Highway Concrete Pavement Technology

Development and Testing: Volume V—

Field Evaluation of Strategic Highway

Research Program (SHRP) C-206 Test

Sites (Bridge Deck Overlays)

PUBLICATION NO. FHWA-RD-02-086 AUGUST 2006

Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296
Foreword 

Two types of concrete overlays (silica fume concrete (SFC) and latex-modified Type III portland 

cement concrete (LMC-III) were installed and tested as part of the Strategic Highway Research 

Program (SHRP) Project C-206: Optimization of Highway Concrete Technology—Bridge Deck 

Overlays. The two different overlay types were chosen for their ability to fill two different needs: 

use of SFC as a long-term, low-permeability overlay; and use of LMC-III as a high earlystrength concrete for use when traffic had to be restored after as little as 24 hours. This report 

summarizes the 5-year study to evaluate the long-term performance of the overlays. Evaluation 

and comparison of SFC and LMC-III overlays were performed at four locations. The test sites 

were in Ohio and Kentucky. Each location included SFC and LMC-III overlays on opposite 

directions of a bridge structure. All overlays were installed in 1992. This study evaluated the 

overlays each year between 1994 and 1998. All overlays had high initial bond strengths, and the 

bond strengths remained high over the study period when tested away from delaminations. The 

overlays were generally rated as good condition in 1998, after 6 years of service, though some 

individual sites were rated as fair due to extensive cracking. Though good performance was 

achieved from both SFC and LMC-III overlays, the service life of the overlays tended to vary 

based on the site location. Generally, cracking and delamination of the overlays tend to increase 

with time. Typically, all overlays should be inspected biannually for cracking and delamination 

and routine maintenance including consideration of crack and delamination repairs to extend the 

service life of the SFC and LMC-III overlays. 

Gary L. Henderson 

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 its 

contents or use thereof. This report does not constitute a standard, specification, or regulation. 

The U.S. Government does not endorse products or manufacturers. Trade and manufacturers’ 

names appear in this report only because they are considered essential to the object 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. 2. Government Accession No. 3. Recipient's Catalog No. 

FHWA-RD-02-086 

 4. Title and Subtitle 5. Report Date 

Highway Concrete Technology Development and Testing: Volume V—Field 

Evaluation of Strategic Highway Research Program (SHRP) C-206 Test Sites 

(Bridge Deck Overlays) 

August 2006 

 6. Performing Organization Code 

 8. Performing Organization Report No. 

 7. Author(s) 

Stephen R. Boyd and Paul D. Krauss; Wiss, Janney, Elstner Associates, Inc. 

 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

ERES Division of Applied Research 

Associates Inc. 

 

505 W. University Avenue 11. Contract or Grant No. 

Champaign, IL 61820 DTFH61-94-C-00009 

 13. Type of Report and Period Covered 

 12. Sponsoring Agency Name and Address Final Report 

 Office of Engineering and Highway Operations R&D 

 Federal Highway Administration 

 6300 Georgetown Pike 14. Sponsoring Agency Code 

 McLean, VA 22101-2296 

 15. Supplementary Notes 

FHWA Contracting Officer's Technical Representative: Monte Symons, P.E. 

This work was conducted under subcontract by Wiss, Janney, Elstner Associates, 

Inc. 

 16. Abstract 

Two types of concrete overlays (silica fume concrete (SFC) and latex-modified Type III portland cement concrete (LMC-III) were 

installed and tested as part of the Strategic Highway Research Program (SHRP) Project C-206: Optimization of Highway Concrete 

Technology—Bridge Deck Overlays. The two different overlay types were chosen for their ability to fill two different needs: use of 

SFC as a long-term, low-permeability overlay; and use of LMC-III as a high early-strength concrete when traffic had to be restored 

after as little as 24 hours. This report summarizes the 5-year study to evaluate the long-term performance of the overlays. Evaluation 

and comparison of SFC and LMC-III overlays were performed at four locations. The test sites were in Ohio and Kentucky. Each 

location included SFC and LMC-III overlays on opposite directions of a bridge structure. All overlays were installed in 1992. This 

study evaluated the overlays each year between 1994 and 1998. All overlays had high initial bond strengths, and the bond strengths 

remained high over the study period when tested away from delaminations. The overlays were generally rated as good condition in

1998, after 6 years of service, though some individual sites were rated as fair due to extensive cracking. Though good performance 

was achieved from both SFC and LMC-III overlays, the service life of the overlays tended to vary based on the site location. 

Generally, cracking and delamination of the overlays tend to increase with time. Typically, all overlays should be inspected 

biannually for cracking and delamination and routine maintenance, including consideration of crack and delamination repairs to 

extend the service life of the SFC and LMC-III overlays. 

 17. Key Words 

Concrete pavement, high early-strength, early opening, fulldepth repair 

18. Distribution Statement 

No restrictions. This document is available to the public 

through the National Technical Information Service, 

Springfield, Virginia 22161.

 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No of Pages 1. Price 

Unclassified Unclassified 80 

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

SI* (MODERN METRIC) CONVERSION FACTORS 

APPROXIMATE CONVERSIONS TO SI UNITS

Symbol When You Know Multiply By To Find Symbol 

LENGTH 

in inches 25.4 millimeters mm 

ft feet 0.305 meters m 

yd yards 0.914 meters m 

mi miles 1.61 kilometers km 

AREA 

in2 square inches 645.2 square millimeters mm2

ft2 square feet 0.093 square meters m2

yd2 square yard 0.836 square meters m2

ac acres 0.405 hectares ha 

mi2 square miles 2.59 square kilometers km2

VOLUME 

fl oz fluid ounces 29.57 milliliters mL 

gal gallons 3.785 liters L 

ft3 cubic feet 0.028 cubic meters m3 

yd3 cubic yards 0.765 cubic meters m3 

NOTE: volumes greater than 1000 L shall be shown in m3

MASS 

oz ounces 28.35 grams g

lb pounds 0.454 kilograms kg

T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t") 

TEMPERATURE (exact degrees) o

F Fahrenheit 5 (F-32)/9 Celsius oC 

or (F-32)/1.8 

ILLUMINATION 

fc foot-candles 10.76 lux lx 

fl foot-Lamberts 3.426 candela/m2 cd/m2

FORCE and PRESSURE or STRESS 

lbf poundforce 4.45 newtons N 

lbf/in2 poundforce per square inch 6.89 kilopascals kPa 

APPROXIMATE CONVERSIONS FROM SI UNITS 

Symbol When You Know Multiply By To Find Symbol 

LENGTH

mm millimeters 0.039 inches in 

m meters 3.28 feet ft 

m meters 1.09 yards yd 

km kilometers 0.621 miles mi 

AREA mm2

 square millimeters 0.0016 square inches in2 

m2 square meters 10.764 square feet ft2 

m2 square meters 1.195 square yards yd2 

ha hectares 2.47 acres ac 

km2 square kilometers 0.386 square miles mi2 

VOLUME 

mL milliliters 0.034 fluid ounces fl oz 

L liters 0.264 gallons gal 

m3 cubic meters 35.314 cubic feet ft3 

m3 cubic meters 1.307 cubic yards yd3 

MASS 

g grams 0.035 ounces oz

kg kilograms 2.202 pounds lb

Mg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T 

TEMPERATURE (exact degrees) o

C Celsius 1.8C+32 Fahrenheit oF 

ILLUMINATION 

lx lux 0.0929 foot-candles fc 

cd/m2 candela/m2 0.2919 foot-Lamberts fl

FORCE and PRESSURE or STRESS 

N newtons 0.225 poundforce lbf 

kPa kilopascals 0.145 poundforce per square inch lbf/in2

*SI is the symbol for th International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E e 380. 

(Revised March 2003)
iii 

TABLE OF CONTENTS 

CHAPTER 1. INTRODUCTION................................................................................................ 1

CHAPTER 2. SUMMARY OF TESTING TECHNIQUES...................................................... 3

Visual Survey and Distress Mapping......................................................................................... 3 

Delamination Surveys ................................................................................................................ 3 

Copper/Copper Sulfate Half-Cell Potential Testing .................................................................. 3 

Polarization Resistance (PR) Testing......................................................................................... 4 

Chloride Sampling And Testing ................................................................................................ 5 

Shear Bond Testing.................................................................................................................... 6 

Inspection Schedule Description................................................................................................ 6 

CHAPTER 3. INTERSTATE 270 (I—270) IN COLUMBUS, OH .......................................... 7

Introduction................................................................................................................................ 7 

Visual Inspection........................................................................................................................ 9 

Delamination Survey.................................................................................................................. 9 

Half-Cell Potential Survey ....................................................................................................... 10 

Polarization Resistance (PR) Testing....................................................................................... 15 

Shear Bond Testing.................................................................................................................. 17 

Chloride Analyses .................................................................................................................... 18 

Sumary of I–270 Tests (Columbus, OH) ................................................................................. 19 

CHAPTER 4. U.S. 52 IN NEW RICHMOND, OH.................................................................. 21

Introduction.............................................................................................................................. 21 

Visual Inspection...................................................................................................................... 23 

Delamination Survey................................................................................................................ 24 

Half-Cell Potential Survey ....................................................................................................... 25 

Polarization Resistance (PR) Testing....................................................................................... 30 

Core Testing............................................................................................................................. 32 

Chloride Analysis..................................................................................................................... 33 

Summary of U.S. 52 Test (New Richmond, OH) .................................................................... 34 

CHAPTER 5. I–265 OVER KY 22, JEFFERSON COUNTY, KY ........................................ 35

Introduction.............................................................................................................................. 35 

Visual Inspection...................................................................................................................... 37 

Delamination Survey................................................................................................................ 38 

Half-Cell Potential Survey ....................................................................................................... 39 

Polarization Resistance (PR) Testing....................................................................................... 45 

Core Testing............................................................................................................................. 46 

Chloride Analyses .................................................................................................................... 47 

Summary of I–265 Over KY 22 (Jefferson County, KY)........................................................ 48 

CHAPTER 6. U.S. 41 OVER KY 351, HENDERSON, KY.................................................... 49

Introduction.............................................................................................................................. 49 

Visual Inspection...................................................................................................................... 52 

Delamination Survey................................................................................................................ 53 
iv 

Half-Cell Potential Survey ....................................................................................................... 55 

Polarization Resistance (PR) Testing....................................................................................... 63 

Core Testing............................................................................................................................. 65 

Chloride Analysis..................................................................................................................... 66 

Summary of U.S. 41 Test (Henderson, KY) ............................................................................ 67 

CHAPTER 7. PROJECT SUMMARY..................................................................................... 69
v 

LIST OF FIGURES 

Figure 1. Schematic drawing of polarization resistance test setup. ................................................ 5 

Figure 2. Photograph showing test section on I–270 northbound (1995)...................................... 7 

Figure 3. Photograph showing test section on I–270 southbound (1995)...................................... 7 

Figure 4. Histogram of half-cell potentials for I–270 NB SFC test section for 

1994 and 1997....................................................................................................................... 12 

Figure 5. Equipotential map of half-cell potentials for I–270 NB (silica fume-modified 

concrete)................................................................................................................................ 12 

Figure 6. Histogram of half-cell potential readings for the I–270 southbound LMC-III 

test section for 1994 and 1997. ............................................................................................. 14 

Figure 7. Equipotential map of half-cell potentials for I–270 southbound (latex-modified 

concrete)................................................................................................................................ 14 

Figure 8. Cumulative frequency diagram for I–270 (NB and SB) for years 1994 and 1997........ 15 

Figure 9. Photograph showing the eastbound deck of U.S. 52 over Raymond 

Run in Columbus, OH. The overlay is latex-modified. ........................................................ 21 

Figure 10. Photograph of westbound travel lane of U.S. 52 over Raymond 

Run in Columbus, OH. The overlay is latex-modified. ........................................................ 22 

Figure 11. Photograph showing westbound passing lane of U.S. 52 over Raymond Run 

in Columbus, OH. The overlay is silica fume concrete. ....................................................... 22 

Figure 12. Histogram of half-cell potential readings for U.S. 52 eastbound travel lane 

LMC in 1994 and 1997. ........................................................................................................ 27 

Figure 13. Histogram of half-cell potentials for U.S. 52 westbound travel lane LMC 

in 1994. ................................................................................................................................. 28 

Figure 14. Histogram of half-cell potentials for U.S. 52 westbound passing lane SFC 

in 1997. ................................................................................................................................. 29 

Figure 15. Equipotential map of half-cell potentials for eastbound travel lane U.S. 52 

in 1997 (latex-modified concrete)......................................................................................... 29 

Figure 16. Equipotential map of half-cell potentials for westbound passing lane of U.S. 52 

in 1997 (silica fume concrete)................................................................................................ 30 

Figure 17. Photograph of I–265 northbound lanes with latex-modified overlay.......................... 35 

Figure 18. Photograph showing I–265 southbound lanes with silica fume concrete overlay....... 36 

Figure 19. Histogram of half-cell potential readings for I–265 southbound SFC test section. .... 40 

Figure 20. Histogram of half-cell potential readings for the I–265 northbound LMC 

test section............................................................................................................................. 42 

Figure 21. Equipotential maps of half-cell potentials of the three southbound spans SFC 

of the I–265 test section in 1997. .......................................................................................... 43 
vi 

Figure 22. Equipotential maps of half-cell potentials of the three northbound spans LMC 

of the I–265 test section in 1997. .......................................................................................... 44 

Figure 23. Photograph of northbound test section of U.S. 41 (latex-modified 

concrete overlay)................................................................................................................... 49 

Figure 24. Photograph of southbound test section of U.S. 41 (silica fume concrete overlay). ... 50 

Figure 25. Photograph showing typical cracking found in the northbound deck of the 

U.S. 41 test section LMC...................................................................................................... 52 

Figure 26. Photograph showing typical cracking associated with the southbound test 

section of U.S. 41 SFC.......................................................................................................... 53 

Figure 27. Histogram of half-cell potential readings for U.S. 41 southbound in 1994 SFC. ....... 56 

Figure 28. Histogram of half-cell potential readings for U.S. 41 southbound in 1997 SFC. ...... 57 

Figure 29. Histogram of half-cell potential readings for U.S. 41 southbound SFC in 

1994 and 1997....................................................................................................................... 58 

Figure 30. Histogram of half-cell potential readings for U.S. 41 northbound LMC in 1994....... 59 

Figure 31. Histogram of half-cell potential readings for U.S. 41 northbound LMC in 1997....... 60 

Figure 32. Histogram of half-cell potential readings for U.S. 41 northbound spans in 

1994 and 1997....................................................................................................................... 61 

Figure 33. Cumulative frequency diagram for U.S. 41 (NB and SB) for years 1994 

and 1997................................................................................................................................ 61 

Figure 34. Equipotential maps of half-cell potentials for the three spans of the 

southbound test section of U.S. 41 in 1997 SFC. ................................................................. 62 

Figure 35. Equipotential maps of half-cell potentials for the three spans of the northbound test 

section of U.S. 41 in 1997 LMC. .......................................................................................... 62 
vii 

LIST OF TABLES 

Table 1. Mix proportions for LMC-III and SFC overlays (lb/yd3

)................................................. 8 

Table 2. Number and areas of delaminations ( I–270 northbound SFC)...................................... 10 

Table 3. Number and areas of delaminations (I–270 southbound LMC). .................................... 10 

Table 4. Cumulative percent of half-cell potentials for I–270 NB in 1994 

(silica fume-modified). ......................................................................................................... 11 

Table 5. Cumulative percent of half-cell potentials for I–270 NB in 1997 

(silica fume-modified). ......................................................................................................... 11 

Table 6. Cumulative frequency of half-cell potentials for I–270 SB in 1994 (latex-modified). .. 13 

Table 7. Cumulative frequency of half-cell potentials for I–270 SB in 1997 (latex-modified). .. 13 

Table 8. Corrosion rate testing on I–270 northbound SFC (1994). .............................................. 16 

Table 9. Corrosion rate testing on I–270 southbound LMC (1994). ............................................ 16 

Table 10. Results of polarization resistance testing at I–270 (1997)............................................ 17 

Table 11. Shear bond testing of cores from I–270 (1994). ........................................................... 18 

Table 12. Shear bond testing of cores from I–270 (1997). ........................................................... 18 

Table 13. Results of chloride content testing of cores from I–270 (1994). .................................. 19 

Table 14. Results of chloride content testing of cores from I–270 (1998). .................................. 19 

Table 15. Potentials more positive than –250mV (Cu/CuSO4) (percent of measurements)......... 20 

Table 16. U.S. 52 concrete proportions and characteristics.......................................................... 23 

Table 17. Number and areas of delaminations LMC (eastbound passing U.S. 52)...................... 25 

Table 18. Number and areas of delaminations LMC (westbound travel U.S. 52)........................ 25 

Table 19. Number and areas of delaminations SFC (westbound passing U.S. 52). ..................... 25 

Table 20. Cumulative frequency of half-cell potentials for U.S. 52 EB travel in 1994 LMC...... 26 

Table 21. Cumulative frequency of half-cell potentials for U.S. 52 EB travel in 1997 LMC...... 26 

Table 22. Cumulative frequency of half-cell potentials for U.S. 52 for WB travel 

in 1994 LMC......................................................................................................................... 27 

Table 23. Cumulative frequency of half-cell potentials for U.S. 52 for WB passing 

in 1997 SFC. ......................................................................................................................... 28 

Table 24. Corrosion rate testing on U.S. 52 eastbound travel lane, LMC-III (1994)................... 30 

Table 25. Corrosion rate testing on U.S. 52 westbound travel lane, LMC-III (1994).................. 31 

Table 26. Results of polarization resistance testing at U.S. 52 (1997). ........................................ 31 

Table 27. Shear bond testing of cores from U.S. 52 (1994). ........................................................ 32 

Table 28. Shear bond testing of cores from U.S. 52 (1997). ........................................................ 32 
viii 

Table 29. Results of chloride content testing of cores from U.S. 52 (1994). ............................... 33 

Table 30. Results of chloride content testing of cores from U.S. 52 (1998). ............................... 34 

Table 31. Potentials more positive than –250mV (Cu/CuSO4) 

(percent of measurements).................................................................................................... 34 

Table 32. I–265 concrete proportions and characteristics. ........................................................... 36 

Table 33. Number and areas of delaminations, southbound I–265 SFC. ..................................... 38 

Table 34. Number and areas of delaminations, northbound I–265 LMC. .................................... 38 

Table 35. Cumulative frequency of half-cell potentials for I–265 for SB travel lane, 

SFC (1994)............................................................................................................................ 39 

Table 36. Cumulative frequency of half-cell potentials for I–265 for SB travel lane, 

SFC (1997)............................................................................................................................ 40 

Table 37 Cumulative frequency of half-cell potentials for I–265 for NB travel lane, 

LMC (1994). ......................................................................................................................... 41 

Table 38. Cumulative frequency of half-cell potentials for I–265 for NB travel lane, 

LMC (1997). ......................................................................................................................... 42 

Table 39. Corrosion rate testing on I–265 southbound in 1994 SFC............................................ 45 

Table 40. Corrosion rate testing on I–265 northbound in 1994 LMC. ......................................... 45 

Table 41. Results of polarization resistance testing at U.S. 52 (1997). ........................................ 46 

Table 42. Shear bond testing of cores from I–265 (1994). ........................................................... 46 

Table 43. Shear bond testing of cores from I–265 (1997). ........................................................... 47 

Table 44. Results of chloride content testing of cores from I–265 (1994). .................................. 47 

Table 45. Results of chloride content testing of cores from I–265 (1998). .................................. 48 

Table 46. U.S. 41 over KY 351 concrete proportions and characteristics.................................... 51 

Table 47. Number and area of delaminations (U.S. 41 southbound SFC).................................... 54 

Table 48. Number and area of delaminations (U.S. 41 northbound LMC). ................................. 54 

Table 49. Cumulative frequency of half-cell potentials for U.S. 41, SFC (SB travel lane 1994). 55 

Table 50. Cumulative frequency of half-cell potentials for U.S. 41, SFC (SB travel lane 1997). 57 

Table 51. Cumulative frequency of half-cell potentials for U.S. 41, LMC 

(NB travel lane 1994)............................................................................................................ 58 

Table 52. Cumulative frequency of half-cell potentials for U.S. 41, LMC 

(NB travel lane 1997)............................................................................................................ 59 

Table 53. Corrosion rate testing on U.S. 41 southbound, SFC (1994). ........................................ 63 

Table 54. Corrosion rate testing on U.S. 41 northbound. ............................................................. 64 

Table 55. Results of polarization resistance testing at U.S. 41 (1997). ........................................ 65 

Table 56. Shear bond testing of cores from U.S. 41 (1994). ........................................................ 65 
ix 

Table 57. Core Testing Results from U.S. 41 Henderson, KY (1997). ........................................ 66 

Table 58. Results of chloride content testing of cores from U.S. 41 (1994). ............................... 66 

Table 59. Results of water-soluble chloride content testing of cores from U.S. 41 (1998).......... 67 

Table 60. Results of acid-soluble chloride content testing of cores from U.S. 41 (1998)............ 67 

Table 61. Potentials more positive than –250mV (Percent of measurements)............................. 68 

Table 62. Summary of all test sites............................................................................................... 70 

1 

CHAPTER 1. INTRODUCTION 

This volume of the report describes the investigation and evaluation of silica fume and latexmodified concrete overlays used in bridge deck rehabilitation projects. The overlays were installed 

as part of the Strategic Highway Research Program (SHRP) Project C-206: Optimization of 

Highway Concrete Technology—Bridge Deck Overlays, which is detailed in the report issued at 

the conclusion of that study. Two types of concrete were tested in the overlays, silica fume 

concrete (SFC) and latex-modified Type III cement concrete (LMC-III). The two different overlay 

types were chosen for their ability to fill two different needs. The use of the SFC overlay was 

anticipated for use as a long-term low-permeability overlay, while use of the LMC-III was foreseen 

as a high early-strength concrete for use when traffic had to be restored after as little as 24 hours. 

This report summarizes the 5-year study to evaluate the long-term performance of the overlays. 

3 

CHAPTER 2. SUMMARY OF TESTING TECHNIQUES 

The four bridge deck overlay sites were visited by contractor personnel for the first time in 1994. 

During the visits, the test areas were laid out, corrosion testing was performed, samples were 

taken, and the overall condition of the overlays was determined. In most cases, these visits were 

used to establish a detailed initial condition of the structures, as no distress maps of the overlays 

were included in the original SHRP report, and only a few specific observations of the test sites 

were included. The primary testing performed and reported under SHRP C-206 included directtension bond strength testing, bond shear strength, elastic modulus, compressive strength, splitcylinder tensile strength, scaling resistance, American Association of State Highway and 

Transportation Officials (AASHTO) T 277 “coulomb,” and concrete temperature monitoring. 

The work performed during this initial inspection included detailed visual observation and 

distress mapping, delamination surveying, half-cell potential surveying, linear polarization 

testing, chloride sampling, and shear bond testing. Available information was gathered from the 

State highway agencies. In the second, third, and fifth years only the detailed visual observation 

and distress mapping, delamination surveying, and chloride sampling were performed. In the 

fourth year (1997) the work performed included all of the testing performed during the initial 

inspection. 

VISUAL SURVEY AND DISTRESS MAPPING 

The distress mapping was performed in general accordance with the SHRP Long-Term 

Pavement Performance (LTPP) Distress Identification Manual, with modification as required to 

adapt the pavement-oriented manual to use for a bridge. The SHRP LTPP manual is oriented 

primarily towards structural distress of pavements cast on grade and does not address certain 

problems related to bridges. For example, the LTPP manual requires a listing of “corner breaks,” 

“lane-to-shoulder dropoff,” and “joint spalls,” none of which would occur in a bridge deck. Also, 

bridge decks frequently exhibit frequent narrow nonstructural transverse or longitudinal 

cracking. Although this is covered by the LTPP manual, it is far more important on a bridge deck 

than on a jointed pavement. 

DELAMINATION SURVEYS 

The delamination surveys were conducted with a chain drag supplemented by manual rodding or 

hammering as described in the American Society for Testing and Materials (ASTM) D 4580, 

Standard Practice for Measuring Delamination in Concrete Bridge Decks by Sounding. In areas 

where the chains or rodding indicated delaminated areas, hand hammering was used to determine 

the extent of the delamination. 

COPPER/COPPER SULFATE HALF-CELL POTENTIAL TESTING 

The half-cell potential survey was performed as described in ASTM C 876, Standard Test 

Method for Half-Cell Potentials of Uncoated Reinforcing Steel in Concrete, using a 

copper/copper sulfate reference cell and an automatic data recorder. In the test, the voltage 

difference between the reinforcing steel and the reference electrode is measured using a 

voltmeter. The measured voltage difference changes with the changing corrosion state of the 
4 

reinforcing steel, allowing it to be used as an indicator of the corrosion state of the 

reinforcement. The test is performed by connecting the positive terminal of a high-impedance 

voltmeter to the reinforcing steel and the negative terminal to the reference cell. On the bridges, 

all of the connections to the reinforcing steel were made by coring through the concrete to the 

upper mat of reinforcing steel, removing the concrete around the bar with a cold chisel, and 

attaching to the reinforcing bar with locking pliers, an electrical clamp or by drilling and tapping 

into the steel. Once the connections were made, the readings were taken by holding the junction 

sponge of the reference cell in contact with the concrete and monitoring the observed voltage 

until it stabilized, at which point the voltage was recorded. At the bridges, all of the readings 

stabilized quickly and were reproducible within the ASTM-required 10 millivolts (mV) when retested. The high stability of the readings was probably due to the relatively moist condition of the 

concrete in the bridges, as stability is typically related to concrete moisture content. 

POLARIZATION RESISTANCE (PR) TESTING 

The linear polarization testing was performed using a computer-controlled potentiostat using a 

surface electrode assembly patterned after that used by a “3LP” commercial device. The 

polarization resistance technique for the determination of corrosion rates has been used by 

corrosion engineers for a relatively long period of time. However, it has only recently been used 

for more than extremely limited work in reinforced concrete. Polarization resistance uses 

simplified electrochemical corrosion theory to estimate corrosion rates of metals in corroding 

systems, using the electrical properties of the system to determine the rate of the corrosion. This 

is accomplished by forcing the area under test to deviate slightly (20 mV) from its equilibrium 

corrosion potential while measuring the electrical current required to make the change in 

potential. Because the specimen potential and the corrosion current are approximately linear over 

the small potential range measured, the measured changes in potential (ΔE) and applied current 

(Δiapplied) and the Tafel slopes (βa and βc) can be used to determine the corrosion rate (icorr) of the 

system using the following equation: 

2.3 (i ) ( + ) = i

E

corr a c

a c

applied β β

β β

Δ

Δ

(1)

The technique is limited by the accuracy of the test data, and their interpretation. In addition, the 

characteristic Tafel slopes of the anodic and cathodic portions of the specimen's current versus 

potential relationship, βa and βc , must be assumed. Although the equation is relatively 

insensitive to the β values, and a typical assumption of 0.12 volt (V)/decade is reasonable for 

most steel-based systems, the resulting estimates of the corrosion current, icorr can be incorrect by 

up to a factor of 3 or 4. Compensation is used to account for the voltage drop due to the concrete 

resistance (“IR compensation,” or current (I) times resistance (R)), but it is not always entirely 

effective. The greatest limitation of the technique is its poor performance in high-resistance 

media, such as dry concrete. Under those conditions, the voltage output of the potentiostat 

required to penetrate the concrete can overshadow the voltage required to completely polarize 

the metal under test, and the IR compensation may not be able to sufficiently correct for the 

voltage drop between the embedded metal under test and the counter and reference electrodes on 

the concrete surface. 
5 

Practically, the PR test is performed by first making a connection to the reinforcing steel and 

monitoring its potential while an external voltage is applied via a counter-electrode on the 

concrete surface, as shown schematically in figure 1. The test is performed by changing the 

voltage applied between the counter electrode and the reinforcing bars to produce the 20 mV 

potential shift (ΔE) between reinforcing steel and the reference cell described previously. The 

current (iapplied) flowing between the counter electrode and the reinforcing steel is measured and 

used to compute the corrosion rate using the equation shown above. In reinforced concrete, some 

question arises regarding the normalization of the estimated currents to a corroding area. 

Figure 1. Schematic drawing of polarization resistance test setup. 

For this work, the polarized area was assumed to be the surface area of the upper half of the bar 

immediately below the counter electrode. The PR scans were performed using IR compensation 

at each step to determine and correct for the potential drop due to the concrete resistance. The PR 

scans started at a potential 10 mV below the equilibrium rest potential of the area under test and 

continued to a potential 10 mV above the equilibrium potential. Following the testing, the 

polarization resistances were determined by fitting a line to the recorded potential versus current 

plots. Using the polarization resistances, the corrosion rates were estimated by assuming Tafel 

slopes of 0.12, assuming that the upper bars were size number 4, and assuming that the upper 

half of the reinforcing bar directly under the counter electrode was polarized during the testing. 

CHLORIDE SAMPLING AND TESTING 

The chloride sampling was accomplished using cores instead of drilled powder samples. The 

contractor has found removing cores, followed by slicing and grinding the slices, to be a more 

accurate method for determining concrete chloride contents than removing powder samples 

using a rotary impact drill. Once the samples were cut and ground, they were analyzed by either 

an acid- or water-soluble chloride extraction followed by a potentiometric titration. 
6 

SHEAR BOND TESTING 

The shear bond testing was performed using a shear bond guillotine. All of the cores were 

bedded in a plaster-based material before testing to allow for uniform load applications. 

INSPECTION SCHEDULE DESCRIPTION 

The four bridge deck overlay sites were revisited for the annual inspections, as described in Task 

E, Field Evaluation of SHRP C-206 Test Sites of Project DTFH61-94-R-00009. The visits were 

usually in the fall. The cumulative results from the 5 years of inspections are detailed in the 

following sections for each individual site. 
7 

CHAPTER 3. INTERSTATE 270 (I–270) IN COLUMBUS, OH 

INTRODUCTION 

This site consists of two sections on twin bridges over Raymond Run in Columbus, OH. The site 

is located 0.8 kilometers (km) (0.5 miles (mi)) south of Roberts Road overpass over I–270. 

Overall views of both spans are shown in figures 2 and 3. The twin bridges are single span, 6.1 

meters (m) (20 feet (ft)) long, and simply supported at the abutments. The deck is 380 

millimeters (mm) (15 inches) thick. 

Figure 2. Photograph showing test section on I–270 northbound (1995). 

Figure 3. Photograph showing test section on I–270 southbound (1995). 

The decks were originally constructed in 1969 and were covered with a 6-mm (0.23-inch) thick 

latex emulsified asphaltic concrete overlay. In 1991, an inspection by state forces indicated the 

deck to be in generally satisfactory condition with delaminations and patches over 10 percent of 
8 

the deck surface. There were obvious transverse cracks in the decks. The decks were included for 

overlayment as part of a larger rehabilitation project (Ohio Department of Transportation 

(ODOT) 8753-91) that covered 4.3 km (6.9 mi) of I–270. The project included repaving and 

widening of the bridge structures. The northbound lanes were selected for overlay with silica 

fume concrete and the southbound lanes with LMC-III concrete. The I–270 site was inspected on 

the following dates: 

• September 9, 1994. 

• October 10, 1995. 

• November 12, 1996. 

• September 8, 1997. 

• October 13, 1998. 

Northbound (NB) Lanes—Project records indicate that the materials used for the SFC overlay 

mix consisted of: a Type I cement from a local supplier; a sub-rounded to rounded natural sand 

which was a mixture of siliceous and calcareous minerals having a specific gravity of 2.62, 

absorption of 1.54 percent, and a fine modulus (FM) of 3.36; and a crushed limestone coarse 

aggregate having a maximum top size of 12 mm (0.5 inch), a specific gravity of 2.62, and an 

absorption of 1.96 percent. The admixtures used were: Sika-Crete silica fume (slurry form); Sika 

AER, a neutralized Vinsol resin air-entraining agent; Plastocrete 161 MR, a Type D water 

reducer/retarder; and Sikament 300, a Type F high range water reducer. The mixture proportions 

reported for both overlays are shown in table 1. The specification on the fresh properties of the 

silica fume mix include a slump of 100 to 200 mm (4 to 8 inches) and an air content range of 6 to 

10 percent. 

Table 1. Mix proportions for LMC-III and SFC overlays (lb/yd3). 

Material (lb/y3

) LMC-III SFC 

Cement Type III—658 Type I—700

Fine Aggregate 1591 1470

Coarse Aggregate 1306 1292

Water 321 223

Silica Fume - 70

Latex Modifier (gallon) 25 -

Water Reducer (ounce) - 25

High-range water reducer (HRWR) (ounce) - 218

Air entraining agent (AEA) (ounce) - 5

Water-to-cement (W/C) ratio 0.48 0.29

1 ounce = 29.57 mL 

1 gallon =3.785 L 

1 lb/y3 = 0.347 kg/m3 

Southbound (SB) Lanes—The materials used in LMC-III overlay mix included: a Type III 

cement; the same aggregates as the SFC mix; and a Latex, Styrofan 1186, which is a styrenebutadiene latex emulsion. The specifications for the fresh concrete were a slump range of 100 to 

150 mm (4 to 6 inches) and an air content not to exceed 7 percent. 
9 

The asphalt overlay was removed and the surface scarified in preparation for placement of the 

overlays. Both overlays were placed on May 27, 1992. The SFC was placed first on the passing 

lane of the northbound deck. Two 3.82-m3

 (5-y3) batches were delivered. The deck was wetted 1 

hour prior to placement of the overlay. The placement went smoothly with no reported problems. 

The surface was textured with steel tines transversely on 16 mm (0.6 inch) centers, then covered 

with wet burlap and polyethylene sheeting and continuously soaked for a period of 48 hours. The 

LMC-III overlay was placed the afternoon of the same day on the passing lane of the southbound 

deck. Placement appeared to go smoothly, however the state inspectors questioned the 

calibration of the mobile mixer during the pour. Improper calibration led to higher amounts of 

water being used than desired. Calculations showed the water to cement ratio was actually 0.48 

in the mix. The same texture was applied to this overlay and it was then moist cured for 48 hours 

under soaked burlap. Both sections were opened to traffic on June 19, 1992. 

VISUAL INSPECTION 

The undersides of the two bridges were inspected annually as traffic control was being set up. 

The structures have no girders or thickened beam portions, but have flat undersides. Some fine 

cracking was observed on the underside but no efflorescence staining was seen on the underside 

of either span. No corrosion staining occurred at the crack locations. Some leakage was apparent 

at the joint between the bridge decks and the abutments. The drains in the abutment headwalls 

were functioning, with water flowing. A cold joint could be seen on the deck bottom and in the 

abutment where the bridge had been widened. The only other feature of note was rust staining at 

the exposed bar chair tips on the underside of the deck. 

The test sections studied on both spans include the shoulder and travel (outside) lanes. 

Examination of the deck overlay surface indicated several narrow longitudinal cracks in the 

shoulder lanes of both bridges. Cracks were more frequent in the travel lanes. The travel lane of 

the northbound SFC bridge had mostly single nonconnected cracks running in both the 

longitudinal and transverse directions with very little branching. The travel lane of the 

southbound LMC bridge had more and longer longitudinal cracks and also more branching of 

cracks. 

Severe cracking and spalling was noted in the exposed travel surfaces of the abutments of the 

northbound SFC structure. The overlay at the approach joint was spalled away and had been 

patched with a soft tar-like material. The joint between the bridge and the abutment on the leave 

side of the bridge was irregular, with a separate one-foot wide closure pour placed between the 

deck and the abutment. The joint between the closure pour and the abutment was well-sealed, but 

the formed joint between the deck and the closure pour was open and packed with debris. 

DELAMINATION SURVEY 

The chain drag and hammer survey technique was used to locate areas of delamination of the 

overlay from the original concrete deck. Delaminations were found mostly at crack locations. 

The chain drag was used to initially find the delaminations. They were then more clearly 

delineated using hammer tapping and loose sand. Table 2 shows the number and areas of 

delaminations located on the northbound SFC bridge. The area of the northbound test section is 

37.2 m2

 (400 ft2). The number of delamination areas has increased over the last five years from 0 
10 

in 1994 to 6 in 1998. All the delaminations are in the travel lane and are isolated from each other. 

The largest single delamination area in 1998 is 1.16 m2

 (13 ft2). The total area of delaminations 

is 2.46 m2

 (26.5 ft2) or 6.61 percent of the test area and is not considered a serious amount. 

Table 2. Number and areas of delaminations 

( I–270 northbound SFC). 

Year Number 

of Areas 

Total Area 

(m2) 

Percent of 

Total Area 

1994 0 0.00 0.00 

1995 2 0.14 0.38 

1996 3 0.93 2.50 

1997 4 1.48 3.98 

1998 6 2.46 6.61 

Table 3 shows the number and areas of delaminations located on the southbound LMC bridge. 

The area of the southbound test section is 40.9 m2

 (440 ft2). There are the same number of 

delaminations on this bridge (six) as on the northbound bridge but the total area is slightly more 

at 2.87 m2

 (31.9 ft2) or 7.02 percent of the test area. The largest single area of delamination is 

0.56 m2

 (6.0 ft2) but there are two that size and three others slightly smaller. Again all the 

delaminations are in the travel lane. Some delaminated areas are connected by longitudinal 

cracks which may be a precursor to further delamination. 

Table 3. Number and areas of delaminations 

(I–270 southbound LMC).

Year Number 

of Areas 

Total Area (m2

) Percent of 

Total Area 

1994 0 0.00 0.00 

1995 2 0.46 1.12 

1996 4 0.93 2.27 

1997 6 1.25 3.06 

1998 6 2.87 7.02 

HALF-CELL POTENTIAL SURVEY 

The half-cell potential survey was performed using a 0.6-m (2-ft) grid spacing over the entire test 

area (shoulder and outside travel lane) of each span in 1994 and 1997. The electrical connection 

to the top layer of reinforcement was made using a 50-mm (2-inch) diameter core hole drilled to 

the top layer of reinforcing steel. A hole was drilled in the reinforcing bar and a self-tapping 

screw was used to make the connection. The half-cell readings for the northbound lanes SFC in 

1994 ranged from –179 mV to –471 mV, with large potential differences between nearby areas. 

These readings tend to indicate that some corrosion is taking place in the bridge. Table 4 shows 

the cumulative frequency of the half-cell potentials for the northbound SFC structure in 1994. 

Table 5 shows the cumulative frequency of the half-cell potentials measured in 1997. These 

numbers range from –133 mV to –535 mV. A histogram of the data for the I–270 northbound 

SFC structure for 1994 and 1997 is shown in figure 4. The potentials tend to be less negative in 

1997 than in 1994, however, many areas remain very negative, indicating continued corrosion. 
11 

An equipotential map for the northbound SFC test section in 1997 is shown in figure 5. The most 

negative potentials were seen at the ends of the bridge and near the cracked delaminations. No 

area of more negative potentials was associated with the longitudinal construction joint. 

Approximately three-quarters of the readings were more negative than –250 mV, indicating that 

corrosion is likely occurring over most of the deck. The alignment of the areas of rapid potential 

changes with the edges of the bridge and the cracked delaminations indicate that the overlay is 

not providing sufficient protection from water and waterborne chlorides in these locations. 

Table 4. Cumulative percent of half-cell potentials 

for I–270 NB in 1994 (silica fume-modified).

Potential Range 

(mV) 

Number of 

Observations 

Cumulative 

Percentage 

0 to –149 0 0.0 

–150 to –199 3 2.5 

–200 to –249 14 14.2 

–250 to –299 21 31.7 

–300 to –349 35 60.8 

–350 to –399 25 81.7 

–400 to –449 16 95.0 

–450 to –499 6 100.0 

–500 to –549 0 100.0 

Table 5. Cumulative percent of half-cell potentials 

for I–270 NB in 1997 (silica fume-modified). 

Potential Range 

(mV) 

Number of 

Observations 

Cumulative 

Percentage 

0 to –149 3 2.8 

–150 to –199 7 9.3 

–200 to –249 16 24.1 

–250 to –299 23 45.4 

–300 to –349 28 71.3 

–350 to –399 15 85.2 

–400 to –449 11 95.4 

–450 to –499 3 98.2 

–500 to –549 2 100.0 
12 

0

5

10

15

20

25

30

35

40

0 to -149 -150 to -199 -200 to -249 -250 to -299 -300 to -349 -350 to -399 -400 to -449 -450 to -499 -500 to -549

Potential Range (mV)

Number of Observations

I270 NB94 I270 NB97

Figure 4. Histogram of half-cell potentials for 

I–270 NB SFC test section for 1994 and 1997. 

-20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0

Guard Rail

4

6

8

10

12

14

16

18

Traffic Direction 

Figure 5. Equipotential map of half-cell potentials 

for I–270 NB (silica fume-modified concrete). 

The half-cell potentials for the southbound LMC span in 1994 range from –188 mV to –540 mV. 

A cumulative percentage summary of the data is shown in table 6. The data for 1997 is shown in 

table 7. For 1997 the data ranges from –167 mV to –449 mV. A histogram of the data for the 

southbound LMC test section for the years 1994 and 1997 is shown in figure 6. The potential 

generally shift less negative (less corrosion) in 1997 versus 1994. 
13 

Table 6. Cumulative frequency of half-cell potentials 

for I–270 SB in 1994 (latex-modified). 

Potential Range 

(mV) 

Number of 

Observations 

Cumulative 

Percentage 

0 to –149 0 0.0 

–150 to –199 1 0.8 

–200 to –249 1 1.7 

–250 to –299 8 8.3 

–300 to –349 30 33.3 

–350 to –399 38 65.0 

–400 to –449 30 90.0 

–450 to –499 10 98.3 

–500 to –549 2 100.0 

Table 7. Cumulative frequency of half-cell potentials 

for I–270 SB in 1997 (latex-modified). 

Potential Range 

(mV) 

Number of 

Observations 

Cumulative 

Percentage 

0 to –149 0 0.0 

–150 to –199 2 1.5 

–200 to –249 15 13.1 

–250 to –299 35 40.0 

–300 to –349 40 70.7 

–350 to –399 28 92.3 

–400 to –449 10 100.0 

–450 to –499 0 100.0 

–500 to –549 0 100.0 
14 

0

5

10

15

20

25

30

35

40

45

0 to -149 -150 to -199 -200 to -249 -250 to -299 -300 to -349 -350 to -399 -400 to -449 -450 to -499 -500 to -549

Potential Range (mV)

Number of Observations

I270 SB94 I270 SB97

Figure 6. Histogram of half-cell potential readings for the 

I–270 southbound LMC-III test section for 1994 and 1997. 

An equipotential map of the half- cell data for the I–270 southbound test section in 1997 is 

shown in figure 7. The most negative potentials were seen in the areas of the construction joint, 

the ends of the bridge, and near cracked delaminations. The majority of the readings were more 

negative than –250 mV. Also, indicative of corrosion in the structure are the relatively large 

differences in potential across the area surveyed, as indicated by the closely spaced lines on the 

contour plot. The most negative potentials along the edges of the bridge, the construction joint, 

and the cracked delamination indicate that the overlay is not providing sufficient protection from 

water and waterborne chlorides in these locations. 

-22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0

Guard Rail

4

6

8

10

12

14

16

18

20

Traffic Direction 

Figure 7. Equipotential map of half-cell potentials for I–270 

southbound (latex-modified concrete). 
15 

Past experience with research performed at the contractor site and published in FHWA report 

FHWA-RD-86-193, Protective Systems for New Prestressed and Substructure Concrete, 

indicates that corrosion potentials more negative than approximately –230 mV indicate that 

corrosion is taking place in bridge deck type structures. According to the –230 mV criteria, the 

majority of the locations surveyed had potentials indicating that corrosion was taking place. Both 

structures appear to be undergoing corrosion over the majority of their deck area. The ends of the 

bridges and the areas under cracked delaminations appear to be especially vulnerable. A 

cumulative frequency diagram of the potentials is shown in figure 8. The curve for both bridge 

decks is shifted to the left from 1994 to 1997. This indicates a decrease in the overall half-cell 

potentials. The shift is larger for the southbound lanes which have the latex-modified overlay. 

0

20

40

60

80

100

120

0 to -149 -150 to -199 -200 to -249 -250 to -299 -300 to -349 -350 to -399 -400 to -449 -450 to -499 -500 to -549

Potential Range (mV)

Number of Observations

Northbound 94

Northbound 97

Southbound 94

Southbound 97

Figure 8. Cumulative frequency diagram for I–270 

(NB and SB) for years 1994 and 1997. 

POLARIZATION RESISTANCE (PR) TESTING 

In 1994, polarization resistance (PR) tests were performed at six locations on the northbound 

SFC bridge. The test locations were chosen from one low-potential area and five high-potential 

areas. Simulated 3LP tests were also performed at each of the test locations. The PR testing was 

generally more successful than the 3LP testing, with five of the six locations being successfully 

tested. Only three of the six locations were successfully tested using the 3LP technique. The 

results are summarized in table 8. 

The corrosion rate measurements were in general agreement with the half-cell potential 

measurements, with the most negative potentials associated with the highest corrosion rates. The 

location with the least-negative potential, point B8, could not be successfully measured using 

either the polarization resistance or the 3LP technique. This matches previous experience where 

low corrosion rate areas are difficult to measure using these techniques. The difficulties may also 

be due to the high electrical resistance of the SFC overlay. Silica fume is well known for its 
16 

ability to increase the electrical resistance of concrete, one of the reasons for the very low 

AASHTO T 277 “coulomb” values produced by silica fume concretes. 

Table 8. Corrosion rate testing on I–270 northbound SFC (1994).

PR Testing 3LP Testing Grid 

Location 

Equilibrium 

Potential 

(mV)* Rp

(ohm) 

Icorr

(mA/cm2) 

Rp

(ohm) 

Icorr

(mA/cm2) 

H12 –355 300 0.072 - - 

G12 –400 647 0.034 188 0.116 

B8 –205 - - - - 

C6 –451 121 0.179 149 0.145 

G5 –439 157 0.138 - - 

F3 –395 320 0.068 331 0.066 

* Measured using a Cu/CuSO4 reference electrode. 

Polarization resistance tests were also performed at six locations on the southbound LMC bridge 

in 1994. The test locations were chosen from one medium-potential area and five high-potential 

areas. The PR and 3LP testing was generally more successful on the southbound LMC structure 

than on the northbound SFC structure, with all six locations being successfully tested using both 

techniques. The results of the testing are summarized in table 9. 

Table 9. Corrosion rate testing on I–270 southbound LMC (1994).

PR Testing 3LP Testing Grid 

Location 

Equilibrium 

Potential 

(mV)* Rp

(ohm) 

Icorr

(mA/cm2

) Rp (ohm) Icorr

(mA/cm2

) 

G11 –497 337 0.058 991 0.021 

C11 –332 261 0.083 711 0.031 

A9 –336 193 0.109 469 0.046 

C7 –411 346 0.063 1081 0.020 

B5 –269 456 0.048 1123 0.019 

F4 –536 252 0.086 322 0.068 

* Measured using a copper/copper sulfate (Cu/CuSO4) reference electrode. 

On the southbound LMC structure, the corrosion rate measurements were not in general agreement 

with the half-cell potential measurements, as was seen on the northbound structure. On the 

southbound structure, the highest corrosion rates did not necessarily correspond to the most 

negative potentials. The agreement between the corrosion rates estimated using the two techniques 

was encouraging, as all of the estimates were within a factor of two or three, which is considered 

good using these techniques. 

In 1997, linear polarization measurements were performed on both spans at locations with high, 

medium, and low corrosion potentials. The testing was performed using a James Instruments 

GECOR 6 Polarization Resistance Tester. The equipment uses a confinement ring to delineate 

the area under test. For comparison, tests were also performed using an EG&G PARC Model 

270A potentiostat under computer control, as was performed during the initial 1994 tests. The 
17 

test equipment performed poorly on the southbound LMC side, with the current frequently 

unconfined and the readings erratic. Readings for which the signal was not fully confined are 

suspect because the area under test is unknown and cannot be compensated for. The results of the 

testing for both the northbound and the southbound structures are shown in table 10. 

Table 10. Results of polarization resistance testing at I–270 (1997).

Direction Grid 

Location 

Half-Cell 

Potential 

(mV) 

Measured 

Corrosion 

Rate 

(μA/cm2

) 

Notes 

D2 –374 0.725 

Not fully confined, corrosion 

rate measured as 0.604 μA/cm2

using EG&G PARC equipment 

A3 –197 2.759 Not fully confined 

E13 –338 0.055 Not fully confined 

Southbound 

LMC 

B11 –199 0.022 Not fully confined 

H16 –176 0.052 Prewet 

H16 –222 0.110 Prewet 

B16 –149 0.131 Prewet 

B16 –133 1.293 Prewet, not fully confined 

C12 –421 1.184 Uncracked, not fully confined 

G22 –468 0.630 At a crack, prewet 

G22 –390 0.044 Near joint 

B10 –421 0.202 Near bond core, wet from coring 

F4 –384 0.182 After coring 

F4 –385 2.578 Repeat of previous test, not fully 

confined 

F4 –396 0.441 

Same location as Point F4 

above, but opposite side of core 

hole 

F12 –430 0.789 After coring 

F12 –418 0.516 Adjacent bar 

F10 –441 0.491 Surface dry 

Northbound 

SFC 

B14 –250 0.442 Not fully confined, surface dry 

SHEAR BOND TESTING 

In 1994, three of the cores removed from the southbound structure and four of the cores removed 

from the northbound structure were tested to determine their bond strength in direct shear. The 

overlay thicknesses measured ranged from 25 to 102 mm (1 to 4 inches). The observed clear 

cover over the bars ranged from 76 to 102 mm (3 to 4 inches). The results of the testing are 

shown in table 11. 
18 

Table 11. Shear bond testing of cores from I–270 (1994).

Failure Location (percent of failure area) Structure / 

Overlay Type 

Core 

ID 

Bond 

Strength 

MPa (psi) Overlay Bond Line Substrate 

N2 3.16 (459) 5 0 95 

N4 4.09 (593) 15 0 85 

N8 4.52 (656) 15 0 85 

Northbound 

Silica fume 

N9 3.42 (496) 15 0 85 

S6 3.32 (481) 5 5 90 

S7 4.72 (684) 20 0 80 Southbound 

LMC-III S8 4.76 (691) 10 0 90 

The average bond strength for the northbound SFC cores was 3.79 megapascal (MPa) (551 

pounds per square inch (psi) and for the southbound LMC cores was 4.27 MPa (619 psi). The 

failure strengths of the two overlays were similar. This is to be expected as both failed primarily 

in the substrate concrete, which was nominally the same in both concretes. The failure of the 

cores primarily in the substrate concrete indicates that the surface preparation and application 

was excellent for these two overlays, as improper installation or poor surface preparation will 

typically result in failures at the bond line, with the substrate concrete left intact. 

The shear bond testing results for 1997 are shown in table 12. The average bond strength for the 

northbound SFC cores is 5.8 MPa (840 psi) and for the southbound LMC cores is 4.83 MPa (700 

psi). The failure locations were primarily within the base concrete. These results indicate that the 

bond between the overlay and the substrate remains good. 

Table 12. Shear bond testing of cores from I–270 (1997). 

Structure / 

Overlay Type 

Core 

ID Exposure Bond Strength MPa (psi) 

N1 Wheelpath, near delamination 3.6 (520) 

N2 Wheelpath 9.1 (1320) 

N3 Wheelpath 6.2 (900) 

Northbound Silica 

Fume 

N7 Shoulder 4.3 (620) 

S1 Wheelpath 4.1 (600) 

S2 Shoulder 4.6 (670) Southbound LMC-III 

S3 Centerline 5.7 (830) 

CHLORIDE ANALYSES 

Chloride analyses were performed on six cores from each overlay in 1994. The samples were 

taken from the 13- to 25-mm (0.5- to 1-inch) depth surface region and from the 95- to 102-mm 

(3.75- to 4-inches) depth where the reinforcing bars are typically located. All of the slices were 

pulverized and analyzed to determine their acid-soluble chloride content. In addition to the acidsoluble chloride analyses, water-soluble chloride analyses were performed on selected samples. 

The results of the testing are shown in table 13. 
19 

Table 13. Results of chloride content testing of cores from I–270 (1994).

Acid-Soluble Chloride 

Content, percent by 

concrete weight 

Water-Soluble Chloride 

Content, percent by 

concrete weight Structure / 

Overlay Type 

Sample 

Number 0.5 to 1 

inch 

3.75 to 4 

inches 

0.5 to 1 

inch 

3.75 to 4 

inches 

N1 0.017 0.075 - - 

N3 - 0.129 - - 

N5 - 0.076 - - 

N6 - 0.095 - - 

N7 0.018 0.039 - - 

Northbound 

Silica fume 

N8 - 0.018 - - 

S2 - 0.046 - 0.032 

S3 0.048 - - 0.032 

S4 - 0.045 - 0.025 

S5 - 0.093 - - 

S7 - < 0.007 - - 

Southbound 

LMC-III 

S9 0.041 0.034 - - 

All of the locations had moderate to high chloride concentrations at the level of the reinforcing 

bars, except for sample S7 and N8. The threshold for chloride-induced corrosion of black 

reinforcing steel is approximately 0.025 percent by concrete weight, so most of the locations in 

the deck appear to have sufficient chloride to support corrosion. This agrees with the indication 

of corrosion given by the half-cell potential and corrosion rate readings. The chloride analyses 

for the overlays in 1998 are shown in table 14. Two samples were taken from each structure. 

Chlorides in the near surface of the overlays tend to be higher in the LMC concrete than in the 

SFC concrete. Except for one core from the LMC that had high chlorides throughout its depth, 

chlorides typically decrease to moderately low levels at the 15.9 to 25.4 mm (0.625 to 1 inch) 

depth 

Table 14. Results of chloride content testing of cores from I–270 (1998).

Overlay Acid-Soluble Chloride Content, percent by concrete weight 

Type

Sample 

Number 0.25 to 0.5 

inch 

0.625 to 1 

inch 

1.125 to 1.5 

inches 

3.75 to 4 

inches 

Northbound N1 0.210 0.032 0.019 0.059 

Silica fume N2 0.065 0.034 0.020 0.023 

Southbound S1 0.278 0.202 0.218 0.094 

LMC-III S2 0.208 0.065 0.021 0.050 

SUMARY OF I–270 TESTS (COLUMBUS, OH) 

The SFC and LMC-III overlays were placed in May 1992. Overall, the overlays were in good 

condition in 1998. Each overlay had some cracking and delaminations increased for zero to six 

locations between 1994 and 1998. The total area of delamination was moderate and about 2.5 m2

(26.9 ft2

) SFC and 2.9 m2 (31.2 ft2) LMC-III in 1998. This represents 6.6 percent SFC and 7 
20 

percent LMC-III of the total deck area. Delaminations have been increasing in a linear or slightly 

exponential manner since 1994. Shear load tests indicate that the nondelaminated areas maintain 

high bond strength for both overlays. The percentages of half-cell potentials more positive than 

–250mV (CuCuSO4) are presented in table 15. The potential data indicate that corrosion of the 

embedded steel is likely over three-quarters of each deck but that the potentials have shifted 

slightly more positive (less corrosive) with time. 

Table 15. Potentials more positive than –250mV (Cu/CuSO4) 

(percent of measurements).

Year NB (SFC) SB (LMC-III) 

1994 14.2 1.7 

1997 24.1 13.1 

Corrosion rates of the embedded reinforcing were measured in 1994 and in 1997 using various 

techniques. Difficulties in measuring the corrosion rates through the overlays were encountered. 

The rates varied from low to high values. Corrosion of areas of both decks continues. The 

chloride ion content in the original deck concrete at the level of the reinforcing steel is sufficient 

to cause corrosion of mild steel. Redistribution of this chloride with time has occurred and is 

expected. Chloride has also penetrated into the surface of the overlays in large amounts. Future 

corrosion and possibly continued delamination or other distress should be anticipated on this 

bridge. 
21 

CHAPTER 4. U.S. 52 IN NEW RICHMOND, OH 

INTRODUCTION 

This site consists of two medium-length (68 m (225 ft)) three-span parallel bridges carrying U.S. 

52 over Twelve Mile Creek just west of the town of New Richmond, OH. The bridges consist of 

concrete decks on continuous structural steel I-beams and cross-frames. The two end spans are 

22 m (71 ft) long, while the center span is 25 m (82 ft) long. The bridges were originally 

constructed in 1965, and in 1991 were reported to be in “satisfactory” condition, with 

delaminations and patches over approximately 20 percent of the surface. The overlays were 

placed as part of a larger project to extend U.S. 52 to meet I–275 in Cincinnati. The eastbound 

deck shown in figure 9, and the westbound travel lane shown in figure 10, were overlaid with 

LMC-III concrete, while the westbound passing lane shown in figure 11 was overlaid with a SFC 

overlay. The original information provided to the researchers incorrectly indicated that the 

westbound travel lane was overlaid with SFC. 

The U.S. 52 test site was inspected on: 

• September 20, 1994. 

• October 3, 1995. 

• September 17, 1996. 

• September 9, 1997. 

• October 10, 1998. 

Figure 9. Photograph showing the eastbound deck of U.S. 52 over 

Raymond Run in Columbus, OH. The overlay is latex-modified. 
22 

Figure 10. Photograph of westbound travel lane of U.S. 52 over 

Raymond Run in Columbus, OH. The overlay is latex-modified. 

Figure 11. Photograph showing westbound passing lane of U.S. 52 over 

Raymond Run in Columbus, OH. The overlay is silica fume concrete. 

Eastbound Lanes and Westbound Travel Lane—The materials selected for the LMC-III mix 

consisted of: a Type III cement; an angular to rounded natural sand consisting of a mixture of 

siliceous and calcareous minerals having a specific gravity of 2.68, absorption of 1.16 percent, and 

fineness modulus of 2.67; and a partially crushed limestone coarse aggregate having a maximum 

top-size of 12 mm (0.5 inch) with a specific gravity of 2.63 and an absorption of 2.09 percent. The 

latex used was DPS Modifier A, a styrene-butadiene latex emulsion. The specifications on the 

fresh concrete required a slump between 100 to 150 mm (4 and 6 inches) and an air content not to 

exceed 6 percent. 

Westbound Passing Lane—A Type I cement was used in the SFC mix. Aggregates were from the 

same sources used for the LMC-III mix at this site. Admixtures included: (1) Densified Microsilica 
23 

(compacted powder form); (2) Amex-210, a benzyl-sulfonate based air-entraining agent; (3) HyKon 2000R, a Type D water-reducer/retarder; and (4) Hy-Con Super, a Type F high-range water 

reducer. The specifications on the fresh properties of the concrete include a slump of 100 to 200 

mm (4 to 8 inches) and an air content range of 6 to10 percent. The mixture proportions and plastic 

concrete characteristics for both overlays, as reported in the C-206 report, are shown in table 16. 

Table 16. U.S. 52 concrete proportions and characteristics.

Material LMC-III SFC 

Cement (lb/yd3) 658 (Type 

III) 

700 (Type I) 

Fine agg. (lb/yd3) 1703 1480 

Coarse agg. (lb/yd3) 1333 1297 

Water (lb/yd3) 238 285 

Latex modifier (gal/yd3) 24.5 - 

Silica fume (lb/yd3) - 70 

Water reducer (oz/yd3) - 14 

HRWRA (oz/yd3) - 175 

AEA (oz/yd3) - 28 

W/C ratio 0.36 0.37 

Air content (percent) 5.2 9.5 

Slump (inches) 5.5 6.5 

Temperature (oF) 72 74 

Unit weight (lb/ft3) 145.4 139.4 

Placement date 4/23/92 4/23/92 

Weather conditions Clear Clear 

1 lb/yd3 = .347 kg/m3 

1 gal/yd3 = 5 l/m3 

1 oz/yd3 = .037 kg/m3

1 inch = 25.4 mm 

(

o

F - 32/1.8) = oC 

1 lb/ft3

 = 16 kg/m3

The LMC-III overlay was placed using two mobile concrete mixers. The deck was wetted 1 hour 

prior to placement of the overlay and a cement-sand grout was scrubbed into the deck immediately 

prior to placement of the overlay. The surface was textured with steel tines and covered with wet 

burlap and polyethylene sheeting and kept wet for 72 hours. The SFC overlay was placed later the 

same day. A cement-sand grout was scrubbed into the deck immediately prior to placement of the 

overlay. The overlay was moist-cured for 72 hours after placement in a similar manner to the 

LMC-III overlay. Both sections were opened to traffic on April 29, 1992. 

VISUAL INSPECTION 

The underside of the two bridges were inspected during the setup of the lane closure. The three 

span structures are supported by continuous steel girders. Both structures had been widened 

previously because the outermost girder (supporting the right shoulder and curb) is supported on 

single slender columns placed next to the original piers. The original portion of the deck 

underside had transverse cracks on 2.5-m (8-ft) centers, with the cracks occasionally showing 

some efflorescence. The outside widened portion of the deck had underside transverse cracks on 
24 

1.2-m (4-ft) centers, with the cracks near the abutments showing some efflorescence staining. 

Mud and silt staining on the girders, along with conversations with ODOT personnel, revealed 

that the structure had been under water during heavy regional floods of 1995-1996. 

Eastbound Travel and Passing Lanes—Both the travel and passing lanes on this structure have 

the latex-modified concrete overlay. Significant change was not seen in the condition of the 

overlay on this structure over the time of the inspections. The predominant feature of the visual 

inspection was short transverse cracks filled and covered with an acrylic-like material or an 

opaque white resinous material. Also there were some small transverse cracks that were 

unsealed. Most transverse cracks were along the edges of the deck structure. Areas of 

concentrated longitudinal cracks were seen, with more cracking on the two end spans than on the 

center span. The travel lanes were more affected than the shoulders. The cracks were short and of 

various widths. They appeared to be caused by plastic shrinkage. 

Westbound Travel Lane—This lane also has the latex-modified concrete overlay. There is some 

plastic cracking throughout the lane. There are several transverse cracks up to 1.2 m (4 feet) long 

extending from the barrier side of the lane. Overall, the latex modified overlay was in visually 

good condition. 

Westbound Passing Lane—This lane has the silica fume concrete overlay. Cracking in this lane 

is less than in the other three lanes. There are some scattered plastic cracks and some short 

transverse cracks extending from the edge on the shoulder side of the lane. An area of rough, 

open finish was noted in the last (leave) third of the bridge. 

DELAMINATION SURVEY 

Chain drag and hammer survey techniques were used to locate and delineate areas of 

delamination of the overlay concrete from the original concrete deck. Delaminations were found 

mostly at crack locations. The number and total area of delaminations on the U.S. 52 bridge are 

shown in tables 17, 18, and 19. The eastbound travel lane LMC had no delaminations. The next 

best lane was the westbound travel lane LMC with three delaminated areas in 1998 totaling 0.37 

m2

 (4 ft2). The eastbound passing lane had only three areas totaling 0.84 m2 (9 ft2)in 1988. 

The section with the most delaminations is the westbound passing lane SFC with seven areas and 

a total area of 2.16 m2

 (23.2 ft2). All of the delaminations on this lane were associated with 

cracks within the delamination area. The percent delaminated area is shown in the tables. The 

total surface area of the passing lanes are 249 m2

 (2,680 ft2) and for the travel lanes and 

shoulders are 456 m2

 (4,900 ft2). It appears that the silica fume concrete overlay is performing 

slightly worse than the latex modified overlay but the silica fume overlay only has delaminations 

over only 0.87 percent of the surface which is very low. Generally both overlays are performing 

well with minimal delaminations. 
25 

Table 17. Number and areas of delaminations LMC 

(eastbound passing U.S. 52). 

Year Number of 

Areas 

Total Area 

(m2

) 

Percent of 

Total Area 

1994 0 0 0 

1995 0 0 0 

1996 3 0.84 0.34 

1997 3 0.84 0.34 

1998 3 0.84 0.34 

Table 18. Number and areas of delaminations LMC 

(westbound travel U.S. 52).

Year Number of 

Areas 

Total Area 

(m2) 

Percent of 

Total Area 

1994 0 0 0 

1995 0 0 0 

1996 1 0.14 0.03 

1997 1 0.14 0.03 

1998 3 0.37 0.08 

Table 19. Number and areas of delaminations SFC 

(westbound passing U.S. 52).

Year Number of 

Areas 

Total Area 

(m2) 

Percent of 

Total Area 

1994 0 0 0 

1995 Not tested Not tested Not tested 

1996 3 0.60 0.24 

1997 3 0.60 0.24 

1998 7 2.16 0.87 

HALF-CELL POTENTIAL SURVEY 

The half-cell potential surveys were performed using a grid marked on 0.6-m (2-ft) centers. The 

travel lanes were numbered starting with Row 1 at the leave end of the bridge, with the "A" grid 

line near the stripe separating the travel and passing lanes and the “J” line 0.6 m (2 ft) from the 

shoulder barrier rail. The longitudinal rows of points were numbered from 1 to 114 from the 

leave side to the approach side. Rows G, H, I, and J on the shoulder were not surveyed as they 

were reinforced with epoxy-coated reinforcing steel during the widening and all locations 

initially produced erratic half-cell potentials all more positive than –0.100 V. The readings for 

the eastbound travel lane LMC in 1994 range from approximately –0.008 V to –0.386 V. Table 

20 shows that over 98 percent of the readings were less negative than –0.250 V. 

The readings for the eastbound travel lane in 1997, shown in table 21, range from –0.089 V to 

-0.412 V. Over 97 percent of the readings are below –0.250 V. A histogram for the eastbound 

travel lane in 1994 and 1997 is shown in figure 12. The half-cell readings for the westbound travel 
26 

lane LMC in 1994 are shown in table 22 and in a histogram in figure 13. The readings ranged from 

–0.001 V to –0.307 V, and table 22 indicates 99 percent are below 0.25 V. This is similar to the 

eastbound LMC data and indicates a small probability of scattered corrosion occurring in the 

westbound travel lane. 

Table 20. Cumulative frequency of half-cell 

potentials for U.S. 52 EB travel in 1994 LMC.

Potential Range 

(mV) 

Number of 

Observations 

Cumulative 

Percentage 

0 to –49 5 0.7 

–50 to –99 100 15.6 

–100 to –149 385 72.9 

–150 to –199 123 91.2 

–200 to –249 48 98.4 

–250 to –299 8 99.6 

–300 to –349 1 99.7 

–350 to –399 2 100.0 

–400 to –449 0 100.0 

–450 to –499 0 100.0 

–500 to –549 0 100.0 

Table 21. Cumulative frequency of half-cell 

potentials for U.S. 52 EB travel in 1997 LMC.

Potential Range 

(mV) 

Number of 

Observations 

Cumulative 

Percentage 

0 to –49 0 0.0 

–50 to –99 5 0.8 

–100 to –149 269 40.8 

–150 to –199 298 85.2 

–200 to –249 81 97.3 

–250 to –299 15 99.6 

–300 to –349 1 99.7 

–350 to –399 1 99.8 

–400 to –449 1 100.0 

–450 to –499 0 100.0 

–500 to –549 0 100.0 
27 

Table 22. Cumulative frequency of half-cell 

potentials for U.S. 52 for WB travel in 1994 LMC.

Potential Range 

(mV) 

Number of 

Observations 

Cumulative 

Percentage 

0 to –49 20 2.6 

–50 to –99 457 61.0 

–100 to –149 242 91.9 

–150 to –199 41 97.2 

–200 to –249 14 99.0 

–250 to –299 7 99.9 

–300 to –349 1 100.0 

–350 to –399 0 100.0 

–400 to –449 0 100.0 

–450 to –499 0 100.0 

–500 to –549 0 100.0 

0

50

100

150

200

250

300

350

400

450

0 to 

-49

-50 to 

-99

-100 

to

-149 

-150 

to

-199

-200 

to 

-249

-250 

to

-299 

-300 

to

-349 

-350 

to

-399 

-400 

to

-459 

-450 

to 

-499

-500 

to 

-549

Potential 

Range (mV)

Number of 

Observations

US52 

EB 94

US52 

EB 97

0

50

100

150

200

250

300

350

400

450

0 to 

-49

-50 to 

-99

-100 

to

-149 

-150 

to

-199

-200 

to 

-249

-250 

to

-299 

-300 

to

-349 

-350 

to

-399 

-400 

to

-459 

-450 

to 

-499

-500 

to 

-549

Potential 

Range (mV)

Number of 

Observations

US52 

EB 94

US52 

EB 97

Figure 12. Histogram of half-cell potential readings for U.S. 52 eastbound 

travel lane LMC in 1994 and 1997. 
28 

0

50

100

150

200

250

300

350

400

450

500

0 to 

-49

-50 to 

-99

-100 

to

-149 

-150 

to

-199 

-200 

to 

-249

-250 

to 

-299

-300 

to 

-349

-350 

to 

-399

-400 

to 

-449

-450 

to 

-499

-500 

to

-549 

Potential 

Range (mV)

Number of Observations

US52 WB Travel 1994

0

50

100

150

200

250

300

350

400

450

500

0 to 

-49

-50 to 

-99

-100 

to

-149 

-150 

to

-199 

-200 

to 

-249

-250 

to 

-299

-300 

to 

-349

-350 

to 

-399

-400 

to 

-449

-450 

to 

-499

-500 

to

-549 

Potential 

Range (mV)

Number of Observations

US52 WB Travel 1994

Figure 13. Histogram of half-cell potentials for U.S. 52 

westbound travel lane LMC in 1994. 

The westbound passing lane SFC was studied in detail in 1997 after it was discovered that it is the 

only lane with the silica fume overlay. It was not studied in 1994. The corrosion potential readings 

shown in table 23 range from –0.065 V to –0.360 V and almost 97 percent of the readings are less 

than –0.250 V. A histogram of the readings for westbound passing lane SFC is shown in figure 14. 

The SFC data is similar to the LMC data and indicates a low probability of corrosion. 

Table 23. Cumulative frequency of half-cell 

potentials for U.S. 52 for WB passing in 1997 SFC.

Potential Range 

(mV) 

Number of 

Observations 

Cumulative 

Percentage 

0 to –49 0 0.0 

–50 to –99 34 3.8 

–100 to –149 590 69.7 

–150 to –199 171 88.8 

–200 to –249 71 96.8 

–250 to –299 21 99.1 

–300 to –349 7 99.9 

–350 to –399 1 100.0 

–400 to –449 0 100.0 

–450 to –499 0 100.0 

–500 to -549 0 100.0 
29 

0

50

100

150

200

250

300

350

400

450

500

0 to 

-49

-50 to 

-99

-100 

to

-149 

-150 

to

-199 

-200 

to 

-249

-250 

to 

-299

-300 

to 

-349

-350 

to 

-399

-400 

to 

-449

-450 

to 

-499

-500 

to

-549 

Potential 

Range (mV)

Number of Observations

US52 WB Travel 1994

0

50

100

150

200

250

300

350

400

450

500

0 to 

-49

-50 to 

-99

-100 

to

-149 

-150 

to

-199 

-200 

to 

-249

-250 

to 

-299

-300 

to 

-349

-350 

to 

-399

-400 

to 

-449

-450 

to 

-499

-500 

to

-549 

Potential 

Range (mV)

Number of Observations

US52 WB Travel 1994

Figure 14. Histogram of half-cell potentials for 

U.S. 52 westbound passing lane SFC in 1997. 

Figure 155. Equipotential map of half-cell potentials for eastbound travel 

lane U.S. 52 in 1997 (latex-modified concrete). 
30 

Figure 16. Equipotential map of half-cell potentials for westbound 

passing lane of U.S. 52 in 1997 (silica fume concrete). 

POLARIZATION RESISTANCE (PR) TESTING 

Polarization resistance tests were performed at five locations on the eastbound bridge and four 

locations on the westbound bridge in 1994. All nine locations were located in the travel lanes. At 

the time it was thought the westbound travel lane had a silica fume concrete overlay and the 

eastbound travel lane had a latex-modified concrete overlay but it was discovered both travel 

lanes had a latex-modified overlay. The test locations on the eastbound travel lane were chosen 

from two low-potential areas (–0.109 V and –0.115 V), one moderate-potential area (–0.130 V), 

and two high-potential areas (–0.224 V and –0.200 V). Simulated 3LP tests were also performed 

at each of the test locations. The PR testing was slightly more successful than the 3LP testing, 

with four of the five locations being tested successfully. Only three of the five locations were 

successfully tested using the 3LP technique. One test spot could not be successfully tested using 

either technique. The results of the testing are summarized in table 24. The corrosion rate 

measurements were generally low. 

Table 24. Corrosion rate testing on U.S. 52 eastbound travel lane, LMC-III (1994). 

PR Testing 3LP Testing 

Grid Location 

Equilibrium 

Potential 

(mV)* 

Rp

(ohm) 

Icorr

(mA/cm2

) Rp (ohm) Icorr

(mA/cm2

) 

B110 –0.224 - - - - 

B19 –0.109 339 0.064 200 0.108 

C10 –0.115 429 0.050 417 0.052 

C20 –0.130 232 0.093 517 0.042 

D110 –0.200 449 0.048 - - 

*Measured using a Cu/CuSO4 reference electrode. 

The test locations on the westbound travel lane were chosen from two medium-potential areas and 

two low-potential areas. Simulated 3LP tests were also performed at each of the test locations. The 
31 

PR and 3LP testing was generally successful on the westbound structure, with all four locations 

being successfully tested using both techniques. The results of the testing are summarized in 

table 25. 

Table 245. Corrosion rate testing on U.S. 52 westbound travel lane, LMC-III (1994).

PR Testing 3LP Testing 

Grid Location 

Equilibrium 

Potential 

(mV)* 

Rp

(ohm) 

Icorr

(mA/cm2

) Rp (ohm) Icorr

(mA/cm2

) 

B100 –0.135 395 0.055 174 0.125 

C110 –0.146 330 0.065 275 0.076 

F10 –0.064 705 0.031 253 0.085 

F27 –0.099 286 0.076 225 0.097 

* Measured using a Cu/CuSO4 reference electrode. 

All of the corrosion rates were similar and low. This confirms the general indication given by the 

half-cell potential measurements. The agreement between the corrosion rates estimated using the 

two techniques was generally good, with all of the estimates within a factor of 2 or 3. In 1997, 

linear polarization measurements were performed on the eastbound travel lane LMC-III and the 

westbound passing lane SFC. Tests were made at locations with high, medium, and low 

corrosion potentials. The testing was performed using a James Instruments GECOR 6 

Polarization Resistance Tester. The results of the testing for both the eastbound travel and the 

westbound passing lanes are shown in table 26. The corrosion rates were moderate and are 

higher in 1997 than in 1994 LMC. There is no appreciable difference in the corrosion rates 

between the two types of overlay. 

Table 26. Results of polarization resistance testing at U.S. 52 (1997). 

Direction Grid 

Location 

Half-Cell 

Potential 

(mV) 

Measured 

Corrosion 

Rate (μA/cm2)

Notes 

B10 –129 0.137 Low potential, wheel path 

D98 –139 0.135 Low potential, wheel path 

C68 –185 0.160 Centerline 

C108 –183 0.173 Centerline 

B110 –199 0.232 Centerline, cracks 

Eastbound Travel 

LMC 

D34 –264 0.232 - 

F38 –202 0.160 - 

C60 –133 0.078 Shoulder, not confined 

D38 –315 0.114 Delam in base concrete, not 

confined 

D102 –97 0.179 Low potential 

H110 –337 0.132 At edge of delam 

H110 –378 0.145 Over delam 

E120 –97 0.175 Centerline 

Westbound 

Passing 

SFC 

G180 –139 0.086 Wheelpath 
32 

CORE TESTING 

Concrete cores were taken through the overlays in 1994 and 1997. They were inspected to 

determine the overlay thickness and the cover over the uppermost reinforcing bars. The overlay 

thickness on the eastbound and westbound travel lanes, which are both latex-modified concrete, 

ranges from 25 to 50 mm (1 to 2 inches). The clear cover above the reinforcing steel ranges from 

76 to 102 mm (3 to 4 inches). In 1994, three of the cores removed from the westbound travel 

lane and three cores removed from the eastbound travel lane were tested to determine their bond 

strength in direct shear. 

The results of the testing are shown in table 27. All of these cores have the latex-modified concrete 

overlay and there is little difference between the two spans. This is to be expected as both failed 

primarily in the substrate concrete, which was nominally the same in both locations. The failure of 

the cores primarily in the substrate concrete indicates that the surface preparation and application 

was excellent for the latex-modified overlay, as improper installation or poor surface preparation 

will typically result in failures at the bond line. 

In 1997, three cores from the eastbound travel lane LMC-III and three cores from the westbound 

passing lane SFC were tested in shear. The results are shown in table 28. The bond strengths of the 

cores from the westbound passing lane SFC are less than that of the cores from the eastbound 

travel lane LMC, but there is significant scatter among the data. Failures occurred mainly in the 

substrate concrete. If the test result from the core taken in the shoulder of the eastbound lane or the 

core taken from the center line of the westbound lane is excluded, there is little difference between 

the two sections. 

Table 27. Shear bond testing of cores from U.S. 52 (1994).

Failure Location (percent of failure area) Overlay 

Type 

Core 

ID 

Bond 

Strength 

MPa (psi) Overlay Bond Line Substrate 

Eastbound 1 4.1(596) 5 0 95 

Travel 2 2.8 (407) 10 0 90 

LMC 5 3.6 (517) 10 0 90 

Westbound 1 4.9 (716) 0 0 100 

Travel 2 4.0 (580) 10 0 90 

SFC 3 3.4 (486) 10 0 90 

Table 28. Shear bond testing of cores from U.S. 52 (1997).

Location and Overlay Type Core ID Exposure Condition Bond Strength 

MPa (psi) 

3 Wheel path 4.7 (680) 

5 Centerline 5.9 (850) 

Eastbound Travel LMC 

7 Shoulder 7.2 (1040) 

Average 5.9 (857) 

3 Shoulder 4.9 (710) 

8 Centerline 3.2 (470) 

Westbound Passing SFC 

9 Wheel path 5.0 (720) 

Average 4.4 (633) 
33 

CHLORIDE ANALYSIS 

In 1994, following the visual examination of the cores, chloride analyses were performed on six 

cores from the eastbound travel lane and seven cores from the westbound travel lane. Concrete 

slices were taken from the 

12- to 25-mm (0.5- to 1-inch) depth surface region and from the 95- to 120-mm (3.75- to 4.75-

inches) depth where the reinforcing bars are typically located. All of the slices were pulverized and 

analyzed to determine their acid-soluble chloride content. In addition to the acid-soluble chloride 

analyses, water-soluble chloride analyses were performed on selected samples. The test results for 

1994 are shown in table 29. In 1998, chloride analyses were performed on two cores from the 

eastbound passing lane LMC, one core from the eastbound travel lane LMC, one core from the 

westbound travel lane LMC and two cores from the westbound passing lane SFC. The acid-soluble 

chloride contents were measured at 4 depths up to the 95- to 120-mm (3.75- to 4-inch) depth. The 

results are shown in table 30. 

All of the locations had low to moderate chloride concentrations at the level of the reinforcing bars. 

The approximate threshold for chloride-induced corrosion of black reinforcing steel is 

approximately 0.025 percent by concrete weight, so most of the locations in the deck appear to 

have only marginally sufficient chloride to support corrosion. This agrees with the indication of 

little corrosion given by the half-cell potential and corrosion rate readings. The relatively high 

chloride contents at the bond line area (28 to 38 mm (1.125 to 1.5 inches)) indicate that chloride 

contamination of the surface of the original deck remained when the overlays were placed. 

Chloride ingress into the overlay concrete has occurred with time both from the surface and from 

the chlorides that were present in the surface region of the substrate concrete. 

Table 29. Results of chloride content testing of cores from U.S. 52 (1994).

Acid-Soluble Chloride 

Content, percent by 

concrete weight 

Water-Soluble Chloride 

Content, percent by 

concrete weight Location and 

Overlay Type 

Sample 

Number 0.5 to 1 

inch 

3.75 to 4 

inches 

0.5 to 1 

inch 

3.75 to 4 

inches 

1 - 0.033 - - 

2 0.011 0.036 - - 

3 0.027 0.047 0.010 0.017 

4 - 0.018 - - 

5 0.017 0.018 - - 

Eastbound 

Latex Modified 

6 - 0.024 - < 0.007 

1 - 0.008 - - 

2 - 0.039 - - 

4 0.048 0.025 - - 

5 0.022 0.046 < 0.007 0.018 

6 - 0.017 - < 0.007 

Westbound 

Latex Modified 

7 0.025 0.018 - - 
34 

Table 30. Results of chloride content testing of cores from U.S. 52 (1998).

Acid-Soluble Chloride Content, 

Location and percent by weight of concrete 

Overlay Type 0.25 to 0.5 

inch 

0.625 to 1 

inch 

1.125 to 1.5 

inches 

3.75 to 4 

inches 

Eastbound Passing 

#1 LMC 0.179 0.104 0.151 0.048 

Eastbound Passing 

#2 LMC 0.152 0.139 0.197 0.090 

Eastbound Travel 

LMC 0.109 0.063 0.089 0.022 

Westbound Travel 

LMC 0.067 0.050 0.133 0.035 

Westbound Passing 

#1 SFC 0.119 0.049 0.248 0.052 

Westbound Passing 

#2 SFC 0.091 0.097 0.289 0.053 

SUMMARY OF U.S. 52 TEST (NEW RICHMOND, OH) 

The SFC and LMC-III overlays were placed in April 1992. Overall, the overlays were in good 

condition in 1998. Each overlay has developed some delamination but the percent delaminated 

area is very low and less than 1 percent. Some plastic cracking is present, predominantly in the 

LMC-III overlays. The bond remains strong in both sections. 

Half-cell potential data and corrosion rate measurements indicate a low probability of 

widespread corrosion. Table 31 shows the percent of potentials more positive than –250 mV, 

indicating the areas with a low probability of corrosion. The chloride content at the level of the 

reinforcing in moderately low. Some chloride ingress into the overlays was noted, however, their 

performance is considered very good. 

Table 31. Potentials more positive than –250mV 

(Cu/CuSO4) (percent of measurements).

Year NB (SFC) SB (LMC-III) 

1994 - 98.8 

1997 96.8 97.3 
35 

CHAPTER 5. I–265 OVER KY 22, JEFFERSON COUNTY, KY 

INTRODUCTION 

This test site consists of two medium-length (42 m, 243 ft) three-span parallel bridges carrying 

I–265 over KY 22, approximately 11 km (7 miles) northeast of the Louisville city limits on KY 

22. The end spans are 15 m (49.5 ft) long, and the center span is 42 m (137 ft). The decks were 

constructed in 1969, and were rated as "satisfactory" by State forces in 1991. They were 

described as having a few transverse cracks and isolated spalled areas that had been patched with 

asphaltic material. During work to maintain the riding surface and replace deteriorated joints, the 

deck was overlaid with concrete overlays. The northbound lanes shown in figure 17, received a 

LMC-III overlay and the southbound lanes shown in figure 18, received a SFC overlay. 

Northbound Lanes – Materials for the LMC-III mix consisted of: Type III cement; a subangular to 

rounded natural sand consisting of a mixture of siliceous and calcareous minerals having a specific 

gravity of 2.60, absorption of 1.40 percent, and fineness modulus of 2.56; and a crushed limestone 

coarse aggregate having a maximum topsize of 12 mm (0.5 inch) with a specific gravity of 2.71 

and an absorption of 0.6 percent. The latex used was DPS Modifier A, a styrene-butadiene latex 

emulsion. 

Southbound Lanes – A Type I cement was used in the SFC mix. Aggregates were from the same 

sources used for the LMC-III mix at this site. Admixtures included: Force 10,000 silica fume 

(slurry form); Darex II AEA, an organic-acid salt based air-entraining agent; and WRDA-19, a 

Type F high-range water reducing admixture. The mixture proportions and plastic concrete 

characteristics for both overlays, as reported in the C-206 report, are shown in table 32. 

Figure 17. Photograph of I–265 northbound lanes with latex-modified overlay. 
36 

Figure 18. Photograph showing I–265 southbound lanes with silica fume concrete overlay. 

Table 32. I–265 concrete proportions and characteristics.

Material LMC-III SFC 

Cement (lb/yd3) 658 (Type III) 658 (Type I) 

Fine aggregate (lb/yd3) 1708 1395 

Coarse aggregate (lb/yd3) 1162 1531 

Water (lb/yd3) 219 240 

Latex modifier (gal/yd3) 24.5 - 

Silica fume (lb/yd3) - 50 

HRWRA (oz/yd3) - 105 

AEA (oz/yd3) - 39 

W/C ratio 0.33 0.34 

Air content (percent) 5.5 6.5 

Slump (inches) 5.0 6.0 

Temperature (°F) 79 82 

Unit weight (lb/ft3) 144.0 143.8 

Placement date 6/08/92 6/29/92 

Weather conditions Clear Clear 

1 lb/yd3 = .347 kg/m3 

1 gal/yd3 = 5 l/m3 

1 oz/yd3 = .037 kg/m3 

1 inch = 25.4 mm 

(oF - 32/1.8) = oC 

1 lb/ft3 = 16 kg/m3 

The Kentucky Department of Highways (KYDOH) specifications on fresh properties of LMC-III 

include a range of slump from 100 to 150 mm (4 to 6 inches) and an air content not to exceed 7 

percent. Specifications for SFC mixes include a slump range of 100 to 178 mm (4 to 7 inches) 

and an air content range of 5 to 8 percent. As required by the State specifications, the 

placements took place at night to prevent the hot conditions typically seen during the daytime of 
37 

the summer months. The LMC-III overlay was placed on June 8, 1992 using two mobile 

concrete mixers. The water used to pre-wet the deck was noted in inspector diaries to be 

"excessive" with some water remaining at the bottom of deeply-excavated areas at the time of 

placement. The surface was textured with a stiff-broom finish. The surface was covered with wet 

burlap and polyethylene film immediately following the finishing, although no soaker hoses 

were used. The curing was removed after 24 hours, and no further curing was applied. The 

LMC-III overlay was opened to traffic two days after casting. 

The concrete for the SFC overlay was placed on June 29, 1992 and was delivered using transitmix trucks. It was placed smoothly and without problems. The surface was finished in a similar 

manner to the LMC-III overlay. The curing was also similar to that of the LMC-III overlay, 

except that the wet burlap and polyethylene was maintained on the concrete for 72 hours. 

Although soaker hoses were not used at the site, the burlap was wetted at the start of each day of 

curing. The SFC overlay was opened to traffic 13 days after casting. 

The northbound and southbound structures are not identical. The northbound structure LMC-III 

is wider, carrying a merge area across the bridge. Due to the extreme difficulty in closing the 

northbound travel lane through the merge area, the test section was set up in the shoulder and 

merge area, and it does not receive “main line” traffic exposure. 

VISUAL INSPECTION 

The underside of the structure was inspected annually while the traffic control was being set up 

on the lanes above. The southbound SFC span sits on only seven simple-span girders, and it does 

not carry a merge lane. The girders were noted to be somewhat rusty and the underside of the 

bridge exhibited occasional transverse cracks, some with efflorescence. The joints on the edges 

of the structure exhibited cracking and delamination with exposed bars. The bearing blocks 

under the rocker bearings were cracked and spalled. 

The deck of the structure was inspected visually for appearance and performance. In 1994, the 

southbound SFC deck had several areas of concentrated "spidery" cracks, with Span 1 appearing 

worse than the other spans. The cracks were a mix of longitudinal and transverse cracks, and 

were concentrated primarily in the travel lane. In 1998, the cracking had become more noticeable 

and was generally more severe in the travel lane than the shoulder. Span 1 had the most severe 

cracking with some located in the shoulder as well as the travel lane. In all three spans, the 

cracking is more severe in the wheel paths. Most of the cracking is longitudinal with some 

shorter transverse cracking. The crack widths of the major cracks range from 0.127 to 0.381 mm 

(0.005 to 0.015 inches). 

The northbound structure LMC is wider than the southbound structure, carrying a merge area 

across the bridge. Because of the merge area, the northbound traffic on the south side of the 

bridge was brought into one lane, into which the on-ramp traffic was merged. Because of these 

traffic control requirements, the test section was set up in the shoulder and merge area, and does 

not receive “main line” traffic exposure. The initial inspection in 1994 showed narrow cracks, 

many of which had healed by 1998. Cores showed cracks about 6 mm (0.25 inch) deep. The 

inspection in 1998 showed the overlay to be in good condition. There were several rough surface 

areas both in the shoulder and the merge lane but very little cracking. There were occasional 
38 

short transverse and longitudinal cracks but no major cracks. The condition of the latex modified 

concrete overlay is much better than the silica fume concrete overlay but this is partly because 

the latex-modified overlay test section is subjected to a lesser amount of traffic. 

DELAMINATION SURVEY 

The chain drag and hammer survey techniques were used to locate and delineate areas of 

delamination of the overlay concrete from the old concrete deck. Delaminations were found 

mostly at crack locations. The number and total area of delaminations on the I–265 bridge are 

shown in tables 33 and 34. The southbound SFC spans have many more delaminations, both in 

number and area, than the northbound LMC spans. 

Table 33. Number and areas of delaminations, 

southbound I–265 SFC. 

Year No. Areas Total Area 

(m2

) 

Percent of 

Total Area 

1994 0 0.00 0.00 

1995 11 1.48 0.33 

1996 25 7.75 1.71 

1997 45 13.33 2.95 

1998 60 20.20 4.47 

Table 34. Number and areas of delaminations, 

northbound I–265 LMC.

Year No. Areas Total Area 

(m2

) 

Percent of 

Total Area 

1994 0 0.00 0.00 

1995 2 0.18 0.05 

1996 6 0.97 0.25 

1997 13 1.62 0.42 

1998 17 3.46 0.90 

Of the southbound spans, the first span on the approach end of the bridge has the most severe 

delaminations of the three spans. Also, most of the delaminations are located in the travel lane 

and not in the shoulder areas. For the northbound structure, almost all of the delaminations are 

located in the center span. The areas of the two test sections are different because the northbound 

section tapers at the end where the merge lane ends. The area of the southbound SFC section is 

452 m2

 (4,860 ft2) and the area of the northbound section LMC is 384 m2 (4,130 ft2). Tables 33 

and 34 show the percentage of the total area delaminated is 4.47 percent for the southbound 

sections SFC and 0.90 percent for the northbound LMC section. The southbound section appears 

much worse than the northbound but still has moderately little delaminated area and also has 

much more traffic than the northbound section. 
39 

HALF-CELL POTENTIAL SURVEY 

The potential survey test grid on the southbound SFC bridge was marked using a 0.6-m (2-ft) 

grid beginning at the approach end of each span. Each span was numbered independently. The 

transverse rows were numbered from 1 to 25 and 1 to 68 from the approach side to the leave 

side, for the end and center spans, respectively. The longitudinal rows were lettered A to K, with 

the A-line placed along the paint stripe separating the travel lane from the passing lane. In the 

survey from 1994, the half-cell potential readings ranged from approximately +50 mV to –414 

mV, with large potential differences between nearby areas. These readings tend to indicate that 

some limited corrosion is taking place in the bridge. Span 1 appeared to have the most corrosion 

activity, with rapid potential changes noticeable between nearby areas and an average potential 

reading of –211 mV. Span 2 had the highest (most negative) potential reading but also the lowest 

average potential reading of –136 mV. Span 3 had an average potential reading of –191 mV. 

In 1997, the half-cell potentials ranged from +265 mV to –600 mV. Span 1 again had the highest 

average potential reading of –207 mV. Span 2 again had the highest potential reading at –600 

mV and the lowest average reading at –149 mV. Span 3 had an average potential reading of –160 

mV. Tables 35 and 36 give the cumulative frequencies of the half-cell potentials for the 

southbound test section of I–265 for 1994 and 1997, respectively. In 1994, over 85 percent of the 

readings were less negative than –250 mV. In 1997, over 86 percent of the readings were less 

negative than –250 mV. A histogram of the half-cell potential readings for the southbound test 

section in 1994 and 1997 is shown in figure 19. 

Table 35. Cumulative frequency of half-cell potentials for I–

265 for SB travel lane, SFC (1994).

Potential Range 

(mV) 

Number of 

Observations 

Cumulative 

Percentage 

0 to –49* 54 4.1 

–50 to –99 259 23.5 

–100 to –149 312 46.9 

–150 to –199 272 67.3 

–200 to –249 244 85.6 

–250 to –299 128 95.2 

–300 to –349 50 99.0 

–350 to –399 10 99.8 

–400 to –449 2 100.0 

–450 to –499 0 100.0 

–500 to –549 0 100.0 

*Note. Any positive reading is counted as 0 for tabulation. 
40 

Table 36. Cumulative frequency of half-cell potentials for I–

265 for SB travel lane, SFC (1997).

Potential Range 

(mV) 

Number of 

Observations 

Cumulative 

Percentage 

0 to –49* 53 4.0 

–50 to –99 215 20.1 

–100 to –149 355 46.6 

–150 to –199 323 70.7 

–200 to –249 212 86.5 

–250 to –299 113 94.9 

–300 to –349 48 98.5 

–350 to –399 17 99.8 

–400 to –449 1 99.9 

–450 to –499 1 100.0 

–500 to –549 0 100.0 

*Note. Any positive reading is counted as 0 for tabulation. 

0

50

100

150

200

250

300

350

400

0 to 

-49

-50 to 

-99

-100 to

-149 

-150 to

-199 

-200 to 

-249

-250 to

-299

-300 to

-349

-350 to

-399 

-400 to

-449 

-450 to 

-499

-500 to

-549 

Number of 

Observations

I-265 SB94

I-265 SB97

Potential 

Range (mV)

0

50

100

150

200

250

300

350

400

0 to 

-49

-50 to 

-99

-100 to

-149 

-150 to

-199 

-200 to 

-249

-250 to

-299

-300 to

-349

-350 to

-399 

-400 to

-449 

-450 to 

-499

-500 to

-549 

Number of 

Observations

I-265 SB94

I-265 SB97

Potential 

Range (mV)

Figure 19. Histogram of half-cell potential readings for 

I–265 southbound SFC test section. 

The 0.6-m (2-ft) grid for the northbound LMC spans was started at the approach side of the 

bridges. The transverse rows of points were numbered from 1 to 25 and 1 to 69 on the end and 

center spans, respectively. The longitudinal were lettered A to K, beginning at the paint stripe 

between the travel and passing lanes. Due to tapering of the merge lane across the bridge, row H 

was the last row at the leave end of the bridge. The half-cell potential for the northbound test 

section in 1994 readings ranged from +59 mV to −356 mV, with the more negative potentials 
41 

occurring primarily at the joints. In 1994, span 3 had the highest average potential reading at 

−102 mV. 

Span 2 had the highest individual reading at –356 mV but had an average reading of only –65 

mV. Span 1 had an average potential reading of –55 mV. In 1997, span 3 again had the highest 

average potential reading at −86 mV but also had the highest individual reading at −352 mV. 

Span 2 had an average potential reading of −61 mV and span 1 had an average of −27 mV. 

Tables 37 and 38 show the cumulative frequency of the half-cell readings for the northbound 

spans in 1994 and 1997. A histogram of the half-cell potential readings for the northbound test 

section for 1994 and 1997 is shown in figure 20. In 1994 and 1997, approximately 98 percent of 

the readings were less negative than −250 mV. In areas away from the joints, the potentials were 

generally less negative than −100 mV, indicating that very little corrosion is taking place in the 

bridge. 

Figure 21 shows an equipotential map of the half-cell readings for the southbound SFC test 

section for 1997. Spans 1 and 3 appear to have more isolated spots of corrosion (anodic) activity 

than the main span. An equipotential map of the half-cell potential readings for the northbound 

LMC test section for 1997 is shown in figure 22. The magnitude of the half-cell readings is much 

lower in the northbound LMC test section than in the southbound SFC test section. However, 

some anodic areas are present, mainly near the joints and in the main span. 

Table 37 Cumulative frequency of half-cell potentials 

for I–265 for NB travel lane, LMC (1994).

Potential Range (mV) Number of 

Observations 

Cumulative 

Percentage 

0 to −49 494 46.1 

−50 to −99 317 75.7 

−100 to −149 134 88.2 

−150 to −199 74 95.1 

−200 to −249 33 98.2 

−250 to −299 15 99.5 

−300 to −349 4 99.9 

−350 to −399 1 100.0 

−400 to −449 0 100.0 

−450 to −499 0 100.0 

−500 to −549 0 100.0 
42 

Table 38. Cumulative frequency of half-cell potentials 

for I–265 for NB travel lane, LMC (1997).

Potential Range (mV) Number of 

Observations 

Cumulative 

Percentage 

0 to −49 626 60.0 

−50 to −99 226 81.6 

−100 to −149 98 91.0 

−150 to −199 45 95.3 

−200 to −249 32 98.4 

−250 to −299 14 99.7 

−300 to –349 2 99.9 

–350 to –399 1 100.0 

–400 to –449 0 100.0 

–450 to –499 0 100.0 

–500 to –549 0 100.0 

Potential 

Range (mV)

0

100

200

300

400

500

600

700

Number of 

Observations

I-265 NB94

I-265 NB07

0 to 

-49

-50 to 

-99

-100 to

-149 

-150 to

-199 

-200 to 

-249

-250 to

-299

-300 to

-349

-350 to

-399 

-400 to

-449 

-450 to 

-499

-500 to

-549 

Potential 

Range (mV)

0

100

200

300

400

500

600

700

Number of 

Observations

I-265 NB94

I-265 NB07

0 to 

-49

-50 to 

-99

-100 to

-149 

-150 to

-199 

-200 to 

-249

-250 to

-299

-300 to

-349

-350 to

-399 

-400 to

-449 

-450 to 

-499

-500 to

-549 

0

100

200

300

400

500

600

700

Number of 

Observations

I-265 NB94

I-265 NB07

0 to 

-49

-50 to 

-99

-100 to

-149 

-150 to

-199 

-200 to 

-249

-250 to

-299

-300 to

-349

-350 to

-399 

-400 to

-449 

-450 to 

-499

-500 to

-549 

Figure 20. Histogram of half-cell potential readings for the I–265 

northbound LMC test section. 
43 

Figure 21. Equipotential maps of half-cell potentials of the three 

southbound spans SFC of the I–265 test section in 1997. 
44 

Figure 22. Equipotential maps of half-cell potentials of the three 

northbound spans LMC of the I–265 test section in 1997. 
45 

POLARIZATION RESISTANCE (PR) TESTING 

Polarization resistance tests were performed at five locations on the southbound SFC bridge in 

1994. The test locations were chosen from low, moderate and high-potential areas. The PR tests 

were performed using a EG&G Princeton Applied Research Company (EG&G PARC) model 

273A potentiostat under computer control. Simulated 3LP tests were also performed at each of 

the test locations. Only three of the five locations were successfully tested using the PR or the 

3LP technique. The results of the testing are summarized in table 39. 

Table 39. Corrosion rate testing on I–265 southbound in 1994 SFC.

PR Testing 3LP Testing Grid 

Location 

Equilibrium 

Potential 

(mV)* Rp

(ohm) 

Icorr

(mA/cm2

) 

Rp

(ohm) 

Icorr

(mA/cm2

) 

Span 1, I8 –0.259 - - 565 0.048 

Span 1, I28 –0.231 254 0.085 - - 

Span 2, G21 –0.103 390 0.055 195 0.111 

Span 3, F10 –0.199 - - 76 0.286 

Span 3, E18 –0.305 696 0.031 - - 

* Measured using a Cu/CuSO4 reference electrode 

The corrosion rate measurements were variable and did not generally agree with the half-cell 

potential measurements, as some of the most negative potentials were associated with the lowest 

corrosion rates. The 3LP measurements indicated higher corrosion rates than the PR tests. The 

difficulties encountered may have been related to the high resistivity of the silica fume overlay 

concrete. 

The PR and 3LP testing was only slightly more successful on the northbound LMC structure 

than on the southbound structure, with four of the six locations being successfully tested using 

either technique. This may have been due to the overall low corrosion rates observed on the 

structure, as very low corrosion rates are typically more difficult to measure than actively 

corroding areas. The results of the testing are summarized in table 40. 

Table 40. Corrosion rate testing on I–265 northbound in 1994 LMC. 

PR Testing 3LP Testing 

Grid Location 

Equilibrium 

Potential 

(mV)* 

Rp

(ohm) 

Icorr

(mA/cm2) 

Rp

(ohm) 

Icorr

(mA/cm2) 

Span 1, C0 –0.151 701 0.030 2400 0.009 

Span 1, EF4 –0.119 325 0.067 - - 

Span 1, D16 –0.000 - - - - 

Span 3, C18 –0.163 - - 281 0.077 

Span 3, C50 –0.147 11300 0.002 1283 0.016 

Span 3, C47 –0.122 8802 0.002 5021 0.004 

* Measured using a Cu/CuSO4 reference electrode 
46 

In 1997, linear polarization measurements were performed on both spans at locations with high, 

medium, and low corrosion potentials. Because the southbound SFC structure appeared to have 

more corrosion activity occurring, the corrosion rate was measured at eight locations while only 

one location was measured on the northbound structure. The one location on the northbound test 

section was chosen because it was one of the few areas that had a higher negative potential. The 

testing was performed using a James Instruments GECOR 6 Polarization Resistance Tester and 

the results are shown in table 41. There is some scatter in the corrosion rate measurements. The 

corrosion rates vary from very low to moderately low. Some corrosion appears to be occurring in 

local areas but at low to moderate rates. 

Table 41. Results of polarization resistance testing at U.S. 52 (1997).

Direction Grid 

Location 

Half-Cell 

Potential 

(mV) 

Measured 

Corrosion Rate 

(μA/cm2) 

Notes 

E62 –171 0.093 Random half-cell 

EF34 –212 0.104 Wheelpath 

EF31 –329 0.157 Moderate potential

H20 –211 0.154 Moderate potential

C20 –124 0.054 Low potential 

H12 –334 0.061 Negative potential 

E90 –245 0.110 Moderate potential

Southbound Travel 

SFC 

EF130 –243 0.114 Delamination area 

LMC (NB) F22 –282 0.212 Delaminated area 

CORE TESTING 

Cores were taken from both test sections in 1994 and 1997. In the laboratory, the cores were 

examined to determine the overlay thickness and the cover over the uppermost reinforcing bars. 

The overlay thicknesses ranged from 32 to 50 mm (1.25 to 2.0 inches) and the observed clear 

cover over the reinforcing bars ranged from 64 to 95 mm (2.5 to 3.75 inches). In 1994, shear 

bond testing was performed on three cores from each test section. The test results are shown in 

table 42. The test result for one of the cores from the northbound test section was much higher 

than all the others. This is because the failure occurred completely in the overlay. Without this 

result, there is no appreciable difference in the bond strength of the cores from either test section. 

All the other cores failed mostly or completely in the base concrete. 

Table 42. Shear bond testing of cores from I–265 (1994). 

Overlay Failure Location (percent of failure area) 

Type 

Core 

ID 

Bond Strength 

MPa (psi) Overlay Bond Line Substrate 

Southbound 1 3.4 (493) 25 0 75 

Travel 4 3.9 (570) 30 0 70 

SFC 8 2.9 (420) 40 20 40 

Northbound 1 5.7 (827) 100 0 0 

Travel 2 2.9 (424) 10 0 90 

LMC 3 4.0 (580) 0 0 100 
47 

In 1997, four cores from the southbound travel lane and one core from the northbound travel lane 

were tested in shear. The results are shown in table 43. The bond strength of all the cores remains 

good and most failures occurred in the substrate or overlay concrete. 

Table 43. Shear bond testing of cores from I–265 (1997). 

Location and 

Overlay Type Core ID Exposure Condition 

Bond Strength 

MPa (psi) 

4 Shoulder 3.7 (540) 

5 Centerline 3.9 (570) 

6 Centerline 4.4 (640) 

Southbound Travel LMC 

7 Wheel path 3.9 (560) 

Average 4.0 (578) 

Northbound Travel SFC 4 Wheel path 3.2 (460) 

CHLORIDE ANALYSES 

Following the visual examination of the cores, chloride analyses were performed on six cores 

from each overlay taken in 1994. The samples were taken from the 25- to 50-mm (0.5- to 1-inch) 

depth surface region and from the 75- to 95-mm (3- to 3.75-inches) depth where the reinforcing 

bars would have been located. All of the slices were then pulverized and analyzed to determine 

their acid-soluble chloride content. In addition to the acid-soluble chloride analyses, watersoluble chloride analyses were performed on selected samples. The results of the testing are 

shown in table 44. 

Table 44. Results of chloride content testing of cores from I–265 (1994). 

Acid-Soluble Chloride 

Content, percent by 

concrete weight 

Water-Soluble Chloride 

Content, percent by 

concrete weight Overlay 

Type 

Sample 

Number 0.5 to 1 

inch 

3 to 3.75 

inches 

0.5 to 1 

inch 

3 to 3.75 

inches 

S 2A 0.031 0.117 0.015 0.065 

S 5 < 0.007 0.018 - - 

S 6 - < 0.007 - - 

S 7 0.010 0.095 - - 

S 9 - 0.040 - - 

Southbound 

Travel 

SFC 

S GRND - 0.065 - - 

N 1 - 0.027 - - 

N 5 0.019 0.034 0.011 0.017 

N 7 0.039 0.034 0.018 0.018 

N 8 0.010 0.080 - - 

N GRND 3 0.016 - - - 

Northbound 

Travel 

LMC-III 

N X - 0.039 - - 
48 

All of the locations had moderate to low chloride concentrations at the level of the reinforcing 

bars. The water-soluble chlorides were considerably lower than the acid-soluble results. The 

approximate threshold for chloride-induced corrosion of black reinforcing steel is approximately 

0.025 percent by concrete weight, so only some of the locations in the deck appear to have 

sufficient chloride to support corrosion. In 1998, one core from each test section was analyzed 

for chloride. The chloride was measured at four depths as shown in table 45. 

Table 45. Results of chloride content testing of cores from I–265 (1998).

Location and Acid-Soluble Chloride Content, percent by weight of concrete 

Type Overlay 0.25 to 0.5 

inch 

0.625 to 1 

inch 

1.125 to 1.5 

inches 

3.75 to 4 

inches 

Southbound Travel 

SFC 0.110 0.045 0.100 0.021 

Northbound Travel 

LMC 0.077 0.047 0.151 0.076 

The chloride levels at the reinforcing bars are similar to those in 1994. Some chloride has 

penetrated into the near surface of the overlays and to a depth of 25 to 50 mm (0.5 to 1 inch). 

Elevated chloride levels are present at the 28 to 38 mm (1.125 to 1.5 inches) level likely due to 

chloride contamination in the original deck surface. 

SUMMARY OF I–265 OVER KY 22 (JEFFERSON COUNTY, KY) 

The SFC and LMC-III overlays were placed in June 1992. The SFC test section carries main line 

traffic while the LMC-III test section carries a shoulder and merge lane. The SFC overlay has 

developed progressive cracking with cracking being most severe in the wheelpaths. 

Delaminations have increased with time and 4.5 percent of the overlay was delaminated in 1998. 

The LMC-III overlay test area has much less cracking and few delaminations, 0.9 percent in 

1998, however, it does not handle main line traffic. 

The half-cell potential data had values more positive than –250 mV (noncorrosive) for 86 percent 

of the measurements on the SFC overlay and 98 percent of the measurements on the LMC 

overlay. These percentages did not change between 1994 and 1997. Local anodic locations were 

present for both overlays. The corrosion rates tended to be low with some areas being moderate 

to low. The bond of the overlays, away from delaminations, remained high over the test period. 

Chloride has penetrated into the surface of the overlays and some chloride was present in the 

near surface of the existing substrate concrete. The chloride content at the level of the reinforcing 

steel remains low to moderately low. 
49 

CHAPTER 6. U.S. 41 OVER KY 351, HENDERSON, KY 

INTRODUCTION 

This test site consists of twin three-span (48 m (159 ft)) parallel bridges located on U.S. 41 over 

Kentucky State Highway at milepost 12 on the Henderson City bypass route. The three spans are 

each 16 m (53 ft) long. The spans are of composite deck/girder construction. The bridges were 

constructed in 1959, and a low-slump concrete overlay was placed on the decks in the mid1970's. In 1992, an inspection by State forces indicated that the overlays were mapcracked and 

exhibiting considerable wear. The deck had also been patched numerous times and the patches 

were noted to be deteriorating. Because of the deck condition, the bridges were scheduled for 

overlay. A LMC-III overlay was applied to the northbound lanes, figure 23, and a SFC overlay 

was applied to the southbound lanes, figure 24. 

Figure 23. Photograph of northbound test section of U.S. 41 

(latex-modified concrete overlay). 
50 

Figure 24. Photograph of southbound test section of U.S. 41 

(silica fume concrete overlay). 

The concrete materials and proportions, as reported in the C-206 report, are as follows: materials 

selected for the LMC-III mix consisted of a Type III cement; an angular to rounded siliceous 

natural sand having specific gravity of 2.61 and an absorption of 1.00 percent; and a crushed 

limestone coarse aggregate having a maximum top size of 12 mm (0.5 inch) with a specific 

gravity of 2.71 and an absorption of 0.7 percent. The latex used was DPS Modifier A, a styrenebutadiene latex emulsion. 

A Type I cement was used in the SFC mix. Aggregates were from the same sources used for the 

LMC-III mix at this site. Admixtures included: (1) MB-SF silica fume (compacted powder 

form); (2) Micro-Air, a synthetic air-entraining agent; and (3) Rheobuild-1000, a Type F highrange water reducing admixture. The mixture proportions and plastic concrete characteristics, as 

reported in the C-206 report, are shown in table 46. 
51 

Table 46. U.S. 41 over KY 351 concrete proportions and characteristics.

Material LMC-III SFC 

Cement (lb/yd3) 658 (Type III) 658 (Type I) 

Fine Aggregate (lb/yd3) 1610 1366 

Coarse Aggregate (lb/yd3) 1260 1536 

Water (lb/yd3) 260 236 

Latex Modifier (gal/yd3) 24.5 - 

Silica Fume (lb/yd3) - 50 

HRWRA (oz/yd3) - 98 

AEA (oz/yd3) - 8 

W/C ratio 0.39 0.33 

Air content (percent) 6.0 5.6 

Slump (inches) 6.5 3.8 

Temperature (oF) 77 75 

Unit Weight (lb/ft3) 138.0 140.8 

Placement Date 8/13/92 7/8/92 

Placement Time 19:35 21:15 

Weather Conditions Clear Clear 

1 lb/yd3 = .347 kg/m31 1 oz/yd3 = .037 kg/m3

1 inch = 25.4 mm (o

F - 32/1.8) = oC 

1 gal/yd3 = 5 l/m3

 1 lb/ft3 = 16 kg/m3

The SFC was placed on the southbound structure on the night of July 8, 1992. The night 

placement was in compliance with State specifications. The SFC concrete was delivered in 

transit-mix trucks. The bonding grout was noted to be applied unevenly, and in some cases the 

mortar was brushed out of the concrete in lieu of a grout. Mr. Robbie Hecker of the Kentucky 

Transportation Cabinet told the contractor that on the first span, the bonding grout was spread 

too far ahead of the paver during placement. This resulted in its possible drying before the 

overlay concrete was placed. The placement of the second span proceeded normally. The 

concrete placed on the third span had a high slump of 190 to 200 mm (7.5 to 8.0 inches). This 

resulted in possible segregation, bleeding, and finishing problems with the concrete. After the 

overlay was placed, the surface was textured with a stiff-broom finish. The concrete was cured 

by covering with wet burlap and polyethylene immediately following the finishing operation. 

Soaker hoses were used to maintain the deck in a saturated condition for the full 72-hour curing 

period. The SFC overlay was opened to traffic on July 20, 1992, 12 days after casting. 

The LMC-III overlay was not placed on the northbound structure until August 13, 1992. The 

concrete was delivered using mobile concrete mixers. Similarly to the SFC overlay site, there 

was a nonuniform application of the bonding grout brushed out of the concrete. The surface was 

finished in the same manner as the SFC deck. The curing was also the same as for the SFC 

overlay, except that the moist curing was carried out for only 24 hours. The section was opened 

to traffic on August 18, five days after placement. 
52 

VISUAL INSPECTION 

The underside of the two bridges was inspected each year while the traffic control was being set 

up. The underside of the deck was in good condition except for rust, spalls, and leakage at the 

joints. The substructure was showing signs of deterioration, especially at the bent caps. The bent 

caps were cracked, spalled, and corrosion stained. Many of the cracks were part of full map 

patterns with associated efflorescence. Horizontal cracks were also noted in the pier caps. The 

bearing blocks in the abutments were cracked and spalled. 

Horizontal cracks in the bridge beams were seen in the exterior beams of both bridges near the 

abutments. The structures have six integrally cast concrete beams, with joints between the three 

simple spans. The beams do not sit on bearing pads, instead tie to integral diaphragms that are 

keyed into the pier caps. The piers of both structures were in moderate to poor condition, with 

large cracks, spalls, corrosion products, and efflorescence stains present. Some horizontal 

cracking, staining, and efflorescence was seen in the south abutment of the northbound structure. 

The underside of the deck of the northbound structure was mainly crack-free although some fine 

transverse cracking could be seen on the underside of the deck near the southern abutment where 

closer examination was possible. The underside of the deck of the southbound structure was in 

similar condition. 

Inspection of the deck surface of the northbound LMC structure indicated the performance of the 

three spans was quite different, with Spans 1 and 3 exhibiting heavy transverse and longitudinal 

cracking and Span 2 exhibiting hardly any cracking. Figure 25 shows typical cracking on the 

northbound deck. Over the last two years of the study the cracking became worse. Several cracks 

had lengthened or were becoming interconnected with other cracks. The surface of all three 

spans in the driving lane was heavily abraded compared to that of the passing lane. 

Figure 25. Photograph showing typical cracking found in the 

northbound deck of the U.S. 41 test section LMC. 
53 

Inspection of the deck of the southbound SFC structure revealed the three spans also performing 

differently. Span 1 was different than Spans 2 and 3 due to its many large and raveled cracks. 

Many of the cracks increased in length or joined nearby cracks over the five years of the study. 

In Spans 2 and 3, many of the newer cracks were longitudinal but a few transverse cracks also 

developed. Span 3 was more heavily cracked than Span 2. In the last year of the study, many of 

the cracks in the two spans that earlier were only visible after a rainstorm, were now plainly 

visible when the deck was dry. Figure 26 shows some typical cracking associated with the 

southbound test section. 

DELAMINATION SURVEY 

The delamination surveys were performed using a chain drag. The integrally cast beams made 

defining the edges of the delaminated areas difficult as the sound of the chains varied over the 

beams. Hammer tapping with a dry sand was also used to define the edges of the delaminated 

areas. The results of the delamination survey for all 5 years are shown in tables 47 and 48. The 

number and area of delaminations in each span is given because there are considerable 

differences between the different spans of each test section. 

The southbound test section SFC is performing well. No delaminations were found in any of the 

spans in 1994 or 1995 and the center span had no delaminations found in any year of the study. 

The total delaminated area of all three areas is 6.59 m2

 (71 ft2), 3.72 percent of the total area. The 

northbound LMC test section performed much worse than the southbound SFC section. All three 

spans of the northbound structure had delaminations in the first year of the study (1994). The 

center span is performing the best with only 4.46 m2

 (48 ft2) square meters or 7.55 percent of the 

area delaminated. The two end spans are performing much worse with 16.40 m2

 (176 ft2) (27.8 

percent) and 11.47 m2

 (123 ft2) (19.4 percent) of the surface area delaminated. 

Figure 26. Photograph showing typical cracking associated with the 

southbound test section of U.S. 41 SFC. 
54 

Table 47. Number and area of delaminations (U.S. 41 southbound SFC).

Year Span 

Number 

Number 

of Areas 

Total Area 

(m2

) 

Percent of 

Total Area 

1994 All 0 0.00 0.00 

1995 All 0 0.00 0.00 

1 

2 

3 

7 

0 

2 

0.70 

0.00 

0.14 

1.18 

0.00 

0.24 

1996 

Total 9 0.84 0.47 

1 

2 

3 

18 

0 

8 

1.67 

0.00 

0.60 

2.82 

0.00 

1.02 

1997 

Total 26 2.27 1.28 

1 

2 

3 

30 

0 

9 

4.92 

0.00 

1.67 

8.32 

0.00 

2.82 

1998 

Total 39 6.59 3.72 

Table 48. Number and area of delaminations (U.S. 41 northbound LMC).

Year Span 

Number 

Number 

of Areas 

Total Area 

(m2

) 

Percent of 

Total Area 

1 

2 

3 

2 

1 

3 

0.37 

0.18 

1.02 

0.63 

0.30 

1.72 

1994 

Total 6 1.57 0.88 

1 

2 

3 

14 

5 

19 

2.60 

0.46 

2.50 

4.40 

0.78 

4.23 

1995 

Total 38 5.56 3.14 

1 

2 

3 

21 

8 

28 

4.78 

0.88 

3.90 

8.09 

1.49 

6.60 

1996 

Total 57 9.56 5.39 

1 

2 

3 

27 

11 

31 

10.36 

1.53 

5.57 

17.53 

2.59 

9.42 

1997 

Total 69 17.46 9.85 

1 

2 

3 

19 

14 

32 

16.40 

4.46 

11.47 

27.75 

7.55 

19.41 

1998 

Total 65 32.33 18.24 

The number of delaminations increased each year on the southbound structure from 0 in 1994 to 

39 in 1998. On the northbound structure, the number of delaminations increased from 6 in 1994 
55 

to 69 in 1997 then decreased to 65 in 1998. This decrease was because several delaminated areas 

merged together to form larger delaminations. 

HALF-CELL POTENTIAL SURVEY 

A 0.6-m (2-ft) grid was marked out beginning at the approach end of the bridges. The 

longitudinal rows of points were numbered from 1 to 26 from the approach side to the leave side. 

The transverse rows were lettered A to F, beginning approximately at the paint stripe separating 

the travel lane from the passing lane. Each span was numbered independently. The half-cell 

potentials were measured at every point of the 

0.6 m (2 ft) grid spacing over both entire bridges. 

A summary of the half-cell potential measurements for the southbound travel lane SFC of the 

U.S. 41 test section in 1994 is shown in table 49. Span 1 had the most negative (corrosive) halfcell potentials of the three spans. The most negative measurement was –389 mV and the least 

negative was –71 mV. The average half-cell measurement for Span 1 was –201 mV compared to 

–28 mV for Span 2 and –84 mV for Span 3. Span 2 had 54 half-cell readings out of 189 that were 

positive. The most positive reading was +74 mV. For tabulation, the positive half-cell 

measurements were classified as 0 mV. Overall, the southbound SFC test section was in good 

condition in 1994. For Span 1, 76 percent of the half-cell readings were less negative than –250 

mV. This compares to 100 percent for Span 2 and 98.4 percent for Span 3. Overall, 91 percent of 

the measurements were less negative than –250 mV. A histogram of the distribution of half-cell 

measurements for the three spans in 1994 is shown in figure 27. Span 1 has clearly shifted more 

negative (corrosive) compared to the other two spans. 

Table 49. Cumulative frequency of half-cell potentials 

for U.S. 41, SFC (SB travel lane 1994). 

Potential Range Number of Observations 

(mV) Span 1 Span 2 Span 3 Total 

Cumulative

Percentage 

0 to –49* 0 140 53 193 34.0 

–50 to –99 9 39 81 129 56.8 

–100 to –149 32 5 35 72 61.6 

–150 to –199 67 4 13 84 84.3 

–200 to –249 35 1 4 40 91.4 

–250 to –299 27 0 3 30 96.6 

–300 to –349 15 0 0 15 99.3 

–350 to –399 4 0 0 4 100.0 

–400 to –449 0 0 0 0 100.0 

–450 to –499 0 0 0 0 100.0 

–500 to –549 0 0 0 0 100.0 

–550 to –599 0 0 0 0 100.0 

–600 to –649 0 0 0 0 100.0 

–650 to –699 0 0 0 0 100.0 

* Note. Any positive reading is counted as 0 for tabulation. 
56 

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

0 to -

49

-50 to -

99

-100 to

-149

-150 to

-199

-200 to

-249

-250 to

-299

-300 to

-349

-350 to

-399

-400 to

-449

-450 to

-499

-500 to

-549

-550 to

-599

-600 to

-649

-650 to

-699

Potential Range (mV)

Number of Observations

US41 SB Span1

US41 SB Span2

US41 SB Span3

Figure 27. Histogram of half-cell potential readings 

for U.S. 41 southbound in 1994 SFC. 

A summary of the half-cell measurements for the southbound structure in 1997 is shown in table 

50. The half-cell measurements were more negative for all three spans in 1997 than in 1994. 

Span 1 had an average reading of 258 mV with a maximum negative reading of −435 mV and a 

minimum negative reading of −134 mV. Span 2 had an average of −108 mV with a maximum of 

−305 mV and a minimum of −19 mV. Span 3 had an average reading of −142 mV with a 

maximum of −383 mV and a minimum of −16 mV. The average half-cell reading for Span 1 was 

above the 250 mV threshold for corrosion to occur. A histogram comparing the distribution of 

half-cell readings for the southbound section in 1997 is shown in figure 28. A histogram 

comparing the distribution of half-cell measurements for the entire southbound test section in 

1994 and 1997 is shown in figure 29. The curve for 1997 is shifted significantly to the right 

which indicates a probability of increased corrosion activity, especially in Span 1. 

A summary of the half-cell potential readings for the northbound LMC spans in 1994 is shown in 

table 51. Span 3 has higher magnitude half-cell readings than the other two spans. The average 

half-cell potential reading for Span 3 was −281 mV, compared to −235 mV for Span 1, and −171 

mV for Span 2. The average for Span 3 was over the threshold limit of 250 mV needed for 

corrosion. The maximum half-cell potential for Span 3 is −499 mV, for Span 1 is −425 mV, and 

for Span 2 is −320 mV. All three spans had half-cell potentials indicative of corrosion occurring 

in the deck. A histogram of the distribution of half-cell potentials for the northbound LMC spans 

in 1994 is shown in figure 30. Span 3 had the most negative potentials (most corrosive). 

A summary of the half-cell potentials for the northbound LMC spans in 1997 is shown in table 

52. Span 3 again has higher negative half-cell potentials than the other two spans. The average 

half-cell potential for Span 3 is −299 mV, compared to −249 mV for Span 1, and −193 mV for 
57 

Span 2. The average potential for Span 3 is over the threshold limit of 250 mV and the average 

for Span 1 is right at the threshold limit. The maximum half-cell potential for Span 3 is −652 

mV, for Span 1 is −496 mV, and for Span 2 is −473 mV. 

Table 50. Cumulative frequency of half-cell potentials 

for U.S. 41, SFC (SB travel lane 1997). 

Potential Range Number of Observations 

(mV) Span 1 Span 2 Span 3 Total 

Cumulative

Percentage 

0 to –49* 0 8 3 11 1.9 

–50 to –99 0 101 39 140 26.6 

–100 to –149 4 53 82 139 51.4 

–150 to –199 45 15 41 101 69.0 

–200 to –249 43 5 8 56 78.8 

–250 to –299 47 6 6 59 89.2 

–300 to –349 25 1 6 32 94.9 

–350 to –399 18 0 4 22 98.8 

–400 to –449 7 0 0 7 100.0 

–450 to –499 0 0 0 0 100.0 

–500 to –549 0 0 0 0 100.0 

–550 to –599 0 0 0 0 100.0 

–600 to –649 0 0 0 0 100.0 

–650 to –699 0 0 0 0 100.0 

* Note. Any positive reading is counted as 0 for tabulation. 

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

Potential Range (mV)

Number of Observations

US41 SB Span1

US41 SB Span2

US41 SB Span3

0 

to

-49

-50 

to

-99

-100 

to

-149

-150 

to

-199

-200 

to

249

-250 

to

-299

-300 

to

-349

-350 

to

-399

-400 

to

-449

-450 

to

-499

-500 

to

-549

-550 

to

-599

-600 

to

-649

-650 

to

-699

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

Potential Range (mV)

Number of Observations

US41 SB Span1

US41 SB Span2

US41 SB Span3

0 

to

-49

-50 

to

-99

-100 

to

-149

-150 

to

-199

-200 

to

249

-250 

to

-299

-300 

to

-349

-350 

to

-399

-400 

to

-449

-450 

to

-499

-500 

to

-549

-550 

to

-599

-600 

to

-649

-650 

to

-699

Figure 28. Histogram of half-cell potential readings for 

U.S. 41 southbound in 1997 SFC. 
58 

0

20

40

60

80

100

120

140

160

180

200

Number of 

Observations

US41 SB 1994

US41 SB 1997

0

to

-49

-50 

to

-99

-100 

to

-149

-150 

to

-199

-200 

to

249

-250 

to

-299

-300 

to

-349

-350 

to

-399

-400 

to

-449

-450 

to

-499

-500 

to

-549

-550 

to

-599

-600 

to

-649

-650 

to

-699

Potential 

Range (mV)

0

20

40

60

80

100

120

140

160

180

200

Number of 

Observations

US41 SB 1994

US41 SB 1997

0

to

-49

-50 

to

-99

-100 

to

-149

-150 

to

-199

-200 

to

249

-250 

to

-299

-300 

to

-349

-350 

to

-399

-400 

to

-449

-450 

to

-499

-500 

to

-549

-550 

to

-599

-600 

to

-649

-650 

to

-699

Potential 

Range (mV)

Figure 29. Histogram of half-cell potential readings for 

U.S. 41 southbound SFC in 1994 and 1997. 

Table 51 Cumulative frequency of half-cell potentials 

for U.S. 41, LMC (NB travel lane 1994). 

Potential Range Number of Observations 

(mV) Span 1 Span 2 Span 3 Total 

Cumulative

Percentage 

0 to –49* 0 0 0 0 0 

–50 to –99 0 6 0 6 1.0 

–100 to –149 7 55 0 62 12.0 

–150 to –199 54 78 12 144 37.4 

–200 to –249 62 43 63 168 67.0 

–250 to –299 37 5 57 99 84.5 

–300 to –349 17 2 21 40 91.5 

–350 to –399 11 0 19 30 96.8 

–400 to –449 1 0 11 12 98.9 

–450 to –499 0 0 6 6 100.0 

–500 to –549 0 0 0 0 100.0 

–550 to –599 0 0 0 0 100.0 

–600 to –649 0 0 0 0 100.0 

–650 to –699 0 0 0 0 100.0 

*Note. Any positive reading is counted as 0 for tabulation. 
59 

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

0 to -

49

-50 to -

99

-100 to

-149

-150 to

-199

-200 to

-249

-250 to

-299

-300 to

-349

-350 to

-399

-400 to

-449

-450 to

-499

-500 to

-549

-550 to

-599

-600 to

-649

-650 to

-699

Potential Range (mV)

Number of Observations

US41 NB Span1

US41 NB Span2

US41 NB Span3

Figure 30. Histogram of half-cell potential readings for 

U.S. 41 northbound LMC in 1994. 

Table 52. Cumulative frequency of half-cell potentials 

for U.S. 41, LMC (NB travel lane 1997). 

Potential Range Number of Observations 

(mV) Span 1 Span 2 Span 3 Total 

Cumulative

Percentage 

0 to –49* 0 0 0 0 0 

–50 to –99 0 5 0 5 0.9 

–100 to –149 18 33 0 51 9.9 

–150 to –199 44 71 18 133 33.3 

–200 to –249 49 64 47 160 61.6 

–250 to –299 33 9 47 89 77.2 

–300 to –349 14 4 38 56 87.1 

–350 to –399 20 1 10 31 92.6 

–400 to –449 5 1 14 20 96.1 

–450 to –499 6 1 8 15 98.8 

–500 to –549 0 0 5 5 99.6 

–550 to –599 0 0 1 1 99.8 

–600 to –649 0 0 0 0 99.8 

–650 to –699 0 0 1 1 100.0 

* Note. Any positive reading is counted as 0 for tabulation. 

All three spans have a considerable number of half-cell readings above the −250 mV threshold 

for corrosion. A histogram of the half-cell potential readings for the northbound spans in 1997 is 
60 

shown in figure 31. A histogram of the half-cell potential readings for the entire northbound 

structure in 1994 and 1997 is shown in figure 32. The distribution appears similar but the curve 

for 1997 is shifted to the right, indicating a probability of increased corrosion. 

A cumulative frequency diagram for both test sections of U.S. 41 is shown in figure 33. The 

figure shows the shift to the right for both test sections. The shift in the curve for the southbound 

SFC spans is much greater than that for the northbound spans LMC. However, the northbound 

spans LMC had more negative values both initially and at the end of the study than the 

southbound SFC spans. An equipotential map of the half-cell readings for the southbound spans 

SFC of U.S. 41 is shown in figure 34. The figure for Span 1 indicates there is corrosion 

occurring along the edge between the travel and passing lane and at the two ends of the span. 

The figures for Span 2 and Span 3 indicate corrosion is occurring in isolated areas and also at the 

ends of the spans. An equipotential map for the half-cell readings for the northbound spans LMC 

is shown in figure 35. The maps for Span 1 and Span 3 indicate corrosion occurring over much 

of both spans and especially along the edge between the travel and passing lanes. The map for 

Span 2 indicates isolated areas of corrosion but most areas are at the ends of the span. 

US41 NB Span1

US41 NB Span2

US41 NB Span3

0

to

-49

-50 

to

-99

-100 

to

-149

-150 

to

-199

-200 

to

249

-250 

to

-299

-300 

to

-349

-350 

to

-399

-400 

to

-449

-450 

to

-499

-500 

to

-549

-550 

to

-599

-600 

to

-649

-650 

to

-699

Potential 

Range (mV)

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

Number of Observations

US41 NB Span1

US41 NB Span2

US41 NB Span3

0

to

-49

-50 

to

-99

-100 

to

-149

-150 

to

-199

-200 

to

249

-250 

to

-299

-300 

to

-349

-350 

to

-399

-400 

to

-449

-450 

to

-499

-500 

to

-549

-550 

to

-599

-600 

to

-649

-650 

to

-699

Potential 

Range (mV)

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

Number of Observations

Figure 31. Histogram of half-cell potential readings 

for U.S. 41 northbound LMC in 1997. 
61 

0

20

40

60

80

100

120

140

160

180

200

0 to -

49

-50 to -

99

-100 to

-149

-150 to

-199

-200 to

-249

-250 to

-299

-300 to

-349

-350 to

-399

-400 to

-449

-450 to

-499

-500 to

-549

-550 to

-599

-600 to

-649

-650 to

-699

Potential Range (mV)

US41 NB 1994

US41 NB 1997

Figure 32. Histogram of half-cell potential readings 

for U.S. 41 northbound spans in 1994 and 1997. 

0

20

40

60

80

100

120

0 to -49 -50 to -

99

-100 to

-149

-150 to

-199

-200 to

-249

-250 to

-299

-300 to

-349

-350 to

-399

-400 to

-449

-450 to

-499

-500 to

-549

-550 to

-599

-600 to

-649

-650 to

-699

Potential Range (mV)

Cumulative Percent Observations

US-41 SB94

US-41 SB97

US-41 NB94

US-41 NB97

Figure 33. Cumulative frequency diagram 

for U.S. 41 (NB and SB) for years 1994 and 1997. 
62 

Figure 34. Equipotential maps of half-cell potentials for the three 

spans of the southbound test section of U.S. 41 in 1997 SFC. 

Figure 35. Equipotential maps of half-cell potentials for the three spans 

of the northbound test section of U.S. 41 in 1997 LMC. 
63 

POLARIZATION RESISTANCE (PR) TESTING 

In 1994, the PR tests were performed using an EG&G PARC model 273A potentiostat under 

computer control. The PR scans were performed using IR compensation at each step to 

determine and correct for the potential drop due to the concrete resistance. The PR scans started 

at a potential 10 mV below the equilibrium “rest” potential of the area under test and continued 

to a potential 10 mV above the equilibrium potential. Following the testing, the polarization 

resistances were determined by fitting a line to the recorded potential versus current plots. Using 

the polarization resistances, the corrosion rates were estimated by assuming Tafel slopes of 0.12, 

assuming that the upper bars were size No. 4, and assuming that the upper half of the reinforcing 

bar directly under the counter electrode was polarized during the testing. Simulated 3LP tests were 

also performed at each of the test locations. 

Following the half-cell potential testing, PR tests were performed at six locations on the 

southbound SFC spans. Two test locations were located on each span. The test locations on Span 

2 had relatively low potentials while the locations on Spans 1 and 3 had moderate potentials. The 

PR and 3LP testing was generally more successful on the southbound SFC structure than on the 

northbound LMC structure. The results of the testing are summarized in table 53. On the 

southbound SFC structure, the corrosion rate measurements were not in general agreement with 

the half-cell potential measurements. The highest corrosion rates did not necessarily correspond 

to the most negative potentials. The agreement between the corrosion rates estimated using the 

two techniques was encouraging, as all of the estimates were within a factor of 2 or 3, which 

would generally be considered good using these techniques. Polarization resistance tests were 

also performed at six locations on the northbound LMC bridge. Two test locations were selected 

from each span. Only two of the six locations were successfully tested using the 3LP technique. 

The results of the testing are summarized in table 54. 

Table 53. Corrosion rate testing on U.S. 41 southbound, SFC (1994).

Equilibrium PR Testing 3LP Testing Grid 

Location Potential 

(mV)* Rp (ohm) Icorr

(mA/cm2

) Rp (ohm) Icorr

(mA/cm2

) 

Span 1, B4 –272 397 0.054 2571 0.008 

Span 1, F4 –167 594 0.037 2449 0.009 

Span 2, E5 –46 375 0.057 1587 0.013 

Span 2, D4 –74 - - 297 0.073 

Span 3, D11 –130 732 0.03 489 0.044 

Span 3, E11 –146 200 0.108 243 0.089 

* Measured using a Cu/CuSO4 reference electrode. 
64 

Table 54. Corrosion rate testing on U.S. 41 northbound.

PR Testing 3LP Testing Grid 

Location 

Equilibrium 

Potential (mV)* Rp (ohm) Icorr

(mA/cm2

) Rp (ohm) Icorr

(mA/cm2

) 

Span 1, C22 –251 475 0.046 - - 

Span 1, E22 –160 247 0.087 127 0.170 

Span 2, C30 –320 26 0.834 - - 

Span 2, A30 –205 - - - - 

Span 3, D48 –315 400 0.054 145 0.150 

Span 3, B48 –343 449 0.048 - - 

* Measured using a Cu/CuSO4 reference electrode. 

The corrosion rate measurements were not in general agreement with the half-cell potential 

measurements, as the most negative potentials were associated with some of the lowest corrosion 

rates. The location with the least-negative potential, point A30, could not be successfully 

measured using either the polarization resistance or the 3LP technique. The very high corrosion 

rate observed at point C30 does not agree with the observed condition of the bridge. 

In 1997, linear polarization measurements were performed at six locations on each structure. On 

each structure three locations were selected on Span 1, one was chosen on Span 2 and two were 

chosen on Span 3. More locations were chosen on Span 1 of each bridge because the half-cell 

potentials were generally higher. The testing was performed using a James Instruments GECOR 

6 Polarization Resistance Tester. The results of the testing for both the southbound travel lane 

SFC and the northbound travel lane LMC-III are shown in table 55. There is considerable scatter 

in the corrosion rate measurements for both sections in 1997 but the corrosion rate measurements 

within a span generally coincide with the half-cell potentials within that span. Corrosion rates 

varied from low to moderately high on the SFC overlay and from low to moderately low on the 

LMC-III overlay. 
65 

Table 55. Results of polarization resistance testing at U.S. 41 (1997). 

Direction Span Grid 

Location 

Half-Cell 

Potential 

(mV) 

Measured 

Corrosion 

Rate 

(μA/cm2

) 

Notes 

1 A40 –348 0.147 More negative potential 

1 EF40 –218 0.930 Not confined, moderate 

potential 

1 C20 –161 2.368 Not confined 

2 C50 –134 0.056 Moderate potential 

3 A10 –154 0.042 Moderate potential 

Southbound 

Travel SFC 

3 EF10 –193 0.069 Moderate potential 

1 E17 –362 0.079 Relatively high potential 

1 BC9 –197 0.022 Two locations at same grid 

point, 

1 BC9 –197 0.022 Different concrete 

2 G50 –291 0.146 Moderately high potential 

3 DE20 –162 0.004 Low potential 

Northbound 

Travel 

LMC-III 

3 G29 –293 0.039 High potential 

CORE TESTING 

The cores were inspected to determine the overlay thickness and the cover over the uppermost 

reinforcing bars. The thickness of the silica fume concrete overlay on the southbound structure 

ranged from 25 to 100 mm (1 to 4 inches) and the depth to the top mat of reinforcing steel ranged 

from 65 to 90 mm (2.5 to 3.5 inches). The thickness of the latex-modified concrete overlay on 

the northbound structure ranged from 0.75 to 3.25 inches (19 to 83 mm) and the depth to steel 

ranged from 65 to 95 mm (2.5 to 3.75 inches). In 1994, three cores from each structure were 

tested for bond strength. The results are shown in table 56. The test results for northbound cores 

LMC are higher than the cores from the southbound structure SFC. The cores from the 

northbound LMC structure have a higher percentage of the failure occurring in the base concrete. 

Generally the bond strength of all the cores is quite high. This indicates both overlays were well 

bonded to the base concrete in 1994. 

Table 56. Shear bond testing of cores from U.S. 41 (1994). 

Failure Location (Percent of Failure Area) 

Overlay Type Core 

ID 

Bond 

Strength 

MPa (psi) Overlay Bond Line Substrate 

2 3.9 (574) 50 0 50 

4 2.6 (384) 25 25 50 Southbound 

Travel SFC 5 3.9 (565) 40 10 50 

3 4.9 (716) 40 0 60 

5 4.5 (649) 0 5 95 Northbound 

Travel LMC 7 4.4 (645) 20 0 80 
66 

In 1997, four cores from the southbound travel lane and three cores from the northbound travel 

lane were tested in shear. The results are shown in table 57. The average bond strength of the 

cores from the northbound travel lane LMC is slightly higher than that of the cores from the 

southbound travel lane SFC but the bond strength of all the cores is very good. This indicates 

that away from delaminations both overlays were still well bonded to the base concrete in 1997. 

Table 57. Core Testing Results from U.S. 41 Henderson, KY (1997). 

Location and Overlay Type Core ID Exposure 

Condition 

Bond Strength 

MPa (psi) 

4 Wheel path 3.0 (430) 

5 Wheel path 3.6 (530) 

6 Wheel path 4.0 (580) 

7 Wheel path 4.7 (680) 

Southbound Travel SFC 

Average 3.8 (555) 

2 Wheel path 5.2 (750) 

3 Centerline 4.5 (650) 

10 Wheel path 3.4 (490) 

Northbound Travel LMC-III 

Average 4.3 (630) 

CHLORIDE ANALYSIS 

Following the visual examination of the cores, chloride analyses were performed on six cores 

taken from each overlay in 1994. The samples were taken from the 12- to 25-mm (0.5- to 1-inch) 

depth surface region and from the 70- to 89-mm (2.75- to 3.5-inch) depth where the reinforcing 

bars would have been located. All of the slices were then pulverized and analyzed to determine 

their acid-soluble chloride content. In addition to the acid-soluble chloride analyses, watersoluble chloride analyses were performed on selected samples. The results of the testing are 

shown in table 58. The levels of chloride in the overlays are generally very low and the levels in 

the northbound LMC overlay may be slightly higher than in the southbound SFC overlay. 

Table 58. Results of chloride content testing of cores from U.S. 41 (1994).

Acid-Soluble Chloride Content, 

percent by concrete weight 

Water-Soluble Chloride 

Content, percent by concrete 

weight 

Overlay 

Location 

and Type 

Sample 

Number 

0.5 to 1 inch 2.75 to 3.5 inches 0.5 to 1 inch 2.75 to 3.5 

inches 

S1 < 0.007 0.025 < 0.007 0.013 

S5 0.007 < 0.007 - - 

S6 - < 0.007 - < 0.007 

S7 < 0.007 < 0.007 - - 

S8 0.014 0.012 - - 

Southbound 

Silica Fume 

S9 - < 0.007 - - 

N4 - 0.061 - - 

N5 - 0.045 - - 

N6 0.039 0.008 - - 

N7 < 0.007 0.037 - - 

N8 0.010 0.017 - - 

Northbound 

LMC-III 

N9 - 0.017 - 0.011 
67 

All of the locations had low chloride concentrations at the level of the reinforcing bars, except 

for samples N 4 and N 5. The approximate threshold for chloride-induced corrosion of black 

reinforcing steel is approximately 0.025 percent by concrete weight, so most of the locations in 

the deck do not appear to have sufficient chloride to support corrosion. 

In 1998, chloride water-soluble chloride contents were measured in five locations in the 

southbound SFC overlay and six locations in the northbound LMC overlay. The results are 

shown in table 59. The chloride levels down to a 25-mm (1-inch) depth in 1998 are elevated in 

the northbound LMC structure where many of the locations now have chloride levels above the 

0.025 percent threshold. The acid-soluble chloride content was also measured on one core from 

each structure. The results are shown in table 60. The chloride level generally decreases with 

depth. 

Table 59. Results of water-soluble chloride content testing 

of cores from U.S. 41 (1998).

Water-Soluble Chloride Content, percent by weight of concrete Location and 

Overlay Type 0.25 to 0.5 

inch 

0.625 to 1 

inch 

1.125 to 1.5 

inches 

2.75 to 3.25 

inches 

0.005 0.004 < 0.004 0.009 

- < 0.004 - - 

- 0.004 - - 

0.118 0.017 0.018 0.020 

Southbound 

SFC 

- 0.012 - - 

0.139 0.096 0.060 0.044 

- 0.031 - - 

0.116 0.059 0.030 0.024 

- 0.077 - - 

0.041 0.012 < 0.007 0.011 

Northbound 

LMC 

- < 0.007 - - 

Table 60. Results of acid-soluble chloride 

content testing of cores from U.S. 41 (1998). 

Acid-Soluble Chloride Content, percent by weight of concrete Location and 

Overlay Type 0.25 to 0.5 

inch 

0.625 to 1 

inch 

1.125 to 1.5 

inches 

3.75 to 4 

inches 

Southbound 

SFC 0.048 0.010 0.035 < 0.007 

Northbound 

LMC 0.070 0.010 < 0.007 < 0.007 

SUMMARY OF U.S. 41 TEST (HENDERSON, KY) 

The SFC and LMC-III overlays were placed in July and August 1992, respectively. Concern on 

the application of the bonding agent on Span 1 of the SFC and on the LMC-III overlays was 

expressed by State inspectors. Span 1 of the SFC overlay developed many large cracks. Spans 1 
68 

and 3 of the LMC-III overlay exhibited heavy transverse and longitudinal cracks while Span 2 

had little cracking. Cracking generally increased with time. Delamination of the various spans 

within each test section, varied, with more delamination occurring in the end spans and less 

occurring in the center spans. The center span of the SFC overlay had no delaminations during 

the 5-year study. The average percent surface area that was delaminated was 3.7 percent for the 

SFC overlay and 18.2 percent for the LMC overlay. 

Half-cell potentials also varied with span. Span 1 of the SFC overlay and Span 3 of the LMC 

overlay had more negative potentials than the other spans. However, the potentials were typically 

low to moderate. Table 61 summarizes the potential data. 

Table 61. Potentials more positive than 

–250mV (Percent of measurements). 

Year NB (SFC) SB (LMC-III) 

1994 91.4 67.0 

1997 78.8 61.6 

The potentials shifted slightly more negative (corrosive) over the 5-year study. Local anodic 

areas were identified especially near joints and between lanes. Corrosion rates varied from low to 

moderate on both structures. Bond strengths away from delaminated areas remained high 

throughout the study. Chlorides have ingressed into the surface of the LMC-III overlay and into 

the SFC overlay to a lesser degree. The chloride at the level of reinforcing remains generally 

low. 
69 

CHAPTER 7. PROJECT SUMMARY 

Evaluation and comparison of SFC and LMC-III overlays were performed at a total of four 

locations. The test sites were in Ohio and Kentucky. Each location included SFC and LMC-III 

overlays on opposite directions of a bridge structure. All overlays were installed in 1992. This 

study evaluated the overlays each year between 1994 and 1998. Table 62 summarizes the test 

data and observations for all test sites. All overlays had high initial bond strengths, and the bond 

strengths remained high over the study period when tested away from delaminations. The 

overlays were generally rated as good condition in 1998, after 6 years of service. However, both 

overlays at the U.S. 41 Henderson, KY site were rated as fair due to extensive cracking. 

Cracking was found in portions of the overlays at each site. Most of the cracking increased with 

time. However, some spans of each type were crack-free in 1998. 

The percent delamination varied with test site. The U.S. 52 test site in Ohio had the least amount 

of delamination (less than 1 percent). The LMC-III overlay at U.S. 41 KY had the highest 

amount of delamination in 1989 with 18.2 percent. At I–270 in Ohio, both overlays had 

moderately high levels of delamination, about 7 percent. 

The bridge at I–270 OH had the highest chloride in the existing deck and corrosion of the steel 

was likely before the overlays were placed. A high probability of corrosion was measured over 

most of the two I–270 decks in 1994. The potentials had shifted more positive in 1997 indicating 

that corrosion may be slowing slightly, with an additional 10 percent of both decks becoming 

more positive than –250 mV CuCuSo4 half-cell potential. U.S. 41 KY, NB LMC-III may have 

had sufficient chloride in the original deck to initiate corrosion and had moderately high negative 

potentials in about one third of the deck (1994). The potentials of both overlays at this site have 

shifted more negative (corrosive) between 1994 and 1997. The remaining two sites, I–265 KY 

and U.S. 52 OH, had mostly positive potentials in 1994 and they did not shift significantly in 

1997. 

By 1998, the average (acid-soluble) chloride in the SFC overlays was 0.10 percent at 9.5 mm 

(0.375 inch) and 0.04 percent at 20.6 mm (0.8125 inch) depth. The LMC-III overlays were 

similar but slightly higher at 0.13 percent at 9.5 mm (0.375 inch) and 0.08 percent at 20.6 mm 

(0.8125 inch). 

Good performance can be achieved from both SFC and LMC-III overlays. However, the service 

life of the overlays tends to vary based on the site location. While most of the overlays continue 

to provide good service after 6 years, the SFC and LMC-III overlays on U.S. 41 in Henderson, 

KY, show significant distress in the form of cracking and delamination. Significant repairs are 

needed for these two overlays. Generally, cracking and delamination of the overlays tend to 

increase with time. All overlays should be inspected bi-annually for cracking and delamination. 

Routine maintenance including crack and delamination repairs should be considered to extend 

the service life of the SFC and LMC-III overlays. 
70 

Table 62. Summary of all test sites. 

Potentials More Positive 

Than –250 mV 

Location Type 

General 

Condition 

(1998) 

Cracking 

Percent 

Delamination 

1998 

(m2) 1994 1997 Difference 

Chlorides 

Exceed 

Threshold Prior 

to Overlay ? 

(water-soluble) 0.25 

I–270 NB, OH SFC Good-Fair Yes 6.60 14.2 24.1 + 9.9 Yes I–270 SB, OH LMC-III Good-Fair Yes 7.00 1.7 13.1 + 11.4 Yes U.S. 52 WB-P, OH SFC Good Yes-Minor 0.87 - 96.8 − No U.S. 52 EB, WB-T, OH LMC-III Good Yes 0.14 98.8 97.3 −1.5 No I–265 SB, KY SFC Good-Fair Yes 4.50 85.6 86.5 + 0.9 Maybe I–265 NB, KY LMC-III Good Yes-Minor 0.90 98.2 98.4 + 0.2 Maybe U.S. 41 SB, KY SFC Fair Yes 3.70 91.4 78.8 −12.6 No U.S. 41 NB, KY LMC-III Fair Yes 18.20 67.0 61.6 − 5.4 No-Maybe 

Average SFC - - 3.90 63.7 71.5 + 7.8 - Average LMC-III - - 6.50 66.4 67.6 + 1.2 - 

* Average of acid- and water-soluble data.
Recycled

Recyclable HRDI-13/08-06(WEB)E