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Half-cell Potential Method &

Electrical Resistivity Method

By,K.SANGEEHA RA!

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Non Destructive Testing serve as a vital tool notonly in estimating the strength, integrity andtypes of active deterioration mechanism, but alsoguide the engineers to plan and devise strategies

for executing repair & rehabilitation projects.

The Presence of Corrosion ctivity can beassessed by

!"#alf$Cell Potential %ethod"'lectrical (esistivity %ethod

d and interpreted by experienced specialists because to many engineers the features, and especially the limitations of available test methods are unknown and consequently left to experts.

Non-Destructive Testing

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This test method covers the estimation ofthe electrical corrosion potential ofuncoated reinforcing steel in)eld and

laboratory concrete, for the purpose ofdetermining the corrosion activity of thereinforcing steel.

Copper$Copper *ulphate 'lectrode +C*'"

*ilver$*ilver Chloride 'lectrode +**'"The potential values become more and

more negative as corrosion becomes more

and more active

Half Cell Potential Survey

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Copper *ulphate *olution

Porous Plug +*ponge"

Copper (od

Transparent PlasticTube

(einforcement Potential%easurement

ea- #alf Cell of aattery

'lectrod

e 'lectrolytic%aterial

Principle/ 0'lectric Potential Di1erence2

HALF-CELL POTENTIAL METHOD

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DigitalValues

Iso - PotentialContours

Gray ScaleColore Scale

Test Proceure

E!a"#le

Gri Mar$ing %&etting o' Concrete

Sur'ace

Testing is inProgress

Measure"ent o' ElectricalPotential Di(erence

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ccording to *T%C345

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ELECT)ICAL )ESISTIVIT* METHOD

Princi#le+,Electrical )esistance o' Concrete

6lo7 of current generated is assessed in terms of electrolytic (esistivity ofconcrete.

)esisti.ity Meter/)ESI0 )esisti.ity

Measure"ents

)esisti.ity o' Concrete/0 1 2 S V3I-cm

Instru"ent

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The electrical resistance of concrete plays animportant role in determining the 8uality of concretefrom the point of vie7 9corrosion susceptibilitypotential: at any speci)c location. This parameter isexpressed in terms of 0(esistivity2 in ohm$cm.

6or general monitoring, a resistivity chec- isimportant because long$term corrosion can beanticipated in concrete structures 7here accuratelymeasured values are belo7 !;;;; ohm$cm. further

if resistivity values fall belo7

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)esisti.ity o4"-c" Corrosion Pro5a5ility

=reater than ;,;;; Negligible

!;,;;; > ;,;;; ?o7

!;;;; #igh

?ess than

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The CNANB instrument provides t7omethods for investigating and assessing thecorrosion of steel in concrete.

!"%easurement of corrosion potential

"%easurement of electrical resistivity ofreinforced concrete components

)The indo7s based soft7are CNAN Pro@ista,

developed by Proce8 *, ma-es it possible todo7nload, present and edit data measured bythe CNANB half$cell instrument in a fast andeasy 7ay using an A%$compatible PC.

CANIN INSTR!MENT

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The program generates a potential map, arelative fre8uency and a cumulative fre8uencydiagram and provides a chipping graph.

This statistical presentation is the basis for an

ecient interpretation of the half$cell potentialsby the corrosion engineer.

*ingle )les can be opened and processedseparately.

y rotating or mirroring in intervals of ;E thesingle potential maps can be combined to forma complete graph representing the totalinvestigated surface area.

CANIN INSTR!MENT

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Potential %ap, (elative and

Cumulative 6re8uency Diagram

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The CNANB Corrosion nalyFing Anstrumenthighlights corrosion activity before rustbecomes visible.

This early detection can be -ey in preventingan unanticipated structural failure.

CNANB is ideally suited for assessment ofcorrosion potentials on large areas of 3,;;;

mGor multiple thereof, depending on theindividual selectable grid siFe.

H

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*econdly, the instrument can measure the resistivity of the

concrete.

lo7er concrete resistivity indicates a greater chance

of corrosion of the reinforcement and also a greater corrosion

rate.

The resistivity of concrete can vary extensively dependingon the local conditions and environmental inIuence factors.

The combination of resistivity and potential measurementimproves the information about the corrosion condition ofthe rebarJs.

The concrete resistivity is measured by the four$point ennerprobe.

ll information is indicated on a large clear display.

The instrument can also store up to

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Corrosion Analy6ing Instru"ent/CANIN0

TestingInstru"ent

)oElectroe Multi -Electroes &4eel -Electroe

&ire % Cli# 'or)ein'orce"ent

Connection

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THAN7*O8