A6 may be considered by regrouting the void. However, if 

strands also exhibit surface corrosion but no section loss (PD4), then the grade 6 is assigned and

actions A3 and A6 result. In other words, the highest PD determines the grade and recommended 

action. The term “section loss” refers to any reduced cross section for all strands in a particular 

tendon, as affected by fractures. For example, if a tendon has 22 strands and 1 has fractured 

but the others remain load bearing, then section loss is 4.5 percent (PD5 in table 33) in 

combination with other deficiencies. If grade 8 CD3 is selected, actions A2, A4, A5, and A6 

are recommended. Conversely, if there are 18 strands, then 1 fracture translates to 5.6 percent 

section loss (PD6), which is a grade of 10, and actions A2 and A4 through A8 should be taken. 
90 

Table 32. CD classifications as determined by grout Cl− levels from an option 1 inspection 

and resultant recommended actions. 

CDa

CD1 Cl− ≤ 0.08 X

CD2 0.08 < Cl− ≤ 0.20 X

CD3* 0.2 < Cl− ≤ 0.50b X

CD4 Cl− > 0.50b X

Action

Grade

1 5 7 9

A1 None X

A2 Expand sampling X X

A3 Reinspect in 5 years X

A4 Reinspect in 2 years X X 

A5 Tendon monitoring X X a Chloride concentration units are wt percent cement.

b If strand corrosion or fracture(s) are found (PD5 or PD6 under option 2 in table 33), then 

grade 9 or 10 should be assigned as appropriate per option 2 actions.

 * Revised on 10/22/2013
Table 33. CD and PD classifications as determined by grout Cl− levels and in-place grout structure by an option 2 inspection 

and resultant recommended actions. 

CDa

CD1 Cl− ≤ 0.08 X X X X

CD2 0.08 < Cl− ≤ 0.20 X X

CD3* 0.2 < Cl− ≤ 0.50 X X

CD4 Cl− > 0.50 X X

PD 

PD0 Sound grout X

PD1 Grout air pocket X X X X X X X X X

PD2 Exposed strand/tendon X X X X X X X X

PD3 Soft or segregated grout X X X X X X X

PD4 Tendon surface corrosion (no section loss) X X X X X

PD5 Tendon surface corrosion (< 5 percent section loss) X X X

PD6 Tendon with partial or full fracture (≥ 5 percent section loss) X

Action

Grade

1 2 3 4 5 6 7 8 9 10

A1 None X X

A2 Expand sampling X X X X

A3 Reinspect in 5 years X X X

A4 Reinspect in 2 years X X X X

A5 Tendon monitoring X X X X

A6 Consider repairing deficiency as necessaryb X X X X X X X X X

A7 Structural evaluation/load rating X

A8 Tendon replacement X a Chloride concentration units are wt percent cement.

b This applies to PD1, PD2, and PD3. 

* Revised on 10/22/2013

91
92 

The protocol is simpler in the option 1 inspection case in that the determined Cl− translates 

directly to a respective grade as indicated in table 32 and table 33. However, if strand corrosion 

and/or fractures are observed as part of option 1 grout sampling activities, then, as indicated, this 

reverts the action recommendation from table 32 to that in table 33. Figure 79 and figure 80

summarize these decision processes for options 1 and 2, respectively. 

Figure 79. Flowchart. Inspection, sampling, evaluation, and actions for levels 1 and 2 

inspections for option 1. 

Figure 80. Flowchart. Inspection, sampling, evaluation, and actions for levels 1 and 2

inspections for option 2. 

Evaluation of test and inspection results should be performed by treating tendons of a common 

type as a group and assigning a grade to individual tendons of that group according to the 

protocol provided in table 32 for option 1 inspection and table 33 for option 2. An option 1 

inspection may be either level 1 with no further sampling required or expanded to level 2, which 

involves additional sampling depending on the table 32 grading. Typically, for an option 2 

level 2 inspection, all tendons of the types considered are inspected. 

Examples 

1. Typical Span-by-Span Segmental Bridge with Complete Grouting Records 

Preliminary information is as follows:

• Grouting record was available. 

• Option 1 (level 2) inspection was selected.

Inspection Results: 

Inspection results are as follows:

• A total of 10 samples were collected from 10 different tendons. 

• There were no other deficiencies.
93 

• Laboratory grout test results indicated that 60 percent of the samples have Cl−

 content in 

the range of 0.08 to 0.2 wt percent cement, and 40 percent of samples have Cl− content 

lower than 0.08 wt percent cement. 

Recommended Course of Action: 

Table 32 should be used as follows: 

• Group 1 tendons (60 percent of the total samples): 0.08 to 0.2 wt percent cement 

Cl−

 content = CD2, and grade 5 is assigned. As a result, action A3 is required. 

• Group 2 tendons (40 percent of the total samples): Less than 0.08 wt percent cement

Cl− content = CD1, and grade 1 is assigned. As a result, action A1 is required. 

Conclusions: 

Discontinue inspection and reinspect all tendon types in group 1 in 5 years. 

2. Typical Span-by-Span Segmental Bridge 

Preliminary information is as follows:

• No grouting record was available.

• Option 2 level 2 inspection was conducted (95 percent confidence level).

Inspection Results: 

Inspection results are as follows:

• All grout samples collected have Cl−

 content below 0.08 wt percent cement. 

• A total of 30 percent of the tendons inspected have soft/segregated grout, voids, exposed 

strands, and corrosion with more than 5 percent section loss. 

• A total of 25 percent of the tendons inspected have voids, exposed strands, with corrosion 

with less than 5 percent section loss. 

• A total of 45 percent of the tendons inspected have no issues. 

Recommended Course of Action: 

Table 33 should be used as follows: 

• Group 1 tendons (30 percent of the total samples): Soft/segregated grout, voids, and 

corrosion with more than 5 percent section loss = CD1, PD2, PD3, and PD6, and 

grade 10 is assigned. As a result, actions A2 and A4 through A8 are required. 
94 

• Group 2 tendons (25 percent of the total samples): Voids with corrosion of less than 

5 percent section loss = CD1, PD1, PD2, and PD5, and grade 4 is assigned. As a result, 

actions A2 and A4 through A6 are required. 

Conclusions: 

Based on the examples, the following procedure was created:

1. Expand inspection to all tendon types in groups 1 and 2. 

2. Reevaluate the results of the new samples, including the previous samples. 

3. Make a decision based on the combined results either to inspect all tendons or 

discontinue inspection. 

Probable final course of actions could be the combination of the following items: 

• Replace corroded tendons with section loss larger than 5 percent. 

• Repair deficiencies, such as regrouting voids. 

• Perform structural evaluation/load rating considering PT section loss. 

• Determine that tendon monitoring may not be necessary since Cl−

 is below 

0.08 wt percent cement. 

• Reinspect the tendons in 2 years. If the results are satisfactory, the next reinspection 

period can be adjusted to 5 years. 

Reinspections, Non-Destructive Testing (NDT), and Monitoring

It is intended that the term “reinspect” in table 33 refers to further inspection and sampling, as 

described in chapters 5 through 8 of this report, in order to either increase reliability of the 

findings or determine if any deterioration has progressed since an earlier inspection and 

sampling. In addition, consideration can be given to adapting one or more of the following 

NDT technologies that are available: 

• Main magnetic flux method. 

• Magnetic flux leakage method. 

• Pulsed eddy current examination method. 

• Magnetostrictive sensor technology. 

• Microwave thermoreflectometry. 

• Remnant magnetic system. 
95 

• Vibration method. 

• Ultrasonic pulse velocity. 

• Acoustic emission. 

Each of these has attributes, but a common limitation is that section loss or fracture of wires or 

strands within internal tendons and within deviation blocks and anchorages of external tendons, 

which is where problems are most likely to occur, cannot currently be detected by these methods. 

Improvement in these NDT techniques remains an area of active ongoing research.

Monitoring tendons for wire and strand breaks is an option for assuring that any fractures are 

detected in a timely manner. Passive acoustic emission instrumentation with remote monitoring 

is an option in this regard, and commercial systems are available for implementation.

APPENDIX A. TYPICAL BALANCED CANTILEVER BRIDGE PLANS

Figure 81. Illustration. Segment layout—part 1.

97
Figure 82. Illustration. Segment layout—part 2. 

98
Figure 83. Illustration. Bulkhead details. 

99
Figure 84. Illustration. Longitudinal PT layout—part 1. 

100
Figure 85. Illustration. Longitudinal PT layout—part 2. 

101
Figure 86. Illustration. Longitudinal PT layout—part 3. 

102
Figure 87. Illustration. Longitudinal PT layout—part 4. 

103
Figure 88. Illustration. Longitudinal PT layout—part 5. 

104
Figure 89. Illustration. Longitudinal PT layout—part 6. 

105
Figure 90. Illustration. Longitudinal PT layout—part 7. 

106
Figure 91. Illustration. Longitudinal PT layout—part 8.

107

APPENDIX B. TYPICAL SPLICED GIRDER BRIDGE PLANS

Figure 92. Illustration. Plan and elevation—main channel unit.

109
Figure 93. Illustration. Bridge section. 

110
Figure 94. Illustration. Pier cap PT details.

111
Figure 95. Illustration. Tendon profile—main channel unit.

112
Figure 96. Illustration. Modified Florida bulb-T78 beam end segment.

113
Figure 97. Illustration. Modified Florida bulb-T78 beam haunch segment.

114
Figure 98. Illustration. Modified Florida bulb-T78 beam drop-in segment.

115
Figure 99. Illustration. Modified Florida bulb-T78 beam end block detail.

116
Figure 100. Illustration. Typical sections—haunch segment.

117

119 

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HRDi-60/10-13(750)E Recycled

Recyclable