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Treating corrosion in reinforced concrete structures using galvanic - - PowerPoint PPT Presentation

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Treating corrosion in reinforced concrete structures using galvanic anodes Presented by: Gareth Glass Concrete Preservation Technologies Your Organisation Logo here Agenda Causes & Implications of Corrosion Influential

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SLIDE 1

Treating corrosion in reinforced concrete structures using galvanic anodes

Presented by:

Gareth Glass

Concrete Preservation Technologies

Your Organisation Logo here

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SLIDE 2
  • Causes & Implications of Corrosion
  • Influential Factors
  • Repair Solutions
  • Case Studies

Agenda

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SLIDE 3
  • Concrete is alkaline
  • Protective passive film is

formed on steel

  • The passive film can break

down causing the steel in concrete to corrode

Corrosion of Steel in Concrete

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SLIDE 4
  • Sea water
  • Chloride accelerators
  • Atmospheric carbon dioxide

Why does steel in concrete corrode? ACID

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SLIDE 5

Corrosion is an electrochemical process

Concrete

Steel

Passive Film

HCl HCl

HCl HCl

HCl HCl

ANODE CATHODE

e- OH- O2 Cl-

Corrosion of Steel in Concrete

HCl HCl

Cl- Fe2+ H2O

Co rro sio n spre ads side ways

  • Current flows
  • Products are expansive
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SLIDE 6

a) Falling objects – Public safety at risk b) Structural w eakening – Public safety at risk c) Aesthetic issues d) Loss of structure value

Highway Overpass Collapse in 2006 due to corrosion of steel Manor Road Bridge, M6, UK, 2014

Reinforcement Corrosion Concerns

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SLIDE 7

Concrete Corrosion Testing

Concrete corrosion testing;

  • Visual inspection and assessment
  • Delamination survey
  • Cover depth meter survey
  • Carbonation depth
  • Dust sampling (Chloride profiling)
  • Steel potential survey

Car Parks Buildings Bridges Marine

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SLIDE 8

Corrosion Repair Solutions

  • Do nothing
  • Patch Repair
  • Electrochemical Treatments
  • Monitor
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SLIDE 9

Concrete Patch Repair

  • Basic option
  • Short term solution
  • On-going corrosion
  • Incipient anode
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SLIDE 10

Steel bar passive in chloride free concrete Zinc/ Steel anodes in chloride containing m ortar

Zinc/Steel Anodes

120 120 600 Steel Rebar Zinc/Steel Anode Cl- Contaminated Mortar Bulk Concrete

I

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SLIDE 11

Anode response to outdoor climate

50 100 150 55 60 65 70 75 Time (Days) Steel Anode 10 20

55

Anode Current (mA/m2) (mm) (˚C) Rainfall Temperature

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SLIDE 12

Anode response to outdoor climate

100 200 300 400 500 600 700 55 60 65 70 75 Anode Current Density (mA/m2) Time (Days) Zinc Anode Steel Anode

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SLIDE 13

Corrosion is an electrochemical process

Concrete

Steel

Passive Film

HCl HCl

HCl HCl

HCl HCl

ANODE CATHODE

e- OH- O2 Cl-

Corrosion of Steel in Concrete

HCl HCl

Cl- Fe2+ H2O

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SLIDE 14

Galvanic anode operation

HCl HCl

HCl HCl

HCl HCl

HCl HCl

Cl- Fe2+ e- OH- O2 Cl- OH- O2 e- Zn2+

ANODE CATHODE

1 st Generation: Galvanic anodes in patch repair to stop anodes on steel

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SLIDE 15

Galvanic anode operation

HCl HCl

HCl HCl

HCl HCl

HCl HCl

Cl- Fe2+ e- OH- O2 Cl- OH- O2 e- Zn2+

ANODE CATHODE

2 nd Generation: Galvanic anodes in parent concrete to stop anodes on steel

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SLIDE 16

Patch Repair

Galvanic Protection for Concrete Repairs

  • Simple installation
  • Maintenance free
  • Proven technology
  • Typically 15 - 20 years lifetime
  • Smaller anode
  • Closer to area of need
  • Performance not degraded by

high quality repair materials

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SLIDE 17

Patch Repair

Galvanic Anode Installation on a Car Park in Letchworth, UK

  • 1. Drill a hole and

apply Mortar

  • 2. Insert the anode
  • 3. Fix anode wire to

steel and apply repair mortar

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SLIDE 18

Electrochemical Treatment

Hybrid Anode Technology

  • Extends life by 30 to 50 years
  • Simple installation with less

concrete breakout

  • Low maintenance
  • Innovative dual technology
  • Cost-effective
  • Performance can be monitored
  • Conforms to international

standard ISO 12696: 2012

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SLIDE 19

Electrochemical Treatment

Hybrid Anode Technology

OH- OH-

HCl

Pit Re-alkalisation

Oxide Film Galvanic Anode Concrete Steel

O2 Cl-

Brief Impressed Current: Restore pH at acidic pits Galvanic Protection: Maintain pH

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SLIDE 20

Electrochemical Treatment

Hybrid Anode Installation at Crystal House, Preston, UK

  • 1. Drill a hole and soak it with water
  • 2. Connect anode to the wire
  • 3. Apply Mortar
  • 4. Install the anode
  • 5. Apply repair mortar
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SLIDE 21

Monitoring

Why monitor? “If a corrosion risk is identified then steps shall be taken to increase the protection current, by supplementing the galvanic anode system, to minimize this risk.” Section 8.6 and Galvanic Anodes:

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SLIDE 22

Monitoring

Corrosion Science, 1991

  • 700
  • 600
  • 500
  • 400
  • 300
  • 200
  • 100

1 10 100 1000

Potential (mV vs SCE) Corrosion Rate (mA/m²)

0.1

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SLIDE 23

Case Histories

Grosvenor Car Park, UK

PROBLEM

  • Visible cracking and spalling to deck

areas and columns

SOLUTION

  • Galvanic Anode
  • Independent assessment of sacrificial

anode performance

  • Car park in use during repair work
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SLIDE 24

Case Histories

Grosvenor Car Park, UK

Close Interval Potential Mapping

  • 450
  • 400
  • 350
  • 300
  • 250
  • 200
  • 150
  • 100
  • 50

200 400 600 800 1000 1200 1400

Distance from Patch (mm) Potential Change (mV)

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SLIDE 25

Case Histories

Grosvenor Car Park, UK

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SLIDE 26

Case Histories

Kyle of Tongue Bridge Beams, UK

PROBLEM

  • Chloride induced corrosion

SOLUTION

  • Targeted application of Galvanic

and Hybrid anodes

  • Low maintenance and long-term

solution

  • On-going monitoring of steel

condition

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SLIDE 27

Case Histories

Kyle of Tongue Bridge Beams, UK

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SLIDE 28

Kyle of Tongue Bridge Beams, UK

Case Histories

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SLIDE 29

Kyle of Tongue Bridge Beams, UK

Case Histories

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SLIDE 30

Case Histories

Kyle of Tongue Bridge Beams, UK

Corrosion rate comparison

Span Date Corrosion Rate (mA/m2) Date Corrosion Rate (mA/m2) Span 8-9 01/9/2011 39.9 12/1/2012 0.74 Span 9-10 02/9/2011 6.03 12/1/2012 1.19 Span 12-13 1/10/2011 2.47 12/1/2012 0.54 Span 16-17 21/7/2011 6.8 12/1/2012 0.86

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SLIDE 31

Laverock Hall Bridge, UK

PROBLEM

  • Chloride induced corrosion

SOLUTION

  • Targeted application of Hybrid

Anode technology

  • Low maintenance and long-term

solution

  • On-going monitoring of steel

condition

Case Histories

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SLIDE 32

Laverock Hall Bridge, UK

Ste e l c o rro sio n po te ntials and rate s in a 2006 b ridg e installatio n

  • 300
  • 250
  • 200
  • 150
  • 100

100 200 300 400 500 600 700

Time (days) Potential (mV vs SCE)

1 2 3 4

Corrosion Rate (mA/m2)

Corrosion rate Potential

Ste e l c o rro sio n po te ntials and rate s in a 2006 b ridg e installatio n

  • 300
  • 250
  • 200
  • 150
  • 100

100 200 300 400 500 600 700

Time (days) Potential (mV vs SCE)

1 2 3 4

Corrosion Rate (mA/m2)

Corrosion rate Potential

  • 300
  • 250
  • 200
  • 150
  • 100

100 200 300 400 500 600 700 100 200 300 400 500 600 700

Time (days) Potential (mV vs SCE)

1 2 3 4

Corrosion Rate (mA/m2)

Corrosion rate Potential

Case Histories

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SLIDE 33

Laverock Hall Bridge, UK

  • 350
  • 300
  • 250
  • 200
  • 150
  • 100
  • 50

1 2 5 6 7 8

Time (Years) Potential vs Ag/AgCl (mV)

Case Histories

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SLIDE 34

Whiteadder Bridge, UK

PROBLEM

  • Chloride induced corrosion

SOLUTION

  • Targeted application of Hybrid

anode technology

  • Low maintenance and long-term

solution

  • On-going monitoring of steel

condition

Case Histories

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SLIDE 35

Whiteadder Bridge, UK

5 10 15 20 25 30

  • 600
  • 550
  • 500
  • 450
  • 400
  • 350
  • 300
  • 250
  • 200
  • 150
  • 100

4.80 5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40

Galvanic current (mA) Couple Potential v. Ag/AgCl (mV) Time (years)

Galvanic potential Galvanic current

Anodes Passive Anodes Active >100mV polarisation Increased Current x10

Case Histories

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SLIDE 36

Swimming pool at Leisure Centre Durham, UK

PROBLEM

  • Visible delamination and

spalling

  • Low budget

SOLUTION

  • Iterative testing &

evaluation

  • Targeted application of

Galvanic Anode

Case Histories

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SLIDE 37

Birmingham New Street, Network Rail, UK

PROBLEM

  • Visible cracking & spalling to main

beams

  • Short timescale
  • To avoid use of permanent power

supply

SOLUTION

  • Visual assessment & evaluation
  • Hybrid anode technology

Case Histories

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SLIDE 38

Dagenham Jetty, UK

PROBLEM

  • Chloride attack affecting structural

integrity

  • Avoid the use of permanent power supply

SOLUTION

  • Visual assessment & evaluation
  • Hybrid anode technology
  • The structure remained in use
  • No requirement for permanent power

supply

  • Minimal whole life care cost

Case Histories

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SLIDE 39

Fuel Loading Facility, Shell

PROBLEM

  • Sea water affecting structural integrity
  • No external power allowed
  • Structure to remain in use at all times

SOLUTION

  • Visual assessment & evaluation
  • Galvanic anode system
  • Structure remained in use
  • No permanent external power supply

Case Histories

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SLIDE 40

Power plant, South Africa

Koeberg Nuclear Power Station

Case Histories

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SLIDE 41

Housing, Saudi Arabia

CPT corrosion protection products are widely used in environments with hot temperatures which can rapidly accelerate the corrosion process

Case Histories

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SLIDE 42

Case Histories

Lighthouse & Saline Water Containment Tank, Australia

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SLIDE 43

Summary

  • Corrosion is an electrochemical process
  • Galvanic and Hybrid technologies provide valid strategies

to manage corrosion in accordance with international standards

  • Benefits include:
  • Limit disruption during application
  • Targeted to area of need
  • Increase service life
  • Reduced breakout