cp application on a pre-tensioned bridge in belgium · pdf filecp application on a...

CathodicCathodic protection Flyoverprotection Flyover

CP application on a preCP application on a pre--tensioned bridge in Belgiumtensioned bridge in Belgium

J. Leggedoor, G.H. Schuten,

A. Laemont

CathodicCathodic protection Northprotection North--South viaductSouth viaduct

Situated over the main roads � Brussels Airport Zaventem

North-South bridge


- concrete damage- reinforcement corrosion on column side of the joints

the main problem


Investigation

2000-2001

Shrinkage cracks <= Shrinkage cracks <= 0.02mm, locally very high0.02mm, locally very highporosityporosity

MicroscopicMicroscopicresearchresearch

1010--50mm50mmConcrete coverConcrete cover

73.573.5--101.7 N/mm2101.7 N/mm2Compressive StrengthCompressive Strength

0.0090.009-- 0.477%0.477%Chloride content Chloride content (depth)(depth)

00--10mm10mmCarbonation depthCarbonation depth


Problem Analysis/ Solution

- Chloride induced reinforcement corrosion on the column side of the joints

- Logical solution: Cathodic protection- cost aspects � locally protection

Complication: Pre-tensioned deck elements

Rules: NEN-EN12696Cathodic protection combined with pre-stressed steel:Monitoring potentials: Eon > -900mV versus Ag/AgCl/0,5 m KCl


Cathodic protection installation

Basic principle

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Impressed current disturbs the electrochemical reactions (rust) on such a way that it stops or is reduced to an acceptable level.


Monitoring pre-stressed steel

True potential (Manganese Dioxide)reference Electrode type ERE-20


Localised CATHODIC PROTECTION

detail plan (joint surrounding)

Rebar Rebar

Cadweld

Ref

eenc

e E

lekt

rode

Titanium wire3mm White, isolatedwith 4mm tubingVD-wire

0,75mm2 blue

VD-wire2,5mm2 black

spotwelding

Titanium gridANODE(10,9m1)

Titanium gridANODE (1m1)

spotwelding

VD-wire2,5mm2 black

Cable protection

Prefabricatedconcreteelements

Columnside

Titanium wire3mm White, isolatedwith 4mm tubing


CATHODIC PROTECTION

�� Remove loose parts concreteRemove loose parts concrete�� Continuity reinforcementContinuity reinforcement�� Reference Reference ElectrodeElectrode mounting mounting �� Field CablingField Cabling�� Anode mounting (titanium)Anode mounting (titanium)�� Anode embeddingAnode embedding�� MountingMounting--/ adjustments of power/ adjustments of power--

supplysupply’’ss


CATHODIC PROTECTION

Rebar continuity


CATHODIC PROTECTION

Anode (titanium) mounting


CATHODIC PROTECTION

Example repaired joint


CATHODIC PROTECTION

Power-supply placement and adjustments

Field connections

Monitoring installation


CATHODIC PROTECTION

Operation and maintenance

NEN-EN 12696At least 2 times a Year inspections, with at least ones a visual inspection

Inspection parts:1. electrical system check2. measurements of current and voltages3. Assessment of data4. Measurement of Instant Off potentials and depolarisation5. Readjust power-supply’s when necessary 6. Visual inspection of the complete system

Point 1-5 Zaventem performed by a full remote controlled Monitoring system


CATHODIC PROTECTION

Effectiveness control by means of decay measurements

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CATHODIC PROTECTION

Decay measurement North-South bridgeZaventem decay 25-10-06 (24hr)

-1000

-900

-800

-700

-600

-500

-400

-300

-200

-100

00,0 5,0 10,0 15,0 20,0 25,0

Time (hr)avg decay = -171,3 mV

Pote

ntia

l (m

V)

RE-1 (LHN)

RE-2 (P1N)

RE-4 (P2N)

RE-5 (P2Z)

RE-7 (P3Z)

RE-8 (P4N)

RE-9 (P4Z)

RE-10 (P5N)

RE-12 (P6N)

RE-13 (P6Z)

RE-14 (P7N)

RE-15 (P7Z)

RE-17 (P8Z)

RE-18 (LHZ)


CATHODIC PROTECTION

Monitoring prestressed steel during decay measurement

No visible decay � no polarisation as result of CP other construction parts

Decay pres-stressed steel

-800

-700

-600

-500

-400

-300

-200

-100

00,0 5,0 10,0 15,0 20,0 25,0 30,0

Time

mV

RE-3 (P1Z)ERRE-6 (P3N)ERRE-11 (P5Z)E

RE-16 (P8N)E


Conclusion:

-CP can be used for all types of concretestructures

-To safeguard the prestressed steel againsthydrogen embrittlement , the true potentialsshould be measured

cp application on a pre-tensioned bridge in belgium · pdf filecp application on a...

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