NBSIR 73-295

Interim Report No. 7. Chemical

Resistance and Physical Durability

Testing of Coating Materials

Nonmetallic Coatings for Concrete Reinforcing Bars

James R. C lifton Hugfi F. Beegtily

Robert G. Mathey

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

August 1973

Interim Report for Period

April - June 1973

Prepared for Federal Highway Administration

U. S. Department of Transportation

Washington. D. C. 20590
»
NBSIR 73-295

INTERIM REPORT NO. 7. CHEMICAL

RESISTANCE AND PHYSICAL DURABILITY

TESTING OF COATING MATERIALS

Nonmetallic Coatings for Concrete Reinforcing Bars

James R. Clifton

Hugh F. Beegiily

Robert G. Mathey

Center for Bunding Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

August 1973

Interim Report for Period

April - June 1973

Prepared for Federal Highway Administration

U. S. Department of Transportation

Washington, D. C. 20590

U. S. DEPARTMENT OF COMMERCE, Frederick B. Dent. Secretary

IMATIOIMAL BUREAU OF STANDARDS. Richard W. Roberts, Director

TABLE OF CONTENTS

Page

1. Project Information 1

2. Introduction 1

2.1 Background 1

2.2 Objectives 1

3. Discussion of Activities 2

3.1 Chemical Resistance Testing 2

3.1.1 Epoxy Disc Specimen 2

3.1.2 Coating on Reinforcing Bars 3

3.2 Chloride Permeability 4

3.3 Impact Test 4

3.4 Hardness of Coatings • 5

3.5 Corrosion Studies of Coated Reinforcing Bars Embedded in Concrete.. 6

3.6 Creep Tests 6

3.7 Qualification Specifications 7

3.8 Talk Based on Project 7

3.9 Pertinent Visits by NBS Staff 8

4. Status of Project 8

5. Problems 8

6. Work Planned for Next Quarter 8

7. References , 9

i

Interim Report No. 7 Chemical Resistance and Physical Durability

Testing of Coating Materials

1. Project Information . Order No. 2-1-0614 Title : Nonmetallic

Coatings for Concrete Reinforcing Bars.

Date Project Initiated . 9-17-71

Research Agency . National Bureau of Standards

2 . Introduction

2.1 Background . The early deterioration of the concrete of bridge

decking, due to the corrosion of steel reinforcing bars, has become a

major problem during the past decade. The annual cost of repairing bridge

decks damaged in this manner is probably over 70 million dollars.

Normally, reinforcing steel is passive to corrosion when in an

environment of the high basicity inherit in portland cement concrete.

Chloride ions, however, are able to depassivate steel and thereby promote

the active corrosion of steel.

Sodium chloride and calcium chloride are extensively used as de-icing

agents on highways and bridges. When dissolved in water, these de-icing

agents permeate through concrete decks to the regions where reinforcing

bars are located. This leads to the corrosion of steel and subsequent

cracking and spalling of the concrete. The amounts of sodium chloride and

calcium chloride used as de-icing agents has increased substantially

during the past decade.

2.2 Obj ectives . To investigate the protective qualities of organic

coatings, especially epoxy systems, and to select the most promising

materials for corrosion protection of concrete reinforcing bars, the
selection to be based upon physlochemical testing with consideration

given to the economics invo^-ved in coating and fabrication.

3. Discussion of Activities

The long-term chemical-resistance and chloride-permeability testing

of coating materials has been completed and the final results are given

in this report, along with the results of indentation-hardness and

impact-resistance determinations of coating on reinforcing bars. The

corrosion testing and structural-type testing (creep) is continuing,

and will be mentioned.

Descriptions of the coating materials selected for evaluation in this

work are listed in table 1. The methods of selecting and procuring the

materials are discussed in NBS Report 10968 [1]. The techniques of preparing or obtaining test specimens (epoxy discs, coated rebars, thin epoxy

films, etc.) were also described in NBS Report 10968 and will not be

repeated in this current report.

Grade 60, No. 6 steel reinforcing bars were used exclusively throughout this project.

3 . 1 Chemical Resistance Testing

3.1.1 Epoxy Disc Specimens . Disc shape castings of cured epoxy

specimens (liquids in their uncured states) were each immersed in the

following: in water, in an aqueous solution of 3M CaCl2; in an aqueous

solution of 3M NaOH; and in a solution saturated with both Ca(0H)2 and

CaSO^.2H20 which also contained 0.5M CaCl2. The specimens were immersed

in water for a few minutes and wiped dry before measuring the original

weights. Original weights of the discs varied from ca. 20 grams for

solvent-containing systems to ca. 50 grams for the solventless epoxy
systems. The temperatures of the test solutions were 24 ± 1°C.

The specimens were immersed for over a year and the final

immersion data are presented in table 2. In some cases two separate

castings were made; indicated by two sets of data with different immersion

times. In general, weights of the specimens changed by less than ±4

percent. The epoxies which in their uncured state contained solvents,

generally lost weight and had greater weight changes than the solventless

epoxies. In contrast to most specimens, No s . 4, 9, and 16 gained weight in

the NaOH and lost weight in the other solutions. An exception to the

solvent containing epoxies is No. 7, which had the largest weight increase

(13 to 19 percent) of all epoxies studied. The surfaces of both No. 7 and

No. 9 specimens were converted from smooth to rough textures during the

immersion period. No apparent deterioration was observed with the other

epoxy specimens. x

The weight losses of solvent-containing epoxies possibly may be

associated with the gradual loss of retained solvents. Large weight

increases may be indicative of porosity or swelling.

3.1.2 Coating on Reinforcing Bars . The chemical resistances of

powdered epoxy systems were investigated by immersing coated reinforcing

bars in aqueous solutions of 3M NaOH and of saturated Ca(0H)2. The coatings

were inspected for evidence of softening,' color change, disbonding and

changes in film integrity. The data are presented in table 3 for three

polyvinyl chloride coatings, Nos. 23, 24, and 30; one pseudo-powder epoxy.

No. 19; 10 powder epoxy coatings; and uncoated bars.

The rusting of some coated reinforcing bars and the uncoated bars

in saturated Ca(0H)2 solutions is an interesting phenomenon, especially

3
since the corrosion was only observed in the weaker alkaline solution,

i.e. saturated CaCOH)^ rattier than 3N NaOH. The pH of saturated CaCOH)^,

however, is near 13 which is sufficient to passivate steel. Therefore,

the cause of the corrosion apparently lies in either the surface preparation or in the composition of the coatings. Note that the surfaces of the

rusting specimens of numbers 38, 39 and 40 were phosphatized before the

epoxy was applied. Also, it was noted that the epoxy over the phosphated

surfaces had softened during immersion. The surfaces of the companion

non-rusting specimens were only sand blasted and the epoxy film had not

softened. It is not obvious at this date why the same rusting phenomenon was not observed when the rebars with various surface preparations

were immersed in the 3M NaOH.

3.2 Chloride Permeability . The chloride permeability characteristics

of thin films (3-7 mils) of cured epoxies have been measured by the

methods described in NBS Report 10968 [1]. The final data are presented

in table 4. Many of the epoxy films, Nos. 1, 17, 19, 31 and 39, appear to

be essentially impervious to chloride ions. Only two films, Nos. 13 and

16, permitted sufficient chloride ions to migrate through so that the

corrosion threshold concentration of 0.2 M [2] was reached.

3.3 Impact Test

The resistance of coatings on reinforcing bars to mechanical damage

was assessed by the falling weight method. A test apparatus similar to

that described in ASTM Designation G14-69T [3] was used along with a four

pound tup. Impact occurred on the low-lying areas on the coated bars,

i.e. areas between the deformations. The test was performed at 25°C.

4
The type and extent of damage to the coating caused by impact of

120 in-lb was visually assessed and the area of damage was measured. The

data are listed in table 5. It has been concluded, arbitrarily, that the

area of damage on a acceptable coating for rebars should not exceed

2 0.15 in for a 120 in-lb impact.

3.4 Hardnesses of Coatings

The microhardness of coatings on steel reinforcing bars were

measured by the indentation method, using an apparatus of the type described in ASTM Designation D1474-68 [4], and following the methods

outlined therein. A 10 gram load was used.

The Knoop Hardness Number (KHN) was calculated with the equation:

KHN = _L_ = L

Ap UC^

where L is the load applied to the indenter in kilograms; £ is the measured

length of the long diagonal of the indentation in the coating in milli-

-2

meters; Cp is a constant with the value of 7.028 x 10 ; Ap is the

projected area of the indentation.

The results for five coatings on rebars are given in table 6. No. 30

is a polyvinylchloride and has a relatively low hardness of 6.7 KHN, while

the other four coatings are powder epoxies having hardnesses above 18 KHN.

No. 22 and No. 31 are rebars coated with the same epoxy material but

applied by different methods yielding different film thicknesses. The film

thickness of No. 22 is ca. 25 mils (applied by the fluidized bed technique),

while the film thickness of No. 31 is ca. 8 mils (applied using electrostatic spray gun). The microhardness was determined to be 20.7 KHN for

both coating films; therefore, it seems that the microhardness of the

5
coating film alone was being measured and not the composite hardness of

the coating and the steel substrate.

3 . 5 Corrosion Studies of Coated Reinforcing Bars

Embedded in Concrete

The protective qualities of coating materials are also being

evaluated by corrosion studies of coated rebars embedded in concrete

specimens. These specimens have been partially immersed in an aqueous

solution of 3.5 percent NaCl. Any corrosion occurring is being monitored

by taking both electrical potential and electrical resistance measurements. The fabrication of test specimens and the method of testing have

been previously described [5].

The current data are presented in table 7. No evidence of cracks

developing in the concrete cover nor of rust stain have been observed.

3.6 Creep Tests

The creep characteristics of coated steel reinforcing bars embedded

with one end in concrete prisms and loaded under tension are being

assessed and compared to the creep of uncoated reinforcing bars embedded

and loaded in the same manner. The work in this reporting quarter

involved loading the creep specimens and recording the initial measurements. The fabrication of test specimens and preparation of the test

apparatus have been covered in a previous report [5].

Two levels of tensile stresses in the steel reinforcing bars, 15,000

and 30,000 psi, are being exerted by the compression of steel coil springs.

The tensile stress in the rebar for each creep specimen is listed in

table 8. Strain gages, with small intrinsic creep properties, and

measurements of the changes in length of the compressed springs are being

used for monitoring tensile loads in the rebars [5]. Both the

6
free and loaded-end slip of the reinforcing bars embedded in the concrete

prisms are being measured with dial gages.

The tests were just commenced at the end of this reporting quarter.

Possibly, sufficient data will be available in the next reporting quarter

to make tentative interpretations of the creep characteristics of coated

and uncoated rebars.

3 . 7 Qualification Specifications

Qualification specifications that cover the requirements new coatings

must meet for approval as acceptable coating for steel reinforcing of

concrete bridge decks have been drafted by the NBS staff and forwarded

to the FHWA.

3.8 Talk Based on Project

The following talk based on the project was given by Dr. James R.

Clifton:

"Organic Coatings for the Protection of Steel Reinforcement in

Concrete Bridge Decking," staff meeting of the Center for Building

Technology of NBS, April 19, 1973.

3.9 Pertinent Visits by NBS Staff

1. Dr. Clifton and Mr. Beeghly visited the Westinghouse Power Cooling

Systems Department, Media, Pennsylvania, on April 25, 1973, to discuss the

use of epoxy coated reinforcing bars in the reinforced concrete of power

plant cooling towers.

2. Mr. Beeghly visited H. C. Price Company, Fairless Hills,

Pennsylvania on May 31, 1973, to witness the applications of a powder epoxy

coating of duPont Company to rebars on a production-line basis. This production run was performed for the duPont Company and the Bethlehem Steel

Company.
3. Mr. Beeghly visited Taylor-Davis Company, Wilmington, Delaware,

on June 5, 1973, to observe fabrication (bending, and cutting to size) of

the bars coated by Price on May 31, 1973. The coating was only slightly

damaged by the fabrication process.

4 . Status of Project

All of the tests specified in the project-contract are either

completed or are currently being performed.

5. Problems

It is the opinion of the NBS staff that both the creep and corrosion

testings of reinforcing bars embedded in concrete should be continued

until either the specimens fail or unequivocal test results are obtained.

This will certainly necessitate continuance of these tests beyond the

contract expiration date of September 30, 1973. It is recommended that

these studies continue for at least one year beyond the contract expiration date.

6. Work Planned for the Next Quarter

The corrosion testing and creep testing of coated and uncoated

reinforcing bars embedded in concrete will be continued.

Many of the drawings, photographs and tables to be included in the

final report will be prepared.

Studies on the protective qualities of epoxy coatings on rebars

will be completed and the results analyzed.

8
References

1. J. Clifton, H. Beeghly and R. Mathey, "Interim Report No. 4, Screening

Tests for Evaluating Materials." NBS Report 10968 (1973).

2. D. A. Hausman, "Steel Corrosion in Concrete," Materials Protection,

6, 19 (1967).

3. ASTM Designation 614-69T, Impact Resistance of Pipeline Coatings

(Falling Weight Test).

4. ASTM Designation D 1474-68, Test for Indentation Hardness of

Organic Coatings.

5. J. Clifton, H. Beeghly, E. Anderson and R. Mathey, "Interim Report

No. 6, Corrosion and Creep Testing of Coated Reinforcing Bars in

Concrete," NBS Interagency Report 73-229 (1973).

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TABLE 3 IMMERSION TESTING OF COATINGS ON 1/ REINFORCIMG BARSCode

Number 3N NaOH^^ 2/ Saturated Ca(OH)—

19

22

No

No

Change

Change

A.

B

.

No

3/ Very Badly Rusted—

RaHIv Rii«?tpH3/

Change

23 No Change No Change

24 No Change No Change

25 No Change No Change^

27 No Change No Change

28 No Change Slightly Rusted

29 No Change Slightly Rusted

30 No Change No Change

31 No Change No Change

32 No Change No Change

38 No Change B.

P.

4/ 5/ Rusted- -

Rusted^/ 1'

39 No Change B.

P.

4/ No ChangeRust edi/ 1/

40 No Change B.

P.

4/ No ChangeRustedi' A/

41 No Change No Change

Uncoated

Rebar No Change Rusted

— No. 6 reinforcing coated by firms handling the respective

coatings

.

2/ Immersion time of 270 days.

A and B are specimens from companion bars. 3/

4/— B denotes bars that were only sandblasted prior to

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surfaces were also phosphatized prior to being coated. — Rusting took place during the first 15 days of immersion;

afterward rusting lifted most of epoxy from bar.

6 / — No rust. Numerous small blisters, apparently caused by

penetration of water through coating, had been formed.

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ni H cd 1-4 p, <H H -a X) CO p Q H CO X)

I—

1

TivJ o (U a O 0) pP (J Ti frt *>y P-t r"w u ri»-< 4-1 i-< XI XI X) a 4.) ri Pp X3

M-l Q Q 4.1 Q Q c C 4-1 Q H

rJ—' c CO r\ CO CO CO c CO *H *H frt *>y CO

tf) H CO Q C/3 CO •H Q CO pP

*rH H *H *H 60 60 60 CO r-* »-' »-« H Ti Q 60 c CO C c c C CO Q Q Ti UJ C H o 0) •H •H •H o H-l 0) *H •H H 1] ,| •H

t-rl H •H o W Ti J-i Vj »-i •H 0 11 4-J T^ fit J-i

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cO W-< 01 OJ 0) 4-1 CO CO CO 00 0)

(Tt nj frt ^y 4-1 frt ^y CO CO 4-1 4J 4-1 to 4-1 j_j frt ^y ]

1 1-t 4-» 0) Q 4-1 C 60 4-1 4-1 4-1 C 60 c frt *>y *H U

CO W) c 00 p rt-i 00 00 p CO CO to (U 00 to

fTl 0) *H O rl H x. 0) 0 .p^ Ti r; CO QJ H QJ X) e Tl *H *H CO X) E Ti *H CO

r*U-i ii d j_i H J CO \-t 1

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(U ut e 4-» CO bO i-> 4-1 tj CO 60 60 60 60 60 60 4-J 4-» cn 60

frt Q >-i cO frt d) •H •H •H iH >-i CO CO •H

x: CO r-( tH rH CO CO CO rH

4-i O CO cn CO CO CO CO i-J m u 0 C/3

to

X)

0160

COE

CO Q

0 (30 CNJ n-i a^ 00 00 00 00 00 <r 0 ON 1^ CO

CM ao C30 00 CN CO rH rH 0 0 cn 0 rH 0 0 0 0 CNI 0 rH 0 0 0

cn

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in

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CM

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Cv4 in in I 00

00 CTn CN

CN mCN CN in

CN CM 00

CN

15
• 60

CO

C

CD •H

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cO ac re 60d

4-1 CO 60 . •H 60 . o o d CO T3 d CO CO 4-) 60 •H QJ d •H QJ 60 a 4-1 O C U o U d S x: CO a CO XI o CO •H

•H 60

•I-l dm ck ra 4-1 is ra iJ ck

4-1 iH

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CO cn 4J cr 4J

pa •u 4-1 pa

cr 60 >^ CO X B X XI B c +j 60 •H 60 60 •H •u

•rH 60 x: •H •H •H

X

4-1 Td 60

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CO 0)

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CO CO

ar

CO CO ar

CO o QJ QJ XI QJ QJ XI

O eo 14-1 ea ar ar re ar ar re ea 00 a o u c CJ CO 4-1 4-1 4-1 4-1 CO

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C 4-1 • CO CO • CO CO • CO • CO 4-1 * c 60 •H O c D- a. d cx d cx d O d

0) o d CO o 0 B o 60

B o B o 60 CO o M X) •H c a •H •H •H •rl d •H •H •H •rl d cx •rl

CtJ CO 4-) o e 60 60 •H 60 60 •H

B 60 6 •rH CO XI •H QJ 4-1 QJ •U 4-1 QJ 4-1 QJ 4-1 •H QJ

CO t3O CO CO CO I-l CO CO J-i COU CO

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CO. CO 0) 60 •H 60 60

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rrl. QJ •H QJ QJ •H QJ QJ •H •H

QJ 6 4-1

d +J 4-1

d 4-1

d 4-1

d

X

d

<!)- 60 60 •H 4J

O QJ 4-1 4-1 QJ >1 QJ •U QJ >^ cn QJ •H !-i CO CO 4-1 CO CO 4-J CO 4-1 CO U rH CO 4J iH CO 4J x: i-l x; x: X d x: X x: X S X

CO

J COu Q) CO Q) o C/2 QJ (/3 QJ 8 CO QJ

to

to

QJ

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QJ QJ X) J3 O S o d

00 o O (TV 00 00 00 CJN 00 00 00

CNI rH rH CN CO CN

m CN o rH rH o o o o o O o o I

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CN 00

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d

•H

CO

>-l CO CN X O 60d CO •H •H UU Cl. O d

14H 4-1 dH QJ

0) x:

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QJ XI

QJ

4-1 CO od

»H

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16
TABLE 6 INDENTATION HARDNESSES OF

COATINGS ON REINFORCING BARS

Code Hardness

Number KHN

^

22 20.7

29 19.8

30 6.7

31 20.7

39 21.2

—^ Knoop Hardness Number

17
TABLE 7 ELECTRICAL POTENTIAL AND RESISTANCE MEASUREMENTS

OF CORROSION-TEST SPECIMENS IN AQUEOUS SOLUTION

OF 3.5 PERCENT NaCl.

Coating , Code No.-

Exposure Time (Hour)

24 3480 EMF

(MV)

Resistance

(ohms) EMF(MV)

Resistance

(ohms)

Protective , Rating -

1-1

1-S

3

18

19

25

27

28

29

30

31 A

B

38

39-Phos A

40-Phos A 40-Phos B

40

41

-345.0

-408.8

-337.0

-484.5

-285.6

-260.3

-339.2 -130.0

-575.6

-484.0

-^138.0

-542.7

-654.6

-571.5

-461.5

-376.3

-403.4

-058.0

-448.2

-359.8

-092.2

-392.7

-513.0

-536.2

-282.2 -382.5

-431.8 -377.0

-540.5

-575.9

3.8 X lo; 7.0 X lO'

2.5 X 10

4.8 X 10

3.1 X 10' 2.7 X 10

2.4 X 10^ 1.0 X 10

6.0 X 10"

5.6 X 10 6.1 X 10

4.1 X 10

1.3 X 10, 6.8 X 10'

5.2 X 10

6.4 X 10' 6.6 X 10

1.0 X lo; 1.5 X 10'

1.5 X lo; 9.8 X 10-

3.2 X 10

4.9 X 10' 5.0 X 10

2.5 X 10^ 3.4 X 10

2.9 X 10^ 2.8 X 10

6.0 X 10^ 5.4 X 10

-283.0

-362.4

-215.0

-371.5

-432.4 -365.5

-142.3

-115.5

3/ -003.0^'

-399.5

-282.0

3/ -271.4-

3/ -167.0^' -542.0

-^62.8 3/

3/ -163.0^'

-360.5

N.C.

-127. 4-'

3/ -038.5-

-013.5

-165.7

-348.0

-402.0

-256.6

-325.5

-398.0

-316.9

-^32.2

-324.4

3.9 X 10 8.2 X 10^

2.5 X 10

4.2 X 10

2.2 X 10' 2.4 X 10

1.1 X 10^ 1.4 X 10

1.0 X 10

5.4 X lo: 6.0 X 10^

5.1 X 10

7.2 X 10" 1.1 X 10

5.4 X 10

7.8 X 10' 5.4 X 10

2.1 X 10^ 1.6 X 10^

9.8 X 10^ 6.2 X 10

4.1 X 10

4.7 X 10' 4.8 X 10

2.2 X 10^ 2.7 X 10

3.1 X 10^ 2.3 X 10

1.3 X 10^ 2.5 X 10

Uncoated A -334.2 -264.02.7 X 10' 2.6 X 10 -206.6 -180.32.3 X 10' 2.2 X 10

1/ A and B denote duplicate specimens.

2/ — Ratings from Table 8 of reference [1].

3/ — Large shifts In electrical potential attributed to silicone seal. sealing small holes in the

18
TABLE 8 CREEP TEST SPECIMENS

PC Impn

No.

Coating

No.

Stress in

(psi)-^

("Inn p TP t* No.

1 19 30,000 2

2 u.c.A/ 30,000 2

3 39 30,000 2

4 39 15,000 2

5 U.C. 15,000 1

6 - 30 30,000 1

7 38 30,000 2

8 31 30,000 2

9 25 15,000 1

10 30 15,000 1

11 U.C. 30,000 1

12 25 30,000 1

13 1 15,000. 2

14 31 15,000 2

15 41 30,000 1

16 29 30,000 1

17 38 15,000 2

18 U.C. 30,000 2

19 19 15,000 2

20 29 15,000 1

21 41 15,000 1

22 18 30,000 1

23 1 30,000 2

24 18 15,000 1

Tensile stresses in the steel reinforcing bars 1/

2/ — Identification of batch of concrete used to fabricate specimen

3/ — Denotes uncoated rebars

19

FORM NBS-114A 11-71) U.S. DEPT. OF COMM. 1. PUBLICATION OR REPORT NO. 2. Gov't Accession

BIBLIOGRAPHIC DATA mucti, Ti oq:: SHEET NBSIR 73-295

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Interim Report No. 7. Chemical Resistance and Physical

Durability Testing of Coating Materials. Nonmetallic Coating

for Concrete Reinforcing Bars.

5. Publication Date

Ai 1 cri 1 G t- 1 Q7

^4. Performing Organization Code

7. AUTHOR(S)

James R. Clifton, Hugh F. Beeghly, Robert G. Mat?

8. Performing Organization

ey NBSIR 73-295

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/ Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Address

Federal Highway Administration

U. S. Department of Transportation

Washington, D. C. 20590

13. Type of Report & Period Covered Interim

April— June 1973

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) The possibilities of Protecting steel reinforcing bars embedded in concrete of bridge

decks from corrosion by using organic barrier-type coatings are being investigated

in this project. This corrosion is accelerated by the chloride ions of the two most

commonly applied deicing materials, sodium chloride and calcium chloride.

In this report, physiochemical studies performed on coatings and coated bars are discussed, including: immersion studies of coatings in corrosive solutions; impact ajnd

embedded in concrete.

17. KEY WORDS (Alphabetical order, separated by semicolons) -n • j Bridge decks; corrosion; creep testing;

epoxy coatings; polyvinylchloride coatings; steel reinforcing bars

18. AVAILABILITY STATEMENT

fx] UNLIMITED.

I I FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

19

22. Price

USCOMM-DC 66244.P71