half cell potential measurement for concrete

7/30/2019 Half Cell Potential Measurement for Concrete

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Half Cell Potential

Measurement Testing (HCPM)

The Objectives of Concrete Testing

Principle of Measurement &Equipment (HCPM)

Nondestructive Vs Destructive Test

Comparison with Other Tests Tips of Prevention for Corrosion

Discussion


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The Objectives of TheConcrete Testing


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Useful of Concrete Testing

Prediction of in-place concrete strength (relativestrength comparison, unless correlated with laboratorystrength tests, for example, core compressive strengthtests);

Location and extent of delaminations due toreinforcement corrosion;

Location, size, and distribution of reinforcement bars;

Location and extent of concrete cracking;

Severity, location, and extent of fire and frost damage; Location and extent of void honeycombing;

Determination of concrete thicknesses; and

Evaluation of reinforcement corrosion activity and rate.


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Concrete Condition Assessment

Testing data helps Engineer on assessing abuilding structure condition

Testing data helps Owner to monitor and controltheir building structure condition

Testing data helps Engineer to design suitablesolutions on mitigating defects.

Testing data helps Owner to budget their buildingmaintenance cost, insuranceetc.

Testing data provide a good trend record onbuilding management


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Example (1) A Building Ceiling


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Example (2) Car Park


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Principle of Measurement& Equipment


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What kind of parameter is useful for concrete

assessment?

Temperature

HumidityPH value

Potential difference

Polarization resistance

Current density data

HCPM method uses potential difference.

Useful Parameters


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Corrosion in Concrete

AnodeReaction

Fe 2e Fe2+

Cathode Reaction

2H2O + O2 + 4e

4OH-

H2O H2OO2 O2

Cl-

Cl

-

OH- OH-

Cathode Cathode

Anodee

-e

-Fe2+

rustrustCl-

Cl-

Cl-

Cl-

Cl

- Cl-Cl

-


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Concrete ResistivityTesting Mechanism

I~

V

S S S

Voltmeter

Ammeter

Alternating

Current Supply

Electrodes

Current Flow Lines

Equipotential Surface


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Corrosion Values

In ASTM C876 to determine possibility of corrosionfor a Copper-Copper Sulfate Reference Electrode

mV Range Probability of Corrosion

0 to -200 > 90% No Corrosion

-200 to -350 Uncertain Corrosion Activity

Less than -350 > 90% Corrosive Activity


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Tips for using Half-cell

1. Concrete cover less than 75mm2. Temperature range: 0 - 493. Steel does not have metallic coating

4. Condition required experience corrosionengineer or specialist:a) Concrete is saturated in waterb) Carbonated at the depth of reinforcing steelc) Steel is coated

d) Contains chloride or bromide


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Instrument

Wire Port to rebar

Cell Holder

Meter

Meter Set


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Nondestructive Test (NDT)Vs Destructive Test (DT)


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Nondestructive Test Vs

Destructive Test

Destructive Testing (DT) involves the physicaldestruction of a components. A variety of testingmethods can be employed to evaluate thecomponent's characteristics, it always refer to a

sampling inspections.

Destructive Testing (NDT) involves inspection ofa components by subjecting them to the requiredservice conditions to determine suitability. They

will not break or alter the structure orappearance of the friction of a component.


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Destructive Test for Concrete

Tensile Test

Impact / Compression Test

Hardness Test Fracture Test

Bend Test

Core Sample Test


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Comparsion of Testing Method

Non-destructive Test

On-site

Simple & faster

No damage toinstallation

Cost effective

Require usually hand-

held equipment Easy space allocation

Usually outdoor andweather dependent

Destructive Test

Workshop or Laboratory

Heavy & time consuming

Rebuilt the testing point Higher cost

Require elaborateequipment

Difficult to somelocations

Indoor and weatherindependent


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Comparison with OtherTests


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Comparison to Other Tests

Rebound Hammer ASTM C805

Penetrating Probe ASTM C803

Ultrasonic Wave VelocityThrough transmission testingASTM C597

Impact Echo testing ASTM C1383Pullout Test ASTM C900


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Rebound HammerASTM C805


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Rebound Number Correlations


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Penetrating Probe Correlations


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Ultrasonic Wave Evaluation


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Ultrasonic

Pulse

VelocityASTM

C597


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Comparsion Table


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Tips of Prevention forCorrosion in Concrete


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Corrosion may be prevented or

controlled by:

materials selection

reducing the temperature

applying physical barriers

adding inhibitors

cathodic protection

using metals that form a protective oxide

layer Painting/coating


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Example of Applying Physical Barriers

Now aday Special coating such as epoxy or silicate are used

History of Development of Physical Barriers


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Example of adding inhibitors

Spray-applied reactive penetrants combine with alkaliswithin the concrete, reducing the pH and permeability

to moisture vapor


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Discussion

half cell potential measurement for concrete

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