TECHBRIEF Material Characterization of

Field-Cast Connection Grouts

FHWA Publication No.: FHWA-HRT-13-042.

NTIS Accession No. of the report covered in this TechBrief: 

PB2013-130231.

FHWA Contact: Ben Graybeal, HRDI-40, (202) 493-3122, 

benjamin.graybeal@dot.gov.

This document is a technical summary of the unpublished 

Federal Highway Administration (FHWA) report Material 

Characterization of Field-Cast Connection Grouts, available 

through the National Technical Information Service (NTIS) at 

www.ntis.gov.

Objective

Prefabricated bridge element and system (PBES) construction 

concepts frequently rely on field-cast grouts to complete the 

connections between discrete precast concrete elements. A 

variety of grouts are available, each with unique performance 

attributes. The objective of this research is to evaluate the 

performance of a representative sample of grouts in terms 

of relevant material properties. This study both reports 

on the performance of eight specific grouts and provides 

general insight into the performance of five different types 

of grout. Although many of these grouts could be used in 

a post-tensioned connection system, the tests completed 

herein investigated the performance of the grouts in a nonpost-tensioned condition.

Introduction

There is a growing need for durable and resilient highway 

bridge construction/reconstruction systems that facilitate rapid 

completion of onsite activities, thus minimizing intrusion on 

the traveling public. Modular components can provide highquality, accelerated, and safe construction; however, offsite 

prefabrication of bridge components necessitates increased 

reliance on the performance of field-installed connections 

between components. The mechanical and durability responses 

of the grouts used in these connections are critical to the 

overall performance of the infrastructure system.

Constructability and serviceability problems have arisen in 

connections on some past projects. These issues have been 

attributed to a variety of causes, including construction 

Research, Development, and 

Technology

Turner-Fairbank Highway 

Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

www.fhwa.dot.gov/research/
2

techniques, materials, and poor designs. Much 

attention has been placed on making better 

connections between components. One area 

of investigation relates to the different fieldcast materials that might be used to complete 

the connections. Selection of a grout with 

appropriate fresh and hardened properties is a 

critical step in any PBES project. 

Field-Cast Connection Grouts

The grouts used in PBES construction projects 

tend to be prebagged, proprietary materials. 

The grouts are used to fill the interstitial void 

spaces within the details connecting adjacent 

prefabricated components. In most cases, 

the grouts serve to complete the connection 

wherein reinforcements emanating from one or 

both of the prefabricated pieces tie together the 

bridge system. A variety of grouts are available, 

and selection depends on the cost and the fresh 

and hardened properties that are of greatest 

interest to the bridge owner. 

Many grouts are cementitious products; however, 

materials based on alternate chemical reactions 

are also available. In this study, three commonly 

available cementitious grouts were tested. These 

grouts are referred to as G1, G2, and G3. A 

thixotropic cable grout (T1) and two ultra-high 

performance concretes (UHPC) (U1 and U2) were 

also tested. Each of these materials develops 

hardened properties through hydration reactions 

of the included cementitious constituents. A 

magnesium phosphate grout (M1) and an epoxy 

grout (E1) were also tested. These grouts rely 

on different chemical reactions but can perform 

similarly to conventional cementitious grouts. 

This study also included a traditional bridge deck 

concrete mix design (C1) as a control. 

Each of the grouts tested was acquired from 

a domestic manufacturer with a national 

distribution network. A technical data sheet 

from the manufacturer of each grout indicated 

necessary production information as well as 

anticipated material properties. At the time of 

purchase, most of the grouts ranged in cost 

from $800 to $2,200/yd3

, with the UHPC and 

magnesium phosphate grouts at the upper end 

of this range. The lone exception was the epoxy 

grout, which cost nearly $4,600/yd3. Owners and 

specifiers considering the use of these grouts 

must recognize that the grouts tend to be used 

in relatively small quantities and in applications 

requiring specialized equipment and technical 

skills. Bulk material cost is only one aspect of 

the overall determination of the cost-benefit 

relationship inherent in the deployment of a 

particular bridge construction system.

Testing Program

The testing program executed in this study 

focused on assessing the performance of the 

grouts in five distinct topic areas. In each case, 

standardized test methods were used where available and appropriate. When existing tests were 

not appropriate, alternate test methods were 

devised to investigate the property of interest.

Constructability

Constructability considerations relating to fieldcast grouts include rheological considerations, 

setting properties, and necessary construction 

equipment. These performance measures were 

assessed through standardized flow tests, 

standardized penetration resistance tests, and 

qualitative assessment of the construction site 

equipment and process demands.

Mechanical Properties

The mechanical properties of the grouts were 

assessed through a range of compression and 

tension tests. Standardized assessments for density, modulus of elasticity, compressive strength, 

and splitting tensile strength were completed.

Dimensional Stability

The dimensional stability of castable materials 

is critical to the short- and long-term performance of the constructed element. Most grouts 

marketed for use in infrastructure applications 

are referred to as “non-shrink” grouts. However, 

even within this nomenclature, grouts are known 

to express a wide range of shrinkage depending 

on the materials, mix design, and curing environment. Long-term unrestrained and restrained 

shrinkage of the bulk grout materials were 

investigated in this study through standardized 

tests. Short-term unrestrained shrinkage was 
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also investigated through a novel test method 

that captured dimensional stability beginning at 

initial placement.

Bond Properties

The bonding of a field-cast grout to the prefabricated component at the grout-component 

interface can be of critical importance to the 

long-term performance of the constructed 

system. Lack of bond can result in leakage at 

the interface and eventual degradation of the 

grout, bridging reinforcements, and precast 

component. Three bond tests were completed 

to assess the bond strength between field-cast 

grouts and prefabricated bridge deck concrete 

substrates. The slant shear bond test and the 

split cylinder bond test were based on existing 

mechanical tests, and the restrained ring bond 

test was based on an existing shrinkage test.

Durability

Durability considerations are critical in the 

selection of a field-cast connection grout, as 

grout degradation can prematurely lead to 

the need to rehabilitate the entire structure. 

A select set of grouts were assessed through 

the standardized freeze/thaw resistance test 

and the rapid chloride penetrability test.

Results

The grouts assessed in this study exhibited a 

wide range of performance on nearly every 

material characteristic. Depending on the 

application, different performance levels may 

be appropriate or may be of little relevance. 

Full details on the test methods and results are 

presented in NTIS report PB2013-130231. 

A summary of the compressive strength results

is shown in figure 1. Results collected at 24  h,

7  days, and 28 days after mix initiation are 

plotted. Exceptionally high 7- and 28-day 

compressive strengths are clearly possible with 

E1, U1, and U2. The rapid-setting nature of 

M1, indicative of this class of grouts commonly 

used for repairs, affords substantial compressive 

strength soon after mix initiation.

The overall shrinkage response of the grouts is 

presented in figure 2. These results were captured via an embedded strain gauge beginning 

at the time of casting. As such, these results 

show the initial dimensional instability that many 

grouts express early in their curing reactions. 

One grout, M1, was expansive. All of the other 

grouts exhibited shrinkage greater than the 

control concrete, C1. The conventional grouts 

(G1, G2, and G3) all shrank more than E1 and U1.

A representative sample of the bond strength 

results is provided in figure 3. These results 

pertain to the splitting tensile bond strength test, 

wherein the field-cast grout is cast against the 

sandblasted face of a precast half-cylinder. The 

interface bond strength is measured through a 

splitting cylinder test with the interface aligning 

with the location of maximum tensile stress.

For these tests, the interface was a finished 

Figure 1. Compressive strength results.
4

concrete surface that had been sandblasted 

prior to the grout cast. The results show that 

three of the grouts, E1, U1, and U2, exhibited 

sufficient bond strength to force failure to occur 

within the precast concrete substrate.

Four of the grouts were tested for freeze/

thaw resistance. The results are presented in 

figure  4. The test was extended beyond the 

normal 300 cycles in order to facilitate differentiation between three of the grouts. Grout M1 

Figure 2. Shrinkage results.

Figure 3. Splitting tensile bond strength results.

Figure 4. Freeze/thaw resistance results.
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deteriorated rapidly under the cycling, while U2, 

G1, and E1 resisted the environmental stressor.

A graphical synopsis of the study’s overall 

results is presented in figure 5. The results for 

each parameter denoted on the left are plotted 

on the adjacent linear scale, and the limits of the 

linear scale are shown. This graphic allows for 

visual interpretation of the overall results of the 

research program, thus providing a simplified 

presentation of the performance of each grout.

Summary and Recommendations

The test program focused on characterizing 

basic mechanical, dimensional stability, and 

bond properties for eight field-cast grouts that 

could be used in connecting precast concrete 

bridge components. The results demonstrate 

that material characteristics, practical construction considerations, and cost can vary widely. 

These results and others must be carefully considered when selecting the appropriate grout to 

use in a particular construction project.

For accelerated construction projects requiring 

high compressive strengths within 1 day, E1 and

U2 displayed acceptable properties. E1 had 

sufficient strength gain, was one of the most 

dimensionally stable materials, and had good 

workability and high tensile strength. The 

material also developed strong bonds with the 

precast concrete in all three bond tests and 

expressed good durability properties. However, 

its comparatively high cost may limit its viability. 

U2 also displayed appropriate strength gain; 

was comparatively dimensionally stable; and 

had good workability, high tensile strength, and 

high modulus of elasticity. The material contains internal fiber reinforcement that can arrest 

Figure 5. Summary of overall performance of the tested materials.
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Researchers—This study was led by Ben Graybeal at FHWA’s Turner-Fairbank Highway Research 

Center. For additional information, contact him at (202) 493-3122 or in the FHWA Office of Infrastructure 

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

Distribution—The unpublished report covered in this TechBrief is being distributed through the 

National Technical Information Service at www.ntis.gov.

Availability—This TechBrief may be obtained from the FHWA Product Distribution Center by 

email to report.center@dot.gov, fax to (814) 239-2156, phone to (814) 239-1160, or online at 

http://www.fhwa.dot.gov/research.

Key Words—Field-cast grout, Prefabricated bridge elements and systems (PBES), Mechanical strength, 

Shrinkage, Bond strength, Durability, Constructability.

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 TechBrief only 

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

Quality Assurance Statement—The Federal Highway Administration 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.

January 2013 FHWA-HRT-13-042

HRDI-40/01-13(250)E

cracking. This material expressed good durability properties. The material developed strong 

bonds to the precast concrete and had a unit 

price approximately half that of E1.

An alternative for this type of project and for 

other projects requiring exceptionally rapid 

strength gain is M1. The greatest concerns with 

this material relate to constructability considerations, including its very limited working time, 

and its durability. The limited work time created 

problems when trying to quickly cast the 

material in the formwork. The freeze/thaw test 

specimens rapidly deteriorated. 

The C1 mix performed as well as grouts G1, 

G2, and G3 in most cases. The conventional 

grouts shrank more, had only modestly higher 

compressive strengths and bond strengths, 

cracked earlier, and cost substantially more. 

However, the rheological properties of conventional concretes combined with the sizes of 

aggregate commonly included in conventional 

concrete present fundamental hurdles that are 

addressed by the conventional grouts.

Owners, specifiers, and designers considering 

the use of field-cast grouts for PBES connections 

should carefully consider the performance 

measures that are of greatest interest before, 

during, and after deployment of the application. 

Many classes of grout-type material are available, with each offering different performance 

levels relative to different performance metrics. 

In all cases, it is important to ensure that the 

connection design is constructible, durable, and 

economical in the near term and over the life of 

the constructed facility.