Active Protection of Fiber-Reinforced Polymer Corrosion--libre

8/10/2019 Active Protection of Fiber-Reinforced Polymer Corrosion--libre

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CORROSION SCIENCE SECTION

CORROSIONVol. 67, No. 2 025002-1

Submitted for publication March 19, 2009; in revised form, June24, 2010.

Corresponding author. E-mail: [email protected]. * Department of Civil Engineering, Indian Institute of Technology

Bombay, Mumbai 400076, India.** Indian Institute of Technology Bombay, Mumbai 400076, India.

Present address: Thapar University, Patiala 147004, India.*** Department of Material Science and Metallurgical Engineering,

Indian Institute of Technology Bombay, Mumbai 400076, India.

Active Protection of Fiber-Reinforced Polymer-Wrapped Reinforced Concrete StructuresAgainst Corrosion

S. Gadve,,* A. Mukherjee,** and S.N. Malhotra***

ABSTRACT

Large numbers of reinforced concrete (RC) structures that have

been damaged from corrosion of steel reinforcements are reha-

bilitated with fiber-reinforced polymer (FRP) composites. This

paper investigates active protection of the steel embedded

in concrete that is treated with surface-bonded carbon FRP.

The electrically conductive carbon fiber is used as an anode

while the reinforcing bar is used as a cathode. Concrete cyl-

inder specimens with embedded steel bars are immersed in

salt water, and anodic current is passed through the reinforce-

ment to initiate cracking in concrete as a result of acceler-

ated corrosion of steel. Carbon FRP sheets have been bonded

adhesively to the cylinders. The adhesive has been modified

to impart electrical conductivity. Specimens were exposed to

a highly corrosive environment for a specified time. Pullout

strength, mass loss, potentiodynamic scans, and the half-cell

potential of steel are reported as metrics of performance of the

samples. The proposed technique has been very effective inretarding the corrosion of steel.

KEY WORDS: active protection, anodic current, corrosion, fiber-

reinforced polymer, pullout strength, reinforced concrete

INTRODUCTION

Reinforced concrete has been developed and applied

extensively for a century. However, there are many

instances of premature failure of reinforced con-crete components from corrosion of reinforcement.

The economic implications of such damage are enor-

mous. Overall, repair and maintenance of reinforced

concrete structures cost 1% to 2% of the yearly rate

of new construction. In a tropical country like India,

where approximately 80% of the annual rainfall takes

place in the two monsoon months, corrosion-related

problems are more alarming. India also has a very

long coastline where marine weather prevails. Typi-

cally, a building in the coastal region requires major

restoration work within 15 years of its construction.

Recent developments in the field of fiber-rein-

forced polymer (FRP) have resulted in highly efficient

construction materials. FRP are being used increas-

ingly to rehabilitate corrosion-affected structures. FRP

sheets are wrapped around beams and columns to

rehabilitate them from the loss of shear capacity and

confinement attributable to the corrosion of links or

stirrups. The efficiency of FRP in the enhancement of

bending,1shear capacities of flexure elements,2and

enhancement of concrete confinement in compres-

sion elements3is well established. An important spin-

off from the FRP treatment of RC structures can be

their resistance to corrosion. There have been vari-

ous attempts of passive protection of steel reinforce-ments with surface-bonded FRP, both in labs and

ISSN 0011-9312 (print), 1938-159X (online)11/000013/$5.00+$0.50/0 2011, NACE International


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025002-2 CORROSIONFEBRUARY 2011

at sites.4FRP are unaffected by electromechanical/

electrochemical deterioration and can resist aggres-

sive corrosive effects of acids, alkalis, salts, and simi-

lar aggregates under a wide range of temperatures.

Therefore, unlike steel reinforcement, they are less

susceptible to environmental degradation. Arguably,

FRP wraps prevent the increase in the volume of rein-

forced concrete (RC) members from rusting by apply-

ing confinement pressure, thereby resisting dislodging

of the concrete cover.

The FRP wraps provide a barrier layer that should

impede further corrosion of the steel. Site applications

have been on structures that have been damaged by

corrosion.5FRP has been applied primarily to com-

pensate for the lost steel and to improve confinement

of the concrete. However, there is near unanimity that

FRP wraps have slowed down the rate of corrosion,

albeit in varying degrees. The experience of the pres-

ent authors on the performance of glass fiber-rein-

forced polymer (GFRP) wraps on RC in coastal Gujarathas been very good. The FRP wraps in the corrosion-

affected areas have not shown any sign of deteriora-

tion in six years.

The general procedure of laboratory experiments

has been to accelerate corrosion in steel embedded in

concrete and then apply the FRP to observe its effects

on corrosion.6-21Corrosion has been accelerated

through the application of impressed potential on the

reinforcements7,10,14,16or by simulating wet and dry

cycles in chloride-rich environments.22The main indi-

cators of performance are mass loss of reinforcement,

pullout strength, electric resistance, half-cell poten-tials, and potential scans. The suitability of perfor-

mance indicators depends on the method of imparting

corrosion. It is noted that the benefit of FRP depends

on several factors, such as adhesive, fiber, method of

application, and environment.

So far, researchers have used FRP as a passive

barrier layer that would impede ingress of moisture

and corrosive chemicals. One class of FRP, namely

carbon FRP (CFRP), is electrically conductive. There-

fore, they may be used in the active protection of RC

structures. The authors are unaware of any previ-

ous investigation on the active protection of the steel

using FRP. This paper investigates the use of FRP

wraps for active protection of steel in concrete. We

briefly introduce active protection.

ACTIVE PROTECTION

The corrosion of steel reinforcing bars is an elec-

trochemical process that requires a flow of electric

current and several chemical reactions. The three

essential components of a galvanic corrosion cell are

anode, cathode, and electrolyte. At the anode, iron is

oxidized to the ferrous state and releases electrons:

Fe e +e ++ 2 (1)

hese electrons migrate to the cathode where they

com ine with water and oxygen to orm hydroxyl ions:

2e O OO

+ +++ O+ O

(2)

he hydroxyl ions com ine with the errous ions to

orm errous hydroxide (Fe[OH]2):

e e++ 2( ) (3)

In the presence of water and oxygen, the Fe(OH)2is

oxidized urther to orm erric oxide (Fe2O3):

2

2 2 2

3 2 2

Fe O HH

2 2

H

2 2

F4Fe

Fe Fe O HH

2

H

2

O

HH )O H

HH

+ +

2 2

+

2 2

H+H

2 2

H

2 2

+

2 2

4H

2 2

O FF

2

2

e ee e

2

e

2

2

2e

2

HHHH

2

H

2

2

2H

2

(4)

Corrosion of steel in concrete in the presence of chlo-

ides, but with no oxygen (at the anode), takes placen several steps. At the anode, iron reacts with chlo-

ide ions to orm an intermediate solu le iron-chloride

complex:

Fe e+ +22 2 2 )Cl 2222+ 22e 2e 2 222 2 2 2 2 2 22e 2 22 2 22 2 2 (5)

When the iron-chloride complex diffuses away from

the ar to an area with higher pH and concentra-

tion o oxygen, it reacts with hydroxyl ions to orm

Fe(OH)2. This complex reacts with water to orm

Fe(OH)2

( Fe Cl

HO

Cl+ ++ + +++222

2 2

Cl 2l + 2+ 2+l +l 2l +l 2 222e F 2F 2O 2O 2H2H2 2 + +2 + 22222O 2O 2 2 2 22 222 222 2O 2O 2O 2O 22 2H2H2 H 2H22 2 2 2 F 2 (6)

he hydrogen ions then combine with electrons to

form hydrogen gas:

eee

e e e (7)

As in the case of corrosion of steel without chlorides,

the Fe(OH)2, in the presence o water and oxygen, is

oxidized urther to orm Fe O3:

2

2 2 2 3

3 2 2

Fe O HH

2 2

H

2 2

F4Fe

Fe Fe O HH

2

H

2

O

HH )O H

HH

+ +

2 2

+

2 2

H+H

2 2

H

2 2

+

2 2

4H

2 2

O FF

2

2

e ee e

2

e

2

2

2e

2

HHHH

2

H

2

2

2H

2

(8)

he principle of active protection lies in connecting

an external anode to the metal to e protected and

the passing o an electric direct current to make all

areas o the metal sur ace cathodic. There ore, the

onization illustrated in Equations (1) and (5) is pre-

vented. The external anode may e a sacri icial gal-

vanic anode, where the current is a result of the

otential difference between the two metals, or it may

e an impressed current anode, where the current is

mpressed rom an external direct current (DC) power

source. In this paper, we investigate the impressedcurrent anode system. In the impressed current


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system, an inert (zero or low dissolution) anode is

used and an external source of DC power is used to

impress a current from an external anode onto the

cathode (reinforcing steel) surface. The issues on

active protection of RC structures are:

to create an anode around the structure

to maintain adequate electric potential

to avoid sympathetic damage as a result of

overprotection

There have been many alternative anode sys-

tems developed for active protection to RC structures,

such as highway bridge substructures, buildings, and

marine structures.23A variety of anodes, such as tita-

nium wire titanium strip,24titanium mesh,25and zinc

spray,26and conductive systems, such as conductive

concrete mortar27and carbon fiber-reinforced over-

lay,24have been attempted by the researchers. The

driving voltages for protection vary with the type of

anode and environmental conditions. Typical operat-

ing current densities range between 0.2 mA/m2and2.0 mA/m2for the cathodic prevention of new rein-

forced concrete structures and between 2 mA/m2and

20 mA/m2for cathodic prevention of existing salt-

contaminated structures.28A cathodic current density

of 5 mA/m2to 20 mA/m2to the steel reinforcement

reduces its corrosion rate to negligible values.27Over-

voltage or higher current densities for prolonged peri-

ods may lead to damages such as degradation of the

steel-concrete bond, which is associated with soften-

ing of the cement matrix in contact with the metal.29-30

There has been an enhanced risk of expansive alkali

silica reaction in cathodic regions of concrete with sili-ceous aggregates. It has been reported that the risk is

reduced considerably if the cathodic current density is

maintained uniformly and consistently at a level lower

than 20 mA/m2.26Although significant research has

been done on the active protection of RC, the applica-

tion of the technique has remained meager because

of the requirement of special anodes that are often

expensive.

In a previous investigation, the authors have

reported the efficacy of FRP wraps for passive protec-

tion of RC structures.31In addition to passive protec-

tion, the FRP materials that are electrically conductive

can be designed to offer active protection as well. This

has not been reported so far.32With the FRP wraps

acting as anode, no other anode would be necessary.

Therefore, the cost of active protection can be brought

down significantly. Present work investigates active

protection using surface-bonded CFRP sheets as the

anode.

Laboratory samples of RC specimens were pre-

pared. To initiate corrosion, the specimens were

exposed to accelerated corrosion by impressing anodic

current into the reinforcing bar. After a specific period

of exposure, the cracked RC specimens were treated

with surface-bonded FRP. The samples were activelyprotected while subjecting them to a specified envi-

ronment in a salt mist chamber for a specific period.

Results of actively protected samples have been com-

pared with that of unprotected and passively pro-

tected ones.

EXPERIMENTAL PROCEDURES

The experimental program was carried out in the

following steps:

Cylindrical reinforced concrete specimens were

cast.

Initial corrosion was induced into the reinforced

concrete specimens.

Precorroded specimens were wrapped with

CFRP and GFRP sheets.

The wrapped specimens were subjected to fur-

ther corrosion by exposing them to salt mist

while applying active protection.

Corrosion was monitored.

Destructive tests were carried out.

Preparation of Test SpecimensIn the present program, cylindrical specimens

with an embedded steel bar (Figure 1) were used. The

height and diameter of the specimen were 230 mm

and 100 mm, respectively, with an accuracy of 1 mm.

A standard reinforcing bar of 330 mm length and

12 mm nominal diameter of Fe 415 grade was used.

The bar was shot-blasted to Sa 2.5 (ISO 8501:1)33

sur-face and immediately dipped in oil. The white shining

FIGURE 1. Cylindrical-reinforced concrete specimen.


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surface was maintained in the laboratory until it was

embedded in concrete. Before placing the bar in con-

crete, a 2-mm-diameter groove was drilled on one end

of the bar and a copper stud was fixed in the groove.

The plug was used for electrical connections. Polytet-

rafluoroethylene (PTFE) tape was wound around the

bar at two locationsthe bottom edge and at the

interface with the concrete top face. This served as a

bond breaker, and the embedded length of the bar in

concrete was maintained precisely at 152 mm. The

bar was placed in such a way that the transverse

clear cover was 45 mm and the bottom cover was

51 mm. Before casting of the test specimens, each

reinforcing bar was weighed to a 0.1-gm accuracy.

The protruded part of the steel bar was coated with

liquid epoxy resin for corrosion protection.

Ordinary Portland cement of nominal strength

(43 MPa), fine aggregate (medium-sized natural/

river sand), and crushed stone coarse aggregate with

a maximum size of 20 mm was used in the con-crete. The ratio of cement:sand:coarse aggregate

was 1:2.16:2.44. The water-cement ratio was 0.42and aggregate-cement ratio was 4.6. The resulting

strength of concrete was 40 MPa.

A special molding system (Figure 2) was fabri-

cated for casting the specimens. The system is able to

maintain accurately the position and inclination of the

bar with respect to that of the cylinder.

Inducing CorrosionThe objective of inducing corrosion to the bar is to

simulate corrosion-damaged concrete. The commonly

used methods of inducing corrosion in RC specimens

are salt mist,11,14,18

chloride diffusion,19-21

alternatedrying and wetting in salt water,14,19and impressing

anodic current.10,16

In this investigation, the impressed current tech-

nique has been used. Specimens were kept immersed

in 3.5% sodium chloride (NaCl) solution for 24 h to

ensure full saturation. A stainless steel mesh rolled

into a hollow, open cylinder was used as the cathode

(Figure 3). The cathode and the specimen were placed

in 3.5% NaCl solution. The level of NaCl solution was

3 cm below the top surface of the specimen to allevi-

ate corrosion at the steel-concrete interface. The

DC-regulated power supplier (DCRPS) used in the

present study could supply 500 mA DC at 60 V. The

reinforcing steel bar was connected to the positive

terminal of the external DC source and the negative

terminal was connected to the stainless steel mesh.

The 100-mA direct electrical constant current (CD =

1,740.67 A/cm2) was impressed between the rein-

forcing bar and the stainless steel mesh. It is more

common to maintain a constant voltage between the

cathode and the anode.6-7,19However, in this inves-

tigation, a constant current was preferred because

the goal of this investigation was to examine the

active protection through maintenance of constant

cathodic current. A total of 12 specimens was usedin this experiment, divided into three groups. Con-

FIGURE 2. Specimen casting system.

FIGURE 3. Schematic representation of the device for accelerated

corrosion.


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stant current was impressed for 2 days, 4 days, and

8 days into four specimens of each group, respec-

tively. Anode-to-cathode voltage, corresponding to a

constant current of 100 mA, was monitored every day

for all specimens. Half-cell potential of the corroding

reinforcement bar was also noted every day with ref-

erence to a standard silver/silver chloride (Ag/AgCl)

electrode. Using this method, the concrete was found

to develop cracks within 2 days. There were brown

stains of rust on the concrete. The crack widths were

measured after 2 days, 4 days, and 8 days. Potentio-

dynamic electrochemical anodic polarization scans

were obtained for all the specimens after initial cor-

rosion. Cracks initiated at the surface of the cylinder

and ran along the direction of the reinforcement on

the sides of the cylinder (Figure 4). Voltage between

the reinforcing steel anode and stainless steel mesh

cathode decreased with time, indicating that the resis-

tance lessened with the progression of the crack.

Wrapping of Precorroded SpecimensTwo fiber materials are popular in the rehabilita-

tion of structures in Indiaglass and carbon. Because

of the electrical conductivity of carbon fiber, only CFRP

has been used for active protection. However, compar-

ison has been made between the active and the pas-

sive protection offered by both glass and carbon fiber

sheets. The fibers are applied in the form of unidirec-

tional sheets. Glass fiber sheets are thicker than the

carbon fiber sheets. In this investigation, two often

used, commercially available, unidirectional CFRP and

GFRP sheets and compatible epoxy adhesive are used.Properties of the sheets are presented in Table 1.

Samples were air-dried prior to the application of

FRP wraps. Manufacturers specification was followed

in the application of the wraps. Out of the four speci-

mens in a group, one was kept unwrapped. One layer

of either CFRP or GFRP sheet was wrapped around

the test specimens with the fiber along the circumfer-

ential direction of the cylinder. The entire length of the

cylinder was covered. A 25-mm overlap was provided

at the ends of the sheets. The remaining specimens

were used for active protection. These CFRP-wrapped

test specimens were provided with additionally adhe-

sively bonded 25-mm to 30-mm wide, vertically ori-

ented carbon sheet (Figure 5) to facilitate uniform

distribution of direct current throughout the speci-

men for effective active protection. The epoxy adhesive

used was modified to be conductive.32

Active ProtectionSince carbon is electrically conductive, an

attempt was made to use this property in apply-

ing active protection to the reinforced concrete sys-

tem without using any external anode. In this case,

the carbon fiber sheets that were wrapped around the

cylindrical reinforced concrete specimen themselves

were used as anodes and the reinforcing steel bar as

FIGURE 4. Specimens after initial exposure.

FIGURE 5. Schematic representation of cathodically protected

specimen.

TABLE 1Properties of Fibers Used in the Experiment

Thickness Tensile Tensile Ultimate Electrical

Material (mm) Strength (GPa) Modulus (GPa) Strain Conductivity (s/cm)

Carbon sheet (net fiber) (CS) 0.13 3.79 230 0.015 551

Glass sheet (net fiber) (GC) 0.35 2.30 76 0.018 Adhesive 15 4.3 0.02


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cathode. To achieve this, the wrapping system had to

be modified in two ways.

One of the requirements of the system was to

make its electric conductivity uniform. A ribbon of

carbon fibers was stitched through the CFRP sheet in

the perpendicular direction of the fibers. The ribbon

was extended beyond the sheet by about 25 mm. It

was used as the anode terminal for supplying electric-

ity to the CFRP sheet. The ribbon pressed against the

fibers of the sheet and ensured proper contact and

uniform conductivity.32The only non-conductive part

in the system was the epoxy adhesive used to bond

carbon sheets onto the concrete. In the present study,

the epoxy was made conductive by mixing conductive

particulates into the epoxy. The conductive particu-

lates that were used are commercially available graph-

ite powder of particle size in the range from 0.1 to

10 . An experiment was carried out to find the opti-

mum amount of the particulate to be mixed into theepoxy, such that the epoxy became sufficiently con-

ductive without losing the required consistency for

proper coverage of the concrete surface. The workabil-

ity and conductivity were studied by adding 2% to

20% conductive particulates by weight of epoxy.32

An external DC power supply was used to

impress the constant current for active protection. The

positive terminal of the DC power supplier was con-

nected to the protruding ribbon of the carbon sheet

and the negative terminal was connected to the rein-

forcing bar, to be protected from corrosion. A constant

current of 50 mA (current density = 870 A/cm2) was

impressed between the carbon fiber, cathode and rein-

forced steel, anode. To simulate the practical condi-

tion of applying active protection to the reinforced

concrete structures in a corrosive environment, the

specimens were kept in a salt mist chamber, with all

necessary electrical connections for active protection,

for 60 days (Figure 6).

Exposure of Wrapped SpecimensTo simulate corrosion-damaged structures, prior

to the application of the wrap, an initial exposure

was applied. In practice, the FRP wraps are applied

on structures that are corroded to varying degrees.

Therefore, different exposure durations were cho-

sen prior to the application of the wrap. Three expo-

sure durations2, 4, and 8 dayswere applied. The

details of the samples are presented in Table 2. In two

days, the first crack appeared in all the samples. In

4 days and 8 days, the crack became wider and cor-

rosion products oozed out in larger volumes. The con-

trol samples were not wrapped. GPP and CPP indicatepassive protection with glass and carbon FRP wraps,

respectively. CAP indicates active protection that is

active protection applied to the RC specimens using

carbon FRP wraps.

All specimens with varying degrees of initial cor-

rosion, both control and treated, then were exposed to

a severe corrosive environment created in a salt mist

chamber. The salt mist chamber was designed accord-

ing to IS 1186434(Figure 6). The salt mist test was

carried out with 5% NaCl solution at 50C. Injection

of salt fog was put on for 8 h and put off for 16 h,

keeping the samples in the chamber. On switching

off, the temperature inside the chamber subsequently

would have come down to ambient temperature

(~27C). The total duration of exposure in the salt

mist chamber under the specified condition was

1,500 h, i.e., 60 days.

Corrosion MonitoringSeveral parameters have been monitored during

the entire process. Some of these are nondestructive,

such as half-cell potential, cell voltages, and potentio-

dynamic scans. These studies were carried out simul-

taneously on all specimens. Half-cell potential was

noted every day. Cell voltages were observed every dayduring induction of initial corrosion by impressing the

FIGURE 6. Passive protection and active protection applied to FRC-

wrapped specimens exposed to salt mist.

TABLE 2Test Specimens

Wrap Anodic Salt

Material Current Mist Protection Nomenclature

Unwrapped 2 60 No Control-24 60 No Control-48 60 No Control-8

Glass 2 60 Passive GPP-24 60 Passive GPP-48 60 Passive GPP-8

Carbon 2 60 Passive CPP-24 60 Passive CPP-48 60 Passive CPP-8

Carbon 2 60 Active CAP-24 60 Active CAP-48 60 Active CAP-8

Exposure in

Days


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Mass Loss

TABLE 3Pullout Strength and Mass Loss

Percent Pullout

Difference Strength

Specimen Percentage (Equation [9]) (MPa)

Control-2 6.47 8.86Control-4 4.29 5.87Control-8 10.71 5.21GPP-2 2.86 55 12.99GPP-4 2.5 42 13.05GPP-8 8.57 20 11.15CPP-2 6.2 5 13CPP-4 4.6 7 10.32CPP-8 8.27 23 11.2CAP-2 1.65 75 7.81CAP-4 1.38 68 4.15CAP-8 2.87 73 5.63

The lack of corrosion products in actively protected

samples does not lead to the improvement in grip.However, this point should be examined before arriv-

ing at a firm conclusion. The authors are planning

another set of experiments by varying the protection

current density. The microstructure of the bar-con-

crete interface shall also be studied.

The variations of mass loss with pullout strength

for all the specimens are plotted in Figure 10. A lin-

ear fit though the data of different systems has been

carried out. Understandably, pullout strength varies

inversely with the mass loss, i.e., corrosion reduces

bond strength. The rate of loss of pullout strength in

CPP and GPP samples is the lowest. This illustratesthat even with the same level of corrosion, the pas-

sively protected specimens exhibit a better bond with

concrete. As a result of corrosion, the bars exert a

bursting pressure on the concrete. In absence of the

FRP wrap, tensile stresses develop in the concrete

that result in its cracking and spalling. The FRP-

wrapped samples resist the expansion pressure by

developing a hoop stress. As a result, concrete goes

in compression. This results in better grip of concrete

on steel. In the case of actively protected samples,

the corrosion products did not develop. Therefore, the

compressive force in concrete was also absent. The

ribs on the bars, on the other hand, were lost. This

results in the loss of bond strength. For the success

of the active protection technique, it is imperative that

an optimum protection current density is achieved

such that the loss of bond strength is avoided.

Along with the destructive tests that were car-

ried out at the end of the exposure, each sample was

non-destructively monitored. Potentiodynamic scans

were obtained after induction of initial corrosion and

then every 2 weeks during their exposure to salt mist.

The corrosion current (Icorr) was determined. Fig-

ure 11 shows Icorrfor different samples. Understand-

ably, the scatter in data was very large. A linear fit ofthe data was carried out to determine the trends. It

FIGURE 10. Variation of mass loss with pullout strength.

is clear from the figures that the control sample had

higher corrosion currents throughout the exposure

time. The corrosion current increased with exposure.

The trend was similar for all the samples, regardless

of the length of impressed current exposure prior to

salt mist exposure. The protected samples, both pas-

sive and active, exhibited much lower Icorr. This dem-

onstrates that FRP wraps are extremely effective in

protecting the corroding reinforcements in concrete.

Moreover, the current reduced with time. This indi-

cates passivation of steel. Therefore, the efficacy of the

proposed protection systems is established.The initial current was higher in passively pro-

tected systems. However, they passivated at a fast

rate with time. The active system exhibited a lower

Icorrthroughout the period of exposure. It is postulated

that the mechanisms of passivation in the active and

passive systems are different. In the passive systems,

the resistance offered by the FRP wrap to expansive

pressure from corrosion does not allow the corrosion

products to dislodge. As a result, the electrical resis-

tance at the steel-concrete interface goes up. Thus,

the passivation is created. In the active systems the

passivation is from the prevention of ionization of

iron. Therefore, the rate of decay in Icorrin the two sys-

tems was different. The Icorrdecayed faster in the pas-

sive systems.

CONCLUSIONS

v A novel system for the active protection of steel

bars in concrete is reported. The electrical conductiv-

ity of the carbon FRP is utilized in creating an anode

around the steel. Thus, the proposed system elimi-

nates any requirement of an external anode and so

has a very favorable impact on cost.

v The efficacy of the system was established througha set of experiments and performance metrics, both


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Active Protection of Fiber-Reinforced Polymer Corrosion--libre

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