NATIONAL BUREAU OF STANDARDS REPORT10 690

QUARTERLY PROGRESS REPORT NO. 1

SEPTEMBER 17 TO DECEMBER 31, 1971

Title of Project

NONMETALLIC COATINGS FOR CONCRETE REINFORCING BARS

Sponsored by

Federal Highway Administration

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards 1 was established by an act of Congress March 3, 1901. Today,

in addition to serving as the Nation’s central measurement laboratory, the Bureau is a principal

focal point in the Federal Government for assuring maximum application of the physical andengineering sciences to the advancement of technology in industry and commerce. To this endthe Bureau conducts research and provides central national services in four broad program

areas. These are: (1) basic measurements and standards, (2) materials measurements and

standards, (3) technological measurements and standards, and (4) transfer of technology.

The Bureau comprises the Institute for Basic Standards, the Institute for Materials Research, theInstitute for Applied Technology, the Center for Radiation Research, the Center for ComputerSciences and Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the UnitedStates of a complete and consistent system of physical measurement; coordinates that system with

measurement systems of other nations; and furnishes essential services leading to accurate and

uniform physical measurements throughout the Nation’s scientific community, industry, and com-

merce. The Institute consists of an Office of Measurement Services and the following technicaldivisions:

Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic and Molec-ular Physics—Radio Physics -—Radio Engineering -—Time and Frequency -—Astro-physics -

—

Cryogenics. 2

THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to im-proved methods of measurement standards, and data on the properties of well-characterized

materials needed by industry, commerce, educational institutions, and Government; develops,

produces, and distributes standard reference materials; relates the physical and chemical prop-

erties of materials to their behavior and their interaction with their environments; and provides

advisory and research services to other Government agencies. The Institute consists of an Office

of Standard Reference Materials and the following divisions:

Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Physical Chemistry.THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promotethe use of available technology and to facilitate technological innovation in industry and Gov-

ernment; cooperates with public and private organizations in the development of technological

standards, and test methodologies; and provides advisory and research services for Federal, state,

and local government agencies. The Institute consists of the following technical divisions and

offices:

Engineering Standards—Weights and Measures— Invention and Innovation — VehicleSystems Research—Product Evaluation

—

Building Research—Instrument Shops—Meas-urement Engineering—Electronic Technology—Technical Analysis.

THE CENTER FOR RADIATION RESEARCH engages in research, measurement, and ap-plication of radiation to the solution of Bureau mission problems and the problems of other agen-

cies and institutions. The Center consists of the following divisions:

Reactor Radiation—Linac Radiation—Nuclear Radiation—Applied Radiation.THE CENTER FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research andprovides technical services designed to aid Government agencies in the selection, acquisition,

and effective use of automatic data processing equipment; and serves as the principal focus

for the development of Federal standards for automatic data processing equipment, techniques,

and computer languages. The Center consists of the following offices and divisions:

Information Processing Standards—Computer Information— Computer Services— Sys-tems Development—Information Processing Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination andaccessibility of scientific information generated within NBS and other agencies of the Federalgovernment; promotes the development of the National Standard Reference Data System and a

system of information analysis centers dealing with the broader aspects of the National Measure-

ment System, and provides appropriate services to ensure that the NBS staff has optimum ac-cessibility to the scientific information of the world. The Office consists of the following

organizational units:

Office of Standard Reference Data—Clearinghouse for Federal Scientific and TechnicalInformation 1—Office of Technical Information and Publications—Library—Office ofPublic Information—Office of International Relations.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.a Located at Boulder, Colorado 80302.;l Located at 5285 Port Royal Road, Springfield, Virginia 22151.

NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT

4216442

NBS REPORT

January 24, 1972 10 690

QUARTERLY PROGRESS REPORT NO. 1

SEPTEMBER 17 TO DECEMBER 31, 1971

Title of Project

NONMETALLIC COATINGS FOR CONCRETE REINFORCING BARS

Sponsored by

Federal Highway Administration

U. S. Department of Transportation

Washington, D. C. 20590

i

by

j^VJames R. CliftonRobert G. Mathey

Ramon L. Cilimberg

Building Research Division

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

IMPORTANT NOTICE

NATIONAL BUREAU OF STAN r

for use within the Government. Bel

and review. For this reason, the pi

whole or in part, is not authorizec

Bureau of Standards, Washington, I

the Report has been specifically pre

Approved for public release by the

director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015

accounting documents intended

>jected to additional evaluation

ting of this Report, either in

ffice of the Director, National

te Government agency for which

es for its own use.

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

m ' I

.

"

e

..

PREFACE

This is the first progress report for the project Nonmetallic

Coatings for Concrete Reinforcing Bars . The period from September 17

to December 31,

1971 is included in this report. Subsequent reports

will be issued on a quarterly basis.

l

I1 _

Quarterly Progress Report No. 1(September 17 to December 31, 1971)

1. Study Identification: Order No. 2-1-0614

Title: Nonmetallic Coatings for Concrete Reinforcing Bars.

2. Date Work Started: 9/17/71

Date of Report: 12/31/71

3. Research Agency: National Bureau of Standards

4. Background

The early deterioration of the concrete of bridge deckings has

become a significant problem during the past decade. The annual cost

of repairing such bridge deckings is about 70 million dollars.

The major portion of the early deterioration of concrete bridge

decks has been attributed to the corrosion of steel reinforcing bars

embedded in the concrete, which causes delamination and subsequent

spalling of the concrete. Normally, reinforcing steel is passive

towards corrosion in a basic environment as provided by concrete. This

passivity, however, is destroyed by the presence of chloride ions and

active corrosion takes place.

Presently, the two mostly used de-icing agents on highways and

bridges are sodium chloride and calcium chloride. These de-icing

agents when dissolved in water are able to penetrate the concrete decks,

thus, leading to corrosion of steel reinforcement and subsequent

cracking and spalling of the concrete. In the past decade, the amounts

of sodium chloride and calcium chloride used as de-icing agents has

increased multi- fold.

1

A reasonable method to prevent the corrosion of the steel reinforcing

bars is by coating them with a barrier-type protective coating. It

is felt that epoxy systems are the most promising coatings for this

application.

5. Objectives

To investigate the feasibility of using epoxy systems to protect

steel reinforcing bars and to select the epoxy systems that provide

the best protection. The selection will be based on physiochemical

testing with consideration given to economics involved in coating and

fabricating of reinforcement.

6. Progress

The work in the first quarter primarily consisted of (1) attaining

an overall view of epoxies, their chemical and physical properties and

the feasibility of using them to protect steel reinforcing bars from

the accelerated corrosive attack caused by chlorides from de-icing

salts used on bridge decking. This was accomplished by a thorough

literature search, discussions with experienced researchers and

contact with epoxy manufacturers, formulators and applicators;

(2) ascertaining what appropriate epoxy systems are commercially

available; (3) the preliminary selection of promising epoxy systems;

(4) consideration of existing methods of test applicable to various

phases of this project and the development of new test methods, when

necessary; (5) investigation of methods and techniques for applying

protective coatings; (6) determining what surface condition of the steel

reinforcing bars is necessary to obtain a sound protective coating.

2

The names and addresses of prospective epoxy manufacturers and

formulators were obtained by consulting the Thomas Register and by

reviews of such journals as Corrosion Abstracts, Corrosion, and

Materials Performance and Protect ion^ and by consulting with members

of the National Bureau of Standards staff and the staffs of other

organizations. The epoxy manufacturers and formulators contacted by

letter, inquiring if they have epoxy coatings applicable to the

present project, are listed in Table 1 along with comments regarding

the nature of their replies and products. Six firms were visited

by the NBS staff assigned to this project and the firms are listed

in Table 2. Twenty of the firms given in Table 1 have replied to

the initial inquiry. Three of those who replied stated that they

had no materials suitable for the protection of steel reinforcing

bars. Five firms, although advertised to handle epoxies, forwarded

only information on non-epoxy systems. Altogether (Tables 1 and 2),

17 firms handling epoxy systems have been receptive to our contacts.

It has been decided to investigate only 100 percent solid

epoxies, which can be either solids or liquids, as solvent containing

coatings are highly susceptible to the formation of holidays

necessitating the application of several coats. Furthermore,

epoxy formulations with coal tars will not be studied since such

formulations performed badly in reinforcing bar pull out tests ^

.

The epoxy floor covering materials do not appear to be very promising

as protective coatings for reinforcing bars. To date 11 firms have

been requested to submit samples for testing. Two samples have

been received and the remaining samples will probably be received

3

during January 1972. It is still possible that other firms,

including some not listed in Tables 1 and 2, may be requested to

submit test samples in the near future.

For the purpose of simulating in-shop applications, the epoxy

manufacturers or formulators that are willing to submit test sample

are being requested to coat a few bars during a later portion

of this project. Reinforcing bars were supplied by NBS to five

of the firms visited for them to apply their coatings. These bars

had different surfaces such as rust, mill scale and sandblasted

surfaces, in order to determine what surface preparations will

be necessary. At least one firm would not agree to application

of their coatings to a surface which had not been sandblasted

or pickled for mill scale and rust removal. The majority of firms

stated that bars should be sandblasted for the best coating

performance with pickling being the minimum surface preparation

that is acceptable.

Other facets of the development of an epoxy system to coat

reinforcing bars that have been considered are: (1) holiday

detection; (2) determination of thickness of coatings; (3)

application methods such as electrostatic spray, conventional

air spray, hydraulic spray, dipping electrodeposition, and fluid

beds; (4) site of application, in-situ or in-shop. Presently,

in-shop application appears to be the most feasible method.

A general work plan-time schedule is presented in Table 3. In

the following quarter's progress report more detailed schedule will

be submitted. It is felt that the current work is progressing

according to schedule.4

7. Problems

A. Casting of Specimens for Pull-Out and Creep Testing

Wooden forms in which specimens for the pull-out and creep

tests will be cast are being designed and will be fabricated at

the National Bureau of Standards. It is felt the specimens should

be cast with concrete having the same properties as that used in

the current corrosion testing being carried out at the Fairbank

Station of the Bureau of Public Roads. We are requesting, therefore,

that the Bureau of Public Roads cast and cure the creep and pull-out

specimens at the Fairbank Station using forms and reinforcing bars

provided by the National Bureau of Standards. Control concrete

cylinders cast along with the creep and pull-out specimens will

be tested at NBS . Concrete proportions and method and time of

mix should be provided to NBS.

B. Procurement and Logistics

As could be anticipated, the procurement of test samples

is a slow process, however, it is hoped that most samples will

be received by the end of January 1972. The logistics involved

in shipping reinforcing bars, having them coated and returned

will probably be time consuming and will be dependent on the

speed of the applicator.

8. Work Planned for the Next Quarter

In the next quarter, the chemical resistance of cured

epoxies, cast as discs, will be investigated in order to eliminate

from further consideration any unacceptable systems. Disc specimens

will be exposed to water, chloride and sulfate ion solutions.

5

aqueous saturated CaCOH)^ solution, steel, and cement paste and

concrete. The permeability of thin films of epoxies to moisture

and chloride ions will also be tested.

Corrosion testing of coated reinforcing bars toward chloride

ions will be commenced. This will include such methods as visual

inspection and electrochemical measurement.

The initial phases of pull-out and creep testing will be

started. This includes the fabrication of specimen forms and

setting-up of test equipment.

Some other aspects to be explored will be the feasibility

of application of epoxy to reinforcing bars in-situ and the degree

of surface preparation necessary for epoxies to adhere well to the

steel reinforcing bars.

9 . Acknowedgment

The contribution of Mr. Hugh F. Beeghly to this project is

appreciated

.

Reference

1. D. G. Moore, D. T, Klodt and R. J. Hensen, Protection of Steel

in Prestressed Concrete Bridges, National Cooperative Highway

Research Program Report 90, 1970.

6

TABLE

1.

Epoxy

Manufacturers

and

Formulators

Contacted

by

Letter

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1

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54

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r-4 rH t-4 1-4 1-4 r4 r-4

- 8 -

Gates

Engineering

Division

Products

are

Neoprene

and

Hypalon

and

epoxies.

Have

Wilmington,

Delaware

been

requested

to

submit

sample

and

to

coat

reinforcing

ba

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9

Kordell

Industries,

Inc.

N.R

Mishawaka,

Indiana

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10

37.

Robray

Industries

Applied

powder

coatings.

Recommends

their

PVC

coating.

Verona,

Pennsylvania

Has

epoxy

system.

Agreed

to

coat

reinforcing

bars.

60 COd i—

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60 4-J o rHd cO P^ >, o

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Ph M CLX) X) 4-» a>

X 4-4 -X CU CU do CO d 4-) 4J cu XCL O CO CO co CO cucu o 4-J 4-J 4-J Ph

CO CO 3X cu o u rH o i-H Pd

TABLE

2

Epoxy

Manufacturers,

Formulators,

and

Applicators

Visited

by

NBS

Staff

CO CD

CO G G X GG CO cd •H •HO •H X) X > >«. 4-»P > G O X cdX X cd 4-> • G O 4-1O cd 4-1 CO CL CL COG CO i—

1

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a) o G O o CD CD E CL 43CO >s G CL O 4-4 o G 4-> bQ cd cd 4-1a) cd CD 4-1 C co G•H X*H «H & 4-1 i—

1

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CD

X & &•HX X & s

CL X o cd i—

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cd

•rH

ccd

> G Ci—

i

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co G co CL G B X>> G X G g ra o ^ GG C G O G O G cdcd G £ X O G CO t—

i

CL CL G X X G >> ^E Z £ rH cd G G GO « G cd £ G X cd cdo cd «\ Z G G •H CL £

•H G •H £x E £ EG 43 G g G G o «G CL > 4-1 G « 43 Z O G•H X X CO 43 ^ O GG G K G U G #\ X OCL X G P x C X g

cd co 43 x X •H O o x• rH < -

TABLE 3

GENERAL PROJECT SCHEDULE

0->

-

—