TECHBRIEF Guidelines for Sampling, 

Assessing, and Restoring

Defective Grout in 

Prestressed Concrete Bridge 

Post-Tensioning Ducts

FHWA Publication No.: FHWA-HRT-13-027

FHWA Contact: Paul Virmani, HRDI-60, (202) 493-3052, 

paul.virmani@dot.gov and Hamid Ghasemi, HRDI-60, 

(202) 493-3042, hamid.ghasemi@dot.gov

This document is a technical summary of the Federal 

Highway Administration report, Guidelines for Sampling, 

Assessing, and Restoring Defective Grout in Prestressed 

Concrete Bridge Post-Tensioning Ducts (FHWA-HRT-13-028).

Introduction

The objectives of this study were to provide recommended 

guidance for grout sampling, testing, data analysis, and interpretation of results and to propose courses of action by State 

transportation departments where grout deficiencies are 

identified. Grout is a cementitious material typically used to 

provide corrosion protection to the prestressing strands used 

in post-tensioned (PT) concrete bridges. Based on collected 

information and data analysis, State transportation departments can evaluate if grout deficiencies are present in the 

tendons of their PT bridges and determine the significance 

of those deficiencies.

Durability concerns associated with PT tendons were raised 

as early as 1999. Tendon failures were seen in some PT 

bridges as a result of strand corrosion due to the collection 

of bleed water in grout voids at tendon profile locations 

like anchorages and crest areas. While the development of 

prepackaged thixotropic grout was thought to provide a 

solution to the bleed water problem, corrosion-caused 

tendon failures on relatively new PT bridges have occurred, 

and the forensic studies performed to-date have revealed 

separation and segregation of grout materials as well as the 

presence of soft material, free water, and high chloride, and 

sulfate content in some instances.(1–3) Consequently, it is 

important to examine the overall quality of materials

and construction for some in-place grouts in existing

PT bridges. The product of this study is a guide for State

Research, Development, and 

Technology

Turner-Fairbank Highway 

Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

www.fhwa.dot.gov/research
2

transportation departments to employ in 

sampling in-place grouts from tendons in 

PT bridges.

Approach

A review is provided for different types of 

PT tendons, bridge design, and construction 

approaches. In addition to discussing the role 

of chlorides and other chemical deficiencies in 

causing strand corrosion and tendon failure, 

the main report also covers other deficiencies 

such as lack of consistency and consolidation, segregation, and presence of free water. 

Specific issues and topics addressed in the 

main report include the following:

•	 The types of tendons from which grout 

samples should be obtained.

•	 The number of extracted grout samples 

required from each tendon type on a 

statistical basis.

•	 An explanation of proposed methods 

for retrieving grout samples from 

tendons, including anchorages, such that 

any impact on future durability is not 

compromised.

•	 Recommendations regarding the amount 

of grout and the tests required for property characterization.

•	 Recommendation of a systematic procedure for recording and reporting grout 

composition in order to define its quality 

and project its future performance. 

•	 Recommended repair/rehabilitation procedures for tendons in order to minimize 

the impact on future durability caused 

by sampling.

•	 Presentation on a decision path guideline based on the grout analysis 

results that recommends future tendon 

inspection and, if necessary, grout 

sampling intervals.

Sampling Methodology and Risk 

Projection

It is important that the number and location 

of acquired grout samples are statistically 

representative of the overall PT tendons. 

Factors to be considered in this regard 

include the number of grout lots employed, 

the availability of a grouting log, and the 

quality of workmanship. There are two grout 

sampling options: option 1 involves sampling 

for chlorides only, and option 2 tests for all 

grout deficiencies. Under each option, there 

are two levels of grout sampling: level 1 

provides an initial indication of grout condition via preliminary screening tests, and level 

2 involves the following steps, as shown in 

figure 1: (1) review the as-built plans, PT 

shop drawings, specifications, and construction records; (2) conduct a walk-through 

visual inspection for the length of the bridge; 

(3) examine and document the grout condition, obtain grout samples, and inspect for 

any indications of tendon defects; and 

(4) analyze and evaluate the grout samples.

Each tendon is classified as being of low, 

medium, or high risk of failure. This classification is defined as the product of an 

indicator of defect probability and a consequence of failure indicator (see figure 2). 

The indicator of defect probability is comprised of the following four factors:

1. Bridge condition.

2. Availability of construction records.

3. Visual condition evaluation.

4. Tendon geometry and length.

Examples

In order to show how the proposed guidelines can be implemented, example analyses 

are provided for four different types of PT 

bridges including a typical precast balanced 

cantilever segmental bridge, a typical PT 

spliced girder bridge, a typical span-by-span 

segmental bridge, and a typical PT bridge 

with draped internal tendons. The precast 

segmental balanced cantilever and PT spliced 

girders are from actual projects, whereas the 

other two cases were conceived as examples.

Analysis of Grout Samples

Grout sampling should be performed during the overall bridge and tendon inspection 
3

process and can be performed at an opened 

end cap or at an intermediate coupling location. Grout sampling can also be performed by 

cutting away a section of duct, which involves 

concrete excavation due to internal tendons. 

Researchers should collect free water and 

corrosion products, if present, and acquire 

samples of each grout type (i.e., segregated, 

soft, etc.). 

Grout characterization requires that both 

composition and structure (macro and 

micro) be determined. Composition should 

be determined by wet chemistry analysis for total chlorides and soluble chlorides 

and by analytical techniques such as ion 

chromatography (solution only), X-ray 

florescence (solid or powdered samples 

only), and energy dispersive spectroscopy (solid or powdered samples only).(4)

The structure should be determined by 

petrographic methodologies, electron microscopy, and X-ray diffraction. 

Minimally, X-ray florescence and wet chemistry analysis for total chlorides should be 

performed. Petrographic analysis should be 

performed in accordance with the applicable ASTM standard.(5) If strand corrosion is 

ongoing, then corrosion state and rate can 

be assessed by appropriate electrochemical 

methods.(6–8)

Sampling Locations

After the number of randomly selected 

tendons to be sampled is determined, sampling locations should be strategically 

located. Typically, grout chemical and physical deficiencies are found at high elevations 

along tendons, so the most straightforward 

approach is to collect grout samples from cap 

internal areas. Duct or coupler removal, as is 

Figure 1. Grout inspection processes.

Pre-Inspection Activities

Review As-Built

Plans

Review Construction 

Records

Review Inspection

Documents

Review Load Rating

Visual Inspection and 

Non-Destructive Testing

Walk Through

Duct Sounding

(External Tendon)

Cracked Concrete

Signs of Water 

Leakage

Corrosion Protection 

System

Signs of Corrosion

Grout Sampling 

Inspection

Grout Sample 

Evaluation

Presence of Voids

Grout Segregation

Grout Consistency

Grout Discoloration

Present of Corrosion

Borescope 

Inspection

Grout Sample 

Collection

Grout Petrographic 

Evaluation

Corrodant 

Concentration

Moisture Content
4

required for access to grout at intermediate 

locations, has a greater chance of causing 

distress. It is not always possible to remove 

grout samples from a cut window in a duct 

away from anchorages of internal tendons 

because of strand configuration. For both 

option 1 and option 2 inspections, at least 

one grout sample should be collected from 

each preselected tendon.

Restoration Methods

Proper restoration of tendon damage that 

results from inspection and grout sampling is 

critical because paths for ingress of corrosives 

into the PT system may result, and long-term 

durability may be compromised. Restoration 

can either be temporary or permanent, where 

temporary restoration is due to short-term 

adverse weather or unexpected findings (or 

both). Conversely, permanent restoration 

meets the original design life.

Materials and methods should be included 

in a work plan for the restoration and be 

approved by the bridge owner. Methods and 

materials may vary for external versus internal tendons.

Interpretation of Results and Courses of 

Action

Table 1 lists chemical deficiency (CD) classifications for option 1 inspections in terms 

of four chloride (Cl−

) levels. Based on the 

findings, individual tendons are assigned a 

grade from 1 to 10, where a higher grade 

indicates a more problematic tendon condition. This in turn defines the recommended 

courses of action(s) (A). Table 2 shows the 

CD classification for option 2 in terms of the 

same four chloride levels as in option 1 as well 

as six degrees of physical deficiency (PD) 

(note that it is six degrees since PD0 has no 

deficiency). 

Figure 2. Risk matrix.

Table 1. CD classifications as determined by grout Cl− levels from an option 1 inspection 

and resultant recommended actions.

CDa

CD1 Cl− ≤ 0.08 X

CD2 0.08 < Cl− ≤ 0.20 X

CD3 0.08 < Cl− ≤ 0.20b X

CD4 Cl− > 0.50b X

Action

Grade

1 5 7 9

A1 None X

A2 Expand sampling X X

A3 Reinspect in 5 years X

A4 Reinspect in 2 years X X

A5 Tendon monitoring X X

a

 Chloride concentration units are weight percent cement.

b

 If strand corrosion or fracture(s) are found (PD5 or PD6 under option 2 in table 2), then grade 9 or 10 should be assigned as 

appropriate per option 2 actions.
5

Table 2. CD and PD classifications as determined by grout Cl− levels and in-place grout structure by an 

option 2 inspection and resultant recommended actions.

CDa

CD1 Cl− ≤ 0.08 X X X X

CD2 0.08 < Cl− ≤ 0.20 X X

CD3 0.08 < Cl− ≤ 0.20 X X

CD4 Cl− > 0.50 X X

PD

PD0 Sound grout X

PD1 Grout air pocket X X X X X X X X X

PD2 Exposed strand/tendon X X X X X X X X

PD3 Soft or segregated grout X X X X X X X

PD4 Tendon surface corrosion (no section loss) X X X X X

PD5

Tendon surface corrosion (< 5 percent section 

loss) X X X

PD6

Tendon with partial or full fracture 

(≥ 5 percent section loss) X

Action

Grade

1 2 3 4 5 6 7 8 9 10

A1 None X X

A2 Expand sampling X X X X

A3 Reinspect in 5 years X X X

A4 Reinspect in 2 years X X X X

A5 Tendon monitoring X X X X

A6 Consider repairing deficiency as necessaryb X X X X X X X X X

A7 Structural evaluation/load rating X

A8 Tendon replacement X

a Chloride concentration units are weight percent cement.

b

 This applies to PD1, PD2, and PD3. 
6

Researchers—Researchers for this project include Mr. Teddy S. Theryo of Parsons Brinkerhoff, Inc. 

and Dr. William H. Hartt of Florida Atlantic University.

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

distribution is being made to the Divisions and Resource Center.

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

to report.center@fhwa.dot.gov, fax to (814) 239-2156, phone to (814) 239-1160, or online at http://www.

fhwa.dot.gov/research. The full report is available online at: http://www.fhwa.dot.gov/research.

Key Words—Bridges, Post-tensioning, Grout, Chlorides, Corrosion, Fracture, Inspection, Sampling, 

Repair.

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 report 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 the Government, industry, and 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.

References

1. Merrill, B.D. (2011). TxDOT PT/Grout Issues, 

Presentation at the American Segmental 

Bridge Institute 23d Annual Convention, 

Washington, DC. Obtained from: http://ftp.

dot.state.tx.us/pub/txdot-info/brg/0212_

webinar/merrill.pdf.

2. Bertolini, L. and Carsana, M. (2011). “High 

pH Corrosion of Prestressing Steel in 

Segregated Grout,” Modeling of Corroding 

Concrete Structures, RILEM Series, 5, 

147–158. Cedex, France.

3. Lau, K., Lasa, I., and Parades, M. (2011). 

Corrosion Development of PT Tendons 

with Deficient Grout: Corrosion Failure in 

Ringling Causeway Bridge, Draft, Florida 

Department of Transportation State 

Materials Office, Gainesville, FL. 

4. AASHTO T 260-97. (2009). Sampling and 

Testing for Chloride Ion in Concrete 

and Concrete Raw Materials, American 

Association of State Highway and 

Transportation Officials, Washington, DC.

5. ASTM C856-11. (2011). “Standard 

Practice for Petrographic Examination of 

Hardened Concrete,” Book of Standards 

Volume 04.02, ASTM International, 

Conshohocken, PA.

6. ASTM G59-97(2009). (2009). “Standard Test 

Method for Conducting Potentiodynamic 

Polarization Resistance Measurements,” 

Book of Standards Volume 03.02, ASTM 

International, Conshohocken, PA.

7. ASTM G102-89(2010). (2010). “Standard 

Practice for Calculation of Corrosion 

Rate and Related Information from 

Electrochemical Measurements,” Book 

of Standards Volume 03.02, ASTM 

International, Conshohocken, PA.

8. ASTM C876-09. (2009). “Standard Test 

Method for Corrosion Potentials of 

Uncoated Reinforcing Steel in Concrete,” 

Book of Standards Volume 03.02, ASTM 

International, Conshohocken, PA.

May 2013 FHWA-HRT-13-027

HRDI-60/05-13(600)E