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Federal Highway Administration 

(FHWA) Coatings and Corrosion 

Laboratory (CCL):

Ongoing Research on Tendon 

Corrosion

Office of Infrastructure Research and Development

FHWA CCL 

October 2023

Frank Jalinoos

Coatings and corrosion lab manager

Long-Term Infrastructure Performance Team 

© USchools / iStock.
CCL Coatings and 

Corrosion Laboratory

Outline

► CCL expertise, mission, and research disciplines.

► CCL’s past tendon corrosion laboratory studies.

► CCL’s recently completed tendon corrosion laboratory studies.

► Planned tendon corrosion laboratory studies.

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CCL Coatings and 

Corrosion Laboratory

Turner-Fairbank 

Highway Research 

Center Expertise ► Structural design and performance. ► Pavement design and evaluation. ► Safety design and operations. ► Human factors analytics. ► Connected vehicle technologies. ► Intelligent transportation systems.

Source: FHWA. 3
CCL Coatings and 

Corrosion Laboratory

Laboratories

Safety

Source: FHWA.

4
CCL Coatings and 

Corrosion Laboratory

CCL Goals

1. Conduct research to discover innovative solutions for the most critical 

materials-related problems that affect durability and serviceability of 

transportation infrastructure.

2. Focus on research that can yield field-applicable results.

3. Make the Nation’s infrastructure safer and last longer by providing useful

research products to stakeholders (e.g., State and local highway 

agencies, industries, and academia).

5
CCL Coatings and 

Corrosion Laboratory

Corrosion Modeling and Simulation

Data sources: 

► Construction 

documents.

► Field assessment.

► Laboratory testing. 

Modeling corrosion:

► Chloride ingress.

► Corrosion initiation and 

propagation.

► Corrosion damage to 

steel and concrete.

6
Source: FHWA.

CCL’s Past Tendon Corrosion Laboratory 

Studies
CCL Coatings and 

Corrosion Laboratory

Technical Assistance: 

San Francisco-Oakland Bay Bridge (2006) 

(Lee 2022) All figures source: FHWA. (Lee 2022)

Background: Caltrans inspectors discovered many ungrouted internal tendons during the construction 

of the San Francisco-Oakland Bay Bridge Construction in 2006. At the request of the FHWA California 

division office, CCL participated in the corrosion investigative work.

Based on the analysis of water samples collected from the site and findings from the lab investigation, 

the study concluded that most seven-wire prestressing strands were not exposed to a very 

aggressive environment for pitting corrosion.

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CCL Coatings and 

Corrosion Laboratory

► Background: The discovery in 2010 of elevated chloride levels in a posttensioning (PT) concrete bridge in Texas triggered a follow-up investigation by a 

grout manufacturer (Sika), which determined that grout produced had chloride 

levels exceeding the specified limit—well above the American Association of 

State Highway and Transportation Officials- (AASHTO) and Post-Tensioning 

Institute- (PTI) recognized limit of 0.08 percent chloride by weight of cementitious 

material (AASHTO 2010; PTI 2011). As a result, Sika and FHWA each initiated 

independent research programs to understand better the effects of chlorides at 

various levels on the long-term corrosion resistance of PT systems (Lee, S-K., 

and J. Zielske 2014). 

► Relevant literature survey: A total of 35 reports and specifications were reviewed, 

and an FHWA summary report based on the literature survey was published 

(Lee 2012). 

Determination of Chloride Thresholds for 

Tendon Corrosion (2012–2014) (1/5)

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CCL Coatings and 

Corrosion Laboratory

► Objectives: 

Determine chloride threshold value(s) experimentally for PT strands in different 

conditions. 

Perform an immediate corrosion risk assessment of the PT strands exposed to 

the chloride-contaminated Sika grout (Lee and Zielske 2014). 

Evaluate the overall long-term safety of the affected bridge structures 

containing the unacceptable grout. 

► Potential impacts: The study provided the basis for tolerable chloride 

concentrations (Lee and Zielske 2014).

Determination of Chloride Thresholds for 

Tendon Corrosion (2012–2014) (2/5)

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CCL Coatings and 

Corrosion Laboratory

Determination of Chloride Thresholds for 

Tendon Corrosion (2012–2014) (3/5)

All figures source: FHWA (Lee and Zielske 2014).

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CCL Coatings and 

Corrosion Laboratory

Determination of Chloride Thresholds for Tendon 

Corrosion (2012–2014) (4/5)

7-wire 

strand

7-wire 

strand

7-wire 

strand

All figures source: FHWA (Lee and Zielske 2014).

All figures source: FHWA (Lee and Zielske 2014).

Major conclusions (Lee and Zielske 2014):

• Chloride threshold for corrosion initiation = 0.4 percent by weight of cement or 0.2 percent by weight of sample.

• Chloride threshold for corrosion propagation = 0.8 percent by weight of cement or 0.4 percent by weight of sample.

• These thresholds are for normally hardened grout. There are much lower thresholds for defective grout and other unfavorable conditions.

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CCL Coatings and 

Corrosion Laboratory

Determination of Chloride Thresholds for Tendon 

Corrosion (2012–2014) (5/5)

(Lee 2012)

https://www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/12067/12067.pdf

(Lee and Zielske 2014)

https://www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/14039/14039.pdf

(FHWA 2013)

https://www.fhwa.dot.gov/bridge/t514033.pdf

Supplementary 

Report Related to 

PT Tendons

(Theryo, Hartt, and Paczkowski 2013)

https://www.fhwa.dot.gov/publications/research

/infrastructure/structures/bridge/ 

13028/index.cfm

All figures source: FHWA.

13
CCL Coatings and 

Corrosion Laboratory

Grout Segregation and Sulfate Corrosivity 

Study (2014–2019) (1/8)

► Background: The first corrosion problem associated with segregated 

grout was reported in the United States in 2011 when two ruptured PT 

tendons were discovered in the Ringling Causeway Bridge in Sarasota, 

FL, after 7 years of service. The segregated grout was made with a 

prepackaged, commercial product. Since then, similar instances have 

been reported in the US, including in FHWA lab studies and other 

countries. In many cases, the segregated grout contained elevated levels 

of water-soluble sulfate which was responsible for rapid tendon corrosion 

and occasional complete failure.

► Relevant literature survey: 18 reports, including investigative Florida 

Department of Transportation (FDOT) reports, were reviewed to develop 

a research plan.

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CCL Coatings and 

Corrosion Laboratory

Grout Segregation and Sulfate Corrosivity 

Study (2014–2019) (2/8)

► Objectives: This study had three objectives: 

 Investigate the corrosion behaviors of center wires exposed to sulfate 

and chloride ions in high and low-pH aqueous solutions.

 Characterize the physical characteristics of various types of grout 

samples.

 Determine the total amounts of water-soluble sulfate ions in raw grout 

powder ingredients and hydrated grout samples.

► Potential impacts: Better understanding of grout segregation phenomena 

and a corrosion relationship between pH and sulfate concentration.

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CCL Coatings and 

Corrosion Laboratory

Grout Segregation and Sulfate Corrosivity 

Study (2014–2019) (3/8)

Free sulfate contractions 

ranged from 0 to 1.5 percent 

by weight of grout samples. 

 

 

All figures source: FHWA (Lee and Zielske 2014).

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CCL Coatings and 

Corrosion Laboratory

Grout Segregation and Sulfate Corrosivity 

Study (2014–2019) (4/8)

All figures source: FHWA (Lee 2021).

17
CCL Coatings and 

Corrosion Laboratory

Grout Segregation and Sulfate Corrosivity 

Study (2014–2019) (5/8)

All figures source: FHWA (Hartt and Lee 2018).

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CCL Coatings and 

Corrosion Laboratory

Grout Segregation and Sulfate Corrosivity 

Study (2014–2019) (6/8)

[Product 1 

- normal]

[#2 Old Product 3 

- Extra water]

All figures source: FHWA (Lee 2021).

Major conclusions (Lee 2021):

• Water-soluble sulfate concentration in the raw grout powders was 0.35 ~ 1.01 percent by sample weight. 

• Product 1 contained the highest mean concentration (0.92 percent); product 2 and product 3 had similar mean 

concentrations of 0.69 and 0.62 percent, respectively. 

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CCL Coatings and 

Corrosion Laboratory

Grout Segregation and Sulfate Corrosivity 

Study (2014–2019) (7/8)

0

2

4

6

8

10

12

14

8.0 10.0 12.5 13.6 Mean corrosion rate (mpy)

pH

0 0.08 Cl 0.4 Cl 0.8 Cl 2.0 Cl 

[Cl-]

0.8

7.3

9.5

11.6

13.0

0.4

7.0

9.3

10.5

9.9

0.1

1.6

4.6

6.97.3

0.2 0.2

0.8

2.4 2.1

0

2

4

6

8

10

12

14

8.0 10.0 12.5 13.6 Mean corrosion rate (mpy)

pH

0 0.2 SO4 0.4 SO4 0.8 SO4 1.5 SO4 3.0 SO4

[SO4

2-

]

8.9

10.6

9.5

10.8

0.10.2

2.6

0.7 0.8

7.7

9.2

8.5

11.6

9.6

0.4

9.0

4.1

3.6

All ≤ 0.2

All figures source: FHWA (Lee 2021).

Major conclusions (Lee 2021):

• Chloride and sulfate ions exhibited similar mean corrosion rates in pH 8.0 and 10.0 aqueous solutions.

• Corrosion rate by sulfate ions decreased as pH increased to 12.5 and 13.6 → virtually zero in pH 13.6. 

• Chloride ions exhibited higher corrosion rates than sulfate ions as pH increased to 12.5 and 13.6. 

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CCL Coatings and 

Corrosion Laboratory

Grout Segregation and Sulfate Corrosivity 

Study (2014–2019) (8/8)

[Cl-]

Chloride ions produced relatively high mean corrosion rates (from 7 to 13 mils per year) in the 2 lower pH 

solutions of 8 and 10. In the higher pH solutions of 12.5 and 13.6, chloride ions yielded lower mean 

corrosion rates (from 0.03 to 7 mils per year) compared to those observed in the pH 8 and 10 solutions. 

[SO4

2-

]

Sulfate ions in the pH 8.0 and 10.0 solutions produced relatively high mean corrosion rates (from 7 to 

13 mils per year). In an intermediate pH of 12.5, the mean corrosion rate was substantially reduced 

compared to those obtained in the lower pH solutions. In the highest pH of 13.6, the corrosion rate 

dropped noticeably. 

Major conclusions (Lee 2021):

• Chloride and sulfate ions exhibited similar mean corrosion rates in pH 8.0 and 10.0 aqueous solutions.

• Corrosion rate by sulfate ions decreased as pH increased to 12.5 and 13.6 → virtually zero in pH 13.6. 

• Chloride ions exhibited higher corrosion rates than sulfate ions, as pH increased to 12.5 and 13.6. 

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Source: FHWA.

Recently Completed Tendon Corrosion 

Laboratory Study
CCL Coatings and 

Corrosion Laboratory

Corrosion Resistance of Alternative 

Metallic Strands (2020–2022) (1/4)

► Background: The tendons are always buried in grout/ducts 

(grouted external tendons) or in grout/ducts/concrete (grouted 

internal tendons), thus corrosion damage cannot be detected 

before it is too late. Therefore, more corrosion-resistant 

materials are needed for new construction and effective 

corrosion control methods are desirable for existing tendons. 

► Relevant literature survey: More than 10 reports and company 

brochures were reviewed to develop a research plan.

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CCL Coatings and 

Corrosion Laboratory

Corrosion Resistance of Alternative 

Metallic Strands (2020–2022) (2/4)

► Objectives: Conduct accelerated corrosion testing to quantify corrosion 

resistance of various metallic strand materials—bare strand, hot-dip 

galvanized strand, 95-percent zinc/5-percent aluminum coating strand, 

ECS (flow-filled type, no grit), and 2205 duplex SS strand—exposed to 

different concentrations of chloride (0.08, 0.2, 0.4, 0.8, 2.0 percent) and 

sulfate ions (0, 0.1, 0.2, 0.4, 0.8, 1.5, 3.0 percent).

► Potential impacts: Identify highly corrosion-resistant and economical 

“next-generation” strand material(s) for new construction PT bridges in 

the United States. 

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CCL Coatings and 

Corrosion Laboratory

Corrosion Resistance of Alternative Metallic 

Strands (2020–2022) (3/4)

Aqueous test

solution

Ag/AgCl reference electrode (RE)

Cylindrical stainless 

steel mesh (counter electrode (CE))

Unstressed 7-wire 

strand with epoxy Encapsulated cut ends 

(working electrode 

(WE))

Plastic container

CE

WE #4 WE #3 WE #2

RE

Connect to electrochemical

instrument WE #1

Testing in aqueous solutions.

Testing in poor-quality grout.

ZD Z HD H B

S E

ED Type 316 stainless steel mesh

Sponge for 

RE tip contact

Testing in good-quality grout.

All figures source: FHWA (Lee Forthcoming b).

.

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CCL Coatings and 

Corrosion Laboratory

Corrosion Resistance of Alternative Metallic 

Strands (2020–2022) (4/4)

1

10

100

1,000

10,000 B-0% S-0% H-0% Z-0% B-C0.08% S-C0.08% H-C0.08% Z-C0.08% B-C0.2% S-C0.2% H-C0.2% Z-C0.2% B-C0.4% S-C0.4% H-C0.4% Z-C0.4% B-C0.8% S-C0.8% H-C0.8% Z-C0.8% B-C2.0% S-C2.0% H-C 2.0% Z-C2.0%Mean polarization resistance (ohm)

Category

Baseline @ 77F 7 days @ 104F

All figures source: FHWA (Lee Forthcoming b).

.Mean polarization resistance data.

1.0E+00

1.0E+02

1.0E+04

1.0E+06

1.0E+08

1.0E+10

1.0E+12

1.0E+14

0 50 100 150 Cumulative mean coating resistance (ohm)

Time (day)

E mean-C0.4% ED mean-C0.4% E mean-S0.4% ED mean-S0.4%

Defect-free ECS

Damaged ECS

Cumulative mean coating resistance data. 

ECS = epoxy-coated strand.

Major preliminary findings (Lee Forthcoming b):

• The conventional bare strand (B) exhibited the lowest corrosion resistance.

• Duplex 2205 SS strand (S) performed very well with the most positive corrosion potential and the highest polarization resistance 

(PR), and the lowest macrocell corrosion current (Imacro).

• The hot-dip galvanized (H) and 95-percent zinc/5-percent aluminum coated strands (Z) were the most active materials with very 

negative corrosion potential, the lowest PR, and the largest Imacro.

• The flow-filled epoxy strand (E) showed encouraging performance due to its high-quality electrical insulation barrier; when artificial 

coating defects were introduced (ED), the mean coating resistance was reduced significantly.

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Source: FHWA.

Planned Tendon Corrosion Laboratory 

Studies
CCL Coatings and 

Corrosion Laboratory

Effectiveness of Silicon-Based Polymer 

Corrosion Inhibitor by Impregnation Method

Research objective: to 

collect quantitative 

scientific data from the 

grouted specimens 

experiencing different 

levels of corrosion 

under an accelerated 

corrosion testing setup.

© 2014 Vector Corrosion Technologies (Lee 2022).

Injection of corrosion inhibitor.

Source: FHWA.

Field trial in Varina-Enon Bridge.

208 days in 5% NaCl fog chamber

© 2017 FDOT (Lee 2022; Lee Forthcoming a).

Laboratory evaluation at the

FDOT.

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CCL Coatings and 

Corrosion Laboratory

CCL Web Page

https://highways.dot.gov/research/laboratories/coatings-corrosion-laboratory/publications (FHWA n.d.)

Google® search: “FHWA Corrosion Lab”

© 2020 Google. 

Search FHWA site

Explore Research and 

Technology

Coatings and Corrosion 

Laboratory Overview

Laboratories Overview

Projects

Publications

Source: FHWA (FHWA n.d.). 

.

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CCL Coatings and 

Corrosion Laboratory

References

AASHTO. 2010. LRFD Bridge Construction Specifications, 3rd Edition. Washington, DC: AASHTO.

PTI. 2011. Specifications for Grouting of Post-Tensioned Structures. PTI M55.01-03. Farmington Hills, MI: PTI.

Lee, S.-K.. 2012. Literature Review of Chloride Threshold Values for Grouted Post-Tensioned Tendons. Report No. FHWA-HRT-12-067. 

Washington, DC: Federal Highway Administration. 

https://www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/12067/12067.pdf, last accessed May 19, 2023.

FHWA. 2013. Recommendations for Assessing and Managing Long-Term Performance of Post-Tensioned Bridges Having Tendons 

Installed with Grout Containing Elevated Levels of Chloride. Technical Advisory 5140.33. Washington, DC: Federal Highway 

Administration. https://www.fhwa.dot.gov/bridge/t514033.pdf, last accessed May 22, 2023.

Lee, S-K., and J. Zielske. 2014. An FHWA Special Study: Post-Tensioning Tendon Grout Chloride Thresholds. Report No. FHWA-HRT14-039. Washington, DC: Federal Highway Administration. 

https://www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/14039/14039.pdf, last accessed May 22, 2023.

Hartt, H. H., and S.-K., Lee. 2018. Corrosion Forecasting and Failure Projection of Post-Tensioned Tendons in Deficient Cementitious 

Grout. Report No. FHWA-HRT-17-074. Washington, DC: Federal Highway Administration. 

https://www.fhwa.dot.gov/publications/research/infrastructure/bridge/17074/17074.pdf, last accessed May 22, 2023.

Theryo, T. S., H. H. Hartt, and P. Paczkowski. 2013. Guidelines for Sampling, Assessing, and Restoring Defective Grout in Prestressed 

Concrete Bridge Post-Tensioning Ducts Report No. FHWA-HRT-13-028. Washington, DC: Federal Highway Administration. 

https://www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/13028/index.cfm, last accessed July 7, 2023.

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CCL Coatings and 

Corrosion Laboratory

References (Continued)

Lee, S-K. 2021. Corrosivity of Water-Soluble Sulfate Ions in Simulated Pore Water Solutions and Different Types of Grout Samples. 

Report No. FHWA-HRT-21-052. Washington, DC: Federal Highway Administration. 

https://www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/21052/21052.pdf , last accessed May 22, 2023.

Lee, S-K. 2022. Corrosion-Induced Durability Issues and Maintenance Strategies for Post-Tensioned Concrete Bridges. Report No. 

FHWA-HRT-22-090. Washington, DC: Federal Highway Administration. https://highways.dot.gov/sites/fhwa.dot.gov/files/2022-

09/FHWA-HRT-22-090.pdf, last accessed May 22, 2023.

Lee, S-K. Forthcoming a. Corrosion-Induced Major Tendon Failures in PT Concrete Bridges. Washington, DC: Federal Highway 

Administration.

Lee, S-K. Forthcoming b. Laboratory Evaluation of Five Metallic Strand Materials for Corrosion Control of Post-Tensioned Tendons: 

Summary of Preliminary Findings. Washington, DC: Federal Highway Administration.

FHWA. n.d. “Corrosion and Publications.” (web page). https://highways.dot.gov/research/laboratories/coatings-corrosionlaboratory/corrosion-coating-publications, last accessed October 21, 2021.

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CCL Coatings and 

Corrosion Laboratory

Contact

Frank Jalinoos

frank.jalinoos@dot.gov

32
CCL Coatings and 

Corrosion Laboratory

Disclaimer

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

or manufacturers’ names appear in this presentation only because they are 

considered essential to the objective of the presentation. They are included for 

informational purposes only and are not intended to reflect a preference, 

approval, or endorsement of any one product or entity.

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