Overview of FHWA Current Coatings and Corrosion Research

TURNER-FAIRBANK HIGHWAY RESEARCH CENTERTURNER-FAIRBANK HIGHWAY RESEARCH CENTER

Overview of FHWA Current Coatings and Corrosion Research Programs

Overview of FHWA Current Coatings and Overview of FHWA Current Coatings and Corrosion Research ProgramsCorrosion Research Programs

Seung-Kyoung LeeManager of Coatings and Corrosion Laboratory

Office of Infrastructure R&DTurner-Fairbank Highway Research Center

Federal Highway Administration

AASHTO Bridge 2009, New Orleans, July 6, 2009


Current Research ProgramsCurrent Research ProgramsCoatingsCoatings• Performance Evaluation of One-Coat Systems• Exploration of 100-Year Maintenance-Free Coating Systems• Development of Field Coating Performance Monitoring MethodologyCorrosionCorrosion• Laboratory Evaluation of Corrosion Resistance of Metallic Dowel Bars• Field Performance Monitoring of a Thin Polymer Overlay (TPO)• Development of a Design Guideline for Selecting Optimum Rebar

Materials in Concrete Bridge Decks• Evaluation of NDE Technologies for High Strength Wire Corrosion





One-Coat SystemsOne-Coat Systems1. 3-coat control (Organic Zn + Epoxy + Polyurethane)2. 2-coat control (MCU-Zn + Polyaspartic)3. Polyaspartic (ASP)4. Epoxy Mastic (EM)5. Calcium Sulfonate Alkyd (CSA)6. Glass Flake Polyester (GFP)7. High Build Acrylic (HBAC)8. Waterborne Epoxy (WBEP)9. Polysiloxane (SLX)10. Urethane Mastic (UM)


Test PanelsTest Panels


Outdoor Exposure TestingOutdoor Exposure Testing

Periodic performance evaluation every six months

TFHRC, VA Sea Isle City, NJ


Comparative PhotographsComparative Photographs

3-coat (6,840) 2-coat (6,840) CSA (6,840) GFP (6,840) EM (6,840)

HBAC (5,040) WBEP (5,040) ASP (4,320) SLX (4,320) UM (4,320)





100-Year Life Coating Systems100-Year Life Coating Systems

1. This is a FHWA in-house study under a Congress mandated High Performance Steel program.

2. Main objective is to identify and evaluate coating materials that can provide 100 years of virtually maintenance-free service life for the steel bridge structures.

3. This study started in November 2008 as a 42-month in-house research project.


Coating Systems SelectedCoating Systems SelectedSystem

Number Category Generic Coating Name

1 Control - Conventional 3-coat Shop System IOZ / Epoxy / Aliphatic Polyurethane

2 Control -3-coat OZ Shop System Zn-rich Epoxy / Epoxy / Aliphatic Polyurethane

3 3-coat Fluoro-Topcoat System MCU Zn / Epoxy / Fluorourethane

4 2-coat Fast Dry Coating Zn-rich Epoxy / Aliphatic Polyurethane

5 2-coat Polysiloxane Inorganic Zinc / Polysiloxane

6 Metallizing (conventional) + Topcoat Thermal Sprayed Zinc / Linear Epoxy

7 Organic Zinc Rich Epoxy (Zinc Flake)/Linear Epoxy Experimental Primer / Topcoat

8 Calcium Sulfonate Alkyd HR Single Coat CSA


100-Year Coating Study - Test Panels100-Year Coating Study - Test Panels





Field Coating Performance Monitoring Field Coating Performance Monitoring

Golden Gate Bridge, San Francisco, CA


Field Coating Performance Monitoring Field Coating Performance Monitoring

Octoraro Creek Bridge, Conowingo, MD





Concrete Slab Concrete Slab


Extracted Dowel Bars after 450 Days in ConcreteExtracted Dowel Bars after 450 Days in Concrete





Field Monitoring Study of TPOField Monitoring Study of TPO

Black Creek Bridge, New Paltz, NY


Field Monitoring Study of TPOField Monitoring Study of TPO

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Feb. 26, 2009 (2ndfield measurement)

June 3, 2009 (3rdfield measurement)

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ObjectivesObjectives

• To determine mean chloride threshold values and time-to-corrosion initiation for twelve types of reinforcing steel materials

• To develop a concrete bridge deck design guideline for use of reinforcing steel materials based on corrosion performance data and life cycle cost analysis.


Reinforcing Steel MaterialsReinforcing Steel Materials

• Twelve types of #5 or #6 reinforcing materials were acquired from 11 sources and they were embedded in eight slabs.

• The rebars were placed in the top and bottom mats.

• Three levels of artificial defects (0.15, 0.5 and 1.0 %) were introduced on ECR, Zbar, and galvanized. EnduraMet 3212

Arminox (2304)112201103Cr129

NX Infrastructure8CMC7

Duracorr6MMFX5

Galvanized 4Zbar3ECR2Black1


Slab ConfigurationSlab Configuration

[Plan]

Left section Right section

Internal ducts

Transverse bar

Longitudinal bar

[Profile] [Cross-section]

Insulator


OverviewOverview


Cross-sectionCross-section


Concrete CastingConcrete Casting


Final Experimental SetupFinal Experimental Setup


Experimental Procedure – Data MeasurementsExperimental Procedure – Data Measurements

1. Galvanic (Mixed) Potential

2. Macro-cell Current Between Top and Bottom Mats ( circuit break)

3. AC Resistance Between Top and Bottom Mats

4. Open Circuit (Corrosion) Potential in the Top Mat

5. Corrosion Rate (Linear Polarization Resistance) in the Top Mat

6. Electrochemical Impedance Spectroscopy


Experimental Procedure – Chloride DataExperimental Procedure – Chloride Data• As soon as a top mat rebar indicates corrosion initiation, concrete

powder will be collected adjacent locations accessible from the sides.

• Acid-soluble chloride concentration will be determined as a chloride

threshold value.

• This process will be repeated for every rebar in the top mat.

• Average chloride threshold value and its time-to-corrosion initiation

will be determined for the particular rebar material.


Future Studies Related to ReinforcementFuture Studies Related to Reinforcement

• Determination of Time-to-Corrosion Propagation (Lab Study)

• Development of a Bridge Deck Design Guideline

• Field Survey of Representative Bridge Decks Containing Various Rebar Materials

• Full Scale Accelerated Corrosion Testing Using Environmental Chamber and Wheel Loading





Corrosion of Post-Tensioned TendonsCorrosion of Post-Tensioned Tendons

After 16 Years, Niles Channel Bridge, Keys, FL (1999)


Corrosion of Post-Tensioned TendonsCorrosion of Post-Tensioned Tendons

After 13 Years, Sunshine Skyway Bridge, Tampa, FL (2000)


After 6 years, Mid-Bay Bridge, Destin, FL (2000)

Corrosion of Post-Tensioned Tendons


Corrosion of Ungrouted PT TendonsCorrosion of Ungrouted PT Tendons


Deterioration of Stay CablesDeterioration of Stay Cables

After 25 years, Luling Bridge, LA (2007)


Deterioration of Suspension Main CablesDeterioration of Suspension Main Cables

Courtesy of Parsons/Maine DOT

After 70 years, Waldo-Hancock Bridge, Maine (2002)


Corroded Post-Tensioned Tendons

Corroded Post-Tensioned Tendons

After 17 years, Varina-Enon Bridge, Richmond, VA (2007)


Laboratory Study of PT Tendon CorrosionLaboratory Study of PT Tendon Corrosion


Artificial Defects by Saw CutsArtificial Defects by Saw Cuts


Artificial Defects by Impressed CurrentArtificial Defects by Impressed Current


Artificial Defects for Internal PT TendonsArtificial Defects for Internal PT Tendons


NDE Technologies EvaluatedNDE Technologies Evaluated• Ultrasonic and Sonic Echo/Impulse Response (SE/IR) – Olson

Engineering

• Magnetostrictive Sensor (MsS) Technology for Guided Long-Range Waves - SwRI

• Microwave Thermoreflectometry - Dr. Ralf Arndt

• Remnant Magnetic System/ Post-TechTM CBD System – UT Berlin and Vector Corrosion Technologies

• Magnetic Main Flux Method (MFM) – Tokyo Rope MFG, Inc.


Main Flux Method (MFM)Main Flux Method (MFM)

Tokyo Rope MFG and Carlton Lab at Columbia University


MFM on PT Tendons – 1st GenerationMFM on PT Tendons – 1st Generation


MFM PrincipleMFM Principle

N Pole S Pole

Area S

Flux φ

Area S’

Flux φ’

Normal Section

Corroded Section

Magnetic Flow磁束

全磁束検出波形

損傷部モデル

損傷部と検出波形サーチコイルSearch Coil

Damage Model

Detecting Wave

Flux

* The absolute value of metallic area can be evaluated by * The absolute value of metallic area can be evaluated by measuring the parameter measuring the parameter ΔΔØØ..


Magnetic Flux Chart of Specimen AMagnetic Flux Chart of Specimen A

Estimation of Section Loss (%) 0.2 2.0 0.2


Autopsy Result of Specimen AAutopsy Result of Specimen A

Estimation (%) 99.8 98.0 99.8Actual (%) 99.8 87.6 (16.5 wires) 99.8


MFM on PT Tendons – 2nd GenerationMFM on PT Tendons – 2nd Generation


Test ResultsTest Results

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Remaining Cross-sectional Area (%)

Rat

e o

f M

agnetic F

lux

(%)

Tendon A - 2 strands cut

Tendon C - 1 strand cut

Tendon C - 1 wire cut

Tendon A - 1 wire cut

Tendon A - 1 wire cut


Test Results – Linear RegressionTest Results – Linear Regressiony = 0.999x - 0.1935

R2 = 0.9918

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Remaining Cross-sectional Area (%)

Rate

of

Magn

etic F

lux

(%)


Findings - MFMFindings - MFM• MFM was determined to be the most accurate NDE system in terms of

defect location and section loss in the current evaluation study.

• It has a great potential for detecting insidious corrosion as well as

calculation of section loss in the external PT tendons, stay cables, and

suspension cables.

• However, it needs to modify configuration of the magnetizer and

reduce weight of the system in order to be practical in the field.


ConclusionsConclusions

• None of the NDE systems was able to detect intentional defects in the internal PT tendons.

• Presence of grout in the external PT tendons made propagating signals attenuate significantly and resulted in some NDE technologies ineffective.

• Main Flux Method (MFM) is the most promising technology for external PT tendons, stay cables, and suspension cables.


Next StepsNext Steps

• The MFM will be tried in two bridge structures with known deterioration problems.

• If these field trials yield good results, the MFM will be employed for two or three more bridges in Maine and Florida.

• With successful performance proven in the field trials, a transportation pool fund study will be initiated to deploy this NDE system in various states.


Challenges Ahead of Us…Challenges Ahead of Us…

• We still need to develop innovative NDE technologies to detect corrosion inside PT anchorage zones, internal PT tendons, and pre-tensioned prestressed strands.

• Also, we need to develop reliable monitoring sensors for new and existing structures containing tensioned high-strength wires.


Thank You.Thank You.


Example of Corrosion Potential Data (Assorted Slab)Example of Corrosion Potential Data (Assorted Slab)

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Time (day)

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etia

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, CSE

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ECR-0 Zinc clad-0 SS clad (A)-0 SS clad (C)-0

Galvanized-0 SS clad (B)-0 Black-0

Sudden potential shift in the negative direction indicated time to corrosion initiation. For zinc materials (galvanized and zinc-clad), corrosion potential started at negative potentials as expected for active metals.

Documents

Overview of FHWA Current Coatings and Corrosion Research