A111D2 S753D^

Measuring the Corrosion Rate of

Reinforcing Steei Concrete - Finai Report

E. Escalante, E. Whitenton, F. Qiu

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Institute for Materials Science and Engineering

Metallurgy Division

Gaithersburg, MD 20899

October 1986

^ C l(j [jy; 100 I Highway Administration

.1156 igton, DC 20590

86-3^56

1986

0.2

NBSIR 86-3456

MEASURING THE CORROSION RATE OF

REINFORCING STEEL CONCRETE - FINAL REPORT

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RESEA,RCH

INFORMATION CENTER

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E. Escalante, E. Whitenton, F. Qiu

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Institute for Materials Science and Engineering

Metallurgy Division

Gaithersburg, MD 20899

October 1986

Sponsored by;

Federal Highway Administration

Washington, DC 20590

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

TABLE OF CONTENTS

Page

Abstract 1

Introduction 1

Background 2

Approach 2

System Description 3

Laboratory Measurements 5

Procedure - Laboratory 5

Results and Discussion - Laboratory 6

Field Measurements 7

Procedure - Field 7

Results and Discussion - Field 8

Summary 9

Acknowledgement 10

References 1

Tables 13

Figures 18

Appendices
LIST OF TABLES

Table Page

1 Information Printed During Polarization Measurement 13

2 Composition of Concrete Mixes 14

3 Conditions of Exposure of Laboratory Specimens 15

4 Weight Loss and Polarization Resistance Data 16

5 Calculated Corrosion Rates of Three Bridge Decks 17
LIST OF FIGURES

Figure Page

1 Schematic diagram showing relationship of the three

electrodes, control switches, power supply 18

2 Magnified view of a portion of the Potential of the

working electrode during "Holding" stage

a) Potential trace From oscilloscope

b) Idealized trace of Potential 19

3 Magnified view of a portion of the applied Current

during "Holding" stage

a) Current trace from oscilloscope

b) Idealized trace of applied Current 20

View of entire trace of the Potential of the

working electode and applied Current

a) Trace from oscilloscope

b) Idealized trace 21

5 Circuit diagram of dummy load simulating electrodes

in concrete environment 22

6 Plot of Known Resistance added to Dummy load versus Resistance eliminated by computer system using

current-interrupt technique 23

7 Configuration of steel rod in concrete cylinders 24

8 Plot of Calculated Corrosion Rate versus Time for

specimens #1, #3, and #7 25

9 Plot of Calculated Weight Loss versus Gravimetric

Weight Loss for twelve specimens in a laboratory

controlled environment 26

10

Schematic diagram of electrode configuration on

a bridge deck 27
LIST OF APPENDICES

Appendix

A Corrosion calculations

B Hardware and software

1 ) Overview of system

2) Detail of 3421 A Data Logger

3) Custom D/A board

4) Computer software

C FHWA forms
Measuring the Rate of Corrosion of Reinforcing Steel in Concrete

Final Report

E. Escalante and E. Whitenton

Metallurgy Division

F. Qiu

Fujian Institute of Research on the Structure of Matter

Peoples Republic of China

ABSTRACT

This report describes a three phase study directed at developing a portable system for measuring the corrosion of steel in concrete

bridge decks. A small, portable computer system is used to control

the measurement of polarization resistance of steel in concrete, and

using current interruption, iR error is eliminated. During the first

two phases, the system hardware and software were constructed, then

measurements were made on small steel specimens in concrete cylinders

in a laboratory controlled environment. The results of the weight

losses calculated from the electrochemical measurement are compared

to gravimetrically determined weight losses. In the third phase, the same portable system was used to measure the corrosion of three bridge

decks in Frederick County MD, over a four month period. The results

of these field measurements and the problems encountered are discussed.

INTRODUCTION

It is now well recognized that steel in concrete will corrode under

certain conditions (1~3)» and many studies have been directed at

identifying the factors that influence this deterioration (4-8). An

early review of the literature revealed a dearth of information in

this area (9). A means of measuring the corrosion rate of steel in

concrete would be extremely useful for many applications, and several

laboratories, including the National Bureau of Standards (NBS), have

devoted time to developing some understanding of how this measurement

can be made in a nondestructive manner (10-12).

The ability to measure the corrosion rate of steel in concrete is

useful for several reasons. First, a better understanding of the

corrosion processes in concrete could be developed by making con- trolled changes in the concrete (oxygen, chloride, pH, moisture) and

observing the effects on corrosion rate. Secondly, the performance of

corrosion control systems could be monitored as a function of time,

and thus, the effectiveness of overlays, reinforcing steel coatings,

corrosion inhibitors, and cathodic protection could be measured and

evaluated

1
Recent advances in computer technology have led to commercially

available, portable, battery operated computers and accessories

that give us the capability of extending laboratory techniques to

field measurements. The object of this study is to take a step

in this direction.

BACKGROUND

In 1978 , an effort was initiated at NBS to develop an understanding

of the conditions and processes that control or effect the corrosion

of steel in concrete. As a result, three reports have been issued

(9,13»1^). The first report was a literature survey covering the

period from 196^ to 1978 in which 394 references were cited (9).

Examination of this literature revealed that much of the effort had

been concentrated in learning about the role of the chloride ion

and the concrete mixture design on the corrosion process. Only one reference considered the effect of oxygen, and none were found on the

corrosion of steel in an alkaline environment. On the basis of these

findings, a study seeking to learn more about the interaction of

oxygen, pH, and chloride was started. In addition, preliminary

efforts were directed at developing a nondestructive, electrochemical

technique for measuring the corrosion of steel in concrete. The

results of this initial study are described in the second report (13)-

The third report considered the problem of current distribution

during the polarization process, and included our first attempt at

controlling the measurement with a microprocessor system (14).

This report describes our most recent effort at applying a useful

laboratory technique to a field situation, and can be broken down

into three major phases as follows:

1 ) Design and assembly of the microcomputer-controlled

corrosion measuring system,

2) Testing of the microcomputer-controlled device under

laboratory controlled conditions, and

3) Testing the microcomputer-controlled device in the field.

The general format of this report will be developed around these

topics

APPROACH

Judging from our early studies, it became apparent that there were two

major obstacles to measuring the corrosion rate of steel in concrete,

namely: (a) determining the area of the steel being polarized during

the measurement, and (b) compensating for iR error, an error arising

when potential measurements are made in the presence of an electric

current in a resistive medium. Knowledge about current distribution

during a measurement on a bridge deck is important for the simple

2
reason that only a very small area of the steel in the bridge deck is

polarized at a time, and this area must be known so that a corrosion

rate may be calculated. Anticipating this problem earlier in the

project, a study was initiated as previously described (14). This

study indicated that current distribution in concrete is very limited

and is concentrated to the immediate vicinity of the source of current,

the counter electrode (CE). Thus, by knowing the location and size

of the steel in the region of the CE of a given size, the area of the

steel rebar being polarized can be determined. Elimination of iR error

was accomplished through the use of a current interrupt technique

whereby the potential of the steel is measured while current is zero

( 15 , 16 ).

Preliminary studies using manually controlled equipment indicated that

the corrosion of steel in concrete, also referred to as the working

electrode (WE), can be measured by polarization techniques (13.14).

However, the procedure is very slow and tedious, and not at all suited

for field measurements. Furthermore, iR compensation is always difficult and, at times, questionable with these manually controlled

methods. The use of portable computer equipment opens new avenues to

the application of laboratory methods to field measurements especially

where a resistive medium may be encountered. The remainder of this

report is a description of the operation of such a computer-controlled

system and the results obtained in the laboratory and in the field.

System Description

The computer controlled device operates by modulating the current

applied to the electrodes so as to maintain a potential (E) difference

between the WE and the reference electrode (REF), Ew - Er, which is

10 mV less than the same potential difference at open circuit (o.c.):

(Ew - Er) - (Ew - Er)o.c. = -10 mV = AE

The reading, however, is taken during a brief period while the current

is interrupted, so that the potential due to the iR drop is absent,

but soon enough after the interruption of the current that the potential due to polarization of the WE has not yet decayed significantly.

The entire process occurs as follows. Initially, during the "setting"

portion of the measurement, the current is gradually increased or decreased depending on whether AE is smaller or larger than -10 mV.

Once the desired value of AE is reached, it is maintained for 3.5 min,

during the "holding" portion of the measurement. The duty cycle is

2.2 s with the current on and 0.4 s with the current off. The sampling

of the voltage occurs approximately 75 ms after current interruption.

The error in the voltage reading introduced by its decay during 75 ms

is of the order of 55t if the decay constant of the electrode potential

(assuming an RC parallel circuit) were of the order of 1 s . This, for

instance, could be given by a polarization of 10^ ohm cm^ and a capacitance of 10 uF/cm^. This is a conservative approximation of error since

transport processes in concrete are likely to be very slow, and the

decay constants observed experimentally are much longer than 1 s.

3
Figure 1 is a schematic diagram showing the relationship of the three

electrodes, the current control switches, and the power supply. The

details of the operation of the computer controlled system are as follows. First, the three potentials VI, V2, and V3 are measured in

the open circuit condition. A voltage, V, equal and opposite to VI is then applied by the power supply. Switch, SI, in series with a 4.7 k ohms resistor, closes and the applied current, 12, through the

circuit is determined by measuring V2 across a 100 ohm resistor

(12 = V2/100). The power supply voltage, V, is then adjusted to make

12 equal to zero so that applied current at the start of the measurement is zero. This current zeroing process is repeated more accurately

when the second switch, S2, is closed. The entire current zeroing

procedure occurs in less than 10 s and prepares the system for the

polarization measurement.

There are two stages to the measurement as described earlier, the

initial "setting" stage when the WE is polarized to -10 mV and the

"holding" stage when the WE is maintained at -10 mV while the data are collected. During the "setting" period, the power supply voltage, V,

is increased in small increments (28 mV during the first 5 mV of AE and

1.4 mV as it approaches AE) until AE = -10 mV as measured at V3. This

"setting" period can vary in length from a few seconds to a maximum of

5 minutes, depending on the amount of current necessary to polarize the

WE. If the WE cannot reach a AE of -10 mV within 5 minutes, then the

system is programmed to accept the AE reached at the end of the 5

minute period, a rare occurrence. Once AE = -10 mV or the 5 minute

maximum is reached, the system goes into the "holding" stage where AE

is held constant and the WE potential, V3, is measured during every

"current off" cycle and the applied current, 12, is determined during

the "current on "cycle.

All data taken during the "holding" period are stored on the cassette

mass memory, and each file is identified by name, date, and time.

Table 1 is a typical printer listing from the computer memory

displaying, on the first four groups of data, the potential between

the WE and the CE, VI, the applied current, 12, the potential between

the WE and the REF, V3, and elapsed time, in seconds, after each set of

measurements during a run. The fifth and sixth groups of data are the

minimum, maximum, average, standard deviation, and number of readings

for the WE potential, V3, and the polarizing current, 12, respectively.

The polarization resistance is then calculated from these data and

listed as shown.

The voltage and current signals were independently monitored with a digital oscilloscope during a measurement period giving us a visual

record of the progress of the measurement sequence. This record can

be saved in the memory of the oscilloscope for later analysis. Furthermore, the recorded trace can be expanded in the X or Y axis for

close examination of any portion of the trace. The following figures,

generated using this capability, illustrate some of the details of thmeasurement. Figures 2 and 3 magnified portions of the measuremen*’

sequence shown in its entirety in Figure 4. Figure 2a is a recording

of the potential of a steel rod in concrete during the on-off cycling

4
of the current. The schematic representation of the recording in

Figure 2b identifies the significant por’^.ions of the trace. The

corresponding trace for current is shown in Figure 3a illustrating the

"current on" and "current off" characteristics as a function of time.

The idealized trace of the current is shown in Figure 3b. A typical

trace of an entire polarization measurement, from which 2a and 3a were

taken, is shown in Figure Ma, and illustrates the two important regions

of the measurement, the "setting" and the "holding" portions. Figure

i^b identifies the regions of this trace.

To evaluate the computer system's ability to eliminate iR error, a circuit simulating the WE, CE, and REF in a concrete environment, was constructed as illustrated in Figure 5. The resistive R component

(not shown) in iR was added in series with the WE. Using known values

of resistance for R in the range from from 1 to 5000 ohms, it was determined that 95? of the iR error is eliminated throughout the

resistance range as shown in Figure 6. The straight line represents

100^ elimination of iR and the six data points are the values

eliminated by the computer system and almost lay on the plot of ideal

correction for R.

The calculation of polarization resistance, corrosion rate, and weight

loss are described in Appendix A. The computer system hardware and a listing of the program that controlled the measurement are shown in

Appendix B. Except for the custom digital to analog converter board

(Custom D/A Board), all hardware is commercially available. The

program is fully documented with remark statements identifying the

major routines and subsets of these routines.

LABORATORY MEASUREMENTS

Procedure - Laboratory

Cleaned and weighed steel rods 1.3 cm (0.5 in) in diameter and 15.2 cm

(6 in) long encased in small cylindrical concrete cylinders 5 cm (2 in)

in diameter and 15.2 cm (6 in) long as shown in Figure 7 were used for

laboratory measurements. Two concrete mixes were used; one chloride

free and one with chloride added as described in Table 2. After

casting in molds, the concrete was mechanically vibrated to remove

large air bubbles. Approximately 2U h later, the specimens were removed from the molds, and the protruding steel rod and the top

surface of the concrete were coated with a primer and a rubber based

coating. This was followed by immersing the specimens in either a simulated pore solution (0.6 M KOH, 0.2 M NaOH, and 0.001 M Ca(0H)2),

a sodium chloride saturated pore solution or a pure sodium chloride

saturated solution (17). The surface area of steel imbedded in the

concrete was approximately 62 cm^ (9.6 in^).

In an effort to stimulate oxygen diffusion and, thereby, accelerate

the corrosion process, some of the specimens were immersed in their

respective solution for only two hours per day and allowed to air dry

the remaining 22 h. The rest of the specimens were kept continuously

5
immersed to reduce oxygen diffusion. The specimens and conditions of

immersion are shown in Table 3* The solutions were contained in 2

liter stainless steel containers which also served as counter electrodes for the laboratory polarization measurements. Saturated calomel

electrodes were used as reference. The period of exposure for these

specimens was approximately 115 to 148 days, and measurements were made on each specimen once a day, 5 days per week.

At the end of the exposure period, the cylindrical specimens were removed from their environment and the imbedded steel rods immediately

extracted from the concrete by breaking up the concrete cylinders.

The rods were then cleaned in Clark's solution prior to weighing for

determination of weight loss as described in ASTM Standard Practice for

Preparing, Cleaning, and Evaluating Corrosion Test Specimens (G1-81).

Results and Discussion - Laboratory

As an example of the results obtained on a day to day basis, the

calculated corrosion rates of three specimens (#1, #3, and y/7 ) are plotted as a function of time and illustrated in Figure 8. Specimen

#1 was not expected to corrode since it was exposed to chloride-free

conditions, however, some corrosion was expected on specimen #3 since

it was cast in chloride-free concrete, but immersed into a solution

containing chloride. Specimen #7 was exposed to the highest concen- tration of chloride with chloride in the concrete mix and in the

immersion solution. Hence, specimen #7, was expected to undergo the

most severe corrosion of the three illustrated. All three were maintained in conditions of alternate immersion to increase oxygen

availability

There were extensive fluctuations in the corrosion rate during the

first few days, but after this initial period, the conditions

stabilized. These data indicate that specimen #7 did exhibit the

highest corrosion attack, and specimen #1 the least corrosion attack.

Furthermore, the data also show that the corrosion rate of specimen

#3 was between #1 and #7, as expected.

A test of these results was made by gravimetrically measuring the

weight loss of steel for each rod as previously described and

comparing this actual weight loss with the weight loss calculated

from the electrochemical data. This comparison is shown in Table 4 where the twelve specimens are ranked by order of increasing gravimetric weight loss. Also listed is the corresponding average of the

polarization resistance and the calculated weight loss during the

period of exposure. Indeed, these data show that specimen //7 did

experience the most weight loss, specimen ih the least weight loss,

and specimen #3 a weight loss in between specimens #1 and in, as predicted by the electrochemical measurements. This listing shows

an agreement between the gravimetrically determined weight loss and

the calculated weight loss over the entire range encountered. A more graphic view of this relationship is shown in Figure 9 which displays

6
a plot of gravimetric weight loss versus calculated weight loss. In

general, the calculated weight loss data underestimated the actual

weight loss.

The anodic and cathodic Tafel slopes were assumed to both equal 150 mV

for the calculations of weight loss, and these values were picked on

the basis of preliminary Tafel slope measurements made on steel in

concrete indicating that both slopes were higher than those normally

encountered in solutions. These same measurements further indicated

that the anodic Tafel slope is larger than the cathodic slope. It

is conceivable that these unusually high Tafel slopes result from the

physical characteristics of concrete (voids in a matrix of concrete,

sand and stone) where transport and diffusion processes can be expected

to be very slow compared to those in solutions.

FIELD MEASUREMENTS

Procedure - Field

Though the problems encountered in the field measurements were completely different to those in the laboratory, in essence, the

measurement and approach to obtaining the data were very similar.

These similarities include the use of the same equipment programmed

as previously described. Furthermore, the current and potential

ranges encountered in both cases were of the same order of magnitude.

The differences, on the other hand, were mostly mechanical. For

example, the configuration of the electrodes in the field was as illustrated in Figure 10 showing the use of a Cu/CuS04 reference

electrode, a lead (Pb) ring for a counter electrode, and the steel

reinforcing bar (rebar) in the concrete bridge deck as the working

electrode. Note that the CE and the REF are on a wetted absorbent

material (towel or sponge) and are supported by a clear plastic holder

that facilitates alignment of the electrodes. The wetting agent used

on the absorbent material is a solution of \% liquid detergent in tap

water which helped wet the concrete and dispersed the oil film on the

surface of the bridge deck. Scrubbing with a wire brush proved useful

in some cases where the concrete was heavily encrusted with soil.

Another difference was the manner in which the connection was made to

the WE. To be assured of good electrical contact to the rebar, a small

15 X 1 5 cm (6 X 6 in) portion of the concrete over the rebar was removed on each span of the bridge deck. The location of the exposed

rebar was chosen to minimize maintenence problems during the several

months of the measurements. These rebar contact points were located

off the traffic lanes on the centerline separating oncoming traffic.

Measurements made on sections of bridge decks early in the program

revealed that the grid of rebar in a bridge deck is electrically

continuous, and making a contact anywhere on this grid provides electrical contact to the entire grid. Thus, measurements could be made

on all lanes of traffic from one rebar contact point. The one difference that generated the most serious problems was the electronic

equipment damage resulting from mechanical vibration generated during

transportation between the laboratory and the field. Vibration caused

7
breakage of wires resulting in equipment failure at inopportune moments.

This destructive effect was reduced by carefully packing the equipment

in shock absorbing foam material during transit. Cable and contact

continuity had to be checked constantly. Using the dummy cell shown

earlier in Figure 5, the equipment and cables were checked before and

after every series of measurements.

Three bridges located in Frederick County, MD, were chosen for the

study on the basis of age, known history, and condition. Thus, bridge

number 10029 was a 54 year old structure with fine cracks scattered

over the surface of the deck, but otherwise in good condition. Bridge

number 10100, along a major Interchange, was 17 years old and appeared

to be in excellent condition. The newest bridge, number 10059, was 13

years old and also in good condition, but cracks are beginning to

appear along the rebar positions. Deicing salts for snow removal are used on all three bridges.

Three measurents were made on each bridge span every two weeks over

a four month period during the summer. The location of each measure- ment was permanently marked on the bridge deck surface so that the

measurements could be repeated at the same location each time.

Results and Discussion - Field

The first 90 days of the four month period were spent in improving the

equipment and developing our ability to make the measurements in the

field. One problem encountered, not yet mentioned, was that of electrical noise in the measurement, and unfortunately, eliminating this

interference was a time consuming process. The noise can be placed

in three categories and listed in order of discovery and elimination.

First, there was interference from alternating current (a.c.) sources;

second, we had interference from our gasoline motor driven a. c. generator used to power the digital oscilloscope monitoring the

measurements; and finally, we discovered interference from current

generated by the corrosion of the counter electrode. The first

problem, a. c. interference, was relatively easy to eliminate

through shielding of all cables. However it was several weeks after

starting the measurements that the second problem, effects of the

generator, were discovered. This interference took the form of direct

current (d. c.) coming through the power line and a. c. voltage spikes

at random times that caused strange things to happen to the data.

After extensive filtering attempts, changes in configuration of the

equipment, and much time, it was finally decided that removing the

offending generator was the best alternative, and a battery powered

oscilloscope was used for monitoring instead. The third problem was

the irreproducibili ty of the WE potential. Investigation revealed

that localized corrosion of the steel counter electrode plate on the

detergent wetted towel was generating an electric current that affected

the potential measurement. By trial and error it was discovered that a lead (Pb) CE reduced the effect to a tolerable level.

8
After this initial period, measurements were continued, and the

resulting data are displayed in Table 5. As this Table reveals, data were collected on three dates, October 8, October 23, and November 6.

It was possible to make measurements on bridge number 10029 on only one occasion during this period because of weather constraints. Data for

two positions on bridge number 10100 are missing because of problems

(e.g. electrical continuity) that developed during those measurements.

The results show that the 5^-year old bridge, number 10029, on the

average exhibited the lowest average corrosion rate (0.5 MDD) of the

three bridges. The 17 year old bridge, number 10100, had an average

corrosion rate of 1.1 MDD, and the 13 year old bridge, number 10059,

exhibited the highest average corrosion rate of 1.9 MDD (Milligrams per

square Decimeter per Day).

It is difficult to assess the reliability or accuracy of these data

obtained through these preliminary field measurements. We hesitated

to carry out a coring examination of the rebar because of the destructive nature of this action and the very limited amount of data collected.

However, the results can be compared to the visual appearance of the

bridge deck surface in the immediate vicinity of the measurement. On

this basis we can make the following observations. Visual examination

of the surfaces of the bridge decks revealed the following. The

5^-year old bridge, though it has suffered wear and tear through the

years, is in surprisingly good condition with small cracks randomly

scattered over the surface of the deck. The 17 year old bridge appears

to be relatively crack-free with little evidence of wear to the

original surface, and is judged to be in good condition. The 12 year

old bridge, in general, looks good, but a close examination of the

surface reveals cracking of the concrete above and in line with many of

the rebar. This crack alignment is not evident on the other two

bridges. Thus, the visual appearance of the bridge deck surfaces tends

to support the electrochemical data. In spite of this apparent

agreement between the electrochemical measurements and the visual

appearance of the bridge deck, we are reluctant to place much meaning

to the results because of the very limited amount of useful data

obtained. Nevertheless, the exercise of making this corrosion

measurement in the field was very valuable in providing information on

the problems encountered.

SUMMARY

In order to evaluate the effectiveness of bridge deck protection

systems and gain a better understanding of corrosion processes in

concrete, a fast, reliable, nondestructive means of measuring the

corrosion of steel in concrete is needed. In an effort to meet this

need, NBS undertook a study of the application of an electrochemical

technique to measure the corrosion of steel in concrete. Using a portable computer as a basis for control of the measurment , a procedure was developed that applied the polarization resistance technique

and current interruption to the measurement. Through this approach,

measurements of corrosion of steel in concrete were carried out in

the laboratory indicating that there is a relationshop between the

9
polar! zatuon resistance measured and the corrosion observed. This

same approach was then applied to the measurement of corrosion of steel

rebar in a bridge deck. After overcoming many problems of mechanical

breakdown of the equipment and electrical interference, the measurement

was successfully carried out on three bridges in Frederick County, MD.

This preliminary venture into field measurements indicated that the

corrosion measurement can be performed, and furthermore, revealed many

of the obstacles that can be expected.

ACKNOWLEDGEMENT

We wish to thank Dr. Ugo Bertocci for his many helpful discussions

and suggestions; Mr. Denzil Mathews for his assistance in performing

the measurements; Mr. Wayne Clingan and Mr. Edward W. Feeser of the

Maryland Department of Transportation for their cooperation in

providing the bridges and traffic control; and finally. Dr. Paul Y.

Virmani for his guidance and financial support through the Federal

Highway Administration.

10
REFERENCES

1. Tonini, D. E. and Gaidis, J. M., Eds., Corrosion of Reinforcing

Steel in Concrete, ASTM STP 71 3 » American Society for Testing and

Materials, 1980.

2. Tonini, C. E. and Dean, S. W., Eds., Chloride Corrosion of Steel

in Concrete, ASTM STP 629, American Society for Testing and Materials,

1977.

3. Slater, J. E., Corrosion of Metals in Association with Concrete,

The Metal Properties Council, Inc., N. Y., July 1981.

M. Gouda, V. K. and Monrad, H. M., Galvanic Cells Encountered in the

Corrosion of Steel Reinforcement; Parts I-IV, Corrosion Science, 15, 1975

5. Whiting, D., Influence of Concrete Materials, Mix, and

Construction Practices on the Corrosion of Reinforcing Steel, Materials

Performance, NACE, 12, 1978.

6. Gjorv, 0. E., Vennesland, 0. et al . , Diffusion of Dissolved Oxygen

Through Concrete, Procceedings NACE '76, Paper No. 17, 1976.

7. Berman, H. A., The Effect of Sodium Chloride on the Corrosion of

Concrete Reinforcing Steel and the pH of Sodium Hydroxide Solution, J.

American Concrete Inst., 72, ^4, 1975.

8. Hausmann, D. A., Steel Corrosion in Concrete, How Does it Occur,

Materials Protection, _6, 1 1, 1967.

9. Escalante, E. and Ito, S., A Bibliography on the Corrosion and

Protection of Steel in Concrete, NBS SP 550, National Bureau of

Standards, August 1979.

10. Locke, C. E. and Siman, A., Electrochemistry of Reinforcing Steel

in Salt-Contaminated Concrete, ASTM STP 713, American Society for

Testing and Materials, 1980.

11. Hansson, C. M., Comments on Electrochemical Measurements of the

Rate of Corrosion of Steel in Concrete, Cement and Concrete Research,

Pergamon Press, jj4, 1984.

12. Gonzalez, J. A., Algaba, S., and Andrade, C., Corrosion of

Reinforcing Bars in Carbonated Concrete, British Corrosion J., 15, 3,

1980 .

13 . Escalante, E. Ito, S., and Cohen, M., Measuring the Rate of

Corrosion of Reinforcing Steel in Concrete, NBSIR 80-2012, National

Bureau of Standards, March 1980.

14. Escalante, E., Cohen, M. and Kahn, A. H., Measuring the Rate of

Corrosion of Reinforcing Steel in Concrete, NBSIR 84-2853, National

Bureau of Standards, April 1984.

11
15. Britz, D. and Crocke , W. A., Elimination of IR-Drop in

Electrochemical Cells by the Use of a Current Interruption

Potentiostat , Electroanalytical Chemistry and Interfacial

Electrochemistry, Elsevier Sequoai S.A., 108, 1980.

16. Williams, L. F. G. and Taylor, R. J., IR Correction; Parts I and

II, J. Electroanalytical Chemistry, Elsevier Sequoai S. A., 108, 1980.

17. Wheat, H. G. and Eliezer, Z., Some Electrochemical Aspects of

Corrosion of Steel in Concrete, Corrosion, 41, 11, 1985.

12
TABLE 1

Information Printed During Polarization Measurement

Specimen ID

Date

Time

Open Circuit Measurement at t=0 : WE Potential, V3

Current, 12

WE-CE Potential, VI

Time

Closed Circuit Measurement after Current Zeroing

WE Potential, V3

Current, 12

WE-CE Potential, VI

Time, s

First Measurement During "Holding":

WE Potential, V3

Current, 12

WE-CE Potential, VI

Time , s

Last Measurement During "Holding":

WE Potential, V3

Current, 12

WE-CE Potential, VI

Time, s

Summary of WE Potential During "Holding":

Minimum V3

Maximum V3

Average V3

Standard Deviation V3

Number of Readings

Summary of Applied Current During "Holding":

Minimum 12

Maximum 12

Average 12

Standard Deviation 12

Number of Readings

Polarization Resistance, ohms

^'^^Avg. “ ^3 )o.cy ^2/^vg.

13
TABLE 2

Composition of Concrete Mixes

(Weight Ratio of exponents to Cement

Without Chloride With Chloride

Cement 1 1

Sand 1 .7 1 .5

Pea Gravel 2.5 2.3

Sodium Chloride none 0.06

Water 0.5 0.4

14
TABLE 3

CONDITIONS OF EXPOSURE

SPEC

NO

1

1 TYPE OF

IMMERSION

j

1 CONDITION

1

1

1 ALTERNATE

1

J Cl FREE CONCRETE

1

1 Cl FREE PORE SOLUTION

2

1 CONTINUOUS 1 Cl FREE CONCRETE

1

1 Cl FREE PORE SOLUTION

3

I ALTERNATE I Cl FREE CONCRETE

I

1 Cl IN PORE SOLUTION

4

I CONTINUOUS I Cl FREE CONCRETE

1

1 Cl IN PORE SOLUTION

5

1 CONTINUOUS 1 Cl IN CONCRETE

1

1 Cl IN PORE SOLUTION

6 I CONTINUOUS 1 Cl IN CONCRETE

J

1 Cl IN PORE SOLUTION

7

I ALTERNATE 1 Cl IN CONCRETE

1

1 Cl IN PORE SOLUTION

8

1 ALTERNATE 1 Cl IN CONCRETE

1

1 Cl IN PORE SOLUTION

9

1 CONTINUOUS 1 Cl IN CONCRETE

I

1 Cl IN DISTILLED WATER

10 j CONTINUOUS J Cl IN CONCRETE

1

1 Cl IN DISTILLED WATER

1

1 ALTERNATE J Cl IN CONCRETE

J

1 Cl IN DISTILLED WATER

12 I ALTERNATE j Cl IN CONCRETE

I Cl IN DISTILLED WATER

15
TABLE 4

WEIGHT LOSS AND POLARIZATION

(Ba = Be = 0.

RESISTANCE DATA

15 V)

SPEC

NO.

TIME

DAYS

AVG Rp

OHMS

GRAVIMETRIC

WT LOSS

g

CALCULATED

WT LOSS

g

STD DEV

SUM

g

1 142 38042 0.001

0.0054 0.00214

2 148 13210 0.0083 0.0235 0.01004

TO 115 10307 0.0228 0.0179 0.00231

9 115 3606 0.0345 0.0326 0.00282

1115 4740 0.0357 0.0253 0.00239

12 109 3091 0.0466 0.0348 0.00325

6 148 1556 0.1700 0.4258 0.10582

3 138 1630 0.1913 0.0970 0.01015

4 148 1919 0.2522 0.1195 0.01293

5 142 895 0.4149 0.3678 0.09256

8 148 362 0.4510 0.3650 0.02841

7 148 231 0.4771 0.5427 0.03947

16
TABLE 5

CALCULATED CORROSION RATE, MDD

AT SIX POSITIONS ON THREE BRIDGES

DATE SPAN 1 SPAN 2

POSITION

A1 A3 A4 B1

POSITION

B3 B4

ROUTE 28 BRIDGE (1931) NUMBER 10029

OCT 8 - - - - - -

OCT 23 0.6 0.3 0 .8 0.3 0.6

NOV 6 (BRIDGE UNDER WATER ! !) - -

Average Corrosion Rate = 0.5

ROUTE 15 BRIDGE (1968) NUMBER 10100

OCT 8 0.4 3.2 0.5 1 . 3 2.6 1.7

OCT 23 0.8 0.5 1 .

1 . 3 1 .

0.6

NOV 6 0.8 1.0 0.9 0.2

Average Corrosion Rate = 1 . 1

ROUTE 80 BRIDGE ( 1972) NUMBER 10059

OCT 8 3.6 2.8 2.3

OCT 23 3.5 1 .1 .

0 . 7 0.8 2.1

NOV 6 3.1 2.1 2.6 0 .6 1 .

1.0

Average Corrosion Rate = 1.9

17
. >/ <irw.

iffl '^W'' •' T" " ’^ " ' 'a

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r Mt iM to» -to» -toAk 3h^jg i 8 Tool

.

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'l.j^.pi&A aotJao^noO •.Saf-^VA

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st-.i Bff'C.i C.C® CS TOO

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f, If '•, ,iiS *^-

JSr e . f - aoi»OttC>0 5|«|*T«>VA

i

Ill
V2 V3

Figure 1
AE

,

mV

(a)

Time,s

(b)

Figure 2
. BLOCK 2 •

-\A

' '

• .

• /- 8.e 3 1 . 38 «V 1

(a)

Time,s

(b)

Figure 3
Current,

jLlA

AE,

mV

}ILOCK 2

. . \yy/i“? ^'y. f

** r*

•** •*/*

• ^r•-

'

1

' r ^ S.

1 //

»4 • / 1 ' . /

i\

1 i/-

1 r

1

j

1

j

1

* .-I'.'Wnri t*»***'‘^

***** *' y'"

1

t i

j

1

f t

• • 4B.p t

1

1 1 ;8.5* aV

(a)

(b)

Figure 4
1.5 V

Figure 5
Compensated

Resistance,

ohms

Figure 6
2 in. O.D.

Concrete

Figure 7
Calculated

Corrosion

Rate,

MOD

Figure 8
Figure 9
Figure 10
APPENDIX A

Corrosion Calculations

Corrosion calculations are based on Stern and Geary's (1) equation:

dv

di

®a Bb

i--»-0 2.3026(Bg^+BQ )Icorr

dv

where is the slope of the polarization curve near the

di

corrosion potential, ohms

the anodic Tafel slope, V

the cathodic Tafel slope, V

icorr corrosion current, A

dv

let: R = di

where Rp is polarization resistance, ohms

then: i ®a ^c corr 2.3026(Ba+Bc)Rp

(equation 1)

Assuming = B^ = 0.15 V,

0.03257

then: corr (equation 2)

where i^orr corrosion current, A
Polarization Resistance, Rp , is calculated from the values obtained

during a measurement sequence.

(V3avg.- V3o.c.)

(equation 3)

the open circuit potential (at t=0) of the

working electrode, V

12

avg.

where V3o.c.

^^avg. is the average polarized potential of WE

during the "holding” period, V

^^avg. is average current applied to the WE

during the "holding" period.

Rp represents a period of 3«5 min ("holding" period) when the polarization data are collected, but it is assumed that this value of

Rp also represents the entire period, t, between measurements (e.g.

24, 48, 72 hrs, etc.). This assumption allows the calculation of

weight loss for the entire time of exposure of the WE. Using

Faraday's law (2):

W ^^^corr (equation 4)

where W is weight loss, the amount of metal reacted, g

t the time period of corrosion, s

k the electrochemical constant, g/C (grams/coulomb )

For Fe — Fe±± + 2 e ; k = 2.8938x10"^ g/C

Combining equations 1 and 4:

Ba Bq kt

]fj ^ 2.3026(B3+Bc)Rp
substituting: W - 0.15(0.15)(2.8938x10"^)t

2.3026(0.15 0.15)Rp

9.^257x 10"6 t y . (equation 5)

Total weight loss, is the sum of all the "daily” weight losses,

'^daily. calculated from Rp(daily)

^ total X" ‘daily

'^total “ yy ^p(daily)

0

The term "daily" is used loosely since can also represent a

two-day weekend when measurements were not performed.

If we know the area of the working electrode being polarized, corrosion

rate, MDD, can be calculated.

W

MDD

where; A is the area of the working electrode, dm^

t the period of exjxjsure, d

Calculations of corrosion rates on the bridge decks were based on an area of rebar of 60.3 sq.cm which is twice the area of projection from

a 6 cm (2.5 in) diameter CE on a 1.6 cm (5/8 in) rebar with a 5 cm (2

in) concrete cover. The time p>eriod was 30 days, the period of the

final measurements.

REFERENCES

1. Stern, M. and Geary, A. L., Electrochemical Polarization, A Theoretical Analysis of the Shape of {olarization Curves, J

Electrochemical Society, 104, 1, p56-63t 1957.

2. Uhlig, H. H. and Revie, R. W., Corrosion and Corrosion Control,

third edition. Join Wiley and Sons, N. Y., 1985.
;

,v® , '411

-/d i/m '^W

i^!i*?s;t.i,:*’/' • : ,

ifc:a:iS;:-»itliil®|--' . .:

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,ef E*Od lo tiw*‘>’i ..lo

, ,pio*<pfcn*i«iW Unn

TM-fc.

, , ^

liK.<.. ' »,A br^.j.H •*’ 1o*«q«a ’•/iJf lP. «l«tl*flA l*oni.'>P*^T

1*9/ »v la^oMW ••'—

^ i»ntmnooni9dii

wli»'J.:;^,''*^ i«JI'»l>: ,,&flt?^|.’ OflU — i!l Kf-
Over

view

of

System

oaX

UJ

D_

Q.

External

To

Structure

To

External

Current

(CE,WE,REF)

Battery

Pack

Measurement

(±

18V

for

D/A

Board)
Detail of 3421 A Data Logger

APPENDIX B2
Battery

Pack

Custom

D/A

Board

3 0)®

Q. (0 O)

o> o> at y

w

(O

pjBoa 0/1 iB»i8ia uiojj

APPENDIX

B3
APPENDIX B4

10 ! POTENTIAL TEST **********t********t**t****t*t*

20 ERIC P WHITENTON

30 NATIONAL BUREAU OF STANDARDS

40 MARCH 1986

50

60

DOCUMENTED VERSION OF 'C0R6'

70

80 ! *******t***t*t*********%*t*1Hti SET UP **********t**t*t***t******t**$**t*t

90 DISP 'SETTING UP COMPUTER'

1 00 OPTION BASE 1 110 GOSUB 3920 ! HPIL CONFIGURATION

1 20 DIM E$C2] ! CARRIAGE RETURN / LINE FEED

130 E$=CHR$ ( 13) 8<CHR$ < 10)

140 DIM F*C203 ! CASSETTE FILE NAME

150 DIM D (4, 4) ! DATA ARRAY FOR WHOLE TEST

160 t D(l, *)-Vl

170 I D(2, *)-I2

180 1 D (3, *) -V3

190 1 D(4, *)-TIME

200 1 D(», D-OPEN CIRCUIT

210 1 D(»,2)-INITIAL

220 1 D(*,3)-SET

230 1 D(#,4)-FINAL

240 P=0 ! D(»,P) FOR SUBROUTINE 'READALL'

250 M=0 ! MODE FOR SUBROUTINE 'READALL'

260 DIM C*C63 ! CARD FOR D/A (REALLY DIGITAL I/O BOARD DRIVING D/A)

270 C$=' ; WRT2,

280 B=0 ! BINARY VALUE OF v, THE D/A VOLTAGE

290 B0,B1,B2=0 ! TEMP BINARY VALUES

300 P1=0 ! BINARY TO VOLT SLOPE FOR v 310 P2=0 ! BINARY TO VOLT INTERCEPT FOR v 320 S=0 ! ERROR STATUS

330 DIM S(10) ! COUNTER FOR EACH TYPE OF ERROR

340 E=-l ! ERROR LOCATION

350 T=0 ! TARGET VOLTAGE FOR V3

360 D=.01 ! ATTEMPTED DELTA VOLTAGE FOR V3

370 Kl = .5 1? K2=20 ! USED IN SUBROUTINE SET V3 - 380 1 WHILE SETTING V3, IF THE PRESENT V3 IS MORE THAN

390 1 D*K1 AWAY FROM T, THEN CHANGE B BY K2 UNITS,

400 1 ELSE CHANGE B BY 1 UNIT

410 T1,T2=0 ! TEMP TIMES

420 C1,C2=0 ! TEMP COUNTERS

430 F1,F2,F3,F4=0 ! TEMP FLAGS

440 QO, Q1 , Q2, Q3, 04=0 ! TEMP VAR

450 05,06,07,08,09=0 ! TEMP VAR

460 DIM oiciOOI ! TEMP STRING

470 DIM D1$:30:,02*C303 ! TEMP STRING

480 R2=100 ! VALUE OF RESISTOR USED TO MEASURE 12

490 22=0 ! 12 2ER0

500 24=0 ! TIME 2ER0

510 DIM V(5) , I (5) ! STATS FOR V3,I2 DURING HOLD

520 1 (1 )-MIN

530 1 (2) -MAX

540 f (3)-AVE

550 1 (4) -STD

56 O

1 (5)-# PTS

570 1 FILE ASSIGNMENTS

5oO 1 IF F$<>"NO" THEN

590 1 #1-A BASIC FILE CALLED 'TTTT' FOR DATA WHILE

600 1 WHILE HOLDING V3
610

620

630

640

650

660

670

680

690

700

710

720

730

740

750

760

770

780

790

800

810

820

830

840

850

860

870

880

890

900

910

920

930

940

950

960

970

980

990

1 (jOO

1 0 1

1 020

1030

1 C>40

1 050

1 060

1070

1 080

1090

1 1 00

1 1 10

1 120

1 1 30

1140

1 1 50

1160

1 1 70

1 ISO

1 1 90

1 200

FOR C2=l TO 4

FOR Cl=l TO 4

NEXT 02

FOR 01=1 TO 5

GOSUB 3420

GOSUB 3480

GOSUB 3720

IF 8<>0 THEN

SENDIO ’

: DL’

#2-A TEXT FILE OALLED F$ GENERATED FROM FILE

#1 WHEN TEST IS OVER

AT END OF TEST FILE #2 IS OOP I ED ONTO OASSETTE

AND BOTH FILE #1 #2 ARE ERASED IN MEMORY.

IF YOU STOP THE PROGRAM EARLY, THEN ONE OR

BOTH OF THE FILES MAY BE LEFT IN MEMORY AND

EVENTUALLY HAVE TO BE PURGED.

m*t********illitt*****t MAIN PROGRAM  t** **t**t*******

! OLEAR ARRAYS

i±' D<01,G2)=0 I? NEXT 01

G- V(01) , I <01)=0 e NEXT 01

OLEAR ERROR

INITIALIZE DATA LOGGER

OALIBRATE D/A & SET PI,

E=0 & GOSUB

'UNL,LAD#’ ,

1860 (? GOTO 740

F1RA1Z1N4’&E$ !

&

cassette -File

2 TO Ft.TEXT

DISP "OONNEOT WIRES" ® BEEP 280,1

IF KEY$=’ = THEN GOTO 800

ON ERROR GOTO 810 ! BEEP 280,1 I? INPUT ’enter

IF F$O"N0" THEN ASSIGN #

OFF ERROR

IF F$<>"NO" THEN PRINT F$

PRINT DATE* G' PRINT TIME* ! Z2=0 G' Z2=FNB G' Z4=TIME ! P=1 G' M=0 G- GOSUB 3000 ! IF SOO THEN E=1 G' GOSUB 1860 G- GOTO 880

B=INT(Pl)t:D(l, l)+P2+.5) G GOSUB 3340 ! IF SOO THEN E=2 G' GOSUB 1860 & GOTO 900

GOSUB 3560 ! IF SOO THEN GOSUB 1860 G* GOTO 920

Tl = 120 I? GOSUB 2120 !

SET UP VOLTMETER

CONNECT WIRES TO STRUCTURE

Q*=KEY*

GET FILE NAME FOR

name or NO ’ ; F*

HOLD V3 DATA

IF SOO THEN

GOSUB 3600 ! IF SOO THEN

GOSUB 3640 ! IF SOO THEN

E=3 G' GOSUB 1860 ® GOTO 940

GOSUB 1860 & GOTO 960

GOSUB 1860 I? GOTO 980

Tl = 120 G- GOSUB 2120 ! IF SOO THEN E=4 G> GOSUB

P=2 G' M=1 G- GOSUB 3000 ! IF SOO THEN E=5 G- GOSUB

1860 G' GOTO

1860 ® GOTO

T=D (3

PR I NT

PR I NT

PRINT

PR I NT

T 1 =300 G'

1 ) -«-D !

PRINT DATE, TIME

SET ZEROES

READALL

SETv, SO V CLOSE TO VI

CLOSE SI, CONNECTING D/A, THRU RES.

ZEROI FOR A MAX OF T1 SECONDS

CLOSE S2, CONNECTING D/A, NO RES.

OPEN SI, DONT NEED ANY MORE

ZEROI FOR A MAX OF T1 SECONDS

1000

READALL

1020

TARGET VOLTAGE FOR V3

’ TARGET

T

VOLTAGE’

T2=3 G> GOSUB 2330 !

IF S<>0 THEN E=6 G- GOSUB 1860 G* GOTO

P=3 G' M=1 G’ GOSUB 3000 ! IF SOO THEN E=7 I? GOSUB 1860 G- GOTO

Tl = 180 G' T2=3 I? GOSUB 2630 !

IF SOO THEN E=8 G' p=4 G' M=1 G‘ GOSUB 3

IF SOO THEN E=9 G' GOSUB 3480 I IF SOO THEN E=10 G'

GOSUB

000 ! GOSUB

1860 @ GOTO

1860 G' GOTO

GOSUB 1860 G' GOTO

SET V3

WITH T2

1040

READALL

1 120

HOLD V3

WITH T2

1140

READALL

1170

INITIALIZE

1190

FOR T1 SECONDS,

SECOND TEST-ADJUST CYCLES

FOR T1

SECOND

SECONDS,

TEST-ADJUST CYCLES

DATA LOGGER
1210

1 220

1230

1240

1250

1260

1270

1280

1290

1 300

1310

1 320

1 330

1 340

1350

1 360

1370

1 380

1390

1 400

1410

1420

1 430

1440

1 450

1460

1470

1480

1490

1 500

1510

1 520

1 530

1 540

1 550

1 560

1 570

1 580

1 590

1 60(1) 1610

1 620

1 630

1 640

1 650

1 660

1 670

1 680

1690

1 700

1710

1 720

1 730

1740

1 750

1760

1 770

1780

1790

1 BOO

GOSUB 1570 ! PRINT RESULTS

IF F$="ND" THEN GOTO 1370 ! IF F^O’ND’ THEN CONVERT TEMP

! FILE TO LOTUS . PRN FILE AND

! SAVE ON CASSETTE

DELAY 0

READ # 1,1 ; D1

FOR Q2=l TO Q1

READ # 1,10*Q2 ; Q3,Q4,Q5

Q$=FNS$(Q3,S, 10)8<FNS$(Q4,2, 10) 8<FNS* (Q5, 3, 10)

DISP li' PRINT # 2,Q2 ; Q*

NEXT Q2

DELAY 1 !*• PURGE 'TTTT’ I? Q$=F*

DISP ’PUTTING DATA ON CASSETTE’ ® ON ERROR GOTO 1750

COPY F$ TO Q$?<’:CA’

OFF ERROR

PURGE F*

DIBP "DONE" li- BEEP 280,1 @ Q*=KEY* ! DONE

FOR Cl = l TO 5 li- PRINT (? NEXT Cl

JF KEY$=’ ’ THEN GOTO 1390

GOTO 680 ! LOOP BACK FOR ANOTHER TEST

END

I

! t*%ttt*t*t*t***ttt********t* ROUTINES t*t*t****t**tt**ttt********tt**t*

I

! ttt CENTER NUMBER IN STRING »** A FUNCTION

! D6 IS NUMBER TO PUT IN STRING

! Q7 IS LOCATION OF DECIMAL POINT

! QS IS STRING WIDTH

! MODIFIES Q1$,Q2«,Q0,Q9

DEF FNS$(Q6,D7,Q8)

Ql$i:i,Q8] = " " li- 09=10“^ (Q8-Q7) & Q2«=STR* ( INT ( . 49+Q6»Q9) /Q9)

D9=P0S(Q2$, ". ") I? Q0=LEN(Q2*) 6- IF Q9=0 THEN Q9=Q0

Q9=Q7-Q9+1 6- IF Q9>0 THEN Q1$C 09, 09+00-13=02*

FNS*=Q1*

END DEF

I

! *** PRINT RESULTS *** A SUBROUTINE

! VIEWS D(*, *) , V(*) , I (*)

! MODIFIES Cl, C2, 01, 02

DISP ’PRINTING RESULTS’

PRINT

FOR C2=l TO 4

FOR Cl = l TO 4 li- PRINT D(C1,C2) 8 NEXT Cl

PRINT

NEXT C2

FOR Cl = l TO 5 I? PRINT V<C1) 6- NEXT Cl

PRINT

FOR Cl = l TO 5 li- PRINT I (Cl) i? NEXT Cl

PRINT li- PRINT "COR. RES. IN OHMS"

IF I(3)=INF OR V(3)=INF THEN PRINT "NOT COMPUTABLE" I? GOTO 1730

Q1 = I C3) -D (2, 1

li- Q2=D (3, 1

) -V (3)

IF 01=0 THEN PRINT SGN(02)*INF ELSE PRINT 02/01

RETURN

I

! *** CASSETTE ERROR **t NOT A SUBROUTINE - EXITS WITH A GOTO

I MODIFIES 0*

! CALLS HPIL CONFIGURATION

PRINT li- PRINT ’CASSETTE ERROR’

PRINT ’TRY AGAIN’ li- PRINT

INPUT ’enter cassette -file name ’ ; 0*
laio

1S20

1 830

1 B40

1850

1880

1 870

1880

1 890

1 900

1910

1 920

1930

1 940

1 950

1 960

1970

1980

1990

2000

20 1

2020

2030

2040

2050

2060

2070

2080

2090

2 1 00

21 10

2120

2130

2140

2150

2160

2170

2 1 80

2190

2200

2210

2220

2230

2240

2250

2260

2270

2280

2290

2300

2310

2320

2330

2340

2350

2360

2370

2380

2390

2400

GOSUB 3920 ! HPIL CONFIGURATION

IF Q$="NO" THEN GOTO 1350

PRINT 'NEW FILE NAME’ i? PRINT Q$ i5 PRINT

GOTO 1330

#Sc*ERROR ROUTINE*** NOT ALWAYS A SUBROUTINE - EXITS WITH EITHER A

POP, GOTO OR A RETURN

MANY OF THE VALUES OF S<*) LEFT UNDEFINED FOR FUTURE EXPANSION

MODIFIES S,S(*) ,E,QO

CALLS CLEAR ERROR, INITIALIZE DATA LOGGER

IF S(5) THEN PRINT "SOFTWARE TIME OUT (";S(5);")"

IF S<6) THEN PRINT "DELAY BETWEEN READINGS TO SHORT <";S(6);")"

IF S(7) THEN PRINT "DATA LOGGER ERROR (";S(7);")"

PRINT "LAST ERROR"

IF E=0 THEN PRINT "WHILE SETTING UP FOR TEST"

IF E=1 THEN PRINT “WHILE READING OPEN CIRCUIT VALUES"

IF E=2 THEN PRINT "WHILE SETTING INITIAL VI"

IF E=3 THEN PRINT "WHILE COURSE ZEROING 12"

IF E=4 THEN PRINT "WHILE FINE ZEROING 12"

IF E=5 THEN PRINT "WHILE READING INITIAL VALUES"

IF E=6 THEN PRINT "WHILE SETTING V3"

IF E=7 THEN PRINT "WHILE READING SET VALUES"

IF E=8 THEN PRINT "WHILE HOLDING V3"

IF E=9 THEN PRINT "WHILE READING FINAL VALUES"

IF E=10 THEN PRINT "AFTER TEST OVER"

Q0=0 li' INPUT "(1) AGAIN / END (2) " s QO

DISP

IF Q0=1 THEN GOSUB 3410 & RETURN

IF 00=2 THEN GOSUB 3480 I? GOSUB 3410 Q POP (? GOTO 1210

GOTO 2060

! *** ZEROI *** A SUBROUTINE

! VIEWS T1

! MODIFIES Q1,Q2,Q3,Q4,F1,F2,F3,F4,S,S<5) ,B

f CALLS FNBjSETv

DISP ’ZEROING 12’

Q1=S ! SAVE OLD STATUS

02=0 I PRESENT 12

F1=0 1? F2=10 li' F3=20 ! OVER /UNDER ZERO FLAGS

03=TIME I START TIME

! LOOP

04=02 ! LAST 12

02=FNB ! PRESENT 12

IF SOOl THEN RETURN

F4=F3 I? F3=F2 i? F2=F1 I? F1=SGN(Q2)

IF F1=0 THEN RETURN

IF F4=F2 AND F3=F1 AND ABS (02X=ABS (04) AND F10F2 AND F30F4 THEN RETURN

IF TIME-03>=T1 THEN S=S+1 & S(5)=S(5)+1 (? RETURN

B=B+F1 li- GOSUB 3340 ! SETv

IF BOQl THEN RETURN

GOTO 2210

! *** SET V3 *** A SUBROUTINE

! VIEWS D, T1 , T2, K1 , hc:2

I MODIFIES 01,02,Q3,Q4,F1,F2,F4,T,B,S,S(6)

! CALLS OPEN S2, CLOSE S2,FNC,SETv

DISP ’SETTING V3’

01 =S I SAVE OLD STATUS

02=TIME ! START TIME

03=TIME ! NEXT TIME
2410 F4=0 ! REACHED TARGET FLAG

2420 GOSUB 3680 ! OPEN S2

2430 F 1 , F2=SGN ( FNC-T

2440 GOSUB 3340 ! CLOSE S2

2450 IF SOQl THEN RETURN

2460 ! LOOP

2470 IF F10F2 AND F4=0 THEN F4=l I? PRINT "TARGET REACHED" 9 PRINT TIME* 9 PRIN'

2480 IF TIME-Q2<T1 THEN GOTO 2510

2490 IF F4=0 THEN T=FNC 9 PRINT "NEW TARGET" 9 PRINT T I? PRINT

2500 RETURN

2510 F2=F1

2520 GOSUB 3680 ! OPEN S2

2530 Q4=FNC-T 9 F1=SGN(Q4)

2540 IF ABS(Q4)>K1*D THEN B=B+K2»F1 ELSE B=B+F1

2550 GOSUB 3340 ! SET v 2560 GOSUB 3600 ! CLOSE S2

2570 IF SOQl THEN RETURN

2580 Q3=Q3+T2 ! NEXT TIME

2590 IF TIME>Q3 THEN S=S+1 9 S(6)=S(6)+1 9 RETURN

2600 IF TIME<Q3 THEN GOTO 2600

2610 GOTO 2460

2620 ! 2630 ! HOLD V3 *** A SUBROUTINE

2640 ! VIEWS T,T1,T2,F*

2650 ! MODIFIES FILE #1,Q1,Q3,Q4,Q5,Q6,Q7,B,S,S<6> ,V(») , !<*)

2660 ! CALLS OPEN S2, CLOSE S2, SETv, FNC, FNB

2670 DISP ’HOLDING V3’

2680 IF F*O"N0" THEN ASSIGN # 1 TO ’TTTT’, BASIC

2690 Q1=S ! SAVE OLD STATUS

2700 V(1)=INF 1? V(2)=-INF 9 V(3)=0 9 V(4)=0 9 V(5)=0

2710 I(1)=INF 9 I(2)=-INF 9 I(3)=0 9 I(4)=0 9 I(5)=0

2720 Q3=TIME ! START TIME

2730 Q4=TIME ! NEXT TIME

2740 ! LOOP

2750 Q5=FNB li' Q7=B

2760 GOSUB 3680 ! OPEN S2

2770 Q6=FNC

2730 B=B+SGN(Q6-T) 9 GOSUB 3340 ! SETv

2790 GOSUB 3600 ! CLOSE S2

2800 IF SOQl THEN GOTO 2910

2810 I (1)=MIN(I (1) ,Q5) 9 I (2) =MAX (I (2) , Q5)

2820 I(3)=I(3)+Q5 9 I (4) =I (4) +Q5-^2 9 I(5)=I(5)+1

2830 V(1)=MIN<V(1) ,Q6) ® V (2) =MAX ( V (2) , Q6)

2340 V(3)=V<3)+Q6 9 V (4) =V (4) +06-^2 (? V(5)=V(5)+1

2850 IF F$O"N0" THEN PRINT # 1,1 ; 1(5) (? PRINT # 1,10*1(5) ; Q7,Q5,Q6

-2860 IF TIME-Q3>=T1 THEN GOTO 2910

2870 Q4=Q4+T2

2880 IF TIME>Q4 THEN S=S-*-l 9 S(6)=S(6)-H 9 GOTO 2910

2890 IF TIME<Q4 THEN GOTO 2890

2900 GOTO 2740

2910 ! COMPUTE STATS 8< RETURN

2920 Q3=I (3) 9 Q4=I (4) @ Q5=I (5)

2930 IF Q5>=1 THEN I(3)=Q3/Q5 ELSE I(3)=INF

2940 IF Q5>=2 THEN I (4) = ( (Q5*Q4-Q3*Q3) / (Q5* (Q5-1 ) )

) ''. 5 ELSE I(4)«INF

2950 Q3=V(3) 9 Q4=V(4) i? Q5=V(5)

2960 IF Q5>=1 THEN V(3)=Q3/Q5 ELSE V(3)=INF

2970 IF Q5>=2 THEN V (4) = ( (Q5*Q4-Q3*Q3) / (Q5* (Q5-1 ) )

) '^. 5 ELSE V(4)-INF

2980 RETURN

2990 ! 3000 ! *** READ ALL *** A SUBROUTINE
3010

3020

3030

3040

3050

3060

3070

3030

3090

3100

3110

3120

3130

3140

3150

3160

3170

3180

3190

3200

32 1

3220

3230

3240

3250

3260

3270

3280

3290

3300

3310

3320

3330

3340

3350

3360

3370

3380

$

3390

3400

3410

3420

3430

3440

3450

3460

3470

3480

3490

3500

35 1

3520

3530

3540

3550

3560

3570

3580

3591.*

! VIEWS Z4,M,P

! MODIFIES D(*,P)

! CALLS FNA, FNB, FNC, OPEN S2, CLOSE S2

DISP 'READING VI , 12, V3, TIME’

D(1,P)=FNA

D(2,P)=FNB

D(4,P)=TIME-Z4

IF M=1 THEN 60SUB 3680 ! OPEN S2

D(3,P)=FNC • IF M=1 THEN GOSUB 3600 ! CLOSE S2

RETURN

I

! *** READ VI *** A FUNCTION

! VIEWS E$

DEF FNA

SENDIO ’ ;DL’ , ’UNL,LAD#’ ,

’ CLS2; T2’ ?<E« FNA=-VAL (ENTI0$ ( ’ : DL’ ,

’ UNL, TAD#, SDA’ )

END DEF

I

! READ 12 *** A FUNCTION

! VIEWS E$,R2,Z2

DEF FNB

SENDIO ’ :DL’ . ’UNL, LAD#’ ,

’ CLS3; T2’ &E$

FNB=VAL (ENTIO$ ( ’ : DL’ ,

’ UNL, TAD#, SDA’ ) ) /R2-Z2

END DEF

I

! *** READ V3 *** A FUNCTION

! VIEWS E*

DEF FNC

SENDIO ’ :DL’ , ’UNL,LAD#’ , ’CLS4;T2’?<E*

FNC=VAL(ENTlb$(’ :DL’ ,

’ UNL, TAD#, SDA’ )

END DEF

I

! *** SETv *** A SUBROUTINE VIEWS C*,E« MODIFIES B, BO, B1 , B2, Q$

IF B<0 THEN B=0

IF B>4095 THEN B=4095

B0=4095-B li' B2=B0 DIV 64 IP B1=M0D (BO, 64)

Q$=C$ C 2 , 6 3 8<STR$ < B2+64 ) &C«8<STR$ < B2+ 1 92 ) 8<C*8<STR* ( B 1 ) &C*8tSTR* ( B 1 + 1 28 ) 8<C*8< ’ 0 ’ ?-<{ SENDIO ’ :DL’ , ’UNL,LAD#’ ,Q$

RETURN

I

! *** CLEAR ERROR *** A SUBROUTINE

! MODIFIES C1,S(*) ,S,E

FOR Cl = l TO 10 e S(C1)=0 IP NEXT Cl

S=0 I? E=-l

RETURN

I

! *** INITIALIZE DATA LOGGER »«* A SUBROUTINE

! MODIFIES Q$,S,S<7)

DISP ’CLEARING DATA LOGGER’

CLEAR ’:DL’ i? WAIT 2 ! CLEAR DATA LOGGER

Q$=ENT I 0$ ( ’ ; DL ’

,

’ UNL , TAD# , SST ’ ) ! READ STATUS

IF NUM(Q$)01 THEN S=S+1 ip S(7)=S(7)+1 ! IF STATUS NOT 1 THEN ERROR

RETURN

I

! *** CLOSE SI A SUBROUTINE VIEWS E«

SENDIO ’ :DL’ , ’UNL, LAD#’ , ’CLSO’&E*

RETURN

I
3600

36 1

3620

3630

3640

3650

3660

3670

36S0

3690

3700

3710

3720

3730

3740

3750

3760

3770

3780

3790

3800

3810

3320

3830

3340

3850

3860

3870

3330

3390

3900

39 1

3920

3930

3940

3950

! *** CLOSE 82 *** A SUBROUTINE VIEWS E*

SENDIO ’

; DL' ,

’ UNL, LAD#' ,

’ CLSl ’ RETURN

I

! *** OPEN SI *** A SUBROUTINE VIEWS E«

SENDIO ’ ;DL’ , 'UNL, LAD#' , '0PN0’8«E*

RETURN

I

! *** OPEN S2 A SUBROUTINE VIEWS E«

SENDIO ’

; DL' ,' UNL, LAD#' ,

’ OPNl ' &E*

RETURN

I

! *** CALIBRATE D/A & SET P1,P2 *»» A SUBROUTINE

! VIEWS E$

! MODIFIES Q1 ,Q2,Q$,B,P1,P2

! CALLS OPEN SI, OPEN S2,SETv

DISP 'CALIBRATING D/A’

Q$=KEY$

GOSUB 3640 ® GOSUB 3680 ! OPEN S1,S2

B=4095 ® GOSUB 3340 ! SETv

SENDIO ' :DL' , 'UNL,LAD#' , 'CLS5;T2'8<E* ! READ D/A OUTPUT (v)

Q1=-VAL(ENTI0$(' :DL' ,

' UNL, TAD#, SDA’ )

IF ABS(Q1X.1 THEN DISP 'TURN D/A ON' ® BEEP 560,. 02 ® WAIT 1 ® GOTO 3790

B=0 ® GOSUB 3340 ! SETv

SENDIO ’ ;DL' , 'UNL,LAD#' , 'CLS5;T2'8<E« ! READ D/A OUTPUT (v)

D2=-VAL (ENTIO$ ( ' ; DL' ,' UNL, TAD#, SDA' )

Pl=4095/ (Q1-Q2) ® P2=-Q2*P1

Q*=KEY$

DISP 'TOTAL RANGE IS ' ; ABS (Q1-Q2)

IF Q$=" THEN GOTO 3790

RETURN

! HPIL CONFIGURATION **

ASSIGN 10 ' :DL, :PR, :CA'

PRINTER IS ':PR'

RETURN
APPENDIX Cl

Technical Report Documentation Page

1 . Report No. 3. Recipient’s Cotalog No. FHWA/RD-86/

2. Government Accession No.

4. Title and Subtitle Measuring the Rate of Corrosion of Reinforcing Steel in

Concrete—Final Report

5. Report Date November 1986

6. Performing Organizotion Code

7. Author^s) E. Escalante, E. Whitenton, F. Qlu

8. Performing Organization Report No.

NBSIR 86-3456

9. Performing Organization Name and Address National Bureau of Standards

Gaithersburg, MD 20899

10. Work Unit No. (TRAIS)

35Q2034

11. Contract or Gront No. DTFH-893-Y-10025

12. Sponsoring Agency Name end Address Federal Highway Administration

McLean, Virginia

13. Type of Report and Period Covered

Final

Id. Sponsoring Agency Code

15. Supplementary Notes

16. Abstroct

This report describes a two phase study directed at developing a portable

system for measuring the corrosion of steel in concrete bridge decks.

A small, portable computer system is used to control the measurement of

polarization resistance of steel in concrete, aind using current interruption, iR compensation is accomplished. During the developxnent stage,

measurements were made on small specimens in a laboratory controlled

environment, and the results of the calculated weight loss measurements

based on the electrochemical measurement are compared to gravimentrically

determined weight loss. In the second phase, the portable system was used to measure the corrosion of three bridge decks in Frederick Country

Maryland, over a four month period. 'The results of these field measurements and the problems encountered are discussed.

17. Key Words ... i , bridge deck corrosion

corrosion of steel

corrosion rate measurement

polarization resistance

steel in concrete

18. Distribution Statement

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21- No. of P ages 22. Price

Form DOT F 1700.7 (8 72) Reproduction of completed page authorized
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5
NBS-114A (REV. 2-601 U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 86-3456

2. Performing Organ. Report No.| 3. Publication Date

October 1986

4. TITLE AND SUBTITLE

Measuring the Rate of Corrosion of Reinforcing Steel in Concrete - Final Report

5. AUTHOR(S)

E. Escalante, E. Whitenton, F. Qiu

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions)

national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Con tract/Grant No. DTFH=893-Y-10025

8. Type of Report & Period Covered

Final

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City. State, ZIP)

Federal Highway Administration

McLean, Virginia

10.

SUPPLEMENTARY NOTES

FHWA Contract Manager: Y. P. Virmani

Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

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

bibliography or literature survey, mention it here)

This report describes a two phase study directed at developing a portable

system for measuring the corrosion of steel in concrete bridge decks.

A small, portable computer system is used to control the measurement of

polarization resistance of steel in concrete, and using current interruption, iR compensation is accomplished. During the development stage,

measurements were made on small specimens in a laboratory controlled

environment, and the results of the calculated weight loss measurements

based on the electrochemical measurement are compared to gravimentrically

determined weight loss. In the second phase, the portable system was used to measure the corrosion of three bridge decks in Frederick Country,

Maryland, over a four month period. The results of these field measurements and the problems encountered are discussed.

12.

KEY WORDS (S;x to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

bridge deck corrosion; corrosion of steel; corrosion rate measurement; polarization

resistance; steel in concrete.

13.

AVAILABILITY

[2Q Unlimited

I I For Official Distribution. Do Not Release to NTIS

Order From Superintendent of Documents, U.S, Government Printing Office, Washington, D.C.

20402.

[IQ Order From National Technical Information Service (NTIS), Springfield, VA, 22161

14. NO. OF

PRINTED PAGES

49

15. Price

$9.95

USCOMM-DC e043-Pe0
\