FHWA Publication No.: FHWA-HRT-22-087

FHWA Contacts: 

Benjamin Graybeal, Research Structural Engineer, HRDI-40, benjamin.graybeal@dot.gov 

Zachary Haber, Research Structural Engineer, HRDI-40, zachary.haber@dot.gov

TECHNIQUES TO INHIBIT CORROSION IN BRIDGE DECK 

REINFORCEMENT PRIOR TO OVERLAY INSTALLATION

TABLE OF CONTENTS

OBJECTIVE 1

INTRODUCTION 1

EXPERIMENTAL DETAILS 3

TEST RESULTS AND DISCUSSION 7

CONCLUSIONS 10

RECOMMENDATIONS 10

REFERENCES 10

Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

https://highways.dot.gov/research

TECHNOTE

Authors:

Robert Spragg, Concrete Materials Engineer, 

ORCID 0000-0001-9205-1486

Zachary Haber, Research Structural Engineer, 

ORCID 0000-0002-4471-2830

Benjamin Graybeal, Research Structural Engineer, 

ORCID 0000-0002-3694-1369

Naveen Saladi, Concrete Structural Engineer, 

ORCID 0000-0002-5240-4416

Igor De la Varga, Concrete Materials Engineer, 

ORCID 0000-0003-4374-212X

OBJECTIVE

Corrosion of steel reinforcement is one of the primary 

contributing factors to bridge deck deterioration. 

Depending on its severity, different corrosion-inhibiting 

strategies can be used to increase the service life of a 

bridge deck. One strategy is to apply a bridge deck 

overlay. To date, a number of different overlay solutions 

are commonly deployed, including concrete-based and 

polymer-based systems. Additionally, in recent years, 

bridge owners have become increasingly interested 

in ultra-high performance concrete (UHPC) overlays. 

Another strategy commonly used in conjunction with 

overlays is to apply corrosion-inhibiting chemicals 

and sealers to reduce the ingress of deleterious ions. 

The primary objective of this document is to explore a 

series of techniques to inhibit the corrosion of existing 

reinforcement in conventional concrete bridge decks 

prior to installing an overlay, with an emphasis on 

UHPC overlays. The secondary objective is to assess 

the bond strength between the overlay and the 

concrete substrate in the presence of these different 

corrosion-inhibiting techniques.

INTRODUCTION 

Background

Deterioration of bridge decks across the United States 

can largely be attributed to the synergistic exposure to 

aggressive environmental conditions, deicing operations, 

and repeated traffic loading. The result of these 

actions can range widely and are highly dependent 

on numerous factors described in the literature 

(Ellingwood 2005). The deterioration mechanism most 

relevant to this document is corrosion of the bridge 
deck’s steel reinforcement. Corrosion of reinforcing steel 

causes the bars to lose their cross-sectional area, and 

the formation of iron oxide is a major contributing factor 

to the delamination and spalling of cover concrete, both 

of which result in reduced deck capacity (Kayser and 

Nowak 1989). Preservation or maintenance actions are 

typically required as the delamination and spalling of 

cover concrete become more widespread, causing the 

deck’s condition rating to decline. These actions might 

take the form of localized removal and patching of 

concrete or could require a more thorough approach, 

such as a bridge deck overlay.

Bridge deck overlays are a common bridge deck 

preservation strategy. They can be used to maintain 

or extend service life and upgrade a deck’s condition 

rating (Krauss, Lawler, and Steiner 2009). Common 

overlay solutions include high-density or microsilica 

concretes, high performance concretes, latex-modified 

concretes (LMC), and asphalt with waterproofing 

membranes. Several different polymer-based solutions 

are also available on the market. Recently, U.S. interest 

in the use of UHPC overlays has grown due to positive 

experiences reported from Europe (Brühwiler and 

Denarie 2013). Presently, 17 bridges in the United 

States employ UHPC overlays (FHWA 2021). Some 

of these bridges are long-span signature structures 

(FHWA 2021). Graybeal and Haber (2018) reported 

additional information on UHPC overlays for bridge 

decks in the United States.

Regardless of the overlay solution selected, the 

following question must be addressed: What action 

should be taken if there is evidence or a high probability 

that reinforcement corrosion is occurring? The common 

approach is to try to slow down or inhibit the corrosion 

process. The corrosion protection strategies for steel 

reinforcing bars embedded in concrete include 

corrosion inhibitors, surface protection systems, and 

sealers. Corrosion inhibitors are substances that, 

when added in small quantities to the concrete in an 

aggressive environment, reduce the corrosion rate 

of a particular metal in that environment. Sealers are 

used to reduce the ingress of deleterious ions, moisture, 

and oxygen. 

This TechNote investigates the use of corrosion 

inhibitors and sealers in conjunction with the application 

of bridge deck overlays to inhibit ongoing corrosion 

of steel reinforcement on an in service bridge deck. 

The laboratory investigation presents corrosion 

rate measurements to assess the corrosion activity 

in reinforced concrete slab specimens designed 

to simulate an in service bridge deck. Prior to the 

application of either an LMC or UHPC overlay, different 

sealers and/or corrosion-inhibiting chemicals were 

applied to the concrete substrate. Specimens were 

subjected to a 3-percent sodium chloride solution 

while corrosion rate measurements were taken. After 

110 weeks of exposure, the overlay-to-concrete bond 

performance was assessed to investigate the effect of 

each of the corrosion-inhibiting techniques.

Previous Research

This section presents a summary of several studies 

that have been conducted on the application and 

effectiveness of corrosion inhibitors and sealers on 

concrete bridge decks.

Corrosion inhibitors can be applied before or after the 

placement of concrete. Research has demonstrated that 

applying corrosion inhibitors at the time of concrete 

placement is more effective than installing inhibitors at 

a later stage (El-Hacha, Cook, and Rizkalla 2011). 

El Hacha, Cook, and Rizkalla (2011) observed in 

their study that the corrosion inhibitors delayed the 

corrosion process and were more effective at lower 

levels of chloride contamination. Sealers are applied 

to the surface of the concrete deck after the placement 

and adequate curing of concrete or after many years 

of service. The application of protective sealers prior 

to chloride contamination has been found to prevent 

corrosion initiation, but sealers have been shown to be 

less effective in cases where there is ongoing corrosion 

(Tabatabai, Pritzl, and Ghorbanpoor 2009). In some 

cases, the penetration depth of the sealer has been 

found to be an additional factor that influences sealer 

performance. Pincheira and Dorshorst (2005) reported 

that sealers with greater penetration depth resulted 

in better protection against chloride ingress. Other 

studies have shown no correlation between chloride 

penetration and the depth of sealant penetration 

(Basheer, Cleveland, and Long 1998).

Information about the long-term effectiveness of sealers 

and corrosion inhibitors is limited. Pritzl et al. (2015) 

assessed the long-term performance of sealers and 

corrosion inhibitors by measuring chloride profiles in 

multiple bridge decks in Wisconsin after 12 to 16 years 

of service. Results from that study indicated that chloride 

profiles obtained from bridge decks treated with sealers 

at the time of construction were similar to those obtained 

from untreated decks. Pritzl et al. (2015) also found that 

surface chloride penetration was significantly reduced 

when sealers were reapplied periodically. In the 

Pritzl et al. (2015) study, some sealers were reapplied 

every 4 years. The effect of corrosion inhibitors on 

the diffusion coefficients was greatly affected by the 

permeability of the concrete. The diffusion coefficients 

2
3

of low permeability concrete were not significantly 

affected by the use of corrosion inhibitors (Pritzl, 

Tabatabai, and Ghorbanpoor 2015). Another study 

conducted by the Virginia Transportation Research 

Council (VTRC) demonstrated that corrosion inhibitors 

were not effective in reducing corrosion activity when 

applied to bridge decks prior to the installation of 

overlays and patch repairs. Additionally, the VTRC 

investigated the effect of corrosion inhibitors on the 

overlay bond strength to the substrate concrete. Results 

indicated that the topical application of inhibitors did 

not affect short-term bond strength. However, the results 

also demonstrated an apparent reduction in long-term 

bond strength that was attributed to the high-chloride 

content in the substrate concrete (Sprinkel 2003). 

EXPERIMENTAL DETAILS 

The following sections outline the materials, methods, and 

details of the experiments conducted for this TechNote.

Materials

Reinforcing Steel

Steel reinforcing bars were of ASTM A615 grade 60 

U.S. #4 (grade 420 M13) (ASTM 2020a). 

Corrosion-Inhibiting Chemicals 

Four different corrosion-inhibiting chemicals were used 

in this study. The handling and application of these 

chemicals followed manufacturer recommendations: 

• Soy-based sealer (S): Single-part liquid product 

that includes a polystyrene blended in a soy methyl 

ester solvent that is applied to the concrete surface. 

The polystyrene precipitates blocking the pores 

and the potential to bind chlorides. The sealer was 

applied in two coats using a brush about 24 hours 

prior to the application of the overlay to allow for it 

to dry and penetrate. 

• Amino alcohol-based corrosion inhibitor (CI): 

Single-part liquid product designed to penetrate 

the concrete surface and then diffuse in vapor 

or liquid form to the rebar level for additional 

protection. This corrosion inhibitor was applied 

in two coats using a brush. A minimum of 1 hour 

wait time was maintained between each coat. 

The product was applied about 24 hours prior to 

the application of the overlay to allow for it to dry 

and penetrate. 

• Hybrid silane-based sealer and corrosion 

inhibitor (SCI-1): Single-part liquid product 

designed to penetrate the concrete surface down 

to the rebar level and form a protective layer on 

the steel surface that inhibits corrosion. This product 

was applied in two coats using a brush about 24 

hours prior to the application of the overlay to 

allow for it to dry and penetrate.

• Hybrid silane-based sealer and corrosion 

inhibitor (SCI-2): Single-part liquid product 

designed to penetrate the concrete surface down 

to the rebar level and form a protective layer on 

the steel surface that inhibits corrosion. This product 

was applied in two coats using a brush about 

24 hours prior to the application of the overlay 

to allow for it to dry and penetrate. The research 

team waited at least 15 min between each coat.

Substrate Concrete

The substrate concrete mix design was based on a 

common bridge deck concrete mixture used in the State 

of Virginia. Class A4 concrete was based on Virginia 

Department of Transportation (VDOT) specifications 

(VDOT 2016). The reactive component of the mixture 

included type I/II portland cement and Class F fly ash. 

Fly ash was used as partial replacement for portland 

cement with a mass fraction of 35 percent. The concrete 

was designed to have a water-to-cementitious materials 

ratio (w/cm) of 0.43 and fine and coarse aggregate 

volume contents of 26 percent and 38 percent, 

respectively. Fine aggregates had an absorption 

capacity of 0.93 percent. The number 57 stone was 

used as coarse aggregate and had an absorption 

capacity of 0.44 percent. The concrete exhibited 

an air content of 6.5 percent, a slump of 3 inches 

(76 mm), and a 28-day compressive strength of 

5,100 psi (35 MPa).

UHPC Overlay

The UHPC overlay material was commercially available 

and was designed to be thixotropic. Thixotropy 

is a property that makes the material less viscous 

when subjected to mechanical agitation. The solid 

components, except the steel fibers, of the UHPC were 

supplied as a preblended and prebagged powder that 

included cementitious materials and inert fillers. The 

supplier also provided one liquid chemical admixture, 

likely a superplasticizer. The UHPC was dosed with 

3.25 percent of steel microfiber reinforcement by 

volume. The material exhibited a 5-inch (127-mm) 

static flow and a 7-inch (178-mm) dynamic flow after 

20 drops, per ASTM C1437 (ASTM 2020b). Lastly, 

the UHPC overlay material had a mature compressive 

strength greater than 18,000 psi (124 MPa).
4

LMC Overlay

An LMC overlay mix design was based on a 

common bridge deck concrete overlay mixture used 

in the State of Virginia. LMC was based on VDOT 

specifications (VDOT 2016). The reactive component 

of the mixture included type I/II portland cement. The 

concrete was designed to have a w/cm of 0.38 and 

fine and coarse aggregate contents of 39 percent and 

29 percent by volume, respectively. Fine aggregates 

had an absorption capacity of 0.93 percent. The 

number 8 stone was used as coarse aggregate and had 

an absorption capacity of 0.49 percent. A commercially 

available latex admixture was included in the concrete 

at a dosage of 30 percent by weight of cement. 

The LMC exhibited an air content of 6.5 percent, a 

slump of 4 inches (102 mm), and a 28-day compressive 

strength of 6,500 psi (45 MPa).

Specimen Details 

Four concrete slabs were used as substrates in this study. 

Figure 1 shows a schematic of these substrate slabs. 

Slabs 1 and 2 had multiple test regions, whereas slabs 

3 and 4 only had a single test region. The area of each 

test region measured 24-inches (610-mm) wide and 

24-inches (610-mm) long. The layout and spacing of 

the reinforcing rebars aligned with that described in the 

ASTM G109 test method, where one bar was installed 

1 inch (25 mm) below the top surface of the concrete, 

and two other bars were installed 3.5 inches (90 mm) 

below the top bar (center to center) (ASTM 2013). 

Specimen Preparation

Prior to constructing the concrete substrate slabs 

and casting concrete, the rebars were immersed for 

7 days in a supersaturated sodium chloride solution 

until significant visible corrosion was observed on the 

surface of the bars. This step was taken to simulate 

corrosion that may be found in a highway bridge deck 

reinforcement. At the time of installation, only 8 inches 

(203 mm) of steel were exposed in the concrete after 

wrapping both ends of the rebar with electroplaters 

tape and coating the taped ends with epoxy. 

To simulate the conditions that may be found in an 

in-service bridge deck exposed to deicing salts, sodium 

chloride was added into the mixing water prior to the 

concrete-mixing process. Four pounds (2.4 kg/m3

) 

of sodium chloride were added per cubic yard of 

concrete. This addition resulted in a chloride content of 

Figure 1. Illustration. Schematic of the concrete substrate slabs and test regions. 

Source FHWA.

Note: 1 inch = 25.4 mm.
5

approximately 900 ppm, which is commensurate with 

what might be found in the field at the reinforcement 

level. This chloride level was based on findings from a 

recent project bridge deck overlay project in the U.S. 

northeast. After casting concrete, the slabs were cured 

under laboratory environmental conditions of 73°F 

(23°C) and 50-percent relative humidity for 28 days. 

After that, a 3-percent sodium chloride solution was 

ponded on the top surface of the slabs for a period of 

3 mo to promote a continuous corrosion process, as 

seen in figure 2. 

Generally, on overlay installation projects, the deck 

surface requires preparation and roughening prior to 

the installation of the overlay to remove poor-quality 

concrete and promote bonding between the substrate 

concrete and the overlay. In this study, the concrete 

surfaces were prepared using hydromilling completed 

by a regional hydromilling contractor. Hydromilling 

is a popular deck preparation method in overlay 

applications because it has a low risk of inducing 

microcracking to the concrete substrate (International 

Concrete Repair Institute 2013). Figure 3 depicts the 

concrete substrate after hydromilling. This surface 

had an International Concrete Repair Institute surface 

roughness value greater than 10 and had significant 

micro and macrotexture, as seen in figure 3. The 

concrete slabs were then maintained in laboratory 

conditions for an additional 2 mo before the overlay 

materials were applied. A 3-percent sodium chloride 

solution was ponded on the top surface of the slabs 

during this 2-mo period. 

Test Matrix 

Eight different overlay cases (regions (R)) were 

evaluated in this study, as shown in table 1.

Figure 2. Photograph. Specimen undergoing 

chloride ponding, with solution being held in 

place by a foam dam.

Source: FHWA.

Source: FHWA.

Figure 3. Photograph. Concrete substrate 

after hydromilling.

Table 1. Test matrix parameters. 

Sample Region Slab Overlay Type Overlay Thickness Sealer/CorrosionInhibitor Useda Bond Testing

R1 

(control) 1 None N/A N/A No

R2 3 LMC 2 inch (51 mm) None Yes

R3 1 UHPC 1.5 inch (38 mm) None Yes

R4 1 UHPC 1.5 inch (38 mm) S Yes

R5 2 UHPC 1.5 inch (38 mm) CI Yes

R6 2 UHPC 1.5 inch (38 mm) SCI-1 Yes

R7 2 UHPC 1.5 inch (38 mm) SCI-2 Yes

 R8b 4 UHPC ≈ 4 inch (102 mm) None No

Note: N/A = not applicable; a = prior to applying these chemicals, substrate concrete surfaces were kept clean, dry, and free of 

laitance; b = reinforcing bars were cleaned prior to the installation of the overlay using a steel wire brush.
6

Each region consisted of three reinforcing bars in which 

the corrosion rate was evaluated over approximately 

2 years (110 weeks) using the technique described in 

the next section. During the 110-week corrosion testing 

period, the top of each specimen was ponded every 

2 weeks with a 3 percent sodium chloride solution to 

promote an accelerated continuous corrosion process. 

All the specimens were kept in laboratory environmental 

conditions of 73°F (23°C) and a 50-percent relative 

humidity throughout the testing period.

Test Methods

Corrosion Rate

Cyclic polarization testing was performed to determine 

the corrosion rate of the steel reinforcement of the 

concrete slabs, following a method similar to ASTM 

G61; however, due to the aggressive nature of the test 

method, testing was only performed two times over the 

2-year chloride ponding period (ASTM 2018). Testing 

was performed during the wet chloride ponding cycle 

of those weeks. Cyclic polarization is a technique that 

provides information about a material’s (i.e., alloy) 

corrosion rate and its potential for and susceptibility 

to pitting corrosion placed in a particular environment 

(Poursaee 2009). To conduct the test, a current is 

applied through the metallic material of interest, and the 

response of the material is monitored at a constant scan 

rate of 2 mV/s until the end of the testing cycle. 

Cyclic polarization testing was performed at 75 and 

110 weeks after the placement of the overlay materials. 

A potentiostat was used to measure the corrosion 

potential of the rebar. This metric served as a reference 

point to shift the potential of the rebars for evaluating the 

corrosion rates. The potentiostat automatically estimates 

the corrosion rate of the steel rebar based on Faraday’s 

law (Andrade and Alonso 1996). Figure 4 shows a 

schematic of the test configuration, and table 2 provides 

details related to the testing parameters. The lower scan 

rate of 2 mV/s was selected due to the rebars being 

subjected to a corrosive environment prior to placement 

in the concrete (Poursaee 2009).

Figure 4. Schematic. Schematic representation of cyclic polarization test.

Source FHWA.

Note: NaCI = sodium chloride.

Table 2. Cyclic polarization test parameters. 

Test Parameters Values Units

Initial voltage versus Eoc −0.01 Volts

Apex voltage versus Eoc 1 Volts

Final voltage versus Eoc −0.1 Volts

Forward scan rate 2 Millivolts/second

Reverse scan rate 2 Millivolts/second

Sample period 1 Seconds

Apex current 0.006 (1) Milliamperes/inch2

 (milliamperes/centimeter2)

Exposed rebar surface area 12.57 (81.07) Inches2

 (centimeters2)

Density of steel 0.28 (7.87) Pounds/inch3

 (grams/centimeter3)

Equivalent weight 0.06 (27.92) Pounds (grams)
7

Interface Bond Testing

A direct tension pull-off bond strength test was performed 

in accordance with ASTM C1583, commonly used to 

evaluate the bond between overlays and substrates 

(ASTM 2020c). Bond testing was performed on all 

test regions except for R1 and R8. The pull-off tests 

were performed after the 2-year ponding period to 

evaluate the effect that some of these corrosion-inhibiting 

chemicals (sealers and corrosion inhibitors) may have 

on the overlay-concrete bond strength. Test sample 

locations were prepared by gluing a 2-inch- (51-mm) 

diameter steel disc to the overlay. Once the adhesive was 

cured, a core was drilled through the overlay such that 

it penetrated 1 inch (25 mm) into the concrete substrate. 

Testing was then completed using a specialized pull-off 

bond testing device. Load was applied at a rate of 

5 ± 2 psi/s (0.035 MPa/s) until failure. The failure load 

and the failure mode were recorded upon completion 

of the test. Three pull-off tests were performed per test 

region (R2–R7). 

TEST RESULTS AND DISCUSSION

Corrosion Rates

Results from corrosion rate testing are shown in figure 5. 

The vertical dashed line denotes the corrosion rate 

for the control region (R1), which did not have an 

overlay. The dashed line was determined by taking the 

average of the corrosion rate at 75 and 110 weeks 

of conditioning, which was used as a reference for 

comparison purposes since it exhibited the highest 

corrosion rate compared to all the other cases. These 

results were expected because the control region was 

subjected to more diffusion of moisture, oxygen, and 

chlorides into the concrete substrate compared with 

the test regions (R2–R8) that employed overlays and/

or sealers and corrosion inhibitors. In the latter cases, 

the combination of the overlay and corrosion-inhibiting 

techniques were expected to provide enhanced 

protection from contaminants. The level of protection 

is dependent on the thickness and permeability of 

the overlay material and the performance of the 

corrosion-inhibiting chemicals. As such, test regions 

employing LMC (R2) and UHPC (R3) overlays, without 

corrosion-inhibiting chemicals, exhibited average 

corrosion rate reductions of 20 percent and 50 percent, 

respectively, compared to the control region (R1). The 

LMC overlay was slightly thicker than UHPC overlay 

but has a coarser microstructure and thus a greater 

permeability, which explains the higher corrosion rate 

compared to the test region with the UHPC overlay. 

R4 through R7 all employed UHPC overlays and sealers, 

corrosion inhibitors, or hybrid products. Each of these 

cases exhibited a reduced corrosion rate compared 

to R3, which only employed a UHPC overlay. In 

comparison with R3, the average corrosion rates of R4 

(S), R5 (CI), R6 (SCI-1), and R7 (SCI-2) were reduced 

by 12 percent, 41 percent, 37 percent, and 58 percent, 

respectively. The differences in performance among 

Figure 5. Bar graph. Measured corrosion rates.

Source FHWA.

Note: mpy = mils (thousandths of an inch) per year.
8

Figure 6. Photograph. Bars extracted from regions R1–R7 after 110 weeks of conditioning.

Source: FHWA. Note: 1 inch = 25.4 mm.

sealers and corrosion inhibitors can be attributed to the 

different compositions of the products. 

Lastly, R8, which was prepared by excavating the 

concrete around the reinforcement and cleaning off 

the corrosion products prior to placing the UHPC 

overlay, exhibited the lowest measured corrosion rate 

(an 87-percent average reduction with respect to 

the control region (R1). Notably, all of the average 

corrosion rates measured in this study are considered 

negligible, as defined in RILEM TC-154, and can be 

attributed to general corrosion occurring on the surface 

of the metal (RILEM TC 154-EMC 2004). These findings 

were confirmed by extracting the rebars from all regions 

at the end of the testing period. (See figure 6.)

Bond Testing

Direct tension bond test results are shown in figure 7

for R2 through R7. As noted, tests were completed 

after 2 years. The data reflect the average of four 

samples, and the error bars depict plus or minus one 

standard deviation. The LMC (R2) and UHPC (R3) 

overlays exhibited failure in the concrete substrate, 

indicative of a strong bond between the overlay 

materials and the substrate concrete. The average bond 

strength of test regions employing UHPC overlays and 

corrosion-inhibiting chemicals (R4–R7) all exhibited 

lower bond strengths than the respective regions 

that did not employ these products. Furthermore, in 

each of these cases, failure occurred at the overlayconcrete interface. These results align with previous 

research conducted by VDOT that concluded applying 

corrosion inhibitors prior to the placement of the 

overlay will negatively affect the bond performance 

of the overlay system (Sprinkel 2003). This study 

hypothesized that the corrosion-inhibiting chemicals 

will act as a potential bond breaker. Additionally, 

bond strength in the presence of corrosion-inhibiting 

chemicals may have a time-dependency or exposuredependency component. Figure 8 compares two sets 

of bond test data obtained at the Turner-Fairbank 

Highway Research Center (TFHRC): One set collected 

7 days after the placement of the overlay (shown in 

figure 7) and another set collected after 2 years of 

ponding with salt and undergoing corrosion. Bond 

tests conducted after 7 days indicate minimal impact 

with the introduction of corrosion-inhibiting chemicals, 

while results from testing undergoing 2 years of chloride 

ponding indicate a reduction in bond strength. These 

results demonstrate the potential of a time-dependency 

or exposure-dependency component to bond strength 

when corrosion-inhibiting chemicals are installed or 
9

Figure 7. Bar graph. Pull-off bond results for tests completed after 2 years of conditioning.

Source: FHWA.

Figure 8. Bar graph. Early versus later age pull-off bond test results.

Source: FHWA.
10

applied prior to the placement of the overlay. Further 

research is needed to better understand this potential 

negative effect of sealers and corrosion inhibitors at later 

ages and after chloride and moisture exposure. 

CONCLUSIONS

This TechNote summarizes the recent study conducted 

by TFHRC researchers to evaluate available techniques 

to inhibit existing corrosion of bridge deck reinforcement 

prior to an overlay application. A commercially 

available UHPC overlay material was tested with and 

without common corrosion-inhibiting chemicals, such as 

sealers and corrosion inhibitors. The corrosion-inhibiting 

chemicals were applied directly to the prepared 

concrete substrate prior to the placement of the UHPC 

overlays. The data were collected for a conventional 

LMC overlay as well. The corrosion activity was 

monitored using corrosion rate measurements, and bond 

testing was completed at the end of the corrosion rate 

testing period. The following conclusions can be made:

• The use of an LMC or a UHPC overlay reduced 

average corrosion rates by 20 percent and 

50 percent, respectively, when compared to a 

control test case that did not employ an overlay. 

The reduction in the corrosion rates was attributed 

to the additional protective layer (i.e., the overlay), 

which prevented external chlorides, moisture, and 

oxygen from penetrating the concrete and further 

corroding the reinforcement.

• The use of sealers, corrosion inhibitors, or 

hybrid products in combination with a UHPC 

overlay further reduced the rate of corrosion. 

The percentage for which the rate of corrosion 

was reduced depended on the type of sealer/

corrosion inhibitor used. As a result, these 

corrosion-inhibiting chemicals further reduced 

corrosion rates by as much as 45 percent when 

compared to the region with only a UHPC overlay.

• The best performing test case was R8. In this case, 

substrate concrete around the reinforcement 

was removed by hydromilling, and the corrosion 

products around the reinforcement were removed 

prior to placing the UHPC overlay. R8 exhibited 

an 87 percent average reduction in the rate of 

corrosion compared to the control region (R1). 

This result was likely due to the removal of existing 

chlorides in the substrate concrete.

• Despite their good performance in reducing the 

rate of corrosion, the long-term presence of sealers 

and corrosion inhibitors had a clear negative 

impact on the overlay to concrete bond strength 

at a late testing age. Bond strength was reduced 

by as much as 80 percent, depending on the type 

of corrosion-inhibiting chemicals applied prior to 

overlay installation. More research is needed to 

better understand this negative effect at later ages, 

since it was not observed with one of the products 

used in the study at early ages.

RECOMMENDATIONS

Since this research focused more on UHPC overlays 

used in conjunction with corrosion inhibiting chemicals, 

the recommendation provided only covers UHPC 

overlays, not LMC overlays. The reader should refer to 

previous research for recommendations related to the 

use of corrosion-inhibiting chemicals in conjunction with 

LMC overlays. The authors of this TechNote recommend 

the following:

• In cases where existing substrate concrete is 

removed but the top mat of reinforcing steel is 

not exposed: The application of sealers with or 

without corrosion inhibitors directly to the substrate 

concrete prior to the placement of the UHPC 

overlay is not needed unless specific long-term 

interface bond performance data are available 

for the engineer’s review and consideration. 

Adequately designed UHPC overlays have very 

low permeability and do not require additional 

protection from moisture. However, if needed, 

sealers should be applied to the surface of the 

UHPC overlay. 

• In cases where existing substrate concrete is 

removed and the top mat of reinforcing steel is 

exposed and cleaned: The application of sealers 

with or without corrosion inhibitors directly to the 

substrate concrete prior to the placement of the 

UHPC overlay is not recommended. The corrosion 

potential will be greatly reduced if UHPC fully 

encapsulates the top mat of steel that has been 

cleaned and the surrounding chloride laden 

substrate concrete has been removed. 

REFERENCES

Andrade, C. 2007. “Corrosion of Steel Reinforcement.” 

In WIT Transactions on State of the Art in Science 

and Engineering, Vol. 28. Madrid, Spain: WIT Press, 

185–216. https://www.witpress.com/Secure/

elibrary/papers/9781845640323/978184564

0323006FU1.pdf.

Andrade, C., and C. Alonso. 1996. “Corrosion 

Rate Monitoring in the Laboratory and On-Site.” 

Construction and Building Materials 10, 

no. 5: 315–328.
11

ASTM. 2020a. Standard Specification for Deformed 

and Plain Carbon-Steel Bars for Concrete 

Reinforcement. ASTM A615/A615M. West 

Conshohocken, PA: ASTM International.

ASTM. 2020b. Standard Test Method for Flow of 

Hydraulic Cement Mortar. ASTM C1437. West 

Conshohocken, PA: ASTM International.

ASTM. 2020c. Standard Test Method for Tensile 

Strength of Concrete Surfaces and the Bond 

Strength or Tensile Strength of Concrete Repair 

and Overlay Materials by Direct Tension (Pull-off 

Method). ASTM C1583. West Conshohocken, PA: 

ASTM International.

ASTM. 2018. Standard Test Method for Conducting 

Cyclic Potentiodynamic Polarization Measurements 

for Localized Corrosion Susceptibility of Iron-, 

Nickel-, or Cobalt-Based Alloys. ASTM G61. West 

Conshohocken, PA: ASTM International.

ASTM. 2015. Corrosion Potentials of Uncoated 

Reinforcing Steel in Concrete. ASTM C876. West 

Conshohocken, PA: ASTM International.

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Researchers—This study was conducted by FHWA’s Office of Infrastructure Research and Development. The 

research was led by Robert Spragg, Zachary Haber, and Benjamin Graybeal from FHWA and conducted by 

researchers Naveen Saladi and Igor De la Varga under contract DTFH61-17-D-00007. 

Availability—This TechNote may be obtained at https://highways.dot.gov/research.

Key Words—Overlay, bridge deck, corrosion, inhibitors, bond, UHPC.

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

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

information contained in this document. The U.S. Government does not endorse products or manufacturers. 

Trademarks or manufacturers’ names appear in this Technote only because they are considered essential to the 

objective of the document.

Quality Assurance Statement—The Federal Highway Administration (FHWA) provides high quality 

information to serve Government, industry, and the public in a manner that promotes public understanding. 

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

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

continuous quality improvement.

 

 JUNE 2022 FHWA-HRT-22-087

HRDI-40/06-22(WEB)E

Recommended citation: Federal Highway Administration, 

Techniques To Inhibit Corrosion In Bridge Deck Reinforcement Prior 

To Overlay Installation (Washington, DC: 2022) 

https://doi.org/10.21949/1521916.