Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike, McLean, VA 22101-2296

www.fhwa.dot.gov/research

FHWA Publication No.: FHWA-HRT-17-097

FHWA Contacts: Ben Graybeal, HRDI-40, 202-493-3122, benjamin.graybeal@dot.gov; Zach Haber, 

HRDI-40, 202-493-3469, zachary.haber@dot.gov

TECHNOTE

Ultra-High Performance 

Concrete for Bridge Deck 

Overlays

Introduction

There is urgent need for effective and durable 

rehabilitation solutions for deteriorated 

highway bridge decks. Deck deterioration 

is commonly caused by a combination of 

vehicle loading, freeze–thaw degradation, 

cracking, delamination of cover concrete, 

and/or corrosion of internal reinforcement. 

Deteriorated bridge decks are commonly 

rehabilitated using overlays depending on 

the cause of deck deterioration, available 

budget, and desired service life of the 

rehabilitated structure. Common overlay 

materials include conventional concretes, highperformance concretes (HPCs), latex-modified 

concretes (LMCs), asphalt with waterproofing 

membranes, and polymer-based materials. The 

performance objectives of bridge deck overlays 

include protecting the underlying deck and 

reinforcement from contaminates, providing 

additional strength and stiffness to the deck 

system, and extending the service life of the 

overall structure.

One emerging solution for bridge deck 

rehabilitation is thin, bonded ultra-high 

performance concrete (UHPC) overlays. As 

an overlay material, UHPC can provide both 

structural strengthening and protection from 

ingress of contaminates using a 1-inch (25-mm) 

to 2-inch (51-mm) layer of material. This 

minimizes required material volume and can 

minimize additional dead load on the bridge 

structure compared with some traditional 

overlay solutions. The concept and use of UHPC 

overlays has been researched in Europe and 

has been deployed on more than 20 European 

bridges.(1) 

This TechNote introduces UHPC as a potential 

solution for bridge deck overlays. A brief 

review of the history and development of 

UHPC is presented, followed by a summary 

of the properties that make UHPC a viable 

overlay solution. A laboratory investigation on 

the tensile bond strength of a UHPC specially 

formulated for overlay applications is then 

presented. This investigation provides a 

comparison between UHPC and LMC overlays 

using different substrate materials and surface 

preparations. Lastly, this TechNote highlights 

the findings of a field study and subsequent 
2

laboratory investigation aimed at evaluating the 

bond between a recently installed UHPC overlay 

and the existing reinforced concrete bridge deck. 

The full details and findings of this field study 

are available in a report by Haber et al. (2017).(2)

UHPC 

Advances in concrete technology, such as 

high-strength steel microfiber reinforcement, 

superplasticizers, gradation optimization, and 

supplementary cementitious materials, began 

to be packaged together into a new generation 

of cementitious composite materials in the 

1970s and 1980s. In the 1990s, this new class of 

materials was brought to market and has since 

become known as UHPC. Today, preblended, 

prepackaged, proprietary formulations of UHPC 

are commercially available in the United States 

along with nonproprietary mixes that have been 

developed by academic research groups.(3)

UHPC offers several advantages, including 

enhanced material and durability properties, 

over conventional concretes and other 

cementitious materials, which led to it gaining 

the attention of the highway bridge design 

community. Since 2005, there have been 

more than 140 highway bridges constructed 

using UHPC in the United States and Canada 

combined. Those deployments use UHPC in a 

variety of bridge construction and rehabilitation 

applications, including prefabricated structural 

bridge elements made entirely of UHPC; 

retrofit and repair of bridge decks, girders, 

and substructures; and field-cast connections 

between prefabricated bridge elements. This 

last application is currently the most popular 

within the United States and Canada and is a 

common entry point for many owners who are 

new to this technology.(4)

UHPC as an Overlay Material

The primary difference between typical UHPC 

formulations and UHPCs that have been 

specially formulated for overlay applications 

are the rheological properties. Most UHPCs are 

formulated to flow under the force of gravity 

and be self-consolidating. UHPCs formulated 

for overlay applications are typically thixotropic. 

Thixotropy is a time-dependent shear thinning 

property of a non-Newtonian fluid, which 

causes a material to remain solid-like under 

static conditions and to flow when agitated or 

sheared. Bridge decks are not level. If a typical 

(nonthixotropic) UHPC were to be used as 

a bridge deck overlay, it would flow from the 

crown, or high side, of the superelevation to 

lower points on the structure. This would likely 

cause difficulty with screeding and profiling.

UHPC is a viable option for use as a bridge deck 

overlay material given the following potential 

advantages:

• UHPC has a very low permeability and 

very good resistance to freeze–thaw 

damage. Thus, the potential for ingress of 

contaminates and freeze–thaw damage 

is significantly reduced compared with 

conventional overlay materials, which 

enhances durability.

• UHPC has good abrasion resistance, which 

means reduced potential for rutting.

• Compared with conventional concretes, 

a well-designed UHPC mix will exhibit 

relatively low shrinkage, thus reducing the 

potential for shrinkage-induced cracking. 

If the UHPC does crack, crack widths are 

typically significantly smaller than those 

that would form in a conventional concrete 

system because of the UHPC’s internal 

microfiber reinforcement.

• UHPC has high strength and high 

stiffness. Thus, a thin layer could provide 

both enhanced durability and increased 

strength with minimal added dead load. 

Traditionally, rigid concrete overlays range 
3

Overlay Type Overlay Thickness, Inches (mm) Cost, $/ft2

 ($/m2)

HPC* 1–5 (25–127) 17–25 (183–269)

Low slump concrete* 1.5–4 (38–102) 13–19 (140–204)

LMC* 1–5 (25–127) 18–39 (193–419)

Asphalt with a membrane* 1.5–4 (38–102) 3–8 (32–86)

Polymer-based* 0.13–6 (3–152) 10–17 (107–183)

Non-proprietary UHPC 1–2 (25–52) 3–6 (32–64)†

Proprietary UHPC 1–2 (25–52) 9–18 (97–184)‡

Rehabilitation of the Chillon Viaduct 

(Switzerland) using a proprietary 

UHPC overlay

1.6 (40)** 20 (215)**

Bridge deck replacement* n/a 43–53 (462–570)

*Data collected from Krauss et al. (2009).(5) The costs shown reflect average values from low and high ranges.

**Data collected from Brühwiler et al. (2015).(7) Price reflects cost of material and installation.

†Price reflects material cost only, assumes UHPC cost of $1,000 per cubic yard.

‡Price reflects material cost only, assumes UHPC cost of $3,000 per cubic yard.

n/a = not applicable.

Table 1. Approximate cost of different overlay solutions compared with bridge deck replacement.

in thickness between 2.5 inches (51 mm) 

and 6 inches (152 mm), which corresponds 

to dead loads between 30 psf (1.4 kN/m2

) 

and 75 psf (3.6 kN/m2

).(5) Previous deployments of UHPC as an overlay have used 

overlay thicknesses between 1 inch (25 mm) 

and 2 inches (51 mm), which corresponds 

to dead loads between 13 psf (0.57 kN/m2

) 

and 26 psf (1.2 kN/m2

).(1)

• UHPC bonds well to existing concrete 

surfaces if proper surface preparation 

is employed, such as using an exposed 

aggregate or roughened surface finish.(6)

Cost of UHPC Versus 

Conventional Solutions

The cost of UHPC is generally higher than 

most highway bridge construction materials. 

Furthermore, the material cost and bid line 

item cost for UHPC-class materials can differ 

substantially. Table 1 provides a comparison 

of the approximate costs of different overlay 

solutions. The UHPC costs shown only reflect 

the cost of the material and do not include costs 

associated with installation, and thus, they 

appear relatively low. In general, the cost of 

UHPC overlays in the United States would likely 

be higher than most traditional overlay solutions 

until the technology becomes more established. 

In Switzerland, UHPC overlays are being more 

commonly deployed, and therefore, the costs are 

becoming more competitive. Table 1 includes 

the approximate cost of a UHPC overlay on a 

signature bridge structure, the Chillon Viaduct, 

in Switzerland; this cost is comparable to the 

upper-end cost of some of the conventional 

solutions in the United States.(7)
4

Figure 1. Direct tension pull-off bond test based on ASTM C1583.

Source: FHWA.

Laboratory Investigation

It is critical that bonded overlays achieve and 

maintain good bond with existing bridge deck 

concrete. A study was carried out at the Federal 

Highway Administration’s (FHWA) TurnerFairbank Highway Research Center (TFHRC) to 

investigate the bond behavior between UHPC 

and existing concrete. The UHPC tested was 

specially formulated for bridge overlays and 

had thixotropic properties. The main objective 

of this research was to compare the tension 

bond strength of a UHPC overlay to that of 

a commonly used overlay material, LMC. 

Tests were conducted on different substrate 

materials using different substrate surface 

preparation methods. 

Test Method—Direct Tension Pull-Off Bond 

Strength

The bond strength was assessed according 

to ASTM C1583, which is the direct tension 

bond pull-off test.(8) A schematic of this test is 

shown in figure 1. Specimens were prepared 

by gluing a 2-inch (51-mm) diameter steel pulloff disc to the overlay material, which was 

roughened prior to disc installation to promote 

bonding at the desired test location. Once 

the adhesive layer cured, a partial core was 

drilled through the overlay material and into 

the substrate material. This created a load path 

directly through the interface between the two 

materials. A specialized pull-off test fixture was 

then used to apply load and record data. Tensile 

load was applied to the steel disc at a constant 

rate of 5 ± 2 psi/s (34.5 ± 13.8 kPa/s) until failure. 

The failure load and the failure mode were 

recorded upon completion of the test.

Test Parameters

Bonded overlays, in most cases, are placed atop 

existing reinforced concrete decks or, in some 

cases, may be placed atop an existing, failing 

overlay. Regardless of the substrate type, the 

substrate is usually roughened prior to overlay 

installation to promote bonding; in some cases, 

additional bonding agents may be used as well. 

There are a variety of commercially available 

tools currently employed to mechanically 

roughen the deck substrate prior to overlay 

installation.(9) Two of these technologies were 

selected for the research presented herein: 

scarification and hydrodemolition. Scarification 

is achieved by the rotatory action of cutters 

(toothed washers) on the surface to fracture 

or pulverize the material. Scarified or removal 

depths may range from 1/4 inch (6 mm) to 
5

Figure 2. Concrete substrate surface prepared 

using scarification.

Figure 3. Concrete substrate surface prepared 

using hydrodemolition.

Source: FHWA. Source: FHWA.

3/4 inch (19 mm). In this study, scarification 

was achieved using a small-scale walk-behind 

scarifier to remove approximately 3/8 inch 

(9.5 mm) of substrate material. Figure 2 shows 

a picture of the concrete substrate base slab 

after scarification. A series of grooves can be 

observed along with some of the concrete’s 

internal coarse aggregate. Hydrodemolition 

uses high-pressure (up to 45,000 psi (310 

MPa)) water jetting to remove material from 

the substrate in a controlled manner. In this 

case, a pressure of 15,000 psi (103 MPa) was 

used to remove 1/2 inch (12.7 mm) of the 

substrate material. Figure 3 shows a photo of 

the post-hydrodemolition concrete substrate 

base slab used in this study. 

UHPC has become increasingly popular for 

connections between prefabricated concrete 

bridge deck elements. Thus, there may arise a 

case where a UHPC (or conventional concreteor asphalt-based) overlay may be placed atop 

an existing UHPC connection. Therefore, 

it would be equally critical that the overlay 

bond to the UHPC used in the connection. As 

such, a second base slab was produced using 

a commercially available UHPC-class material 

commonly deployed in prefabricated concrete 

bridge deck connections. One of the UHPC 

base slabs was prepared using scarification 

to remove approximately 3/8 inch (9.5 mm) of 

substrate material (shown in figure 4), and the 

other one was prepared using hydrodemolition 

with a pressure of 40,000 psi (276 MPa) to 

remove 1/2 inch (12.7 mm) of the substrate 

material (shown in figure 5).

As previously noted, two overlay materials 

were used: a proprietary UHPC mixture 

specially formulated for bridge deck overlays 

and an LMC overlay. The LMC was designed in 

the lab, with a 28-d compressive strength of 

5,000 psi (34.5 MPa), 6-inch (152-mm) slump, 

and 30 percent latex (by mass of cement 

content). This mix design was similar to that 

deployed on several bridges in the State of 

Virginia.(10) Both overlay materials were placed 

with the assistance of a handheld trowel with 

motorized vibration. Table 2 summarizes the 

parameters considered in this preliminary lab 

testing phase. 
6

Figure 4. UHPC substrate surface prepared using 

scarification.

Figure 5. UHPC substrate surface prepared using 

hydrodemolition.

Source: FHWA. Source: FHWA.

Overlay Material 

Concrete 

Substrate 

Prepared With 

Scarification

Concrete 

Substrate 

Prepared With 

Hydrodemolition

UHPC Substrate 

Prepared With 

Scarification

UHPC Substrate 

Prepared With 

Hydrodemolition

LMC √ √ √ √

UHPC √ √ √ √

Table 2. Laboratory test matrix.

Results

Figure 6 and figure 7 present the peak tensile 

stresses at failure of the overlay materials 

cast over concrete and UHPC substrates, 

respectively. In general, UHPC overlays exhibit 

comparable, if not higher, bond strengths than 

LMC overlays, except for the case where a 

scarified concrete substrate was used. Another 

observation is that bond strengths tended to 

be higher when a UHPC substrate was used, 

compared to those obtained over a concrete 

substrate. Finally, the hydrodemolition 

technique offers the possibility of obtaining 

higher bond strengths than scarification. 

This is attributed to the fact that mechanical 

preparation methods may introduce 

microcracking on the substrate material, which 

might eventually affect the bond performance.
7

Source: FHWA.

Source: FHWA.

Figure 6. Peak stresses recorded from direct tension bond testing on a concrete substrate.

Figure 7. Peak stresses recorded from direct tension bond testing on a UHPC substrate.
8

Field Testing of a UHPC Overlay

Background

The first U.S. deployment of UHPC as a bridge 

deck overlay was completed in May 2016 on 

a reinforced concrete slab bridge located 

in Brandon, Iowa; the bridge is located on 

Laporte Road. A few months after installing 

the UHPC overlay, a field inspection revealed 

some locations along the length of the bridge 

where delamination may have been present. 

These locations were identified by sounding 

the deck using a chain drag. However, it was 

not known whether delamination, if actually 

present, was located at the interface between 

the UHPC overlay and substrate concrete, 

within the existing concrete deck, or within the 

UHPC overlay itself. Thus, there was a need to 

assess the bond between the UHPC overlay 

and substrate concrete to determine whether 

locations of potential delamination were a result 

of poor bond between the UHPC overlay and the 

concrete deck or a result of preexisting issues.

In November 2016, researchers from FHWA 

TFHRC conducted a field study on the Laporte 

Road Bridge to evaluate the bond between the 

UHPC overlay and the substrate concrete bridge 

deck.(2) The approach included both field-based 

and laboratory-based investigations.

Bridge and Overlay Details

Constructed in 1960s, the Laporte Road Bridge 

over Mud Creek is a three-span reinforced 

concrete slab bridge located approximately 35 mi 

(56.3 km) northwest of Cedar Rapids, Iowa. The 

bridge was originally designed using H20-44 

loading, and although it has a low average daily 

traffic, it carries large trucks with agricultural 

loads. The abutment-to-abutment length of the 

bridge is 100 ft (30.5 m). The width of the bridge 

is 28 ft (8.53 m), and it services two lanes 

of traffic. The slab has a uniform thickness of 

16.9 inches (430 mm), is reinforced in the 

longitudinal direction with bars ranging 

between #6 and #10, and is reinforced with #6 

and #7 bars in the transverse direction. The 

original design drawings specify a 2-inch 

(51-mm) clear cover between the top mat of steel 

and the bare ride surface of the concrete deck. 

The bridge deck has a 5-percent superelevation.

The bridge deck was beginning to exhibit 

delamination and spalling along the curbline 

nearest the deck drains and at each end at the 

expansion joints. It is likely that the deterioration 

was related to chloride laden water ingress into 

the concrete and past the strip seal expansion 

joints, leading to reinforcement corrosion and 

freeze–thaw cycle-related distress. For example, 

figure 8 shows one of the distressed regions 

found on the deck after removing a thin layer of 

cover concrete. This region was selected as a 

test location. As shown, this deterioration had 

progressed to the point that maintenance actions 

were necessary. A UHPC overlay solution was 

selected to repair the deteriorated deck. This 

project was considered a demonstration project 

for UHPC overlays. 

The UHPC overlay material used was 

proprietary, and the material supplier provided 

onsite technical support to the contractor during 

the installation of the overlay. The overlay was 

constructed in two stages. The overlay was 

first installed on the westbound lane (stage I)

and subsequently on the eastbound lane (stage II). 

Prior to installation, the deck surface was 

prepared with a truck-mounted diamond grinder 

to promote bonding with the UHPC overlay 

(shown in figure 9). The diamond ground 

concrete deck was pre-wetted a few hours 

before placement of the overlay. The UHPC 

overlay was mixed onsite and placed using 

motorized buggies and hand tools (shown in 

figure 10). Once completed, the overlay surface 

was coated with a wax-based curing compound 

and covered with plastic sheeting to prevent 

dehydration.
9

Figure 8. Distressed region on the westbound lane near the western abutment: test region B1.(2)

Source: FHWA.

Figure 9. Deck surface after diamond grinding.(2) Figure 10. UHPC overlay installation on the 

westbound lane.(2)

Source: FHWA. Source: FHWA.

Evaluation Methodology 

The evaluation methodology included synthesis 

of photographic evidence, a field inspection 

of the bridge deck surface using a chain drag, 

physical testing of the UHPC–concrete bond 

strength, and microstructural analysis of the 

UHPC–concrete interface using scanning 

electron microscopy (SEM). Test locations were 

selected on both westbound and eastbound 

lanes, with and without potential delamination, 

and with and without deck grinding. The curb 

lines of the existing bridge deck were not 

diamond ground prior to overlay installation. 

The first step in the evaluation process was to 

identify regions of potential delamination along 

with a few regions where the bond between the 

UHPC overlay and substrate concrete appeared 

intact. Photographic evidence, like that depicted 

in figure 8, was gathered and synthesized 

prior to arriving onsite. Once onsite, the entire 

bridge deck was evaluated using a chain drag. 
10

Location ID Lane (Construction 

Stage)

Potential 

Delamination*

Diamond 

Ground 

Substrate

Existing 

Distressed 

Concrete

Number 

of Pulloff Tests

SEM 

Analysis

G1 Westbound (I) No Yes No 4 No

G2 Eastbound (II) No Yes No 4 Yes

G3 Eastbound (II) No No No 2 Yes

B1 Westbound (I) Yes Yes Yes** 2 No

B7 Eastbound (II) Yes Yes No 2 Yes

Table 3. Test location details.

*As determined by chain drag.

**As determined by photographic evidence.

Regions of potential delamination were marked 

on the surface of the deck and were recorded 

using a global positioning satellite-based 

mobile mapping unit. A total of eight potential 

delamination regions were found, of which 

two were selected for testing. Three regions 

exhibiting intact bond were also selected for 

testing. Table 3 lists the details of each test 

location. 

The interface bond strength between the 

existing concrete deck and the UHPC overlay 

material was assessed using the direct tension 

bond pull-off test method discussed previously 

and shown in figure 1. 

Select specimens, noted in table 3, were subject 

to microstructural analysis using a SEM. 

The goal of this analysis was to quantify the 

integrity of UHPC at the microstructural level. 

This analysis was conducted using an FEI 

Quanta 650 SEM equipped with a concentric 

backscatter detector. Large backscatter electron 

mapping areas were collected using AZtec 

2.4 energy dispersive spectroscopy (EDS) microanalysis software. The interface was mapped 

in consecutive 10-μm wide bands (shown in 

figure 11), starting from the location where the 

UHPC cement paste contacted the concrete deck 

substrate. This analysis was conducted 10 times, 

moving backward into the bulk of the UHPC 

paste (100-μm away from the interface line). This 

process was previously used by Beushausen, 

Höhlig, and Talotti (2017) to characterize the 

microstructure of bonded concrete overlays and 

is currently being used by researchers at TFHRC 

to characterize bond between fresh cementitious 

materials and existing concretes.(11) This analysis 

provided a quantitative measure of the porosity, 

aggre-gate, hydration products, and unhydrated 

cement particle content near the interface.

Results

Figure 12 presents the peak tensile stresses 

captured during direct tension pull-off testing 

at the five different test locations. This graph 

reports the minimum and maximum stresses 

recorded along with the failure mode exhibited 

by each specimen group. 

The results indicated a good bond between 

the UHPC overlay and the substrate concrete 

deck with and without diamond grinding. The 

peak tensile stresses sustained by specimens 

in regions G1, G2, and G3 prior to failure 

were comparable to, if not higher than, the 

bond strengths of other UHPC-class materials 

(nonthixotropic) bonded to a roughened concrete substrate.(12) Furthermore, the peak tensile 

stresses sustained by these specimens were, 

in most cases, higher than those exhibited by 

conventional grout-like materials bonded to a 

roughened concrete substrate.(6) For the locations with potential delamination (B1 and B7), 
11

Figure 11. Composite SEM micrograph used for microstructural analysis.(2)

Source: FHWA.

Figure 12. Peak stresses recorded from direct tension bond testing.

Source: FHWA.

†Concrete deck at this location was not diamond ground prior to overlay installation.

‡ Minimum peak stresses were zero at these locations; damaged deck concrete was present.

pull-off test specimens failed in the substrate 

concrete at relatively low stresses. Some 

specimens tested at these locations did not hold 

any load at all. Instead, these specimens could 

be removed from their core locations by hand, 

indicating existing damage in the substrate 

concrete layer.

Once testing was completed, the tested core 

samples were removed from their respective 

test locations. In some cases, specimens failed 

in the adhesive layer between the test disc and 

the UHPC overlay. These removed samples were 

first inspected visually, and then, select samples 

were subject to microstructural analysis. Figure 
12

 Figure 13. Representative images from specimens at test locations G2 and B7.

Source: FHWA.

13 shows representative images of samples 

from the G2 and B7 test locations. Samples 

from other test locations appeared similar 

to those shown in figure 13. In all cases, the 

bond between the UHPC overlay and the 

substrate concrete appeared intact based on 

visual inspection. It was evident that failure of 

specimens from regions B1 and B7 was a result 

of preexisting concrete deck delamination. An 

example of preexisting damage in the concrete 

deck can be observed in figure 14. Preexisting 

damage caused specimens to carry little to no 

tensile load prior to failure. It should be noted 

that other regions of potential delamination 

(B2–B6, and B8) were not tested, and findings 

from tests completed at locations B1 and B7 

may not extrapolate to these locations. 

SEM revealed that the UHPC–concrete interface 

regions were very much intact. Furthermore, 

the SEM investigation revealed that the UHPC 

overlay was well-consolidated along the 

interface line. This can be observed in figure 

15, which depicts a SEM micrograph of a 

sample taken from test location B7. This image 

is representative of test location B7 along with 

the other two test locations analyzed with the 

SEM, G2 and G3. It can be observed that there 

is no apparent void space (porosity) between 

the interface line and the UHPC overlay. Using 

the AZtec 2.4 EDS microanalysis software, the 

material contents located along the interface 

line were quantified.(13) A portion of these 

results are presented in figure 16, which shows 

the hydration products, unhydrated cement, 

and porosity of the UHPC overlay 10-μm from 

the interface line. Figure 16 shows that, for all 

three test locations analyzed, UHPC hydration 

products were the principle phase present. 

This indicates good consolidation and bond at 

the interface location. In contrast, unhydrated 

cement particles and void space contents 

were nearly absent. As a point of comparison, 

figure 16 shows a set of data collected by De 

la Varga et al. (2017), which is denoted “nonshrink grout.” The data was collected near the 

interface line between a roughened concrete 

surface and a non-shrink grout overlay. 

Analysis shows a high concentration of 

unhydrated products and porosity, which has a 

deleterious impact on bond strength.(11)
13

Figure 15. SEM micrograph from a sample taken from test location B7.

Source: FHWA.

Figure 14. Photo of B7 test location after core removal.(2)

Source: FHWA.
14

Figure 16. Representative results from microstructural analysis near the UHPC–concrete interface line.

Source: FHWA.

†Aggregate content is not shown but was between 0 and 2.0 percent in each case.

‡Data from an on-going study at TFHRC– Grout A, control condition, bonded to an exposed aggregate surface.

Summary and Conclusions

UHPC has mechanical and durability properties 

that make it a well-suited candidate for concrete 

bridge deck overlays. This TechNote highlights 

some of the recent work being conducted 

by researchers at FHWA TFHRC to better 

understand UHPC-class bridge deck overlays. 

This work included a laboratory investigation 

on tensile bond strength and a field study 

and subsequent laboratory investigation of a 

U.S. bridge that was recently repaired using a 

specially formulated UHPC overlay. 

The laboratory investigation described in this 

report resulted in comparable, if not better, 

bond performance of UHPC overlays compared 

to that of LMC overlays, making it possible to 

think about the potential use of UHPC overlays 

in bridge decks. It can also be concluded that 

the type of substrate material influences the 

bond strength, as the UHPC substrate exhibited 

higher bond strengths than concrete substrates. 

Likewise, the substrate surface preparation 

method seems to be important to obtaining 

good bond. The substrate surfaces treated 

with hydrodemolition resulted in higher bond 

strengths than those obtained on a scarified 

substrate surface.

The first U.S. deployment of UHPC as a bridge 

deck overlay was completed in May 2016 on 

a reinforced concrete slab bridge located in 

Brandon, Iowa (Buchanan County). A few 

months after installing the UHPC overlay, a 

field inspection of the bridge concluded that 

isolated delaminations might be present in 

the deck. Thus, there was a need to assess the 

bond between the UHPC overlay and substrate 

concrete. In November 2016, a field study was 

conducted to evaluate the bond between the 

UHPC overlay and the substrate concrete bridge 

deck.

Based on the observations and data collected 

during that field study, it can be concluded 
15

that the bond between the UHPC overlay and 

the existing concrete bridge deck was intact. 

Mechanical testing verified that the locations 

suspected of having good UHPC–concrete bond 

were able to carry relatively high tensile stresses 

without bond failure. It can also be concluded 

that good bond was achieved even at locations 

where deck concrete was not roughened prior 

to placement of the UHPC overlay; however, 

this is dependent on the surface quality of the 

substrate concrete and is not a recommended 

practice. The two test locations suspected 

of delamination were indeed found to have 

delaminated concrete. However, delamination 

was preexisting within the deck concrete and 

was likely present prior to placement of the 

UHPC overlay.

Visual inspection of the UHPC field specimens’ 

interface indicated, in all cases, that the interface 

between the UHPC overlay and deck concrete 

appeared intact. This was further investigated 

through microstructural analysis using a 

scanning electron microscope. Microstructural 

analysis revealed that there was a high density 

of UHPC in direct contact with the concrete 

substrate surface. This high density was caused 

by the high content of hydration products from 

the UHPC and low porosity adjacent to the 

interface. The consequence of this was a high 

degree of direct contact between the UHPC and 

the concrete surface, which translated into high 

tensile strength of the interface.

References

1. Brühwiler, E. and Denarié, E. (2013). 

“Rehabilitation and Strengthening of 

Concrete Structures Using Ultra-High 

Performance Fibre Reinforced Concrete,” 

Structural Engineering International, 23(4), 

pp. 450–457, International Association for 

Bridge and Structural Engineering, Zurich, 

Switzerland.

2. Haber, Z., Munoz, J., and Graybeal, B. 

(2017). Field Testing of an Ultra-High 

Performance Concrete Overlay, Report No. 

FHWA-HRT-17-096, p. 57, Federal Highway 

Administration, Washington, DC.

3. Wille, K. and Boisvert-Cotulio, C. (2013). 

Development of Non-Proprietary UltraHigh Performance Concrete for Use in 

the Highway Bridge Sector, Report No. 

FHWA-HRT-13-100, p. 59, Federal Highway 

Administration, Washington, DC.

4. Graybeal, B.A. (2014). Design and 

Construction of Field-Cast UHPC 

Connections, Report No. FHWA-HRT-14-084, 

p. 36, Federal Highway Administration, 

Washington, DC.

5. Krauss, P., Lawler, J., and Steiner, K. (2009). 

Guidelines for Selection of Bridge Deck 

Overlays, Sealers, and Treatments, NCHRP 

Project 20-07 Report, p. 51, Transportation 

Research Board, Washington, DC.

6. De La Varga, I., Haber, Z., and Graybeal, 

B. (2017). Bond of Field-Cast Grouts to 

Precast Concrete Elements, Report No. 

FHWA-HRT-16-081, p. 19, Federal Highway 

Administration, Washington, DC.

7. Brühwiler, E., et al. (2015). Strengthening the 

Chillon viaducts deck slabs with reinforced 

UHPFRC, Proceedings of the 2015 IABSE 

Conference, Geneva, Switzerland, p. 8, 

International Association for Bridge and 

Structural Engineering, Zurich, Switzerland.

8. ASTM C1583/C1583M-13. (2013). 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 International, West Conshohocken, 

PA.

9. ICRI Committee 310. (2013). Selecting and 

Specifying Concrete Surface Preparation for 

Sealers, Coatings, Polymer Overlays, and 
16

Researchers—This document was prepared under the direction of Benjamin Graybeal at 

the Federal Highway Administration (FHWA) Turner-Fairbank Highway Research Center. The 

document content was prepared by Jose F. Munoz and Igor De la Varga of SES Group and 

Associates, LLC under laboratory support contract DTFH61-13-D-00007. Work was also completed 

under laboratory support contract DTFH61-16-D-00033. For additional information, contact Ben 

Graybeal at (202) 493-3122, Zach Haber at (202) 493-3469, or at the FHWA Office of Infrastructure 

Research and Development, 6300 Georgetown Pike, McLean, VA 22101-2296.

Distribution—This TechNote is being distributed according to a standard distribution. Direct 

distribution is being made to the Divisions and Resource Center.

Key Words—Overlay, bridge deck, rehabilitation, bond, cracking, deterioration, UHPC.

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

Transportation in the interest of information exchange. The U.S. Government assumes no 

liability for the use of the information contained in this document. The U.S. Government does 

not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this 

document only because they are considered essential to the objective of the document.

Quality Assurance Statement—The Federal Highway Administration (FHWA) provides highquality 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.

FEBRUARY 2018 FHWA-HRT-17-097

HRDI-40/02-18(200)E

Concrete Repair, International Concrete 

Repair Institute, Rosemont, IL.

10. Buchanan, P.M. (2002). Shrinkage of Latex 

Modified and Microsilica Concrete Overlay 

Mixtures, Ph.D. Dissertation, Virginia 

Polytechnic Institute and State University.

11. Beushausen, H., Höhlig, B., and Talotti, M. 

(2017). “The Influence of Substrate Moisture 

Preparation on Bond Strength of Concrete 

Overlays and the Microstructure of the 

OTZ,” Cement and Concrete Research, 

92, pp. 84–91, Elsevier, Amsterdam, 

Netherlands. 

12. Haber, Z. and Graybeal, B. (2016). 

Performance of Different UHPC-Class 

Materials in Prefabricated Bridge Deck 

Connections, Proceedings of the First 

International Interactive Symposium on 

Ultra-High Performance Concrete, Des 

Moines, IA, p. 10.

13. Oxford Instruments. (2013). AZtec User 

Manual, 2.1, pp. 505, Oxford Instruments.