NBSIR 73-401

Performance of Coated Steel

Reinforcement in Concrete.

Part 1. Investigation of Bond in

Pullout Specimens

Robert G. Mathey. James R. Clifton. Erik D. Anderson, Hugh F. Beeghly

Center for Building Tectinology

Institute for Applied Technology

National Bureau of Standards

Washington. D. C. 20234

May 1973

Prepared for Federal Highway Administration

U. S. Department of Transportation

Washington. D. C. 20590

j NBSIR 73 401

PERFORMANCE OF COATED STEEL

i REINFORCEMENT IN CONCRETE.

I PARTI. INVESTIGATION OF BOND IN PULLOUT SPECIMENS

Robert G. Mathey. James R. Clifton. Erik D. Anderson. Hugti F. Beeghly

Center for Building Technology

Institute for Applied Tectinology

National Bureau of Standards

Washington. D. C. 20234

May 1973

Prepared for Federal Highway Administration

U. S. Department of Transportation

Washington. D. C. 20590

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

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director
I II
ABSTRACT

Bond strengths of coated deformed steel reinforcing bars were compared

with uncoated bars by means of pullout specimens. The bond strengths

were determined for 23 epoxy-coated (10 different epoxy coatings) , 6

polyvinyl chloride-coated (3 different coating materials) , and 5 uncoated deformed reinforcing bars. The tensile reinforcement in the

pullout specimen consisted of No. 6 deformed bars, having either a barrel or diamond shaped deformation pattern, with a nominal yield

strength of 60,000 psi. The length of embedment of the reinforcing bar

in the concrete was 12 inches.

The load or bond stresses corresponding to a loaded-end slip of 0.01 inch

or a free-end slip of 0.002 inch were considered as critical values in

determining the bond strength, depending on which of these values of

slip developed first.

For coating film thickness of approximately 10 mils or less, the

epoxy-coated bars developed bond strengths essentially equal to the

bond strengths for the uncoated bars. Experimental values of bond

strengths for these coated bars were higher than minimum acceptable

values given in building code and highway bridge requirements. Bond

strengths of the polyvinyl chloride-coated bars and bars with thick

epoxy coatings were unacceptable.

i
TABLE OF CONTENTS

Page

Abstract ^

1. Project Information 1

2. Project Background 1

3. Pullout Test 1

3.1 Materials and Specimens 2

3.1.1 Reinforcement 2

. ; 3.1.2 Concrete 2

3.1.3 Coatings on Reinforcing Bars 3

3.1.4 Pullout Specimens ^

3.1.5 Fabrication and Curing of the Specimen. ... ^

3.2 Testing Procedure. . ^

3.3 Results and Discussion » ^

3.3.1 Load-Slip Relationships ^ 3.3.2 Bond Stress . 8

3.4 Summary and Conclusions 9

4. References.

ii
1. Project Information : Order No. 2-1-0614.

Title: Nonmetallic Coatings for Concrete Reinforcing Bars.

Date Project Initiated : September 17, 1971.

Research Agency : National Bureau of Standards.

2. Project Background . The premature deterioration of concrete bridge

decks in 5-10 years has become a major problem during the past decade

[1-7]. Often, this early deterioration has been attributed to accelerated corrosion of steel reinforcing bars (rebars) caused by chloride

ions from deicing materials [8-9]. The use of the two more commonly

applied deicing materials, sodium chloride and calcium chloride, has

increased substantially during the past decade. Corrosion of reinforcing

bars results in spalling and cracking of concrete, necessitating extensive

and expensive repairs.

In the present project, the possibilities of protecting steel

reinforcing bars with organic-type coatings are being investigated.

Evaluations of the physical and chemical durabilities of 47 different

coatings including epoxy and polyvinyl chloride materials were given in

a previous report [10]. Assessments of their protective qualities were

also included. It was concluded that among the organic materials,

epoxy coatings had the most promise as a protective coating for reinforcing bars. The epoxies that had the best protective qualities and

physiochemical durabilities were selected for testing in a comprehensive

evaluation program. This program includes determining the structural

characteristics, creep and bond strengths, of coated reinforcing bars

embedded in concrete prisms. The bond strengths were measured in tests

using pullout specimens (described in Section 3.1.4) and the results are presented in this report. Determinations of creep strength are currently

being performed and the results will be given in a future report.

3. Pullout Tests . Little attention has been previously devoted to

epoxy materials as protective coatings for rebars because of the

supposition that the coated reinforcing bars will have unacceptable bond

strengths [11]. No reports were found in the literature of any type of

structural testing performed on epoxy coated rebars embedded in concrete.

In this section the methodology of pullout testing will be described

along with a discussion of the experimental results. Altogether, 34

1
pullout specimens were tested, which were comprised of 5 specimens with

uncoated reinforcing bars, 23 specimens with epoxy-coated bars, and 6

specimens with polyvinyl chloride-coated bars.

3 . 1 Materials and Specimens . 3.1.1 Reinforcement . The tensile reinforcement in the pullout tests

consisted of No. 6 deformed bars (3/4 inch nominal diameter) having

either a barrel (B) or diamond (D) shaped deformation pattern, as shown

in figure 1. These bars were randomly selected and may not have been from

the same heat of steel. A 4 foot length of each tjpe of bar was tested

to rupture in tension. The yield strengths determined by the "0.2 percent

offset" [12] method were 67,600 psi for No. 6 rebais (D) and 62,500

psl for No. 6 rebars. These bars did not exhibit a. well-defined yield

point, however, their stress-strain relationships (figure 2) were

linear up to a stress of about 64,000 psi for the (D) bars and approximately 62,000 psi for the (B) rebars. Tensile properties of the bars

are listed in table 1. The yield and tensile strengths of the bars met

the requirements of ASTM A615-72 [12] for Grade 60 bars. The properties

of deformations were determined from three specimens from each type of

bar and are given in table 2. The bar deformations also met the

requirements of ASTM A615-72.

3.1.2 Concrete. The concrete was procured from a transit-mix concrete

company. The mix proportions of portland cement (type III), sand, and coarse aggregate were approximately 1:1.7:2.5, by weight. The sand was

a siliceous aggregate and the coarse aggregate was crushed stone.

Maximum size of the coarse aggregate was 3/4 in. Water content of the

concrete was about 5 1/2 gallons per sack of concrete and the slump

ranged from 3 to 5 in. Three batches of concrete were used to cast 34

pullout specimens (12 specimens each from concrete batch Nos. 1 and 2,

and 10 specimens from concrete batch No. 3).

Six standard 6 x 12 in. cylinders were cast from each batch of

concrete along with the pullout specimens. The cylinders were stored

and cured in the same manner as the pullout specimens; and their compressive strengths were measured at the same time as the specimens were

tested. The compressive strength was determined in accordance with ASTM

2
C39-66 [13]. The average compressive strengths at 27 to 29 days were

6170 psi for concrete batch No. 1, 6620 psi for batch No. 2 and 5730 psi

for batch No. 3. The range and coefficient of variation [14] of the

strength of the concrete cylinders was 226 psi and 1.5, 136 psi and 0.8,

355 and 2.3 for concrete batches numbered 1, 2 and 3 respectively.

3.1.3 Coatings on Reinforcing Bars . Coating materials were applied to

No. 6 reinforcing bars supplied by the National Bureau of Standards by

the applicators or manufacturers handling the respective coatings.

The applicator or manufacturer blasted the surface of the bars to a white finish [15], applied and cured the coatings as recommended by the

manufacturer, and then returned the bars to NBS for testing.

The coating materials and the methods by which they were applied

are described in table 3. The coating materials have been assigned

code numbers for laboratory identification purposes with the numbering

sequence indicating the chronological order in which the materials were

received. The pullout specimens have been assigned the same code

number as the coating on the respective embedded reinforcing bars.

3.1.4 Pullout Specimens . The pullout specimens were 10 x 10 x 12 in.

concrete prisms with the 4 foot length of reinforcing bar concentric

with the longitudinal axis of the specimens, so that the length of

embedment of the bar in concrete was 12 inches. This length of embedment of the deformed bar was selected based on previous studies at NBS

([15] and unpublished data) and because the current ACI Standard 318-71,

"Building Code Requirements for Reinforced Concrete" states that the

development length should not be less than 12 inches [17]. The pullout

specimen was designed so that the loaded-end slip reached a value of

0.01 inch corresponding to a steel stress of approximately one half its

tensile strength when uncoated bars were embedded in the specimen.

Load-end slip is defined as the relative movement between a point on

the loaded portion of the reinforcing bar and the surface of concrete.

Splitting of the concrete was minimized by reinforcing the specimen with

a cylindrical cage of 2 x 2 - 12/12 welded wire fabric. The cages had

a diameter of 8 in. , extending the length of the specimen, and were

concentric with the reinforcing bar. An instrumented pullout specimen

is illustrated in figure 3.

3
3.1.5 Fabrication and Curing of the Specimen . The pullout specimens

were cast with the reinforcing bar in a horizontal position in wooden

forms, which were lined with stripping oil. The specimens were removed

from the forms after 2 days, moist cured for 14 days with wet burlap

and room cured at 73°F and 50 percent relative humidity until tested

27 to 29 days after being cast.

Two pullout specimens with uncoated (U) reinforcing bars were

fabricated from each of concrete batch Nos. 1 and 2 and one such

specimen was cast from batch No. 3. Two specimens were fabricated for

each coating material from the same batch of concrete with the exception

that only one pullout specimen was fabricated that contained coating

No. 1-S.

3.2 Testing Procedure . Pullout specimens were tested in a 200,000

lb. capacity universal electromechanical testing machine. A pullout

specimen positioned on the testing machine is shown in figure 4.

The pullout specimen shown in figure 3 is seated on leather cushions,

on two segments of a 2 in. base plate attached to a spherical bearing

block. Free- and loaded-end slips of the reinforcing bar were measured

-4

with 1 X 10 in. micrometer dial gages. Free-end slip is defined as

the relative movement between the unloaded end of the bar and the surface

of concrete. At the loaded end of the specimen, two dial gages were attached to a steel bar fastened to the face of the concrete by bolts

secured into inserts cast in the concrete. The gages bore on a steel

yoke fastened to the reinforcing bar about 1 in. below the face of the

concrete. The bar supporting the dial gages and the yoke was free to move in the recess in the base plate. The average of the two gage

measurements gave the displacement of the point on the reinforcing bar

where the yoke was attached, with reference to the face of the concrete.

Slip at the free end was measured with a gage that bore on the exposed

end of the reinforcing bar (any coating material on the exposed end of

the reinforcing bar was removed prior to testing) . The gage was mounted

on a support attached to the top face of the concrete by bolts secured

into insert cast in the concrete. Loads were applied in increments of

2,000 pounds to the reinforcing bars in the pullout tests until failure

4
occurred either by yielding of the steel or excessive slip between the

bar and concrete was attained. At each load increment measured displacement data was recorded.

3.3 Results and Discussion . An important requirement for coated steel

reinforcing bars is the necessity of having adequate bond strength when

embedded in concrete. Adequate mean bond strengths of coated bars

denotes values equal to or greater than those for the uncoated bars.

Variability of the test results can allow acceptable bond strengths of

coated rebars slightly less than the mean value of bond strengths of

uncoated bars. In the present study, the relative bond strengths of

coated and uncoated bars were determined by testing pullout specimens.

Bond failure in a reinforced concrete flexural member is defined as excessive slip, or movement (greater than 0.002 in.), of the free end

of a bar stressed in tension caused by only a slight increase in the

applied load [16]. This slight increase in load results in a significant

change in the slope of the load-slip curve. In the bond study of Mathey and Watstein [16] critical bond stresses

were determined from bond stress-slip relationships. The critical bond

stress was taken as the lower value of bond stress corresponding to a loaded end slip of 0.01 inch or a free end slip of 0.002 in. It was observed in general that significant changes in slope of the bond stressslip relationship occurred at these values of the slip for various

lengths of embedments in beams containing No. 4 or No . 8 bars.

Comparison of bond strength data for beam and pullout specimens in

the study of Mathey and Watstein [16] indicated that considerably lower

critical bond strengths were developed in pullout specimens compared to

beam specimens having the same length of embedment. The length of

embedment to bar diameter ratios in these specimens containing No. 4 and

8 bars having comparable concrete strengths were 14, 21, 28 and 34. The

critical bond strengths for the pullout specimens ranged from 43 to 96

percent of the critical bond strengths for the beam specimens. The

average value of critical bond strength for the pullout specimen was

75 percent of the values determined from beam specimens. In that study

the values of steel stresses corresponding to the critical bond strengths

were considerably lower than the yield strengths of the steel bars.

5
3.3.1 Load-Slip Relationships . The relationships between applied load

and the free-end and loaded-end slip are plotted in figure 5 for the 34

pullou^ speciTienr: te.cted. Reman numerals denote the concrete batch

number while the Arabic numbers next to the plots identify the coating

materials (table 3). The loaded-end slip was larger than the free-end

slip for all specimens tested primarily because slipping initiates at

the loaded-end and extends toward the free-end as the load is increased.

Test results indicate that the critical bond stress is as important as the maximum load carried by the reinforcing bar in evaluating the

performance of coated reinforcing bars in the pullout tests.

In the comparison of the bond strengths developed in the pullout

tests of uncoated and coated reinforcing bars the variation in the

concrete strength, f^, was considered. Values of , ^ , were 1.00,

c c 0.97 and 1.04 for the three batches of concrete designated I, II, and

III respectively. The average strength of concrete, f^, for all three

batches was 6170 psi. The values of all calculated bond stresses were

adjusted for the differences in concrete strength by multiplying them

by the ratio of /j-, j ^, c c Yielding of the reinforcing bar was attributed as failure in most

tests, with the exception being pullout specimens containing bars coated

with materials Nos. 22, 23, 24 and 30. Although yielding of the reinforcing bar occurred in most tests, the critical bond strength corresponded

to steel stresses well below the yield strength of the steel. It will

be recalled that the critical bond strength or bond stress is defined

as the lower value of bond strength or bond stress corresponding to a loaded-end slip of 0.01 in. or a free-end slip of 0.002 in. The critical

bond strength corresponded to applied loads ranging from 17,000 to

21,600 lb. for uncoated bars and for coated bars except those coated

with materials Nos. 22, 23, 24 and 30 (table 4). Material No. 22 is

a powder epoxy applied by the fluidized bed method producing a cured

film about 24 mils thick. Coatings Nos. 23, 24 and 30 are polyvinyl

cliloride materials. The other coatings are epoxy coatings ranging

f rom 1 to 11 mils thick. The applied load corresponding to the critical

bond strength in the 19 pullout specimens with bars having epoxy coatings

6
1 to 11 mils thick ranged from 17,000 to 21,500 lb. with an average value

of 19,100 lb. The applied load corresponding to the critical bond strength

in the 5 pullout specimens with uncoated bars ranged from 18,000 to 21,600

lb. with an average value of 20,300 lb. Variability of the test results

can allow acceptable bond strengths of coated rebars to be slightly less

than the mean value of bond strengths of uncoated bars. Adequate mean

bond strengths of coated bars denotes values comparable to those for

uncoated bars. The average value of applied load corresponding to the

critical bond strength in the 19 pullout specimens with the bars having

epoxy coatings 1 to 11 mils thick was 6 percent less than for the pullout

specimens containing the uncoated bars. Therefore, these particular

coated bars are concluded to have acceptable bond strengths.

The average applied loads corresponding to the critical bond

strength in pullout specimens containing rebars with coatings Nos . 22,

23, 24 and 25 were 9,000, 1,100, 60 and 5,700 lb. respectively. Critical

bond strengths developed in pullout specimens containing rebars having

these coatings were considerably less than the values of critical bond

strengths detennined from pullout specimens containing the uncoated bars.

A comparison of the bond strengths based on maximum load can also

be made for coated and uncoated bars. Values of maximum applied loads

are also presented in table 4. It is noted from this table that the

maximum load for all pullout specimens except those containing bars

having coatings Nos. 22, 23, 24, and 30 corresponded to yielding of the

reinforcement. When the steel stresses considerably exceeded the yield

strength of the bar, loading was halted. It will be recalled that the steel

stress corresponding to the critical bond strength was considerably less

than the yield strength of the bar for all the pullout specimens. An

evaluation of the pullout test results (table 4) indicates that epoxycoated reinforcing bars have bond strengths essentially equal to uncoated

bars when the film thicknesses are approximately 10 mils or less.

Both liquid and powder epoxies performed equally well, and

the application method did not significantly effect the bond strength of

coated bars. The polyvinyl chloride coated bars had bond strengths

considerably less than that for uncoated bars and bars with these coatings

are not recommended for structural use. The lower bond strengths for

7
polyvinyl coated bars are attributed in part to the thermoplastic nature

of the polyvinyl chloride. The thicknesses of the polyvinyl chloride film

were greater than most of the epoxy films but thicker films are normal

for thermoplastics [18].

3.3.2 Bond Stress . It was noted in Section 3.3 that in a previous

study the average bond strength of pullout specimens was 75 percent of the

average value for beam specimens. Although pullout test results are not

recognized as being comparable to beam test results, the authors believe

that relative bond characteristics of reinforcing bars can be determined

from pullout tests. The lower value of bond stress corresponding to a loaded-end slip of 0.01 in. or a free-end slip of 0.002 in. is defined

as the critical bond stress. The bond stresses corresponding to these

values of slip are presented in table 4. Bond stresses were computed

from the formula

u = f A (1)

s s

I L

o where f is the stress in the reinforcing bar, A is the nominal cross

s

' s sectional area of the bar, Z is the nominal perimeter of the bar and

o

^ L is the length of embedment, in inches, of the reinforcing bar in the

pullout specimen. Values of A^ and for each of the two types of

rebars are given in table 1. The value of f^ is given by

f = P (2)

^ A~s where P is the load or tensile force applied to the reinforcing bar in

pounds. Therefore, equation (1) can be reduced to u = (3)

Z L

o which was used to calculate u. Values of bond stress developed in the

pullout specimens were compared with allowable values given in codes

and specifications. The American Concrete Institute Building Code,

318-63 [19], allowed a working bond stress design for deformed bars

(other than top bars) conforming to ASTM A 305 calculated from

4.8 but not more than 500 psi

c

^

8
where D is the nominal diameter of the bar in inches. Using the average

value of f as 6170 psi the bond stress, u, is 490 or about 500 psi.

c The Standard Specification for Highway Bridges Adopted by the

American Association of State Highway Officials [20] states that slabs

(decks) designed for bending moment in accordance with the given provisions

shall be considered satisfactory in bond and shear. In another section

of this Standard Specification on concrete design the allowable bond

stress for tension bars conforming to AASHO M31 [20] and ASTM A615 [12]

is

4.8 /

f ^ , 500 psi maximum

and is the same as that given by the ACI 318-63 Code.

The critical bond stresses and bond stresses corresponding to one half the maximum applied load, Um given in table 4 for all pullout

2 specimens except those having bars coated with materials 22, 23, 24 and

30 were greater than 600 psi.

3,4 Summary and Conclusions . Bond strengths were determined in 34

pullout specimens with 23 epoxy coated (10 different epoxy coatings)

,

6 polyvinyl chloride coated (3 different materials), and 5 uncoated No.

6 deformed reinforcing bars. In general, the comparable pullout tests

indicated that bars with epoxy coatings approximately 10 mils or less

in thickness developed essentially the same bond strengths as the uncoated

bars. When the film thickness of the epoxy coating was 25 mils or when

polyvinyl coatings were used the bond strength was considerably less for

these coated bars than for the uncoated bars. It is recommended that

thick epoxy coatings (greater than approximately 10 mils) and polyvinyl chloride

coatings not be used as protective coatings for reinforcement in concrete

flexural members.

As stated in Section 3.3, the bond strengths from pullout tests do

not necessarily agree with the bond strengths of comparable flexural

members. Although the information on relative bond strengths of coated

and uncoated reinforcing bars determined by means of pullout tests are believed valid by the authors, it is recommended that tests of flexural

members (slabs) be carried out to confirm these results. Furthermore,

the authors recommend that studies on the creep properties of coated

9
bars be conducted to determine if deformation of the coatings will cause excessive slip of the reinforcing bar in the concrete over a long period

of time. Determinations of creep strengths are currently being performed

by means of pullout type specimens and the results will be given in a future report.

10
4. References

1. "Durability of Concrete Bridge Decks: A Cooperative Study, State

Highway Commission of Kansas, Bureau of Public Roads and Portland

Cement Association". Report 1 (1965).

2. "Durability of Concrete Bridge Decks: A Cooperative Study, Michigan

State Highway Department, U. S. Department of Commerce, Bureau of

Public Roads and Portland Cement Association". Report 2 (1965).

3. "Durability of Concrete Bridge Decks: A Cooperative Study, U. S.

Department of Transportation, Bureau of Public Roads and Portland

Cement Association". Report 3 (1967).

4. "Durability of Concrete Bridge Decks: A Cooperative Study, Missouri

State Highway Commission, U. S. Department of Transportation, Bureau

of Public Roads and Portland Cement Association". Report 4 (1968).

5. "Durability of Concrete Bridge Decks: A Cooperative Study; California,

Illinois, Michigan, Minnesota, New Jersey, Ohio, Texas, and Virginia

Highway Departments, U. S. Department of Transportation, Bureau of

Public Roads and Portland Cement Association". Report 5 (1969).

6. "Durability of Concrete Bridge Decks: A Cooperative Study; California,

Illinois, Kansas, Michigan, Minnesota, Missouri, New Jersey, Ohio,

Texas, and Virginia Highway Departments, U. S. Department of

Transportation, Bureau of Public Roads and Portland Cement Association".

Final Report (1970).

7. T. D. Larson, P. D. Cady, and J. C. Theisen, "Durability of Bridge

Deck Concrete", Report No. 7, College of Engineering, The Pennsylvania

State University, April (1969).

8. R. F. Stratfull, "The Corrosion of Steel in a Reinforced Concrete

Bridge", Corrosion, 13_, 173t (1957).

9. J. D. Mozer, A. C. Bianachini and C. E. Kelser, "Corrosion of

Reinforcing Bars in Concrete", J. Am. Concrete Inst. Proceedings,

62, 909 (1965).

10. J. R. Clifton, H. F. Beeghly and R. G. Mathey, "Interim Report No. 4

Screening Test for Evaluating Materials" , National Bureau of Standards

Report 10968.

11. R. C. Robinson, "Design of Reinforced Concrete Structures for

Corrosive Environments", Materials Performance, ]A, 15 (1972).

12. Standard Specification for Deformed and Plain Billet-Steel Bars for

Concrete Reinforcement, ASTM Designation A615-72.

13. Standard Method of Test for Compressive Strength of Molded Concrete

Cylinders, ASTM Designation C39-66.

11
14. ACI Standard, Recommended Practice for Evaluation of Compression

Test Results of Field Concrete (ACI 214-65), American Concrete

Institute, 1965.

15. Steel Structures Painting Council Surface Preparation Specification

SSPC-SP5-63, amended 1971.

16. R. G. Mathey and D. Watstein, "Investigation of Bond in Beam and

Pullout Specimens with High-Yield-Strength Deformed Bars," ACI

Journal, 32, 1071 (1961).

17. ACI Standard Building Code Requirement for Reinforced Concrete,

(ACI 318-71), February 1971.

18. N. E. Hamner, "Coatings for Corrosion Protection," Chapter 14, in

NACE Basic Corrosion Course , A. des. Brasunas and N. E. Hamner, ed .

,

National Association of Corrosion Engineers, Houston, Texas, 1970.

19. ACI Standard Building Code Requirements for Reinforced Concrete

(ACI 318-63) , June 1963.

20. Standard Specifications for Highway Bridges, Adopted by Tfie American

Association of State Highway Officials, Eleventh Edition 1973.

12
Captions for Figures

Figure 1. View of No. 6D (upper bar) and No. 6B (lower bar) reinforcing

bars. D indicates diamond shaped deformation pattern and B

indicates barrel pattern.

Figure 2. Typical stress-strain characteristics of reinforcing bars.

Figure 3. Schematic of pullout specimen.

Figure 4. Pullout specimen on electromechanical testing machine being

prepared for testing.

Figure 5. Applied load to reinforcing bar in pullout specimens versus

free-end and loaded-end slip. Roman numbers indicate concrete

batch number, while Arabic numbers identify the coating

materials (table 3)

13
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15
TABLE 3 . COATED REINFORCING BARSCoating

Code No.

Type of

Coating Materials

Film

Thickness

(mil)

Application

Method

U No Coating

1 Epoxy, liquid 4-5 Brush

1-S Material No. 1 mixed with

sand

4-5 Brush

3 Epoxy, liquid 2-5 Brush

18 Coal tar epoxy, liquid 4 Brush

19 Epoxy, liquid 1 Dipping

22 Epoxy, powder 25 Fluidized Bed

23 Polyvinylchloride, powder 23 Fluidized Bed

24 Polyvinylchloride-plastisol,

powder ; -- 35 Fluidized Bed

25 Epoxy, powder 6-11 Electrostatic Spray Gun

29 Epoxy, powder 1-2 Electrostatic Spray Gun

30 Polyvinylchloride, powder 15 - 18 Fluidized Bed

31 2/Epoxy, powder- 8-9 Electrostatic Spray Gun

38 Epoxy, powder 2-4 Electrostatic Spray Gun

38 -Ph Rebar surface phosphatized,

then material Noc 38 applied

2-4 Electrostatic Spray Gun

39 Epoxy, powder 2-4 Electrostatic Spray Gun

41 Epoxy, powder 3-7 Electrostatic Spray Gun

]J No. 6 steal reinforcing bars coated by Applicators or coating producers. Mill

scale removed by sandblasting. i

1 2_/ Same material as No. 22, but applied by different method, by different applicator

16
TABLE 3. COATED REINFORCING BARS-'

Coating

Code No.

Type of

Coating Materials

Film

Thickness

(mil)

Appl icat ion

Method

U No Coating

1 Epoxy, liquid 4-5 Brush

1-S Material No. 1 mixed with

sand

4-5 Brush

3 Epoxy, liquid 2-5 Brush

18 Coal tar epoxy, liquid 4 Brush

19 Epoxy, liquid 1 Dipping

22 Epoxy, powder 25 Fluidized Bed

23 Polyvinyl chloride, powder 23 Fluidized Bed

24 Polyvinyl chloride-plastisol

,

powder

35 Fluidized Bed

25 Epoxy, powder 6-11 Electrostatic Spray Gun

29 Epoxy, powder 1-2 Electrostatic Spray Gun

30 Polyvinyl chloride, powder 15-18 Fluidized Bed

31 Epoxy, powder—^ 8-9 Electrostatic Spray Gun

38 Epoxy, powder 2-4 Electrostatic Spray Gun

38-Ph Rebar surface phosphatized,

then material No. 38 applied

2-4 Electrostatic Spray Gun

39 Epoxy, powder 2-4 Electrostatic Spray Gun

41 Epoxy, powder 3-7 Electrostatic Spray Gun

J No. 6 steel reinforcing bars were coated by applicators or coating producers. Mill

scale was removed by sandblasting.

1/ Same material as No. 22, but was applied by a different method and by a different

appl icator

17
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I

SLIP (inches xiO'^) n

SLIP (inches x 10'^)

SLIP (inches xlO'^)

1 owM NbS-1 MA 11-71) " S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

Ndo IK / J -i+U 1

2. Gov't Accession No.

3. Recipient's Accession No.

4. TirLE AND SUBTITLE

Performance of Coated Steel Reinforcement in Concrete.

Part 1. Investigation of Bond in Pullout Specimens

5. Publication Date May 1973

6. Performing Organization Code

7. AUTH0R{S) James R. Clifton, Hugh F. Beeghly, Robert G. Mathey 8. Performing Organization

NBSIR 73-401

9. PERFORMING ORGANIZATION NAME AND ADDRESS

MAX ir^M A T fll ID 1^ A 1 T CW^ A \1 A T3 l^Q IN A I iiJiN A 1- nUKCAU olAiNUAKUo

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

Department of Transportation

Washington, D. C. 20590

13. Type of Report & Period

Covered

Final

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.) Bond strengths of coated deformed steel reinforcing bars were compared with

uncoated bars by means of pullout specimens. The bond strengths were determined

for 23 epoxy-coated (10 different epoxy coatings) , 6 polyvinyl chloride-coated

(3 different coating materials), and 5 uncoated deformed reinforcing bars. The

tensile reinforcement in the pullout specimen consisted of No. 6 deformed bars,

having either a barrel or diamond shaped deformation pattern, with a nominal

yield strength of 60,000 psi. The length of embedment of the reinforcing bar

in the concrete was 12 inches.

The load or bond stresses corresponding to a loaded-end slip of 0.01 inch or a free-end slip of 0.002 inch were considered as critical values in determining the

bond strength, depending on which of these values of slip developed first.

For coating film thickness of approximately 10 mils or less, the epoxy-coated

bars developed bond strengths essentially equal to the bond strengths for the

uncoated bars. Experimental values of bond strengths for these coated bars were

higher than minimum acceptable values given in building code and highway bridge

requirements. Bond strengths of the polyvinyl chloride-coated bars and bars

with thick epoxy coatings were unacceptable.

17, KEY WORDS (Alphabetical order, separated by semicolons)

Bond strengths; concrete; epoxy coatings; polyvinyl chloride coatings; pullout tests;

steel reinforcing bars

18, AVAILABILITY STATEMENT 19. SECURI IT CLASS 21. NO, OF PAGES

(THIS REPORT)

28

1 1 UNLIMITED.

UNCLASSIFIED

g*^l-OR OFFICIAL DISTRIBUTION. DO NOT RELEASE 20. SECURITY CLASS 22. Price ^TO NTIS. (THIS PAGE)

UNCLASSIFIED

USCOMM-DC 68244-P71


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